JPH0455976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing A-type zeolite having a small particle size and uniformity. In recent years, the use of zeolites has been expanding, as zeolite builders in detergent compositions, and as fillers in polymeric materials such as natural and synthetic rubber compositions and plastic compositions, and in various papers. Furthermore, the use of zeolites in fields such as pigments, adhesives, and fibers is also being planned. Zeolites used in these fields are required to be chemically stable, homogeneous, and composed of fine particles. The fine A-type zeolite obtained by the present invention is suitable for use in the above-mentioned fields in view of its physical properties. As a method for producing A-type zeolite, for example,
Hydrothermal synthesis methods using aluminate-silicate-alkali-water mixtures are generally known, as described in USP 2,882,243. In this case, the above-mentioned raw material mixture is usually crystallized into type A zeolite, which is sparingly soluble in water, using a reaction at high temperatures. On the other hand, alumina hydrate (Al ₂ O ₃ xH ₂ O) or silica-alumina clay minerals may be used instead of the aluminates mentioned above, and silica gel may be used instead of silicate to absorb dioxide such as activated silicic acid. A method for synthesizing type A zeolite using silicon as a starting material has also been published. Type A zeolites obtained by these known methods tend to have large particles, making it difficult to use them in the above-mentioned fields where fine particles are required. On the other hand, for the purpose of obtaining A-type zeolite consisting of fine particles, during its hydrothermal synthesis, stirring at 3000 to 5000 rpm using a high-speed stirrer,
Alternatively, the use of turbine agitators, phase gear resolvers, dispersion pumps, whirlpool pumps, circulation pumps, etc. has also been published as a method of applying shearing force to the reaction products to make particles finer (Japanese Patent Application Laid-Open No. 1983-1998-
70289, JP-A-51-84790). However, the above-mentioned micronization method based on mechanical means consumes a large amount of electric power, so it cannot be said to be an economical method, and there is also a limit to the degree to which particles can be micronized using such a method. As a result of further intensive study on the invention described in the above patent application, the present inventor has discovered the composition of the raw material liquid used, the method of producing the slurry liquid, the aging process of the slurry liquid, and the amorphous aluminosilicate constituting the slurry liquid. The heating rate of the slurry liquid for crystallization of the sol, the alkalinity of the aqueous phase during the manufacturing process, and especially the fluctuation of alkalinity during the entire manufacturing process, significantly affect the quality of the final A-type zeolite. The present invention has been completed based on the discovery that it provides the following properties. An object of the present invention is to provide easily and inexpensively a type A zeolite consisting of ultrafine particles with an average primary particle size of 2.5 μm or less. Another object is to provide a Type A zeolite useful as a builder for detergents and as a filler for polymeric materials. That is, the method for producing ultrafine particle size A-type zeolite of the present invention includes: (A) an aqueous solution in which an alkali metal aluminate and an alkali metal hydroxide are dissolved (hereinafter referred to as liquid a); When preparing three liquids: an aqueous solution in which an alkali metal silicate is dissolved (hereinafter referred to as liquid B) and an aqueous solution in which an alkali metal hydroxide is dissolved (hereinafter referred to as liquid C), The contents of alkali metal aluminate and alkali metal silicate in liquids a and b are Al ₂ O _3
M2O / _Al2O3 = 1.1 to _{4.4 SiO2} / _Al2O3 = _{1.2 to 2.3} (M represents an alkali metal). In addition, the alkalinity of liquids a and b is adjusted so that the alkalinity of liquids a and b is adjusted such that the alkalinity of the aqueous solution phase changes during each step during the entire process from the second step to the fourth step below. A first step of preparing each solution so that the alkalinity of the c solution is within ±0.2N, while the alkalinity of the c solution is 1.4 to 3.5N; (B) Each of the prepared solutions was heated to a temperature of 55°C or lower,
Liquids A and B are injected simultaneously from the start to the end of the stirring into liquid C through independent injection ports to generate a slurry liquid consisting of amorphous aluminosilicate sol. Second
