JPH0397649A - Inorganic powder suspension and inorganic powder sintered material produced from the suspension - Google Patents

Abstract

PURPOSE:To facilitate the operation in forming and to improve the productivity of the sintered material by adding >=1 kind of polysaccharide to a dispersion of inorg. powder in solvent to obtain an inorg. powder suspension or further sintering the formed material obtained from the suspension. CONSTITUTION:One or more kinds of polysaccharides selected from pectin, pectic acid, 1,3-glucan originated from microbes and animal polysaccharides are added to an aq. dispersion of inorg. powder (e.g. ceramic powder) or the dispersion in water and alcohol. In this case, the reaction is carried out at pH7.0-12.0, the reaction temp. is ordinarily controlled to room temp., and the reaction time is adjusted to about 24hr. The inorg. powder is deflocculated and dispersed in a solvent by the treatment to obtain the inorg. powder suspension having the above mentioned characteristics. The suspension is formed by casting, press forming, etc., and the formed material is sintered to obtain an inorg. powder sintered material, namely a ceramic sintered material.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to an inorganic powder suspension and an inorganic powder sintered product produced from the suspension, and more specifically, for example, to ceramic suspensions. The present invention relates to a suspension liquid and a ceramic sintered product manufactured from the suspension, and provides one that facilitates operability during molding treatment and improves the productivity of the sintered product.

<Prior art> For example, the ceramic sintered product described above is generally produced by adding a dispersant, a binder, and water (solvent) to a powder raw material mixture to prepare a ceramic powder suspension, and (1) Pressurize or shape granules made from a suspension, (2) Shape granules by other methods, and then sinter the resulting product.

In this case, methods for preparing the above suspension include: (1) adjusting the pH with an acid or base such as hydrogen chloride, sodium hydroxide, ammonia, etc. (2) using a polyester such as soda ash, water glass, polyphosphate, etc. Methods of adding inorganic salts that form insoluble salts or complex salts for valent cations Methods of adding borianion dispersants such as CMC salts, lignin sulfonates, polyacrylates, etc. are known. ．． Methods (2) and (2) above have long been widely used in the field of ceramic manufacturing, but these dispersants have a high risk of leaving impurities such as sodium compounds in the sintered product, and are used for IC boards, capacitors, etc. In the field of fine ceramics, typified by electronic parts and artificial bones, their use is undesirable from the viewpoint of dissatisfaction with trace amounts of impurities, and borianion dispersants (2) are commonly used.

That is, the borianion dispersant has functional groups such as a carboxyl group and a sulfonic acid group in its molecular structure, so that
It dissociates in water to produce borian anions, which collect polyvalent ions such as calcium ions and magnesium ions adsorbed on inorganic powders (e.g. clay particles), and monovalent ions replace the clay particles. This functions to promote peptization by imparting electrostatic repulsion to the particles.

In addition, the dispersant is a hydrocarbon or artificial polysaccharide-based polymer, and the components are blown away during sintering, so impurities are less likely to remain in the sintered product compared to the dispersants described in ■ to ■ above. Problems to be Solved by the Invention In general, in the ceramic molding process, the water content of the ceramic powder suspension is reduced as much as possible in order to improve productivity by shortening drying time and to facilitate handling. It needs to be small and fluid.

However, since the above dispersant (■) is a polymer, it can be assumed that when it is added to a suspension, the viscosity of the entire liquid will inherently increase, and the functional group of the polymer will contain calcium ions. When it reacts with polyvalent ions such as polyvalent ions, the functional groups of the polymer may be crosslinked and gelled through the polyvalent ions, which may increase the viscosity.

Therefore, when the water content of the suspension is small (that is, when the mixed concentration of the dispersant increases), there is a strong possibility that the viscosity of the suspension will increase and the handling properties will deteriorate. On the other hand, JP-A-58-172227 discloses a technique for preparing an aqueous zeolite suspension that is stable over a long period of time by adding carrageenan, which is a natural polysaccharide, as a dispersant. However, according to Table 1 of the above publication, as the amount of carrageenan mixed increases,
It was found that the viscosity of the suspension increased dramatically, especially when the carrageenan mixture ratio increased from 0.2 to 0.4% by weight.
The viscosity of the 42.5% by weight zeolite suspension is 700 → 40
00 cP, which indicates that the addition of an organic polymer dispersant poses a problem in terms of handling. On the other hand, since the above-mentioned lagenane has a sulfonic acid group, the sulfur content of the functional group combines with the metal contained in the inorganic powder during sintering, forming a metal sulfide ball and causing coloration of the sintered product. This is fine in fields where coloring is not a big problem, such as in detergents and desiccants, but it is undesirable for applications such as the fine ceramics mentioned above. The main technical problem of the present invention is to improve the handling properties during molding of inorganic powder and the handling of sintered products produced from molded products.

