JP2020073712A - Method and device for producing nickel fine particles and nickel fine particles - Google Patents

Abstract

To solve the problem of inhibition of good-quality continuous synthesis of fine particles such as inhibition of absorption of a microwave of a reaction liquid caused by sticking of a metal deposit on the inner wall of a reaction tube when the reaction liquid is produced by mixing a liquid containing a raw material liquid of metal fine particles with a liquid containing a reductant of the liquid, distributed to the reaction tube, and irradiated with the microwave so as to be set to a temperature suited for reduction, thus progressing reduction reaction.SOLUTION: An inactive gas or a reactive gas is inserted into a reaction liquid containing metal salts and a reductant, and the reaction liquid is distributed.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a method and an apparatus for producing nickel ultrafine particles, and nickel ultrafine particles produced thereby. More specifically, a raw material liquid containing components of ultrafine particles mainly of ultrafine nickel particles that can be used for electronic parts is mixed with a solution containing a reducing agent thereof and is circulated in a reaction tube as a reaction liquid, At least a part of the reaction tube is irradiated with microwaves, the temperature of the reaction solution is introduced to a set temperature in a short time, and the reduction reaction of the raw material solution is allowed to proceed to produce ultrafine particles. To ultrafine nickel particles. The main purpose of the ultrafine particles is 30 nm, but the average particle size may be 200 nm or less, 100 nm or less, 30 nm, or 10 nm or less depending on the purpose and application. It may also be in the form of a colloid or paste containing ultrafine particles.

  In recent years, research and development of nanoparticles having a particle size of 200 nm (nanometer) or less have been actively conducted, and many proposals have been made. For example, a reaction solution obtained by mixing a solution of a metal salt as a raw material of metal nanoparticles and a solution containing a reducing agent of the metal salt is circulated in a reaction tube, and at least a part of the reaction tube is provided with a micro One example is an attempt to irradiate a wave to heat the reaction liquid in the reaction tube to a predetermined temperature suitable for the reduction reaction, thereby reducing the metal salt and continuously producing metal nanoparticles. is there.

  For example, a reaction solution containing silver nitrate as a metal salt and a reducing agent thereof is circulated in a reaction tube made of glass or resin, the reaction solution is irradiated with microwaves and heated, and the temperature of the reaction solution is suitable for the reduction reaction. It has been proposed to raise the temperature to a certain temperature to cause a reduction reaction of silver nitrate to obtain silver nanoparticles. However, if the reduction of silver nitrate is attempted to continue, silver will deposit and adhere to the inner wall of the reaction tube in a relatively short time. Since the silver adhering to the inner wall reflects microwaves, the microwaves are not absorbed by the reaction liquid, and the temperature of the reaction liquid drops sharply. As a result, there is a problem that a large amount of unreacted silver nitrate is mixed in the product, resulting in a low yield of silver nanoparticles. In addition, there were serious problems such as the inability to produce high-quality silver nanoparticles. However, because there are not many examples of attempting mass production of metal nanoparticles using microwave irradiation to a reaction tube, there are not many patent documents that discuss the above problem.

  In many cases, the reduction reaction of the metal salt is carried out by heating the metal salt and the reducing agent to an appropriate reduction temperature, not at room temperature, to synthesize ultrafine particles. As the heating means, microwave irradiation may be used as a uniform and quick heating means.

  Many patent documents describe that irradiation of a reaction solution with microwaves is expected to have an effect of causing a uniform and rapid rise in temperature of the reaction solution, and the reduction reaction can be effectively advanced. Then, it is described that variations in the particle size of nanoparticles to be produced can be reduced, reaction time can be shortened, and production cost can be reduced.

  In the experiments by the inventors, a reaction liquid containing a metal salt, a reducing agent and a dispersant was passed through a reaction tube to accelerate the reduction reaction under heating by microwave irradiation, and when producing metal nanoparticles, a metal layer was formed. Has been confirmed to adhere to the inner wall of the reaction tube. Especially in the case of silver nanoparticles, the level is serious. When metal nanoparticles are deposited on the wall surface of the reaction tube, the deposited layer on the wall surface of the reaction tube reflects microwaves. As a result, it has been confirmed that problems such as damage to the oscillator and the reaction tube, heating of the reaction solution with high uniformity cannot be achieved, and the heating effect does not occur at all. This problem is also a major problem in cases other than silver, such as copper and nickel.

  In addition, in the experiments conducted by the present inventors, it has been confirmed that when the metal nanoparticles are continuously produced while flowing the reaction solution in the reaction tube, the heating effect by the microwave causes a problem. In addition, the reaction tube becomes clogged and the reaction liquid stops flowing, which may cause an explosion, significantly deteriorate the production quality of the metal nanoparticles, and require the reaction tube to be replaced. It has been confirmed that major problems such as increase in manufacturing cost are caused. In addition, it has been confirmed that there arises a problem that the advantage of microwave irradiation is greatly impaired.

  However, there have been proposals to solve the above-mentioned problems that occur when nanoparticles are produced while irradiating microwaves, but they are not sufficiently effective. When the reaction solution is irradiated with microwaves in a batch process to carry out the reduction reaction of the metal salt in the reaction solution, metal deposits may adhere to the inner wall of the container, causing problems such as damage to the container. Patent Document 1 discloses a method for solving the above problem.

  Patent Document 1 describes that a reaction solution obtained by dissolving a metal oxide or a metal hydroxide in an organic solvent is reduced in a glass container to generate metal nanoparticles. Further, it is described that when the temperature of the reaction liquid is raised by using microwaves and the reduction reaction is continued for a certain period of time, the metal fine particles adhere to the inner wall surface of the container. Further, it has been pointed out that there is a risk that the adhered material absorbs microwaves and is heated, the temperature of the container locally becomes high, and the glass is broken.

  In order to solve this, in Patent Document 1, a mixed solvent of an organic solvent that easily absorbs microwaves and an organic solvent that hardly absorbs microwaves is placed in a separable container of 1 L (1 liter), and a metal oxide is added to the mixed solvent. Substance or metal hydroxide and an organic modifier in an equimolar amount or less with respect to the metal element, a reducing agent is added to the obtained solution to form a reaction solution, which is irradiated with microwaves from the outside of the container. It is described that the reaction solution is heated to produce metal nanoparticles. One of the reasons for using a mixed solvent of an organic solvent that easily absorbs microwaves and an organic solvent that does not easily absorb microwaves is that it is close to the wall surface of the container when the reaction solution is irradiated with microwaves from the outside of the container. By the way, they are providing mitigation measures against the absorption of microwaves. Many types of metal salts, solvents that easily absorb microwaves, solvents that hardly absorb microwaves, organic modifiers, and the like have been proposed.

  In Patent Document 1, a microwave transparent material is further used in a portion of the reaction container where the metal fine particles are deposited and does not adhere, and a microwave shielding member is arranged in a portion of the reaction container where the metal fine particles are deposited and adhered. Is listed.

  According to the experiments of the present inventors, a reaction solution is circulated in a tubular reaction tube made of a fluororesin, a part of which passes through a microwave irradiation field, the reaction solution is irradiated with microwaves, metal ions are reduced, and thus, When producing metal nanoparticles, it has been found that deposition of deposits on the inner wall of the reaction tube cannot be avoided by the conventional methods including Patent Document 1. It also turned out to be a very serious problem.

For example, the reaction liquid is circulated through a fluororesin reaction tube having an inner diameter of 2 mm, an outer diameter of 3 mm, and a portion to be inserted into a cylindrical microwave cavity having a length of 100 mm. Further, this reaction tube is irradiated with TM ₀₁₀ mode microwave having a frequency of 2.4 to 2.5 GHz to generate copper nanoparticles, silver nanoparticles, and the like. In such a case, it is obvious that the method disclosed in Patent Document 1 cannot be used.

