JPS63277544A - Production of ceramic green sheet - Google Patents

Abstract

PURPOSE:To shorten blending time of slurry and to enable improvement in productivity in preparing slurry useful as a raw material for ceramic green sheet, by adding a binder to raw materials and blending the raw materials in a high-temperature state. CONSTITUTION:A blender is charged with a main material of ceramic powder, a sintering agent, an organic solvent, an organic binder, etc., blended and kneaded to prepare slurry useful as a raw material for ceramic green sheet. In the operation, the raw material containing the organic binder is kneaded in a high-temperature state wherein the raw material has lower viscosity than that in a normal temperature state. The raw material containing the organic binder is preferably blended and kneaded in a viscosity state in a temperature range at >=30 deg.C and <=the boiling point of the solvent contained in the raw material of <=a temperature wherein the raw material is gelatinized and the viscosity is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement in a method for manufacturing ceramic green sheets.

[Conventional technology]

Generally, methods for producing ceramic green sheets include a doctor blade method, a roll method (calendar roll method), and the like. The doctor blade method generally involves mixing inorganic powders such as a ceramic main material, a sintering aid, etc. with an organic binder, a plasticizer, an organic solvent, etc. for a long period of time to form a slurry.

Furthermore, the viscosity of this slurry is raised to an appropriate value by vacuum defoaming, and then applied to a carrier film to a predetermined thickness using a doctor blade, and the organic solvent is evaporated by drying to solidify. Further, the roll method is a method in which a similar slurry is kneaded while being dried and heated, and then formed into a sheet by rolling, and is technically the same as the doctor blade method.

Conventionally, the preparation method of the slurry used to manufacture these green sheets is described in the document "Fine Ceramics Molding and Organic Materials" published on August 26, 1985, published by Jisku Co., Ltd., and as shown below. (1) Inorganic powder such as ceramic main material, water and alumina balls are thoroughly ground and mixed in a container, dried until the moisture content is less than α1%, and then the binder is prepared. , a plasticizer, 2 dispersants, and an organic binder, and further 1) - 15 hours of mixing to produce a slurry.

(2) A method in which an inorganic powder whose particle size has been adjusted and an organic solvent are first mixed for 2 hours, and then a binder and a plasticizer are added and the mixture is mixed for 15 hours to produce a slurry.

(3) A method in which the binder and the solvent are added in two portions, and finally mixed for 12 to 14 hours to produce the intermediate layer.

It is.

However, in the above conventional technology, (1) or 3)
In either case, the ball mill mixing after addition of the binder required an extremely long time of 12 hours or more, which caused a problem in the productivity of the green sheet. this is,
This is because the viscosity of the slurry after adding the binder is relatively high, making it difficult for inorganic substances to be dispersed within the slurry. In such a case, if the amount of solvent added is increased, the 1,1-viscosity of the slurry will be lowered, and the time for uniformly dispersing the inorganic material can be shortened. However, when manufacturing green sheets using the doctor blade method, etc., a slurry with a higher viscosity than that used during mixing is required, and it is necessary to remove the solvent from a slurry containing a large amount of solvent by vacuum degassing to increase the viscosity. It takes a long time! 7. Also. Adjustment will also become difficult. moreover,
If vacuum defoaming is insufficient and the amount of solvent contained in the slurry is large, the amount of solvent that evaporates when forming into a sheet using the doctor blade method and drying it will increase, causing cracks in the green sheet. The yield rate will easily decrease. Also,
The solvent used is often a harmful organic solvent, and it is not preferable to increase the amount of solvent added from the viewpoint of safety. Therefore, it has been necessary to mix the slurry for a long time at a relatively high viscosity.

[Problem that the invention seeks to solve]

In the above conventional technology, the temperature at the time of slurry mixing is controlled from room temperature to a high temperature, that is, a binder that softens when heated is used, and the slurry viscosity is also reduced by heating, and the slurry viscosity is lowered at high temperatures. By mixing the inorganic substances in a small amount of solvent in a short period of time, the inorganic substances can be uniformly dispersed using a small amount of solvent, and by lowering the temperature of the slurry after mixing, the viscosity of the slurry can be reduced to produce green sheets using the doctor grade method, etc. However, there was a problem in that no consideration was given to utilizing this phenomenon, and mixing took a long time, reducing the productivity of green sheets.

The present invention has been made in view of the above situation.

The object of the present invention is to provide a method for manufacturing ceramic green sheets that can shorten slurry mixing time and improve productivity.

[Failure to solve the problem]

The above object is a method for manufacturing a ceramic green sheet, which comprises charging the main material of ceramic powder, a sintering agent, an organic solvent, an organic binder, etc. into a mixing container, mixing and kneading to prepare a slurry of raw materials for the ceramic green sheet. In,
This is achieved by a ceramic green sheet manufacturing method in which, when preparing the slurry, the raw materials containing the organic binder are mixed and kneaded at a high temperature such that the viscosity of the raw materials is lower than that at room temperature.

