JPH06102537B2 - Manufacturing method of high production rate kaolinite - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a raw material for ceramics,
The present invention relates to a production method of high production rate kaolinite, which is widely used as a binder for forming ceramics and a filler for paper making, and is attracting attention as a new functional material.

[0002]

2. Description of the Related Art Conventionally, natural clay containing kaolinite as a main component has been used as a raw material for ceramics. This kaolinite is the main mineral of the kaolinite group in clay minerals and is a white, gray or yellow mineral. The quality of high-quality natural clay mainly composed of kaolinite, especially Kibushi Clay and Frogme Clay, which are produced in the Seto area of Aichi Prefecture, has decreased due to long-term consumption and rapid housing development in recent years. is doing. Therefore, research and development of artificial clay has been promoted as a new functional material utilizing the fact that it is a plate crystal as a material replacing these natural clays.

As a method for producing the above kaolinite, a hydrothermal synthesis method is usually used. This hydrothermal synthesis method is a method of synthesizing a desired mineral by sealing the raw material in an autoclave in the presence of water and maintaining it at a high temperature and high pressure for a certain period of time, and is widely used as a synthetic means for various artificial minerals. Has been. Methods for producing kaolinite by such a hydrothermal synthesis method include Shibasaki and Watamura (Clays an
d Clay Minerals, 1983), a method of hydrothermally synthesizing a raw material in which silica sol and alumina sol are mixed in an autoclave, and a method of hydrothermally synthesizing a raw material in which an aluminum compound is mixed with allophane, diatomaceous earth, montmorillonite, zeolite, etc. A method of hydrothermally synthesizing sodium silicate and aluminum chloride as raw materials in an autoclave is known.

The above-mentioned synthetic method can be a solid / solid reaction, a solid / liquid reaction, or a liquid / liquid reaction, but solid mixing or solid / liquid mixing results in insufficient homogeneity and homogeneity. Since there are non-reactive silica and alumina fine crystal powder portions, the reaction does not proceed 100% and the kaolinite production rate does not increase. Further, in a system using a natural raw material, there is a problem that impurities such as metal oxides and quartz contained in the raw material remain in the product and coloring occurs. Therefore, as an ideal reaction system, it is desirable that the synthesis raw material is liquid / liquid.

Therefore, the present inventors have found that hydrothermal treatment of a synthetic gel in which cations other than protons are mixed in the synthetic gel inhibits crystallization, and first exchanges it with a proton type by an ion exchange resin. Method (Japanese Patent Application No. 2
No. 230230) and a method of performing ammonium ion exchange and then firing treatment (Japanese Patent Application No. 230230/1990). However, it was newly found that crystallization is inhibited when not only cations but also anions exist in the synthetic gel in a certain amount or more, and the present invention has been proposed.

That is, an object of the present invention is to provide a method capable of producing kaolinite having a higher reaction rate than conventional methods and having a high production rate of impurities and unreacted substances.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have obtained the kaolinite production method of the present invention. That is, the present invention is
A silicate aqueous solution and an aluminum compound aqueous solution are mixed to cause gelation in a pH range of 4 to 12, and then the molar ratio of cations contained in the gel is 0.02 or less relative to Al and the content of anionic species is 3000 ppm or less. The present invention relates to a method for producing a kaolinite having a high production rate, which comprises subjecting the gel to a hydrothermal treatment as it is or after a calcination treatment as it is controlled.

[0008]

The present invention will be described in more detail below. Kaolinite in the present invention is a chemical formula {Al ₂ Si ₂ O ₅ (O
H) ₄ }, which is a layered aluminosilicate composed of a 1: 1 tetrahedral sheet consisting of silicon and four oxygens and an octahedral sheet surrounding aluminum with six oxygens.

The above-mentioned silicate used in the present invention is water,
There is no particular limitation as long as it is soluble in acid and alkali, and water glass, calcium silicate, fluorosilicate, etc. are usually used. The aluminum compound is not particularly limited as long as it is water-soluble, but salts such as sulfates, nitrates, phosphates and halides are usually used.

The gel synthesis method of the present invention is performed by mixing an aqueous solution of a gayate salt and an aqueous solution of aluminum. The silicate aqueous solution and the aluminum aqueous solution are mixed by dropping one of the aqueous solutions at a constant rate or by adding and mixing them all at once, and / or by gradually dropping and mixing the two aqueous solutions at the same rate. Or, any method such as a method of mixing all at once can be adopted, but in order to uniformly mix silica and alumina particles in the gel, a method of dropping both solutions in the same volume and continuously mixing them Most preferably, it is adopted. The dropping rate is not particularly specified, but is controlled to about 50 to 200 ml / min in view of the mixing degree of the liquid and workability.

