JP2010195889A - Metal ultrafine particle dispersion and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal ultrafine particle dispersion exhibiting uniform particle size and uniform dispersibility of the metal ultrafine particle, and a high storage stability; and to provide a method for manufacturing the same. <P>SOLUTION: The metal ultrafine particle dispersion is obtained by mixing a hyperbranched polymer (A) having a site exhibiting a reducing power, and a solution (B) containing a metal ion, wherein only the metal ion guided inside the hyperbranched polymer (A) is reduced by the site exhibiting a reducing power to form the metal ultrafine particle in the hyperbranched polymer (A) only. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrafine metal particle dispersion obtained by uniformly dispersing ultrafine metal particles in a solution using a hyperbranched polymer, and a method for producing the same.

  The metal ultrafine particles can be obtained by reducing metal ions in a solution containing metal ions. In the production of such a metal ultrafine particle dispersion, the metal ultrafine particles generated in the solution by reduction are very likely to aggregate because intermolecular force acts between the particles. The intermolecular force increases as the particles become smaller.

  Conventionally, in the manufacture of ultrafine metal particles, a dispersant is added in advance to a solution in order to suppress aggregation (Patent Document 1, Non-Patent Document 1). That is, a dispersant is added to a solution containing metal ions, a reducing agent is added to the solution containing the metal ions and the dispersant, and the ultrafine metal particles generated by the reduction are held in a dispersed state by the dispersant. , Suppresses aggregation of particles.

  For example, in Patent Document 1, a polymer compound (X) having a linear polyalkyleneimine chain (a), a hydrophilic segment (b), and a hydrophobic segment (c) is used as a dispersion. Body, metal salt or metal ion solution (Y), and reducing agent (Z) are mixed, metal ions in this mixed solution are reduced, and metal nanoparticles (metal ultrafine particles) are mixed in the mixed solution. It is deposited and dispersed.

  In the production of such ultrafine metal particles, a method using a dendritic polymer as a dispersant has been proposed in order to further enhance the dispersion performance of ultrafine metal particles (Patent Document 2). In this method, metal ions are introduced into the space formed inside the dendritic polymer, and the space is used as a field for the production of ultrafine metal particles. It is said that nanoparticles can be generated.

  In Patent Document 1 and Patent Document 2 described above, a reducing agent is used as a reducing means for precipitating metal ions in a solution on metal ultrafine particles. Instead of using a reducing agent, metal ions and a dispersing agent ( A method of reducing metal ions by irradiating a solution containing a dendrimer) with actinic radiation has also been proposed (Patent Document 3).

  The conventional ultrafine metal particle dispersion is a “solution in which ultrafine metal particles are held in a dispersed state” composed of a solution containing metal ions and a dispersant, and is a catalyst, electronic material, magnetic material, optical material, or sensor material. And mixed with a composition according to various uses such as a coloring material and a medical examination material. For example, when used for a conductive paste, a metal ultrafine particle dispersion is mixed with a paste composition.

JP 2008-37949 A JP 2006-225669 A JP 2002-179820 A

N Toshima and T. Takahashi, Bull. Chem. Soc. Jpn, 65, 400 (1992)

  In the above conventional method, in order to reduce the metal ions in the dispersant, it is necessary to add a reducing agent to the whole solution or to irradiate the whole solution with actinic radiation having a reducing action. Since the reducing agent or actinic radiation is added to or applied to the entire solution, the metal ions present in the solution outside the dispersant such as the dendritic polymer are simultaneously reduced. As a result of the reducing action performed on the whole solution, for example, when a dendritic polymer is used as a dispersant, ultrafine metal particles precipitated from metal ions inside the dispersant (dendritic polymer), There are two types of metal ultrafine particles, which are metal ultrafine particles precipitated in the solution. Of these two types of ultrafine metal particles, the latter ultrafine metal particles are not fixed by a dispersant (resin-like polymer), so that aggregation is likely to occur between the particles. A precipitate formed as the particle size increases is formed. Because such a phenomenon occurs, the metal ultrafine particle dispersion obtained by the conventional method has a large variation in the particle size of the metal ultrafine particles, and also includes a metal precipitate, and is used for various applications. There is insufficient quality.

  The present invention has been made in view of the above-described conventional circumstances, and provides a metal ultrafine particle dispersion having a uniform particle size and dispersibility of ultrafine metal particles and high storage stability, and a method for producing the same. It is in.

In order to solve the above-mentioned problems, the present inventors have conducted various experiments and studies, and as a result, have obtained the following knowledge.
As the dispersant, a hyperbranched polymer having a site (atomic group) having a reducing ability was used. This hyperbranched polymer was reacted with metal ions in a solution to obtain a metal ultrafine particle dispersion. The metal ion induced in the hyperbranched polymer interacts with the lone pair of sites having the reducing ability of the hyperbranched polymer, and remains in the molecular chain skeleton of the hyperbranched polymer. Then, the site having the reducing ability reduces the metal ions captured by the interaction therewith and deposits ultrafine metal particles. This reduction action acts only on the metal ions induced in the hyperbranched polymer, and the metal ions in the solution outside the hyperbranched polymer are dissolved in the solution as they are. As a result, it is possible to prepare metal ultrafine particles having a uniform and small particle size throughout the solution (dispersion). Furthermore, when a suitable atomic group as a site (atomic group) having the reducing ability of the hyperbranched polymer was screened and the characteristics of the metal ultrafine particles were evaluated in detail, the particles were found in specific functional groups (amino groups or sulfide groups). It has been found that the ultrafine metal particles having the most excellent characteristics of uniformity and small diameter can be prepared.

  The present invention has been made based on the above findings, and provides a metal ultrafine particle dispersion adopting the following constitution and a method for producing the same.

[1] An ultrafine metal particle dispersion obtained by mixing a hyperbranched polymer (A) having a site having a reducing ability and a solution (B) containing metal ions, the hyperbranched polymer (A) A metal ultrafine particle dispersion, wherein only metal ions induced therein are reduced by the site having the reducing ability to form metal ultrafine particles only in the hyperbranched polymer (A).

[2] The ultrafine metal particle dispersion according to [1], wherein the hyperbranched polymer (A) is a spherical molecule having a diameter of 1 nm or more and less than 100 nm.

[3] The metal ultrafine particle dispersion according to the above [1] or [2], wherein the site having the reducing ability is an amino group or a sulfide group.

[4] The ultrafine metal particle dispersion according to any one of [1] to [3], wherein the hyperbranched polymer (A) has a protective layer for the ultrafine metal particles.

[5] A first step of preparing a hyperbranched polymer (A) having a site having a reducing ability, a second step of preparing a solution (B) containing a metal ion, and the hyperbranched polymer (A) By mixing the solution (B), a metal ion is induced in the hyperbranched polymer (A), and only the metal ion induced in the hyperbranched polymer (A) has the reducing ability. And a third step of forming metal ultrafine particles only in the hyperbranched polymer (A) by reduction by the method, and producing a metal ultrafine particle dispersion.

