JP2002179641A - Method for producing peroxyurea - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing peroxyurea having excellent high- temperature stability and high crystal yield. SOLUTION: In this method for producing peroxyurea by allowing hydrogen peroxide to react with urea followed by crystallization of the peroxyurea formed, a sulfate salt is added to the reaction mother liquor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing urea peroxide by crystallization by adding a sulfate when producing urea peroxide by a crystallization method. More specifically, by adding a water-soluble sulfate to the reaction mother liquor and uniformly dissolving it to carry out the reaction crystallization, the yield of urea peroxide is improved, and the high-temperature storage stability is improved. The present invention relates to a method for producing urea.

[0002]

2. Description of the Related Art It has long been known that urea peroxide is a solid organic peroxide and can be easily obtained by reacting hydrogen peroxide with urea. However, there is a problem that heat stability and hygroscopicity are inferior to those of percarbonate and perborate, which are the same hydrogen peroxide adducts.

[0003] Some attempts to improve the stability of urea peroxide have been published, and as an example having an effect on storage stability, it is known to add an acidic substance such as an organic acid or an inorganic acid into a reaction system. Have been. However, these methods can improve the storage stability of urea peroxide at room temperature, but have not been studied for high-temperature stability. As an example of using an inorganic acid, Japanese Patent Publication No. 45-3
Japanese Patent No. 4370 discloses a technique for improving storage stability at room temperature using an orthophosphate, a pyrophosphate or the like, but about 15 to 33% by weight of urea peroxide is used. Therefore, the obtained crystal is a mixture of a phosphoric acid compound and urea peroxide, rather than called urea peroxide,
Other techniques have also been disclosed for preparing a mixture with gypsum and a mixture with metaboric acid, but none of these techniques are insufficient to obtain high-purity urea peroxide.

Also, urea peroxide needs to be dried as quickly as possible after obtaining wet powder in order to prevent liberation and decomposition of hydrogen peroxide. However, urea peroxide produced by the conventional technique has poor high-temperature stability, and when drying is performed at a high temperature in the drying process, a reduction in the amount of active oxygen due to the decomposition of urea peroxide and a problem in purity and quality occur. Therefore, there is also a problem in productivity, such as the need to limit the temperature in the drying step, the need to carry out drying under reduced pressure, and the need to increase the drying time at low temperatures.

As described above, in the method of producing urea peroxide, which has been conventionally studied, there is an example in which the storage stability is improved by using a known stabilizer, but an attempt is made to improve the stability in a high-temperature atmosphere. There were no examples, and there were many problems with industrial production.

[0006]

SUMMARY OF THE INVENTION As described above, it is an object of the present invention to solve the problems with urea peroxide obtained by the prior art manufacturing method. It is an object of the present invention to provide a method for producing urea peroxide having improved productivity by imparting properties and suppressing loss in a drying step.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when producing urea peroxide by a crystallization method, a sulfate was contained in a reaction mother liquor. Is added, and the reaction crystallization is carried out in a uniformly dispersed state, whereby the crystal yield (based on the urea charged) is improved, and the sulfate is uniformly incorporated into the crystal, so that the high temperature stability is excellent. The present inventors have found that urea peroxide which can suppress a decrease in active oxygen in the drying step can be obtained, and completed the present invention. That is, the present invention is characterized in that a sulphate is added to a reaction mother liquor to cause a reaction, thereby improving the crystal acquisition yield and efficiently producing urea peroxide crystals having excellent high-temperature stability. The present invention relates to a method for producing urea.

[0008]

Next, the method of the present invention will be described specifically. The present invention uses an aqueous solution of hydrogen peroxide and urea,
It can be carried out by the crystallization method of precipitating urea peroxide crystals from an aqueous solution, the solution method of reacting in the form of a slurry in an inert solvent, or the dry spray method of spraying hydrogen peroxide on powdered urea. The sulphate to be added is uniformly dispersed in the urea peroxide crystals by performing the crystallization method of continuously obtaining urea peroxide crystals using the reaction mother liquor, and the effect of improving the stability at high temperatures is obtained. This is the most preferred method.

