Stable peroxide composition and method of preparation thereof

A stable succinyl peroxide composition comprising in solid particulate form a mixture of succinyl peroxide, a water-soluble dehydrating agent which is unreactive to succinyl peroxide, e.g., magnesium or sodium sulfate, and water, the water being bound to the dehydrating agent as water of hydration; and a method of preparation thereof comprising mixing a paste of succinyl peroxide in water with a water soluble dehydrating agent, the dehydrating agent being mixed with the succinyl peroxide paste in an amount and for a time sufficient to bind all of the water in the paste and provide a dry mixture.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a stable succinyl peroxide composition and a 
method of preparation thereof. 
2. Description of the Prior Art 
Succinyl peroxide, which is also known as disuccinyl peroxide or succinic 
acid peroxide is a compound of the formula: 
EQU (HOOC.CH.sub.2.CH.sub.2.CO).sub.2 O.sub.2 
Succinyl peroxide is known for use as a polymerization initiator, as a 
deodorant and as an antiseptic. In the past the compound has been sold in 
the dry powder form for use as a polymerization initiator, but it was 
found that the dry powder is friction sensitive and, under certain 
circumstances, could explode. In order to overcome this problem succinyl 
peroxide is currently marketed as a 70 percent by weight paste in water. 
However, succinyl peroxide as a paste in water is unstable at ambient 
temperatures, the peroxide decomposing by hydrolysis, and stability can 
only be ensured by storing the paste under refrigerated conditions, 
typically at -10.degree. C. It will be appreciated that the need to store 
and transport the paste under refrigerated conditions is a significant 
disadvantage, especially when the succinyl peroxide is required for use in 
applications where for instance relatively small unit doses of the 
peroxide are to be stored before use, for example, as an antiseptic. 
The encapsulation of perphthalic acids in protective coatings of hydrated 
or partially hydrated salts such as partially hydrated and hydrated 
magnesium and sodium sulfate is described in the prior art, e.g., see U.S. 
Pat. Nos. 3,494,786 and 3,494,787 to Nielsen, and U.S. Pat. No. 3,622,366 
to Piester. 
U.S. Pat. No. 3,639,285 to Nielsen discloses that the stability of 
monoperphthalic acids can be substantially improved by incorporating 
therewith certain alkali metal and alkali earth metal salts such as 
anhydrous magnesium and sodium sulfate. 
British Pat. No. 1,456,591 to The Procter & Gamble Company describes 
bleaching compositions of excellent storage stability comprising a 
specified peroxyacid material, a peroxyacid-stabilizing agent mixture 
consisting essentially of a specified proportion of magnesium sulfate and 
a particular alkali metal sulfate, and a specified amount of bound water 
of hydration. 
British Pat. No. 1,456,592 to The Procter & Gamble Company describes peroxy 
bleaching granules comprising, in specified amounts, a normally solid, 
organic, water-soluble peracid admixed with a bleach-stabilizing agent 
such as magnesium or sodium sulfate, water of hydration, and a fatty 
alcohol coating material. 
Research Disclosure, September, 1974, No. 12510, pp. 4-6, teaches the 
stabilization of a peroxygen compound selected from p-nitroperbenzoic 
acid, diperazelaic acid and m-chloroperbenzoic acid by contacting spray 
droplets of the peroxygen compound with a fluidized bed of magnesium 
sulfate particles having a moisture content of less than 10%, and mixing 
for a time sufficient for the water content of the spray droplets to be 
bound by the magnesium sulfate to give a substantially dry and 
free-flowing magnesium sulfate coated peroxygen compound. 
None of the foregoing references describe stable succinyl peroxide 
compositions. 
SUMMARY OF THE INVENTION 
It has now been found surprisingly that an intimate mixture of succinyl 
peroxide, a water-soluble dehydrating agent which is unreactive to 
succinyl peroxide, and water, the water being bound to the dehydrating 
agent as water of hydration, provides a composition which is stable on 
storage at ambient temperature and which does not possess the friction 
sensitivity of dry, powdered succinyl peroxide. 