[6] The method for producing a metal ultrafine particle dispersion according to the above [5], wherein the hyperbranched polymer (A) is spherical with a diameter of 1 nm or more and less than 100 nm.

[7] The ultrafine metal particles according to [5] or [6] above, wherein the hyperbranched polymer (A) prepared in the first step is a hyperbranched polymer that itself has a reducing ability. A method for producing a dispersion.

[8] The hyperbranched polymer (A) prepared in the first step itself has no reducing ability, but is a hyperbranched polymer imparted with reducing ability by contacting with a pH adjuster. The method for producing an ultrafine metal particle dispersion as described in [5] or [6] above.

[9] The hyperbranched polymer (A) prepared in the first step itself has no reducing ability, but is a hyperbranched polymer provided with reducing ability by separately condensing a compound. The method for producing a metal ultrafine particle dispersion according to [5] or [6] above, which is characterized by the following.

[10] The method for producing a metal ultrafine particle dispersion according to any one of the above [5] to [9], wherein the site having the reducing ability is an amino group or a sulfide group.

[11] The ultrafine metal particle dispersion according to any one of [5] to [10], wherein the site having the reducing ability functions as a protective layer for the ultrafine metal particles. Production method.

  The ultrafine metal particle dispersion according to the present invention is an ultrafine metal particle dispersion obtained by mixing a hyperbranched polymer (A) having a reducing ability site and a solution (B) containing metal ions. Therefore, when the metal ion in the solution is induced in the hyperbranched polymer (A), the lone pair of sites having the reducing ability of the hyperbranched polymer interacts with the vacant orbit of the metal ion, It remains inside the molecular chain skeleton of the hyperbranched polymer. Then, the site having the reducing ability reduces the metal ion captured by interaction with the site, and ultrafine metal particles are deposited at the site.

  Based on the above-described mechanism in the present invention, since the hyperbranched polymer itself as a dispersant also serves as a reducing agent, it is not necessary to cause a reducing action on the entire solution as in the conventional method, and as a result, The metal ions are reduced only within the branched chain skeleton of the hyperbranched polymer to be generated as metal molecules and grow to form ultrafine metal particles.

  Thus, in the metal ultrafine particle dispersion and the production method thereof according to the present invention, the metal ions present in the solution outside the hyperbranched polymer are not exposed to the reducing agent by contact with the reducing agent or light irradiation. Since the metal ultrafine particles are not formed, the metal ultrafine particles having a large particle diameter are not formed in the solution, nor are they aggregated and precipitated. In the present invention, the reaction of the metal ions present in the solution does not occur, but the ions are dissolved in the solution as they are, and the metal ions only in the hyperbranched polymer as the dispersant are reduced, so that the particle size is very small. A plurality of metal ultrafine particles having a narrow particle size distribution are generated. In addition, since all the generated ultrafine metal particles are protected by the branched chain skeleton of the hyperbranched polymer, the dispersion stability of the ultrafine metal particles in the dispersion is very high.

The metal ultrafine particle dispersion of the present invention is a metal ultrafine particle dispersion obtained by mixing a hyperbranched polymer (A) having a site having a reducing ability and a solution (B) containing metal ions, Only the metal ions induced in the hyperbranched polymer (A) are reduced by the site having the reducing ability, and metal ultrafine particles are formed only in the hyperbranched polymer (A).
Hereinafter, each component of the present invention will be described in detail.

(Hyperbranched polymer)
The hyperbranched polymer, which is the main component of the dispersion used in the present invention, is a general term for polymers having a large number of branch points in the molecule, and is classified as a dendritic polymer together with a dendrimer. There are a number of differences in physical properties from conventional linear polymers, and examples include surface polyfunctionality, low viscosity, and amorphousness. In particular, further compounds can be condensed to the polymer surface functional groups due to the surface multifunctionality.

  The weight average molecular weight (Mw) of the hyperbranched polymer used in the present invention is preferably 500 to 100,000, and more preferably 6,000 to 28,000. Here, the weight average molecular weight (Mw) of the polymer can be determined by preparing a 0.5 mass% aqueous solution and performing gel permeation chromatography (GPC) measurement at a temperature of 40 ° C. For example, it can be determined by using “RI-71 (trade name)” manufactured by Shodex as a measuring device, using water as a mobile solvent, and using polyethylene glycol as a standard substance. In the examples described later, measurement is performed under these conditions. In addition, the polydispersity (Mw / Mn) of the polymer is preferably 1 to 10, and more preferably 1 to 5. In addition, Mn of the denominator of the polydispersity (Mw / Mn) is a number average molecular weight.

Furthermore, the absolute molecular weight of the hyperbranched polymer is preferably 1,000 to 1,000,000, and more preferably 28,000 to 154,000. Here, the absolute molecular weight of the hyperbranched polymer can be measured by a multi-angle laser light scattering (MALLS).
The measurement conditions can be performed, for example, by connecting a Wyatt multi-angle light scattering detector (trade name “DAWN DSP-F”) to the aforementioned gel permeation chromatography (GPC) measurement line, which will be described later. In the examples, the measurement is performed under these conditions.

  The hyperbranched polymer used as the main component of the dispersant in the ultrafine metal particle dispersion of the present invention is not particularly limited as long as it has the above-mentioned properties. Among them, the preferred hyperbranched polymer is glycidyl. The following general formula (I) containing an ether group and a hydroxyl group:

（式（Ｉ）中、Ｘは分子中にヘテロ原子を有していてもよい置換アルカンを示し、グリシジルエーテル基および水酸基は置換アルカンＸを構成する炭素のうち共通の炭素に結合していてもよいし、それぞれ異なる炭素に結合されていてもよく、ｍは２以上の整数を示し、ｎは１以上の整数を示し、ｍ＞ｎ＞０である。）
で表される化合物（ａ）を含むグリシジルエーテル化合物（イ）を塩基性触媒（ロ）の存在下で付加重合させることにより得られる、末端にエポキシ基を有するハイパーブランチポリマーである。
かかるハイパーブランチポリマーについて、以下に詳しく説明する。

(In the formula (I), X represents a substituted alkane which may have a hetero atom in the molecule, and the glycidyl ether group and the hydroxyl group may be bonded to a common carbon among the carbons constituting the substituted alkane X. May be bonded to different carbons, m represents an integer of 2 or more, n represents an integer of 1 or more, and m>n> 0.)
Is a hyperbranched polymer having an epoxy group at the terminal, obtained by addition polymerization of a glycidyl ether compound (a) containing the compound (a) represented by formula (b) in the presence of a basic catalyst (b).
The hyperbranched polymer will be described in detail below.

(Starting material (I))
As a starting material for obtaining the hyperbranched polymer, a glycidyl ether compound (I) including “a hydroxyl group and a compound having a larger number of glycidyl ether groups than the hydroxyl group” is used. As the “compound having a hydroxyl group and a larger number of glycidyl ether groups than the hydroxyl group” contained in the starting material (a), the compound (a) represented by the above general formula (I) is used. The compound (a) represented by the general formula (I) is a compound containing one or more hydroxyl groups and a larger number of glycidyl ether groups than the hydroxyl groups, and two or more reactive equivalent glycidyl ether groups are converted to glycerol. In other words, it is a compound possessed in the skeleton.