[Effect]

As will be described later in the description of the embodiment, a slurry 1 and alumina balls 2 are housed in a mixing vessel 3 which is rotated in a water tank 5 containing hot water 4. The viscosity of the slurry 1 in the mixing container 3 decreases significantly as the temperature rises from around 20°C at room temperature, as shown by curve B in Figure 2, and if mixing and kneading are performed while this viscosity is low, the dispersion of inorganic substances will be improved. This can be done uniformly and in a short time, and the amount of solvent required is small enough to be suitable for manufacturing green sheets using a doctor blade method or the like. If the temperature of the slurry 1 is returned to room temperature after mixing, the viscosity will increase to a value suitable for manufacturing green sheets by a doctor blade method or the like.

〔Example〕

The method for manufacturing a ceramic green sheet of the present invention will be explained below using examples. Generally, the factors that determine the viscosity of a slurry include the particle size and particle size distribution of the inorganic particles contained, as well as the selection of binders and solvents. Furthermore, the viscosity changes depending on the mixing ratio and the temperature of the slurry. This is because the properties of the organic binder contained in the slurry are affected by temperature. Therefore, if a binder that softens when heated is used, the viscosity of the slurry will also be reduced by heating.

Therefore, according to the above properties, if only a small amount of solvent suitable for manufacturing green sheets is added in advance by the doctor blade method etc., and mixing is performed at a high temperature where the viscosity of the slurry is low, Inorganic substances are uniformly dispersed in a short time. Furthermore, by lowering the temperature of the slurry after mixing (returning it to room temperature), the viscosity of the slurry increases to a value suitable for manufacturing green sheets by a doctor blade method or the like.

Next, an example will be explained with reference to FIGS. 1 and 2. FIG. 1 is a sectional view of a slurry mixing device, and FIG. 2 is an explanatory diagram of the relationship between temperature and viscosity of a slurry, with temperature on the horizontal axis and viscosity on the vertical axis. In the figure, 1 is slurry, 2
3 is a hollow cylindrical mixing container which accommodates slurry 1 and alumina balls 2 inside. 4
The water tank 5 is filled with hot water (#), and the mixing container 6 is configured to be rotated in the direction of arrow A within the hot water 4. The slurry 1 put into the mixing container 3 is mixed through the alumina balls 2 while being heated by hot water 4.

First, ceramic powder with an average particle size of 2
Alumina (A) 205) adjusted to μ- is used as a sintering aid, talc (Mg, 5i40..(OH),),
Clay [A)2Si□05(OH)4) was charged with the following composition, and a total of 40 parts of trichlorethylene, tetrachlorethylene, and butyl alcohol were added as organic solvents.
Furthermore, in order to improve the mixability of these, %15-40
(2) Add 200 parts by weight of alumina balls 2 of φ and mix for 2 hours at a room temperature of 20° C. and a rotational speed of 7 rpm.

Next, polyvinyl butyral (hereinafter referred to as PVB) is used as an organic binder, and dibutyl phthalate (hereinafter referred to as DBP) is used as a plasticizer.
・・・・・・・・・ 7 parts by weight DBP ・・・・・・
・・・・・・・・・・ Added at a composition of 3 parts by weight, and further added to the water tank 5 installed outside the mixing container 5 for 30 parts by weight.
The mixture is mixed for 6 hours in a state where it is filled with hot water 4 whose temperature is controlled at ℃. After mixing, the temperature of slurry 1 was changed from 30°C to room temperature (
By cooling to 20° C.), the viscosity of slurry 1 increases from 1.900 cps to 5.300 cps.

Furthermore, the viscosity of the slurry 1 is adjusted to 15.000 cps by removing the alumina balls 2 and performing vacuum defoaming.

Next, using this slurry 1, a green sheet having a width of 400 mb and a thickness of L2 m is manufactured by a doctor blade method.

Here, the above example will be further explained in detail using FIG. 2, which shows the relationship between temperature and viscosity after mixing the vacuum defoaming agent of slurry 1 in the above explanation as curve B. . In FIG. 2, in the slurry 1 of this example, as the temperature rises, the binder PVB in the slurry 1 becomes softer, so that the slurry viscosity decreases.

As the slurry viscosity decreases, the dispersibility of inorganic particles such as alumina in the slurry 1 improves, so the time required for mixing can be shortened. For example, in curve B of Figure 2, after adding the binder PVB, the time required to mix the slurry is 15 hours according to an experiment when mixing at room temperature of 20°C, but when mixing at 30°C. In the case of this embodiment described above, 6 hours is sufficient, and the mixing time can be reduced by 9 hours. As shown in Figure 2, when the slurry temperature is 30°C, its viscosity is 2.
Approximately 1/3 of that at room temperature of 0℃ (5,300 → 1.90
0cps). Furthermore, when the temperature becomes high, slurry 1
This is because the solubility of the binder in the solvent increases, allowing the binder to dissolve more quickly.

