JP2000237572A - Granulating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of granulating particles in a desired state by controlling conditions in a method in which granulation is made by fluidizing solid powder by an air stream and spraying the a proper quantity of granulating liquid to the fluidized solid powder. SOLUTION: In a method of granulating powder particles while fluidized by an air stream, this method is characterized in that by causing the air stream to flow in from a part of the bottom surface of a granulating part 2 in which the powder particles are housed, the air stream is caused to flow in the granulating part 2 in a deviated state to fluidize the powder particles, and also granulating liquid 14 is sprayed while agitated by an agitating blade 9. The granulating liquid 14 is preferably jetted from the upper surface or side face of the granulating part 2, and by adding fiber together, fluffed base material particles can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for granulating particles, and more particularly, to a method for granulating particles having a low density which is fluffy in a distorted shape with many irregularities, and also relates to a friction material for a brake and a building. The present invention relates to a granulation method for obtaining nap-like base particles that can be used in a wide range of technical fields such as wall materials for electronic parts and materials for electronic parts by stirring granulation.

[0002]

2. Description of the Related Art In a granulation method for producing particles having a certain size from a solid powder, a method of rolling granulation is widely used, which is carried out in a rotating flat bread horizontally or inclinedly arranged. The particles are formed by rolling the powder into a roll and spraying an appropriate amount of a granulating liquid from above to adhere the powders to each other. Since this method has low productivity, there is also a method of flowing a solid powder and spraying an appropriate amount of a granulating liquid on it.However, the collision between the droplets of the sprayed granulating liquid and the solid powder causes powder mutual interaction. Adhesion was difficult, and it was difficult to granulate particles of uniform size.

[0003] In such a granulation method based on the flow of solid powder, a general fluidized bed technique is applied. In a generalized fluidized bed, an air flow is uniform from a dispersion plate, which is the floor of the fluidized bed. Because of the characteristics of the fluidized bed, even if the size of the obtained particles is changed or the production state is changed, the inflow velocity of the airflow is lower than the lower limit. Since the fluidized bed state cannot be maintained unless it is within the range of the upper limit, the range of the inflow speed of the airflow is limited. In addition, if the gas flow is not uniformly ejected from the floor of the fluidized bed, undesirable phenomena such as bubbling of gas, channeling of the fluidized bed, and falling of particles from the floor may occur. Could not be changed much. For this reason, there are various problems in using the fluidized bed technology in the granulation method.

[0004]

SUMMARY OF THE INVENTION A solid powder is made to flow,
In addition, the method of granulating by spraying an appropriate amount of granulating liquid has many degrees of freedom from the opposite side,
It is considered that there is an extremely excellent advantage that the particle size of the solid powder, the type of the solid powder, the flow rate of the airflow, the production amount, and the like can be changed in a wide range. An object of the present invention is to provide a method of granulating particles in a desired state in a method of granulating by flowing a solid powder by an air stream and spraying an appropriate amount of a granulating liquid thereon. . Further, the present invention provides a method of granulating by flowing a solid powder by an air current and spraying an appropriate amount of a liquid for granulation, wherein a method of granulating particles in a desired state by controlling granulation conditions. The goal is to obtain

[0005]

The present invention has solved the above-mentioned problems by the following means. (1) In a method of granulating while powder particles are caused to flow by an airflow, an airflow is supplied to a portion of the bottom surface of a granulation portion containing the powder particles so that the airflow is biased to the granulation portion. A granulation method, wherein the granulation liquid is sprayed while the powder particles are caused to flow in and flow while being stirred by a stirring blade. (2) The granulation method according to (1), wherein the granulating liquid is sprayed from an upper surface or a side surface of the granulation unit. (3) The granulation method according to the above (1), wherein nap-like base particles are obtained by adding fibers together.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, there is provided a method for granulating while powder particles are caused to flow by an air current, wherein the granulation is carried out by flowing an air current from a part of the bottom surface of the granulating section containing the powder particles. As a structure of the device for flowing the powder particles by flowing the airflow in a state of being biased to the part, the air-permeable member such as a net, a perforated plate, etc. Is provided, and the airflow is caused to flow in from below. Further, the entire bottom surface of the tank is formed of a gas-permeable member, and a portion excluding a part of the bottom surface is covered with an air-impermeable member, for example, a plate material, so that only the portion is gas-permeable. In this case, by changing the size or arrangement of the plate material,
It is easy to freely change the location or area of the air-permeable portion. When making a part of the bottom surface of the tank air-permeable, various forms can be considered as the size and shape of the part, but when the bottom surface is circular, it is divided by a line passing through the center. However, some of the portions can be made breathable. In the case of FIG. 2, the bottom is divided into six equal parts, and one of the parts is made air-permeable.

