WO2016193087A1 - Method and technical process for the production of micro- and nanoparticles of different sizes - Google Patents

Abstract

2.1 The invention relates to a method and a technical process for the production of small particles, which are synthesised in a preferably continuous method, and the size of which can be precisely set in the process. This occurs using specific nozzles, at the outlet of which two reactants are brought into contact in such a manner that small particles are produced. The size of the particles is predetermined primarily via the flow parameters of the fluids at the outlet of the nozzle. The particle diameter can also be influenced via the addition of special surface-active materials in different concentrations to said fluids, or via the changing of the concentration or temperature of the reaction solutions. 2.2 The invention also relates to a uniform technical process and is also based on specifically constructed nozzles. In this way, the circumstance arises wherein the diameter of the obtained particles can be predetermined by changing the flow parameters of the reaction solutions, by changing their surface characteristics, their concentration or temperature. 2.3 A method of this type can be used for the production of metallic or non-metallic micro- and nanoparticles for highly diverse applications.

Description

 Process and technical process for the production of micro- and nanoparticles of different grotto

description

The invention relates to a method and a technical process for the production of small particles, which are synthesized in a preferably continuous process and whose size can be precisely adjusted in the process. This is done with the help of special nozzles, at the outlet of which two reactants are brought into contact so that small particles are formed. The size of the particles is primarily determined by the flow parameters of the liquids at the outlet of the nozzle. The addition of special surfactants in different concentrations to these liquids or the change in the concentration or temperature of the Reaktionsiösungen the particle diameter can be additionally influenced. Depending on the design and setting of the nozzle, the particle diameter can be in a granulometric range of a few nanometers to several micrometers. The specially designed nozzles ensure a high yield and a narrow size distribution of the particles obtained.

The developments of recent years have led to an increasing demand for micro- and nanoparticles, which have well-defined granulometric and morphological properties. This is not surprising, since such small particles are used in different applications, some of which are mentioned below.

1. Cosmetics

 Micro and nanoparticles such as e.g. Titanium oxide, zinc oxide are often used in sunscreen products as a so-called UV blocker. In hair care products, e.g. Aluminum oxide particles are used as a stabilizer, while calcium phosphate particles are used in dentifrices as active ingredients on a biological model.

2. Food / food

Particles of partially coated silicon dioxide are used, for example, to improve the flowability or of processing or surface properties. Other particles such as carotenoids or titanium dioxide are used in different foods as a dye. 3. Paints and varnishes

 Large quantities of particles, for example of titanium oxide or barium sulfate are used as fillers or pigments. Other particles improve the reflective properties of the colors or their UV or corrosion protection.

4. Pharmacy / Medicine

 Here, microparticles and nanoparticles such as e.g. highly dispersive silica as a drug transporter or depot. Metal particles such as e.g. Silver gives special preparations an antibacterial effect, yet other particles are used as contrast agents in various diagnostic procedures.

5th automobile

 The automotive industry is also a big buyer of micro- and nanoparticles. In addition to the above-mentioned paints and varnishes, this application can be found in various components and additives such as e.g. Tires. Drive belts or in lubricants of all kinds.

6. Microelectronics

 A number of electronic components such as e.g. LED or even special capacitors could in today's quality without micro- and nanoparticles, e.g. nickel, silver, silicon, silicon carbide, etc. are not built.

Micro- and nanoparticles are also used in many other fields, such as in the textile industry or in the manufacture of special ceramics or detergents. All these examples show the high demand for such products. In particular, particles of high quality, ie those of the highest possible purity and monodispersibility, are needed.

Given this wide range of applications, there are several established methods for the engineering of small particles. These can be classified as follows:

1. Mechanical processes: They are essentially based on grinding large particles in suitable mills, such as ball mills.

2. Physical methods: The basis of these methods is the evaporation of metals and subsequent condensation at low temperatures (eg arc evaporation, plasma flame spraying) or the spraying of molten metal with subsequent cooling. 3. Chemical Processes: This type of preparation is based on a precipitation of suitable salts in the presence of special reagents.

 4. Electrochemical process: Here, metallic powder is obtained in the course of electrolysis or other electrochemical processes.

Against the background of this variety of production possibilities, it is not surprising that the literature already describes numerous processes for the production of small particles, some of which are also used on an industrial scale. By way of example, some of these are summarized below:

The laid-open specification DE 3703377A1 describes a process for the preparation of small barium sulfate particles by chemical precipitation from barium chloride and sodium sulfate. In this case, nozzles or other devices are used to bring the two reactants as possible in a thin film or as a drop in contact. The particle diameter obtained should in any case be less than 1 pm.