<Means for Solving the Problems> The present inventors have discovered that by selecting certain types of natural polysaccharides as dispersants, inorganic powders (e.g. ceramic powders)
It was discovered that the viscosity of the entire liquid could be lowered while increasing the dispersion stability of the slurry, and based on this discovery, the present invention was completed.

That is, the first invention adds at least one polysaccharide selected from the group of pectin, pectic acid, microbial origin 1.3-glucans, and animal origin polysaccharides to a solvent system in which inorganic powder is dispersed, 6. The second invention is an inorganic powder suspension characterized by peptizing and dispersing inorganic powder in a solvent. A third invention is characterized in that the polysaccharide in the first or second invention is one that has been treated to have a lower molecular weight by enzymatic decomposition, acid decomposition, etc. That is.

The fourth invention provides an inorganic powder by adding at least one polysaccharide selected from the group of pectin, pectic acid, microbial origin 1,3-glucan, and animal origin polysaccharide to a solvent system in which the inorganic powder is dispersed. This is an inorganic powder sintered product, which is characterized by preparing a powder suspension, producing a molded product from the suspension, and sintering the molded product. A fifth invention is the fourth invention, characterized in that granules are granulated from the suspension using a spray dryer, and the granules are pressure-molded to obtain a molded product.

The above-mentioned inorganic powder refers to the following individual powder or mixed powder.

■Oxides such as alumina, silica, magnesia, zirconia, titania, ferrite, barium titanate, synthetic cordierite, mullite, etc.■Silicon carbide, boron carbide,
Carbides such as titanium carbide ■Nitrides such as silicon nitride, boron nitride, aluminum nitride, titanium nitride ■Borides such as zirconium boride and titanium boride ■Kaolin, kaolinite, bentonite, zeolite, talc, Seviolite, Hekai clay , natural or synthetic minerals such as hydroxyapatite (calcium phosphate compound), carbon, carbon black or graphite powder, magnetic material powder such as magnets, iron sand powder, fuel powder, pigment powder, superconducting material powder, etc. The inorganic powder also has the above-mentioned microbial origin 1.
3-glucan is a polysaccharide whose main component is D-glucose as a monosaccharide unit and a 1,3-bond polymer produced by microorganisms, for example, the following (a) to (c). Refers to β-1,3-conjugates and α-1-conjugates shown in . (a)
^lcaligenes fae, a type of soil bacteria
calisvar. ＋＊yoxgenes 10C3
Curdlan (agricultural biological chemistry) produced from K, etc.
ral Biological ChemistryJ
．． Volume 30. p. 196 {1966}) (b) Valamilon produced by the unicellular alga EugIena gracilis (see JP-A-64-37297) (c) Pachyman obtained from Poria cocas, scleroglucan produced by Sclerocius glucanicum Therefore, among polysaccharides of microbial origin, 1.

The above-mentioned animal-derived polysaccharides refer to polysaccharides obtained from the oval tissue of animal bodies, and include chondroitin & EM, hyaluronic acid, and the like.

On the other hand, the polysaccharide of the present invention is a specified polysaccharide of natural origin (i.e., obtained from natural products) that satisfies the following requirements (a) or (b).

(a) Commonly known natural polysaccharides obtained from natural products as they are or through a prescribed extraction process.

(b) Chemically treated natural polysaccharides mentioned in (a) above.

In this case, the chemical treatment mentioned above refers to the following treatment, etc.

■Non-metallic basic substances such as ammonia and triethanolamine, or sodium hydroxide, potassium hydroxide,
Aging performed in the presence of an aqueous solution of a basic substance such as baking soda or calcium carbonate (or in the presence of a mixture of the aqueous solution and an aqueous solvent such as acetone, ethanol, or methanol).

■Low-molecularization through enzymatic decomposition. ■Low molecular weight reduction by acid decomposition (for example, 90% curdlan)
When dissolved in formic acid and reacted at 100°C for 10 to 20 minutes, curdlan with a polymerization degree of about 400 to 500 reduced to a low molecular weight of about 70 to 100 is obtained.

■Reducing the degree of methyl esterification of carboxyl groups by heating in water or mixing with dilute acid.

■Esterification treatments such as carboxymethylation, nitration, and sulfation.

Incidentally, among the above polysaccharides, when pectin or pectic acid is aged, the free carboxyl groups in the polysaccharide are neutralized and become basic salts, and dissociation into carboxyl anions progresses, and some degradation occurs due to hydrolysis. Lower molecular weight occurs. The reaction conditions for the above aging are as follows.

