Note: Descriptions are shown in the official language in which they were submitted.
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CLEANING METHOD AND COMPOSITION
The present invention relates to a method for cleaning profiled hard surfaces,
especially
those coated with zinc silicate or the like, and to compositions suitable for
cleaning such surfaces.
Zinc silicate primers are extensively used throughout industry to coat ferrous
metal
structures and combat corrosion thereof by acting as a sacrificial anode.
Examples of such
primers typically include compositions formulated with a builder or binder
such as a polysiloxane
or epoxy resin. When applied to the surface of, for example, steel to a
typical thickness of 60 to
70 microns and allowed to cure they produce a ceramic coating which is hard,
abrasion resistant
and resistant to oxidation. This makes them especially useful for coating the
internal surfaces of
tanks especially those used in marine applications where the possibility of
physical damage and
exposure to corrosive salt spray exists.
One drawback of such primed surfaces is that they are less smooth than the
corresponding
bare metal. This profiling makes them somewhat difficult to clean which in
turn can lead to
problems in certain circumstances. For example, when a ship's hold, which has
previously
contained say a heavy hydrocarbon, is to be used subsequently to transport
another cargo, e.g. an
alcohol such as methanol, the cleaning cycle can be lengthy and require the
entry of humans into
a closed, hazardous environment to ensure that cleaning is complete.
US 6716804 discloses a three-component cleaning composition comprising an
amphoteric
surfactant and two different non-ionic surfactants which are ethoxylates of
differing water
solubilities.
US 2012/0277140 generally discloses a surfactant system for surface cleaning
comprising
one or more anionic surfactants and one or more non-ionic surfactants. A wide
range of
candidate surfactants is speculated upon including unspecified EO/PO block
copolymers but
exemplified are systems in which a combination of two ethoxylate non-ionic
surfactants, one of
which is water soluble and the other water-insoluble, is also employed. In one
embodiment an
inorganic salt is also included.
We have now developed cleaning compositions which, relative to those currently
in use
today or disclosed in the above-mentioned references, represent an improvement
in both the
extent to and the speed with which tank cleaning can occur. Furthermore, their
improved
performance can reduce substantially the need for steam-cleaning thereby
leading to significant
environmental and energy savings. Thus, according to one aspect of the present
invention, there
is provided a method of removing contaminants from a profiled hard surface
characterised in that
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2
H8323747CA
it comprises the step of contacting the surface with a cleaning composition
comprising (a) from 5
to 50% by weight of an anionic surfactant, (b) from 5 to 50% by weight of a
first non-ionic
surfactant having the general formula R'-(A0)5-OH wherein R' is C9 to C20
alkyl; each AO unit is
either -OCH2CH2 or -OCH2CH(CH3)- and n is greater than 6 and (c) from 5 to 50%
by weight of a
second non-ionic surfactant having the general formula, R'-(OCH2CH2)n-OH
wherein R' is C9 to C20
alkyl and n is less than 6; each of said weight percentages being with respect
to the total weight of
(a), (b) and (c).
In certain circumstances, the various surfactants described above may be
sourced in
water-diluted as opposed to pure form. For example, commercially available
anionic surfactants
typically comprise a 25-40% solution of the active component in water. Since
the various weight
ranges defined herein are with respect to 100% actives, any dilution effect
will need to be taken
into account when making up any cleaning composition derived therefrom.
It will also be readily appreciated that in the cleaning compositions taught
herein the
density of the individual components are approximately equal to 1 g/cc so that
the formulations
can alternatively be made up using the same ranges on a volume basis to give
substantially the
same result.
= In one working embodiment, the cleaning composition comprises a
concentrate suitable
for spot cleaning duties. In another, it comprises a corresponding diluted
form derived from the
concentrate by addition of water in one or more steps. Typically such diluted
forms will comprise
less than 5%, more preferably less than 1%, most preferably less than 0.75% by
volume of the
concentrate itself. In yet another embodiment, the diluted form of the
cleaning composition will
be one which is prepared directly by mixing water with the three constituent
surfactants whose
relative proportions are in accordance with the various ranges defined above.
In use, the pH of the
cleaning composition is suitably in the range from 6 to 9 most preferably from
7 to 8.
In addition to the three components of the cleaning composition described
above it is
envisaged that other useful additives, for example dyes, anti-foams,
hydrotropes and the like, can
be present if so desired.
