JPH0549623B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing ceramics and/or ceramic materials using oxide-based raw materials, and more specifically, the present invention relates to a method for producing ceramics and/or ceramic materials using oxide-based raw materials. Production of ceramics and/or ceramic materials characterized by improving moldability by reducing the viscosity of slurry prepared using oxide-based raw materials, or increasing or imparting plasticity to clay or kneaded clay prepared using oxide-based raw materials. Regarding the method. [Prior art] Raw materials for ceramics include oxides such as non-plastic raw materials such as silica, feldspar, alumina, magnesia, zirconia, spinel, and ferrite, and hydrous oxides such as kaolinite, which are plastic raw materials. Clay minerals are used. Conventionally, ceramics have been made by mixing these raw material powders with water and small amounts of additives, followed by molding, drying, and firing. In other words, clay is used, which is made by adding highly plastic clay (mainly composed of clay minerals) to non-plastic raw materials such as silica and feldspar to improve moldability (workability, plasticity, shape retention, etc.). Ceramics are made by adding small amounts of clay and organic plasticizers to highly pure non-plastic raw materials such as alumina, and what is called neuceramics. Furthermore, fine ceramics are made by adding only a synthetic organic plasticizer to increase the purity of the ceramics and firing them. For example, alumina (α-Al ₂ O ₃ ) is extremely abundant as a resource and has excellent properties such as mechanical strength, chemical durability, thermal shock resistance, and electrical insulation, making it superior to other ceramics. Compared to raw materials, its production volume is large and its uses are extremely wide. Furthermore, with the development of finer particles (particles of 1 μm or less) and highly purified (99.9% purity) alumina powder raw materials that take into account sinterability and homogeneity, the functionality of materials has progressed, and electronic materials. , widely used in the fields of biomaterials and optical materials. Recently, the depletion of high-quality clay resources that provide plasticity has become a serious problem in Japan's ceramics industry, and methods for producing synthetic kaolinite are rapidly progressing in hopes of finding alternative raw materials. Currently, synthetic kaolinite does not have the high plasticity found in natural clay. In the molding process of new ceramics or fine ceramics, a large amount of synthetic organic materials (plasticizers, binders, etc.) are used to improve moldability, so a new degreasing operation is required in the firing process. At the same time, the shrinkage caused by firing becomes significantly larger than that of ceramic products, resulting in problems such as large distortions in shape. For this reason, there is currently no technology to completely form the desired ceramic shape, and there is a strong desire to develop additives such as plasticizers that can solve these problems. By the way, the production of ceramics consists of the processes of preparing powder raw materials, molding, and firing, and these processes are closely related to each other. Especially in powder raw materials and their preparation, the selection of raw materials and forming aids and control of slurry properties have a great impact on the evaluation of ceramic materials. Forming methods for ceramics include pressurization, extrusion, casting, and injection molding, and the forming method is selected depending on the shape of the material, purpose of use, etc., and ultimately the yield and economic efficiency of the manufacturing process are selected. considered important. Among the above molding methods, the slurry casting method (sludge removal,
Solid method) requires only porous mold material,
It does not require expensive equipment and has many advantages, such as being suitable for manufacturing products with complex shapes and manufacturing ceramics in small quantities of a wide variety of products.
In addition, in recent years, along with the development of ceramic turbochargers for automobiles, the slurry casting method has gained further recognition and attention. The basic requirements of the casting method are how to prevent the formation of agglomerated particles (secondary particles) during the process of mixing powder raw materials and forming aids to prepare slurry.
The next step is to obtain a slurry in which the particles are peptized. Furthermore, in the case of slurry for casting, since the amount of water absorbed by porous mold materials such as plaster molds is extremely small, it is necessary to reduce the amount of water in the slurry to make it highly concentrated, and to improve its viscosity. It is essential to keep the stock price low and maintain appropriate liquidity. In general, it is said that the standard for high-concentration slurry is that the packing density (bulk density) of the particles of the molded body is preferably 60% or more of the theoretical density. If the porosity is less than this, sintering will not be achieved sufficiently due to the high porosity, and the molded product will shrink so much that it will have no practical value. Therefore, it is essential to stably hold and disperse the powder in a dispersion medium, and for this purpose, inorganic electrolytes (hydrochloric acid, tetramethylammonium hydroxide, water glass) or organic electrolytes (ionic surfactants) are used. etc. are used as dispersants. However, since the former slurry whose pH has been adjusted with acids and alkalis significantly damages the plaster mold, in recent years polycarboxylic acid type ammonium salts (anionic), which cause a decrease in the interfacial energy between solid and liquid, have generally been oxidized. It is used as a dispersant for physical raw material powders. In addition to the dispersant (or deflocculant), the slurry contains binders (polyvinyl alcohol, cellulose emulsion, wax emulsion, acrylic emulsion, etc.) for imparting strength to the molded object.
