JP7097938B2 - Wet medium crushing method - Google Patents

Description

In the present invention, a suspension (slurry) of a material to be pulverized using a liquefied inert gas as a dispersion medium is pulverized and pulverized by the pulverizing medium by stirring the suspension (slurry) of the material to be pulverized together with a pulverizing medium such as balls and beads. And / or disperse, the present invention relates to a wet medium pulverization method.

A wet medium crushing device such as a bead mill or a stirring type ball mill generally has a rotating shaft driven by an electric motor or the like, and a stirring member attached to the rotating shaft. This stirring member has various forms, for example, a disk-shaped or rod-shaped member extending in a direction crossing the axis of the rotating shaft, fixed to the end of the rotating shaft, and at regular intervals. It is composed of a plurality of stirring pins extending parallel to the rotating shaft, rotating blades of various shapes arranged around the rotating shaft, and the like. These stirring members rotate in a crushing chamber defined in a vessel together with a rotating shaft driven by an electric motor or the like.

In order to crush the material to be crushed by such a wet medium crushing device, a suspension (slurry) in which the powder or granular material of the material to be crushed is suspended in a liquid (medium solution) as a dispersion medium in a crushing chamber, a ball or the like. A crushing medium such as beads is charged, and the rotating shaft and the stirring member are rotated in this crushing chamber. These rotating shafts and agitating members rotate in a mixture of the suspension and the pulverizing medium, agitate the mixture of the suspension and the pulverizing medium, and apply thrust to the pulverizing medium. The thrusted crushing medium travels through the suspension and collides with the material to be crushed, thereby crushing, crushing and / or dispersing the material to be crushed. As used herein, the term material to be ground is used to mean not only the raw material to be ground, but also the raw material to include additives such as dispersants, which may be mixed as needed.

Japanese Patent Application Laid-Open No. 1-107855 states that when a powder or granular material is pulverized with a wet medium using a ball mill or the like, the viscosity of the suspension (slurry) increases even if the pulverization progresses and the particle size of the material to be pulverized becomes smaller. Disclosed is a method for crushing powders and granules, which can prevent the above and obtain the desired crushing effect.

In this crushing method, first, the dispersion medium of the suspension is liquid carbon dioxide gas, and the liquid carbon dioxide gas is pressed into a crushing container having a pressure-resistant structure in which the material to be crushed and the crushing medium are inserted by a high-pressure pump. Then, pulverization is started at the temperature and pressure at which the liquid carbon dioxide gas is in a liquid state. As a result, "the particle size becomes finer and the viscosity of the medium increases as the crushing progresses, but at the same time, the temperature inside the mill rises due to the heat generated by the movement of the crushing medium, and when it exceeds 31 ° C, it becomes a supercritical fluid. In this state, although the density of the medium is close to that of the liquid, the viscosity is about 1/100 of that of the liquid, and as a result, the effect of lowering the pulverization limit particle size is brought about. " Page 2, right column, lines 5 to 11).

Further, according to Japanese Patent Application Laid-Open No. 6-39307, when the powder or granular material is pulverized with a wet medium by a ball mill or the like, the viscosity of the suspension (slurry) increases even if the pulverization progresses and the particle size of the material to be pulverized becomes smaller. Disclosed is a method for crushing powder or granular material, which can prevent the crushing effect and obtain the desired crushing effect.
In this crushing method, a suspension (slurry) in which a material to be crushed is mixed with a dispersion medium such as acetone and a crushing medium such as a ball are placed in a crushing container having a pressure resistant structure, and then the crushing container is filled with liquid carbon dioxide gas by a high pressure pump. Is press-fitted and added, and pulverization is started at a temperature and pressure at which the liquid carbon dioxide gas as an additive is in a liquid state. As a result, "as the pulverization progresses, the particle size becomes finer and the viscosity of the medium increases, but at the same time, the temperature inside the mill rises due to the heat generated by the movement of the pulverization medium, and when it exceeds 31 ° C, it becomes a supercritical state. In this state, although the density of the additive is close to that of the liquid, the viscosity is about 1/100 of that of the liquid, and as a result, the effect of lowering the pulverization limit particle size is brought about. " Paragraph 0007).

Japanese Patent Application Laid-Open No. 2003-1129 is characterized in that a suspension in which an object to be pulverized is dispersed in a liquefied inert gas is pulverized with a medium stirring mill, and then the liquefied inert gas is vaporized to obtain a dry powder. Discloses a method for producing a fine powder (claim 1 of the same publication). The publication also discloses that in this method for producing fine powder, the liquefied inert gas is one kind of liquefied gas selected from liquid helium, liquid neon, liquid nitrogen, liquid argon, liquid krypton, and liquid xenone. A method for producing a powder is disclosed (claim 2 of the same publication). The publication further states, "In this way, when the liquefied inert gas is used as a dispersion medium for suspension and pulverized with a medium stirring mill, the cold heat possessed by the liquefied inert gas is utilized. In addition to improving the temperature dependence of the powder characteristics, the influence of frictional heat during crushing work can be reduced. Further, when crushing a suspension using a liquefied inert gas as a dispersion medium. In addition, since the object to be crushed does not dissolve in the liquefied inert gas or react with the liquefied inert gas, it can be pulverized while maintaining the original properties. "( It is described as paragraph 0015) of the same publication.

Paragraph 0101 of International Publication No. 2011/059074 describes wet medium crushing using liquid nitrogen as a dispersion medium. Therefore, it is necessary to replenish the vessel 4 with a predetermined amount of liquid nitrogen. In order to determine the timing and amount of replenishment of the liquid nitrogen, the weight of the vessel 14 is measured by the load cell, and the liquid level of the liquid nitrogen is controlled. In the following examples, pulverization was performed while controlling the weight of the vessel 14 within the range of ± 10 g based on the total weight of the vessel 14 immediately after the start of pulverization. "

Japanese Unexamined Patent Publication No. 1-107855 Japanese Unexamined Patent Publication No. 6-39307 Japanese Patent Application Laid-Open No. 2003-1129 International Publication No. 2011/059074

In the pulverization method described in Patent Document 1, the liquid carbon dioxide gas constituting the dispersion medium of the suspension is transferred to the supercritical fluid by the heat generated by the pulverization, and the viscosity of the medium is 1/100 of the viscosity of the liquid carbon dioxide gas. It is characterized by lowering the pulverization limit particle size by adjusting the degree. Carbon dioxide is a gas at normal temperature and pressure, and in order to keep carbon dioxide in a liquid, a temperature and pressure of a triple point (-56.6 ° C., 0.52 MPa) or higher are required. Therefore, in this crushing method, a suspension is generated at a temperature and pressure above the triple point of carbon dioxide, and crushing is started at a temperature and pressure below the critical point of carbon dioxide (31.1 ° C., 7.38 MPa). There must be. Further, the temperature inside the mill rises with the progress of pulverization, and when the carbon dioxide gas becomes a supercritical state, the viscosity of the medium liquid decreases to about 1/100. However, when the viscosity of the medium solution decreases, the thrust of the beads also decreases, and the crushing force of the beads decreases. This is because the thrust of the beads is considered to be transmitted from the stirring member to the beads by the viscosity of the medium solution. Therefore, in order to obtain a powder or granular material having a desired particle size by this pulverization method, a suspension is produced by controlling the pressure and temperature in the mill, and further, the temperature and pressure in the mill are controlled to perform pulverization. It is necessary to control when to start and when the liquid carbon dioxide transitions to the supercritical state.