  X in the general formula (I) represents a substituted alkane. In the present invention, the “substituted alkane” means one in which at least a part or all of the hydrogen atoms constituting the alkane are replaced with a substituent. The substituted alkane X of the general formula (I) is an alkane in which at least a part or all of the hydrogen atoms constituting the alkane are substituted with a chemical bond with a glycidyl ether group or a hydroxyl group.

  The number of carbon atoms constituting the substituted alkane is preferably 1-20, more preferably 1-10, and particularly preferably 1-5. If it exceeds 20, the desired degree of branching may not be ensured.

  The structure of the substituted alkane may be linear, branched or cyclic, and may include two or more thereof. Of the hydrogen atoms constituting the substituted alkane, a hydrogen atom that is not substituted with a glycidyl ether group or a hydroxyl group may be substituted with a halogen atom. Furthermore, a part of the substituted alkane may contain a hetero atom such as an oxygen atom or a nitrogen atom. That is, some of the substituted alkanes have bonds such as —C (═O) O— (ester bond), —C (═O) NH— (amide bond), —O— (ether bond). May be. Further, a part of the substituted alkane may be dehydrogenated and may have a double bond or a triple bond.

  Specifically, examples of the alkane constituting the substituted alkane include methane, ethane, propane, isopropane, butane, isobutane, pentane, isopentane, and cyclohexane.

  In the general formula (I), the bonding site of the glycidyl ether group and the hydroxyl group to the substituted alkane X is not particularly limited. That is, each glycidyl ether group and hydroxyl group may be bonded to a common carbon among the carbons constituting the substituted alkane X, or may be bonded to different carbons. For example, glycidyl ether groups and hydroxyl groups may be bonded alternately, or each may be unevenly distributed.

  M and n in the general formula (I) represent the number of bonds between the glycidyl ether group and the hydroxyl group in the compound represented by the general formula (I), respectively. m is an integer of 2 or more. When m is large, the number of remaining epoxy groups that can be converted into various functional groups increases, which is preferable. However, when the number of epoxy groups is excessively large compared to the number of hydroxyl groups, the reaction may not proceed, so the upper limit of m is preferably 10, more preferably 5, and even more preferably 3. n represents an integer of 1 or more and is in a relationship of m> n> 0 with m. That is, n is an integer smaller than m.

  The compound (a) represented by the general formula (I) is preferably a compound having a glycerol skeleton. The glycerol skeleton means a skeleton in which hydrogen of three hydroxyl groups of glycerin (glycerol) is removed. Note that the glycerin includes a derivative having a substituent such as an alkyl group. Since the glycerol skeleton has oxygen atoms bonded to three different carbon atoms, it is the smallest molecule with the advantage that the reactivity of the glycidyl ether group is equivalent, and a hyperbranched polymer with a high degree of branching can be obtained. In addition, since glycerin is required to be developed as a surplus substance in the oil and fat industry, the compound represented by the general formula (I) can be said to be a preferable compound to be used.

  There are no particular limitations on the production conditions of the compound (a) represented by the general formula (I), and examples thereof include 2 such as glycerol, diglycerol, triglycerol, trimethylolpropane, penquelithritol, sorbitol, sucrose, and degraded starch. And compounds derived from a compound having one or more hydroxyl groups and ebichlorohydrin.

  Specific preferred compound names for the derivative compound include glycerol diglycidyl ether, glycerol-1-glycidyl-3- (propyl-3-chloro-2-glycidyl ether) ether, diglycerol polyglycidyl ether, trimethylol. Propane diglycidyl ether, pentaerythritol polyglycidyl ether, and the like.

The diglycerol polyglycidyl ether is preferably diglycerol diglycidyl ether or diglycerol triglycidyl ether.
Examples of the pentaerythritol polyglycidyl ether include pentaerythritol diglycidyl ether.

  Among the above specific examples, glycerol diglycidyl ether is preferable. Glycerol diglycidyl ether includes glycerol-1,3-diglycidyl ether (formula (II)), trimethylolpropane diglycidyl ether (formula (III)) represented by the following structural formulas (II) to (IV), and 1- (2-oxiranylmethoxy) -3- [2-chloro-3- (2-oxiranylmethoxy) propoxy] propan-2-ol (formula (IV)) can be mentioned, among these In particular, glycerol-1,3-diglycidyl ether represented by the structural formula (II) is preferable. These specific glycerol diglycidyl ethers can be obtained from, for example, Denacol series manufactured by Nagase ChemteX Corporation. The product manufactured by Nagase ChemteX Corporation contains the diglycidyl ether compound represented by the structural formulas (II) to (IV), that is, the diglycidyl ether compound (a) represented by the general formula (I). It is a diglycidyl ether compound, not a compound consisting only of the diglycidyl ether compound (a) represented by the general formula (I). That is, the said commercial item is a mixture of the diglycidyl ether compound (a) represented by general formula (I) and another glycidyl ether compound.

  In addition, the ring-opening addition polymerization starting material (a) for obtaining the hyperbranched polymer used as the main carrier of the active ingredient holder of the present invention includes the compound (a) represented by the above general formula (I). In addition, a glycidyl ether compound other than the compound (a) represented by the general formula (I) may be included.

(Glycidyl ether compounds other than the compound (a) represented by the general formula (I))
Examples of the glycidyl ether compound other than the compound (a) represented by the general formula (I) include the following general formula (I-2):

（式（Ｉ−２）中、Ｙは水酸基を含有しない置換基を示し、ｋは１以上の整数を示す。）
で表される化合物（ａ２）、及び下記一般式（Ｉ−３）：

(In formula (I-2), Y represents a substituent containing no hydroxyl group, and k represents an integer of 1 or more.)
And the following general formula (I-3):

（式（Ｉ−３）中、Ｚはエポキシ基を含有しない置換基を示し、ｌは１以上の整数を示す。）
で表される化合物（ａ３）からなる群から選ばれる少なくとも１種を挙げることができる。

(In formula (I-3), Z represents a substituent containing no epoxy group, and l represents an integer of 1 or more.)
The at least 1 sort (s) chosen from the group which consists of a compound (a3) represented by these can be mentioned.

  The compound (a2) represented by the general formula (I-2) is not particularly limited, and examples thereof include 1,2-epoxypropane, 1,2-epoxybutane, 1,2-epoxypentane, 1,2 -Epoxyhexane, 1,2-epoxyoctane, oxiranylcyclohexane, glycidyl methyl ether, glycidyl ethyl ether, glycidyl propyl ether, glycidyl butyl ether, glycidyl pentyl ether, glycidyl hexyl ether, glycidyl cyclohexyl ether, glycidyl phenyl ether, glycidyl acrylate, Examples thereof include glycidyl methacrylate, 1,2: 5,6-diepoxyhexane, and 1,2: 7,8-diepoxyoctane.

