Metal-containing colloidal silica and its manufacturing method

Abstract

This metal-containing colloidal silica has a mixture layer obtained by dispersing a metal M in silica. The mixture layer is positioned between silica particles serving as a core and a silica layer located on the surface of the metal-containing colloidal silica. The metal M is at least one type of element selected from Au, Ag, Cu, Zn, Ti, Pt, Mg, Zr, Fe, Sr, Ca, V, Mo, Bi, Nb, Ga, Ge, Sn, Ba, W, Co, Ni, and Mn. The molar ratio (Si / M) of silicon to the metal M in a coating layer obtained by combining the mixture layer and the silica layer is 10-10,000. The metal M is uniformly and finely dispersed in the mixture layer.

Description

[Technical Field]

[0001] The present invention relates to metal-containing colloidal silica in which the surface of colloidal silica is modified with a metal, and to a method for producing the same. [Background technology]

[0002] Colloidal silica has been used in a variety of applications, including as a catalyst carrier, a chromatographic filler, silica glass, a filler for resins, a polishing composition, an adhesive binder for phosphors in the manufacture of cathode ray tubes, a gelling agent, a thixotropic agent, and a shatterproofing agent for electrolytes in batteries, an inorganic adhesive, and a paint.

[0003] A technique for supporting metals on the surface of silica particles is known in order to provide properties suitable for these applications. For example, Patent Document 1 provides a method for supporting metal fine particles on the surface of silica particles by plasma treatment, rather than using metal fine particles themselves, in consideration of lightness, dispersibility, cost, etc. Patent Document 2 describes that, as a result of investigating improvements in the polishing rate and surface smoothness of colloidal silica for polishing applications, this objective was achieved by using metal-supported silica particles. Other techniques related to colloidal silica using silica particles supported, coated, or containing metals have been disclosed (see, for example, Patent Documents 3 to 10).

[0004] Generally, colloidal silica has a particle size of about 5 to 300 nm. However, when it comes to the minute range of 100 nm or less, from the viewpoint of modifying colloidal silica with metal particles, it is necessary to make the metal particles even smaller. Furthermore, the influence of the metal particles causes aggregation of silica particles, making it difficult to obtain colloidal silica modified with metal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-152079 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-193486 [Patent Document 3] Japanese Patent Application Publication No. 2-292201 [Patent Document 4] Japanese Patent Application Publication No. 4-210606 [Patent Document 5] Japanese Patent Application Publication No. 4-310235 [Patent Document 6] Japanese Patent Application Publication No. 8-253310 [Patent Document 7] Japanese Patent Application Laid-Open No. 2001-130910 [Patent Document 8] Japanese Patent Application Laid-Open No. 2005-119909 [Patent Document 9] Japanese Patent Application Laid-Open No. 2006-306708 [Patent Document 10] Special Publication No. 2010-505734 Summary of the Invention [Problem to be solved by the invention]

[0006] The modification of colloidal silica with metals using the above-mentioned conventional technology is a method in which a metal compound is reacted with silica particles to support or coat the silica particle surface with the metal to be modified, but the smaller the silica particles, the larger the specific surface area becomes, and a large amount of metal compound must be used to support the metal, which is inefficient. Furthermore, when considering that colloidal silica is used to disperse in base materials such as paints and films, it is required that the colloidal particles be stable over a long period of time. Therefore, an object of the present invention is to provide a metal-containing colloidal silica in which colloidal particles are resistant to aggregation and which has excellent storage stability. [Means for solving the problem]

[0007] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that colloidal particles are less likely to aggregate when a silica layer is formed on the surface of metal-containing colloidal silica obtained by allowing a metal salt compound to coexist during the particle growth process of silica particles, by further reacting active silicic acid thereon, thereby completing the present invention.

[0008] That is, the present invention provides a metal-containing colloidal silica having a mixed layer in which a metal M is dispersed in silica, wherein the mixed layer is located between a core silica particle and a silica layer located on the surface of the metal-containing colloidal silica, the metal M is one or more selected from Au, Ag, Cu, Zn, Ti, Pt, Mg, Zr, Fe, Sr, Ca, V, Mo, Bi, Nb, Ga, Ge, Sn, Ba, W, Co, Ni, and Mn, the molar ratio of silicon to the metal M (Si / M) in the coating layer comprising the mixed layer and the silica layer is 10 or more and 10,000 or less, and the metal M is uniformly and finely dispersed in the mixed layer.

[0009] The present invention also provides a method for producing metal-containing colloidal silica, comprising the steps of: (a) adding a metal salt compound to an aqueous solution of activated silicic acid to prepare an aqueous solution of activated silicic acid containing a metal salt compound; (b) reacting the aqueous solution of activated silicic acid containing the metal salt compound in the presence of colloidal silica under alkaline conditions to form a mixed layer on the surface of the colloidal silica, in which the metal is uniformly and finely dispersed in the silica; and (c) reacting the colloidal silica that has formed the mixed layer with an aqueous solution of activated silicic acid under alkaline conditions to form a silica layer on the surface of the mixed layer. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a metal-containing colloidal silica having excellent storage stability and a method for producing the same. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a TEM photograph of the silver-containing colloidal silica obtained in Example 1. [Figure 2]1 shows the results of elemental mapping by TEM-EDX of the silver-containing colloidal silica obtained in Example 1. [Figure 3] 1 is an XPS spectrum of the silver-containing colloidal silica obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] The metal-containing colloidal silica of the present invention has a mixed layer in which metal M is uniformly and finely dispersed in silica, and the mixed layer is located between the silica particle serving as the core material and the silica layer located on the surface of the metal-containing colloidal silica.

