JPH0376177B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention focuses on core particles (hereinafter referred to as base particles).
Microparticles (hereinafter referred to as child particles) are placed on the surface of
The child particles are adhered to the surface of the mother particle by being attached or not attached, and further, all or part of the child particles are softened and melted to form a film on the surface of the mother particle. Concerning how to do it. Conventionally, various treatments have been used to prevent caking of solid particles, prevent discoloration, improve dispersibility, improve fluidity, improve catalytic effect, control digestion and absorption, improve magnetic properties, and improve light resistance. Surface modification can be performed using physical adsorption method, chemical adsorption method, vacuum evaporation method, electrostatic deposition method,
Methods such as coating with dissolved substances and special spray drying methods have been used. Among these, in particular, when the surface of solid particles is modified with solid particles, that is, the surface of powder with powder, it is necessary to modify the surface of solid particles with powder for a long period of time (several hours to Modification has been carried out by applying electrostatic phenomena and mechanochemical phenomena that occur with stirring (for several tens of hours), but the modification has been carried out by applying the electrostatic and mechanochemical phenomena that occur with stirring. The adhesion of the child particles is not sufficient, so when the modified powder is mixed, kneaded, dispersed, made into a paste, etc. in the next process, the child particles may easily fall off or component segregation may occur. This not only significantly limits the operating conditions, but also becomes the biggest cause of variations in the quality of processed products. Furthermore, in surface modification of powder-powder systems using the above-mentioned various mixers, ball mills, etc., the fixing force of child particles to the mother particle surface is generally weak, so it is difficult to obtain the desired surface modification. It takes several hours to several tens of hours, which results in large-sized equipment and problems such as poor processing efficiency. The present invention has been made in view of the above-mentioned circumstances, and solves the problems of the prior art, and as shown in FIG. The child particles are forcibly buried or fixed using thermal means, and all or part of the child particles are softened and melted to form a film, resulting in a uniform and stable film in an extremely short period of time (several seconds to minutes). The present invention provides a method for forming a film on the surface of powder particles, thereby obtaining a functional composite material (hybrid powder).
The gist is that a rotary disk with an impact pin arranged around it is placed in the impact chamber, and a collision ring is placed along the outermost orbital surface of the impact pin with a certain space therebetween, and The airflow generated by the rotation of the pin is guided and circulated through the impact chamber and a circulation circuit that opens from a part of the impact ring near the center of the rotary disk, and the particle size is adjusted along with the airflow.
The entire amount of powder particles consisting of solid particles of 100 to 0.1 μm and other fine solid particles with a particle size of 10 to 0.01 μm smaller than the solid particles is repeatedly passed through the shock chamber and the circulation circuit. While or after adhering the other microscopic solid particles to the surface of the solid particles by passing through the impact pin and the impact ring within a range that does not crush the solid particles. , due to the thermal energy generated by sticking and continuing the blow,
A method for forming a film on the surface of a solid particle is characterized in that the fine solid particle is softened and dissolved, and all or part of adjacent fine solid particles are fused to each other to form a film on the surface of the solid particle. . Typical base particle powders that can be surface-treated by the method of the present invention include pigments such as titanium dioxide and iron oxide, which generally have a particle size of about 0.1 μm to 100 μm, epoxy powder, nylon powder, polyethylene powder, polystyrene powder, etc. Synthetic polymeric materials, and natural materials such as starch, cellulose, and silk powder. Typical child particle powders include nylon powder, polyethylene powder, and acrylic powder, which generally have a particle size of about 0.01 μm to 10 μm. , styrene powder, polypropylene powder, ABS powder, polyvinyl alcohol, gelatin, various waxes, sulfur, low melting point alloys, and other organic substances, inorganic substances, and metals. However, without being limited to these materials, industries such as various chemical industries, electrical, magnetic industrial materials, cosmetics, paints, printing inks, toners, coloring materials, textiles, pharmaceuticals, foods, rubber, plastics, ceramics, etc. It can be applied to each combination of components of various materials used in Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 2 and 3 show an example in which a powder impact device is used as the impact type striking means. In the figure, 1 is a casing of a powder impacting device used to carry out the method of the present invention, 2 is a rear cover, 3 is a front cover, 4 is a rotary disk that rotates at high speed inside the casing 1, and 5 is a A plurality of impact pins are provided radially around the outer periphery of the rotary disk 4 at predetermined intervals, and are generally hammer-shaped or plate-shaped. 6 is a rotating shaft that rotatably supports the rotary disk 4 in the casing 1; 8 is a rotary shaft provided along the outermost orbital surface of the impact pin 5 and at a constant interval of 0.5 to 20 mm therefrom; This is a collision ring of various shapes, such as a concave-convex type or a circumferential flat plate type. Here, the reason why the distance between the outermost orbital surface of the impact pin 5 and the impact ring 8 is set in the range of 0.5 to 20 mm is due to the size of the powder impact device used to carry out the method of the present invention, and the size of the rotary disk. Although it depends on the circumferential speed, since the rotary disk is a device that rotates at high speed, there is a risk that the impact pin and the impact ring will come into contact with each other due to the vibration caused by the rotation of the rotary disk and warping of the rotary disk due to centrifugal force. The impact chamber 18 is specified at this interval, and if this interval is narrow, the volume of the impact chamber becomes small, and the This is because the amount of processing will be extremely reduced. On the other hand, when the interval is 20 mm or more, the amount of processing per batch increases dramatically, but the combination of powder particles, the particle size of each mother particle and child particle,
Depending on the degree of film formation, the impact force of the powder particles on the collision ring may become weaker, making it impossible to obtain the desired modification treatment, or it may take a long time to perform the desired modification treatment. This is because processing efficiency deteriorates due to the need for time. Reference numeral 9 denotes an on-off valve for discharging the modified powder, which is provided by cutting out a part of the collision ring. Depending on the case, this may also be provided by cutting out a part of the front cover or rear cover facing the grinding chamber. . 10 is the valve shaft of the on-off valve 9; 11 is the on-off valve 9 via the valve shaft 10;
The actuator 13 that operates the collision ring 8 has one end opening in a part of the inner wall of the collision ring 8, and the other end opening in the rotary disk 4.
