JP2017019927A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous coating composition having mortar specific alkali resistance, moisture adjustment property and mold resistance, not only suitable for a formation of a coated film excellent especially in strength and weather resistance, but also capable of forming a coated film suitable for wet-on-wet coating.SOLUTION: There is provided an aqueous coating composition containing slaked lime particles, where the slaked lime particles contain (a) particles with particle diameter of 0.1 to 0.5 μm and (b) particles with particle diameter of 3.0 to 20.0 μm in a particle size distribution based on volume measured by a laser diffraction scattering method, the total amount of (a) and (b) is 80 vol.% or more of the total slaked lime amount and the (a) exists 0.2 to 1.2 times amount (volume ratio) to the (b).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composition suitably used as a coating composition comprising slaked lime and water as main components, applied to a predetermined substrate, and dried to form a coating film. More specifically, the present invention relates to an aqueous coating composition that is excellent in strength and weather resistance, and forms a coating film excellent in properties such as alkali resistance, humidity conditioning, and antifungal properties peculiar to plaster. Furthermore, this invention relates to the building material which has a coating film formed by apply | coating and drying this water-based coating composition.

  As a paint that can form a coating film excellent in properties such as alkali resistance, humidity control, and mold prevention, a paint containing slaked lime (calcium hydroxide), which is a stucco-forming component, as a main component is known (Patent Literature). 1).

  Since the paint mainly composed of slaked lime has a large shrinkage after drying and curing after coating, the coating film tends to crack, float and peel off. In order to prevent these cracks, floats, and exfoliation, an organic binder such as an acrylic resin (Patent Document 1) or a polysaccharide (Patent Document 2) is blended at a specific ratio with respect to slaked lime. A method for increasing the adhesive strength with an object to be coated has been proposed.

  However, depending on the components of the organic binder, not only may it cause mold and algae, but the performance as a binder is weakened due to deterioration over time, and the coating film tends to peel off. In particular, when used as an exterior wall coating application, there is a problem that performance deterioration due to ultraviolet rays is remarkable and further discoloration occurs.

  In addition, in paints mainly composed of slaked lime, when stored for a long time without stirring or the like, solid-liquid separation phenomena such as precipitation of slaked lime or separation of the solvent are likely to occur, and stability over a long period of time. There is also a problem such as low.

  Patent Document 3 proposes a coating composition that solves the above problems and can form a coating film having excellent properties such as strength and weather resistance.

  The coating composition of Patent Document 3 contains ultrafine slaked lime (calcium hydroxide) particles having a particle size of 1 μm or less, and calcium hydroxide reacts with carbon dioxide in the air to produce calcium carbonate. Using this principle, a coating film is formed. That is, such ultrafine calcium hydroxide particles react with carbon dioxide gas to produce calcium carbonate in which the particles are firmly and densely bonded. For this reason, the amount of the organic binder can be extremely reduced, which leads to an improvement in strength and weather resistance.

  However, according to experiments by the present inventors, the surface of a coating film formed from a composition containing ultrafine calcium hydroxide as a main component as in Patent Document 3 is smooth, and thus on such a smooth surface. It was found that the coating film formed by overcoating was easily peeled off. In the painting of the inner wall and the outer wall of a general house, overcoating and repainting are performed, and peeling of the coating film formed by overcoating becomes a problem.

  As an inorganic paint containing almost no organic binder, for example, as in Patent Document 4, a paint using silica as a main ingredient and a calcium compound as a hardener has been proposed. Because the main component is silica, the coating film formed is different from plaster. Moreover, in order to ensure the permeability to base materials such as concrete, the particle diameter of silica and calcium compounds is 1 μm or less, the surface of the formed coating film is smooth, and as described above, it is not suitable for overcoating. .

Japanese Patent No. 3094227 JP 2003-171167 A Japanese Patent Application No. 2014-011996 JP 2012-131882 A

  The object of the present invention is to provide a coating film having alkali resistance, humidity control and antifungal properties peculiar to plaster, not only suitable for forming a coating film particularly excellent in strength and weather resistance, but also suitable for overcoating. An object of the present invention is to provide an aqueous coating composition that can be formed.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies.

  As a result, the inventors of the present invention have an aqueous coating composition in which extremely fine slaked lime particles and coarser slaked lime particles are dispersed in water. It is possible to maintain stability, and by applying the aqueous coating composition and drying, a coating film having excellent strength is formed without containing an organic binder, and the coating film is overcoated on the coating film. In this case, the present inventors have found that a coating film that does not easily peel off is formed, and further has excellent strength and weather resistance, thereby completing the present invention.

