JPH0735247B2 - Granular calcium hypochlorite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to granular calcium hypochlorite. Granular calcium hypochlorite is used in large quantities for water sterilization and disinfection, especially for swimming pool water.

The currently known crystal system of calcium hypochlorite is
It is a plate crystal, a twin crystal (laminated crystal), a needle crystal, and a tetragonal double truncated pyramid crystal described later, and in the present specification, the former three are collectively referred to as a "plate crystal".

[Conventional technology]

As the known granular calcium hypochlorite, an amorphous crushed substance having a sharp edge obtained by compression-molding a partially dried crystal into a sheet between heavy rolls and crushing and sizing, , Calcium hypochlorite wet cake and sufficient dry powder, spherical particles formed by stirring and mixing in a notch mixer, further calcium hypochlorite wet composition, compressed and extruded from a die. There is a columnar product or the like obtained by molding. As the classification of the molding method, the crushed material that is compression molded at a low water content is the dry granulation method,
Spherical and columnar products that are molded by adding water (binder) to give plasticity belong to the wet granulation method.

Almost all of these granular calcium hypochlorite are produced by using plate-like crystal calcium hypochlorite as a starting material and molding it. In fact, it can be confirmed by observing the fracture surface of these particles with a microscope.

[Problems to be solved by the invention]

These conventional granules have many problems due to their shape and granulation method.

That is, since the crushed material has irregular and sharp edges, the edges are easily broken due to friction between particles during production, transportation and handling, and powder and dust are generated. In addition, the fluidity is poor and it becomes an obstacle during packaging and use. Furthermore, because of the dry granulation method, the molding pressure is high, the particles are dense and hard, and they are not completely dissolved when sprinkled in a pool. Residue deposits on the bottom of the pool and damages the bottom.

In addition, spherical particles have a particularly low granulation pressure during molding, and the resulting molded body is soft and has a low bulk density and weak strength, so it cannot resist when exposed to severe conditions, and powders to generate dust. .

On the other hand, since the columnar material is extruded and molded, one particle generally has a mixture of a rough portion and a dense portion and is easily broken, and dust is generated.

As described above, conventional granules have various problems, but the disadvantages common to all granules are that the strength of the molded body is weak, it is easily subject to friction and crushing, and dust is generated. It is to be.

Calcium hypochlorite dust causes health problems such as respiratory irritation and eye irritation.

Further, these granules have the following problems in production.
That is, since the crushed material is produced by mechanically crushing the sheet material pressed between the rolls, a large amount of powder is produced as a by-product during crushing. Since this molded product is pressed, it is hard and inferior in solubility. Since the particle size of the granules must be reduced in order to increase the solubility, the pulverization rate becomes 50% or more. The by-product powder is screened by a classifier,
The fine powder, which is a powder, is collected and circulated to the compression process. Since the circulation amount is large, the device becomes large in size, and the manufacturing cost is significantly increased.

In addition, spherical particles have a low granulation pressure, weak strength, and pulverization during drying poses a problem. Originally, calcium hypochlorite was
In the presence of water, the higher the temperature, the more likely it is to undergo thermal decomposition, and therefore it is necessary to carry out drying in a short time, so a fluidized bed dryer is used exclusively. Therefore, spherical particles, which are weak in strength, are easily pulverized because they are exposed to the severe condition of collision of particles with each other, and as a result, the product recovery rate decreases, and the size of the device becomes large and the installation of dust collectors and classifiers etc. It becomes necessary and the manufacturing cost is greatly increased.

On the other hand, the columnar product is produced by pressurizing the wet composition and extruding it from a die or the like.
It is not homogeneously extruded and has rough and dense parts. Therefore, unevenness occurs in strength, breakage occurs in the drying process, and corners at both ends are broken by friction or the like to cause pulverization. As a result, it is necessary to collect and circulate the powdered product, which complicates the process and increases the size to increase the manufacturing cost.

Furthermore, dust generation in the process of manufacturing these granular products deteriorates the working environment and causes health problems such as respiratory irritation and eye irritation of drivers.

A common drawback of all the granules produced by the conventional dry granulation method or wet granulation method is that they are weak against friction and crushing and easily pulverized. This easiness of pulverization means that the cohesive force between the crystals is weak. It is thought that if agglomerated with a sufficient binding force, the strength also rises and pulverization can be suppressed. However, in reality, the dust problem due to the pulverization of these particles remains unsolved.