[0013] The silica particles serve as the core material of the metal-containing colloidal silica of the present invention and are covered with the mixed layer. The particle diameter of the silica particles may be such that the resulting metal-containing colloidal silica can maintain a colloidal state, and is preferably, for example, from 0.5 nm to 100 nm, particularly preferably from 1 nm to 50 nm.

[0014] The mixed layer is composed of silica and metal M, and is in a state where metal M is uniformly and finely dispersed in silica.

[0015] The metal M is preferably one or more selected from Au, Ag, Cu, Zn, Ti, Pt, Mg, Zr, Fe, Sr, Ca, V, Mo, Bi, Nb, Ga, Ge, Sn, Ba, W, Co, Ni, and Mn, and can be appropriately selected depending on the application of the metal-containing colloidal silica. For example, when the metal-containing colloidal silica is used as an antibacterial agent, a bactericide, an antiviral agent, or a virucide, the metal M is preferably one or more selected from Ag and Cu.

[0016] In the present invention, "antibacterial" means inhibiting bacterial growth, "sterilizing" means killing bacteria, and "antiviral" and "viricidal" both mean inactivating viruses.

[0017] The metal M of the present invention may be a simple metal or a metal compound. That is, the mixed layer of the metal-containing colloidal silica of the present invention has a form in which a simple metal is uniformly and finely dispersed in silica, a form in which a metal compound is uniformly and finely dispersed, or a form in which a simple metal and a metal compound are uniformly and finely dispersed in silica.

[0018] The metal compound is preferably an oxide or hydroxide, from the viewpoint of being easily finely dispersed in the silica of the mixed layer and stably retained. For example, when the metal-containing colloidal silica of the present invention is used for an antibacterial agent, a bactericide, an antiviral agent, or a virucidal agent, when the metal M is Ag, it is preferably finely dispersed in the mixed layer as metallic silver, silver oxide (Ag2O, AgO, Ag2O3), and silver hydroxide (AgOH), and when the metal M is Cu, it is preferably finely dispersed in the mixed layer as metallic copper, copper oxide (CuO, Cu2O), and copper hydroxide (Cu2O, Cu(OH)2).

[0019] In the present invention, "the metal M is uniformly and finely dispersed in the mixed layer" means that "the presence of the metal M is confirmed by elemental analysis of the metal-containing colloidal silica by X-ray photoelectron spectroscopy (XPS analysis), and the presence of the metal M in the mixed layer is not confirmed in an elemental mapping image obtained by analyzing the metal-containing colloidal silica at 1,000,000 times magnification by transmission electron microscope-energy dispersive X-ray spectroscopy (TEM-EDX)." In other words, the state in which the metal M is uniformly and finely dispersed means that the metal M is dispersed and present at a size that cannot be detected by the resolution of TEM-EDX, and there are no sites where the metal M aggregates.

[0020] The particle size of the metal-containing colloidal silica of the present invention can be a general particle size of about 5 to 300 nm as long as the silica particles can maintain a colloidal state, but when used as an antibacterial, antiviral, bactericidal, or virucidal material, for example, the effect is enhanced if the particle size is in the range of 100 nm or less, which is close to the size of bacteria and viruses. From this perspective, the average particle size of the metal-containing colloidal silica of the present invention is preferably 1 nm or more and 100 nm or less, particularly 2 nm or more and 80 nm.

[0021] The mixed layer is made of silica containing a metal, and the molar ratio of silicon to metal M (Si / M) is preferably from 5 to 5,000, more preferably from 10 to 3,000, and particularly preferably from 50 to 1,000. If this molar ratio is less than 5, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 5,000, the properties of containing a metal cannot be utilized.

[0022] The mixed layer, in which the metal is uniformly and finely dispersed in the silica, can prevent the metal from falling off the silica particles, and since the surface of the silica particles is coated with the mixed layer, the silica particles can be efficiently modified with a small amount of metal.

[0023] The thickness of the mixed layer is preferably 1 nm or more and 50 nm or less from the viewpoint of efficient modification and production of silica particles, and more preferably 1 nm or more and 10 nm or less.

[0024] The silica layer is located on the outer surface of the metal-containing colloidal silica of the present invention and covers the mixed layer. The thickness of the silica layer is preferably 0.5 nm or more and 10 nm or less, from the viewpoint of preventing the metal M from falling off while making the most of the properties of the metal M, such as antibacterial, bactericidal, antiviral, and virucidal properties, and more preferably 1 nm or more and 5 nm or less.

[0025] The metal-containing colloidal silica of the present invention has a coating layer that is a combination of the mixed layer and the silica layer. The molar ratio of silicon to metal M (Si / M) in this coating layer that is a combination of the mixed layer and the silica layer is 10 to 10,000, preferably 20 to 8,000, and particularly preferably 50 to 5,000. If this molar ratio is less than 10, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 10,000, the properties of containing the metal cannot be utilized.

[0026] The molar ratio of silicon to metal M (Si / M) in the metal-containing colloidal silica of the present invention varies depending on the size of the silica particles that serve as the core material, but is preferably from 10 to 20,000, more preferably from 20 to 10,000, and particularly preferably from 30 to 5,000. If this molar ratio is less than 10, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 20,000, the properties of containing a metal cannot be utilized.

