Note: Descriptions are shown in the official language in which they were submitted.
1079~83
Thls invention relates to an improved calcium hypo-
chlorite composition and, more particularly, this invention concerns a
cnlclum hypochlorlte compositlon having improved storage stability and
safety, that ls whlch ls resistant to spontaneous decomposition and
self-propagating decompositlon.
Calcium hypochlorite compositions which are co~mercially
handled as a high-grade hypochlorite composition generally con-
tain about 65% to 75% of calcium hypochlorite [Ca(OCl)2], about
15 to 20% of chlorides and about 5 to 7% of alkalis, and the water con-
tent is generally less than 2%. The composition decomposes when it is
sub~ected to hea~ or is contacted with readily oxidizable organic
materials. me decomposition is exothermic and proceeds rapidly. Even
under normal storage conditions at ambient temperature the calcium
hypochlorite in the composition decomposes gradually and will lose 3 to
5% of the available chlorine content ln a year.
Several processes have been proposed for making the
calcium hypochlorite composition safe, and one of the most promising means
suggested is to maintaln the proper amount of water in the composition.
U.S. Patent 3,645,005 teaches a composition contain-
ing 6 to 15~ of water in a calcium hypochlorite composition that is resis-
tant to self-propagating decomposition with storage stability comparable
to that of substantially dry compositions.
Another reference (Japanese Kokai 75-70297) teaches
a water content of 16 to 22~ for a composition having excellent safety.
Insofar as safety of the composition is concerned, the
aforementioned te~chings facilitate preparation of a safer composition;
however, the storage stability of the former is not entirely satisfactory
a6 shown in Test 1, described herein, and in the latter ~here is
difficulty in obtaining a composition having high available chlorine
content.
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The present invention provides a calcium hypochlorite composition
rcsistant to self-propagating decomposition and having improved storage
stability so that it is as stable as a substantially anhydrous calcium
hypochlorite composition.
The present invention further provides a calcium hypochlorite
composition having high available chlorine.
Other advantages of the invention will become apparent hereinafter.
In the accompany drawings:
Fig. 1 shows the relationship between water content of calcium
hypochlorite compositions and corresponding rate of loss of available
chlorine when the compositions are stored under different conditions.
Fig. 2, Fig. 3 and Fig. 4 show X-ray diffraction patterns of
calcium hypochlorite compositions.
The present invention provides a calcium hypochlorite composition
composed of a heterogeneous mixture of a hydrated granular calcium hypo-
chlorite component and an anhydrous granular calcium hypochlorite somponent,
which composition has excellent storage stability and safety.
The hydrated and anhydrous components are preferably granular
and composed of particles ranging in size from 8 to 100 mesh.
The hydrated component is a calcium hypochlorite having available
chlorine of at least 50%, and the water is all in the form of water of
crystallization i.e. Ca(OCl~2.3H20. The amoant of water of crystallization
is calculated to be from 2 to 3 ~oles per mole of Ca(OCl)2, and the
hydrated calcium hypochlorite is completely crystalline Ca(OCl)2.3H20 or
crystalline Ca(OCl)2.3H20 together with some crystalline Ca(OCl)2.
The hydrated component is characterized structurally by comparing
X-ray diffraction patterns as follows:
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Fig. 2 (diagram of a hydrated calcium hypochlorite composition
employed as one component of the present invention) indicates the presence
of mainly Ca(OCl)2.3H2O.
Fig. 3 (diagram of an anhydrous calcium hypochlorite composition)
indicates the presence of mainly Ca(OCl)2.
Fig. 4 (diagram of a hydrated calcium hypochlorite composition
prepared by the prior art and containing 6% of water) indicates the presence
of both Ca(OCl)2.3H2O and Ca(OCl)2 intermediately.
The hydrated component of the composition according to the
invention is preferably obtained at an early stage in the drying of wet
neutral calcium hypochlorite crystals which have been separated from a slurry
of the chlorinated mixture obtained in the commercial production of high-
grade calcium hypochlorite.
The anhydrous component is a calcium hypochlorite composition which
is available commercially as high-grade calcium hypochlorite containing about
65 - 75~ of available chlorine and less than 2% water of crystallization.
The invention is predicated on the discovery that the anhydrous
component which is of satisfactory stability but is unsafe can be improved
as to safety when it is properly combined with the hydrated component which
is not only surprisingly resistant to self-propagating decomposition but is
also fairly stable at ordinary temperatures.
The proportion-ofhydrated component to anhydrous component varies
in accordance with the properties of the hydrated component, and is deter-
mined by consideration of the safety requirements of the blended composition.