  A reaction solution containing a dispersant of metal nanoparticles, which is synthesized with a metal salt and a reducing agent, is flown into a reaction tube passing through a microwave cavity, and the reaction solution is heated by irradiating microwaves to heat the metal. When nanoparticles are continuously produced, for example, when the metal salt is changed to a silver salt, silver deposits are formed on the inner wall of the reaction tube. In addition, the microwave is reflected thereby. As a result, the microwave does not reach the reaction solution and the temperature of the reaction solution, which was at the appropriate temperature for the reduction, is lowered to an inappropriate temperature for the reduction, and the unreacted metal salt is mixed in the product. As a result, the yield of nanoparticles decreases.

  As described above, a reaction solution containing a solution in which a silver salt is dissolved, a dispersant for silver nanoparticles, and a reducing agent for the silver salt is circulated in the reaction tube, and the reaction solution is irradiated with microwaves for reaction. When the temperature is raised to the temperature suitable for reduction and the reduction reaction is carried out, silver deposits start to adhere to the inner wall of the reaction tube, causing various problems.

  That is, the microwave deposited on the reaction tube from the outside of the reaction tube is reflected by the silver deposits attached to the inner wall of the reaction tube, and the temperature of the reaction solution, which was at the appropriate temperature for the reduction, becomes an inappropriate temperature for the reduction. Will lower it. Moreover, the unreacted solution is mixed in a predetermined amount or more, and the quality of the silver nanoparticles to be manufactured is deteriorated. There are major obstacles to the production of metal nanoparticles. Problems such as a large change in the temperature distribution of the reaction tube occur.

  Such a phenomenon is considerably different depending on the kind of metal to be produced, but it is a problem to be solved which requires attention even for metals other than silver. For example, it has been confirmed that the above phenomenon also occurs with copper, nickel and the like.

  The continuous synthesis of various metal nanoparticles has begun to be proposed by published patents, and the synthesis / purification method thereof discloses the possibilities of productivity, convenience, low cost, scale-up, and the like. However, no proposal has been made to actually solve the above problem.

  It has been quite a long time since the synthesis of nanoparticles was proposed, but there are still many unclear points and things that must be solved for commercialization. One example is the relationship between the particle size of the nanoparticles and the physical properties.

  Although nickel nanoparticles are expected to have various uses such as internal electrodes for multilayer capacitors, bonding materials, and electromagnetic wave shielding materials, there is no established synthetic method for synthesizing nickel ultrafine particles with a particle size of 300 nm or less. The current situation. This is due to the difficulty of the synthetic reaction of nickel nanoparticles.

  In Patent Document 2, fine nickel particles are obtained, but silver ions are mixed with a raw material to function as a catalyst and seeds to form particles. Although it is a reduction by irradiation with microwaves, it is a reduction by an amine, so that the reaction is performed at 200 ° C. or higher to obtain nickel particles having an average particle diameter of 40 to 90 nm.

  In Patent Document 3, nickel particles aggregated in a spherical shape of 25 nm to 30 nm are obtained, but ethyl acetate or toluene, which is a dangerous and highly harmful organic solvent, is used as the dispersion medium.

  In Patent Document 4, although 28 nm nickel particles are obtained, Rongalit which is a sodium salt of a reducing agent is used.

  In Patent Document 5, nickel particles of 50 nm are obtained, but nickel chloride or sodium hydroxide is used. Completely removing impurities such as alkali metals and chlorine requires a great deal of expense.

JP, 2011-012290, A JP, 2013-7070, A JP, 2004-124237, A JP, 2007-284715, A JP, 2005-194415, A

  When nickel nanoparticles are used as a material for wiring with an ink jet or the like, when they are used as a coating film, or when they are used for bonding, they are fine particles of 100 nm or less, and a hydrophilic alcohol-based dispersion medium. There is a demand for a colloid having good dispersibility in water.

When a metal is used as a material for wiring or electrodes, if an alkali metal such as sodium or potassium or an impurity such as chlorine is present in the metal, ion migration may occur. Ion migration is most likely to occur in silver, and the susceptibility to occurrence depends on the metal species. Nickel has a data rate of 10 ^{−3 that} of silver, but electronic components are becoming smaller and smaller, so nickel nano It is desired that the particles do not contain such impurities.

  The problem to be solved by the present invention is to provide ultrafine metal particles that solve the above-mentioned needs of the market with high quality and at an industrial level, ultrafine metal particle colloid, paste manufacturing method, manufacturing apparatus, ultrafine metal particle colloid, and paste. To do.

  The problem to be solved by the present invention is, in particular, a nickel ultrafine particle colloid capable of providing nickel ultrafine particles which have solved the needs of the market in good quality at an industrial level, a method for producing a paste, a manufacturing apparatus, a nickel ultrafine particle colloid, and a paste. To provide.

  The first invention of the present invention (hereinafter referred to as invention 1) made to solve the problems is to add a amine having an acid dissociation constant of 13 or more to a nickel-hydrazine complex formed from a nickel precursor solution and a hydrazine compound. In this way, the aqueous solution in which the hydroxide of the nickel-hydrazine complex has been formed is continuously irradiated with microwaves and heated to produce a nickel ultrafine particle colloid.

  A second invention of the present invention (hereinafter referred to as invention 2) made by developing invention 1 is that the amine having an acid dissociation constant of 13 or more is 1,1,3,3-tetramethylguanidine. The method for producing the Nikkell ultrafine particle colloid described in 1.

  A third invention of the present invention (hereinafter referred to as invention 3) made by developing inventions 1 and 2 is characterized in that nickel single nanoparticles are added to a reaction solution, and the invention 1 or 2 is described. This is a method for producing a nickel superfine particle colloid.

  A fourth invention of the present invention (hereinafter referred to as invention 4) made by developing inventions 1 to 3 is characterized in that microwave heating is performed under pressure at a reaction temperature of 90 ° C to 170 ° C. The method for producing a nickel superfine particle colloid according to any one of Inventions 1 to 3.

  A fifth invention of the present invention (hereinafter referred to as invention 5) made by developing inventions 1 to 4 is characterized in that a polyol is added to a reaction liquid, and the invention is described in any one of inventions 1 to 4. This is a method for producing a nickel superfine particle colloid.

  A sixth invention of the present invention (hereinafter referred to as invention 6) made by developing inventions 1 to 5 is characterized by using a dispersant soluble in water and a hydrophilic alcohol. 5. The method for producing the nickel ultrafine particle colloid according to any one of 5 above.

  The seventh invention of the present invention (referred to as invention 7) made by developing Inventions 1 to 6 is an alkali metal or chlorine obtained by the method for producing a nickel colloid solution according to any one of Inventions 1 to 6. It is a nickel ultrafine particle colloidal solution which is dispersed in a hydrophilic alcohol or water containing no.

  An eighth invention of the present invention (hereinafter referred to as invention 8) made to solve the problem is to add a amine having an acid dissociation constant of 13 or more to a nickel-hydrazine complex formed from a nickel precursor solution and a hydrazine compound. This is a method for producing a nickel ultrafine particle paste, characterized in that the aqueous solution in which the hydroxide of the nickel-hydrazine complex is formed is continuously irradiated with microwaves and heated.

  A ninth invention of the present invention (hereinafter referred to as invention 9) made by developing invention 8 is that the amine having an acid dissociation constant of 13 or more is 1,1,3,3-tetramethylguanidine. The method for producing the Nikkell ultrafine particle paste described in 1.

  The tenth invention of the present invention (hereinafter referred to as invention 10) made by developing invention 8 or 9 is characterized in that nickel single nanoparticles are added to the reaction solution. This is a method for producing a nickel superfine particle paste.

  An eleventh invention of the present invention (hereinafter referred to as invention 11) made by developing Inventions 8 to 10 is characterized in that microwave heating is performed under pressure at a reaction temperature of 90 ° C. or higher and 170 ° C. or lower. The method for producing a nickel ultrafine particle paste according to any one of Inventions 8 to 10.

  A twelfth invention of the present invention (hereinafter referred to as invention 12) made by developing inventions 8 to 11 is characterized in that a polyol is added to a reaction solution, and the invention is described in any one of inventions 8 to 11. This is a method for producing a nickel superfine particle paste.

  A thirteenth invention of the present invention (hereinafter, referred to as invention 13) made by developing the inventions 8 to 12 is characterized by using a dispersant soluble in water and a hydrophilic alcohol. 13. The method for producing a nickel ultrafine particle paste according to any one of 12 above.

