Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVEMENTS TO FL~RD STJR.FACE CI~EAI~IERa
The present invention relates to foaming hard surface
cleaners and a process for preparing the same in packaged
form.
It is known, to provide foaming hard surface cleaners in a
metal can together with a propellant to dispense the
cleaner through a valve. Such cleaners normally comprise
a surfactant (to provide a detergent action), a solvent
(to assist in cleaning), a sequestrant for metal ions such
as EDTA (to aid in the removal of limescale/iron stains)
and a perfume. The pH of such compositions is alkaline.
Known, commercially available compositions, are sprayed
onto a hard surface, such as bathroom and kitchen
surfaces, to facilitate the removal of limescale, soap
deposits and other soiling. The cans are conventionally
formed from tinned steel plate although other metals such
as aluminium may be used.
It is known that corrosion may occur on the interior
surface of the can, both in regions where the can contacts
the liquid phase and more especially in regions where the
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can contacts the vapour phase (ie. in the headspace of the
can). Corrosion in the headspace is believed to be caused
by the presence of water vapour in the propellant of the
headspace. Corrosion not only leads to a weakening of the
can, but can also lead to a significant discolouration of
the can contents requiring partially used cans to be
discarded. Such discarding of cans needlessly releases
surfactants and other materials into the ecosystem and
generally wastes resources.
In known compositions, a high pH and alkaline silicates
are used to prevent corrosion in regions of the can which
contact the liquid phase. It is believed that corrosion
is inhibited by the formation of a protective film on the
inner surface of the can. With conventional tinned steel
cans this layer is believed to comprise a layer of tin
oxide on the inner surface of the can, although the
precise composition of the layer is not known.
For the purposes of the present specification components
present in the liquid phase which inhibit corrosion of the
portion of the can in contact with the liquid phase will
be referred to as liquid phase corrosion inhibitors.
Even in the presence of liquid phase corrosion inhibitors
(such as alkaline silicate), corrosion can still occur in
the regions of the can which contact the gas phase,
particularly around the periphery of the upper domed
portion of the can, in the upper portion of any side-wall
seal and in the valve fitting. This second form of
corrosion again leads to a weakening of the can and a
significant discoloration of the can contents.
A further problem associated with corrosion is the loss of
active sequestrant due to the release of metal ions into
~~~4~~'~
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the composition. As sequestrant plays an important role
in the lime-scale removing action of the composition this
loss of sequestrant leads to a corresponding reduction in
performance.
In order to prevent corrosion in those parts of the can
contacted by the gas-phase, it is known to include in such
compositions a volatile amine, preferably a primary or
secondazy amine or ammonia. For the purposes of the
present specification ammonia is considered to be an amine
unless the context demands otherwise.
It is well known that ammonia has a characteristic,
persistent and undesirable odour, which requires a high
level of strong perfiune to be present in the composition.
In prior compositions, measured ammonia levels of up to
and above 1000 ppm have been employed. The odour of
ammonia is noticeable at levels above around 700-750 ppm.
Odour assessment of hard surface cleaners in the
marketplace reveals a noticeable and characteristically
unpleasant odour of ammonia. Given the known threshold
for the detection of ammonia by the human nose, it is
believed that the ammonia levels in these prior products
is always above 750 ppm.
Figures for the measured ammonia level in products
obtained in the marketplace are expected to give lower
analysed than actual values, possibly due to loss of
vapour on opening the can for inspection and adsorption of
ammonia onto the inner surface of the can.
From the above, it can be seen that it is known to prevent
corrosion from occurring in the headspace of the can by
the addition of ammonia to the formulation of the can
contents. However, it is desirable to prevent said
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corrosion in the gas phase while maintaining an acceptable
product fragrance and the known methods of preventing
corrosion require the presence of unacceptably high levels
of ammonia.
We have determined that adequate corrosion protection in
the headspace of the can can be attained with lower levels
of ammonia than were hitherto employed and that ammonia
levels can be attained at which the odour of ammonia is
either acceptable per se or can be effectively masked by a
perfume.
In the compositions disclosed herein, adequate head space
corrosion protection is attained with ammonia levels of
above about 100 ppm, preferably above 190 ppm. In typical
compositions, the odour of ammonia is not objectionable
when ammonia is present at a level of below about 700-750
ppm, depending on the particular perfume composition being
used.
It is also desirable to avoid EDTA as a sequestrant. EDTA
is non-biodegradable and has been criticised due to its
potential to sequester and solubilise heavy metal ions
such as cadmium and mercury from river sludges and
sediments. Surprisingly, we have determined that
modification of the sequestrant system brings a benefit fn
reducing the extent of corrosion in the can while reducing
any negative effects of sequestrant in the biosphere.