A similar method, which does not use nozzles but rotating slides to form thin liquid films, is described in DE 602 12 136 T2. With this method, both metallic and non-metallic particles with diameters well below 1 pm can be produced by the choice of suitable starting liquids.

DE 10 2005 048 201 A1 likewise relates to a method in which nanoscale particles are produced. Here, the particles are obtained by the interaction of aqueous solutions in the interior of a specially designed microreactor in the presence of surface-active substances. in the published patent application DE 23 47 375.8 a process for the production of finely divided, spherical nickel powder is described. The metallic powder is obtained by the reduction of an aqueous-alcoholic suspension of nickel hydroxide with hydrogen at about 200 ° C and up to 100 at pressure in the presence of organic Ni- compounds. The resulting particles have diameters in the range of 0.03pm-0.7pm.

The production of metallic mixed powders is concerned with the patent application AT 304 090 B. The invention is based on the effect that when pouring particles of a metal B, which is more electronegative than a metal A in a salt solution of the metal A in the particles one Displacement of the metal B by A takes place. In this way receives composite metallic particles consisting of a central core of metal B and an outer layer of metal A.

A process for producing a nickel powder and a method for producing an electrically conductive paste for capacitors based thereon are the subject of patent application EP 1151815 A1. The Ni powder is obtained in the course of the reduction of Ni-Suifat Hexaydrat with hydrazine in an alkaline medium at a corresponding temperature. The reactants are simply added dropwise and stirred, and the precipitated Ni is filtered off. Since the complex of the resulting in the second phase of the reaction, the metallic nickel, forms in the liquid, its particle size and thus the resulting metallic grains is largely dictated by the mixing of the starting materials, which tends to expect unsatisfactory results.

The published patent application DE 102009057251A1 relates to a method for the production of small metallic particles, which are produced by precipitation of two reagents in the outlet region of a specially designed nozzle. The size distribution of the particles obtained is very narrow. however, the process does not provide for adjusting the particle size by the flow parameters in the nozzle.

Another method for producing a fine Ni powder is described in the application US 3,748,118. In this case, an organic Ni compound is reduced with hydrogen at the appropriate temperature and pressure in the presence of other organic substances.

All these references show that, according to the state of the art, small metallic and non-metallic particles can be obtained in many different ways. A common method is the precipitation of these particles at the contact surface of two liquid reactants with the aid of nozzles or other devices. Although the particles obtained have defined diameters in z.T. have narrow size distribution, none of the methods describes a continuous process. can be defined by the different particle sizes.

Based on this situation, the present invention has the object to synthesize micro and nanoparticles in a continuous process on an industrial scale, in which the size of these particles can be specified by changing individual parameters of the process. The basic idea of the process is to combine the reactants from which the particles are to be formed in the outlet region of a specially designed nozzle. By the contact of the different liquids they react with each other, whereby the particles arise. The size of the particles is determined primarily by the flow conditions inside and at the outlet of the nozzle, which can be changed during the manufacturing process.

A central point in the method according to the invention is thus influencing the particle size by changing the physical parameters in the interior and at the outlet of the nozzle used. Although a whole series of different nozzles are commercially available, a special construction must be used here. The nozzle must ensure good mixing of the reactants with the smallest possible size distribution of the drops. At the same time, it must provide sufficient flow under preferably laminar flow conditions.

For this purpose, modified, so-called dual-fluid nozzles come into consideration. Normal two-component nozzles are commercially available in a wide variety of designs. Frequently, these nozzles are used for spraying liquids, with the simultaneous action of a gas.

In the literature special two-fluid nozzles are described, which are used for the dripping of highly viscous media. Particularly suitable for this purpose are nozzles in which a gas stream is blown concentrically to the liquid-carrying capillaries, which ensures a clean drop break and a narrow droplet distribution. Such nozzles are for example the subject of the published patent application DE102004026725A1. In order to achieve a sufficient volume throughput, multi-capillary nozzles are used here. In these nozzles, both the capillaries for liquid transport, as well as the channels for the concentric gas flowing around them are incorporated in superimposed plates.

In the present invention, nozzles were adapted as described above so that instead of the gas stream provided for the defined drop break, a second liquid stream could be passed through the nozzle. This second liquid stream gets in contact with the first of the inner capillaries only at its outlet point, whereby the particles are formed. According to the invention, a multiple nozzle is used, which is constructed as follows: Capillaries are located in the center of several, vertical, cylindrical channels. The inner diameter of the capillaries and the free cross section of the cylindrical channels has a diameter of a few millimeters. The capillaries and the cylindrical channels are flowed through by each of the reaction liquids. The dimensions of the resulting cross-sections through which the liquids pass are comparable and selected so that, even in the case of laminar flows, the throughput per channel is in the region of a few liters per minute. The individual cylindrical channels and the capillaries in their interior are interconnected within the nozzle by horizontal channels so that the flow conditions in each channel and in each capillary are almost equal.