The pulverization method described in Patent Document 2 is characterized in that liquid carbon dioxide gas is added to a suspension, and the liquid carbon dioxide gas is transferred to a supercritical state by heat generation accompanying the movement of the pulverization medium to function as a dispersant. And. Since carbon dioxide in the supercritical state is a low-viscosity, highly diffusible fluid, when added to the suspension, it reduces the frictional force between the dispersion medium of the suspension and the pulverized particles, and also It is possible to improve the wettability of the medium to the crushed particles and prevent aggregation. However, since carbon dioxide in the supercritical state also lowers the viscosity of the medium itself, if the amount of carbon dioxide in the supercritical state is too large, the thrust of the beads decreases and the desired crushing force cannot be obtained. .. Therefore, in order to obtain a powder or granular material having a desired particle size by this pulverization method, it is necessary to control the pressure and temperature in the mill when adding liquid carbon dioxide gas to the suspension, and it is generated during pulverization. It is necessary to control the amount of carbon dioxide in the supercritical state. Since carbon dioxide maintains a fluid state at a temperature of 31.1 ° C. (critical temperature) at a pressure of 7.38 MPa (critical pressure), the critical temperature is even if the critical pressure of the medium is 7.38 MPa or less. If is higher than 31.1 ° C., the medium can coexist with carbon dioxide in a supercritical state. Incidentally, the critical pressure of acetone exemplified as the medium solution in Patent Document 2 is 4.70 MPa, but the critical temperature thereof is 234.94 ° C.

In wet medium pulverization, the solid content concentration of the suspension (slurry) affects the pulverization efficiency of the material to be pulverized. The solid content concentration of the suspension in wet medium grinding is the ratio of the total weight of the material to be ground and the grinding medium to the weight of the dispersion medium in the suspension. In wet medium pulverization, the existence of the optimum solid content concentration is recognized for each material to be pulverized. In wet medium pulverization using water or alcohol as a dispersion medium, when the solid content concentration of the suspension exceeds a certain ratio, the viscosity of the mixture of the dispersion medium, the material to be crushed and the pulverization medium increases, and the pulverization medium moves. It becomes inactive and cannot be crushed (thickening state). On the other hand, since the viscosity and surface tension of the liquefied inert gas are smaller than the viscosity and surface tension of water, respectively, the mixture of the suspension using the liquefied inert gas as the dispersion medium and the pulverizing medium is thickened. It has the characteristic that it is difficult to be in a state. For example, the viscosity of liquid nitrogen is about 1/3 of the viscosity of water, and the surface tension of liquid nitrogen is about 1/7 of the surface tension of water. However, when a suspension of a material to be crushed using a liquefied inert gas as a dispersion medium is crushed in a wet medium under normal temperature and pressure, the liquefied inert gas in the crushing chamber is constantly vaporized by heat intrusion from the outside and heat generated by crushing. .. Therefore, in order to keep the suspension in a liquid state and continue the wet medium pulverization, it is necessary to replenish the liquefied inert gas for the vaporized portion to the pulverization chamber. Paragraph 0101 of Patent Document 4 describes a method of controlling the liquid level of liquid nitrogen in a vessel by using a load cell.

An object of the present invention is to raise the temperature of a pulverized chamber in a wet medium pulverization method in which a liquefied inert gas in a pulverized chamber, a material to be pulverized, and a mixture of a pulverized medium are pulverized at normal temperature and pressure to pulverize the material to be pulverized. It is an object of the present invention to provide a wet medium pulverization method capable of preventing a decrease in pulverizing power due to the above-mentioned factors and thereby promoting pulverization of a material to be pulverized.

Another object of the present invention is to provide a wet medium pulverization method in which the pulverization process can be easily automated.

In order to achieve the above object, in the wet medium crushing method of the present invention, a mixture of a suspension of a material to be crushed using a liquefied inert gas as a dispersion medium and a crushing medium such as balls and beads is stirred in a crushing chamber. In a wet medium crushing method in which the material to be crushed is crushed, crushed and / or dispersed by the crushing medium, the crushing chamber is used so as to lower the temperature of the dispersion medium during stirring of the mixture. Is supplied with a liquefied inert gas having a temperature lower than the temperature of the crushing chamber, whereby the viscosity of the dispersion medium is adjusted by the crushing medium to crush, crush and / or disperse the material to be crushed. It is characterized by keeping the viscosity.

The wet medium pulverization method of the present invention is also characterized in that the liquefied inert gas supplied to the pulverization chamber during stirring of the mixture reduces the solid content concentration of the mixture.

The wet medium pulverization method of the present invention is also characterized in that the liquefied inert gas supplied to the pulverizing chamber during stirring of the mixture is a liquefied inert gas having a temperature lower than the boiling point of oxygen.

The wet medium crushing method of the present invention is also characterized in that the liquefied inert gas supplied to the crushing chamber during stirring of the mixture is a liquefied inert gas degassed by a gas-liquid separator. do.

The wet medium pulverization method of the present invention is also characterized in that the mixture in the pulverization chamber is covered with a vapor layer of the liquefied inert gas.

The wet medium crushing method of the present invention also comprises the total weight of the mixture and the vessel defining the crushing chamber to maintain the set weight measured prior to crushing during stirring of the mixture. When the weight becomes less than the set weight, the liquefied inert gas is supplied to the crushing chamber, and then when the total weight reaches the set weight during stirring of the mixture, the supply of the liquefied inert gas is stopped. It is characterized by doing.

In the wet medium crushing method of the present invention, when the exterior temperature of the crushing chamber reaches a preset temperature during stirring of the mixture, the liquefied inert gas is supplied to the crushing chamber, and the mixture is combined with the mixture. When the total weight of the vessel reaches a preset weight, the supply of the liquefied inert gas is stopped.

The wet medium pulverization method of the present invention also issues an alarm when the temperature of the liquefied inert gas supplied to the pulverization chamber rises above a preset temperature and an abnormality determination is made. It is a feature.

In the wet medium pulverization method of the present invention, the dispersion medium of the suspension is a low-temperature liquid that is chemically inert at room temperature, such as liquid nitrogen, liquid helium, liquid neon, and liquid argon.

In the wet medium crushing method of the present invention, the crushing medium is made of ceramic beads or balls, steel, tungsten carbide, stainless steel, etc., which are made of materials such as alumina, menow, zirconia, silicon nitride, and titania. Glass beads or balls made of metal beads or balls, soda glass, quartz glass, etc., resin beads or balls made of materials such as urethane, and / or agglomerates of dry ice (solid carbon dioxide). Alternatively, it is characterized by being a molded body or a granular body.

The wet medium crushing method of the present invention is characterized in that a pharmaceutical product, a pharmaceutical additive, a resin, a metal, a ceramic or glass, and other medical or industrial raw materials are selected as the material to be crushed.

In wet medium pulverization, as the pulverization progresses, heat is generated by the collision between the pulverized medium and the material to be crushed, heat is generated by the collision between the pulverized media, heat is generated by the collision between the pulverized medium or the material to be pulverized and the stirring disk, and external. The temperature of the crushing chamber rises due to the intrusion of heat from the crushing chamber. When the temperature of the crushing chamber rises, the temperature of the liquefied inert gas used as the dispersion medium of the material to be crushed rises, and the viscosity of the liquefied inert gas decreases. The rotational force of the stirring member rotating in the pulverization chamber is transmitted to the pulverization medium by the viscosity of the liquefied inert gas and becomes the thrust of the pulverization medium. Therefore, when the viscosity of the liquefied inert gas decreases, the thrust of the pulverization medium decreases. , The crushing power of the crushing medium is reduced. At this time, if the low-temperature liquefied inert gas is supplied to the crushing chamber, the temperature of the liquefied inert gas used as the dispersion medium of the material to be crushed can be lowered and the viscosity thereof can be increased. As a result, the viscosity of the liquefied inert gas used as the dispersion medium of the material to be crushed can be maintained at a viscosity suitable for crushing, crushing and dispersing the material to be crushed, so that crushing of the material to be crushed is promoted. can do.

