JPH051205B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a process for producing stabilized sodium percarbonate. Specifically, a polymer derived from α-hydroxyacrylic acid is added to sodium percarbonate crystal particles obtained by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, and the crystal particles are impregnated. Concerning a method for producing sodium percarbonate. Background Art Sodium percarbonate (2Na ₂ CO ₃ 3H ₂ O ₂ ), which is obtained by reacting sodium carbonate and hydrogen peroxide by various methods, is mainly used as a bleaching agent and is usually easy to handle. It is manufactured in the form of particles. The reaction mode when sodium carbonate and hydrogen peroxide are reacted to obtain sodium percarbonate is: (1) A large amount of aqueous solution (mother liquor) is interposed, raw materials are supplied to this, the reaction is carried out, and sodium percarbonate is crystallized. (wet method): spraying an aqueous sodium carbonate solution and an aqueous peroxide solution onto sodium percarbonate seed crystals in a flowing air stream;
Methods can be broadly classified into methods in which a mother liquor is not involved during the reaction (drying method), such as a method in which crystals are grown while drying, or a method in which a hydrogen peroxide solution is directly added to solid sodium carbonate for reaction. Regardless of the manufacturing method used, the stability of sodium percarbonate is largely affected by trace amounts of impurities that must be mixed in from raw materials, etc., and the essence is that the active ingredients are likely to be lost over time. Therefore, efforts have been made to improve stability using various stabilizers in order to improve stability in any of the methods.
For this purpose, many proposals have been made for stabilizing using silicic acids, phosphoric acids, magnesium salts, or various organic chelating agents alone or in combination.For example, in Japanese Patent Publication No. 47-36636, phosphoric acids,
JP-A-56-41808 describes a method of stabilizing sodium percarbonate by using three or more agents selected from silicic acids, ethylenediaminetetraacetic acids, and nitrilotriacetic acids during reaction crystallization. Methods have been shown in which polymers derived from alpha-hydroxyacrylic acid are used as stabilizers. Problems to be Solved by the Invention The dry method is an advantageous manufacturing method in that sodium percarbonate can be directly obtained without involving a mother liquor, but the resulting percarbonate The use of sodium may be limited due to problems such as an unnecessarily high specific gravity, and in many cases, a wet method is selected as a manufacturing method because of its flexibility in these respects. However, in the wet method in which sodium carbonate and hydrogen peroxide are reacted in an aqueous solution to crystallize sodium percarbonate, if this is simply carried out, sodium percarbonate will form fine needle-shaped crystals that form mutually. Since crystallization occurs in a fallen state, the liquid state of the reaction slurry deteriorates, making it difficult to carry out a smooth reaction, and the resulting crystal particles are extremely hyperactive and impractical. In particular, these problems have been solved by allowing a crystal modifier (crystal modifier) to coexist during crystallization. However, the various stabilizers present during crystallization often inhibit the proper crystal modification action of crystal modifiers, so they must be used in limited amounts, or they must be used in large amounts. Due to the presence of the mother liquor, there are problems such as the ability to effectively stabilize the sodium percarbonate crystal particles, which is the original purpose of using a stabilizer, in proportion to the amount used. It has the disadvantage that it is difficult to produce ideally stabilized sodium percarbonate, and the stabilizer disclosed in JP-A-56-41808 mentioned above is also not satisfactory for these reasons. Unable to exhibit stabilizing effect. The purpose of the present invention is to effectively improve the insufficient stability of sodium percarbonate obtained by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, and to eliminate the problem of quality deterioration during its utilization. The objective is to provide a method for manufacturing high quality products. Means for Solving the Problems As a result of intensive research to obtain higher quality sodium percarbonate with excellent stability, the present inventors found that α
The present inventors have discovered that the stability of sodium percarbonate can be greatly improved by impregnating sodium percarbonate crystal particles with a polymer derived from -hydroxyacrylic acid, and have completed the present invention. That is, in the present invention, an aggregate derived from α-hydroxyacrylic acid is added to sodium percarbonate crystal particles obtained by reacting sodium carbonate and hydrogen peroxide in an aqueous solution. This is a method for producing stabilized sodium percarbonate for impregnation. Sodium percarbonate to be stabilized in the present invention is generally contained in a solid or It is produced batchwise or continuously by supplying sodium carbonate as an aqueous solution and hydrogen peroxide at a concentration of 35 to 80% by weight, and performing reaction crystallization at a temperature of 10 to 35°C with stirring. , crystal modifiers selected according to the purpose, such as condensed phosphates such as tripolyphosphates, hexametaphosphates, polyelectrolytes such as polyacrylates, or other agents having crystal modifying effects. In addition to crystallizing sodium percarbonate having a desired granular or powder shape, various water glasses, silicic acids such as metasilicates, phosphoric acids such as orthophosphates and polyphosphates, and ethylenediamine are interposed. Aminopolycarboxylic acids such as tetraacetate, diethylenetriaminepentaacetate, etc., organic sulfonic acids such as 1-hydroxyethylidene-1,1-diphosphonic acid, magnesium salts such as magnesium sulfate, and other stabilizing agents. The presence of one or more agents stabilizes the sodium percarbonate to the required extent. The feature of the present invention is that the sodium percarbonate produced by the general method described above is separated from the mother liquor by filtration, and after drying to form wet crystal particles or dry crystal particles, α-hydroxy The object is to highly stabilize sodium percarbonate by impregnating crystal particles with a polymer derived from acrylic acid. The polymer derived from α-hydroxyacrylic acid in the present invention is a substance described in Japanese Patent Publication No. 60-1360, and has an average molecular weight of 300 to 1,000,000 and contains a unit represented by the following general formula. Polymers derived from acrylic acid ()