[0027] The method for producing metal-containing colloidal silica of the present invention comprises the steps of: (a) adding a metal salt compound to an aqueous solution of activated silicic acid to prepare an aqueous solution of activated silicic acid containing a metal salt compound; (b) reacting the aqueous solution of activated silicic acid containing the metal salt compound in the presence of colloidal silica under alkaline conditions to form a mixed layer on the surface of the colloidal silica, in which metal is uniformly and finely dispersed in the silica; and (c) reacting the colloidal silica that has formed the mixed layer with the aqueous solution of activated silicic acid under alkaline conditions to form a silica layer on the surface of the mixed layer.

[0028] In the step (a) of the present invention, an aqueous solution of activated silicic acid containing a metal salt compound is prepared as a raw material for the mixed layer formed in the step (b) described below.

[0029] The activated silicic acid aqueous solution in the step (a) is preferably obtained by contacting an alkali silicate aqueous solution with a cation exchange resin. As the alkali silicate aqueous solution used as a raw material, a sodium silicate aqueous solution called water glass (water glass No. 1 to No. 4, etc.) is preferably used. Water glass is relatively inexpensive and easily available. The alkali silicate aqueous solution can be diluted with water as needed before use.

[0030] The cation exchange resin can be appropriately selected from known ones and is not particularly limited. The contacting step between the aqueous alkali silicate solution and the cation exchange resin can be carried out, for example, by diluting the aqueous alkali silicate solution with water to a silica concentration of 3 to 10% by weight, then contacting it with an H-type strongly acidic cation exchange resin to dealkalize it, and if necessary, contacting it with an OH-type strongly basic anion exchange resin to deanionize it. This step produces activated silicic acid. Various detailed contact conditions have been proposed in the past, and any of these known conditions can be used in the present invention.

[0031] The metal salt compound in step (a) is preferably at least one selected from nitrates, chlorides, acetates, phosphates, and sulfates, and the metal in the metal salt compound is preferably at least one selected from Au, Ag, Cu, Zn, Ti, Pt, Mg, Zr, Fe, Sr, Ca, V, Mo, Bi, Nb, Ga, Ge, Sn, Ba, W, Co, Ni, and Mn, and can be appropriately selected depending on the application of the metal-containing colloidal silica.

[0032] The metal salt compound is preferably added to the aqueous activated silicic acid solution at a concentration such that the molar ratio of silicon to metal M (Si / M) in the resulting coating layer, which is a combination of the mixed layer of metal-containing colloidal silica and the silica layer, is from 10 to 10,000, more preferably from 20 to 8,000, and even more preferably from 50 to 5,000. That is, the molar ratio of silicon to metal M (Si / M) in the resulting mixed layer of metal-containing colloidal silica is preferably from 5 to 5,000, even more preferably from 10 to 3,000, and even more preferably from 50 to 1,000.

[0033] Next, a mixed layer is formed by the above-mentioned step (b), in which an alkaline agent is added to the activated silicic acid aqueous solution containing a metal salt compound in the presence of colloidal silica, the pH is adjusted to 8 or higher, and the solution is heated to 60 to 240°C, thereby forming a mixed layer on the surface of the colloidal silica in which the metal is uniformly and finely dispersed in the silica.

[0034] As the alkaline agent, alkali metal hydroxides such as sodium hydroxide are the most inexpensive materials. If alkali metals are not preferred, nitrogen-containing organic alkaline compounds such as amines and quaternary ammonium hydroxides can be used. As amines, low-volatility tertiary amines such as triethanolamine, secondary amines such as piperazine, and aliphatic amines such as ethylenediamine can be used. As quaternary ammonium hydroxides, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and trimethyl-2-hydroxyethylammonium hydroxide (also known as choline hydroxide) can be used.

[0035] By using the nitrogen-containing organic alkali compound, the alkali metal content per silica can be reduced to 50 ppm or less. This level of alkali metal content is preferable for applications such as ceramics, catalyst binders, and abrasives for electronic materials. A content of 30 ppm or less is more preferable.

[0036] The colloidal silica can be prepared, for example, by ion exchange. In the ion exchange colloidal silica production process, an aqueous solution of alkali silicate is first diluted with water to a silica concentration of 3 to 10% by weight, then contacted with an H-type strongly acidic cation exchange resin for dealkalization, and optionally with an OH-type strongly basic anion exchange resin for deanionization, to produce activated silicic acid. Various types of ion exchange resins and conditions have been proposed, and any of these known methods can be used. Next, an alkaline agent is added according to a conventional method to adjust the pH to 8 or higher, and the mixture is heated to 60 to 240°C to produce colloidal silica from the activated silicic acid. Depending on the heating temperature, colloidal silica with a particle size of 5 to 300 nm can be obtained. Alternatively, commercially available colloidal silica can be used.

[0037] The mixed layer obtained by the step (b) of the present invention is one in which the metal M is uniformly and finely dispersed in silica.

[0038] The metal M is preferably one or more selected from Au, Ag, Cu, Zn, Ti, Pt, Mg, Zr, Fe, Sr, Ca, V, Mo, Bi, Nb, Ga, Ge, Sn, Ba, W, Co, Ni, and Mn, and can be appropriately selected depending on the application of the metal-containing colloidal silica. For example, when the metal-containing colloidal silica is used as an antibacterial agent, bactericide, antiviral agent, or virucide, the metal M is preferably one or more selected from Ag and Cu.

[0039] The metal M of the present invention may be a simple metal or a metal compound. That is, the mixed layer of the metal-containing colloidal silica of the present invention has a form in which a simple metal is uniformly and finely dispersed in silica, a form in which a metal compound is uniformly and finely dispersed, or a form in which a simple metal and a metal compound are uniformly and finely dispersed in silica.

