JP2010265153A - Composition for slip casting and method for forming slip casting formed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a poorly-packed or porous formed body in molds for slip casting, where near-net shape molding can be performed, and to obtain poorly-packed or porous ceramics by firing the poorly-packed or porous formed body. <P>SOLUTION: A composition for slip casting is composed of ceramic particles, a dispersion medium, a dispersant and a binder. Microfibrillated cellulose, which is insoluble in water and has a very fine fibrous shape, and a fine cellulose crystallization are used as the binder. As a result, the poorly-packed or porous ceramics can be formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ceramic slip cast molding method and ceramics using the molding method.

  Conventionally, to produce ceramics with a near net shape by the slip cast molding method, a slip composed mainly of ceramic particles, a dispersion medium (water), a dispersant, a binder (a slurry), or a composition for slip cast molding. (Also referred to as a product) is cast in a mold made of a porous material such as gypsum, and the molded product is manufactured and then fired. For the binder, water-soluble polymers such as starch powder, methylcellulose, and polyvinyl alcohol are used. In addition, there are water-soluble and water-insoluble emulsion resins. The ceramic obtained here is dense and has the same bulk density and electrical properties as a single ceramic.

  On the other hand, unlike ceramics produced by the conventional slip cast molding method, alumina ceramics having low dielectric properties and porous PTZ ceramics are produced by a combination of ceramic raw material particles and a firing aid.

JP 2000-272951 A JP-A-5-254955

Ceramics by the conventional slip cast molding method have high heat resistance, but have the same high density and electrical properties as the component ceramics alone, so they are extremely heavy and have high dielectric properties compared to resin, resin-based particle-dispersed composite materials and fiber-reinforced composite materials. Have a rate. In addition, the production of ceramics having low dielectric properties by slip casting is limited.
One of the main objects of the present invention is to provide a composition for slip casting which has a high heat resistance and can form a porous ceramic material having a lower density and lower dielectric properties than conventional products.

  The slip cast molding composition of the present invention is a slip cast molding composition comprising ceramic particles, a dispersion medium, a dispersant, and a binder, wherein the binder has a cross-sectional diameter perpendicular to the longitudinal direction of the ceramic particles. The water-insoluble cellulose having an aspect ratio of 5 or less was obtained.

  According to the present invention, it is possible to form a porous ceramic having high heat resistance and lower density and lower dielectric properties than conventional ones.

It is a figure for demonstrating Embodiment 1 of this invention. It is a figure for demonstrating Embodiment 1 of this invention. It is a figure for demonstrating Embodiment 2 of this invention. It is a figure for demonstrating Embodiment 2 of this invention. It is the table | surface which showed the composition of the slip in Embodiment 3-5 of this invention. In Embodiments 3-5 of this invention, it is the table | surface which showed the characteristic of the sintered body obtained by the slip cast molding method using the slip of Table 1. It is the table | surface which showed the composition of the slip in Embodiment 6-8 of this invention. In Embodiments 6-8 of this invention, it is the table | surface which showed the characteristic of the sintered body obtained by the slip cast molding method using the slip of Table 3. FIG.

Embodiment 1 FIG.
Inorganic particles containing silica, alumina, zirconia, and clay can be used for the ceramic particles that are constituents of the slip in the slip cast molding method of the present invention. If the average particle size is less than submicron, slip casting is difficult.
The binder according to the present invention has a cross-sectional diameter perpendicular to the longitudinal direction of the thread-like shape, which is smaller by one digit or more than the average diameter of ceramic particles of submicron or more (diameter of 1/10 or less), and has an aspect ratio of Five or more water-insoluble celluloses, cellulose and cellulose derivatives such as viscose rayon and acetate fibers, microfibrillated natural fibers, and high-purity crystalline cellulose are used. In addition to the above, a fine fibrous substance having a diameter one or more orders of magnitude smaller than the average particle diameter of the ceramic can be used for the binder without melting in the ceramic particle dispersion medium.

The binder is preferably used in a range of 0.3 to 3.0% by weight with respect to inorganic particles such as ceramic. In the case of 0.3% by weight or less, since the strength of the molded product after slip casting is reduced, it is difficult to maintain the shape until drying. On the other hand, if it is 3.0% by weight or more, the slip viscosity increases, casting becomes difficult, and the binder removal step during firing becomes difficult.
FIG. 1 is a schematic view of a slip for slip casting molding according to the present invention. 1 is ceramic particles, 2 is a dispersing agent, 3 is a binder, 4 is a dispersion medium (water).

  FIG. 2 is a schematic view of a slip cast molded body obtained by casting the slip of FIG. 1, removing the mold, and drying. 5 is a ceramic particle, 6 is a dispersing agent, 7 is a binder, It turns out that it is bulky by the fibrous binder. By firing this, a bulky porous ceramic having low dielectric properties can be produced. Casting molding may be pressure casting.