(C) A third step of aging the slurry liquid while stirring it while maintaining the liquid temperature at 55°C or less; (D) Next, the aged slurry liquid is aged while stirring, a fourth step of crystallizing the aluminosilicate produced by raising the temperature to a temperature of at least 70°C or higher and subsequently heating at that temperature; (E) finally, fractionating the crystallized aluminosilicate; It is characterized by comprising a fifth step of washing, washing with water, and drying. In the present invention, the alkalinity refers to the alkalinity obtained by taking a certain amount of the aqueous solution phase, diluting it with water if necessary, adding phenolphthalein as an indicator, and performing neutralization titration with a standard hydrochloric acid solution. regularity of
(N). First, the first step of the present invention will be explained in detail. a
The liquid is alkali metal aluminate (MAlO ₂ )
and alkali metal hydroxide (MOH) dissolved in water. It is prepared by adding aluminum hydroxide or aluminum salts to an aqueous solution containing excessively dissolved alkali. Examples of alkali metal aluminates include sodium aluminate and potassium aluminate. This liquid serves as a source of alumina (Al ₂ O ₃ ) and some alkali (M ₂ O) necessary for the synthesis of A-type zeolite. Liquid b is an aqueous solution in which an alkali metal silicate (M ₂ O·nSiO ₂ , generally n=0.5 to 4) is dissolved, for example, sodium silicate, potassium silicate, or water glass is dissolved in water. Prepare.
At this time, the aqueous solution is hydrolyzed and becomes alkaline. In addition, in order to adjust the alkalinity fluctuation described later, the alkalinity of the liquid may be adjusted by actively adding and dissolving an alkali metal hydroxide. This liquid serves as a source of silica (SiO ₂ ) and some alkali (M ₂ O) necessary for the synthesis of A-type zeolite. On the other hand, C liquid is an aqueous solution in which alkali metal hydroxide is dissolved so that the alkalinity falls within the range of 1.4 to 3.5, and the concentration, or alkalinity, is determined for the alkalinity fluctuation control adjustment described below. need to be oriented in advance. Furthermore, when preparing these three solutions, first of all, in solutions a and b, the respective contents of alkali metal aluminate and alkali metal silicate dissolved therein are equal to or less than the total M ₂ based on Al ₂ O ₃ . Each molar ratio of O and SiO ₂ satisfies M ₂ O / Al ₂ O ₃ = 1.1 to 4.4 SiO ₂ /Al ₂ O ₃ = 1.2 to 2.3 (where M represents an alkali metal). At the same time, the alkalinity of liquids a and b is determined during the entire process from the second step (slurry liquid generation step) to the fourth step (crystallization step), which will be described later. The alkalinity of the liquid must be adjusted to within ±0.2N of the alkali of the previously prepared c liquid. As the alkali metal in the present invention, as mentioned above, sodium or potassium is generally preferred since it exhibits strong alkalinity, but sodium is more preferred since it is inexpensive. Each of the solutions thus prepared is maintained at a temperature of 55° C. or less and mixed in the second step of the present invention as described below to produce a slurry liquid consisting of an amorphous aluminosilicate sol. In other words, liquids A and B are gradually injected into the stirring liquid C from independent injection ports from the start to the end of the injection, and an amorphous form is formed depending on the injection amount. A slurry liquid consisting of aluminosilicate sol is produced. By doing so, the slurry particles produced can be extremely fine particles with an average primary particle size of 0.5 μm or less, and have a narrow particle size distribution, that is, homogeneous particles with uniform particle sizes. can get. This ultimately leads to the extremely fine particle size of type A zeolite (final product), which is a feature of the present invention. When injecting liquids A and B into liquid C, from the start of the injection to the end,
It is preferable to continuously inject at a constant rate (however, the injection speeds for liquids A and B are different depending on their predetermined injection amounts), and it is said that the particle size distribution of the generated slurry will be narrower. Tend. The composition of the amorphous aluminosilicate obtained in this step is the general formula _of A-type zeolite: (1.0±0.2) _M2O・_Al2O3・(1.85±0.5) _SiO2・
It was confirmed that the composition was in the xH ₂ O composition range. Furthermore, if slurry is generated in a temperature range of 55℃ or higher, some amorphous substances will crystallize as the temperature increases.
