Preparation and characteristics of a waterborne preventive stain coating material with organic-inorganic composites.With the goal of developing a waterborne coating material coating material, n a biologically acceptable, usually porous nonmetal applied over the surface of a metallic implant with the expectation that tissue ingrowth will occur in the pores. Often a carbon polymer or ceramic substance. that prevents staining, organic-inorganic composites prepared from colloidal colloidal of the nature of a colloid. colloidal bath a bath containing gelatin, bran, starch or similar substances, to relieve skin irritation and pruritus. silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. and two types of acrylic resin emulsions were investigated as exterior coatings. Conventional acrylic resin emulsion emulsion: see colloid. emulsion Mixture of two or more liquids in which one is dispersed in the other as microscopic or ultramicroscopic droplets (see colloid). Emulsions are stabilized by agents (emulsifiers) that (e.g. and organic silane silane or silicon hydride Any of a series of inorganic compounds of silicon and hydrogen with covalent bonds and the general chemical formula SinH(2n + 2). hybridized acrylic resin emulsion prepared by emulsion polymerization Emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with were mixed with colloidal silica to form organic-inorganic composite films. The addition of colloidal silica to emulsions yielded films with higher hydrophilicities, as indicated by lower water contact angles for these films in comparison to films without colloidal silica. The water contact angles of organic silane hybridized acrylic resin emulsion/colloidal silica films were lower than those of acrylic resin emulsion/colloidal silica films. Composite films containing colloidal silica particles smaller than 100 nm in diameter showed high hydrophilicities. Observations of the dispersed dis·perse v. dis·persed, dis·pers·ing, dis·pers·es v.tr. 1. a. To drive off or scatter in different directions: The police dispersed the crowd. b. state of colloidal silica particles in organic-inorganic composite films by scanning electron microscopy electron microscopy Technique that allows examination of samples too small to be seen with a light microscope. Electron beams have much smaller wavelengths than visible light and hence higher resolving power. (SEM) and transmission electron microscopy “TEM” redirects here. For other uses, see TEM (disambiguation). Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is transmitted through a specimen, then an image is formed, magnified and directed to appear either (TEM TEM 1. transmission electron microscope. 2. triethylenemelamine. 3. transmissible encephalopathy of mink. ) demonstrated that colloidal silica particles were densely aggregated on the film surface. Outdoor exposure tests of the coating materials prepared from organic silane hybridized acrylic resin and colloidal silica particles with diameters of 7.5 nm showed excellent stain resistance. Keywords: Acrylics, latexes, colloids, emulsions, silicones, silicates, stain resistance, weatherability, architectural, water-based ********** The maintenance and preservation of buildings and other structures requires high quality coating materials with excellent weather durability, and water and stain resistance. Recently, attempts have been made to improve weather durability and stain resistance of exterior coating materials used in architecture. Improvements of binder binder: see combine. An earlier Microsoft Office workbook file that let users combine related documents from different Office applications. The documents could be viewed, saved, opened, e-mailed and printed as a group. resins in coating materials (1,2) and the use of additives, such as hindered amine Hindered amines are chemical compounds conatining an amine functional group surrounded by a crowded steric environment. They have uses such as gas scrubbing, as stabilizers against light-induced degradation of polymers, and as reagents for organic synthesis. light stabilizers (HALS) (3) and ultraviolet absorbers (UVA), (4) have provided materials with good weather durability. However, these approaches were not sufficient enough to guard against stains that appear uniformly or partially on coating surfaces. Further improvements in the weather and the stain resistances of external wall coatings are needed. Stains result from rain, which carries stain materials to coating materials; these stain materials stick to the coating surfaces and appear as traces of rain. In addition, the lipophilic lipophilic, adj/n the ability to dissolve or attach to lipids. lipophilic (lipōfil´ik), adj 1. showing a marked attraction to, or solubility in, lipids. 