JPS58208105A - Manufacture of fine adduct of hydrogen peroxide to sodium carbonate - Google Patents

Abstract

PURPOSE:To manufacture fine crystals of the adduct of hydrogen peroxide to sodium carbonate by adding Na2CO3 and H2O2 to mother liquor contg. Na2CO3, H2O2 and a silicic acid compound as a stabilizer for H2O2 by a restricted amount basing on the amount of Mg<++> and by reacting the compounds. CONSTITUTION:Na2CO3 and H2O2 are simultaneously added to mother liquor contg. 7-20wt% Na2CO3, 1.5-6wt% H2O2 in 1.3-0.2 molar ratio between Na2CO3 and H2O2, an Mg compound such as MgSO4 as a stabilizer for H2O2 by 0.001-0.5wt% expressed in terms of Mg<++>, and a water soluble silicic acid compound such as sodium silicate as a stabilizer for H2O2 by 0.003-0.1% expressed in terms of Si in <=12 molar ratio of Si to Mg<++>, and the compounds are reacted to obtain a slurry contg. fine crystals of the adduct (PC) of hydrogen peroxide to sodium carbonate. Fine seed crystals of PC are inoculated into the slurry to manufacture PC as a superior oxygen type bleaching agent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fine sodium carbonate hydrogen peroxide adduct (2N
a2CO3-3H202 is hereinafter referred to as pc. PC, which has been gaining importance in recent years as an oxygen bleaching agent, is usually manufactured as a granular product that is easy to handle. One method for providing this granular form is to granulate powdered crystals, and it is desirable to use as fine a powdered PC as possible as the granulation raw material3. A method for producing PC by reaction with an aqueous hydrogen peroxide solution is known, but if one attempts to obtain fine powdered PC by simply carrying out this reaction, the crystals will crystallize in the form of fine needles. , the aqueous hydrogen peroxide solution fed into the mother liquor as a raw material, resulting in an increase in the viscosity of the crystal suspension slurry? The rapid dispersion of sodium carbonate or its aqueous solution into the reaction mother liquor is inhibited.
As a result of the local concentration increase, the liquid quality deteriorates even further, and batch-type production has to be performed in which all of the crystallized crystals are separated by filtration and the reaction is then carried out again, resulting in very poor production efficiency. Not only are there serious problems industrially, but the crystals obtained under such conditions have poor dehydration properties, and the separated cake has an extremely high water activity, making it difficult to carry out commercially. For this reason, known methods mostly use polyelectrolytes such as polyphosphates or polyacrylates to reduce the particle size of the crystals.
Efforts have been made to provide a method for obtaining PC with good flowability and anti-wear properties by coarsening it to improve manufacturing operability, and the formation of fine crystals will impede filterability and other properties. It has been avoided as such. 1- PC that has become coarse in this way is not originally suitable for purposes such as granulation, and even if granulated, the characteristics such as high dissolution rate and high dispersibility that granulated particles should have mutually is not fully demonstrated. For the reasons of 2t et al., the known method is unsuitable and cannot be used as an industrial method for producing fine powdered PC.

Therefore, as a result of intensive research into a method for producing fine PC with good manufacturing operability, the inventors of the wood industry found that the desired PC can be easily produced industrially in a slurry state and in a state with good dehydration properties. I found a way to do it, and finally completed it.

Accordingly, the present invention provides a method for adding and coexisting Mg+ when sodium carbonate and hydrogen peroxide are supplied and reacted in a mother liquor containing sodium carbonate and hydrogen peroxide to crystallize PC. Furthermore, by limiting the use of a coexistence lid with a silicate compound added to this system as a hydrogen peroxide stabilizer for Mg+, the crystals that crystallize are modified and modified, resulting in good production operability. This invention relates to a machine for producing fine PC in a continuous or batch manner.

Conventionally, Mg+ has been used as a stabilizer to further improve its stability by using it in combination with a silicic acid compound added as a pcf stabilizer, and is generally added for this purpose, but for example, , Japanese Patent Publication No. 52-11789
According to No. 7, M g++ is used for the purpose of increasing the hardness of the particles, and in JP-A-53-146996, it is also used for the purpose of improving the free flow properties and anti-wear properties of the particles. However, these methods are carried out in combination with other strong modifiers, and their purpose of use, method, and form of the obtained PC are largely different from the present invention.

