Aqueous or water-dispersible solid coating composition

Abstract

To provide an aqueous or water-dispersible solid composition by suppressing the volatilization of organic solvents during the manufacturing and application of coatings, in which the composition is intended to reduce the environmental burden on the Earth and mitigate adverse effects on human health, while also enabling the reduction of greenhouse gases (GHG) by lowering the energy required during the manufacturing, transportation, and application of coatings.SOLUTION: A solid composition comprising a water-soluble polymer (a) and a polyhydric alcohol (b) that are in a solid state at 20°C or higher, particularly a polyhydric alcohol (b) with a melting point of 130°C or lower, is obtained by melt-kneading these components so that their weight mixing ratio is 50:50 to 90:10, and is a solvent-free type melt-kneaded composition in which no solvent is added during the melt-kneading process. This composition can be used as an aqueous paint by dissolving or dispersing it in water.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-soluble or water-dispersible solid composition (hereinafter, sometimes simply referred to as "the solid composition of the present invention"), a method for producing the composition, and a method for dissolving or dispersing the composition in water and using it as a water-based paint. [Background technology]

[0002] In recent years, various social issues, such as global environmental problems and health issues, have come into the spotlight. Taking paint as an example, there are concerns that the volatilization of organic solvents during paint manufacturing and application may have a negative impact on the global environment and human health. Furthermore, the production, transportation, application, and disposal of paint consumes a large amount of energy, which is one of the reasons for the increase in greenhouse gas (GHG) emissions. Against this background, various methods are being considered with the aim of reducing the amount of organic solvents used and curbing energy consumption.

[0003] The first example is a method in which the organic solvent is removed from an existing solvent-based paint and then dispersed in water. By converting from an existing solvent-based paint to a water-based paint, the evaporation of organic solvents during painting can be suppressed without having to develop a new water-based paint. However, a lot of energy is required to completely remove the organic solvent. Also, since the non-volatile matter remains in a fixed state after the organic solvent is removed, a process such as fine grinding is required to disperse it in water, which increases the number of manufacturing steps and requires even more energy. As a result, no substantial GHG reduction is achieved.

[0004] Compared to solvent-based paints, water-based paints are more susceptible to storage stability concerns, such as spoilage and mold growth. Furthermore, with both solvent-based and water-based paints, disposing of the excess paint that remains unpainted after the paint can is often problematic. Therefore, powder paints can be used as a second example. Because powder paints do not use organic solvents, they can reduce the evaporation of organic solvents during paint manufacturing and application. They also have the advantages of high coating efficiency and the ability to reuse recovered powder, making them preferable from the perspective of reducing energy consumption and contributing to GHG reduction. However, there are some disadvantages to this method, such as the need for specialized equipment, the need for the object to be coated to be conductive due to electrostatic coating, and the need for baking after coating.

[0005] Taking into account the advantages and disadvantages of powder paints mentioned above, a third example is water-dispersed powder paint. With water-dispersed powder paint, only the required amount of powder paint is extracted before application, dispersed in water, and adjusted to the desired concentration, allowing for control of the amount of excess paint disposed of. Also, because water is used as the medium, there is less concern about the volatilization of organic solvents during application. Furthermore, because the product is in the form of a solid that does not contain solvents, the volume required for product transportation is small, reducing the energy required for transportation. Therefore, water-dispersed powder paint is preferable from the perspective of reducing energy consumption and can also contribute to reducing GHG emissions.

[0006] Patent Document 1 discloses a powder paint having water redispersibility, which contains a powder enamel obtained by drying an aqueous dispersion containing a water-dispersible resin and a coloring pigment in an amount of 1 to 200 parts by weight of pigment per 100 parts by weight of the resin solids, and which is characterized in that an aqueous medium is added, stirred, and mixed at the time of use to liquefy the paint. As the water-dispersible resin, particularly from the viewpoint of ensuring redispersibility in water, an emulsion obtained by emulsion polymerization of a polymerizable unsaturated monomer using at least one kind of protective colloid selected from known water-soluble polymers such as polyvinyl alcohol-based resins, cellulose derivatives, and water-soluble acrylic resins can be preferably used, and it has been shown that polyvinyl alcohol-based resins are particularly suitable as protective colloids from the viewpoint of water redispersibility. On the other hand, the aqueous dispersion can be dried and powdered according to previous reports, and it has been shown that a drying temperature of approximately 80 to 150°C is usually suitable. In particular, it is described that the aqueous dispersion is desirably adjusted, for example, by diluting with water, so that the solids concentration is usually in the range of 1 to 60% by weight, preferably 20 to 50% by weight, for ease of spray drying, etc. Although the medium is water rather than an organic solvent, a large amount of energy is required for powderization, as in the first example. In addition, a large amount of wastewater treatment is required.