The inventors of the present invention, the reason why the conventional granular material is easily pulverized is due to the crystal shape of the calcium hypochlorite dihydrate that is the raw material, not to mention the molding method, that is, the usual industrial The crystal shape of the calcium hypochlorite dihydrate obtained by the manufacturing method is a plate crystal, etc., but the cohesive force of the crystals is weak as inferred from the shape, for example, when compression molding is performed by the dry granulation method, the plate shape is obtained. Crystals and the like tend to be oriented and piled up, and if they are molded by a wet granulation method with water to have plasticity, entanglement is unlikely to occur because they are plate-like crystals. Even in the granulation method (2), the bonding strength between the crystals becomes insufficient, and as a result, a granular material having weak strength and easily pulverized is obtained.

[Means for solving problems]

As a result of various attempts to improve the entanglement of the crystals, calcium hypochlorite having different crystal shapes, in particular, tetragonal bipyramidal coarse calcium hypochlorite dihydrate,
Starting material is a suitable mixture of conventional plate crystals, etc.
Granular calcium hypochlorite obtained by molding this mixed crystal composition by granulation, not only shows a stronger resistance to friction and crushing than conventional granules, it was found that the solubility is also good in the present invention Arrived The four-sided, double-pyramidal-shaped coarse dihydrate referred to here is a crystallized form of the coarse dihydrate as a method for producing the coarse calcium hypochlorite dihydrate described in JP-B-57-244. At this time, the ratio of a, b and c axes of calcium hypochlorite dihydrate as a seed crystal is 0.5 ≦ b / a ≦ 2.
0, c / a ≧ 1.5, and refers to a crystal produced by adding and growing columnar calcium hypochlorite dihydrate having a c-axis of 5 microns or more.

The present invention will be described in more detail.

The granular calcium hypochlorite of the present invention (hereinafter referred to as the granular material of the present invention) is a calcium hypochlorite dihydrate such as a plate crystal and / or its anhydride and a tetragonal bipyramidal coarse hypochlorous acid. Calcium dihydrate and / or its anhydride in a weight ratio of 1:
Must be 9-9: 1 mixed and shaped granules.
Preferably, the mixing weight ratio is in the range of 2: 8 to 8: 2.

The granular material of the present invention preferably contains 55 wt% or more of calcium hypochlorite. If it is less than 55 wt%, a large amount must be used for sterilization and disinfection, resulting in poor efficiency. It is preferably 60 wt% or more.

There is no restriction on the shape, and any shape may be used. From the viewpoint of physical properties such as strength, solubility and fluidity, spherical and columnar shapes are preferable. Further, a so-called elliptical shape is more preferable, in which the columnar shape is processed by rolling granulation or marumerizer (spherical sizing machine) to make the corners round and homogenized.

The particle size may be in the range of about 3400 microns (6 mesh) to 150 microns (100 mesh), preferably about 2400 microns (8 mesh) to about 250 microns (60 mesh). If it is larger than this, the solubility is lowered, and if it is smaller, it tends to scatter.

Further, it is desirable that the granular material of the present invention contains 4 to 22 wt% of water. If it is less than 4wt%, the product safety is 22w.
If it exceeds t%, the stability deteriorates. Calcium chloride may be included, but 5 wt% or less is preferable from the viewpoint of stability. When other components are contained, it is desirable that the components are 2 to 7% by weight of calcium hydroxide which acts as a stabilizer, and the remaining main component is sodium chloride.

The above-mentioned granular material of the present invention can be advantageously produced by the method described below.

Both plate crystals and coarse crystals mixed as raw materials are mixed with dihydrate, or one is mixed with dihydrate and the other is partially dehydrated, or both are partially dehydrated. The above dihydrates may be mixed, or any mixture may be used. Here, the partially dehydrated dihydrate refers to a crystal in which the dihydrate is heated and dehydrated and a part thereof is transformed into the dehydrated product.
The yield of this anhydride is 60% or less, preferably 50% or less, and if it is more than this, the influence of the anhydride having a different crystal shape becomes strong, and when it is granulated, the binding force is lowered and the powder is easily pulverized.

Such mixing of plate-like crystals and coarse crystals may be performed with a mixer. The mixing ratio is in the range of 1: 9 to 9: 1, preferably 2: 8 to 8: 2.

Then, it is molded by a granulator. At this time, it is necessary to adjust the water content by the granulation method.