[0007] Further, a stirring blade is provided on the bottom surface of the granulating device, and the powder is stirred by rotating the stirring blade.
In addition, by disturbing the air flow spouting from the bottom surface by the rotation of the stirring blade, the powder flows and stirs well in the tank, and further, is stirred in a specific direction.
For this reason, as can be seen from the side view of FIG. 1, when the granulating liquid is sprayed from the side of the tank, the powder is biased upward due to the unevenly introduced airflow, and thus is rising. The droplets of the granulating liquid hit only one side of the powder, and therefore the position of the powder wet by the liquid on the other powder is biased, thereby possibly changing the mutual adhesion state of the powder and forming. It is considered that the particles to be formed tend to have irregularities. In addition, since the adhesive force changes depending on the position, the adhesive particles become small, and the formed particles are fluffy, and hard particles are hardly formed.

In spraying the granulating liquid, the granulating liquid can be sprayed from the top surface or the side surface of the tank. In this case, it is desirable that the granulating liquid is not directly sprayed on the stirring blade. By such an operation, the form and physical properties of the granulated product can be controlled. In this case, only a part of the powder particles is wet with the granulating liquid, so that a portion of the granulated material to which other dry powder particles adhere is generated. Are formed. Any substance may be used as the powder for granulation.
Further, since granulation is performed in an agitated gas stream, powder having a wide particle size range can be used, and a mixture of two or more powders may be used. In particular, in this method, fiber can be used as one of the raw materials. When fibers are used, the napped particles can be produced by selecting the length of the fibers.

The fibers used in the production of the nap-like base particles can be made of various materials, and include organic fibers, inorganic fibers, and metal fibers. In terms of the practicality of the particles, organic fibers are most preferable, and among organic fibers, synthetic fibers having high strength are preferable, and examples thereof include aramid fibers. Regarding the length and thickness of the fiber, from the point that the fiber comes out of the particle in the form of nap, the state where the fiber comes out from the particle cannot be obtained if the length is too short. If the length is too long, the fibers become entangled with each other and do not form particles, but form a lump. The thickness of the fiber is
Although it is related to the strength of the fiber, it is preferably about 5 to 200 μm. Thereby, the length of the fibers coming out of the obtained nap-like base particles varies depending on the length of the fibers used and the particle size of the obtained particles. Depending on the length of the protruding fiber, the properties of a molded article or the like obtained by using the napped base particles vary.

As for the material other than the fibers used for producing the raised substrate particles, various substances can be used according to the use of the raised substrate particles. It is common to use binders to form particles with organic and inorganic powders. For example, in the case of obtaining nap-like base particles for producing a friction material, a fibrous base material, a friction modifier, a lubricant such as graphite, a phenol resin as a binder, and the like are used. In the case of producing such nap-like base particles, it is preferable to use alcohol as a granulating liquid and spray it to form an alcohol mist for granulation. In the case of producing particles used for producing a building wall material, a main substance of the material is an inorganic powder, and a binder is used in addition to a crushed stone or a powder of silica, calcium carbonate, or the like. Used.

In the case of the friction material as described above, examples of the inorganic filler include metal particles such as copper, aluminum and zinc, scaly inorganic substances such as vermiculite and mica, and particles such as barium sulfate and calcium carbonate. Examples of the organic filler include synthetic rubber and cashew resin. Examples of the thermosetting resin binder include phenolic resins (including various modified phenolic resins such as straight phenolic resins and rubbers), melamine resins, epoxy resins, and cyanate ester resins. Examples of the friction modifier include metal oxides such as alumina and silica, magnesia, zirconia, chromium oxide, and quartz. Examples of the solid lubricant include graphite and molybdenum disulfide.

In the granulation method of the present invention, when the alcohol mist is sprayed on the raw material powder during the stirring granulation of the material as described above, the alcohol mist is stirred while the powder of the material is stirred. It is preferable to spray a certain amount of alcohol as a mist with respect to the powder amount of the material. The ratio of the amount is, for example, 15 to 30 parts with respect to 100 parts (weight, the same applies hereinafter) of the powdery material. As the kind of alcohol to be used, lower alcohol is preferable, and even from the viewpoint of safety, ethyl alcohol is most preferable. At the time of spraying the alcohol mist, it is preferable to spray the alcohol on the air stream and spray the alcohol mist on the powder of the material being stirred, but other forms are also possible. According to experiments conducted up to now, the stirring of the material powder is the most preferable form when the stirring is performed by a mixer of a type in which two stirring blades arranged in parallel to the bottom surface of the granulation tank are rotated. It appears that nap-like substrate particles can be obtained.

