JP2006036599A - Sodium percarbonate particle having excellent safety and stability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide sodium percarbonate particles which exhibit excellent storage stability even when they are blended in a household detergent containing a bleaching composition or a bleaching component and which has little danger of combustion when they are brought into contact or mixed with a combustible substance or the like. <P>SOLUTION: The sodium percarbonate particles are obtained by adding 0.1-10 parts by weight of sodium bicarbonate to 100 parts by weight of sodium percarbonate, then granulating the resulting mixture, and coating granulated particles with 5-20 parts by weight of an alkali metal carbonate and 0.1-2 parts by weight of silicate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to safe sodium percarbonate particles having excellent storage stability and a method for producing the same. The sodium percarbonate particles of the present invention are suitably used in a bleach composition or a household detergent containing a bleach component.

  It is well known that sodium percarbonate and sodium perborate are blended in a powdered detergent as a bleaching component. Sodium percarbonate and sodium perborate dissolve during washing and decompose to exert a bleaching effect. At this time, sodium perborate has a slow dissolution rate in water at a low temperature, and in Japan where water is mainly used, it is not preferable because the bleaching effect is not exerted as a bleaching component to be blended in a detergent. Moreover, since boron is contained in the waste water after use, it is not preferable from increasing the load of boron on the environment. On the other hand, sodium percarbonate is preferred because it has a high dissolution rate in low-temperature water and can sufficiently exert a bleaching effect. Sodium percarbonate does not produce a substance that adversely affects the environment even when decomposed. Demand is increasing.

  However, sodium percarbonate is sensitive to water and the like and is easily decomposed by moisture in the detergent composition, and the zeolite and enzyme contained in the detergent act as a catalyst for the decomposition and promote the decomposition. Further, sodium percarbonate itself is not a flammable material and does not burn alone, but may come into contact with or mix with the flammable material for any reason during handling or storage, which may promote combustion under certain conditions. Accordingly, various methods for preventing the decomposition of sodium percarbonate and improving the stability and safety have been proposed.

  For example, reaction of sodium percarbonate, method of adding silicate, magnesium compound, chelating agent, etc. as stabilizer during crystallization, method of adding phosphoric acid, etc. as additive when granulating sodium percarbonate in a wet state And a method of coating sodium percarbonate particles with various coating agents.

  Of these, the method of coating with a coating agent is the most effective, and various types of coating agents have been proposed. For example, a method is disclosed in which the surface of sodium percarbonate particles is contacted with an alkaline earth metal salt aqueous solution to form a coating film of alkaline earth carbonate carbonate on the surface of the sodium percarbonate particles (see Patent Document 1). However, this method has little effect of improving the stability, and when sodium percarbonate reacts with alkaline earth metal salt, a part of the effective oxygen is decomposed, reducing the effective oxygen concentration of sodium percarbonate and reducing insolubility. It has the disadvantage that the alkaline earth carbonate carbonate is formed and the dissolution performance is significantly reduced. Also disclosed is a method of coating sodium percarbonate particles with boric acid and an alkali metal silicate (see Patent Document 2). In this method, the effect of increasing the stability is sufficient, but it can be pointed out that when the coated product is dissolved, an insoluble material is formed as a reaction product of boric acid and silicate, and the dissolution rate is lowered. Further, the surface of the sodium percarbonate is at least one selected from the group consisting of borate and alkali metal silicate and at least one coating selected from carbonate, bicarbonate and sulfate in an aqueous slurry state. A method of coating is disclosed (see Patent Document 3). Since this method coats the coating agent in a slurry state, it is difficult to keep the coating solution composition in a uniform state, and it can be pointed out that it is difficult to form a coating film with good reproducibility.

As a method for reducing the risk of combustion when sodium percarbonate and combustible materials are mixed, methods for adding various risk inhibitors have been proposed. For example, a method of adding sodium bicarbonate to sodium percarbonate (refer to Patent Document 4), at least one of boric acid, inorganic magnesium compound and inorganic aluminum compound, and alkali metal carbonate, alkali metal bicarbonate, alkali metal sulfate Although a method of adding at least one kind (see Patent Document 5) is disclosed, these are not sufficiently stable when blended in a detergent or the like, and have poor solubility.
Japanese Patent Publication No.57-7081 Japanese Patent No. 2969794 Japanese Patent No. 2869310 JP-A-2-296705 JP-A-3-28111

  The object is to provide sodium percarbonate particles which overcome the above-mentioned various disadvantages and are stable even when incorporated in a detergent or the like and have a low risk of combustion when in contact with or mixed with combustible materials.

