JPS5833161B2 - Calcium hypochlorite composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel calcium hypochlorite composition with improved physical properties such as water solubility and dust generation, and more specifically, to a calcium hypochlorite composition, The calcium hypochlorite consists essentially of a single crystal of calcium hypochlorite trihydrate, and the calcium hypochlorite contains 60% of the calcium hypochlorite.
The specific surface area (value determined by the plain method = plain value) of a calcium hypochlorite composition containing less than 5 weight φ of calcium hydroxide is 1500 cni/? The present invention relates to a calcium hypochlorite composition having the following characteristics.

Calcium hypochlorite is a strong oxidizing agent and is a useful compound that is widely used for water treatment such as swimming pools, water supply and sewage facilities, and bleaching of cotton, pulp, etc. due to its sterilizing and bleaching effects.

This composition containing calcium hypochlorite as a main component is commonly called ``highly bleached powder'' and is commercially available as 60%, 65%, and 70% highly bleached powder based on its effective chlorine content.

Traditionally, calcium hypochlorite compositions are in the form of granules.

Two types of tablets have been manufactured and sold; tablets have been used in cases where a low dissolution rate is required, and granules have been used in cases where a high dissolution rate is required.

The primary use of calcium hypochlorite compositions is for disinfecting pool water.

In this case, it is necessary to keep the free chlorine concentration constant from the viewpoint of pool water management (0.4 ppm or more according to the Ministry of Health and Welfare notification).

Therefore, if you want to use the pool immediately, it is necessary to use a calcium hypochlorite composition that has a high dissolution rate.

If the solution velocity with respect to water is low, Boo 1 will be charged for a long time before it can be used.

On the other hand, if you increase the amount used in an attempt to shorten the time, undissolved calcium hypochlorite composition will accumulate at the bottom of the pool.
Not only does it cause discomfort to swimmers, but there is also a risk that swimmers may accidentally swallow it.

Therefore, granules have traditionally been used for this purpose.

However, the dissolution rate of this granule product was not very high and was not completely satisfactory.

This granular product is obtained by drying and granulating calcium hypochlorite trihydrate in the shape of a flat rectangular plate to obtain a substantially anhydrous granular calcium hypochlorite composition.

Its size is usually 1 to 3 towers, and it is flame-like. Poor resistance to sparks, contact with organic matter, and impact;
Severe dust generation due to friction between particles.

Furthermore, it has many problems such as consuming a large amount of energy for drying.

To address these problems, methods to increase moisture content, e.g.
There is a method in which the calcium hypochlorite in the calcium hypochlorite composition is substantially converted into calcium hypochlorite trihydrate.

In this case, the dissolution rate in water is high, it is resistant to flame, sparks, contact with organic matter and impact, and requires less drying energy.

However, since calcium hypochlorite trihydrate is in the form of fine, flat rectangular plates, its ungranulated, glass, and powdered products lack free-flowing properties, making them difficult to transport and package.

There are some difficulties in handling, such as taking out the product.

In addition, this crystal is brittle and is easily crushed by physical impact into fine crystal pieces, resulting in the generation of dust.

This impairs the health of the operator and makes maintenance of the equipment difficult and difficult.

Furthermore, since the bulk density is low, it is necessary to make the storage container and product container larger.

Furthermore, there is also the problem of caking during storage.

These problems can be solved to some extent by performing a granulation operation to produce granules.

However, granules have a lower dissolution rate in water,
Further, even in the case of granular products, there remains a problem that fine powder is generated due to friction between particles during transportation and becomes dust.

The present inventors conducted extensive studies17 in order to find a calcium hypochlorite composition that not only has a high dissolution rate in water, but also does not generate dust and is highly free-flowing.

As a result, if the calcium hypochlorite composition is substantially composed of a single crystal of calcium hypochlorite trihydrate and the specific surface area of the composition has a specified value, They discovered the surprising fact that the above object can be distantly related, and completed the present invention.

