JPS621808B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing ceramic slurry (hereinafter referred to as "slip") for obtaining ceramic green sheets (hereinafter referred to as "green sheets") with a good mixing yield and a stable firing shrinkage rate. Generally, green sheets are made by dispersing alumina and sintering aids in a vehicle consisting of a binder, plasticizer, solvent, and dispersant to form a slip, then casting it onto a polyester film and drying the solvent. . On the other hand, a ceramic substrate is made by punching a green sheet into a predetermined shape and then firing it, and the dimensions of the board are determined by the shrinkage rate during firing. Therefore, in order to improve dimensional accuracy, the firing shrinkage rate must always be kept constant. In addition, there is a correlation between the firing shrinkage rate and the bulk density of the green sheet, and it is important to keep the bulk density of the green sheet, that is, the degree of clogging (filling rate) of the ceramic raw powder particles constant, in order to keep the firing shrinkage rate constant. It is. Conventionally, ceramic raw material powder, binder, plasticizer, solvent, etc. are put together in a ball mill mixer and mixed all at once. However, in this mixing method, the viscosity of the slip is high, so the particles of the agglomerated ceramic raw material powder cannot be disintegrated into single particles, and the binder, plasticizer, etc. are not well dispersed throughout the particles, which causes the bulk density of the green sheet to vary. It's summery. There is also a method in which the ceramic raw material powder is dispersed in advance in a solvent (first step) and then a binder, plasticizer, etc. are added (second step), but with this method, pseudo-agglomeration is likely to occur in the first step. Therefore, if the ball mill is continuously and repeatedly used in this manner, the firing shrinkage rate of the green sheet will vary. The object of the present invention is to provide a method for manufacturing slips that does not have the above-mentioned drawbacks. As a result of various studies on the above-mentioned drawbacks, the inventors of the present invention found that the viscosity of the solution containing the binder and plasticizer in the solvent is below the level that does not hinder the disintegration of the ceramic raw material powder, and the disintegrated particles come into direct contact with each other. Adding amounts of binders and plasticizers that prevent
A green sheet can be obtained by mixing and disintegrating the ceramic raw material powder into single particles, then adding and mixing the amount of binder and plasticizer necessary to give the sheet properties necessary for tape forming and punching. It was confirmed that slips with small variations in the bulk density of green sheets and small variations in firing shrinkage of green sheets could be obtained even when the ball mill was continuously used repeatedly. The present invention provides a method for producing ceramic slurry in which a mixture of ceramic raw material powder, a solvent, a binder, and a plasticizer is mixed in a container, in which the viscosity of the solution in which the binder and plasticizer are added to the solvent does not hinder the disintegration of the ceramic raw material powder. A binder and a plasticizer are added and mixed in an amount that is below the level that prevents the disintegrated particles from coming into direct contact with each other, and the ceramic raw material powder is disintegrated into single particles, and then subjected to tape forming and punching. Adding the amount of binder and plasticizer necessary to impart the required sheet properties;
This invention relates to a method for manufacturing slips for mixing. In the present invention, alumina, glass, frit, etc. are used as the ceramic raw material powder, and in addition, magnesia, calcia, silica, zirconia, etc. may be used as necessary. As the binder, polyvinyl butyral, acrylic resin, vinyl acetate copolymer, polyvinyl alcohol, vinyl chloride, methacrylate, etc. are used. For plasticizer
Phthalate esters such as DOP and DBP, and glycol esters such as triethylene glycol and polyalkylene glycol are used. Trichlorethylene, butanol, ethyl alcohol, methyl alcohol, etc. are used as the solvent. It is preferable that the viscosity of the solution in which the binder and plasticizer are added to the solvent is at most 20P (poise),
It is more preferable if it is in the range of 1P to 3P. The amount of binder and plasticizer added is 0.5 to 2.0 parts by weight per 100 parts by weight of ceramic raw powder.
It is preferable that the plasticizer is 0.25 to 1.0 parts by weight,
More preferably, the binder is 0.8 to 1.8 parts by weight and the plasticizer is 0.4 to 0.9 parts by weight. The amount of binder and plasticizer required to impart the sheet properties necessary for tape molding and punching is 3.0 to 6.6 parts by weight of binder and 1.5 to 3.3 parts by weight of plasticizer per 100 parts by weight of ceramic raw powder.
Parts by weight are preferably from 4.0 to 4.0 parts by weight.
More preferably, the amount is 5.6 parts by weight and the plasticizer is 2.0 to 2.8 parts by weight. The present invention will be explained below with reference to Examples. In the first step, the ingredients shown in Table 1 are blended and mixed in a ball mill for 30 hours to thoroughly disintegrate α-alumina and glass frit into single particles, and form a uniform coating on the surface of the disintegrated single particles. did.

