KR20190020789A - Metal nanoparticle water dispersion - Google Patents

Abstract

The present invention relates to a process for producing a composite material comprising a composite of a metal nanoparticle (X) and an organic compound (Y) (the composite in which the organic compound (Y) is polyvinylpyrrolidone) and polyvinylpyrrolidone (Z) Thereby providing a metal nanoparticle aqueous dispersion. The organic compound (Y) is a monomer mixture containing a (meth) acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, A dispersion of metal nanoparticle water dispersion. The dispersion of metal nanoparticles in water has excellent dispersion stability even when a thermal load such as heating or melting after freezing is applied which may occur during storage or transportation, Surface activity.

Description

Metal nanoparticle water dispersion

The present invention has an excellent dispersion stability even when a thermal load such as warming or melting after freezing is applied, which may occur during storage or transportation, and has a sufficient adsorptivity to a substrate, Metal nanoparticle water dispersion.

The metal nanoparticles are industrially used as a catalyst, an antibacterial agent, and a conductive material. The main form is paste, ink, or paint in which metal nanoparticles are dispersed and stabilized, and metal nanoparticles can be added to arbitrary sites of the target substrate by a method such as printing, coating, or immersion treatment.

As the solvent for dispersing the metal nanoparticles, both an organic solvent and an aqueous solvent have been studied, and the metal nanoparticles can be selected depending on the purpose or process for imparting the metal nanoparticles to the substrate. However, from the viewpoint of reducing the load on the environment, It is preferable to use a solvent.

One of the basic properties required for such an aqueous dispersion of metal nanoparticles is long-term dispersion stability. In general, this can be increased by increasing the amount of the dispersant in the dispersion. However, the surplus dispersant tends to adversely affect the surface activity of the metal nanoparticles and the adsorption to the substrate, and the inherent functions of the material (catalyst activity, Activity, conductivity, etc.) may be damaged.

As a technique for achieving both dispersion stability and function, a method of using a polymer dispersant having a high dispersing performance instead of increasing the amount of a dispersant has been disclosed (see, for example, Patent Document 1) The aqueous dispersion has an adsorption property to a substrate and a surface activity which can be used as a catalyst for electroless plating (for example, see Patent Document 2).

In a temperature range from room temperature to a refrigerated state, long-term dispersion stability and function can be achieved by a method of using a high-performance dispersant in a minimum amount. On the other hand, depending on the storage environment and transportation conditions of the product, freezing of metal nanoparticle aqueous dispersion and temperature rise are assumed. In the conventional aqueous dispersion of silver nanoparticles, there is a problem of irreversible coagulation due to such a thermal load and a performance deterioration accompanying the irregular flocculation. Therefore, in order to maintain the quality of the metal nanoparticle dispersion, the conditions of use are limited, and temperature control is required during storage and transportation, and management cost is also a problem.

Japanese Patent No. 4697356 Japanese Patent No. 5648232

A problem to be solved by the present invention is to provide a resin composition which has excellent dispersion stability even when a thermal load such as a temperature rise or melting after freezing is applied which may occur during storage or transportation, And a metal nanoparticle dispersion liquid containing the metal nanoparticles.

The inventors of the present invention conducted intensive studies in order to solve the above-mentioned problems, and as a result, they found that the aforementioned problems can be solved by constituting the dispersion of metal nano-particles in a specific composition, thereby completing the present invention.

That is, the present invention relates to a process for producing a composite material comprising a composite of metal nanoparticles (X) and an organic compound (Y) (excluding the composite wherein the organic compound (Y) is polyvinylpyrrolidone), polyvinylpyrrolidone (Z) The present invention also provides a dispersion of metal nanoparticles in water.

INDUSTRIAL APPLICABILITY The metal nanoparticle aqueous dispersion of the present invention can improve the dispersion stability without deteriorating the adsorptivity and activity of the silver nanoparticles to the substrate. Therefore, it is possible to prevent deterioration (aggravation or deterioration of the liquid appearance) of the material even if a thermal load such as melting or melting after warming or freezing is applied without lowering the usability as an industrial material. As described above, since the metal nano-particle water dispersion of the present invention has excellent dispersion stability against the thermal load, it is possible to reduce the temperature management cost in transportation (land transportation, shipping, air supply) and storage.

Fig. 1 shows the extinction spectrum of the silver nanoparticle dispersion liquid before heating (Example 1) and after heating (Example 1 and Comparative Example 1).
Fig. 2 is an extinction spectrum of the silver nanoparticle dispersion liquid before freezing (Example 1) and after a freeze-thaw cycle (Example 1 and Comparative Example 1).