  A fourteenth invention of the present invention (referred to as invention 14) made by developing the inventions 8 to 13 includes an alkali metal and chlorine obtained by the method for producing a nickel paste according to any one of the inventions 8 to 13. It is a nickel ultrafine particle paste which is not contained and is dispersed in hydrophilic alcohol or water.

  When using metal nanoparticles for electronic parts such as wiring, it is required that they do not contain impurities that may promote ion migration or deterioration.The nickel colloid of the present invention contains alkali metals and chlorine. Since it is not present, it can be preferably used. Moreover, since the synthesis is carried out at 90 ° C. to 170 ° C. or less in the continuous method, the energy cost is excellent and the manufacturing cost is low. Furthermore, since it is a colloid dispersed in a hydrophilic alcohol-based dispersion medium without using a harmful organic solvent, it is environmentally friendly.

It is a schematic diagram of the nickel nanoparticle manufacturing apparatus used for the example of embodiment of this invention. It is a schematic diagram of the nickel nanoparticle manufacturing apparatus used for the other embodiment of this invention. It is a figure which shows the temperature change of the reaction liquid by microwave irradiation in the synthesis | combination of the nickel ultrafine particle as an Example of this invention. It is a figure which shows the reflected wave intensity change of the microwave by microwave irradiation in the synthesis | combination of the nickel ultrafine particle as an Example of this invention.

1: Microwave irradiation port 2, 2a: Microwave irradiation field 4: Electric field monitor 5: Thermometer 6: Microwave oscillator / controller 7, 7a to 7n, 7r: Reaction tube 8: Reaction liquid 21, 21a to 21c: Gas sources 22 to 25: T-shaped joint 30: Connection parts 30a to 30e: Reaction liquid extraction parts 31, 32, 33, 33a to 33c: Liquid sources 34, 34a, 34c, x: Recovery tanks 71a to 71c, 72 to 78, 78a to 78c: Flow paths a-1 to a-30: Arrows S-1 to S-14: Sensors 101, 101a, 101b, 101c: Temperature curves 102, 102a, 102b, 102c: Reflected wave intensity of microwaves curve

  Embodiments of the present invention will be described below. In addition, in order to avoid duplication of description, the description of the manufacturing method and the description of the nanoparticles may be combined with the description of the apparatus for producing nanoparticles, and vice versa. Further, for convenience of explanation of the example of the present invention, each drawing used for explaining the embodiment of the present invention may be shown by partially changing the enlargement ratio without being particularly noted. It may not be similar to the description. Further, in each of the drawings, the same components are denoted by the same reference numerals, and the description may be omitted.

  FIG. 1 is a schematic view of a nanoparticle manufacturing apparatus created to explain an embodiment of the present invention in consideration of various requirements. In the figure, not all configuration requirements are used for all the form examples, and some form examples are unnecessary and may not be provided, but for convenience of explanation, the case where they are provided will be described. To do. In FIG. 1, reference numeral 1 is a microwave irradiation port (waveguide, etc.), 2 is a microwave irradiation field, 4 is an electric field monitor, 5 is a thermometer, 6 is a microwave oscillator / controller, 7, 7a, 7b are A reaction tube, 8 is a reaction liquid, 21 is an inert gas source, 22 to 25 are T-shaped joints, 30 is a connecting portion, 31 is a first liquid source (for example, A liquid, C liquid, etc.), 32 is a second liquid source. Liquid source (for example, B liquid, D liquid, etc.), 33 is a third liquid source (for example, E liquid, etc.), 34 is a recovery tank, 72 to 78 are liquid passages or liquid / gas mixture passages, Reference numeral 71 is a flow path for an inert gas. Of these, it is not necessary to provide all of them in the nanoparticle manufacturing apparatus, and the apparatus can be configured by using only necessary ones. Reference numerals S-1 to S-14 are sensors for measuring information on the reaction liquid such as temperature, pressure, flow rate, flow velocity, electric field strength, etc. used for control of the reaction system and other purposes, and are a liquid source, a liquid flow path, and a gas flow path. It is located in a recovery tank, microwave irradiation field, etc. The sensor may not be provided if unnecessary. a-1 to a-9 are arrows. The liquid feed pump is not shown. Some of the embodiments may include only a part of the drawings. Although not shown, a stirring device is arranged in each liquid source, recovery tank, etc. to make each liquid, reaction liquid, etc. uniform.

  In FIG. 1, for example, a case where at least the reference numerals 33 and 24 are not described will be described. For example, when there are two kinds of liquids to be mixed, the first kind of liquid is prepared in the liquid source 31, the second kind of liquid is prepared in the liquid source 32, and a plunger, for example, as a liquid delivery means is provided in each of the liquid sources. A pump is provided, and each prescribed liquid transfer rate is set. The respective liquids from the liquid sources 31 and 32 are sent from the liquid sources 31 and 32 at predetermined speeds through the liquid flow paths 73 and 74 in the directions of arrows a-2 and a-7, respectively, and the T-shaped joints 22 and 23 are formed. Then, the inert gas sent from the inert gas source 21 in the directions of arrows a-1 and a-4 is introduced. Then, the respective liquids into which the inert gas is introduced pass through the flow paths 77 and 76, are sent to the T-shaped joint 25, are mixed in the T-shaped joint 25, and are supplied from the remaining flow paths of the T-shaped joint 25. One end is sent to the liquid flow path 78 connected to the reaction tube 7.

  When there is a reference numeral 33 in FIG. 1, the liquid of the liquid source 33 passes through the liquid flow path 72 at a predetermined speed, and after the inert gas from the inert gas source 21 is introduced by the T-shaped joint 24, It is mixed with the liquid from the second liquid source 32 at the T-shaped joint 23. At this time, the inert gas from the inert gas source 21 is also mixed with the liquid from the second liquid source 32. In addition, the inert gas source 21 may be directly arranged also in the second liquid source 32 depending on the type of liquid.

  The liquid from the liquid flow path 78 enters the reaction tube 7 passing through the cavity 2 serving as a microwave irradiation field, and receives microwave irradiation in the microwave irradiation field 2.

  The reaction tube 7 in the microwave irradiation field 2 may have an optimum shape depending on the microwave frequency within the range of 300 MHz to 300 GHz, the microwave mode, the type of liquid, and the like. By appropriately selecting the shape of the reaction tube 7 in the microwave irradiation field 2, the effect of microwave irradiation can be controlled.

  Examples of the shape of the reaction tube 7 include a linear shape, an S shape, a coil shape, and a mixed shape thereof. Further, the effect of microwave irradiation can be controlled by disposing a part of the reaction tube 7 outside the microwave irradiation field 2.

  The connection part 30 is a connection part that connects the output part 7a of the reaction tube 7 and the reaction tube 7b, and may not be provided depending on the purpose of producing nanoparticles, the state of the device, the parts, and the like. In that case, the reaction tube 7b may have the same specifications as the reaction tube 7, or the diameter may be changed depending on the purpose. Reference numeral 30a is a reaction solution take-out section, which may be provided if necessary and used for controlling the reaction. The outer diameter and the inner diameter of the reaction tube can be changed in a portion not shown in the figure depending on the configuration of the apparatus.

  The reaction liquid extraction section has a means for determining the reaction state of fine particles, a particle size observing means, a particle size distribution observing means, a component observing means, a particle size selecting and sorting means such as ultrafiltration, a classifying means, a diversion means, and a heating means. It is preferable to provide at least one of temperature control means including cooling and the like as required. For example, in the case where a reaction status judging means (not shown) is arranged in the reaction liquid extraction section 30a, the reaction liquid of a predetermined level or lower is extracted, and the nanoparticles used in other embodiments of the present invention are used. As will be described later with reference to FIG. 2 which is a schematic view of the manufacturing apparatus of FIG.

