JPH0139961B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing soda percarbonate, and in particular to a method for producing soda percarbonate, which has considerable stability, dissolves very quickly in water, and is foaming when dissolved. Regarding the law. Sodium percarbonate is a typical oxygen bleaching agent along with sodium perborate. Sodium perborate has low solubility at temperatures around room temperature and does not exhibit sufficient bleaching effects. For this reason, in Japan, where there is no custom of washing clothes with hot water, they are not used for anything other than business purposes. Chlorine bleach is also commonly used, but it has drawbacks such as a strong pungent odor and bleaching of dyed clothing. In recent years, it does not have the drawbacks seen in chlorine bleach,
Demand for soda percarbonate, which has high solubility at low temperatures around room temperature, is increasing. The general method for producing soda percarbonate is to react sodium carbonate and hydrogen peroxide to obtain sodium percarbonate crystal powder using a reactive crystallization method, and then perform wet granulation and drying to form a product. be. Generally, when soda percarbonate is left in the air, it absorbs moisture and its active oxygen concentration decreases, so that it no longer exhibits a sufficient bleaching effect when used. For this purpose, inorganic compounds such as water glass, phosphates, silicates, magnesium salts are added to the reaction product, or organic compounds such as polyethylene glycol, starch, CMC, etc.
Alternatively, it is known to spray or coat the granules with the above-mentioned inorganic compounds. However, although the granular soda percarbonate obtained by such a method has superior solubility compared to sodium perborate, its solubility at room temperature is not so great and it cannot be used in normal household use. It takes a long time to dissolve, and therefore, it has the disadvantage that it cannot exhibit sufficient bleaching effect. In an attempt to improve these drawbacks of soda percarbonate, granulated and dried soda percarbonate was reused at 75~
There is a method of imparting quick solubility by heating in a temperature range of 135°C for a specific period of time. Although it is possible to obtain sodium percarbonate having relatively good solubility according to this method, heating for a long time at a relatively high temperature is required to obtain a product with satisfactory rapid dissolution. however,
Processing under such conditions causes the active oxygen possessed by sodium percarbonate to be lost through decomposition, resulting in a fatal defect in that the active oxygen content of the resulting product is low, although it becomes quickly soluble. have In addition, from an industrial perspective, a heating device other than a dryer is required, which is a big disadvantage. In view of the above points, the present inventors completed the present invention as a result of various studies. The object of the present invention is to have excellent solubility in water;
The object of the present invention is to provide a granular soda percarbonate having stability. The present inventors investigated the solubility in water when adding inorganic compounds conventionally used as stabilizers, such as water glass and silicates. When wet granulation is performed by adding the inorganic compound to sodium percarbonate, the added inorganic compound gels and is deposited on the particles during the granulation process. It was discovered that there is a very important relationship between the solubility of sodium percarbonate in water, and it was also found that the type and combination of additives are extremely important. That is, the present invention involves simultaneously adding at least one soluble metal salt and at least one selected from silicate hydrosol or alkali metal silicate to sodium percarbonate when granulating powdered soda percarbonate. It relates to a method characterized by graining. The soluble metal salts, silicate hydrosols, or alkali metal silicate salts used in the present invention may be referred to as additives hereinafter, and are referred to as "soluble metal salts".
are called additives of the first group, and "silicate hydrosol or alkali metal silicate" are called additives of the second group. The soluble metal salt of the first group of additives used in the present invention is one selected from magnesium sulfate, magnesium chloride, aluminum sulfate, and barium chloride. These soluble metal salts are usually used in an amount of 0.01 to 1.0% by weight based on sodium percarbonate to achieve the purpose of the present invention.
Considering the overall balance, 0.05 to 0.5% by weight is suitable. Additionally, these first group additives are generally used as aqueous solutions with a concentration of 1 to 10%. In addition, the silicates that are the second group of additives used in the present invention are alkali metal salts, and are selected from commercially available No. 1 to No. 3 water glass, potassium silicate, lithium silicate, and powdered sodium silicate. This is the type of choice. In the present invention, the silicic acid hydrosol is also called colloidal silica or silica sol, which is known per se, and is an aqueous dispersion of silicon oxide with a particle size of 10 to 100 mμ (a commercially available product is, for example, the trade name Snotex (Nissan Manufactured by Kagaku Kogyo Co., Ltd.)). Hydrous aluminum oxide hydrosol is also called colloidal alumina or alumina sol, and is an amorphous aluminum oxide hydrosol (commercially available products include, for example, alumina sol). The silicate hydrosol or hydrated aluminum oxide hydrosol is usually used at a concentration of 1 to 30%, and SiO ₂ or
It is added as Al ² O ₃ in a range of 0.01 to 0.5% by weight. Also, among the above silicates, commercially available Nos. 1 to 3
No. water glass is used in a concentration of 1 to 25%, and other potassium silicate, lithium silicate _, and powdered sodium silicate are used in a concentration of 1 to 20%. A range of 0.01-0.5% by weight is added. In the present invention, if the amount of the silicate hydrosol (alkali metal silicate) added is larger than the above amount, the solubility will deteriorate, which is not preferable.