2. stain materials preferentially stick to coating surfaces rather than hydrophilic hydrophilic /hy·dro·phil·ic/ (-fil´ik) readily absorbing moisture; hygroscopic; having strongly polar groups that readily interact with water. hy·dro·phil·ic adj. stain materials because of their higher affinity for hydrophobic hydrophobic /hy·dro·pho·bic/ (-fo´bik) 1. pertaining to hydrophobia (rabies). 2. not readily absorbing water, or being adversely affected by water. 3. coating surfaces. Studies on the development of exterior coating materials to prevent soiling behavior have concluded that their stain resistance is influenced by the hydrophilicity and hardness of the coating surfaces. (5-8) Organic-inorganic hybrid composites are expected to provide new highly functional materials. Organic-inorganic hybrid composites have attracted much attention because they combine the flexibility of an organic component and the hardness of an inorganic inorganic /in·or·gan·ic/ (in?or-gan´ik) 1. having no organs. 2. not of organic origin. in·or·gan·ic n. 1. component. Organic-inorganic composite materials composite material or composite, any material made from at least two discrete substances, such as concrete. Many materials are produced as composites, such as the fiberglass-reinforced plastics used for automobile bodies and boat hulls, but the have thus been investigated for a variety of applications including medicine, electronics, cosmetics, adhesives, surface coatings Surface coating A substance applied to other materials to change the surface properties, such as color, gloss, resistance to wear or chemical attack, or permeability, without changing the bulk properties. , (9-11) and separation membranes. (12-17) Tomita et al. (18-20) have reported an additional effect of hydrophilicity and the morphology morphology In biology, the study of the size, shape, and structure of organisms in relation to some principle or generalization. Whereas anatomy describes the structure of organisms, morphology explains the shapes and arrangement of parts of organisms in terms of such of the condensed con·dense v. con·densed, con·dens·ing, con·dens·es v.tr. 1. To reduce the volume or compass of. 2. To make more concise; abridge or shorten. 3. Physics a. alkyl alkyl /al·kyl/ (al´k'l) the monovalent radical formed when an aliphatic hydrocarbon loses one hydrogen atom. al·kyl n. silicate silicate, chemical compound containing silicon, oxygen, and one or more metals, e.g., aluminum, barium, beryllium, calcium, iron, magnesium, manganese, potassium, sodium, or zirconium. Silicates may be considered chemically as salts of the various silicic acids. of tetraalkoxysilane in the coating layer of architectural coating materials. Their method, which is effective for coatings containing two liquids, confers hydrophilicity to the material due to the hydrolysis hydrolysis (hīdrŏl`ĭsĭs), chemical reaction of a compound with water, usually resulting in the formation of one or more new compounds. of alkyl silicate during the film formation. However, it has a limited application for a waterborne coating containing an organic liquid component because these coated materials are not chemically stable. Furthermore, it is essential to replace solvent-based coatings with waterborne-based coatings because the evaporation evaporation, change of a liquid into vapor at any temperature below its boiling point. For example, water, when placed in a shallow open container exposed to air, gradually disappears, evaporating at a rate that depends on the amount of surface exposed, the humidity of organic solvent vapors must be controlled for environmental, health, and safety reasons. Although the addition of a binder to a waterborne coating performed equally well in comparison to a solvent-based coating with regard to coating performance, as judged by high weather durability, water resistance, and mechanical properties, waterborne coatings did not provide satisfactory stain resistance. In this study, we prepared waterborne preventive stain coating materials with organic-inorganic composites in which colloidal silica was employed as an inorganic component. The organic component of the composites included conventional acrylic resin emulsions prepared by the emulsion polymerization of methylmethacrylate (MMA (Microcomputer Managers Association, Inc.) A membership organization with chapters throughout the U.S. that was devoted to educating personnel responsible for personal computers. It disbanded in 1996. Mma - A fast Mathematica-like system, in Allegro CL by R. Fateman, 1991. ), 2-ethylhexylacrylate (2EHA EHA European