  Examples of such other glycidyl ether compounds include those in which hydroxyl groups such as glycerol, diglycerol, triglycerol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, and decomposed starch other than the above are substituted with glycidyl ether groups; Aromatic alicyclic glycidyl ethers, glycidyl esters, EOPO (ethylene oxide and propylene oxide) adducts thereof, and the like.

  Further, the compound (a3) represented by the general formula (I-3) is not particularly limited. For example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, heptanol, octanol, Lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, linolyl alcohol, benzyl alcohol, phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol , Isopropylmethylphenol, dibutylhydroxytoluene, o-hydroxyanisole, m-hydroxyanisole, p-hydroxyanisole, butylhydroxyanisole, hydroxy Tyl acrylate, hydroxyethyl methacrylate, ethylene glycol, 1,3-propanediol, propylene glycol, diethylene glycol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, hydroquinone, 1,1-bis (4-hydroxyphenyl) Examples include cyclohexane, glycerin, trimethylolpropane, erythritol, glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose, talose.

Ring-opening polymerization for obtaining a hyperbranched polymer used as a holding main body of the active ingredient holder of the present invention is a compound represented by the general formula (I) (a) and other compounds having a glycidyl ether group. In order to maintain a high degree of branching, the compound (a) represented by the general formula (I) is 30% by mass or more, more preferably 50% by mass or more of the whole mixture when the mixture is used. Is desirable.

  As a starting material (I) for obtaining a hyperbranched polymer used in the present invention, a mixture of the compound (a) represented by the general formula (I) and other compounds having a glycidyl ether group is used. In the case of obtaining a branch polymer (copolymer), the degree of branching of the obtained hyperbranched polymer can be controlled by adjusting the mixing ratio.

(Basic catalyst (b))
In order to synthesize the hyperbranched polymer, the glycidyl ether compound (I) consisting only of the compound (a) represented by the general formula (I) or the compound (a) represented by the general formula (I) is included. Using the glycidyl ether compound (a) as a starting material, ring-opening addition polymerization using the basic catalyst (b) is performed on the starting material (a). The basic catalyst (b) acts on the hydroxyl group to react with the epoxy group, and does not act directly on the epoxy group. Therefore, a hyperbranched polymer having an epoxy group can be finally obtained.

  Examples of the basic catalyst (b) include alkali metals, alkaline earth metals, hydrides thereof, alkoxides, hydroxides, alkylates, carbonates, and the like. Among these, for example, potassium carbonate, potassium hydroxide, potassium methoxide, sodium carbonate and the like are preferable.

  In the synthesis of the hyperbranched polymer, the glycidyl ether compound (a) consisting only of the compound (a) represented by the general formula (I) or the glycidyl ether containing the compound (a) represented by the general formula (I) The starting material (A) may be subjected to addition polymerization (also referred to as ring-opening polymerization or ring-opening addition polymerization) in the presence of a basic catalyst (b), using the compound (a) as a starting material. The conditions are not particularly limited.

  The blending amount of the basic catalyst (b) used is desirably 0.1 to 30% by mass, and preferably 1 to 20% by mass with respect to the starting material (a).

  As a method for introducing the basic catalyst (b), there are a method in which the basic catalyst is added in advance to the reaction vessel, a method in which the basic catalyst is dropped continuously, a method in which the basic catalyst is dropped into the reaction vessel, or a method in which the basic catalyst (b) is dropped into the reaction vessel divided every predetermined time. Can be mentioned.

  The ring-opening addition polymerization proceeds without the presence of a solvent, but can also be carried out in various solvents. The type of solvent is not particularly limited, but hydrocarbon solvents such as benzene and toluene, ether solvents such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole, dimethoxybenzene, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, methylene chloride, chloroform , Halogenated hydrocarbon solvents such as chlorobenzene, ketone solvents such as acetone, methyl ethyl ketone, and methylisoptyl ketone, alcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, propionitrile, benzonitrile, etc. Nitrile solvents, ester solvents such as ethyl acetate and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, N, - dimethylformamide, N, include amide solvents such as N- dimethylacetamide. These may be used alone or in combination of two or more.

  Also, the reaction concentration [the concentration of the compound (a) represented by the general formula (I) with respect to the solvent (-= in the case of the starting material (I)), or other compounds having a glycidyl ether group as the starting material (I) When used simultaneously, the concentration of the compound and the compound (a) represented by the general formula (I) with respect to the total solvent] is 1% by mass to 100% by mass (no solvent), preferably 10% by mass to It is 100 mass%, More preferably, it is 30 mass%-100 mass%.

In the ring-opening addition polymerization, the monomer solution and the catalyst are preferably mixed under an inert gas (Ar, N _2, etc.). At this time, the monomer solution may be mixed at a time or dropped into the reaction system. The reaction temperature is preferably 30 ° C to 180 ° C, more preferably 60 ° C to 160 ° C. The reaction time is 0.5 to 10 hours, more preferably 1 to 7 hours to complete the polymerization.

  The selection of the reaction temperature and reaction time in the addition polymerization affects the degree of branching and the molecular weight. In the epoxy ring-opening polymerization in the present invention, first, a secondary alkoxide is selectively prepared by ring opening of an epoxy group, and then converted to a primary alkoxide by proton exchange equilibrium. Since active proton exchange improves the degree of branching, in order to promote rapid proton exchange and obtain a highly branched polymer, a reaction at a high temperature (for example, 50 ° C. or more, preferably 80 to 150 ° C.) desirable. If the reaction temperature is still high after the monomer consumption is complete, the terminal epoxy group may be ring-opened due to moisture in the system. It is desirable to quickly reduce to room temperature.

  After completion of the polymerization, the catalyst can be removed from the polymer by filtration, ion exchange, neutralization or the like. At this time, if necessary, the polymer is dissolved in a suitable solvent, for example, methanol. Further, the polymer may be purified by reprecipitation.

  Among the hyperbranched polymers obtained by ring-opening polymerization, for example, the hyperbranched polymer having a glycerol skeleton was measured by 13C-NMR of the preparation. References (Macromolecules 1999, 32, 4240-4246, Macromolecules 2000, 33, 8158-8166), which shows a strong resonance of 79 to 81 ppm specific to the trisubstituted carbon atom of the branching unit, confirming that it is a multibranched body.

Since the hyperbranched polymer suitable for use as the main component of the dispersion in the present invention is a multibranched body as described above, its structure is usually spherical. Confirmation of the spherical structure can be made by checking whether the weight average molecular weight measured by GPC and the absolute molecular weight measured by MALLS differ greatly (Frechet, M. et al. Am. Chem. Soc. 1999, 121, 2313 .; Sawamoto, et al. Macromolecules, 2001, 34, 7629.).
That is, the value of GPC (manufactured by Shodex, trade name “RI-71”) and the value of the absolute molecular weight obtained by a multi-angle light scattering detector: MALLS (manufactured by Wyatt, trade name “DAWN DSP-F”) It was possible to make a judgment according to the difference between the GPC measurement value and the MALLS value, and the examples described later also followed this.