【formula】

[Formula] and polylactone () (in the formula, R ₁ and R ₂ represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms optionally substituted with a hydroxyl group or a halogen atom). As the polymer, poly-α-hydroxyacrylic acid and its polylactone can be particularly preferably used. In the present invention, the polymer () is used as a free acid, or as a salt of an acrylic metal such as Na or K, an alkaline earth metal such as Mg or Ca, or a salt of ammonium or amine. It is preferred to use them as water-soluble salts, especially if desired. Polylactone (), which is a precursor of polymer (), easily reacts with hydroxides of alkali metals, ammonium, etc., and other basic compounds in an aqueous medium, and is at least partially led to polymer (). It can be used in substantially the same manner as polymer (). For stabilization, these polymers are used in an amount of 0.01 to 1.0% by weight, preferably 0.02 to 0.5% by weight, based on the dry weight of sodium percarbonate, and are impregnated into crystalline particles of sodium percarbonate. In this case, if the amount used is too small, the stabilizing effect will be insufficient, and if it is used in excess, it will be economically disadvantageous. In the present invention, in order to make the stabilization by the above polymer more effective, if desired, a magnesium salt or calcium salt of an inorganic or organic acid such as sulfuric acid, hydrochloric acid or acetic acid may be added to the polymer. In combination, Mg and Ca are used in a proportion of 0.001 to 0.1% by weight, preferably 0.002 to 0.05% by weight, based on the dry weight of sodium percarbonate. It is not possible to expect the original effect of using them in combination. In the present invention, the stabilization operation of impregnating the sodium percarbonate crystal particles with a stabilizing agent is carried out on wet crystal particles separated from the mother liquor by filtration after crystallization.
Alternatively, dry crystal particles that have been dried once can be mixed with a general batch or continuous mixer such as a V-type mixer, ribbon mixer, screw mixer, paddle mixer, or airflow mixer, or a double-arm kneader or continuous mixer. This is carried out by feeding the stabilizer into a general kneader such as a kneader, adding an aqueous solution or powder of the stabilizer, and mixing or kneading. In addition, in order to minimize undesirable changes in shape and physical properties of crystal particles, the water content of sodium percarbonate during stabilization treatment is set to 30% by weight or less, preferably 1 to 20% by weight. Adjust and implement. The type of mixer or kneader used for stabilization treatment is not particularly limited as long as it is capable of uniformly dispersing the stabilizer into the crystal particles, but sodium percarbonate If the shape of the particles is particulate or granular, and it is necessary to maintain the shape and physical properties of the particles, it is recommended to avoid using equipment that tends to pressurize or knead the particles, which may cause destruction of the particles. On the other hand, when granulation is performed by secondary means such as granulation after the stabilization treatment, it is advantageous to perform the stabilization treatment using a kneader or kneading machine.
The stabilization time using these mixers or kneaders varies depending on the intensity of mixing, the amount of coexisting moisture, etc., but is usually carried out for 0.5 to 10 minutes.
However, the substantial impregnation of the stabilizer into the crystal particles progresses over a period of time until the water is removed by drying, so the drying process in which the stabilizer is added and mixed and the water is removed by drying The time until the end is 1