Further, in wet medium crushing, as the temperature of the crushing chamber rises as the crushing progresses, the amount of evaporation of the liquefied inert gas increases. The minute concentration increases. When the solid content concentration of the mixture in the crushing chamber increases, the movement of the crushing medium is hindered, so that the crushing power of the crushing medium decreases. At this time, if the liquefied inert gas functioning as a dispersion medium for the material to be crushed is supplied to the crushing chamber, the solid content concentration of the mixture in the crushing chamber can be lowered. As a result, the movement of the pulverizing medium becomes active, and the pulverization of the material to be pulverized is promoted. Further, since the liquefied inert gas supplied to the crushing chamber is a low-temperature liquefied inert gas, the viscosity of the dispersion medium of the material to be crushed is increased, and the thrust transmitted from the stirring member to the crushing medium is increased. Therefore, the moving region of the crushing medium can be expanded and the crushing force thereof can be increased.

It is known that the boiling point fluctuates when oxygen in the atmosphere is mixed into a liquefied inert gas such as liquid nitrogen. For example, under atmospheric pressure, the boiling point of nitrogen is 195.79 ° C (77.36K), whereas the boiling point of oxygen is 182.96 ° C (90.2K), so the state of nitrogen-oxygen. From the figure, the existence of a coexistence zone from 195.79 ° C. (77.36K) to 182.96 ° C. (90.2K) can be confirmed between the liquid phase and the gas phase. Since the composition of air is about 78% nitrogen, about 21% oxygen, and about 1% other gases such as argon, it may be mixed in the dispersion medium when pulverizing the wet medium under atmospheric pressure. The highest substance is considered to be oxygen. When oxygen is mixed in liquid nitrogen, its temperature can rise to the boiling point of oxygen. Therefore, if the boiling point of oxygen is selected as one criterion and a liquefied inert gas having a temperature lower than this criterion is used, the temperature of the dispersion medium in the pulverization chamber can be effectively lowered. This is because the temperature of the dispersion medium cannot be lowered even if the liquefied inert gas having a temperature higher than the temperature of the dispersion medium in the pulverization chamber is used.

Since the storage tank of liquefied inert gas such as liquid nitrogen and the piping for supply have heat intrusion from the outside, the liquefied inert gas gradually vaporizes, and the vaporized liquefied inert gas is a part of it. Mixes with the liquid, and the rest forms a gas layer on the liquid surface. If the vaporized liquefied inert gas can be removed from these tanks and pipes by dissipating it into the atmosphere, the liquid temperature of the liquefied inert gas can be lowered. However, it may be difficult to remove the vaporized inert gas from the storage tank or piping. According to the present invention, by degassing the liquefied inert gas with a gas-liquid separator and supplying it to the crushing chamber, the liquefied inert gas having a temperature lower than the temperature of the crushing chamber can be reliably supplied to the crushing chamber.

When the liquefied inert gas comes into contact with air, components such as oxygen and argon in the air dissolve in the liquefied inert gas, the composition of the liquefied inert gas changes, and the boiling point fluctuates. For example, when liquid nitrogen is used as a dispersion medium, the boiling point of nitrogen is 195.79 ° C., the boiling point of oxygen is 182.96 ° C., and the boiling point of argon is -185 under atmospheric pressure. Since it is .85 ° C, it becomes a factor that raises the boiling point of the dispersion medium mixed with oxygen and argon. In the wet medium pulverization method of the present invention, the interface of the mixture in the pulverization chamber is covered with the vapor layer of the liquefied inert gas to prevent the liquefied inert gas in the mixture from coming into contact with air as much as possible. Further, when the liquefied inert gas is supplied to the pulverization chamber through the vapor layer of the liquefied inert gas covering the mixture, even if bubbles are generated on the liquid surface of the mixture, oxygen, argon, etc. in the air are added to the bubbles. It is possible to prevent the components from being mixed. Thereby, according to the wet medium pulverization method of the present invention, it is possible to prevent the temperature of the pulverization chamber from rising and promote pulverization.

According to the wet medium crushing method of the present invention, the optimum liquid level height in the crushing chamber of the mixture of the liquefied inert gas, the material to be crushed and the crushing medium is set in advance, and the weight of the mixture and the crushing chamber at this time are defined. Only by supplying a low temperature liquefied inert gas so that the total weight with the weight of the vessel is maintained during grinding and the temperature of the dispersion medium is lowered, the evaporation amount of the liquefied inert gas during grinding is reduced. It can be replenished and continued to grind. Therefore, the crushing process can be easily automated.

According to the wet medium pulverization method of the present invention, the temperature inside the pulverization chamber can be estimated by detecting the exterior temperature of the pulverization chamber, and the supply timing of the liquefied inert gas can be selected. Therefore, when the exterior temperature of the crushing chamber reaches a preset temperature during stirring of the mixture, a low temperature liquefied inert gas is supplied to the crushing chamber to promote crushing and also the total weight of the mixture and vessel. When the weight reaches a preset weight, the supply of the low-temperature liquefied inert gas to the crushing chamber can be stopped to prevent the liquefied inert gas from overflowing from the crushing chamber. Therefore, the crushing process can be easily automated.

According to the wet medium pulverization method of the present invention, the temperature of the liquefied inert gas supplied to the pulverization chamber rises above a preset temperature, and when an abnormality is determined, an alarm is issued. can. If the crushing device is stopped by issuing an alarm, it is possible to prevent the liquefied inert gas whose viscosity has decreased due to the temperature rise from being supplied to the crushing chamber. As a result, it is possible to prevent the viscosity of the liquefied inert gas in the crushing chamber from decreasing and to prevent the thrust applied to the pulverizing medium (beads) from decreasing during the wet medium pulverization, so that the desired pulverization result can be obtained. ..

In the wet medium pulverization method of the present invention, as a dispersion medium for a suspension, in addition to liquid nitrogen which is widely used as a liquefied inert gas, liquid helium, liquid neon, liquid argon and the like are chemically inert at room temperature. Cold liquids can also be used.

In the wet medium crushing method of the present invention, the crushing medium is made of ceramic beads or balls, steel, tungsten carbide, stainless steel, etc., which are made of materials such as alumina, menow, zirconia, silicon nitride, and titania. Other commonly used crushed beads or balls such as metal beads or balls, glass beads or balls made of materials such as soda glass and quartz glass, and resin beads or balls made of materials such as urethane. , Agglomerates or moldings or granules of dry ice (solid carbon dioxide) can also be used.

According to the wet medium crushing method of the present invention, for example, pharmaceuticals, pharmaceutical additives, resins, metals, ceramics or glass, and various other medical and industrial raw materials can be crushed.

Other purposes, configurations and effects of the present invention will be clarified from the following description.

