Note: Descriptions are shown in the official language in which they were submitted.
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AQUEOUS LIQUID BLEACH COMPOSITIONS
Technical field
The present invention relates to aqueous liquid bleach
compositions and to a method for disinfecting hard surfaces
using the liquid bleach compositions.
Background and prior art
Aqueous liquid hypochlorite bleach compositions are well
known in the art. On the one hand they are used for
bleaching of and stain removal from laundry, on the other
hand they are used for cleaning and disinfecting hard
surfaces such as kitchen surfaces, floors, bathrooms and in
particular toilets. To increase the contact time between the
bleach and a surface, particularly an inclined or vertical
surface the bleach compositions often have a relatively high
viscosity and such compositions are generally known as
"thick bleach".
Hypochlorite bleach compositions are generally strongly
alkaline, typically pH 10 or higher. At acidic pH
hypochlorite bleach decomposes, forming chlorine gas. For
certain applications this has been considered to be an
undesirable limitation and alternative "active chlorine"
bleaching agents have been used for various applications.
They generally belong to the group of N-chloro compounds
such as mono-, di- and trichloro-isocyanurate, mono- and
dichloro-sulphamic acid, N-chlorohydantoins, N-chloro-
succinimide, N-chlorophthalimide, N-chloro-p.toluene-
sulphonamide (Chloramine T), N-chloroimidodisulphate, N-
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chloromelamine, N-chloroglycoluracil and the like. The
parent NH compounds generally react with chlorine gas under
formation of the N-chloro compound and are thus said to
stabilize hypochlorite at low pH by scavenging the chlorine
formed through decomposition of the hypochlorite. In fact no
stabilization takes place because although one active
chlorine compound (hypochlorite) is substituted by another
(the N-chloro compound), the bleaching power of the N-chloro
compound is generally inferior to the bleaching power of
hypochlorite and therefore the bleaching power of the total
mixture is inferior to that of an equivalent amount of fresh
hypochlorite alone.
US 3,749,672 describes the stabilization of hypochlorite
solutions between pH 4 and 11 by adding an NH compound
suitable for conversion to the corresponding NC1 derivative.
A list of all likely and a lot of less likely candidate NH
compounds is given, but all examples focus on the use of
sulphamic acid.
EP 119560 describes hypochlorite solutions of pH>ll
stabilized by the addition of an NH compound in a C10- : NH
molar ratio of <_ 1. Again a large number of possible NH
candidate compounds are listed, but only sulphamic acid is
exemplified.
US 3,054,753 describes detergent'powders comprising solid
inorganic active chlorine sources such as chlorinated sodium
phosphate or lithium hypochlorite and an organic
sulphonamide as a stabilizing agent for the active chlorine
compound. Likewise, EP 165676 describes solid hypochlorite
containing detergent powders that are stabilized and brought
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into solid form by the addition of anhydrous builders,
particularly sodium phosphates, and p.toluenesulphonamide.
N-chloro-p.toluene-sulphonamide itself is described as being
an inefficient source of active chlorine and providing
little bleach activity. The detergent powders described in
both these documents are typical laundry detergents in which
sodium phosphate and sodium carbonate builders are the
predominant materials in the composition.
WO 9821308 describes acidic bleaching compositions obtained
by mixing an acidic solution of a chlorine deactivating
compound (NH compound) with an alkaline hypochlorite
solution immediately before use. The chlorine deactivating
compound is further specified to be sulphamic acid.
WO 0100029 describes antimicrobial solutions that are called
"stabilized hypochlorite" solutions, but which are
essentially solutions of N-chloro- and N-dichlorosulphamate
and a so-called "dopant" selected from a dialkylhydantoin,
an aryl-sulphonamide, a succinimide and a glycoluracil.