  As a result of various studies of various embodiments of the present invention, in order to prevent deposits from being deposited on the inner wall of the reaction tube in the synthesis step involving reduction reaction of the nanoparticle raw material liquid under microwave irradiation, It has been found preferable to introduce an inert gas into the reaction solution before irradiation. It has also been found that the introduction of the inert gas is an important factor such as the way of circulating each liquid constituting the reaction liquid and the way of introducing the inert gas. Even if the inert gas is introduced into the reaction liquid after the reaction liquid is formed by mixing the first liquid and the second liquid, it is possible to alleviate the mirror phenomenon on the wall of the reaction tube. In addition, a method of introducing an inert gas into the first liquid, a method of introducing an inert gas into the second liquid, or a method of introducing an inert gas into the second liquid to make it flow in the liquid flow path. Where the first liquid is mixed with the first liquid, and where the inert gas is introduced into the second liquid and the first liquid containing the inert gas is mixed with the liquid flowing in the liquid flow path. Etc., there is an appropriate method according to the selection method of the raw material of the nanoparticles and the reducing agent.

  By flowing the reaction liquid into which the inert gas has been introduced into the reaction tube, it is possible to effectively prevent the metal deposits from adhering to the inner wall of the reaction tube. For example, when synthesizing metal nanoparticles, the second liquid containing the reducing agent containing the inert gas is mixed with the first liquid containing the metal salt containing the inert gas while the second liquid is circulating in the pipe. And a method of mixing the first liquid containing the metal salt with the second liquid containing the reducing agent into which the inert gas has been introduced is being circulated in the pipe. Even when the first liquid and the second liquid are mixed to form a reaction liquid and then an inert gas is introduced into the reaction liquid in the next step, the remarkable effect of introducing the inert gas can be exhibited. ..

  For example, a liquid from the first liquid source and a liquid from the second liquid source are made to flow through the flow paths to mix an inert gas with each liquid, and both liquids are mixed at a T-shaped joint to form a reaction liquid. Then, an embodiment of the method of irradiating the reaction liquid with microwaves will be described.

  The measurement results of the electric field monitor 4 and the thermometer 5 shown in FIG. 1 are first fed back to the microwave oscillator / controller 6. The flow rate of the inert gas is measured by the sensors S-8 and S-1 shown in FIG. The sensors S-1 to S-13 are used to detect the flow rate, flow rate, and components of each liquid, gas, and mixture that make up the reaction liquid, the conditions such as the particle size and distribution of nanoparticles, and the mixed state of the reaction liquid and gas. If necessary, measure and send to a microwave oscillator / controller, a liquid flow device for each liquid, a temperature control device (not shown), and a control system that controls the nanoparticle synthesis system in some cases, to synthesize nanoparticles. Can be managed.

  Optical and / or electrical detection means for deposits deposited on the inner wall of the reaction tube can be provided in the reaction tube, the control circuit, or the like. Electrical and / or optical measuring means such as the reaction process of the reaction solution and the particle size, particle size distribution, and average particle size of the nanoparticles after the reaction can be provided in the reaction tube or in the vicinity thereof or in the recovery tank.

  In the embodiment of the present invention, the state of metal deposit adhesion to the inner wall of the reaction tube is determined by measuring the temperature of the reaction solution and the electric field strength of the reflected wave of the microwave, and the result is synthesized into nanoparticles. Used for control. In addition, information from each sensor is also used for controlling the synthesis of nanoparticles as needed.

  In the experiment of the present invention, as an example of the reaction tube, a reaction tube made of a fluororesin that transmits microwaves is used as a basic part in at least a portion irradiated with microwaves. However, the scope of rights of the present invention is not limited to this reaction tube. As the reaction liquid, first, a material such as copper or silver that easily deposits on the inner wall of the reaction tube, that is, a material containing a component that easily forms a copper mirror, a silver mirror, a nickel mirror, etc. on the inner wall of the tube is selected as a dispersant. A reaction solution containing a reducing agent was prepared. The reaction solution was passed through the reaction tube. While irradiating the reaction solution in the reaction tube with microwaves in at least a part of the reaction solution channel, the reduction reaction is allowed to proceed at a predetermined temperature suitable for reducing the reaction solution, and deposits are formed on the inner wall of the reaction tube. Various investigations were carried out.

  The microwave used for heating the reaction solution may be either single mode or multimode. The microwave resonator may be either a cylindrical type or a rectangular type, but a cylindrical type is more preferable. Microwaves are generally sent from a magnetron, a semiconductor oscillator, or the like to a microwave irradiation field that heats a sample via a waveguide. Depending on the microwave mode, a microwave reflector may be provided at one end of the waveguide to reflect the microwave, and a mode for concentrating an electric field or magnetic field at a specific position in the waveguide may be formed so that the sample is heated to be used. it can.

As the microwave frequency band, a frequency in the 2.4 to 2.5 GHz band was used from the viewpoint of easy availability of the device, and an experiment was performed at frequencies other than the above. The microwave mode was mainly a single mode and TM ₀₁₀ mode was used. However, the microwave frequency and mode are not limited to this.

When the TM mode is used as the _microwave mode, it is particularly preferable to use the TM _mn0 mode with m being 0 or more and n being an integer of 1 or more. When using the TE mode, it is particularly preferable to use the TE ₀₁₁ , TE ₁₀₁ , TE ₀₁₂ , and TE ₂₀₁ modes.

  Not only the single mode but also the multi mode can be used. The microwave irradiation is not limited to the cylindrical microwave resonator, and the effects of the present invention can be exhibited as long as the advantages of microwave heating can be used, such as those using a rectangular waveguide.

In the embodiment, a cylindrical microwave resonator having a maximum microwave output of 500 W is used as the resonator, and PFA is used as the material of the reaction tube. As the microwave mode, a single mode TM ₀₁₀ , which is one of the excellent modes in terms of accuracy, was used. The scope of the present invention is not limited to these.

The size of the basic portion of the reaction tube is not limited to this, but an outer diameter of 3 mm, an inner diameter of 2 mm, and a length of the basic portion of the microwave resonator of 41 cm was used. The reaction tube is arranged such that 10 cm of the length of 41 cm of the basic portion is arranged at the center of the microwave cavity in a direction substantially orthogonal to the TM ₀₁₀ mode of microwaves, and the reaction solution flowing through the reaction tube is subjected to microwaves. To effectively heat the reaction solution to a predetermined temperature to promote the reduction reaction. A reaction tube having the same inner diameter was connected before and after the basic portion of the reaction tube in the flow direction of the reaction solution, and the reaction tube was used as an input side and an output side of the reaction solution, respectively.

  Various studies have been conducted on the flow method of the inert gas, and in the case of synthesizing the metal nanoparticles by reducing the metal nanoparticles with the reducing agent, it is possible to optimize the optimum amount depending on the type of the metal nanoparticle precursor and the type of the reducing agent. It was found that there is a difference in the method of introducing the active gas into the reaction liquid and the timing of the introduction. In the reduction reaction of metal nanoparticles, when the mirror reaction is relatively strong, for example, when the metal element is silver and dimethylaminoethanol is used as the reducing agent, an inert gas is introduced into the solution containing the reducing agent of silver nanoparticles. It has been found that it is possible to more effectively prevent the deposition of metal deposits on the inner wall of the reaction tube by allowing the solution to flow and then mixing the raw material liquid of the metal nanoparticles therein. When the metal element is copper and hydrazine is used as the reducing agent, a solution containing copper ions and a solution containing hydrazine are mixed to form a reaction solution, which is allowed to flow in the reaction tube and immediately before the microwave irradiation field. Therefore, it was found preferable to introduce an inert gas into the reaction solution.

  The temperature in the microwave irradiation field easily fluctuates even if the temperature is controlled, because the reaction liquid flows in the reaction tube while undergoing the reduction reaction while the inert gas is inserted. However, as a result of investigating during the synthesis of the silver nanoparticles, it was found that the range of sudden temperature drop was small and the temperature drop was 15 ° C. at the maximum. It was also found that suppressing this temperature decrease to 10 ° C. or less enables the continuous production of nanoparticles to proceed more stably. The temperature change of the reaction solution was measured every second. The momentary temperature drop means a peak value when the temperature fluctuates in a pulse from the set temperature and drops. That is, the "abruptly decreased temperature range in a moment" refers to a decreased range in a pulsed manner from the set temperature when the temperature in the microwave irradiation field is measured every one second. Further, in the present invention, it is preferable that the "abrupt temperature drop range" is 15 ° C, preferably 10 ° C or less.

