JPH0891939A - Molded article of metal oxide powder and method for molding same powder - Google Patents

Abstract

PURPOSE: To obtain a molded article of metal oxide powder having high mechanical strength without damaging chemical and physical properties of powder by treating and molding metal oxide powder in the presence of an organic pigment as a molding auxiliary, an inorganic binder and/or an organic binder as a strength retaining agent in wet molding of the metal oxide powder. CONSTITUTION: An azo-based pigment, a phthalocyanine-based pigment or a polycyclic organic pigment is used as the organic pigment. A sol of a metal oxide, a hydrous silicate mineral including bentonite, kaolin and sepiolite or an inorganic or an organic acid or their metal salt is used as the inorganic binder. The amount of the organic pigment used is 1-60wt.% and the amount of the inorganic binder used is 1-30wt.% calculated as a metal oxide. In wet molding operation, the metal oxide powder is mixed with the organic pigment in a dry state and kneaded while gradually adding water. After the inorganic (organic) binder is added, kneading operation is carried out. Water is additionally added (10-60wt.%) according to kneading conditions. After molding and drying, the molded article is baked at 300-1,000 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method in which a metal oxide powder is wet-molded, the molding process is smoothly carried out, and a molded product excellent in mechanical strength is obtained.

2. Description of the Related Art Metal oxide powders are used as raw materials for various catalysts, adsorbents, ceramics, etc., and are widely used as intermediate raw materials for supporting various industrial fields. There is not much,
Usually, it is molded and used in a shape suitable for each purpose.

Metal oxide powder molding is classified into a wet method and a dry method depending on the processing method. In the case of the wet method, the raw material powder is moistened and kneaded to obtain an appropriate amount of water, and then processed by an extruder or the like. However, in this case, simply kneading the metal oxide powder in a humidified state does not generally give a kneaded product having physical properties suitable for molding, and the final product after heat treatment (2) Since it often does not have a mechanical strength that can withstand use, various molding aids and binders are added and used, and many organic compounds and inorganic compounds are known as applicable substances.

Among substances usually used as a molding aid or a binder, organic compounds include gum arabic, sodium alginate, carboxymethyl cellulose, corn starch, gelatin, dextrin, polyvinyl alcohol, microcrystalline cellulose, polyacrylamide, polyethylene glycol. , Organic acids, metal salts of organic acids, and the like, and as inorganic compounds, alumina sol, silica sol, metal oxide sol such as titania sol,
Examples thereof include silicates, bentonite, kaolin, hydrous silicate minerals such as sepiolite, phosphoric acid and polyphosphates, various inorganic acids or metal salts thereof.

In the wet molding of the metal oxide powder, the powder is sufficiently moistened and kneaded beforehand, but the extrusion molding is performed smoothly.
Moreover, in order to obtain a molded product having a good appearance, the kneaded product needs to have appropriate plasticity, and a kneaded product containing only ordinary metal oxide powder has a plasticity suitable for the molding. In many cases, it is necessary to add various organic or inorganic compounds as a molding aid or a binder from the viewpoint of improving the physical properties, and it is most suitable in relation to the physical properties of the metal oxide powder to be molded. Things have been selected and used.

Here, the organic compound as a molding aid or a binder is burnt off in a heat treatment step which is usually carried out after the molding treatment, the mechanical strength of the molded product is lost due to the bonding action, and the organic compound is burnt off. Since the shaped body holes are left, the mechanical strength of the molded product further decreases and often does not have the strength that can withstand practical use, and when using only organic additives, measures to compensate for the strength deterioration are usually taken. For example, in European Patent EP-278749, a kneaded product of talc, alumina, amorphous silica, an organic binder and a plasticizer is molded in a cordierite catalyst carrier production, dried, and then heated at high temperature (3). To sinter the molded product, and in Japanese Patent Laid-Open No. 172265/1983, zirconia, alumina, and zirconia are used in the production of a low expansion coefficient zirconia molded product. The kneaded product of the binding agent molded, and then dried after high temperature firing.