  According to the present invention, slaked lime particles are included, and the slaked lime particles are (a) particles having a particle diameter of 0.1 to 0.5 μm and (b) particles in a volume-based particle size distribution measured by a laser diffraction scattering method. It contains particles having a diameter of 3.0 to 20.0 μm, the total amount of (a) and (b) occupies 80% by volume or more of the total amount of slaked lime, and (a) is 0 with respect to (b) A water-based coating composition characterized by being present in an amount (volume ratio) of 2 to 1.2 times is provided.

  The aqueous coating composition of the present invention can form a coating film excellent in strength and weather resistance by coating and drying. For example, such a coating film has high strength, excellent scratch resistance, and calcium hydroxide particles are strongly bonded to each other because calcium hydroxide is formed by contact with the atmosphere to form calcium carbonate. It also has excellent strength and weather resistance, as well as excellent alkali resistance, humidity control and antifungal properties unique to plaster. For this reason, it is suitably used as a coating film-forming composition having the above properties.

  In addition, the coating film formed using the aqueous coating composition of the present invention is characterized in that when the overcoating is performed thereon and further the coating film is formed, the coating film formed by the overcoating is difficult to peel off. Indicates. As understood from this, the water-based paint composition of the present invention is suitably used in the field where frequent overcoating is performed, specifically as a paint for paints such as inner walls and outer walls, and paints. The

The figure which shows the particle size distribution of the slaked lime particle | grains contained in the water-based coating composition of this invention prepared in Example 1. FIG.

  The aqueous coating composition of the present invention contains slaked lime particles, and the slaked lime particles have a particle size distribution showing two maximum peaks. That is, as in the example shown in FIG. 1 showing the particle size distribution measured by the laser diffraction scattering method, the particle size distribution of the slaked lime particles used in the composition of the present invention is the maximum peak X on the small diameter side and the maximum peak X on the large diameter side. Two maximum peaks, including a maximum peak Y, are shown. The maximum peak X on the small diameter side exists in the ultrafine region of 0.1 to 0.5 μm, while the maximum peak Y on the large diameter side exists in the coarse region of 3.0 to 20.0 μm. . As understood from this, the slaked lime particles used in the present invention are aggregates of the small particle group showing the maximum peak X and the large particle group showing the maximum peak Y (that is, By using slaked lime particles having such a particle size distribution, it is possible to form a coating film having excellent strength and overcoating characteristics.

  That is, as already described, slaked lime (calcium hydroxide) has the property of absorbing carbon dioxide in the atmosphere and generating calcium carbonate (ie, stucco). Slaked lime particles having a diameter of 1 μm or less are used, and this corresponds to a group of small diameter particles in the slaked lime particles used in the present invention. Therefore, when the aqueous coating composition of the present invention is applied and dried, the particles are strongly bonded to each other when the ultrafine slaked lime particles rapidly react with carbon dioxide gas to form calcium carbonate, as in Patent Document 3. In addition, even when used in combination with other inorganic pigments, the ultrafine slaked lime particles enter the gaps between the other inorganic pigment particles without any gaps, and in this state, carbonation is performed, so that the slaked lime particles quickly In addition, the inorganic pigment particles can be fixed at the same time as being firmly bonded. That is, the ultrafine particles (small particle group) of slaked lime exhibit a function as a binder, contribute to the formation of a high-strength coating film, and further reduce the amount of organic binder used extremely. And the heat resistance and weather resistance of the formed coating film can be improved.

  By the way, the coating film formed using only the ultrafine particles (small particle group) of slaked lime as described above is unsatisfactory in the overcoating property, and further coating film is formed by overcoating on the formed coating film. When formed, the present inventors have found a problem that the coating film formed by overcoating is easily peeled off. Since the slaked lime particles used in the present invention contain coarse particles of the large particle group together with the ultrafine particles of the small particle group, such overcoating characteristics are also effectively improved.

  The reason why the overcoating characteristics are improved by using slaked lime particles in which coarse particles of such large particles are added to ultrafine particles of small particles has not yet been clearly elucidated. The inventors estimate as follows.

  That is, when a coating film is formed using only ultrafine slaked lime particles (small-sized particle group) composed of particles having a particle diameter of 0.1 to 0.5 μm, the surface of the coating film has a fairly smooth surface with small voids. Form. For this reason, when overcoating is performed using another coating solution, and a coating film is further formed, the coating film formed by overcoating cannot be expected to have an anchor effect, and will peel off even with a slight force. . However, according to the present invention, when the ultrafine slaked lime particles to which coarse slaked lime particles (a large particle group) composed of particles having a particle size of 3.0 to 20.0 μm are added are formed, The smoothness of the surface of the coated film is impaired, and a rough surface is formed at the same time that a large gap is formed. This rough surface and large voids exert an anchor effect, and it is considered that the coating film formed thereon can be stably held by overcoating, and the peeling is effectively prevented.

