JPS5938162B2 - Method for producing calcium hypochlorite composition that does not require a drying process - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcium hypochlorite composition that is economical, has good safety, and has good storage stability.

More specifically, when crystallizing calcium hypochlorite trihydrate, a' of calcium hypochlorite trihydrate is used as a seed crystal.
The ratio of each axis of t b and c is 0.5≦b/a≦2.
0 c / a ≧ 1.5 and the C axis is 5 microns or more. The present invention relates to a calcium hypochlorite composition obtained by adding a removing agent, which has a calcium hypochlorite content of 60 to 80% by weight and a free water content of 5% by weight or less.

Calcium hypochlorite is a strong oxidizing agent and is a useful compound that is widely used for its bleaching and disinfecting properties, such as disinfecting swimming pools, water and sewage systems, and bleaching pulp and cotton.

In particular, calcium hypochlorite compositions with an available chlorine content of 60 W% or more are called highly bleached powders.

There are many different methods for producing this calcium hypochlorite composition, but all of them include a drying step as the final step, and the product is dehydrated using a dryer.

The purpose of this drying is to lower the moisture content of the calcium hypochlorite composition, increase the calcium hypochlorite content, and increase the storage stability of the calcium hypochlorite composition by lowering the moisture content. .

- It is said that the storage stability of calcium hypochlorite compositions deteriorates as the water content increases, and in the past, substantially anhydrous calcium hypochlorite compositions with low water content have been produced. .

In this case, a large amount of energy was required to make the process substantially anhydrous, and the drying process accounted for a large proportion of equipment costs.

In addition, the resulting composition becomes porous due to the evaporation of water and is vulnerable to physical impact, easily destroyed and accompanied by the generation of dust.

Also, this composition is not resistant to flames, sparks, and contact with organic materials, which can cause explosions and fires.

In other words, it lacks safety. If there is no drying process,
If a calcium hypochlorite composition with excellent storage stability could be found using simple equipment, it would be advantageous mainly in the following points.

(1) Drying equipment is unnecessary or becomes light, reducing equipment costs;
Process simplification can be achieved.

(2) Drying energy is unnecessary or insignificant.

(3) The yield of calcium hypochlorite is improved.

(4) It is safe because it has a high water content.

That is, the economical efficiency is dramatically improved, and an inexpensive calcium hypochlorite composition can be provided.

The present inventors have conducted intensive studies on calcium hypochlorite compositions.

As a result, it is possible to avoid the drying process by adding a moisture removal agent to the wet cake of certain calcium hypochlorite dihydrates to obtain a calcium hypochlorite composition with a limited composition. Alternatively, they found that it could be made smaller and completed the present invention.

That is, the present invention uses calcium hypochlorite dihydrate a and b as seed crystals during crystallization of calcium hypochlorite dihydrate.
, the ratio of each axis of c is 0.5≦b / a≦2.0 c / a≧1.5, and the C axis is 5 microns or more. Adding columnar calcium hypochlorite dihydrate. A calcium hypochlorite composition having a calcium hypochlorite content of 60 to 80 parts by weight and a free water content of 5 parts by weight or less using a wet cake of coarse calcium hypochlorite dihydrate obtained as a starting material. It is a thing.

That is, according to the present invention, a calcium hypochlorite composition with good storage stability can be obtained without a drying step or with simple equipment.

The present inventors attempted to use the wet cake of calcium hypochlorite dihydrate as it is as a calcium hypochlorite composition in order to skip the drying process.

However, the composition is sticky, non-free-flowing, and quite difficult to handle, and the storage stability of this composition is poor, making it difficult to commercialize it.

However, when calcium hypochlorite trihydrate crystallizes,
Calcium hypochlorite trihydrate a, b, c as seed crystals
The ratio of each axis is 0.5≦b / a≦2.0 c / a≧1.5, and the C axis is 5 microns or more. Obtained by adding columnar calcium hypochlorite dihydrate. Adding water removers such as anhydrous sodium sulfate, anhydrous sodium carbonate, anhydrous calcium chloride, quicklime powder, and zeolite to the wet cake of coarse calcium hypochlorite dihydrate improves free flow properties and makes handling easier. Not only does it improve its storage stability, but it also increases its commercial value.