That is, the present invention provides a calcium hypochlorite composition in which the calcium hypochlorite is substantially composed of a single crystal of calcium hypochlorite trihydrate, and the calcium hypochlorite is contained in a mass of 60 to 80% by weight. The specific surface area of the calcium hypochlorite composition (value determined by the plain method = plain value) is 1
500cm/? This is a novel calcium hypochlorite composition characterized by:

The composition of the present invention has an extremely high dissolution rate in water,
It is highly free-flowing and generates almost no dust.

Furthermore, it is an energy-saving composition that requires extremely little drying energy.

The calcium hypochlorite composition of the present invention has a calcium hypochlorite content of 60 to 80 w.

Anything less than 60w% does not meet the standards for highly bleached powder.
Products exceeding 80 w% cannot be manufactured due to coexisting crystal water.

Further, it is essential that the calcium hypochlorite in the composition of the present invention is substantially calcium hypochlorite trihydrate.

Calcium hypochlorite is basic calcium hypochlorite (
Ca(CAO) 2.2Ca(OH)2. Ca(C-a
)2''-Ca(OH)2) is unsuitable because its dissolution rate in water is low and a large amount of calcium hydroxide remains as an undissolved substance after dissolution.

Further, when the calcium hypochlorite is anhydrous calcium hypochlorite, it is not preferable because dust is generated violently due to friction between particles and the dissolution rate in water is low.

Note that "substantially" here means that most of calcium hypochlorite is calcium hypochlorite trihydrate and can be regarded as calcium hypochlorite trihydrate. Specifically, Approximately 8 of calcium hypochlorite
It is sufficient if more than a percent is calcium hypochlorite trihydrate.

Also, when there is a lot of water, calcium hypochlorite is calcium hypochlorite trihydrate, and in this case, free water will be present.

When the free water content increases, it becomes sticky and bonds between particles occur, resulting in poor free flow properties and difficulty in handling.

Furthermore, storage stability is poor, which is not preferable.

The free water content is preferably 5 wφ or less. Further, the calcium hypochlorite trihydrate of the present invention should be substantially composed of single crystals and should not be in the form of aggregates or granules.

Aggregates of single crystals break during production and transportation, generating dust, making them difficult to handle, and reducing bulk density, requiring larger storage containers and product containers.

Furthermore, even in granular form, dust is generated due to friction between particles during manufacture and transportation.

However, there are problems such as a decrease in the rate of dissolution in water.

Whether it is a single crystal, an aggregate, or a granule can be identified with the naked eye, but it can be easily determined with an optical microscope.

Actually, a single crystal is almost entirely made up of single crystals and can be considered a single crystal, although a small amount of aggregates may be mixed in when manufactured industrially. Although it is difficult to determine the proportion of the single crystal included in the present invention, conceptually it is sufficient if it is about 80% or more.

Further, typical methods for measuring the specific surface area of powder are the permeation method and the adsorption method, and other methods include the turbidity method and the dissolution method.

The transmission method uses air as the fluid.
ne) method and the Lea-Nurse method are representative.

The Blaine method has the advantages of a simple device (Blaine air permeation device) and a short measurement time, and has also been adopted by JIS as a method for measuring cement fineness, and has been adopted by ASTM (
C-204) is also adopted.

The specific surface area of the present invention is determined by this Blaine method, and the obtained value is expressed as a Blaine value, crtf/
? Indicated by

In the present invention, this Blaine value is 1500 crA/'? The following conditions are required.

The various physical properties of the calcium hypochlorite composition, dissolution rate in water, free flow properties, and dust generation characteristics are that calcium hypochlorite is essentially t*calcium hypochlorite dihydrate. , and only in calcium hypochlorite compositions in which calcium hypochlorite trihydrate is substantially single crystal, there is a close relationship with the specific surface area, that is, the Blaine value, and this Blaine value should be limited. This results in a calcium hypochlorite composition with excellent physical properties.

This is a truly surprising new fact.

The present inventors found that calcium hypochlorite has a composition of 67 to 69
W steamed rice, moisture 16-18w, calcium hydroxide 2-4w
%, calcium chloride 0.5-15Wφ, sodium chloride 8-10w%, calcium hypochlorite is calcium hypochlorite trihydrate, and this trihydrate is substantially single crystal, and Blaine Calcium hypochlorite compositions with different values were investigated for dissolution rate in water, free-flowing properties, and dust generation.