[0007] Patent Document 2 discloses a water-dispersible powder coating in which a powder containing a coating resin is dispersed in water, characterized in that the powder has an average particle size (D50) of 5 to 15 μm, the proportion of particles 20 μm or larger is 10 mass% or less, the proportion of particles 3 μm or smaller is 10 mass% or less, and the solid content is 30 to 60 mass%. Furthermore, Patent Document 3 indicates that by precisely controlling the average particle size and particle size distribution as in Patent Document 2, when water-dispersible powder paints of different colors are mixed together, the color can be adjusted without color mixing or color unevenness. It has been shown that the average particle size of a water-dispersible powder paint is one factor that affects the finish of the paint film. For example, it has been pointed out that if a paint dispersion contains a large amount of excessively fine particles, the viscosity of the paint dispersion increases, significantly impairing the workability of spray painting using a spray gun or the like, and also resulting in poor paint film surface. On the other hand, it has also been pointed out that if a water-dispersible powder paint contains a large amount of coarse particles, not only will the paint film have a rough texture, but the surface irregularities will also become more pronounced, resulting in poor paint film appearance. Furthermore, it has been pointed out that in order to improve the sedimentation (separation) stability of the paint dispersion, a large amount of dispersant or anti-settling agent must be added, which raises the issue of wastewater treatment. It has also been pointed out that even if the average particle size is within a predetermined range, if a water-dispersed powder coating having a wide particle size distribution and a large amount of coarse particles is used as a base coating, the dried coating film will have short unevenness intervals and large unevenness differences, making it difficult to obtain a uniform finished coating film.On the other hand, it has also been pointed out that if a water-dispersed powder coating having a wide particle size distribution and a large amount of fine particles is used as a base coating, the fluidity of the coating will decrease and painting workability will deteriorate. However, there is a concern that the average particle size is very fine and therefore dust is likely to be generated.

[0008] Patent Document 4 discloses a water-redispersible powder coating material that contains a redispersible resin powder and at least one granular colorant, and is characterized in that an aqueous medium is added and stirred and mixed at the time of use to liquefy the material. It can be prepared by adding water and stirring and mixing at the coating site, and is easy to transport, store, and dispose of, so it is disclosed that it can be used for cement mortar coating, gypsum plaster coating, and the like, which are mainly used in construction work. Here, the redispersible resin powder can be any conventionally known one without any particular restrictions, and it has been shown that it can usually be obtained by powdering an emulsion of a resin such as a vinyl acetate resin, an ethylene vinyl acetate resin, or an acrylic (styrene) resin by a method such as spray drying. The granular colorant can be obtained by forcibly emulsifying water, surfactant, and mineral spirits in a homogenizer to obtain a dispersion of solvent particles with an average particle size of approximately 2 μm, adding surfactant and pigment, stirring the mixture in a disperser until uniform, and then spraying the mixture into hot air at 100°C and drying it. The granular colorant thus obtained is preferably primarily spherical, with an average particle size of 1 to 3,000 μm, preferably 20 to 2,000 μm, and a bulk density of approximately 0.2 to 0.6 g / ml. Such water-redispersible powder coatings produce little dust and are easy to handle, but, as with the first example, require a lot of energy to be powderized.

[0009] Similar designs using water-soluble or water-dispersible ingredients have applications outside of paints. Patent Document 5 discloses a readily soluble paste of a water-soluble biopolymer obtained by blending a powdered water-soluble biopolymer with a polyhydric alcohol. Water-soluble biopolymers made from fermented polysaccharides, such as xanthan gum and rhamsan gum, have poor solubility in flowables, liquid fertilizers, and emulsion paints, making them difficult to add directly. Therefore, a diluted solution is prepared and then mixed. However, these water-soluble biopolymers are more susceptible to spoilage than other water-soluble polymers, such as polyvinyl alcohol, carboxymethyl cellulose, and methyl cellulose, necessitating the addition of preservatives each time they are used. On the other hand, it has been shown that blending a polyhydric alcohol such as ethylene glycol, propylene glycol, or glycerin with a water-soluble biopolymer to form a readily soluble paste of the water-soluble biopolymer not only improves its solubility in water, but also has the advantage of being stable against decay for a long period of time because it does not contain water, and that if the readily soluble paste is prepared in advance, the required amount can be used whenever needed.