The calcium hypochlorite content of the composition of the present invention is 60-8
An essential condition is that the content is 0w%.

If it is less than 60w%, it does not meet the standards for highly bleached powder.

If it exceeds 80 w%, it cannot be produced by the method of the present invention due to coexisting crystal water, free water, and water removing agent.

The present inventors added a moisture removing agent to a wet cake of coarse calcium hypochlorite trihydrate, and conducted various studies regarding the amount of the added amount.

As a result, the storage stability of calcium hypochlorite compositions,
Free-flow properties improved with increasing loading.

For example, Ca(CIO)2=69.5w%, Ca(O
H)2=1.1w%, CaC12=0.8w%,
Anhydrous sodium carbonate was added to a wet cake of coarse calcium hypochlorite dihydrate containing 18.2 w% crystal water and 8.9 w% free water in the proportions shown in Table 1, and the mixture was thoroughly mixed until homogeneous. .

Thereafter, storage stability (Note 1) and free flowability (Note 1) were investigated.

The results are shown in Table 1.

Note 1) Described later (physical property test method).

Further, the present inventors used various wet cakes having different free water contents, added and mixed a water removing agent thereto, and conducted storage stability tests and free flow tests of the compositions.

As a result of these extensive studies, it has been found that it is not the amount of water removing agent added that has a major effect on the physical properties, but the free water content.

That is, when the free water content is 5 w% or less, the storage stability is good and the free flow property is good.

If the free water content exceeds 5 w%, the composition not only becomes viscous and difficult to handle, but also has poor storage stability.

Note that the desirable free water content is that substantially no free water exists.

That is, the effect of the water remover is to reduce the free water content in the wet cake.

Furthermore, since the composition of the present invention has a high water content, its storage stability deteriorates at high temperatures, but there is almost no effect at the temperatures at which it is normally handled.

Next, the present invention will be explained in more detail.

A wet cake of coarse calcium hypochlorite dihydrate is obtained by filtering a slurry of coarse calcium hypochlorite dihydrate. Patent application filed by
It is proposed in No. 35357.

That is, during crystallization of calcium hypochlorite dihydrate, the ratio of the a, b, and c axes of calcium hypochlorite dihydrate as a seed crystal is 0.5≦b/a≦2.0. It is obtained by adding columnar calcium hypochlorite dihydrate which satisfies c/a≧1.5 and has a C axis of 5 microns or more.

The slurry of coarse calcium hypochlorite dihydrate thus obtained is processed using a centrifugal filter, vacuum filter, pressure filter, etc. to obtain a wet cake. The wet cake may be washed with an aqueous sodium chlorate solution or the like.

The wet cake has a calcium hypochlorite content of 60% by weight or more, preferably 65% by weight or more, and more preferably 70% by weight or more.

In addition, its free water content is 20 w% or less, preferably 15 w%.
% or less, more preferably 10 w% or less, and can be easily achieved by coarse calcium hypochlorite dihydrate.
The free water content of the wet cake is reduced and the amount of water removing agent added can be reduced.

In the present invention, the water remover is generally any agent that can convert free water in the wet cake into bound water when the calcium hypochlorite composition is handled, and mainly includes the following three types. It can be divided into

(1) Substances that take in free water in the wet cake as crystal water, such as anhydrous sodium sulfate, anhydrous calcium chloride, anhydrous magnesium sulfate, anhydrous aluminum sulfate, anhydrous sodium tetraborate, anhydrous magnesium nitrate, anhydrous sodium metasilicate, anhydrous Anhydrous salts of substances that have water of crystallization, such as sodium carbonate, and crystallized water from substances that have water of crystallization, such as sodium tetraborate hydrate, sodium tetraborate pentahydrate, calcium chloride dihydrate, and magnesium sulfate tetrahydrate. It is also possible to remove a part of it.

(2) Substances that take in the free water in the wet cake as hydration water, such as basic anhydrides such as calcium oxide and magnesium oxide, or those from which a portion of the hydration water has been removed, or condensed phosphoric acid.

(3) There are substances that take in free water in the wet cake as adsorbed water, such as zeolite, alumina gel, and silica gel.

It should be noted that a desirable physical property of the water removing agent is that it has a large water removing ability per unit weight, which is effective in reducing the amount of water removing agent used.

