IMPROVEMENTS RELATING TO LIMESCALE REMOVING COMPOSITIONS

AMELIORATIONS CONCERNANT DES COMPOSITIONS DE DETARTRAGE

English Abstract

In limescale-removing compositions of pH 1-5, comprising 1-15 wt.% of a
dicarboxylic acid and 1-30 wt.% of an anionic surfactant other than fatty
acid, the presence of 0.1-10 wt.% of a fatty acid, prevents low temperature
instability of the product which leads to precipitation of the dicarboxylic
acid.

French Abstract

L'invention concerne des compositions de détartrage dont le pH se situe entre 1 et 5, et comprenant entre 1 et 15 % en poids d'un acide dicarboxylique et entre 1 et 30 % en poids d'un tensioactif anionique autre qu'un acide gras. Dans ces compositions, la présence de 0,1 à 10 % en poids d'un acide gras évite toute instabilité du produit à faible température susceptible de se traduire par une précipitation de l'acide dicarboxylique.

Claims

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1. A limescale-removing composition of pH 1-5, comprising:
a) 1-15%wt of a dicarboxylic acid,
b) 0.1-10%wt of a fatty acid with an average carbon
chain lenght of C10-C16, and
c) 1-30%wt of an anionic surfactant other than fatty
acid
and which is free of organic solvents.
2. Composition according to claim 1 wherein the
dicarboxylic acid comprises one or more of adipic,
glutaric, succinic acid and mixtures thereof.
3. Composition according to claim 1 or 2 wherein the
anionic surfactant comprises one or more of the group
comprising: primary and secondary alcohol sulphates,
alcohol alkoxy sulphates, primary and secondary alkane
sulphonates and alkyl aryl sulphonates.

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4. A limescale-removing composition of pH 3.0-4.9,
comprising:
a) 2-10%wt of one or more dicarboxylic acids selected
from adipic acid, succinic acid and glutaric acid,
b) 0.1-3.0%wt of an (on average) C10-C16 fatty acid,
c) 2-14%wt of C10-C18 alcohol alkoxy sulphate with an
average of 0.5-3 moles of ethoxylation,
d) 0-5% phosphoric acid,
e) 0-5% base
and which is free of organic solvents.

Description

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IMPROVEMENTS RELATING TO LIMESCALE REMOVING COMPOSITIONS
Technical Field
The present invention relates to compositions for the
removal of limescale and/or other mineral deposits from
hard surfaces.
Backcrround to the Invention
Limescale mainly comprises calcium and magnesium
carbonates, and can contain lesser amounts of soap scum,
protein, particulates and other soils. Limescale is
formed on evaporation of water containing said soils.
While the deposit formed by evaporation is initially
paste-like, it hardens with time to form a recalcitrant
deposit.
Conventional cleaning compositions are generally buffered
at alkaline pH so as to attack fatty soils. Limescale is
resistant to the action of alkali and specialist cleaning
compositions, of acid pH, are used to remove it.
It is known that the use of strong acids, such as
hydrochloric acid will result in prompt removal of
limescale but will also result in damage to surrounding
surfaces, such as bath enamels, metals and certain
polymers, where these are susceptible to attack by strong
acids.
Limescale removing compositions of malefic acid in
combination with nonionic surfactants, either in further
combination with ionic detergents or with phosphoric acid

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are known. In the absence of nonionic surfactants
cleaning efficiency is greatly reduced. Malefic acid is
known to be a particularly effective limescale remover and
is less prone to attack surfaces than the inorganic acids.
EP 0496188 (P&G) relates to compositions with 1-15~
nonionic and 4-250 of malefic acid, having a pH of 1-4.
Preferred compositions are formulated at pH 1-4 and
comprise malefic and nonionic at specified levels but which
are substantially free of both ionic detergents and
phosphoric acid.
The use of other organic acids is known: GB-B-2149419
(Colgate-Palmolive: filed November 1983) relates to an
acidic liquid cleaning composition of pH 3-5 which
comprises a surfactant, water, a minor proportion of a
non-sequestering acid which reacts with Ca and Mg soaps of
higher fatty acids in soap scum (examples include glutaric
acid) and a lesser minor proportion of an acid which forms
a water insoluble calcium salt (phosphoric acid is given
as an example), both acids being partially neutralised to
a pH of 3-5.
EP-B-0411708 (Colgate-Palmolive: filed 31 Jul~.~ 1989)
relates to an acidic (pH 1-4) aqueous cleaner for baths
which are acid resistant or of zirconium white enamel
which comprises surfactant, a C2-C10 organic acid other
than oxalic and malonic acid, an aminoalkylenephosphonic
acid and phosphoric acid.
EP-B-0040343 (BASF: filed 16 May 1980) is a granted
European patent which relates to a composition comprising
ethoxylated alcohol nonionic surfactant and C4-C8
aliphatic dicarboxylic acids or mixtures of such. The
acids are present as 'colour stabilizers' and include a
mixture of succinic, adipic and glutaric acids in the
examples of the patent.