  In order to solve such problems, the present inventors have intensively studied to complete the present invention. That is, the present invention (1) granulates by adding 0.1 to 10 parts by weight of sodium bicarbonate to 100 parts by weight of sodium percarbonate, then 5 to 20 parts by weight of alkali metal carbonate and 0. 1 to 2 parts by weight of sodium percarbonate particles, and (2) 100 parts by weight of sodium percarbonate, 0.1 to 10 parts by weight of sodium bicarbonate, and granulated, The present invention relates to a method for producing sodium percarbonate particles, wherein 5 to 20 parts by weight of metal carbonate and 0.1 to 2 parts by weight of silicate are coated.

  According to the present invention, it is possible to obtain sodium percarbonate particles that exhibit high stability even when blended with a detergent containing zeolite, and that are less dangerous when contacted with or mixed with combustible materials.

  Sodium percarbonate is obtained by reacting an aqueous hydrogen peroxide solution and sodium carbonate in the presence of a stabilizer. The obtained sodium percarbonate crystal is a fine crystal and is generally granulated because it is difficult to handle as it is. In the present invention, sodium bicarbonate is added during the granulation. To uniformly disperse sodium bicarbonate in sodium percarbonate, a method of adding sodium bicarbonate to wet sodium percarbonate containing 1 to 20% by weight, preferably 5 to 15% by weight of water is preferred. There are various granulation methods, including a method of performing extrusion granulation with an extrusion granulator having a screen, or a method of performing granulation with a biaxial granulator having a feed region, a kneading kneading region, and a demulsification region. Although it can illustrate, the method of granulating with the extrusion granulator which has a screen is preferable, but it is not limited in order to obtain the sodium percarbonate particle | grains with a small amount of fine powders and being hard to break. As the binder added at the time of granulation, an inorganic binder and an organic binder having a binding effect are used.

  The sodium percarbonate particles obtained by granulation are dried and then coated with alkali metal carbonate and silicate. Examples of the alkali metal carbonate used for the coating include sodium carbonate, potassium carbonate, and lithium carbonate, but sodium carbonate is most preferred. Examples of the silicate include orthosilicate sodium, sesquisilicate sodium, metasilicate sodium, and sodium silicate (water glass), but solution-like sodium silicate (water glass) is preferable.

  The amount of sodium bicarbonate added to sodium percarbonate is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of sodium percarbonate. The amount of alkali metal carbonate coated on the sodium percarbonate particles is 5 to 20 parts by weight with respect to 100 parts by weight of sodium percarbonate, and the amount of silicate coated on the sodium percarbonate is 0.1 to 2 weights. Part.

  If the amount of sodium bicarbonate to be added, the amount of alkali metal carbonate to be coated, or the amount of silicate is less than the above range, the desired stability or risk control effect cannot be obtained, and the addition amount and the cover amount are in the above range. If it is more, it is not preferable because the effective oxygen concentration of sodium percarbonate is lowered and the solubility is deteriorated.

  The coating method is carried out while spray drying the solution of the coating agent while allowing sodium percarbonate particles to flow by flowing hot air from below in a fluidized tank. The solvent is preferably water. The solution is spray dried from a mixture of an alkali metal carbonate solution and a silicate solution, or each solution is spray dried with a separate nozzle. The temperature of sodium percarbonate during spray drying is 40-95 ° C. When the temperature is lower than 40 ° C., flow failure occurs due to aggregation of sodium percarbonate particles by the coating agent, and when the temperature exceeds 95 ° C., decomposition of effective oxygen becomes remarkable.

  The coated sodium percarbonate particles are 200-2000 μm, preferably 400-1000 μm. When the particle size of the sodium percarbonate particles is too small, the surface area per unit weight is increased, and the particle surface is not uniformly coated, and the stability and the dangerous substance suppressing effect are lowered. On the other hand, if the particle size is too large, the flow of particles at the time of coating deteriorates, and uniform coating becomes difficult and particle aggregation tends to occur.

  Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to these examples.