FIG. 1 is a vertical cross-sectional view of an embodiment of a vertical bead mill vessel for carrying out the wet medium pulverization method of the present invention. FIG. 2 is a vertical cross-sectional view of the vessel of FIG. 1 in a state where the wet medium pulverization method of the present invention is carried out under normal temperature and pressure. FIG. 3 is a schematic configuration diagram of a liquid nitrogen supply device that supplies liquid nitrogen to a crusher such as a vertical bead mill that implements the wet medium crushing method of the present invention. FIG. 4 is a table showing an example of the valve opening degree and the supply pressure of the liquid nitrogen supply device of FIG. FIG. 5 is a comparison table between the exterior temperature of the crushing chamber and the temperature of the mixture in the crushing chamber. FIG. 6 shows the VI of Brookhaven National Laboratory's SELECTED CRYOGENIC DATA NOTEBOOK. FIG. 6 is a diagram showing the relationship between temperature and viscosity of liquid nitrogen published in PROPERTIIES OF NITROGEN VI-J-1.2. FIG. 7 shows S. Forester's Viscosity Measurements in Liquid Neon, Argon and Nitrogen, Cryogenics, Vol. 3, 176-177 (1963) is a table showing the relationship between the viscosity and temperature of liquid nitrogen. FIG. 8 is a phase diagram of nitrogen-oxygen under atmospheric pressure. FIG. 9 is a schematic cross-sectional view of the viscosity measuring device. FIG. 10 shows the viscosity data of liquid nitrogen obtained from the National Institute of Standards and Technology (NIST) NIST Standard Reference Database 12 Version 5.0 Thermodynamic and Transport Properties of Pure Fluids, and the viscosity data of liquid nitrogen. It is a comparison table of. FIG. 11 is a table showing the crushing conditions when polyethylene naphthalate (manufacturing company and product number unknown) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. .. FIG. 12 is a table showing the crushing conditions when polyester (ER6640, Nippon Ester Co., Ltd.) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 13 is a table showing the crushing conditions when polyester (NEH2050, Unitika Ltd.) is crushed by the wet medium crushing method of the present invention, the grain size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 14 is a table showing the crushing conditions when the polyimide (PD450 of Mitsui Chemicals, Inc.) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 15 is a table showing the crushing conditions when the polyimide (PD450 of Mitsui Chemicals, Inc.) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 16 shows the crushing conditions when calcium carbonate (NN # 200 of Nitto Powder Industry Co., Ltd.) was crushed by the wet medium crushing method of the present invention, the grain size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. It is a table showing. FIG. 17 shows the crushing conditions when calcium carbonate (NN # 200 of Nitto Powder Industry Co., Ltd.) was crushed by the wet medium crushing method of the present invention, the grain size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. It is a table showing. FIG. 18 shows the crushing conditions when calcium carbonate (NN # 200 of Nitto Powder Industry Co., Ltd.) was crushed by the wet medium crushing method of the present invention, the grain size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. It is a table showing. FIG. 19 shows the crushing conditions when calcium carbonate (NN # 200 of Nitto Powder Industry Co., Ltd.) was crushed by the wet medium crushing method of the present invention, the grain size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. It is a table showing. FIG. 20 is a table showing the crushing conditions when the fly ash (standard powder JIS 5 type) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 21 is a table showing crushing conditions when silicon (MIZUKASIL, Mizusawa Industrial Chemicals Co., Ltd.) is crushed by the wet medium crushing method of the present invention, the particle sizes of raw materials and crushed products, and the exterior temperature of the crushing chamber during crushing. .. FIG. 22 is a table showing the crushing conditions when gallium (manufacturing company and product number unknown) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 23 is a table showing the crushing conditions when nylon (manufacturing company and product number unknown) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 24 is a table showing the crushing conditions when the liquid crystal polymer (manufacturing company and product number unknown) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 25 is a table showing the crushing conditions when rubber (manufacturing company and product number unknown) is crushed by the wet medium crushing method of the present invention, the particle size of the raw material and the crushed product, and the exterior temperature of the crushing chamber during crushing. FIG. 26 is a table showing crushing experimental conditions for comparing the phase transition heat content (ΔH) before and after crushing when phenytoin is crushed by the wet medium crushing method of the present invention. FIG. 27 is a table showing the particle size before and after pulverization when phenytoin is pulverized by the wet medium pulverization method of the present invention. FIG. 28 is a table showing the phase transition heat content (ΔH) before and after pulverization when phenytoin is pulverized by the wet medium pulverization method of the present invention.

Various medical or industrial raw materials were crushed with a vertical bead mill using liquid nitrogen as a dispersion medium and zirconia beads of various media diameters as a crushing medium, and the relationship between the viscosity of the dispersion medium and the crushing result was verified. Further, phenitoin was crushed using liquid nitrogen as a dispersion medium and zirconia beads having a media diameter of φ0.3 mm as a crushing medium, and the phase transition heat content ΔH (J / g) of phenitoin before and after crushing was compared during crushing. The effect of covering the mixture in the crushing chamber with a vapor layer of liquefied inert gas was verified.

As shown in FIG. 1, the vessel 1 of the vertical bead mill (not shown) has a crushing chamber 3 surrounded by a heat insulating vacuum layer jacket 2. The heat insulating vacuum layer jacket 2 forms the vacuum heat insulating layer 6 along the outer surface 4a of the side wall 4 of the crushing chamber 3 and the outer surface 5a of the bottom wall 5. The vacuum heat insulating layer 6 insulates the crushing chamber 3 from the atmosphere around the vessel 1. The crushing chamber 3 has an opening 3a surrounded by an upper edge 4b of the side wall 4. The vessel 1 includes a lid 7 for closing the opening 3a of the crushing chamber 3 during the operation of the bead mill. The lid 7 has a rotary shaft insertion hole 7a for passing the rotary shaft 10 of the bead mill in the central portion thereof, and is further separated from the rotary shaft insertion hole 7a in the radial direction with the liquid nitrogen supply hole 7b. It has a float insertion hole and a nitrogen gas discharge hole 7c.

The stirring discs 11a, 11b, 11c, 11d are spaced apart from the rotating shaft 10, and the stirring discs 11a, 11b, 11c, 11d are together with the rotating shaft 10 when the rotating shaft 10 rotates around its central axis. Rotate. The rotary shaft 10 is rotated at an arbitrary rotation speed by an electric motor (not shown).

The specifications of this vertical bead mill are as follows.
(1) Capacity of crushing chamber 3 of vessel 1: 3 liters (2) Vessel 1: Vessel with vacuum layer jacket 2 for heat insulation (3) Output of electric motor: 0.75KW
(4) Maximum rotation speed of electric motor: 3000 rpm
(5) Maximum peripheral speed of stirring disk 11a-11d: 14 m / sec (6) Material of dust contact part of stirring disk 11a-11d: SUS304

In order to measure the exterior temperature of the crushing chamber 3, a thermocouple type or temperature measuring resistor type thermometer 12a was attached to the outer surface 4a of the side wall 4 of the crushing chamber 3. The thermometer 12a is located inside the vacuum heat insulating layer 6 of the heat insulating vacuum layer jacket 2. The exterior temperature of the crushing chamber 3 measured by the thermometer 12a is the liquid nitrogen 20 (see FIG. 2), the material to be crushed (not shown), and the crushing medium (beads) (not shown) charged in the crushing chamber 3. The thermometer 12a is installed below the optimum liquid level height 13a of the mixture 13 at the start of pulverization so as to correspond to the temperature of the mixture 13 of.). Reference number 13b indicates the height of the upper surface of the stirring disk 11a located at the highest level.