Accordingly, the present invention provides a stable,
packaged, foaming hard surface cleaning composition
wherein said composition comprises, a surfactant, a liquid
phase corrosion inhibitor, 100-750 ppm volatile amine and
is packaged in a metal can.
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In the context of the present invention, acceptable
storage stability is achieved if no significant corrosion
of any part of the internal surface of the can occurs
after 6 weeks storage at ambient temperature.
Generally,- the composition further comprises a perfume.
With typical perfume compositions, a very acceptable odour
is obtained when the amine is ammonia. Alternatively, the
amine can be selected from the group comprising volatile
mono, di and tri alkanolamines, amino-alcohols and
mixtures thereof. Ammonia is preferred amongst the amines
as it has a reduced tendency to form undesired compounds
such as nitrosamines.
Preferably the ammonia level is 400-750 ppm, more
preferably 400-600 ppm. Excellent results are obtained
with ammonia levels of around 450-570 ppm. Lower levels
of ammonia are generally preferred as any residual odour
may be masked by low levels of a mild perfume.
Suitable liquid phase corrosion inhibitors comprises
alkaline silicates. Alternatives can be employed provided
that they are effective at the pH of the liquid phase and
with the metal employed for the can wall. Suitable levels
of liquid phase corrosion inhibitor range from 0.1-l0~wt.
At progressively lower levels of ammonia, protection
against corrosion in regions of the can which contact the
vapour phase is progressively reduced. In the liquid
phase, ammonia in combination with aqueous alkali,
alkaline silicate or other liquid phase corrosion
inhibitors, is effective in preventing corrosion at lower
levels than in the vapour phase. Consequently
compositions according to the present invention preferably
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comprise at least two corrosion inhibitors, one of which
is more volatile and effective in the vapour phase the
other of which is less volatile and effective in the
liquid phase.
Preferably, the composition further comprises a
sequestrant for metals. EDTA, is 3cnown as a suitable
sequestrant, but it is preferred that the sequestrant is
other than EDTA for the reasons given above.
Suitable sequestrants are selected from polycarboxylic
acids, polyacrylates, phosphonates and salts thereof.
Preferably, the sequestrant i.s a polycarboxylic acid or
salt thereof. More preferably, the sequestrant is citric
acid, or citric acid in combination with one or more acids
selected from, adipic, succinic, glutaric acids or salts
thereof. Most preferably, the sequestrant is citric acid
alone or salts thereof.
In the presence of EDTA, the formation of a protective
film on tinned steel cans is characterised by so-called
de-tinning of the inner surface of the can. In the
presence of citric acid salts, de-tinning of the inner
surface of the can is not conspicuous, although corrosion
is reduced significantly.
In prior cans the protective film does not extend to the
upper or dome region of the cans. By ensuring that the
protective effect extends over the inner surface of the
can it is believed that corrosion of the can and hence
discolouration of the product can be substantially reduced
if not totally eliminated for the normal commercial
lifetime of the can.
2~~.~~~
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We have determined that the entire inner surface of a can
may be protected by inverting the can after filling and
holding the can in an inverted position for a sufficient
length of time for a protective film to form in the
eventual upper region of the can, and, subsequently
reverting the can to a conventional attitude to complete
formation of a protective film in the lower region of the
can.
Other manipulative schemes such as rolling or shaking of
the can, may be employed. The operative consideration
being that the entire inner surface of the can is coated
with the contents shortly after filling. It is believed
that this treatment ensures that a protective layer is
formed over the entire inner surface of thd can.
Accordingly, a further aspect of the present invention
subsists in a process for packaging a foaming hard surface
cleaner which comprises the steps of:
a) filling the can with a composition comprising a
liquid component comprising a liquid phase corrosion
inhibitor and a normally gaseous component comprising
a propellant and a volatile amine,
b) sealing the can,
c) storing the can in at least two orientations such
that the entire inner surface of the can is treated
with the liquid component.
In cans which have been treated by this Ninversion
process" or subjected to other re-orientation during
storage, a characteristic double banding of the inner
metal surface of the can, is observed when the can is laid
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open for inspection. Tn the case where the can is simply
inverted, this double banding takes the form of a first
and a second tide mark present on the inner surface of the
can, each tide mark being in a first and second plane
respectively which divides the inner volume of the can
into a first and a second part, the arrangement being such
that the volume of one of the parts bounded by the first
plane is equivalent to the volume of one of the parts
bounded by the other plane.
With tinned steel cans which have been subjected to the
re-orientation process a characteristic dull film is also
seen to extend over the entire inner surface of the can.
In prior Cans the protective film does not extend to the
upper or dome region of the cans and these'retain the
shine of tinned steel plate. By ensuring that the
protective layers cover the inner surface of the can it is
believed that corrosion of the can and hence
discolouration of the product can be substantially reduced
if not totally eliminated for the normal commercial
lifetime of the can.