Although high temperature firing is effective as a method for imparting mechanical strength to a molded product, heat treatment under severe conditions has a negative effect of impairing the physical properties related to the pore structure of the molded product, Depending on the purpose, it may not be possible to obtain a molded product having preferable physical properties. In such a case, an inorganic compound binder is added in addition to the organic compound molding aid and the binder. -392903, in the production of a hollow cartridge for a filter, in addition to alumina, zirconia, an organic binder, and a dispersant as raw materials, colloidal silica is added as an inorganic binder, the kneaded product is molded under reduced pressure, and then dried, It is disclosed that a predetermined molded product is produced by firing.

In addition, depending on the purpose, a method for producing a molded product having preferable physical properties is also carried out by adding an inorganic binder and further firing at a high temperature, for example, JP-A-2-229713.
In the manufacture of a liquid filter, a kneaded product of alumina, silica, polyvinyl alcohol, a foaming agent, and an inorganic compound binder is molded, dried, and then heat-treated at a high temperature to sinter, and JP-A-61-16858.
2. In the production of heat-resistant inorganic molded articles, glass fiber, rock wool, inorganic fiber substances such as ceramic fibers, wood pulp, paper pulp, cellulose pulp,
A kneaded material such as an organic binder such as synthetic fiber, an inorganic binder such as bentonite and sodium silicate is molded, dried, and similarly sintered by high temperature firing.

[0008]

The metal oxide powders are usually used as various industrial materials after being formed into molded products.
In many cases, it is necessary to withstand harsh conditions or long-term use, and therefore it must have excellent mechanical strength. Although a systemic or inorganic molding aid or binder is added, the addition of (4) is often unfavorable because it may change the physical or chemical properties of the molded product, for example, an organic compound system. The addition of molding aids, binders, etc., is significantly reduced in mechanical strength due to the disappearance of the binder effect due to the burning out in those firing steps or the appearance of skeletal pores, etc. As a negative effect, the surface area of the molded product is lost, and a molded product having desirable physical properties cannot be obtained depending on the purpose of use.

On the other hand, in the case of the inorganic compound type additive, there is no decrease in strength due to firing as seen in the addition of the organic compound type substance, but the added inorganic compound is not removed by the heat treatment and is added to the molded product. If they remain and are different in composition from the molded product, they may adversely affect the chemical properties as impurities, so the use of inorganic additives is inevitably limited and, for example, catalysts or catalyst supports, etc. In the molding of metal oxides for use as a metal oxide sol, a metal oxide sol composed of the same metal component as the metal oxide powder to be molded or an inorganic acid is used to prevent the inorganic binder component from becoming an impurity. In addition, organic acids, the same metal salts of these acids, or inorganic binders that do not have a harmful effect even if they remain as impurities in the molded product are used.

Basically, since these molding aids and binders usually act as thickeners, not only the kneading operation becomes difficult depending on the kind or amount of the additive, but also a molding machine at the time of molding the kneaded material. Adhesion of kneaded material to screws, dies, casings, etc., high mechanical load on the molding machine to overcome difficult extrusion molding, heat generation due to friction, difficulty in continuous molding operation due to evaporation of water due to heat generation, or molding There are some problems in the overall molding operation, such as the difficulty of cutting.

[0011]

[Means for Solving the Problems] In the wet molding of metal oxide powder, it is necessary to obtain a molded product which has excellent mechanical strength and does not impair its inherent physical or chemical properties. It is important to effectively utilize the characteristics of the metal oxide powder, but in actual industrial regulations (5) In wet molding in the model, it is necessary to deal with the need for continuous mass powder treatment, Under the present circumstances, various molding aids and binders are added for imparting mechanical strength to withstand practical use, and a practical molded product is obtained at the sacrifice of powder properties to some extent.