  Furthermore, the small-sized particle group in the present invention reacts with carbon dioxide gas quickly after drying to form calcium carbonate, and expresses the initial coating strength in which the particles are firmly bonded to each other, whereas coarse slaked lime particles are Although the reaction with carbon dioxide proceeds with drying, the particle size is large, so the specific surface area is small, and the carbonation reaction rate is quite slow. Therefore, when a laminated coating film is formed by recoating on the formed coating film, a large number of large-diameter particles are present on the surface of the lower coating film. When an elephant is formed, coarse slaked lime present at the interface between the lower layer and the upper layer reacts with carbon dioxide gas over a long period of time, and a strong bond appears when calcium carbonate is formed. As a result, it is considered that a strong bond between layers that suppresses peeling between the upper and lower coating layers is formed.

<Slaked lime particles>
The slaked lime particles having the above-mentioned particle size distribution are ultrafine slaked lime particles of a small particle group produced by a method known per se (that is, the maximum peak X is shown in a particle size range of 0.1 to 0.5 μm, and Particles having a median diameter in terms of volume (D50) within the same range) and coarse slaked lime particles of a large particle group produced by a method known per se (that is, a particle diameter of 3.0 to Particles with a maximum peak Y in the range of 20.0 μm and median diameter (D50) in volume conversion within the same range) are mixed in such a quantitative ratio that the integrated fraction is in the range described later. Can be obtained. For example, slaked lime particles are produced by wet pulverization of calcium hydroxide or calcium oxide in an aqueous medium. In this case, wet pulverization is performed until the average particle size is within the ultrafine region described above. Thus, ultrafine slaked lime particles of a small particle group are obtained, and coarse slaked lime particles of a large particle group can be obtained by performing wet pulverization until the average particle diameter is in the coarse region described above.

  As calcium hydroxide to be used for wet grinding, industrial slaked lime, agricultural slaked lime, calcium hydroxide reagent, and the like can be used. Further, as the calcium oxide, hard calcined lime is preferable from the viewpoint of less aggregation due to digestion reaction. The particle diameter and particle size distribution of these raw material calcium are not particularly limited, and for example, they can be used in the form of a lump.

  The aqueous medium used for the wet pulverization is not particularly limited and may be various, such as tap water, ion exchange water, distilled water, and industrial water. The amount of the aqueous medium is such that when the total amount of calcium hydroxide and water in the aqueous slurry is 100% by weight, the concentration of calcium hydroxide is 20 to 80% by weight, particularly about 30 to 70% by weight. Is preferable. This is because when the solid content concentration is low, the solid-liquid separation tendency of the slurry becomes remarkable, and when the solid content concentration is too high, the viscosity becomes too high and the pulverization efficiency decreases.

  As the pulverizer used for the wet pulverization, a known wet pulverizable pulverizer such as a ball mill, a planetary mill, a stirring tank mill, or a slurry circulation mill is used.

  In order to obtain ultrafine slaked lime particles during wet pulverization, it is particularly preferable to add a polymer dispersant to an aqueous medium as disclosed in, for example, JP-A-2006-298732. .

  That is, when wet pulverization is performed without using a polymer dispersant, the slurry viscosity is remarkably improved. As a result, the pulverization efficiency is lowered, and coarse slaked lime particles having an average particle diameter of about 6 μm can be obtained. Even if possible, it is very difficult to obtain ultrafine slaked lime particles. For example, even if ultrafine slaked lime particles having a particle size of 1 μm or less are contained in the obtained slurry, the amount is extremely small, most of them are large particles, and classification is repeated. Even if the ultrafine slaked lime particles are decorated, cost and time are required, and as a practical problem, it cannot be implemented industrially.

  The polymer dispersant is not particularly limited as long as it has a large molecular weight and can disperse calcium hydroxide, and a conventionally known one can be used. Typical examples thereof include lignin sulfonate, melamine sulfonate, naphthalene sulfonate, polycarboxylate and the like, and among these, polycarboxylate is preferable.