The results are shown in Table 1 below.

For comparison, the results of commercially available granular highly bleached powder are also included.

A number of other studies were conducted on the Blaine value and its physical properties, but similar results were obtained.

That is, when viewed from the dissolution rate in water, calcium hypochlorite is not granular and consists essentially of a single crystal, and from the free-flowing property, the Blaine value of the composition is 1500 cr.
tt/? The Blaine value is preferably 1500cni/'? from the generation of dust. The following are good, but granules are not suitable.

From these, the Brane value is i 500cr; t/' ii
i' or less, and if the calcium hypochlorite trihydrate is substantially single crystal, it will have excellent physical properties.

Note that the desirable Blaine value is 1000a;'t/? In addition, the Blaine value is 800ctrt/
? It is as follows.

If the Blaine value is less than 500cm/P, the reliability of the value will be lacking due to the operating method, but its physical properties will be outstanding.
Included in the present invention.

The composition of the present invention has an extremely high dissolution rate in water and dissolves instantly.

The reason for this is not clear, but it is inferred as follows.

That is, since the calcium hypochlorite trihydrate of the present invention has crystal water, it has a better affinity for water than its anhydride, and has a large bulk density, so it can be quickly dispersed in water. dissolve.

On the other hand, it is believed that when substantially anhydrous calcium hypochlorite comes into contact with water, the surface hydrates with heat generation, and strong bonds between particles occur, reducing the dissolution rate.

Next, minor components other than calcium hypochlorite and water, which are the main components of the composition of the present invention, will be described.

The calcium chloride content is desirably 5 w% or less.

When the calcium chloride content exceeds 5 w%, bonding between particles is observed and the composition becomes viscous.

Therefore, free flowability is poor and handling becomes difficult.

Furthermore, as the calcium chloride content increases, storage stability also deteriorates.

This tendency becomes particularly noticeable when the calcium chloride content exceeds 5 w%.

It is essential that the content of calcium hydroxide be less than 5 w%.

Further, in the composition of the present invention, it is preferable that the component other than calcium hypochlorite, water, calcium chloride, and calcium hydroxide is sodium chloride.

Sodium chloride may adversely affect the physical properties of the composition.
improves free-flowing properties and eases handling.

The particle size of this sodium chloride is preferably as close as possible to the particle size of calcium hypochlorite trihydrate.

If the difference in particle size is too large, classification will occur during production and transportation, resulting in uneven distribution of calcium hypochlorite content.

In particular, calcium hypochlorite trihydrate in the composition of the present invention may be used in Japanese Patent Application No. 53-35357 filed by the applicant.
Coarse calcium hypochlorite trihydrate shown in No.
First, when crystallizing calcium hypochlorite trihydrate, the ratio of the a, b, and c axes of calcium hypochlorite trihydrate is 0.5≦b/a≦2. Coarse calcium hypochlorite trihydrate obtained by adding columnar calcium hypochlorite trihydrate which satisfies 0 c/a≧15 and has a C-axis of 5□chrons or more is suitable.

This coarse calcium hypochlorite trihydrate is usually 20 to 400 microns in width and length in the A-axis and B-axis directions, and 20 to 200 microns in thickness and length in the C-axis directions. It has a truncated pyramid shape, has great resistance to physical impact, is difficult to crush, and generates almost no dust.

It also has good storage stability.

Next, a method for producing the composition of the present invention will be described.

As a method for producing calcium hypochlorite trihydrate, known methods can be applied.

For example, (1) a method by chlorinating slaked lime;

(2) Method of chlorinating slaked lime with caustic soda.

(3) A method using double decomposition of sodium hypochlorite and calcium chloride.

(4) A method of adding a salting out agent such as sodium chloride to an aqueous solution containing calcium hypochlorite.

(5) A method of concentrating an aqueous solution containing calcium hypochlorite.

(6) A method of transferring basic calcium hypochlorite.

