Note: Descriptions are shown in the official language in which they were submitted.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
Acidic cleaning compositions
10
Technical field
The present invention relates to aqueous acidic liquid
cleaning compositions. More specifically, acidic
compositions are described which give optimal performance
in removing limescale stains and encrustations while
ensuring appropriate surface safety. The compositions
herein may be used on a variety of surfaces, ranging from
bathrooms, toilets and kitchen surfaces to various
appliances like automatic dish washers and washing
machines.
2 5 Backctround
Tap water contains a certain amount of solubilized ions
which upon water evaporation eventually deposit as salts
such as calcium carbonate on surfaces which are often in
contact with said water, resulting in an anaesthetic
aspect of said surfaces. This limescale formation and
. deposition phenomenon is even more acute in places where
water is particularly hard.
It is well known in the art that limescale can be removed
chemically with acidic solutions, and a great variety of
CA 02228758 1998-02-OS
WO 97/06228 PCTlUS96/12685
2
acidic cleaning compositions have been described for this
purpose.
However, in many instances acidic compositions may cause
the problem that they present hazards to the surfaces
treated therewith. Indeed the acids which are used in
acidic compositions, such as phosphoric acid and the like
can damage the surfaces being treated. In particular,
some corrosion/staining may occur when metal surfaces
such as aluminium, chromed steel or stainless steel are
treated with such acids.
It is therefore an object of the present invention to
obviate this issue in providing a cleaning composition
possessing excellent limescale removing capacity while
being safe to the surfaces treated therewith.
It is also desirable to formulate a composition
particularly suitable to remove limescale in large
appliances like automatic dish washers and washing
machines. Indeed, limescale deposits in said appliances
may build-up on the heater element making heat exchange
more difficult. In other words, limescale deposits in
said appliances are undesirable not only because they
result in an anaesthetic aspect but also as said
limescale deposits may result in higher consumption of
energy, poorer machine performance and eventually
malfunction.
It is thus a further object of the present invention to
formulate a cleaning composition suitable to be used for
removing limescale in large appliances, said composition
possessing excellent limescale removing capacity while
being safe to the surfaces treated therewith, especially
metal surfaces like heating elements, walls, bottom and
any inner part.
CA 02228758 1998-02-OS
WO 97/Ob228 PCT/US96/12685
3
It has now been found that the above objects are met by
formulating liquid compositions comprising an acid-stable
. thickener and a specific acidic system, i.e. malefic acid
and a second acid which has a first pKa not exceeding 5,
or mixtures thereof. Indeed it has been found that the
compositions of the present invention comprising malefic
acid, said second acid and said acid-stable thickener are
significantly safer to the surfaces treated therewith,
than the same compositions without said acid-stable
thickener, while being also particularly effective in
removing limescale. In other words, the use of acid-
stable thickeners in an aqueous acidic liquid composition
comprising malefic acid and said second acid improves
surface safety of the surfaces treated with said
composition. Furthermore, it has been found, in the
broadest aspect of the present invention, that the use of
an acid-stable thickener, in an aqueous acidic liquid
composition comprising malefic acid improves limescale
removing performance.
An advantage of the aqueous acidic liquid compositions of
the present invention particularly suitable for removing
limescale in large appliances such as automatic dish
washers and/or washing machines is that said compositions
provide excellent limescale removal on different types of
limescale deposition present in said automatic dish
washers and/or washing machines, e.g. on the severe
limescale deposits which build up on the warm parts such
as the heating element as well as on homogeneous lighter
deposits which build up on the extended surfaces like the
walls. The aqueous acidic liquid compositions according
to the present invention allow to obtain better limescale
removing performance at lower total acid level as
, 35 compared to the powder/granular limescale removal
compositions available on the market. Another advantage
is that the aqueous acidic liquid compositions according
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
4
to the present invention allow to prevent tough limescale
encrustations build-up that provokes higher energy
consumption, less washing effectiveness and possible
damages to the machines.
A further advantage of this invention is that said
compositions are safe to different hard-surfaces
including metal surfaces such as aluminium, chromed steel
or stainless steel as well as synthetic materials such as
rubber hoses, plastic trays and polymeric connections
that are for example found in large appliances.
EP-A-0 496 188 discloses a composition comprising
nonionic surfactants together with malefic acid whereby
good limescale removal is provided. Although EP-A-0 496
188 discloses thickeners in general as an optional
ingredient, no levels are disclosed.