IV! Although it was found that the addition and coexistence of g ~ had a sufficient effect on the dehydration of crystals and the slurry state of tunki as shown in Examples 2 and 3, it was not found to have practical utility as the only modifier. It has also been found that in order to have and use it, certain conditions must be simulated. That is, PC
In order to ensure sufficient stability during storage and to avoid decomposition loss of hydrogen peroxide during production, the coexistence of a silicic acid compound is essential, and Mg'' alone cannot achieve this purpose. Due to the presence of silica, it is impossible to add and coexist a silicic acid compound to the reaction system, but due to this addition and coexistence, Mg+?
The effect of crystal modification and modification is significantly inhibited, and depending on the quantitative relationship, the effect cannot be expected to be expressed at all. In order to avoid such inconveniences and produce fine powdered PC with industrial value, it is necessary to satisfy a specific relationship between the two and other reaction crystallization conditions. .

According to the invention, 7! in the mother liquor with a controlled composition!
Monolithic sodium carbonate or its aqueous solution and hydrogen peroxide aqueous solution are supplied continuously or intermittently, and the reaction is performed while stirring in the reaction vessel, and the desired PC is crystallized, and this is continuously or intermittently fed. In a method in which the filtrate is extracted from the container by a batch method in which the target or the entire amount is extracted, solid-liquid separation is performed according to a conventional method, and the filtrate is recycled into the container immediately or after adjusting the composition. The mother liquor composition has a sodium carbonate concentration of 7 to 20% by weight, preferably 9 to 17% by weight, and a hydrogen peroxide concentration of 15% by weight.
-6% by weight, preferably 2-4% by weight, carbonated sugar
The molar ratio of hydrogen peroxide to IJ is not particularly limited when the supplied sodium carbonate is in an aqueous solution state, but when it is in a solid state, it is between 13 and 02, preferably between 0 and 1. to manage.

When the molar ratio exceeds the upper limit, partial formation of atomic coarse PC occurs, which is undesirable.
% by weight or more, and the water-soluble Si concentration is 0003 to 0.1
% by weight, and the molar ratio of Si0 to Mg+ is 12
It is preferably maintained at 8 or less. The sodium carbonate to be supplied can be in the form of an aqueous solution, solid powder, anhydrous sodium carbonate, or hydrated sodium carbonate17), but an aqueous solution has the advantage of being difficult to produce coarse particulate sodium percarbonate. On the other hand, since an excessive increase in the mother liquor occurs, it is necessary to concentrate or partially discard the mother liquor when recycling the mother liquor.In particular, it is advantageous to use solid anhydrous sodium carbonate as long as it is desired. It is also necessary to select and use the hydrogen peroxide concentration so as not to cause variations in the amount of mother liquor. Generally 4
0 weight? Preferably, a 0 to 80% by weight aqueous hydrogen peroxide solution is used. 1. The supply of Mg+ provides substantially Mg++; 1. The type of magnesium compound is not particularly limited as long as it is inert to the decomposition of hydrogen peroxide.
Generally, a water-soluble magnesium salt such as magnesium sulfate or magnesium chloride is dissolved in an aqueous solution or an aqueous hydrogen peroxide solution, and the solution is added continuously or intermittently to the reaction mother liquor.

In order to obtain a sufficient effect for modifying the crystals and improving the ST1j- state and dehydration property, the amount of Mg+'' added should be 100:0.01 to 100:1 to the supplied sodium carbonate.
1.0 is preferably 100:0.02 or more, and this addition causes the PL crystals to change from a needle-like shape to a plate-like shape, including intermediate shapes, which is the main cause of slurry state and deterioration of dehydration properties. As a result, the slurry state and dehydration properties are greatly improved as a result of the disentanglement between the crystals forming the PC. Addition of a compound is essential, and although stability is improved by this addition, the above-mentioned modification effect by Mg+ is significantly inhibited. Therefore, the amount of the silicic acid compound added must be within a limited range in relation to the amount of Mg+ added, and the amount must be such that the produced PC has sufficient stability for practical use. The amount of silicic acid compound supplied for this purpose is 100:0.02 to 100: as water-soluble Si to the weight of sodium carbonate supplied.
0.5 good ma 1 degree is 100:0.04~100:0.
2, and the molar ratio between Si/M and Mg is
g++ must be 25 or less, preferably 10 or less.

