Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/06—Metal silicides
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
  • C11D3/12—Water-insoluble compounds
  • C11D3/124—Silicon containing, e.g. silica, silex, quartz or glass beads
  • C11D3/1246—Silicates, e.g. diatomaceous earth
  • C11D3/1253—Layer silicates, e.g. talcum, kaolin, clay, bentonite, smectite, montmorillonite, hectorite or attapulgite
  • C11D3/1273—Crystalline layered silicates of type NaMeSixO2x+1YH2O
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
  • C01B33/36—Silicates having base-exchange properties but not having molecular sieve properties
  • C01B33/38—Layered base-exchange silicates, e.g. clays, micas or alkali metal silicates of kenyaite or magadiite type

Definitions

• the present invention relates to a process for preparation of crystalline layered sodium disilicate and more particularly, to an improved process for preparation of crystalline layered sodium disilicate, being useful as a builder for detergent composition or water softener, which is fabricated in a simple manner by adding an aqueous solution of sodium silicate, a binder, to anhydrous sodium disilicate cullet powder used as a starting material, in a certain composition ratio, to give granules and thereafter charging dried granules to a furnace for crystallization process.
• the purity of the product is increased, the preparation process is simplified and the consumption of energy is remarkably reduced, whereas the cost of the product is reduced and also the deposition of reactant in a calcined device is improved.
• cullet as a starting material in the present invention, which has been frequently used as a raw material in the field of preparation of an aqueous solution of sodium silicate, means a compound consisting of small mass or fragments of amorphous sodium silicate formulated in such a manner that silica and sodium carbonate are mixed in a suitable molar ratio [ratio of SiO 2 to Na 2 O, i. e. , (SiO 2 /Na2O)] and then, the mixture is heated and melted at a high temperature of about 1 ,000 ⁇ 1 ,400 ° C and cooled.
• the layered sodium silicate is a crystalline silicate represented by the following formula: Wherein , y/x depends on the crystal structure, and has the value ranging between 2 - 1 1. Among them, crystalline layered sodium disilicate represented by Na 2 Si 2 O 5 has been reported to be present in a -, ⁇ -, ⁇ - and ⁇ -type. Such crystalline layered sodium disilicate has been effectively used not only as a catalyst supporter, but also as a material in various chemical processes such as separation and refining processes, etc. due to its unique absorption property and ion-exchange capacity in terms of structural characteristics.
• ⁇ -crystalline layered sodium disilicate has a higher binding capacity for ions such as Ca 2+ and Mg 2+ that represent hardness in water, it has been recently developed for various uses such as a water softener or a builder for detergent composition, etc.
• the U. S. Patent No. 4,585,642 and the European Patent No. 293,640 comprise adjusting a molar ratio of SiO2:Na 2 O to 1.9 ⁇ 2. 5 using aqueous solutions of both sodium silicate and sodium hydroxide, dehydrating the mixed solution using a spray dryer, and then crystallizing the above dehydrated material at 550 ⁇ 800 ° C .
• Heisei 4-238809 disclosed that an aqueous solution of sodium silicate with the molar ratio of SiO 2 /Na 2 O adjusted to 1.9 - 3.2 is directly introduced into the heating section maintaining the temperature at 680 - 830 ° C to crystallize, thus simplifying its preparing process.
• energy is consumed excessively because of generation of a large amount of vapor in the dehydrating process at high temperature, the crystallization device corrodes easily and the reactant is deposited inside the apparatus when sudden shut-down occurs.
• Other disadvantages are such as a) easy corrosion of the crystallization device, and b) the deposition of reactant inside the apparatus associated owing to sudden shut-down.
• the Japanese Laid-open Patent No. Heisei 3-93649 disclosed that after anliydrous sodium silicate being prepared by adding part of an alumina constituent for improving water-resistance, it is pulverized and crystallized to improve layer-like structure.
• this method has also recognized a shortcoming in that a large amount of impurities are mixed, while particles are sintered to each other.
• Heating and dissolution processing step A large amount of water is first added to the cullet, followed by heating and dissolving the mixture to form an aqueous solution of sodium silicate (water content: 50 - 60 weight %);
• Drying processing step Sodium hydroxide is added to the aqueous solution of sodium silicate to adjust a molar ratio of SiO 2 /Na 2 O to the desirable level, and water(50 - 60 weight %) contained from the above aqueous solution is dried at 140 ° C or higher using a spray dryer;
• Crystallization processing step The intermediate in powder form is charged into the furnace to effect crystallization at 600 - 800 ° C .