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EP 0606712 (Clorox: published July 1994) relates to pH
approx 2-3.5 cleaning formulations for the removal of
mineral deposits which contain 3-10% in total of both a
weak acid and its conjugate base at a molar ratio of 1:30
to 30:1 in which the weak acid has a pKa of 2-3.5. The
compositions disclosed in this specification comprise
citric acid (a tricarboxylic acid) and sodium citrate
dehydrate as the limescale removing acids.
Despite the formulation work which had been done in this
area it is believed that it is difficult to make
formulations which are stable at low temperatures and/or
which contain significant levels of succinic and adipic
acids. This is especially true of concentrated systems
which comprise around 84 of the dicarboxylic acid or acids
when these compositions are shipped or stored at
temperatures below 5 Celcius, where the precipitation of
the acid is irreversible. Such temperatures may be
encountered both during storage and shipping of a product
prior to its commercial sale and while the product is
being stored by the end user. j,~jrllle reversible
precipitation may occur at lower acid levels this can
still cause difficulties for the user who may not be aware
that the precipitation has occurred (due to the opaque
packaging which is used for these products) and may use
the liquor above the precipitate without first warming the
composition.
Brief Description of the Invention
' We have no~:a determined that limescale-removing
compositions of pH 1-5, comprising:
a) a dicarboxylic acid,

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b) a fatty acid and
c) an anionic surfactant other than fatty acid
are stable at lower temperatures than similar compositions
which do not contain the fatty acid. It is believed that
the fatty acid acts as a solubiliser for the dicarboxylic
acids but the details of the mechanism are not fully
understood.
Accordingly a first aspect of the present invention
provides a limescale-removing composition of pH 1-5,
comprising:
a) 1-15%wt of a dicarboxylic acid,
b) 0.1-10%wt of a fatty acid, and
c) 1-30owt of an anionic surfactant other than fatty
acid
A second aspect of the present invention provides for the
use, as a low temperature stabilising additive in a
limescale removing composition comprising 1-15%wt of a
dicarboxylic acid and 1-30owt of an anionic surfactant
other than fatty acid, of 0.1-l0owt of a fatty acid.
Detailed Description of the Invention
In the following description all quantities are given in
wt% on product unless noted otherwise.

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Dicarboxylic Acids:
Dicarboxylic acids suitable for use in the present
invention include adipic, glutaric and succinic acid and
mixtures thereof. The mixtures are preferred as these are
commercially available. Typical mixtures which can be
found in the marketplace comprise 30-35% adipic acid, 45-
50% glutaric acid and 10-18% succinic acid. Such a
mixture is available in the marketplace as Sokalan DCS
(TM, ex. BASF). Another suitable mixture is available as
Radimix (TM, ex. Radici). The use of essentially pure
acids is not excluded but these have limited commercial
availability and the mixed acids are preferred.
Typical levels of total dicarboxylic acid in the product
range from 2-10%wt. Levels of 3-5o are preferred for
dilute compositions and levels of 6-9o for concentrates.
Fatty Acids:
Fatty acids suitable for use in the compositions of the
present invention include moncarboxylic acids with an
average carbon chain length in the range C10-C18,
preferably C12-C16.
C14 average chain length linear fatty acids (derivable
from lauric acid oils such as coconut and palm-kernel
fats) are particularly preferred. Longer chain length
fatty acids are less soluble in the absence of expensive
hydrotropes (such as alcohol and alkaryl sulphonates) or
organic solvents. Suitable fatty acids are available in
the marketplace as PRIFAC 7907 (TM ex. Unichema).
Typical levels of fatty acids range from 0.1-3owt on
product, with a range of 0.1-lowt being particularly

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preferred. Typical levels in dilute compositions are
0.25%wt with 0.5%wt being used in more concentrated
products.
Surfactants:
Preferably the anionic surfactant comprises one or more of
the group comprising: primary and secondary alcohol
sulphates, alcohol alkoxy sulphates, primary and secondary
alkane sulphonates and alkyl aryl sulphonates.
The preferred anionic surfactants are the alcohol alkoxy
sulphates, preferably the ether-sulphates. Most
preferably C,~-C,r, average chain length ether sulphates with
an average of 0.5-3 moles of ethoxylation. Lauryl ether
sulphate (1E0) is a suitable anionic surfactant for
compositions of the invention.
Preferred levels of anionic surfactant range from 2-14%wt.
Preferably 3-7%wt surfactant is present in dilute
compositions and 8-12%wt is present in concentrated
compositions.
Corrosion Inhibitors:
Typically the compositions of the invention comprise one
or more corrosion inhibitors. Phosphoric acid is a
suitable corrosion inhibitor, and when present is
conveniently employed at a level of 0.1-5%wt with levels
of 0.5%wt being used in ditute product and 1%wt being used
in concentrated products.