As a result, amorphous particles and crystal particles coexist, and the shapes of the particles become irregular. Even when such a slurry liquid is crystallized, the shape distribution of the zeolite particles obtained becomes broader, and fine homogeneous particles tend not to be obtained. Next, it is easy to maintain the alkalinity of the produced slurry mixture and the molar ratio of the raw materials within the above-mentioned ranges. That is, a
The above-mentioned three types of raw material liquids are prepared separately so that the predetermined alkalinity and molar ratio of the raw material substances are maintained when the mixing of the liquid, B liquid and C liquid is completed according to the above operation. This is because the composition and alkalinity of these liquids may be adjusted in advance.
Further, according to the raw material liquid addition method of the present invention, there is an advantage that the slurry mixture can be always produced with the alkalinity kept almost constant. That is, as liquids A and B are separately injected into a stirring reaction tank containing liquid C, the amount of slurry mixture produced gradually increases, but the alkalinity in the reaction tank increases. The alkalinity is kept approximately constant during slurry production, and is adjusted in the present invention to be approximately the same as the alkalinity of the pre-prepared c-liquid. By mixing these raw material liquids while keeping the alkalinity constant, a slurry liquid containing extremely fine, homogeneous particles with little compositional variation can be obtained. The characteristics of slurry particles made of poorly water-soluble amorphous aluminosilicate sol produced by carrying out the method of mixing raw materials unique to the present invention as described above are summarized as follows. (i) In the present invention, since slurry particles are generated under conditions where the alkalinity is kept constant, particles that are homogeneous and have the same composition range as A-type zeolite can be obtained. (ii) The particles obtained by this method have a fine structure, the shape and size of the particles are uniform, and the average particle diameter of the primary particles is 0.5 μm or less. (iii) By keeping alkalinity and temperature constant;
The particles are extremely fine because care has been taken to ensure that the particles produced are uniform and that their growth is also uniform. Therefore, it has the advantage that it has a large surface area and high activity, and can be crystallized into type A zeolite in an extremely short time. (iv) There is little variation in the chemical composition of the amorphous aluminosilicate obtained by this method. This amorphous material has ion exchange ability and also exhibits a fairly high calcium or magnesium binding ability (see Example 1). (v) The purity of the A-type zeolite obtained from the slurry of this method is extremely high, and the by-products such as amorphous substances and other X-type zeolites and P-type zeolites are suppressed to a minimum. Next, after completing the generation of the slurry liquid, in the present invention, the slurry liquid is aged (third step). Aging is carried out by keeping the slurry liquid under stirring and keeping the liquid temperature below 55°C. The aging step is carried out for the purpose of making the produced particles more homogeneous, and the required time is sufficient within several hours, for example within 2 hours. The alkalinity of the slurry liquid in the main ripening step fluctuates only slightly, and its alkalinity is kept almost the same as that of liquid c prepared in the first step. After completing the maturing step of the slurry liquid, the temperature of the slurry liquid is raised while stirring to reach a predetermined temperature, and crystallization is performed (fourth step). In the process of raising the temperature of the slurry liquid, a sudden temperature rise was avoided to minimize the possibility that the temperature distribution in the reaction tank would become uneven during the temperature rise and the growth of particles would become uneven. It's better. The temperature increase rate is preferably 80℃/hr or less.
30 to 80°C/hr is a very preferable range. Next, the crystallization process of type A zeolite will be described.