WO 9627651 and 9627652 describe bleach compositions giving
reduced skin malodour and comprising an active chlorine
bleach such as hypochlorite and an NH compound. The
compositions are said to be particularly useful to prevent
the hands of the user which are in prolonged contact with
the composition from acquiring the well-known bleached-skin
malodour.
Although active chlorine compounds and particularly
hypochlorite are known to be powerful disinfectants, after
treatment of a substrate with the chlorine compound the
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disinfectant activity is normally short-lived. Thus, after a
surface has been treated with hypochlorite it can quickly
become microbially recontaminated again. This is
particularly true if the surface is afterwards rinsed with
water, because rinsing will wash away any traces of
hypochlorite left on the surface.
There'`'s a need for methods for oxidative cleaning/bleaching'
of a surface that provide powerful initial disinfectancy as
well as give sufficient residual antimicrobial activity on a
surface to prevent bacterial regrowth for extended periods
of time. Also, compositions suitable for use in such methods
should be sufficiently stable to be manufactured, shipped
and stored without appreciable loss of active chlorine.
Su mnary of the invention
It has now been found that treatment of hard surfaces with a
liquid composition comprising a combination of hypochlorite
and one or more specific N-chloro compounds provides
thorough oxidative cleaning and removal of stains while at
the same time not only initially disinfecting the surface,
but providing antimicrobial activity on the cleaned surface
for an extended period of time, even after repeated rinsing.
The selected N-chloro compounds provide compositions that
are stable and can be stored for long periods without
appreciable loss of active chlorine.
Thus, the invention provides an aqueous liquid bleaching
composition comprising an amount of hypochlorite salt
sufficient to give 0.0014-1.4 mol/1 of hypochlorite ion and
an N-chloro compound and having pH above 7 characterized in
that the N-chloro compound is chosen from N-chloro-aryl-
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sulphonamides, and N-chloro-imidodisulphate salt and the
composition comprises at least one surfactant.
Furthermore, the invention specifically provides a method of
cleaning and disinfecting toilet surfaces, particularly
toilet bowls, comprising applying to the surface a liquid
bleaching composition comprising hypochlorite and one or
more specific N-chloro compounds.
Also, the invention provides stable liquid bleaching
compositions suitable for use in the methods described
above.
Detailed description of the invention
All percentages mentioned herein are by weight unless
specified otherwise.
Accordingly, the invention provides a method for providing
lasting antimicrobial activity on a substrate as well as an
aqueous liquid bleaching composition suitable for use in
that method. The method comprises treating the substrate
with a composition comprises a hypochlorite salt and an N-
chloro compound chosen from N-chloro-arylsulphonamides and
N-chloro-imidodisulphate salt, the composition having pH
above 7. The method may be used on any substrate including
textiles, but is particularly useful for application on hard
surfaces.
The hypochlorite salt is generally an alkali metal or
alkaline earthmetal salt although other salts may be used.
The K, Na and Ca salts are preferred and the latter two
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particularly preferred. The compositions used for the
purposes of the invention generally comprise 0.01-10% NaC1O
or an equivalent amount of other hypochlorite salt, which is
equivalent to 0.0014-1.4 mol/l of hypochlorite ion.
Preferably the hypochlorite ion content is 0.005-1.0 mol/l,
more preferably at least 0.01 mol/l.
The compositions according to, and used for the purposes of
the invention generally comprise 0.00001-0.5 mol/1 of the N-
chloro compound, preferably at least 0.00002 mol/l or even
0.00005 mol/l, more preferably 0.0001-0.2 mol/l, most
preferably at most 0.1 mol/l. The molar ratio between
hypochlorite ion and N-chloro compound is usefully kept
between 15000:1 and 1:1, preferably at most 5000:1. Even
more useful ratios are between 200:1 and 1:1, more
preferably at most 100:1, even more preferably between 100:1
and 2:1, most preferably between 50:1 and 5:1.