Also, it has high solubility in water, which is required when it is used as a disinfectant for pool water, which is its main use.

Furthermore, it is important that it has no reactivity with calcium hypochlorite and that it is inexpensive.

Incidentally, if the water removing agent has a large dehydrating power, a part of the calcium hypochlorite dihydrate may be made anhydrous, but this does not matter.

For example, anhydrous calcium chloride, calcium oxide, etc.

One or more types of moisture removing agents may be used.

In addition, the wet cake and the water removing agent can be mixed in a conventional ribbon mixer, V-type mixer, screw mixer, or pneumatic conveyor, which is usually used for mixing powders. Both are possible.

Further, the composition obtained by mixing may be in the form as it is, or it may be granulated into granules or molded into tablets.

The lower the calcium chloride content of the components other than calcium hypochlorite, water, and water remover in the composition of the present invention, the more desirable.

This is because, as has been conventionally said, calcium chloride deteriorates storage stability.

Due to the presence of calcium chloride, the following reaction proceeds,
It is believed that this is because chlorine gas is generated and this chlorine gas further attacks calcium hypochlorite.

Ca(CIO)2・2H20+CaCl2→2Ca(O
H) 2+2C12 Desired calcium chloride content is 5w%
It is as follows.

If it is 5 w% or less, there is almost no difference in storage stability (the stability is good).

Furthermore, when the content of calcium hydroxide in the composition is high, the storage stability is significantly improved and the adverse effects of calcium chloride are eliminated.

A desirable calcium hydroxide content is 5 to 10w.

This is because the effect of increasing storage stability becomes noticeable from 5w% or more, and when it exceeds 10w%, not only does the storage stabilization effect become slow, but also the generation of dust increases.

Moreover, as a component other than these, it is desirable to use IJium chloride.

This is because sodium chloride improves free-flowing properties without adversely affecting the storage stability of the composition, has high solubility in water, and does not cause dust generation.

Next, the features of the present invention will be listed.

(1) The drying process is unnecessary or only a small amount required, and equipment costs can be greatly reduced.

(2) The process is simplified and operation management becomes easier.

(3) Electricity, steam, heavy oil, etc. as drying energy sources become unnecessary or insignificant.

(4) Since there is no or only a minor drying process, calcium hypochlorite, which was conventionally decomposed in the drying process, can be used effectively, which improves the yield.

(5) No dust is generated, making it extremely effective in terms of hygiene management for operators and general handlers.

(6) The dissolution rate of the composition is extremely high.

(7) Despite the high water content, the composition has good storage stability.

(8) The safety of the composition is excellent, resistant to flame, sparks, contact with organic matter and impact.

(9) Despite the high water content, the composition has good free-flowing properties and is easy to handle.

It has many characteristics such as.

A further unexpected feature is that when a water removal agent is used, heat is generated and some free water evaporates.

If air is supplied at this time, the amount of evaporated water will further increase.

Therefore, the amount of water removing agent used can be reduced.

Another unexpected feature is that the free-flowing properties of the compositions are better when a water removing agent is added, even if the free water content is the same.

Examples and comparative examples of the present invention are shown below, and unless otherwise specified, parts and sections are based on weight.

The methods for measuring the physical property values shown in Examples and Comparative Examples will be described later.

Example 1 Calcium hypochlorite 67.2%, calcium chloride 0.
5%, calcium hydroxide 2.0%, crystal water 17.4%,
10 parts of anhydrous sodium carbonate was added to 100 parts of a wet cake of coarse calcium hypochlorite trihydrate containing 11.9% free water, and the mixture was thoroughly mixed with a ribbon blender for 15 minutes to obtain a calcium hypochlorite composition.

This composition contains 61.3% calcium hypochlorite, 0.8% calcium chloride, and 1.8% calcium hydroxide.
Free water was in charge 3.2.

Next, this composition was subjected to a storage stability test and a free flow test.

As a result, the decomposition rate was 5.5, and the free flow was not obstructed (rating: ○).

Comparative Example 1 The wet cake of Example 1 was directly subjected to a storage stability test and a free flow test.

As a result, the decomposition rate was 18.2%, and the free flow was poor and clogging occurred (judgment: ×).