Organic materials such as plasticizers (glycerin, polyethylene glycol, etc.), wetting agents (n-butanol, isopropanol, etc.), and antifoaming agents may be added as molding aids. When a peptizer and a binder are added in combination when preparing this slurry, the viscosity of the slurry becomes extremely high, and for example, in the case of a highly concentrated slurry, casting becomes impossible, resulting in a decrease in the peptization state. There is. The reason for this seems to be the quality of compatibility between the organic materials. That is, for example, the raw material alumina used when manufacturing alumina ceramics for the purpose of compactness is fine particles with an average particle size of about 0.5 μm, and because of its high surface activity, these fine particles tend to aggregate strongly. shows. For this reason, it is necessary to use large amounts of water and molding aids to prepare the slurry. On the other hand, regarding dispersants and binders among forming aids, although they are anionic materials with the same effect, when they are added together, the viscosity of the slurry increases. ,
At high slurry concentrations or at high amounts of binder, casting becomes extremely difficult. That is, in preparing the slurry, the peptization state of the slurry may be poor depending on the characteristics of the alumina powder raw material or the compatibility of the forming aid. However, these organic materials (dispersants,
As for the compatibility of binders), their effects and actions have not been fully elucidated scientifically because their compositions are complex. Regarding the stability of alumina slurry, there is a problem in that it may gel over time due to small amounts of components contained in raw material alumina, and the pot life of the slurry is significantly shortened. Furthermore, in the ceramics industry, there is a large barrier to know-how, and as a result, sufficient solutions to these problems have not yet been obtained. [Problem to be solved by the invention] As mentioned above, in the production of ceramics using oxide-based raw materials, whether in the field of traditional ceramics or fine ceramics, which is a new material, there are problems during molding. Additives that provide good moldability when added in small amounts are necessary, and the quality of the additives not only affects the quality of the ceramic product but also determines whether or not it can be manufactured. However, high-quality clay, which is a natural resource, is in danger of being depleted in Japan, and synthetic kaolinite, which should compensate for this, has not yet been given sufficient plasticity. Furthermore, in the case of fine ceramics, which is expected to be a new material, the raw material powder is highly pure and fine particles, so it has less plasticity than natural raw materials, and the additives that give it plasticity depend on the high purity of the raw material. It is required that it not be damaged. The purpose of the present invention is to provide these oxide raw materials with moldability, which is a common problem in the production of ceramics using these oxide raw materials.
The aim is to solve problems such as the depletion of plastic raw materials for traditional ceramics and the production of fine ceramics using new oxide raw materials. Another object of the present invention is to use conventionally known organic binders for slurry (e.g.
Unlike polyvinyl alcohol-based, cellulose-based, wax-based emulsions, acrylic acid-based emulsions, etc.), it does not have the effect of increasing the clay in the slurry.
Furthermore, it is possible to prevent the gelation phenomenon caused by raw material alumina, and it is also effective against anionic (for example, polycarboxylic acid type ammonium salt) or cationic (for example, quaternized ammonium salt) dispersants. Another object of the present invention is to produce ceramics or ceramic materials with high interparticle strength by using an organic molding aid, ie, a sugar alcohol, which can enhance the peptized state of the slurry and maintain its stability. By achieving the above objects, the present invention can extend the usable life of slurry, and can easily prepare slurry with high concentration and low clay required for molding. control becomes easier, and there is no need to worry about workability issues.