  Examples of the polycarboxylic acid salt include a styrene-maleic anhydride copolymer or a salt of a partial ester thereof (see JP-A-1-092212), an allyl ether-maleic anhydride copolymer or a salt of a derivative thereof (JP-A-63). -285140), salts of (meth) acrylic acid- (meth) acrylic acid ester copolymers or derivatives thereof (see JP-A-58-074552, JP-A-1-226757, etc.), isobutylene-maleic anhydride copolymer Examples include salts of polymers or derivatives thereof (see JP-A-60-103062) and those obtained by grafting alkylene glycol chains to the side chains of these polycarboxylates (see JP-A-2007-332027). Can do. Examples of the salt form include alkali metal salts, alkaline earth metal salts, lower amine salts, and lower alkanolamine salts. In the present invention, among these polycarboxylic acids, those having an alkylene glycol chain are preferably used, and the weight average molecular weight is preferably in the range of 1,000 to 100,000.

  Moreover, it is preferable to use said polymer dispersing agent in the quantity of 0.5 mass part-20 mass parts per 100 mass parts of slaked lime (calcium hydroxide) which should be wet-ground. If the amount of the polymer dispersant used is too small, it will be difficult to pulverize to an ultrafine region. If the polymer dispersant is used in an excessive amount, the viscosity of the aqueous slurry of slaked lime will increase with time. This is because the physical properties may become unstable.

<Water-based paint composition>
The water-based coating composition of the present invention includes the above-described ultrafine slaked lime particles of small particle groups, or an aqueous slurry in which ultrafine slaked lime particles of small particle groups are dispersed, and coarse slaked lime particles of large particle groups It is obtained by mixing powder or an aqueous slurry in which coarse slaked lime particles of a large particle group are dispersed.

  When mixing ultrafine slaked lime particle powder and coarse slaked lime particle powder, an aqueous medium is added to form an aqueous slurry. When mixing an aqueous slurry of ultrafine slaked lime particles with coarse slaked lime particle powder or an aqueous slurry of coarse slaked lime particles, an aqueous slurry of ultrafine slaked lime particle powder or ultrafine slaked lime particles, and coarse slaked lime When mixing with the aqueous slurry of particles, the aqueous coating composition obtained can be used as it is or diluted with water as appropriate to obtain the aqueous coating composition of the present invention.

  The most important point in the aqueous coating composition of the present invention is that the slaked lime particles constituting the aqueous coating composition are (a) a particle size of 0.1 to 0 in a volume-based particle size distribution measured by a laser diffraction scattering method. The total amount of .5 μm particles and (b) particles having a particle diameter of 3.0 to 20.0 μm occupies 80% by volume or more of the total amount of slaked lime, and (a) is a. The amount is 2 to 1.2 times (volume ratio).

  When the abundance of (a) with respect to (b) is 0.2 times the volume (volume ratio) or less, the amount of calcium carbonate formed by reacting quickly with carbon dioxide gas during the formation of the coating film is insufficient. Thus, the initial strength of the formed coating film is impaired. In addition, when the abundance of (a) to (b) is 1.2 times (volume ratio) or more, the surface of the coating film to be formed becomes smooth and large voids are difficult to form. The anchor effect is not exerted, and the upper coating film peels off.

  Furthermore, when the total amount of the above (a) and (b) is less than 80% by volume of the total amount of slaked lime, the strength of the obtained coating film is lowered and there are sufficient voids for expressing the anchor effect. When it is not formed and overcoated, peeling of the upper layer coating film occurs. In addition, the upper limit of the total amount of the above (a) and (b) is not particularly limited, but if too much is added, the cost of classification of slaked lime particles increases, so 95 volume% or less is preferable, and 90% Volume% or less is more preferable.

  As understood from the above description, the aqueous coating composition of the present invention is a composition in which slaked lime particles having a predetermined particle size distribution are dispersed in water. In order to stably maintain such a characteristic particle size distribution, the aqueous coating composition of the present invention preferably contains a polymer dispersant.

  As the polymer dispersant, those used for wet pulverization of the slaked lime particles described above can be suitably used. Examples thereof include lignin sulfonate, melamine sulfonate, naphthalene sulfonate, polycarboxylate, and the like, and among these, polycarboxylate can be particularly preferably used.

  As addition amount in the case of using said polymer dispersing agent for the water-based coating composition of this invention, 0.5-5.0 mass parts is preferable per 100 mass parts of total slaked lime, and 0.7-4.5 Part by mass is more preferable.

  As described above, the water-based coating composition of the present invention contains slaked lime particles and water as main components, but if necessary, a known compounding agent used in a coating solution for forming a coating film is added. Depending on the application, the viscosity is adjusted to an appropriate value for the formation of the coating film by dilution or concentration. Here, “main component” means that 80 parts by mass or more, preferably 85 parts by mass or more of water and slaked lime particles in 100 parts by mass of the total aqueous coating composition. Moreover, in the total 100 parts by mass of water and slaked lime, the concentration of slaked lime is preferably 40 to 85 parts by mass, more preferably 45 to 80 parts by mass, and particularly preferably 45 to 75 parts by mass.