As the silicic acid compound, it is possible to use known stabilizers such as hydrolase, various water-soluble sodium silicates such as sodium metasilicate, magnesium silicate, or colloidal silica, but difficult or insoluble silicic acid compounds can be used. Since most of the added substances are suspended in the mother liquor in a substantially insoluble state, the above values are not absolute amounts, but represent the water-soluble portion or the portion that essentially dissolves in the mother liquor. It should be understood as an object. These silicic acid compounds are usually fed continuously or intermittently as an aqueous solution into the reaction mother liquor or into the circulated mother liquor. The sodium carbonate, hydrogen peroxide Mg++, and silicate compound are fed into the reaction vessel while being controlled so that the composition of each component in the mother liquor is within the range to be maintained.

Sodium carbonate and hydrogen peroxide supplied by the above method react in the mother liquor and crystallize and grow as PC, but if the raw material supply rate exceeds the crystallization rate, transient Due to the formation of a highly supersaturated system, the crystals become predominant needle-shaped crystals and rapidly precipitate, making it impossible to achieve the purpose.1.2 For this reason, sodium carbonate supplied continuously or intermittently The feeding rate is 00:50 or less, preferably 100% per unit time for the mother liquor.
: It is recommended that the crystals suspended in the mother liquor have a sufficient surface area in order to obtain a sufficient crystallization rate for the modified crystals and to avoid the formation of an excessively supersaturated system. , it is preferable that crystal growth be performed on them in an amount corresponding to the amount of crystallization. From this point of view, it is generally advantageous to have a larger amount of PC present in the mother liquor, but if it is too large, physical stimulation due to friction between crystals will also increase, making it easier to induce the formation of needle-like crystals. Therefore, it is preferable to extract the slurry from the reaction vessel so that its concentration is adjusted to 200 f/l to 400 y/l. In continuous reaction crystallization, in order to constantly obtain crystals with a stable grain size, it is necessary to constantly generate new crystal nuclei, but this depends not only on the degree of supersaturation but also on various other factors. It is not necessarily easy to control the supersaturation level as it is greatly influenced by the degree of supersaturation.Therefore, when carrying out the present invention, in order to reduce the influence of the degree of supersaturation and to control the grain size and size of the crystals over a fairly wide range,
By carrying out a so-called inoculation method in which fine PC is supplied as a seed crystal to the reaction crystallization system, control of the grain size or size of the crystals can be carried out more reliably.

The seed crystals used for this purpose are preferably plate-shaped crystals that have been pulverized by a conventional method such as a dry or wet method, either as a powder or suspended in a circulating mother liquor. The amount of seed crystals used is particularly limited depending on the desired crystal grain size, etc. Although it is not a problem, the use of loud noise leads to a decrease in production efficiency, so it is generally desirable to use a volume of 1:2 or less, preferably 1:05 or less, based on the weight of sodium carbonate to be supplied.

The average residence time of crystals, which can be determined from the raw material supply rate, the amount of slurry in the reaction vessel, the slurry concentration, the slurry withdrawal speed, etc., is important as it is a comprehensive consideration of various conditions, and if it is too short, Formation of an excessively supersaturated system for crystallization not only adversely affects the modification of crystals, but also impairs the complete progress of the reaction, especially when sodium carbonate is fed in solid form. For this reason, it is theoretically desirable for the residence time to be long, but this is not advantageous industrially because it leads to a decrease in production efficiency per unit time or reactor capacity.
It has an upper limit in this sense.

In the present invention, the residence time is 20 minutes to 4 hours, preferably 40 minutes or more. The liquid temperature at the stage of reaction crystallization is 10°C to 40°C, preferably 15″C to
Cooling is performed as necessary to maintain the temperature at 30°C; however, if the temperature exceeds 40°C, it is undesirable because it will cause a significant loss of hydrogen peroxide, while if it is too low, the hydrogen peroxide will not be supplied. If the sodium carbonate used is solid, it will be difficult to completely dissolve the raw material in the reaction vessel, and the reaction will be insufficient and it will be discharged.