The specifications of the thermometer 12a are as follows.
(1) Platinum resistance temperature detector RESUSTABCE THERMOMETER
(2) Hayashi Denko Co., Ltd. Pt100-B-2-L 139293-11-001

The bottom surface 2a of the heat insulating vacuum layer jacket 2 of the vessel 1 is supported by the load cell 14.
The load cell 14 can measure the static load of equipment such as the vessel 1, the lid 7, the thermometer 12a, and the float scale 15, as well as the liquid nitrogen 20 charged in the crushing chamber 3 and the crushing medium (not shown). ), The static load of the material to be crushed (not shown) can be measured individually. Further, the load cell 14 can measure the static load of the mixture 13 of the liquid nitrogen 20 charged in the crushing chamber 3, the crushing medium (not shown), and the material to be crushed (not shown).
The main components of the static load immediately before the start of operation and the dynamic load during operation measured by the load cell 14 are the weight of the vessel, the weight of the lid 7, and the weight of the pipe 18 for supplying liquid nitrogen. It is the total weight of the pipe 19 for discharging nitrogen gas, the weight of the liquefied inert gas or liquid nitrogen 20, the weight of the material to be crushed (not shown), and the weight of the crushing medium (not shown). Therefore, in the present application, the weight, total weight, and dynamic load of the vessel or vessel 1 mainly refer to the vessel 1, the lid 7, the pipe 18 for supplying liquid nitrogen, and the pipe 19 for discharging nitrogen gas. It is used to include the weight of a liquefied inert gas or liquid nitrogen 20, a material to be crushed (not shown), and a crushing medium (not shown).
Since the float scale 15 is made of styrofoam, it is extremely lightweight.
As shown in FIG. 2, the load cell 14 rotates the rotating shaft 10 of the vertical bead mill and measures the dynamic load of the vessel 1 when the mixture 13 is stirred by the stirring disks 11a, 11b, 11c, 11d. Can be done. In FIG. 2, reference number 16 indicates a fixed surface supporting the load cell 14, and reference number 17 indicates the liquid level of the mixture 13 being stirred by the stirring disks 11a, 11b, 11c, 11d.

The specifications of the load cell 14 are as follows.
(1) Unipulse Corporation (2) Hermetically sealed stainless steel single point load cell USC-50KG
(3) Rated capacity: 50 kg

The specifications of the float scale 15 are as follows.
(1) Material: Styrofoam (polystyrene)
(2) Total length: 200 mm (scales in 1 mm units are shown)
(3) Diameter: 10 mm

In FIG. 2, reference number 18 indicates a pipe for supplying liquid nitrogen, and reference number 19 indicates a pipe for discharging nitrogen gas. The liquid nitrogen supply pipe 18 is connected to the liquid nitrogen supply hole 7b of the lid 7 when the liquid nitrogen 20 is charged into the crushing chamber 3 before the start of crushing, and stays in the liquid nitrogen supply hole 7b until the crushing is completed. It is connected. A thermocouple type or temperature measuring resistor type thermometer 12b can be attached to the pipe 18 for supplying liquid nitrogen . The thermometer 12b can detect the temperature of the liquid nitrogen 20 supplied to the crushing chamber 3 through the pipe 18 for supplying the liquid nitrogen. The specifications of the thermometer 12b are the same as the specifications of the thermometer 12a.
The nitrogen gas discharge pipe 19 is connected to the float insertion hole and nitrogen gas discharge hole 7c of the lid 7. As shown in FIG. 1, before the start of pulverization, the float scale 15 is inserted into the float insertion hole and nitrogen gas discharge hole 7c, and the optimum liquid level height 13a of the mixture 13 in the pulverization chamber 3 is set. As will be described later, the nitrogen gas discharge pipe 19 is connected to the float insertion hole and nitrogen gas discharge hole 7c after the float scale 15 is taken out and the material to be pulverized (not shown) is charged. The nitrogen gas discharge pipe 19 is connected to the float insertion hole and the nitrogen gas discharge hole 7c until the pulverization is completed.

As shown in FIG. 3, the storage tank 31 for liquid nitrogen 20 is supported by the support members 32 and 33 and installed inside the sealed container 34. A vacuum heat insulating layer 35 is formed between the outer surface of the storage tank 31 and the inner surface of the sealed container 34. The vacuum heat insulating layer 35 is formed to prevent heat from entering the inside of the storage tank 31 from the atmosphere around the sealed container 34. However, the heat around the sealed container 34 is transferred from the support members 32 and 33 to the storage tank 31, and heats the liquid nitrogen 20 in the storage tank 31. As a result, the nitrogen gas 20a stays in the upper part of the internal space of the storage tank 31. In order to prevent the nitrogen gas 20a of the storage tank 31 from being boosted to a predetermined pressure or higher, a release valve or a safety valve (not shown) can be provided in the storage tank 31.

As shown in FIG. 3, the liquid nitrogen outlet 31a of the storage tank 31 of the liquid nitrogen 20 is connected to the liquid nitrogen filling port 37a of the gas-liquid separator 37 via a pipe 36 for transporting liquid nitrogen. The pipe 36 for transporting liquid nitrogen is a vacuum heat insulating pipe covered with a vacuum heat insulating layer (not shown) like the storage tank 31. A main supply valve 38 is interposed in the pipe 36, and a pressure gauge 40 is attached to the downstream side of the main supply valve 38. The pipe 36 has a branch pipe 36a that branches on the upstream side of the main supply valve 38 and joins on the downstream side of the main supply valve 38. A flow rate adjusting valve 41 is interposed in the branch pipe 36a, and a solenoid valve 42 is interposed on the upstream side of the flow rate adjusting valve 41. The solenoid valve 42 only opens and closes the branch pipe 36a. FIG. 4 shows an example of the valve opening degree of the main supply valve 38 and the flow rate adjusting valve 41, and the measured value of the pressure gauge 40 at the valve opening degree. The measured value of the pressure gauge 40 indicates the supply pressure of the liquid nitrogen 20 in the pipe 36. At this time, the solenoid valve 42 is fully open.

As shown in FIG. 3, the gas-liquid separator 37 is composed of a hollow tubular container 37b as a whole, and the liquid nitrogen filling port 37a to which the pipe 36 for transporting liquid nitrogen is connected is opened on the side surface of the tubular container 37b. do. A gas-liquid separation chamber 37c is defined inside the tubular container 37b, and a collision plate 37d and a rectifying plate 37e are attached to the gas-liquid separation chamber 37c. The collision plate 37d is attached at a position facing the liquid nitrogen filling port 37a so that the liquid nitrogen 20 discharged from the liquid nitrogen filling port 37a into the gas-liquid separation chamber 37c hits the collision plate 37d. Nitrogen gas 20a is still mixed in the liquid nitrogen 20 discharged from the liquid nitrogen filling port 37a to the gas-liquid separation chamber 37c, but the nitrogen gas 20a in the liquid nitrogen 20 is generated by the impact when it hits the collision plate 37d. Mostly degassed. The degassed nitrogen gas 20a is released into the atmosphere from the nitrogen gas discharge port 37f opened in the ceiling of the gas-liquid separation chamber 37c. The liquid nitrogen 20 that hits the collision plate 37d and is degassed from the nitrogen gas 20a falls down the gas-liquid separation chamber 37c by its own weight and reaches the straightening vane 37e. A large number of pores P having a diameter of 3 mm are formed on the straightening vane 37e. When the liquid nitrogen 20 passes through these pores P, the nitrogen gas 20a in the liquid nitrogen 20 is further degassed, and the liquid nitrogen is supplied from the liquid nitrogen outlet 37 g formed at the bottom of the gas-liquid separation chamber 37c. It flows into the liquid nitrogen supply hole 7b of the lid 7 and is supplied to the crushing chamber 3 of the vessel 1 through the pipe 18.