[0040] The metal compound is preferably an oxide or hydroxide, from the viewpoint of being easily finely dispersed in the silica of the mixed layer and stably retained. For example, when the metal-containing colloidal silica of the present invention is used for an antibacterial agent, a bactericide, an antiviral agent, or a virucidal agent, when the metal M is Ag, it is preferably finely dispersed in the mixed layer as metallic silver, silver oxide (Ag2O, AgO, Ag2O3), and silver hydroxide (AgOH), and when the metal M is Cu, it is preferably finely dispersed in the mixed layer as metallic copper, copper oxide (CuO, Cu2O), and copper hydroxide (Cu2O, Cu(OH)2).

[0041] The mixed layer is made of silica containing a metal, and the molar ratio of silicon to metal M (Si / M) is preferably from 5 to 5,000, more preferably from 10 to 3,000, and particularly preferably from 50 to 1,000. If this molar ratio is less than 10, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 5,000, the properties of containing a metal cannot be utilized.

[0042] The mixed layer, in which the metal is uniformly and finely dispersed in the silica, can prevent the metal from falling off the silica particles, and since the surface of the silica particles is coated with the mixed layer, the silica particles can be efficiently modified with a small amount of metal.

[0043] The thickness of the mixed layer is preferably 1 nm or more and 50 nm or less from the viewpoint of production efficiency, and more preferably 1 nm or more and 10 nm or less.

[0044] Next, a silica layer is formed by the step (c) in which an active silicic acid aqueous solution and an alkali agent are added to the colloidal silica that has formed the mixed layer, the pH is adjusted to 8 or higher, and the mixture is heated at 60 to 240°C to form a silica layer on the surface of the mixed layer.

[0045] The activated silicic acid aqueous solution may be the same as the activated silicic acid aqueous solution in the step (a), and the alkaline agent may be the same as the alkaline agent in the step (b).

[0046] The amount of the active silicic acid aqueous solution added is adjusted depending on the scale of the operation, but from the viewpoint of the storage stability of the resulting metal-containing colloidal silica, it is preferably added so that the thickness of the silica layer becomes 1 nm or more and 20 nm or less, particularly 1 nm or more and 10 nm or less.

[0047] The particle size of the metal-containing colloidal silica obtained by the production method of the present invention can be a general particle size of about 5 to 300 nm as long as the silica particles can maintain a colloidal state, but when used as, for example, an antibacterial agent, antiviral agent, bactericide, or viricide, the effect is greater if the particle size is in the range of 100 nm or less, which is close to the size of bacteria and viruses. From this perspective, the average particle size of the metal-containing colloidal silica of the present invention is preferably 1 nm or more and 100 nm or less, particularly 2 nm or more and 80 nm or less.

[0048] The metal-containing colloidal silica obtained by the above procedure has a molar ratio of silicon to metal M (Si / M) in the coating layer, which is the combined coating layer of the mixed layer and silica layer, of 10 to 10,000, preferably 20 to 8,000, and particularly preferably 50 to 5,000. If this molar ratio is less than 10, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 10,000, the properties of containing a metal cannot be utilized.

[0049] In the present invention, after the step (c), a step of concentrating the metal-containing colloidal silica may be carried out. This concentration is carried out by ultrafiltration. Although concentration by evaporation of water may also be used, ultrafiltration is more advantageous in terms of energy.

[0050] This section describes the ultrafiltration membranes used when concentrating silica by ultrafiltration. Ultrafiltration membranes are used to separate particles ranging in size from 1 nm to several microns, but because they also target dissolved polymeric substances, filtration accuracy in the nanometer range is expressed in terms of molecular weight cutoff. In the present invention, ultrafiltration membranes with a molecular weight cutoff of 15,000 or less can be suitably used. Using membranes in this range allows for the separation of particles of 1 nm or larger. More preferably, an ultrafiltration membrane with a molecular weight cutoff of 3,000 to 15,000 is used. Membranes with a molecular weight cutoff of less than 3,000 have too high a filtration resistance, resulting in uneconomical processing times, while membranes with a molecular weight cutoff of more than 15,000 result in a low degree of purification.

[0051] The membrane may be made of polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, or other materials, and any of these may be used. From the standpoint of heat resistance, filtration speed, and other factors, polysulfone membranes are preferred. The membrane may be spiral, tubular, or hollow fiber, and any of these may be used, although hollow fiber membranes are compact and easy to use. It is preferable to concentrate the silica in this step to a concentration of 5 to 50% by mass.

[0052] The particle size of the metal-containing colloidal silica obtained by the production method of the present invention can be a general particle size of about 5 to 300 nm as long as the silica particles can maintain a colloidal state, but when used as, for example, an antibacterial agent, antiviral agent, bactericide, or viricide, the effect is greater if the particle size is in the range of 100 nm or less, which is close to the size of bacteria and viruses. From this perspective, the average particle size of the metal-containing colloidal silica of the present invention is preferably 1 nm or more and 100 nm or less, particularly 2 nm or more and 80 nm or less.

[0053] The metal-containing colloidal silica obtained by the above procedure has a molar ratio of silicon to metal M (Si / M) of 10 to 20,000, preferably 20 to 10,000, and particularly preferably 30 to 5,000, although this depends on the size of the colloidal silica that serves as the core material. If this molar ratio is less than 10, the colloidal silica becomes unstable, which can cause the silica particles to settle or gel, and if it exceeds 20,000, the properties of containing a metal cannot be utilized.