Crystallization of A-type zeolite depends on alkali concentration, temperature,
Affected by factors such as time. In this crystallization step, the temperature of the reaction tank is maintained at at least 70° C. or higher, and the alkalinity of the aqueous solution phase is maintained approximately the same as that of the c liquid prepared in the first step. If the crystallization temperature is lower than 70° C., it is not economical because the time required for crystallization increases as the temperature decreases. On the other hand, when the liquid temperature exceeds 110°C, the liquid boils under normal pressure, so it is necessary to carry out the process under pressure. The crystallization temperature range is preferably 75 to 109°C, more preferably 80 to 105°C. If the crystallization is carried out in the temperature range from 80 to 105°C, its duration is at most 2 hours. After undergoing such a crystallization step, the slurry liquid is cooled and then separated into a crystallized aluminosilicate phase (type A zeolite phase) and a mother liquid phase by another method or a centrifugation method. The separated A-type zeolite phase is washed with hot water to remove free alkali, and then dried to obtain the desired A-type zeolite phase.
type zeolite is obtained. The A-type zeolite thus obtained is composed of ultrafine particles with an average primary particle size of 2.5 μm or less, and has excellent ion exchange and adsorption properties, and can be used as a builder for detergents or as a filler for polymeric materials. It is extremely useful as such. EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited thereto. Example 1 Liquids a, b, and c, which are the starting materials of the present invention, were prepared as follows. Liquid a Aluminum hydroxide [Al(OH) ₃・xH ₂ O;x
3] 32.3 kg and 39.1 kg of 49% sodium hydroxide solution were collected, and water was added thereto and dissolved by heating to prepare a sodium aluminate solution containing excess alkali. The total volume of this solution was finally maintained at 72.5 by adding more water. The alkalinity of the prepared solution a was 7.17N. Solution b 70 kg of sodium silicate, which is specified as a No. 3 product in JIS K1408-1966, was collected, and water was added to it to maintain the total liquid volume at 71 kg. The alkalinity of the prepared solution b was 2.72N. Solution C Water was added to 15.9 kg of 49% sodium hydroxide solution to maintain the total liquid volume at 71.5 kg. The alkalinity of the prepared c liquid was 2.73N. While putting the above C liquid into a reaction tank and maintaining it under stirring at 200 rpm, liquids A and B were added to it.
Both liquids were injected continuously at a constant rate from separate injection ports, and the injection of both solutions was completed within _the same time ( _{70 minutes ) .} A slurry liquid consisting of O was produced. The temperature of these three liquids was maintained at approximately 40°C from the start to the end of injection. Subsequently, the obtained slurry liquid was aged at a temperature of 40 to 42°C for 55 minutes while stirring at 200 rpm. After aging, the slurry liquid is
The temperature was raised at a temperature increase rate of 36°C/hr while stirring at 250 rpm, and crystallization of type A zeolite was finally carried out at a temperature of 100±2°C for 2 hours. During the manufacturing process, samples of the aqueous and solid phases were taken and tested. After the crystallization was completed, the reaction tank was water-cooled and maintained below 60°C. Next, two-phase separation of the A-type zeolite phase and the mother liquor was performed by centrifugation. The resulting A-type zeolite phase was washed with warm water at about 50°C to remove free alkali therein. In this case, the A-type zeolite phase was washed with hot water until the pH of the liquid reached around 10. Type A zeolite that has been washed with water is 100
After drying at around °C, it was pulverized to obtain 50.7 kg of crystalline fine powder of A-type zeolite. The type A zeolite obtained in this example has a true specific gravity of 2.20, a specific surface area of 669 m ² /g, and a chemical composition of 0.98Na ₂ O・Al ₂ O ₃・1.91SiO ₂・xH ₂ O. The average primary particle size was 1.8 μm. On the other hand, the average primary particle size of amorphous aluminosilicate particles generated when mixing raw materials is
0.2μm

[Table] The following is 1.02Na ₂ O・Al ₂ O ₃・
It had a chemical composition of 2.19SiO ₂ xH ₂ O. Table 1 shows the alkalinity of the aqueous solution phase in this manufacturing process. As is clear from Table 1, the alkalinity in each step of the present invention is within the range of 2.73 to 2.83N, and the variation in alkalinity is slight. Throughout the entire process of mixing, aging, heating, and crystallizing the raw material liquid, the alkalinity of any aqueous solution phase is maintained at approximately the same value as that of the initially prepared raw material liquid c. By minimizing variations in alkalinity throughout the entire synthesis process, it is possible to produce homogeneous, highly pure, type A zeolite with ultrafine particle size. As described above, the ultrafine type A zeolite obtained by the present invention has physical properties suitable as a zeolite builder for detergents and as a filler for polymeric materials. Table 2 shows the binding ability of type A zeolite obtained according to the present invention to calcium and magnesium. Calcium binding capacity is 10
Minutes

[Table] It was found that the concentration reached an almost constant value (180CaOmg/g) after a period of time. This is a preferable value for a zeolite builder for detergents. As shown in the description, the magnesium binding capacity of this product is after 10 minutes.