In order to carry out the wet medium crushing method of the present invention using liquid nitrogen 20 as a dispersion medium, first, a predetermined amount of a crushing medium (not shown) such as beads is charged into the crushing chamber 3 of the vessel 1. Next, the lid 7 is attached to the vessel 1, and a predetermined amount of liquid nitrogen 20 is supplied to the crushing chamber 3 from the gas-liquid separator 37 through the liquid nitrogen supply pipe 18 and the liquid nitrogen supply hole 7b of the lid 7. Supply and cool down. Next, the float scale 15 is inserted into the float insertion hole / nitrogen gas discharge hole 7c of the lid body 7, and the scale of the float scale 15 is read with reference to the upper edge portion of the float insertion hole / nitrogen gas discharge hole 7c. Further, while visually observing the scale of the float scale 15, the liquid nitrogen 20 is supplied to the crushing chamber 3 from the liquid nitrogen supply hole 7b, and the supply of the liquid nitrogen 20 is stopped when the scale of the float scale 15 reaches 186 mm. At this time, the liquid level 13a of the liquid nitrogen 20 in the crushing chamber 3 is 20 mm higher than the height 13b of the upper surface of the stirring disk 11a located at the uppermost position, so this was set as the appropriate liquid level of the liquid nitrogen 20. In FIG. 1, A = 166 mm and B = 20 mm. Next, the float scale 15 is removed from the float insertion hole / nitrogen gas discharge hole 7c, and a predetermined amount of the material to be crushed (not shown) is charged into the crushing chamber 3 from the float insertion hole / nitrogen gas discharge hole 7c. When the charging of the material to be pulverized (not shown) is completed, the nitrogen gas discharge pipe 19 is connected to the float insertion hole and nitrogen gas discharge hole 7c. The nitrogen gas discharge pipe 19 can be connected to a natural exhaust pipe (not shown) or a forced exhaust pipe (not shown) equipped with a blower or the like. can. This completes the preparation for crushing.

In this state, the rotary shaft 10 is rotated to start crushing, and the mixture 13 of the liquid nitrogen 20 in the crushing chamber 3, the material to be crushed (not shown) and the crushing medium (not shown) is mixed with the stirring disk 11a. Stir with 11b, 11c, 11d. The temperature of liquid nitrogen 20 at the start of pulverization is approximately at the boiling point (-195.79 ° C.). At this time, the weight of the vessel 1 at the start of pulverization (vessel dynamic load) is measured by the load cell 14 to obtain the weight of the vessel 1 at the start of pulverization (vessel dynamic load).

As the grinding progresses, the temperature of the mixture 13 rises. The cause of the temperature rise of the mixture 13 is the heat that has entered the crushing chamber 3 from the outside, the heat generated by the collision between the material to be crushed (not shown) and the crushing medium (not shown), and the crushing medium. (Not shown) Heat generated by the collision between each other, or heat generation due to the collision between the crushing medium (not shown) or the material to be crushed (not shown) and the stirring disk can be considered. Of these, the heat that enters the crushing chamber 3 from the outside mainly enters from the upper edge portion 4b of the side wall 4. The temperature of the mixture 13 is measured by a thermometer 12a attached to the outer surface 4a of the side wall 4 of the crushing chamber 3. The temperature measured by the thermometer 12a is the exterior temperature of the crushing chamber 3, not the temperature of the mixture 13, but since it is difficult to directly measure the temperature of the mixture 13 during crushing, the temperature of the crushing chamber 3 is increased. It was decided to estimate the temperature of the mixture 13 being pulverized from the exterior temperature.

FIG. 5 is a comparison table between the exterior temperature of the crushing chamber 3 during crushing and the liquid temperature of the mixture 13 immediately after the completion of crushing when the dispersion medium is water and the dispersion medium is liquid nitrogen 20. .. As described in the table, in each case, the difference between the exterior temperature of the crushing chamber 3 during crushing and the liquid temperature of the mixture 13 immediately after the completion of crushing was about 40 ° C.

The liquid nitrogen 20 in the pulverization chamber 3 is constantly vaporized under normal temperature and pressure, but as shown in FIG. 2, when the pulverization of the material to be pulverized (not shown) progresses and the temperature of the mixture 13 rises, The amount of evaporation of liquid nitrogen 20 increases. The liquid nitrogen 20 vaporized in the crushing chamber 3 becomes nitrogen gas 20b, and flows out to the nitrogen gas discharge pipe 19 through the float insertion hole and nitrogen gas discharge hole 7c of the lid 7.
In order to keep the mixture 13 in the pulverization chamber 3 in a liquid state and continue the wet medium pulverization, it is necessary to replenish the pulverization chamber 3 with the vaporized amount of liquid nitrogen 20. The vaporized amount of liquid nitrogen 20 is supplied from the storage tank 31 of FIG. As shown in FIG. 2, the liquid nitrogen 20 flowing out from the storage tank 31 to the pipe 36 flows into the liquid nitrogen supply hole 7b of the lid 7 from the liquid nitrogen supply pipe 18. At this time, the gas-liquid separator 37 arranged immediately before the liquid nitrogen supply pipe 18 separates the nitrogen gas 20a mixed in the liquid nitrogen 20 while being stored in the storage tank 31, so that the gas-liquid The low-temperature liquid nitrogen 20 can be supplied to the crushing chamber 3 from the liquid nitrogen discharge port 37 g of the separator 37.

As shown in FIG. 2, the temperature of the liquid nitrogen 20 supplied to the crushing chamber 3 through the liquid nitrogen supply pipe 18 is monitored by the thermometer 12b attached to the liquid nitrogen supply pipe 18. It is possible to prevent liquid nitrogen 20 having a temperature higher than the temperature of the period from flowing into the crushing chamber 3.
The temperature rise of liquid nitrogen 20 may occur, for example, in the following cases.
(1) When the nitrogen gas 20a is insufficiently degassed due to a defect in the collision plate 37d or the rectifying plate 37e of the gas-liquid separator 37 (2) A sealed container due to a defect in the vacuum heat insulating layer 35 of the liquid nitrogen storage tank 31. When heat invades the inside of the sealed container 34 from the outside of the 34 (3) Due to a defect in the vacuum heat insulating layer (not shown) of the liquid nitrogen transport pipe (vacuum heat insulating pipe) 36, the pipe is piped from the outside of the pipe 36. When heat invades the inside of 36 (4) Liquid nitrogen 20 leaks from the liquid nitrogen storage tank 31 due to damage to the liquid nitrogen storage tank 31, and as a result, the flow rate of the liquid nitrogen 20 decreases and the temperature rises. (5) Liquid nitrogen 20 leaks from the pipe 36 due to damage to the pipe 36 for transporting liquid nitrogen, and as a result, when the flow rate of the liquid nitrogen 20 decreases and the temperature rises, the thermometer 12b displays the liquid nitrogen. When the temperature rise of 20 is detected, for example, the following measures can be taken. When the thermometer 12b detects an abnormal temperature higher than the preset temperature and continues to detect the abnormal temperature beyond the preset time, the temperature control program of the liquid nitrogen 20 makes an abnormality determination. Issue an alarm (alarm). Next, the main supply valve 38 is manually stopped, the solenoid valve 42 is closed by an interlock mechanism (not shown), and the supply of liquid nitrogen 20 is stopped. Then, the operation of the vertical bead mill is stopped by the operation of the interlock mechanism.
By adopting such a configuration, it is possible to prevent the liquid nitrogen 20 whose viscosity has decreased due to the temperature rise from being supplied to the crushing chamber 3, so that the decrease in the viscosity of the liquid nitrogen in the crushing chamber 3 can be prevented. be able to. Thereby, the thrust applied to the crushing medium (beads) can be maintained during the crushing of the wet medium, and the desired crushing result can be obtained.