[0010] Patent Document 6 discloses a solid watercolor composition characterized by containing 30% by mass or more of pigment, 25% by mass or less of water, a wetting agent, and polyethylene glycol with an average molecular weight of 1000 or more. It also discloses that the solid watercolor composition can be obtained by the following steps: (1) kneading predetermined amounts of pigment, water-soluble polymer, wetting agent, PEG with an average molecular weight of 1000 or more, surfactant, preservative, and water in a kneader; (2) molding the kneaded mixture into a long, thin rod shape, specifically a rectangular prism, in a clay kneader and drying at 45°C for 24 hours; (3) cutting the molded product to a predetermined size; and (4) allowing the cut product to dry naturally.

[0011] Patent Document 7 discloses a water-soluble solid painting material that uses a partially saponified polyvinyl acetate binder with a saponification degree of 50 to 95 mol% (in vinyl alcohol units) and a colorant. The partially saponified polyvinyl acetate is a thermoplastic, water-soluble polymer that dissolves in water and melts in heat. This material is characterized by being molded by heat without using water. Compared to water-based kneading and molding, the thermal kneading and molding process results in less change over time and does not require a long drying process, resulting in excellent dimensional stability between and within lots, resulting in a water-soluble solid painting material with consistent quality. Furthermore, the high molding strength of the material has been shown to result in good extrusion moldability.

[0012] Patent Document 8 discloses a water-soluble solid drawing material characterized by containing at least a colorant and a surfactant with a specific structure having an ethylene oxide skeleton. It is disclosed that the water-soluble solid drawing material can be obtained by adding water to the above components, if necessary, and mixing them using a heated stirring device or kneading them in a kneader, roll mill, or other kneading machine to form a molten state, pouring the molten material into a mold, cooling, injection molding, or extrusion molding, and then drying and molding into a predetermined shape if necessary. It is also disclosed that the inclusion of the surfactant with a specific structure having an ethylene oxide skeleton further improves the solubility of the water-soluble solid drawing material, reduces moisture absorption even in humid environments, and enables excellent writing properties. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-052293 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-002707 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-099871 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-269860 [Patent Document 5] Japanese Patent Application Publication No. 02-229843 [Patent Document 6] Japanese Patent Application Publication No. 2019-123848 [Patent Document 7] Japanese Patent Application Laid-Open No. 2002-201399 [Patent Document 8] Japanese Patent Application Laid-Open No. 2004-359805 Summary of the Invention [Problem to be solved by the invention]

[0014] In light of the prior art described above, the present invention aims to discover a more environmentally friendly paint composition. More specifically, the paint composition can be dissolved or dispersed in water and used as an aqueous paint, and aims to reduce the burden on the global environment and the adverse effects on human health by suppressing the volatilization of organic solvents during the process from the production of the composition to the preparation and application of the aqueous paint. Another aim is to reduce GHG emissions by reducing the energy required for production, transportation, and application. [Means for solving the problem]

[0015] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered a composition for use in a paint, which contains a water-soluble polymer and a polyhydric alcohol, is water-soluble or water-dispersible, and is in a solid state, and have thereby completed the present invention. More specifically, the inventors have discovered a coating composition that is water-soluble or water-dispersible and solid, which comprises a water-soluble polymer that is solid at room temperature and a polyhydric alcohol, in particular a polyhydric alcohol having a melting point of 130°C or less, and which is melt-kneaded at a weight mixing ratio of 50:50 to 90:10. Here, "room temperature" refers to the average temperature in a normal manufacturing process. From the viewpoint of manufacturing workability, it is preferable that the composition is in a solid state at 20°C or higher. Furthermore, the coating composition characterized by being in a solid state is a solvent-free melt-kneaded composition to which no solvent is added during the manufacturing process, i.e., it is characterized by not including a drying step. [Effects of the Invention]

[0016] The solid composition of the present invention can be used as an aqueous paint (hereinafter sometimes referred to as "the aqueous paint of the present invention") by dissolving or dispersing it in water. In other words, the solid composition of the present invention can be a precursor of the aqueous paint of the present invention. Therefore, compared with conventional liquid coating compositions, not only can the evaporation of organic solvents be suppressed in the processes from the production of the composition to the preparation and application of the aqueous coating, but the volume of the product when transported can be small, thereby reducing the energy required for transportation. In particular, it is advantageous in that the product can be filled in a lighter and simpler form, without being limited to metal cans or glass bottles as in the case of conventional liquid coating compositions. Furthermore, since no solvent is added during the manufacturing process, a drying step is not required, and energy consumption due to drying can be reduced compared to the process described in Patent Document 6. Furthermore, by using a polyhydric alcohol having a melting point of 130°C or less, less energy is required to melt-knead and produce the composition, compared to when a partially saponified product of polyvinyl acetate is used as in Patent Document 7. The solid composition of the present invention has the above-mentioned characteristics, and therefore the following effects can be expected. 1. Reduced environmental impact due to the volatilization of organic solvents. 2. Reduces the adverse effects on human health caused by the evaporation of organic solvents. 3. The smaller volume compared to liquid paint reduces the energy required for transportation. 4. By dissolving the required amount in water and using it, the amount of excess paint disposed of can be reduced. 5. GHG emissions are reduced because no solvent is added during the melt-kneading process and no drying process is required. DETAILED DESCRIPTION OF THE INVENTION