Therefore, the temperature at this stage must be maintained at a necessary and sufficient temperature.7 However, since PC exhibits high solubility at high temperatures, the hydrogen peroxide concentration in the mother liquor inevitably increases at high temperatures. Increase hydrogen peroxide loss per volume of mother liquor. In order to avoid the disadvantages mentioned above, the reaction temperature should be kept at the lowest temperature necessary for complete reaction, and if desired, the slurry drawn out after the reaction may be cooled secondarily and added to the mother liquor. It is advantageous to further crystallize the dissolved PC and reduce the hydrogen peroxide concentration.The crystal size obtained by implementing this method is 300.
85-98% below micron, 45-98% below 150 micron
It is 80% fine powder crystal and is suitable as a raw material for granulation and other purposes.

When carrying out this method, in addition to the silicic acid compound, known stabilizers such as sodium pyrrolinoate, sodium tripolyphosphate, etc. or compounds such as E
Although it is possible to further improve the stability by using an organic chelating agent such as DTA, the stabilizing effect by Kota et al. is essentially based on complexation and sequestration of gold E, and Mg
It also partially blocks Sol g ++ and reduces the effect of Sol g ++. Therefore, when using these together illegally, the amount of Mg + added and coexisting should be increased depending on the combined amount and Mg + sequestering ability. In addition, when carrying out this method, known crystal modifiers such as polyelectrolytes such as sodium metaphosphate and sodium polyacrylate can be used together, but unless particularly desired. 91
This method does not require its addition at all.

The present invention will be explained below using examples.

Comparative Example 1 Sodium carbonate 139% by weight, hydrogen peroxide 2.6% by weight
, SiO,003% by weight was put into a reaction vessel with a diameter of 40 mm and stirred at a speed of l 3 Q i, p, m using a stirring blade with a diameter of 226 m, and the liquid temperature was kept at 25°. Add granular anhydrous sodium carbonate while maintaining at 6.C. OI'l/)Ir, 60% by weight hydrogen peroxide 49
79/Hr, 20% aqueous solution of No. 3 sodium silicate at 100? , /4ir continuously into the reaction vessel, the viscosity of the slurry increased 25 minutes after the start of the reaction, and the supplied sodium carbonate was not dispersed below the liquid surface.
Since it solidified on the liquid surface, it was impossible to continue the reaction any further. The slurry was taken out from the container using a wide sieve and dehydrated using a centrifuge at 1200 G for 2 minutes, and the dehydrated cake showed a water content of 29.4%.

Example 1 Sodium carbonate 13.9% by weight, hydrogen peroxide 26% by weight
, Mg + O, OO 7% by weight, Si 0.004% by weight, and further 200% by weight Mg5O
The reaction was carried out under the same conditions as in Comparative Example 1, except that the aqueous solution was continuously supplied at a rate of 122 f/Hr. After 1 hour of reaction, the slurry was taken out and dehydrated at 1200G for 2 minutes.The cake had a moisture content of 14.8%.Example 2 Sodium carbonate 139% by weight, hydrogen peroxide 2.6% by weight
, using a mother liquor having a composition of 4g 0.013% by weight, SiO, 007% by weight, and further 200% by weight MgSO
4 Aqueous solution is continuously supplied at a rate of 234 f/Hr 1-
The reaction was carried out under the same conditions as in Comparative Example 1 except for the following. The slurry was taken out 1 hour after the start of the reaction, and the moisture content of the cake after 2 minutes of centrifugal dehydration was 12.5%. Example 3 Carbonate + thorium 139% by weight, hydrogen peroxide 2.6% by weight
, Mg” 0. Mother liquor 30 with a composition of 5% by weight of OO
J was placed in a reaction vessel with a diameter of 40 mm and stirred at a speed of 10 Or, p, m using a stirring blade with a diameter of 22 C++. While maintaining the liquid temperature at 20 °C, it was added to granular anhydrous sodium carbonate 57 at 9/Hr, 60 °C. wt% hydrogen peroxide 4.66 iV
'Hr.

