JP6365544B2 - Continuous production method of metal nanoparticles - Google Patents

Description

  The present invention relates to a continuous method for producing metal nanoparticles.

  In recent years, as a new circuit formation (patterning) method that replaces the conventional plating method and vapor deposition-photolithography method, “printed electronics”, a technology that directly forms circuits by printing, has been attracting attention as the next generation industrial base Has been. This technology forms a desired circuit pattern by printing a conductive paste and conductive ink on a substrate. In addition to basic circuit components such as thin film transistors, resistors, inductors and capacitors, batteries and displays , Sensors, RFID (Radio Frequency Identification), solar cells, etc., can be applied to many applications. As a result, the manufacturing process of electronics-related products is dramatically simplified, and the time is shortened, and further resource saving and energy saving can be achieved at the same time.

  Either a glass substrate or a plastic film substrate can be used as a substrate for printed electronics. However, if a PET (Polyethylene terephthalate) film substrate can be used among plastic film substrates, there is a strong demand in the market in terms of cost. It is thought that it will be. However, since it is generally said that the heat resistance of a PET film is about 120 ° C., a conductive paste capable of obtaining sufficient conductivity and adhesion with a base material by heat treatment at a temperature not exceeding this, and conductive There is a need for the development of functional inks. Various proposals have been made to satisfy the above requirements. Among these, nano-sized metal particles are excellent in low-temperature sinterability and conductivity, and are considered promising.

  As a method for producing metal nanoparticles, for example, Patent Document 1 describes a method for producing metal nanoparticles that forms a protective layer having high particle dispersibility using citric acid. However, since the metal nanoparticles obtained by the above method are dispersed in a dilute concentration in the solution, a special concentration method such as ultrafiltration is required for the recovery. It's hard to say. Furthermore, when a protective layer that inhibits sinterability is present on the surface of the metal particles, such as a citric acid layer, it is not detached by heat treatment at a low temperature, and the metal nanoparticles are fused when used as a conductive material. Will be disturbed. For this reason, the low-temperature sintering reaction that is characteristic of the nanoparticles becomes insufficient, and satisfactory conductivity cannot be obtained. Therefore, it cannot be said that the metal particles produced by the above method sufficiently bring out the original characteristics of the metal nanoparticles.

As an industrial method for producing metal nanoparticles capable of solving the above problems, Patent Document 2 describes a continuous method for producing metal nanoparticles. However, the method of Patent Document 2 uses a harmful and explosive substance such as hydrazine as a reducing agent, and there is a concern about the difficulty in terms of safety.
Patent Document 3 describes a production method using a continuous particle production apparatus using a barrel-screw. If it is the said method, a metal nanoparticle can be manufactured, performing efficient heating and slow heating by making it react little by little continuously. However, in the method of Patent Document 3, it is necessary to perform a reducing agent or electrochemical reduction, and there is a concern that chemical and mechanical safety is insufficient. This method is insufficient as a method for industrially mass-producing metal nanoparticles.

  Patent Document 4 describes a method for producing metal nanoparticles using silver oxalate. Since this method can recover metal nanoparticles from a concentrated liquid without using a reducing agent having a safety problem as described above, it can be used for conductive pastes and inks with excellent productivity. It is regarded as a promising method for producing metal nanoparticles.

Patent 4919595 Patent 4534098 Special table 2005-531405 JP2012-162767

However, when the present applicant tried to produce metal nanoparticles by the method described in Patent Document 4, in order to industrially produce metal nanoparticles, the following two types of carbon dioxide gas generated by thermal decomposition of oxalic acid were used. It became clear that two problems occurred.
First, the generated carbon dioxide gas contains an amine compound such as an alkylamine used for the reaction, and it is necessary to exhaust it through a heat exchanger in order to eliminate adverse effects on the environment. However, since the amount of carbon dioxide generated is large, a heat exchanger with high capacity is required, and the equipment cost increases.
Secondly, since the liquid level of the reaction liquid rises due to the generation of carbon dioxide, the contents may leak from the reaction vessel. In order to prevent this, it is necessary to suppress the amount of the reaction solution per volume of the reaction vessel, so that the production amount per batch is lowered, and thus the production cost is increased.
Accordingly, the present invention provides a method for solving the above-mentioned problems caused by the generation of carbon dioxide gas, and capable of producing metal nanoparticles industrially efficiently and at low cost while suppressing the influence on safety and the environment. Let it be an issue.

In order to solve the above-mentioned problems, the present inventor repeated research, and as a raw material composition, an alkylamine (a), an organic solvent (b), and a metal compound (c) that decomposes by heating to produce a single metal or an alloy. Using the contained composition, this is continuously introduced into the reaction vessel, and the thermal decomposition reaction of the metal compound (c) proceeds in the reaction vessel, thereby controlling the increase in the internal pressure of the reaction vessel by controlling the reaction amount. As a result, it has been found that the leakage of the reaction liquid from the reaction vessel can be suppressed and the production efficiency of the metal nanoparticles can be improved.
The present invention has been completed based on the above findings, and provides the following method and apparatus for continuously producing metal nanoparticles, and metal nanoparticles obtained by this method or apparatus.

Item 1. A raw material composition containing an alkylamine (a), an organic solvent (b), and a metal compound (c) that is decomposed by heating to produce a single metal or an alloy is continuously introduced into the reaction vessel, and the metal is contained in the reaction vessel. A process for continuously producing metal nanoparticles having an average particle diameter of 1 nm or more and 200 nm or less, comprising a reaction step of causing a thermal decomposition reaction of the compound (c).
Item 2. Item 2. The production method according to Item 1, wherein the metal compound (c) is a metal oxalate salt.
Item 3. Item 3. The method according to Item 1 or 2, wherein the temperature of the thermal decomposition reaction is 250 ° C or lower.
Item 4. The organic solvent (b) has a boiling point of 150 ° C. or more and 350 ° C. or less under normal pressure and 1 g / L or more in water at 20 ° C. under normal pressure, and the organic solvent (b) in the raw material composition The manufacturing method in any one of claim | item 1 -3 whose content of is 50 to 500 weight part with respect to 100 weight part of metal compounds (c).
Item 5. Item 5. The production method according to any one of Items 1 to 4, wherein the content of the alkylamine (a) in the raw material composition is 1 equivalent or more and 10 equivalents or less with respect to the substance amount (mol) of the metal compound (c). .
Item 6. Item 2. The production method according to Item 1, wherein the raw material composition further contains a fatty acid (d).
Item 7. Item 6 wherein the total amount of the fatty acid (d) and alkylamine (a) in the raw material composition is 1 equivalent to 10 equivalents relative to the amount (mol) of the metal compound (c). The manufacturing method as described in.
Item 8. Item 8. The production method according to any one of Items 1 to 7, wherein in the reaction step, the thermal decomposition reaction proceeds with the raw material composition forming a film on the heating surface in the reaction vessel.
Item 9. Item 9. The method according to Item 8, wherein the heating surface is an inner wall surface of the reaction vessel.
Item 10. Item 10. The method according to Item 8 or 9, wherein the raw material composition is formed into a film by allowing the heated surface in the reaction vessel to flow down naturally.
Item 11. Item 11. The production method according to Item 9 or 10, wherein the film is formed by allowing the raw material composition to naturally flow down the heated wall surface of the reaction vessel inside the reaction vessel and further wiping with a wiper blade. .
Item 12. Furthermore, the manufacturing method in any one of claim | item 1 -11 including the process of refine | purifying the metal nanoparticle produced | generated at the reaction process.
Item 13. A raw material composition containing a reaction vessel, a heating device attached to the reaction vessel, an alkylamine (a), an organic solvent (b), and a metal compound (c) that decomposes by heating to produce a single metal or an alloy. A supply device that continuously supplies the reaction vessel; a product recovery vessel that stores a product containing metal nanoparticles generated in the reaction vessel; and a volatile content recovery device that recovers volatile matter generated in the reaction vessel. An apparatus for producing metal nanoparticles having an average particle diameter of 1 nm to 200 nm.
Item 14. Item 13. Metal nanoparticles having an average particle diameter of 1 nm to 200 nm obtained by the method according to any one of Items 1 to 12.