[0017] The solid composition of the present invention will be described in detail below. However, the present invention is not limited to the examples shown here. Here, "solid" is a general term for a lump, granule, tablet, powder, etc. From the viewpoint of being used as an aqueous paint by dissolving or dispersing in water, a powder form is preferable, but it is not limited to a powder form. It may also be used as a slurry or gel.

[0018] <Water-soluble polymer (a)> The water-soluble polymer (a) in the present invention is used by melt-kneading at least with the polyhydric alcohol (b) described below. Simply mixing these cannot provide the effects of the present invention. As the water-soluble polymer (a) in the present invention, either a naturally occurring component or a synthetic product can be used. Examples of naturally derived ingredients include plant polymers such as gum arabic, guar gum, karaya gum, alginic acid, carrageenan, agarose, and starch; animal polymers such as gelatin; and microbial polymers such as xanthan gum and dextran. Other examples include cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; and processed products such as modified starch and dextrin. Examples of synthetic materials include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyethylene glycol, and derivatives thereof. In the present invention, from the viewpoints of manufacturing workability, crushability after being made into a paste, and reducing the energy required for melt-kneading, materials that are solid at room temperature and can be thermally melted at 130°C or less are preferred. Specifically, from the viewpoint of manufacturing workability, a temperature of 20°C or higher and 130°C or lower is preferred. Therefore, polyvinyl alcohol, polyvinylpyrrolidone, and their derivatives, which have a melting point of 150°C or higher, are not preferred. Polyethylene glycol and its derivatives, which have a melting point of less than 100°C, are preferred from the viewpoint of the energy required for melt-kneading, but those with low molecular weights are not preferred because they tend to adhere to an extrusion kneader (hereinafter abbreviated as "kneader") and reduce manufacturing workability. On the other hand, materials with high molecular weights are less likely to adhere to a kneader, but are undesirable because they have a linear structure, which makes them highly ductile and difficult to pulverize. However, this does not preclude their use within a range that does not significantly impair ductility or adhesion. For these reasons, in the present invention, it is preferable to use ingredients derived from natural products, and xanthan gum and dextrin are particularly preferable. The water-soluble polymer (a) preferably has a water content of less than 10%, more preferably 3% or less. If the water content is high, the water-soluble polymer (a) may become sticky when made into a paste, which may adhere to the kneader and reduce the efficiency of production.

[0019] <Polyhydric alcohol (b)> The polyhydric alcohol (b) in the present invention refers to a compound having two or more alcoholic hydroxy groups in one molecule, and is preferably solid at room temperature and has a melting point of 130° C. or less from the viewpoints of production workability, the crushability of the paste described below, and reducing the energy required for melt-kneading. Specifically, from the viewpoint of production workability, it is preferably 20° C. or more and 130° C. or less. Such polyhydric alcohols are preferably sugar alcohols, and examples thereof include erythritol, threitol, arabinitol, xylitol, ribitol, iditol, galactitol, sorbitol, maltose monohydrate, and trehalose dihydrate. From the viewpoint of compatibility with the water-soluble polymer (a), it is preferable to use sorbitol. When the compatibility with the water-soluble polymer (a) is good, even if the water-soluble polymer (a) is difficult to melt alone, it can be kneaded in a kneader, which is preferable from the viewpoint of manufacturing workability. Furthermore, when a sugar alcohol is used, the solid composition of the present invention can be easily dissolved in water at 10°C by manual stirring.

[0020] <Prepaste (A)> The prepaste (A) of the present invention is obtained by melt-kneading the water-soluble polymer (a) and the polyhydric alcohol (b) using a kneader, and is characterized in that it can be melt-kneaded at a temperature of 130°C or less and does not require the addition of a solvent during the kneading process. The weight mixing ratio of the water-soluble polymer (a) and the polyhydric alcohol (b) is preferably 50:50 to 90:10, more preferably 60:40 to 80:20. Since the polyhydric alcohol (b) is difficult to solidify even when cooled after being melted, if the mixing ratio is high, it is likely to adhere to the kneader during kneading, which may reduce production workability. In addition, blocking is likely to occur, which is a concern from the viewpoint of storage stability.

