JPH0415163B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing sodium percarbonate having excellent wear resistance and stability. Specifically, sodium carbonate and hydrogen peroxide are reacted in an aqueous solution, and sodium percarbonate is crystallized in the presence of a specific substance, and a specific substance is further added to the obtained sodium percarbonate and impregnated into crystal particles. The present invention relates to a method for producing sodium percarbonate having excellent abrasion resistance and stability, which involves drying. BACKGROUND ART Sodium percarbonate (2Na ₂ CO ₃・3H ₂ O ₂ ) obtained by reacting sodium carbonate and hydrogen peroxide by various methods is mainly used as a bleaching agent. Manufactured in particulate form. Methods for producing these forms include (1) reacting sodium carbonate and hydrogen peroxide in an aqueous solution, and adding various crystal modifiers (modifiers) during the reaction crystallization to crystallize sodium percarbonate; (2) A method of spraying an aqueous sodium carbonate solution and a hydrogen peroxide solution onto sodium percarbonate seed crystals in a fluidized air stream to coarsen the particles. It is taken. Although the method (2) allows easily obtaining wear-resistant particles without requiring a crystal modifier, the crystal particles usually have the disadvantage that they have an unnecessarily large bulk specific gravity. Although it is difficult to obtain relatively wear-resistant particles with method (1), by selecting the type and amount of crystal modifier used, the particle shape and bulk specific gravity can be selected from a wide range, so it is possible to Many methods have been proposed using various crystal modifiers. For example, in British Patent No. 1278059, various phosphates are used to obtain crystal grains with low specific gravity.
Furthermore, Japanese Patent Publication No. 53-15475 discloses a method of obtaining dense crystal grains with excellent wear resistance using a polymer electrolyte acrylic acid polymer, and Japanese Patent Publication No. 54-101798 discloses a method using sodium hexametaphosphate. There is. On the other hand, sodium percarbonate has an essential drawback in that its stability during storage is greatly affected by trace amounts of impurities that must be mixed in from its raw materials, etc., and this drawback has been improved. To this end, a large number of proposals have been made to use silicic acids, phosphoric acids, magnesium salts, various organic chelating agents, etc. alone or in combination. For example, Japanese Patent Publication No. 47-36636 discloses a method for stabilizing sodium percarbonate using three or more agents selected from phosphoric acids, silicic acids, ethylenediaminetetraacetic acids, and nitrilotriacetic acids. . Problems to be Solved by the Invention The method of crystallizing sodium percarbonate by reacting sodium carbonate and hydrogen peroxide in an aqueous solution is such that when this method is simply carried out, the crystals of sodium percarbonate are fine needle-like crystals. Since they crystallize in a mutually entangled state, the liquid state of the reaction liquid slurry deteriorates, making it difficult to carry out a smooth reaction, and the resulting crystal particles have very poor filterability, making them unsuitable for practical use. , making it unsuitable as an industrial method. For this reason, these problems have been solved industrially by the presence of a crystal modifier during reaction crystallization, and efforts are being made to obtain crystal particles having physical properties that meet the objectives. However, as can be easily expected, the characteristics and quality of crystal particles greatly depend on the type of modifier present, and vary greatly depending on the type of modifier. The above-mentioned manufacturing process problems and various physical properties such as abrasion resistance that should be desirable when sodium percarbonate crystal particles are put into practical use have been improved to a sufficiently satisfactory degree. isn't it. Furthermore, in addition to the physical quality of the crystal particles as described above, the chemical properties of sodium percarbonate, such as the loss of its active ingredients over time, are also important issues that should be improved as much as possible. What is desired is a method that can provide more effective stabilization than the various stabilization methods currently available.
The purpose of the present invention is to improve both the physical properties of sodium percarbonate crystal particles represented by abrasion resistance and the chemical properties represented by stability, and to solve various problems in the manufacturing process. The objective is to provide a method for producing high-quality products that do not cause problems in handling or using. Means for Solving the Problems In order to solve the above-mentioned problems and obtain higher quality sodium percarbonate, the present inventors conducted extensive research and found that a polymer derived from α-hydroxyacrylic acid When hydrogen peroxide and sodium carbonate are reacted in an aqueous solution to crystallize sodium percarbonate, wear-resistant particles can be obtained which exhibit extremely effective crystal modification effects, and other specific stabilizing agents can be used. Particles with excellent wear resistance and stability can be obtained when present in combination with and during reaction crystallization, and furthermore, a specific stabilizer can be obtained by impregnating and drying the resulting sodium percarbonate crystal particles. The present inventors have discovered that the stability can be further improved in this method, and have completed the present invention. That is, one aspect of the present invention is a method for producing sodium percarbonate by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, in which a polymer derived from α-hydroxyacrylic acid (hereinafter referred to as group (A)) is used. The second invention relates to crystallizing sodium percarbonate in the presence of at least one compound of group (A) and aminopolycarboxylic acids, organic phosphonic acids, silicon acids,
The present invention relates to crystallizing sodium percarbonate in the presence of at least one selected from phosphoric acids, magnesium salts, and calcium salts (hereinafter sometimes referred to as group (B)). Yet another invention provides a method for producing sodium percarbonate by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, comprising: () at least one compound selected from group (A); ) A step of crystallizing sodium percarbonate in the presence of at least one compound selected from group (B) and separating the sodium percarbonate, and () adding the sodium percarbonate to group (A) or This invention relates to a method for producing sodium percarbonate having excellent wear resistance and stability, which comprises two steps: impregnating with at least one compound selected from group (B) and then drying. Sodium percarbonate is a mother liquor containing sodium carbonate and hydrogen peroxide, or a mother liquor with a controlled composition in which a salting-out agent such as sodium chloride is interposed to reduce the amount of sodium percarbonate dissolved in the mother liquor. Into the solution, sodium carbonate in solid form or an aqueous solution and a hydrogen peroxide solution having a concentration of 35 to 80% by weight are supplied at a ratio such that the molar ratio of hydrogen peroxide to sodium carbonate is 1.3 to 2.0, and the mixture is stirred. It is produced batchwise or continuously by performing reactive crystallization at a temperature of 10 to 35°C. The produced sodium percarbonate is separated from the mother liquor by filtration, and the mother liquor is recycled to the reaction crystallization step for use. In conventional methods, it is common to use phosphoric acids or sodium polyacrylate as a crystal modifier during reaction crystallization, but one of the features of the present invention is that the following general formula From α-hydroxyacrylic acid with an average molecular weight of 300 to 1,000,000 containing units represented by