EP-A-601 990 discloses a self thickened acidic
composition having a viscosity of 10 cps to 700 cps at 60
rpm shear rate at 20°C and comprising an organic acid or
mixtures thereof, preferably malefic acid and a thickening
system comprising from 0.5% to 15% by weight of the total
composition of a mixture of a nonionic surfactant and a
cationic surfactant. More particularly, EP-A-601 990
discloses compositions which are thickened without the
use of a thickener compound.
US-5 232 632 discloses foam liquid hard surface detergent
compositions, suitable to be packed in a non-aerosol
spray delivery package, comprising a mixture of
zwitterionic and nonionic surfactants, a hydrophobic
solvent, a polycarboxylate detergent builder and a
polymeric shear thinning thickener such as xanthum gum.
Preferred compositions 'have a pH of from 1 to 5.5,
however no malefic acid is disclosed.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
US-4 891 150 discloses thickened acidic cleansing and
descaling compositions. Thickening i;~ obtained by adding
different surfactants or mixtures thereof. Pure
thickeners such as xanthum gum are mentioned as not being
5 suitable to be used in the acidic compositions disclosed
in US 4 891 150. No malefic acid is disclosed.
GB-A-2 106 927 discloses toilet bowl cleaners which have
a pH between 2.2 and ~3.5 and comprise a non-volatile
l0 water soluble organic acid such as dicarboxylic acids
having from 2 to 3 carbon atoms, a detergent and a
cellulose ether thickener, preferably methyl
hydroxypropyl cellulose at levels of from 0.5% to 1.2°s by
weight of the total composition. GB 2 106 927 teaches
away from the use of malefic acid. Indeed it is mentioned
in it that malefic acid was not screened for its
solubility because of its inherent toxicity.
WO 95/07957 discloses acidic cleansing compositions for
cleaning hard surfaces, said compositions being
particularly suitable to be applied thereto by means of
spray-type dispensers. Said compositions comprise a
strong acid alone or in combination with a weak acid, a
surfactant and a thickening amount of an organic polymer
thickener such as xanthum gum. Malefic acid and
sulphamic acid are mentioned amongst the weak acids and
sulphuric acid is mentioned amongst the strong acids.
However no levels for the weak organic acids are
disclosed in the description and no example discloses
malefic acid.
EP-A-411 708 discloses an acidic aqueous liquid
. composition comprising a detergent, an organic acid
having 2 to 10 carbon atoms, an aminoalkylenephosphonic
and phosphoric acid. Indeed the addition of an
aminoalkylenephosphonic and phosphoric acid on top of
mixtures of acids likes succinic, glutaric and adipic
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
6
acid, improves the safety of the acidic compositions for
use on enamel surfaces. The compositions therein are
microemulsions which may be thickened by the addition of
a thickener such as alkyl cellulose. However the acidic
system of the present invention comprising malefic acid at
a given level and a second acid which has a first pKa not
exceeding 5 is nowhere disclosed in EP-A-411 708.
None of the above mentioned prior art documents discloses
the compositions of the present invention whereby
improved limescale removal performance and improved
safety to the surfaces treated therewith is achieved.
Also none of the above mentioned prior art documents
discloses the use of a thickened aqueous acidic liquid
composition comprising malefic acid and a second acid
which has a first pKa not exceeding 5, or mixtures
thereof, for removing limescale in large appliances like
automatic dish-washers and/or washing machines.
Summary of the invention
The present invention is an aqueous acidic liquid
cleaning composition suitable for removing limescale
deposits from hard-surfaces, having a pH below 2 and
comprising from 0.05% to 45% by weight of the total
composition of malefic acid, a second acid which has a
first pKa not exceeding 5 and from 0.01% to 5% by weight
of the total composition of an acid-stable thickener.
The present invention further encompasses a process of
treating hard-surfaces, wherein a composition according
to the present invention, is applied in its neat form or
in a diluted form, onto said surfaces, then left to act
onto said surfaces and then removed by rinsing.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
7
The present invention also encompasses the use of a
thickened aqueous acidic liquid composition comprising
malefic acid and a second acid which has a first pKa not
exceeding 5, or mixtures thereof, for removing limescale
in automatic dish washers and/or washing machines.
Y
The present invention also encompasses the use of an
acid-stable thickener, in an aqueous acidic liquid
composition comprising malefic acid and a second acid
which has a first pKa not exceeding 5 to improve surface
safety of the surfaces treated therewith.
The present invention yet encompasses the use of an acid-
stable thickener, in an aqueous acidic liquid composition
comprising malefic acid to improve limescale removing
performance.
