JP2018039947A - Method for producing emulsion clear coating material - Google Patents

Abstract

An emulsion clear coating material capable of forming a clear coating film excellent in weather resistance and transparency is provided. A method for producing an emulsion clear coating comprises mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound to prepare a suspension of precursor particles of an inorganic silicate polymer, and an inorganic silicate. Removing a by-product salt from a suspension of polymer precursor particles, a suspension of inorganic silicate polymer precursor particles from which the salt has been removed, and oxidizing at least a portion of the surface After mixing the base material in which titanium is present, a step of hydrothermal reaction to obtain a suspension of titanium oxide / inorganic silicate polymer composite particles; A step of mixing the suspension and the resin emulsion. [Selection figure] None

Description

  The present invention relates to a method for producing an emulsion clear coating and a method for forming a clear coating film.

  Paints are usually applied to the surface of various materials, products, and parts with a film thickness of several to hundreds of μm. In addition to protecting the substrate (prolonging the service life), depending on the application , Their functions are demonstrated by giving them a color, texture, luster and radiance. The main functions of the coating are aesthetics and protection of the object. One of the important functions of the coating film is the durability that keeps the aesthetic appearance with sub-millimeter order film thickness and protects the object to be coated from harsh environment for a long time.

  The coating film is always exposed to some form of contact with the outside world, and is subjected to natural exposure due to ultraviolet light, rain, etc., and strong physical and chemical attack of human factors. The performance of the coating will be determined by how durable it is to various external stimuli including these external environmental factors. For this reason, the durability evaluation test is performed on all machines and structures used outdoors such as automobiles, civil engineering machinery, bridges, large steel structures such as storage tanks, and large public buildings such as buildings and gymnasiums. It is used as an important criterion for evaluating the overall performance of the system.

  With the development of petrochemistry since the 1960s, research fields of resin synthesis and polymer chemistry have advanced, and research and development of materials with excellent weather resistance have been conducted. Furthermore, in recent years, in addition to conventional weather resistance, technical development of coating films having stain resistance has been performed, and the market needs are extremely high. In particular, buildings in recent years have been increasing in height and design, and there are many cases in which re-coating is difficult because the coating film is easily contaminated. In particular, it has been pointed out as a problem that rain streak is easily formed due to the contaminants attached to the wall surface as rainwater flows down, and the aesthetic appearance is impaired.

  Thus, there is an increasing demand for paints that can reduce the occurrence of rain stains and maintain the aesthetics of buildings over a long period of time. One of the methods attracting attention in recent years is to make the surface of the coating film hydrophilic. This is a method of making the surface of the coating film hydrophilic to prevent adhesion of highly hydrophobic contaminants and facilitating the removal of contaminants by diffusing rainwater to the surface.

  Generally, colloidal silica is known as an inorganic dispersion stabilizer for paints, and at present, it relates to a technique for imparting stain resistance to a paint film by adding colloidal silica to make the paint film hydrophilic. Research is underway.

  However, if the amount of colloidal silica added is increased, the hydrophilicity of the coating film is improved, but the hardness of the coating film is remarkably increased, and there is a problem that cracks are generated in the coating film.

  In light of these points, it is desirable to construct a clear coating film that simultaneously exhibits transparency and stain resistance while suppressing an increase in hardness on a substrate or substrate designed for various applications. Yes.

  On the other hand, many methods for decomposing and removing organic compounds by the photocatalytic ability of titanium oxide have been reported. For example, photolysis of water with a titanium oxide photoelectrode is called the Honda-Fujishima effect because of the name of the discoverer. This photocatalytic reaction is expected to be used as a low environmental load chemical process using solar energy. It is believed that when titanium oxide is irradiated with light, electrons having a strong reducing action and holes having a strong oxidizing action are generated, and molecular species in contact with oxygen species generated on the surface are decomposed. By utilizing the photocatalytic ability of titanium oxide, for example, it is possible to decompose and remove environmental pollutants such as organic solvents, agricultural chemicals, and surfactants present in the aqueous phase, harmful substances in the gas phase, and bad odors.

  The method using the photocatalytic ability of titanium oxide is excellent in durability, and most of the reaction product is carbon dioxide, so that the load on the use environment is low. In addition, this method has very few restrictions related to setting of reaction conditions such as temperature and setting of operating conditions such as treatment of metabolite as compared with biological treatment methods that depend on the metabolism of microorganisms. In addition, this method has an advantage that substances such as organic halogen compounds and organophosphorus compounds that are difficult to treat by biological treatment methods can be easily decomposed and removed.

  This method has already been put to practical use in fields such as sterilization, antifouling, and deodorization. Further, removal of nitrogen oxides in combustion exhaust gas, decomposition of volatile harmful organic compounds in houses, purification of waste water, etc. Application to environmental purification is being studied.

  However, in the research on the decomposition and removal of organic compounds by titanium oxide, the titanium oxide powder is used as it is, and there are problems in assembly, maintenance, and handling. It was extremely difficult to develop.

  Thus, for example, an attempt has been made to use titanium oxide by kneading it with a medium such as fiber and plastic that are easy to handle.

  However, since titanium oxide causes not only decomposition of harmful organic compounds and environmental pollutants due to photocatalytic activity, but also decomposition and deterioration of fibers and plastics as kneading media, there is a problem in using such media.

  Moreover, when using titanium oxide as an antibacterial and antifungal material, for example, under running water of contaminated water, the affinity of bacteria for titanium oxide is low, and the adsorption of bacteria on the surface of titanium oxide is inhibited. There was a problem that titanium oxide could not be expected to fully exhibit the photocatalytic activity.

  At present, an attempt is made to exhibit a photocatalytic function by coating a paint containing titanium oxide on a base material such as a wall material. The coating film formed by such a paint not only decomposes the contaminants attached to the surface due to the photocatalytic activity of titanium oxide, but also has hydrophilic titanium oxide particles exposed on the surface of the coating film, so that the dirt is stained. Demonstrates the property of being difficult to adhere. That is, the coating film containing titanium oxide particles has a self-cleaning function that removes dirt by itself.