• the U. S. Patent No. 5,268,156 employed a method of increasing the bulk density by pulverizing a powder-form intermediate to the particle size of about 1 - 50 ⁇ m so as to prevent products from depositing inside the calcined device and to inhibit the occurrence of dust.
• the U. S. Patent No. 5,183,651 suggested another method of reducing the number of necessary devices and energy costs by improving several complicated processing steps that the conventional methods have encountered hitherto.
• This method has been evaluated as an economical process, since a -crystalline layered sodium disilicate is obtained while several types of crystalline are not mixed.
• this method also there exist some recognized disadvantages in that a) a recycle process of a final product is additionally necessary, and b) the final product cannot be used as a builder for water softener and detergent composition, since the majority of the final product is composed of a -crystalline layered sodium disilicate and has quite lower binding capacity on the hardness constituents in water than ⁇ -crystalline layered sodium disilicate has, as disclosed in the U. S. Patent No.
• the preparing conditions for granules will become more complicated in relation with the amount of water added. For example, if water is less added to cullet powder in terms of its characteristics, the process for preparation becomes difficult and the purity of the final product formed after crystallization becomes poor; in case of using too much water, the resulting slurry form cannot support the shape of granules qualified properly. Therefore, it is necessary that the amount of water added be accurately adjusted for preparation of optimal granules.
• the object of the present invention is to provide a process for preparation of crystalline layered sodium disilicate designed to simplify the complicated granulation process and improve the purity of the final product.
• the present invention relates to a process for preparation of crystalline layered sodium disilicate from crystallized granules, which are formed by adding a binder to anhydrous sodium silicate cullet powder; characterized in that it consists in adding an aqueous solution of sodium silicate as a binder instead of water to the anhydrous sodium silicate powder.
• Fig. 1 is the schematic flow diagram showing the process of manufacturing crystalline layered sodium disilicate
• Fig. 2 shows the X-ray diffraction pattern of the sample prepared from example 1 according to the present invention.
• anhydrous sodium disilicate cullet powder consisting of certain composition is prepared by adding an aqueous solution of sodium silicate containing certain amount of water as a binder, and the addition of an aqueous solution of sodium silicate is one of the pivotal processes in the present invention, since it functions as a binder not only to easily control the size of granules in the process, but also to facilitate a hydration. Because an aqueous solution of sodium silicate in the present invention is used as a binder, the role of water and the process mechanism are entirely different from those of the prior arts in which water is simply added.
• an aqueous solution of sodium silicate in the present invention has the following advantages in that a) it contributes to the ease of granulation of pulverized cullet powder, b) water can be easily removed from the crystallization process, thus contributing to improvement of purity and disassembling due to formation of homogeneous crystalline and pore, and c) with the addition of very small amount, it may, on the contrary, give an mechanism to shorten the processing steps without any problems in the device or the physical properties of the final product.
• the majority of crystalline layered sodium disilicate, so prepared by the process of the present invention has ⁇ -type crystalline and thus can be in particular used as a water softener or detergent supplement.
• the process for preparation of crystalline layered sodium disilicate according to the present invention is composed of the following three processing steps: a) silica and sodium carbonate are mixed, heated and melted to prepare anhydrous sodium disilicate cullet, b) an aqueous solution of sodium silicate is added to the cullet- pulverized powder to give granules, and c) the resulting granules are heated and calcined to effect crystallization.
• the first processing step is that silica and sodium carbonate are mixed in a molar ratio of SiO 2 /Na 2 O to 1. 80 - 2. 20, melted at 1,000 - 1 ,400 * 0 for 1 - 3 hours and cooled at room temperature to prepare the cullet. Since the molar ratio of
• the second processing step the cullet, so prepared in the above step, is pulverized to give powder having the particle size of 850 ⁇ m (Dso ⁇ ⁇ XOO ⁇ m) or less and an aqueous solution of sodium silicate (solid contents: 15 - 40 weight %) in a molar ratio of SiO 2 /Na 2 O to 2.0 - 3. 3 is added as a binder; then, the resulting mixture is granulated to give 1 - 50 mm diameter size of granules (bulk density: 1.1 - 1.6
• the particle size of the cullet powder is larger than 850 ⁇ m, longer retention time becomes inevitably necessary for granulation; further, much longer time is also required in infiltrating a high-temperature energy into the inside of the prepared granules during the crystallization, thus deteriorating the physical property of the final product in the crystallization process.