[0021] <Coloring material (B)> The colorant (B) of the present invention is not particularly limited, and examples thereof include titanium oxide, zinc oxide, iron oxide, yellow iron oxide, carbon black, azo pigments, phthalocyanine pigments, threne pigments, quinacridone pigments, dioxazine pigments, isoindoline pigments, anthraquinone pigments, perylene pigments, and diketopyrrolopyrrole pigments. In addition to these organic and inorganic pigments, luster pigments can also be used within the scope of the present invention. Examples of luster pigments include metals such as aluminum, zinc, copper, silver, brass, and nickel; metal oxides such as aluminum oxide; glass flakes; mica; and mica coated with a metal oxide. Known dyes can also be used. The solid composition of the present invention, which does not contain the coloring material (B), can be dissolved or dispersed in water and used as a water-based clear coating.

[0022] <Paste (C)> The paste (C) of the present invention is obtained by mixing the prepaste (A) and the coloring material (B) and kneading the mixture in a kneader. The weight mixing ratio of the prepaste (A) to the coloring material (B) is preferably 100:30 to 100:200, and more preferably 100:50 to 100:150. If the mixing ratio of the coloring material (B) is low, when the solid composition of the present invention is dissolved or dispersed in water and used as an aqueous paint, the coloring power may be low and the hiding power may be insufficient. Also, if the mixing ratio of the coloring material (B) is high, the load on the kneader during kneading increases, which is undesirable. Although the use of a process for obtaining paste (C) via prepaste (A) in this way increases the total number of steps, it has the advantage of enabling the development of multiple colors using a common prepaste. It is also possible to obtain paste (C) by directly kneading the water-soluble polymer (a), the polyhydric alcohol (b), and the colorant (B) in a kneader without going through prepaste (A).

[0023] <Solid (D)> The solid (D) of the present invention is obtained by crushing the paste (C). The size can be adjusted depending on the application, but taking into account ease of dissolution or dispersion in water, a particle size of 500 μm or more and 2 mm or less is preferable. If the particle size is smaller than 500 μm, it is susceptible to the influence of moisture in the air and may aggregate over time. In addition, dust is easily generated, which raises concerns about workability.

[0024] Additive (E) When used as the aqueous paint of the present invention, it is easily affected by the surface tension of water, so additive (E) can be added to improve coating workability. In the present invention, the surface tension of a 5% aqueous solution is preferably 40 mN / m or less, and more preferably 35 mN / m or less. Siloxane-based additives have a strong effect of lowering surface tension, but are prone to foaming when used as the aqueous paint of the present invention, so it is preferable to select an appropriate additive taking into account coating workability and finish. The surface tension was measured using a pendant drop surface / interfacial tensiometer and an automatic contact angle meter (DSA25, manufactured by KRUSS). The additive (E) is preferably added in an amount of 1 to 15 parts by weight per 100 parts by weight of the prepaste (A). If the amount added is too large, color separation may occur in the paint when used as the aqueous paint of the present invention. Also, color separation may occur on the paint film after application. On the other hand, if the amount added is too small, coating workability may be reduced.

[0025] <Other ingredients added during mixing> In addition to the above, resins, pigments, additives, etc. may be added as other components during kneading within the scope of the present invention.

[0026] The resin may be any known resin different from the water-soluble polymer (a). For example, acrylic resin, urethane resin, alkyd resin, polyester resin, epoxy resin, etc. These resins may be used alone or in combination of two or more to produce the prepaste (A). From the viewpoint of energy efficiency in production, however, resins that can be melt-kneaded at 130°C or less are preferred.

[0027] The pigment may be different from the colorant (B), and may be an extender pigment or aggregate such as talc, clay, kaolin, calcium carbonate, barium sulfate, or silica. Porous materials such as diatomaceous earth, activated alumina, and zeolite may also be used. Because porous materials have excellent adsorption capabilities, when used as the aqueous coating material of the present invention, they can impart effects such as deodorizing, humidity control, and formaldehyde adsorption to the coating film. These pigments may be used alone or in combination of two or more to produce the prepaste (A).

[0028] The additives that can be used are different from the additive (E) and are generally added to water-based paints, such as dispersants, surface conditioners, antifoaming agents, thickeners, film-forming aids, preservatives, mildew inhibitors, antibacterial agents, antiviral agents, insect repellents, etc. These additives can be used alone or in combination of two or more types in the production of the prepaste (A). For example, hinokitiol, which is known to be effective as an antibacterial agent, is a slightly soluble substance in water, but has a melting point of about 50°C and can be incorporated by melt-kneading during the production of prepaste (A).When used as the aqueous coating material of the present invention, it can be dispersed in water and can impart antibacterial properties to the coating film.

[0029] <Other components added when used as the water-based paint of the present invention> In addition to the above, resins, additives, etc. may be added as other components when used as the water-based paint of the present invention, within the scope of the present invention.