The metal nano-particle water dispersion of the present invention is a dispersion of metal nanoparticles in water, wherein a composite of the metal nanoparticles (X) and the organic compound (Y) (excluding the composite in which the organic compound (Y) is polyvinylpyrrolidone), polyvinylpyrrolidone (Z).

Examples of the metal constituting the metal nanoparticles (X) include, for example, silver, copper, palladium, alloys thereof, and the like. Examples of the metal nanoparticles (X) include silver core copper shell particles, copper shells, core particles, particles in which silver is partially substituted with palladium, particles in which copper is partially substituted with palladium, and the like. These metals or alloys may be used singly or in combination of two or more. These metals or alloys may be appropriately selected in accordance with the purpose, but silver and copper are preferable when they are used for the purpose of forming wiring and the conductive layer, and silver, copper and palladium are preferable from the viewpoint of the catalytic function . From the viewpoint of cost, silver, copper, an alloy thereof, some substituents, or a mixture thereof is preferable.

The shape of the metal nanoparticles (X) is not particularly limited so long as the dispersion stability in an aqueous medium is not impaired, and nanoparticles of various shapes can be appropriately selected depending on the purpose. Specifically, particles of a spherical shape, a polyhedral shape, a plate shape, a rod shape, and a combination thereof can be cited. As the metal nanoparticles (X), a single shape or a mixture of plural shapes can be used. Among these shapes, spherical or polyhedral particles are preferable from the viewpoint of dispersion stability.

The metal constituting the metal nanoparticles (X) is a metal in which the organic compound (Y) is adsorbed on the surface of the metal nanoparticles (X) in order to maintain a stable and uniformly dispersed state for a long period of time in an aqueous dispersion medium Is used as a composite of the metal nanoparticles (X) and the organic compound (Y). The organic compound (Y) may be appropriately selected and used depending on the purpose, but from the viewpoint of dispersion stability, the compound (Y1) having an anionic functional group is preferable. The organic compound (Y) is other than the polyvinyl pyrrolidone (Z) to be described later.

The compound (Y1) having an anionic functional group is a compound having at least one anionic functional group in the molecule. Further, as long as the dispersion stability is not impaired, a compound having a cationic functional group in addition to the anionic functional group in the molecule may be used. The compound (Y1) having an anionic functional group may be used singly or in combination of two or more.

The compound (Y1) having an anionic functional group is preferably a compound having an anionic functional group such as a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, or a sulfonic acid group from the viewpoint of achieving both long-term dispersion stability in an aqueous dispersion medium and maintaining activity of the surface of metal nanoparticles after being imparted on a substrate. (Y2) of a monomer mixture (I) containing a (meth) acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of a sulfonic acid group and a sulfinic acid group.

The polymer (Y2) may be a single polymer or a copolymer. In the case of a copolymer, it may be a random copolymer or a block copolymer.

Since the polymer (Y2) has at least one anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, a sulfinic acid group and a sulfinic acid group, the metal nanoparticles (X (Y2) and the metal nano-particles (X) in water, and it is possible to prevent agglomeration of the colloid particles due to charge repulsion between the particles, The composite of the particles (X) can be stably dispersed.

It is preferable that the polymer (Y2) has three or more anionic functional groups in one molecule because adsorption to the metal nanoparticles (X) and dispersion stability in an aqueous dispersion can be further improved.

The weight average molecular weight of the polymer (Y2) is preferably in the range of 3,000 to 20,000, more preferably in the range of 4,000 to 8,000, because adsorption to the metal nanoparticles (X) and dispersion stability in the aqueous dispersion can be further improved More preferable.

Further, when a polyoxyalkylene chain such as polyethylene glycol chain is introduced into the polymer (Y2), a collision protection effect due to the steric repulsion effect can be utilized at the same time as the repulsive force is developed by the charge, and the dispersion stability is further improved desirable.

(Y2) having a polyethylene glycol chain can be obtained by copolymerizing a (meth) acrylic acid-based monomer having a polyethylene glycol chain in the monomer mixture (I) and a (meth) acrylic acid-based monomer having an anionic group, Can be easily obtained.

In particular, the polymer (Y2) polymerized by using a (meth) acrylic acid-based monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more has a high ability to stabilize nano-particles of noble metals, particularly silver and copper, Which is preferable. Such a polymer having an anionic functional group and a polyethylene glycol chain can be easily synthesized by, for example, the methods described in Japanese Patent No. 4697356, Japanese Patent Application Laid-Open No. 2010-209421, and the like.

The weight-average molecular weight of the (meth) acrylic acid-based monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more is preferably in the range of 1,000 to 2,000. When the weight average molecular weight is in this range, the water dispersibility of the composite with the metal nanoparticles (X) becomes better.