(1) The basic substance is added in an amount equal to or more than the free carboxyl group of pectin or pectic acid.

(2) The pH is adjusted to 7.0 to 12.0, preferably 8.0 to 10.5. However, the reaction is accelerated when the pH becomes basic.

(3) The reaction temperature is usually room temperature. However, heating accelerates the reaction. (4) Reaction time is usually about one day's vision.

In the enzymatic decomposition treatment shown in (2) above, pectin and pectic acid are degraded by pectin main chain degrading enzymes such as pectinase EC-3, 2, 1, and 15, and pectin trans-eliminase, which will be described later. Polysaccharides are also broken down by glucanase enzymes.

The above suspension essentially contains an inorganic powder and a specified polysaccharide, but may also contain other fillers such as a sintering aid, a binder, a lubricant, and a plasticizer. There is no problem.

The dispersion solvent system for the above-mentioned inorganic powder is not limited to an aqueous system, but also a mixed liquid system of water and alcohol, or an inorganic powder that shows some solubility in water, such as calcia or magnesia. Organic solvents such as ethanol may also be used. On the other hand, the above-mentioned inorganic powder suspension is molded by a casting method, a doctor blade molding method, a pressure molding method, or the like. The casting method includes those shown in (a) to (e) below. (a) @ Sludge casting molding method in which the suspension is poured into a porous mold, and when a cast with a predetermined thickness is formed by water absorption in the mold, the excess suspension is discharged to obtain a molded body. A solid casting method in which a suspension is poured into a mold and all of the suspension in the mold is solidified to obtain a molded object. (d) Pressure casting method, in which high pressure is applied to the suspension poured into the mold. (e) Vibration casting method, which uses suspension in water-soluble molds, solvent-disintegrating molds, temperature-disintegrating molds, etc. The soluble mold casting or shaping method, which involves pouring a liquid into the mold, and the pressure molding method, in which the suspension is turned into granules using a spray dryer, and then molded under pressure. The methods include dry or semi-dry press method, isotactic press method (CIP method), hot press method (HP method), and isotactic hot press method (HIP method).
P method) etc.

Incidentally, in the above-mentioned doctor blade molding method, an organic solvent is normally used as a dispersion medium, but when the present invention is applied, water can be used.

Examples> Examples of suspensions according to the present invention will be sequentially described below, and examples of sintered products produced from the suspensions will also be described.

《Example 1》 200mj of curdlan with an average particle size of 60μ! It was weighed into a beaker, 50 g of distilled water was added, and the mixture was stirred with a magnetic stirrer for 30 minutes to fully disperse it in the distilled water. Separately, purity 99.99%, BET surface fi14m2/g
, 50g of high purity alumina powder with an average particle size of 0.22μ was weighed out, added to the dispersion water of the above Cadran while stirring, and stirred with a magnetic stirrer for 30 minutes to form a 50% by weight alumina suspension. A liquid was prepared.

In this case, the mixing ratio of curdlan to 100 parts by weight of alumina powder is 0.2 to 1.0 as shown in Figure 1.
A total of 5 types of alumina suspensions were prepared by changing the parts by weight in 5 steps (For example, in the suspension of composition 1, 50 g (100 parts by weight) of alumina and 0.1 g (0.0 ．．
2 parts by weight).

Then, the viscosity of each suspension was measured immediately after preparation using a viscometer (ELD type manufactured by Tokyo Keiki Co., Ltd.) at a rotor rotation speed of 5 rpm and 20°C, and the suspension was stored at room temperature for one week and then tested again. The viscosity was measured.

However, an alumina powder suspension without the addition of curdlan was used as a comparative example.

Figure 1 shows the results. Immediately after preparation, the viscosity of the alumina suspension is at its minimum when the mixing fraction of Riki-Dran is 0.2 to 0.4 parts by weight; It can be seen that when increasing or decreasing, the viscosity increases.

In the above mixing range, the viscosity is reduced to 65-66% of that of the comparative example, which can effectively improve the handling performance in certain processing.

In addition, Figure 2 shows the change over time of the alumina suspension.
It can be seen that the viscosity remains stable and low even after several weeks.

<<Example 2>> An alumina suspension was prepared under the same conditions as in Example 1 above by replacing curdlan with varamylon as the dispersant, and the viscosity of the suspension was measured. A viscous effect was observed. <<Example 3>> A 50% by weight alumina suspension was prepared under the same conditions as in Example 1, except that the dispersant was changed from curdlan to pectin (lime pectin), and the pectin mixing fraction was set to 0.2 to 0.2. 1,
The viscosity of each suspension was measured by varying the suspension in 6 steps of 5 parts by weight.

Note that an alumina suspension without addition of pectin was used as a comparative example.