【formula】

[Formula] (wherein 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), especially Preferably, poly-α-hydroxyacrylic acids and polylactones in which R ₁ and R ₂ are substituted with hydrogen atoms are used as crystal modifiers. This substance is a substance used for stabilizing hydrogen peroxide or sodium percarbonate solutions for bleaching as described in Japanese Patent Publication No. 1360/1983.
As can be seen from the fact that it exhibits a specific metal-sequestering effect based on its structure, it is a substance with properties significantly different from ordinary sodium polyacrylate. In the present invention, the polymer () can be used as a free acid or as an alkali metal such as Na, K, or
It is used as a salt of alkaline earth metals such as Mg and Ca, or ammonium and acine, but
It is preferable to use it as a water-soluble salt unless otherwise desired. Polylactone (), which is a precursor of polymer (), easily reacts with alkali metals, ammonium hydroxides, alkali carbonates, amines, etc. in an aqueous medium, and is at least partially induced into polymer (). Therefore, it can be used in substantially the same way as polymer (). In the present invention, in the reaction of the polymer derived from α-hydroxyacrylic acid with a residence time of 20 minutes to 4 hours and the crystallization step of sodium percarbonate, 0.005~0.5
It is used by adding it batchwise or continuously at a ratio of 0.02 to 0.3% by weight, but the method of addition may be such that the polymer is added in advance to the mother liquor used in circulation. Any method can be selected without particular limitation as long as it is introduced into the reaction crystallization system. The use of an appropriate amount of the polymer can improve the slurry properties during reaction crystallization due to its crystal modification effect, provide sodium percarbonate crystal particles with the desired shape, and stabilize hydrogen peroxide. The effect prevents undesirable decomposition of hydrogen peroxide present in the mother liquor, but if it is too little, the effect is insufficient, and if it is too much, it may give crystal particles with an unnecessarily high specific gravity. This may cause adverse effects such as a decrease in the active ingredient content of sodium percarbonate. Indeed, considering the method of JP-A-56-41808 in which a polymer is used as a stabilizer for sodium percarbonate, the stability of sodium percarbonate is advantageously improved by using a large amount of the polymer. It is estimated that However, since the production method of sodium percarbonate in the present invention is completely different from those methods, the sodium percarbonate crystal particles cannot be sufficiently stabilized even by using a large amount of polymer. In addition, in the present invention, in which reactive crystallization is performed in an aqueous solution, the polymer exhibits a strong crystal modification effect, which causes the above-mentioned disadvantages and limits the amount of use. It is difficult to improve the stability of sodium percarbonate to a sufficiently satisfactory extent only by adding this polymer. Therefore, in other inventions of the present invention, in addition to the polymer derived from α-hydroxyacrylic acid, at least one selected from aminopolycarboxylic acids, organic phosphonic acids, silicic acids, phosphoric acids, magnesium salts, and calcium salts is used. It is present when one type is used in combination for reaction crystallization. Alternatively, the sodium percarbonate crystal particles obtained by further filtration are subjected to a secondary stabilization treatment. The aminopolycarboxylic acids present during reaction crystallization include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, (N-hydroxyethyl)ethylenediaminetriacetic acid, nitrilotriacetic acid, triethylenetetraminehexaacetic acid, and their alkali metals and alkaline earth metals. , ammonium or amines, and organic phosphonic acids include 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid),
Aminotri(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and their salts with alkali, alkaline earth metals, ammonium, amines, etc. In addition, silicic acids include alkali metal salts of orthosilicic acid and metasilicic acid, various water glasses, colloidal silica, etc., and phosphoric acids include orthophosphoric acid, polyphosphoric acid, polymetaphosphoric acid, and their salts of alkali metals, ammonium, etc. Furthermore, magnesium salts and calcium salts are magnesium or calcium salts of inorganic and organic acids such as sulfuric acid, hydrochloric acid or acetic acid. Select at least one type of these substances,