200 wt% Mg5O, aqueous solution at 150 f/Hr,
50% by weight aqueous solution of No. 3 sodium silicate at 110P
/Hr, and the reaction mother liquor composition was 13.5-15.0% by weight for sodium carbonate.
, hydrogen peroxide was supplied while adjusting the concentration to be 2.5 to 3.5% by weight, and the slurry concentration in the reaction vessel was 2.5% to 3.5% by weight.
The slurry was continuously drawn out from the container so as to maintain the temperature of 50 f/73, and after crystal filtration and separation using a centrifuge, the filtrate was circulated into the reaction container for continuous reaction crystallization. The dehydrated cake obtained after 4 hours had a moisture content of 143%. The crystals after drying were 95.2% by weight of 300 microns or less, 68.7% by weight of 150 microns or less,
The effective oxygen content was 146%.

Example 4 Carbonate) IJium 15.5% by weight, hydrogen peroxide 2.4%
Using a mother liquor having a composition of 0.013% by weight and 0.013% by weight of Mg++, granular anhydrous carbonic acid was added while maintaining the liquid temperature at 27°C). hydrogen s, s 4'l/rs 20.0% by weight M
g5O, aqueous solution 222? ,/kl,r, a 50% by weight aqueous solution of No. 3 sodium silicate was fed into the reaction vessel at a rate of 84 f'/Hr, and the reaction mother liquor composition was 14.5 to 16.0% by weight of sodium carbonate and hydrogen peroxide. About 2.3・~3333 weight slurry concentration is 32C) f/l
In the same continuous reaction as in Example 3, except that the water content was maintained at
, 15050 Mifuronri 04 weight 1%, and the effective oxygen content was 14.7%.

Example As a seed crystal, a part of the wet cake that was continuously extracted after the reaction and dehydrated was suspended again in the circulating mother liquor at a ratio of 1:1, wet-pulverized to form fine crystals, and the dry weight was A continuous reaction was carried out under the same conditions as in Example 4, except that sodium carbonate was continuously fed into the reaction vessel at a ratio of 100:15. After 6 hours of dehydration, the moisture content of the dried cake was 10.3%, and the crystal size after drying was 3 (10 mm+').
It was a fine powder crystal with a size of 982% smaller than 150 microns and 74.5% smaller than 150 microns - Nippon Peroxide Co., Ltd.

Claims (1)

[Scope of Claims] 1. Fine carbonic acid, characterized in that when sodium carbonate and hydrogen peroxide are reacted in an aqueous solution containing them and crystallized as a sodium carbonate-hydrogen peroxide adduct, 1 Mg is added thereto. Method for producing sodium carbonate-hydrogen peroxide adduct - Sodium dicarbonate and hydrogen peroxide are continuously or intermittently supplied to the mother liquor, and after reacting them, the produced sodium carbonate-hydrogen peroxide adduct is filtered from the mother liquor. The method according to claim 1, which is a continuous method or a batch method in which the filtrate is recirculated. 3. The manufacturing method according to claims 1 and 2, in which the amount of Mg added is 100:0.01 to 100:1 with respect to the weight of sodium carbonate supplied. 4. The stabilizer is a silicate or silicic acid. The amount of added water-soluble Si chopped into the supplied sodium carbonate is 100:0.02 to 100:05, and the molar ratio to the added Mg+ is 25 or less. The manufacturing method described in Items 1 and 2. 5 Mother liquor composition: 7 to 20% by weight for sodium carbonate concentration, 1.5 to 6% by weight for hydrogen peroxide concentration, Mg
Claim 81 characterized in that the ++ concentration is 0001 to 05% by weight, the Si concentration is 0.003 to 0.1% by weight, and the molar ratio of Si to Mg+ is maintained at 12 or less. The manufacturing method described in Items 1 and 2. 6 When performing reaction crystallization, fine sodium carbonate hydrogen peroxide adduct is added at a ratio of 1:2 to the weight of sodium carbonate to be supplied.
The manufacturing method according to claims 1 and 2, wherein the inoculation is supplied at the following ratios.