Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MpF( ~y~ Ls RT'T.ATING TO SURFACT~NT-OIh
rrTcRoT~MuhcIoN CONCE:NTRATES
Techn~ cal Field
The present invention re~ates to surfactant-oil
microemulsion concentrates, especially those suitable for
use both neat and diluted as cle ning compositions, and to
a method of cleaning using the said concentrates.
P~knrClln~ oi' the I~vention
A~ueous cleaning compositions generally comprise at least
one surfactant component. Many known cleaning
compositions further comprise water-immiscible components,
such as oils, fatty alcohols and/or terpenes. It is known
that systems comprising a surfactant, water and these
water immiscible components can assume different phase
structu~es. _ _
Three types of phase which comprise surfactant and water
25 are generally recognised: the rod-phase, the 1AmPllAr
phase and the spherical micellar phase.
In the spherical phase, surfactant molecules align in
spheres havlng a diameter approximately twice the
molecular length. For anionic actives in common use,
these structures are less than lOnm in diameter. Systems
exhibiting this phase structure are clear, have a
viscosity similar to water and cannot suspend particles.
The rod phase can be considered as a spherical phase which
has been encouraged to grow along one dimension. It is
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known that this can be achieved by the addition of oils.
Typically, the rods grow to relatively large length as
compared with the diameter, resulting in highly viscous,
often opague solutions. Although the viscosity of these
systems is relatively high as compared with spherical
micellar solutions, any suspended particles will
eventually phase separate.
The l~m~ r phase is believed to be characterised by the
presence of extensive bi-layers of aligned surfactant
molecules separated by water layers. These systems are
generally of lower viscosity than the rod phase systems,
are often opa~ue and can suspend particles.
When an oil is added to a surfactant-water system the oil
can remain in a separate phase or form part of a mixed
phase. The so-called 'microemulsions~ are believed to be
oil-in-water emulsions wherein the oil droplets are
sulficiently small that a visibly clear system results.
For the purposes of the present invention, the term
~microamlllci~nl is restricted to those systems in which
particle size measurements reveal a particle size range of
lO-lOOnm. These systems have a low viscosity and will not
suspend particles, but differ from spherical micelles in
that they exhibit low interfaciaI tensions in the presence
of other oily materials such as are common in fatty soils.
It is helieved that the low interfacial tension enables
the microemuIsions to spontaneously emulsify such oily
materials, giving a contribution towards a particular
cleaning benefit as compared with spherical micelles.
As will be appreciated, microemulsions have a similar
overall composition to the rod micellar systems which can
be obtained by adding oil to a spherical mlcellar system
AMEND~D SHEE~ -
-3-
but have completely different phase structure and
distinct physical properties. It is believed that in the
microemulsions the oil phase is segregated into discrete
droplets stabilised by a surfactant shell whereas in the
rod phase, the oil phase is mixed with the surfactant to
form a mixed micellar structure.
For environmental reasons and for convenience to the user
it is preferred that liquid surfactant compositions should
be as concentrated as is convenient given the mode of use.
This not only reduces the energy cost in transport but
also reduces the packaging requirement for a given
quantity of product.
GB 2190681 (Colgate: 1987) and EP 316726 (Colgate: 1987)
relate to systems which comprise both anionic and nonionic
surfactant, together with a cosurfactant, a water-immiscible
hydrocarbon such as an oily perfume and water.
Surfactants may comprise solely anionic surfactants
although mixtures of anionics and nonionics are preferred.
According to these texts, (see page 5, lines 31ff. of the
GB specification) the cosurfactant is essential in that in
the absence of this component the surfactants and the
hydrocarbon will form a non-microemulsion phase structure.
Suitable cosurfactants are said to include glycol ether
solvents such as Butyl Carbitol (RTM) which is miscible
with water and Butyl Cellosolve (RTM) which is highly
water soluble. These systems are very sensitive to the
type of surfactant present and it appears difficult to
reproduce these systems without using the precise
components specified.
GB 2144763 (P&G: 1983) relates to microemulsion systems
which contain magnesium salts. Examples demonstrate that
aqueous liquid compositions can be prepared with anionic
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surfactants alone and with mixtures of anionic and
nonionic surfactants.