  According to the method of the present invention, the amount of the raw material composition introduced into the reaction vessel per hour is controlled, and consequently, the reaction amount per hour is controlled, so that the internal pressure increasing factor or reaction liquid of the reaction vessel such as carbon dioxide gas is controlled. It is possible to control the generation amount of the liquid level increasing factor, thereby suppressing the leakage of the reaction liquid from the reaction vessel. Therefore, the capacity of the reaction liquid per volume of the reaction vessel can be increased, and metal nanoparticles can be produced efficiently at low cost.

  Further, in the conventional batch method, in order to suppress the discharge of carbon dioxide gas, the production amount of metal nanoparticles per one time is small, and only the laboratory scale production can be performed. In this regard, according to the method of the present invention, it is possible to manufacture or mass-produce metal nanoparticles on an industrial scale.

  In addition, the method of the present invention produces metal nanoparticles having a protective layer using a raw material composition containing an alkylamine, an organic solvent, and a metal compound that decomposes by heating to form a single metal or an alloy. The conductive paste containing the metal nanoparticles thus formed has good dispersibility of the metal nanoparticles and can form a circuit having high conductivity even when sintered at a low temperature.

  Moreover, according to the method of the present invention, metal nanoparticles having a protective layer can be obtained without using a reducing agent. Since many reducing agents used for the production of metal nanoparticles are harmful, the method of the present invention is also safe and less harmful to the environment.

  In the method of the present invention, the raw material composition is continuously introduced into the reaction vessel, and the raw material composition is reacted in a state where a film is formed on the heated surface (for example, the heated wall surface of the reaction vessel). Since the raw material composition quickly reaches the thermal decomposition temperature in a short time, the production efficiency of the metal nanoparticles is further improved.

It is a figure which shows one embodiment of this invention apparatus.

  Hereinafter, the present invention will be described in detail.

(1) Method for Producing Metal Nanoparticles The method of the present invention comprises a raw material composition containing an alkylamine (a), an organic solvent (b), and a metal compound (c) that decomposes by heating to produce a single metal or alloy. It is a continuous production method of metal nanoparticles having an average particle diameter of 1 nm or more and 200 nm or less, including a reaction step of continuously introducing the reaction mixture into a reaction vessel and causing a thermal decomposition reaction of the metal compound (c) to proceed in the reaction vessel.

Raw Material Composition The raw material composition used in the method of the present invention contains an alkylamine (a), an organic solvent (b), and a metal compound (c) that decomposes by heating to produce a single metal or an alloy.

  The raw material composition used in the present invention must have fluidity in order to continuously generate metal nanoparticles by being continuously introduced into a reaction vessel and subjected to a thermal decomposition reaction, for example, liquid or slurry It needs to be in the shape. Moreover, in order to perform a thermal decomposition reaction efficiently, it can be in the state which formed the film | membrane on the surface so that a thermal decomposition reaction can be performed on the heated surface (for example, the heated wall surface of reaction container). It is preferable. The nature of the raw material composition is not particularly limited as long as it can be continuously introduced into the reaction vessel. The viscosity of the raw material composition is preferably about 20 Pa · s or less, and more preferably about 10 Pa · s or less. The viscosity of the raw material composition is usually about 1 mPa · s or more.

In order to prevent aggregation of the metal nanoparticles in the conductive ink and the conductive paste and to disperse them well in a desired solvent, the surface of the present invention is a protective layer or a dispersion layer (hereinafter referred to as “ Metal nanoparticles coated with "protective layer" are produced. Therefore, the raw material composition used in the production method of the present invention contains an alkylamine having a substituent, which can be a protective layer, in addition to the metal compound (c) before forming the metal nanoparticles. Alkyl compounds other than amines can also be used.
The alkyl compound binds to the metal compound (c) in the composition, and further functions as a protective layer on the surface when metal nanoparticles are formed by thermal decomposition, and the metal nanoparticles are dispersed in the conductive ink. The state can be maintained well.
Examples of the substituent of the alkyl compound include an aldehyde group, a hydroxy group, a sulfo group, an amino group, a carboxyl group, a mercapto group, a cyano group, a cyanato group, an isocyanato group, and an isothiocyanato group. Among them, an amino group, A carboxyl group is preferred.

  Specific examples of the alkyl compound include alkyl amine, fatty acid, alkyl thiol, alkyl aldehyde, alkyl cyanate, alkyl isocyanate, alkyl isothiocyanate, alkyl sulfonic acid, alkane nitrile and the like. As the alkyl compound, an alkylamine is suitable, and in addition to the alkylamine, a fatty acid may be included.

  If necessary, the raw material composition can contain additives within a range that does not affect the effects of the present invention. Examples of the additive include a viscosity adjusting agent, a drying inhibitor, an antifoaming agent, a leveling agent, and a surfactant.

<Alkylamine (a)>
The alkylamine (a) has only the ability to bind to the metal compound (c) and functions as a protective layer on the surface of the metal nanoparticles when the metal nanoparticles are generated.

The alkylamine (a) may be any alkyl group having 3 to 18 carbon atoms, and preferably has an alkyl group having 4 to 12 carbon atoms.
Specific examples of the alkylamine (a) include ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, isoamylamine, tert- Amylamine, 3-pentylamine, n-amylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-octylamine, 2-ethylhexylamine, n-nonylamine, n-aminodecane, n-aminoundecane, n -Dodecylamine, n-tridecylamine, 2-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-oleylamine, 3 -Methoxy Propylamine, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3- (2-ethylhexyloxy) propylamine, N-ethyl-1,3-diaminopropane, N , N-diisopropylethylamine, N, N-dimethyl-1,3-diaminopropane, N, N-dibutyl-1,3-aminopropane, N, N-diisobutyl-1,3-diaminopropane, N-lauryldiaminopropane Etc. can be illustrated.
Furthermore, secondary amines such as dibutylamine and cyclic alkylamines such as cyclopropylamine, cyclobutylamine, cyclopropylamine, cyclohexylamine, cycloheptylamine, and cyclooctylamine can also be used.
Among these, the dispersion stability of metal nanoparticles in a solvent when conductive ink or conductive paste is produced using the obtained metal nanoparticles is improved, and the protective film derived from alkylamine is conductive. N-Propylamine, Isopropylamine, Cyclopropylamine, n-Butylamine, Isobutylamine, sec-Butylamine, Tert-Butylamine, Cyclobutylamine, n-Amylamine, n-Hexyl are easily eliminated at low temperatures during film formation. Amine, cyclohexylamine, n-octylamine, 2-ethylhexylamine, n-dodecylamine, n-oleylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, N , N-Dimethyl-1,3-diamy Nopropane, N, N-dibutyl-1,3-aminopropane, n-butylamine, n-hexylamine, cyclohexylamine, n-octylamine, n-dodecylamine, N, N-dimethyl-1,3-diamino More preferred is propane, N, N-dibutyl-1,3-aminopropane.
Alkylamine (a) can be used alone or in combination of two or more. When using 2 or more types of alkylamine (a), you may use 2 or more types of different carbon numbers.