Furthermore, the particle filling of the compact is made more homogeneous, and since the forming aid is safe and ash-free, the compactness of the ceramic is improved without adversely affecting the structure of the sintered compact. . [Means for Solving the Problems] The present invention provides a means for imparting high plasticity necessary for a molding process by adding sugar alcohol to an oxide-based raw material for ceramics. The sugar alcohol used in the present invention is a reducing group (aldehyde group, ketone group) of sugars that are carbohydrates.
is replaced with an alcoholic hydroxyl group, and although it exists naturally and may also be produced by microorganisms, it is usually produced industrially by reducing reducing sugars with hydrogen in the presence of a catalyst. Manufactured. Most sugar alcohols can be used, but raw sugars include monosaccharides and/or oligosaccharides whose constituent sugars are hexoses, monosaccharide alcohols in which the reducing group is replaced with an alcoholic hydroxyl group, or / and oligosaccharide alcohols are useful as industrial raw materials. As the monosaccharide alcohol, sorbitol and mannitol are preferable, and as the oligosaccharide alcohol, oligosaccharide alcohols ranging from disaccharide alcohols such as maltitol and lactitol to trisaccharide alcohols and up to 10 sugar alcohols can be used alone or in combination. I can do it. As commercially available sugar alcohols, oligosaccharide alcohols whose constituent sugars are glucose and whose bond type is α-1, 4 or/and α-1, 6 bonds, such as those manufactured by Nikken Chemicals (SE), can also be used. . As the oxide-based raw material used in the present invention, any oxide-based raw material that is a raw material mineral for ceramics, such as feldspar, semi-feldspar, silica, silicates, and various clay minerals, can be used, and synthetic or processed oxidation As the physical raw material, any synthetic oxide raw material for ceramics can be used, such as synthetic kaolinite, spinel, mullite, alumina, zirconia, and ferrite. The purity of the alumina material used in the present invention is preferably 90% or more, particularly preferably 99% or more, and high-purity ceramics can be produced from high-purity fine alumina particles with a purity of 99.9% or more. The amount of sugar alcohol used in the present invention is 10% or less by weight based on the oxide raw material, preferably 0.1% or more, and more preferably 0.2% to 5%. Addition of sugar alcohol to oxide-based raw materials
It can be added in advance to the oxide-based raw material powder and/or water, or it can be added at the same time when preparing the slurry or kneaded clay before molding. Further, when granulating an oxide-based raw material as a ceramic material, it can be used by adding it to water and/or oxide-based raw material powder and/or other additives in advance. Any molding method can be used as long as it is molded in a moist state, such as cast molding, pressure molding, or molding using a potter's wheel. The present inventors have investigated the effect of sugar alcohols on sugar alcohols when fine powders of oxide-based raw materials or their constituent crystals come into contact with each other through water during molding and slide together while causing friction. The present invention was completed based on the assumption that the surfaces of these powders and crystals act on the surfaces and water to improve the slippage between the surfaces of these powders and crystals, and after conducting various studies. For example, when 0.5% to 5% sorbitol is added to the slurry used for casting molding, the clay content of the slurry decreases significantly.This property can be used to reduce the water content of the slurry and perform high-density casting molding. I can do it. This water-reducing effect is also observed for clay during potter's wheel molding. In other words, it has become clear that sugar alcohol further enhances the effect of water, which is thought to bring about a sliding effect between oxide fine particles. Furthermore, considering that the unique plasticity of clay is also a property brought about by the sliding properties of water and the surface of clay particles, we are considering substances that can impart fluidity and water-reducing properties to non-plastic or low-plastic oxide materials. As a result, it was found that adding sugar alcohol to oxide-based raw materials imparts or increases fluidity and plasticity, resulting in improved moldability. These effects are similar for all oxide-based raw materials such as natural minerals, synthetic kaolinite, and high-purity oxides. This is considered to be a common effect that sugar alcohols have on the physical properties of. Regarding the effect of the degree of polymerization of sugar alcohol, as the degree of polymerization increases, the dry strength of the ceramic molded article improves, so that a binder effect is also observed. Additionally, as illustrated in the examples below, the addition of sugar alcohols to alumina slurry in accordance with the present invention reduces the clay content of the slurry and increases its fluidity, thereby