If the initial pressure of both fluids flowing through such a nozzle is changed, the flow parameters also change through the capillaries and through the vertical, cylindrical channels. It could be proven experimentally that with laminar flows through the nozzle, thus at values of the Reynolds characteristic number under 10,000. the diameter of the particles obtained is given by the flow velocity. Thus, for example, with the same nozzle at low flow rates particle diameter in the order of well over 1 μπι, while at higher flow rates, which are close to the boundary to the turbulent flow. Particles with a diameter of about 0.5 pm are formed. In the area of turbulent flow, the particle diameter then remains constant at about 0.5 pm. By the addition of a surface-active liquid, such as a detergent. the diameter of the particles obtained can be further reduced to below 0.1 pm. In this case, the smaller the particles, the higher the concentration of detergent in both of the nozzle supplied solutions. Similar effects can be observed by changing the concentration and / or the temperature of the reaction solutions.

Accordingly, in order to specify the diameter of the particles in a uniform process, according to the present invention, there are, inter alia, the following possibilities:

1. In the laminar flow area:

 • by changing the pre-pressure on the nozzle and thus the

Flow rate of the reaction solutions inside the nozzle

 - By changing the concentration of the reaction solutions mixed

Detergent, at constant pre-pressure of the reaction solutions - By changing the pre-pressure of the reaction solutions while changing the concentration of a detergent mixed with the reaction solutions

2. In the turbulent flow area

 by changing the concentration of a detergent added to the reaction solutions

Particles as described in the invention can be prepared as follows: Example 1

 A 0.5 M aqueous solution of barium chloride is prepared and placed in a storage vessel. In a second vessel, an aqueous 0.5 M Natruimsulfatlösung is filled. These two solutions are then fed to a nozzle which is constructed as described above and in which the one solution flows through the capillary, the other the surrounding cylindrical channel. At the outlet of the nozzle, barium sulfate particles are obtained in an aqueous suspension. By varying the admission pressure on the nozzle, different flow conditions are generated inside the nozzle. At each change, samples of the resulting particles are taken and analyzed. The result is as follows:

Total flow through the nozzle: 0.4 l / min: particle diameter:> 1, 5 pm

Total flow through the nozzle: 0.8 l / min: particle diameter: approx. 0.7 pm

Total flow through the nozzle: 1, 6 l / min: particle diameter: about 0.5 pm

Total flow through the nozzle: 2.0 l / min: particle diameter: approx. 0.5 pm

In a second step, 0.5 mmol of polyethylene glycol ether was added as a detergent to the two reaction solutions in advance. At a total flow through the nozzle of 2.0 l / min, the particle diameter dropped below 0.1 pm.

Example 2:

A 1 M aqueous magnesium chloride solution is prepared and placed in a storage vessel. In a second vessel, an aqueous 2 M Natruimhydroxidlösung is filled. These two solutions are then fed to a nozzle which is constructed as described above and in which one solution flows through the capillary and the other through the surrounding cylindrical channel. At the outlet of the nozzle, magnesium hydroxide is obtained as an aqueous suspension. By varying the admission pressure on the nozzle, different flow conditions are generated inside the nozzle. At each change, samples of the resulting particles are taken and analyzed. The results are comparable to those of Example 1.

Example 3:

 An example of a possible engineering process for producing small particles as illustrated in the present invention is shown in FIG. 2:

In the process (Fiq.2), the starting substances Komp. 1 and Komp. 2 are first placed in appropriate containers [V1 and V2], dissolved in water or other suitable solvent and adjusted to the concentration required for the process. The solutions thus prepared are at the top of one or two continuously operated reactors [R1; R2] and are there reacted by a suitable nozzle or nozzle arrays. The nozzles and the reactors can be brought to the required temperature by means of a heater. The actual reaction takes place at the outlet of the nozzle device, where the particles are discharged as a suspension. The diameter of the particles obtained is predetermined by the admission pressure to the nozzles or nozzle arrays. If necessary, a detergent can be added to the two reaction solutions in order to additionally influence the particle size.

The continuously operated reactor is suitably carried out, either as a heated flow tube, baffle plate or stirred tank, e.g. from the outside or by elements from the inside, heated or cooled to adjust the reaction temperature can. The reactor may additionally contain internals which favor the reaction result. Depending on requirements, a temperature gradient can additionally be set in the reactor.