In view of this situation of industrial wet molding of metal oxide powders, the present inventors have been earnestly studying organic compounds as molding aids. The scope of investigation was expanded without being limited to the more used organic compounds, and many organic compounds were taken up and systematically investigated the effect of the particle shape on the molding aid effect. When a pigment is added as a molding aid, a kneaded product having an appropriate viscosity can be obtained during the kneading of powder, and the molding process is very smooth with almost no exothermic phenomenon, and the extruded product can be easily molded. I found that

Moreover, this molded product has a very high mechanical strength after being dried and fired, and it is forcibly extruded while applying a large mechanical load to a molding machine without adding a usual organic compound molding aid. It was confirmed that a molded product that has the same strength as the baked product obtained by the above, and in addition to this, a very good appearance can be obtained, and in more detail the addition of an organic pigment as a molding aid. The present invention has been completed by adding a study.

What was not particularly expected of the organic pigment as the molding aid was that the mechanical strength was very high despite the addition of a considerable amount of the organic pigment to the powder to be molded, A molded product obtained without the addition of an organic compound molding auxiliary, in which no remarkable decrease in strength after firing, which is seen with ordinary organic compound additives, or no increase in pore volume due to the appearance of skeletal pores caused by the burning of organic compounds was observed. The case was completely the same not only in its mechanical strength but also in its pore volume.

In the metal oxide wet molding, it is not known why the addition of an organic pigment as a molding aid does not cause the formation of pores after the organic pigment is burned out. The reason for this shall be left to the study in (6). However, unlike the case of adding a normal organic pigment to a molded product, a molded product excellent in mechanical strength can be obtained without affecting the pore structure. It can be said that it is a very excellent molding aid, since a molded product that does not impair the properties described above is obtained.

Wet molding of metal oxide powder by adding an organic pigment can be carried out in the same manner as molding by adding a usual organic compound molding aid and an organic or inorganic binder,
A predetermined amount of an organic pigment and an organic or inorganic binder are added to the powder to be molded, and then water is gradually added with stirring to knead to form a paste-like kneaded product having an appropriate viscosity and then extruded. Then, the desired molded product can be obtained by subsequent drying and firing.

The organic pigment as a molding aid may be simply added to the metal oxide powder to be molded without pretreatment, and the kind of the metal oxide powder that can be added and used is not particularly limited. For example, pelletized or honeycomb-shaped molded products of metal oxide powders such as alumina, silica, titania, zirconia used as raw material powders for catalyst carriers, adsorbents, ceramics, inorganic filters, etc. Inorganic binder that can be applied to the wet molding of the above, and when a molded product with higher strength is required, does not interfere with the purpose of use even if it remains in the molded product. You can do it.

The organic pigments have different effects as molding auxiliaries depending on the type, but all of the pigments used as ordinary pigments are applicable, for example, β-naphthol type and β-oxynaphthoic acid type which belong to azo pigments. , Β-oxynaphthoic acid allylide type, acetoacetic acid allylide type, pyrazolone type, and condensed azo type pigments, copper phthalocyanine type, which belongs to phthalocyanine pigments, metal-free phthalocyanine type pigments, and the like, quinacridone, dioxazine, which belongs to polycyclic pigments, It is possible to use isoindoline, quinophthalone, various slene-based pigments, and the like, and those having a needle (7) -like or fibrous morphology by an electron microscope observation tend to be preferable.

The amount of the organic pigment used varies depending on the type of powder to be molded, but it is necessary to add it in the range of 1 to 60%, preferably 5 to 40%. %
In the following, the effect as a molding aid is insufficient and the molding operation is not improved, and 60 wt. When the content is more than 100%, the molded product does not have a problem in physical properties, but the effect as a molding aid corresponding to the added amount cannot be expected and it is not economically preferable.

On the other hand, the inorganic compound binder is added in order to impart higher mechanical strength to the molded product, and remains in the molded product even after heat treatment at a high temperature. Therefore, a preferable binder is selected according to the purpose of use. Must be,
As the inorganic binders usually used, for example, alumina oxide sol, silica sol, metal oxide sol such as titania sol,
Hydrous silicate minerals such as bentonite, kaolin, and sepiolite, various metal salts such as sodium silicate, sodium phosphate, sodium polyphosphate, and inorganic and organic acids or metal salts of these acids, etc., and these binders are molded powders. Is added and mixed following the operation of kneading with the organic pigment,
At this time, a commonly used organic compound-based binder may also be added, if necessary.