[0054] The metal-containing colloidal silica of the present invention obtained by the above-mentioned production method has antibacterial, antiviral, bactericidal, and virucidal properties, and can be used as an antibacterial agent, antiviral agent, bactericidal, or virucidal agent as it is, but depending on the application, it is preferable to further contain a solvent. The solvent is not particularly limited, and examples thereof include water and organic solvents. Examples of the organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.

[0055] The metal-containing colloidal silica of the present invention has excellent dispersibility in various resins and little tendency to discolor, and therefore can be blended with various resins to form antibacterial, bactericidal, antiviral, or virucidal resin compositions and molded resin articles, such as fibers, films, sheets, pipes, panels, containers, building materials, structural materials, etc. The metal-containing colloidal silica of the present invention can also be blended with paints and the like to form antibacterial, bactericidal, antiviral, or virucidal coating films.

[0056] Molded resin articles formed from resin compositions containing the metal-containing colloidal silica of the present invention can be of any shape. Examples include fabric products such as woven fabrics, nonwoven fabrics, mesh fabrics, and knitted fabrics; sheet products such as paper and film; and shaped articles such as plates, rods, boxes, and porous bodies. Furthermore, paints containing the metal-containing colloidal silica of the present invention can be of any form. Examples include powder products such as dusting agents and sprays; liquid or paste products such as brush-applied paints, spray paints, and roller-applied paints; adhesives and sealants. Furthermore, the metal-containing colloidal silica can be incorporated into deodorants, antiperspirants, soaps, shampoos, moisturizers, cosmetics, toothpastes, mouthwashes, lubricants, creams, lotions, surface cleaners, laundry detergents, and other products to achieve antibacterial, bactericidal, antiviral, or virucidal properties.

[0057] Examples of resin molded articles formed from resin compositions containing the metal-containing colloidal silica of the present invention and articles using paints containing the metal-containing colloidal silica of the present invention include freshness-preserving films, sanitary products, kitchen and bath products, toiletries, cosmetics, water treatment products, medical equipment, building materials, and fishing nets. Furthermore, paints containing the metal-containing colloidal silica of the present invention can be added to cement mortar or applied to molded cement concrete bodies to produce antibacterial, bactericidal, antiviral, or virucidal cement concrete products. The resin compositions and paints containing the metal-containing colloidal silica of the present invention can also be used in various other products for the purpose of achieving antibacterial, bactericidal, antiviral, or virucidal properties. [Example]

[0058] The present invention will be described below with reference to examples, but the scope of the present invention is not limited to these examples. The properties in the examples were measured by the following methods.

[0059] (1) Average particle size A 10 g sample was taken, diluted hydrochloric acid was added to adjust the pH to 4, heated to solidify, washed with pure water, re-dried, and then dried at 150°C to obtain a powder sample, and the nitrogen adsorption BET specific surface area (SA) was measured using a NOVA4200 manufactured by Quantachrome. The density of the silica was 2.2 g / cm. 3 The average particle size was calculated using the following formula (1). Particle diameter D (nm)=6×10 3 / [density(g / cm 3 )×SA(m 3 / g)] (1) (2) Molar ratio of silicon to metal in the coating layer The silicon content in the metal-containing colloidal silica and the core silica particles was measured by back titration using hydrochloric acid and potassium hydroxide solution. The metal content in the metal-containing colloidal silica was measured using an ICP-OES 5100 ICP optical emission spectrometer manufactured by Agilent Technologies. The molar ratio of silicon to metal M in the coating layer was calculated from the obtained measurements using the following formula (2): Si / M = (Si amount in metal-containing colloidal silica - Si amount in core colloidal silica) / Metal M amount in metal-containing colloidal silica (2) (3) Observation of metals in the mixed layer Metals were observed using elemental mapping images at a magnification of 1,000,000 times using a transmission electron microscope-energy dispersive X-ray spectrometer (TEM-EDX analyzer; Hitachi High-Tech, HD-2700). (4) Measurement of metals contained in metal-containing colloidal silica The metal M was confirmed from the peak of the spectrum obtained by an X-ray photoelectron spectrometer (XPS analyzer; manufactured by ULVAC-PHI, PHI5000VersaProbe) using monochromated AlKα (1486.6 eV) as the X-ray source.

