JP3314526B2 - Method for producing stabilized sodium percarbonate particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sodium percarbonate particles having high storage stability and a method for producing the same. The sodium percarbonate particles of the present invention are suitably used for a bleaching composition or a household detergent containing a bleaching component.

[0002]

2. Description of the Related Art It is known that hydrogen peroxide adducts such as sodium percarbonate and sodium perborate are blended as a bleaching component in powdery detergent compositions (synthetic household detergents). Hydrogen peroxide addition compounds such as sodium percarbonate and sodium perborate dissolve during washing and decompose to exert a bleaching action. In this case, the dissolution rate of sodium perborate at a low temperature is low, and in particular, in Japan in which water or lukewarm water is mainly used, it is not preferable as a bleaching component to be added to a detergent. On the other hand, the demand for sodium percarbonate has been rapidly increasing in recent years because the dissolution rate at a low temperature is fast and the bleaching effect can be sufficiently exhibited.

[0003] However, sodium percarbonate is relatively sensitive to moisture, and is easily decomposed at room temperature by moisture in the detergent composition or moisture and moisture in the air. Further, the detergent composition may contain a substance such as zeolite or enzyme which promotes the decomposition of sodium percarbonate, and may be decomposed by contact with these substances. Therefore,
Prevents or suppresses the decomposition of sodium percarbonate,
Various methods have been proposed for obtaining stabilized sodium percarbonate. For example, during the crystallization of sodium percarbonate, stabilizers such as sodium metasilicate, magnesium compound, and chelating agent are added to stabilize. During wet granulation, additives such as binder or phosphate are added to stabilize. And stabilization by coating the surface of dried sodium percarbonate. Among them, the third method of coating sodium percarbonate particles with various coating agents is most effective. Various coating agents have been proposed, such as alkaline earth metal salts or mixed salts of sodium carbonate and sodium sulfate.

[0004] As a method of coating with an alkaline earth metal salt, the method of Japanese Patent Publication No. 57-7081 is known. In this method, the surface of sodium percarbonate particles is brought into contact with an aqueous solution of an alkaline earth metal salt to form a film composed of the alkaline earth metal salt on the surface of the sodium percarbonate. Can be somewhat increased but has the following two disadvantages. One is that sodium carbonate in sodium percarbonate reacts with an alkaline earth metal salt, and the liberated hydrogen peroxide is decomposed during drying, so that the active ingredient as sodium percarbonate decreases. The other is that the formation of insoluble alkaline earth metal carbonates significantly lowers the dissolution rate, making it difficult to use. on the other hand,
In the case of coating with a mixed salt of sodium carbonate and sodium sulfate (Japanese Patent Publication No. 58-24361), the solubility is relatively good, but the blending stability with detergent is slightly lower than that of uncoated sodium percarbonate. Although it has improved, it has not reached the practical level.

[0005]

SUMMARY OF THE INVENTION It is difficult to simultaneously satisfy the conflicting factors of the stability of the sodium percarbonate component and the solubility of sodium percarbonate particles. In particular,
When blended with a detergent component, the stability of the sodium percarbonate component tends to decrease. An object of the present invention is to provide sodium percarbonate particles having high stability especially in blending stability with a detergent and having a high dissolution rate.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, sprayed an aqueous solution of silicate, an aqueous solution of magnesium sulfate and an aqueous solution of an alkali metal sulfate onto particles of sodium percarbonate. The present inventors have found that sodium percarbonate obtained by drying to form a coating layer has a high dissolution rate and a very good blending stability with a detergent, thus completing the present invention.

[0007] The coating of sodium percarbonate is specifically carried out as follows. That is, after coating the first layer by drying while spraying an aqueous silicate solution on the particles of sodium percarbonate, further drying while spraying an aqueous solution of a mixture of magnesium sulfate and an alkali metal sulfate to form a second coating. Form a layer. In addition, the above-mentioned 2
The aqueous solution may be dried while spraying simultaneously with separate nozzles to form a coating layer on the surface of the sodium percarbonate particles. At this time, the order of spraying is reversed, and the particles of sodium percarbonate obtained by spraying the liquid containing magnesium sulfate first and then spraying the silicate aqueous solution have a decrease in the available oxygen amount. Further, the sodium percarbonate particles are dried by spraying simultaneously or sequentially with three kinds of aqueous solutions of a silicate aqueous solution, a magnesium sulfate aqueous solution, and an alkali metal sulfate aqueous solution with separate nozzles, and coated on the surface of the sodium percarbonate particles. A layer may be formed.