Here, as shown in Figure 2, the temperature of slurry 1 is about 30°C, which is about 1/2 of the viscosity at room temperature (20°C), so 3
Although it can be seen that the effect of sufficiently shortening the mixing time can be obtained under conditions of 0° C. or higher, a temperature of 40° C. or higher is preferable to further stabilize the viscosity. In addition, from FIG. 2, 30
If the temperature is raised above ℃, the slurry viscosity can still be lowered, but in the case of this example, among the solvents contained in slurry 1, trichlorethylene has a boiling point of 8.
Since the temperature is as low as 8° C., if the slurry temperature is increased too much, the internal pressure of the mixing container 3 will increase. Therefore, from the viewpoint of safety, the upper limit of the slurry temperature is preferably around 70°C, and the optimal mixing temperature is in the range of 30°C to 70°C as shown in FIG.

On the other hand, when using a binder or solvent other than those used in this embodiment, it is preferable to set the optimum mixing temperature depending on the type of binder or solvent. For example, when using methylcellulose (MC), a thermosetting resin binder, when heated, the viscosity decreases like PVB, but at a certain temperature (which varies depending on the amount of methoxy groups, etc.), gelation occurs and the viscosity decreases. Therefore, the upper limit of the set temperature needs to be below the temperature at which gelation begins. Therefore, in order to determine the set temperature for mixing, it is preferable to actually create a slurry, examine the relationship between the slurry's temperature and viscosity, and then apply a temperature that will reduce the viscosity as much as possible, taking safety into consideration. .

By the way, in addition to the above-mentioned examples, there are other slurry mixing methods.
As described in the prior art, there is a method of mixing inorganic powder and water, drying it again, and then adding a binder, bath agent, etc., and a method of adding a binder and a solvent in several portions.

However, no matter which method is used, this example is effective by mixing at a high temperature after adding the binder. In addition to the slurry for green sheets formed by the doctor blade method, the mixing of raw materials used in the roll method (calendar roll method) or the mixing and kneading of raw materials by the extrusion molding method can also be performed at high temperatures as in the case of the doctor blade method. By carrying out the process in a low viscosity state, the time required for this process can be shortened.

Further, this embodiment is particularly effective when using fine powder ceramic grains. In other words, when manufacturing green sheets using finely powdered ceramic, it is necessary to increase the amount of binder added, and in the conventional mixing method, it was necessary to add a large amount of solvent to achieve a mixable slurry viscosity. On the other hand, in this example, the viscosity of the cis slurry can be reduced by mixing at high temperature even with a small amount of solvent.

As described above, according to the method of manufacturing a ceramic green sheet of this embodiment, by using an organic binder that softens when heated, the viscosity of the slurry decreases due to this heating, and this viscosity decrease allows the slurry to be produced in a small amount within a short period of time. Inorganic substances can be uniformly dispersed by adjusting the amount of solvent, and by lowering the temperature of the slurry after mixing, the viscosity of the slurry can be increased to a value suitable for manufacturing green sheets by the doctor blade method or the like. Therefore, slurry mixing time can be shortened and productivity can be increased.

〔Effect of the invention〕

As described above, the method for manufacturing ceramic green sheets of the present invention has the effect of shortening slurry mixing time and improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a slurry mixing apparatus for carrying out the method of manufacturing a ceramic green sheet of the present invention, and FIG. 2 is an explanatory diagram of the relationship between temperature and viscosity of slurry when slurry is mixed by the apparatus of FIG. 1. 1...Slurry 3...Mixing container 4...Hot water 5...Water tank, 1 Slurry 4 iL shaku 33 Biaiyoudake 5 Tree I

Claims (1)

[Claims] 1. The ceramic green, in which the main materials of ceramic powder, a sintering agent, an organic solvent, an organic binder, etc. are charged into a mixing container, mixed and kneaded to prepare a slurry of raw materials for ceramic green sheets. In the sheet manufacturing method, when preparing the slurry, mixing at a high temperature such that the viscosity of the raw material containing the organic binder is lower than at room temperature;
A method for producing a ceramic green sheet, which comprises kneading. 2. A viscosity state in which the viscosity of the raw material containing the organic binder is 30°C or higher, and the temperature range is below the boiling point of the solvent contained in the raw material, or below the temperature at which the raw material gels and becomes highly viscous. A method for producing a ceramic green sheet according to claim 1, wherein the ceramic green sheets are mixed and kneaded. 3. The method for producing a ceramic green sheet according to claim 1, wherein polyvinyl butyral is used as the organic binder, and the slurry containing the polyvinyl butyral is mixed and kneaded at a temperature range of 30°C to 70°C. . 4. The method for producing a ceramic green sheet according to claim 1, wherein the mixing container is rotated and heated in a water tank containing hot water set at a temperature that reduces the viscosity of the slurry.