  When the GPC measurement value and the MALLS value are greatly different, it can be determined that the polymer is a spherical polymer. Usually, if the absolute molecular weight measured by MALLS is 2 times or more, preferably 3 times or more the weight average molecular weight measured by GPC, it can be determined as a spherical structure. Moreover, although an upper limit is not prescribed | regulated in particular, Usually, it is 10 times or less.

  The hyperbranched polymer suitable for use as the main component of the dispersion in the present invention has an epoxy group at the terminal and a hydroxyl group in the molecule. The term “end” means the end of a branched chain constituting the polymer. The branched chain is formed from an alkane containing -C (= O) O- (ester bond), -C (= O) NH- (amide bond), ether bond (-O-), etc. in the middle. It has abundant substituents containing oxygen.

(Reducing ability)
The “reducing ability” referred to in the present invention refers to the ability to give electrons and reduce metal ions. When metal ions are reduced, ultrafine particles of simple metals are generated.

(Site with reducing ability)
In addition, the “site having a reducing ability” in the present invention refers to an atomic group (functional group or the like) having the ability to reduce metal ions. The “site having reducing ability” is reduced by imparting an electron to a metal ion and is itself oxidized.

(Hyperbranched polymer with a site with reducing ability)
The hyperbranched polymer having a site having a reducing ability can be prepared by the following three methods (i) to (iii).

(I)
When the hyperbranched polymer is synthesized, the hyperbranched polymer that already has “reducing ability” is used as it is. Examples of such hyperbranched polymers that themselves have reducing ability include those in which the “site having reducing ability” is a hydroxyl group, and commercially available ones include polyethyleneimine (manufactured by Kanto Chemical Co., Inc.), Polyamide amine dendrimer (manufactured by Sigma Aldrich) and the like.

(Ii)
The hyperbranched polymer which does not have a reducing ability itself is used as a raw material, and a site having a reducing ability is acquired by adding a pH adjuster (such as NaOH) separately to the hyperbranched polymer.

  Examples of the method for providing the site having the reducing ability include a method of adding a pH adjuster to the hyperbranched polymer solution and adjusting the pH to be 10 to 14. As a result of the pH adjustment, the terminal hydroxyl group of the hyperbranched polymer is converted into an alkoxide group, whereby a “site having a reducing ability” is formed in the hyperbranched polymer, and the hyperbranched polymer itself has the reducing ability. As the pH adjuster in this case, sodium hydroxide, potassium hydroxide, an aqueous ammonia solution or the like is used.

  The hyperbranched polymer thus provided with a “site having a reducing ability” can also be used in the ultrafine metal particle dispersion according to the present invention. As such hyperbranched polymers, “Polyglycerin-10 (trade name)” and “Polyglycerin-X (trade name)” manufactured by Daicel Chemical Industries, Ltd., “PG-2 (Product) manufactured by Hyperpolymers Co., Ltd. Name) ”,“ Top Brain (trade name) ”manufactured by Toei Sangyo Co., Ltd.,“ Hyperbranched 2,2-bis (hydroxymethyl) propanoic acid polyester (trade name) ”produced by Sigma Aldrich,“ Bolton H2003 (product name), “Bolton H2004 (product name)”, “Bolton H30 (product name)”, “Bolton H40 (product name)”, and the like.

(Iii)
A hyperbranched polymer that does not have reducing ability itself is used as a raw material, and a site having acquired reducing ability is provided by condensing a separate compound to the hyperbranched polymer.
The application of the site having the reducing ability can be performed, for example, as follows.

A compound that introduces an amino group, sulfide group, etc. has a site that originally has a reducing ability by condensation reaction with a reaction site of a hyperbranched polymer (which can be exemplified by a hydroxy group, an epoxy group, or an isocyanate group). A site having a reducing ability (such as NH-R or S-R) can be introduced into a non-hyperbranched polymer (HBP). An example of the reaction formula of this reaction is as follows.
HBP-RG + R-NH ₂ → HBP-NH-R
HBP-RG + R-SH → HBP-SR
(In the formula, HBP is a hyperbranched polymer that does not originally have a site having a reducing ability, RG represents a reactive site of the hyperbranched polymer, and R represents an organic group.)

  More specifically, by condensing the following compounds, a hyperbranched polymer having a site having an ability to reduce (amino group, fill group) can be synthesized.

(Amino group)
The compound for introducing an amino group is not particularly limited, and tertiary amines, secondary amines, primary amines, and other aromatic amines can be used.

  Examples of the tertiary amine include trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tricyclohexylamine, N-methylpyrrolidine, N-methylpiperidine, N-ethylpyrrolidine, N-ethylpiperidine and the like. it can.

  Examples of the secondary amine include N-methyl-D-glucamine, N-methylaminopropanediol, dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine, di-i. Examples include -butylamine, di-sec-butylamine, di-t-butylamine, dicyclohexylamine, pyrrolidine, piperidine and the like.

  Examples of the primary amine include D-glucamine, methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, sec-butylamine, t-butylamine, cyclohexylamine and the like.

  Examples of the other aromatic amines include aniline, o, m, p-toluidine, o, m, p-ethylaniline, xylidine, mesidine, o, m, p-chloroaniline, chlorotoluidine, dichloroaniline, and trichloroaniline. O, m, p-fluoroaniline, o, m, p-bromoaniline, fluorochloroaniline, o, m, p-aminophenol, o, m, p-aminothiophenol, anisidine, phenetidine, o, m, p-aminobenzoic acid, aminochlorophenol, aminobenzonitrile, cresidine, toluidinesulfonic acid, sulfanilic acid, chlorotoluidinesulfonic acid, aminonaphthalenesulfonic acid, aminobenzotrifluoride, aminobenzenesulfonic acid, p-aminoacetanilide, naphthylamine, Naphthylami Sulfonic acid or aminonaphthol sulfonic acid, N-methylaniline, N-ethylaniline, N-ethyltoluidine, diphenylamine, hydroxyphenylglycine or N-methylaminophenol sulfate, N, N-dimethylaniline, N-ethyl-N-hydroxy Ethyltoluidine, N, N-diethyltoluidine, N-benzyl-N-ethylaniline or N, N-diglycidylaniline, o, m, p-phenylenediamine, chloro-p-phenylenediamine, chloro-m-phenylenediamine, Phenylenediamines such as fluorophenylenediamine, dichlorophenylenediamine, methylphenylenediamine, dimethylphenylenediamine, chloromethylphenylenediamine, xylylenediamine, and tolylenediamine; Benzidines such as benzene, o-tolidine, dianicidin, dichlorobenzidine, diphenylmethanes such as diaminodiphenylmethane, diaminodichlorodiphenylmethane, diaminodimethyldiphenylmethane, diaminodiethyldiphenylmethane, naphthalenediamine, diaminobenzanilide, diaminodiphenyl ether, diaminostilbenzenedisulfonic acid, diamino Examples include phenol dihydrochloride, leucodiaminoanthraquinone, amino-N, N-diethylaminotoluidine hydrochloride or amino-N-ethyl-N- (β-methanesulfonamidoethyl) -toluidine sulfate hydrate. Of these, any compound having at least one amino group in the molecule may be used.