Detailed description of the invention
The compositions according to the present invention are
designed for removing limescale or soils comprising
limescale as an essential component. Thus the
compositions according to the present invention comprise
malefic acid as an essential ingredient. The compositions
according to the present invention comprise from 0.01% to
45% by weight of the total composition of malefic acid,
preferably from 1% to 25% and more preferably from 6% to
20%. This percentage is calculated on the basis of the
molecular weight of the acid form, but malefic anhydride
is equally convenient for use in the compositions
according to the present invention. Indeed malefic
anhydride is generally cheaper and it is transformed into
the acid form when incorporated in an aqueous medium.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
8
The compositions of the present invention further
comprise as an essential ingredient a second acid which
has a first pKa not exceeding 5, or mixtures thereof.
Said second acid is desired to strengthen the limescale
removal performance. Preferably the second acids to be
used herein which are particularly efficient to remove ,
limescale on many surfaces, have their first pKa not
. exceeding 4, more preferably not exceeding 3, and most
preferably not exceeding 2. According to the present
invention said acids can be organic or inorganic acids.
Examples of inorganic acids are sulphonic acid
derivatives, sulphamic acid (pKa=0.1), hydrochloric acid
(pKa<0), nitric acid (pKa<0), phosphoric acid (pKa=2.1)
and sulphuric acid (pKa=0.4). An example of organic acid
is citric acid (pKa=3.06). Particularly suitable to be
used herein are sulphonic acid derivatives including
alkyl sulphonic acids and aryl sulphonic acids.
Suitable alkyl sulphonic acids for use herein are C1-C6
linear or branched alkylsulphonic acids or mixtures
thereof, such as methanesulphonic acid (pKa=1.9)
commercially available for example from Aldrich, William
Blythe & Co. Ltd. or Elf. Atochem.
Suitable aryl sulphonic acids for use herein are
according to the formula .
R4 R5
R ~ ~ S03 H
R2 R
3
i _ ~
CA 02228758 1998-02-OS
WO 97/OG228 PCT/US96/12685
9
wherein R1, R2, R3, R4 and R5 are each H or S03H, or
linear or branched CO-C4 alkyl chain; or mixtures
thereof .
Preferred arylsulphonic acids to be used according to the
present invention are those which comprise no or only one
alkyl chain. Indeed, we have found that said
arylsulphonic acids are particularly effective at
remaving limescale, which is not the case for their
longer alkyl chain homologues. Also we have found that
said arylsulphonic acids are particularly safe to the
surface treated therewith. Particularly suitable
arylsulphonic acids for use herein are benzene sulphonic
acid (pKa=0.7), toluene sulphonic acid and cumene
sulphonic acid. Amongst these three, at equal weight %,
we have found that the shorter the alkyl chain, down to
no chain at all, the better the limescale removing
performance.
2o Preferred acids having a first pKa not exceeding 5 to be
used herein are sulphamic acid, sulphuric acid, aryl
sulphonic acids, alkyl sulphonic acids, or mixtures
thereof, more preferred are sulphamic acid, sulphuric
acid, benzene sulphonic acid or mixtures thereof and
highly preferred is benzene sulphonic acid. Indeed,
benzene sulphonic acid is the most preferred acid which
has a first pKa not exceeding 5 to be used herein, as it
has been found to be significantly safer for the surfaces
treated than the other acids which have a first pKa not
exceeding 5, whilst maintaining the advantage in
limescale removal performance of said acids.
The compositions of the present invention comprise from
0.1% to 20%, by weight of the total composition of a
second acid which has a first pKa not exceeding 5, or
mixtures thereof, preferably from 0.1% to 10% and more
preferably from 0.1% to 7%.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
The acidic system of the present invention comprising
malefic acid and a second acid which has a first pKa not
exceeding 5, or mixtures thereof, has been found to -
5 provide excellent limescale removal performance and
improved surface safety as compared to the same acidic
system without malefic acid, this at a given contact time.
More particularly the weight ratio of malefic acid to said
second acid is such that the surface safety is improved.
10 Accordingly the weight ratio of malefic to said second
acid which has a first pKa not exceeding 5, is greater
than 3, preferably is from 3 to 50 and more preferably
from 3 to 25. Said ratio is dependent on the specific
second acid used and thus is different for each second
acid or mixtures thereof used.
The compositions according to the present invention
further comprise an acid-stable thickener as an essential
ingredient. By "acid-stable thickener" it is meant herein
any thickener which allows when stored in acidic medium
in rapid aging test (RAT) at 50°C for 10 days that said
acidic medium does not loose more than 50% of its initial
viscosity and does not separate from said medium.
