JPH0542925B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing clay for ceramics, and more particularly to a method for producing clay characterized by finely pulverizing and uniformly mixing raw materials. (Prior art) The general method for producing clay that has been carried out in the past is to coarsely crush raw stone raw materials using a crusher, etc., and then wet-pulverize the raw materials using a ball mill to form a suspension. This was mixed with the same clay raw material that had been made into a suspension, and then subjected to certain operations to form clay. FIG. 9 shows the flow of the manufacturing process. To specifically explain the steps shown in this figure, first, raw stone raw material or shad, etc. is crushed using a crusher, and then this is wet-pulverized using a ball mill to form a suspension. Separately, a clay raw material is made into a suspension, and this is uniformly mixed together with the suspension of the raw stone raw material. Next, the mixed solution is applied to a filter press to form a cake, and from the cake, a desyne powder with a water content of 7 to 8% is made using a desyne granulator, and used as clay for dry molding. Alternatively, a mixture of the above suspensions is dried and granulated using a spray dryer to produce a spray powder having a water content of about 7 to 8%. This is also used as clay for dry molding. Alternatively, you can dry and adjust the moisture content of raw materials that have been passed through a filter press to a moisture content of 20 to 25.
% of clay for wet molding is obtained. (Problem to be Solved by the Invention) However, this method uses a large ball mill for finely pulverizing the raw material, and a filter press or spray dryer for dehydration, drying, etc., and these devices occupy a large amount of space. Not only that, but also the amount of processing required at one time was large, making it impossible to adequately handle high-mix, low-volume production. In addition, when looking at the resulting clay, there was a problem in that it was difficult to obtain a clay that had sufficient properties in both reactivity and fluidity, no matter which process it went through. For example, when dry molding clay is produced using a deshine granulator, the shape of the resulting secondary particles (desyne powder) is uneven, as shown in Figure 8A, due to the characteristics of desyne granulation. The clay powder has a regular shape, and the fluidity of the powder when press-molding is poor, resulting in uneven packing density of raw material particles in the compact, resulting in shrinkage during firing and This increases the variation in dimensions between products. On the other hand, in the case of spray powder, its shape is close to spherical as shown in Figure 8B, and the fluidity during dry molding is good, but the powder structure is similar to that of decine powder. Because the surface area of the primary particles is small (based on the fact that the primary particles are formed by pulverization with a ball mill), the reactivity of the powder during firing is still insufficient. (First Means for Solving the Problem) The present invention was made to solve the above problem, and its gist is to coarsely crush and finely crush raw materials for ceramics, and then homogeneously mix them to form a mold. When producing soil, the coarsely crushed raw material is finely pulverized using a dry crusher that crushes the particles by colliding them with each other at high speed in a dry state, and then the finely crushed raw material is The purpose is to uniformly disperse and mix the ingredients using a rotating dynamic mixer equipped with a rotating container and a stirring rotor disposed inside the container and rotating at high speed in the opposite direction to the container. That is, in the present invention, raw materials for ceramics, generally raw stone raw materials such as feldspar, pottery stone, and rouseki, or shamots, etc. are crushed, and then finely pulverized using a dry crusher. Here, a dry-type crusher is a machine that crushes raw material particles by colliding with each other at high speed using air or the like as a carrier, thereby turning them into fine particles.An example of such a dry-type crusher is Mineral Mining.
An air impact mill manufactured by Technology GmbH is known. Since this dry pulverizer breaks or crushes particles by colliding with each other, the surfaces of the obtained particles have a jagged surface with minute and small irregularities. That is, in the case of pulverization using a conventional ball mill, the resulting particles have a round overall shape and a smooth surface, as shown in FIG. As shown in FIG. 1, the particles have a round shape as a whole, but the surface has a jagged uneven surface. In addition, when pulverizing the raw materials with a dry type pulverizer, it is of course possible to mix clay raw materials and perform the pulverization of the raw materials in the mixed state. In the present invention, the raw materials pulverized by the above operation are uniformly dispersed and mixed using an inverted dynamic mixer (reverse flow mixer; the same applies hereinafter). The reversing dynamic mixer is equipped with a rotating container and a stirring rotor disposed inside the rotating container, and rotates the container slowly while rotating the internal stirring rotor at high speed in the opposite direction of the container. The R-type mixer manufactured by Eirich Co., Ltd., for example, is known as such a reversing dynamic mixer. As described above, the present invention uses a dry grinder and an inverted dynamic mixer to perform everything from fine pulverization to uniform mixing of raw materials, so there is no need for a ball mill conventionally used for pulverizing and mixing raw materials. These dry crushers and rotary dynamic mixers have a smaller capacity and are smaller than conventional ball mills, so the installation space for the entire device is small, and they can process small quantities. , many varieties,
It can also fully respond to requests for small-scale production. In addition, in the present invention, in order to dryly process the raw materials,
Water supply and drainage equipment, piping, etc. are no longer necessary. In addition, there is an advantage that the setup time when changing the product type is shortened. In the case of the conventional method, it was necessary to spend a long time cleaning the ball mill when changing the product type, but in the present invention, the raw materials are processed dryly and the amount of processing at one time is small, making it easier to change the product type. This has the effect of significantly shortening setup time and increasing production efficiency. In addition to the above, a feature of the present invention is that the obtained clay particles have excellent sintering reactivity. As described above, the primary particles obtained in the present invention have a jagged surface with small irregularities, and thus have a larger surface area than primary particles obtained by a conventional ball mill. This is clearly seen in FIG. 3, which shows the results of experiments conducted by the inventor. This figure compares the surface area of each primary powder particle when the raw material is finely pulverized using a conventional ball mill and when it is dry pulverized according to the present invention. In this case, the surface area of the primary particles is significantly larger than that in the former case using a ball mill. For this reason, in the present invention, the reactivity of the clay and the molded article using the clay is increased, and the sintering performance is improved. If the sintering performance is improved in this way, it will be possible to perform firing at a lower temperature than before, or if the firing temperature is the same as before, the fineness of the primary particles will be lower than before. It is possible to make it rough. For example, if the conventional method required the material to be rubbed down to a depth of 20 μm, the present invention
It becomes possible to stop the pulverization of primary particles at about 30 μm. In this case, the obtained powder has a certain particle size distribution width, and it naturally contains fine particles mixed with coarse particles, so clay is obtained from such particles and then processed. When molded, the filling of the clay particles becomes more dense, which has the effect of reducing the shrinkage of the molded product during firing. (Second means for solving the problem) Next, the second invention of the present application is to rotate the above-mentioned inverted dynamic mixer at high speed to uniformly disperse and mix the raw material powder, and then rotate it at low speed. The method is characterized in that the mixed raw materials are granulated under a predetermined moisture condition. That is, when using the above-mentioned R type mixer as a reversing dynamic mixer, for example, it is rotated at a high speed of about 1800 rpm to mix raw material powder, and then a predetermined amount of water is added to this.
It is rotated at a low speed of about 400 rpm, and the primary particles pulverized in the previous operation are granulated into secondary particles of about several tens of micrometers. It has been confirmed through experiments that the powder (secondary particles) granulated using such an inverted dynamic mixer has a round overall shape. Since the shape of the secondary particles, that is, the shape of the clay powder is round in this way, the powder has good fluidity when the clay is dry-molded. In other words, according to the second invention, a powder having two characteristics of sintering reactivity and fluidity can be obtained, and based on the good fluidity, a molded body when molded from clay is obtained. The packing density of the raw materials in the mold becomes high and uniform, which further reduces shrinkage during firing and variations in the dimensions of fired products. In addition, in the second invention of the present application, in order to perform mixing of raw materials and granulation using the same inverted dynamic mixer,
Conventional equipment such as a desine granulator and spray dryer is no longer required, which further reduces the installation space of the overall equipment, and allows processing of raw materials in small quantities, from pulverization to granulation. . (Third Means for Solving the Problems) The third invention of the present application is to granulate the mixed raw materials uniformly dispersed and mixed by the high-speed rotation of the inverted dynamic mixer by an agglomeration granulation method. This is a characteristic feature. Equipment for agglomerating and granulating mixed raw materials includes:
For example, there is a CB type mixer manufactured by Lodige.
The powder (secondary particles) obtained by such a method exhibits excellent fluidity comparable to that of powder obtained by a conventional spray dryer. In addition, the powder obtained by this method is soft, and therefore, when press-molded, the powder is well-mixed and evenly filled into the molding cavity. Therefore, the density of the raw material in the molded body becomes more uniform and dense, and the firing shrinkage is further reduced, and the variation in product dimensions is accordingly reduced. In the case of this method as well, the primary particles constituting the clay powder are obtained by the above-mentioned dry pulverization and have high sintering reactivity. This also applies to the second invention and the fourth invention described below. In the case of this method, a device for agglomeration and granulation is required compared to the second invention, but the installation space for the device is smaller than that of conventional granulators (Deshine granulator, Spray dryer). Furthermore, since it is possible to process small quantities at a time, it can fully respond to requests for high-mix, low-volume production. (Third Means for Solving the Problems) The fourth invention of the present application is to add a predetermined amount of water to the mixed raw materials uniformly dispersed and mixed by high-speed rotation of the inverted dynamic mixer, and then knead the mixture. It is characterized by: Here, the raw materials can be kneaded using the same rotary dynamic mixer that was used for the above-mentioned mixing operation.
The present invention is for producing clay for wet molding, and the final moisture content of the clay is controlled to a moisture content suitable for wet molding, for example, 20 to 25%. As mentioned above, the clay obtained by the present invention is for wet molding, and the fluidity of the clay powder is not a particular problem as in the case of dry molding. Compared to clay, the particles that make up the clay have better reactivity, and when molded, the packing density of raw materials in the molded body is higher. (Example) Next, in order to make the present invention more specific, examples thereof will be described below. Figures 4, 6, and 7 show the dry crusher 15 (Mineral Mining) used in the examples.
An air impact mill manufactured by Technolgy GmbH), an inverted dynamic mixer 25 (R type mixer manufactured by Eirich), and an agglomeration granulator 35 (CB type mixer manufactured by Lodige) are shown.
First, the configurations of these devices will be briefly explained.
In FIG. 4, reference numeral 10 denotes a screw feeder, and the raw material supplied from a hopper 12 is sent by this screw feeder 10, then divided into two branch paths 14 and 16, and further fed from a compressor 34. The particles are transported at high speed in the opposite direction by high-pressure air, and are made to collide with each other in the grinding zone 18 to be crushed into pieces. The finely divided particles are passed through the passage 20.
, and then enters the classification chamber 22. The particles that have entered the classification chamber 22 are lifted up by the flow of air blown out from the blower 24, and further collected in the tank 30 via the air classifier 26 and the passage 28. Next, in FIG. 6, reference numeral 36 denotes a rotating container in which rotating blades 38 are arranged eccentrically. When the container 36 is rotated in the direction of arrow P, and the blades 38 are rotated at high speed in the opposite direction, the raw material contained inside flows in the direction shown by the arrow, and in the process, it is uniformly mixed with In the agglomeration granulator 35 shown in FIG. 7, 40 is a container in which a rotating shaft 42 and blades 44 are provided. By supplying a predetermined amount of moisture from the tip, the container 40
The raw material particles contained therein aggregate and granulate. Example 0