In certain embodiments of the inventions disclosed herein, the first non-ionic
surfactant
has a cloud point in the range 50-90, preferably 60-70 C as determined by ASTM
D-2024 09 at a 1%
by weight level of the surfactant in de ionised water and/or the second non-
ionic surfactant has a
cloud point in the range 30-70, preferably 40-60 C as determined with 5g
surfactant in 25g of a
25% butyl diglycol (BDG) aqueous solution.
#1332865
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In other embodiments of the invention; (1) the anionic surfactant (in the un-
ionised, acid
form) has a logioP value in the range 5 to 7 and/or (2) the first non-ionic
surfactant has a logioP
value in the range 0.1 to 3 and/or (3) the second non-ionic surfactant has a
logioP value in the
range 0.1 to 3. As used herein, the term logioP means the logarithm of the
partition coefficient P
for the given component measured with respect to a standard two-phase n-
octanol/water
system. Further information about this methodology may be found, for
example, ion
Ecotoxicology and Environmental Safety, 11(3) 1986, pp.251-260.
Turning to the anionic surfactant, in one embodiment it is one or a mixture of
compounds
selected from C12 to C18 alkyl sulphonic or sulphuric acids or a corresponding
salt thereof,
preferably a Group IA or Group IIA metal or an amine or alkanolamine salt, or
from linear alkyl
benzene sulfonic acids or a salt thereof, preferably a Group IA or Group IIA
metal salt or an amine
or alkanolamine salt. In another embodiment, it is selected from C12 to C18
alkyl polyether
sulphuric acids or a corresponding salt thereof, preferably a Group IA or
Group IIA metal or an
amine or alkanolamine salt. Examples of preferable anionic surfactants include
sodium lauryl
sulphonate or sulphate, magnesium lauryl sulphonate or sulphate,
tetraethylammonium lauryl
sulphonate or sulphate, mixed C14 to Ci6 alkyl sulphate or sulphonate salts of
sodium, potassium
or magnesium and mixed C12 to C14 alkyl sulphate or sulphonate salts of
sodium, potassium or
magnesium. Preferable linear alkyl benzene sulphonic acids or salts thereof
include C6 to C12 alkyl
benzene sulphonic acids or salts thereof. In the case of polyether sulphates,
which are
characterised by a polyether unit between the aliphatic or aromatic component
and the sulphate
group, this is suitably a polyether comprised of up to 20 ¨OCH2CH2- units. The
alkyl groups in any
of the above may be branched or unbranched.
When the anionic surfactant is an amine or alkanolamine salt, the
corresponding cation is
suitably selected from the genus of species having the general formula R3NH+
wherein each R
group is independently H or a C1 to C6 substituted or un-substituted
hydrocarbyl group with the
proviso that at least one is a substituted hydrocarbyl group. As used herein,
the term 'substituted
hydrocarbyl group' means a hydrocarbyl, preferably an alkyl group of general
formula C9H2x,1,
which has been substituted with one or more polar groups such as ¨OH, -SH, -N
H2, -NHR or the
like. In one preferred embodiment, such substituted alkyl groups are
hydroxyalkyl groups
comprising at least one hydroxyl group; in a sub-embodiment at least one of
these hydroxyl
groups is attached to the end of the alkyl group remote from that connected to
the nitrogen. In
another embodiment, at least two of the R groups are hydroxyalkyl groups and
in yet another all
three R groups are hydroxyalkyl groups. In preferred sub-embodiments,
independently applicable
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to each of the embodiments and sub-embodiments described above, each R group
is suitably
independently H or a C2 to C6 un-substituted or substituted alkyl group; more
preferably H or a C2
to C4 un-substituted or substituted alkyl group.
One especially preferred sub-genus of the R31\11-1* cations described above is
comprised of
.. species which can be regarded as protonated mono-, di- or tri-
alkanolamines in which each
alkanol group has from two to four carbon atoms. Examples of such species
include protonated
mono-ethanolamine, di-ethanolamine, tri-ethanolamine, mono-propanolamine, di-n-
propanolamine, tri-n-propanolamine, di-iso-propanolamine or tri-iso-
propanolamine. Preferably
the cation is protonated tri-ethanolamine or protonated tri-n-propanolamine.