  With respect to the synthesis of silver nanoparticles, in the configuration shown in FIG. 1, a liquid containing silver nitrate as a first liquid is used as a first liquid source, and a liquid containing a reducing agent of silver nitrate as a second liquid is used as a second liquid. Prepared in the liquid source, sent to the T-shaped joint through each liquid flow path at each predetermined liquid feeding speed with the plunger pump, and when both liquids are mixed with the T-shaped joint, the reduction suitable temperature rises. It was observed that both liquids mixed before the reaction started reduction, and the reaction liquid flowing through the liquid flow path connected to the T-shaped joint changed from transparent to black.

  In order to insert nitrogen gas at an early stage, the length of the liquid flow path through which the reaction liquid flows is set to about 3 cm, and the end of the liquid flow path opposite to the end connected to the T-shaped joint is set to the second end. Liquid which is connected to the T-shaped joint of No. 2, and nitrogen gas is inserted from the flow path connected to one end of the second T-shaped joint, and is connected to one end of the second T-shaped joint together with the reaction liquid. It was made to flow into the reaction tube passing through the flow passage and the microwave irradiation field. As a result, the synthesis of silver nanoparticles could be performed for a long period of time without causing deposition of deposits on the inner wall of the reaction tube.

  Further, at least a part of the reaction tube other than the part passing through the microwave irradiation field is temperature-controlled using a temperature control means other than the microwave as a heating source or a cooling source to control the particle size of the metal nanoparticles. be able to. Although not narrowly limited to this, for example, the above part is brought into contact with an object having a relatively good thermal conductivity in which a Peltier element is arranged, or is passed through such a container, or the first or second liquid source By controlling the temperature of at least one of them using a Peltier element, the particle size of the metal nanoparticles can be controlled.

  Since the Peltier element can be selectively used to raise or lower the temperature by electrically controlling it, it is possible to appropriately control the particle size control of the metal nanoparticles, the reaction suitability temperature and the particle size control temperature.

  Further, in the production process of the metal nanoparticles, at least a part of each of the first liquid, the second liquid, the gas, the reaction liquid, or the vicinity thereof, the temperature, the flow rate, the reaction progress information regarding the liquid, and the like. It is possible to arrange a sensor that detects at least one piece of information regarding the particle size, and feed back the output to a predetermined control system to perform control.

  Further, a means for measuring the particle size of the metal nanoparticles in the flow path or the shunt of the reaction liquid in the continuous production process of the metal nanoparticles can be provided to measure the particle size of the metal nanoparticles at that time.

A T-shaped or Y-shaped joint is provided in the flow path or shunt of the reaction solution, and the reaction solution is sampled from the joint to measure the particle size of the metal nanoparticles. A means for directly measuring the particle size of the nanoparticles, for example, a measuring means utilizing the phase rotation of laser light can be provided.
The information on the particle size, the temperature control information, and the flow rate control information are useful for controlling the particle size distribution of the metal nanoparticles to be synthesized, for example.

  As a result of investigating the flow rate of nitrogen gas, even a slight amount helps reduce the mirror phenomenon, but in the case of the above-mentioned fluororesin reaction tube having an inner diameter of 2 mm and a microwave irradiation area of 100 mm, when the reaction solution is silver, the amount of the reaction solution is 0. At 4 L / min or more, the effect of introducing nitrogen gas into the reaction solution is great. It has been found that controlling the total flow rate suitable for mass production to 0.5 L / min or more, more preferably 1 L / min or more has a stable effect. More preferably, the total flow rate is 2 L / min or less.

When the average inner diameter of the reaction tube through which the reaction solution flows is 2r (mm), the total amount of the inert gas inserted into the reaction solution is preferably 0.4 × r ² (liter) / minute or more, and 0 It is more preferably 0.5 × r ² (liter) / min or more, and further preferably 1.0 × r ² / min or more. However, economically, it is desirable that it does not exceed 3.0 × r ² (liter) / min.

  The linear velocity of the inert gas inserted into the reaction solution in the reaction tube is preferably 2 m / sec or more, and when the linear velocity is 5 m / sec or more, stable synthesis can be continued.

  Further, as a result of conducting experiments by changing various kinds of gas as the inert gas, it was found that the same effect can be obtained even with an inert gas other than nitrogen such as argon. However, nitrogen gas is economically preferable.

  In addition, before mixing the first liquid and the second liquid into a reaction liquid, a gas is inserted into at least one of the first liquid and the second liquid to form a multiphase flow, and By mixing the liquid 1 and the second liquid into a reaction liquid, it is possible to precisely control the reaction system.

  Before mixing the first liquid and the second liquid into a reaction liquid, different kinds of gases can be used as the gas to be inserted into the first liquid and the second liquid. Further, the quality of control can be adapted to the kind of metal by further providing a step of inserting a gas after mixing the first liquid and the second liquid.

  Further, it is preferable to have a step of controlling the pressure or linear velocity of the gas to be inserted.

  Although an example using M-1000, PVP, a tartaric acid derivative, and Diperbyk-2015 as a dispersant for nanoparticles has been described, the dispersant is preferably a hydrophilic one, for example, polyoxyalkyleneamine, although not limited thereto. There are many dispersants such as monoamines, diamines and polyacrylic acid. Further, a magnetic stirrer was used in utilizing the stirring action for adjusting the liquid constituting the reaction liquid, but the present invention is not limited to this, and it is possible to use other methods such as using ultrasonic waves. Is. When using ultrasonic vibration, for example, a low-frequency ultrasonic wave such as 30 KHz, a medium-frequency ultrasonic wave such as 200 KHz, and a relatively high-frequency ultrasonic wave near 500 KHz are used by utilizing their frequency characteristics. Then, the effect of the present invention can be further enhanced.

  When irradiating the reaction liquid with microwaves, it is possible to propagate ultrasonic waves, thereby controlling the particle size and distribution of the nanoparticles to be synthesized.

  Examples of means for purifying the metal nanoparticle colloid include filtration with a filter and ultrafiltration.

  Further, in the examples and the like, the T-shaped joint was used for mixing the liquid A and the liquid B and the reaction liquid and the inert gas, but the present invention is not limited to this, and the Y-shaped joint or the mixture is used. The effect of the reduction reaction is precisely controlled by using a joint designed so that various kinds of liquids and gases can be mixed in consideration of the types and properties of the liquids and the inert gas, The effect can be further enhanced.

  Then, among the liquid containing the reducing agent of the metal nanoparticle precursor to be circulated in advance and the liquid containing the metal nanoparticle precursor mixed with it, the liquid containing at least the reducing agent of the metal nanoparticle precursor, It is further preferable to insert the gas before mixing the liquid containing the particle precursor. It has been found that the use of an inert gas as the gas exerts a particularly great effect.

Further, although an example in which the TM ₀₁₀ mode is used as the microwave mode used to accelerate the reaction of the reaction solution is described as an example, the present invention is not limited to this. For example, in a microwave standing wave of TM _mn0 mode (m is 0 or more and n is an integer of 1 or more), electrolysis is concentrated in the radial direction of the cylinder, and uniform electric field strength is obtained at a position parallel to the central axis. Have and are available as well.

  In microwave heating, heating by an electric field can be used, but heating by a magnetic field can also be used.

  In order to stabilize the synthesis of nanoparticles, prolong the synthesizable time, and improve the synthesis quality, it is preferable to better control the flow of the reaction solution.

  As one of the means, as described above, there is a method in which various measuring means for monitoring the reaction progress of the reaction solution and the like are installed everywhere. At least one of an electric field monitor that monitors the electric field of microwaves and a thermometer that detects the temperature in the microwave irradiation field or the temperature of the reaction tube is installed in the microwave irradiation field, and the measurement results are fed back to the microwave oscillator / controller. In addition to controlling the microwave transmission status, it is possible to build a high-level automatic manufacturing system.