Hematology Association EHA Economic History Association EHA Emmanuel Hospital Association EHA Education for All Handicapped Children Act of 1975 EHA Empty Homes Agency EHA English Hockey Association EHA Electrohydrostatic Actuator ), methacrylic acid methacrylic acid /meth·a·cryl·ic ac·id/ (meth?ah-kril´ik) an organic acid that polymerizes easily to form a ceramic-like mass. Its esters, methyl and polymethyl methacrylate, are used in the manufacture of acrylic resins and plastics. (MA), and an organic silane hybridized acrylic resin emulsion prepared by the core/shell emulsion polymerization of MMA, 2EHA, MA, and 3-methacryloxypropyl trimethoxysilane (3MOPTMOS). The performance characteristics of the organic-inorganic composite films, including their stain resistance, were investigated. EXPERIMENTAL Materials Methacrylic acid (MA), methylmethacrylate (MMA), and 2-ethylhexylacrylate (2EHA), purchased from Wako Pure Chemical Industries, Japan, were used as monomers in the emulsion polymerization reactions. Potassium peroxodisulfate (KPS KPs keratic precipitates. ), also purchased from Wako Pure Chemical Industries, was employed as an initiator. Polyoxyethylene alkyl ether ether, in chemistry ether, any of a number of organic compounds whose molecules contain two hydrocarbon groups joined by single bonds to an oxygen atom. sulfates (HITENOL 08E), obtained from Dai-Ichi Kogyo Seiyaku Co. Ltd., Japan, were used as emulsifiers. 3-Methacryloxypropyltrimeth-oxysilane (3MOPTMOS), purchased from Shin-Etsu Chemical Co., Ltd., was used as an organic silane component for the synthesis of organic silane hybridized acrylic resin emulsions. Colloidal silicas with median diameters of 7.5, 25.0, 62.0, 112.6, 223.5, and 330.3 nm were obtained from Catalysts & Chemicals Ind. Co., Ltd., Japan, and Nissan Chemical Industries Ltd., Japan. The colloidal silicas used were monodispersed. The ratio of the weight average particle sizes Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. to number average particle sizes for the colloidal silicas used was in the range of 1.02 ~ 1.05. 2,2,4-Trimethyl-1,3-pentanediolmonoisobutyrate, obtained from Chisso Corporation, Japan, was used as a coalescence coalescence /co·a·les·cence/ (ko?ah-les´ens) the fusion or blending of parts. co·a·les·cence n. See concrescence. coalescence a fusion or blending of parts. agent. Titanium titanium (tītā`nēəm, tĭ–) [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.88; m.p. 1,675°C;; b.p. 3,260°C;; sp. gr. 4.54 at 20°C;; valence +2, +3, or +4. dioxide (JR-901S), purchased from Tayca Corporation, Japan, was employed as a pigment pigment, substance that imparts color to other materials. In paint, the pigment is a powdered substance which, when mixed in the liquid vehicle, imparts color to a painted surface. . Synthesis of Emulsions The synthesis of two types of emulsions used as organic components in this study was performed according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. a previously described procedure. (21) The ingredients for the preparation of the two emulsions are listed in Table 1. The acrylic resin emulsion polymerization was carried out as follows: a heterogeneous aqueous aqueous /aque·ous/ (a´kwe-us) 1. watery; prepared with water. 2. see under humor. a·que·ous adj. solution was prepared by dissolving HITENOL 08E (1 part) in deionized water Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. (267 parts), MMA (333 parts), 2EHA (242 parts), and MA (10 parts). The solution was emulsified at 1000 rpm using a mixer (T.K. Homo Mixer Mark II Model 2.5, PRIMIX Corporation). The emulsified mixture (5 wt%) and KPS (1 part) were added in a separate flask flask (flask) 1. a laboratory vessel, usually of glass and with a constricted neck. 2. a metal case in which materials used in making artificial dentures are placed for processing. containing HITENOL 08E (1 part) dissolved in deionized water (275 parts) at 75[degrees]C. The mixture was kept at 80[degrees]C for 10 min; both the remaining emulsified mixture (95 wt%) and KPS (1 part) dissolved in deionized water (50 parts) were continuously dropped with stirring at 80[degrees]C for three hours. The reaction mixture was kept at 80[degrees]C for one hour and then cooled and neutralized neu·tral·ize tr.v. neu·tral·ized, neu·tral·iz·ing, neu·tral·iz·es 1. To make neutral. 2. To counterbalance or counteract the effect of; render ineffective. 