In order to describe the granulation method of the present invention more specifically, the case of granulating the napped base particles used for producing the friction material will be described under specific conditions. The production of the napped base particles is performed in this order. Aramid fiber was put into the tank shown in FIG. 1 equipped with a stirrer, and air was introduced from below at a part of the bottom of the tank,
Stir with a stirring blade while flowing. For example, 600 rpm
Stir for 1 minute at a rotation speed of m. A predetermined amount of other raw material powder is weighed and charged into the tank. After the introduction of each component, the stirring blade is rotated at a predetermined rotation speed (eg, 600 rpm) for a predetermined time (5 minutes) while flowing.
Stir and mix the raw materials dry. Next, a stirring operation is performed while spraying ethanol from a spray nozzle. The discharge air flow rate when spraying ethanol with a spray nozzle is 10-100 liters /
Minutes. The ethanol supply rate is in the range of 0.1 to 10 ml / sec. In the steps (1) to (3), the nap-like base particles are obtained. In this case, it is a batch type.

When the amount of ethanol supplied in the above step is more than 10 ml / sec, the diameter of the obtained particles increases, and when it is less than 0.1 ml / sec, the diameter of the obtained particles decreases. The treatment time while spraying the alcohol is about 30 seconds to 5 minutes. If the treatment time is short, the obtained particles become soft, and if the treatment time is long, the obtained particles become hard. The rotation speed of the stirring blade in the process also greatly affects the formability of the particles,
Usually, it is performed in a range of 5 to 300 rpm. When the rotation speed is high, hard particles having a small particle size are obtained, and when the rotation speed is low, soft particles having a large particle size are obtained. The napped substrate particles obtained in the step are sent to the thermoforming step as they are to be thermoformed, whereby a thermoformed body having high strength can be obtained. Is subjected to a heat treatment for a predetermined period of time, and after a treatment such as polishing, is made a finished product. In the production of friction materials, if conventional material particles were not used before they were preformed, when the material particles were directly put into the mold of the thermoforming step and thermoformed, the product was easily broken due to weak bonding force between the particles. However, the nap-like base particles have a large number of fibers coming out from the particle surface, and this large number of fibers are entangled with each other during thermoforming and are mutually welded by heat. There is nothing.

As an apparatus used in the granulation method of the present invention, for example, it is preferable to use a mixer 1 shown in FIG. FIG. 1 is a vertical cross-sectional view thereof, which is shown as an explanatory diagram.
In this mixer 1, the bottom plate 4 of the tank 3 serving as the granulation unit 2 is a
The bottom plate 5 is divided into six equal parts by a line passing through the center as shown in FIG.
Has a shape in which some holes 6 are opened. These holes 6 are covered with a net 7 and are air-permeable. Air 8 is introduced from below and flows into the tank 3 as an air current. For this reason, the airflow flows in the tank 3 in an uneven state in the tank 3 and flows in the tank 3. Inside the mixer 1, two stirring blades 9 are provided slightly above the bottom plate 4, and the stirring blades 9 are provided below the bottom plate 4 of the tank 3 via a rotating shaft 10. It is designed to be rotated by an electric motor 11. The air flow in the tank 3 is further disturbed by the stirring blades 9 to form a complicated flow state.

The material powder 12 charged into the tank 3 flows violently in the tank 3 due to the complicated flow of the air, but the air flows above the permeable hole 6 because of the rising airflow. It becomes a particularly violent fluid state than the part.
As shown in FIG. 1, a granulating liquid 14 is sprayed from a spray nozzle 13 composed of a two-fluid nozzle onto the material powder in such a fluidized state, so that a spray mist 15 is formed.
Is formed, another material powder adheres to the wet material powder to form large particles, and by repeating the process, particles of a desired size are obtained. In the present invention, the granulating liquid 1 is placed where the material powder is in an uneven flow state.
Spraying 3 weakens the condition of the other material powder adhering to the wet material powder and seems to form soft particles. It seems that the tendency of the air flow generated by the rotation of the stirring blade 9 is further promoted.
When alcohol is used as the granulating liquid in the tank 3, an alcohol mist is formed by spraying, and the spray nozzle 13 for that purpose can be installed so as to open inside through the wall of the tank 3. A cover is provided in the tank 3,
The spray nozzle 13 may be inserted from there.