The sulfate used in the present invention is at least one selected from alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as magnesium, aluminum salt, ammonium salt and double salts thereof. And
Alkali metal salts are preferred, with sodium and potassium salts being particularly preferred. Further, the high-temperature stability of urea peroxide is improved by being used in combination with a known urea peroxide stabilizer described below.

The addition amount of these sulfates to the reaction mother liquor varies slightly depending on the sulfate used, but is generally 0.05% to 10.0%, preferably 0.1% to 5%, based on the reaction mother liquor. It is preferably used in the range of 0.0%.

Next, the method of adding sulfates in the present invention is most preferably a method of dissolving in an aqueous solution and adding to and dissolving in a mother liquor to be circulated, as a method of uniformly dispersing them in a reaction mother liquor. The urea peroxide is taken into the crystals and contributes to the improvement of the high-temperature stability of the urea peroxide, and the remainder is circulated together with the mother liquor, so that the effect of improving the crystal acquisition yield during crystallization is obtained.

Next, in the present invention, the high-temperature stability is improved by the addition of sulfate, but a known stabilizer of urea peroxide is added to stabilize the reaction and improve the storage stability of the obtained crystals. is necessary. These urea peroxide stabilizers are:
It can be used in combination with the sulfate of the present invention. Examples of known stabilizers of urea peroxide added together with the sulfate include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, and tripolyphosphoric acid, and boric acids such as metaboric acid. Alternatively, they may use an alkali metal salt such as sodium, an alkaline earth metal salt such as calcium, or an ammonium salt.

Examples of the organic acids include carboxylic acids such as citric acid, tartaric acid, malic acid, succinic acid, gluconic acid, benzoic acid, malonic acid, sorbic acid, erythorbic acid, and glutamic acid. , An alkali metal salt such as sodium, an alkaline earth metal salt such as calcium, or an ammonium salt.

Furthermore, a method of adding an aminophosphonic acid-based chelating agent or an acid or salt of an aminocarboxylic acid-based chelating agent for the purpose of suppressing the decomposition of hydrogen peroxide during the reaction crystallization can be used together with the present invention. . Examples of the aminophosphonic acid-based chelating agent include aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid,
1,2-propylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), hexamethylenediaminetetraphosphonic acid, triethylenetetraminehexa (methylenephosphonic acid), triaminotriethylaminehexa (methylenephosphonic acid), trans- 1,2-cyclohexanediaminetetra (methylenephosphonic acid), glycol etherdiaminetetra (methylenephosphonic acid), tetraethylenehepta (methylenephosphonic acid), etc.
1,2,4-triacetic acid, 3-phosphonopentane-1,3
5 triacetic acid and the like. Examples of the aminocarboxylic acid chelating agent include hydroxyethylenediaminetriacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and iminodiacetic acid. In addition, alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, ammonium salts, and organic amine salts may be used.

The method for producing urea peroxide, which is an object of the present invention, is to obtain urea peroxide crystals continuously by crystallization from a reaction mother liquor in which urea and hydrogen peroxide are previously dissolved, It is most preferable that the urea and hydrogen peroxide are used as a mother liquor in a continuous crystallization method in which urea and hydrogen peroxide are newly circulated. Although the specific production conditions are not particularly limited, in the case of the crystallization method, the reaction temperature is 50 ° C. or lower, preferably in the range of 0 to 40 ° C., and the reaction time is the average residence time of the crystallization slurry. 0.5 to 3 hours, preferably 0.5 to 1.5 hours, stirring speed is 100 rpm or more
600 rpm, preferably 200 rpm to 400 rpm
m. The mother liquor p during the reaction
H is carried out in the range of 1 to 8, preferably pH 2 to 6. Furthermore, the molar ratio of urea to hydrogen peroxide in the reaction mother liquor is
In order to obtain urea peroxide efficiently, one or more is preferable. It is necessary that the crystals of the obtained urea peroxide be filtered off by a centrifuge or filtration as soon as possible and dried. Specifically, the drying temperature is preferably 30 to 80 ° C. under reduced pressure or atmospheric pressure.

In addition, materials used in each process, such as a reactor, a dryer, and piping, are inert to urea peroxide to prevent metal impurity contamination and hydrogen peroxide decomposition. It is important to use a suitable material. For example, a material such as glass lining, Teflon (registered trademark) lining, stainless steel, and aluminum can be used for the reactor and the piping.

