CA2126202A1 - Alkaline hydrogen peroxide formulation - Google Patents

Abstract

2126202 9313012 PCTABS00024 It would be desirable to produce stabilised aqueous alkaline hydrogen peroxide compositions for domestic use as a general purpose bleach and disinfectant as an alternative to hypochlorite solutions, in view of fears concerning the effect environmentally of chlorinaceous compounds. A stabilised buffered alkaline hydrogen peroxide solution is obtained by incorporating disodium tetraborate decahydrate and cyclohexane-1,2-diaminotetramethylene phosphonic acid as buffer and stabiliser respectively.

Description

2 PCT/GB92/02365 ~, Alkaline hvdroqen ~eroxide formulation `~
The present invention relates to aqueous alkaline -hydrogen peroxide formulations, and~more particularly to ;;-~
a stabilised and buffered formulation.
HousehoIds, for many years have employed a general purpose bleach and disinfectant for cleaning and `~
disinfecting hard surfaces such as~floors, work surfaces `
or walls, and especially or disinfecting sanitaryware and waste pipework. one class~of formulation~which has ~2,, 20 been~especially popular is based on aqueous alkaline li;
~ hypoch~lorite solutions. Such formulations have been - ~ very effective, but the general public has become aware of academic studies which have shown that in certain t~
circumstances, chlorinaceous compounds can interact with ~`"
the organic compounds in the environment with~the generation of carcinogens or other noxious substances.
In consequence, a nee~ has arisen to develop substitute products to offer~a "green" alternative for those who ; wish to avoid contacting hypochlorite with domestic waste `~
30 or introducing it into effluents that will eventually pass into the municipal sewage treatment works.
- Hydrogen peroxide is a product whiçh is generally acceptable environmentally, because its decomposition -~ products are oxygen and water. It has been supplied to ~`~
35 the household market in acidic formulations, but it would be preferable to employ alkaline formulations in order to enhance the performance of hydrogen peroxide. However, .