As a more specific synthesis method of the polymer (Y2) having a phosphoric acid group and a polyethylene glycol chain, for example, commercially available 2-methacryloyloxyphosphate (for example, " Ester P-1M ") and a commercially available methacrylic acid ester monomer having a polyethylene glycol chain (for example," Brenma PME-1000 "manufactured by Nichiyu Kagaku K.K.) in the presence of a polymerization initiator Initiator " V-59 ").

If the ratio of the (meth) acrylic acid ester monomer having a phosphoric acid group is less than 30 mass% in the monomer mixture (I), the content of the (meth) acrylic acid ester monomer having a polyethylene glycol chain not involved in the protection of the metal nano- Generation of by-products such as a single polymer of the monomer is suppressed, and dispersion stability by the obtained polymer (Y2) is improved.

The monomer mixture (I) may contain a third polymerizable monomer other than a (meth) acrylic acid-based monomer having an anionic group and a (meth) acrylic acid-based monomer having a polyethylene glycol chain. When the third polymerizable monomer is a hydrophobic monomer, the amount of the third polymerizable monomer to be used is preferably 20 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the (meth) acrylic acid monomer having a polyethylene glycol chain, And more preferably not more than 1 part by mass. The range in which the third polymerizable monomer is not a hydrophobic monomer is not limited to this range.

As described above, the weight average molecular weight of the polymer (Y2) is preferably in the range of 3,000 to 20,000, but when the (meth) acrylic acid monomer having a polyethylene glycol chain is used in combination, the polymer (Y2) , And a molecular weight distribution. The smaller weight average molecular weight does not include the structure derived from the (meth) acrylic acid monomer having a polyethylene glycol chain, so that it does not contribute to the dispersion stability in the case of dispersing the composite with the metal nanoparticles (X) in an aqueous medium From this viewpoint, the weight average molecular weight of the polymer (Y2) is more preferably 4,000 or more. On the contrary, when the weight average molecular weight is large, the weight average molecular weight of the polymer (Y2) is 8,000 or less from the viewpoint that coarsening of the composite with the metal nanoparticles (X) tends to easily occur and precipitation tends to occur in the catalyst liquid More preferable.

In order to adjust the weight average molecular weight of the polymer (Y2) within the above-mentioned range, a known chain transfer agent described in, for example, Japanese Patent Application Laid-Open No. 2010-209421 may be used. .

As the complex used for the metal nanoparticle aqueous dispersion of the present invention, a complex with metal nano-particles (X) such as silver, copper, and palladium prepared by using the above-mentioned polymer (Y2) as a colloid protective agent can be used.

As a method of preparing the composite used for the metal nanoparticle aqueous dispersion of the present invention, for example, the polymer (Y2) may be dissolved or dispersed in an aqueous medium, and thereafter a solution of silver nitrate, copper acetate, palladium nitrate The metal compound is reduced by mixing a reducing agent and a reducing agent so that the reduced metal is a nano-sized particle (fine particle having a nanometer order size) And simultaneously obtaining an aqueous dispersion of the metal nanoparticles (X) complexed with the polymer (Y2). When a complexing agent is used, it may be mixed with a reducing agent at the same time.

The composite of the metal nanoparticles (X) and the organic compound (Y) used in the present invention is preferably a mixture of the metal nanoparticles (X) and the organic compound (Y) in terms of wire adhesion, favorable adhesion at low temperature, Is preferably in the range of 0.5 to 100 nm.

The average particle diameter of the metal nanoparticles (X) can be estimated by a transmission electron microscope photograph, and the average value of 100 of them is in the range of 0.5 to 100 nm is, for example, described in Japanese Patent No. 4697356 Can be easily obtained by the method described in publications, Japanese Patent Application Laid-Open No. 2010-209421, and the like. The metal nanoparticles (X) thus obtained can be obtained by being protected by the polymerizate (Y2) and being independently present one by one and being dispersed in an aqueous dispersion medium.

The average particle diameter of the metal nanoparticles (X) is determined by the kind of the metal compound, the molecular weight, the chemical structure and the amount of the organic compound (Y) as the colloid protecting agent, the kind and amount of the complexing agent and the reducing agent, And the like can be easily controlled by referring to the embodiments described in the above patent documents and the like.

The content of the organic compound (Y) in the composite of the organic compound (Y) and the metal nanoparticle (X) is preferably in the range of 1 to 30 mass%, more preferably in the range of 2 to 20 mass% Do. That is, the metal nanoparticles (X) occupy most of the mass of the composite in the wiring, the conductive layer formation, and various catalysts.