The first non-ionic surfactant, which is employed in the cleaning composition
and which is
relatively hydrophilic, is suitably one or mixture of compounds having the
general formula, R'-
(A0)5-OH wherein R' is C9 to Cm alkyl, preferably C9 to C16 alkyl; each AO
unit is either ¨OCH2CH2-or
¨OCH2CH(CH3)- and n is greater than 6. In one embodiment, the molar ratio
[¨OCH2CH(CH3)-]/[¨
OCH2CH2-] is in the range up to 8, preferably from 0.1 to 4 and/or n is from 7
to 15. The different
AO units may be arranged randomly or in blocks. In some embodiments, the end
block of the AO
chain is made of ¨OCH2CH(CH3)- units; in others it is made of ¨OCH2CH2- units.
The first non-ionic
surfactants are typically prepared by alkoxylating the corresponding fatty
alcohol R'OH which
itself can be derived from naturally-occurring sources or from precursor lower
molecular weight
alcohols using for example the Guerbet synthesis. Such surfactants are
sometimes referred to as
'linker surfactants' and are characterised by exhibiting a critical micelle
concentration (CMC)
which is relatively low. The alkyl groups mentioned above can be branched or
unbranched.
The second non-ionic surfactant, which is employed in the cleaning composition
and which
is relatively hydrophobic, is suitably one or mixture of compounds having the
general formula, R'-
(OCH2CH2)n-OH wherein R' is C9 to C20 alkyl, preferably C9 to C16 alkyl, and n
is less than 6,
preferably from 2 to 5. Such surfactants are also typically prepared by
ethoxylating the
corresponding fatty alcohol R'OH which itself can be derived from naturally-
occurring sources or
from precursor lower molecular weight alcohols using by the Guerbet synthesis.
The alkyl groups
mentioned above can be branched or unbranched.
The R' groups employed in the first and second non-ionic surfactants can be
the same or
different.
Preferably either or both of the first and second non-ionic surfactants
comprise from 10 to
45% by weight of the cleaning composition.
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The method of the present invention is generally applicable to the cleaning of
all fouled
hard surfaces which have become profiled (i.e. roughened) by virtue of use,
corrosion or being
coated with a corrosion-resistant layer (e.g. a primer). Its use is beneficial
where the hard surface
includes a profiled, sacrificial coating of zinc silicate or an equivalent and
is especially so for
cleaning the dirty surfaces of coated stainless or mild steel storage tanks.
It can be used to
particular advantage to clean the cargo tanks or holds of ships where the
space is confined and
discharge of the waste cleaning composition is environmentally problematic.
Any method of
using the cleaning composition can be employed to effect cleaning although
typically it will be
brought into contact with the dirty surface using an industrial sprayer
assembly which is adapted
to collect and recirculate the liquid. If so desired, the surfaces can at the
same time be brushed or
scrubbed. Thereafter, once a suitable period of cleaning time has elapsed, the
cleaned surfaces
can be rinsed with clean water and/or a sample of the next cargo to be used.
Suitably the
cleaning composition is sprayed onto the dirty surfaces at a temperature of
less than 100 C,
typically from 60 to 80 C.
The cleaning composition of the present invention, which is designed for
industrial as
opposed to personal care or household use, is especially suitable for removing
contaminants
comprising high molecular weight hydrocarbons such as diesel, gas-oil,
kerosene, vegetable oils
and the like from hard surfaces of the type mentioned above. Typical vegetable
oils which can be
removed with the cleaning compositions of the present invention include palm
oil, soya bean oil,
rapeseed oil, sunflower oil, peanut oil, olive oil, cottonseed oil, palm
kernel oil and coconut oil
along with refined fractions thereof.
The method of the present invention will now be illustrated with reference to
the following
tests which demonstrate the superiority of the cleaning compositions of the
present invention
over the prior art.
General Test Methodology for Examples 1 to 11
Test panels made of stainless steel or mild steel coated with an industry
standard zinc
silicate coating were immersed in ultra-low sulphur diesel for a period of
three days to simulate
the contamination occurring in a cargo tank. After removal and being allowed
to drain, the panels
were tested in a rig designed to remove as much of the residual diesel
adhering to the panel as
possible under a standard set of cleaning conditions. In this rig, the
cleaning composition was
applied to the test panel by means of a sprayer adapted for continuous liquid
recycle thereby
enabling the contaminated panel surfaces to be continuously contacted with the
cleaning
composition for a period of 2 hours. During this time, the temperature of the
cleaning
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composition was maintained at 70 C. At the end of the test period, spraying
was stopped, the
panels washed with clean water and the residual diesel on the panels
determined by immersing
the panels in a standard volume of methanol at room temperature for 5 minutes
and then
measuring the amount of diesel extracted using UV/visible spectroscopy. By
calibration with
__ standard samples of known concentrations, the amount of diesel in the
methanol was quantified
as an average residual hydrocarbon reading (ARHR) indicative of the
effectiveness of the cleaning
composition. Here, the higher the ARHR the less effective is the cleaning
composition.