[0060] Example 1 (a) Preparation of an aqueous solution of activated silicic acid containing silver nitrate 2,200 g of No. 3 sodium silicate (SiO: 28.8% by mass, NaO: 9.7% by mass, HO: 61.5% by mass) was added to 13,750 g of deionized water and mixed uniformly to prepare diluted sodium silicate with a silica concentration of 4% by mass. This diluted sodium silicate was dealkalized by passing it through a 4-liter column packed with H-type strongly acidic cation exchange resin (Amberlite® IR120B, manufactured by Organo Corporation) that had been regenerated with hydrochloric acid in advance, to obtain 14,000 mL of an active silicic acid aqueous solution with a silica concentration of 4% by mass and a pH of 3.1. To 3,283 g of the obtained aqueous solution of activated silicic acid, 0.653 g of silver nitrate was added with stirring to prepare an aqueous solution of activated silicic acid containing silver nitrate. (b) Preparation of silver-containing colloidal silica 65 g of colloidal silica (Silicadol 30S, manufactured by Nippon Chemical Industry Co., Ltd.) with an average particle size of 9 nm was diluted with 2,500 g of deionized water and then heated to 95°C to obtain aqueous colloidal silica. A 10% by mass aqueous solution of sodium hydroxide was added to this aqueous colloidal silica to adjust the pH to 9.9, and the mixture was heated again and maintained at 95°C. 9,074 g of the silver nitrate-containing activated silicic acid aqueous solution was added over 3.2 hours, and the surface of the colloidal silica was coated with a mixed layer to obtain silver-containing colloidal silica. The temperature was maintained at 95°C during the addition, and 10% by mass sodium hydroxide was simultaneously added to maintain the pH at 9.5 to 10.5. (c) Preparation of silica-coated silver-containing colloidal silica Next, 8,415 g of the activated silicic acid aqueous solution obtained in step (a) above was added to the resulting silver-containing colloidal silica over a period of 3.6 hours to coat the surface of the silver-containing colloidal silica with a silica layer. The temperature was maintained at 95°C during the addition, and 10% by mass of sodium hydroxide was simultaneously added to maintain a pH of 9.5 to 10.5. After the addition was completed, the mixture was allowed to cool to room temperature, yielding 16,500 g of silica-coated silver-containing colloidal silica. The obtained silica-coated silver-containing colloidal silica was subjected to pressure filtration by pump circulation using a hollow-fiber ultrafiltration membrane (Microza® UF Module SIP-1013, manufactured by Asahi Kasei Corporation) with a molecular weight cutoff of 6,000. The silica was concentrated to a silica concentration of 35% by mass, and 1,200 g of silica-coated silver-containing colloidal silica was recovered. This silica-coated silver-containing colloidal silica had a pH of 10 at 25°C and an average particle size of 21 nm. Furthermore, ICP atomic emission spectrometry revealed that the molar ratio of silicon to silver (Si / Ag) in the coating layer of the obtained silver-containing colloidal silica was 2,256. Furthermore, when the obtained silver-containing colloidal silica was analyzed by TEM-EDX, the elemental mapping image did not confirm the presence of silver in the mixed layer. On the other hand, XPS analysis of the silver-containing colloidal silica yielded a spectrum attributable to metallic silver. These results confirmed that metallic silver, as the metal M, was uniformly and finely dispersed in the mixed layer. The mixed layer had an average thickness of 4 nm, and the silica layer had an average thickness of 4 nm.

[0061] Example 2 (a) Preparation of an aqueous solution of activated silicic acid containing silver nitrate 2,200 g of No. 3 sodium silicate (SiO: 28.8% by mass, NaO: 9.7% by mass, HO: 61.5% by mass) was added to 13,750 g of deionized water and mixed uniformly to prepare diluted sodium silicate with a silica concentration of 4% by mass. This diluted sodium silicate was dealkalized by passing it through a 4-liter column packed with H-type strongly acidic cation exchange resin (Amberlite® IR120B, manufactured by Organo Corporation) that had been regenerated with hydrochloric acid in advance, to obtain 14,000 mL of an active silicic acid aqueous solution with a silica concentration of 4% by mass and a pH of 3.1. To 5,027 g of the obtained aqueous solution of activated silicic acid, 0.53 g of silver nitrate was added with stirring to prepare an aqueous solution of activated silicic acid containing silver nitrate. (b) Preparation of silver-containing colloidal silica 100 g of colloidal silica (Silicadol 30S, manufactured by Nippon Chemical Industry Co., Ltd.) with an average particle size of 9 nm was diluted with 2,500 g of deionized water and then heated to 95°C to obtain aqueous colloidal silica. A 10% by weight aqueous solution of sodium hydroxide was added to this aqueous colloidal silica to adjust the pH to 9.9, and the mixture was heated again and maintained at 95°C. 5,027 g of the silver nitrate-containing activated silicic acid aqueous solution was added over 4.2 hours, and the surface of the colloidal silica was coated with a mixed layer to obtain silver-containing colloidal silica. The temperature was maintained at 95°C during the addition, and 10% by weight sodium hydroxide was simultaneously added to maintain the pH at 9.5 to 10.5. (c) Preparation of silica-coated silver-containing colloidal silica Next, 5,233 g of the activated silicic acid aqueous solution obtained in step (a) above was added to the resulting silver-containing colloidal silica over a period of 1.9 hours to coat the surface of the silver-containing colloidal silica with a silica layer. The temperature was maintained at 95°C during the addition, and 10% by mass of sodium hydroxide was simultaneously added to maintain the pH at 9.5 to 10.5. After the addition was complete, the mixture was allowed to cool to room temperature, yielding 14,500 g of silica-coated silver-containing colloidal silica. The obtained silica-coated silver-containing colloidal silica was subjected to pressure filtration by pump circulation using a hollow fiber ultrafiltration membrane (Asahi Kasei Corporation, Microza (registered trademark) UF module SIP-1013) with a molecular weight cutoff of 6,000, and concentrated to a silica concentration of 35% by mass, recovering 1,200 g of silica-coated silver-containing colloidal silica. This silica-coated silver-containing colloidal silica had a pH of 9.9 at 25°C and an average particle size of 21 nm. Furthermore, ICP atomic emission spectrometry showed that the molar ratio of silicon to silver (Si / Ag) in the coating layer of the obtained silver-containing colloidal silica was 2,615. The average thickness of the mixed layer was 4 nm, and the average thickness of the silica layer was 2 nm.