US 4511488 (Penetone: 1985~ relates to compositions which
are described as clear, flowable compositions and which
comprise 10-60wt% of d-limonene (a citrus oil), 10-30wt%
surfactant, and, 20-~Owt% water, in the presence of a
coupling agent such as a glycol ether soluent, in
particular Butyl Carbitol. It has been found by
experiment that high nonionic compositions such as are
described in example ~ of this patent are not stable and
phase separate rapidly on standing both in neat form and
at x4 dilutlon.
~P 0418~86 ~Colgate 1989~ discloses low vi~scosity
microemulsions in the concentrated form which give rise to
higher viscosity li~uid crystal systems on dilution.
These li~uid crystalline li~uors convert to microemulsions
only on incorporation of another component, i.e. when it
is brought into contact with a fatty soil.
From the above it can be seen that microemulsions
generally comprise water, a surfactant mixture, an oil and
a solvent. The surfactants are typically mixtures of
anionic and nonionic surfactant. The oil is generally a
perfume oil. The soluent is often referred to as a
'cosurfactant' or a Icoupling agent' and is generally a
glycol ether.
~rie~ Descri~tlon o~ the Invention
We have ~Prmined that stable, concentrated
microemulsions can be prepared, by simultaneous selection
~5 of specific surfactants, specific oils and specific
sclvents. While these compositions are not microemulsions
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as defined herein, they are dilutable to give a stable
microemulsion which exhibits excellent fatty soil removal.
For the purposes of the present specification a
concentrated microemulsion is a composition which can be
diluted with water to produce a microemulsion as defined
above.
AMEN~D SHEET
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Accordingly, the present invention provides an a~ueous
cleaning composition which upon a~ueous dilution by a
factor of at least two produces a stable microemulsion
directly, said microemulsion having a measured dispersed
phase particle size of 10-100 nanometeres, said
composition including:
a) 20-70wt~ water,
b) from 15-~Owt% of a surfactant system comprising at
least one alkoxylated alcohol ~onionic surfactant and
not more than 20wt% on surfactant of anionic,
cationic, amphoteric or ~witterionic surfactant,
c) from 5-30wt~ of a solvent, said s~olvent having a
solubility of greater than 2%w/w but less than 12~w/w
in water, and,
d) 5-20wt% of a subst~nt;~lly water-insoluble oil,
said composition having a measured dispersed phase
particle si7e of greater than lOD~m prior to ~ilnt;~n, and
not being a microemulsion prior to dilution.
Advantageously the compositions according to the invention
are of relatively high viscosity and exhibit the property
of clinging to a sloping surface, while, on dilution, they
form mobile microemulsions.
Det~tled DescrlDeion of the Inveneion
It is believed that the combined use of the specified
level of nonionic surfactant in the presence of low levels
of charged surfactant or even in the complete absence of
charged surfactant, together with the specified levels of
AMENDEosHEET
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size; leads to the formulation of a viscous concentrate
which is dilutable to give a microemulsion which exhibits
improved fatty soil removal when compared with known
compositions which contain conventional levels of anionic
or which employ hisher levels of solvent and or oil. We
have also determined that neat compositions according to
the invention show excellent cleaning performance and
cling to sloping surfaces.
The compositions of the present invention, in their
undiluted form, generally exhiblt the-property of bi-
refringence, thereby indicating that a l~m~ r phase
structure is present. Upon dilution, the bi-refringent
property is lost, indicating that the lamellar phase
structure is no longer present.
In many applications it is important that a composition
should form a microemulsion over a range of dilution. In
particular, if dilution takes the composition into a rod
phase it is possible that the resulting increase in
viscosity will hinder further dilution. Moreover, if
dilution takes the composition into the spherical phase
the advantages of a microemulsion are lost, especially if
physical separation of the oil phase occurs. Preferred
compositions according to the present invention form
microemulsions when diluted with water to any dilution in
the range x2-x16.
It is believed essential that the compositions of the
present invention have a particle size of above lOOnm in
the neat (i.e. concentrated) form. As mentioned above
microemulsions are characterised by a measured particle
size of 10-100 nm. In general the products of the present
invention will be viscous li~uids or gels which dilute to
thin li~uids on addition of at least an e~ual volume of
water. As indicated hy the bi-refringence and viscosity
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it is believed that the compositions according to the
invention are not microemulsions in their neat form.