The acid-stable thickeners to be used herein can be any
acid-stable thickener known in the art to thicken liquid
compositions and especially aqueous compositions. Acid-
stable thickeners are desired in the compositions of the
present invention as they allow to formulate thickened
compositions at low total thickening compound level, as
compared for example to the level of acid-stable
thickening surfactant systems which would be required in
absence of said acid-stable thickeners to get the same
viscosity.
Particularly preferred acid-stable thickeners to be used
herein include synthetic thickeners such as polyurethanes
CA 02228758 1998-02-OS
WO 97/OCn228 PCT/US96/12685
11
or co-polyacrilates or polyacrilamides, polysaccharide
thickeners such as substituted cellulose materials or
carboxymethylcellulose or hydroxymethylcellulose and
naturally occurring thickeners like xanthum gum or
derivatives thereof, or mixtures thereof.
Particularly suitable acid-stable thickeners to be used
herein are polysaccharide thickeners such as xanthum gum
and derivatives thereof. Xanthum gum and derivatives
l0 thereof may be commercially available for instance from
Kelco under the trade name Keltrol RD~, Kelzan S~ or
Kelzan T~ .
Xanthum gum or derivatives thereof are preferred to be
used herein as they are physically and chemically stable
in the acidic conditions of the compositions of the
present invention, this even at pH below 1.5. Also the
acidic liquid compositions of the present invention are
chemically stable, i.e. there is virtually no chemical
changes of the different ingredients due to reaction
between different ingredients, and physically stable,
i.e. that no phase separation occurs when stored in rapid
aging test (RAT) at 50 °C for 10 days.
The compositions according to the present invention
comprise from 0.05% to 5% by weight of the total
composition of an acid-stable thickener, or mixtures
thereof, preferably from 0.05% to 1% by weight, more
preferably from 0.05% to 0.8% and most preferably from
0.1% to 0.7%.
Accordingly, the compositions according to the present
invention have a viscosity of from 30 cps to 1500 cps at
20°C, preferably of from 40 cps to 800 cps and more
. 35 preferably of from 100 cps to 600 cps, when measured with
a Carri-med rheometer CLS 100 at 7.5 rpm.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
12
It has now been found that the compositions of the
present invention comprising malefic acid, a second acid
which has a first pKa not exceeding 5 and an acid-stable
thickener exhibit improved surface safety to the surface
treated therewith as compared to the same compositions
without any acid-stable thickener. This surface safety
benefit is even more noticeable when the second acid
which has a first pKa not exceeding 5 is present at high
levels, e.g., more than 3o by weight of the total
l0 composition. Thus an aspect of the present invention is
the use of ,an acid-stable thickener, in an aqueous acidic
liquid composition comprising malefic acid and a second
acid which has a first pKa not exceeding 5 to improve
surface safety of the surfaces treated therewith.
By "surface safety improvement" it is to be understood
that less damage to the surface treated is observed with
the compositions of the present invention compared to the
same compositions without any acid-stable thickener, this
at a given time of contact. A method suitable for
measuring surface safety is a visual grading method
mentioned hereinafter in the examples.
It has also been observed that the compositions of the
present invention comprising malefic acid, a second acid
which has a first pKa not exceeding 5 and an acid-stable
thickener exhibit improved limescale removal properties
as compared to the same compositions but without such
acid-stable thickener, this when applied neat onto the
surfaces treated, i.e. per se in a liquid form, and
especially when applied in the form of a spray. It has
further been observed that the addition of an acid-stable
thickener, or mixtures thereof, improves limescale
removal performance of an aqueous acidic liquid
composition, even in the absence of said second acid.
Thus another aspect of the present invention is the use
of an acid-stable thickener, in an aqueous acidic liquid
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
13
composition comprising malefic -acid to improve limescale
removing performance.
Improved limescale removing performance has been observed
for different types of limescale stains, including the
kitchen-type stains and the bathroom-type stains, i.e.
for stains which contain not only calcium carbonate but
also soap scum and/or grease. Also excellent limescale
performance has been observed when used under diluted
conditions. Accordingly the compositions of the present
invention are particularly suitable for removing
limescale in large appliances like automatic dish washers
and/or washing machines.
A further advantage with a composition according to the
present invention suitable to be used for removing
limescale in an automatic washer and/or washing machine
is that when dispensed onto the interior walls of said
washer/machine the drainage of said composition to the
bottpm of said washer/machine is slowed down, thereby
avoiding that said composition is evacuated from the
interior of said washer/machine before the washing cycle
starts, or stays in dead corners of said washer/machine
during the washing cycle (e. g., parts of a washing
machine that are not involved in the washing process like
the drainage hose before the pump in washing machines).
