KR100400178B1 - Method of preparing alumina sols of high thixotropy and viscosity - Google Patents

Abstract

The present invention relates to a method for preparing a high viscosity alumina sol having excellent thixotropy, and more particularly, an alkali is added to the discarded aqueous aluminum chloride solution to produce aluminum hydroxide, and then immediately before the acid is added to solvate. By adding a predetermined amount of the polymerized polyaluminum chloride solution [Al ₂ (OH) ₅ Cl] _n , when the conventional alumina sol is used as a base coating or a binder, it takes a lot of time to be immobilized, unlike workability, Rapid viscosity increase and excellent thixotropy make it easy to form the film when coating on the base, and it has excellent binding property. It utilizes waste resources to produce eco-friendly and economical high viscosity alumina sol. It is about a method.

Description

Method of preparing high viscosity alumina sol with excellent thixotropy {Method of preparing alumina sols of high thixotropy and viscosity}

The present invention relates to a method for preparing a high viscosity alumina sol having excellent thixotropy, and more particularly, an alkali is added to the discarded aqueous aluminum chloride solution to produce aluminum hydroxide, and then immediately before the acid is added to solvate. By adding a predetermined amount of the polymerized polyaluminum chloride solution [Al ₂ (OH) ₅ Cl] _n , when the conventional alumina sol is used as a base coating or a binder, it takes a lot of time to be immobilized, unlike workability, Rapid viscosity increase and excellent thixotropy make it easy to form the film when coating on the base, and it has excellent binding property. It utilizes waste resources to produce eco-friendly and economical high viscosity alumina sol. It is about a method.

Unlike the name alumina sol, it refers to a state in which alumina hydrate is not dispersed in water in colloidal form, but is alumina particles, but is conventionally called alumina sol.

Alumina and its hydroxide are one of the typical refractory materials and can be used at high temperatures of 1000 ° C. or higher, and are very stable materials such as oxidizing atmospheres, acids, and alkalis. Therefore, the alumina solvate component is a hydroxide of alumina, but after dehydration at low temperature, it is excellent in oxidation resistance and chemical stability as general alumina porcelain, so that it can be used in areas where high temperature oxidizing atmosphere and erosion to acid or alkali are concerned. In addition, the alumina sol has a form in which very fine alumina hydroxide of several hundred nm or less is simply dispersed in water, but has adhesiveness and binding property that adheres well to the base like a general grass. By utilizing these properties, alumina sol has many uses as a high temperature binder or surface coating agent.

On the other hand, silica sol, which is currently used as a high temperature binder of inorganic materials, is an inorganic material having an acid of silica itself, and thus easily reacts with and erodes with basic materials such as cement or magnesia.

On the other hand, alumina is one of the representative neutral refractory materials, which does not have erosion to various materials and maintains its properties even at high temperatures, and thus can be regarded as a higher inorganic binder than a silica sol binder. In addition, the alumina sol has the ability to form a film, and thus a good film is formed by drying. The alumina sol also has flexibility because the sol particles have a fibrous structure. In addition, alumina sol has water retention, antistatic property, and ion adsorption property, so it is used for various applications such as fiber surface treatment agent, plastic coating agent, adsorbent, and paint additive.

Among the various applications of alumina, especially when used as a surface coating or binder, it is desirable that the alumina sol has a high thixotropy so that the alumina sol can be set up quickly after the operation. Here, thixotropy is a property of low viscosity when there is an external force and rapid increase of viscosity when there is no external force, that is, the gel turns into a fluid sol by simply stirring or shaking. It is the property of returning to the gel again. As a substance having such thixotropy, an appropriate amount of sodium chloride is typically added to a sol such as aluminum oxide.

On the other hand, as for the general production method of alumina sol, several methods are known. For example, the method of peptizing the precipitate which hydrolyzed aluminum isopropoxide [BE Yoldas, Am. Ceram. Soc. Bull., 54, 289 (1975), Japanese Patent No. Hei 6-64919], a method of peptization of boehmite powder with acid [Japanese Patent No. 59-78925], Bayer from bauxite light Beyer) a method of solvating aluminum hydroxide obtained by reacting NaAlO ₂ as an intermediate raw material produced by an acid, and more recently a method of hydrating metal aluminum powder to produce a stable sol [Japanese Patent No. 7-89717] There is this.

On the other hand, as a study for improving the viscosity characteristics of the alumina sol, Japanese Patent Laid-Open No. 7-291621 dilutes commercially available 10% alumina sol with water to simply dissolve a certain amount of polyaluminum chloride to increase viscosity stability and thixotropy. Here's how. However, this method is judged to be an effect of increasing the amount of ions present in the sol solution by simply dissolving polyaluminum chloride, and the increase in thixotropy in a short period of time is not sufficient for practical use.