Among the N-chloro-arylsulphonamides the benzene- and
p.toluene-sulphonamide and N-chloro-saccharine (or the N-
chloro compound derived therefrom) are preferred, the N-
chloro-benzenesulphonamide and p.toluene-sulphonamide are
more preferred. P.toluene-sulphonamide is especially
preferred and is commercially available as its Na salt as
Chloramine T. The N-Chloro compounds can be added to the
composition as such or they can be made in situ by adding
the corresponding NH compound to the hypochlorite solution.
In order to have complete control over the amount of N-
chloro compound present in the composition and not to
consume part of the hypochlorite it is preferred to add the
N-chloro compound as such.
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For long-term stability the compositions used for the
purposes of the invention need to be alkaline, i.e. have pH
above 7. Preferably the pH is kept at or above 8 or even 9.
At the pH of the compositions according to the invention the
N-chloro compounds may primarily be present as their salts,
which are preferably alkalimetal or alkaline earthmetal
salts.
The method according to the invention involves treating the
surface either with a dilute composition within the range
described above, i.e. a composition in which the
hypochlorite and the N-chloro compound are present in
concentrations in the lower parts of the ranges described
above, or with a concentrated composition i.e. a composition
in which the components are present in the higher parts of
the concentration ranges. The dilute compositions can be
conveniently made by the consumer by proper dilution of a
concentrated composition. Such concentrated compositions
preferably have a hypochlorite concentration of 0.1-1.0
mol/l, an N-Cl compound concentration of 0.01-0.5 mol/1,
more preferably 0.02-0.2 mol/1) and a pH of at least 9 and
can conveniently be diluted 10-100 fold.
The concentrated compositions according to the invention are
generally not suitable to come in contact with the skin and
therefore should be diluted before being applied to a
surface manually (e.g. with a wipe or cloth or other
implement). Alternatively, and in preferred embodiments of
the invention, compositions according to the invention,
either dilute or concentrated, are applied to the surface to
be treated without coming in contact with the skin of the
user and are left in contact with that surface for a
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sufficiently long time to oxidatively clean and disinfect
that surface, whereafter the surface may be rinsed if
desired. Generally, contact times of 1 minute are sufficient
for initial disinfectancy, with contact times of at least 5
minutes being used to obtain long term disinfectancy,
preferably at least 15 minutes, more preferably at least 30
minutes. One example of such embodiment involves applying a
composition according to the invention with a spraying
device such as a trigger spray or similar, as well known in
the art of hard surface cleaning. Another embodiment of the
invention involves applying to the surface to be treated a
squirt of concentrated solution straight from the container
in which it is provided.
The invention particularly provides a method for cleaning
and disinfecting toilet surfaces comprising applying to the
surface a composition as described above. In a preferred
embodiment, wherein the toilet surface to be treated is the
toilet bowl, a concentrated composition as described above
is applied directly from the container to the bowl, either
above the water table to the surface of the bowl e.g. under
the rim, or to the water in the bowl, without coming in
contact with the skin of the user. Particularly suitable
containers for that purpose are well known in the art.
Typically for such containers the longitudinal axis of the
dispensing opening in the cap makes an angle of generally
less than 90 (preferably 10-80 ) with the longitudinal axis
of the container to enable easy application of the
composition under the rim of the toilet bowl. An example of
such a bottle is depicted in the UK Industrial Design
registration no. 1057823. Applying the concentrated
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composition to the water in the bowl will generate a dilute
solution according to the invention.
As outlined above, treating a surface with a bleaching
composition according to the invention not only oxidatively
cleans and disinfects that surface, but also provides
extended antimicrobial activity on that surface such that
regrowth of micro-organisms is prevented for many hours
after the treatment is completed, particularly if the
composition is left to dry out on the surface. This
antimicrobial activity remains even after repeated rinsing
of the surface, in spite of the fact that the active
chlorine compounds in the composition are soluble in water
and would be expected to be rinsed away.