Accordingly the compositions of the present invention
when used for descaling large appliances allow a further
descaling action during the washing cycle and very simple
usage instructions, without the need to open the
washer/machine after the cycle has started and without
the need of a specifically designed package execution for
controlled/delayed delivering of the composition.
Indeed, the composition is applied neat directly on the
interior surfaces of said washer/machine where it starts
its descaling action and continues said descaling action
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
14
during the washing cycle before being finally removed by
rinsing which occurs at the end of the washing cycle.
The compositions according to the present invention have
a pH below 2, preferably of from 0 to 1.5 and more
preferably of from 0.3 to 1. t
The compositions according to the present invention may
further comprise optional ingredients such as a
surfactant or mixtures thereof. Preferably the
compositions according to the present invention comprise
up to 30% by weight of the total composition of said
surfactant or mixtures thereof, more preferably from
0.05% to 10%, more preferably from 0.1% to 8% and most
preferably from 0.1% to 3%. All types of surfactants may
be used in the present invention including nonionic,
anionic, cationic, amphoteric or zwitterionic
surfactants. It is also possible to use mixtures of such
surfactants without departing from the spirit of the
present invention.
Suitable nonionic surfactants to be used herein are
alkoxylated alcohol nonionic surfactants which can be
readily made by condensation processes which are well
known in the art. However, a great variety of such
alkoxylated alcohols, especially ethoxylated and/or
propoxylated alcohols is also conveniently commercially
available. Surfactants catalogs are available which list
a number of surfactants, including nonionics.
Accordingly, preferred alkoxylated alcohols for use
herein are nonionic surfactants according to the formula
RO (E) a (P) pH where R is a hydrocarbon chain of from 2 to
24 carbon atoms, E is ethylene oxide and P is propylene
oxide, and a and p which represent the average degree of,
respectively ethoxylation and propoxylation, are of from
0 to 24. The hydrophobic moiety of the nonionic compound
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
can be a primary or secondary, straight or branched
alcohol having from 8 to 24 carbon atoms. Preferred
nonionic surfactants for use in the compositions
according to the invention are the condensation products
5 of ethylene oxide with alcohols having a straight alkyl
chain, having from 6 to 22 carbon atoms, wherein the
degree of ethoxylation is from 1 to 15, preferably from 5
to 12. Such suitable nonionic surfactants are
commercially available from Shell, for instance, under
10 the trade name DobanolR or from Shell under the trade
name LutensolR~ These nonionics are preferred because
they have been found to allow the formulation of a stable
product without requiring the addition of stabilisers or
hydrotopes. When using other nonionics, it may be
15 necessary to add hydrotopes such as cumene sulphonate or
solvents such as butyldiglycolether.
Suitable anionic surfactants for use herein are according
to the formula R1S03M wherein RI represents a
hydrocarbon group selected from the group consisting of
straight or branched alkyl radicals containing from 6 to
24 carbon atoms and alkyl phenyl radicals containing from
6 to 15 carbon atoms in the alkyl group. M is a salt
forming cation which typically is selected from the group
consisting of sodium, potassium, ammonium, and mixtures
thereof.
Other suitable anionic surfactants can be represented by
the water-soluble salts of an alkyl sulfate or an alkyl
polyethoxylate ether sulfate wherein the alkyl group
contains from 6 to 24 carbon atoms, and preferably from 1
to 30 ethoxy groups for the alkyl polyethoxylate ether
sulfates.
Suitable cationic surfactants to be used herein include
derivatives of quaternary ammonium, phosphonium,
imidazolium and sulfonium compounds. Preferred cationic
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
16
surfactants for use herein are according to the formula
R1R2R3R4N+ X-, wherein X is a counteranion, R1 is a Cg-
C20 hydrocarbon chain and R2, R3 and R4 are independently
selected from H or C1-C4 hydrocarbon chains. In a -
preferred embodiment of the present invention, R1 is a
C12-Clg hydrocarbon chain, most preferably C14~ C16 or i
Clg, and R2, R3 and R4 are all three methyl, and X is
halogen, preferably bromide or chloride, most preferably
bromide. Examples of cationic surfactants are stearyl
trimethyl ammonium bromide (STAB), cetyl trimethyl
ammonium bromide (CTAB) and myristyl trimethyl ammonium
bromide (MTAB) .