The sodium percarbonate used in the present invention is prepared by kneading a wet powdered sodium percarbonate (water content: 6 to 15%) produced by reaction, crystallization and dehydration by a known method together with a binder. It is obtained by coagulation and granulation by a granulator, then sizing by an extruder, and drying. In addition, a recovered powder partially containing wet powdered sodium percarbonate and a coating component such as a silicate component, a magnesium sulfate component or an alkali metal sulfate component recovered from the granulation step and / or the coating step. Sodium percarbonate mixed with sodium carbonate and granulated by the method described above is also preferably used. The weight ratio of the wet powdered sodium percarbonate to the recovered sodium percarbonate is preferably in the range of 50:50 to 99: 1. In particular, when the recovered sodium percarbonate is in the form of fine powder having a diameter of 300 μm or less, preferably 5 to 100 μm, the stability of sodium percarbonate is further improved. After the granulation step used in the present invention, the sodium percarbonate particles before the coating step have a diameter of usually 300 to 2000 μm, preferably 500 to 10 μm.
A thing of 00 μm is used.

As a sulfate of an alkali metal as a coating agent, sodium sulfate, potassium sulfate, lithium sulfate and the like can be used. These may be used in combination. Among them, sodium sulfate is most preferable from the viewpoint of economic convenience. The coverage of alkali metal sulfate is sodium percarbonate (Na ₂ CO _{3
· 3 / 2H 2 O 2)} 0.05 to 0.2 mol is preferred for 1 mole. That is, sodium percarbonate (molecular weight: 157)
When the alkali metal sulfate is anhydrous sodium sulfate (molecular weight 142) with respect to 100 parts (weight, the same applies hereinafter), the amount is 4.5 to 18 parts. If the coating amount is less than 0.05 mol, the blending stability with the detergent is insufficient. On the other hand, if it is 0.2 mol or more, not only the dissolution rate becomes slow, but also it is not preferable in terms of economy.

As the alkali metal salt, it is also preferable to use a combination of an alkali metal sulfate and an alkali metal bicarbonate. As the bicarbonate of the alkali metal, sodium bicarbonate, potassium bicarbonate, lithium bicarbonate and the like can be used. These may be used in combination. Among them, sodium bicarbonate is preferred in terms of economy. When alkali metal sulfate and alkali metal bicarbonate are used in combination, the amount of each coating is 0.05 mol of alkali metal sulfate per 1 mol of uncoated sodium percarbonate.
Mol to 0.2 mol, preferably 0.04 mol to 0.17 mol of bicarbonate of alkali metal.

As the silicate as a coating agent, sodium orthosilicate, sodium metasilicate, water glass 1
Nos. 2, 2 and 3 may be used. Among them, water glasses are liquid and are preferable in terms of convenience in use. The coverage of the silicate is 0.01 mol to 0.06 mol is preferred as SiO ₂ with respect to uncoated sodium percarbonate mole. That is, for 100 parts of sodium percarbonate, the silicate is 0.3 as SiO ₂ (molecular weight 60.3).
Parts to 2.2 parts. If the coating amount of the silicate is too small, the spreadability of the coating decreases, and the blending stability with the detergent becomes insufficient. Conversely, if it is too large, the dissolution rate will be slow.

The coating amount of magnesium sulfate as a coating agent is 0.006 per mole of uncoated sodium percarbonate.
Mol to 0.06 mol is preferred. That is, magnesium sulfate (molecular weight 12
0.3) 0.45 to 4.5 parts. If the coating amount is 0.006 mol or less, the mixing stability with the detergent becomes insufficient. Conversely, if the coating amount is 0.06 mol or more, the dissolution rate becomes slow. In addition to the above-mentioned coating agent, a conventionally known chelating agent (for example, nitrilotriacetic acid, ethylenediaminetetraacetic acid or a salt thereof) or the like may be used in combination with the coating agent to stabilize sodium percarbonate.