The addition amount of the inorganic binders must be determined in consideration of the strength required by the target molded product, and when the binder is expressed in terms of metal oxide, The content is usually 1 to 30 wt. %, Preferably 5 to 2
0 wt. It is necessary to add in the range of%, and the amount is 1
wt. % Or less, the effect of improving the plasticity of the kneaded product of the metal oxide powder to be molded is small, and sufficient mechanical strength cannot be imparted to the molded product after firing, and the amount is 30 wt. If it is more than%, the viscosity of the kneaded product is too high, which hinders the molding operation.

In the wet molding operation, metal oxide powder,
After dry-mixing the organic pigment molding aid, first perform a kneading operation by gradually mixing with water and then, if necessary, (8) add various inorganic binders and / or organic binders. After that, the kneading operation is continued, and depending on the kneading condition, water is further mixed to adjust the water content, and the water content is suitable for extrusion molding, but the water content is affected by the properties of the molding powder,
Usually 10 to 60 wt. %, Preferably 15-50 wt.
%, And the amount is 10 wt. % Or less, a kneaded product having a plasticity suitable for molding cannot be obtained, and 6
0 wt. If it is more than 0.1%, the kneaded product becomes a slurry and a molded product having a preferable shape cannot be obtained.

The kneaded product is then molded by an extruder. The kneaded product according to the present invention can be easily molded into a molding machine of a type normally used for wet molding, for example, a pellet-shaped molding product by a screw type extruder. Not only that, it can also be applied to the molding of honeycomb-shaped moldings under reduced pressure, and the molding operation can be performed very smoothly, and the friction between the kneaded material and the screw, die or casing. Not only does it generate almost no heat, the adhesion of the kneaded material to the contact points with the kneaded material in the molding machine does not occur, and the molding of the molding is easy. It is possible to obtain a molded product that is good and has high mechanical strength.

Next, the molded product is dried and calcined. The drying operation is intended to remove the free water contained in the molded product by evaporation, and the temperature is 50 to 200 ° C., preferably 80 to 1
The firing operation is carried out by completely decomposing and burning off the organic pigment contained in the molded product while decomposing and removing the molding powder, the bound water of the inorganic binder, etc. It is an essential operation for imparting strength and physical stability to the molded product, and it is necessary to be carried out in a temperature range of usually 300 to 1000 ° C, preferably 350 to 800 ° C, and an organic pigment at a temperature of 300 ° C or lower. Incomplete removal of combustion powder, removal of molding powder, binding water of inorganic binder, etc., and sintering at a temperature of 1000 ° C or higher promotes sintering of the molded product, and a molded product having desirable physical properties can be obtained depending on the purpose. Absent.

When the physical properties of the molded product after firing were measured, the mechanical strength was surprisingly high, and a large mechanical load was applied to the molding machine without adding organic compounds as molding aids (9). It shows the same mechanical strength as the molded product obtained by forced extrusion molding, while its pore volume shows the appearance of skeletal pores due to the burning of organic compounds found in ordinary molded products using organic compound additives. However, it was almost the same as the pore volume of the molded product obtained by adding no organic compound as a molding aid.

[0026]

EFFECTS OF THE INVENTION A kneaded product having an excellent molding aid effect by adding an organic pigment as a molding aid in the wet molding of metal oxide powder instead of an ordinary organic compound and having a plasticity suitable for wet molding At the same time, the adhesion of the kneaded material to the contact point with the kneaded material in the molding machine is small, so the molding operation can be performed smoothly, the molding of the molding is easy, and the appearance is good. A molded product is obtained, and the mechanical strength after firing is very high, so that a molded product that does not develop voids due to burning of the organic pigment is obtained.

[0027]

EXAMPLES Next, the contents of the present invention will be specifically described by way of examples, and the physical properties described therein were measured by the following instruments, respectively. Mechanical strength Kiya type hardness meter Pore volume Mercury injection type pore measuring device In addition, the current value flowing to the extruder motor at the time of molding was also displayed as a standard to show the ease of molding the kneaded material in the extrusion molding operation.