The composite in which the metal nanoparticles (X) are protected with the polymer (Y2) is dispersed in the range of about 0.01 to 70 mass% in a mixed solvent of an aqueous medium, that is, water or an organic solvent compatible with water The metal nanoparticles (X) and the organic compound (Y) can be mixed with the polyvinyl pyrrolidone (Z) in the dispersion even when a thermal load such as melting is applied by heating or after freezing by coexistence of the polyvinyl pyrrolidone ) Can maintain excellent dispersion stability, high adsorptivity to a substrate, and surface activity.

Although the mechanism for exhibiting such an effect by the coexistence of polyvinyl pyrrolidone (Z) is not certain, from the correlation with the coagulation mechanism of the metal nanoparticles (X), the following conjecture can be made. The coagulation of the metal nanoparticles (X) in the dispersion by heating is attributed to the fact that the temperature of the organic compound (Y) tends to shift from the surface of the metal nanoparticles (X) And the collision frequency of the metal nanoparticles (X) exposed on the active surface is increased. On the other hand, coagulation by freezing occurs when the dispersion of metal nanoparticles is frozen, and when the water in the dispersion is crystallized into ice, crystal growth occurs while excluding metal nanoparticle complexes, which are contaminants in water, It can be considered that the metal nanoparticle complex is extremely concentrated. Therefore, in order to inhibit irreversible agglomeration of the particles by heating or freezing, it is considered effective to allow a compound having adsorbed on the surface of the metal nanoparticles (X) to coexist in a dispersion.

The fact that the metal nanoparticle composite is a driving force adsorbed on a substrate is mainly an electrostatic interaction between the charge on the surface of the substrate and the charge of the metal nanoparticle complex. Therefore, when an additive having the same sign as that of the metal nanoparticle complex is allowed to coexist, it is considered that the additive and the metal nanoparticle complex are competing with the adsorption point on the substrate to inhibit the adsorption of the metal nanoparticle complex to the substrate . Conversely, when the metal nanoparticle complex and the additive having the opposite sign are coexisted, it is conceivable that the metal nanoparticle complexes shield the electrostatic repulsion between the metal nanoparticle complexes and cause agglomeration of the metal nanoparticle complex. Therefore, in order to maintain the dispersion stability and the high adsorptivity to the substrate, it is considered that it is preferable to use a nonionic compound as an additive as a compound adsorbing and protecting the metal nanoparticles (X).

Further, as the compound having a property of adsorbing and protecting the metal nanoparticles (X) strongly adsorbs to the metal nanoparticles (X), the metal nanoparticles (X) It is considered that it becomes more difficult to expose the active surface of the substrate X. Therefore, in order to maintain the surface activity, it is considered that it is preferable that the metal nanoparticles (X) do not have a strong adsorption property as a compound having a property of adsorbing and protecting the metal nanoparticles (X).

As described above, the compound having a property of adsorbing and protecting the metal nanoparticles (X) is not very weak to the metal nanoparticles (X), has adsorptivity that is not too strong, is water-soluble, , Excellent dispersion stability, high adsorption to a substrate, and surface activity of the metal nanoparticles (X). Polyvinyl pyrrolidone (Z) conforms to this condition.

The dispersion of aqueous metal nano-particles of the present invention contains polyvinylpyrrolidone (Z) as an essential component in addition to the complex of the metal nanoparticles (X) and the organic compound (Y), but a mixture of polyvinylpyrrolidone The method is not particularly limited, but a method of adding polyvinylpyrrolidone (Z) to an aqueous dispersion of a composite of the metal nanoparticles (X) and the organic compound (Y) is simple and preferable.

The polyvinylpyrrolidone (Z) may be added to an aqueous dispersion of a complex of the organic compound (Y) and the metal nanoparticle (X) obtained by the above-mentioned preparation method, and used as an excess complexing agent, a reducing agent, It is possible to use a purification process such as a counter-ion or the like contained in a metal compound by various purification methods such as ultrafiltration, precipitation, centrifugation, vacuum distillation and vacuum drying, Volatile matter) or an aqueous medium may be changed so as to be newly prepared as a dispersion. When it is used for mounting purpose such as electronic circuit formation, it is preferable to use a method of adding to the aqueous medium through the above-described purification step.

The weight average molecular weight (hereinafter abbreviated as " Mw ") of the polyvinylpyrrolidone (Z) used in the present invention is higher than that of the polyvinylpyrrolidone (Z) From the viewpoint of providing a metal nanoparticle aqueous dispersion in which the surface activity is simultaneously maintained, it is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 500,000. The weight average molecular weight is a value obtained by gel permeation chromatography (GPC).