[0030] The resin may be a conventionally known water-soluble or water-dispersible resin other than the water-soluble polymer (a). For example, acrylic resin, urethane resin, alkyd resin, polyester resin, epoxy resin, etc. These resins may be used alone or in combination with the solid composition of the present invention, and may be used as an aqueous coating material by dissolving or dispersing in water.

[0031] The additives that can be used are different from the additive (E) and are generally added to water-based paints, such as dispersants, surface conditioners, antifoaming agents, thickeners, film-forming aids, preservatives, antifungal agents, antibacterial agents, antiviral agents, insect repellents, etc. These additives can be used alone or in combination of two or more.

[0032] <Method of producing the solid composition of the present invention> The method for producing the solid composition of the present invention will be outlined below with reference to an example. First, a predetermined amount of water-soluble polymer (a) and polyhydric alcohol (b), which are solid at room temperature, are mixed and melt-kneaded in a kneader to obtain a pre-paste (A) (Step 1). Since the mixture can be melted at a temperature of 130°C or less without adding a solvent, a drying step is not required.

[0033] Next, the pre-paste (A) and the coloring material (B) are melt-kneaded to obtain a paste (C) (Step 2). Here, since the pre-paste (A) can be melted at a temperature of 130°C or less without adding a solvent, a drying step is not required, as in Step 1. The paste (C) can also be obtained by directly kneading the water-soluble polymer (a), the polyhydric alcohol (b), and the colorant (B) in a kneader without going through the process of preparing the prepaste (A). Furthermore, by proceeding to the next step without adding the coloring material (B), the solid composition of the present invention can be used as a clear coating.

[0034] Finally, the paste (C) is crushed to obtain a solid (D) (step 3). For the crushing, for example, a hammer mill, a stamp mill, a roller mill, an edge runner, a cutter mill, or the like can be used.

[0035] A cutting step (step 4) or a classification step (step 5) may be included to adjust the size of the solid (D) depending on the intended use. The part removed by classification can be reused by mixing it in another kneading process.

[0036] <Evaluation methods for pre-paste (A), paste (C), and solid (D)> ·Manufacturing workability The manufacturing workability of pre-paste (A) and paste (C) was evaluated according to the following criteria based on the stickiness of the raw material components in the kneader. A comprehensive evaluation was also conducted, taking into account the degree of load on the kneader. A grade of △ or higher was considered acceptable. 〇: No problem. Good / Poor: There is some stickiness in the kneader. △: The kneader is slightly sticky, but the load is not great. △×: The kneader was very sticky and the load on the kneader was large. ×: The load on the kneader was too great and dispersion was not possible.

[0037] · Friability of paste (C) The crushability of the paste (C) was evaluated according to the ease of processing using the following criteria. A score of △ or higher was considered to be acceptable. 〇: No problem. 〇△: There are some uncrushed pieces. △: Approximately 50% of the product remains uncrushed. △×: Approximately 80% of the product remains uncrushed. ×: Impossible to crush.

[0038] · Water-soluble or water-dispersible solid (D) The water solubility or water dispersibility of the solid (D) was evaluated by preparing a 2 wt % solution or dispersion, forming a film on a glass plate to a dry thickness of 3 μm, and visually evaluating the presence or absence of aggregates, the uniformity of the coating film, and the color development according to the following criteria. A score of △ or better was considered to be acceptable. 〇: No problem. ◯△: No aggregates, uniform but slightly low color development. △: No aggregates, uniform but low color development. △×: Some aggregates present, uniform. ×: Many aggregates and not uniform.

[0039] <Method of using the solid composition of the present invention> The solid composition of the present invention obtained by the above series of steps can be used as a water-based paint by taking only the required amount and dissolving or dispersing it in water to a desired concentration. The solid composition of the present invention can be used alone or in combination of two or more types. The solid compositions of different colors can also be mixed to adjust the desired color tone. For example, purple can be obtained by mixing red and blue. In this case, the red and blue will be mixed uniformly and will not form a mottled pattern. In order to improve the physical properties of the coating film, the solid composition of the present invention may be dissolved or dispersed in water, and then additives such as water-dispersible resins such as acrylic emulsions and urethane dispersions; water-soluble resins such as acrylic resins and urethane resins; water-soluble polymers such as polyvinyl alcohol and polyvinylpyrrolidone; water-soluble cellulose derivative resins such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; surface conditioners, antifoaming agents, thickeners, preservatives, antifungal agents, antibacterial agents, antiviral agents, and insect repellents may be added. The solid composition of the present invention may also be used by mixing with other water-based coating materials.