The timing of replenishing the crushing chamber 3 of the vessel 1 with the liquid nitrogen 20 during crushing can be determined based on the dynamic load of the vessel 1 detected by the load cell 14. That is, when the dynamic load of the vessel 1 decreases by a predetermined amount from the dynamic load of the vessel 1 at the start of pulverization as the pulverization progresses, the solenoid valve 42 is manually opened and the liquid nitrogen 20 is supplied to the pulverization chamber 3. can do. Then, when the dynamic load of the vessel 1 reaches the dynamic load of the vessel 1 at the start of pulverization, the solenoid valve 42 can be manually closed to stop the supply of the liquid nitrogen 20. Such an opening / closing operation of the solenoid valve 42 can be automated. Further, the lower limit value of the dynamic load for opening the solenoid valve 42 and the upper limit value of the dynamic load for closing the solenoid valve 42 can be set separately from the dynamic load at the start of pulverization.

The timing for replenishing the crushing chamber 3 of the vessel 1 with the liquid nitrogen 20 during crushing can be determined in consideration of the exterior temperature of the crushing chamber 3 detected by the thermometer 12a. That is, as the pulverization progresses, when the exterior temperature of the pulverization chamber 3 reaches a predetermined temperature, the solenoid valve 42 can be manually opened and the liquid nitrogen 20 can be supplied to the pulverization chamber 3. Then, when the dynamic load of the vessel 1 reaches a predetermined dynamic load, the solenoid valve 42 can be manually closed to stop the supply of the liquid nitrogen 20. Such an opening / closing operation of the solenoid valve 42 can be automated.

FIG. 6 is a diagram showing the relationship between the viscosity of liquid nitrogen and the temperature. In the figure, reference numeral C indicates a temperature near the boiling point of liquid nitrogen, and reference numeral D indicates a temperature near the boiling point of liquid oxygen. FIG. 7 is a table showing typical numerical values on the diagram of FIG. 6, and reference numbers C and D in FIG. 7 correspond to reference numbers C and D in FIG.

10 shows the viscosity data of liquid nitrogen obtained from the database of the National Institute of Standards and Technology (NIST) and the numerical values of FIG. 7 in order to verify the relationship between the viscosity and the temperature of the liquid nitrogen shown in FIGS. It is a comparison table with. The numerical value surrounded by the square line in the conversion value column of the data of NIST 12 in FIG. 10 and the S.I. Comparing the numerical values surrounded by the square line in the column of the measured values of Forester, it can be seen that both numerical values are almost the same.

The relationship between the viscosity of liquid nitrogen and the temperature can be measured by a viscosity measuring device as shown in FIG. Explaining the method of measuring the viscosity and temperature of liquid nitrogen with reference to FIG. 9, first, nitrogen gas is filled in a nitrogen container located in the innermost part. At this stage, only nitrogen gas is present in this nitrogen container. Next, liquid helium is gradually injected into the helium container surrounding the nitrogen gas container. Since the boiling point of liquid helium under atmospheric pressure is -269 ° C. (about 4K), the nitrogen gas container is gradually cooled, and the nitrogen gas in the container is gradually liquefied. Then, the disk of the viscometer is rotated in the liquefied nitrogen gas, the viscosity of the liquid nitrogen is measured from the rotation resistance, and the relationship with the temperature measured by the thermometer is obtained. As the nitrogen gas in the nitrogen gas container gradually liquefies, the pressure in the nitrogen gas container gradually decreases. The pressure inside the nitrogen gas container is measured with a pressure gauge. That is, the pressure does not measure the change in the process of increasing the pressure, but measures the change in the process of decreasing the pressure. However, it is known that the viscosity of a liquid hardly changes with a change in pressure.

As shown in FIGS. 6, 7, and 10, the viscosity of liquid nitrogen decreases as the temperature of liquid nitrogen rises. When pulverizing a wet medium using liquid nitrogen as a dispersion medium, if the viscosity of the liquid nitrogen decreases, the thrust of the pulverized medium such as balls and beads decreases, and the impact force given to the material to be pulverized by the pulverized medium decreases. .. From these figures, the viscosity of liquid nitrogen at the boiling point of liquid nitrogen under atmospheric pressure is 0.15 to 0.16 centipores (cP). In wet medium pulverization, water is often used as the dispersion medium, but as shown in FIG. 5, when water is used as the dispersion medium, the water temperature of the dispersion medium during pulverization is about 60 ° C., which is 60 ° C. Since the viscosity of water is 0.467 centipores (cP), the viscosity of liquid nitrogen near the boiling point of liquid nitrogen under atmospheric pressure is about 1/3 of the viscosity of water (60 ° C.) during grinding. Further, since the viscosity of liquid nitrogen when the boiling point of liquid nitrogen rises to near the boiling point of liquid oxygen is 0.11 to 0.12 centipores (cP), liquid nitrogen near the boiling point of oxygen under atmospheric pressure. The viscosity of is about 1/4 of the viscosity of water (60 ° C.) being pulverized. On the other hand, the surface tension of water is 66.18 mN / m at 60 ° C, whereas the surface tension of liquid nitrogen is 8.85 mN / m at 195.79 ° C, which is about 1 of the surface tension of water. / 7. Therefore, if the temperature of liquid nitrogen is kept as close to its boiling point as possible, the liquid nitrogen sufficiently wets the surface of the material to be crushed or the crushing medium, keeping the individual particles separated from each other, and of these particles. Allows free exercise. In addition, since liquid nitrogen is constantly boiling due to the intrusion of heat from the outside and the heat generated by crushing, its boiling power also promotes the free movement of individual particles. Therefore, the viscosity of liquid nitrogen can impart sufficient thrust to a pulverizing medium such as a ball or beads. Further, since the surface tension of liquid nitrogen is smaller than the surface tension of water, there is an advantage that it is difficult to obtain a thickened state when wet medium pulverization is performed using liquid nitrogen as a dispersion medium.

FIG. 8 is a phase diagram of nitrogen-oxygen under atmospheric pressure. When wet medium crushing is performed using liquid nitrogen as a dispersion medium, heat intrusion from the outside, heat generation due to collision between crushing media, heat generation due to collision between the crushing medium and the material to be crushed, crushing medium and subject Due to the heat generated by the collision between the crushing material and the stirring disk, liquid nitrogen evaporates, a gas phase of nitrogen is generated in the dispersion medium, air containing oxygen is mixed in these gas phases, and the boiling point of the dispersion medium fluctuates. In some cases. At this time, as shown in FIG. 8, liquid nitrogen ranges from a nitrogen boiling point of 195.79 ° C. (77.36K) to an oxygen boiling point of 182.96 ° C. (90.2K) between the liquid phase and the gas phase. And gaseous oxygen coexistence area is generated. Therefore, in the present invention, as shown in FIG. 2, a nitrogen gas layer 43 covering the liquid surface 17 is retained between the liquid level 17 and the lid 7 of the mixture 13 being pulverized, and the liquid nitrogen 20 in the mixture 13 is retained. Prevented contact with air. Further, if the nitrogen gas layer 43 is generated, even if bubbles are generated on the liquid surface 17 when the liquid nitrogen 20 falls from the liquid nitrogen supply hole 7b of the lid 7 to the liquid surface 17 of the crushing chamber 3. Since the liquid surface 17 is covered with the nitrogen gas layer 43, oxygen and the like in the air do not mix in the bubbles. This prevents the formation of the coexistence zone of FIG. 8 as much as possible and promotes the pulverization of the material to be pulverized.