  Typical examples of the compounding agent include inorganic pigments, drying regulators (drying retarders), antifreeze agents, antifoaming agents, rheology modifiers, surfactants, matting agents, and inorganic fine bone agents. is there.

  In addition, when blending the above-mentioned various compounding agents, the excellent binding function (coating strength improving function) and roughening function (overcoat improving function) of the slaked lime particles having the particle size distribution described above, the coating formed It is necessary to ensure that the strength, weather resistance, water resistance, alkali resistance, humidity control, and antifungal properties of the film are not impaired.For this reason, the slaked lime concentration in the total solid content in the aqueous coating composition is Generally, it is desirable to maintain at 80% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more. That is, the addition amount of various compounding agents is determined so that the concentration of slaked lime particles is maintained within this range.

  The inorganic pigment is used for adjusting the hue of the formed coating film. That is, slaked lime (calcium hydroxide) and calcium carbonate produced by carbonization of this function as a white pigment or extender pigment, but by adding other inorganic pigments to these, the whiteness is strengthened. Alternatively, the color can be adjusted to a color other than white.

  The particle diameter of such an inorganic pigment is generally measured by a laser diffraction scattering method, and the median diameter (D50) in terms of volume should be in the range of about 0.1 to 10 μm, particularly 20 μm or more. The coarse particles are preferably not included.

  Examples of inorganic pigments include zinc white, lead white, lithopone, titanium dioxide, red lead, iron oxide red, yellow lead, zinc yellow, ultramarine blue, prussian blue, carbon black, aluminum powder, and bronze powder. Inorganic pigments of various colors can be mentioned.

  Also used are natural mica surfaces coated with metal oxides, pearl pigments with synthetic mica surfaces coated with metal oxides, and extender pigments such as aluminum hydroxide, calcium carbonate, barium sulfate, and calcium sulfate. can do.

  Furthermore, organic pigments can be used in place of inorganic pigments, but the use of organic pigments may impair the heat resistance and weather resistance of the coating film formed. The use of inorganic pigments is preferred.

  As the addition amount in the case of using the inorganic pigment described above, the slaked lime particles (total slaked lime amount) are usually provided on the condition that the concentration per solid content of the slaked lime particles having the particle size distribution described above is within the range described above. The amount is preferably 0.05 to 3 parts by mass, more preferably 0.10 to 2.0 parts by mass, and still more preferably 0.20 to 1.5 parts by mass per 100 parts by mass.

  Examples of the drying regulator (drying retarder) and antifreezing agent include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, 1,3-butylene glycol, thiodiethylene glycol, 1,5- Glycols such as pentanediol and glycerin, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, triethanolamine and the like can be used alone or in admixture of two or more. When these are used, they are usually added in an amount of 0.5 to 10% by weight in the aqueous coating composition of the present invention.

  In particular, when the aqueous coating composition of the present invention is used for applications such as overcoating and color mixing (for example, painting materials for walls and water-based paints), the drying adjustment is performed so as to suppress rapid drying. It is desirable to add an agent.

  Antifoaming agents include animal and vegetable oils, fatty acids, nonionics (especially polyethers), acetylenic diols, fluorines, silicones, mineral oils, phosphate esters, etc. Fatty acid type and nonionic type (especially polyether type) are particularly preferable. When using these, the usage-amount is 0.1-5.0 weight% in an aqueous coating composition.

  Examples of rheology modifiers include benite, methylcellulose or derivatives thereof, casein or salts thereof, carboxyl copolymers, hydroxyl copolymers, polyalkylallyl sulfonates, melamine formalin sulfonates, and aromatic aminosulfonates. It has a polymer as a main component and can be used alone or in combination of two or more. When using these, the usage-amount is preferable 0.2 to 5.0 weight% as a density | concentration per solid content of an aqueous coating composition.

  The surfactant is used to stably and uniformly disperse the additives and calcium hydroxide fine particles that are appropriately blended in the water-based coating composition in water and has a molecular weight as compared with the above-described polymer dispersant. Although it is considerably low, such a surfactant may be aqueous, and any of ionic, amphoteric and nonionic surfactants can be used. These surfactants are, of course, 1 One species can be used alone, or two or more species can be used in combination, and they are used in an appropriate amount so as to ensure good dispersion.