The gelling pH is 4 to 12, preferably 1.
It is important to control from 0 to 12. Then pH4
If it is less than the above, the solubility of Al rapidly increases, and as a result, the composition ratio of Si / Al of the synthetic gel becomes nonuniform. On the other hand, p
When it exceeds H12, the solubilities of both Si and Al increase, which causes a decrease in gel yield. Further, since the solubilities of Si and Al are different from each other, the Si / Al molar ratio becomes non-uniform.

The pH at the time of synthesizing the gel varies depending on the mixing method. However, when the synthesizing method in which the pH deviates from the specified range at the time of synthesizing, the acid required for neutralization is adjusted so that the pH at the end of mixing is 4 to 12. And it is important to control the amount of alkali added. For example, when the pH at the end of the synthesis deviates from 4 to 12, the acid or alkali is newly added.

The Si / Al molar ratio in the synthetic gel is a Si / Al molar ratio for controlling by-products in the hydrothermal reaction.
It is preferably close to = 1. When the composition ratio is different, it can be controlled by adding a Si source or an Al source after completion of the synthesis.

The lower limits of the concentrations of the aqueous silicate solution and the aqueous aluminum solution during gel synthesis are not particularly limited, and the upper limits are also allowed up to the saturated concentration.

From the viewpoint of improving work efficiency, it is desirable that the concentration of the aqueous solution is high, but an increase in the concentration leads to an increase in the clay, and in order to improve the uniformity of gel synthesis, Al
It is desirable that the Si concentration and the Si concentration be about 0.5 to 2.0 mol / liter.

The temperature for synthesizing the mixed gel is not particularly limited, but it is preferable to synthesize in a temperature range of about 35 ° C. to 60 ° C. in consideration of operability, reaction heat at neutralization, and air temperature.

The gel synthesis is not greatly affected by the presence or absence of stirring, but it is preferable to carry out the stirring under stirring in consideration of the homogenization of the reaction due to the mixed state of silica and alumina particles in the gel. Furthermore, the gel is further stabilized by stirring for several hours or more and aging for one day or more even after the mixing of the liquids is completed.

Ion-exchangeable or non-exchangeable anions and cations are incorporated into the gel synthesized by the above method. The present inventors have found that hydrothermal treatment of a synthetic gel in a state where cations and anions other than H ⁺ are present in a certain amount or more in the synthetic gel inhibits crystallization, making it difficult to improve the production rate of kaolinite. I found that.

FIG. 1 and FIG. 2 show the effects of residual cations and anions in the gel on the kaolinite production rate during hydrothermal treatment. As is clear from the figure, the kaolinite production rate decreases with the increase of residual cations and anions. Therefore, the generation rate is 90% or more,
Preferably, in order to obtain a high production rate kaolinite having a production rate of 95% or more, the molar ratio of the cations remaining in the gel is controlled to 0.02 or less, more preferably 0.005 or less, relative to Al, and the contained anions are contained. An important factor is to control the seeds to 3000 ppm or less, more preferably 2000 ppm or less.

The method of removing the cations and anions in the gel is not particularly limited, but it is usually carried out by an ion exchange method, a neutralization hydrolysis method, washing or the like.

The above-mentioned ion exchange method is performed by a method using an ion exchange resin and a method of chemically performing ion substitution.

The ion exchange resin used for this ion exchange is not particularly limited, and in the case of a cation, a proton type ion exchange resin having a sulfonic acid group or a carboxylic acid group as a functional group is usually used. In the case of an anion, an ion exchange resin having an alkylammonium group, an amino group or the like is used, but its effect is lower than that of a cation.

At this time, the ion exchange capacity and the like are not particularly limited and can be selected depending on the amount of exchanged ions in the gel used for ion exchange. Further, the amount of ion exchange resin and the reaction temperature are preferably set under mild conditions so as not to cause a composition change of Si / Al due to excessive use of ion exchange resin or ion exchange at high temperature. For example,
In the case of sodium ion, it is possible to perform ion exchange into a proton type without changing the composition by using an ion exchange resin having an amount equal to or less than the contained ion amount and performing ion exchange several times in a greenhouse. Further, as the ion exchange method, any method such as a batch method or a flow method can be used.

The chemical ion exchange method can be easily carried out by dispersing a synthetic gel in a solution containing exchange ions. Among them, by using an ammonium salt that is relatively easy to decompose and remove by calcination, the contained anions are simultaneously removed not only by cation exchange but also by neutralizing action.

The ammonium salt is not particularly limited, and ammonium nitrate, ammonium sulfate, ammonium chloride and the like are usually used. The concentration and temperature are not particularly limited, but the higher the concentration, the higher the exchange efficiency. But,
Since it causes a problem in terms of economy, it is wise to properly select the ion exchange amount.