  Although not shown, various measuring means can be provided in various places as needed. At least a part of the electric field monitor and the thermometer is fed back to the microwave oscillator / controller. In addition to the above, with respect to the flow rate of the inert gas, for example, means for measuring the flow rate per minute can be provided in a part of the flow path or the inert gas source, and the flow rate of each liquid constituting the reaction liquid and the components The measuring means can be provided in the T-shaped joint or the liquid flow path in front of it, and the temperature measuring means can be provided not only in the thermometer but also in other important places. And / or electrical detection means can be provided in the reaction tube, the control circuit, etc., and the electrical and / or electrical characteristics such as the reaction process of the reaction solution, the particle size of the nanoparticles after the reaction, the particle size distribution, the average particle size, etc. An optical measuring means can be provided in the reaction tube or in the vicinity thereof or in a recovery tank.

  The reduction suitability temperature differs depending on the metal salt and additives such as a reducing agent and a dispersant.

  In the case of silver, the reduction suitability temperature is 70 ° C in the embodiment, so the microwave power was set to 70 ° C and the reflected power and temperature were measured. In the case where the inert gas was not introduced into the reaction solution, the reflected power in the 86 seconds from 54 seconds to 140 seconds when the reaction temperature reached 70 ° C. after starting the microwave irradiation was 75 to 308W. Further, during this time, 150 W or more was recorded 46 times, and during that time, 300 W was exceeded twice. The reflected power for 152 seconds from 140 seconds to 292 seconds to stop was 38 to 503 W, 78 times for 150 W or more and 22 times for 300 W or more. It was dangerous to continue any more, so I stopped microwave irradiation. On the other hand, in the case of the above-described embodiment in which an inert gas is introduced into the reaction liquid, after the microwave irradiation is started, 52 seconds after the reaction temperature reaches 70 ° C. and 352 seconds after the experiment ends. The reflected power during 300 seconds was 0 to 219W. Further, during that time, 100 W or more was recorded 12 times, of which 150 W or more was recorded 5 times, and 200 to 230 W was recorded 2 times. Moreover, it was not over 230W. From this, it can be said that a mirror can be easily formed at least when the number of appearances of the reflected power of 150 W or more is 8 or more in 20 seconds. It is necessary to consider the effect of liquid backflow.

  The measurement results of these various measuring means can be controlled by manufacturing specifications and the like. For example, the measured particle size, particle size distribution, etc. can be controlled by feeding back the measured data to the microwave oscillator / controller and / or the system control circuit (not shown) to control the manufacturing system.

  Hereinafter, the present invention will be described in more detail with reference to FIG. 2, which is a schematic view of an apparatus for producing nanoparticles used in another embodiment of the present invention.

  The inventors introduced simulation software for microwave irradiation, heat transfer conditions, chemical reactions, etc., depending on the manufacturing conditions, and examined the correspondence between the manufacturing conditions and their progress, manufacturing speed, manufacturing quality, and the like. As software, simulation software such as software for simulating microwave mode and overheating condition, software for simulating heat transfer condition and temporal change, and software for simulating chemical reaction condition were used. For example, the simulation is performed by appropriately using a COMSOL MULTIPHYSICS RF module, a heat transfer module, a chemical reaction engineering module, a particle tracing module, a CFD module, an optimization module, and the like. Then, the simulation results were compared with the partial experiments and the actual manufacturing process, and consideration was added. Process control data was created by combining the results with actual experiments and part or all of the manufacturing process. It was used for actual manufacturing control.

  In addition to the metal salt and reducing agent, if necessary, a dispersant, a surfactant, a protective material, a solvent and the like are mixed to prepare a reaction solution. It is irradiated with microwaves in the microwave irradiation field. The reaction solution which promoted the reduction reaction is sent to the reaction solution extraction section. When a reaction status determination means (not shown) is arranged in the reaction liquid outlet of FIGS. 1 and 2 which will be described later, a reaction tube which extracts a reaction liquid of a predetermined level or lower and passes through the microwave irradiation field again. And irradiate with microwave.

  The frequency of the microwave to be irradiated can be selected according to the reaction purpose. In most cases, 2.4 to 2.5 GHz is preferable because it is economically available, but it is suitable for delicate adjustment of heating rate, flow rate, condition of reaction tube, etc. depending on the purpose of reaction treatment and control conditions. We also conducted studies using different frequencies.

  In FIG. 2, reference numeral 2a is a microwave irradiation field, 7a to 7n and 7r are reaction tubes, 21a to 21c are gas sources, 30b to 30e are reaction liquid outlets, 33a to 33c are liquid sources, and 34a, 34c, x are The recovery tanks 71a to 71c and 78a to 78c are flow paths, and a-10 to a-30 are arrows.

  In the apparatus for producing fine particles such as nanoparticles of the present invention, particle size selection such as reaction state determination means for fine particles, particle size observation means, particle size distribution observation means, component observation means, ultrafiltration, etc. can be carried out at necessary locations such as the reaction liquid extraction section. It is possible to improve the production quality of the fine particles to be produced by providing at least one of a separating means, a classifying means, a flow dividing means, a temperature adjusting means including heating and cooling, and the like.

  The flow of the reaction solution in the embodiment of the present invention will be described with reference to FIG. The reaction liquid that has passed through the flow path 78 of FIG. 1 in the direction of arrow a-8 and enters the reaction tube 7 and has been irradiated with microwaves proceeds through the reaction tube 7a in the direction of arrow a-9, passes through the connection portion 30, and reacts. The pipe 7a advances in the direction of the arrow a-10 to reach the reaction liquid outlet 30a. The reaction liquid that has reached the reaction liquid extraction unit 30a is subjected to the first predetermined standard and the second predetermined value by the reaction status determination means (not shown) and the classification means (not shown) arranged in the reaction liquid extraction portion 30a. It is classified into a standard according to the prescribed standard. The reaction liquid classified into the first predetermined standard advances through the reaction tube 7b in the direction of arrow a-11 and is stored in the recovery tank 34. The reaction liquid classified into the second predetermined standard travels through the reaction tube 7c in the direction of arrow a-12 and reaches the reaction liquid outlet 30b.

The reaction liquid that has reached the reaction liquid extraction unit 30b is subjected to a third predetermined reaction in which the reaction is insufficient by a reaction status determination unit (not shown) or a classification unit (not shown) arranged in the reaction liquid extraction unit 30b. standards and the particle size of the classified large fourth predetermined standard, the fourth reaction mixture, which is classified into a predetermined standard, the process proceeds to arrow a-13 direction, is accommodated in the recovery tank 34a for a given application Or it is redissolved and placed in a reaction solution of the third predetermined standard.

  The reaction liquid of the third predetermined standard travels through the reaction tube 7d in the direction of arrow a-14 and reaches the reaction liquid extraction section 30c. The reaction solution that has reached the reaction solution extraction section 30c advances in the reaction tube 7e in the direction of arrow a-17, enters the reaction tube 7f, and is again irradiated with microwaves. In the reaction liquid extraction section 30c, the gas flowing from the gas source in the direction of arrow a-15 in the flow passage 71a is introduced into the liquid flowing from the liquid source 33a in the flow passage 78a as a reaction liquid, if necessary.

  The reaction liquid that has entered the reaction tube 7f and has been subjected to microwave irradiation again travels through the reaction tube 7g in the direction of arrow a-18 and reaches the reaction liquid extraction section 30d. In the reaction liquid extraction section 30d, the reaction liquid classified into the fifth predetermined standard advances through the reaction tube 7n in the direction of arrow a-20 and is stored in the recovery tank 34b. Alternatively, when the reaction liquid is the same as the reaction liquid passing through the reaction tube 7a, the reaction flows through the reaction tube 7h in the direction of arrow a-19, reaches the connecting portion 30, and flows through the reaction tube 7a in the direction of arrow a-10. Become a liquid. When the reaction liquid is other than those, it flows through the reaction tube 7i in the direction of the arrow a-21 and reaches the reaction liquid extraction section 30e. In the reaction liquid take-out section 30e, the liquid from the liquid source 33b flowing in the flow path 78b in the direction of arrow a-23 is mixed with the gas from the gas source 21b flowing in the flow path 71b in the direction of arrow a-22. It flows through the flow path 78b in the direction of arrow a-24, and is mixed with the reaction liquid from the reaction tube 7i. The mixed liquid enters the reaction tube 7k from the reaction solution extraction section 30e through the reaction tube 7j, receives microwave irradiation, flows through the reaction tube 7l in the direction of arrow a-26, and reaches the reaction solution extraction section 30f. The microwave irradiation at this time may be performed under different conditions from those applied to the reaction tube 7, and in that case, a microwave irradiation field different from the microwave irradiation field can be used.