Wo93/l30l2 21 2 ~: . J ~ PCT/GB92/02365 ~

its employment in the past in aqueous alkaline media has ~;
been hindered because alkaline peroxide solutions are prone to decomposition during storage, such as occurs -~
inevitably during the period of distribution from the S manufacturer to sales outlets in supermarkets or the like, and storage on their shelves and subsequently in the home of the consumer. The net result of excessive ~-decomposition is that the product progressively loses its ~i;
efficacy and thereby its shelf life is curtailed.
lO The stability of aqueous alkaline hydrogen peroxide ;
solutions has been improved in GB 2 072 643 and EP-B-Oo 76 166, both to Interox Chemicals Limited, by employing an aminomethylene phosphonic acid together with a low weight alcohol such as ethanol or isopropanol as a '-15 stabiliser system, but the presence of the aloohol -inevitabIy reduces the flash point of the composition and introduces additional processing costs. The~
incorporation of certain aminomethylene phosphonic acids -~as stabiliser in alkaline hydrogen peroxide solutions has 20 also been described in International Application W0 91/09807 also to Interox Chemicals Limited.
During the transportation and storage of alkaline hydrogen peroxide solutions, theré is also a tendency for Ir a downwards drift of its pH to occur. This can be ::i., `
counteracted to some extent by the incorporation of a ~o buffer~appropriate for the desired pH range. ~ It would be convenient to incorporate a buffer in aqueous hydrogen `
peroxide solutions tbat is encompassed within the broad descriptive term borates, because a mildly alkaline pH
....
30 can thereby be maintained longer, but processing difficulties have been encountered in the incorporation of certain borates. `~
~ The incorporation of certain borate compounds together - with a silicate as stabiliser in short-term alkaline ,``!,`, 35 hydrogen peroxide bleaching baths has been described in ~- EP-B-0 119 920 to Atochem, but such solutions are not WO93/13012 ~ 'J J~ PCT/GB92/02365 suitable for distribution and sale to the general public, because they have a much restricted shelf life.
It is an object of the present invention to provide an alkaline hydrogen peroxide solution which overcomes -S ameliorates one or more of the foregoing difficulties. ~ ;
According to the present invention, there is provided a storage stable composition suitable for use domestically as a general purpose household bleach and disinfectant which consists essentially of an aqueous alkaline lo solution of from about l to about 10% w/w hydrogen peroxide, at least 0.2% w/w of a borate buffer introduced `~
as sodium tetraborate decahydrate, alkali metal hydroxide in an amount which is sufficient together with the borate buffer to generate a pH in the range of from at least 7 5 to about 9.5, cyclohexane-l,2-diaminotetrakismethylene phosphonic acid or water soluble salt thereof in a concentration calculated as the acid of at least lS0 ppm and optionally a surfactant.
Advantageously, a formulation according to the present `
20 invention combines the benefits of stabilising the -.
hydrogen peroxide composition with a most effective compound, cyclohexane-1,2-diaminotetrakis phosphonic acid ~ (CDIMPA) with the practical benefits obtained by - introducing disodium tetraborate decahydrate as a borate buffer. The use of the selected buffer prevents the pH ~-o the composition from dropping quickly during its shelf life, ie the time between manufacture and use. Thus, the two components, cooperate to maintain both peroxide and pH stability, and thereby enable the composition to 30 better retain its efficacy during its inevitable æhelf-life. Moreover, the use of the selected buffer enables ;~
rapid formation of the formulation as a fully dissolved aqueous mixture, thereby minimising the size of plant ~;
required for each unit of manufacture and thus minimise ;
35 processing costs.
In practice, it is preferable to select the concentration of hydrogen peroxide within the range of WO93/13012 ~1 2 ~ 2 J~ PCT/GB92/02365 4 ~
from about 4% to about 7% by weight. Most conveniently, it can be introduced into the composition in the form of -;
a commercially available aqueous acidic concentrate, ~-~
which typically contains from about 30 to about 70% w/w ;~
5 hydrogen peroxide. Such solutions typically contain a small concentration of a stabiliser which is adequate for acidic conditions, but which would be inadequate in the ~ ~-buffered alkaline conditions of the instant invention.
The concentration of disodium tetraborate decahydrate 10 buffer in practice is often selected in the range of from about 0.3% to about 1% w/w. Such a range balances the desire to buffer effectively without employing excessive material. In a number of desirable embod`iments, its concentration falls in the range of from about 0.4 to 15 about 0.6% w~w.
The alkaIi metal hydroxide can conveniently comprise sodium hydroxide, in view of its widespread availability and cost. It is often desirable to introduce it into the formulation in the form of a concentrated aqueous 20 solution, such as a solution of from 30 to about 47% w/w. `~
The stabiliser is most widely available in the acid form, but if desired, it can alternatively be introduced as~an alkali metal salt, an example of a water~soluble salt. ~ In practice, its concentration in the formulation `~
is usually not greater than about 1500 ppm, and in many suitable formulations, the concentration falls in the range of from 200 to lO00 ppm. In selecting the concentration of added stabiliser, CDTMPA to incorporate, the pH of the buffered composition is preferab;ly taken - 30 into account , the higher the pH, the higher the ;
concentration of stabiliser. For a borate buffered composition having a target pH of about pH 8.5, ie +/- -;
about 0.2 pH units, a convenient concentration range of -CDTMPA therein is from about 250 to about 500 ppm.
The invention formulation in many embodiments contains a small concentration of a surfactant, such as at least 0.25~ by weight, which acts to improve the rate and W O 93/13012 2 12 ~ 2 0 2 PC~r/GB92/02365 ., '`
extent of wetting of the surface which will be disinfected by the formulation It is desirable to select a nonionic surfactant and especially an amine oxide Readily available amine oxides can be obtained s containing a total of from about lO to about 20 carbons, ;~
` of which at least one alkyl chain contains at least 8 linear carbons Some particularly~suitable amine oxides ~; ~ comprise a dimethylalkylamine~ oxides in which the alkyl group is~linear ClO to Cl6 or mixtures thereof such as ~those~dèrived~;from~natural sources ~ The concentration of surfactant;~is~often 1e~ss~than about 3% w/w, and in '~
many pract~ical~embodiments~is~selected in the range of from~about~ 0 4 to about 0 8S w/w ~The surfactant can conveniently be~ introduced into the~formulation in the 15~for ~of~an~aqueous~solution,~f~or~examp;~le one conta~ining from l5`to~50$~w/w activé~materi~
In addition, it is preferable to incorporate within the ~formulation~a~perfume~which~is ætable~to oxidation in~
a1kaline~media,~such~a8~in a~conce~ntration of from about O~Q3~ to~about~0~15%~w/w~ It is~often~convenient~to pre ix~ thè~pèrf ~ e~with~the~surfactant~before thèir `~
introduction~into the~if;ormu1ation It~will be~recognised~that`~the~invention comp~sitions ~described~herein~are~essentially free~from alcohols or ~ ;~
concentrations~of~other~;~components which~would~adversely ``~
~?,~ affect tbeir~f1ash~point`~to~àny~s~ignificant extent æ;formu1ation~ of~ t~he~presènt~invé tion càn~be pr ~ ed in~a~number~of~dif~ferent;~sequence~s of~mixing the ~ ;
o ~ nents~togethe~r ~ In~gene~ra1, it is~ desirable to 30~ 0parate~at~0r~n-ar~;amb~ té~perature~ ie from~about lO
to 40C, to avoid~undue~heating costs~and~avoiding the acceleration~of~hydrogen~peroxide;decomposition that could occur at more elevated temperatures It i-~pref-ra~ble~to ~nsure~that~th-~stabilis-r is ~;
35 present in tbe~mixture~at the time that~the peroxide is in odu~-d,;such~as~by~introducing~the~;~stabiliser before js the peroxide~is added~ It is also desirable to add any ~"~