It is used in combination with a polymer to obtain sodium percarbonate by reaction crystallization, but the proportion of its use depends on the amount of sodium percarbonate produced when the selected agent is aminopolycarboxylic acids or organic phosphonic acids. 0.02 to 1% by weight, preferably 0.1 to 0.5% by weight, respectively, and in the case of silicic acids and phosphoric acids, Si and P are used in amounts of 0.005 to 0.5% by weight, 0.005 to 0.4% by weight, respectively, and magnesium. In the case of salts and calcium salts, Mg and Ca are each contained in a range of 0.005 to 0.1% by weight. The reaction crystallization system in the present invention may further contain a polymer electrolyte such as sodium polyacrylate as necessary to obtain crystal particles having a desired shape, but this is not necessary unless particularly desired. It is. By using a polymer derived from α-hydroxyacrylic acid in combination with the above-mentioned agents, sodium percarbonate is produced as wear-resistant crystalline particles with an average particle size of 150 to 2000 microns with the necessary stability as a primary stage. It can be crystallized, and hydrogen peroxide dissolved in the mother liquor is also stabilized to a necessary and sufficient degree. The crystallized sodium percarbonate is separated from the mother liquor by filtration and, either wet or after drying, a stabilizing agent is dispersed and impregnated into the percarbonate crystal particles to ensure a higher degree of stabilization. It can be subjected to a secondary stabilization step. Wet sodium percarbonate after filtration or sodium percarbonate after drying is used to improve the efficiency of drug dispersion and impregnation into crystal particles in this stabilization process, mechanical agglomeration in the treatment process, shape of crystal particles, physical properties, etc. Taking into account the change in water content, the water content is controlled to be 30% by weight or less, preferably 1 to 15% by weight. The agent used in the secondary stabilization step is α
- polymers derived from hydroxyacrylic acid,
At least one kind selected from organic phosphonic acids, aminopolycarboxylic acids, silicic acids, phosphoric acids, magnesium salts, or calcium salts, and specific examples of these drugs are those exemplified as drugs used in reaction crystallization. It is similar to The proportion of the agent used in this step is determined by the dry amount of sodium percarbonate when the agent selected is a polymer derived from α-hydroxyacrylic acid or an organic phosphonic acid or an aminopolycarboxylic acid. When selected from silicic acids, phosphoric acids, magnesium salts, and calcium salts, Si, P, Mg, and Ca are each used in an amount of 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. ~0.4 wt%, 0.005~0.4 wt%,
It is preferably used in a range of 0.001 to 0.1% by weight, 0.001 to 0.1% by weight. The operation of adding and impregnating sodium percarbonate with these agents is carried out using a known batch or continuous mixer or kneader such as a V-type mixer, ribbon mixer, screw mixer, paddle mixer, or air flow mixer.
Moist or dry sodium percarbonate is supplied to these, and an aqueous solution or powder of the drug is added thereto, if necessary, so that the water content of the sodium percarbonate is preferably 1 to 15% by weight. Adjust and mix uniformly. This operation requires strict limitations on the equipment used, moisture content, etc., as long as the drug is sufficiently dispersed in the sodium percarbonate crystal particles and does not cause changes in the physical properties of the crystal particles due to destruction, etc. However, the use of equipment that tends to pressurize or knead is sometimes inappropriate in relation to the moisture content. Through the above operations, the drug is dispersed and impregnated onto the surface and inside of the sodium percarbonate crystal particles, but the progress of dispersion and impregnation is substantially continued until the moisture is removed by drying. Therefore, it is desirable to carry out the process so that the time required for adding and mixing the chemicals and then removing moisture by drying is 1 to 90 minutes. Effect In the present invention, although the mechanism of action by which the polymer derived from α-hydroxyacrylic acid exerts a crystal modification effect on sodium percarbonate crystals is not clear, The crystal modification behavior of the modifier, which is generally explained by adsorption on the surface, precipitation, epitaxy, etc., inhibits the formation of crystal nuclei or changes the rate of solute movement toward the growing crystal surface. As a result, it is thought that the fine needle-like crystals of sodium percarbonate that are originally produced change into wear-resistant crystal particles. On the other hand, regarding the property that sodium percarbonate decomposes over time and loses its active ingredients, although the details of the decomposition mechanism are not necessarily clear, it is generally catalyzed by metals and other substances that are present in trace amounts in sodium percarbonate. It is estimated that the action causes decomposition, and that the presence of heat and moisture significantly accelerates the decomposition, and the polymer derived from α-hydroxyacrylic acid acts on the metal that catalyzes the decomposition. It is thought