The polyvinylpyrrolidone used in the present invention may be a product synthesized using a method known in the art, or a commercially available product may be used. Examples of commercially available products include "Pittscol K-30" (Mw: 40,000) and "Pittschall K-90" (Mw: 360,000) manufactured by Dai-ichi Kogyo Seiyaku Co.,

The amount of the polyvinyl pyrrolidone (Z) to be added is not particularly limited, even if the metal nanoparticles (Z) are melted after being warmed or frozen, from the viewpoint of simultaneously satisfying the dispersion stability, the high adsorptivity to the substrate, Is preferably in the range of 0.1 to 20 mass%, more preferably in the range of 0.5 to 15 mass parts, more preferably in the range of 1 to 10 mass parts, per 100 mass parts of the composite of the organic compound (X) and the organic compound (Y) , And a range of 2 to 8 is particularly preferable.

When the metal nano-particle water dispersion of the present invention is used as an ink or a coating solution for wiring or forming a conductive layer, the concentration of the complex in the aqueous dispersion is preferably in the range of 0.5 to 40 mass% The range of mass% is more preferable.

As a method for imparting a composite of the metal nanoparticles (X) and the organic compound (Y) on a substrate in the case where the dispersion of the metal nanoparticle water dispersion of the present invention is formed as an ink or a coating liquid and a wiring or a conductive layer is formed, And various printing and coating methods for the known art may be appropriately selected in accordance with the shape, size, degree of ferrofluorescence, etc. of the substrate to be used. Concretely, it is possible to use various methods such as a gravure method, an offset method, a gravure offset method, a convex plate method, a convex plate inversion method, a flexo method, a screen method, a microcontact method, a reverse method, an air doctor coater method, A transfer coater method, a transfer coater method, a kiss coater method, a cast coater method, a spray coater method, an ink jet method, a die method, a spin coater method, and a bar coater method.

When the composite is printed or applied on a substrate to form a wiring or a conductive layer by applying the composite on the substrate, the printed or coated substrate is dried and fired to directly form a wiring or a conductive layer Alternatively, electroless plating or electrolytic plating may be performed.

The metal nano-particle water dispersion of the present invention can also be used as a catalyst solution for electroless plating, which is used in an ordinary plating treatment step by an immersion treatment. When the metal nano-particle water dispersion of the present invention is used as a catalyst for electroless plating, the amount of adsorption to the object to be plated can be ensured and the adhesion of the plating film to the object to be plated can be improved. The concentration of the complex in the particle water dispersion is preferably in the range of 0.05 to 5 g / L, and more preferably in the range of 0.02 to 2 g / L in view of economical efficiency.

By subjecting the surface of the metal nano-particle water dispersion of the present invention to the surface to which the composite is adhered on the surface thereof by the above-described method, a metal coating can be efficiently formed on the surface thereof by performing a known electroless plating treatment have.

Examples of the aqueous medium used in the metal nanoparticle aqueous dispersion of the present invention include water alone or a mixed solvent of an organic solvent compatible with water. The organic solvent may be selected without particular limitation as long as the dispersion stability of the composite is not impaired and the object to be plated is not damaged. Specific examples of the organic solvent include methanol, ethanol, isopropanol, and acetone. These organic solvents may be used singly or in combination of two or more.

In the aqueous medium, the mixing ratio of the organic solvent is preferably 50 mass% or less from the viewpoint of dispersion stability of the composite, and more preferably 30 mass% or less from the viewpoint of convenience in the plating process.

The base material for imparting the composite of the metal nanoparticles (X) and the organic compound (Y) using the metal nanoparticle aqueous dispersion of the present invention is not particularly limited and examples of the material include glass fiber reinforced epoxy , Epoxy-based insulating material, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, liquid crystal polymer (LCP), cycloolefin polymer (COP), polyetheretherketone (PEEK) (PPS), a glass, a ceramic, a metal oxide, a metal, a paper, a synthetic or natural fiber, and the like, A fibrous shape, a tubular shape, or the like.

The metal nanoparticle aqueous dispersion of the present invention can form a wiring, a conductive layer, or the like by applying a composite of metal nanoparticles and an organic compound to a substrate by a simple method such as printing, coating, or dipping, As a catalyst solution for electroless plating, it is preferably usable.

(Example)

Hereinafter, the present invention will be described in detail with reference to Examples.

[Analysis of sample]

The analysis of the samples was carried out using the following apparatuses. The transmission electron microscope (TEM) observation was carried out with " JEM-1400 " manufactured by Nippon Denshoku Chemical Co., The extinction spectrum was measured by "Nanodrop ND-1000" manufactured by Thermo Fisher Scientific.