The ratio of each coating agent is such that alkali metal sulfate is 0.05 mol per mol of sodium percarbonate.
Mol to 0.2 mol, the silicate is 0.01% as SiO _2.
Mol to 0.06 mol, and magnesium sulfate is 0.006 mol to 0.06 mol. The ratio of silicate and magnesium sulfate to sulfate of alkali metal is usually 1: 0.05: 0.03 to 1: 1.2 in molar ratio.
1.2, preferably 1: 0.1: 0.1 to 1: 0.
2: Selected between 0.2. When an alkali metal sulfate and an alkali metal bicarbonate are used in combination, the ratio of silicate, magnesium sulfate and alkali metal bicarbonate to alkali metal sulfate is usually 1: 0 in molar ratio. .05: 0.03: 0.2 to 1: 1.2:
1.2: 0.85, preferably 1: 0.1: 0.1:
0.4 to 1: 0.2: 0.2: 0.85.

In the case of coating with sodium percarbonate, the solvent for these coating agents is selected from solvents that dissolve the coating agents, but water having high solubility, safe and inexpensive is most preferred. The concentration of the coating agent at the time of spraying may be not more than the saturated dissolution concentration at the use temperature, but if the concentration is too low, not only drying time is required but also the calorific value of the water to be evaporated becomes large, which is preferable in terms of economy. Absent. On the other hand, if the concentration is too high, crystals will precipitate in the pipes and nozzles, and are undesirably easily clogged. Therefore, the solution concentration of the silicate is 0.1% as SiO ₂ .
It is preferably from 5 to 9% by weight, more preferably from 1 to 6% by weight. On the other hand, the liquid concentration of magnesium sulfate is selected from 0.2 to 15% by weight, preferably 0.5 to 10% by weight, and more preferably 0.5 to 5% by weight. The concentration of the alkali metal sulfate is preferably 3 to 20% by weight, and 5 to 15% by weight.
Is more preferred.

The temperature of sodium percarbonate during spray drying is 4
The temperature is 0 to 95 ° C, preferably 50 to 90 ° C. If the temperature of the sodium percarbonate is too low, the sodium percarbonate particles are undesirably aggregated. On the other hand, when the temperature of sodium percarbonate is too high, sodium percarbonate tends to decompose, and the crystal of the coating material grows, so that the spreadability deteriorates and uniform coating becomes difficult.

[0016]

Next, the method of the present invention will be described more specifically with reference to examples and comparative examples. The present invention can be practiced without being limited to these Examples. In Examples,% means% by weight unless otherwise specified.

Example 1 Sodium percarbonate having an average particle size of 500 μm (effective oxygen amount 1
4.4%) 300 g was placed on the perforated plate of the fluidized drying type coating device (Yamato Scientific Co., Ltd. "Pal bis coating"), was then fluidized by feeding 0.25 m ³ / min of air. Thereafter, by heating the inlet air, the temperature of the flowing sodium percarbonate was raised to 75 ° C. 75
After the temperature stabilizes at ℃, keep the fluid
5 g of an aqueous solution of sodium metasilicate (concentration: 2% by weight as SiO ₂ )
Spraying was continued at a flow rate of g / min for 21 minutes. After completion of the spraying, the coating was dried for 5 minutes to form a first coating layer. Then, after replacing the nozzle, a mixture aqueous solution of magnesium sulfate and sodium sulfate (magnesium sulfate concentration 4.2% by weight,
100 g of sodium sulfate (15% by weight) was sprayed at a flow rate of 5 g / min for 20 minutes. After spraying, 5
After drying for a minute, a coated second layer was formed. The product temperature during coating was controlled at 73 to 77 ° C. The coating amount of each component as a solid content is as follows. Sodium metasilicate in first coating layer: 2.1 g (as SiO ₂ ) (0.7% of raw sodium percarbonate particles) Magnesium sulfate in second coating layer: 4.2 g (1.4 of raw sodium percarbonate particles) %) Sodium sulfate in the coated second layer: 15.0 g (5.0% of the raw material sodium percarbonate particles)

