JPS629526B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing lead oxide granules, and more particularly, the present invention relates to a novel method for producing lead oxide granules, and more particularly, to produce cubic-shaped lead oxide granules by chemical granulation means instead of conventional mechanical granulation means. Relating to a method of manufacturing. Lead monoxide (Resurge) and trilead tetroxide (Komeitan) are useful substances in themselves as rust preventives, pigments, light conductors, vinyl chloride resin stabilizers, etc., and are also used in lead glass, glazes, storage batteries, PVC stabilizer, yellow lead,
These lead oxides are useful materials as raw materials for electroceramics, etc., but the particle size of these lead oxides is generally in the range of 3 to 7 μm, and when they are handled, they tend to generate dust, which contaminates the working environment. cause problems. Moreover, in order to solve this problem, there is the inconvenience that the exhaust gas containing lead dust generated in all parts handling lead oxide must be subjected to an expensive dust collection operation. To remedy this problem, lead oxide has already been formed into granules and supplied to various applications. However, known methods for producing lead oxide granules include granulating lead oxide powder by mechanical means such as rolling granulation, extrusion granulation, and spray drying granulation, or using a lead oxide precursor. The method consists of granulating zinc oxide powder using the above-mentioned granulating means and firing the granulated material in an oxygen-containing atmosphere. Since all known lead oxide granules are mechanically granulated, they have a strong tendency to powder due to mutual contact or friction, and the fluidity of the granules is generally low. In this respect, I was still not completely satisfied. The inventors have discovered a new method of chemically granulating lead oxide. That is, the present inventors believe that when firing cubic crystal particles of basic lead nitrate with a side length of 0.05 mm or more, lead monoxide or trilead tetroxide in a form that substantially maintains the cubic shape. It has been found that these lead oxide granules exhibit significantly superior abrasion resistance (dusting resistance), fluidity, etc., as compared to known lead oxide granules. 〓〓〓〓
The coarse cubic particles of basic lead nitrate are preferably prepared by mixing lead monoxide and ammonium nitrate in an amount of 0.2 to 2.0 moles per lead monoxide in an aqueous medium under conditions such that the pH of the final slurry is 4.0 to 10.0. It is obtained by mixing and leaving this slurry to grow cubic grains of basic lead nitrate. The lead oxide granules according to the present invention use the coarse cubic crystals of basic lead nitrate as a precursor and are formed by sintering, so the compressive strength, abrasion strength, etc. of the particles are compared to those produced by mechanical granulation. It is extremely large in size and has little tendency to powder even when subjected to harsh handling. As a practical value, the conventional mechanical granulation method shows a degree of pulverization of more than 90%, as measured by the example method described below, whereas the cubic granules according to the present invention have a degree of pulverization of 10% or more. %, especially 5% or less. It will thus be clear that by using the lead oxide granules according to the invention, the generation of lead oxide dust during handling can be significantly reduced. Furthermore, as is clear from the micrograph in Figure 1 (magnification: 50x), the lead oxide granules according to the present invention consist of a clear cube, and the length of each side is
Coarse particles of 0.05 mm or more, especially 0.1 mm or more,
Furthermore, in connection with its extremely uniform particle size distribution, it exhibits excellent fluidity that is comparable to that of conventional lead oxide granules. Furthermore, since the method of the present invention does not require any means for mechanically granulating lead oxide, it has the remarkable advantage of manufacturing lead oxide granules with high efficiency and on a large scale. There is. Furthermore, ammonium nitrate used as an auxiliary raw material is
The ammonium component is recovered when basic lead nitrate is produced, and the nitric acid accompanying the lead component is eventually recovered as ammonium nitrate by absorbing the gas generated during firing into ammonia, making it extremely economical. It is clear that lead oxide granules can be produced. In the present invention, the lead monoxide used as a raw material is produced by a known dry method, that is, metal lead particles are placed in a tube mill and air is blown into the tube mill to reduce heat generation due to friction and oxygen in the air. Through the accompanying oxidation, the powder of lead zinc oxide ( _PbO is removed from the tube mill along with air,
The lead monoxide is then heated and oxidized in a separate reaction vessel to form red to yellow lead monoxide, which is preferably used. It is desirable that the particle size of this lead monoxide is as fine as possible, and particles of 10 μm or less, especially 5 μm or less are preferably used. As lead monoxide, the wet method proposed by the present inventors or activated lead monoxide (US Patent No. 4117104
(see specification) can also be used. In the present invention, in order to produce coarse cubic particles of basic lead nitrate, first, this lead monoxide and ammonium nitrate of 0.2 to 2.0 times the lead monoxide, particularly 1.0 to 1.7 moles per lead monoxide, are mixed in an aqueous medium. Mix with When the amount of ammonium nitrate is less than the above range,