  However, when an organic paint containing a resin is used as the paint component, the resin comes into contact with the surface of the titanium oxide as described above. There was a problem causing.

  Therefore, recently, a paint containing titanium oxide composite particles in which calcium phosphate such as apatite is coated on titanium oxide has been proposed (see, for example, Patent Documents 1 to 3). In these paints, titanium oxide is obtained by adding calcium chloride to a dispersion in which titanium oxide is dispersed in a simulated body fluid in which sodium chloride, calcium chloride, potassium dihydrogen phosphate, disodium hydrogen phosphate and the like are dissolved. Manufactures composite particles.

  In this type of titanium oxide composite particles, the apatite does not completely cover the surface of the titanium oxide but is dispersed and deposited on the surface of the titanium oxide. That is, since the surface of titanium oxide is partially exposed, the photocatalytic ability of titanium oxide is not deactivated. In addition, since the surface of titanium oxide is coated with apatite, the apatite serves as a spacer, and titanium oxide does not directly contact the resin, so that decomposition of the resin is suppressed and an organic paint can be used. In addition, since apatite is excellent in the ability to adsorb substances such as proteins and aldehydes, the titanium oxide composite particles can adsorb substances during quenching. As a result, the substances adsorbed during quenching are oxidized during light irradiation. Decomposes due to the photocatalytic activity of titanium.

  However, the simulated body fluid used for producing the titanium oxide composite particles contained in the paints described in Patent Documents 1 to 3 contains a large excess of ionic species such as sodium ions, potassium ions, calcium ions, and chloride ions. For this reason, when the dispersion liquid in which the titanium oxide composite particles are dispersed is used as it is for the coating material, the resin may aggregate due to the influence of such coexisting ion species, resulting in poor dispersion. In order to prevent the resin from agglomerating, the dispersion must be decanted many times, resulting in an increase in production steps and a decrease in production efficiency. In addition, in the method using a simulated body fluid, the growth of apatite crystals is very slow, and as a manufacturing technique for industrial products, the productivity is low, so that practical application is difficult. Furthermore, in the coating film formed by the coating material containing the titanium oxide composite particles produced by this method, the resin may aggregate and the homogeneity may be lowered. For this reason, this type of paint does not satisfy the weather resistance, and there has been a strong demand to develop a new paint or coating film that can solve the problem.

  As other prior art, various combinations of titanium oxide and other inorganic compounds have been performed. For example, at least one pigment selected from diatomaceous earth, activated alumina, activated clay, and zeolite, and titanium oxide A water-based paint for indoor pollution control (see Patent Document 4) containing moisture, a humidity-control building material substrate (see Patent Document 5) obtained by coating with a water-based emulsion paint containing a humidity-controllable inorganic powder supporting titanium oxide, and oxidation Emulsion paint obtained by blending titanium in colloidal silica copolymer acrylic resin emulsion (see Patent Document 6), tetravalent metal phosphate, divalent metal hydroxide, and aqueous emulsion containing titanium oxide as essential components A coating composition (see Patent Document 7), a coating composition containing titanium oxide particles partially coated with calcium phosphate (Patent Document 8) Irradiation), and the like have been proposed.

JP 2000-1631 A Japanese Patent Laid-Open No. 2003-80078 JP 2004-58050 A JP 2002-338897 A JP 2002-235382 A JP 2002-348525 A JP 2003-20438 A JP 2008-88436 A

  In order to acquire the adsorptivity of organic compounds that pollute the environment, it is effective to use a solid with a high specific surface area and mesopores, and the charge of the solid matrix can be used for trapping polar molecules in the atmospheric system. It is desirable to control the distribution. For example, as a weathered mineral of volcanic ejecta, silicate groups produced in the Earth's surface layer have a high specific surface area and pore volume due to the fine structure resulting from their unique shape, and have a selective ion exchange capacity. Is clear.

  Under such circumstances, the present inventors have aimed to develop a method for producing an emulsion clear paint capable of forming a clear coating film having excellent weather resistance and transparency in view of the above prior art. As a result of earnest research.

  As a result, the present inventors are inactive as a photocatalyst, have a property of adsorbing various germs and the like, are useful as an environmentally friendly material, are porous, and have a controlled chemical composition and pore structure. It is possible to produce emulsion clear coatings that can form clear coatings with excellent weather resistance and transparency by coating silicate polymers around titanium oxide using hydrothermal reaction. The present inventors have found a new knowledge and have further researched to complete the present invention.

  An object of one embodiment of the present invention is to provide an emulsion clear coating material capable of forming a clear coating film having excellent weather resistance and transparency.

  One aspect of the present invention is a method for producing an emulsion clear coating, which comprises mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound to prepare a suspension of inorganic silicate polymer precursor particles. A step of removing a salt of a by-product from the suspension of inorganic silicate polymer precursor particles, and a suspension of inorganic silicate polymer precursor particles from which the salt has been removed, A step of mixing and stirring a base material containing titanium oxide on at least a part of the surface and then hydrothermally reacting to obtain a suspension of titanium oxide / inorganic silicate polymer composite particles; and the titanium oxide / A step of mixing a suspension of inorganic silicate polymer composite particles and a resin emulsion.

  According to one embodiment of the present invention, an emulsion clear paint capable of forming a clear coating film having excellent weather resistance and transparency can be provided.

It is the photograph of the side in which the clear coating film of the test piece after a weather resistance test is formed.

(Method for producing emulsion clear paint)
The method for producing the emulsion clear coating comprises mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound to prepare a suspension of inorganic silicate polymer precursor particles, and an inorganic silicate polymer precursor. A step of removing a salt of a by-product from a suspension of body particles, a suspension of inorganic silicate polymer precursor particles from which the salt has been removed, and a group in which titanium oxide is present on at least a part of the surface And mixing and stirring the material, followed by a hydrothermal reaction to obtain a suspension of titanium oxide / inorganic silicate polymer composite particles, a suspension of titanium oxide / inorganic silicate polymer composite particles, And a step of mixing the resin emulsion. Thereby, the clear coating film excellent in a weather resistance and transparency can be formed.