[0062] Example 3 (a) Preparation of an aqueous solution of activated silicic acid containing silver nitrate An active silicic acid aqueous solution and an active silicic acid aqueous solution containing silver nitrate were prepared in the same manner as in Example 2. (b) Preparation of silver-containing colloidal silica Silver-containing colloidal silica was prepared in the same manner as in Example 2. (c) Preparation of silica-coated silver-containing colloidal silica To the resulting silver-containing colloidal silica, 8,415 g of the activated silicic acid aqueous solution obtained in step (a) above was added over 3.6 hours to coat the surface of the silver-containing colloidal silica with a silica layer. The temperature was maintained at 95°C during the addition, and 10% by mass of sodium hydroxide was simultaneously added to maintain the pH at 9.5 to 10.5. After the addition was complete, the mixture was allowed to cool to room temperature, yielding 16,500 g of silica-coated silver-containing colloidal silica. The obtained silica-coated silver-containing colloidal silica was subjected to pressure filtration by pump circulation using a hollow fiber ultrafiltration membrane (Asahi Kasei Corporation, Microza (registered trademark) UF module SIP-1013) with a molecular weight cutoff of 6,000, and concentrated to a silica concentration of 35% by mass, recovering 1,200 g of silica-coated silver-containing colloidal silica. This silica-coated silver-containing colloidal silica had a pH of 10 at 25°C and an average particle size of 25 nm. Inductively coupled plasma (ICP) emission spectrometry revealed that the molar ratio of silicon to silver (Si / Ag) in the coating layer of the obtained silver-containing colloidal silica was 4,503. The mixed layer had an average thickness of 4 nm, and the silica layer had an average thickness of 4 nm.

[0063] Example 4 (a) Preparation of copper sulfate-containing activated silicic acid aqueous solution 700 g of No. 3 sodium silicate (SiO: 28.8 wt%, Na2O: 9.7 wt%, HO: 61.5 wt%) was added to 4,375 g of deionized water and mixed uniformly to prepare diluted sodium silicate with a silica concentration of 4 wt%. This diluted sodium silicate was passed through a 4-liter column packed with H-type strongly acidic cation exchange resin (Amberlite® IR120B, manufactured by Organo Corporation) that had been previously regenerated with hydrochloric acid to dealkalize the mixture, yielding approximately 5,075 mL of an activated silicic acid solution with a silica concentration of 4 wt% and a pH of 3.1. 2.61 g of copper sulfate pentahydrate was added to 2,062 g of the resulting activated silicic acid solution with stirring to prepare a copper sulfate-containing activated silicic acid solution.

[0064] (b) Preparation of copper-containing colloidal silica 100 g of colloidal silica (Silicadol 30S, manufactured by Nippon Chemical Industry Co., Ltd.) with an average particle size of 9 nm was diluted with 3,000 g of deionized water and then heated to 95°C to obtain aqueous colloidal silica. A 10% by weight aqueous solution of sodium hydroxide was added to this aqueous colloidal silica to adjust the pH to 9.9, and the mixture was heated again and maintained at 95°C. 2,062 g of the copper sulfate-containing activated silicic acid aqueous solution was added over 2.2 hours, and the surface of the colloidal silica was coated with a mixed layer to obtain copper-containing colloidal silica. The temperature was maintained at 95°C during the addition, and 10% by weight sodium hydroxide was simultaneously added to maintain the pH at 9.5 to 10.5. (c) Preparation of silica-coated copper-containing colloidal silica Next, 3,788 g of the activated silicic acid aqueous solution obtained in step (a) above was added to the resulting copper-containing colloidal silica over 2.0 hours to coat the surface of the copper-containing colloidal silica with a silica layer. The temperature was maintained at 95°C during the addition, and 10% by mass of sodium hydroxide was simultaneously added to maintain a pH of 9.5 to 10.5. After the addition was completed, the mixture was allowed to cool to room temperature, yielding 10,053 g of silica-coated copper-containing colloidal silica. The obtained silica-coated copper-containing colloidal silica was subjected to pressure filtration by pump circulation using a hollow fiber ultrafiltration membrane (Microza (registered trademark) UF module SIP-1013, manufactured by Asahi Kasei Corporation) with a molecular weight cutoff of 6,000. The silica was concentrated to a silica concentration of 35% by mass, and 500 g of silica-coated copper-containing colloidal silica was recovered. This silica-coated copper-containing colloidal silica had a pH of 10 at 25°C and an average particle size of 20 nm. Furthermore, ICP optical emission spectroscopy revealed that the molar ratio of silicon to copper (Si / Cu) in the coating layer of the obtained copper-containing colloidal silica was 338. Furthermore, when the obtained copper-containing colloidal silica was analyzed by TEM-EDX, the elemental mapping image did not confirm the presence of copper in the mixed layer. On the other hand, XPS analysis of the copper-containing colloidal silica revealed a spectrum derived from copper oxide (CuO). These results confirmed that copper oxide (CuO) was uniformly and finely dispersed as the metal M in the mixed layer. The mixed layer had an average thickness of 2 nm, and the silica layer had an average thickness of 2 nm.

[0065] Comparative Example 1 The same procedure as in Example 1 was carried out, except that (c) the preparation of silica-coated silver-containing colloidal silica was not carried out, to obtain silver-containing colloidal silica having no silica layer. This silver-containing colloidal silica had a pH of 10 at 25°C and an average particle size of 18 nm. Furthermore, ICP atomic emission spectrometry showed that the molar ratio of silicon to silver (Si / Ag) in the mixed layer of the obtained silver-containing colloidal silica was 761. The average thickness of the mixed layer was 4 nm.

[0066] Comparative Example 2 The same method as in Example 4 was carried out, except that (c) the preparation of silica-coated copper-containing colloidal silica was not carried out, to obtain copper-containing colloidal silica having no silica layer. This copper-containing colloidal silica had a pH of 10 at 25°C and an average particle size of 15 nm. Furthermore, the results of ICP emission spectrometry showed that the molar ratio of silicon to copper (Si / Cu) in the mixed layer of the obtained copper-containing colloidal silica was 151. The average thickness of the mixed layer was 2 nm.