The invention also extends to a process for cleaning a
surface which comprises the step of treating the surface
with a composition according to claim 1.
Sur~actAntEl
It is esseatial that the compositions of the invention
comprise alkoxylated alcohol nonionic surfactant.
Suitable alkoxylated alcohol nonionic surfactants can be
broadly descrlbed as compounds produced by the
~n~n~1 on of alkylene oxide groups, which are
hydrophilic in nature, with an organic hydrophobic
compound which may be aliphatic or alkyl aromatic in
nature.
The length of the hydrophilic or polyox,valkylene radical
which is condensed with any particular hydrophobic group
can be readily adjusted to yield a water-soluble compound
having the desired degree of balance between hydrophilic
and hydrophobic elements.
Particular examples include the condensation product of
aliphatic alcohols having from 8 to 22 carbon atoms in
either straight or branched chain configuration with
ethylene oxide, such as a fatty alcohol ethylene oxide
condensate having from 2 to 15 moles Qf ethylene oxide per
mole of fatty alcohol. A plurality of such materials are
described in Schick, ;Nonionic Surfactants', [pub. Arnold,
New York].
~
AMEI~DED SH~~T
~3600 wo 2 ~ ~ 1 8 5 7
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Particularly preferred nonionic surfactants are those
wherein the average composition conforms to the general
formula:
C2nE~n t/- 2~'
Particularly preferred surfactants include the C8~3E~a
(average) alcohol ethoxylates. Exa3mples of these
materials include IMBENTIN 91-35 OFA (RTM) and DOBANOL 23-
6.5 ~
Alternatives include the condensates o~ alkylphenols whosealkyl group contains from 6 to 12 carbon atoms with 5 to
25 moles of ethylene oxide per mole of alkylphenol. The
alkyl nonionics are preferred over the alkylphenyl
nonionics for environmental and ease ot formulation
reasons.
It is believed that shorter EO chain nonionics suffer from
the disadvantage of a reduced cloud point, whereas longer
EO chains lead to a surfactant which is difficult to
formulate into a composition which dilutes to form a
microemulsion phase.
Preferably, the nonionics have a monomodal distribution of
EO chain lengths, i.e. mixtures of different ethoxylates
are not preferred.
The amount of nonionic detergent active to be employed in
the detergent composition of the invention will generally
be from 15 to 30~, preferably from 20 to 30% by weight.
It is preferred ~hat the compositions are essentially free
of anionic surfactants and preferably essentially free of
any charged surfactants. Preferably the level of anionic
is below 2~wt of the level of nonionic surfactant present.
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solvents
It is particularly preferred that the aqueous solubility
should lie in the range 4-11%. Solubility can be
s determined by experimental methods known to the skilled
worker.
Solvents which have an aqueous solubility above 11~w/w in
water, such as ethanol (miscible~, 2-butanol (solubility
>20%), isopropyl alcDhol (miscible), ethylene glycol
derivatives (including butoxy ethanol ~available as Butyl
CellosoIve tTM)~: miscibility >20%), Butyl Digol
(miscible~ and diethylene glycol tmissible) do not give
good results as the products become thin. It is preferred
that the comDositions according to the invention are
essentially free of these solvents.
The preferred alcoholic solvents include n-Butanol
tsoluble to 8%wt in water) and iso-butanol (soluble to
10%wt in water).
Relatively insoluble glycol ethers are particularly
preferred. We have determined that excellent performance
is attained when the solvent has a solubility in water of
from 5-10%. ~Solvents which are particularly preferred are
those selected from the group comprising n-butoxy propanol
(available as Dowanol PnB (RTM~: soluble to 6%), di-
propylene glycol monobutyl ether (available as Dowanol
DPnB (RTM): soluble to 5%) and mixtures thereof.
~ =
Mixtures of solvents having an aqueous solubility in the
range 4-11% with other, more highly water-soluble
solvents having an aqueous solubility above 12~ are not
excluded, but is preferred that the more highly water-
soluble solvents are absent.