  The inorganic silicate polymer particles have a porous structure whose surface is covered with a hydrophilic group (aluminol group and / or silanol group).

The BET specific surface area of the titanium oxide / inorganic silicate polymer composite particles is preferably 200 m ² / g or more, and more preferably 250 m ² / g or more. When the specific surface area of the titanium oxide / inorganic silicate polymer composite particles is 200 m ² / g or more, the exposure ratio of hydroxyl groups on the surface of the titanium oxide / inorganic silicate polymer composite particles is improved, and the titanium oxide / The dispersibility of the inorganic silicate polymer composite particles in water can be improved.

  The content of titanium oxide contained in the titanium oxide / inorganic silicate polymer composite particles is preferably 20 to 40% by mass. When the content of titanium oxide is 40% by mass or less, the coverage of the surface of titanium oxide with the inorganic silicate polymer is improved, and deterioration of the resin can be suppressed. Moreover, when the content of titanium oxide is 20% by mass or more, the photocatalytic ability of the titanium oxide / inorganic silicate polymer composite particles is improved.

  The particle size of the titanium oxide / inorganic silicate polymer composite particles is preferably in the range of 0.1 to 100 μm, and more preferably in the range of 0.1 to 10 μm.

  The silicon compound is not limited as long as it is monosilicic acid or a derivative thereof, and examples thereof include sodium orthosilicate, alkyl orthosilicate, sodium metasilicate, amorphous colloidal silicon dioxide (aerosil, etc.) and the like. One type or two or more types can be used in combination.

  The aluminum compound is not limited as long as it can generate aluminum ions in an aqueous solution. For example, aluminum such as aluminum chloride, aluminum nitrate, sodium aluminate, aluminum hydroxide, aluminum isopropoxide An alkoxide etc. are mentioned and it can use combining 1 type (s) or 2 or more types.

  The substrate has titanium oxide on at least a part of its surface. The substrate is preferably exemplified by titanium oxide particles, but is not limited thereto.

  The titanium oxide particles used as the carrier for the inorganic silicate polymer used in the present embodiment preferably have a crystal form of brookite or anatase from the viewpoint of high photocatalytic ability. The rutile or amorphous titanium oxide having a crystalline form has a lower photocatalytic ability than the above crystalline form of titanium oxide, but these can also be used. In addition, the particle size of the titanium oxide particles is not limited. However, if it is assumed that the titanium oxide / inorganic silicate polymer composite particles are kneaded with a medium such as organic fibers and plastics, The diameter is preferably submicron or less.

  The concentration of the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound is preferably 1 mmol / L to 10 mol / L, and more preferably 20 mmol / L to 0.5 mol / L. Thereby, the production | generation of a by-product can be suppressed.

  When preparing a suspension of inorganic silicate polymer precursor particles, it is preferable to rapidly mix an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound. Thereby, the production | generation of a by-product can be suppressed.

  Further, when preparing a suspension of inorganic silicate polymer precursor particles, an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound may be mixed simultaneously.

  The speed at which the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound are rapidly mixed is preferably 1 mL / min to 10000 L / min, and more preferably 1 mL / min to 50 L / min. Thereby, the production | generation of a by-product can be suppressed.

The molar ratio of silicon to aluminum in preparing the suspension of inorganic silicate polymer precursor particles is preferably 0.1 to 5.0, and preferably 0.5 to 3.0. Is more preferable. Thereby, the pore structure of the inorganic silicate polymer particles can be controlled. Suppressing the formation of boehmite (α-AlO (OH)) or gibbsite (α-Al (OH) ₃ ) as a by-product when the molar ratio of silicon to aluminum is 0.1 or more. In addition, by being 5.0 or less, it is possible to suppress the generation of amorphous silica as a by-product.

  The pH of the liquid obtained by mixing the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound is preferably 3 to 10, and more preferably 6 to 8. Thereby, the chemical composition of the inorganic silicate polymer particles can be controlled.

  In order to adjust the pH of the mixture of the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound, an acid component is added to the aqueous solution of the aluminum compound in advance, or an alkaline component is added to the aqueous solution of the silicon compound in advance. It is also effective.

  Examples of the acid component include hydrochloric acid, nitric acid, sulfuric acid and the like.

  Examples of the alkali component include sodium hydroxide, potassium hydroxide, calcium hydroxide and the like.

  At this time, a reagent such as polyethylene glycol, polyvinyl alcohol, or a surfactant may be added as an aggregation inhibitor together with the acid component or the alkali component.

  If the pH of the solution obtained by mixing the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound is weakly acidic, the alkaline aqueous solution is dropped at a rate of 0.1 to 5 mL / min so that the pH is near neutral. In this way, inorganic silicate polymer precursor particles can be produced.

  Examples of the alkaline aqueous solution include aqueous solutions of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, and the like.

  Of course, inorganic silicate polymer precursor particles are produced even when the pH of the solution obtained by mixing the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound is in the range of 6.5 to 8 near neutrality.

  It is preferable to stir or shake before removing the by-product salt from the suspension of inorganic silicate polymer precursor particles.

  The temperature at which the suspension of the inorganic silicate polymer precursor particles is stirred or shaken is preferably 10 to 50 ° C, more preferably 20 to 40 ° C.

  The time for stirring or shaking the suspension of the inorganic silicate polymer precursor particles is preferably 0.1 to 72 hours, and more preferably 1 to 24 hours.

  The method for removing the salt of the by-product from the suspension of the inorganic silicate polymer precursor particles is not particularly limited, and examples thereof include dialysis membrane desalting, ultrafiltration, and centrifugation.

  After removing the by-product salt from the inorganic silicate polymer precursor particle suspension, add approximately the same amount of water as the inorganic silicate polymer precursor particle suspension. It is preferable to disperse.