that blocking this will contribute to stabilization. Furthermore, it is known that metal sequestering agents used as stabilizers have different sequestering abilities for different metal species depending on their type, and in the present invention, polymers and other stabilizing agents are used as stabilizers. The effect of using drugs in combination is that the combined stabilizing drugs compensate for the lack of each other's abilities against the various harmful metals present in sodium percarbonate, resulting in more efficient and synergistic stabilization. It is expected that this will have a positive effect. When sodium percarbonate crystal particles are exposed to various atmospheres, such as high temperatures or high humidity, decomposition is significantly accelerated and the active ingredient is lost within a short period of time. In this case, it is thought that thermal factors act on the entire surface and inside of the crystal particles and accelerate decomposition, whereas moisture particularly affects the surface layer of the crystal particles and decomposes them. It is estimated that this will promote Hydrogen peroxide, which is the active ingredient in sodium percarbonate, produces water as a by-product when it decomposes, so the progress of decomposition leads to further self-promotion of decomposition.
The surface layer of the crystal grains particularly needs to be highly stabilized. The stabilization method in the present invention is as follows:
Particularly rational for stabilizing the internal and surface layers of crystal particles, and as a result, obtaining sodium percarbonate that is highly stable even at high temperatures and high humidity, which could not be achieved with conventional methods. It is assumed that this made it possible. Effects of the Invention According to the present invention, as a result of effective modification of sodium percarbonate crystal particles, a good reaction crystallization state can be obtained, and since crystal particles with a low water content can be filtered out, drying is not a burden. Provides a manufacturing method that has many advantages in the production of sodium percarbonate, such as a reduction in hydrogen peroxide production and an improved yield of hydrogen peroxide because the crystal modifier simultaneously contributes to stabilizing hydrogen peroxide in the mother liquor. It is of great industrial significance in that it is possible to produce and provide high-quality sodium percarbonate that has particularly excellent practicality such as abrasion resistance and storage stability. 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 10 Using mother liquor 150 having a composition of sodium chloride concentration 22.0 wt%, sodium carbonate concentration 4.7 wt%, and hydrogen peroxide concentration 0.9 wt%, granular sodium carbonate was added at 30.0 Kg/hr, 60 wt% while stirring. hydrogen peroxide
Continuously supplies sodium chloride (normal salt) at a rate of 24.1 Kg/hr to maintain its initial concentration, while at the same time deriving from α-hydroxyacrylic acid in the proportion shown in Table 1. Polymers and other stabilizing agents were also continuously added to the reaction vessel. The temperature during reaction crystallization was 25℃, the slurry was extracted from the reaction vessel and filtered so that the average residence time was 60 minutes, and the filtrate was recycled for use, resulting in a continuous reaction for 2 to 3 hours. I went there. Various stabilizing agents were added to the wet sodium percarbonate obtained by filtration using a ribbon mixer, mixed for 5 minutes to impregnate the agent, and then fluidized for 30 minutes to obtain dry sodium percarbonate. . The obtained sodium percarbonate was measured for storage stability and other physical properties.
The results are shown in Table 1. In addition, various measurements were performed in the following manner. Moisture content The slurry extracted from the reaction vessel was dehydrated by centrifugation at 1400G for 3 minutes, the obtained wet particles were dried, and the moisture content was calculated from the loss on drying. Storage stability Thermal stability: 2g of a sample with a known organic oxygen content was placed in an open styrene container and left in a drying oven at a temperature of 50°C for two weeks, after which the remaining effective oxygen content was measured. The residual rate was calculated from the ratio with the effective oxygen content before leaving. Humidity stability: Similarly, the sample was left at a temperature of 40°C and a relative humidity of 100% for 24 hours, and the effective oxygen residual rate was calculated. Abrasion resistance 30g of sample from which 100Me' had passed was removed in advance
diameter with mm stainless steel ball 30g
It was placed on a 75 mm 100Me' sieve and vibrated for 20 minutes with the electromagnetic vibration intensity fixed, the amount passing through the 100Me' sieve was measured, and the ratio of the amount passing through to the sample amount was calculated.