Figure 3 shows the results, and the alumina suspension of this example showed a low viscosity of 8.5% or less compared to the comparative example, and in particular,
．． It can be seen that the 4 parts by weight suspension has an extremely low viscosity of 127 CP (viscosity reduction rate of 1.2% compared to the comparative example). A 60% by weight alumina suspension was prepared by changing the mixing ratio of water to the mixed powder of alumina powder and pectin, and the pectin mixing ratio was 0.1 to 1.0 parts by weight. The viscosity of each suspension was measured using an alumina suspension without pectin as a comparative example. Figure 4 shows the results.
At 0.4 parts by weight, the 60 wt% alumina suspension exhibits a lower viscosity of 5.1-10.4% relative to the comparative example, and the concentration of the alumina suspension increases by 10 wt%. 3→4〉
, it can be seen that pectin has a large viscosity-reducing effect. <<Example 5>> A 60% by weight alumina suspension was prepared under the same conditions as in Example 4, except that pectin was replaced with pectic acid as the dispersant.
The pectin mixing fraction was changed to 0.1 and 0.2 parts by weight, and the viscosity of each suspension was measured using an alumina suspension without pectic acid as a comparative example. FIG. 5 shows the results, and the alumina suspension of this example showed a lower viscosity of 5.8 to 11.0% compared to the comparative example.
It can be seen that pectic acid exhibits a large viscosity-reducing effect similar to pectin.

<<Example 6>> Pectin (lime pectin) was mixed with 100 g of Gakkai cordierite powder at a mixing ratio of 0.1 to 1.0 parts by weight in five stages, and each mixture was dry mixed in a plastic bag. .

Then, 100g of distilled water was weighed into a 500mf corundum pot for a ball mill, and 100g of the above mixed powder was added to it.
After adding with stirring, 25 corundum balls with a diameter of 20 mm were added, and the mixture was stirred for 30 minutes at a pot rotation speed of 500 rpm using a planetary ball mill to prepare five types of 50% by weight cordierite suspensions. At the same time,
Using a synthetic cordierite suspension without addition of pectin as a comparative example, the viscosity of each suspension was measured at 20°C.

Figure 6 shows the results, with the mixing fraction of pectin ranging from 0.1 to
At 0.6 parts by weight, the cordierite suspension has a lower viscosity of 2.6-10.3% compared to the comparative example, in particular with 0.4 parts by weight pectin it shows a minimum viscosity of 58 cP.

That is, pectin has a remarkable viscosity-reducing effect even on cordierite suspensions.

《Example 7》 100g of New Zealand kaolin powder and pectin (
0.4 g of each lime pectin was weighed out and dry mixed in a plastic bag.

Then, 150 g of distilled water was weighed into a 500 ml corundum pot for a ball mill, and 100 g of the above mixed powder was added to this.
．． 4 g was added with stirring to prepare a 40% by weight kaolin suspension in the same manner as in Example 6. A kaolin suspension without pectin was used as a comparative example, and the viscosity of each suspension was adjusted to 20% by weight. Measured at °C. Figure 7 shows the results, and the kaolin suspension of this example has a viscosity 7.1% lower than that of the comparative example. Therefore, pectin exhibits a very effective viscosity-reducing effect not only on alumina and synthetic cordierite suspensions but also on kaolin suspensions.

<<Example 8>> 100 g of pectin (lime pectin), curdlan, and high-purity alumina powder were each weighed, and as shown in Figure 8, the mixed weight parts of pectin and curdlan were calculated based on 100 parts by weight of the alumina powder. were varied in four stages, and each was dry mixed in a plastic bag.

Then, weigh out 67g of distilled water into a ball mill pot,
The above mixed powder was added to this while stirring, and four types of approximately 60% by weight alumina suspensions were prepared in the same manner as in Example 6, and alumina suspensions without a dispersant were compared. As an example, the viscosity of each suspension was measured at 20°C.

FIG. 8 shows the results. The mixture of pectin and curdlan has a remarkable viscosity-reducing effect even on an alumina suspension with a high concentration of 60% by weight. 0-1
It exhibits a low viscosity of 5.6%.

Furthermore, when compared with Example 3 (see Figure 4), which deals with a 60% by weight alumina suspension mixed with pectin alone, for example, the viscosity when 0.6 parts by weight of a dispersant is mixed is as follows. In Example 4, it was 2680 cP, whereas in this example, composition 2 <pectin; curdlan = 0.2:0.4
) shows 201.1 cP, and it can be seen that when more than half of the pectin is replaced with curdlan, the viscosity is further reduced.