In order to control the morphology of the inorganic silicate polymer particles, an acidic aqueous solution may be added to the suspension of inorganic silicate polymer precursor particles from which salts have been removed, if necessary.
The pH of the suspension of inorganic silicate polymer precursor particles to which an acidic aqueous solution has been added is preferably 3 to 6, and more preferably 3.5 to 4.5.

  Examples of the acidic aqueous solution include aqueous solutions of hydrogen chloride, sulfuric acid, nitric acid, acetic acid, perchloric acid, and the like.

  Titanium oxide / inorganic whose chemical composition and pore structure are controlled by mixing and stirring the suspension of inorganic silicate polymer precursor particles from which the salt has been removed and the substrate, followed by hydrothermal reaction Silicate polymer composite particles can be produced.

  The temperature for mixing and stirring the suspension of the inorganic silicate polymer precursor particles from which the salt has been removed and the base material is preferably 10 to 50 ° C, and more preferably 20 to 40 ° C.

  The time for mixing and stirring the suspension of the inorganic silicate polymer precursor particles from which the salt has been removed and the base material is preferably 0.1 to 72 hours, and more preferably 1 to 24 hours. preferable.

  The temperature at which the mixture of the inorganic silicate polymer precursor particles from which the salt has been removed and the suspension of the substrate is subjected to hydrothermal reaction is preferably 20 to 150 ° C, and preferably 40 to 105 ° C. Further preferred.

  The time for hydrothermal reaction of the mixture of the inorganic silicate polymer precursor particles from which the salt has been removed and the suspension of the base material is preferably 12 to 240 hours, and preferably 24 to 72 hours. Further preferred.

  When the mixture of the inorganic silicate polymer precursor particles from which the salt has been removed and the suspension of the base material are subjected to hydrothermal reaction, the mixture may be heated and aged in such a manner that the water does not evaporate. As a closed vessel such as an autoclave, a mantle heater with a cooling pipe, or the like can be used.

  Suitable conditions for hydrothermal reaction of the mixture of the inorganic silicate polymer precursor particles from which the salt has been removed and the suspension of the substrate are about 100 ° C. and about 48 hours.

  The resulting suspension of titanium oxide / inorganic silicate polymer composite particles may be used as it is or after being washed several times with water.

  Further, by adding an alkaline aqueous solution to the suspension of titanium oxide / inorganic silicate polymer composite particles, the pH is adjusted to about 8 to 12, and the product is aggregated and recovered as a gel substance. Also good.

  Examples of the alkaline aqueous solution include aqueous solutions of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, and the like.

  When an aggregation inhibitor is added, it may be extracted and removed in an organic solvent at 200 ° C. or lower for 1 hour or longer. Examples include methanol, ethanol, acetone, toluene, xylene, and benzene.

  In the present embodiment, as the precursor of the inorganic silicate polymer, an allophane precursor which is a kind of amorphous aluminum silicate mineral or an amorphous or quasicrystalline body of a derivative thereof may be used. . Thereby, hollow spherical allophane can also be produced as inorganic silicate polymer particles.

  Titanium oxide / inorganic silicate polymer composite particles with physical properties changed by controlling reaction conditions, molar ratio of silicon to aluminum, and titanium oxide content in composite particles as described above Can be synthesized.

  In the present embodiment, the titanium oxide / inorganic silicate polymer composite particle is a precursor of an inorganic silicate polymer in which the porosity, pore size distribution and shape of the inorganic silicate polymer covering the surface of the substrate are changed. It can be controlled by changing the body composition, the temperature and time of the hydrothermal reaction. When the concentration of the aqueous solution of the silicon compound or the aqueous solution of the aluminum compound, the temperature of the hydrothermal reaction, or the time is decreased, a thin-film inorganic silicate polymer domain is generated. On the other hand, when the concentration of the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound, the temperature and time of the hydrothermal reaction are increased, the inorganic silicate polymer domain can be enlarged. By appropriately selecting these conditions, the film thickness and precipitation state of the inorganic silicate polymer covering the surface of the substrate can be controlled.

  The titanium oxide / inorganic silicate polymer composite particles of this embodiment are coated with an inorganic silicate polymer film whose surface is inactive as a photocatalyst. Furthermore, since the inorganic silicate polymer film has an action of adsorbing proteins, amino acids, bacteria, viruses and the like, it can adsorb bacteria and the like in water and air. The titanium oxide / inorganic silicate polymer composite particles have pores on the surface of the inorganic silicate polymer film, and in the bottom of the pores, active titanium oxide as a photocatalyst is exposed. It has a quality structure.

  Therefore, when titanium dioxide / inorganic silicate polymer composite particles are irradiated with artificial light, sunlight, etc. from fluorescent lamps, incandescent lamps, black lights, UV lamps, mercury lamps, xenon lamps, halogen lamps, metal halide lamps, etc. The exposed titanium oxide is irradiated with light. The inorganic silicate polymer film quickly and continuously decomposes adsorbed proteins, amino acids, bacteria, viruses, etc. due to the redox action of electrons and holes generated in titanium oxide by light irradiation. Can be removed.

  Moreover, the titanium oxide / inorganic silicate polymer composite particles of the present embodiment are used as an environmental purification material, for example. When the above environmental purification material is used by kneading it in a medium such as organic fiber or resin, the portion in contact with the medium is ceramic that is inactive as a photocatalyst, so it does not induce decomposition of the medium. .

  Titanium oxide / inorganic silicate polymer composite particles dissolve in malodorous substances, harmful substances in the air such as toluene, xylene, ethyl acetate, p-dichlorobenzene, nitrogen oxides, sulfur oxides, or water. It adsorbs organic compounds that pollute the environment, such as organic solvents and agricultural chemicals. Therefore, when titanium dioxide / inorganic silicate polymer composite particles are irradiated with artificial light or sunlight from fluorescent lamps, incandescent lamps, black lights, UV lamps, mercury lamps, xenon lamps, halogen lamps, metal halide lamps, etc. By the redox action of electrons and holes generated in titanium, the adsorbed organic compound can be decomposed and removed rapidly and continuously.