【table】

[Table] Examples 11-15 Sodium carbonate concentration 13.0wt%, hydrogen peroxide concentration
A mother liquor 150 having a composition of 3.1 wt% was used, sodium chloride was not used as a salting-out agent, and the types and amounts of polymers derived from α-hydroxyacrylic acid and stabilizers were as shown in Table 2. The same continuous reaction as in Examples 1 to 10 was carried out except for the following changes, and wet sodium percarbonate was obtained by continuous filtration. Next, each of these was supplied to a paddle mixer, and mixed while continuously adding a stabilizer in the proportion shown in Table 2. After a residence time of 3 minutes, the mixture was taken out from the mixer and dried. The storage stability and other properties of the obtained sodium percarbonate were as shown in Table 2.

[Table] Comparative example 1 450g/hr of No. 3 sodium silicate as a stabilizer
The same reaction crystallization as in Example 1 was carried out without using any other stabilizer or crystal modifier except that the slurry condition deteriorated and it became difficult to continue the reaction. 1400G of slurry after reaction crystallization
The moisture content of wet sodium percarbonate obtained by centrifugal dehydration for 3 minutes at
The humidity stability was 87.4%, and the humidity stability was 62.7%.

[Brief explanation of drawings]

Figure 1 is a micrograph (500x) of sodium percarbonate crystals obtained in Comparative Example 1, Figure 2 is an example
This is a micrograph (50x magnification) of the crystal particles (36 to 60 meshes) obtained in step 10.

Claims (1)

[Scope of Claims] 1. A method for producing sodium percarbonate by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, comprising: (A) at least one polymer derived from α-hydroxyacrylic acid; A method for producing sodium percarbonate, characterized by crystallizing it in the presence of sodium percarbonate. 2. In a method for producing sodium percarbonate by reacting sodium carbonate and hydrogen peroxide in an aqueous solution, at least one species is selected from each of the following groups (A) and (B), and in the presence of these compounds, A method for producing sodium percarbonate, characterized by crystallizing it. (A) Polymer derived from α-hydroxyacrylic acid (B) Aminopolycarboxylic acids, organic phosphonic acids, silicic acids, phosphoric acids, magnesium salts and calcium salts 3 Reaction of sodium carbonate and hydrogen peroxide in an aqueous solution In the method for producing sodium percarbonate, () at least one compound selected from the following group (A), or at least one compound each selected from the following groups (A) and (B); a step of crystallizing sodium percarbonate in the presence of a compound of
A method for producing sodium percarbonate, which comprises two steps: impregnating with at least one compound selected from group (B) and then drying. (A) Polymers derived from α-hydroxyacrylic acid (B) Aminopolycarboxylic acids, organic phosphonic acids, silicic acids, phosphoric acids, magnesium salts and calcium salts.