This is a manufacturing method such as.

The thus obtained slurry of calcium hypochlorite trihydrate is processed using a centrifugal filter, a vacuum filter, a pressure filter, etc. to obtain a wet cake.

At this time, if necessary, it may be washed with water, an aqueous sodium hypochlorite solution, etc.

This wet cake may be partially dried to prevent calcium hypochlorite trihydrate from converting to anhydrous salt.

In this way, a partially dried product is obtained, but if it is desired to lower the calcium hypochlorite content at this time, sodium chloride powder may be added.

However, this addition may be done before partial drying.

A composition is thus obtained, the Blaine value of which must be less than or equal to 1500 ct,/f.

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

(1) The dissolution rate in water is extremely high.

(2) No dust is generated, which is extremely beneficial in terms of hygiene control for operators, packaging materials, and consumers.

(3) Highly free-flowing, easy to transport, package, and take out the product.

(4) Extremely high resistance to flame, sparks, contact with organic matter, and impact.

(5) It has a high bulk density, allowing the product storage container and product container to be made compact.

(6) Very little drying energy is required during production.

(7) There is no need for granulation, and the manufacturing process of the calcium hypochlorite composition can be simplified.

It has many characteristics such as.

A further unexpected feature is that the storage stability of the calcium hypochlorite compositions of the present invention is better than that of conventional calcium hypochlorite compositions.

This is particularly advantageous for calcium hypochlorite compositions that require long transportation distances (transportation times).

Examples and comparative examples of the present invention are shown below, in which parts and weights are based on weight unless otherwise indicated.

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

Examples 1-6. Comparative Example 1 10Ll) 30 g of citric acid aqueous solution, 1 part of calcium hydroxide
12 g, 48 g of caustic soda aqueous solution 239 g, water 4491
was placed in a 1 ton crystallization tank equipped with a stirrer and maintained at 15°C while adding 201P of chlorine gas to about 150? The air was blown at a speed of /br-A.

The pH at the end of chlorination is 10.3, and the a-axis and b-axis are 5.
~15 microns, C axis 20-120 microns, c/a
A slurry of columnar seed crystals was obtained from which columnar calcium hypochlorite dihydrate having a particle size of about 7 was obtained.

Note that the slurry concentration was 9.5 ml.

Next, 4.0% Ca (C10)2 and Ca C1
Aqueous solution of 36.0% 276.9? /hr.

40φ calcium hydroxide slurry 88.6 S' /
hrs chlorine gas 33.1'? /hr The columnar seed crystal sluices IJ-8, 42f/h1- were each separately and continuously 3
It was introduced into the crystallization tank maintained at 0°C and chlorinated.

At the same time, slurry was extracted at 207 S'/hr.

The growth of columnar seed crystals was good, and the apparent residence time of the crystals was 45
After an hour, the a-axis and b-axis are 20 to 400 microns, and the c-axis is 2
A slurry of coarse calcium hypochlorite trihydrate having a shape of approximately 0 to 150 square truncated cones was obtained.

This slurry of coarse calcium hypochlorite trihydrate was separated using a Baskent type centrifuge at 300 rpm for 1 minute and washed for 2 minutes (the washing liquid was water and its amount was 65% of the wet cake). A wet cake A containing 68.5 k of calcium hypochlorite, 0.8% of calcium chloride, 0.8% of calcium hydroxide, and 28.4 k of water was obtained.

Next, this wet cake A was treated with a hot air dryer maintained at 90°C, with calcium hypochlorite of 76.3, calcium chloride of 12φ, calcium hydroxide of 15, and water of 19.5.
Blaine value is 640 cnt/f at 0.5% free water
A calcium hypochlorite composition (composition A) was obtained.

It was confirmed by diffraction X-rays and an optical microscope that the calcium hypochlorite of Composition A was calcium hypochlorite dihydrate and was substantially single crystal.

Next, Composition A was sieved to give a 100 mesh product (
Composition B), 145-200 mesh product (composition C),
One piece of 300 mesh anda (composition D) was obtained.