The ion-exchanged ammonium is removed by decomposition by firing, but at a temperature of 900 ° C. or higher, the silica-alumina gel undergoes a phase transition and causes a decrease in reactivity during hydrothermal treatment. It is preferable to bake at ° C.

Next, as a neutralization hydrolysis method, in the case of removing cations, acids such as sulfuric acid, hydrochloric acid and nitric acid are added, and in the case of removing anions, alkalis such as caustic soda and ammonia are added, and the mixture is stirred and mixed, filtered and washed. Is done by doing.

First, in the case of cation removal, the acid concentration is 1 to 1.5 times the molar equivalent of the cation to be removed, and more preferably 1 to 1.2 times the molar equivalent of the acid. When the amount of acid added is 1 molar equivalent or less, cations are not sufficiently removed and cations other than protons remain in the gel. Further, when the amount is 1.5 times equivalent or more, Al may be dissolved with a decrease in pH to cause a composition change of Si / Al ratio. Also, although there is no particular limitation on the temperature,
When the temperature is elevated, it is desirable to perform the treatment at around room temperature because it may accelerate the dissolution of Al.

On the other hand, in the case of removing anions, it is important to carry out solid-liquid separation for the purpose of removing anionic compounds by-produced after gel synthesis, and then maintain the pH at 7 or higher and age it. By changing the pH from weakly alkaline to alkaline, the gelation of the unreacted raw material is promoted, and the residual rate of anions can be reduced. This aging effect is promoted by leaving the solid-liquid separated and then allowed to stand in the state of being dispersed in water if the pH is 7 or more, but by heating, the reaction is further promoted and the time is shortened.

As an efficient treatment method for the above-mentioned neutralization hydrolysis, there is a method in which the synthetic gel is maintained at pH 7 or above and aged to bring the anion species to a predetermined concentration or less, and then the cation is removed by adjusting the pH to 3 to 4. Adopted.

The hydrothermal reaction in the present invention can be carried out using an ordinary autoclave or pressure cup.
The slurry concentration, reaction temperature, and reaction time in the hydrothermal reaction are not particularly limited, but the slurry concentration is preferably 1 to 20 wt%, the reaction temperature is 100 ° C. or higher, and the reaction time is preferably 1 hour or longer. If necessary, the reaction time can be shortened by performing stirring and / or adding seed crystals. By performing the above-described processing, it becomes possible to synthesize kaolinite with a production rate close to 100%.

[0032]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these.

(Example 1) No. 3 water glass (S
iO ₂ = 29.3 wt%, Na ₂ O = 9.35 wt%) and aluminum sulfate (Al ₂ O ₃ = 8.02 wt%),
The raw materials were continuously mixed while stirring so that the molar ratio was Si / Al = 1. At the same time, a silica-alumina gel was prepared by adding sodium hydroxide and neutralizing it so that the reaction pH was 10-12. When the composition of this gel was analyzed, the molar ratios were Si / Al = 1 and Na / Al =
0.81 was SO ₄ ion = 25000 ppm.

This synthetic gel was ion-exchanged with sodium in the gel using an ion-exchange resin. Ion exchange resin is Organo's cation exchange resin Amberlite 2
00C (functional group = sulfonic acid, ion exchange capacity = 1.7)
5 meq) was used twice as much as the amount of sodium in the gel, and ion exchange was performed at room temperature. When the composition of this gel was analyzed again, the molar ratios were Si / Al = 1, Na /
Al = 0.01 and SO ₄ ions = 10000 ppm.

Next, anion exchange resin Amberlite I manufactured by Organo is used for ion exchange and removal of SO ₄ ions.
After RA-900 (functional group = alkyl ammonium, ion exchange capacity = 1.0 meq) was exchanged for OH form, ion exchange operation was performed 3 times at room temperature using 5 times equivalent amount of SO ₄ ion in the gel. The composition of the synthetic gel at this time was Si / Al = 1, Na / Al = 0.01, and SO ₄ ions = 2000 ppm in molar ratio.

The above raw materials were charged into an autoclave so that the slurry concentration was 10 wt%, and hydrothermal reaction was carried out at 220 ° C. for 10 days. After cooling, the product was washed with water, filtered and dried to obtain a product. The X-ray-diffraction result of the obtained product is shown in FIG.

The product showed only the X-ray pattern of kaolinite. Further, the weight loss of the kaolinite due to dehydration of the structured water was measured by thermogravimetric analysis (TG) to quantify the amount of kaolinite produced, and the content of kaolinite in the product was 98%.

Comparative Example 1 A product was obtained by performing the same operation as in Example 1 except that ion exchange was not carried out. The X-ray diffraction pattern of the obtained product is shown in FIG.