• the bulk density of cullet powder is 0. 5 - 0.6 g/cu and its loss on ignition at 700 ° C is 0.4 - 1. 0 weight %.
• an aqueous solution of sodium silicate being used as a binder designed for granulation of cullet powder; if the molar ratio deviates said range, a lot of a - or ⁇ -type in crystalline phase is formed so that they may be present as impurities.
• the solid contents in an aqueous solution of sodium silicate should be 15 - 40 weight %; if such solid contents are less than 15 weight %, a lot of water makes it difficult to properly control the granulation process and in case of exceeding 40 weight %, homogeneous addition of the solution on cullet powder becomes difficult due to its higher viscosity.
• An aqueous solution of sodium silicate having the above conditions is added in the range of 10 - 30 weight % per cullet powder; if the amount is added in less than
• Said granules, so prepared have 1 - 50 mm in diameter; if the size of granules is less than 1 mm in diameter, extremely small size of granule makes it difficult to maintain a certain retention time in a crystallization device and in case of exceeding 50 mm, some impurities may be formed due to the fact that a heat is not delivered into the inside of granules during the crystallization process.
• the bulk density of granules, so prepared, is in the range of 1. 1 - 1. 6g/ ⁇ f.
• the granulators according to the present invention can be selected from pan types, extruder types, disc types, and fluid layer types.
• the third processing step is to obtain a desired product of the present invention, crystalline layered sodium disilicate, by drying, heating and calcining process of the granules, so formed as described in the above.
• granules are dried, prior to charging them into a continuous calcined device.
• the adhesiveness of an aqueous solution of sodium silicate, being present at the surface of granules may be removed to prevent granules from binding one another, b) it makes granules move easily, c) hydration induced by water within the inside of granules is facilitated so that the phase-transition in crystallization may be made available.
• a drying temperature is extremely high, the purity of the final product may be affected by the formation of impurities.
• the drying process it is preferred to perform the drying process at 80 - 200 ° C until the evaporation contents of the moisture become 0.2 - 1.0 weight %.
• the exhaust gas which is discharged from a calcined device at next process can be used with the advantage as a heat source in the drying process to reduce energy consumption.
• the bulk density of granules, so dried, is maintained at 1.1 - 1.6 g/cu .
• the molar ratio of SiO 2 /Na 2 O in cullet which may affect the purity of a final product, is adjusted at 1. 80 - 2. 20; a small amount of an aqueous solution of sodium silicate necessary for the granulation is added to granulate and then the granules, so formed, are calcined.
• the present invention has economical benefits in that it makes it unnecessary to provide devices and heating energy designed to be used for some common process such as heating, dissolution, drying and recycle, whereby the time required for total preparation is markedly reduced and the production amount per unit may be expected to be enhanced;
• the use of an aqueous solution of sodium silicate as a binder makes it easier to control the granulation process; and by the drying process to dry the surface of prepared granules, any possible problems in the storage and delivery of granules may be prevented; homogenous crystallization of granules within a calcined device, by charging into the furnace the granule-type materials having the minimum moisture necessary for phase transition, is enabled; the deposition of reactant in the furnace does not occur; local sinter may be prevented so that the disassembling properties are favorable; in particular, the final product,
• Crystalline layered sodium disilicate of the present invention so prepared by the above process for preparation, has proven to be superior to that of well known methods in that the former has calcium ion binding capacity of 98 - 108 nig Ca 2 7g and magnesium ion binding capacity of 78 - 86 nig Mg 2 7g at the temperature of 25 ° C . Further, the majority of crystalline phase according to the present invention has proven to be ⁇ -type. The present invention is explained in more detail by the following examples, but the claims are not limited to these examples.