14 is a raw material hopper; 15 is a chute for supplying raw materials that connects the raw material hopper 14 and the circulation circuit 13; 16 is a raw material measuring feeder;
17 is a raw material storage tank. Reference numeral 18 indicates a shock chamber provided between the outer periphery of the rotary disk 4 and the collision ring 8, and reference numeral 19 indicates a circulation port to the circulation circuit 13. 20 is a modified powder discharge chute, 21 is a cyclone, 22 is a rotary valve, 23 is a bag filter, 24
25 is a rotary valve, 25 is an exhaust fan, 31 is a time control device for controlling the operation of the powder impact device used to carry out the method of the present invention, and 32 is a device for attaching child particles to the surface of the mother particles in advance. Various types of mixers, electric mortars, and other known preprocessors used in certain cases are shown. When carrying out the method of forming a film on a powder surface according to the present invention using the above-mentioned apparatus, the following procedure is performed. First, the on-off valve 9 for discharging the reformed powder is kept in a closed state, and the rotating shaft 6 is driven by a driving means (not shown) while introducing inert gas into the apparatus as necessary. , 5m/sec to 160m/sec where the base particles are not crushed depending on the nature of the material to be modified.
The rotary disk 4 is rotated at a circumferential speed within the range of . At this time, a rapid airflow of air/inert gas is generated as the impact pin 5 on the outer periphery of the rotary disk 4 rotates, and the circulation circuit 13 opens into the impact chamber 18 due to the fan effect based on the centrifugal force of this airflow. A circulating flow of air flows from the circulation port 19 through the circulation circuit 13 and back to the center of the rotary disk 4, that is, a completely self-circulating flow is formed.
Furthermore, since the amount of circulating air generated per unit time is significantly larger than the total volume of the shock chamber and circulation system, an enormous number of air circulation cycles are formed in a short period of time. Next, a powder to be treated, in which child particles are attached to the surface of a certain amount of mother particles using, for example, an electrostatic phenomenon, is fed into the raw material hopper 14 from the metering feeder 16 in a short time. If it is not necessary to use the preprocessor 32, the mother particles and child particles are weighed separately and placed into the raw material hopper 14. The powder to be processed passes from the raw material hopper 14 through the chute 15 and enters the shock chamber 18 . The powder particles sent into the impact chamber 18 are instantaneously impacted by a large number of impact pins 5 of the rotary disk 4 rotating at high speed, and further collide with the surrounding impact ring 8 to form a matrix. Child particles on the particle surface are selectively subjected to strong compression. At the same time, the powder to be treated is circulated through the circulation circuit 13 along with the flow of the circulating gas and returned to the shock chamber 18 again.