The content of the alkylamine (a) in the raw material composition may be about 1 equivalent or more, preferably about 1.5 equivalents or more with respect to the amount (mol) of the metal compound (c), about 2 More than equivalent is more preferable. If it is the said range, the conductive paste or conductive ink containing the obtained metal nanoparticles has a good dispersibility of the metal nanoparticles in the liquid and a circuit having high conductivity even when sintered at a low temperature. Can be formed.
Further, the content of the alkylamine (a) in the raw material composition may be about 10 equivalents or less, preferably about 5 equivalents or less with respect to the substance amount (mol) of the metal compound (c). In addition, if it is the said range, the ratio of a metal compound (c) will not become low too much, and the production | generation efficiency of a metal nanoparticle will not fall. In addition, most of the alkylamine (a) is desorbed from the surface of the metal nanoparticles by the heat treatment when forming the conductive film by subjecting the resulting conductive ink, conductive paste or the like containing the metal nanoparticles to the heat treatment. Therefore, even if the raw material composition contains a large amount of alkylamine (a), the conductivity of the conductive film is hardly affected.
The content of the alkylamine (a) is about 1 equivalent to about 5 equivalents, about 1 equivalent to about 10 equivalents, about 1.5 equivalents to about 5 equivalents with respect to the amount (mol) of the metal compound (c). Equivalents, about 1.5 equivalents to about 10 equivalents, about 2 equivalents to about 5 equivalents, about 2 equivalents to about 10 equivalents.

<Fatty acid (d)>
In addition to the alkylamine (a), the fatty acid (d) may be further added to the raw material composition as necessary. Since the fatty acid (d) binds strongly to the surface of the metal nanoparticles, it contributes to improving the dispersibility of the metal nanoparticles in the conductive ink and conductive paste. The fatty acid (d) is not particularly limited as long as it has an ability to bind to the metal compound (c) and functions as a protective layer on the surface of the metal nanoparticles when the metal nanoparticles are generated. be able to.

The alkyl group of the fatty acid (d) may have 3 to 18 carbon atoms, and preferably has 4 to 18 carbon atoms.
Specific examples of fatty acid (d) include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid , Linoleic acid, α-linolenic acid and the like. Cyclic alkyl carboxylic acids such as cyclohexane carboxylic acid can also be used. Among these, caproic acid, 2-ethylhexanoic acid, oleic acid, linoleic acid, and α-linolenic acid are preferable in terms of good dispersion stability of the metal nanoparticles during and after generation in the reaction solution.
The fatty acid (d) can be used alone or in admixture of two or more.

The content of the fatty acid (d) in the raw material composition is such that the total amount of the alkylamine (a) and the fatty acid (d) is about 1 equivalent or more with respect to the amount (mol) of the metal compound (c). The amount of about 1.5 equivalents or more is preferable, and the amount of about 2 equivalents or more is more preferable. If it is the said range, the dispersibility of the metal nanoparticle in a conductive ink and a conductive paste can fully be improved.
Further, the total amount of the alkylamine (a) and the fatty acid (d) may be about 10 equivalents or less with respect to the amount (mol) of the metal compound (c), and about 5 equivalents or less. Is preferred. It is known that the fatty acid (d) strongly binds to the metal nanoparticles. When the conductive ink, conductive paste or the like containing the obtained metal nanoparticles is subjected to a heat treatment to form a conductive film, Many of the fatty acids used on the surface of the particles remain. However, within the above range, the residual fatty acid does not adversely affect the conductivity.
The total amount of alkylamine (a) and fatty acid (d) relative to the amount (mol) of metal compound (c) is about 1 equivalent to about 10 equivalents, about 1 equivalent to about 5 equivalents, about 1.5 equivalents. Equivalent to about 10 equivalents, about 1.5 equivalents to about 5 equivalents, about 2 equivalents to about 10 equivalents, about 2 equivalents to about 5 equivalents.

  As described above, it is known that fatty acid (d) binds strongly to metal nanoparticles, and when a conductive ink, conductive paste or the like containing the obtained metal nanoparticles is subjected to heat treatment to form a conductive film In addition, most of the fatty acids contained in the composition remain on the surface of the metal nanoparticles. Therefore, when the alkylamine (a) and the fatty acid (d) are contained in the raw material composition, the molar ratio of the alkylamine (a) and the fatty acid (d) is about 90% when the alkylamine (a): fatty acid (d) is about 90%. : 10 to about 99.9: 0.1, preferably about 95: 5 to about 99.9: 0.1, and about 95: 5 to about 99.5: 0. More preferably, it is in the range of .5. Within the above range, the dispersibility of the metal nanoparticles in the conductive ink and conductive paste can be sufficiently improved, and the conductivity of the conductive film formed using the conductive paste containing the obtained metal nanoparticles can be obtained. Good.

<Organic solvent (b)>
The organic solvent (b) used in the present invention imparts fluidity to the raw material composition to such an extent that the raw material composition is continuously introduced into the reaction vessel and the thermal decomposition reaction of the metal compound (c) proceeds favorably. Anything is possible. Further, the organic solvent (b) is preferably one that can form a film on the heated surface of the raw material composition (for example, the heated wall surface of the reaction vessel). The organic solvent (b) is used without any particular problem as long as the viscosity of the raw material composition is low (for example, about 20 Pa · s or less, and preferably about 10 Pa · s or less). be able to.

Examples of the organic solvent (b) include alcohols, glycols, glycol ethers, aprotic polar solvents, and the like.
Among them, those having a high boiling point are preferable so that the raw material composition introduced into the reaction vessel does not evaporate to dryness. For example, the boiling point under normal pressure may be about 150 ° C. or higher and about 350 ° C. or lower, preferably about 150 ° C. or higher and about 330 ° C. or lower, more preferably about 150 ° C. or higher and about 300 ° C. or lower.
Furthermore, the organic solvent (b) can dissolve about 1 g / L or more in water at 20 ° C. under normal pressure in that the metal nanoparticles produced during the purification of the metal nanoparticles can be easily solid-liquid separated. What is necessary is just what can be melt | dissolved about 10 g / L or more, and what can melt | dissolve about 100 g / L or more is more preferable.