After cooling, the coated sodium percarbonate particles were removed and no aggregates were observed. The effective oxygen content of the obtained sodium percarbonate determined by sodium thiosulfate titration was 13.4%. This value indicates that the decomposition of sodium percarbonate at the time of coating was very small, and that the coating material was coated almost as expected. Theoretical value: 14.4% × (1 / (1 + 0.07)) = 13.5% The solubility of the obtained coated sodium percarbonate particles and a storage stability test after mixing with a detergent were carried out as follows. The results are shown in Table 1 together with the results of the available oxygen amount and the dissolution rate. The obtained sodium percarbonate particles had good solubility and very good blending stability, and a significant improvement in stability was observed as compared with uncoated sodium percarbonate described below.

Solubility test 5 g of sodium percarbonate particles are placed in 1 liter of water and 2
The time required for the particles to completely dissolve was measured by conducting an electrical conductivity method at 0 ° C. and stirring at 200 rpm.

Storage Stability Test 1 g of synthetic zeolite 4A powder and 1 g of coated sodium percarbonate particles which had been sufficiently absorbed for one day at 30 ° C. and 80% relative humidity were mixed in a polyethylene bag (manufactured by Nippon Shokuhin Co., Ltd.). (Uni-Pack A-4, with water permeability) and mix well. This was allowed to stand at 30 ° C. and 80% relative humidity for 4 days, and the amount of available oxygen before and after storage was analyzed, and the accelerated blending stability with zeolite was examined. The results were evaluated based on the residual ratio of available oxygen after storage for 4 days. The available oxygen amount was determined by sodium thiosulfate titration, and the available oxygen remaining rate was calculated by the following equation.

## EQU1 ## Effective oxygen remaining rate (%) = (available oxygen after storage) / (available oxygen before storage) × 100

Storage stability test Commercially available compact detergent (including zeolite, enzyme, etc.) 1
200 g of sodium percarbonate particles coated on 300 g or uncoated sodium percarbonate particles (1
(3.3%) was uniformly mixed, placed in a carton box and sealed with vinyl tape. This was stored for 21 days in a thermostat maintained at 30 ° C. and 80% relative humidity. The results were evaluated by the residual ratio of available oxygen after storage for 21 days as in the storage stability test.

Example 2 Coated sodium percarbonate particles were obtained in the same manner as in Example 1 except that potassium sulfate was used at the same concentration instead of sodium sulfate as a coating agent. Sodium metasilicate: 2.1 g (as SiO ₂ ) (0.7% of raw material sodium percarbonate particles) Potassium sulfate: 15.0 g (5.0% of raw material sodium percarbonate particles) Magnesium sulfate: 4.2 g (raw material) (1.4% of sodium percarbonate particles) When the available oxygen amount of the obtained sodium percarbonate particles was analyzed, it was 13.4%. This indicates that the coating agent was coated almost as theoretically without decomposition of sodium percarbonate during coating. When the dissolution rate was examined in the same manner as in Example 1, it was dissolved in 2 minutes. The stability of the blend was examined in the same manner as in Example 1, but it was good. The results are also shown in Table 1.

Example 3 Except for using No. 1 water glass instead of sodium metasilicate and adding 0.6% by weight of ethylenediaminetetraacetic acid tetrasodium salt to a mixed solution of magnesium sulfate and sodium sulfate. In the same manner as in Example 1, coated sodium percarbonate particles were obtained. No. 1 water glass: 4.5 g (as SiO ₂ ) (1.5% of raw material sodium percarbonate particles) Sodium sulfate: 15.0 g (5.0% of raw material sodium percarbonate particles) Magnesium sulfate: 4.2 g ( (1.4% of raw material sodium percarbonate particles) Ethylenediaminetetraacetic acid tetrasodium salt: 0.6 g (0.2% of raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined. However, as in Example 1, the solubility was excellent and the blending stability was also good. The results are shown in Table 1.