It is hit again. This type of impact operation is repeated many times in a row in a short period of time, and the child particles are buried or firmly attached to the surface of the mother particle, and then receive (thermal) energy from the impact and impact action. The child particles are softened and melted in a short time, and all or part of the child particles fixed to the surface of one mother particle are fused together. This series of impact operations, that is, film-forming operations by softening and melting the child particles on the surface of the mother particle, is continued until the entire surface of the mother particle is in the desired fused state, but the shock chamber and circulation system are Since a large amount of gas (air and inert gas) circulates in the system compared to its volume, the powder to be processed (mother particles and child particles) that circulates with the gas undergoes a tremendous impact in an extremely short period of time. You will receive the number of times. Although it depends on the amount of treatment per batch, the time required to form a film on the surface is generally completed within an extremely short time of several seconds to several minutes, even including the time for supplying the powder to be treated. Figure 1 shows a model diagram. In the figure, the mother particle,
Child particles are not limited to spherical shapes. Figures 1 and 2 show the state in which child particles b and b' are attached to mother particles a and a' by static electricity in advance, but these mother particles and child particles are attached to the mother particles a and a' by the above-mentioned impact and impact action as shown in 3 to 5. In this way, the mother particles are not crushed, but the surfaces of the child particles attached to their surfaces are softened and melted, and fusion of the child particles occurs partially or over the entire surface, forming a film. Further, depending on various combinations of child particles and the supply order, as shown in 6 to 8, different child particles b and c can be formed into a single layer or a multilayer film on a mother particle a. After the above film-forming work is completed, the on-off valve 9 for discharging the modified powder is moved to the position shown by the chain line and opened, and the powder subjected to the film-forming process is discharged. The centrifugal force acting on the film-forming powder is exerted on itself (the discharge valve 9 may be located at a different location as long as the centrifugal force is acting on the treated powder).
Then, it is discharged from the shock chamber 18 and the circulation circuit 13 in a short period of time (several seconds) by the suction force of the exhaust fan 25, and is discharged from the cyclone 21 and circulation circuit 13 through the chute 20. 21 and a bag filter 23, the powder is collected and discharged to the outside of the system via rotary valves 22 and 24. After discharging the powder that has been formed into a film, the on-off valve 9 is immediately closed, and a certain amount of the powder to be processed for the next time is supplied from the metering feeder 16 to the shock chamber again to form a film through the same process. Chemically treated powder is produced one after another. Note that these series of batch film formation processing operations are controlled and continued by a time limit control device 31 whose time limit is set in advance in relation to the operating time of related equipment. In addition, during the film forming process, if it is necessary to use supplementary thermal treatment (for example, when it is necessary to increase the difference in hardness between the mother particles and child particles), the collision ring 8 or the circulation The circuit 13 has a jacket structure, and it is possible to set temperature conditions convenient for the film-forming process of the powder to be processed through various heating mediums and coolants. In addition, in the powder impact device used to carry out the method of the present invention, auxiliary blades may be attached to the rotary disk 4 to further apply force to the circulating flow. That is, if the circulating air volume is increased, the number of times of circulation within a unit time increases, and therefore the number of collisions of powder particles also increases, so that the film forming process time can be shortened. Next, in the process of forming a film on the surface of the powder in the powder impacting apparatus used to carry out the method of the present invention, it is necessary to prevent oxidative deterioration during film formation of the powder to be treated, and prevent ignition and explosion. We will explain the use of various inert gases such as nitrogen gas for the purpose of preventing this. FIG. 4 shows a powder impact device according to the present invention,
An example using this inert gas will be shown. In the description of this embodiment, the same members as in the previous embodiment are designated by the same reference numerals, and the explanation thereof will be omitted. Fourth
In the figure, 26 is a raw material supply valve provided at the bottom of the raw material hopper 14, and 27 is a chute 1 for supplying raw materials.
5 is an inert gas supply valve opened, 28 is an inert gas supply source, and 29 is an inert gas supply path.
In this embodiment, the circulation circuit 13 is connected to the casing 1.
Shows how it is stored inside. When starting the operation, first, the raw material supply valve 26 is closed, the on-off valve 9 is opened, and then the inert gas supply valve 27 is opened to fill the shock chamber 18 and circulation circuit 13 with inert gas. The substitution of inert gas into the shock chamber and circulation circuit, which is performed prior to the start of this film-forming operation, is usually completed within a few minutes. Next, after closing the on-off valve 9 and the supply valve 27 at the same time, the raw material supply valve 26 is immediately opened, and the pre-measured powder to be processed is passed through the chute 15 into the shock chamber 1.