Existing alumina sol as described above has room for improvement in thixotropy related to the rate of change of viscosity of the sol or the starting material is expensive.

Thus, the present inventors made an effort to prepare alumina sol at an environmentally friendly and low cost, but to enhance the thixotropy to improve the workability when applied to a surface coating or binder. As a result, an aqueous aluminum chloride solution discarded in the petrochemical process of making styrene monomer or aluminum chloride discarded as a by-product in the aluminum sheet manufacturing process for capacitors is used as a raw material. Through the process of addition and solvation, the rate of increase in viscosity is significantly increased, and the time of setting (coating) the coating on the base is not only shortened, but also has excellent binding properties.

Accordingly, an object of the present invention is to provide a novel and useful method for producing a high viscosity alumina sol having excellent thixotropy and binding property from waste aluminum aqueous solution.

Figure 1 shows the change in viscosity according to the rotor speed of the viscometer after maintaining the alumina sol prepared according to the present invention for 24 hours.

The present invention provides a method for preparing an alumina sol by solvating an aluminum hydroxide precipitate with an acid,

A first step of adding an alkaline solution to an aqueous waste aluminum chloride solution to obtain an aluminum hydroxide precipitate and then aging at 20 to 100 ° C. for 0.1 to 10 hours,

Washing and filtering the precipitate, and then adding a predetermined amount of water and acid to obtain a slurry solution, and

It characterized by the manufacturing method of an alumina sol containing the 3rd process of heat-processing the said slurry solution at 80-130 degreeC for 3 to 30 hours, and obtaining an alumina sol.

In addition, the present invention may further include a step of washing and filtering the aluminum hydroxide precipitate, if necessary, and then leaving it at 10 to 80 ° C. for 0.1 to 24 hours immediately before adding polyaluminum chloride. Thus, when the alumina sol manufactured by the said method is dried, an alumina gel can be obtained, and when this is sintered at 1,000-1,500 degreeC, an alumina sintered compact can be obtained.

The present invention will be described in more detail as follows.

In the first step, an alkaline solution is added to the waste aqueous aluminum chloride solution to obtain an aluminum hydroxide precipitate, and then aged at 20 to 100 ° C. for 0.1 to 10 hours. At this time, the waste aluminum chloride solution may be used aluminum chloride which is discarded as a by-product in the petrochemical process for producing a styrene monomer, aluminum thin plate manufacturing process for the capacitor, etc., it is preferable to use a concentration of 5 to 15% by weight. In addition, as the alkaline solution, an aqueous solution of sodium hydroxide or ammonium hydroxide can be used, and a concentration of 5 to 40% by weight is preferable. And, the aging is carried out to improve the uniformity of the precipitate and to improve the filtration characteristics, there is a problem that requires a long time if the temperature is too low during aging, on the other hand, if the temperature exceeds 100 ℃ has a serious problem of evaporation of water Not desirable

In the second step, the precipitate is washed with water and filtered, and then a polyaluminum chloride aqueous solution is added and then solvated with an acid to obtain a slurry solution. Here, after washing with water and filtering, further including the step of leaving for 0.1 to 24 hours at 20 to 80 ℃ or the addition of an aqueous solution of polyaluminum chloride may affect the rate of viscosity increase and thixotropy of the final sol produced. have. The polyaluminum chloride is used as an aqueous solution of 10 to 30% by weight based on Al ₂ O ₃ , and the aqueous solution is 0.1 to 50% by weight based on the total slurry concentration (converted to Al ₂ O ₃ ), preferably 10 to When added in an amount of 30% by weight, too little addition can not be expected, the addition of too much, there is a problem that the stability of the sol is lowered. In addition, it is preferable to add ion-exchanged water so that the concentration of the final alumina sol (when converted into Al ₂ O ₃ ) is 5 to 15% by weight. Acids such as acetic acid and hydrochloric acid are added in an amount of 0.01 to 0.2 mol, preferably 0.05 to 0.1 mol, per mol of aluminum, followed by stirring at room temperature for about 2 hours to prepare an aluminum hydroxide slurry.

In a third process, the slurry solution is heat treated to complete pseudo boehmite crystalline alumina sol. At this time, the heat treatment is carried out while stirring for 3 to 30 hours at 80 to 130 ℃, preferably for 10 to 15 hours at 90 to 110 ℃, the heat treatment at a temperature of less than 80 ℃ deteriorates the stability of the resulting sol There exists a problem and there exists a problem that a boehmite structure is not obtained in the temperature exceeding 130 degreeC.