[Table] Next, as a second step, 4.8 parts by weight of polyvinyl butyral and 2.4 parts by weight of phthalate were added to the mixture obtained above and mixed for 24 hours to obtain a slip. Then insert the slip into the inner wall of the ball mill,
Leave 20% in the ball mill as a part to adhere to cobblestones, etc.
The remaining 80% was used to obtain a first green sheet using a commonly known method. Next, in order to obtain a second green sheet, 28.36 parts by weight of the remaining slip in the ball mill was mixed with an azeotropic mixture of trichlorethylene and methanol.
Add 32.0 parts by weight and mix for 1 hour, then add 76.8 parts by weight of the same α-alumina and 3.2 parts by weight of glass frit and mix for 30 hours to disintegrate α-alumina and glass frit into single particles.
A uniform coating was formed on the surface of the disaggregated single particles. Next, 48.0 parts by weight of polyvinyl butyral and 24.0 parts by weight of phthalate were added to the mixture obtained above and mixed for 24 hours to obtain a second slip. Thereafter, a second green sheet was obtained by a commonly known method, with 20% of the slip remaining in the ball mill and 80% of the slip being attached to the inner wall of the ball mill, cobblestones, etc. Thereafter, third and fourth green sheets were obtained in the same manner as above. The green sheets obtained in the above examples were fired in a hydrogen atmosphere at a temperature of 1550° C. for 1 hour. As a result, the firing shrinkage rate was 15.50% for the first time and 15.50% for the second time.
15.52%, 3rd time 15.51%, 4th time 15.55%
It was confirmed that there was little variation even though the ball mill was used continuously. On the other hand, as a comparative example, α-alumina and glass frit were pre-dispersed in a dispersant and a solvent, and then a binder and a plasticizer were added. The sheet was obtained and fired in the same manner as in the example. As a result, the firing shrinkage rate was 16.00% in the first firing, 15.23% in the second firing, 16.52% in the third firing, and 15.05% in the fourth firing. It varied widely. In the embodiments of the present invention, slips for ceramic substrates have been described, but similar effects can be obtained with slips for tape molding. Further, in the embodiments of the present invention, the mixture was explained using a ball mill, but the same effect can be obtained by using a crusher or other mixing method. The present invention uses the binder and plasticizer in an amount such that the viscosity of the solution obtained by adding the binder and plasticizer to the solvent is below the level that does not prevent the disintegration of the ceramic raw material powder, and in an amount that prevents the disintegrated particles from coming into direct contact with each other. The ceramic raw material powder is added and mixed to disintegrate it into single particles, and then the amount of binder and plasticizer required to give the sheet properties necessary for tape forming and punching is added and mixed, resulting in a green sheet. It is possible to produce a slip with little variation in the bulk density of the green sheet, and also with little variation in the firing shrinkage rate of the green sheet even if a mixer such as a ball mill is used continuously and repeatedly.

Claims (1)

[Claims] 1. In a method for producing ceramic slurry in which a mixture of ceramic raw material powder, a solvent, a binder, and a plasticizer are mixed in a container, the viscosity of the solution containing the binder and plasticizer in the solvent is below a level that does not hinder the disintegration of the ceramic raw material powder. A binder and a plasticizer are added in an amount that prevents the disintegrated particles from coming into direct contact with each other, and the ceramic raw material powder is disintegrated into single particles. A method for producing a ceramic slurry, which comprises adding and mixing a binder and a plasticizer in amounts necessary to impart sheet properties.