• KS-M-1415 liquid-phase sodium silicate
• the cullet mass was first pulverized into small pieces by a jaw crusher (Daegabunche Co., Korea), further pulverized by a ball-mill (material: alumina, capacity: 3. 6 I , ball: ⁇ 20 mm) for 3 hours and distributed.
• the cullet powder (bulk density: 0.5 - 0.6 g/cuf) having the particle size of 850 ⁇ m (D 5 o: ⁇ 300 ⁇ m) or less was prepared, while its loss on ignition at 700 ° C was 0.40 weight %.
• a disk-type granulator Yungjin Machine, Korea
• the granules, so formed, were dried for 30 minutes in a fan-type dryer maintained at 120 ° C (moisture evaporation: 0.5 weight %, bulk density: 1.31 g/cuf), charged to the rotary furnace (Lindberg Co. , U. S. A., Model No. 54579) maintained at 725 ° C in the air and crystallized for 20 minutes (angle of inclination: 0.5 ° . rotation: 8 rpm). During the above process, the resulting materials did not adhere within the device. While maintaining the initial shape of granules, 498g of white porous crystalline layered sodium disilicate having the expanded bulk density of about 0.26 g/cuf was obtained.
• Example 1 was charged to a disc-type granulator and rotated at 15 rpm. With the addition of 18 weight % of an aqueous solution of sodium silicate (contents of solid constituents: 30 weight %, Sinheung Kyusan Co.) having the molar ratio of
• Example 2 SiO 2 /Na 2 O on 3. 20, granules were prepared under the same conditions as Example 1. The next process was carried out by the same conditions as Example 1 so that crystalline layered sodium disilicate was obtained.
• COMPARATIVE EXAMPLE 1 The cullet powder, so collected by the same conditions as Example 1, was crystallized and disassembled without granulation process so that crystalline layered sodium disilicate was prepared. In the process of preparation, some product was melted and adhered to the inside of calcined device; there were a lot of dusts during the addition of raw materials; and the disassembling of the product was poor due to sinter.
• the cullet (molar ratio of SiO 2 /Na 2 O: 2. 50) obtained from accurately weighed 600g of silica and 432. Og of sodium carbonate, respectively, was treated by the same procedure as described in Example 1 so that crystalline layered sodium disilicate was prepared.
• Example 2 By the same procedure as described in Example 1 , the reaction was carried out. 125g of water instead of the aqueous solution of sodium silicate was added to 500g of cullet powder, so formed, to give some granules. By the same conditions as described in Example 1, the granules were crystallized and disassembled to prepare crystalline layered sodium disilicate.
• EXPERIMENTAL EXAMPLE 1 MEASUREMENT OF BINDING CAPACITY WITH HARDNESS CONSTITUENTS
• t is consumed amount of EDTA (in*)
• w is a sample weight (g)
• f is a factor of used EDTA solution.
• Mg 2+ binding capacity was calculated by the following equation.
• Mg 2+ binding capacity (mg Mg 2+ /g) (12. 5-(t X f))/w X 120/12.5
• t is consumed amount of EDTA (ml)
• w is a sample weight (g)
• f is a factor of used EDTA solution.
• X-ray diffraction analyzer Rasterkusa, Japan, D/MAX-3B
• the process of preparing crystalline layered sodium disilicate according to the present invention has the following advantages: that, as adjusting the composition of cullet powder to some specific range, the final product is mainly composed of ⁇ -type layered crystalline; after preparing the cullet powder having a certain particle size, an aqueous solution of sodium silicate is added to easily modulate the size of granules; the granules, so prepared, is dried so as to prevent any problems associated with the granulation process; crystalline layered sodium disilicate with excellent physical properties can be easily obtained when granules are crystallized.

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• Life Sciences & Earth Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
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• Silicates, Zeolites, And Molecular Sieves (AREA)

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• 1997
  • 1997-07-16 KR KR1019970033207A patent/KR100225603B1/ko not_active Expired - Fee Related
  • 1997-12-17 CN CN97182298A patent/CN1262664A/zh active Pending
  • 1997-12-17 JP JP2000503023A patent/JP2001510135A/ja active Pending
  • 1997-12-17 WO PCT/KR1997/000269 patent/WO1999003782A1/en not_active Ceased
  • 1997-12-17 EP EP97947975A patent/EP1003691A1/de not_active Withdrawn

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