Representative examples of the ionic surfactant include the following anionic surfactants and cationic surfactants.
Anionic surfactant: sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl ether ammonium sulfate, polyoxyethylene alkyl Phenyl ether ammonium sulfate salt, polyoxyethylene alkyl ether phosphate ester, polyoxyethylene alkyl phenyl ether phosphate ester cationic surfactant: lauryltrimethylammonium chloride, trimethyloctadecylammonium chloride Typical examples of amphoteric surfactants are as follows: Can be mentioned.
Amphoteric surfactants: lauryl betaine, lauryl dimethylamine oxide Further, typical examples of nonionic surfactants include the following.
Nonionic surfactants: polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oxypropylene block polymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester Eliminates gloss and presents a prominent luxury. For example, silica, aqueous colloidal silica, potassium titanate, talc, hydrocarbon wax, silica wax, polyethylene powder, polypropylene powder, acrylic resin powder, styrene 1 type resin powder etc. are used individually by 1 type or in combination of 2 or more types. When using these, the usage-amount is preferable 0.2 to 10 weight% as a density | concentration per solid content in an aqueous coating composition. If it is less than 0.2% by weight, the original purpose of matting of the coating film cannot be sufficiently achieved, and if it exceeds 10% by weight, the strength of the coating film, particularly scratch resistance may be lowered.

  Inorganic fine aggregates are used to give moderate strength to the coating film to be formed. Silica sand, cold water sand, mica, glazed quartz sand, glazed mica, ceramic sand, glass beads, perlite, blast furnace water Crushed slag, fly ash, silica fume, calcium carbonate, calcium sulfate, barium sulfate, aluminum hydroxide and the like are used. Some of these are also used as extender pigments, but as an inorganic fine aggregate, the median diameter (D50) in terms of volume is generally 0.1 to 100 μm as measured by a laser diffraction scattering method. Granules that are within a range are used. However, since the inorganic fine aggregate with a median diameter (D50) in volume conversion of 200 μm or more may impair the bonding function by the ultrafine slaked lime particles described above, its usage is as small as possible. And most preferably it should not be used.

  In the water-based coating composition of the present invention, in addition to the above-mentioned compounding agents, for example, thickeners, plasticizers, antibacterial agents, ultraviolet absorbers and the like are appropriately added in such an amount that the advantages of the present invention are not impaired. Can be blended. Further, contrary to the above-mentioned drying regulator (drying retarder), a water-soluble organic solvent can be blended in order to improve the drying property when the aqueous coating composition is applied, and in particular such a water-soluble agent. The organic solvent is particularly effective when the aqueous coating composition of the present invention is used as an ink.

  As such a water-soluble organic solvent, alcohol solvents such as ethyl alcohol, isopropyl alcohol and butyl alcohol are suitable, and these can also be used in the form of a mixed solvent with water. When such a water-soluble organic solvent is used, it is generally preferable that the water concentration in the entire solvent be maintained at about 85 to 98% by weight.

  The aqueous coating composition of the present invention can form a coating film having sufficient strength and weather resistance without using an organic binder, but the organic binder is used within the range not impairing the characteristics of the present invention. It may be added. As such an organic binder, a water-soluble resin or an aqueous resin emulsion is used.

  Examples of the water-soluble resin include natural proteins such as gelatin, casein, albumin, gum arabic, and fish mulberry, alginic acid, methylcellulose, carboxymethylcellulose, polyethylene oxide, hydroxyethylcellulose, polyvinyl alcohol, polyacrylamide, aromatic amide, and polyacrylic acid. And general polymers such as synthetic polymers such as polyvinyl ether, polyvinyl pyrrolidone, acrylic, polyester, alkyd, urethane, amide resin, melamine resin, and styrene maleic acid resin.

  Further, as the aqueous resin emulsion, an emulsion in which a monomer, an oligomer or a polymer thereof is dispersed in an aqueous medium can be used without any particular limitation. Specific examples of such aqueous emulsions include synthetic polymer emulsions such as acrylic resin, vinyl acetate, urethane resin, and styrene / butadiene rubber.

  By the way, as described above, since the organic binder as described above lowers the heat resistance and weather resistance of the coating film, the blending amount is preferably as small as possible, and the organic binder is used in a large amount. If it is used, the smoothness of the surface of the coating film is improved, and there is a possibility that the overcoating characteristics expressed by the roughening of the coarse particles of slaked lime described above may be impaired. For this reason, it is desirable that the amount of the organic binder used be as small as possible, for example, 10 parts by mass or less, particularly 2 parts by mass or less per 100 parts by mass of slaked lime particles (total amount of slaked lime).

  The above organic binder is usually mixed with the aqueous slurry described above in the form of an aqueous solution or an emulsion. An emulsion or aqueous suspension of an organic binder may be obtained by producing a resin that becomes a binder by emulsion polymerization or suspension polymerization. What was obtained by mixing and stirring with water with an agent and a dispersing agent may be used.