As is clear from FIG. 4, the peak of kaolinite does not appear in the X-ray diffraction pattern.

(Comparative Example 2) A product was obtained in the same manner as in Example 1, except that SO ₄ ions were not removed by the anion exchange resin. The X-ray diffraction pattern of the obtained product is shown in FIG.

As is apparent from FIG. 5, in addition to the kaolinite peak, aluminum sulfate hydrate (2θ = 15.5)
It can be seen that (°, 17.9 °, 29.9 °) coexist. The production rate of kaolinite by thermogravimetric analysis was 78%.

Example 2 The synthetic gel of Example 1 (molar ratios of Si / Al = 1, Na / Al = 0.81, SO ₄ ion = 25000 ppm) was added to an aqueous ammonium nitrate solution corresponding to 4 times the molar amount of sodium salt. It was dispersed and exchanged with ammonium ion at room temperature. After this operation was performed 4 times, the composition of the gel was analyzed.
= 0.98, Na / Al = 0.005 , SO 4 ion =
It became 1800 ppm.

After washing with water, filtering and drying, in air,
Firing treatment was performed at 600 ° C. for 2 hours to decompose and remove ammonia. Quantitative analysis according to total nitrogen by pressure acid decomposition-steam distillation titration method revealed that ammonium ion was outside the detection limit. This gel was pulverized to a size of 250 μm or less, classified, made into a slurry of 15% with pure water, charged in a titanium autoclave, and hydrothermally treated at 250 ° C. for 3 days while stirring.

The X-ray diffraction pattern of the obtained product is shown in FIG.
And the kaolinite production rate by thermogravimetric analysis was 100%.

Example 3 The synthetic gel of Example 1 (Si / Al = 1, Na / Al = 0.81, SO ₄ ion = 25000 ppm in molar ratio) was filtered and washed to obtain by-produced sodium sulfate and water. After removing sodium oxide, pH =
The slurry was adjusted to 10, and heat treatment was performed at 100 ° C. for 1 hour to dissolve the residual SO ₄ ions. Then nitric acid was added dropwise to control the pH to 3 to 4 and aged in a greenhouse for 24 hours. After exchanging sodium ions with protons, filtration and washing were carried out to elute and remove sodium ions to obtain a gel for hydrothermal treatment. did. When the composition of this gel was analyzed, the molar ratios were Si / Al = 1, Na / Al = 0.003, SO ₄
The ion was 1000 ppm.

The above gel was placed in an autoclave so that the slurry concentration was 10 wt%, and was hydrothermally treated at 220 ° C. for 10 days. The X-ray pattern of the obtained product showed a kaolinite pattern as in FIG. The kaolinite production rate by thermogravimetric analysis was 98%.

[0047]

As described above, the silicate aqueous solution and the aluminum compound aqueous solution are mixed and gelled so that the pH becomes 4 to 12, and then the molar ratio of the cations contained in the gel is 0.02 or less relative to Al. In addition, the content of anion species is 300
After controlling the content to 0 ppm or less, the gel is hydrolyzed as it is or after being calcined, so that kaolinite having a higher production rate than in the past can be synthesized.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of residual cations in a gel on the production rate of kaolinite during hydrothermal treatment.

FIG. 2 is a diagram showing the effect of residual anions in the gel on the kaolinite production rate during hydrothermal treatment.

FIG. 3 is an actual measurement diagram showing an X-ray diffraction result of the product obtained in Example 1.

FIG. 4 is an actual measurement diagram showing an X-ray diffraction result of the product obtained in Comparative Example 1.

5 is an actual measurement diagram showing an X-ray diffraction result of the product obtained in Comparative Example 2. FIG.

Front Page Continuation (72) Inventor Ritsuro Miyawaki 199 Sunahara-cho, Nishi-ku, Nagoya, Aichi Prefecture (72) Inventor Setsuo Yoshida 23-3 Nagata-cho, Shinnanyo-shi, Yamaguchi (72) Inventor Yasushi Osaki 4 New Nanyo-cho, Yamaguchi Prefecture 3-chome 10-306 (72) Soichiro Samejima 2-6-10 Miyanomae, Shinnanyo-shi, Yamaguchi Prefecture East Soryo Dormitory (72) Inventor Shigeo Satokawa 2-14-8 Tabata, Kita-ku, Nagoya, Aichi Prefecture Examiner Koji Amamiya

Claims (1)

[Claims] 1. A silicate aqueous solution and an aluminum compound aqueous solution are mixed to cause gelation in a pH range of 4 to 12, and then the molar ratio of cations contained in the gel is 0.0 to Al.
A high production rate kaolinite production method, characterized in that the content of anion species is controlled to 2 or less and 3000 ppm or less, and then the gel is hydrothermally treated as it is or after being subjected to a calcination treatment.