The compositions according to the invention can optionally
contain other components known in the art to be useful in
bleach compositions. Particularly useful among these
optional components are those which provide increased
viscosity to the aqueous solutions. Viscous bleaching
compositions known in the art as "thick bleach" are
particularly useful for treating inclined and vertical
surfaces, such as toilet bowls, because they can be applied
to such surfaces and left there. The high viscosity causes
the composition to slowly flow down the surface, thus
providing prolonged contact time between the composition and
the surface, leading to improved cleaning and disinfection,
and without any manual intervention. Typically such
bleaching compositions have a viscosity of 50-5000 mPa.s,
preferably 100-2000 mPas.s, more preferably 200-1000 mPas.s
(measured with a Haake RT20 Rotovisco rheometer fitted with
a coaxial cylinder sensor DIN 53018 (Z41 rotor and Z43
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measuring cylinder), using a 3 mm gap. Flow curves obtained
at 25 C over the shear rate range 0.1 to 1000 s-1)
Components to increase viscosity of bleaching compositions
are well known in the art. They may be chosen from polymeric
thickening agents comprising natural or synthetic polymers,
with the proviso that the polymers should be stable in
active'echloririe bleach environment. Such polymers have e.g.
been described in EP 636689. They may also be chosen from
thickening clays or thickening silica's known in the art.
Particularly useful thickening systems are provided by
suitable structuring surfactants. Many organic sulphate or
sulphonate surfactants are known in the art to be suitable
for this purpose, particularly in combination with nonionic
or amine oxide surfactants. A very useful thickening system
is formed by the combination of amine oxide surfactants and
fatty acids. The amine oxides are preferably chosen from C8-
C20 alkyl-dimethylamine oxide, preferably in an amount of
0.1-5%, and the fatty acids from C8-C20 fatty acids,
preferably in an amount of 0.1-3%.
Other optional components include antioxidants, radical
scavengers, chelating agents for metals prone to induce or
accelerate hypochlorite decomposition (such as silicates or
periodates), hydrotropes and anticorrosion agents. Solid
abrasives may be added as well. On the other hand inorganic
phosphate builders have no useful role to play in
compositions according to the invention. Thus, they are
preferably present in only minor amounts (less than 0.1%,
preferably less than 0.01%), if at all. Most preferably they
are completely absent. Likewise, large amounts of carbonate
builders are preferably not used either, although small
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amounts of alkalimetal carbonate (<_ 5%, preferably <_ 1%) may
be used as alkalising/buffering agent to set the desired pH.
Further hypochlorite-stable surfactants may be added to
improve cleaning properties, specifically anionic, nonionic,
amphoteric and zwitterionic surfactants. Examples of suitable
surfactants are given in the well-known textbooks: "Surface
Active'Agents" Vol.1, by Schwartz & Perry, Interscience
1949; "Surface Active Agents" Vol.2 by Schwartz, Perry &
Berch, Interscience 1958; the current edition of
"McCutcheon's Emulsifiers and Detergents" published by
Manufacturing Confectioners Company; "Tenside-Taschenbuch",
H. Stache, 2nd Edn., Carl Hauser Verlag, 1981. Total
surfactant content in the compositions will normally be at
most 10%, preferably at most 5%.
Thus, the aqueous liquid bleach compositions according to
the invention preferable contain at least one surfactant,
either added for improved cleaning only, or as part of a
thickening system thereby also providing the improved
cleaning.
Colourants, dyes and pigments may be added to impart a
desired colour to the compositions and perfumes to give the
compositions a desired odour, particularly to overcome the
hypochlorite odour which many people do not appreciate. The
components should be chosen to be bleach-stable, as is well
known in the art.
As outlined above, the compositions according to the
invention are alkaline and sufficient alkali, preferably
alkalimetal hydroxide, should be present to ensure this. The
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compositions could also usefully contain buffer to ensure
long term pH stability. Alkalimetal carbonates/bicarbonates
and silicates are particularly useful for that purpose.