Not only does the yield of basic lead nitrate decrease, but it also becomes difficult to form coarse cubic crystals. Moreover, if this amount exceeds the above range, basic lead nitrate other than cubic crystals will be produced. Mixing of lead monoxide and ammonium nitrate is suitably performed by adding and mixing an aqueous slurry of lead monoxide and an aqueous solution of ammonium nitrate. It is desirable that the amount of the aqueous medium is sufficient to completely dissolve the ammonium nitrate used, but of course a combination of a small amount of the aqueous medium and more ammonium nitrate than the dissolved amount can also be used. When mixing lead monoxide and ammonium nitrate in an aqueous medium, it is also possible to select conditions such that the pH of the final aqueous slurry is in the range of 4.0 to 10.0, especially 7.0 to 8.0. It is important for formation. When this PH is higher than the above range, it becomes difficult to form clear cubic coarse particles, while when this PH is lower than the above range, the yield of cubic basic lead nitrate decreases. become. Adjustment of the final PH of the slurry can be easily accomplished by heating the slurry to drive liberated ammonia from the aqueous medium. For this purpose,
It is desirable to heat the slurry to a temperature of 50°C or higher, especially 80°C or higher. The heating time can be determined as appropriate so that the pH of the liquid falls within the above range, but generally it is between 1 and 2.
A range of 10 hours is preferred. It is also possible to mix lead monoxide and ammonium nitrate in an aqueous medium from the beginning at the above temperature, but in terms of operation, first mix them at room temperature or at a temperature lower than 50°C. 〓〓〓
It is then desirable to heat the homogenized slurry formed to said temperature. The aqueous slurry of basic lead nitrate thus formed is left to stand, with a side length of 0.05 mm or more, especially 0.1
Crystallize cubic coarse particles of mm or more. Crystallization is usually completed after standing overnight, and cubic coarse particles can be obtained with a yield close to 100%. The coarse particles are separated from the mother liquor by filtration, centrifugation, etc., washed with water if necessary, and then dried. Coarse cubic particles of basic lead nitrate are fired to form cube-shaped lead monoxide or trilead tetroxide particles. That is, when this firing is performed at a temperature of 400 to 500°C and in an oxygen-containing atmosphere such as air, coarse cubic particles of trilead tetroxide (Komeitan) are obtained, and these coarse particles of Komyotan are When calcined at a temperature of °C, cubic coarse particles of lead monoxide are obtained. Of course, instead of producing coarse particles of lead monoxide using the two-stage method, it is also possible to produce cubic particles of lead monoxide by firing at the above-mentioned temperature in one stage. The invention is illustrated by the following example. Reference Example 1 A method for producing lead oxide by a wet method (hereinafter, in this example, lead oxide prepared by a wet method may be abbreviated as W-PbO) is described in U.S. Patent No. 4117104. Manufactured according to the method described. i.e. density of 8.3 to 9.2 g/cc, 0.2μ
A method for producing lead monoxide having a number average particle size, an infrared absorption peak at a wave number of 1400 to 1410 cm ^-1 , and a chromic anhydride reaction rate of 94% or more will be outlined below. Metal lead with a diameter of 2 to 7 mm (electrolytic lead purity 99.99
%) granules in a rotary stainless steel tube mill (inner diameter 34.5cm, length 130cm, internal volume approx. 120cm)
) and fill it with water and oxygen (2 kg gauge pressure), and by rotating this tube mill, a part of the metal lead moistened with water is moved into the oxygen gas phase above the water surface by centrifugal force. pushed up by
The ultra-thin layer of water around the metal lead grains absorbs oxygen,
Lead monoxide is generated here, and the ultrafine particles of lead monoxide that are generated when the metallic lead particles rub against each other in the water are dispersed in the water, resulting in a concentration of PbO33.5g/100ml.
A dispersion liquid (sample number W-PbO-1) was obtained. The wet method lead monoxide slurry obtained here is
The powder was filtered and then dried at about 80° C. and then ground to prepare a wet lead monoxide dry powder product (sample number W-PbO-2). Reference Example 2 As a method for producing lead monoxide by a dry method (hereinafter, in this example, lead oxide prepared by a dry method may be abbreviated as D-PbO), the
It was produced according to the method described in Publication No. 37-11801. First, an electrolytic lead ingot was molded into a cylinder with a diameter of 2.5 cm and a length of 2.0 cm using a lead molding machine.
Genzo Shimazu's research report, Journal of the Japan Society of Mechanical Engineers, Volume 28 (No.
100) According to the so-called Shimadzu lead powder method described on pages 489-516 (1925), metallic lead is ground using a dry grinding method in a rotary mill, and dark gray-green lead zinc oxide powder (so-called lead powder). The zinc oxide powder collected here is then placed in a rotary furnace, mixed with oxygen, and burnt with stirring. Oxidized at a temperature of approximately 630 to 720 degrees Celsius, the temperature rise due to the heat of combustion of the zinc oxide is measured. As soon as the temperature no longer increases due to combustion, it is rapidly discharged into a cooling chamber and cooled, yielding yellow granular lead oxide.