  Furthermore, when blending the above-mentioned various compounding agents, in order to uniformly disperse them, the viscosity of the aqueous coating composition in the form of an aqueous slurry is appropriately adjusted by diluting or concentrating with water as appropriate. The range can also be adjusted. Moreover, it is also possible to mix various compounding agents simultaneously when mixing the aqueous slurry of ultrafine slaked lime particles and the aqueous slurry of coarse slaked lime particles.

  Thus, the water-based coating composition of the present invention in which various compounding agents are appropriately blended is used as a coating composition by itself because the ultrafine slaked lime particles contained therein have a function as a binder. For example, depending on the type of compounding agent to be blended as appropriate, as a water-based paint, water-based ink, paint, paint marker, etc., using equipment such as brush coating, dipping, spray coating, screen printing, printers, etc. It is applied to a substrate such as paper by printing, drawing with a writing instrument, etc., and further used for forming a coating film by air drying, heat drying or the like.

  In the coating film formed in this way, calcium hydroxide is carbonated by contact with the atmosphere to form calcium carbonate, so that it has high strength, for example, excellent scratch resistance, and further alkali resistance. Is also excellent. In particular, by reducing the blending amount of the organic binder to zero or a small amount within the above-described range, this coating film has excellent heat resistance and weather resistance, and maintains stable characteristics without causing film deterioration over a long period of time. be able to.

  Further, when the aqueous coating composition of the present invention is used for various applications, it is usually stored in a sealed container such as a tank or a tube in order to prevent carbonation of slaked lime particles. desirable.

  The coating film formed by the water-based coating composition of the present invention contains coarse slaked lime particles in a predetermined quantity ratio together with ultrafine slaked lime particles, so that it has excellent overcoating properties and is coated on this by overcoating. In this case, peeling of the coating film formed by overcoating is effectively prevented. For this reason, the water-based paint composition of the present invention is suitably used as a drawing material for painting a wall or a building material to be overcoated, a paint (particularly a water-based paint), or the like. Furthermore, the bonding function of ultrafine slaked lime particles makes it possible to form a coating film that is firmly fixed to an uneven wall surface and the like, and is suitably used for the restoration of murals such as frescoes.

  Furthermore, the above-described aqueous coating composition of the present invention is preferably adjusted to an appropriate viscosity by diluting or concentrating an aqueous medium in order to ensure appropriate applicability according to the application. When used as a paint, water-based paint, paint marker or the like, for example, the viscosity (25 ° C.) is adjusted to a range of 500 to 50000 mPa · s.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

  The test methods and materials used in the examples are shown below.

[Evaluation of adhesion]
About the coating film formed on the conditions shown in each Example and a comparative example, and the coating film formed in piles on the coating film, those adhesiveness is prescribed | regulated according to prescription | regulation of JISK5600-5-6 (cross cut method). evaluated.
Category 0: No peeling of eyes in any lattice Category 1: Small peeling of coating film at the intersection of cuts (within 5%)
Classification 2: The coating peels off at the intersection along the cut line (5% or more and less than 15%)
Classification 3: The coating film peels partially or entirely along the cut line (15% or more and less than 35%)
Classification 4: The coating film peels partially or completely along the cut line (35% or more and less than 65%)
Classification 5: Exfoliation more than classification 4 (65% or more)

[Accelerated weather resistance test]
The accelerated weather resistance test uses a xenon lamp type weather resistance tester, and conforms to JIS K 5600-7-7 (General paint test method-Long-term durability of paint film-Xenon method). Then, the irradiance is 60 W / m ² , the black panel temperature is 63 ° C. ± 2 ° C., the irradiation is performed for 102 minutes, and the water is sprayed for 18 minutes. This was defined as one cycle, and 150 cycles were repeated for an accelerated weather resistance test. Thereafter, the sample was taken out and each sample was visually observed to confirm the cracking condition. Furthermore, the amount of paint constituents (paint removal amount) adhered to the adhesive tape after the adhesive tape was applied to the paint surface and peeled off was visually confirmed. The cracking condition and the paint peeling amount were evaluated according to the following criteria.

Crack condition classification 0: Cannot be seen even if magnified 10 times.
Classification 1: A magnification of 2 times can be visually recognized.
Classification 2: Recognized only with normally corrected visual acuity.
Classification 3: Clearly recognizable with normally corrected visual acuity.
Classification 4: Large cracks generally reaching 1 mm in width.
Classification 5: Very large crack generally exceeding 1 mm in width.

Paint peeling amount ○: No peeling was confirmed.
Δ: Some peeling is confirmed.
X: Peeling is clearly confirmed.