Suitable zwitterionic surfactants contain both cationic
and anionic hydrophilic groups on the same molecule at a
relatively wide range of pH's. The typical cationic group
is a quaternary ammonium group, although other positively
charged groups like phosphonium, imidazolium and
sulfonium groups can be used. The typical anionic
hydrophilic groups are carboxylates and sulfonates,
although other groups like sulfates, phosphonates, and
the like can be used. A generic formula for some
preferred zwitterionic surfactants is
R1-N+(R2)(R3)R4X-
wherein R1 is a hydrophobic group; R2 and R3 are each C1-
C4 alkyl, hydroxy alkyl or other substituted alkyl group
which can also be joined to form ring structures with the
N; R4 is a moiety joining the cationic nitrogen atom to
the hydrophilic group and is typically an alkylene,
hydroxy alkylene, or polyalkoxy group containing from 1
to 4 carbon atoms; and X is the hydrophilic group which
is preferably a carboxylate or sulfonate group.
Preferred hydrophobic groups R1 are alkyl groups
containing from 8 to 22, preferably less than 18, more
preferably less than 16 carbon atoms. The hydrophobic
CA 02228758 1998-02-OS
WO 97J06228 PCT/US96/12685
17
group can contain unsaturation and/or substituents and/or
linking groups such as aryl groups, amido groups, ester
groups and the like. In general, the simple alkyl groups
. are preferred for cost and stability reasons.
Other specific zwitterionic surfactants have the generic
formulas:
R1-C.(O) -N (R2 ) - (C (R3 ) 2 ) n-N (R2 ) 2 (+) _ (C (R3 ) 2 ) n-S03 ( -)
or R1-C(O)-N(R2)-(C(R3)2)n-N(R2)2(+)_(C(R3)2)n-COO(-)
wherein each R1 is a hydrocarbon, e.g. an alkyl group
containing from 8 up to 20, preferably up to 18, more
preferably up to 16 carbon atoms, each R2 is either a
hydrogen (when attached to the amido nitrogen), short
chain alkyl or substituted alkyl containing from one to 4
carbon atoms, preferably groups selected from the group
consisting of methyl, ethyl, propyl, hydroxy substituted
ethyl or propyl and mixtures thereof, preferably methyl,
each R3 is selected from the group consisting of hydrogen
and hydroxy groups and each n is a number from 1 to 4,
preferably from 2 to 3, more preferably 3, with no more
than one hydroxy group in any (C(R3)2) moiety. The R1
groups can be branched and/or unsaturated. The R2 groups
can also be connected to form ring structures. A
surfactant of this type is a C10-C14 fatty
acylamidopropylene(hydroxypropylene)sulfobetaine that is
available from the Sherex Company under the trade name
"Varion CAS sulfobetaine"~.
Suitable amphoteric surfactants are surfactants which are
similar to the zwitterionic surfactants but without the
quaternary group. However, they contain an amine group
that is protonated at the low pH of the composition to
form cationic group and they may also possess an anionic
group at these pHs.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
18
The compositions according to the present invention are
aqueous. Accordingly, the compositions according to the
present invention comprise from 10% to 95% by weight of
the total composition of water, preferably from 50% to -
90%, most preferably from 70% to 85%.
The compositions according to the present invention may
further comprise a variety of other ingredients including
perfumes, colorants, bactericide, dyes., chelants,
pigments, solvents, stabilizers, corrosion inhibitors and
the like.
The compositions according to the present invention are
particularly suitable for treating hard-surfaces
including metal surfaces which can be found in a kitchen
or in a bathroom. Indeed, the compositions of the
present invention exhibit good limescale removing
properties for both the kitchen-type stains and the
bathroom-type stains, i.e. for stains which contain not
only calcium carbonate but also soap scum and/or grease.
Accordingly, the present invention encompasses a process
of treating hard-surfaces wherein an aqueous acidic
liquid composition according to the present invention is
applied in its neat form or in diluted form, onto said
surfaces, then left to act onto said surfaces and then
removed by rinsing. Said process can be used both for
treating metal surfaces found in bathrooms, kitchens or
appliances.
The expression ~~used in diluted form~~ herein includes
dilution by the user. Typical dilution levels are of from
0.5% to 50% by weight of the composition.
The expression ~~treating~~ includes removing limescale
deposits while being safe to the surfaces treated as well
CA 02228758 1998-02-OS
WO 97/05228 PCT/LTS96/12685
19
as washing when the compositions according to the present
invention further comprise surfactants.
The compositions according to the present invention are
also particularly suitable for treating hard-surfaces
including metal surfaces which can be found in large
appliances such as automatic dish washers and/or washing
machines. It has now been found that thickened aqueous
acidic liquid compositions comprising malefic acid and a
second acid which has a first pKa not exceeding 5 are
particularly suitable for descaling large appliances.
Thus a broader aspect of the present invention is the use
of thickened aqueous acidic liquid compositions
comprising malefic acid and a second acid which has a
first pKa not exceeding 5 for removing limescale in
automatic dish washers and/or washing machines. Said
thickened compositions have a viscosity as already
defined herein before.