Therefore in one aspect, the invention provides a stable succinyl peroxide 
composition comprising in particulate solid form a mixture of succinyl 
peroxide, a water-soluble dehydrating agent which is unreactive to 
succinyl peroxide, and water, the water being bound to the dehydrating 
agent as water of hydration. 
In another aspect, the invention provides a method for preparing a stable 
succinyl peroxide composition comprising in particulate solid form a 
mixture of succinyl peroxide, a water-soluble dehydrating agent which is 
unreactive to succinyl peroxide, and water, the water being bound to the 
dehydrating agent as water of hydration, which method comprises mixing a 
succinyl peroxide paste consisting of succinyl peroxide and water with a 
water-soluble dehydrating agent selected from the group consisting of 
anhydrous dehydrating agent and partially hydrated dehydrating agent, the 
dehydrating agent being mixed with the succinyl peroxide paste in an 
amount and for a time sufficient to bind all the water in the paste and 
provide a dry mixture. 
The compositions of the invention are microbiocidal and are useful for 
preparing aqueous solutions having utility as disinfecting and/or 
sterilizing and/or antiseptic agents. 
DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PREFERRED EMBODIMENTS 
In the compositions of the invention, the dehydrating agent, as more fully 
defined hereinbelow, must be water-soluble, sufficiently inert not to 
react with the succinyl peroxide, and have bound thereto water as water of 
hydration, preferably water of crystallization. The dehydrating agent 
should be such that a use-solution of the composition in water has a pH 
below 5, and in fact should not materially alter the pH of succinyl 
peroxide in solution. Essentially all of the water present in the 
compositions must be bound to the dehydrating agent as water of hydration. 
The relative amounts of water and dehydrating agent in the compositions 
can be such that the dehydrating agent is either in partially hydrated 
form or approaches the fully hydrated form. It should be understood 
however that as used herein in describing the compositions of the 
invention, the term dehydrating agent refers to such agent on an anhydrous 
basis. Thus, the parts by weight of dehydrating agent in the compositions 
as specified herein are on an anhydrous basis. 
In practicing the method of the invention, the dehydrating agent to be 
employed can be either in anhydrous or partially hydrated form. Although 
any dehydrating agent which meets the criteria of water-solubility and 
inertness to succinyl peroxide as specified hereinbefore is suitable, 
preferred dehydrating agents employed in the method of the invention are 
inorganic dehydrating agents, especially anhydrous and partial hydrates of 
sodium and magnesium sulfate. Of these, magnesium sulfate is the more 
preferred since it combines more rapidly and more firmly with water and 
thus leads to more stable compositions. A preferred form of magnesium 
sulfate is the partially hydrated form having the formula 
MgSO.sub.4.nH.sub.2 O, where n has a value of 1 to 4, preferably 1 to 2. 
Since the dehydrating agent acts to remove water from the paste, i.e., by 
binding the water as water of hydration, the level of hydration, if any, 
of the dehydrating agent initially employed in the method of the invention 
will of course be below that in the final composition of the invention. 
Thus, in the case of hydrates of magnesium sulfate, in the final 
compositions, in the formula MgSO.sub.4.nH.sub.2 O, n will have values 
greater than the corresponding values for n specified above, and typically 
can have a value of from 2 to less than 7, preferably 2 to 3, i.e., for 
each mole of magnesium sulfate in the final composition there can be from 
2 to less than 7 moles of water of hydration, preferably 2 to 3 moles of 
water of hydration. 
In the compositions of the invention, it is preferred that for each part by 
weight of succinyl peroxide there are from about 0.1 to about 12.5 parts 
by weight of water as water of hydration, and from about 1 to about 50 
parts by weight dehydrating agent, more preferably from about 0.4 to about 
1 part by weight of water and from about 1 to about 3.5 parts by weight of 
dehydrating agent, and most preferably from about 0.4 to about 0.7 parts 
by weight of water and from about 1.1 to about 2.2 parts by weight of 
dehydrating agent. 