  Moreover, the titanium oxide / inorganic silicate polymer composite particles can be used at low cost, energy saving, and maintenance-free simply by irradiating light. And, when the metal such as platinum, rhodium, ruthenium, palladium, silver, copper, iron, zinc is supported on the internal skeleton of the inorganic silicate polymer coated on the base material, Environmental purification effects such as organic compound decomposition and antibacterial and antifungal effects are further increased.

  In the present embodiment, as the medium for the environmental purification material, for example, polyethylene, nylon, polyvinyl chloride, polyvinylidene chloride, polyester, polypropylene, polyethylene oxide, polyethylene glycol, polyethylene terephthalate, silicone resin, polyvinyl alcohol, vinyl acetal resin, Polyacetate, ABS resin, epoxy resin, vinyl acetate resin, cellulose, cellulose derivative, polyamide, polyurethane, polycarbonate, polystyrene, urea resin, fluororesin, polyvinylidene fluoride, phenol resin, celluloid, chitin, starch sheet, etc. It is possible to apply organic fibers, plastics, or copolymers thereof.

  In this embodiment, the titanium oxide / inorganic silicate polymer composite particle has a porous structure in which the surface is covered with a silanol group or an aluminol group that is a hydrophilic group, and the surface has pores. Therefore, the hydrophilicity is extremely high.

  Further, even when the suspension of titanium oxide / inorganic silicate polymer composite particles and the resin emulsion are mixed, the portion in contact with the resin of the titanium oxide / inorganic silicate polymer composite particles is the photocatalyst. Since these are different inert ceramics, decomposition of the resin can be suppressed.

  The form of the emulsion clear coating of the present embodiment is not particularly limited as long as it does not impair or improve the design of an object to be coated which becomes a base layer when applied. Specific forms of the emulsion clear paint include clear paints such as transparent clear, translucent clear, and colored clear.

  The resin constituting the resin emulsion is not particularly limited as long as it can be applied to an emulsion clear coating. For example, acrylic resin, silicone resin, acrylic silicone resin, epoxy resin, vinyl acetate resin, urethane resin, styrene Examples thereof include synthetic resins such as resins and fluororesins. Of these, acrylic silicone resins are preferred.

  The content of the silicone component in the acrylic silicone resin is preferably 1 to 60% by mass, and more preferably 5 to 40% by mass. When the content of the silicone component in the acrylic silicone resin is 1% by mass or more, the weather resistance of the clear coating film can be improved. On the other hand, when the content of the silicone component in the acrylic silicone resin is 60% by mass or less, when the emulsion clear coating is repeatedly applied, the emulsion clear coating is likely to adhere to the previously formed coating film. The clear coating film is difficult to break.

  The mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear paint is preferably 0.1 to 5.0, although it depends on the form and design of the emulsion clear paint. More preferably, it is 1-3.0. In particular, when it is desired to achieve the appearance of a clear coating film having high transparency, the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating is 0.1 to 2.0. preferable. When the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating is 0.1 or more, the hydrophilicity of the clear coating can be improved. On the other hand, when the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating is 2.0 or less, the appearance, transparency and weather resistance of the clear coating can be secured. . At this time, when the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating exceeds 2.0, the transparency of the clear coating film is slightly lowered. It is a design called translucent clear known as an external design for (soft focus). In order to maintain the transparency that can be referred to as this translucent clear, the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating is determined by the film thickness and form, and the type of base material to be coated. However, it is preferably 5.0 or less.

  The solid content concentration of the emulsion clear coating is preferably 2 to 70% by mass, more preferably 2 to 60% by mass, and particularly preferably 3 to 50% by mass. Thereby, the film forming property of a clear coating film can be improved.

  The emulsion clear paint may contain a film-forming aid as required.

  Examples of film-forming aids include ethylene glycol ether modified products such as ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monobutyl ether. Examples include propylene glycol ether-modified products, texanol and the like.

  In addition, the emulsion clear coating can be used as necessary, such as an antifoaming agent, a viscosity modifier, a freeze inhibitor, a wetting agent, a water-soluble resin, a penetration aid, a preservative, a surface conditioner, a matting agent, a gelling agent, In addition to additives such as UV absorbers and antioxidants, it is compatible with emulsion clear paints such as colored pigments, extender pigments, luminance pigments, heat-shielding pigments, cryogenic stones, colored stones, colored beads, matte beads, and colored resin chips. A design material that does not melt may further be included.

According to the method for producing an emulsion clear coating of this embodiment, since titanium oxide / inorganic silicate polymer composite particles can be easily produced, the productivity is good and the emulsion clear coating is obtained. In addition, the aggregation of the resin is suppressed and the storage stability is excellent. In addition, the clear coating film formed by the emulsion clear coating has a hydrophilic surface, and is difficult to adhere to pollutants such as smoke and dust. It can retain the contamination and aesthetics. Furthermore, since the deterioration of the resin can be reduced, the clear coating film is stable.
(Method for forming clear coating film)
The method for forming a clear coating includes a step of producing an emulsion clear coating by a method for producing an emulsion clear coating, and a step of applying the emulsion clear coating to an object to be coated to form a clear coating.

  The film thickness of the clear coating film is preferably 1 to 50 μm, and more preferably 1 to 30 μm. When the film thickness of the clear coating film is 1 μm or more, the strength of the clear coating film can be improved and the occurrence of cracks can be suppressed. On the other hand, when the film thickness of the clear coating film is 50 μm or less, the abundance of titanium oxide / inorganic silicate polymer composite particles in the surface layer of the clear coating film increases. Contamination improves.

  As a method for applying the emulsion clear paint, for example, a known method such as a brush, a roller, an air spray, or an airless spray can be used.

  In order to make the film thickness uniform, the emulsion clear coating may be applied multiple times.

  Moreover, after apply | coating an emulsion clear coating material to a coating target object, you may dry naturally and you may heat-dry as needed.

  Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. In addition, a part means a mass part.