The resulting suspension then passes into the two washing tanks [W1 and W2], and then into the filtration unit [filtration]. This unit can be designed both as a filter of different design as well as a decanter or centrifuge. The now separated particles are then dried. For very small particles, it may be advantageous not to dry the particles and to use the filter cake as such.

1 shows an exemplary embodiment of a nozzle array, as can be used in the method according to the invention. At the top of the two reaction solutions are fed through openings in the cover plate the nozzle assembly, where they through holes directly on the distributor plate 1 meet. Through channels on the top and bottom of the distributor plate 1, the two liquid streams are divided into eight Einzetströme and so supplied to the distributor plate 2, wherein it is avoided that they come into contact with each other. Seals 1 and 2 seal the structure to the outside and prevent the fluid streams from hitting each other. The distributor plate 2 has the task of supplying the now 8 liquid streams of the first reaction solution and the 8 liquid streams of the second reaction solution separately to the 8 Kapiliarmodulen. In each capillary module, the one reaction solution is passed through the capillaries, the other through a special channel in the module, which supplies the second reaction solution to the horizontal channels of the outlet plate, from where it enters the vertical holes of the outlet plate. The capillaries of the modules are located in the center of these holes and are lapped by the second reaction solution. The two reaction liquids come in this way only at the outlet, ie in the lower part of the outlet plate, in contact, where they react with each other.

A nozzle array as described herein may also be equipped with multiple or fewer capillary modules than indicated in the example. Also, the structure can be heated.

Such nozzle assemblies can be operated at different flow rates. Both laminar and turbulent flow conditions in the context of the present invention can be produced inside and at the outlet. The constructions are also very suitable for large-scale technical applications, especially since volume flows of a few cubic meters per hour can be realized.

Claims

claims 1. Method and technical process for the synthesis of small particles, in which the starting materials in the outlet region of a nozzle come into contact and react with one another, whereby the particles are formed, characterized in that by changing the parameters in the interior and at the outlet of the nozzle and / or or by adding surface-active or other substances, the diameter of the particles obtained can be predetermined. 2. Method and technical process for the synthesis of small particles according to claim 1, characterized in that in the process individual nozzles or arrangements of several nozzles are used, which bring the starting substances in a suitable manner to react. 3. Process and technical process for the synthesis of small particles according to claim 1 to 2 characterized in that the particle sizes can be specified by changing one or more of the following parameters: By changing the laminarity or turbulence of the flow of the reaction solutions in and / or on Outlet of the nozzle, by changing the flow rate of the reaction solutions in and / or at the outlet of the nozzle, by changing the concentration of the reaction solutions, by changing the surface properties of the reaction solutions, eg by the addition in different concentrations of surfactants, e.g. Detergents, by changing the temperature of the reaction solutions. 4. Method and technical process for the synthesis of small particles according to claim 1 to 3, characterized in that it runs continuously. 5. Method and technical process for the synthesis of small particles according to claim 1 to 4, characterized in that it is discontinuous, so runs in batch. 6. Process and technical process for the synthesis of small particles according to claim 1 to 5, characterized in that the particles obtained Diameter in a range between, for example, 0.01 pm to 500 pm may have. 7. Method and technical process for the synthesis of small particles according to claim 1 to 6, characterized in that in the outlet region of the nozzle, the particles are formed by a chemical reaction, for example by a reduction reaction or a precipitation reaction. 8. Plant according to claim 1, which operates by a process according to claims 1 to 7, characterized in that it comprises one or more of the following main components:  - Reservoir V1 and V2 for the starting substances  - One or more reaction vessels R with nozzle internals  • One or more containers for washing W of the obtained suspension - A filtration or other device for separating the particles 9. Plant according to claim 8, characterized in that it operates as shown in FIG. 2 and / or their components are arranged as shown in FIG. 2 and / or connected to each other. Installation according to claim 8 and 9, characterized in that it is operated with one or more heatable nozzle assemblies, which are e.g. 1 and / or include one or more of the following elements: • Cover plate to which both reaction solutions are added  • Distribution plate 1. divides the liquid streams of the two reaction solutions into several individual streams  - Distribution plate 2, which supplies the liquid streams individual Kapillarmodulen - One or more capillary modules, which guide the one reaction solution through the capillaries and the other on to the channels of an outlet plate - Outlet plate, at the bottom of two liquid streams are brought by contact to the reaction, wherein the one reaction solution is first passed into vertical channels and the other reaction solution through the capillaries of the modules, whereby the two liquid streams meet only in the outlet  • Seals that prevent mixing of fluids inside the structure and seal the structure to the outside.