: .

2 I 2 ~ 2 ~ PCT/GB92/02365 .~

alkali as the final step in the process in order to ~.
attain a predetermined pH.
A preferred production sequence comprises~
i dissolving sodium tetraborate decahydrate in a `:~
s precalculated quantity of water from which alkaline earth metal ions have been removed; ;
ii introducing the aminomethylene phosphonic acid; ~`:
iii blending in an aqueous mixture of the surfactant and ;
the perfume;
10 iv mixing in aqueous hydrogen peroxide solution, containing nominally 30 to 35% w/w; ~":
v mixing concentrated sodium hydroxide, nominally 47%
w/w up to a preset pH.
Advantageously, the stabilised and buffered alkaline ;~
15 hydrogen peroxide formulations of the present lnvention are able to combine the benefits of improved performance accruing from operation in alkaline conditions compared with operation in acidic conditions with the ability to retain their efficacy for a considerable period of time, !~
20 both as a disinfectant and as a stain remover from cloth ~.
; , or ceramic surfaces, .
Having described the invention in general terms, `
specific embodiments will now be described in greater : detail, by way of example only. `-~
ExampIe l ~.
A buffered aqueous alkaline bleach composition was prepared by dissolving 5 parts by weight of disodium ::
tetraborate decahydrate in 825 parts by weight of demineralised water at ambient temperature. l Part by 30 weight of a solution containing 30% w/w of cyclohexane- `
l,2-diaminotetrakismethylene phosphonic acid (the ::~
stabiliser) was then introduced with stirring into the -~
clear solution, followed shortly after by an aqueous solution containing 6~25 parts by weight of t~-35 tetradecyldimethylamine oxide and 0.9 parts by weight of ` ~:
a perfume that is resistant to oxidation which had been made up with water to a total of 25.9 parts by weight. -., ~: `