Example 1 (Comparative)
In this example, a baseline was established using water at 70 C. The ARHR
reading was
__ 550.
Example 2 (Comparative)
In this example, the cleaning composition was a 0.5% by weight aqueous
solution of
Accell Clean (ex- Advanced BioCatalytics Corporation) a material which has
been rated for use in
cleaning marine tanks and which comprises a mixture of a surfactant and
proteins having a pH in
the range 5.5 to 6.5. The ARHR reading obtained was 50.
Example 3
In this example, the cleaning composition (pH 7-8) was a 0.5% by weight
aqueous solution
of a cleaning composition concentrate according to the present invention
comprising (by volume):
45.0% Hansanol AS24OA (a 30% aqueous solution of a sodium salt of a
sulphonated mono C12 to
C14 alkyl ester surfactant; ex Hansa Group);
27.5% Berol 185 (a non-ionic surfactant of formula
C10_16(OCH2CH2)p(OCH2CH(CH3))q0H; cloud
point 64-70 C in water; ex AkzoNobel);
27.5% Ethylan 1005 (a non-ionic surfactant of formula C9(OCH2CH2)50H; cloud
point 47-53 C in
BDG solution; ex AkzoNobel) and
__ 0.5% anti-foam JH FDP (silicone anti-foam; ex Julius Hoesch).
The ARHR reading obtained was 25.
Example 4
Example 3 was repeated except that the weight component of the three
surfactants was
respectively 35%, 30% and 5% and no anti-foam was employed. The ARHR reading
obtained was
__ 35.
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Example 5
Example 4 was repeated except that 35% Serdet DSK-30 (sodium salt of a C12-
C14
alcohol sulphate (30% solution); ex Elementis Specialities) was employed
instead of the Hansanol
AS240A. The ARHR reading was 28.
Example 6 (Comparative)
In this example, the cleaning composition (pH 7-8) was a 0.8% by weight
aqueous solution
of a cleaning composition concentrate comprising (by volume):
25.0% BioSoft D-40 (sodium, 2-dodecylbenzene sulphonate surfactant; ex Stepan
Company);
45% Lutensol XP90 (a non-ionic surfactant of formula C10(OCH2CH2)90H; wherein
the C10
alkyl group is branched and derived from a C3.0 Guerbet alcohol; ex BASF);
30% Ethylan 1005 (non-ionic surfactant of formula C941(OCH2CH2)50H; ex
AkzoNobel)
and
0.5% anti-foam JH FDP (silicone anti-foam; ex Julius Hoesch).
The ARHR reading obtained was 25.
Example 7 (Comparative)
In this example, the cleaning composition concentrate comprised 15% Serdet DLK-
9/30 ,
45% Lutensol XP90 and 30% Ethylan 1005 and was used at a 1% dilution level
in water. The
ARHR reading was 40.
Example 8 (Comparative)
In this example, a binary cleaning composition concentrate comprising 30%
Hostapur
SAS30 (sodium secondary C14-17 alkyl sulphonate; ex Hostapur) and 70%
Lutensol XP90 was
employed at 1% dilution. The ARHR reading was 48.
Example 9
In this example the cleaning composition concentrate comprised 25% by weight
Biosoft D-
40, 45% by weight Berol 185 and 30% by weight Ethylan 1005 together with 0.1%
by weight of
NFA antifoam. The product so obtained was used at a 0.5% dilution level in
water. The ARHR
reading was 48 (average of two results).
Example 10 (Comparative)
Example 9 was repeated except that the Berol 185 was replaced with Lutensol
XP90. The
product so obtained was used at a 0.5% dilution level in water. The ARHR
reading was 60 (average
of two results).
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Example 11 (Comparative)
Example 9 was repeated except that the Ethylan 1005 was replaced with a 50:50
by
weight mixture of Ethylan 1005 and Dowanol EPH (aromatic ethylene glycol
ether C-
6H5OCH2CH2OH; ex Dow Chemicals). Thereafter a further 10% by weight water was
added to the
mixture. The product so obtained was used at a 0.5% dilution level in water.
The ARHR reading
was 58 (average of two results).
Examples 9 to 11 demonstrate that under equivalent conditions the cleaning
compositions of the present invention are superior to those described in
US2012/0277140.