[0040] <Application method of the water-based paint of the present invention> The method for applying the water-based paint of the present invention is not particularly limited, and can be carried out by any conventionally known means, such as brush, roller, spray, etc., which can be appropriately selected depending on the application. The coating may be applied in one or more coats to achieve the desired thickness. The coating film can be dried naturally or by heating. The heating method is not particularly limited and can be performed by any known method, for example, a drying oven such as a hot air oven, an electric oven, a near-infrared heating oven, a far-infrared heating oven, or an induction heating oven. [Example]

[0041] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Appropriate modifications can be made within the scope of the present invention.

[0042] The following products were used as raw materials: <Water-soluble polymer (a)> Akadama Dextrin No. 151-F (manufactured by Nippon Starch Chemical Co., Ltd., roasted dextrin, moisture content 3% or less) Akadama Dextrin No. 102-S (manufactured by Nippon Starch Chemical Co., Ltd., roasted dextrin, moisture content 10% or less) Labol Gum GS-C (MP Gokyo Food & Chemical Co., Ltd., xanthan gum) Keldent SFT (MP Gokyo Food & Chemical Co., Ltd., xanthan gum) PEG-6000S (Sanyo Chemical Industries, Ltd., polyethylene glycol, molecular weight 6,000) Alcox L-6 (Meisei Chemical Industry Co., Ltd., polyethylene oxide, molecular weight 60,000) K-30 (Nippon Shokubai Co., Ltd., polyvinylpyrrolidone) Metrolose SM-400 (Methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd.) <Polyhydric alcohol (b)> Powdered sorbitol Ueno 20M (Ueno Food Techno Co., Ltd., D-sorbitol) <Coloring material (B)> RAVEN450 POWDER (Birla Carbon, carbon black) OXIDE RED 120-ED (manufactured by Toda Kogyo Co., Ltd., iron oxide pigment) BAYFERROX 3910 (Yellow iron oxide pigment, manufactured by Lanxess) JR-600A (Teika Corporation, titanium oxide pigment) <Additive (E)> BYK-DYNWET800 (BYK, silicone-free surface conditioner) DISPERBYK-2055 (BYK, silicone-free wetting and dispersing agent)

[0043] Example 1 Akadama dextrin No. 151-F (90 parts by weight) as the water-soluble polymer (a) and powdered sorbitol Ueno 20M (10 parts by weight) as the polyhydric alcohol (b) were charged into a kneader (PCS46-11R, manufactured by BUSS) and kneaded at a temperature of 110°C and a stirring speed of 100 rpm to obtain a pre-paste (A-1). Next, the pre-paste (A-1) and the color pigment as the colorant (B) in the amount shown in Table 1 were added and kneaded at a temperature of 110°C and a stirring speed of 100 rpm to obtain a paste (C-1). The paste (C-1) was placed in a free speed mill (FS-20, manufactured by LaboNext Co., Ltd.) and crushed at a stirring speed of 10,000 rpm for 5 seconds to obtain a solid (D-1). The solid (D-1) was classified into particles of 2 mm or less to obtain a solid composition 1.

[0044] (Examples 2 to 11, Comparative Examples 1 to 5) Examples 2 to 11 (solid compositions 2 to 11) and Comparative Examples 1 to 5 (solid compositions 12 to 16) were obtained using the same production method as in Example 1, except for the compositions changed as shown in Tables 1 and 2. Table 1 shows Examples 1 to 11, and Table 2 shows Comparative Examples 1 to 5.

[0045] In Comparative Example 1, in which the pre-paste (A) did not contain the polyhydric alcohol (b) and only polyethylene glycol having a molecular weight of 6,000 was used as the water-soluble polymer (a), the manufacturing workability and dispersibility of the paste (C) were poor. On the other hand, in Comparative Example 2, in which only polyethylene oxide having a molecular weight of 60,000 was used as the water-soluble polymer (a), the crushability of the paste (C) was poor. In Comparative Examples 3 to 5, in which the ratio of polyhydric alcohol (b) to water-soluble polymer (a) was high, stickiness was likely to occur when preparing pre-paste (A), and the crushability of paste (C) was poor.

[0046] [Table 1]

[0047] [Table 2]

[0048] (Comparative Example 6) The raw materials were mixed without melt-kneading in the composition of Example 3 to obtain a solid composition of Comparative Example 6. When this solid composition of Comparative Example 6 was mixed with water, it did not become homogeneous, and the solid and liquid were separated.

[0049] (Comparative Example 7) A commercially available powder paint (white, manufactured by Sakura Color Products Corporation) was used as Comparative Example 7, and was compared with Example 11 in terms of compatibility with water, paint workability, and coloring properties (Table 3).