In the reaction liquid extraction section 30f, the liquid of the liquid source 33c mixed with the gas from the gas source 21c flowing in the flow path 71c in the direction of arrow a-27 flows in the flow path 78c in the direction of arrow a-28 under a predetermined condition. And mixed with the reaction liquid from the reaction tube 7l. The mixed solution flows through the reaction tube 7m in the direction of arrow a-29 and is subjected to microwave irradiation in the microwave irradiation field 2a.

  The reaction liquid that has been subjected to microwave irradiation in the microwave irradiation field 2a flows through the reaction tube 7r in the direction of arrow a-29 and enters the recovery tank x. In the recovery tank x, the reaction liquid can be subjected to physical, chemical, electrical or other synthesis or processing. For example, formation of a synthetic substance or device can be performed.

  In FIG. 2, the sensors as shown in FIG. 1 are not shown in order to avoid complication of the figure, but various sensors are arranged where necessary, and the detection results are used for system and part control. It is reflected.

  One of the methods for producing nanoparticles with uniform particle size is to weaken the microwave irradiation conditions to reduce the reactivity, classify by using reaction progress judgment means, classification means, etc. It can be mentioned that the particle size is controlled by selectively repeating irradiation. As a means for selecting the particle size, for example, ultrafiltration can be used. In addition, the nanoparticles can be modified by using a reactive gas.

  In the microwave irradiation field, by providing a means for changing the traveling direction of the microwave incident on the microwave irradiation field (microwave direction changing means), the condition of the microwave applied to the reaction liquid can be changed.

  The microwave direction changing means can change the traveling direction of the microwave by computer control based on the detection data of a predetermined sensor, for example. It is possible to detect the microwave absorption field and the microwave absorption state of the reaction solution after microwave irradiation, and the change status of the reaction solution such as temperature, and respond appropriately to the subtle changes in the reaction solution to enable appropriate control of manufacturing conditions. Is.

  It is highly possible that the metal nanoparticles produced by the method of the present invention are mixed with at least a small amount of a gas, an inert gas, a nitrogen gas, etc., which is inserted into the reaction solution to form a multiphase flow in the production.

  The metal nanoparticles of the present invention can be made into products in various forms as described above according to the customer's request. The present invention is not narrowly limited to the various examples described above, and many variations are possible in accordance with the technical idea of the present invention. For example, based on the detection information from the sensor of FIG. 1 and FIG. 2, how to combine each constituent element, selection of use / non-use, and, depending on nanoparticles, hydrogen with reducing power or reactive gas with substance modification property may be selected. It can be used to improve nanoparticles, clean components, and so on. Further, the present invention described with reference to FIG. 2 is a manufacturing process for manufacturing nanoparticles using a reaction liquid in which a gas from a gas source is not mixed with a reaction liquid, a manufacturing apparatus, and nanoparticles manufactured using them. It is also applicable to, and exerts a great effect that nanoparticles having a uniform particle size can be provided at low cost.

In the description of the present invention, the explanation has been centered on the introduction of an inert gas as a gas into the reaction solution to prevent the deposition of deposits on the inner wall of the reaction tube. Reducing hydrogen gas can be introduced instead of inert gas, and reactive gas used in the semiconductor field can also be introduced to prevent mirrors and add or modify physical properties. It is also possible. It is also possible to provide a plurality of microwave irradiation portions in multiple stages and use them for various purposes by control, that is, to carry out the reduction reaction and the like with high accuracy. It is also possible to use a plurality of types of wavelengths as the microwave.
In combination with a measuring device for the fine particles themselves, various measurements and processing are possible.

  In the example of the present invention described below, a solution of a nickel complex containing a reducing agent is continuously heated to 170 ° C. or less under pressure by utilizing the fact that microwave can rapidly and uniformly heat. In a method for producing a nickel colloid having a particle size of 100 nm or less, the reduction is performed by adding a polyol in the presence of a nickel colloid having a single nanoparticle and a dispersant soluble in water or a hydrophilic alcohol. And a method for producing a nickel colloid.

  The solution of the nickel complex containing the reducing agent is 1,1,3,3-tetramethylguanidine, 1,3-, in order to make the reducing agent hydrazine, to make it soluble in water, and to carry out the reaction quickly. An amine having a pKa of 13 or more such as diphenylguanidine is added as an alkali to form a hydroxide of a nickel-hydrazine complex.

  It was found that the acid dissociation constant of 1,1,3,3-tetramethylguanidine was 13.6 and that of 1,3-diphenylguanidine was 14.5, which was sufficient to reduce nickel ions. It was also found that 1,1,3,3-tetramethylguanidine can be made water-soluble by converting the nickel hydrazine complex into a hydroxide. Amines having an acid dissociation constant of 13 or more may be used alone or may be mixed.

  Further, in order to raise the pH and increase the reaction rate, alkanolamine or amine can be added in addition to 1,1,3,3-tetramethylguanidine. Although not limited, ethanolamine having a high boiling point of 170 ° C. is preferable.

  Nickel acetate is preferable as the nickel precursor for preparing the solution of the nickel complex containing the reducing agent, and nickel formate, nickel oxalate, nickel nitrate, and nickel chloride are insufficient. In order to obtain a nickel colloid of 100 nm or less in which coarse particles are not present, it is important to reduce the nickel complex in a solution state.

  By filtering the solution of the nickel complex containing the reducing agent, excess hydrazine can be separated and the reduction reaction can be carried out. In that case, when only 1,1,3,3-tetramethylguanidine is added to obtain an aqueous solution, an alkanolamine can be added to obtain an aqueous solution.

  The method for producing a nickel colloid of the present invention is a method in which heating is performed by applying microwaves under pressure to continuously reduce the pressure.

  The pressurization is for increasing the reaction temperature to accelerate the reaction rate and generate nickel particles of 100 nm or less. It was found that a large number of nickel particles of 200 nm or more were generated when the reaction was performed at 90 ° C. or lower without applying pressure.

  The above-mentioned pressurization is not limited, but 0.1-0.5 MPa is effective from the viewpoint of safety.

  In the above continuous reduction, a gas such as nitrogen gas can be passed through the reaction tube. When metal is generated by reduction, metal precipitates in the reaction tube, absorbs microwaves and cannot be heated, and eventually sparks.However, by flowing gas into the reaction tube, it precipitates. Can be prevented. The type of gas is not limited, but nitrogen gas is preferable, and the flow rate is preferably such that the flow rate of the reaction liquid is constant.

  In the above continuous reduction, ultrasonic waves can be emitted by passing the reaction tube through the ultrasonic device before the reaction tube enters the cavity of the microwave device. Specifically, in FIG. 1, when a nickel-hydrazine complex hydroxide solution is put into a liquid source 32 and allowed to flow, an ultrasonic device can be provided in the channel 74 or channel 76.

  By irradiating the liquid with ultrasonic waves before heating by microwave irradiation, it is possible to reduce the particle size of nickel generated.

  The frequency of the microwave device can be set to, for example, 2450 MHz, and it is preferable to use a single mode microwave device whose frequency is controlled.

  The method for producing a nickel colloid of the present invention is to subject a liquid containing nickel particles of single nanoparticles to microwave heating.