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pH:
It is believed important that the pH of the composition is
below the pKa of the fatty acid being employed. In
general, the pKa of a C12-C16 fatty acid will be close to
4.9, consequently the pH of the compositions will
generally be below this figure. Given that damage to
surfaces can occur at pH's below 3.0 it is particularly
preferred that the pH of the compositions of the invention
falls into the range 3.0-4.5, with a pH of around 3.5
being typical. Sodium hydroxide or another suitable base
is used to regulate the pH if required. Typical levels of
base in the products of the invention are 0.1-lowt.
Minors:
Preferred levels of perfume range from 0.1-2awt. Acid
stable perfumes are available from a variety of sources
including the Quest company.
Various minor components may be present in the
compositions of the present invention, these include
opacifiers, colours, preservatives and fluorescers.
Typically, the present invention provides a limescale-
removing compositions of pH 3.0-4.9, comprising:
a) 2-l0owt of one or more dicarboxylic acids selected
from adipic acid, succinic acid and glutaric acid,
' b) 0.1-3.Oowt of an (on average) C,,-C;.. fatty acid,
c) 2-14%wt of C1~,-C1~, alcohol alkoxy sulphate with an
average of 0.5-3 moles of ethoxylation,

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d) 0-5o phosphoric acid,
e) 0-5% base
Pre ferred formulations for direct use comprise:
a) 3-5%wt of a mixture of adipic acid, succinic acid and
glutaric acid,
b) 0.1-0.5owt of an (on average) C,-C,,. fatty acid,
c) 3-7%wt of C;~-C1;_; ether sulphate (0.5-3 EO) ,
d) 0.1-5o phosphoric acid,
e) 0-5o base
Preferred
concentrated
formulations:
a) 6-9owt of a mixture of adipic acid, succinic acid
and glutaric acid,
b) 0.3-l.Oowt of an (on average) C:-C:. fatty acid,
c) 8-13 owt of C,!,-C1;, ether sulphate ( 0 . 5-3 EO) ,
d) 0.1-5% phosphoric acid,
e) 0-5o base
The present invention will be further described with
reference
to
the
following
non-limiting
examples.

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Examr~les
Materials used in the examples are identified as follows:
~ 5 LES 1E0 Lauryl ether sulphate with one mole of
ethoxylation
Fatty Acid PRIFAC 7907 (TM) ex. Unichema
Dicarb Acid Radimix (TM) ex. Radici or Sokalan DCS (TM)
ex. BASF or Succinic acid
Phos. Acid Phosphoric Acid
Base Sodium Hydroxide
Preservative PROXEL GXL(TM, ex ICI) (1,2-
benzisothiazolin-3-one)
Perfume GC 1550 A ex Quest
Compositions were prepared by mixing of the components.
Compositions were prepared with proportions as given in
Table 1 below, all components being given in wto as
10 0 owt .
TABLE 1
Example 1 2
LES 1E0 5.0 10.0
Fatty Acid 0.25 0.5
Dicarb Acid 4.0 8.0
Phos. Acid 0.5 1.0
Base 0.38 0.76
Preservative 0.016 0.032
Perfume 0.5 1.0
Water to 100 to 100

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Experiments were also performed with each of the
dicarboxylic acids mentioned above in the absence of the
fatty acid. It was determined that after storage at
temperatures below 5°C . irreversible precipitation of the
mixed dicarboxylic acids as crystals occurred when these
were present at a concentration of 8%. In the diluted
composition (4o mixed acids) the precipitation is
reversible. Similar results were obtained with succinic
acid alone: in this case, we have problems of irreversible
20 precipitation were encountered at 0°C even with the
diluted version (4.0o succinic acid).
For the compositions given in table 1 above no solubility
problem was detected with both Sokalan DCS and Radimix and
also with Succinic acid alone: while the product became
slightly turbid at low temperatures precipitation of
dicarboxylic acid crystals did not occur.