Example 1-1 Pseudo-boehmite gel-based alumina hydrate (alumina content 7
5 wt. %) 450 g, and 130 g of an organic azo pigment (insoluble azo, disazo yellow type) as a molding aid are weighed in a universal mixer and preliminarily dry mixed to obtain 5 wt. % Nitric acid aqueous solution (450 cc) is gradually added with stirring and mixed, and further kneading is continued for about 30 minutes to obtain an intermediate kneaded product, and then 2 wt. % Ammonia water (130 cc) was added, and kneading was continued (10) for about 30 minutes to form a paste-like kneaded product, and then a 1/8 inch size extruded product was obtained by a screw type extruder.

The molded product was dried in a dryer at 110 ° C. overnight and then transferred to an electric furnace and baked at 600 ° C. for 4 hours to obtain an alumina molded product of Example 1-1. Table 1 shows the measurement results of the electric current value of the molding machine motor at the time of the extrusion operation as an index of easiness, the strength of the alumina molded product, and the pore volume.

Examples 1-2, 1-3 In Example 1-1, organic azo pigments (insoluble azo, disazo yellow type) as a molding aid, 5 wt. % Nitric acid aqueous solution, 2 wt. %. Alumina moldings of Examples 1-2 and 1-3 were prepared by the same treatment method as that of Example 1-1, except that the amount of% ammonia water used was changed as shown in the table below. Table 1 shows the measurement results of the motor current value of the molding machine during the extrusion operation as an index of the property, the strength of the alumina molded product, and the pore volume.

Example 1-4 Except that in Example 1-1, 130 g of a polycyclic organic pigment (quinacridone type) was added instead of the organic azo pigment (insoluble azo, disazo yellow type) as a molding aid. Example 1-4 By the completely same treatment method as Example 1-1
Alumina molded product was prepared, and the measured values of the molding machine motor current at the time of extrusion operation as an index of kneaded product molding easiness, strength of alumina molded product, and measurement of pore volume are shown in Table-1.
It was on the street (11).

Comparative Example 1 In Example 1-1, 130 g of CMC (carboxyl methyl cellulose) which is usually used as a molding aid was added in place of the organic azo pigment (insoluble azo, disazo yellow type) as a molding aid. The alumina molded product of Comparative Example 1 was prepared by exactly the same treatment method as in Example 1-1 except for the above, but the motor current value of the molding machine at the time of extrusion operation and the strength of the alumina molded product as an index of moldability of the kneaded product. The measurement results of the pore volume are shown in Table 1.

Example 2 Pseudo-boehmite gel-based alumina hydrate (alumina content 7
5 wt. %) 450 g, and 130 g of an organic azo pigment (insoluble azo, disazo yellow type) as a molding aid are weighed in a universal mixer and preliminarily dry mixed, and then 300 g of alumina sol (alumina content 10 wt.%) Is stirred. Was gradually added and mixed, 180 cc of water was added with stirring, and kneading was continued for about 30 minutes to form a paste-like kneaded product. Then, a 1/8 inch size extruded product was obtained by a screw type extruder. .

The molded product was dried in a dryer at 110 ° C. overnight, transferred to an electric furnace, and calcined at 600 ° C. for 4 hours to obtain an alumina molded product of Example 2. The kneaded product was easy to mold. Table 1 shows the measurement results of the motor current value of the molding machine at the time of the extrusion operation, the strength of the alumina molded product, and the pore volume, which were used as indicators of the above.

Comparative Example 2-1 In Example 2, 130 g of CMC (carboxyl methyl cellulose) which is usually used as a molding aid was added in place of the organic azo pigment (insoluble azo, disazo yellow type) as a molding aid. Except for the above, the alumina molded product of Comparative Example 2-1 was prepared by exactly the same treatment method as in Example 2, and was used as an index of moldability of the kneaded product. (12) Current value of molding machine motor during extrusion operation, and alumina The measurement results of the strength and the pore volume of the molded product are shown in Table 1, respectively.

Comparative Example 2-2 Pseudo-boehmite gel alumina hydrate (alumina content 75
wt. %) 450 g in a universal mixer, 300 g of alumina sol (alumina content 10 wt.%) Was added and mixed without adding an organic compound-based molding aid, and then water 1
After 50 cc was gradually dropped to continue kneading to form a paste, the mixture was molded by a screw type extruder.