  Specific examples of the organic solvent (b) include linear or branched alkanes having 6 to 18 carbon atoms; aromatics such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and benzonitrile. Ketones such as acetone, acetylacetone and methyl ethyl ketone; fatty acid esters such as ethyl acetate, butyl acetate, ethyl butyrate and ethyl formate; ethers such as diethyl ether, dipropyl ether, dibutyl ether, tetrahydrofuran and 1,4-dioxane Halogenated hydrocarbons such as dichloromethane, chloroform, tetrachloromethane, dichloroethane; 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3- Butanediol, 1,2-hexanediol, 1, -Diols such as hexanediol, 1,2-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol; Linear or branched aliphatic alcohols, cyclohexanol, alcohols such as 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol; polyethylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl Ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, 3-methoxybutyl acetate, ethylene glycol monomethyl ether, ethyl Glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monohexyl ether, ethylene Glycol monohexyl ether acetate, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-2-ethylhexyl ether acetate, ethylene glycol monophenyl ether, ethylene glycol monophenyl ether acetate, ethylene glycol monobenzyl ether, ethylene glycol Nobenzyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether , Dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol Glycols or glycol ethers such as monobutyl ether; methyl-n-amyl ketone; methyl ethyl ketone oxime; triacetin; γ-butyrolactone; 2-pyrrolidone; N-methylpyrrolidone; acetonitrile; N, N-dimethylformamide; Examples thereof include terpenes such as ethyl) piperazine; dimethyl sulfoxide; terpineol.

Among them, alcohols (especially 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol) are used in terms of the ease of handling due to the boiling point at ordinary pressure, the polarity, and the viscosity of the solvent. , Glycol ethers (particularly ethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether) and γ-butyrolactone are preferred.
The organic solvent (b) may be used alone or in combination of two or more so that the viscosity of the raw material composition is appropriate.

The content of the organic solvent (b) in the raw material composition may be about 50 parts by weight or more, preferably about 60 parts by weight or more, and about 75 parts by weight or more with respect to 100 parts by weight of the metal compound (c). Is more preferable. Further, it may be about 500 parts by weight or less, preferably about 450 parts by weight or less, more preferably about 400 parts by weight or less with respect to 100 parts by weight of the metal compound (c).
If it is the said range, fluidity | liquidity can be provided to a raw material composition to such an extent that a raw material composition is continuously introduce | transduced into a reaction container and the thermal decomposition reaction of a metal compound (c) advances favorably, Moreover, the raw material composition can be made into the state which formed the film | membrane on the heated surface in the reaction process.
The content of the organic solvent (b) with respect to 100 parts by weight of the metal compound (c) is about 50 parts by weight to about 400 parts by weight, about 50 parts by weight to about 450 parts by weight, about 50 parts by weight to about 500 parts by weight, About 60 parts by weight to about 400 parts by weight, about 60 parts by weight to about 450 parts by weight, about 60 parts by weight to about 500 parts by weight, about 75 parts by weight to about 400 parts by weight, about 75 parts by weight to about 450 parts by weight; About 75 parts by weight to about 500 parts by weight are included.

Metal compound (c)
Metals such as organometallic compounds (for example, carboxylates), sulfonates, thiol salts, chlorides, nitrates, carbonates, etc., as metal compounds (c) that decompose by heating to produce simple metals or alloys Salts can be exemplified. Among these, organic metal compounds and carbonates are preferable and organic metal compounds are more preferable in that it is easy to remove a counterion-derived substance after the metal is generated. Among the organometallic compounds, carboxylates such as formic acid, acetic acid, oxalic acid, malonic acid, benzoic acid and phthalic acid are preferable, and oxalate is more preferable from the viewpoint of easiness of thermal decomposition.

  Examples of the metal species of the metal compound (c) include gold, silver, copper, platinum, palladium, nickel and the like. Among these, gold, silver and platinum are preferable in terms of good conductivity and oxidation resistance, and silver is more preferable in terms of low cost and low temperature sintering.

As the metal compound (c), silver oxalate, copper oxalate, nickel oxalate, aluminum oxalate, silver formate, copper formate, nickel formate, aluminum formate, silver acetate, copper acetate, nickel acetate, aluminum acetate, silver malonate, malonic acid Examples include copper, nickel malonate, aluminum malonate, silver benzoate, copper benzoate, nickel benzoate, aluminum benzoate, silver phthalate, copper phthalate, nickel phthalate, and aluminum phthalate. Among these, silver oxalate, copper oxalate, nickel oxalate, and aluminum oxalate are preferable.
A metal compound (c) can be used individually or in combination of 2 or more types.

  A commercially available product can be purchased and used for the metal compound (c) which is decomposed by heating to produce a single metal or an alloy. Moreover, it can also manufacture according to the method currently disclosed by Unexamined-Japanese-Patent No. 2012-162767.

The content of the metal compound (c) in the raw material composition may be about 12% by weight or more, preferably about 15% by weight or more, and more preferably about 20% by weight or more based on the total amount of the composition. If it is the said range, the conductive paste or conductive ink containing the obtained metal nanoparticles has a good dispersibility of the metal nanoparticles in the liquid and a circuit having high conductivity even when sintered at a low temperature. Can be formed.
The content of the metal compound (c) in the raw material composition may be about 55% by weight or less, preferably about 50% by weight or less, more preferably about 40% by weight or less based on the total amount of the composition. . If it is the said range, a metal compound (c) and an alkylamine (a) will interact efficiently, and the effect of this invention, especially the efficient manufacture of a metal nanoparticle can be achieved.
The content of the metal compound (c) in the raw material composition is about 12 to about 55% by weight, about 12 to about 50% by weight, about 12 to about 40% by weight, about 15 to Examples include about 55%, about 15 to about 50%, about 15 to about 40%, about 20 to about 55%, about 20 to about 50%, about 20 to about 40% by weight.

Preparation process of raw material composition Each component of the raw material composition is in a state of being uniformly dispersed in the raw material composition in order to advance the thermal decomposition reaction of the metal compound (c) efficiently in the reaction vessel. Cost. The order of adding each component and the mixing method are not particularly limited as long as each component is uniformly dispersed in the obtained raw material composition.
Examples of the mixing method of each component include a method using a mechanical stirrer, magnetic stirrer, vortex mixer, planetary mill, ball mill, three rolls, line mixer, planetary mixer, dissolver and the like. A mixing device can be appropriately selected according to the scale and production capacity of the manufacturing facility.

  During mixing of each component, the temperature of the composition rises due to the influence of heat of dissolution or frictional heat and the thermal decomposition reaction of the metal compound (c) may start. It is preferable to carry out so that it may become about 60 degrees C or less, and it is more preferable to carry out, suppressing the temperature of a composition to about 40 degrees C or less. You may mix, cooling a composition as needed. The mixing time of each component is not particularly limited as long as each component is in a state of being uniformly mixed in the composition. For example, the mixing time may be in the range of 1 minute to several hours.

  The method of the present invention may use an already prepared raw material composition, or an alkylamine (a), an organic solvent (b), and a metal compound (c) that decomposes by heating to form a single metal or alloy. Including a step of preparing a raw material composition containing (for example, a step of mixing the components (a), (b), and (c)), and following this step, the reaction step described below can also be performed. .

By continuously introducing the raw material composition for the reaction process into the reaction vessel, a thermal decomposition reaction of the metal compound occurs continuously, and metal nanoparticles having a film derived from alkylamine are generated. As a method for continuously introducing the raw material composition into the reaction vessel, it is possible to adjust the introduction rate so that the thermal decomposition reaction of the metal compound proceeds efficiently while suppressing the amount of generated carbon dioxide. For example, it can be used without particular limitation.