The performance and Theological behaviour of said
thickened compositions are adapted to the dishwasher and
washing machine cycle and allow maximum performance with
an usage procedure that does not impact on consumer
habits (e.g. no need to open the machine after the
washing cycle has started) and without the need of
specifically designed package execution for delayed
controlled release of the compositions. Indeed said
thickened compositions may be applied directly on the
limescale deposits present in the dishwasher and/or
washing machine, thereby performing their action before
the washing cycle and during said washing cycle once said
dishwasher and/or washing machine has been switched on.
Accordingly the present invention further encompasses a
process for .removing limescale in a large appliance like
an automatic dish washer and/or a washing machine,
wherein a thickened aqueous acidic liquid composition
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
comprising malefic acid and a second acid which has a
first pKa not exceeding S, or mixtures thereof, is
dispensed onto the surfaces to be treated in its neat
form, then left to act onto said surfaces, preferably -
5 during 2 minutes to 20 minutes and more preferably during
5 minutes to 10 minutes, before said appliance ,
(washer/machine) is switched on. In this latter stage
said washer and/or machine undergoes a washing cycle
which allow to complete the descaling action and finally
10 removes said composition by rinsing.
By "to switch on" it is to understood herein that said
washer and/or machine undergoes a washing cycle without
prewash. It is to understood also that said washing
15 cycle is conducted without the addition of any detergent
and in so called empty conditions, i.e. without charge
(free of clothes or free of dishes).
The compositions to be used in the application of
20 treating large appliances preferably contain low levels
of surfactants if present, preferably below 1% by weight
of the total composition and more preferably from 0.1% to
0 . 9% . In the application of treating large appliances it
is preferred to use the cationic surfactants described
hereinbefore as the surfactant, if surfactants are
present.
The compositions according to the present invention have
been found to provide excellent limescale removal
performance under usage conditions of large appliances,
i.e. said compositions can be used diluted and in hot
conditions (up to 90 °C).
The compositions according to the present invention are
also particularly suitable to be applied to the surfaces
to be treated by means of a spray-type dispenser while
being safe both to the user and to the surfaces treated
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
21
therewith. Accordingly the compositions according to the
present invention are easy to handle in a safe way.
Indeed, the addition of an acid-stable thickener such as
xanthum gum which is a shear thinning thickener in an
acidic aqueous liquid composition also allows to prevent
the inhalation by the user of said acidic composition
when sprayed via spray-type dispenser and thus avoid any
potential health issue due to the presence of acids in
said acidic liquid composition. Thus another aspect of
the present invention is an acidic composition packaged
in a spray-type dispenser, said acidic liquid composition
comprising from 0.01% to 45% by weight of the total
composition of malefic acid, a second acid which has a
first pKa not exceeding 5, and an acid-stable shear
thinning thickener.
Another advantage of the present invention is that the
acidic liquid cleaning compositions of the present
invention comprising an acid-stable thickener such as
xanthum gum which is a shear thinning thickener may be
easily dispensed onto the surface to be treated via a
spray-type dispenser such as, for instance a trigger-
sprayer. Indeed, said compositions result in a shear
thinning behaviour for ease of dispensing, i.e. said
compositions are thinner at higher shear rates. Thus said
compositions pass easily through the pumping mechanism of
a spray-type dispenser where the shear rate is high and
immediately after recover their thickened character when
reaching the surface to be treated and adhere thereto.
Also, the life time of a spray-type dispenser head is
extended, i.e. the shear thinning behaviour of said
compositions prevents clogging of said head.
Suitable spray-type dispensers to be used according to
the present invention include manually operated foam
trigger-type dispensers sold for example by Specialty
Packaging Products, Inc. or Continental Sprayers, Inc.
CA 02228758 1998-02-OS
WO 97/OC228 PCTNS96/12685
22
These types of dispensers are disclosed, for instance, in
US-4,701,311 to Dunnining et al. and US-4,646,973 and US-
4,538,745 both to Focarracci. Particularly preferred to
be used herein are spray-type dispensers such as T 8500~
commercially available from Continental Spray
International or T 8100~ commercially available from
Canyon, Northen Ireland. In such a dispenser the liquid
composition is divided in fine liquid droplets resulting
in a spray that is directed onto the surface to be
treated. Indeed, in such a spray-type dispenser the
composition contained in the body of said dispenser is
directed through the spray-type dispenser head via energy
communicated to a pumping mechanism by the user as said
user activates said pumping mechanism. More particularly,
in said spray-type dispenser head the composition is
forced against an obstacle, e.g. a grid or a cone or the
like, thereby providing shocks to help atomise the liquid
composition, i.e. to help the formation of liquid
droplets.