(Preparation of suspension of titanium oxide / inorganic silicate polymer composite particles)
A 100 mmol / L sodium orthosilicate and aluminum chloride aqueous solution was prepared. Next, a sodium orthosilicate aqueous solution and an aluminum chloride aqueous solution were rapidly mixed at room temperature so that the molar ratio of Si to Al was 0.9 and stirred for 1 hour. At this time, since the pH was basic of 7 or more, the pH was adjusted to 7 using 1 mol / L hydrochloric acid to obtain a suspension of inorganic silicate polymer precursor particles. The suspension of inorganic silicate polymer precursor particles was stirred at 20 ° C. for 1 hour to fully complete the precursor formation reaction. Using a centrifuge, thoroughly wash the suspension of inorganic silicate polymer precursor particles with deionized water to remove by-product salts, and then the inorganic silicate polymer precursor. The same amount of deionized water as the particle suspension was added and well dispersed.

  A suspension of titanium oxide (brookite) particles was added to the suspension of inorganic silicate polymer precursor particles after washing, and the mixture was stirred at 20 ° C. for 1 hour. (Registered trademark) Enclosed in a container, heated at 100 ° C. for 48 hours to cause a hydrothermal reaction, the surface of the titanium oxide particles was coated with an inorganic silicate polymer, and the titanium oxide / inorganic silicate polymer composite particles were Generated.

  Then, using a centrifuge, the titanium oxide / inorganic silicate polymer composite particles were sufficiently washed with deionized water to obtain a suspension of titanium oxide / inorganic silicate polymer composite particles. Here, the inorganic silicate polymer that coats the surface of the titanium oxide particles contains an allophen and an analogous compound obtained from the allophane precursor.

  The suspension of titanium oxide / inorganic silicate polymer composite particles was dried at 40 ° C. using an electric dryer to obtain titanium oxide / inorganic silicate polymer composite particles.

  Next, the X-ray diffraction pattern, BET specific surface area, and chemical composition of the titanium oxide / inorganic silicate polymer composite particles were measured.

(X-ray diffraction pattern)
The X-ray diffraction pattern of the titanium oxide / inorganic silicate polymer composite particles was measured using an automatic X-ray diffractometer RINT2100V / PC (manufactured by Rigaku Corporation).

  As a result, from the X-ray diffraction pattern of the titanium oxide / inorganic silicate polymer composite particles, peaks due to the brookite phase of titanium oxide were confirmed, and amorphous silicate or amorphous so as to cover them. The broad peaks characteristic of the quality aluminum silicate mineral (allophane) were confirmed around 25 ° and 40 °.

(Specific surface area)
The specific surface area of the titanium oxide / inorganic silicate polymer composite particles was measured by a flow-through nitrogen adsorption method using a catalyst analyzer BELCAT-A (manufactured by Microtrack Bell).

As a result, the specific surface area of the titanium oxide / inorganic silicate polymer composite particles was 253 m ² / g.

(Chemical composition)
The chemical composition of the titanium oxide / inorganic silicate polymer composite particles was measured using a fluorescent X-ray analyzer MESA-500 (manufactured by Horiba, Ltd.).

  Table 1 shows the chemical composition of the titanium oxide / inorganic silicate polymer composite particles.

  From Table 1, the titanium oxide / inorganic silicate polymer composite particles have a titanium oxide content of 33.7% by mass, and there are amorphous aluminum silicate polymers around and on the surface. It was revealed that the molar ratio of Si to Al in the crystalline aluminum silicate polymer was 1.05.

(Particle size distribution)
The particle size distribution was measured by a dynamic light scattering method using a particle size distribution measuring apparatus ZETASIZER-3000HSA (manufactured by Malvern Instruments).

  As a result, it was confirmed that the titanium oxide / inorganic silicate polymer composite particles had a particle size distribution curve in which the particle size was distributed in the range of 0.4 μm to 1.1 μm and the particle size showed a sharp peak near 1 μm. . The titanium oxide / inorganic silicate polymer composite particles had a volume average particle size of 0.8 μm.

  Next, an emulsion clear coating was prepared using titanium oxide / inorganic silicate polymer composite particles.

(Preparation of emulsion clear paint base)
First, deionized water and titanium oxide / inorganic silicate polymer composite particles were mixed at a ratio of 94: 6 (mass ratio) and subjected to ultrasonic dispersion treatment to obtain a mill base.

  Next, as a resin emulsion, Polydurex G-659 (made by Asahi Kasei Co., Ltd.) having a solid content of 42% by mass, ethylene glycol monobutyl ether (made by KH Neochem) as a film forming aid, and IPA (Taihei as a surface conditioner) Kasei) and water were mixed at a ratio of 62.0: 1.0: 10.0: 27.0 (mass ratio) to obtain a letdown base.

Example 1
Mix with a mill base, let-down base, and water so that the mass ratio of titanium oxide contained in the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating is 0.063. Further, an appropriate amount of a viscosity modifier Adecanol UH-420 (manufactured by ADEKA) was added to adjust the viscosity to about 2 Pa · s to obtain an emulsion clear paint. At this time, the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating was 0.19.

(Example 2)
Emulsion clear paint in the same manner as in Example 1 except that the mass ratio of titanium oxide contained in the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear paint was changed to 0.32. Got. At this time, the mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating was 0.94.

(Example 3)
Emulsion clear paint in the same manner as in Example 1 except that the mass ratio of titanium oxide contained in the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear paint was changed to 0.63. Got. The mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear coating at this time was 1.86.

(Comparative Example 1)
An emulsion clear coating was obtained in the same manner as in Example 1 except that the titanium oxide / inorganic silicate polymer composite particles were not added.

(Comparative Example 2)
The emulsion clear paint base, a suspension of titanium oxide (brookite) particles, and water are mixed so that the mass ratio of titanium oxide to the solid content of the emulsion clear paint is 0.063, and the viscosity modifier Adecanol is further mixed. An appropriate amount of UH-420 (manufactured by ADEKA) was added to adjust the viscosity to about 2 Pa · s to obtain an emulsion clear paint.