[Table] In this example, the raw materials having the composition shown in Table 1 were pulverized using the dry pulverizer 15 shown in Fig. 4 (pulverization pressure 7 Kg/cm ² , completely dried to a moisture content of 0%), and Mixing and granulation tests were conducted using an inverted dynamic mixer 25 (R type mixer: capacity 80) shown in FIG. The test conditions at that time are as shown in Table 2. That is, 36.6 kg of the raw material pulverized by the dry pulverizer 15 and 5.1 kg of frog's eye clay (water content 35 to 40%) were placed in the reversible dynamic mixer 25, and the rotary blades 38 were rotated at a rotation speed of 1800 rpm for 15 minutes. After mixing (the operation up to this point is referred to as A), water was added to control the water content to be 12%, that is, the water content was 12% based on the solid content. Next, the blade 38 is rotated at a rotational speed of 400 rpm for 4 minutes to granulate the dispersed raw material particles, and then the blade 38 is further rotated.
It was crushed by rotating at 1800 rpm for 2 minutes. Note that this crushing step is for crushing the secondary particles again to the desired diameter because the secondary particles become larger than the desired diameter due to the previous low-speed rotation operation, that is, the granulation operation. After this crushing was completed, it was dried (100° C.) using a fluidized bed dryer 45 as shown in FIG. 5, to finally obtain a dry molding clay having a moisture content of 7%. When the properties of the obtained samples were investigated, they were as shown in Tables 3 to 5.