In the dry granulation method, compression molding is usually performed with a water content of 4 to 25 wt%. On the other hand, in the wet granulation method, water content is 25 to 45 wt% by adding plasticity and water as a binder, preferably
25 to 35 wt%. As a method for adjusting the water content, an undried so-called filter cake and dry powder of the raw material calcium hypochlorite dihydrate may be appropriately mixed. There is no great difference in the water content required during granulation for both spherical and cylindrical materials. If the water content is high, the particle size will be large or will be nodular in the spherical molding, and if the water content is low, the cohesive force will be weak and the particles will be soft. In the columnar formation, when the water content is large, the water content adheres to each other to form a nodule, and when the water content is small, extrusion cannot be performed.

As the granulator, a rolling granulator, a high-speed agitation-type mixing granulator or the like can be used to obtain a spherical material. For the columnar material, an apparatus having an extrusion mechanism and a screen, for example, a screw type extrusion granulator, a roll type extrusion granulator, or a blade type extrusion granulator can be used.

The molded body thus obtained is dried by a dryer, if necessary, until the above-mentioned water content becomes 4 to 22 wt% to obtain a product. Further, it is more preferable to dry the columnar shaped body into an elliptical shape with a rolling granulator or a mulmelizer before drying. As the dryer, a device capable of reducing the water content to 4 to 22 wt% in a short time and capable of uniformly drying is preferable. This is because the higher the temperature and the longer the time of calcium hypochlorite, the more it decomposes, resulting in a decrease in available chlorine. Therefore, a drying method using heated air or a suitable gas is suitable. For example, a fluidized bed dryer, a band dryer, a rotary dryer and the like are preferable. Normally, hot air of about 60 to 200 ° C is supplied to the dryer.

〔The invention's effect〕

The granular material of the present invention has, as a starting material, a plate-like crystal dihydrate obtained by an ordinary industrial production method and / or an anhydride thereof, and a tetragonal bipyramidal-shaped coarse dihydrate obtained by a seed crystal addition method. Since it is a granular material formed by molding a mixture obtained by mixing and / or its anhydride, it has strength, is excellent in abrasion resistance and crush resistance, and suppresses pulverization extremely well. In particular, the granules obtained by wet granulation have the above-mentioned physical properties further improved, and further have suitable fluidity, good metering property, good handleability, good solubility, excellent aesthetics, etc. Have the advantageous properties of.

When plate-like crystals with different crystal shapes and coarse crystals are mixed and molded, the strength of the molded body increases significantly.The fact that the crystals are heteromorphic causes sufficient entanglement, resulting in stronger cohesion between the crystals. It is thought to be a tame.

This improvement in strength has high resistance to destruction and crushing due to friction or collision even under severe conditions between the manufacturing process and the product as it reaches the user, and even during severe conditions during transportation. Due to the reduction in the size of equipment, the manufacturing cost is reduced, and the health hazards such as respiratory irritation, eye irritation, and discomfort caused by dust of operators and users are eliminated, and it has the advantage of being extremely easy to handle. ing.

〔Example〕

Hereinafter, examples and comparative examples of the present invention will be shown, but unless otherwise indicated,% and parts are based on weight.

Each physical property was measured as follows.

(1) Put a granular material with a bulk density of 50.0 g into a 100 cc graduated glass graduated cylinder, read the volume Acc when tapping, and
Calculate and obtain A (g / cc).

(2) Strength (pulverization test) 30.0 g of sieved granules and 15 g of glass beads with a diameter of 1 mm were put into a 200 cc cylindrical glass bottle with a lid, and shaker (Iwaki KM)
Shake for 10 minutes with a universal shaker (220 round trips per minute). The amount Bg of the sample passed through a 60-mesh sieve is measured and determined to be B / 30.0 × 100 =% pulverization rate.

(3) Solubility 60 g of granules are placed in a glass beaker (3) containing 20 ± 1 ° C water and stirred with a magnetic stirrer (80-100 rpm), effective chlorine content in the liquid after 3 minutes Sg And the effective chlorine amount Stg in the liquid at the time of complete dissolution are measured, and expressed as S / St × 100 = dissolution rate after 3 minutes.

The present invention is not limited to these.