Examples 2 to 9, Comparative Example 2 30 grams of citric acid aqueous solution, 112 grams of calcium hydroxide
Section 48 Caustic Soda Aqueous Solution 239 f.

Pour 449 g of water into a 1 ton crystallization tank equipped with a stirrer at 15°C.
201g of chlorine gas to about 150? /hr
It was blown at speed A.

The pH at the end of chlorination is 10.3, and the a-axis and b-axis are 5.
~15 microns, a-axis 20-120 microns, c/
A nearly cylindrical columnar calcium hypochlorite trihydrate with a of about 7 was obtained, and a slurry of columnar seed crystals was obtained.

Note that the slurry concentration was 9.5%.

Next, in a 1 ton stirrer-equipped cylindrical crystallization tank equipped with an overflow tube, Ca(Ca)2 was placed at 4.0, and CaC4° was placed at 3.
6.0% aqueous solution 76.9 S'/hr, 40%
Calcium hydroxide sura IJ-88,6? /hr
, Chlorine is 33, IP/hr Slurry of columnar seed crystals 8.42t? /hr were individually and continuously introduced into the crystallization tank maintained at 30°C for chlorination.

2.07′ at the same time? /hr' and the slurry was extracted.

The growth of columnar seed crystals is good (apparent crystal residence time of 5 hours is 45
After an hour, the a-axis and b-axis are 20 to 400 microns, and the a-axis is 2
A slurry of coarse calcium hypochlorite trihydrate having a square shape of 0 to 150 microns on each side was obtained.

This slurry of coarse calcium hypochlorite trihydrate was processed at 3000 rpm in a basket-type centrifuge for 10 minutes.
After separating for 5 minutes and washing for 5 minutes, a wet cake containing 71.9% calcium hypochlorite, 1.3 parts calcium hydroxide, 22.7% water, and 0.5 parts calcium chloride was obtained. was gotten.

The cleaning liquid is water, and the amount used is 1. of the wet cake.
It was 5 times more.

A water removing agent as shown in Table 2 was added to this wet cake and thoroughly mixed for 15 minutes using a ribbon blender to obtain a calcium hypochlorite composition.

Table 2 shows the calcium hypochlorite content, free water content, storage stability test, and free flow test results of this composition.

For comparison, the results obtained when no water remover was added are also shown.

Next, the physical property testing method of the present invention will be described.

(Storage Stability Test) Approximately 1,001 samples are placed in a 200 ml wide-mouthed polyethylene bottle, sealed and stored indoors at room temperature (20 to 25°C).

After a certain period of time, samples were taken out and changes in each component over time were examined.

Stability was indicated by the decomposition rate of calcium hypochlorite.

(Free-flow property test) A glass funnel equipped with a thin tube having an inner diameter of 6 mm and a length of 70 m was vertically erected, a sample 30f was supplied for 5 seconds, and the free-flow property was judged from the state of the sample passing through the funnel.

Free flow was divided into three stages:

◎: Passes through extremely smoothly.

○: The entire amount passes through with intermittent or light vibration.

×: Passes easily due to intense vibration.

Or it gets blocked in the middle.

(Measurement of free water) Approximately 101 samples were accurately weighed and treated with dry nitrogen gas maintained at 30° C. for 2 hours, and the weight loss at that time was defined as free water (expressed as a weight percentage).

Claims (1)

[Scope of Claims] 1. Calcium hypochlorite trihydrate a as a seed crystal during crystallization of calcium hypochlorite trihydrate. Add columnar calcium hypochlorite trihydrate in which the ratio of each axis of b and c is 0.5≦b / a≦2.0 c / a≧1.5, and the C axis is 5 microns or more. The calcium hypochlorite content obtained by adding a moisture removing agent to the wet cake of the coarse calcium hypochlorite trihydrate obtained is 60 to 80% by weight, and the free water content is 5% by weight or less. Calcium hypochlorite composition. 2. The calcium hypochlorite composition according to claim 1, wherein the water removing agent removes some or all of the water of crystallization from a compound having water of crystallization. 3. The calcium hypochlorite composition according to claim 1, wherein the water removing agent removes some or all of the hydration water of a compound having hydration water. 4 Claim 1 in which the moisture remover is a moisture adsorbent
The calcium hypochlorite composition described in Section 1.