(Synthesis Example 1: Synthesis of polymer (Y2-1) having anionic functional group)

32 parts by mass of methyl ethyl ketone (hereinafter abbreviated as " MEK ") and 32 parts by mass of ethanol were charged into a four-necked flask equipped with a thermometer, a stirrer and a reflux condenser and heated to 80 DEG C while stirring under a nitrogen stream. Next, 20 parts by mass of phosphoroxyethyl methacrylate ("Light Ester P-1M" manufactured by Kyoeisha Chemical Co., Ltd.), 20 parts by mass of methoxypolyethylene glycol methacrylate (manufactured by Nissui Chemical Industries, 80 parts by mass of PME-1000, molecular weight 1,000), 4.1 parts by mass of methyl 3-mercaptopropionate and 80 parts by mass of MEK, and a polymerization initiator (V-65 of Wako Pure Chemical Industries, Azobis (2,4-dimethylvaleronitrile)) and 5 parts by mass of MEK were each added dropwise over 2 hours. After completion of the dropwise addition, 0.3 part by mass of a polymerization initiator ("Perbutyl O" manufactured by Nichifusa Chemical Co., Ltd.) was added twice every 4 hours, and the mixture was stirred at 80 ° C for 12 hours. Water was added to the resulting resin solution to effect phase transfer phase emulsification, depressurized and solvent removed, and then water was added to adjust the concentration to obtain an aqueous solution of a polymer (Y2-1) having a nonvolatile content of 76.8% by mass. The polymer (Y2-1) has a methoxycarbonylethylthio group, a phosphoric acid group and a polyethylene glycol chain, and has a weight average molecular weight (polystyrene conversion value measured by gel permeation chromatography) of 4,300, 97.5 mg KOH / g.

(Preparation Example 1: Preparation of silver nanoparticle water dispersion)

463 g (4.41 mol) of an 85% by mass aqueous solution of N, N-diethylhydroxylamine, 30 g of an aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (23 g as the polymer (Y2-1)) and 1,250 g of water To prepare a reducing agent solution.

Next, 15 g of the aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (11.5 g as the polymer (Y2-1)) was dissolved in 333 g of water, 500 g (2.94 mol) of silver nitrate was dissolved in 833 g of water, Add and stir well. To the mixture was added dropwise the reducing agent solution obtained above at room temperature (25 占 폚) over 2 hours. The obtained reaction mixture was filtered through a membrane filter (pore size 0.45 micrometer), and the filtrate was circulated through a hollow fiber type ultrafiltration module ("MOLSEP module FB-02 type" manufactured by Daicel Membrane Systems Co., Ltd., fraction molecular weight: 150,000) The amount of water corresponding to the amount of the filtrate to be filtrated (flowed out) was often added and purified. After confirming that the conductivity of the filtrate became 100 mu S / cm or less, the water injection (pouring) was stopped and concentration was performed. The concentrate was recovered to obtain an aqueous dispersion of a silver nanoparticle-containing complex having a nonvolatile content of 36.7 mass%. The average particle size of the composite by the dynamic light scattering method was 39 nm, and it was assumed to be 10 to 40 nm from the transmission electron microscope (TEM) image.

(Example 1)

272.5 parts by mass of the silver nanoparticle aqueous dispersion obtained in Preparation Example 1 (100 parts by mass as a silver nanoparticle-containing composite) was coated with polyvinyl pyrrolidone ("Pittschall K-30" manufactured by Daiichi Kyoei Co., Ltd., Mw: (4 parts by mass as polyvinylpyrrolidone) were added to 20 mass% of a 20 mass% aqueous solution of silver nanoparticles (manufactured by Nippon Aerosil Co., Ltd., 40,000), uniformly stirred and ion-exchanged water was added so that the concentration of the silver nanoparticle- An aqueous dispersion (1) was obtained.

[Appearance Evaluation of Silver Nanoparticle Water Dispersion]

As an index for evaluating the dispersion stability of the silver nanoparticle dispersion (1) obtained above, the appearance was visually observed to confirm the presence or absence of a suspension. Further, regarding the appearance evaluation after the heating test described later or the freeze-thaw test, changes in color were also confirmed.

[Evaluation of Adhesion to Substrate and Measurement of Coating Coverage Ratio]

As an index for determining the activity of silver nanoparticles, electroless copper plating treatment was performed using the metal nanoparticles imparted on the substrate as a catalyst.

A slide glass was prepared as a substrate and the slide glass was immersed in a 2 mass% aqueous solution of polyethyleneimine ("Epomin SP-200" manufactured by Nippon Shokubai Co., Ltd.) for 1 minute and taken out. And then dehydrated by an air blow to obtain a surface-treated slide glass.