[0050] -Easy to mix with water Each was mixed with water to a concentration of 2% by weight or 10% by weight, stirred 50 or 100 times, and the compatibility with water was evaluated according to the following criteria. Average or better was considered acceptable. ○: No precipitate. ◯△: A small amount of sediment is present. △: There is some sediment. △×: Most of the material remains as a precipitate. ×: Does not mix with water. The product in Example 11 was easily mixed with water, whereas the product in Comparative Example 7 tended to easily produce precipitates.

[0051] -Painting workability (ease of brush smearing) Each was diluted with water to 10% by weight, and the same amount was added to a brush, and the ease with which the brush rubbed the wood was evaluated according to the following criteria. Average or better was considered a pass. 〇: No smearing. Can be painted evenly. ◯△: Slight smearing occurs, but the paint can be applied evenly. △: It is easy to get smudges, but it can be painted evenly by applying multiple coats. △×: Smearing occurs easily, and even if repainted, the paint cannot be applied uniformly. ×: Scratches appear immediately and the coating cannot be applied uniformly. In Example 11, the coating was uniformly applied without any smearing, whereas smearing was likely to occur in Comparative Example 7. In addition, cissing was likely to occur during the coating process, and multiple coats were required to achieve a uniform coating.

[0052] ·Colorability Each was diluted with water to 10% by weight, and the number of times it took to paint the same amount onto wood with a brush was compared and evaluated. The degree of coloring was also compared and evaluated according to the following criteria. A score of △ or higher was considered to be acceptable. 〇: The color is fixed in one coat. △: The color will set after multiple coats. ×: The color is not easily fixed, and the substrate is easily visible through. In Example 11, the color was easily fixed and the hiding power of the substrate was good, but in Comparative Example 7, the color was not easily fixed and the hiding power of the substrate was poor, and the substrate tended to be easily see-through.

[0053] [Table 3]

[0054] As described above, the solid composition of the present invention can exhibit the following effects. 1. Reduced environmental impact due to the volatilization of organic solvents. 2. Reduces the adverse effects on human health caused by the evaporation of organic solvents. 3. The smaller volume compared to liquid paint reduces the energy required for transportation. 4. By dissolving the required amount in water and using it, the amount of excess paint disposed of can be reduced. 5. GHG emissions are reduced because no solvent is added during the melt-kneading process and no drying process is required.

Claims

1. A composition comprising a water-soluble polymer (a) and a polyhydric alcohol (b), the water-soluble polymer (a) and the polyhydric alcohol (b) are in a solid state at 20°C or higher; The polyhydric alcohol (b) has a melting point of 130°C or less, the weight mixing ratio of the water-soluble polymer (a) to the polyhydric alcohol (b) is 50:50 to 90:10; It is a solvent-free melt-kneading composition to which no solvent is added during melt-kneading, It is characterized by being water-soluble or water-dispersible and being in a solid state at 20°C or higher. Compositions for paints.

2. The water-soluble polymer (a) and / or the polyhydric alcohol (b) are naturally occurring components. The composition of claim 1.

3. The water content of the water-soluble polymer (a) is less than 10%. The composition of claim 1.

4. The polyhydric alcohol (b) is a sugar alcohol. The composition of claim 2.

5. The polyhydric alcohol (b) is at least one selected from the group consisting of erythritol, threitol, arabinitol, xylitol, ribitol, iditol, galactitol, sorbitol, maltose monohydrate, and trehalose dihydrate. The composition of claim 4.

6. The particle size is 500 μm or more and 2 mm or less. The composition of claim 1.

7. a step (step 1) of obtaining a pre-paste (A) by melt-kneading the water-soluble polymer (a) and the polyhydric alcohol (b); a step (step 2) of obtaining a paste (C) by melt-kneading the pre-paste (A) and the coloring material (B); A step (step 3) of crushing the paste (C) to obtain a solid (D). characterized in that it comprises A method for producing the composition of claim 1.

8. A step of obtaining a paste (C) by melt-kneading the water-soluble polymer (a), the polyhydric alcohol (b), and the colorant (B) without going through the step 1. characterized in that it comprises A method for producing the composition of claim 7.

9. A step of crushing the pre-paste (A) to obtain a solid (D) without going through the step 2. characterized in that it comprises A method for producing the composition of claim 1.

10. A method of dissolving or dispersing the composition according to any one of claims 1 to 6 in water and using it as a water-based paint.

11. 10. A method for using the composition obtained by the method of claim 9 as a water-based clear coating by dissolving or dispersing it in water.

12. The additive (E) has a surface tension of 40 mN / m or less in a 5% aqueous solution. The composition of claim 1.

13. The additive (E) is contained in an amount of 1 to 15 parts by weight based on 100 parts by weight of the prepaste (A). The composition of claim 1.

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