3. by the addition of aqueous ammonia ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. solution (5 parts). Preparation of the organic silane hybridized emulsion polymerization followed the above processes up to the continuous dropping of the remaining emulsified mixture and dissolution of KPS in deionized water at 80[degrees]C for three hours. At this stage, a mixture of MA (45 parts) and 3MOPTMOS (5 parts) was continuously dropped into the reaction mixture at 80[degrees]C for three hours, followed by the addition of KPS (1 part). The mixture was kept at 80[degrees]C for one hour and then cooled, followed by addition of aqueous ammonia solution (5 parts) to neutralize neutralize to render neutral. the mixture. Properties of Acrylic Resin Emulsion Solid contents, viscosities, and minimum film-forming temperatures (MFFTs) of acrylic resin emulsions and organic silane hybridized acrylic resin emulsions were determined by the methods described in a previous paper. (21) The properties of the emulsions are summarized in Table 2. In film formation at room temperature, we used an excess of coalescing coalescing (kō  les´ing),n a joining or fusing of parts. solvent for each emulsion. The coating films were dried at room temperature for two weeks to completely remove any coalescing solvent in the films. We measured them using pencil hardness. As a result, they were the same value for pencil hardness, HB. Film Preparation Casting solutions for the films were prepared by mixing colloidal silica with either the acrylic resin emulsion or the organic silane hybridized acrylic resin emulsion, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate as a coalescent co·a·lesce intr.v. co·a·lesced, co·a·lesc·ing, co·a·lesc·es 1. To grow together; fuse. 2. To come together so as to form one whole; unite: in appropriate ratios. The films were prepared by spreading these casting solutions onto black acrylic resin plates, followed by complete drying at room temperature. The thickness of the dried films ranged from 30 ~ 50 [micro]m. Surface Measurements of Acrylic Emulsion-Colloidal Silica Composite Films The distribution of colloidal silica in the two types of emulsions was observed by a scanning electron microscope scan·ning electron microscope n. Abbr. SEM An electron microscope that forms a three-dimensional image on a cathode-ray tube by moving a beam of focused electrons across an object and reading both the electrons scattered by the object and (SEM, field emission scanning electron microscope JSM-6700F, from JEOL JEOL Japan Electron Optics Laboratory . Ltd.) and a transmission electron microscope electron microscope: see microscope. (TEM, JEM-100CX, also from JEOL. Ltd.). The contact angle for water was measured at 25[degrees]C by an automatic dynamic contact angle meter an instrument for measuring angles, esp. for ascertaining the dip of strata. See also: Angle (CA-V, Kyowa Interface Science Co., Ltd.). The surface gloss was measured at 60[degrees] with a micro-TRI gloss reflectometer re·flec·tom·e·ter n. An instrument for measuring the reflectance of a surface. Noun 1. reflectometer - a meter that measures the reflectance of a surface (GM-268, Konica Minolta Holdings, Inc.). Silica in the acrylic resin emulsion was detected by X-ray photoelectron spectroscopy X-ray Photoelectron Spectroscopy (XPS) is a quantitative spectroscopic surface chemical analysis technique used to estimate the empirical formula or elemental composition, chemical state and electronic state of the elements on the surface (upto 10 nm) of a material. (XPS (1) See XML Paper Specification. (2) A brand name for certain models of Inspiron laptops from Dell. 7000, Rigaku Co.). Coating Formulation The formulation of a waterborne coating material, along with a protocol for the mill base, is shown in Table 3. The mill base was prepared by dispersing titanium dioxide in water containing a dispersant dis·per·sant n. Chemistry A liquid or gas added to a mixture to promote dispersion or to maintain dispersed particles in suspension. , wetting agents wet·ting agent n. A substance that reduces the surface tension of a liquid, causing the liquid to spread across or penetrate more easily the surface of a solid. Noun 1. , and defoamer using a mixer at 3000 rpm for 30 min. Coating materials were prepared in a let-down phase by blending the mill base, an emulsion, and additives such as thickeners and defoamer, using a mixer at 1000 rpm for 30 min. Exposure Tests Outdoor exposure specimens were prepared by applying a white waterborne coating material (300 g/[m.sup.2]) on the substrate. The dimensions and some details of these specimens are shown in Figure 1. Outdoor exposures of the specimens were performed in Ota-ku, Tokyo, Japan. The specimens were placed facing south and given exposure for up to one year. The stain resistance of the exposed specimens was observed by a color meter (Minolta CR-200, Konica Minolta Holdings, Inc.). The degree of stain resistance, [DELTA]L*, was evaluated by the difference in lightness values before and after exposure as expressed in equation (1). (22) Thus, a negative value indicates darkening dark·en v. dark·ened, dark·en·ing, dark·ens v.tr. 1. a. To make dark or darker. b. To give a darker hue to. 2. To fill with sadness; make gloomy. 