Comparative Example 1 From a slurry obtained by adding lime milk to an aqueous solution containing calcium hypochlorite and sodium chloride as main components to form dibasic calcium hypochlorite, and adding caustic soda to the metalysis and then chlorinating the mixture. Calcium hypochlorite dihydrate prepared by separating mother liquor and drying (calcium hypochlorite 59.3%, moisture 18.1%, square plate crystals with a particle size of 10 to 50 microns and a thickness of 5 microns or less A)
After compression molding with a roll compactor, the mixture was supplied to a crushing granulator and the product was extruded through a screen having a predetermined size to obtain a crushed material. Recovery rate between 8 and 60 mesh is 41
% And all others were powdered.

Example 1 Chlorine was blown into an aqueous slurry of calcium hydroxide and caustic soda to a chlorination rate of 55%, and columnar calcium hypochlorite dihydrate (citric acid coexisted in an aqueous slurry of calcium hydroxide and caustic soda). Chlorinated and crystallized a, b axis 5 to 15 micron, c axis 30 to 100 micron) was added as a seed crystal, followed by chlorination to grow 25 times to separate the mother liquor from the slurry, Coarse calcium hypochlorite dihydrate prepared by the method of drying (calcium hypochlorite 72.8%, water content 21.3%, a, b axis 25-
50 parts of 80 micron, c-axis 30 to 100 micron tetragonal bipyramidal crystals) and 50 parts of the plate-shaped dihydrate used in Comparative Example 1 were granulated under the same conditions as in Comparative Example 1, The recovery rate between ~ 60 mesh was 72%.

Example 2 Comparative Example 2 70 parts of the plate-shaped dihydrate used in Comparative Example 1 was mixed with 30 parts of the coarse dihydrate used in Example 1 in a high-speed stirring type mixing granulator (HMA-6).
5: Nara Machinery) and add 15 parts of water to the main wing stirring blade
The mixture was stirred and mixed at 200 rpm and a granulating blade at 3000 rpm to obtain a granulated product.
Then, put it in a fluid dryer and send hot air at 100 ° C for 30 minutes to dry it. Calcium hypochlorite content 67.8%, water content 1
Spherical calcium hypochlorite having a particle size of 8-48 mesh consisting of 0.9% was obtained. Example 2 15 parts of water was added to 100 parts of the plate-shaped dihydrate, granulated in the same manner and dried, and the calcium hypochlorite content was 66.3% and the water content was 8.
A sphere having a particle size of 8 to 48 mesh consisting of 6% was obtained. ......
Comparative Example 2 The physical properties of these spherical materials were measured and the results were as follows.

Physical properties Example 1 Comparative example 1 Bulk density (g / cc) 0.94 0.89 Strength (pulverization rate%) 9.1 17.6 Solubility (dissolution rate after 3 minutes%) 97.4 96.8 Examples 3 and 4 Comparative example 3 Comparative example 1 Using the crystal used in Example 1 as a raw material, 30 parts of a plate dihydrate and 70 parts of a coarse dihydrate were put into a kneader, 15 parts of water was added, and the mixture was kneaded for 5 minutes. 1 mm of this mixture
A die having a hole diameter of (plate thickness of 1.5 mm) was used for extrusion and granulation to form a columnar formed body. The cylindrical molded body was divided into two parts, half of which was dried in a fluidized dryer as it is, and the calcium hypochlorite content was 73.2% and the water content was 14.2%.
A columnar product of 2 to 10 mmL was obtained. ...... Example 3 The remaining half amount was put into a marumerizer (Q-230: made by Fuji Paudal), and 400 rpm until the corners of the cylindrical molded body were rounded.
It is rotated in a slab and made into an ellipsoid, then dried in a fluid dryer, and consists of calcium hypochlorite content of 73.1% and water content of 13.9%.
An ellipse of 1 mm × 2 to mm L was obtained. Example 4 On the other hand, only the plate-shaped dihydrate was molded in the same manner as in Example 3, and the calcium hypochlorite content was 62.6% and the water content was 13.3%.
A columnar product consisting of ... Comparative Example The physical properties of these granules were measured and the results were as follows.

Claims (1)

[Claims] 1. A ratio of a, b and c axes is 0.5 ≦ b / a ≦ 2.0, c / a
A coarse calcium hypochlorite dihydrate and / or an anhydride thereof produced by growing a columnar calcium hypochlorite dihydrate having a c axis of 5 μm or more and ≦ 1.5 as a seed crystal; Granular calcium hypochlorite in which the plate-like crystal calcium hypochlorite dihydrate and / or its anhydride is in a weight ratio of 1: 9 to 9: 1.