Next, this yellow granular lead oxide was crushed and classified using a gas cyclone method to prepare an orange yellow lead monoxide powder (raw material number D-PbO). Example Production of lead oxide coarse particles will be explained. As the lead raw materials, three types of lead oxides prepared in the above reference examples by wet and dry methods were selected. As a method for producing coarse particles, each lead oxide is
Dispersed in water to a concentration of 300g/concentration,
After preparing a homogeneous aqueous slurry of lead oxide, the aqueous slurry was heated to about 40°C and, with stirring, an ammonium nitrate solution prepared to a concentration of 10Mol/PbO was added (with a molar ratio of NO ₃ ^- /PbO of 0.2 to 40°C). (Amount in the range of 2.0) Slowly add the mixture, and then further boil at 40℃ after addition.
Stirring was continued for 30 minutes to allow ammonium nitrate to become fully accustomed to lead oxide, and then heated to 80-90℃ to volatilize the ammonia contained, and the pH of this reaction solution was 7.5.
Heating continued until . This took 5 hours. Thereafter, the reaction solution was allowed to stand at room temperature, and the coarse crystals formed were filtered off. The lead compound obtained by the above treatment is coarse cubic basic lead nitrate (Pb(NO ₃ ) (OH), Pb ₃
(NO ₃ ) (OH) ₅ , etc.). Next, the obtained lead compound was dried at 130°C for 2 hours, and then dried at low temperature.
A sample was obtained. This drying changes the basicity of the lead compound, resulting in Pb ₃ (NO ₃ ) (OH) ₅ , Pb ₇ (NO ₃ ) ₄
It became basic lead nitrate such as (OH) ₁₀ , but the rough cubic shape did not change. Furthermore, the samples obtained by low-temperature drying were fired at 450°C and 600°C for 2 hours, respectively, to obtain samples fired at 450°C and 600°C. This firing changed the lead compound into trioxide and lead monoxide, but the coarse cubic shape remained unchanged. In addition, where the content of the manufacturing conditions was changed in the above manufacturing conditions, the content shown in Table 1 was followed. Each physical property of the coarse particles produced here was measured by the following method. a Grain density Measured using a pycnometer in a conventional manner. b. Specific Volume (ml/g) The specific volume was measured by performing a drop impact for 20 minutes using a specific volume tester manufactured by Ishiyama Scientific Instruments Co., Ltd., which rotates 15 times per minute and performs a drop impact 30 times. c Number average particle size (μ) Observed using an optical microscope at a magnification of 40 times,
The size of the particles was measured, and the average particle diameter (μ) was determined from the number average of the size of each particle. d Crystal type Measured by powder measurement method using an X-ray self-recording diffractometer manufactured by Rigaku Denki Co., Ltd. In addition, the crystal forms were indicated using the following abbreviations. Lissage type - Lead oxide: L-PbO Mashkoto type - Lead oxide: M-PbO Trilead tetraoxide: Pb ₃ O ₄ Basic lead nitrate: BNL BNL stands for Pb (NO ₃ ) (OH), Pb ₃ (NO ₃ )
(OH) ₅ and Pb ₇ (NO ₃ ) ₄ (OH) ₁₀ were collectively named. e Angle of repose (degrees) Measured using a powder angle of repose measuring device manufactured by Takabayashi Rika Co., Ltd. f Degree of pulverization (%) Take 100 g of a granular sample into a plastic cylindrical container with an internal volume of 140 ml, fix it on a shaker that makes horizontal reciprocating motion (amplitude 40 mm, number of shakes 300 R.PM), and shake it for 10 minutes. It was collected and classified using a 150 mesh sieve, and the degree of pulverization was determined from the amount A (g) passing through the sieve. The above results are also shown in Table 1. As a comparative example, the wet and dry lead oxide used as the raw material in this example was subjected to rolling granulation extrusion granulation, spray drying granulation, and sintering at 600°C for 2 hours in an oxygen atmosphere. and granular lead oxide produced according to the method described in US Pat. No. 3,623,838, each physical property was measured in the same manner as in this example, and the results are also shown in Table 2. The rolling granulation of lead oxide was carried out by supplying each lead oxide to a rotating disk-type rolling granulator, and spraying water while rotating the tray. Extrusion granulation was carried out by adding 60 ml of water to 1 kg of each lead oxide, kneading the mixture to obtain a homogeneous wet state, and then extruding the mixture into a cylinder with a diameter of 2 mm using a meat grinder type granulator. Also, for spray drying granulation, add 400ml of water to 1kg of each lead oxide.
was added to make a homogeneous paste, and then dried under hot air at 250°C using a disc-type spray dryer. Furthermore, for granulation according to the method described in US Pat. No. 3,623,838, 60 ml of water was added to 1 kg of lead zinc oxide (so-called lead powder) prepared by the method described in Reference Example 2, and the mixture was kneaded to obtain a homogeneous product. After the mixture was brought into a moist state, it was extruded into a cylindrical shape with a diameter of 2 mm using a meat grinder type granulator. Each of the obtained granules was dried at 130°C for 2 hours if necessary, and then calcined at 550-600°C for 2 hours. Each of the obtained granular fired products is coarsely crushed if necessary.
Classify using a 150 mesh sieve and 246
Granular lead oxide between 104μ and 104μ was obtained (sample numbers H-1 to H-7)