(Sulfide group)
The compound for introducing a sulfide group is not particularly limited, and alkylthiols (eg, α-thioglycerol, methyl mercaptan, ethyl mercaptan, etc.) that are thiol group-containing compounds, aryl thiols (eg, thiophenol). Thionaphthol, benzyl mercaptan, etc.), amino acids or derivatives thereof (eg, cysteine, glutathione, etc.), peptide compounds (eg, dipeptide compounds containing cysteine residues, tripeptide compounds, tetrapeptide compounds, 5 or more amino acid residues Including oligopeptide compounds), or proteins (for example, globular proteins having metallothionein or cysteine residues arranged on the surface). Of these, any compound having at least one sulfide group in the molecule may be used.

  As described above, a hyperbranched polymer that is acquired with a “site having a reducing ability” can also be used in the ultrafine metal particle dispersion according to the present invention. Examples of such hyperbranched polymers include the products listed in (ii) above as commercially available products, and poly (glycerol-1,3-diglycidyl ether) derivatives can also be used.

(Metal ions)
The metal that can be used in the ultrafine metal particle dispersion targeted by the present invention is not particularly limited. For example, Au, Ag, Pt, Cu, Pd, Zn, Cd, Hg, Ni, Co, Rh Ir, Fe, Ru, Os, Mn, Cr, V, Ti, Al, Ga, etc. can be mentioned.
Sources of metal ions used to obtain these ultrafine particle dispersions of metals include halides, sulfates, nitrates, acetates, acetylacetonate salts, perchlorates, and organic acid salts of the above metals. Can be mentioned.

(Solvent for solutions containing metal ions)
Although the metal ions are present in the solution, polar solvents such as water and alcohols are mainly used as the solvent of the solution. However, if the solvent dissolves the metal, such a non-polar solvent is also used. Is possible. Examples of the alcohols include methanol, ethanol, propanol, and butanol. Examples of other polar solvents include ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, acetone, dimethyl sulfoxide (DMSO), Examples thereof include dimethylformamide (DMF).

(Protective layer)
The protective layer refers to an atomic group that improves the dispersion stability of metal ultrafine particles generated by reduction of metal ions. The protective layer can be introduced by condensing the protective layer-introducing compound with the terminal functional group of the hyperbranched polymer.

(Protective layer introduction compound)
Examples of the compound that condenses to the terminal functional group of the hyperbranched polymer as the protective layer include, for example, a hydroxy group, a ketone group, an acetyl group, an aldehyde group, a carboxyl group, an ester group, a thioester group, a nitrate ester group, a phosphate ester group, and an amide. Groups, thioamide groups, imide groups, amidine groups, amino groups, cyano groups, oxime groups, thiol groups, sulfide groups, disulfide groups, sulfonic acid groups, urea groups, urethane groups, nitro groups, ether groups, and the like. .

  More specifically, examples of the hydroxy group include glycidol and glycerin. Examples of the ether group include glycidol, glycerin, polyethylene glycol, and polypropylene glycol. Examples of the carboxyl group include citric acid. Carboxylic acids and carboxylic anhydrides can be mentioned.

  In the case where an atomic group having a function as a protective layer such as an amino group or a sulfide group is already provided as a site having a reducing ability, it is not necessary to introduce a protective layer.

  Below, the Example of the metal ultrafine particle dispersion concerning this invention and its manufacturing method are described. In addition, this invention is not limited by the following examples.

(Preparation of hyperbranched polymer having a site with reducing ability)
Hyperbranched polymers (HBP-1 to HBP-12) having the following 13 types of functional groups having reducing ability were prepared as hyperbranched polymers having a reducing ability used in the examples.
(HBP-1): manufactured by Toei Sangyo Co., Ltd., “Top Brain (trade name)”, the site having reducing ability is a hydroxyl group.
(HBP-2): “Polyglycerin-X (trade name)” manufactured by Daicel Chemical Industries, Ltd., the site having reducing ability is a hydroxyl group.
(HBP-3): “PG-2 (trade name)” manufactured by Hyperpolymers Co., Ltd., a site having a reducing ability is a hydroxyl group.
(HBP-4): “PAMAM dendrimer” manufactured by Sigma-Aldrich, a site having a reducing ability is a hydroxyl group or an amino group.
(HBP-5 to 12): Newly synthesized product (the synthesis process is shown below)

(HBP-5)
A 300 mL four-necked separable flask equipped with a stirrer, a reflux condenser and a nitrogen inlet tube is charged with 100 g of glycerol diglycidyl ether and 15 g of potassium carbonate, and the four-necked separable flask through the nitrogen inlet tube while stirring. Nitrogen gas was introduced into the inside. Subsequently, the four-neck separable flask into which nitrogen gas was introduced was heated in an oil bath at 140 ° C. for 300 minutes. After heating, the reaction mixture was dissolved in methanol, the solid content was removed by filtration, and then the solvent was distilled off to obtain a hyperbranched polymer (I) as a viscous liquid.
The obtained hyperbranched polymer (I) has a converted molecular weight (weight average molecular weight) by GPC of 6000, an absolute molecular weight by MALLS of 28000, and an absolute molecular weight by MALLS of 4.7, which is a weight average molecular weight by GPC. there were.

100 g of ultrapure water was added to 100 g of the hyperbranched polymer (I) and dissolved. To this, 20 g of 1% sulfuric acid was slowly added dropwise in an ice bath, and after completion of the addition, the mixture was stirred for 1 hour at room temperature. After completion of stirring, the mixture was neutralized with 1N aqueous sodium hydroxide solution and the pH was adjusted to around 7.
The obtained reaction solution was transferred to a dialysis membrane and dialyzed against ion exchange water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain hyperbranched polyglycerin (hyperbranched polymer (HBP-5)).
The site having the reducing ability of the obtained HBP-5 is a hydroxyl group, the converted molecular weight (weight average molecular weight) by GPC is 75000, the absolute molecular weight by MALLS is 31000, and the absolute molecular weight value by MALLS is the weight by GPC. The average molecular weight value was 4.1.

(HBP-6)
20 g of the hyperbranched polymer (I) was dissolved in 10 g of methanol, 3.6 g of diethylamine (site introduction component having a reducing ability) was added, and the mixture was heated and stirred for 18 hours under reflux condition at 65 ° C. The solvent was distilled off from the obtained reaction product with an evaporator, transferred to a dialysis membrane, and dialyzed against ion-exchanged water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain diethylamino-hyperbranched polyglycerin (hyperbranched polymer (HBP-6)).
The site having the reducing ability of the obtained HBP-6 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 13000, the absolute molecular weight by MALLS is 49000, and the absolute molecular weight value by MALLS is by GPC. The weight average molecular weight was 3.8.