The compositions are preferably clear aqueous liquids.
In a particularly useful and preferred embodiment the
invent,kon provides products for.cleaning toilet bowls
comprising an oblong container having a dispensing opening
of which the longitudinal axis makes an angle of at least 5 ,
but less than 90 (preferably 10-80 ) with the longitudinal
axis of the container, the container containing a
concentrated aqueous liquid bleaching composition as
described above and having a viscosity of 50-5000 mPa.s
Examples
Aqueous liquid bleaching compositions were prepared
according to the formulations 1-3 (amounts in %):
1 2 3
Na hypochlorite 4.80 4.80 4.80
Chloramine T trihydrate 1.00 0.75 1.00
Empigen OD * 1.75 2.10 1.16
Lauric acid 0.30 0.35 0.60
Perfume 0.06 0.06 0.06
Alkaline Na silicate 0.05 0.05 0.05
All examples contain sufficient NaOH to pH 12.5
All examples contain demineralised water to 100%
*) C1o-C18 alkyl-dimethylamine oxide marketed by Huntsman
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Comparative tests:
The stability of Formulation 3 above and of compositions
comprising hypochlorite and various other N-chloro compounds
was tested. For the other N-chloro compounds or their NH
precursors 1% of each compound was added instead of
Chloramine T to a formulation according to Formulation 3.
Some o the tested materials immediately reacted with the
hypochlorite, evolving heat and in some cases effervescing
or giving a colour change or precipitate. No assays of
available chlorine were carried out on these unstable
mixtures. For samples that were of higher stability the
residual available chlorine content, expressed as a
percentage of the initial available chlorine content, was
assessed after 7 days storage in the dark at ambient
temperature. The results are presented in Table 1. From the
table it can be seen that only the first three N-chloro
compounds, which are compounds according to the invention,
are sufficiently stable and thus have a negligible or small
effect on the amount of available chlorine, whereas the
other N-chloro compounds decompose and thereby consume an
appreciable amount of hypochlorite.
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Table 1 (X = not assayed, for the reasons stated)
N-chloro compound or precursor % residual available C12
None 100
N-chloro-p-toluene-sulfonamide, 100
Na salt (Chloramine-T)
Tri-sodium imidodisulfate 99
N-chlor,o-saccharine 92%
Sulfamic acid X (exothermic; effervesced)
Methylsulfamic acid 51
Cyclohexylsulfamic acid, Na salt 41
Dichloroisocyanuric acid, Na X (exothermic; effervesced)
salt (NaDCCA)
N-chloro-succinamide X (exothermic; effervesced;
white precipitate)
Indoline-2-carboxylic acid X (dark brown precipitate)
1,3-dichloro-5,5-dimethyl X (exothermic; effervesced)
hydantoin
Sarcosine X (exothermic; effervesced)
Iminodiacetic acid, Na salt X (exothermic; effervesced,
white precipitate)
Melamine 3
Glycoluracil 4
The residual available chlorine present was analysed
iodometrically, using the following procedure:
A known weight of the test solution (w) was placed in an
iodine flask. The sample was diluted with approximately 20
ml distilled water. 10 g of 5% potassium iodide solution was
added followed by 10 ml of 0.5 M sulphuric acid. The flask
was stoppered, and swirled to mix the contents before placing
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in the dark for 5 minutes, until the brown colour of the
evolved iodine had fully developed. The liberated iodine was
titrated against 0.1 M sodium thiosulphate solution until
the solution became colourless, with addition of soluble
starch indicator near the end point to increase accuracy.