The composition of the invention can be prepared by intimately mixing 
succinyl peroxide, an appropriate dehydrating agent and water. It should 
be understood that the term dehydrating agent as used herein in connection 
with the method of the invention refers to either anhydrous dehydrating 
agent or partially hydrated dehydrating agent. Conveniently the 
compositions are prepared by mixing the dehydrating agent with a paste of 
succinyl peroxide in water. Although a paste comprising a mixture of 70% 
by weight of succinyl peroxide and 30% by weight of water is preferred 
since such paste is available commercially, pastes having a succinyl 
peroxide content generally down to about 40% by weight and up to about 90% 
by weight can, if desired, be employed. Whatever the succinyl peroxide 
content of the paste, it can be treated to provide a dry mixture by mixing 
generally with from about 40% to about 95% by weight of dehydrating agent, 
preferably a sodium or magnesium sulfate as described above, based on the 
total weight of dehydrating agent and succinyl peroxide paste. Preferably 
from about 45% to about 80% by weight of dehydrating agent is employed 
based on the total weight of dehydrating agent and succinyl peroxide 
paste. Where the dehydrating agent is a partially hydrated material, it is 
to be understood that the amount employed may have to be increased in 
proportion to the degree of hydration of the agent. 
Preferably the dehydrating agent is employed as a fine powder, and the 
treatment may be effected by simple mixing for a suitable time to provide 
a dry mixture. Generally a mixing time of from about 15 minutes to about 6 
hours will be sufficient, and typically a mixing time of from about 30 
minutes to about 4 hours may be employed. 
In the method of the invention, the amount of dehydrating agent and the 
mixing time generally are adjusted so that there is produced an intimate 
mixture of ingredients in particulate solid form which gives the 
appearance of a dry solid, for example, a dry powder. Such a dry solid is 
a dry mixture of the kind required herein whether or not the mixture as a 
whole is dry in any absolute sense. Thus, provided any water present is 
captured by dehydrating agent and is not free to wet the peroxide, the 
mixture is dry. 
In preparing the compositions of the invention, other optional ingredients 
may be included as and when desired. Thus, the compositions may include 
one or more detergent materials, chelating agents, hydrogen peroxide 
donors, e.g., urea hydrogen peroxide adduct or sodium perborate, and 
coloring agents. For example, the compositions may include from about 1% 
to about 2% by weight of a solid anionic detergent, e.g. sodium lauryl 
sulfate, or non-ionic detergent, and color may be provided using either a 
dyestuff or a pigment, e.g. ultramarine. In particular, the compositions 
preferably may include a dyestuff (typically one giving a blue color) 
which is stable in the presence of succinyl peroxide when in aqueous 
solution at dilutions such as those mentioned below. As an example of such 
a dyestuff there may be mentioned the copper phthalocyanine complex C.I. 
Acid Blue 254. 
The compositions of the present invention are biocidal, and accordingly are 
useful as cleaning and/or disinfecting and/or sterilizing and/or 
antiseptic compositions. The compositions by virtue of the fact that they 
contain succinyl peroxide are not only bactericidal, but also fungicidal, 
sporicidal and perhaps virucidal. In particular, the compositions of the 
invention may be used as general purpose hard surface cleaners, as 
instrument sterilizers, or as a replacement for iodophors. 
Moreover, because the compositions are in a stable dry powder form, they 
may be packaged for distribution, storage and use without any special 
restrictions being imposed on transport and storage conditions. As shown 
below, the compositions remain in active condition even after a storage 
period well in excess of one year. 
In use the compositions are dissolved in water at a high dilution, 
typically at a dilution of from 0.05% to 2% w/w (based on a succinyl 
peroxide content of about 20% by weight) and are used immediately after 
they are made up in diluted form. 
Following is a description by way of examples of the preparation of 
stabilized peroxide compositions in accordance with the invention.

EXAMPLE 1 
0.2 kg of a 70% by weight succinyl peroxide paste in water obtained from 
Laporte Industries was mixed with various proportions of sodium and 
magnesium sulfate to obtain a dry mixture. The dehydrating agent employed, 
its amount and the mixing conditions and time are shown in Table 1 below; 
and the parts by weight of water (as water of hydration) and of 
dehydrating agent (DA) (anhydrous basis) for each part by weight of 
succinyl peroxide (SP) in the compositions obtained are given in Table 2. 