11 to 25 show the results of pulverizing various materials to be pulverized by the wet medium pulverization method of the present invention. Each table shows the material name, bead material, bead diameter, stirring disk rotation speed, crushing time, suspension dispersion medium, dynamic load of vessel, exterior temperature of crushing chamber during crushing, and raw materials and crushed products. The particle size measurement results are described.
When crushing was performed twice under the same conditions, the particle size measurement results of each crushing were described separately as in the case of the crushed product (1) and the crushed product (2). The reason why the exterior temperature of the crushing chamber during crushing of the crushed product (2) is higher than the exterior temperature of the crushing chamber during crushing of the crushed product (1) is because the outside air temperature at the time of crushing the crushed product (2) is high. It is conceivable that the temperature of the crushed product (1) is higher than the outside air temperature at the time of crushing. In any case, when the particle sizes of the pulverized polyimide products (1) and (2) of FIG. 14 and the particle sizes of the pulverized calcium carbonate products (1) and (2) of FIGS. 16 to 19 are compared, the exterior temperature of the pulverized chamber is compared. It can be seen that the lower the value, the more the pulverized product is becoming finer.
Most of the crushing results shown in FIGS. 11 to 25 were crushed on days with different outside air temperatures, and similarly, even in the crushing example in which a plurality of crushing results are displayed in the same table, the outside air temperature is also used. Some were carried out on different days.
The equipment used for measuring the particle size distribution of the material to be crushed before and after pulverization in FIGS. 11 to 25 is the laser diffraction type particle size distribution measuring device SALD-2100 manufactured by Shimadzu Corporation.
According to the wet medium crushing method of the present invention, in addition to the materials to be crushed shown in FIGS. 11 to 25, silicon, bark (sugi), carbon black, phenitoin, manidipine, ibprofen, salbutamoll sulfate, polyethylene wax, etc. Good pulverization results could also be obtained for hydroxypropyl cellulose, crystalline cellulose, ultra-high molecular weight polyethylene, and chitosan.

FIGS. 26 to 28 show a phenomenon in which liquid nitrogen in the dispersion medium rapidly takes in oxygen in the air when phenitoin is pulverized by the wet medium pulverization method of the present invention using liquid nitrogen as the dispersion medium (object to be pulverized). The pulverization experiment conditions, the fenitoin particle size before and after pulverization, and the phase transition heat content (ΔH) of fenitoin before and after pulverization are shown when it was verified whether or not the oxidation reaction of the above occurs. At this time, the device used for measuring the particle size distribution of phenytoin is the laser diffraction type particle size distribution measuring device SALD-2100 manufactured by Shimadzu Corporation. The phase transition heat content (ΔH) before and after pulverization was measured by using a differential scanning calorimeter DSC-60 manufactured by Shimadzu Corporation. As is clear from FIG. 28, since the change in the phase transition heat content (ΔH) before and after pulverization was slight, it was judged that the crystal change due to oxidation did not occur. It is probable that the reason why the change in the phase transition heat content (ΔH) before and after pulverization was slight in this experiment was that the liquid level 17 of the mixture 13 was shielded from the air by the nitrogen gas layer 43 in FIG.

By stirring a mixture of the liquefied inert gas in the crushing chamber, the material to be crushed, and the crushing medium under normal temperature and pressure, it is possible to prevent a decrease in crushing power due to an increase in the temperature of the crushing chamber when crushing the material to be crushed. The crushing of the material to be crushed can be promoted.

1 Vessel 2 Insulation vacuum layer jacket 3 Crushing chamber 6 Vacuum insulation layer 7 Lid 10 Rotating shaft 11a, 11b, 11c, 11d Stirring disk 12a, 12 b Thermometer 14 Load cell 15 Float scale 17 Liquid level 20 Liquid nitrogen 20a Nitrogen Gas 31 Liquid nitrogen storage tank 34 Sealed container 35 Vacuum insulation layer 36 Liquid nitrogen transfer piping (vacuum insulation piping)
37 Gas-liquid separator 38 Main supply valve 40 Pressure gauge 41 Flow control valve 42 Solenoid valve 43 Nitrogen gas layer

Claims (10)

A mixture of a suspension of the material to be crushed and a crushing medium using a liquefied inert gas as a dispersion medium is stirred in a crushing chamber, and the material to be crushed is crushed, crushed and / or dispersed by the crushing medium. In the wet medium crushing method, a liquefied inert gas degassed by a gas-liquid separator is supplied to the crushing chamber during stirring of the mixture, whereby the viscosity of the dispersion medium is crushed. A wet medium pulverization method, wherein the medium maintains a viscosity at which the material to be pulverized, crushed, and / or dispersed. The wet medium according to claim 1, wherein the liquefied inert gas supplied to the crushing chamber during stirring of the mixture reduces the solid content concentration of the mixture. Grinding method. In the wet medium crushing method according to claim 1 or 2, the liquefied inert gas supplied to the crushing chamber during stirring of the mixture is a liquefied inert gas having a temperature lower than the boiling point of oxygen. The wet medium crushing method. The wet medium crushing method according to any one of claims 1 to 3 , wherein the mixture in the crushing chamber is covered with a vapor layer of the liquefied inert gas. In the wet medium pulverization method according to any one of claims 1 to 4 , the total weight of the mixture and the vessel defining the pulverization chamber was measured before pulverization during stirring of the mixture. When the total weight is less than the set weight so as to maintain the set weight, the liquefied inert gas is supplied to the crushing chamber, and then the total weight reaches the set weight during stirring of the mixture. , The method for pulverizing a wet medium, which comprises stopping the supply of the liquefied inert gas. In the wet medium crushing method according to any one of claims 1 to 4 , when the exterior temperature of the crushing chamber reaches a preset temperature during stirring of the mixture, the liquefaction is performed in the crushing chamber. The wet medium, characterized in that the supply of the liquefied inert gas is stopped when the total weight of the mixture and the vessel defining the crushing chamber reaches a preset weight by supplying the inert gas. Grinding method. In the wet medium pulverization method according to any one of claims 1 to 6 , the temperature of the liquefied inert gas supplied to the pulverization chamber rises above a preset temperature, and abnormality determination is made. The wet medium pulverization method, which comprises issuing an alarm when the above-mentioned is performed. The wet medium pulverization method according to any one of claims 1 to 7 , wherein the liquefied inert gas is liquid nitrogen, liquid helium, liquid neon, or liquid argon. Wet medium crushing method. In the wet medium crushing method according to any one of claims 1 to 8 , the crushing medium is a ceramic bead or ball, steel, which is made of a material such as alumina, menow, zirconia, silicon nitride, and titania. Metal beads or balls made of materials such as tungsten carbide and stainless steel, glass beads or balls made of materials such as soda glass and quartz glass, resin beads or balls made of materials such as urethane, and / Or, the wet medium pulverization method, which is a lump, a molded body, or a granular body of dry ice (solid carbon dioxide). In the wet medium crushing method according to any one of claims 1 to 9 , the material to be crushed is a pharmaceutical product, a pharmaceutical additive, a resin, a metal, a ceramic or glass, a medical or industrial raw material. The wet medium crushing method.

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