In summary, the aluminum chloride solution is neutralized with an alkaline solution to form an amorphous aluminum hydroxide [Al (OH) ₃ ] precipitate, which is subjected to thermal energy under the influence of an acid catalyst. It is judged that alumina sol of pseudo boehmite crystalline form (AlOOH) is produced by the polymerization reaction.

Such alumina sol according to the present invention has a high viscosity increase rate, excellent thixotropy, high viscosity, excellent adhesion and binding properties can be widely applied as a surface coating agent or a high temperature inorganic binder of various media. .

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited to the examples.

Example 1

700 g of a solution of about 13% by weight of aluminum chloride (AlCl ₃ ) was placed in a 2 L three-necked round flask, and neutralized to pH 7 by slowly adding 1000 g of 5% by weight aqueous sodium hydroxide (NaOH) solution while stirring. After completion of the reaction, stirring was continued for about 2 hours to allow aging and homogenization of the precipitate. The resulting aluminum hydroxide precipitate was then filtered and washed twice in succession with 1000 g of ion exchanged water to remove impurities. 68 g of ion-exchanged water, 3.3 g of 25.5 wt% polyaluminum chloride solution, and 6.5 g of 99% acetic acid were added to the washed precipitate, which was stirred for about 1 hour. The total concentration of the resulting alumina sol was converted into Al ₂ O ₃ . It was about 10% by weight. The solution was transferred to a 1 L three-necked round flask and heat treated with stirring at about 100 ° C. for 10 hours to complete an alumina sol.

As a result, the obtained alumina sol increased in viscosity from 340 × 10 ³ CPS to 1800 × 10 ³ CPS after about 3 hours.

Example 2

Next to adjust the amount to the composition as shown in Table 1, the same method as in Example 1 except that the precipitate produced by the neutralization reaction in Example 1 was left at room temperature (20 ℃) for 24 hours after washing with water. An alumina sol was prepared.

As a result, the obtained alumina sol increased in viscosity from 340 × 10 ³ CPS to 2230 × 10 ³ CPS after about 3 hours.

Comparative example

Alumina sol was prepared in the same manner as in Example 1, except that the amount of the composition was adjusted to the composition as shown in Table 1, and poly aluminum chloride was not added thereto.

Test Example 1: Viscosity Rising Rate Measurement

The viscosity change of the alumina sol prepared in Examples 1 and 2 and Comparative Examples was measured with a Brookfield viscometer at a spindle speed of 100 rpm, and the results are shown in Table 2 below.

According to Table 2, in the case of the alumina sol prepared in Examples 1 to 2 it can be seen that the viscosity rapidly increases from about 3 to 5 times after 1 hour respectively.

Test Example 2: Thixotropic Test

Using the same production method as in Example 2, a sol having a polyaluminium chloride content of 0, 15, 30% by weight, respectively, was left for 24 hours and then the viscosity change according to the rotor speed of the viscometer is shown in Indicated.

Referring to FIG. 1, the viscosity of the sol decreases as the rotor rate increases, and the faster the viscosity decrease, the higher the thixotropy. Therefore, it was found that thixotropy improved as the content of polyaluminum chloride increased.

As described above, the high viscosity alumina sol having excellent thixotropy according to the present invention uses a solution of aluminum chloride, which is discarded as an industrial by-product, as a starting material, greatly reducing costs, and when used as a surface coating agent or a binder, solidifies quickly after work. It is not only fixed but also excellent in binding property, and can be effectively used for various applications such as surface coating agents and paint additives of various media.

Claims (8)

In a method of preparing an alumina sol by solvating an aluminum hydroxide precipitate with an acid, A first step of adding an alkaline solution to a waste aluminum chloride solution to obtain an aluminum hydroxide precipitate and then aging at 20 to 100 ° C. for 0.1 to 10 hours, The precipitate was washed with water and filtered, and then an aqueous solution of 10 to 30% by weight of polyaluminum chloride was added within a range of 0.1 to 50% by weight based on the total slurry concentration (in terms of Al ₂ O ₃ ). Step of obtaining a slurry solution by adding to a mol of 0.01 to 0.2 mol per mol of aluminum to obtain a slurry solution, and And a third step of obtaining the alumina sol by heat-treating the slurry solution at 80 to 130 ° C. for 3 to 30 hours. The alumina sol according to claim 1, further comprising a step of leaving the aluminum hydroxide precipitate washed with water and filtered, and then left at 20 to 80 ° C. for 0.1 to 24 hours immediately before adding polyaluminum chloride. Manufacturing method. delete delete delete The method of claim 1, wherein the alkaline solution is an aqueous solution of sodium hydroxide or ammonium hydroxide. Alumina gel, characterized in that the alumina sol prepared by the method of claim 1 is dried. The alumina gel produced by the method of claim 7 is sintered at 1000 ~ 1500 ℃ characterized in that the alumina sintered body.