reducing the water content of the slurry. I can do it. Even when gelation occurs due to raw material alumina, gelation can be suppressed by adding sugar alcohol. Furthermore, since sugar alcohols are nonionic, they can exhibit their properties without adversely affecting other ionic additives. In this way, the favorable effects of sugar alcohol on alumina slurry impart desirable physical properties to the alumina slurry as a ceramic slurry, and provide better conditions for the ceramic forming process. There are effects such as contributing to improvement. Furthermore, in the spray granulation of alumina powder as a material for pressure molding, the reduction of slurry clay improves the fluidity of the spray liquid, making it possible to spray a highly concentrated slurry, and also to break up the droplets. It is recognized that it has the effect of improving the As described above, the action of the sugar alcohol is to not only lower the viscosity of the alumina slurry, but also to improve its stability, giving the alumina slurry desirable physical properties as a ceramic slurry without adversely affecting other agents. [Examples] The present invention will be specifically described below with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. In addition, in the following examples, "%" and "part" are based on weight unless otherwise specified. Example 1 30 parts of mackerel (composed of feldspar and quartz), 20 parts of waxite
clay (moisture
15.5%) in a vacuum clay mixer, add 0.2%, 0.5% or 1.0% of a commercially available oligosaccharide alcohol (Nikken Chemical: SE 57, moisture 30%) and water to make a mixture with a moisture content of 20.0%. Three types of clay were prepared. Next, with an extrusion molding machine, the width is 60 mm, the length is 100 mm,
Three types of molded bodies with a thickness of 20 mm were created. This molded body was dried at 30° C. to 40° C. for 48 hours to obtain a dry body, and then fired at a maximum temperature of 1280° C. for 33 hours to prepare three types of fired bodies. As a comparative example, a molded body, a dried body, and a fired body were prepared in the same manner without adding oligosaccharide alcohol. The bending strength of the dried product and the abrasion loss of the fired product were measured in accordance with the ceramic tile testing method of JIS A5209. The number of samples is 10 samples per district, as shown in Table 1.
shows the average value. As shown in Table 1, the bending strength of the dry product was 21.08 to 22.78 Kgf/cm ² compared to 20.52 Kgf/cm 2 of the comparative example.
cm ² , and the abrasion loss of the fired body was 10.3 mg in the comparative example.
It decreased from 9.1 to 8.0 mg. Both values indicate that dense filling is performed during molding, and the strength of intermediate process products and finished ceramics is increased.

[Table] Weight loss mg

Claims (1)

[Scope of Claims] 1. A method for producing ceramics or ceramic materials, which comprises adding a sugar alcohol in the production of ceramics or ceramic materials using oxide-based raw materials. 2. The manufacturing method according to claim 1, wherein an oxide-based raw material having a purity of 90% or more is used as the oxide-based raw material. 3. The manufacturing method according to claim 1, wherein a natural oxide containing alumina and/or silica as a main component is used as the oxide-based raw material. 4. The manufacturing method according to claim 1, wherein synthetic kaolinite is used as the oxide-based raw material. 5. The manufacturing method according to claim 1, wherein alumina with a purity of 90% or more is used as the oxide raw material. 6. The manufacturing method according to claim 1, wherein alumina with a purity of 99% or more is used as the oxide raw material. 7. The manufacturing method according to claim 1, wherein the sugar alcohol contains 25% by weight or more of an oligosaccharide alcohol having a degree of polymerization of 2 to 5. 8. The production method according to any one of claims 1 to 7, wherein the sugar alcohol is a monosaccharide alcohol and/or an oligosaccharide alcohol. 9. The production method according to claim 8, wherein the monosaccharide alcohol is sorbitol and/or mannitol and/or galactitol. 10 Claim 8 The oligosaccharide alcohol contains maltitol and/or lactitol as a component.
Manufacturing method described. 11 As a component of oligosaccharide alcohol, the constituent sugar is glucose residue, and the bond is α-1,
9. The production method according to claim 8, comprising a sugar alcohol having 4 bonds and/or α-1,6 bonds. 12 Add water to oxide-based raw materials to prepare slurry,
2. The manufacturing method according to claim 1, wherein the product is cast in a mold. 13. The manufacturing method according to claim 1, wherein water is added to the oxide-based raw material to prepare clay, which is then plastically formed. 14. The production method according to claim 1, wherein the amount of sugar alcohol added to the slurry is within a range of 5% by weight or less based on the oxide-based raw material. 15. The manufacturing method according to claim 5, wherein the sugar alcohol is added during alumina peptization.