[Table] Example 2 Using the same raw materials and amounts as in Example 1, the above A
After carrying out the above operations, the mixed raw materials are taken out from the inverted dynamic mixer 25 and put into the agglomeration granulator 35 shown in FIG. (The moisture content at this time was 12%, the same as above). Next, this was taken out from the agglomeration granulator 35 and subjected to fluidized bed drying to obtain a clay for dry molding. When the properties of the obtained clay were investigated, they were as shown in Table 3. For comparison, clay for dry molding was manufactured using a conventional method using raw materials with the same composition (desine granulation and spray dryer granulation), and the properties of the obtained clay were investigated and shown in Table 3. It is shown in Table 5. Kneaded clay obtained by finely pulverizing raw materials using a dry pulverizer 15 and mixing and granulating them using an inverted dynamic mixer 25 (inverted dynamic granulated clay); and Kneaded clay granulated using an agglomeration granulator 35. (Agglomerated granulated clay) had better fluidity than conventional desyne powder. In particular, the latter type of clay has a fluidity close to that of spray powder, and the hardness of the powder is soft, so the density of the raw material in the molded product is high and uniform, reducing the degree of lumps, and the fired product The variation in dimensions is also decreasing. Note that Tables 4 and 5 show the average dimensions of the fired products, and s is a numerical value indicating the degree of variation. Example 3 Dry-pulverized raw materials with the same composition as in the first and second examples and frog's eye clay were used at a ratio of 60% and 40%, respectively, and the same volume as in the first and second examples was used. 80
Pour 40kg into the R type mixer.