Example 4 Sodium percarbonate having an average particle size of 500 μm (effective oxygen amount 1
4.4%) was placed on a porous plate of a fluidized drying apparatus ("Midget Dryer" manufactured by Fuji Paudal Co., Ltd.)
Then, 3.2 m ³ / min of air was sent in to fluidize.
Thereafter, the inlet air was heated to 120 to 150 ° C., and the temperature of the flowing sodium percarbonate was raised to 75 ° C. 75
After the temperature of sodium percarbonate was stabilized at ℃, the mixture of sodium sulfate and magnesium sulfate (sodium sulfate concentration 15 wt%, magnesium sulfate concentration 4.3 wt%) and an aqueous solution of sodium metasilicate (SiO ₂
5.6 Kg of a mixed solution of sodium sulfate and magnesium sulfate at a flow rate of 90 g / min, and 34 g / 34 of an aqueous solution of sodium metasilicate 2.1 Kg.
And sprayed simultaneously over a period of 62 minutes. The product temperature during coating was controlled at 73-77 ° C. 5 after coating is completed
Drying was performed by continuously flowing heated air for minutes. Then, heating of the air was stopped, and cooling was performed by flowing cool air. After cooling, the coated sodium percarbonate particles were removed, but no aggregates were observed. The coating amount of each component as a solid content is as follows. Sodium metasilicate: 84 g (as SiO ₂ ) (0.7% of raw material sodium percarbonate particles) Sodium sulfate: 840 g (7.0% of raw material sodium percarbonate particles) Magnesium sulfate: 168 g (1 of raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined and are shown in Table 1. As in the case of the sequential spraying of Examples 1, 2, and 3, the solubility and the blending stability were both good in the case of the simultaneous spraying.

Example 5 An aqueous solution of No. 1 water glass was used at a concentration of 2.8% by weight as SiO ₂ instead of the aqueous solution of sodium metasilicate, and tetrasodium ethylenediaminetetraacetate was added to a mixed solution of magnesium sulfate and sodium bicarbonate. Was sprayed simultaneously over 89 minutes in the same manner as in Example 4 except that 0.3% by weight was added to obtain coated sodium percarbonate particles. No. 1 water glass: 84 g (as SiO ₂ ) (0.7% of raw material sodium percarbonate particles) Sodium sulfate: 1200 g (10.0% of raw material sodium percarbonate particles) Magnesium sulfate: 240 g (of raw material sodium percarbonate particles) 2.0%) Ethylenediaminetetraacetic acid tetrasodium salt: 24 g (0.2% of the raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined. 1 is shown.

Example 6 Example 1 was repeated except that a mixture of 4.2% by weight of magnesium sulfate, 10% by weight of sodium sulfate and 5% by weight of sodium bicarbonate was used instead of the mixture of magnesium sulfate and sodium sulfate. Similarly, coated sodium percarbonate particles were obtained. Sodium metasilicate (as SiO ₂ ): 2.1 g (0.7% of raw material sodium percarbonate particles) Magnesium sulfate: 4.2 g (1.4% of raw material sodium percarbonate particles) Sodium sulfate: 10 g (raw material percarbonate) (3.3% of sodium particles) Sodium bicarbonate: 5 g (1.7% of raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined, and the results are similarly shown in Table 1. Indicated.

As can be seen from Table 1, the sodium percarbonate particles produced according to the present invention require a short time of 2 to 2.5 minutes to completely dissolve, and when formulated with a detergent,
Decomposes only about 10% after one day storage. That is, the sodium percarbonate particles of the present invention both exhibit good properties in terms of solubility and blending stability with a detergent, and have a property balance for use in a bleaching composition or a household detergent containing a bleaching component. It is good.

Comparative Example 1 The dissolution rate and formulation stability of uncoated sodium percarbonate particles used in the raw material of the present invention were determined. The results are shown in Table 2.

Comparative Example 2 Coated sodium percarbonate particles were obtained in the same manner as in Example 1 except that the second layer aqueous solution of a mixture of magnesium sulfate and sodium sulfate was not sprayed. Sodium metasilicate (as SiO ₂ ): 2.1 g (0.7% of raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined. Was. The formulation stability was slightly better than the uncoated Comparative Example 1, but no significant improvement was observed as in Example 1. Also, the solubility became considerably poor.