It is desirable to carry out the test for ~90 minutes. The details of the decomposition mechanism in which sodium percarbonate decomposes over time and loses its active ingredients are not necessarily clear, but in general, decomposition is caused by the catalytic action of trace amounts of metals and other substances present in sodium percarbonate. It is estimated that these effects are significantly accelerated by the presence of heat and moisture. It is presumed that the polymer derived from α-hydroxyacrylic acid acts on the metal that catalyzes decomposition and contributes to stabilization by blocking it. Sodium percarbonate crystal particles are exposed to various atmospheres,
For example, when exposed to high temperatures or high humidity, decomposition is significantly accelerated and active ingredients are lost in a short period of time; While it is thought that moisture acts on the entire surface to accelerate decomposition, it is presumed that moisture affects the crystal particles, particularly from the surface layer, and accelerates decomposition. Hydrogen peroxide, which is an active ingredient in sodium percarbonate, produces water as a by-product upon decomposition, so that the progress of decomposition leads to further self-promotion of decomposition. From these points of view, it is considered that the surface layer of the crystal grain needs to be particularly highly stabilized, and the stabilization method of the present invention involves distributing the stabilizer abundantly and unevenly in the surface layer of the crystal grain. As a result, it is expected that it will be possible to obtain highly stabilized sodium percarbonate, which has not been possible with conventional methods. Effects of the Invention According to the present invention, effective stability improvement is achieved by subjecting sodium percarbonate obtained by reaction crystallization to an extremely simple stabilization treatment, so that sodium percarbonate is produced. In addition, it is possible to reduce the difficulties in manufacturing caused by trying to achieve a high degree of stabilization when producing sodium percarbonate crystal particles, and to reduce the It is of great industrial significance in that it allows highly stabilized sodium percarbonate with high practicality to be obtained without impairing various physical properties. EXAMPLES The present invention will be described below with reference to Examples, but the present invention can be practiced without being limited thereto. Examples 1 to 4 and Comparative Example 1 To an aqueous solution 150 containing sodium chloride at a ratio of 22.0 wt%, 30 Kg/hr of granular sodium carbonate and 25.7 Kg/hr of 60 wt% hydrogen peroxide were added while stirring.
hr, No. 3 sodium silicate was fed at a rate of 0.25 Kg/hr, sodium hexametaphosphate was fed at a rate of 0.1 Kg/hr, the reaction temperature was 25° C., and the reaction time was 60 minutes. Capacity 45Kg of granular wet sodium percarbonate obtained separated from mother liquor
100 in a ribbon mixer, and while mixing, sprayed an aqueous stabilizer solution with the proportions shown in Table 1 over 3 minutes to bring the water content of sodium percarbonate to 15%.
The stabilizer was impregnated by mixing for 7 minutes. The stability of the sodium percarbonate obtained by fluidized drying for 30 minutes after the above operations was as shown in Table 1. The stability was measured in the following manner. (Stability measurement) Put 2 g of a sample with a known effective oxygen content into a styrene container, leave it at a temperature of 40°C and a relative humidity of 80% for 5 days, then measure the remaining effective oxygen content. The residual rate was calculated from the ratio with the content rate.