[0067] <Storage stability evaluation> The colloidal silica obtained in the Examples and Comparative Examples was placed in a 100 mL plastic bottle and sealed. The sealed plastic bottle was then left to stand at room temperature in a light-shielded thermostatic chamber. After 7 days of standing, the liquid in the plastic bottle was visually observed, and the storage stability was evaluated according to the following criteria. ○: No precipitate ×: Precipitation present

[0068] <Evaluation of discoloration resistance> The colloidal silica obtained in the Examples and Comparative Examples was diluted with ion-exchanged water to a SiO2 concentration of 10%, and filter paper was immersed in the resulting sample solution for 5 minutes. The resulting filter paper was air-dried in the dark, then exposed to sunlight for 24 hours, and the filter paper was visually observed and evaluated for discoloration resistance according to the following criteria. ○: No discoloration ×: Discoloration

[0069] [Table 1]

[0070] <Bactericidal effect test> Silver-containing silica sols were prepared by adding deionized water to the silver-containing colloidal silica obtained in Examples 1 and 2 and Comparative Example 1 to adjust the silica concentration to 20% by mass. Tests of the bactericidal effect against Escherichia coli and Staphylococcus aureus were carried out using the silver-containing silica sols in the following manner. Escherichia coli (NBRC3972) and Staphylococcus aureus (NBRC12732) were cultured on nutrient agar medium (manufactured by Eiken Chemical Co., Ltd.) at 35°C ± 1°C for 24 hours, and then diluted with purified water to obtain a bacterial count of 10. 7 ~10 8 A bacterial solution was prepared so that the concentration was 0.1 mL / mL. 0.1 mL of this bacterial solution was mixed with 10 mL of silver-containing silica sol, stirred, and then allowed to stand at 25°C for 5 minutes to obtain a test solution. This test solution was then inoculated into SCDLP medium (manufactured by Nippon Pharmaceutical Co., Ltd.) at a 10-fold dilution and cultured at 35°C ± 1°C for 48 hours. The number of viable bacteria after culture was counted, and the results are shown in Table 2.

[0071] [Table 2]

[0072] From the above results, it can be seen that the silver-containing colloidal silica obtained in Examples 1 and 2 and Comparative Example 1 all have excellent bactericidal properties, but the silver-containing colloidal silica obtained in Examples 1 to 3 is less likely to produce precipitates due to aggregation of colloidal particles, and thus has the effect of improving storage stability. Furthermore, it can be seen that the silver-containing colloidal silica obtained in Examples 1 to 3 also has excellent discoloration resistance. Furthermore, it can be seen that the copper-containing colloidal silica obtained in Example 4 has excellent storage stability and discoloration resistance compared to Comparative Example 2.

Claims

1. A metal-containing colloidal silica having a mixed layer in which a metal M is dispersed in silica, the mixed layer is located between the silica particle serving as the core material and the silica layer located on the surface of the metal-containing colloidal silica; The metal M is at least one selected from Ag and Cu, the molar ratio of silicon to metal M (Si / M) in the coating layer including the mixed layer and the silica layer is 10 or more and 10,000 or less; A metal-containing colloidal silica in which a metal M is uniformly and finely dispersed in a mixed layer. Idal silica.

2. 2. The metal-containing colloidal silica according to claim 1, wherein the mixed layer has a thickness of 1 nm or more and 50 nm or less.

3. 3. The metal-containing colloidal silica according to claim 1, wherein the silica layer has a thickness of 0.5 nm or more and 10 nm or less.

4. 4. The metal-containing colloidal silica according to claim 1, wherein the particle diameter of the silica particles is 0.5 nm or more and 100 nm or less.

5. 5. The metal-containing colloidal silica according to claim 1, wherein the molar ratio of silicon to metal M (Si / M) in the mixed layer is 5 or more and 5,000 or less.

6. An agent containing the metal-containing colloidal silica according to any one of claims 1 to 5.

7. A resin composition comprising the metal-containing colloidal silica according to any one of claims 1 to 5.

8. A paint containing the metal-containing colloidal silica according to any one of claims 1 to 5.

9. (a) adding a metal salt compound to an aqueous solution of activated silicic acid to prepare an aqueous solution of activated silicic acid containing a metal salt compound; (b) reacting the metal salt compound-containing activated silicic acid aqueous solution under alkaline conditions in the presence of colloidal silica to form a mixed layer on the surface of the colloidal silica in which the metal is uniformly and finely dispersed in the silica; and (c) reacting the colloidal silica forming the mixed layer with an aqueous solution of activated silicic acid under alkaline conditions to form a silica layer on the surface of the mixed layer; A method for producing metal-containing colloidal silica, comprising: The method for producing metal-containing colloidal silica, wherein the metal of the metal salt compound is at least one selected from Ag and Cu.

10. 10. The method for producing metal-containing colloidal silica according to claim 9, wherein the activated aqueous silicic acid solution is obtained by contacting an aqueous silicic acid solution with a cation exchange resin.

11. 11. The method for producing metal-containing colloidal silica according to claim 9, wherein the metal salt compound is at least one selected from the group consisting of nitrates, chlorides, acetates, phosphates, and sulfates.

12. 12. The method for producing metal-containing colloidal silica according to claim 9, further comprising, after the step (c), a step of concentrating the metal-containing colloidal silica.

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