<<Example 9>> 2 ml of 25% ammonia aqueous solution was added to 100 g of 4% aqueous solution of lime pectin (degree of methyl esterification 65%) and stirred, and then aged for 3 days to convert carboxyl groups into ammonium salts. A promoted dispersant and a non-processed dispersant were prepared. Weigh out 15g of each of the above dispersants into a ball mill pot, and
Diluted with 5.6 g of distilled water.

Separately, 150 g of alumina powder with a purity of 99.8%, a BET surface of 7 m2/g, and an average particle size of 0.6 μm was weighed out, and added to the diluted pectin solution with stirring, as in Example 6. A 60% by weight alumina suspension was prepared under the conditions of (i.e. using a planetary ball mill apparatus) and
The viscosity of each suspension at 0°C was measured. However, an alumina suspension with a pectin mixing fraction of 0 parts by weight was used as a comparative example.

Figure 9 shows the results, and the viscosity of the alumina suspension was significantly reduced by mixing with pectin (20,000 cp).
-775 cp or less>, the aging of the pectin showed a further decrease, and showed a drop-off reduction of about 1/20 compared to that without aging.

This suggests that the carboxyl groups in the pectin molecules dissociate into anions due to aging, which facilitates peptization between colloidal particles in the suspension. <<Example 10>> 175 g of alumina powder was added to the aged pectin diluted solution prepared in Example 9 above while stirring, and the pectin mixing fraction was adjusted to 4 levels from 0.1 to 0.6 parts by weight. 70% by weight under the same conditions as in Example 6.
Alumina suspensions were prepared and the viscosity of each was measured.

However, an alumina suspension with a pectin mixing fraction of 0 parts by weight was used as a comparative example.

Figure 10 shows the results. In an alumina suspension with a high concentration of 70% by weight, if no dispersant is added, 20,000
However, by using aged pectin as a dispersant, the viscosity was significantly reduced, and especially when the pectin mixing fraction was 0.4 parts by weight, the viscosity of the suspension was It became less than 1/36 of the example.

<Example 11> Using four types of vectins with different degrees of methyl esterification,
After adding 2 ml of a 25% ammonia aqueous solution to 100 g of a 4% aqueous solution of each pectin and stirring, the mixture was aged for 3 days to prepare four types of dispersants.

7.5 g of each of the above dispersants i was diluted under the same conditions as in Example 6, and alumina powder was added to make the alumina 70% by weight.
An alumina suspension containing 0.4 parts by weight of pectin/pectin was prepared, and its viscosity was measured.

Figure 11 shows the results; when the degree of methyl esterification of pectin decreases from 74% to 65%-50%, the viscosity of the alumina suspension also decreases, but the degree of methyl esterification decreases to 50%.
% → 30%, the viscosity increased on the contrary.

In other words, it can be theoretically assumed that when pectin with a low degree of methyl esterification is aged, the formation of ammonium salts is further promoted and the suspension becomes less viscous. Reducing the degree of methyl esterification is considered to be advantageous for reducing the viscosity of the suspension as long as the degree of methyl esterification is within a certain range. All other conditions are implemented above.
Using the same settings as Ait, the viscosity of four types of alumina suspensions was measured.

Figure 12 shows the results, and the amount of ammonia added was 2ml.
→ lml and dilute the ammonia concentration during aging, it was thought that the degree of formation of ammonium salts within pectin molecules would decrease and affect the viscosity of the suspension. There was no significant difference in the viscosity of the suspensions.

《Example 13〉 Lime pectin 50%
Pectinase EC-34-145 (Polygalact
uronase; origin Asbergus niger, SIGM
Company A 1) Add 2.5μ1 of the enzyme and hold each in a 40℃ water bath for 16 to 40 hours while stirring slowly with a magnetic stirrer to carry out the enzyme reaction. The enzyme was left to inactivate for a minute, and two types of vectin solutions were obtained.

After adding 2 ml of 25% ammonia aqueous solution to each of the above pectin solutions and stirring, the mixture was aged for 3 days to prepare two types of dispersants.

Add the above dispersant 1 to a 100ml beaker. 75 g of each was weighed out and diluted with 13.32 g of distilled water.

35 g of separately weighed alumina powder was added to the enzymatically decomposed diluted pectin solution while stirring, and stirring was continued for 30 minutes using a magnetic stirrer to obtain a mixture ratio of 70% alumina/pectin of 0. 2 parts by weight of alumina suspensions were prepared, and the viscosity of each suspension was measured.6 Figure 13 shows the results. It can be seen that the viscosity has decreased (487 → 218 cp). <<Example 14>> 425 of lime pectin (degree of methyl esterification 65%)
Pectin trans-eliminase (product name: Seishin Pharmaceutical Co., Ltd.), which is a pectic acid degrading enzyme, was added to 200 g of an aqueous solution.
After adding 50 mg of ``vectolyase'' and carrying out the enzyme reaction at 45°C while changing the reaction time in 4 steps,
Each pectin solution was obtained by placing it in a high temperature range of 5° C. for 15 minutes to inactivate the enzyme.