A further series of N-chloro compounds or precursor thereof
were assessed in the presence of sufficient hypochlorite to
have 5% available C12 and 0.9o sodium hydroxide giving a
solution pH > 13, but without surfactants or other
formulation components. Materials that are acidic, e.g.
sulphamic acid, were first neutralised by mixing with the
sodium hydroxide solution before addition of the sodium
hypochlorite. The residual available chlorine contents of
these samples were examined after various periods of storage
in the dark and results of these stability tests, expressed
as the percentage of the initial available chlorine content,
are shown in Table 2. Most of these materials (sulfamic
acid, NaDCCA, TCCA, uracil, taurine) underwent immediately
reaction with the hypochlorite, evolving heat and
effervescing. The residual available chlorine of some of
these samples was examined within 30 minutes and found to be
low (> 55% of the initial content).
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Table 2 (X = not further assayed)
N-chloro compound or % residual available C12
precursor
30 mins. 3 days 9 days 35 days
None 100 100 99 98
Sulfamic acid 53 26 24 18
DiCl-ig:ocyanuric acid, 40 4 4. 3
Na salt (NaDCCA) (2%)
TriCl-isocyanuric acid 26 5 2 X
(TCCA) (1%)
Uracil (1%) 40 5 X X
Taurine (1%) 22 8 X X
Chloramine-T (1%) 100 100 100 98
Tri-Na imido-disulfate 100 99 99 99
(1%)
These assessments show that of the pre-formed N-chloro
compounds, only Chloramine-T, maintains good stability in
the presence of high levels of sodium hypochlorite, giving
more than 90% residual available chlorine after 1 month at
ambient temperature. Of the N-chloro precursors, only
imidodisulfate also fulfils this criterion.
Hygiene score test
This test measures the ability of a composition to impart
lasting and rinse-resistant disinfection of a surface. The
test uses a high-throughput screening method to assess the
hygienic properties of standard samples of 10pl of
composition, dispensed in microtitre plate wells that have
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been left to dry (at 30 C overnight) and are thereafter
subjected to a number of automatic rinses. Each test was
done in 8 replicates. The rinses were done with an Ascent
WellwashTM plate washer with sterile water of standard
hardness. After a set number of rinses the plates were dried
at 30 C for 45 minutes and left to cool at 20 C for 15
minutes. Each well was thereafter incubated with 50pl of an
aqueous suspension of E.coli (0.5x108 cfu) in 0.3% protein
(BSA) soil and left in contact for lh at 20 C. The wells were
then washed by adding 100pl water of standard hardness and
shaking for l0sec., whereafter the wash liquour and
unattached cells were aspirated off.
Thereafter 270pl of tryptone soya broth growth medium was
placed in each well and the plates were incubated for 24h at
37 C to allow remaining bacteria to re-grow. A test was
classified as successful after the set number of rinses if
at least 90% of the samples showed no regrowth. The highest
number of rinses that lead to a successful test is taken as
the "hygiene score".
Table 3 shows a comparison of the hygiene scores obtained
for a simple 1% aqueous solution of Chloramine-T and two
viscosity matched formulations: formulation 4 which is
according to the invention and contains 1% Chloramine-T, and
formulation 5 which does not contain Chloramine-T. The table
shows that incorporation of Chloramine-T into a hypochlorite
base significantly increases its rinse-resistant long-
lasting hygiene.
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4 5
Na hypochlorite 4.80 4.80
Chloramine T trihydrate 1.00 0
Empigen OD * 2.00 2.00
Lauric acid 0.2 0.5
Perfume 0.06 0.06
Alkaline Na silicate 0.05 0.05
Both formulations contain sufficient NaOH to pH 12.5
Both formulations contain demineralised water to 100%
Viscosity (1-3 s-1): 450 mPa.s for all
Table 3
Formulation Hyg. * score:
composition
1% Chloramine-T 1
Formulation 4 6
Formulation 5 3
Hygiene score expressed as the number of rinses that a
microtitre plate well remained bacteria-free.
The table clearly shows that Chloramine T itself is unable
to provide disinfectancy which is able withstand a single
rinse cycle. The disinfectant effect of hypochlorite lasts
for 3 rinses, but the combination of both is still effective
after 6 rinses.