The visibility of the film and the banding varies with the
type of can employed and the sequestrant used. When EDTA
is present as the sequestrant the banding is conspicuous
and the interior surface of the can becomes quite dull.
When citrate is used as the sequestrant, the banding may
be barely visible and the interior surface retains a
shine. Sufficient protection of the surface to prevent
corrosion for the product lifetime is achieved with either
citrate or EDTA as surfactant.
Taking the above-mentioned aspects of the present
invention into consideration, it can be seen that package-
stable, low-ammonia products may be manufactured which
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have an acceptable odour, and which do not suffer from the
package corrosion problems which would otherwise occur at
such low ammonia levels.
The various aspects of the present invention are unified
in that while low ammonia formulations may have hitherto
been desirable, it had not been possible in practice to
package said formulations in stable form.
In preferred embodiments of the invention, the cleaning
composition comprises at least ammonia, surfactant,
solvent, sequestrant for metals, alkali, and a perfume.
Surfactant is conveniently present at a level of 0.1-10~
wt, preferably 1-5~wt. Suitable surfactants are nonionics
with a HLB in the grange 3-20, preferably 12-16. Alcohol
ethoxylates have been found particularly suitable as
surfactants.
Solvents, are preferably capable of dissolving non-polar
species and can be miscible or immiscible with aqueous
solutions. Such solvents are preferably present at a
level of 0.1-l0~wt, preferably 1-5~wt. Solvents
preferably have a solubility in water greater than 1~.
Glycol ethers, preferably butyl carbitol and alcohols
preferably isopropyl alcohol have been found suitable.
Sequestrant for metals such as calcium and magnesium is
preferably present at levels of 0.1-8~wt, more preferably
0.5-6~wt. As mentioned above trisodium citrate is a
preferable sequestrant.
Suitable alkalis include buffering agents which buffer at
an alkaline pH. Sufficient buffer is preferably present
to raise the pH of the composition to a pH in excess of
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10. Preferably the pH of the composition falls into the
range 11-13. Alkaline silicates, functioning as liquid
phase corrosion inhibitors and buffering to a pH 11-12 are
preferred. Alternative buffering systems comprise
phosphates, carbonates and borates. The use of non-
buffering agents to raise the pH, ie. the presence of
sodium hydroxide is not hereby excluded. Alkaline
silicate are also believed to have a stabilising effect on
the formulations of the present invention.
Typical compositions are such that they comprise:
a) 100-750 ppm ammonia,
b) 0.75-10~ citric acid or salt thereof,
c) 0.05-10~ alkaline silicate, and,
d) 0.10-10~ surfactant.
Alternative compositions comprise:
a) 100-750 ppm ammonia,
b) 0.1-5~ amino polycarboxylic acid,
c) 0.05-10~ alkaline silicate, and,
d) 0.10-10~ surfactant.
Propellants are preferably present at levels of 3-20~.
While halogenated propellants can be employed it is
preferred to use an 'ozone-friendly' propellant such as
compressed air, carbon dioxide, nitrogen and oxides
thereof. a volatile hydrocarbon or mixtures of the same.
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Mixtures of butane and propane have been found
particularly suitable.
In order that the present invention may be further
understood it will be described by way of example.
A foaming hard surface cleaner was prepared with the
composition given in Fable 1:
TABLE 1
Surfactant (Dobanol (RTM) 23/6.5) 2.50~wt
Solvent (Butyl carbitol) ~ 2.OO~wt
Sequestrant (Varies) 1.30-4.OO~wt
Alkaline silicate 0.20~wt
Sodium Hydroxide to pH 11.8
Perfume 0.40~wt
Ammonia 0-1000 ppm
Propellant (Propane/Butane) 6.OO~wt
Water to 100
The alkaline silicate used was Czystal-120 A (Trademark]
available in the marketplace from Crosfields of
Warrington.
The process for packaging the foaming hard surface cleaner
comprised the steps of:
a) filling a tinned steel can with a composition
comprising ammonia, sequestrant, solvent, buffer,
liquid phase corrosion inhibitor, perfume, and
CA 02084868 2002-04-02
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surfactant, mixed under air and dosed in 200 ml
aliquots,
b) dosing tha chilled propellant into the can and
sealing the can, and,
c) storing the can in an inverted orientation for 48
hours after filling and then. a 'normal' orientation
such that the entire inner surface of the can is
treated with the ,liquid phase corrosion inhibitor.
Cans were opened and the internal surface inspected after
storage for a total of 6 weeks at ambient ~ernperature.
At-' level,:s o~ x,000 pp~n am~nania, excel .ent cdrrosion ,
protection was obtained, in the presence of:E~TA, (1.3~)
with or without the inversion process, but the odour of
ammonia evolved by the product was.d~scribed as
unacceptably unpleasant by test;e~s. The odour and.
ccirrosion xes~lts for both control and inverted can..s are
su~nnarised im Table 2 given:below.