Then, each of the above pectin solutions was filtered, and the resulting pectin solution 1
After adding 2 ml of 25% ammonia aqueous solution to 0.0 g and stirring, the mixture was aged for 3 days to prepare four types of dispersants.

Separately, the above-mentioned lime pectin was aged without enzyme treatment and prepared as a dispersant. The molecular weight of each of these five types of dispersants was measured by gel permeation chromatography using bullulan as a standard substance.

On the other hand, each of the above-mentioned dispersants was diluted with distilled water, the alumina powder used in Example 9 was added to the diluted solution, and the mixture was stirred and mixed using a planetary ball mill.
Alumina suspensions containing 0.2 parts by weight of pectin were prepared, and the viscosity of each suspension was measured.

Figure 14 shows the results. When pectin is enzymatically decomposed, both the molecular weight of pectin and the viscosity of the suspension tend to decrease as the treatment time increases. It can be assumed that this causes a decrease in viscosity. In other words, the unexpected result was that the lowering of the molecular weight of pectin, which was mixed in only a trace amount of 0.2 parts by weight, caused a decrease in the viscosity of the entire alumina suspension. <<Example 15>> In Examples 13 and 14 above, changes in the viscosity of the suspension when pectin was enzymatically decomposed were investigated, but in this example, when the degree of methyl esterification of pectin and the enzyme reaction time were changed. Next, the effect on the viscosity of the suspension was investigated.

That is, three types of vectins with different degrees of methyl esterification (
50%, 65%, 74%> and 4% of each pectin.
50 mg of the pectin trans-eliminase was added to 200 g of the aqueous solution, and the reaction was deactivated and P
Each dispersant was prepared by aging the F solution.

Then, in the same manner as in Example 13, alumina powder was added to the diluted solution of the dispersant and stirred with a magnetic stirrer to suspend the alumina at a mixed proportion of 70% by weight of alumina/0.2 parts by weight of pectin. A liquid was prepared and the viscosity of each suspension was measured.

FIG. 15 shows the results, and when the degree of methyl esterification was the same, the following was observed regarding the relationship between the enzyme reaction time and the viscosity of the alumina suspension.

(2) When the degree of methyl esterification was 74% and 65%, the viscosity of the suspension gradually decreased as the enzyme reaction time increased from 1 hour to 2 hours to 4 hours.

■ No decrease in viscosity was observed between reaction times of 4 and 8 hours. 《Example 16》 200g of ben-1-night (viscosity mineral material whose main component is montmorillonite) was added to 800g of synthetic zeolite 4A as a sintering aid, and curdlan Log was mixed therein, and 1500g of distilled water was added. was added to this mixed powder and thoroughly stirred and mixed to prepare a suspension of synthetic zeolite powder, and the viscosity was measured.

Next, this suspension was fed to a spray dryer at a feed rate that allowed the liquid to be fed, so that the particle size was 30 to 150 μm and the water content was approximately 20 μm.
% granules are dry granulated, and the granules are 200 kg/cm"
A tablet-shaped pellet having a diameter of 10 mmφ and a thickness of 3 mm was made by pressure molding, and its compressive strength was measured using a hardness meter.

In addition, after drying this pellet at 115°C for 1 hour,
Sintering was carried out at 670°C for 1 hour to obtain a tablet-shaped sintered product, and the compressive strength of this sintered product was measured.

A synthetic zeolite suspension in which 10 g of methyl cellulose was mixed instead of curdlan was used as a comparative example, and the viscosity of the suspension and the compressive strength of molded and sintered products obtained from the suspension were measured.

FIG. 16 shows the results, and the viscosity of this suspension is approximately 70% lower than that of the comparative example (1050→730 cp), and the fluidity is correspondingly high.

This means that the liquid delivery rate during spray drying increases by 1.22 times compared to the case of methylcellulose (
18.3→22.4 g/min), it is clear that the dry granulation process can be performed quickly and easily.

In addition, curdlan has excellent shape retention when formed into granules,
There is no need to separately add a binder such as polyvinyl alcohol to the molding material. This can be seen from the fact that the strength of the molded product and the baked product of this example were greater than those of the comparative example.

Moreover, in the actual molding process, with methylcellulose, some of the molding material will remain and adhere to the mold when demolding after about 10 molding cycles, but this phenomenon is not observed with curdlan. Also, it has excellent mold releasability. Therefore, curdlan not only functions as an original dispersant, but also effectively functions as a binder and a mold release agent, making the actual shaping and sintering process simple and inexpensive.