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The preferred level of solvent lies in the range 8-15%wt
on product.
QiL~
For applications where the composition of the invention is
intended to remove fatty soil it is believed that the oil
must be a good solvent for fatty matter, especially those
containing triglyceride. The rate at which any particular
fa~ty soil dissolves in an oil can be simply determined by
experiment.
These oils have a miscibility with water of less than 1%
w/w.
Preferred oils are either:
a) cyclic hydrocarbons having 6-15 carbon atoms, or,
~ =
b) ethers of 2-6 carbon alcohols, or,
c) mono-esters of 2-6 carbon fatty acids with 2-6 carbon
alcohols,
wherein for ~b) and (c) the total carbon number of the
molecule is 6-10.
Preferred cyclic hydrocarbon oils are limonene and para-
~ymene. Preferred ethers include di-butyl ether.
Preferred esters include butyl butyrate and amyl acetate.
These are all hydrophobic liquids which can rapidly
dissolve >2Q% of their own weight of triglyceride.
Longer chain esters such as ethyl decanoate are less
preferred. These will dissolve sufficient quantity of fat
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.
but are believed to do so too slowly for effective
cleaning.
Non-cyclic hydrocarbon oils such as dodecane and
hexA~e~An~, and branched species such as citral (polar
acyclic terpene) and the ISOPAR (T~) series (branched
chain hydrocarbons) and water insoluble alcohols such as
n-decanol, which dissolve less than 15~w/w of fat over a
long period (several hours) and are considered less
suitable for use in those embodiments of the present
invention where fatty soil removal from hard surfaces is
important.
It is partic~larly preferred that the ratio between the
weight percentages of the solvent ~c) and the oil (d) is
such that (c):(d) < 1.5:1. In the most preferred
embodiments of the invention the ratio is 0.9-0.4:1 as
solvent:oil. We have determined that the presence of
significantly larger ~uantities of solvent than oil leads
to a product which is not stable over a range of
temperatures or does not form a viscous lamellar phase.
For other applications the important properties of the oil
can extend beyond an ability to dissolve fatty soil. It
is envisaged that by choice of a suitable oil embodiments
of the invention might ensure delivery of a persistent
perfume a sunscreen or an insect repellant.
~ypical levels of oil on product range from ~-18%wt,
levels of 8-l~wt are particularly preferred.
Various inessential components can be presen~ in the
compositions of the present invention where these are
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adapted to particular uses. These optional components can
be selected from the usuaI components employed such as
perfumes, preservatives, colouring agents, antifoaming
components, polymers, pH modifiers and the like, providing
that the composition retains its non-microemulsion form,
of particle size ~laanm when these components are added
and can still be diluted to give a microemulsion.
The level of hydrotrope should preferably not exceed 2% of
la the weight of nonionic surfactant present. More
preferably, the level of hydrotrope should be lower than
the amount effective to destabilise the l~ T phase as
indicated by a removal of the property of birefringence
from the neat product. Compositions according to the
present invention are preferably essentially free of
hydrotropes. Hydrotropes include: aromatic sulphonates
such as cumene, xylene and toluene sulphonate, urea, C1-C5
alcohols particularly ethanol an isopropyl alcohol, C2-C5
glycols, particularly ethylene glycol.
Particularly preferred compositions according to the
present invention include:
a) 2a-30%wt ethoxylated nonionic surfactant selected
from the group comprising: the condensation products
ethylene oxide with aliphatic alcohols having from 8
to 22 carbon atoms in either straight or branched
chain configuration; the condensation products of
ethylene oxide with alkylphenols whose alkyl group
~nt~;nc from 6 to 12 carbon atoms; and mixtures
thereof;
b) 8-13%wt of a solvent selected from the group
comprising: n-Butanol, iso-butanol, n-butoxy
propanol, di-propylene glycol monobutyl ether and
mixtures thereof, and,
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c) 5-18~wt of an oil selected from the group comprising:
limonene, para-cymene, di-butyl ether, butyl butyrate
and mixtures thereof,
said compositions being essentially free of anionic
surfactant, essentially free of hydrotrope and comprises a
weight excess of oil(c) over solvent(b~.