(HBP-7)
20 g of the hyperbranched polymer (I) was dissolved in 7.2 g of methanol to obtain a solution A. Further, 5.2 g of α-thioglycerol (site introduction component having a reducing ability + protective layer forming component) is dissolved in 1.2 g of potassium methoxide (28% methanol solution), and stirred for 1 hour at normal temperature and normal pressure in an argon atmosphere. This was designated as solution B.
The solution B was slowly added dropwise to the solution A, and the mixture was stirred under heating at 65 ° C. for 18 hours. The solvent was distilled off from the obtained reaction product with an evaporator, transferred to a dialysis membrane, and dialyzed against ion-exchanged water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain thioglycerol-hyperbranched polyglycerin (hyperbranched polymer (HBP-7)).
The site having the reducing ability of the obtained HBP-7 is a sulfide group, the converted molecular weight (weight average molecular weight) by GPC is 12000, the absolute molecular weight by MALLS is 65000, and the absolute molecular weight value by MALLS is by GPC. The weight average molecular weight was 5.4.

(HBP-8)
10 g of the hyperbranched polymer (I) is dissolved in 10 g of methanol, 4.8 g of N-methyl-D-glucamine (site introduction component having a reducing ability + protective layer forming component), tetrabutylammonium bromide (condensation catalyst), 0. 16 g was added and the mixture was stirred with heating at 65 ° C. for 18 hours. The solvent was distilled off from the obtained reaction product with an evaporator, transferred to a dialysis membrane, and dialyzed against ion-exchanged water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain methylglucamine-hyperbranched polyglycerin (hyperbranched polymer (HBP-8)).
The site having the reducing ability of the obtained HBP-8 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 13000, the absolute molecular weight by MALLS is 69000, and the absolute molecular weight value by MALLS is by GPC. The weight average molecular weight value was 5.3.

(HBP-9)
30 g of the above hyperbranched polymer (I) is dissolved in 32 mL of methanol, 7.7 g of 3-methylamino-1,2-propanediol (site introduction component having a reducing ability + protective layer forming component), tetrabutylammonium bromide (condensation) (Catalyst) 0.47 g was added, and the mixture was heated and stirred for 18 hours under reflux condition at 65 ° C. The solvent was distilled off from the obtained reaction product with an evaporator, transferred to a dialysis membrane, and dialyzed against ion-exchanged water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain methylaminopropanediol-hyperbranched polyglycerin (hyperbranched polymer (HBP-9)).
The site having the reducing ability of the obtained HBP-9 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 22000, the absolute molecular weight by MALLS is 154000, and the absolute molecular weight value by MALLS is by GPC. The weight average molecular weight value was 7.0.

(HBP-10)
Polyethyleneimine 10 g (site introduction component having reducing ability) was dissolved in 10.9 g of methanol, and this was designated as solution A. Further, 24.6 g of glycidol (protective layer forming component) was dissolved in 10.9 g of methanol, and this was designated as B solution.
After stirring the liquid A under reflux conditions at 65 ° C., the liquid B was dropped in a dropping funnel over 2 hours, and the end of the dropping was regarded as the start of the reaction. The reaction was terminated 18 hours after the start of the reaction, and the contents were transferred to an eggplant flask and methanol was distilled off with an evaporator. The obtained residue was transferred to a dialysis membrane and dialyzed against ion exchange water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain a polyethyleneimine-polyglycerin hyperbranched polymer (hyperbranched polymer (HBP-10)).
The site having the reducing ability of the obtained HBP-10 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 24000, the absolute molecular weight by MALLS is 108000, and the absolute molecular weight value by MALLS is by GPC. The weight average molecular weight was 4.5.

(HBP-11)
Polyethyleneimine 10 g (site introduction component having reducing ability) was dissolved in 10.9 g of methanol, and this was designated as solution A. Moreover, 49.2 g (protective layer forming component) of glycidol was dissolved in 10.9 g of methanol, and this was designated as B solution.
After stirring the liquid A under reflux conditions at 65 ° C., the liquid B was dropped in a dropping funnel over 2 hours, and the end of the dropping was regarded as the start of the reaction. After 18 hours from the start of the reaction, the reaction was completed, the contents were transferred to an eggplant flask, and methanol was distilled off with an evaporator. The obtained residue was transferred to a dialysis membrane and dialyzed against ion exchange water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain a polyethyleneimine-polyglycerin hyperbranched polymer (hyperbranched polymer (HBP-11)).
The site having the reducing ability of the obtained HBP-11 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 28000, the absolute molecular weight by MALLS is 141000, and the absolute molecular weight value by MALLS is by GPC. It was 5.0 of the value of a weight average molecular weight.

(HBP-12)
30 g of the hyperbranched polymer (I) is dissolved in 32 ml of methanol, and 7.7 g of diisopropylamine (site introduction component having a reducing ability + protective layer forming component) and 0.47 g of tetrabutylammonium bromide (condensation catalyst) are added. The mixture was heated and stirred for 18 hours under reflux conditions. The solvent was distilled off from the obtained reaction product with an evaporator, transferred to a dialysis membrane, and dialyzed against ion-exchanged water for 3 days. After dialysis, ion-exchanged water was distilled off with an evaporator to obtain diisopropylamino-hyperbranched polyglycerin (hyperbranched polymer (HBP-12)).
The site having the reducing ability of the obtained HBP-11 is an amino group, the converted molecular weight (weight average molecular weight) by GPC is 11000, the absolute molecular weight by MALLS is 89000, and the absolute molecular weight value by MALLS is by GPC. It was 8.1 of the value of a weight average molecular weight.

The following three types of polymers (CP-1 to CP-3) were prepared as dispersants used in the comparative examples.
(CP-1): Polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.)
(CP-2): Polyvinyl alcohol (manufactured by Kuraray Co., Ltd.)
(CP-3): Polyethylene glycol (manufactured by Kanto Chemical Co., Inc.)

(Examples 1-12)
The addition of HAuCl ₄ aqueous solution to each solution of the hyperbranched polymer HBP-1 to 12, stirred for 3 hours at room temperature to give a Au ultrafine particles solution (ultrafine gold particles dispersion). The component concentration in each solution was set to be dispersant = 0.5 wt% and gold ion = 0.05 wt%.

(Comparative Examples 1 and 2)
An HAuCl ₄ aqueous solution was added to each dispersant polymer (CP-1,3) aqueous solution for comparison, and the mixture was stirred at room temperature for 30 minutes. Thereafter, a predetermined amount of an aqueous NaBH ₄ solution was added as a reducing agent, and the mixture was further stirred at room temperature for 3 hours to obtain an Au ultrafine particle aqueous solution (gold ultrafine particle dispersion). The component concentrations in each solution were such that the dispersant polymer = 0.5 wt%, the gold ions = 0.05 wt%, and NaBH ₄ = 0.05 wt%.

(Examples 13 to 23)
The hyperbranched polymer HBP-1~4,6~12 to each solution of _Ag 2 SO ₄ aqueous solution was added, and stirred for 3 hours at room temperature to obtain a Ag ultrafine particle dispersion solution (silver ultrafine particle dispersion). In addition, each component density | concentration in each solution was made to become dispersing agent = 0.5 wt% and silver ion = 0.05 wt%.