[Table] Examples 5 to 8 and Comparative Example 2 The reaction to produce granular sodium percarbonate was carried out at a concentration of sodium carbonate that did not contain sodium chloride.
13.0wt%, aqueous solution with hydrogen peroxide concentration of 3.1wt% 150
The reaction was repeated under the same conditions as in Example 1, except that a stabilizer was added to the granular wet sodium percarbonate obtained separately from the mother liquor in the same manner as in Examples 1 to 4 in the proportions shown in Table 2. The stability was measured after drying. The measurement results were as shown in Table 2.

[Table] Examples 9 to 11 and Comparative Example 3 14.5 wt% sodium carbonate, hydrogen peroxide
30Kg/hr of granular sodium carbonate was added to an aqueous solution containing 2.5wt% while stirring.
The same reaction as in Example 1 was carried out except that 60 wt% hydrogen peroxide was continuously supplied at a rate of 26.0 Kg/hr, No. 3 sodium silicate at a rate of 0.25 Kg/hr, and 20 wt% magnesium sulfate solution at a rate of 0.45 Kg/hr. 6 kg of finely crystalline sodium percarbonate with a water content of 10.7 wt% obtained by separating from the mother liquor was placed in a double-arm kneader with a capacity of 20, and a solution or powder of a stabilizer in the proportion shown in Table 3 was added. After kneading for 5 minutes, extrusion granulation was performed by performing operations necessary for granulation such as adding a binder, and after drying, granular sodium percarbonate was obtained. The stability of the obtained sodium percarbonate was as shown in Table 3.

[Table] Comparative Example 4 636 g of sodium carbonate was placed in a reaction tube with a diameter of 10 cm at the bottom, a diameter of 20 cm at the top, and an internal volume of 18, and heated air at a temperature of 40 to 80°C was heated at 90 to 300 °C.
54.1 wt% containing PHAS at a rate of 0.45% based on the weight of sodium carbonate used, while feeding from the bottom flow plate at a rate of 1/mm to activate the sodium carbonate.
A reaction was carried out by spraying 566 g of hydrogen peroxide solution onto sodium carbonate while controlling the temperature of the fluid to not exceed 30°C, and after the hydrogen peroxide was sprayed, drying was continued for 20 minutes to obtain an effective oxygen content of 14.3. wt% sodium percarbonate was obtained. 2 g each of the sodium percarbonate obtained by this dry process and the sodium percarbonate obtained in Example 3 using PHAS as a stabilizer were added to 40
Table 4 shows the results of comparing the stability after being left for 24 hours at a temperature of 100% relative humidity.

【table】

Claims (1)

[Claims] 1. Adding at least one kind of polymer derived from α-hydroxyacrylic acid to sodium percarbonate crystal particles obtained by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, A method for producing stabilized sodium percarbonate, which comprises impregnating sodium percarbonate crystal particles. 2. Claim 1 characterized in that a magnesium salt or/and a calcium salt are further added and impregnated into the sodium percarbonate crystal particles.
Manufacturing method described in section. ₃ A polymer derived from α _- hydroxyacrylic acid has the general formula A polymer () with an average molecular weight of 300 to 1,000,000 containing a unit (representing an alkyl group having 1 to 3 carbon atoms) or a polylactone () derived from α-hydroxyacrylic acid, or an alkali metal or alkaline earth thereof 2. The method according to claim 1, which is a salt of a metal, ammonium, or amine. 4. The method according to claim 1, wherein at least one polymer derived from α-hydroxyacrylic acid is used in an amount of 0.01 to 1.0% by weight based on the dry weight of sodium percarbonate. 5. The manufacturing method according to claim 2, wherein the magnesium salt and/or the calcium salt are used in an amount of 0.001 to 0.1% by weight as Mg or Ca based on the dry weight of sodium percarbonate. 6 At least one type of polymer derived from α-hydroxyacrylic acid is poly-α-hydroxyacrylic acid or its alkali metal, alkaline earth metal, ammonium, or amine salts, or poly-α-hydroxyacrylic acid. The manufacturing method according to claim 1, wherein the polylactone is a polylactone.