3. of the surface; that is, staining. [DELTA]L* = [L*.sub.t] - [L*.sub.0] (1) where [L*.sub.0] and [L*.sub.t] are the lightness values before and after exposure, respectively. The [DELTA]L* value determined by this method correlated strongly with the visual observation of stains on the coating surface. [FIGURE 1 OMITTED] [FIGURE 2 OMITTED] [FIGURE 3 OMITTED] [FIGURE 4 OMITTED] RESULTS AND DISCUSSION Characteristics of Films from Conventional and Organic Silane Hybridized Acrylic Resin Emulsions To develop waterborne preventive stain coating materials, two types of emulsions, namely conventional acrylic resin emulsions and organic silane hybridized acrylic resin emulsions, were used as binders for exterior coating materials. The properties of the films prepared from these emulsions are also listed in Table 2. The contact angle for water on the surface of the film prepared from the organic silane hybridized acrylic resin emulsion was smaller than that prepared from the acrylic resin emulsion, suggesting that the former film was more hydrophilic. However, the gloss at 60[degrees] of the former film was lower than that of the latter film. These results could be attributed to an appearance of silanol groups formed by the hydrolysis of 3MOPTMOS. Figure 2 shows X-ray photoelectron spectroscopy (XPS) spectra of the film surfaces obtained from the two types of emulsions. In the spectra of the organic silane hybridized acrylic resin emulsion film, a peak was detected at a binding energy of about 102.5 ~ 105 eV, which was assigned to the Si component in 3MOPTMOS. This result further supports the assumption that the 3MOPTMOS component was incorporated into the organic silane hybridized acrylic resin emulsion film, and that the Si was located at the film surface. A TEM image of a cross-section of the film obtained from the organic silane hybridized acrylic resin emulsion is shown in Figure 3. In the TEM image, where the Si and the resin phases appeared dark and bright, respectively, Si is observed surrounding the polymer particles and the film has a core/shell structure. However, the core/shell particles are inhomogeneously distributed over the range of 90 ~ 440 nm. Stain Resistance of Coating Materials Figure 4 shows the results of the outdoor exposure tests of waterborne coating materials prepared according to the protocol listed in Table 3. The [DELTA]L* of each coating material decreased with increasing time. The [DELTA]L* of the coating material prepared from the organic silane hybridized acrylic resin emulsion was smaller than that from the acrylic resin emulsion at all times. The magnitude of the decrease in the [DELTA]L* of the former coating material was smaller than that of the latter. Since the degree of [DELTA]L* is dependent on the adhesion of stain to the coating surface, these results suggest that the waterborne coating material prepared from the organic silane hybridized acrylic resin emulsion has a high stain resistance. This improved stain resistance could again be attributed to the appearance of a Si layer on the surface of the emulsion particle modified by 3MOPTMOS. The coating material is expected to have a higher stain resistance if the amount of 3MOPTMOS in the silane hybridized acrylic resin emulsion is increased. However, when the amount of 3MOPTMOS was increased, the Si layer hardened, and consequently, a film could not be formed. Therefore, we could not use a large amount of 3MOPTMOS in the preparation of these emulsions. Characteristics of Composite Films from Acrylic Resin Emulsions and Colloidal Silica To evaluate the stain resistance of organic-inorganic composite waterborne coating materials prepared from acrylic resin emulsion and colloidal silica, films were prepared using colloidal silica with six different particle sizes. Acrylic resin/colloidal silica composite films and organic silane hybridized acrylic resin/colloidal silica composite films were prepared with 5 wt% or 10 wt% colloidal silica of different particle diameters. Figure 5 shows the contact angle for water of various organic-inorganic composite films. Water contact angles for all organic-inorganic composite films increased with increasing colloidal silica particle diameter up to 100 nm. The composite films with higher colloidal silica contents showed lower water contact angles in both