KR950004769B1 - Process for the production of erystalline sodium silicate - Google Patents

Abstract

The crystalline sodium silicate, useful as ion exchanger, was manufactured by adding solid sodium hydroxide or aqueous sodium hydroxide to solution type sodium silicate having 2.0 - 4.0 mole ratio of SiO2/Na2O to obtain liquid glass which was adjusted to 2.0 ± 0.2 mole ratio of SiO2/Na2O and then 0.5 - 5 times water soluble organic solvent was added to them on the basis of water amount to precipitate the amorphous sodium silicate. The filtrate was heated for extracting the crystalline sodium silicate.

Description

Method for preparing crystalline sodium silicate

The present invention relates to a process for preparing crystalline sodium silicate which can be used as ion exchanger from liquid sodium silicate.

Crystalline sodium silicate exists in various ways, such as a thing which exists naturally and synthesize | combined artificially. To be present in the natural is sodium in room light _{(Natrosilite, Na 2 Si 2 O} 5), Mark die bit _{(Magadiite, Na 2 Si 14 O} 29 · 11H 2 O), kenyayi agent _{(Kenyaite, Na 2 Si 22 O} 45 10H ₂ O), makatite (Na ₂ Si ₄ O ₉ 5H ₂ O), kanemite (kan emite, NaHSi ₂ O ₅ 3H ₂ O), and the like are known. Artificially synthesized things are known in the formula, such as Na ₂ Si ₂ O ₅ , Na ₂ Si ₃ O ₇ , Na ₆ Si ₈ O _19, and there are many crystal forms corresponding to each formula There can be many kinds of crystals synthesized.

Crystalline sodium silicate can be used as a filler in rubber, plastics, paper, and the like, and in particular, since these crystals have ion exchange capacity, ion exchange as described in US Pat. No. 4,664,839 and US Pat. No. 4,820,439. Can be used as a zero. To use as an ion exchanger, it is advantageous to have a high content of sodium.

There are two methods for preparing crystalline sodium silicate: a hydrothermal process and a phase change method by high temperature firing.

U.S. Patent No. 4,806,327 discloses an aqueous solution containing Na ₂ O and SiO ₂ components in a reactor, the crystal nuclei of the crystals to be produced are added, followed by the stepwise addition of phosphoric acid at a relatively low temperature (70-250 ° C.). The hydrothermal method of adjusting the pH is described. According to this method, crystalline sodium silicate with low sodium content is produced, such as Na ₂ Si ₂₂ O ₄₅ .xH ₂ O, Na ₂ Si ₁₄ O ₂₉ .xH ₂ O, and the like.

The phase change method by high temperature firing is a method of first obtaining amorphous sodium silicate from a suitable source of SiO ₂ and Na ₂ O, and calcining the amorphous sodium silicate at high temperature to obtain crystalline sodium silicate. Crystalline sodium silicate having a high content of sodium such as, Na ₂ Si ₂ O ₅ , Na ₂ Si ₃ O ₇ , Na ₆ Si ₈ O _19, and the like is produced. The method for producing crystalline sodium silicate by the phase change method by high temperature firing can be roughly divided into several methods depending on the preparation method and processing methods of amorphous sodium silicate.

An example of producing amorphous sodium silicate is a method obtained by reacting quartz with sodium carbonate or sodium hydroxide at a temperature higher than the melting temperature, followed by quenching. The crystal form of crystalline sodium silicate, which can be obtained by preparing amorphous sodium silicate having a composition of Na ₂ Si ₂ O ₅ and then subjected to high temperature treatment, has various forms such as α _Ⅰ , α _Ⅱ , α _Ⅲ , β, γ, δ, etc. A branch exists. α forms are ideally present between 700 and 850 ° C., which can be obtained by heating amorphous sodium silicate obtained by melting and quenching sodium carbonate and quartz at 800 to 850 ° C. for 12 to 24 hours. It is known that at this temperature range equilibrates from low temperature to α _III , α _II , α _I , and the ideal transition temperatures between the phases are 680 and 707 ° C., respectively. β-type can be obtained by treating amorphous sodium silicate obtained above at 600-650 ℃ for 18-24 hours, and this crystal phase is transformed to α-type when heat treated again at high temperature of 700 ℃ It does not go back to β. Forms γ and δ are known to be crystalline forms present near 610 ° C., but this method is not easy to manufacture, and in most cases a mixture of the two is obtained. Melting and thus quenching to produce amorphous sodium silicate is disadvantageous because the temperature is required to be 1000 ℃ or more and the reaction time is very long.

Another method for producing amorphous sodium silicate is a method obtained by simply drying liquid sodium silicate (water glass) having a suitable molar ratio of SiO ₂ / Na ₂ O. When amorphous crystalline sodium silicate prepared in this manner is used to grow crystals at high temperature to produce crystalline sodium silicate, even if the molar ratio or firing temperature of SiO ₂ / Na ₂ O is controlled, it is difficult to obtain the desired single crystalline form and various forms. A mixture of crystals is obtained.