(Comparative Examples 3-5)
An Ag ₂ SO ₄ aqueous solution was added to each dispersant polymer (CP-1 to 3) solution for comparison, and the mixture was stirred at room temperature for 30 minutes. Thereafter, a predetermined amount of an aqueous NaBH ₄ solution was added as a reducing agent, and the mixture was further stirred at room temperature for 3 hours to obtain an Ag ultrafine particle dispersion aqueous solution (silver ultrafine particle dispersion). Incidentally, component concentration of each solution, dispersant polymer = 0.5 wt%, silver ion = 0.05 _wt%, was made to NaBH 4 = 0.05 wt%.

(Evaluation of ultrafine particle dispersion)
Whether or not the ultrafine metal particle dispersion is formed in each of the above examples and whether or not the formed ultrafine metal particle dispersion has practically sufficient performance is evaluated as follows, and the results are shown. The results are shown in (Table 1) to (Table 3) and (Table 4) to (Table 6).

(Generation of ultrafine particles)
In each of the above examples, whether or not metal ultrafine particles were generated was confirmed visually. Since Au nanoparticles and Ag nanoparticles change the color of the solution based on surface plasmon absorption due to the formation of nanoparticles, the former changes to red and the latter changes to yellow, confirming the formation of nanoparticles. It can be a criterion. In the case where ultrafine metal particles are formed and stably dispersed, the mark is indicated by ○, and when the ultrafine metal particles are formed but immediately aggregated and precipitated, the mark is indicated by ×.

(Stability over time)
After standing at room temperature and normal pressure, the appearance of the ultrafine particle solution after 1 week, 4 weeks, and 8 weeks was visually observed to determine the period during which the ultrafine particles were stably present. When the ultrafine metal particles agglomerated and adhered to the side wall or bottom of the container, it was indicated by “x”, and when precipitation did not occur and the dispersion remained good, it was indicated by “◯”.

(Stability after adding salt)
Salt (NaCl) was added to the metal ultrafine particle dispersion prepared in each of the above examples so as to have a predetermined concentration, and the appearance of the ultrafine particle solution after 5 days was visually observed. When a precipitate was formed, it was indicated by a cross, and when there was no change in the solution, it was indicated by a mark.

(Redispersibility)
Water was distilled off from the ultrafine metal particle dispersion (aqueous solution) prepared in each of the above examples using an evaporator. After the water was completely distilled off, ultrapure water was added again, and the appearance of the ultrafine particle solution was visually observed to determine the possibility of reconcentration (redispersibility). The above operation was repeated to determine the number of times that concentration and redispersion were possible. The greater the number of times, the higher the performance of the dispersion.

(Particle size and dispersion)
The ultrafine metal particle dispersion prepared in each of the above examples was transferred to a TEM observation grid and vacuum-dried for 3 days, followed by TEM observation. From the obtained TEM image, the particle size of the ultrafine metal particles was measured using image analysis software “Scion Image (trade name)” manufactured by Scion Corporation, USA. The particle diameter was measured at N = 200. Further, the standard deviation σ was calculated from the result. From the average particle diameter R and standard deviation σ, the following general formula (1)
Dispersity K = (standard deviation σ) / (average particle diameter R) (1)
Was used to define the degree of dispersion K, and the degree of dispersion K was calculated for each ultrafine metal particle.

As confirmed from the above (Table 1) to (Table 6), in the ultrafine metal particle dispersions of the examples, the generated ultrafine metal particles have a particle size of 24 nm or less, and the particle size dispersion degree is 0.40 or less. The generated ultrafine metal particles are small and have a uniform particle diameter, and the dispersion stability of the ultrafine metal particles is very high.
On the other hand, in the metal ultrafine particle dispersion of the comparative example, the dispersion stability is low, precipitation is likely to occur, the particle size of the generated metal ultrafine particles is 39 nm or more, and the particle size dispersion degree exceeds 0.40. The generated ultrafine metal particles are large and have a large variation in particle size.

  As described above, the ultrafine metal particle dispersion according to the present invention has ultrafine metal particles having a small particle size and a uniform distribution, and the storage stability of the ultrafine metal particles is high. According to the method for producing a metal ultrafine particle dispersion according to the present invention, a metal ultrafine particle dispersion having a metal ultrafine particle having a small particle size and a uniform distribution and having high storage stability of the metal ultrafine particle is obtained. Can be provided easily. A metal ultrafine particle dispersion having metal ultrafine particles having a small particle size and a uniform distribution and having high storage stability of the metal ultrafine particles has wide industrial applications and is useful.

Claims (11)

An ultrafine metal particle dispersion obtained by mixing a hyperbranched polymer (A) having a site having a reducing ability and a solution (B) containing a metal ion,
A metal characterized in that only metal ions induced in the hyperbranched polymer (A) are reduced by the site having the reducing ability to form ultrafine metal particles only in the hyperbranched polymer (A). Ultra fine particle dispersion.   2. The ultrafine metal particle dispersion according to claim 1, wherein the hyperbranched polymer (A) is a spherical molecule having a diameter of 1 nm or more and less than 100 nm.   The ultrafine metal particle dispersion according to claim 1, wherein the site having the reducing ability is an amino group or a sulfide group.   The metal ultrafine particle dispersion according to any one of claims 1 to 3, wherein the hyperbranched polymer (A) has a protective layer. A first step of preparing a hyperbranched polymer (A) having a site having a reducing ability;
A second step of preparing a solution (B) containing metal ions;
By mixing the hyperbranched polymer (A) and the solution (B), a metal ion is induced in the hyperbranched polymer (A) and a metal ion induced in the hyperbranched polymer (A). A third step of reducing only by the site having the reducing ability to form ultrafine metal particles only in the hyperbranched polymer (A);
A method for producing a metal ultrafine particle dispersion, comprising:   6. The method for producing a metal ultrafine particle dispersion according to claim 5, wherein the hyperbranched polymer (A) has a spherical shape with a diameter of 1 nm or more and less than 100 nm.   The method for producing a metal ultrafine particle dispersion according to claim 5 or 6, wherein the hyperbranched polymer (A) prepared in the first step is a hyperbranched polymer that itself has a reducing ability.   The hyperbranched polymer (A) prepared in the first step is a hyperbranched polymer that itself has no reducing ability but is given a reducing ability by contacting with a pH adjuster. The manufacturing method of the metal ultrafine particle dispersion of Claim 5 or 6.   The hyperbranched polymer (A) prepared in the first step is a hyperbranched polymer that itself has no reducing ability, but is given a reducing ability by condensing a compound separately. The manufacturing method of the metal ultrafine particle dispersion of Claim 5 or 6.   The method for producing a metal ultrafine particle dispersion according to any one of claims 5 to 9, wherein the site having the reducing ability is an amino group or a sulfide group.   The method for producing a metal ultrafine particle dispersion according to any one of claims 5 to 10, wherein the site having the reducing ability functions as a protective layer for the metal ultrafine particles.