Supply to 8. After supplying, the supply valve 26 is immediately returned to the closed state, and upon receiving this signal, the weighing feeder 16 measures and supplies the next powder to be processed to the raw material hopper 14. Thereafter, the powder to be treated is bombarded with an inert gas in the same manner as in the above embodiment, and the powder to be treated is circulated in the circulation circuit 13 while maintaining sufficient contact with the inert gas to form a film. processed. Next, when the on-off valve 9 and the supply valve 27 are opened, the film-formed powder is discharged from the shock chamber 18 and the circulation circuit 13 to the chute 20, and at the same time, the shock chamber 18 and the circulation circuit 13 are replaced by gas. The discharged film-forming powder is treated in the same manner as in the previous example. Thereafter, if the on-off valve 9 and the supply valve 27 are closed and the raw material supply valve 26 is opened, the next film forming process operation will proceed. Note that this series of batch film forming operations including supply and stop of inert gas are controlled and continued by the time control device 31 as in the previous embodiment. As mentioned above, the feature of the method for forming a film on the surface of solid (powder) particles according to the present invention is that the powder impact device as an impact impact means has a strong impact force on the micro powder particles, and By focusing on the difference in hardness between the mother particles and the child particles, it is possible to arbitrarily adjust the magnitude of the impact force itself and the number of times of impact for applying impact force to the entire surface of the mother particle having a certain shape. Furthermore, according to the method of the present invention, as shown in FIG. It is possible to perform microencapsulation in which particles are coated in a film, formation of child particles of two or more components into a film, and further formation of multiple layers of child particles of one or more components. Also, the shape of the child particles is spherical,
It can be of any shape, such as amorphous or fibrous. In addition, the shape of the base particles is not limited, such as spherical or amorphous. Further, the surface of the base particle is not necessarily in a smooth state, but may be uneven in various shapes and sizes, or may have a hole-like or groove-like form, and concave portions of the base particle having these surface configurations may be used. After selectively embedding child particles in the mother particle, the protrusions of the mother particle itself deform due to impact force and heat, forming a film of the mother particle that wraps around the child particles over the entire surface of the mother particle. can. According to the method of the present invention, when the ratio (ratio) of the film-forming particles to each base particle does not need to be so strict (that is, when the overall component ratio only needs to be constant), various mixers, Without using a preprocessor such as an electric mortar, the separately measured mother particle powder and child particle powder can be directly supplied to the impact chamber to form a film of the child particles on the surface of the mother particle. As described above, according to the method for surface modification of solid particles according to the present invention, surface modification is performed by softening and melting child particles to form a film on a mother particle made of a combination of various powder materials. Through this process, functional composite/hybrid powder materials (composite or hybrid powder) with uniform and stable properties can be efficiently produced in an extremely short time. Example 1 The outer diameter of the eight plate-type impact pins installed around the rotary disk is 235 mm, the distance between the outermost orbital surface of the impact pins and the impact ring is 4 mm, and the diameter of the circulation circuit is 235 mm.
The powder impact device of Figure 2, which is 54.9 mm, was used.
Ordered mixtures are prepared by adhering PMMA (polymethyl methacrylate) child particles with an average particle diameter of dp50 = 0.3 μm to the surface of spherical nylon 12 with an average particle diameter of dp50 = 5 μm using a mixer in advance, as shown in the table below. As a result of the softening and melting film formation treatment under these conditions, polymethyl methacrylate (child particles) firmly adhered to the surface of nylon 12 (mother particle, core particle), and some or all of the child particles softened and melted. A uniform and stable surface-modified powder of polymethyl methacrylate of nylon 12 was obtained by melting and forming a film. It is clearly shown that the softening and melting state of the child particles differs depending on the operating conditions (see the scanning electron micrograph in Figure 5), and if the desired modified state is one in which the mother particles are microencapsulated, BaT
This can be satisfied with the condition -1.

[Table] Calculated from the internal volume.
Incidentally, scanning electron micrographs of the immobilized and modified powders obtained in the above Examples (T-1 to T-3) are shown in FIG.

[Brief explanation of drawings]

1 to 8 are conceptual explanatory diagrams showing the aspects of various pre-modified powders and modified film-formed powders treated by the method according to the present invention, and FIG. A conceptual explanatory diagram systematically showing one embodiment of the powder impact device used to carry out the method together with its front and rear devices. FIG. 3 is a side cross-sectional explanatory diagram of FIG.
The figure is an explanatory diagram of another example in which an inert gas is also used. Figure 5 shows a scanning electron micrograph of the powder after surface modification, and Figure 1 shows the powder used in the above example. Electrostatic adhesion product 10,000 times larger, 2 is the above implementation number T-1 and 8,500 times larger, 3 is implementation number T-
2 is 10,000 times, 4 is implementation number T-3 and 10,000 times
It shows twice as much. a... Mother particle, b, c... Child particle, 1... Powder impact device.

Claims (1)

[Claims] 1 A rotary disk surrounding an impact pin is placed in the impact chamber, and a collision ring is placed along the outermost orbital surface of the impact pin with a certain space therebetween, and the rotation of the impact pin is The airflow generated by
The entire amount of the powder particle group consisting of solid particles of 0.1 μm and other fine solid particles with a particle size of 10 to 0.01 μm smaller than the solid particles is repeatedly passed through the shock chamber and the circulation circuit. , while adhering the other fine solid particles to the surface of the solid particles by mechanical impact in a range that does not crush the solid particles between the impact pin and the collision ring, or
After adhering and fixing, the heat energy generated by continuing the impact softens and melts the fine solid particles, and fuses all or part of the adjacent fine solid particles to each other to form solid particles. A method for forming a film on the surface of a solid particle, the method comprising forming a film on the surface of a solid particle.