In order to solve this disadvantage, U.S. Patent No. 4,585,642 discloses amorphous sodium silicate by drying liquid sodium silicate, and when crystals are grown at high temperature, crystals of the form to be produced are crystallized to 100 parts of amorphous sodium silicate. A method of crystallizing by adding 1 to 15 parts by weight relative to the weight has been proposed.

Other methods include K. Beneke et al. (Am. Mine ralogist, Vol. 62, page 663 (1977)). In this method, 1 mol of SiO ₂ is dispersed in 100 ml of methanol, and then, 1 mol of sodium hydroxide is dissolved therein, followed by the slow addition of a cooled saturated aqueous solution to react, but the temperature is controlled not to be higher than room temperature to form amorphous sodium silicate. It was heated at a suitable temperature (700 ° C.) for 5.5 hours to produce crystalline sodium silicate, but the temperature control is complicated in this method.

As described above, in the case of producing crystalline sodium silicate by a conventional method, there is a disadvantage that various crystals are mixed unless the crystal of the desired form is added as crystal nuclei in advance.

Accordingly, it is an object of the present invention to provide an improved process for the preparation of crystalline sodium silicate, which can obtain a single form of sodium silicate crystals without the addition of nuclei.

The structure and species of silicon oxide ions present in liquid sodium silicate depend on the SiO ₂ / Na ₂ O and H ₂ O / Na ₂ O molar ratios, that is, the amount of alkalinity and solids, and also the temperature. Therefore, when heating to dry the liquid sodium silicate, the concentration of the solution is gradually changed as the water is removed, so that the fine structure of the amorphous sodium silicate produced may be different from that produced initially and gradually produced thereafter. When crystals are made of amorphous sodium silicate obtained by simply drying in an electric oven or the like, it appears that various crystals are mixed.

In view of this, the present inventors do not simply dry the liquid sodium silicate and, as described below, make an aqueous solution in which the molar ratio of SiO ₂ / Na ₂ O is suitably adjusted, and add a water-soluble organic solvent to the amorphous silicic acid. It has been found that some form of crystals can be obtained by making a precipitate of sodium, drying it and crystallizing at high temperatures.

In the method for preparing crystalline sodium silicate of the present invention, an aqueous solution having a constant molar ratio of SiO ₂ / Na ₂ O is added to liquid sodium silicate to solid sodium hydroxide or an aqueous sodium hydroxide solution, and an aqueous solution of water-soluble organic solvent is added to the amorphous solution to be amorphous. Sodium silicate precipitate was produced, and the precipitate was filtered off, dried, and calcined.

In the present invention, by adding a solid sodium hydroxide or an aqueous sodium hydroxide solution to the liquid sodium silicate to adjust the molar ratio of SiO ₂ / Na ₂ O, liquid sodium silicate of a specific composition is not required.

The liquid sodium silicate used in the method of the present invention has one, two, three, four, or similar compositions of the Korean Industrial Standards, and it can be used if the molar ratio of SiO ₂ / Na ₂ O is 2.0 to 4.0. It is possible. Impurities do not have to be greatly considered, but it is preferable that the iron content is 0.03% or less and the insoluble component is 0.2% or less. To prepare Na ₂ Si ₂ O ₅ having a molar ratio of SiO ₂ / Na ₂ O of 2.0, sodium hydroxide may be added to the liquid sodium silicate listed above to adjust the molar ratio of SiO ₂ / Na ₂ O to within 2.0 ± 0.2. Preferably, the molar ratio should be adjusted within the range of 2.0 ± 0.1. The amount of solids in the liquid sodium silicate with adjusted molar ratio of SiO ₂ / Na ₂ O ranges from 10 to 60%. Although not limiting, the amount of solids is preferably in the range of 30 to 50% in consideration of the amount of the organic solvent. As described above, in the present invention, the molar ratio of SiO ₂ / Na ₂ O can be started from a wide range of liquid sodium silicate, and since the use range is wide even in the solid content of the desired final liquid sodium silicate, SiO ₂ / Na ₂ O When adjusting the molar ratio, it is possible to use a solid solution of sodium hydroxide or an aqueous solution of a wide concentration range, which has a wide range of operating conditions. When sodium hydroxide is added for molar ratio adjustment, the temperature does not need to be particularly adjusted.

As the organic solvent, ones such as methanol, ethanol, propanol, dimethyl sulfoxide, dimethylformamide or acetone can be used. In terms of cost and performance, alcohols are suitable, especially since methanol is inexpensive and easy to recover. When the organic solvent is added, the temperature does not need to be given a specific temperature range, but may be performed under ambient temperature, so that the temperature does not need to be adjusted separately, such as cooling or heating.