WO 93/13012 212 6 ,~ ~ 2 PCI`/GB9^. '......................... '.~365 -Then, 143 parts by weight of an aqueous hydrogen peroxide --~
solution containing nominally 35% H22 was mixed into the ~-stabiliser-containing mixture and finally an aqueous solution of sodium hydroxide (nominally 47% w/w) was 5 introduced gradually until the composition had a measured pH of 8.5.
The composition was stored in the dark at either ambient temperature, or 28 or 32C in a number of bottles which contained a vented closure. The concentration of o hydrogen peroxide was monitored at regular intervals employing a standard potassium permanganate titration technique and the extent of hydrogen peroxide decomposition during storage was calculated by comparing the measured concentrations before and after storage. ;
15 The results are summarised in the Table below.
The Table Storage Period Storage Measured Loss of (weeks) Temperature H22 conc H22 (%) initial ambient 5 0 - ~
6 " 4.91 0 ;
12 " 5.15 0 initial 28C 4.96 6 " 5.08 0 12 " 4.84 1.2 ;~ initial 32C 4.91 6 " 4.85 1.0 12 " 4.71 3.9 The pH of the compositions~were also measured and were ;~
still at about pH 8.14 after 12 weeks.
From the Table above, it can be seen that the formulation according to the present invention still :
contained substantially the same condentration of hydrogen peroxide at the end of the storage period as at the beginning, the maximum loss still being less than 4%, 35 so that the efficacy of the composition remains ~
substantially intact. ~;

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:
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W O 93/13012 21~ ~ ~ 0 2 PC~r/GB92/02365 ~
Examples 2 to 4 In these Examples, further compositio~s were prepared using the same stabiliser and the process described for Example 1 and having the formulations given in Table 2 d~
5 below. ADM~O represemts alkyl dimethyl amine oxide, and NaBD represents sodium borate decahydrate ;~
Table 2 Component Example 2 Example 3 Example 4 % w/w % w/w % w/w IO ADML~O - O.75 0.15 ~'~
Fragrance 0.08 0.04 - ~.
Hydrogen Peroxide 10.62 10.62 10.62 . Stabiliser 0.10 0.10 0.10 15 NaBD 0-50 0-50 0-50 ~ ,.
NaOH to pH 8.5 to pH 8.5 to pH 8.5 ~.
Soft Water to 100 to 100 to 100 , ~, : ,:
~: `.'' ~' .

;,, ~ .

~`

-, ~.

.:

Claims (11)

CLAIMS:

1 A storage stable composition suitable for use domestically as a general purpose household bleach and disinfectant which consists essentially of an aqueous alkaline solution of from about 1 to about 10% w/w hydrogen peroxide, at least 0.2% w/w of a borate buffer introduced as sodium tetraborate decahydrate, alkali metal hydroxide in an amount which is sufficient together with the borate buffer to generate a pH in the range of from at least 7 to about 9.5, as stabiliser cyclohexane-1,2-diaminotetrakismethylene phosphonic acid or water soluble salt thereof in a concentration calculated as the acid of at least 150 ppm and optionally a surfactant.

2 A composition according to claim 1 in which the concentration of stabiliser is selected in the range of from 200 to 1000 ppm

3 A composition according to either preceding claim in which the concentration of borate buffer is from about 0.4 to about 0.6% w/w calculated as disodium tetraborate decahydrate.

4 A composition according to any preceding claim which has a pH of from about 7.5 to about 8.5.

A composition according to any preceding claim which contains at least 0.25% w/w surfactant.

6 A composition according to any preceding claim which contains an amine oxide surfactant.

7 A composition according to claim 6 in which the amine oxide contains a linear C10 to C16 alkyl and two short chain alkyl substituents.

8 A stabilised alkaline hydrogen peroxide composition substantially as described herein with respect to the Example.

9 A process for producing a stabilised aqueous alkaline solution of hydrogen peroxide in which hydrogen peroxide is introduced to a concentration of at least 3% w/w in the presence of an effective amount of cyclohexane-1,2-diaminotetrakismethylene phosphonic acid or water soluble salt thereof as stabiliser into an aqueous solution of at least 0.2% w/w disodium tetraborate decahydrate, the composition is adjusted to a pH of from 8 to 9.5 where necessary, by the introduction of an alkali metal hydroxide, and at least 1% w/w of a surfactant is introduced, either before or after the hydrogen peroxide.

10 A process for producing a stabilised aqueous alkaline hydrogen peroxide solution substantially as described wherein with respect to the Example.

11 A stabilised aqueous alkaline hydrogen peroxide composition or a process for producing such a composition substantially as described herein with respect to any novel feature or novel combination of features.