Next, as an electroless copper plating bath, an aqueous solution containing 0.04 mol / L of a copper sulfate hydrogencarbonate, 0.04 mol / L of formaldehyde, and 0.08 mol / L of disodium ethylenediaminetetraacetate was adjusted to pH 12.3 with sodium hydroxide A solution was prepared and heated to 55 캜.

The surface-treated slide glass was immersed in a 200-fold dilution of the silver nanoparticle dispersion (1) obtained above at 25 캜 for 10 minutes to adsorb the silver nanoparticles on the surface of the slide glass. Since the silver nanoparticles are colored at this time, the more the amount of silver nanoparticles adsorbed on the surface of the slide glass, the more the color of the slide glass turns yellow. The degree of the coloration was visually observed, and the adsorbability of the base material was evaluated according to the criteria described below, with no additives added (Comparative Example 1) as a standard.

 ○: Equivalent to that of no addition of additives

 DELTA: coloration is less than that with no additive added

 X: Almost no coloration, close to colorless transparent

Next, the slide glass on which the silver nanoparticles were adsorbed was taken out and rinsed for 1 minute, and then immersed in the electroless copper plating bath prepared above for 30 minutes while stirring the air, followed by washing with water for 1 minute, Copper plating was carried out.

Black and white dichroism was performed on the basis of brightness by image processing of photographs of electroless copper plated slide glasses and the coating coverage rate was calculated from the area of the plated portion. From the obtained coating coverage, the activity of the silver nanoparticle composite was evaluated. Here, when the catalytic activity is sufficiently high, the plating is deposited on the entire surface of the base material, and when the activity is lowered, the precipitation area of the plating is lowered. Therefore, it was judged that the activity of the silver nanoparticle composite was good, indicating that the entire surface of the slide glass was plated (plated coverage rate: 100%).

[Heating test]

The silver nanoparticle water dispersion (1) obtained above was placed in a 50 mL screw tube and sealed. Next, this was heated in a thermostatic chamber at 50 DEG C for 14 days. After heating, the appearance was evaluated in the same manner as the above-mentioned method. The silver nanoparticle aqueous dispersion (1) before and after heating was diluted with the silver nanoparticle composite to a concentration of 50 ppm, and the absorption spectrum at the time of extinction was measured (see Fig. 1). The surface of the silver nanoparticle dispersion Absorption spectra were observed. It was confirmed that the dispersion state of the silver nanoparticles in the silver nanoparticle dispersion liquid 1 was not changed since the spectral shape did not change before and after heating when the silver nanoparticles aggregated.

Next, the silver nanoparticle aqueous dispersion (1) after heating was diluted 200 times, and the coating coverage was measured in the same manner as described above.

[Freeze-thaw test]

The silver nanoparticle water dispersion (1) obtained above was placed in a 50 mL screw tube and sealed. Next, this was contacted with a dry ice chip for 5 minutes to freeze it, and thawed at room temperature. The operation of freezing and thawing was set as one cycle, and the operation was repeated three times. After three cycles of freezing and thawing, the appearance was evaluated in the same manner as described above. The silver nanoparticle dispersion (1) after three cycles of freezing and thawing operations before freezing was subjected to extracellular absorption spectroscopy (see Fig. 2). It was confirmed from the measurement results of the absorption spectrum at the time of extinction that the dispersion state of the silver nanoparticles in the silver nanoparticle dispersion liquid 1 was not changed even if freezing and thawing were repeated.

Next, the silver nano-particle water dispersion (1) after three cycles of freezing and thawing operations was diluted 200-fold, and the coating coverage was measured in the same manner as described above.

[Overall evaluation]

From the results of the heating test and the freeze-thaw test performed in the above, the dispersion stability and the adsorbability to the substrate were evaluated, and a comprehensive evaluation was conducted according to the following criteria.

 ?: There was no problem in the dispersion stability and the adsorption to the substrate in the heating test and the freeze-thaw test

 X: There were problems in dispersion stability and adsorption to substrate in the heating test and the freeze-thaw test

(Example 2)

The same procedure as in Example 1 was carried out except that 20 mass% aqueous solution of polyvinylpyrrolidone used in Example 1 was changed from 20 mass parts to 10 mass parts (2 mass parts as polyvinylpyrrolidone) An aqueous dispersion (2) was obtained. The obtained silver nanoparticle water dispersion (2) was subjected to measurement and evaluation in the same manner as in Example 1.

(Example 3)

The same procedure as in Example 1 was carried out except that 20 mass% aqueous solution of polyvinylpyrrolidone used in Example 1 was changed from 20 mass parts to 50 mass parts (10 mass parts as polyvinyl pyrrolidone) An aqueous dispersion (3) was obtained. The obtained silver nanoparticle water dispersion (3) was subjected to measurement and evaluation in the same manner as in Example 1.