  The continuous introduction method of the raw material composition into the reaction vessel in the reaction step includes free fall of the raw material composition from the storage tank, dropping of the raw material composition into the reaction vessel by pressurization, raw material composition using various pumps The method etc. which introduce | transduce into a reaction container can be illustrated. In particular, when the composition has a high viscosity, liquid dropping by pressurization or introduction by a tube pump is preferably used.

In the method of the present invention, the raw material composition introduced into the reaction vessel is preferably subjected to a thermal decomposition reaction in contact with the heating surface in the reaction vessel.
The contact method between the raw material composition and the heating surface is not particularly limited. For example, the raw material composition is heated in the reaction vessel by using a shower or spray to flow down the wall of the heated reaction vessel. The method of dripping or spraying on a wall surface etc. is mentioned. In addition, one or a plurality of surface members (for example, a cylinder, a board, etc.) having a surface are provided in the reaction container, and the surface of the surface member is heated (for example, the inner surface of a heated cylinder or square tube). And / or a method in which the raw material composition is allowed to flow down on the outer surface, the disk or the surface of the disk, or dropped or sprayed using a shower or spray. When a plurality of cylindrical surface members are provided, they may be installed in a nested manner in the reaction vessel.

In the reaction step in the production method of the present invention, when the raw material composition introduced into the reaction vessel is heated, a thermal decomposition reaction of the metal compound (c) occurs, and metal nanoparticles having a film derived from alkylamine are generated. To do.
In the reaction step, the film is formed on the heated surface (for example, on the wall surface of the reaction vessel, on the surface of the surface member installed in the reaction vessel, etc.) in that the thermal decomposition reaction of the metal compound (c) can be performed efficiently. It is preferable to subject the raw material composition in a state of forming a thermal decomposition reaction. The method for forming the film on the heated wall surface of the raw material composition may be any method as long as the raw material composition can flow in a state where the film is formed on the heated wall surface of the reaction vessel.
In the present invention, the “state in which a film is formed on the surface on which the raw material composition is heated” includes a state in which a film is continuously formed on the surface and a portion in which no film is partially formed. A state in which a film is continuously formed, a state in which a film is formed in a spot shape, and the like are included. Moreover, the case where a film thickness is uniform and the case where it is non-uniform | heterogenous are included.

  The thickness of the raw material composition on the heated surface may be a film thickness that reaches the thermal decomposition reaction temperature immediately after the metal compound (c) in the raw material composition contacts the heated wall surface, It can adjust suitably according to reaction temperature, the composition of a raw material composition, etc. The film thickness can be adjusted by selecting the dropping speed of the raw material composition on the surface, the film forming method, and the like. In the present invention, the thickness of the film may be, for example, in the range of about 0.1 μm to about 5,000 μm, and preferably in the range of about 0.1 μm to about 2,000 μm.

  As a mode of forming a film of the raw material composition on the heated surface, the raw material composition is allowed to flow down naturally on the heated wall surface of the reaction vessel or on the surface of the planar member installed in the reaction vessel, and further the wiper A method of forming a film by wiping with a blade or the like (wiper type), the raw material composition is allowed to flow down naturally on the heated wall surface of the reaction vessel or on the surface of the planar member installed in the reaction vessel, A method for forming a film by leveling with a scraper (scraper type), a method in which a raw material composition is transferred to the surface of a rotating disk to form a film (rotary type), or a relative rotating outer cylinder (reaction vessel And a method of forming a film having a gap thickness between the inner cylinder and the inner cylinder (rotary type), a system of forming a film by centrifugal force on both walls between the outer cylinder and the inner cylinder (centrifugal type), etc. be able to. Among them, a method of a wiper type, a rotary type, a centrifugal type is preferable in that a film of a raw material composition having a uniform thickness can be formed on a heated surface, and a thermal decomposition reaction can be efficiently advanced. A wiper system is more preferable.

  As a wiper type or scraper type, using a rotary or reciprocating wiper blade or scraper, etc., the raw material composition that naturally flows down on the heated wall surface, or dripped or sprayed on the wall surface using a spray or shower Examples thereof include a method of forming the raw material composition into a uniform film, a method of flowing the raw material composition onto a rotatable or slidable heating surface, and forming a uniform film with a fixed wiper blade or a scraper. Above all, a raw material composition that naturally flows down the heated surface can be used with a rotary wiper blade in that a uniform film can be efficiently formed on the heated surface and the thermal decomposition reaction can proceed efficiently. A method of forming a uniform film by using is preferable. The material of the wiper blade or scraper used for the reaction is not particularly limited as long as it does not cause corrosion or heat deformation due to the composition in the reaction vessel.

As another mode of forming a film of the raw material composition, a method of forming a film by naturally flowing the raw material composition along the heated wall surface of the reaction vessel (flowing type), inclining the reaction composition in the reaction vessel A method in which the raw material composition is naturally allowed to flow down on the surface of the planar member to form a film (tilt type), and the heating surface is slid while the raw material composition is allowed to flow along the slidable heating surface. A method of forming a film on the heating surface (slide type) can be exemplified.
In the present invention, “flowing down” means flowing downward (vertically downward or diagonally downward) according to gravity.

  A system in which the raw material composition is allowed to flow naturally along the heated wall surface of the reaction vessel to form a film (flowing-down method), and the raw material composition is allowed to flow in a film form from above the heated wall surface of the reaction vessel. Examples include a method in which a raw material composition is dropped or sprayed on a wall surface using a spray or shower to form a film on the heating surface.

As a method of forming a film by allowing the raw material composition to flow down naturally on the surface installed in a reaction vessel (inclined type), a plate-like member installed in a hierarchy with an inclined angle, an inclined angle is added A method of causing the raw material composition to flow down from above along a plurality of columnar members or one or a plurality of coil-shaped members can be exemplified. Also, a reaction vessel such as a tube is installed in an inclined state, and the raw material composition is allowed to flow down along the heated wall surface of the reaction vessel. The heating surface is a curved surface such as a columnar shape or a spherical shape. And a method of flowing down from above.
The inclination angle of the surface of the planar member installed in the reaction vessel and the inclination angle in the case of inclining the reaction vessel wall surface are the rates at which the metal compound (c) in the flowing raw material composition completely undergoes a thermal decomposition reaction. What is necessary is just to adjust to the inclination | tilt angle which a raw material composition flows down, and it does not restrict | limit in particular. The inclination angle may be in the range of about 1 to 90 degrees with respect to the horizontal, and is preferably in the range of about 15 to 90 degrees.
By forming a film of the raw material composition on the heated wall surface of the reaction vessel, the metal compound (c) can be efficiently thermally decomposed to obtain metal nanoparticles efficiently.

  The inner wall material of the reaction vessel used in the reaction step of the present invention can heat the metal compound (c) to a temperature necessary for thermal decomposition by continuously introducing the raw material compound, and the metal nanoparticles are continuously formed by the thermal decomposition reaction. Anything can be used without particular limitation as long as it can be generated. For example, iron, steel (especially stainless steel), glass, or iron, steel, or stainless steel surface (reaction vessel inner surface) baked glass (eg, iron, steel, or stainless steel cylinder) And the inner surface of the glass lining).

  The introduction rate of the raw material composition into the reaction vessel can be appropriately adjusted according to the capacity of the reaction vessel, the components of the raw material composition used for the reaction, and the viscosity, and the thermal decomposition reaction of the composition is completed on the heating surface. Such an introduction speed may be used.