Further, 20 parts of sodium chloride powder having 100 to 200 meshes was added to 100 parts of Composition A and mixed to obtain Composition E.

Next, wet cake A was treated with a hot air dryer maintained at 90°C, containing 71.8 φ of calcium hypochlorite, 11 parts of calcium chloride, 11 parts of calcium hydroxide, and 24.7% moisture.
(6.5% free water) and a Blaine value of 670 crA/f, a calcium hypochlorite composition (composition F) was obtained.

The calcium hypochlorite in this composition was calcium hypochlorite trihydrate, and it was confirmed by diffraction X-rays and an optical microscope that it consisted essentially of a single crystal.

On the other hand, the slurry of the coarse calcium hypochlorite trihydrate was separated using a basket-type centrifuge at 300 rpm for 1 minute, and washed for 2 minutes (the washing liquid was water and the amount was 25 μg per wet cake). Wet Cake B containing 615% calcium hypochlorite, 5.3% calcium chloride, 1.2 cakes of calcium hydroxide, and 30.5% moisture was obtained.

Next, this wet cake B was treated with a hot air dryer maintained at 90°C, and was processed to contain 70.2% of calcium hypochlorite, 6.1% of calcium chloride, 2.3% of calcium hydroxide, and 19% of moisture.
．． Blaine value is 680 cr4 at 7% (free water 0.3φ)
A calcium hypochlorite composition (composition G) was obtained.

It was confirmed by diffraction X-rays and an optical microscope that the calcium hypochlorite of Composition G was calcium hypochlorite trihydrate and was substantially single crystal.

E* Next, physical property tests were conducted on compositions A to G.

The results are shown in Table 2.

These are shown as Examples and Comparative Examples.

When storage stability tests (200 days storage) were conducted on the helmets and Examples 1, 4, and 5.6, the decomposition rates of calcium hypochlorite were 4.0% and 3.5%, respectively.

They were Section 10.2 and Section 7.3.

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

(Measurement of Blaine value) The Blaine value is the specific surface area measured by the Blaine method, and the Blaine air permeation device/powderness measuring device (manufactured by Tokyo Rika Seiki Seisakusho Shin) manufactured in accordance with the provisions of JIS R5201-1964. using JIS R52
The measurement was performed according to the operating method of 01-1964.

(Dissolution rate in water) Dissolution rate in water is JIS R5203-1962
It was measured using a calorimeter (manufactured by Kyushu Maruto Co., Ltd.) manufactured in accordance with the regulations.

Put pure water 3801 in a vacuum bottle, add 20 g of the sample at once while stirring, and continuously record temperature changes to determine the dissolution rate.

(Free-flow test) A glass funnel equipped with a thin tube with an inner diameter of 6 mm and a length of 70 tubes is placed vertically, 30 grams of sample is fed in 5 seconds, and the free-flow property is judged from the state of the sample passing through it. did.

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.

(Dust generation test) Put 5 tons of sample into a 25 ml stoppered test tube, seal it tightly, and process it for 15 minutes with a horizontal plate in a shaker (Yamato Scientific Co., Ltd. 5A-31), then shake it up and down lightly by hand. The state of dust generation was observed.

Based on observations, dust generation can be divided into the following three stages.

◎: Almost no dust generation is observed.

○: A slight amount of dust is observed.

×: Severe dust generation.

(Storage Stability Test) Approximately 100 f of the sample is 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 is indicated by calcium hypochlorite decomposition rate.

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 the free water content (expressed as a weight percentage).

Claims (1)

[Scope of Claims] 1. In a calcium hypochlorite composition, the calcium hypochlorite consists essentially of a single crystal of calcium hypochlorite trihydrate, and the calcium hypochlorite contains 60% of the calcium hypochlorite.
Hypochlorite characterized in that the specific surface area (value determined by plain method - Blaine value) of a calcium hypochlorite composition containing ~80% by weight and less than 5% by weight of calcium hydroxide is 1500crti/ff. Calcium acid composition. 2. The calcium hypochlorite composition according to claim 1, wherein the calcium chloride content of the calcium hypochlorite composition is 5 weight φ or less.