Comparative Example 3 Coated sodium percarbonate particles were obtained in the same manner as in Example 1 except that the first layer of the aqueous solution of sodium metasilicate was not sprayed. Sodium sulfate: 15.0 g (5.0% of raw material sodium percarbonate particles) Magnesium sulfate: 4.2 g (1.4% of raw material sodium percarbonate particles) Dissolution rate and blending stability of obtained sodium percarbonate particles And the results are similarly shown in Table 2. The blending stability was not significantly improved as in Example 1.

Comparative Example 4 Sodium percarbonate having an average particle size of 500 μm (effective oxygen amount 1
4.4%) 300 g was placed on the perforated plate of the fluidized drying type coating device (Yamato Scientific Co., Ltd. "Pal bis coating"), was then fluidized by feeding 0.25 m ³ / min of air. Thereafter, the inlet air was heated to raise the temperature of the flowing sodium percarbonate to 75 ° C. After the product temperature was stabilized at 75 ° C., 180 g of a 10% strength aqueous magnesium chloride solution was sprayed at a flow rate of 5 g / min for 36 minutes from a spray nozzle located 10 cm above the perforated plate while the fluid was kept flowing. After vacuum drying, sodium percarbonate particles were obtained.
Magnesium chloride: 18.0 g (6% of the raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate particles were determined. The results are also shown in Table 2. The blending stability was not significantly improved as in Example 1. In particular, the stability of blending with zeolite is comparative example 1
Low stability, close to uncoated. In addition, a significant decrease in the effective oxygen concentration over the dilution by the coating agent was observed.
Solubility was also low. Theoretical effective oxygen amount: 14.4% × (1 / (1 + 0.0
6)) = 13.6% Actual available oxygen content:
12.9%

Comparative Example 5 Sodium percarbonate having an average particle size of 500 μm (effective oxygen amount 1
4.4%) 300 g was placed on the perforated plate of the fluidized drying type coating device (Yamato Scientific Co., Ltd. "Pal bis coating"), was then fluidized by feeding 0.25 m ³ / min of air. Thereafter, the inlet air was heated to raise the temperature of the flowing sodium percarbonate to 50 ° C. After the temperature was stabilized at 50 ° C., while the fluid was kept flowing, a mixed salt aqueous solution of sodium carbonate and sodium sulfate (sodium carbonate concentration: 8.6%, sodium sulfate concentration: 11.10 cm) was sprayed from a spray nozzle located 10 cm above the perforated plate. (2%) 150 g was sprayed at a flow rate of 5 g / min for 30 minutes. After the spraying was completed, only gas was kept flowing at that temperature for 10 minutes to complete the drying. Then, after cooling with cold air to 30 ° C., the coated sodium percarbonate was taken out, and a little aggregate was observed. Sodium sulfate: 16.8 g (5.6% of raw material sodium percarbonate particles) Sodium carbonate: 13.2 g (4.4% of raw material sodium percarbonate particles) The dissolution rate and blending stability of the obtained sodium percarbonate were determined. Table 2 shows the results. The blending stability was not significantly improved as in Example 1.

Comparative Example 6 After forming the first coating layer by increasing the coating amount of sodium metasilicate, the second coating layer was formed using an aqueous solution of magnesium sulfate alone without using sodium sulfate, and the total coating amount was determined. Was obtained in the same manner as in Example 1 except that the same was used as in Example 1 to obtain coated sodium percarbonate particles. Sodium metasilicate (as SiO ₂ ): 17.1 g (5.7% of raw material sodium percarbonate particles) Magnesium sulfate: 4.2 g (1.4% of raw material sodium percarbonate particles) The solubility and formulation stability were determined, and the results are shown in Table 2.

Comparative Example 7 After forming the first coating layer, the same procedure as in Example 1 was carried out except that the same amount of the second coating layer was formed using a mixed aqueous solution of sodium sulfate and sodium carbonate without using magnesium sulfate. Similarly, coated sodium percarbonate particles were obtained. Sodium metasilicate (as SiO ₂ ): 2.1 g (0.7% of raw sodium percarbonate particles) Sodium sulfate: 15.0 g (5.0% of raw sodium percarbonate particles) Sodium carbonate: 4.2 g (raw material) (1.4% of sodium percarbonate particles) The solubility and blending stability of the obtained sodium percarbonate particles were determined, and the results are shown in Table 2.