  Moreover, what is necessary is just to adjust the introduction speed | rate of a raw material composition so that generation | occurrence | production of the gas etc. in thermal decomposition reaction may not increase too much. The introduction rate of the raw material composition into the reaction vessel is preferably within a range in which the amount of gas generated per minute generated by the thermal decomposition reaction of the metal compound (c) does not exceed the volume of the reaction vessel. It is more preferably 75% or less, and even more preferably 50% or less of the volume of the reaction vessel. Within the above range, the gas discharge rate can be suppressed, and the leakage of the reaction solution from the reaction vessel can be suppressed. Even if the introduction rate of the raw material composition (reaction amount per hour) is increased, it is industrially safe. It is possible to manufacture.

  As the generated gas, in addition to carbon dioxide gas generated by thermal decomposition of metal oxalate or the like, there can be volatile matter derived from alkylamine. However, since most of the generated gas is considered to be carbon dioxide, in the present invention, the amount of carbon dioxide generated by the thermal decomposition reaction is used as the amount of gas. Further, the generation amount of carbon dioxide gas is calculated using a gas state equation (PV = nRT) as an ideal gas. Specifically, P = pressure under gas generation (1 atm for calculation as a volume when released to the outside of the reaction vessel), V = volume of generated gas, n = number of moles of generated gas. (When a metal salt of oxalic acid is used in the composition, it is twice the molar equivalent of oxalic acid), R = gas constant, and T = heating temperature (absolute temperature) during the pyrolysis reaction.

The reaction temperature of the thermal decomposition reaction in the reaction step may be a temperature at which the thermal decomposition reaction proceeds continuously and metal nanoparticles are continuously generated. Specifically, it may be about 250 ° C. or less. More specifically, it may be about 50 ° C. or more and about 250 ° C. or less, preferably about 100 ° C. or more and about 240 ° C. or less, and more preferably about 120 ° C. or more and about 240 ° C. or less. If it is the said temperature range, a metal nanoparticle can be obtained efficiently and continuously by attaching | subjecting the composition which formed the film | membrane in reaction container to a thermal decomposition reaction.
In the present invention, the reaction temperature is a heating temperature by a heater. The temperature in the reaction vessel and the temperature of the reaction vessel wall or the surface of the planar member installed in the reaction vessel are usually almost the same as the heating temperature by the heater.
The reaction time can be arbitrarily set until a target amount of metal nanoparticles is obtained. Usually, it can be about several seconds to several hours.

Purification step The metal nanoparticles produced by the thermal decomposition reaction in the above reaction step are obtained as a mixture containing the organic solvent (b) and unreacted raw materials (alkylamine, fatty acid, etc.). By refine | purifying the mixture obtained by reaction, the metal nanoparticle which has the target physical property can be obtained. Examples of the method for purifying the metal nanoparticles include a solid-liquid separation method by filter filtration and a precipitation method using the specific gravity difference between the metal nanoparticles and the organic solvent. As a specific method of solid-liquid separation, a method such as centrifugation, a cyclone method, or a decanter can be exemplified. Further, when purifying, the mixture may be diluted with a low-boiling solvent such as acetone or methanol in order to improve the work by reducing the viscosity and to efficiently remove unreacted substances.

(2) Metal nanoparticles By the above-described method of the present invention, metal nanoparticles having an alkylamine-derived film can be obtained.
The average particle diameter of the metal nanoparticles can be set to a desired value by appropriately adjusting the reaction conditions and the composition of the raw material composition. The average particle size can be, for example, in the range of about 1 nm to about 200 nm, especially about 1 nm to about 100 nm, especially about 10 nm to about 60 nm. If it is the said range, since the dispersibility is good when it mix | blends with a conductive ink or a conductive paste, the selection range of a solvent becomes wide. In addition, within the above range, a circuit having a sufficiently low volume resistance value can be formed even if the conductive ink or conductive paste containing the metal nanoparticles is heat-treated at a relatively low temperature. You can select and use.
In the present invention, the average particle diameter of the metal nanoparticles is a value measured by a dynamic light scattering method, and specifically, a value measured using the apparatus used in the examples.

  In the method of the present invention, since metal nanoparticles are produced by a continuous method, the generation rate of volatile components such as carbon dioxide gas is suppressed, and as a result, metal nanoparticles can be produced on an industrial scale.

(3) Apparatus for producing metal nanoparticles The above-described method of the present invention includes, for example, a reaction vessel, a heating device attached to the reaction vessel, and a supply device that continuously supplies the above-described raw material composition to the reaction vessel. And a product recovery container for storing a product containing metal nanoparticles generated in the reaction container, and a volatile content recovery device for recovering the volatile matter generated in the reaction container. It can be carried out using a particle production apparatus.
The heating device may heat the atmosphere in the reaction vessel or may heat the reaction vessel wall. Moreover, the apparatus of this invention can be equipped with the surface member for forming the film | membrane of a raw material composition in reaction container, In that case, a heating apparatus should just heat a surface member.
The volatile content recovery device for recovering the volatile content may be a recovery device by reflux or separation of the volatile content.
The apparatus of the present invention can be produced using a generally used thin film distillation apparatus, molecular distillation apparatus, or the like.
Other configurations such as a reaction vessel, a surface member, a device for forming a film of the raw material composition on the surface, a continuous introduction device of the raw material composition into the reaction vessel, and the like are as described for the method of the present invention.

In addition, the apparatus of the present invention attaches a pressure reducing device, a pressure adjusting device, an active force ray irradiation device, an external light shielding mechanism, an inert gas filling device, a heat retention mechanism, a cooling mechanism, and the like to the reaction vessel as necessary. be able to.
One embodiment of the device of the present invention is shown in FIG. This apparatus includes a cylindrical reaction vessel R, a raw material composition supply device 2 that continuously supplies the raw material composition along the vessel wall of the reaction vessel R, a product recovery tank 3, and a volatile component by cooling. And a volatile component recovery device 4 that liquefies and recovers. The reaction vessel R includes a heat exchanger H for heating the reaction vessel R, an exhaust device P for discharging the gas generated by the reaction to the outside through the heat exchanger H, and a raw material along the vessel wall A rotatable stirring blade W for forming a film of the composition and a stirring blade driver M are attached. Further, the heat exchanger H and the heater h for heating the wall surface are covered.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these.

(1) Each component of the raw material composition used in the raw material examples and comparative examples is shown below.

Alkylamine (a)
a1: n-octylamine (carbon number 8, Wako Pure Chemical Industries, Ltd.)
a2: n-butylamine (4 carbon atoms, manufactured by Wako Pure Chemical Industries, Ltd.)

Organic solvent (b)
b1: 3-methoxy-1-butanol (boiling point 161 ° C., manufactured by Wako Pure Chemical Industries, Ltd.)
b2: Triethylene glycol monomethyl ether (boiling point 249 ° C., manufactured by Wako Pure Chemical Industries, Ltd.)

Metal compound (c)
c1: Silver oxalate Silver oxalate was synthesized by the method described in Patent Document 4 (Japanese Patent Application Laid-Open No. 2012-162767).

Fatty acid (d)
d1: caproic acid (carbon number 6, manufactured by Wako Pure Chemical Industries, Ltd.)