56MgOmg/g, 77MgO after 20 minutes
Indicates mg/g. On the other hand, the amorphous aluminosilicate produced at the end of mixing the raw materials (at the end of the first step) had the calcium binding capacity value as shown.

Claims (1)

[Scope of Claims] 1 (A) An aqueous solution (hereinafter referred to as liquid a) formed by dissolving an alkali metal aluminate and an alkali metal hydroxide, and an aqueous solution formed by dissolving an alkali metal silicate. When preparing three liquids: an aqueous solution (hereinafter referred to as liquid B) and an aqueous solution containing an alkali metal hydroxide (hereinafter referred to as liquid C), liquids a and b are aqueous solutions containing an alkali metal hydroxide. The content of aluminate and alkali metal silicate is Al ₂ O _3
M2O / _Al2O3 = 1.1 to _{4.4 SiO2} / _Al2O3 = _{1.2 to 2.3} (M represents an alkali metal). In addition, the alkalinity of liquids a and b is adjusted so that the alkalinity of liquids a and b is adjusted such that the alkalinity of the aqueous solution phase changes during each step during the entire process from the second step to the fourth step below. A first step of preparing each solution so that the alkalinity of the c solution is within ±0.2N, while the alkalinity of the c solution is 1.4 to 3.5N; (B) Each of the prepared solutions was heated to a temperature of 55°C or lower,
Liquids A and B are injected simultaneously from the start to the end of the stirring into liquid C through independent injection ports to generate a slurry liquid consisting of amorphous aluminosilicate sol. Second
(C) A third step of aging the slurry liquid while stirring it while maintaining the liquid temperature at 55°C or less; (D) Next, the aged slurry liquid is aged while stirring, a fourth step of crystallizing the aluminosilicate produced by raising the temperature to a temperature of at least 70°C or higher and subsequently heating at that temperature; (E) finally, fractionating the crystallized aluminosilicate; A method for producing ultrafine particle size A-type zeolite, which comprises a fifth step of washing, washing with water, and drying. 2. The method for producing ultrafine particle size A-type zeolite according to claim 1, wherein the alkali metal in the first step is sodium. 3 In the second step, when injecting liquid a into liquid c, ultrafine particle size A according to claim 1, which is continuously injected at a constant rate from the start to the end of injection.
Method for producing type zeolite. 4. In the second step, when liquid B is injected into liquid C, ultrafine particle size A according to claim 1 is continuously injected at a constant rate from the start to the end of injection.
Method for producing type zeolite. 5 In the fourth step, increase the temperature of the slurry liquid to 30~30℃.
A method for producing ultrafine particle size A-type zeolite according to claim 1, which is carried out at a heating rate of 80° C./hr. 6 In the fourth step, increase the temperature of the slurry liquid to 75
A method for producing ultrafine particle size A-type zeolite according to claim 1 or 5, which is carried out up to a temperature of 109°C.