Properties of coated sodium percarbonate particles

Table 1 Example 1 2 3 4 5 6 Solubility (min) 2.0 2.0 2.5 2.5 2.5 2.5 2.5 Storage stability 95 91 93 95 96 96 Storage stability 91 89 90 92 93 95

Properties of coated sodium percarbonate particles

Comparative Example 1 2 3 4 5 6 7 Solubility (min) 1.5 3.5 1.5 5.0 1.5 1.5 4.0 3.0 Storage stability 30 50 79 43 48 68 72 Storage Stability 50 54 68 75 55 72 70

[0037]

The sodium percarbonate particles of the present invention have a good dissolution rate and a very good blending stability with a detergent. The sodium percarbonate particles of the present invention have a surface silicate,
It is uniformly coated with magnesium sulfate, alkali metal sulfate (and alkali metal bicarbonate) and / or their mutual reaction products, and blocks moisture and other decomposition promoting substances and sodium percarbonate, Excellent stabilizing effect can be obtained. The sodium percarbonate particles of the present invention have extremely excellent blending stability with zeolites having a decomposition promoting property and synthetic detergents. Further, since the sodium percarbonate particles of the present invention have a high dissolution rate, washing at a low temperature can be sufficiently used even in a daily Japanese environment.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Susumu Watanabe 2-4-1-16 Hinagahigashi, Yokkaichi-shi, Mie Mitsubishi Gas Chemical Co., Ltd. Yokkaichi Plant (56) References JP-A-6-40709 (JP, A JP-A-4-31308 (JP, A) JP-A-7-17710 (JP, A) JP-A-50-125999 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 15/10 C11D 3/395 CA (STN)

Claims (8)

(57) [Claims] Claims: 1. Particles of sodium percarbonate, silicate,
A method for producing stabilized sodium percarbonate particles, comprising spraying and drying an aqueous solution of magnesium sulfate and a sulfate of an alkali metal to form a coating layer. 2. The method for producing stabilized sodium percarbonate particles according to claim 1, wherein the temperature of the sodium percarbonate during spray drying is 40 to 95 ° C. 3. The sodium percarbonate particles to be coated are wet powdered sodium percarbonate and a silicate component, a magnesium sulfate component or a sulfate component of an alkali metal recovered from a granulation step or a coating step. 2. The method for producing sodium percarbonate particles according to claim 1, wherein sodium percarbonate particles comprising a mixture with recovered sodium percarbonate partially containing a coating agent component such as the above are used. 4. Spraying and drying an aqueous silicate solution on sodium percarbonate particles to form a first coating layer, and further spraying and drying an aqueous solution of a mixture of magnesium sulfate and an alkali metal sulfate to coat the particles. The method for producing stabilized sodium percarbonate particles according to claim 1, wherein a second layer is formed. 5. A coating layer is formed by simultaneously spraying and drying an aqueous solution of a silicate and an aqueous solution of a mixture of magnesium sulfate and an alkali metal sulfate on particles of sodium percarbonate with separate nozzles. The method for producing stabilized sodium percarbonate particles according to claim 1. 6. A coating layer is formed by simultaneously spraying and drying an aqueous solution of a silicate, an aqueous solution of magnesium sulfate, and an aqueous solution of an alkali metal sulfate on particles of sodium percarbonate using separate nozzles. 2. The method for producing stabilized sodium percarbonate particles according to 1. 7. An aqueous solution of a mixture of magnesium sulfate, an alkali metal sulfate and an alkali metal bicarbonate instead of an aqueous solution of a mixture of magnesium sulfate and an alkali metal sulfate. Item 6. The method for producing stabilized sodium percarbonate particles according to Item 4 or 5. 8. The stabilized solution according to claim 6, wherein an aqueous solution of a mixture of an alkali metal sulfate and an alkali metal bicarbonate is used instead of the aqueous solution of an alkali metal sulfate. A method for producing sodium carbonate particles.