[0017]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to only these examples.

Example 1-Production Example of Friction Material Particles-(Composition of Friction Material) Here, the following composition example was used as the composition of the friction material. Filler Calcium carbonate powder 77 parts (weight, same hereafter) Fiber Aramid fiber (Kevlar) 5 parts Resin Phenol resin powder 8 parts

(Production Apparatus) As the granulation apparatus 1, the mixer 1 shown in FIG. FIG. 1 is a longitudinal sectional view, and FIG. 2 is a plan view of the tank 3. In addition, FIG.
FIG. 2 is a cross-sectional view taken along line A, but FIG. 2 does not show the stirring blade 9 and the like. In this mixer 1, the bottom plate 4 of the cylindrical tank 3 is formed of a bottom plate having a number of large holes 6, a net 7 being stretched over the holes 6 to form a gas-permeable portion 5, and Is divided into six equal parts, and only one sixth of the divided parts are open, and only that part is air-permeable.
Further, two stirring blades 9 are provided on the bottom plate 4 and are rotated. The stirring blade 9 is rotated by an electric motor 11 provided below the bottom of the tank 3 via the rotation shaft. Further, a spray nozzle 13 for spraying the alcohol mist is installed in the mixer 1 so as to open inside through the side wall of the tank 3, and the installation position of the spray nozzle 13 is oriented in the horizontal direction.

(Manufacturing process) Manufacturing was performed in the following operation sequence. Preliminary stirring The aramid fiber is put into the mixer and stirred at 600 rpm for 300 seconds. Main stirring A predetermined amount of other raw materials such as calcium carbonate powder and phenol resin powder are weighed and charged into a mixer. After the introduction of each component, the raw materials are dry-mixed at a rotation speed of 600 rpm for 300 seconds (5 minutes). Spray stirring granulation Next, while performing a stirring operation, granulation is performed while spraying alcohol mist from a spray nozzle on the way. Ethanol was used as alcohol. The rotation speed during granulation is 30
rpm. The discharge air flow rate at the time of spraying ethanol was about 40 liters / minute, and the supply rate of ethanol was 30 parts per 100 parts of the sample. The ethanol was supplied for 120 seconds, and granulation was performed by spraying ethanol mist. . By spraying the ethanol mist, a granulated product of the napped base particles was obtained.

[0021]

According to the present invention, the following effects can be obtained. According to the granulation method of the present invention, the rising airflow in the mixing chamber can be freely biased in a desired direction, so that fluffy low-density particles having a distorted shape with many irregularities can be obtained. By controlling the direction of the air flow to be ejected, the shape and density of the particles can be easily controlled. In this granulation method, granulation can be easily performed even if the particle diameter of the material powder is not uniform, and not only one kind of substance but also a mixture of two or more kinds, or a mixture of fibrous substances may be used. It can be easily granulated. As the production conditions, when the granulation is performed at an increased rotation speed of the stirring blade, hard particles can be obtained. When a fibrous substance is used as one kind of material, nap-like base particles can be easily obtained. In particular, when an aramid fiber or the like is used as the fibrous substance, an effect that the aramid fiber on the surface is entangled between the particles is obtained. For this reason, the strength of the molded article obtained by using the napped base particles is improved. By spraying an alcohol mist during granulation, the napped base particles can be easily obtained.

[Brief description of the drawings]

FIG. 1 shows a sectional side view of a mixer used in the granulation method of the present invention.

FIG. 2 shows a plan view of a mixer used in the granulation method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixer 2 Granulation part 3 Tank 4 Bottom plate 5 Part 6 Hole 7 Net 8 Air 9 Stirrer blade 10 Rotary shaft 11 Electric motor 12 Material powder 13 Spray nozzle 14 Granulation liquid 15 Spray mist

Claims (3)

[Claims] In a method of granulating while causing powder particles to flow by an air flow, an air flow is caused to flow from a part of a bottom surface of a granulation portion containing the powder particles so as to be biased to the granulation portion. A granulation method characterized by flowing an air flow to flow powder particles and spraying a granulating liquid while stirring with a stirring blade. 2. The granulating method according to claim 1, wherein the granulating liquid is sprayed from an upper surface or a side surface of the granulating section. 3. The granulation method according to claim 1, wherein the nap-like base particles are obtained by adding fibers together.