The raw material urea used in the present invention can be used without any pretreatment of industrial urea crystals or granules having a purity of 99% or more, which usually contain trace amounts of metal impurities. The concentration of urea in the reaction mother liquor is limited depending on the solubility of urea, but it is preferable in the present invention to carry out the reaction at about 20 to 40% by weight. On the other hand, commercially available industrial hydrogen peroxide having a concentration of hydrogen peroxide of 3 to 90% by weight can be used as it is. As for hydrogen peroxide, it is preferable to use high-concentration hydrogen peroxide only in consideration of efficiently obtaining the target urea peroxide, but in consideration of handling and safety of hydrogen peroxide, 30 to 70% by weight. It is preferred to use hydrogen peroxide. The concentration of hydrogen peroxide in the reaction mother liquor is desirably 20 to 50% by weight.

Further, a surfactant such as dodecylbenzenesulfonic acid or a polymer flocculant such as polyacrylic acid may be added to the above method for producing urea peroxide.

[0019]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Internal volume 30 equipped with a continuous supply of urea and hydrogen peroxide
In a 0 ml reactor, a reaction mother liquor was prepared containing 35% by weight of urea, a concentration of hydrogen peroxide of about 28%, and the remainder being water. Was supplied at 10 g / hr, 60 g of hydrogen peroxide containing 0.2% of propanediaminetetramethylenephosphonic acid at 48 g / hr, and urea at 50 g / hr, and a continuous operation was performed for 5 hours. The reaction conditions are as follows:
° C, average residence time of crystallization slurry is 1 hr, stirring speed is 3
00 rpm. The crystallized slurry was continuously withdrawn from the reactor, cooled to 5 ° C, and the precipitated crystals were separated by filtration.
Drying was performed. For the crystal after drying, the dry weight and the amount of active oxygen in the crystal were measured to calculate the purity of urea peroxide, the number of moles of the obtained urea peroxide was determined, and the crystal yield based on the charged urea was determined. . The amount of active oxygen is 1 / 10N
It was determined by titration using a potassium permanganate solution.
As a result, the amount of active oxygen was 16.6%, and it was confirmed that high-purity urea peroxide was obtained. Further, 3.0 g of the obtained crystal was placed in a sample container and placed in an atmosphere at 80 ° C. for 1 g.
The amount of decrease in the amount of active oxygen was left for 5 hours and 3 hours, and the stability of the urea peroxide crystal was calculated by equation (1). Stability (%) = active oxygen content after 5 hours / initial active oxygen content * 100 (1) The above results are shown in Table 1.

Examples 2 to 6 The reaction was carried out in the same manner as in Example 1 except that another sulfate was used instead of sodium sulfate. The results are shown in Table 1.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that the sulfate in Example 1 was not added and the other conditions and operations were the same. The results are shown in Table 1.

Comparative Example 2 Sodium silicate was added in place of the sulfate in Example 1, and the same operation as in Example 1 was performed to compare the crystal yield and stability. The results are shown in Table 1.

[0024]

[Table 1]

[0025]

According to the present invention, when urea peroxide is produced by a crystallization method, sulphate is added to the reaction mother liquor to cause crystallization, thereby improving the crystallization yield and improving the high-temperature stability. And an efficient method for producing urea peroxide.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshio Nishimura F-term (reference) 4H006 AA02 AC90 AD15 AD17 AD40 BE63 in Yokkaichi Plant, Yokkaichi, Yokkaichi City, Mie Prefecture

Claims (3)

[Claims] 1. A process for producing urea peroxide by reacting hydrogen peroxide and urea by crystallization, wherein a sulfate is added to the reaction mother liquor. 2. The method for producing urea peroxide according to claim 1, wherein said sulfate is an alkali metal salt, an alkaline earth metal salt, an aluminum salt, an ammonium salt or a double salt thereof. 3. The above-mentioned sulfate is added to the reaction mother liquor in an amount of 0.05 to 0.05.
The method for producing urea peroxide according to claim 1, wherein the urea peroxide is added in an amount of up to 10.0%.