Blending of 0.3 parts by weight or more of hydrated component with 1 part
of the anhydrous component provides a safe composition which is not subject
to self-propagating decomposition as shown in Test 2 described later herein.
A hydrated component having an amount of water of crystallization correspond-
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ing to nearly 3 moles per mole of Ca(OCl)2 is preferably employed for most
efficiently providing
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a component with the necessary safety for handling; however, easily
obtainable hydrated components having water of crystallization corresponding
to 3.0 - 2.5 moles, preferably 3.0 to 2.8 moles, per mole of Ca(OCl)2 are
also employed.
The blending of the components is carried out by means such as
conventional mixing apparatus e.g. ribbon blenders and flash mixers.
The fact that the water in the hydrated component of a composition
of the present invention is not transferred to the anhydrous component (see
Test 3 herein) means that the composition is a heterogeneous mixture of two
different granular components.
The compositions of the invention have available chlorine contents
of more than about 55%, are resistant to self-propagating decomposition, and
; are superior to compositions prepared by the prior art processes in respect
of storage stability.
The present compositions are composed of a specific hydrated calcium
hypochlorite component and an anhydrous calcium hypochlorite component both
of which generate during spontaneous decomposition smaller amounts of chlorine
gas than conventional hydrated calcium hypochlorite compositions, and the
amount of chlorine gas generated is also smaller than from prior compositions
as discussed herein. This has an advantage in less corrosion of metal
containers used for the calcium hypochlorite composition.
Another advantage of the invention concerns calcium hypochlorite
tablets of improved properties. Since the composition is composed of an
anhydrous component which dissolves slowly in water and a hydrated component
which dissolves easily, the dissolution characteristics of the composition
, provide a balanced prolonged sterili~ing effect in water treatment. The cal-
cium hypochlorite compositions may be formed as tablets by molding the granu-
lar compositions with a molding press.
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Tablets are usually molded under pressure to make them resistantto breakage during shipment and dissolution, and therefore, such tablets
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tend to dissolve more 810wly in water. Accordingly, tablets having
good dissolvlng properties but which are strong enough to withstand
breakage during 6hipment are desired.
Since the calcium hypochlorite compositions of the
invention contain a hydrated component which can be molded flrmly by
high pressure molding into tablets without reduction in dissolving
properties the calcium hypochlorite compositions of the present in-
vention provide tablets which are not only safe during manufacture and
handling and are stable but are also resistant to breakage with controlled
dissolution characteristics.
The following examples serve to illustrate the invention,
but are not to be construed as imposing any limitations thereon.
Example 1.
30 kg of a hydrated granular calcium hypochlorite having
64.7% avallable chlorine and water of cry~tallization corresponding to
2 moles per mole of Ca(OCl)2, and 18 kg of an anhydrous granular cal-
cium hypochlorite having 71.3% available chlorine content and 0.9% water
of crystallization were mixed thoroughly by means of a ribbon blender
to obtain 48 kg of a granular heterogeneous calcium hypochlorite com-
position having 67.1% avallable chlorine auntent. The composit~an did
not decompose when a lit match was applied. Samples of the composition
were stored at ambient temperature for 1 year, 200 days at 3~C and 50 days
at 40C respectively and the rate of 1088 of available chlorine content
during storage was measured at 4.4, lQ~8 and 7.2% respectively.
Example 2.
20 kg of a hydrated granular calcium hypochlorite having
58.1% available chlorine content and water of crystallization corres-
panding to 3 moles per mole of Ca(OCl)2, and 30 kg of an anhydrous granular
calcium hypochlorite composition having 71.7% available chlorine
content and 1.2% water of cry~tallization content were mixed to obtaln
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50 kg of a granular hetergeneous calcium hypochlorite composltion havlng
66.3% available chlorlne. m e composlt1on was decomposed by a lit match.
The! rate of ]oss ln available chlorine for samples of the co~positior.
measured after storage conditions of 1 year at ambient temperature,
200 days at 30C and 50 days at 40C respectively and were found to
be 4.5, 10.5 and 7.0%.
Example 3.
A hydrated granular calcium hypochlorite having 55.3
available chlorine content and water of crystallization corres-
ponding to 2.9 moles per mole of Ca(OCl)2 was mixed with 1 part by weight
of an anhydrous granular calcium hypochlorite having 73.5% available
chlorine content and 0.4% water of crystallization to obtain the follow-
ing granular heterogeneous calcium hypochlorite composltons.
Composition (A): 0.3 parts of the hydrated component
Available chlorine content was 69.3%.
(B): 0.5 parts of the hydrated component
Available chlorine content was 67.4%.