organic-inorganic composite films. The organic silane hybridized acrylic resin emulsion/colloidal silica films had lower contact angles for water when compared to the acrylic resin emulsion/colloidal silica films. These results suggest that the hydrophilicity of organic-inorganic composite films prepared from organic silane hybridized acrylic resin emulsions increases with colloidal silica of decreasing particle size and increasing colloidal silica content. Figure 6 shows SEM images of the surfaces of acrylic resin/colloidal silica and organic silane hybridized acrylic resin/colloidal silica composite films. In both types of composite films, silica particles were uniformly distributed on the surface of the composite films containing smaller size colloidal silica particles. This uniform distribution of silica particles in the composite films with smaller colloidal silica particles should make them more hydrophilic, which supports the water contact angle results described previously. The SEM images also show that in the acrylic resin/colloidal silica composite films, colloidal silica exists in a higher proportion within the composite film rather than on the film surface. However, colloidal silica in the organic silane hybridized acrylic resin/colloidal silica composite films exists in a higher proportion on the film surface. The distribution of colloidal silica particles in composite films confirms that the surface of organic silane hybridized acrylic resin composite films with smaller colloidal silica particles are more hydrophilic than those of the acrylic resin composite films. On the basis of the above results, the dispersion dispersion, in chemistry dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. state of colloidal silica particles on film surfaces of the two types of emulsions can be explained as follows: in the silane hybridized acrylic resin emulsion, the surface layer of particles is slightly hard due to the formation of a Si shell layer on the emulsion particle. When emulsion particles aggregate together, smaller colloidal silica particles are excluded; in addition, a number of cohesion bodies are formed, which densely aggregate on the film surfaces. On the other hand, in the acrylic resin emulsion, small colloidal silica particles are covered beneath the acrylic resin emulsion particles and very few are left exposed on the film surface. Thus, the surface characteristics of acrylic resin emulsion/colloidal silica composite films are significantly influenced by the dispersion state of colloidal silica particles on the surface of these films. [FIGURE 5 OMITTED] [FIGURE 6 OMITTED] [FIGURE 7 OMITTED] [FIGURE 8 OMITTED] TEM images of thin cross-sections of organic silane hybridized acrylic resin composite films containing various colloidal silica particles were shown in a previous paper. (21) The authors observed that colloidal silica particles with diameters of 7.5 nm became densely aggregated on the film surface during the drying process in composite film formation. [FIGURE 9 OMITTED] Stain Resistance of Coating Materials with Organic-Inorganic Composites The waterborne preventive stain coating material prepared from the organic silane hybridized acrylic resin emulsions and colloidal silica particles with 7.5 nm diameters were subjected to outdoor exposure tests. In addition, the influence of acrylic resins with different glass transition temperatures The glass transition temperature is the temperature below which the physical properties of amorphous materials vary in a manner similar to those of a solid phase (glassy state), and above which amorphous materials behave like liquids (rubbery state). ([T.sub.g]s) in the organic silane hybridized acrylic resin emulsion was also examined. Theoretical [T.sub.g]s of acrylic resins were calculated from the ratio of MMA and 2EHA in the acrylic resin using the [T.sub.g]s of these homopolymers. Figure 7 shows that the theoretical [T.sub.g] of the acrylic resin (23) increased with increasing MMA content in the acrylic resin of the organic silane hybridized acrylic emulsion. In Figure 8, the relationship between [DELTA]L* after outdoor exposure for over one year and the theoretical [T.sub.g] of the acrylic resin in the coating material is shown. The [DELTA]L* value decreased with increasing theoretical [T.sub.g]s, implying that the theoretical [T.sub.g] of the acrylic resin remarkably influenced the stain on the coating surface. The stain materials could not stick to the coating surface because the surface of coating materials containing acrylic resins have high [T.sub.g]s; that is, they were hard. On the other hand, when colloidal silica with a 7.5 nm particle diameter