(Comparative Example 3)
An emulsion clear coating was obtained in the same manner as in Comparative Example 2 except that the mass ratio of titanium oxide to the solid content of the emulsion clear coating was changed to 0.32.

(Comparative Example 4)
An emulsion clear coating was obtained in the same manner as in Comparative Example 2 except that the mass ratio of titanium oxide to the solid content of the emulsion clear coating was changed to 0.63.

(Formation of clear coating film)
A water-based ceramic tone (black) (manufactured by Fujikura Kasei Co., Ltd.) as a primer was applied on a flat plate made of aluminum. Next, the emulsion clear paints of Examples 1 to 3 and Comparative Examples 1 to 4 were applied onto the primer using an air paint spray gun W-88 (manufactured by Anest Iwata Co., Ltd.), dried, and then subjected to clear coating A film was formed and used as a test piece. At this time, the clear coating film had a thickness of 28 μm.

(Color difference)
The color difference on the side of the test piece on which the clear coating film was formed was measured. The color difference was measured using a color difference meter SM color computer SM-T type (manufactured by Suga Test Instruments Co., Ltd.).

  Table 2 shows the difference in color difference from the test piece of Comparative Example 1.

  Here, the clear coating film of Comparative Example 1 has high transparency because no titanium oxide / inorganic silicate polymer composite particles or titanium oxide (brookite) particles are added.

  From Table 2, it can be seen that the difference in color difference between the test piece of Comparative Example 1 and the test pieces of Examples 1 to 3 is less than 2. For this reason, the clear coating films of Examples 1 to 3 had the same color gamut as the clear coating film of Comparative Example 1, and sufficiently satisfied the characteristics as the clear coating film, that is, the transparency.

  Moreover, when each combination of an Example and a comparative example with the same mass ratio of the titanium oxide with respect to solid content of an emulsion clear coating is compared, the difference of the color difference of a test piece is 0.3 at the maximum (Example 2 and Comparative Example 3). Thus, it can be said that the clear coating film containing the titanium oxide / inorganic silicate polymer composite particles has a color gamut very close to that of the clear coating film containing the titanium oxide (brookite) particles.

  Next, the difference in color difference before and after the weather resistance test of the test piece, the gloss retention, and the appearance after the weather resistance test were evaluated.

(Difference in color difference before and after weather resistance test, gloss retention)
A weather resistance test of the test piece was performed. Specifically, first, using a UV irradiator isuper UV tester W-151 (manufactured by Iwasaki Electric Co., Ltd.) as a test specimen, The test piece was irradiated with ultraviolet rays for 4 hours so that the surface received light with an irradiation intensity of 80 mW / cm ² . Thereafter, the temperature in the tank was set to about 30 ° C. and the humidity was set to 98% RH or more, and the tank was held for 4 hours to cause condensation in the tank. The above-described ultraviolet irradiation and condensation cycle was repeated until 480 hours passed.

  The difference in color difference and the gloss retention on the side of the test piece on which the clear coating film was formed before and after the weather resistance test were measured. In addition, the color difference meter SM color computer SM-T type (manufactured by Suga Test Instruments Co., Ltd.) and the gloss meter micro-TRI-gloss (manufactured by BYK Gardner GmbH) were used for the measurement of color difference and gloss, respectively.

(Appearance after weather resistance test)
The appearance of the side of the test piece on which the clear coating film was formed after the weather resistance test was visually confirmed. The criteria for appearance are as follows.

A: Good surface condition, high transparency, no abnormal changes in gloss and color tone B: Good surface condition, high transparency, but some abnormal changes in gloss and color tone C: The surface condition is poor, the transparency is low, and abnormal changes in gloss and color tone are observed. FIG. 1 is a photograph of the side of the test piece on which the clear coating film is formed after the weather resistance test. Show.

  Table 3 shows the weather resistance of the test pieces and the evaluation results of the appearance after the weather resistance test.

  From Table 3, when Examples 1 to 3 were compared with Comparative Example 1, the difference in color difference before and after the weather resistance test was 0.8 to 1.3, which was almost unchanged. Further, when Examples 1 to 3 were compared with Comparative Example 1, the difference in gloss retention before and after the weather resistance test was 2.5%, which was almost unchanged. Furthermore, when Examples 1 to 3 were compared with Comparative Example 1, the appearance after the weather resistance test was almost unchanged as is apparent from FIG.

  On the other hand, when Comparative Example 3 was compared with Comparative Example 1, the difference in gloss retention before and after the weather resistance test was 4.8%, indicating a decrease in gloss retention. Moreover, when the comparative example 3 was compared with the comparative example 1, the fall of the external appearance after a weather resistance test was recognized so that FIG.

  Furthermore, comparing Comparative Example 4 with Comparative Example 1, the difference in color difference before and after the weather resistance test and the difference in gloss retention were 7.9 and 21.0%, respectively. A significant decrease in the retention rate was observed. Further, when Comparative Example 4 was compared with Comparative Example 1, as is clear from FIG. 1, a remarkable decrease in appearance after the weather resistance test was observed.

  It should be noted that in Comparative Examples 2 to 4, the deterioration phenomenon of the clear coating film was accelerated with an increase in the amount of titanium oxide added, whereas Examples 1 to 3 were respectively compared. Although the addition amount of titanium oxide is the same as in Examples 2 to 4, the deterioration phenomenon of the clear coating film is not recognized.

  From the above, it has been clarified that the weather resistance of the clear coating film is remarkably improved by combining the titanium oxide and the inorganic silicate polymer.

  Further details will be described. As described above, it was shown that the emulsion clear paint containing the titanium oxide / inorganic silicate polymer composite particles exhibits high transparency and excellent weather resistance.