In order to fully achieve the purpose of the present invention and exhibit remarkable effects, it is preferable to add SiO ₂ in an amount of 0.01 to 0.3% by weight. Further, it is preferable to add the additives of the first group and the additives of the second group at a weight ratio of 1/1 in order to increase the abrasion strength of the particles. In the present invention, additives added during granulation,
That is, it is important to add the soluble metal salt and the silicate hydrosol (alkali metal silicate) at the same time during granulation. When the first group additive, soluble metal salt, and the second group additive, silicate hydrosol or silicate or a type of hydrous aluminum oxide hydrosol, are added separately over time, the solubility is significantly impaired, which is undesirable. In the present invention, among the soluble metal salts of the first group of additives, magnesium sulfate and magnesium chloride are particularly preferable, and among the second group of additives, silicate hydrosols and alkali metal silicate salts are particularly preferable.
Lithium silicate and No. 1 to No. 3 water glass are particularly suitable. In the present invention, a wet granulation method is applied to granulate sodium percarbonate, and any type of granulator used in the wet method can be used for the granulation, but A granulator that can perform sufficient granulation is suitable. During granulation, water is added as desired and kneaded and sludged so that the water content of the sodium percarbonate is approximately 10 to 15%. Examples of granulators used for granulation include mixing and kneading raw material powder, binders, other additives, etc. in a batch-type or continuous-type kneader or mixer, and a screw machine with a screen at the tip. Extrusion type pelletizer or extrusion type kneading which the applicant applied for earlier,〓
A Japanese-style granulator is used. The product obtained according to the present invention has excellent storage stability, good solubility in cold water, and foaming property when dissolved. The granular sodium percarbonate obtained according to the present invention can be incorporated into detergents and the like as an oxygen bleaching agent. The powdered soda percarbonate used in the present invention can be obtained by a method in which hydrogen peroxide is applied to an aqueous solution of sodium carbonate to crystallize crystals from the aqueous solution (crystallization method), or a solution in which a slurry is formed in an inert solvent and reacted. However, in general, wet sodium percarbonate obtained by the crystallization method can be used. suitable. Reference example (Example of manufacturing soda percarbonate) Prepare a reaction mother liquor 30 containing 2% H ₂ O ₂ and 12% Na ₂ CO ₃ in a stainless steel reactor equipped with a stirrer, thermometer, and cooling jacket. . 2.5Kg _of 60% _H2O2 under stirring while keeping the mother liquor at a temperature of 15-20℃,
At the same time, 3.0 kg of Na ₂ CO ₃ was gradually added over about 1 hour, and after the addition, the mixture was stirred for an additional 1 hour while maintaining the above temperature. The resulting slurry was separated into sodium percarbonate crystals and liquid using a centrifuge to obtain about 3.5 kg of wet sodium percarbonate. Next, examples will be described. Examples 1 to 10 The wet sodium percarbonate powder obtained by the method of the reference example was fed to a kneader, and the first powder shown in the table was added to the kneader.
A soluble metal salt, which is an additive in the first group, and a silicate hydrosol (alkali metal silicate), which is an additive in the second group, are added at a specified concentration and in a predetermined amount, and the water content is further adjusted to 10 to 15%. Add the desired amount of water and mix for 30 minutes. The kneaded wet mass was granulated using a twin-screw extrusion type pelletizer (manufactured by Fuji Electric Industries, Ltd.), and the granulated product was dried using a fluidized fluidized dryer to obtain a product. The dissolution rate was measured for this product. To measure the dissolution rate, put pure water 1 at 25℃ in a beaker, turn a stirring bar with stirring blades of 40 mm in height and 25 mm in width at 250 rpm, add 5 g of sample, and measure the time until the particles completely disappear. This was done by measuring. In addition, 50 g of the obtained product was placed in a 100 ml beaker and left open for 30 days at 35°C and 80% RH, the amount of effective oxygen before and after the test was determined, and the effective oxygen reduction rate was determined according to the following formula: Storage stability was measured. (Available oxygen reduction rate) = (Initial effective oxygen) - (Available oxygen after 30 days)/(Initial effective oxygen) x 100 (%) The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. When granulating powdered soda percarbonate,
Sodium percarbonate contains (a) at least one selected from magnesium sulfate, magnesium chloride, barium chloride, and aluminum sulfate (hereinafter collectively referred to as soluble metal salts), and (b) silicate hydrosol or silicate alkali. A method for producing soda percarbonate, characterized in that at least one selected from metal salts is added at the same time and granulated. 2. The method according to claim 1, wherein the alkali metal silicate is selected from water glass, potassium silicate, lithium silicate, and powdered sodium silicate as listed in items 1 to 3. 3 Soluble metal salt to soda percarbonate 0.05~
The method according to claim 1, wherein 0.5% (by weight) is added. 4 Silicic acid hydrosol or silicate alkali metal salt to sodium percarbonate as SiO ₂ from 0.01 to
The method according to claim 1, wherein 0.5% (by weight) is added.