【table】

【table】

[Table] Perform dispersion and mixing at high speed, then increase the rotation speed.
The speed was reduced to 1000 rpm and the operation was continued for 6 minutes to knead and control the final moisture content to 21% to obtain clay for wet molding. The obtained clay exhibited good firing reactivity because the primary particles constituting it had a large surface area. Although the embodiments of the present invention have been described in detail above, the present invention is also applicable to cases where clay is not used as a raw material, and is also applicable to dry crushers, rotary dynamic mixers,
It is possible to implement the present invention in various ways without departing from the spirit of the invention, for example, it is possible to use agglomeration and granulation machines other than those exemplified above.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the shape of primary particles obtained when raw materials are pulverized by a dry pulverizer;
The figure shows the shape of primary particles obtained when raw materials are pulverized in a conventional ball mill. FIG. 3 is a diagram showing a comparison of the surface areas of the primary particles in FIG. 1 and the primary particles in FIG. 2, and FIG. 4, FIG. 5, FIG. 6, and FIG. FIG. 2 is an explanatory diagram for explaining the principles of a dry pulverizer, a fluidized bed dryer, an inverted dynamic mixer, and an agglomeration granulator used in the example. Figure 8 is a diagram showing the shapes of desyne powder and spray powder granulated by the conventional method, and Figure 9 is an explanation for explaining each step of the conventional clay manufacturing method. It is a diagram. 15: Dry grinder, 25: Rotating dynamic mixer,
35: Agglomeration granulator.

Claims (1)

[Scope of Claims] 1. When producing clay by coarsely crushing and finely pulverizing raw materials for ceramics and then uniformly mixing them, the coarsely crushed raw materials are made to collide with each other at high speed in a dry state. The pulverized raw material is finely pulverized using a dry pulverizer of the type that pulverizes the raw material, and then the finely pulverized raw material is pulverized using a rotating container and a stirring rotor that is disposed inside the container and rotates at high speed in the opposite direction to the container. A method for producing clay characterized by uniformly dispersing and mixing it using an inverted dynamic mixer. 2. The inverted dynamic mixer is rotated at high speed to uniformly disperse and mix the raw material powder, and then rotated at low speed to granulate the mixed raw materials under a predetermined moisture condition. A method for producing clay for dry molding. 3. A method for producing clay for dry molding, characterized in that the mixed raw materials uniformly dispersed and mixed by rotating the inverted dynamic mixer at high speed are granulated by an agglomeration granulation method. 4. A method for producing clay for wet molding, which comprises adding a predetermined amount of water to the mixed raw materials uniformly dispersed and mixed by rotating the inverted dynamic mixer at high speed, and then kneading the mixture.