<<Example 17>> The Gakkai zeolite granules produced in Example 16 above were put into a press molding machine to form 50×3 particles at a molding pressure of 150 kg/cm2.
Pressure molded into a plate shape of 0 x 2 mm, and this molded product was prepared in Example 8.
Sintered under the same conditions as above, and measured the refractive strength of the plate-shaped sintered material using a 100 kg load cell, it was found to be 1880
It was g. Incidentally, when a plate-shaped object is automatically fed by a machine, a refractive strength of 1,000 g is practically required, and the sintered product of this example fully satisfies this requirement, so it can be used as a desiccant for medicines or food. When this plate-shaped sintered product is automatically packaged together with chemicals and the like in a moisture-proof bag, it can be easily handled without breaking or collapsing.

<<Example 18>> Lime pectin with a degree of methyl esterification of 50% was aged under the same conditions as in Example 9, and alumina powder was added to the diluted solution so that the pectin mixing ratio was 0.2 parts by weight. After the addition, 300g of 10mmφ alumina balls were added and stirred and mixed in a rotary ball mill for 16 hours to prepare two types of alumina suspensions of 80% to 75% by weight. The viscosity was measured.

Next, each suspension was cast into a plaster mold using the solid casting method to produce round bar moldings of 6 mm φ x 60 mm in a molding time of 30 minutes. After drying at 115°C, the three-point bending strength and molding density were evaluated. It was measured.

In addition, each of the above molded bodies was sintered at 1600° C. for 3 hours to produce a round bar sintered product, and its three-point bending strength, molded density, etc. were measured.

Figure 17 shows the results, showing that even with an extremely high concentration of alumina suspension of 75 to 80% by weight, the use of this dispersant maintains the fluidity of the suspension well and enables smooth casting. .

In addition, the obtained compacts and sintered products have extremely high alumina content, so they exhibit excellent properties as seen in the measured values in the above figure. <Effects of the invention> (1) As mentioned above, in general, the higher the inorganic powder content of a suspension, the higher the production efficiency, and the lower the viscosity of the suspension, the better the handling properties. Normally, there is a conflict between handling performance and handleability, but this suspension successfully solves this problem.

That is, as can be seen from Examples 1 to 15 above, when the polysaccharide of the present invention is added to an inorganic powder suspension, compared to one without additives or one with conventional dispersants such as methyl cellulose, The viscosity of the suspension can be made extremely low.

Therefore, when the suspension of the present invention is applied to, for example, casting molding, doctor blade molding, etc., as shown in Example 18, the molding process can be performed in a state with low moisture content and high fluidity, making it easy to handle. and productivity will both improve. Furthermore, as shown in Example 16, when this suspension is applied to pressure molding and granules are granulated by a spray drying method,
Since the suspension can be fed at a high speed, the amount of liquid to be fed can be increased, and the possibility of clogging of the supply pipe or the pressure bomb can be eliminated, thereby effectively improving handling efficiency and productivity.

Incidentally, the suspension of the present invention can be applied to suspensions of various inorganic powders as shown below.

■ Ceramic suspension, which is a manufacturing material for various fine ceramics such as electronic parts, electrical parts, and artificial bones. ■ Ferrite powder suspension, which is a raw material for magnetic materials. ■ Carbon powder, which is a manufacturing material for carbon molded products. - Bomb black suspension ■ Pigment dispersion or dye dispersion ■ Zeolite dispersion which is a raw material for detergent ■ Dispersion of solid fuel ■ Mineral suspension such as cement milk ■ Desiccant such as zeolite (2) Examples As shown in 16 and 17, the molded product and sintered product are dense and have high strength, so there is less risk of chipping or collapse, making it easier to manufacture the sintered product, and automatically packaging the sintered product. Handling becomes easier even in cases such as situations.

In particular, in addition to its original function as a dispersant, curdlan also acts as a dispersant for inorganic powders, as shown in the same example. Increasing the plasticity of the molding raw material prepared by adding the following: 1) During pressure molding, it has a function as a mold release agent and exhibits remarkable effects such as being able to provide excellent inorganic powder granules.

As a result, in the actual molding process, binders, mold release agents, etc. can be omitted, or even if these auxiliary agents are used, only a small amount is sufficient, so that molding can be performed quickly and easily.

Furthermore, as shown in Example 8, when pectin, which has a large viscosity-reducing effect, is used in combination with curdlan, handling properties can be greatly improved, and the productivity of molding and sintering of inorganic powder can be further increased.

(3) When vectin that has been aged in advance with an aqueous ammonia solution is used as a dispersant, as shown in Examples 9 and 10, the suspension can be made more effectively thinner than when no aging is used.