Example 1
Sodium carbonate and hydrogen peroxide were reacted in an aqueous solution, and the produced sodium percarbonate crystals were separated by a centrifuge and dehydrated to obtain wet sodium percarbonate containing 10% by weight of water. Add sodium bicarbonate to wet sodium percarbonate to 5% by weight and binder on a dry basis with respect to sodium percarbonate, and add water to adjust the water content to 11% by weight. Extrusion granulation was performed with a granulator equipped with a screen, followed by drying to obtain sodium percarbonate particles having an average particle diameter of 800 μm. 300 g of the obtained sodium percarbonate particles were coated using a fluidized drying coating apparatus (Palvis coating apparatus manufactured by Yamato Scientific Co., Ltd.). The coating was sprayed with 300 g of a mixed solution containing 15% by weight of sodium carbonate and 1% by weight of sodium silicate from a spray nozzle attached by flowing heated air from the perforated plate while flowing sodium percarbonate, and then dried for 5 minutes. 100 parts of sodium percarbonate particles were coated with 15 parts of sodium carbonate and 1 part of sodium silicate. The temperature of the sodium percarbonate particles in the coating was controlled to be 80 ° C.

The obtained sodium percarbonate particles had a moisture-absorbing zeolite blending stability of 85%, and the number of combustions in the combustion test was 10 times during the test (Table 1). The hygroscopic zeolite blending test and the combustion test method are shown below.
<Hygroscopic zeolite blending test>
Place 1 g of synthetic zeolite 4A powder (reagent manufactured by Wako Pure Chemical Industries, Ltd.), which has been absorbed for 24 hours or more in an atmosphere of 40 ° C. and 80% relative humidity, and 1 g of sample in a polyethylene container with a pinhole and shake well. After mixing, the mixture is allowed to stand for 4 days in an atmosphere of 40 ° C. and 80% relative humidity, and the effective oxygen concentration before and after being left is determined by titration with sodium thiosulfate.
Effective oxygen residual rate (%) = (effective oxygen concentration after test (%) / effective oxygen concentration before test (%)) × 100

<Combustion test>
A sample that passed through a sieve having an opening of 1180 μm was stored in a desiccator containing dry silica gel at a temperature of 20 ± 5 ° C. for 24 hours or more. Moreover, the Japanese cedar sapwood powder that did not pass through a 250 μm sieve and passed through a 500 μm sieve was dried at 105 ° C. for 4 hours, and then stored in a desiccator containing dry silica gel for 24 hours or more. 24g of preserved sample and 6g of preserved wood flour are mixed, put into a cone cup with a ratio of height to base diameter of 1: 1.75, and this is laid on a heat insulating plate to make a conical deposit, Leave in an atmosphere of 20 ± 5 ° C. and 50 ± 10% relative humidity for 1 hour. Thereafter, a ring-shaped nichrome wire heated to 1000 ° C. is brought into contact with the base of the deposit, and the ignition and combustion state are observed. Combustion occurs when the deposits ignite and the flame continues to the end. The test is performed 10 times per sample, and the number of combustion is compared.

Examples 2-5
The same procedure as in Example 1 was performed, except that the addition rate of sodium bicarbonate, the type of coating agent, the coating rate, and the temperature during coating were changed. The conditions and results are shown in Table 1.

Example 6
First, 300 g of a 15 wt% sodium carbonate aqueous solution was sprayed, and then 30 g of a 10 wt% sodium silicate aqueous solution was sprayed. The results are shown in Table 1.

Comparative Examples 1-3
The same procedure as in Example 1 was carried out, with or without the addition of sodium bicarbonate, the type of coating agent, and the coverage. The conditions and results are shown in Table 1.

Claims (7)

  0.1 to 10 parts by weight of sodium bicarbonate is added to 100 parts by weight of sodium percarbonate and granulated, and then 5 to 20 parts by weight of alkali metal carbonate and 0.1 to 2 parts by weight of silicate are coated. Sodium percarbonate particles characterized by that.   The sodium percarbonate particles according to claim 1, wherein the sodium percarbonate to which sodium bicarbonate is added is in a wet state containing 1 to 20% by weight of water.   Granulate by adding 0.1-10 parts by weight of sodium bicarbonate to 100 parts by weight of sodium percarbonate, and then coat 5-20 parts by weight of alkali metal carbonate and 0.1-2 parts by weight of silicate. A method for producing sodium percarbonate particles, comprising:   4. The method according to claim 3, wherein the sodium bicarbonate to which sodium bicarbonate is added contains 1 to 20% by weight of water.   4. The production method according to claim 3, wherein a coating layer is formed by spraying and drying an aqueous solution of a mixture of alkali metal carbonate and silicate on the granulated sodium percarbonate.   4. The production method according to claim 3, wherein an aqueous solution of alkali metal carbonate and an aqueous solution of silicate are sprayed and dried on the granulated sodium percarbonate with separate spray nozzles.   The method for producing sodium percarbonate particles according to claim 3, wherein the temperature of the sodium percarbonate is 40 to 95 ° C when the sodium percarbonate particles are coated.