was added to the organic silane hybridized acrylic resin emulsions, the [DELTA]L* of coating materials became remarkably smaller. The difference between the largest [DELTA]L* and the smallest [DELTA]L* with changing theoretical [T.sub.g] of acrylic resin was about | 2 |. The difference between the [DELTA]L*s of the two coating materials was about | 8 |. These results suggest that the use of colloidal silica improved the stain resistance of the coating material. In Figure 9, the effect of the outdoor exposure period on the stain resistance over one year is shown as a function of the colloidal silica content. The [DELTA]L* of the coating materials increased with longer outdoor exposure, and decreased significantly with increasing colloidal silica content. The extent of increase in [DELTA]L* of the composite coating materials with higher colloidal silica contents over time was smaller, suggesting that composite coating materials with higher colloidal silica contents had higher stain resistance. Photographs of the surface of coating materials with various colloidal silica contents after one year of outdoor exposure are shown in Figure 10. In these photographs, the vertical stripes represent stained areas. Soiled rain traces on the surfaces of the coating films can be seen to decrease for coating materials with higher colloidal silica contents. These results indicate that the stain resistance of acrylic resin/colloidal silica composite films significantly depends on the hydrophilicity of composite film surfaces. [FIGURE 10 OMITTED] CONCLUSIONS In the present study, waterborne preventive stain coating materials obtained from organic-inorganic composites composed of acrylic resin emulsions and colloidal silica were investigated. A conventional acrylic resin emulsion and an organic silane hybridized acrylic resin emulsion were prepared as organic components. In the outdoor exposure test for the exterior coating materials prepared from these emulsions, films from the organic silane hybridized acrylic resins showed better stain resistance than the films from the conventional acrylic resins. In order to further improve the stain resistance, organic-inorganic composite films consisting of acrylic resin emulsion and colloidal silica were prepared. The surfaces of the organic-inorganic composite films, consisting of organic silane hybridized acrylic resin emulsions and colloidal silica, were more hydrophilic than composites with acrylic resin emulsions and colloidal silica. The former composite films showed higher hydrophilicities when higher contents of colloidal silica with small particle sizes were used in their preparation. The composite films with more hydrophilic surfaces showed excellent stain resistance in the outdoor exposure tests over an extended period. In this study, we have demonstrated that waterborne preventive stain coating materials could be designed using organic silane hybridized acrylic resin emulsions as organic components and colloidal silicas as inorganic components. Organic-inorganic composite films composed of organic silane hybridized acrylic resin emulsions and colloidal silica particles with diameters of 7.5 nm show good potential as stain resistant coatings. ACKNOWLEDGMENT acknowledgment, in law, formal declaration or admission by a person who executed an instrument (e.g., a will or a deed) that the instrument is his. The acknowledgment is made before a court, a notary public, or any other authorized person. A part of this work was supported by the Nanotechnology Support Project of the Ministry of Education, Culture, Science and Technology (MEXT MEXT Ministry of Education, Culture, Sports, Science and Technology (Japan) MEXT Ministry of Education, Sports, Science and Technology (Japan) ), Japan, at the Research Center for Ultrahigh ul·tra·high adj. Exceedingly high: an ultrahigh vacuum. Voltage Electron Microscopy, Osaka University Home to many elite and renowned alumni of CEOs, lawyers, doctors, scientists, bureaucrats, and a Nobel laureate, as well as to many advanced research centers, Osaka University is considered one of the most prestigious universities in Japan and Asia. . 