Embodiment 2. FIG.
Inorganic particles containing silica, alumina, zirconia, and clay can be used for the ceramic particles that are constituents of the slip in the slip cast molding method of the present invention. When the average particle size is submicron or less, slip casting is difficult.

  The binder of the present invention is a water-insoluble cellulose, cellulose, or cellulose derivative having a cross-sectional diameter perpendicular to the longitudinal direction of the thread-like shape that is one digit or more smaller than the average diameter of the ceramic particles and an aspect ratio of 5 or more. A natural fiber such as a certain viscose rayon or acetate fiber or a regenerated fiber obtained by microfibrillation, and high-purity crystalline cellulose and water-soluble cellulose are used in a ratio of 100 to 0.5-3. A combination of a fibrous material having an aspect ratio without melting and water-soluble cellulose can be used.

  The binder is preferably used in a range of 0.3 to 3.0% by weight with respect to inorganic particles such as ceramic. In the case of 0.3% by weight or less, since the strength of the molded product after slip casting is reduced, it is difficult to maintain the shape until drying. On the other hand, if it is 3.0% by weight or more, the slip viscosity increases and casting becomes difficult. In addition, the binder removal process during firing becomes difficult.

FIG. 3 is a schematic view of a slip for slip casting molding according to the present invention. 8 is ceramic particles, 9 is water-soluble cellulose, 10 is a water-insoluble fibrous material, and 11 is a dispersion medium (water).

  FIG. 4 is a schematic view of a molded body obtained by casting the slip of FIG. 3, demolding, and drying. 12 is a ceramic particle, 13 is a water-soluble cellulose, 14 is a water-insoluble fibrous substance, and it turns out that it is bulky by the fibrous binder. By firing this, a bulky porous ceramic having low dielectric properties can be produced. Casting molding may be pressure casting.

Embodiments 3 to 5
Table 1 in FIG. 5 is a table showing the slip composition in the third to fifth embodiments.
To 100 g of fused silica particles (SGA; manufactured by Covalent Materials) having an average particle size of 5 μm, a dispersion medium (purified water) and a dispersant polycarboxylic acid-based dispersant (D305; Chukyo Yushi) are added in the proportions shown in Table 1. After mixing with a ball mill to make a slurry, a binder (Serisch; Daicel Chemical Industries) was added to form a slip for casting. This slip was cast into a plaster mold, demolded, and fired at 1200 ° C.

FIG. 6 is a table showing the characteristics of the fired body obtained by the slip cast molding method using the slip of Table 1.
It can be seen that all the fired bodies shown in Table 2 have a low fused silica content and a high porosity.

Embodiments 6 to 8
Table 3 in FIG. 7 is a table showing the slip composition in the sixth to eighth embodiments.
A dispersion medium (purified water) and water-soluble cellulose (CMC; Daicel Chemical Industries) are added at a ratio shown in Table 3 to 100 g of fused silica particles (SGA; manufactured by Covalent Materials) having an average particle size of 5 μm, and ball mill mixing is performed. After slurrying, a binder (Serisch; Daicel Chemical Industries) was added to form a slip for casting. This slip was cast into a plaster mold, demolded, and fired at 1200 ° C.

FIG. 8 is a table showing the characteristics of the fired body obtained by the slip cast molding method using the slip of Table 3.
It can be seen that all the fired bodies shown in Table 4 have a low fused silica content and a high porosity.

  DESCRIPTION OF SYMBOLS 1 Ceramic particle, 2 dispersing agent, 3 binder, 4 dispersion medium (water), 5 ceramic particle, 6 dispersing agent, 7 binder, 8 ceramic particle, 9 water-soluble cellulose, 10 water-insoluble fibrous substance, 11 dispersion medium ( Water), 12 ceramic particles, 13 water-soluble cellulose, 14 water-insoluble fibrous material

Claims (6)

A slip casting composition comprising ceramic particles, a dispersion medium, a dispersant, and a binder,
The binder is water-insoluble cellulose having a cross-sectional diameter perpendicular to the longitudinal direction that is 1/10 or less of the average particle diameter of the ceramic particles and an aspect ratio of 5 or more. A slip cast molding composition. The composition for slip casting according to claim 1, wherein the binder is microfibrillated cellulose having a fine fiber shape. The composition for slip cast molding according to claim 1, wherein the binder is a fine cellulose crystal having a fine fiber shape. The composition for slip casting according to any one of claims 1 to 3, wherein the binder further comprises water-soluble cellulose. The slip-cast molding composition according to claim 4, wherein the water-insoluble cellulose is a fine cellulose crystal having a fine fiber shape, and the water-soluble cellulose is methyl cellulose or carboxymethyl cellulose. Ceramic particles, a dispersion medium, a dispersant, and a water-insoluble material whose cross-sectional diameter perpendicular to the longitudinal direction is 1/10 or less of the average particle diameter of the ceramic particles and the aspect ratio is 5 or more A method for forming a slip-cast molded article, wherein the composition is cast-molded using a composition for slip-cast molding mixed with a cellulose binder, demolded and then dried.

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