The molded product was dried in a dryer at 110 ° C. overnight, transferred to an electric furnace, and calcined at 600 ° C. for 4 hours to obtain an alumina molded product of Comparative Example 2-2. Table 1 shows the measurement results of the electric current value of the molding machine motor at the time of the extrusion operation as an index of easiness, the strength of the alumina molded product, and the pore volume.

Example 3 A composite oxide of manganese oxide and iron oxide (Mn / Fe
Atomic ratio 1/2) of 450 g and 130 g of phthalocyanine pigment (copper phthalocyanine blue) as a molding aid are weighed in a universal mixer, and after dry mixing in advance, 300 g of bentonite is gradually added under stirring and mixed. Then, 180 cc of water was added with stirring to continue kneading for about 30 minutes to form a paste-like kneaded product, and then a 1/8 inch size extruded product was obtained by a screw type extruder.

The molded product was dried in a dryer at 110 ° C. overnight and then transferred to an electric furnace and baked at 450 ° C. for 4 hours to obtain a manganese oxide / iron oxide composite oxide molded product of Example 3. Table 1 shows the measurement results of the motor current value of the molding machine during the extrusion operation, the strength of the manganese oxide / iron oxide composite oxide molding, and the pore volume, which are indicators of the ease of molding the kneaded product. It was (13)

Comparative Example 3 Example 3 was the same as Example 3 except that 130 g of CMC (carboxyl methyl cellulose), which is usually used as a molding aid, was added in place of the phthalocyanine pigment (copper phthalocyanine blue) as a molding aid. The manganese oxide / iron oxide composite oxide molded body of Comparative Example 3 was prepared by using exactly the same treatment method. The molding machine motor current value at the time of extrusion operation and the manganese oxide / iron oxide composite were used as indices of the kneaded product molding ease. The measurement results of the strength and the pore volume of the oxide molded body are shown in Table 1, respectively.

Example 4 In Example 3, instead of the manganese oxide / iron oxide composite oxide as the metal oxide powder, copper oxide / manganese oxide composite oxide powder (Cu / Mn atomic ratio 4/6) was used. ) 450 g
The copper oxide / manganese oxide composite oxide molded body of Example 4 was prepared by the same treatment method as that of Example 3 except that was used, but the molding machine motor current during the extrusion operation was used as an index of the ease of molding the kneaded product. Table 1 shows the measured values of the strength, the strength of the copper oxide / manganese oxide composite oxide molded body, and the pore volume.
It was the street.

Comparative Example 4 Example 4 was repeated except that the phthalocyanine pigment (copper phthalocyanine blue) as a molding aid was replaced with 130 g of CMC (carboxyl methyl cellulose) which is usually used as a molding aid. A copper oxide / manganese oxide composite oxide powder (Cu / Mn atomic ratio 4/6) of Comparative Example 4 was prepared by the same treatment method as described above.
Table 1 shows the electric current values of the molding machine motor at the time of extrusion molding as an index of moldability of the kneaded product, and the strength and pore volume of the copper oxide / manganese oxide composite oxide molded body.

(14)

[Table 1]

Claims (4)

[Claims] 1. A metal oxide powder molded product which is treated and molded in the presence of an organic pigment as a molding aid, an inorganic binder and / or an organic binder as a strength-retaining agent. 2. The organic pigment as a molding aid is an azo, phthalocyanine or polycyclic organic pigment.
The metal oxide powder molding described. 3. An inorganic binder as a strength-retaining agent, a metal oxide sol, or a hydrated silicate mineral containing bentonite, kaolin, sepiolite, or an inorganic or organic acid,
Alternatively, the metal oxide powder molded article according to claim 1, which is a metal salt thereof. 4. The method according to claim 1, which comprises wet-kneading in the presence of an organic pigment as a molding aid, an inorganic binder and / or an organic binder as a strength-retaining agent, then extrusion-molding, followed by drying and firing. 1. A method for producing a metal oxide powder molded article according to claim 1.