(Example 4)

The polyvinylpyrrolidone used in Example 1 was changed to polyvinylpyrrolidone ("Pittschall K-90" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Mw: 360,000), and the concentration of the aqueous solution was changed to 10 The procedure of Example 1 was otherwise repeated to obtain a silver nanoparticle aqueous dispersion (4). The obtained silver nanoparticle water dispersion (4) was subjected to measurement and evaluation in the same manner as in Example 1.

(Comparative Example 1)

Ion exchange water was added to the silver nanoparticle aqueous dispersion obtained in Preparation Example 1 to prepare a silver nanoparticle aqueous dispersion (R1) so that the concentration of the silver nanoparticle-containing complex in the aqueous dispersion became 10 mass%. The obtained silver nanoparticle aqueous dispersion (R1) was subjected to measurement and evaluation in the same manner as in Example 1. The silver nanoparticle water dispersion (R1) was diluted so that the concentration of the silver nanoparticle complex was 50 ppm, and the absorption spectrum at the time of exhalation before heating was measured, and there was no difference from that of Example 1 in which polyvinylpyrrolidone was added . Further, when the extinction spectrum after heating was measured, the spectrum shape was not changed (see Fig. 1).

On the other hand, when this silver nanoparticle dispersion liquid R1 was frozen and thawed for one cycle, the liquid color when diluted to 50 ppm changed from yellow to black green. When the absorption spectrum of the liquid changed to black green was measured, the intensity of the plasmon absorption peak based on agglomeration of the silver nanoparticles was decreased, and the increase in absorption on the long wavelength side was confirmed, and it was confirmed that the dispersion state deteriorated 2).

(Comparative Examples 2 to 15)

The silver nanoparticle aqueous dispersions (R2) to (R15) were prepared in the same manner as in Example 1 except that the polyvinylpyrrolidone used in Example 1 was changed to the additives and the addition amounts shown in Table 1. The silver nanoparticle water dispersions (R2) to (R15) thus obtained were subjected to measurement and evaluation of dispersion stability and activity as in Example 1. [

Table 1 shows the addition amounts of the silver nanoparticle water dispersions (1) to (4) and (R1) to (R15) obtained in Examples 1 to 4 and Comparative Examples 1 to 15, The addition amount in Table 1 represents the amount of the additive to 100 parts by mass of the silver nanoparticle-containing composite (composite of metal nanoparticles (X) and organic compound (Y)).

[Table 1]

Details of the additives described in Table 1 are as follows.

Polyethylene glycol: weight average molecular weight 6,000

Polyvinyl alcohol: degree of polymerization of 500, degree of saponification of 86 to 90 mol%

Polymer (Y2-1): The polymer obtained in Synthesis Example 1 was directly used as an additive.

The change in appearance after the heating test in Table 1 indicates that the silver nanoparticles were suspended in gray by agglomeration of the silver nanoparticles. The reason why the change in appearance after the freeze-thaw test is "present" indicates that the liquid color changed from yellow to black green due to the change in plasmon absorption based on aggregation of silver nanoparticles.

From the evaluation results shown in Table 1, it can be seen that Examples 1 to 4, which are metal nanoparticle dispersions of the present invention, have excellent dispersion stability even when a thermal load such as heating or melting after freezing is repeated, It was confirmed that the adsorbent had a sufficient adsorptivity.

On the other hand, in the case of adding no additives (Comparative Example 1) and adding additives other than polyvinylpyrrolidone (Comparative Examples 2 to 15), by performing the operation of melting after warming or freezing, dispersion stability And the adsorption property to the substrate was lowered.

Claims (7)

Characterized in that it contains polyvinylpyrrolidone (Z) and a composite of the metal nanoparticles (X) and the organic compound (Y) (excluding the composite in which the organic compound (Y) is polyvinylpyrrolidone) Metal nanoparticle water dispersion. The method according to claim 1,
Wherein the organic compound (Y) is an organic compound (Y1) having an anionic functional group. 3. The method of claim 2,
Wherein the organic compound (Y1) is a monomer mixture (I) containing a (meth) acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, ) ≪ / RTI > (Y2). The method of claim 3,
Wherein the monomer mixture (I) contains a (meth) acrylic acid-based monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more. The method according to claim 3 or 4,
And the weight average molecular weight of the polymer (Y2) is in the range of 3,000 to 20,000. 6. The method according to any one of claims 1 to 5,
Wherein the metal nanoparticles (X) are metallic paper, silver, copper or palladium. 7. The method according to any one of claims 1 to 6,
Wherein the metal nanoparticle dispersion has an average particle diameter of 0.5 to 100 nm as determined from a transmission electron microscope photograph of the metal nanoparticles (X).

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