TABLE 1 
______________________________________ 
% w/w 
Succinyl Per- 
% w/w % w/w 
oxide as a 70% 
Magnesium Sodium Mixing 
w/w paste in 
Sulfate Sulfate- Condi- Mixing 
water Monohydrate Anhydrous tions Time 
______________________________________ 
10 90 -- Tumble 4 hours 
mixer 
20 80 -- Tumble 4 hours 
mixer 
30 70 -- Tumble 4 hours 
mixer 
50 50 -- Tumble 4 hours 
mixer 
10 -- 90 Tumble 4 hours 
mixer 
20 -- 80 Tumble 4 hours 
mixer 
30 -- 70 Tumble 4 hours 
mixer 
______________________________________ 
TABLE 2 
______________________________________ 
% w/w 
Succinyl Per- 
% w/w % w/w 
oxide as a 70% 
Magnesium Sodium 
w/w paste in 
Sulfate Sulfate- Parts by Weight 
water Monohydrate 
Anhydrous (SP:Water:DA) 
______________________________________ 
10 90 -- 1:2.1:11.2 
20 80 -- 1:1.2:5 
30 70 -- 1:0.9:2.9 
50 50 -- 1:0.6:1.2 
10 -- 90 1:0.4:12.9 
20 -- 80 1:0.4:5.7 
30 -- 70 1:0.4:3.3 
______________________________________ 
Under storage conditions at ambient temperature each of the above-prepared 
dry mixtures gave results which indicated that a shelf life in excess of 
one year can be obtained in accordance with the present invention. In this 
connection, and by way of example, reference is made to the appended 
drawing in which the sole FIGURE represents a graph of activity (% w/w of 
succinyl peroxide) vs. time in days for a 70% by weight succinyl peroxide 
paste in water compared with two of the dry mixtures prepared as described 
above. The results expressed graphically were obtained from batches stored 
at about 20.degree. C., the % w/w of succinyl peroxide being determined by 
sampling at suitable intervals and estimating the remaining succinyl 
peroxide by standard iodometric methods. 
In the graph, curve A shows the activity of the 70% paste, from which it 
can be seen that activity decreases to a low level within about 60 days 
and at about 90 days the activity is so low as to be virtually not 
measurable. By contrast line B (mixture of 30% w/w of 70% paste with 70% 
w/w magnesium sulfate monohydrate) and line C (mixture of 30% w/w of 70% 
paste with 70% w/w anhydrous sodium sulfate) show that in accordance with 
the present invention activity is maintained at a significant level over a 
much longer period of time. 
EXAMPLE 2 
50 parts by weight of a 70% by weight succinyl peroxide paste in water 
obtained from Laporte Industries were mixed with 50 parts by weight of 
magnesium sulfate monohydrate to obtain a dry mixture. The initial 
succinyl peroxide assay given by the dry mixture was 33.3% w/w and after 
14 months of storage at ambient temperature the mixture gave a succinyl 
peroxide assay of 31.6% w/w. 
EXAMPLE 3 
A large scale batch of 50 kg of a stabilized peroxide composition was 
prepared by mixing 20 kg of a 70% by weight succinyl peroxide paste in 
water with 30 kg of magnesium sulfate dihydrate to form a dry mixture. The 
dry mixture, which for each part by weight of succinyl peroxide contains 
0.9 parts by weight of water and 1.7 parts by weight of magnesium sulfate, 
was then packed as 5 kg lots in polyethylene bags and those in turn were 
stored in a fiberboard drum. 
The initial succinyl peroxide assay given by the dry mixture was 29.0% w/w. 
After storage at ambient temperature for one month there was an initial 
drop in the assay to a figure of 27.0% w/w, but after a total of 5 months 
storage at ambient temperature the succinyl peroxide assay remained at 
27.0% w/w. 
The compositions of Examples 1 to 3, when prepared in use-dilution in 
accordance with the method described hereinabove, provided solutions 
having a pH of about 2.5.