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Dehydration inhibits the growth of microorganisms and often reduces the bulk of food. of an Ethanol/Water Azeotrope azeotrope /azeo·trope/ (a´ze-o-trop?) a mixture of two substances that has a constant boiling point and cannot be separated by fractional distillation.azeotrop´ic a·ze·o·trope n. by Novel Organic-Inorganic Hybrid Membranes Based on Quaternized Chitosan and Tetraethoxysilane," Biomacromolecules, 5, 1567 (2004). (14) Uragami, T, Katayama, T, and Miyata, T., "Pervaporation Properties for an Azeotrope of Ethanol/Water Through Organic-Inorganic Hybrid Membranes from Quaternized Chitosan with Tetraethoxysilane," Trans. Mater. Res. Soc. Jpn., 29, 3295 (2004). (15) Ohshima, T., Matsumoto, M., Miyata, T., and Uragami, T., "Organic-Inorganic Hybrid Membranes for Removal of Benzene benzene (bĕn`zēn, bĕnzēn`), colorless, flammable, toxic liquid with a pleasant aromatic odor. It boils at 80.1°C; and solidifies at 5.5°C;. Benzene is a hydrocarbon, with formula C6H6. from an Aqueous Solution by Pervaporation," Macromol. Chem. Phys., 206, 473 (2005). (16) Ohshima, T., Matsumoto, M., Miyata, T., and Uragami, T., "Structural Design of P(BMA-co-VTES)/TEO Hybrid Membranes for Removal of Benzene from Water by Pervaporation," Macromol. Chem. Phys., 206, 1638 (2005). (17) Uragami, T., Matsugi, M., and Miyata, T., "Pervaporation Characteristics of Organic-Inorganic Hybrid Membranes Composed of Poly(vinyl alcohol-co-acrylic acid) and Tetraethoxysilane for Water/Ethanol Separation," Macromolecules, 38 (8), 440 (2005). (18) Tomita, R., Urano, S., and Kohiki, S., "Quantitative Evaluation of Hydrolysis Ratio and Content of Silicic si·lic·ic adj. Relating to, resembling, containing, or derived from silica or silicon. Ester on Film Surface by X-ray Photoelectron Spectroscopy," J. Jpn. Soc. Colour Mater., 74,460 (2001). (19) Tomita, R., Urano, S., and Kohiki, S., "Elucidation e·lu·ci·date v. e·lu·ci·dat·ed, e·lu·ci·dat·ing, e·lu·ci·dates v.tr. To make clear or plain, especially by explanation; clarify. v.intr. To give an explanation that serves to clarify. of Hydro-philization Mechanism on Film Surface and Design of Silicic Ester by Use of Quantitative Evaluation of Hydrolysis Ratio and Content of Silicic Ester," J. Jpn. Soc. Colour Mater., 74, 466 (2001). (20) Kakui, K., Murakami, N., Osawa, S., Okamoto, H., and Hasegawa, T., "New Technology About the Reduction in Contamination of Ecofriendly Coatings. Development and Evaluation of Water Based High Durability and Stain Resistance Coatings," Summaries of Technical Papers of Annual Meeting Architectural Institute of Japan A-1 Materials and Construction (2002). (21) Wada, T., Inui, K., and Uragami, T, "Properties of Organic-Inorganic Composite Coating Materials Prepared from Acrylic Resin Emulsions and Colloidal Silicas," J. Appl. Polym. Sci., 101, 2951 (2006). (22) Motohashi, K. and Soga, M., "Evaluation of Soiling Due to Rain Trace on the Coated Layers," The 2002 Global Symposium, 760 (2002). (23) Kiryu, H. and Kasamatsu, H., Foundation and Physical Properties of High Efficient Paint, Cmc Shuppan, Japan, 1985. Tamaki Wada -- Kowa Chemical Industries Co., Ltd.* Tadashi Uragami -- Kansai University ([dagger]) * 6-2-10 Hounanchominami, Toyonaka, Osaka Toyonaka (豊中市 Toyonaka-shi 561-0815, Japan. Email: wada-t@jmail.plala.or.jp. ([dagger]) Faculty of Engineering and High Technology Research Center, 3-3-35, Yamate-cho, Suita, Osaka Suita (吹田市 Suita-shi) 564-8680, Japan.
Table 1 -- Ingredients for the Acrylic Resin Emulsion and the Organic
Silane Hybridized Acrylic Resin Emulsion
Organic Silane
Hybridized
Acrylic Resin Acrylic Resin
Ingredients Emulsion Emulsion
Feed portion
MMA 333 333
2EHA 242 242
MA 10 10
Deionized water 275 275
HITENOL 08E 1 1
Reaction phase
Deionized water 267 267
HITENOL 08E 4 4
Initiator
KPS 2 2
Deionized water 50 50
Silane hybridized portion
MMA -- 45
3-methacryloxypropyltrimethoxysilane -- 5
Neutralize
Ammonia 5 5
Table 2 -- Properties of the Acrylic Resin Emulsion and the Organic
Silane Hybridized Acrylic Resin Emulsion and Their Films
Acrylic Organic Silane
Resin Hybridized Acrylic
Emulsion Resin Emulsion
Solid (%) (a) 50.3 50.1
Viscosity (mPas) (b) 120 1500
pH 8.4 8.7
Average particle diameter of emulsion (nm) 154 163
MFT ([degrees]C) 41 47
Contact angle for water on film 84.2 57.3
surface ([degrees])
Gloss at 60[degrees] 87.0 84.4
Transparency (lightness value) 0.53 0.93
(a) 105[degrees]C, 3 hr
(b) BM, 60 rpm, 23[degrees]C
Table 3 -- Formulation of a Waterborne Exterior Coating Material
Ingredients Parts by Weight (g)
Mill base
Deionized water 12.68
Hydroxy ethyl cellulose 0.12
Ammonia 0.05
Dispersant (Dispers 750 W, Tego Chemie Service) 1.00
Wetting agent (Emulgen LS-110, KAO Co., Ltd.) (a) 0.20
Defoamer (SN Defoamer 397, Sannopko Co., Ltd.) 0.05
Titanium dioxide (JR-901S, TAYCA Co.) 21.00
Let down
Mill base 35.10
Emulsion 60.00
Coalescent (b) 4.50
Thickeners (SN Thickener 621N, Sannopko Co., Ltd.) 0.20
Defoamer (SN Defoamer 397, Sannopko Co., Ltd.) 0.20
(a) Polyoxyalkylene alkyl ether, Cloud point 73[degrees]C, HLB 13.4
(b) 2, 2, 4-trimethyl 1,3-pentane-diol monoisobutyrate
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