[Dispersion stability of coating materials]
Each of the paints prepared under the conditions shown in each Example and Comparative Example was filled with 1 kg each in a water-resistant polypropylene container, capped, and stored at room temperature for 30 days. Evaluation was made according to criteria.
○: No water separation occurred.
Δ: Some water separation is confirmed.
X: Water separation has clearly occurred.

[Measuring method of particle size distribution and median diameter (D50)]
Ethanol was used as a dispersion medium, the volume-based particle size distribution of slaked lime was measured using a laser diffraction particle size analyzer, and the volume average particle size was calculated from the measurement result, which was defined as the median size (D50). Moreover, the ratio (volume%) of the predetermined particle diameter range was calculated | required from the measurement result.

[Slaked lime A, Slaked lime B]
Industrial high-purity slaked lime (Ube Materials Co., Ltd., product name: CH-2N) was classified with a sieve to prepare slaked lime A and slaked lime B having the particle diameters shown in Table 1.

[Binder]
Acrylic resin emulsion (polyacrylic acid ester: 40 wt%, Tg: -5 ° C)
[Dispersant]
Polycarboxylic acid-based high-performance AE water reducing agent (solution, solid content: 30%)
[Pigment]
Cadmium selenide (median diameter (D50): 2.2 μm)
[Micro slaked lime slurry A and micro slaked lime slurry B]
The slaked lime was wet pulverized by a planetary mill to produce a micro slaked lime slurry A and a micro slaked lime slurry B. As high-tech slaked lime (product name: CH-2N, manufactured by Ube Materials Co., Ltd.) as slaked lime, the above polycarboxylic acid-based high-performance AE water reducing agent as polymer dispersant, and ion-exchanged water as water. used. The polymer dispersant was added so that the dispersant solid content was 3.0% by weight with respect to the slaked lime solid content, and the slaked lime concentration in the fine slaked lime slurry was adjusted to 50% by solid content concentration. The particle diameters of the produced fine slaked lime slurry A and fine slaked lime slurry B are as shown in Table 1.

Examples and Comparative Examples The fine slaked lime slurry A, the fine slaked lime slurry B, the fine slaked lime slurry B, the slaked lime A, and the slaked lime B shown in Table 1 were prepared so as to have a solid content composition (integrated, weight%) of the aqueous coating composition shown in Table 2. A predetermined amount was mixed to prepare aqueous coating compositions shown in Examples 1 to 7 and Comparative Examples 1 to 5. The particle size distribution of the slaked lime particles contained in the aqueous coating composition prepared in Example 1 is shown in FIG.

  The aqueous coating composition prepared in each of the examples and comparative examples was applied to the surface of a 30 cm × 30 cm gypsum board (JIS standard product manufactured by Chiyodaute, GB-R, thickness: 9.5 mm) with a brush in a range of 15 cm × 15 cm. Coated. Thereafter, the film was dried for 12 hours in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% to form a coating film having a solid content of 0.15 mm in thickness. The adhesion evaluation results of the coating film at this time are shown in Table 3.

  Next, an aqueous coating composition having the same composition was applied onto the 15 cm × 15 cm coating film formed as described above with a brush. Thereafter, the film was dried for 72 hours in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and a coating film having a solid content of 0.15 mm was laminated. The adhesion evaluation results of the coating film at this time are shown in Table 3.

  Next, an accelerated weather resistance test was performed on the gypsum board on which the two-layer coating film was formed in this manner, and the crack and peeling of the upper-layer coating film were evaluated. The results are shown in Table 3.

Claims (5)

An aqueous coating composition mainly composed of slaked lime particles and water, wherein the slaked lime particles are (a) particles having a particle diameter of 0.1 to 0.5 μm in a volume-based particle size distribution measured by a laser diffraction scattering method. And (b) particles having a particle size of 3.0-20.0 μm, the total amount of (a) and (b) occupies 80% by volume or more of the total amount of slaked lime, and (a) An aqueous coating composition characterized by being present in an amount (volume ratio) of 0.2 to 1.2 times that of b). The water-based paint composition according to claim 1, wherein the ratio of slaked lime is 80 parts by mass or more with respect to 100 parts by mass of the solid material obtained after drying. The aqueous coating composition according to claim 1 or 2, wherein the polymer dispersant is contained in an amount of 0.5 to 5 parts by mass with respect to 100 parts by mass of total slaked lime. The aqueous coating composition according to any one of claims 1 to 3, wherein the pigment is contained in an amount of 0.05 to 3.0 parts by mass with respect to 100 parts by mass of total slaked lime. A building material and a painting base material, comprising a coating film formed by applying and drying the aqueous coating composition according to claim 1.

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