TABLE 2
i~i3 tDp~~ ~orrosioa ~Jdour
.. . '
control =averted ..
control ) yes yes UllaCCeptable
190 yes no .unacceptable
380 ' yes no ~unacceptabte'~
580 ~ yes . no unacceptablev;
7 o U yes do unacceptable
1000 tcontrol no no ~unecceptable
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It can be seen that excellent corrosion protection was
obtained with 190-700 ppm ammonia. These examples
constitute examples of the present invention whereas the
examples with 0 and 1000 ppm ammonia are comparative
examples.
Cleaning performance was compared on pre-soiled plastic
sheets. The sheets were prepared by spraying a thin layer
of solvent dispersed calcium stearate onto a sheet formed
from acrylic plastic of. the type used to manufacture bath-
tubs. Prior to the application of the calcium stearate
the sheet was cleaned with a proprietary dish-washing
liquid and rinsed well with water. A solution of 15 gm of
calcium stearate in 500 gm of isopropyl alcohol was
employed so as to deposit approximately one gram of
calcium stearate on a sheet having dimensions of 30 cm x
cm. A small quantity of carbon black was added to aid
visualisation during the cleaning performance test.
Subsequent to the application of the soil, sheets were
20 baked at 50°C for 18 hours.
The performance test comprised the application of a hard
surface cleaning composition to a pre-soiled sheet. Four,
hollow, open ended, clear, glass cylinders, each 5 cm
high/5 cm diameter were placed on the soiled surface of
the sheet. The composition was sprayed into the open
upper end of each cylinder for 2 seconds, half-filling the
cylinders with foam. A time of five minutes was allowed
for the passive cleaning operation. The cylinders were
then lifted off the sheet and the sheet was gently rinsed
in 12 French running cold water (15°C) for 10 seconds.
The flow rate of the water was set at 2 litres/minute
prior to rinsing. The sheets were left to dry in air at
room temperature 4this takes 1-2 hours) then three
replicates of each composition were assessed by a trained
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panel of at least three persons using the scale indicated
in Table 3.
FABLE ~
Results of the panellists and replicates were averaged to
obtain an overall percentage for each composition.
Comparative trials were performed with the sequestrants
given in Table 4. Results were normalised for a 1.3% EDTA
effectiveness of 100. The normalised figure is the
overall composition scores in the performance test
specified above, using the ranking in Table 3 averaged
over the replicates.
For comparative purposes, the affinity for calcium of some
sequestrants is given as the log of the binding constant
between calcium and the sequestrant at constant
concentration of sequestrant and calcium. These figures
should be considered to be indicative of the relative
calcium binding performance rather than as absolute
values.
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TABZ~~ 4
s~
~s ~3DT1~ eect A. Ca
EDTA 1.3~ 100 9.7
EDTA 0.0~ 48 -
Citrate 5.0~ 109 3.5
Citrate 4.0~ 106 -
Citrate 3.0~ 76 -
Dequest 2016 1.0~ 139 4.6
bequest 2060s 1.0~ 122 7.1
bequest 2000 1.0~ 68 6.3
Sokalan DCS 3.0~ 52 -
Trilon ES9910 1.5~ 106 5.6
PA 25 PN 1.5~ 35 -
PA 40 1.5~ 35 -
Sokalan CP5 1.5~ 35 -
Sokalan CP10 1.5~ 70 -
bequest, Sokalan and Trilon are trademarks.
It can be seen from Table 4 that the effectiveness of a
sequestrant is not simply related to the calcium binding
ability: ie. the bequest 2016/2060s/2000 sequestrants have
affinities for calcium which do not differ in the same way
as their effectiveness in the cleaning test ie. bequest
2060s appears to have the highest affinity for calcium on
a theoretical basis whereas the bequest 2016 apparently
has a lower affinity but forms a more effective cleaning
composition according to the experimental results.
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It was noted that, in the presence of both ammonia and
EDTA, the formation of a protective film on tinned steel
cans is characterised by so-called de-tinning of the inner
surface of the can. In the presence of citric acid salts
in combination with ammonia and the silicate, de-tinning
of the inner surface of the can is not conspicuous, while
corrosion is reduced considerably. Surprisingly, citric
acid performed far better that Sokalan DCS which is a
combination of adipic, succinic and glutaric acid.
In the presence of ammonia and citric acid salts without
silicate being present, de-tinning was again noted.
Various modifications may be made to the embodiments of
the present invention without departing from the scope of
the invention when considered in a broad form. For
instance, while the invention has been described with
reference to a can requiring a propellant to dispense the
contents, the use of a pump-action dispensing closure is
not hereby excluded.