  It was found that the addition temperature of nickel of the above-mentioned single nanoparticles can lower the reduction temperature of the nickel complex, and nickel particles of small particle size can be produced. In the prior art document, noble metal ions are added to the reaction solution to generate nickel particles, but nickel nanoparticles can also be used to generate nickel particles. Any method for synthesizing single nanoparticles is acceptable, but nickel by vacuum evaporation is used. Nanocolloids are the best choice. It is a nickel colloid containing no metal other than nickel.

  The method for producing a nickel colloid of the present invention is a method for producing a nickel colloid, which comprises adding a polyol in the presence of a dispersant soluble in water or alcohol.

  The above-mentioned dispersant is a dispersant soluble in water or hydrophilic alcohol, and is a compound that suppresses agglomeration of nickel that easily aggregates to form coarse particles. If it is an amine, M-1000, and if it is an acid, Examples thereof include tartaric acid derivatives, Disperbyk-2015, and the like. If nonionic, polyvinylpyrrolidone and polyethylene glycol are used. These may be used alone or may be mixed.

  The above-mentioned polyol may be any as long as it can dissolve the dispersant, and examples thereof include ethylene glycol, propylene glycol, glycerin, and 1,4-butanediol.

  When the solution of the nickel complex containing the reducing agent is diluted with water, the pH of the solution is lowered and the reduction reaction does not proceed, but when diluted with the same amount of glycol as the water to be diluted, the reduction reaction proceeds. It was found that a nickel superfine particle colloid was generated.

(Example)
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

(Example 1)
(Nickel acetate / hydrazine / 1,1,3,3-tetramethylguanidine / M-1000 / PVP / dibenzoyl-1-tartaric acid / evaporation Ni / EG system)

(Adjustment of liquid A)
5.10 g (0.0205 mol) of nickel acetate.4H 2 O was dispensed into a 200 ml Erlenmeyer flask, and ion-exchanged water was added to make it 40.0 g and dissolved. With stirring, 12.3 g (0.197 mol) of 80% hydrazine.H 2 O was added dropwise, and the mixture was stirred for 40 minutes to be in a suspended state, forming a nickel hydrazine complex. Next, 12.6 g (0.109 mol) of 1,1,3,3-tetramethylguanidine was added and dissolved. Then, 60 g of M-1000 and a separately prepared ethylene glycol solution of polyvinylpyrrolidone K-15 (molecular weight 10,000) were sequentially added. Further, 10.24 g of an ethylene glycol solution containing 0.24 g (0.00067 mol) of dibenzoyl-L-tartaric acid was added. Finally, 30 g of 0.04 wt% nickel nanoparticle / ethylene glycol solution prepared by the evaporation method was added.

(Preparation of solution B)
A solution B was prepared by mixing 210 g of dodecane and 70 g of BDG (diethylene glycol monobutyl ether).

  The tube at the cavity outlet of the microwave device was connected to a pressure vessel, and nitrogen gas was flown to pressurize the nitrogen gas pressure to 0.20 MPa.

Solution A was delivered at 5 ml / min and solution B at 5 ml / min by a pressure-resistant plunger pump.
The target temperature was set to 130 ° C.

  The nickel particles were 150 nm or less.

  The temperature change of the reaction solution due to microwave irradiation is plotted along the vertical axis as temperature (° C) and the horizontal axis as time (sec), and the microwave intensity change data is shown in FIG. 3, and the reflected wave intensity (W (Watts)), and the horizontal axis represents time (seconds), which is shown in FIG.

  3 to 4, reference numeral 101 is a temperature curve, 101a is a temperature curve at the time of rising of microwaves, 101b is a temperature curve after microwave irradiation reaches a steady state, and 101c is temperature at the end of microwave irradiation due to completion of synthesis. A curve, reference numeral 102 is a reflected wave intensity curve of microwaves, 101a is a reflected wave intensity curve at the rising time of microwaves, 101b is a reflected wave intensity curve after microwave irradiation reaches a steady state, and 101c is a micro wave due to the end of synthesis The reflected wave intensity curve at the end of wave irradiation is shown.

  The reaction temperature reached 122 ° C. 30 seconds after the start of microwave irradiation, and was in the range of 121.5 ° C. to 137.2 ° C. after the steady state was reached. The number of times the reflected wave intensity exceeded 60 W was 28 times, of which the number of times exceeded 100 W was 10 times.

(Comparative Example 1)
When the composition was the same as that of Example 1 and the heating was performed at 80 ° C. using an oil bath without microwave irradiation, nickel particles were formed, but contained particles of 200 nm or more.

(Comparative example 2)
When the composition was the same as that of Example 1 and was carried out by a microwave continuous method at a heating temperature of 80 ° C., nickel particles were formed, but they contained particles of 200 nm or more.

(Example 2)
(Nickel acetate / hydrazine / 1,1,3,3, -tetramethylguanidine / Disperbyk-2015 / dibenzoyl-L-tartaric acid / evaporation Ni / EG system)

(Adjustment of liquid A)
5.10 g (0.0205 mol) of nickel acetate.4H 2 O was dispensed into a 200 ml Erlenmeyer flask, and ion-exchanged water was added to make it 40.0 g and dissolved. With stirring, 12.3 g (0.197 mol) of 80% hydrazine.H 2 O was added dropwise, and the mixture was stirred for 40 minutes to be in a suspended state, forming a nickel hydrazine complex. Next, 12.6 g (0.109 mol) of 1,1,3,3-tetramethylguanidine was added and dissolved. 6 g of 10 wt% Disperbyk-2015 / 1,4-butanediol was added thereto.
Further, 10.24 g of a 1,4-butanediol solution of 0.24 g (0.00067 mol) of dibenzoyl-L-tartaric acid was added. Finally, 30 g of 0.04 wt% nickel nanoparticle / 1,4-butanediol solution prepared by the evaporation method was added.

(Preparation of solution B)
A solution B was prepared by mixing 210 g of dodecane and 70 g of BDG (diethylene glycol monobutyl ether).

  The tube at the cavity outlet of the microwave device was connected to a pressure vessel, and nitrogen gas was supplied to pressurize the nitrogen gas pressure to 0.20 MPa.

  Solution A was delivered at 5 ml / min and solution B at 5 ml / min by a pressure-resistant plunger pump. The set temperature was set to 120 ° C.

  The nickel particles were 150 nm or less.

  The nickel ultrafine particle colloid was made to have a high metal concentration to prepare a paste having a metal concentration of about 60% by weight or more.

  A high-boiling organic solvent, for example, BDG (diethylene glycol monobutyl ether) having a boiling point of 230 ° C. or terpineol having a boiling point of 219 ° C. was added to the nickel ultrafine particle colloid of the dispersion medium ethanol obtained in the above description, and heated under reduced pressure. Then, ethanol was distilled off to prepare a nickel ultrafine particle paste using BDG as a dispersion medium. The organic solvent having a high boiling point is selected such that the dispersant in the nickel ultrafine particle colloid can be dissolved.

  Although the present invention has been described above with reference to the embodiments, the present invention is not limited to these examples, and many variations are possible based on the technical idea of the present invention.

  Since the nickel ultrafine particle colloid and paste of the present invention are dispersed in hydrophilic alcohol and do not contain impurities that cause deterioration, they are used as electrode materials for multilayer capacitors, wiring of electronic substrates, and electronic materials. It has a great effect in a wide range of technical fields such as joining parts, nickel plating, etc. in the electronic / electrical industry and the automobile industry. In addition, it can be used as a catalyst for organic synthesis.

Claims (4)

A method of producing a metal ultrafine particle colloid, which comprises heating a solution of an amine having an acid dissociation constant of 13 or more to a metal precursor solution, characterized by containing no alkali metal and / or chlorine. Method for producing ultrafine metal particle colloid. A method of producing a nickel ultrafine particle colloid, which comprises heating a solution obtained by adding an amine having an acid dissociation constant of 13 or more to a metal precursor solution, and heating the solution, wherein an alkali metal and / or chlorine is added. A method for producing an ultrafine metal particle colloid, which is characterized by not containing it . An ultrafine metal particle colloid produced by the production method according to claim 1 or 2, which does not contain an alkali metal and / or chlorine. Ultrafine metal particles produced by the production method according to claim 1 or 2 and free of alkali metal and / or chlorine.