  In the emulsion clear paints of Examples 1 to 3, titanium oxide / inorganic silicate polymer composite particles are added, and in the emulsion clear paints of Comparative Examples 2 to 4, titanium oxide (brookite) particles are added. . That is, the amount of filler added to the emulsion clear paints of Examples 1 to 3 is larger than that of the emulsion clear paints of Comparative Examples 2 to 4, respectively. In general, it is known that the transparency of the clear coating film decreases as the amount of filler added in the emulsion clear coating increases. The factor that most affects the transparency of the clear coating film is the difference in refractive index between the filler and the resin matrix. In addition, the influence of the particle size of the filler on light scattering is also a factor that affects the transparency of the clear coating film to be considered.

  Considering the above, the improvement in transparency shown in Examples 1 to 3 will be considered. First, since the difference in refractive index between the filler and the resin matrix is a characteristic difference inherent in the substance and is difficult to control, it is important to control the particle diameter of the filler.

  Titanium oxide has nano-order primary particles, but when dispersed in an emulsion clear coating, it forms secondary particles that contribute to a decrease in transparency, and the surface of titanium oxide is in direct contact with the resin. Therefore, causing the photodegradation of the resin becomes a cause of white turbidity.

  However, by surrounding the titanium oxide with the inorganic silicate polymer, the growth to secondary particles is inhibited, and the inorganic silicate polymer serves as a spacer. It can be greatly reduced. Therefore, it is thought that the contradictory performance of reduction of the photodegradation of resin and maintenance of transparency is expressed.

  Furthermore, in the weather resistance test, the inorganic silicate polymer that surrounds the surface of the titanium oxide particles buffers the stress that the clear coating film physically “stretches and shrinks” due to changes in temperature and humidity in the sample chamber. It is suggested that the material moderately relaxed, and as a result, contributed to the improvement of the weather resistance of the clear coating film.

  Titanium oxide / inorganic silicate polymer composite particles are functional composite type emulsion clear coating fillers that are in line with existing titanium oxide composite particles using apatite or the like. In addition, since it is known that the strength of the clear coating film increases as the amount of filler added increases, titanium oxide / inorganic silicate polymer composite particles are mechanically maintained while maintaining weather resistance and transparency. It can also be said that it contributes to the improvement of strength.

  As described above, it was revealed that the clear coating films of Examples 1 to 3 had excellent weather resistance and transparency that could not be achieved only with titanium oxide.

  The emulsion clear coating of this embodiment uses the excellent water resistance, heat resistance and corrosion resistance, and unique shape of the added titanium oxide / inorganic silicate polymer composite particles to create an air cleaner, heat It can be used in a wide range of industrial fields such as exchangers and filters for water purification. In addition, titanium oxide and inorganic silicate polymers are used in pharmaceuticals and cosmetics, and are approved for use as food additives, so they are highly safe, low in cost and high in contamination resistance and weather resistance. Is also economical.

  Here, since titanium oxide / inorganic silicate polymer composite particles maintain the weather resistance and transparency of the surface for a long period of time, they can be added as fillers to media such as organic fibers and plastics. It is. For this reason, the emulsion clear paint of this embodiment can be applied to interior spaces such as automobiles and bathrooms.

Claims (13)

A method for producing an emulsion clear paint comprising:
Mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound to prepare a suspension of precursor particles of an inorganic silicate polymer;
Removing by-product salts from the suspension of inorganic silicate polymer precursor particles;
After mixing and stirring the suspension of inorganic silicate polymer precursor particles from which the salt has been removed and a base material on which at least a part of the surface has titanium oxide, the titanium oxide is subjected to a hydrothermal reaction. / Obtaining a suspension of inorganic silicate polymer composite particles;
A method for producing an emulsion clear paint, comprising a step of mixing a suspension of the titanium oxide / inorganic silicate polymer composite particles and a resin emulsion.   The method for producing an emulsion clear paint according to claim 1, wherein the inorganic silicate polymer contains an allophen and an analog compound obtained from an allophane precursor.   3. The method for producing an emulsion clear paint according to claim 1, wherein the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound each have a concentration of 1 mmol / L to 10 mol / L.   The method for producing an emulsion clear paint according to any one of claims 1 to 3, wherein a molar ratio of the silicon to the aluminum is 0.1 to 5.0.   The method for producing an emulsion clear coating composition according to any one of claims 1 to 4, wherein the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound are rapidly mixed at 1 mL / min to 10000 L / min.   The method for producing an emulsion clear paint according to any one of claims 1 to 5, wherein a pH of the liquid obtained by mixing the aqueous solution of the silicon compound and the aqueous solution of the aluminum compound is 3 to 10. A step of stirring the suspension of the inorganic silicate polymer precursor particles at 10 to 50 ° C. for 0.1 to 72 hours;
The emulsion clear coating composition according to any one of claims 1 to 6, wherein the salt of the by-product is removed from the stirred suspension of inorganic silicate polymer precursor particles. Production method.   The suspension of inorganic silicate polymer precursor particles from which the salt has been removed and the base material are mixed and stirred at 10 to 50 ° C. for 0.1 to 72 hours, and then at 20 to 150 ° C. for 12 to 12 hours. The method for producing an emulsion clear paint according to any one of claims 1 to 7, wherein a hydrothermal reaction is performed for 240 hours.   The emulsion clear coating composition according to any one of claims 1 to 8, wherein the titanium oxide / inorganic silicate polymer composite particles have a content of the titanium oxide of 20 to 40% by mass. Production method. 10. The method for producing an emulsion clear paint according to claim 1, wherein the titanium oxide / inorganic silicate polymer composite particles have a specific surface area of 200 m ² / g or more.   The method for producing an emulsion clear paint according to any one of claims 1 to 9, wherein the titanium oxide / inorganic silicate polymer composite particles have a particle size in the range of 0.1 to 100 µm. .   12. The mass ratio of the titanium oxide / inorganic silicate polymer composite particles to the solid content of the emulsion clear paint is 0.1 to 5.0. 13. Of producing an emulsion clear coating. A step of producing an emulsion clear paint by the method of producing an emulsion clear paint according to any one of claims 1 to 12,
A method for forming a clear coating film, comprising the step of forming the clear coating film by applying the emulsion clear coating to an object to be coated.