(2) Preparation of raw material composition Each component of the amount shown in Table 1 below was weighed, put into a container, and then stirred for about 30 minutes using a magnetic stirrer at room temperature to obtain the raw material composition. 1-5 were prepared.
Moreover, the viscosity of each composition was measured by (E-type viscometer BROOKFIELD company VISCOMETER DV-II + Pro, 10 rpm). Table 1 shows the measured viscosity of each composition.

(3) Formation reaction of metal nanoparticles
Example 1
In Example 1, a rotating thin film molecular distillation apparatus (MS-300 manufactured by Shibata Kagaku Co., Ltd.) was used as an apparatus used for the continuous reaction. The total volume of the reaction vessel and the liquid receiving part was about 1.6 L. The vacuum pump attachment part of the apparatus was opened so that the generated gas was released. The rotational speed of the fluororesin wiper blade provided inside the reaction vessel was 60 rpm, and the temperature of the ribbon heater mounted outside the reaction vessel was 180 ° C. Thereby, the temperature of the reaction vessel wall was also about 180 ° C.
Using the raw material composition 1 shown in Table 1, using a tube pump (Peristaltic tube pump MP-1000, manufactured by Tokyo Rika Kikai Co., Ltd.), the reaction vessel was introduced into the reaction vessel at an introduction rate of 1.5 g / min for 20 minutes. The reaction was continued. About 30 g of the raw material composition 1 was continuously charged into the reaction vessel, and it was confirmed whether or not metal nanoparticles were generated by the thermal decomposition reaction.

  Whether or not a mixture of metal nanoparticles can be continuously formed (evaluation of continuous reactivity) is indicated by “○” when the metal nanoparticles are continuously formed, and when the metal nanoparticles are not continuously formed. Was marked “x”. Further, the yield was calculated from the weight of the obtained metal nanoparticles, and the amount of gas generated when the ideal gas was determined from the amount of the raw material composition introduced was calculated. The results are shown in Table 2.

(Example 2)
In Example 2, the reaction was performed in the same manner as in Example 1 except that the raw material composition 2 shown in Table 1 was used. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

Example 3
In Example 3, the raw material composition 2 shown in Table 1 was used, and the reaction was carried out while the rotation of the wiper blade of the molecular distillation apparatus (MS-300, manufactured by Shibata Kagaku Co., Ltd.) used in Example 1 was stopped. For introducing the raw material composition 2 into the reaction vessel, a tube pump (Peristaltic tube pump MP-1000, manufactured by Tokyo Rika Kikai Co., Ltd.) was used, and the reaction was continued for 30 minutes at an introduction rate of 1.0 g / min. About 30 g of composition 2 was continuously charged into the reaction vessel, and it was confirmed whether or not metal nanoparticles were generated by the thermal decomposition reaction. The other operations were the same as in Example 1. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(Example 4)
In Example 4, the raw material composition 3 shown in Table 1 was used, and the reaction was carried out in the same manner as in Example 3. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(Example 5)
In Example 5, a glass tube having a diameter of 20 mm, a length of 800 mm, and an internal volume of about 0.25 L was fixed in a state having an inclination of 15 degrees from a horizontal plane, thereby obtaining a reaction vessel. A ribbon heater set to 150 ° C. around a glass tube was wound around a length of 500 mm, and the raw material composition 2 in Table 1 was introduced into the reaction vessel at a rate of 1.0 g / min with a tube pump. The reaction was continued for 30 minutes, and it was confirmed whether or not metal nanoparticles were generated by the thermal decomposition reaction. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(Comparative Example 1)
In Comparative Example 1, the reaction of metal nanoparticles was performed by a batch method (method described in Patent Document 4) which is a conventional technique. Specifically, using the raw material composition 2 in Table 1, each component was charged in a 500 mL glass beaker in the amount shown in Table 1, and mixed at room temperature with a magnetic stirrer for about 30 minutes. The composition volume was approximately 82 mL. 30 g (about 43 mL) of this mixture was extracted and placed in a 300 mL glass beaker, and the beaker was placed on a hot stirrer (HHE-19G-U manufactured by Koike Seimitsu Seisakusho) set in advance at 150 ° C., and stirring and heating were started. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(Comparative Example 2)
The comparative example 2 was made to react by the same method as Example 1 using the raw material composition 4 (no alkylamine addition) shown in Table 1. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(Comparative Example 3)
In Comparative Example 3, the reaction was carried out in the same manner as in Example 1 using the raw material composition 5 (no organic solvent added) shown in Table 1. Table 2 shows evaluation of continuous reactivity, yield, and amount of gas generated.

(4) Purification of metal nanoparticles In each of the examples and comparative examples, the mixed solution recovered from the reaction vessel is put into a centrifuge tube, and an equal amount of washing solution (methanol) is added to the mixed solution, and dispersed and mixed with a vortex mixer. Then, the silver nanoparticles were spun down by processing at 3000 rpm for 1 minute in a centrifuge (Himac small cooling centrifuge CF7D2 manufactured by Hitachi Koki Co., Ltd.), and the supernatant was removed to purify the metal nanoparticles. The metal nanoparticles were purified by repeating this process three times.

(5) Evaluation of Metal Nanoparticles Metal nanoparticle-dispersed ink was prepared by the method described in Patent Document 4 using metal nanoparticles obtained by each reaction. Specifically, butanol: octane mixed solvent (volume ratio 1: 4) and the obtained silver nanoparticles (about 6.5 to 6.9 g) are put in an equal amount (50 ml sample bottle) at room temperature. By stirring and mixing with a magnetic stirrer, a 50 wt% metal nanoparticle-dispersed ink (about 13 to 13.8 g) was obtained.

  Using the obtained metal nanoparticle-dispersed ink, the average particle size of each metal nanoparticle obtained was measured with a dynamic light scattering particle size distribution measuring device (Spectres Zeta Sizer Nano). Each metal nanoparticle-dispersed ink was spin-coated (3000 rpm, 30 seconds) on a PET film (HK188G-AB500H manufactured by Teijin Chemicals Co., Ltd., cut to 60 × 60 mm) and heat-treated at 100 ° C. for 30 minutes. The thickness of the coating film at this time was measured with a laser microscope (OPTELICS HYBRID manufactured by Lasertec) to obtain an average coating thickness of five measurements. Using the obtained average coating film thickness, the volume resistance value was calculated | required with the conductivity meter (Mitsubishi Chemical Analytech Lorestar AX), and electroconductivity was evaluated. The evaluation results are shown in Table 2.

  In Example 1, it took about 2 minutes from the initial charging of the raw material composition into the reaction vessel until the mixture containing metal nanoparticles was recovered. Moreover, it was after about 2 minutes that the dropping of the mixture containing the silver nanoparticles stopped after the stop of the charging. Meanwhile, a mixture containing metal nanoparticles continuously was obtained. Therefore, the residence time inside the reaction vessel was about 2 minutes. Moreover, the reaction amount per hour was estimated to be about 1.5 g / min from the charging speed. Therefore, the amount of carbon dioxide generated per hour was 0.13 L / min, that is, 8.0% of the reaction vessel volume. Therefore, it can be said that the amount of carbon dioxide generated by the thermal decomposition reaction could be controlled as compared with the batch reaction shown in Comparative Example 1 described later. The obtained mixture was purified by the above-described purification method, and the yield was calculated. As a result, about 6.9 g of metal nanoparticles were obtained with respect to the theoretical value of about 7.4 g of metal nanoparticles generated from 30 g of the composition. It was.