Therefore, as shown in Example 18, it is possible to use a highly concentrated suspension (for example, 80% by weight alumina suspension) in casting molding, which would have been impossible in the past, and the purity of the sintered product can be dramatically improved. can be enhanced.

In this case, the use of pectin with a low degree of methyl esterification is more advantageous in reducing the viscosity of the suspension, as shown in Example 11.

(4) When the polysaccharide of the present invention, including pectin, is previously subjected to enzymatic decomposition treatment, as shown in Examples 13 to 15, there is a tendency to enhance the viscosity-reducing effect of the suspension.

Furthermore, combining the enzymatic decomposition treatment with the aging is advantageous in reducing the viscosity of the suspension.

<5> When the polysaccharide of the present invention is used as a dispersant, for example, in curdlan, it also serves as a binder and a molding aid for the mold release agent, and the total amount mixed in the suspension can be reduced. Therefore, the purity of the sintered product can be increased accordingly.

In addition, the above-mentioned borianion dispersant is a salt in which functional groups such as carboxyl groups and sulfonic acid groups are bonded to metals such as sodium, such as CMC salts, so these metals remain intact even after sintering. Although there is a risk that it may remain as an impurity, ■The dispersant itself is not a salt in the above polysaccharides. ■Even when aging polysaccharides, by selecting ammonia, ethanolamine, etc. as the aging agent, nonmetallic Since a treatment that forms salt can be performed, the purity of the sintered product can be improved from this point as well.

Therefore, the suspension of the present invention containing the above-mentioned polysaccharide is optimal for producing fine ceramic sintered products that require high purity.

[Brief explanation of drawings]

Figures 1 to 15 show examples of suspensions of the present invention, and
Figures 16 to 17 show examples of the sintered product of the present invention, Figure 1 is a chart showing the viscosity of the curdlan mixed alumina suspension, and Figure 2 is the change over time of the same alumina suspension. Figure, 3rd
The figure shows the viscosity of a 50% by weight alumina suspension mixed with pectin, Figure 4 shows the viscosity of a 60% alumina suspension, and Figure 5 shows the viscosity of an alumina suspension mixed with pectic acid. Figure 6 is a diagram showing the viscosity of a pectin-mixed synthetic cordierite suspension, Figure 7 is a diagram showing the viscosity of a pectin-mixed kaolin suspension, and Figure 8 is a diagram showing the viscosity of a pectin- and curdlan-mixed alumina suspension. A chart showing the viscosity of a suspension; Figure 9 is a chart showing the viscosity of an alumina suspension using aged pectin as a dispersant; Figure 10 is a chart showing the viscosity of an alumina suspension using aged pectin as a dispersant. Figure 11 is a diagram showing the viscosity of alumina suspensions with different degrees of methyl esterification of pectin, Figure 12 is the viscosity of pectin-mixed alumina suspensions with different amounts of ammonia added during aging. Figure 13 is a diagram showing the viscosity of an alumina suspension using enzymatically decomposed pectin as a dispersant. Figure 14 is a diagram showing the viscosity of an alumina suspension using enzymatically decomposed pectin as a dispersant. Figure 14 is a diagram showing pectin mixtures and alumina suspensions with different degrees of methyl esterification and enzyme reaction time. A diagram showing the viscosity of the liquid. Figure 15 is a diagram showing the molecular weight of pectin and the viscosity of a pectin-mixed alumina suspension when the enzyme reaction time is changed. Figure 16 is a diagram showing the viscosity of a curdlan-mixed synthetic zeolite suspension. Figure 17 is a chart showing the properties of the pectin mixture/alumina suspension, the molded product, and the sintered product.

Claims (5)

[Claims] 1. At least one polysaccharide selected from the group of pectin, pectic acid, microbial-derived 1,3-glucans, and animal-derived polysaccharides is added to the solvent system in which the inorganic powder is dispersed, and the inorganic powder is dissolved in the solvent. An inorganic powder suspension characterized by being peptized and dispersed in 2. The inorganic powder suspension according to claim 1, wherein the pectin or pectic acid has been aged in the presence of a basic substance. 3. The inorganic powder suspension according to claim 1 or 2, wherein the polysaccharide is one that has been treated to have a lower molecular weight by enzymatic decomposition, acid decomposition, etc. 4. At least one polysaccharide selected from the group of pectin, pectic acid, microbial-derived 1,3-glucans, and animal-derived polysaccharides is added to a solvent system in which the inorganic powder is dispersed to form an inorganic powder suspension. An inorganic powder sintered product characterized by preparing a molded product from the suspension and sintering the molded product. 5. The inorganic powder sintered product according to claim 4, wherein granules are granulated from the suspension using a spray dryer, and the granules are pressure-molded to obtain a molded product.