【table】

[Table] 〓〓〓〓

[Table] As a result, using various lead oxides as raw materials, ammonium nitrate was added to the aqueous slurry at a molar ratio of NO ₃ ^- /PbO in the range of 0.2 to 3.0, and the initial concentration was 50
After thoroughly acclimatizing PbO and NH ₄ NO ₃ at a low temperature below ℃, the ammonia content is volatilized under conditions where ammonia is intercalated, and basic lead nitrate (Pb
Coarse crystals of (NO ₃ ), (OH), etc.) are generated, and after collecting them, they are washed and dried as necessary.
It is well understood that basic lead nitrates such as Pb ₃ (NO ₃ ) (OH) ₅ and Pb ₇ (NO ₃ ) ₄ (OH) ₁₀ are generated, and when fired at higher temperatures, coarse particles of lead oxide are generated and recovered. be done. These coarse particles of lead oxide have a particle size that is more than 5 times larger than lead oxide particles produced by conventional methods, and the larger ones are more than 20 times larger.In addition, they have a small angle of repose, making them easy to handle due to their flowability. It is well understood that it is lead and has a smaller granularity than conventional granular lead oxide and is less likely to turn into powder, making it useful in handling lead compounds that are harmful to the human body.

[Brief explanation of the drawing]

FIG. 1 is an optical micrograph (50x magnification) of lead oxide particles according to the present invention. 〓〓〓〓

Claims (1)

[Claims] 1. A method characterized by firing cubic particles of basic lead nitrate with a side length of 0.05 mm or more to form cubic particles of lead monoxide or trilead tetroxide. Method for producing lead oxide granules. 2. Mix lead monoxide and ammonium nitrate in an amount of 0.2 to 2.0 moles per lead monoxide in an aqueous medium under conditions such that the pH of the final slurry is 4.0 to 10.0, and leave this slurry to form basic lead nitrate. An oxidation process characterized by growing coarse cubic grains with a side length of 0.05 mm or more, and then firing the cubic grains to form cube-shaped lead monoxide or trilead tetroxide particles. Method of manufacturing lead granules.