(C): 0 (The anhydrous component itself)
The compositions were compression molded and tablets
were obtained which were about 30 mm in diameter, 15 mm in height and
20 g in w~ight. The compression hardness of the tablets measured with
a uniaxial compression tester was 120 kg on the average for the tablets.
A tablet of each composition was dissolved in 3 1. of water
maintained at 30C under agitation at 60 RPM and the time necessary for
complete dissolution of the tablet was measured. The results were as
follows:
Tablet from Composition (A) 1~0 mln.
(B) 120
(C) 190
The tablets were sub~ected to a safety ignition test
by applying 2 drops of glycerine thereto at 50C. Results of the safety
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test were as follows:
Tablet from Composition (A) Decomposed after 20 sec-
onds with slow propagation
but stopped shortly. (No
decomposition when tested at
ambient temperatures)
(B) No decomposition
(C) Decomposed after 15 seconds with
a flash, and the decomposition
was complete.
Test 1.
A hydrated calcium hypochlorite having 75% available
chlorine on the basis of the anhydrous state was dehydrated by contact-
ing *ith hot dry air to prepare speclmens of granùlar calclum hypochlorite
whlch dlffered ln water of crystalllzatlon content in the rsnge of
from about 22 to about 1~. These specimen~ were stored under different
conditions, and the relationship between the rate of loss in available
chlorine and the water content of the composition was determined.
The results indicate a striklng effect of water of cry-
~talllzatlon on stability of calcium hypochlorite as shown in Fig. 1,where the storage conditions were as follows;
I ... Ambient temperature for 1 year,
II ... 40C for 50 days, and
III ... 30C for 200 days
Test 2.
A hydrated granular calcium hypochlorite havlng 60.4~
svailable chlorlne and water of crystallization corresponding to 3 moles
per mole of Ca(OCl)2 was employed as the hydrated componen~.
Various parts by weight of the hydrated component were mlxed
with 1 pare of an anhydrous granular calclum hypochlorite having
76.5~ avallable chlorlne and 0.4% water of crystallization. Samples
of the mixture were sub~ected ~o safety tests for calcium hypochlorite
composition6, and the results were as follows:
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Parts by weight of Ignition test with Ignition test with
hydrated component match * glycerine **
pa~t anhydrous component
o Self-propayatin~ Decomposed after 3
decomposition at seconds and propagated
rate of 24 cm/min at rate of 21 cm/min
0.1 Ditto, 10 cm/min Decomposed after 7
seconds and propagated
at rate of 9 cm/min
0.2 Ditto, 6 cm/min At the drop point,
- decomposition contin-
ued for 5 seconds
0.3 No composition No decomposition
* About 100 g of the specimen were placed on a V-type
iron trough of 50 cm length and 10 cm width. The
specimen was lit with a match at one end.
** Two drops of glycerine were applied at one end of
the specimen prepared in the same way as for the
match test.
Further, a hydrated granular calcium hypochlorite having 57.5%
available chlorine and water of crystallization corresponding to 2.2 mole
per mole of Ca(OCl)2 was employed as the hydrated component. This hydrated
component was mixed with an anhydrous granular calcium hypochlorite having
73.4% available chlorine and 0.6% water of crystalli7-ation in varied propor-
tions per 1 part of anhydrous component. Samples of the mixture were sub-
jected to the same safety test as above. A mixture composed of 0.3 parts
of the hydrated component and 1 part of the anhydrous component showed no
propagation by ignition with a match and slight fuming on addition of drops
of glycerine.
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determine any transfer of water between the hydrated component and the
anhydrous component.
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Calclum hypochlorite Available Water of Range of
compositlon chlorine crystalliza- particle size
content tion
(A) 60.1% 2.9 moles * 14 - 20 mesh
(B) .. .. 20 - 42
(C) 73.S 1.0 % ** 14 - 20
(D) .- .. 20 - 42
* Corresponding water of crystallization, moles
per mole of Ca(OCl)2
** Water of crystallization content
Equal amounts of (A) and (D) or (B) and (C) were mixed,
and the mixtures were stored at 30C for a length of time. After stor-
age, the mixtures were sieved with a 20 mesh ~ieve to obtain components
whlch corresponded to lA) or (C) and (B) or (D) respectively.
Water of crystallization of each component was as indicate~ b~lo~.
: Water of crystallization con- Water of crystallization
tent of partlcles passing content of particles
through 20 mesh _ retained by 20 mesh sieve
Mixture of (A) and (D):
After 30 days 0.8% 2.87 moles
1.0 2.88
1.0 2.87
Mixture of (B) and (C):
After 30 days 2.88 moles 1.0
2.9 1.0
2.88 0.9