Preferred compositions according to the invention are
clear and dilute to form clear solutions.
The invention will be described hereafter by way of
example.
~ MP L~ ~
In order that the invention may be further understood it
will be described hereafter with reference to embodiments
o~ the':lnv-en~io~ and comparative examples.
In table 1, the ~NONIONIC~ surfactant was Imbentin 91-35
OFA (RTM) a SEO, 9-11 carbon alcohol ethoxylate. 'SOLVENT'
was DOWANOL PnB (RTM, ex. DOW) and ~OIL~ is limonene.
_ ~
'Score (a)' is representative of extent of the spontaneous
emulsification which the product exhibits on triglyceride
samples on a glass microscope slide. Commercially
available lard - ~Silver Cloud Fat~(T~) was spread onto
the slide using a cotton bud to give a streaky but fairly
uniform fat fiIm. The glass slide was then mounted onto a
microscope, a drop of test solution placed onto the fat
film and the interaction between the li~uor and the fat
monitored over a few minutes at ~T (no mechanical input).
The interaction could also be recorded by means of a video
camera.
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Performance was scored on the following scale:
1 roll-up of fat but no removal,
2 rDll-up of fat with minimal removal and/or
emulsification,
3 roll-up of fat with moderate and/or incomplete,
removal and/or emulsification,
4 roll-up of fat with slow but complete removal
and/or emulsification, and,
roll-up of fat with rapid and complete removal
and/or emulsification.
'Score (b)' is representative of the extent of cleaning
using a 'spot test', in which clean Decamel (RTM~ tiles
are sprayed with a model kitchen soil (a mix of
triglycerides, fatty acid, clay and carbon~ and allowed to
stand at room temperature overnight before use.
Alternatively, the soiled tiles were warmed in an oven at
70C for lO minutes to increase soil a &esion to the tile
and allowed to cool before use. Samples of liquors were
applied to the soiled tiles at room temperature and the
drops allowed to spread and remain in contact with the
soil for about 20/30 seconds (up to about 4 minutes in the
case of particularly ineffective solutions). The spots of
liguid were then rinsed under the tap (hard water) or with
a wash bottle (demin water). 'Spontaneous Cleaning' was
assessed on the following scale according to the amount of
visible soiI remaining on the tile after rinsing.
AMENDFDSHEEr
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Excellent - complete soil removal,
4 Good - almost all soil removed,
3 Moderate - a spot with soil still visible but
which is markedly cleaner than the surroundings,
2 Poor - some soil removal,
1 Very poor - a very faint 'ring' at the edge of
the spot, and,
0 No soil removal.
15 Particle size was determined by use of a Malvern 4700 (TM)
photon correlation spectrophotometer using the method
given in the operating handbook.
: ~able 1
la lb lc ld le 2a 2b 2c 2
NONIONIC: 24 24 24 24 24 24 24 24 24
SOLVENT: 10 10 10 20 - 8 8 8 8
OIL: 12.5 12.5 12.5 - - 16 16 16 16
DILUTION: 1 8 16 1 1 1 4 8 16
Viscosity: High 10W Low Low Low High Low Low Low
Score (a) 4 3 3 - - 3 3 3 3
Score (b) 5 - - o o 5 5 5 5
Particle >100 - 16 - 6 >100 20 17 16
Si~e (nm):
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In the table, examples la and 2a are embodiments of the
invention. Examples lb and lc illustrate the effects of
diluting the composition of example la by factors of 8 and
16 respectively, whereas examples 2b, 2c and 2d illustrate
S the effects of dilution on the composition of example 2a
by 4, 8 and 16 respectively. Examples ld and le are
comparative examples which demonstrate the cleaning
behaviour of compositions which are similar to la but
which have components absent.
From the table it can be seen that both examples la and 2a
provide non-microemulsions, having a particle size above
the lOOnm limit. These compositions both exhibit bi-
refringence. Upon dilution of the compositions of examples
la and 2a, microemulsions are believed to be produced as
the products obtained are thin, clear, have a particle
size consistent with microemeulsions and do not exhibit
bi-refingence. It can be seen, particularly from example
2, that cleaning performance is m~lnt~;n~ at up to 16
times dilution.
AMENDED SHE~T