A further advantage of the present invention is that the
acidic liquid cleaning compositions of the present
invention may be applied uniformly to a relatively large
area of a surface to be treated via a spray-type
dispenser, thereby ensuring improved cleaning
performance, especially on encrustated soils.
Yet another advantage of the present invention is that
also eye irritation and/or damage is prevented when
spraying an acidic liquid cleaning composition according
to the present invention.
The present invention is further illustrated by the ,
following experimental data and examples.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
23
1 ) Exr~erimental data
The following compositions were made by mixing the listed
ingredients in the listed proportions (weight % unless
otherwise specified).
Compositions I II III IV V
Malefic acid 16 16 18 16 18
Benzenesulphonic acid 2 -- -- -_ __
Sulphamic acid -- 2 -- 2 --
Kelzan T~ 0.3 0.3 0.3 -- --
Water and minors -------up to
100%-------
Viscosity (cps) 180 180 180 <10 <10
at 7.5 1/sec
Surface safety B B -- Ref . --
limescale
removal performance B B B Ref. W
Compositions I and II are representative of the
compositions of the present invention they comprise
malefic acid, a second acid which has a first pKa not
exceeding 5 and an acid-stable thickener, i.e. xanthum
gum commercially available from KELCO. Composition III is
also representative of the present invention and
comprises malefic acid as the acid and an acid stable
thickener. Composition IV comprises malefic acid, a second
acid which has a first pKa not exceeding 5 and is free of
> 35 an acid-stable thickener. Composition V comprises malefic
acid and is free of an acid-stable thickener.
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
24
The followincr test were carried out
The surface safety test:
The surface safety test method was conducted on an
aluminium surface. Similar aluminium bars were dipped
into the tested compositions I, II and IV and left soak
for 4 hours at room temperature (25 ° ) . At the end of the
exposure time, the surfaces were rinsed with soft water
and wiped dry. The comparison between the surfaces
treated with the different compositions mentioned herein
before was done visually. The surface treated with
Composition IV was taken as a reference and compared to
the surfaces treated with compositions I and II.
B (better) - less surface damage as compared to
reference.
Limescale removing test:
The limescale removal tests have been conducted measuring
the weight loss of a marble block (6 +/- 0.2 gr.).
Compositions I, II, III and V were compared to
composition IV, taken as a reference. B (better) stands
for more weight loss of the marble block as compared to
the reference. W (worse) stands for less weight loss of
the marble block as compared to the reference.
3 ml. of each of the compositions I to V was applied with
a pipette on blocks put on a 90° (i.e. vertical) plan and
left act for 10 minutes. After this the compositions were
rinsed and the process was repeated three times.
The above results show that the compositions of the
present invention when used to treat hard-surfaces such
as metal surfaces exhibit improved surface safety to the
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
surfaces treated therewith as well as improved limescale
removal performance (see compositions I and II versus
IV). Accordingly the compositions of the present
invention have been found to be particularly suitable for
5 cleaning large appliances like automatic dish washers
and/or washing machines. The above results also
demonstrate that the use of an acid-stable thickener in
an acidic composition comprising malefic acid alone or in
combination with a second acid improves the limescale
10 removal performance of said composition (see composition
II versus composition IV and composition III versus
composition V).
15 2) Examples
Further examples of compositions according to the present
invention are the following. These compositions are made
comprising the listed ingredients in the listed
20 proportions (weight %).
Compositions
Incrredients : 1 2 3 4 5 6
( % by weight )
Malefic acid 16 8 20 16 16 14
Benzenesulphonic
acid 2 2 2 2 / 2
Sulphamic acid 1 / / 1 / 1
Sulphuric acid / / / / 2 /
Xanthum gum 0.3 0.5 0.8 0.6 0.3 0.3
Waters ~ Minors ---- -------- to 100 ---------
up
Viscosity (cps) 180 320 950 480 180 180
CA 02228758 1998-02-OS
WO 97/06228 PCT/US96/12685
at 7.5 1/sec
26
Compositions 1 to 6 were found to provide excellent
limescale removal performance as well as excellent ,
surface safety to the surfaces treated therewith.
Furthermore, said compositions were found to be
particularly suitable for descaling large appliances like
automatic dish washers and washing machines. Finally when
applied on the surfaces to be treated via a spray-type
dispenser said compositions are safe to the user, i.e.
they prevent inhalation by the user of acidic droplets.
r