Although the amount of the organic solvent is slightly different depending on the container solvent to be used, it is generally preferable to use 0.5 to 5 times, preferably 1 to 2 times by weight relative to the amount of water.

The amorphous sodium silicate obtained using an organic solvent is dried at a temperature at which moisture can be dried, i.e., 100 ° C-300 ° C. At this time, in order to increase the drying rate, it is preferable to wash the amorphous sodium silicate using the organic solvent used for precipitation before drying. The moisture content of the dried amorphous sodium silicate is 3 to 25%, preferably about 5 to 20%.

As in the conventional method, amorphous sodium silicate which is simply dried liquid sodium silicate is difficult to grind due to its high strength, but amorphous sodium silicate precipitated and dried using an organic solvent as in the method of the present invention is simply dried. Compared with another advantage that the grinding is easy.

The firing temperature of the amorphous sodium silicate is 600 to 850 ° C, and the firing time is 2 to 60 minutes.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not intended to be limited thereto.

Example 1

100 g of three kinds of sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of the Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 18.3 g of 40% sodium hydroxide aqueous solution was added and mixed well. 120 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. for drying. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, Na ₂ Si ₂ O ₅ having a δ-type structure was produced as in the X-ray diffraction test results of Table 1.

TABLE 1

Example 2

100 g of three kinds of sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of the Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 18.3 g of 40% sodium hydroxide aqueous solution was added and mixed well. 120 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and washed with 20 ml of methanol. It was placed in an electric oven heated to 100 ° C. and dried. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from 500 ° C. to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 3

100 g of three kinds of sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of the Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 7.3 g of solid sodium hydroxide was added and mixed well. 120 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. to dry. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 4

100 g of three types of liquid sodium silicate of Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 7.3 g of solid sodium hydroxide was added and mixed well. 120 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. and dried. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from 500 ° C. to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 5

100 g of three types of liquid sodium silicate of Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 7.3 g of solid sodium hydroxide was added and mixed well. 120 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. to dry. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 600 ° C., and heated at 600 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 6

100 g of three kinds of sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of the Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 7.3 g of solid sodium hydroxide was added and mixed well. 120 ml of dimethyl sulfoxide was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. and dried. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 7

100 g of three kinds of sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of the Korean Industrial Standard KS M 1415 were placed in a polyethylene container, and 7.3 g of solid sodium hydroxide was added and mixed well. 120 ml of dimethylformamide was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. to dry. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Example 8

100 g of three types of liquid sodium silicate (Na ₂ O: 9.1%, SiO ₂ : 28.5%) of KS M 1415 were placed in a polyethylene container, and a solution of 7.3 g of solid sodium hydroxide in 45 ml of water was added thereto. And well mixed. 40 ml of methanol was added and stirred. As a result, amorphous sodium silicate precipitated. The precipitate was filtered off and placed in an electric oven heated to 100 ° C. to dry. This was pulverized into grains of 100 mesh or less, and 5 g of the amorphous sodium silicate thus pulverized was placed in a nickel crucible. The crucible was placed in an electric furnace, heated up at a rate of 15 ° C./min from normal temperature to 700 ° C., and heated at 700 ° C. for 30 minutes. As a result, δ-type Na ₂ Si ₂ O ₅ was produced.

Claims (6)

A solid sodium hydroxide or aqueous sodium hydroxide solution was added to liquid sodium silicate having a molar ratio of SiO ₂ / Na ₂ O of 2.0 to 4.0 to adjust the solid content of 10 to 60% and the molar ratio of SiO ₂ / Na ₂ O to 2.0 ± 0.2. A water glass aqueous solution was prepared, and an aqueous solution of a glass solvent was added to the aqueous solution in an amount of 0.5 to 5 times based on the amount of water to produce an amorphous sodium citrate precipitate, which was then filtered off and then filtered to 100 to 300 ° C. And drying it at 600 to 850 ° C. for 2 to 60 minutes to produce crystalline sodium silicate. The method of claim 1, wherein the organic solvent is selected from the group consisting of methanol, ethanol, propanol, dimethyl sulfoxide, dimethylformamide and acetone. The method for producing crystalline sodium silicate according to claim 1, wherein the molar ratio of SiO ₂ / Na ₂ O in the water glass aqueous solution is 2.0 ± 0.1. The method for producing crystalline sodium silicate according to claim 1, wherein the content of solids in the water glass aqueous solution is 30 to 50%. The method for preparing crystalline sodium silicate according to claim 1 or 2, wherein the organic solvent is used in an amount of 1 to 2 times based on the amount of water upon precipitation. The process for preparing crystalline sodium silicate according to claim 1, wherein the moisture content of the amorphous sodium silicate precipitate is adjusted to 3 to 25% before firing.