  In Example 2, 3-methoxy-1-butanol was used as the organic solvent (b). As a result, the fluidity of the raw material composition was improved, and introduction into the reaction vessel was facilitated. However, the yield was slightly reduced as compared with Example 1. This is because the boiling point of the organic solvent was lower than that of triethylene glycol monomethyl ether used in Example 1, so that the fluidity of the composition when thinned with a rotary wiper blade was lost, and the reaction vessel This is presumed to be due to an increase in the amount of adhesion to the inside. The amount of carbon dioxide generated per hour was 0.13 L / min, that is, 8.0% of the volume of the reaction vessel.

  In Example 3, the raw material composition was introduced into the reaction vessel with the rotation of the rotary wiper blade stopped. As a result, the heating surface in the reaction vessel and the composition reacted efficiently, and the composition and product did not adhere to the wall surface. In addition, compared with the case of thinning with a rotary wiper blade, because the composition is slightly longer until the thermal decomposition temperature is reached, the introduction rate of the composition into the reaction vessel is higher than when using a rotary wiper, Some suppression was necessary. As a result, the amount of gas generated per hour was 0.09 L / min, that is, 5.3% of the volume of the reaction vessel, and gas generation could also be controlled by this method.

  In Example 4, the reaction was carried out by changing the raw material composition to the composition 3 in Example 3. As a result, a slight increase in volume resistance value was observed as compared with Example 3. This is thought to be because the fatty acid (d) was not contained in the composition, which affected the physical properties of the coating film formed by the reduced dispersibility of the metal nanoparticles in the conductive ink. At this time, the amount of gas generated per hour was 0.09 L / min, that is, 5.3% of the volume of the reaction vessel.

  In Example 5, not the apparatus used in Examples 1 to 4, but a heated glass tube was used as a reactor, and the composition was introduced into this reactor. As a result, it took about 3 minutes from the start of introduction until the first product was recovered. This is because when the composition introduced into the heating surface moves downstream, the flow rate is slower than when the heating surface is vertical, and the film is not forcibly thinned by the wiper blade. The time was longer compared to Examples 1-4. Moreover, since the residence time is long, the thermal decomposition reaction proceeds continuously even at 150 ° C., which is a low temperature compared with Examples 1 to 4. At this time, the amount of gas generated per hour was 0.08 L / min, that is, 31.6% of the volume of the reaction vessel.

  In Comparative Example 1, the reaction was carried out in a batch according to the method described in Patent Document 4 (Japanese Patent Application Laid-Open No. 2012-162767) for comparison with a continuous reaction. About 30 minutes were required from the start of heating to the start of the pyrolysis reaction, and the time from the start to the end of the pyrolysis reaction (can be confirmed that the generation of carbon dioxide was stopped) was about 4 minutes. From the amount of the composition, the amount of carbon dioxide generated per hour from the start to the end of thermal decomposition is 0.60 L / min, which is about 5 to 6 times the amount generated in the example, and the reaction vessel (300 mL in 1 minute) It was estimated that carbon dioxide gas of 1.98 times the volume of the glass beaker was generated. Therefore, a large amount of carbon dioxide gas was ejected and the liquid level increased during the reaction. Since it is considered that the pyrolysis time does not change greatly even when the reaction is carried out on a larger scale, it is assumed that the amount of gas generated per hour is increased. Therefore, it is necessary to provide equipment capable of withstanding this gas ejection and liquid level rise, and it has been confirmed that the method of Comparative Example 1 is unlikely to be a safe and low-cost industrial manufacturing method. In addition, since the yield was a small scale, it was a slightly high yield compared with the continuous reaction.

  In Comparative Example 2, the reaction was carried out using a composition containing no alkylamine (a). As a result, the metal nanoparticles themselves were continuously produced, and the amount of gas generated per hour at this time was 0.12 L / min, that is, 7.8% of the volume of the reaction vessel. However, the surface of the metal nanoparticle was bonded to the surface of the metal nanoparticle more strongly than the alkylamine, and the surface was coated with the fatty acid (d) that remained after the coating was formed. Conductivity was not obtained when forming.

  In Comparative Example 3, the composition was introduced into the reaction vessel without using the organic solvent (b). As a result, the composition gradually thickened, and the tube pump could not be introduced into the reaction vessel from the middle. In addition, immediately after the start of introduction, the formation reaction of the metal nanoparticles was confirmed from the composition introduced into the reaction vessel, but the mixture containing the metal nanoparticles produced thereafter was dried and solidified in the reaction vessel. Particles could not be obtained.

  According to the production method and apparatus of the present invention, various metal nanoparticles can be continuously produced safely and at low cost. In addition, the obtained metal nanoparticles can be applied to various printing methods by using them in various conductive inks or conductive pastes, and can be effectively used as printed electronics materials used for electric circuit wiring and electrode formation. Can do. Furthermore, it can be effectively used in various fields such as conductive adhesives, electromagnetic wave absorbers, and light reflectors.

Claims (11)

A raw material composition containing an alkylamine (a), an organic solvent (b), and a metal compound (c) that is decomposed by heating to produce a single metal or an alloy is continuously introduced into the reaction vessel, and heating in the reaction vessel A method for continuously producing metal nanoparticles having an average particle diameter of 1 nm or more and 200 nm or less, comprising a reaction step in which a thermal decomposition reaction of the metal compound (c) proceeds in a state where the raw material composition forms a film on the surface .   The production method according to claim 1, wherein the metal compound (c) is a metal oxalate salt.   The production method according to claim 1 or 2, wherein the temperature of the thermal decomposition reaction is 250 ° C or lower.   The organic solvent (b) has a boiling point of 150 ° C. or more and 350 ° C. or less under normal pressure and 1 g / L or more in water at 20 ° C. under normal pressure, and the organic solvent (b) in the raw material composition The production method according to any one of claims 1 to 3, wherein the content of is 50 parts by weight or more and 500 parts by weight or less with respect to 100 parts by weight of the metal compound (c).   The production according to any one of claims 1 to 4, wherein the content of the alkylamine (a) in the raw material composition is 1 equivalent or more and 10 equivalents or less with respect to the substance amount (mol) of the metal compound (c). Method.   The manufacturing method of Claim 1 in which a raw material composition contains a fatty acid (d) further.   The total amount of the fatty acid (d) and alkylamine (a) in the raw material composition is 1 equivalent to 10 equivalents relative to the amount (mol) of the metal compound (c). 6. The production method according to 6. The manufacturing method according to claim 1, wherein the heating surface is an inner wall surface of a reaction vessel. The manufacturing method in any one of Claims 1-8 which form a film | membrane by making the raw material composition flow naturally on the heating surface in reaction container. The raw material composition within the reaction vessel, the heated walls of the reaction vessel is gravity flow, further by wiping with a wiper blade, to any one of claims 1 to 9, characterized in that to form a film The manufacturing method as described. Furthermore, the manufacturing method in any one of Claims 1-10 including the process of refine | purifying the metal nanoparticle produced | generated at the reaction process.