The present invention relates to a polyaphron dispersion.
A polyaphron dispersion is generally also known as a biliquid foam. This phrase is known, for example, from Sebba, F. (Felix), "Foams and biliquid foams, aphrons", 1987. ISBN: 0471916854. Biliquid foams are known in the art and are described in the following literature references by Sebba: "Biliquid foams", J. Colloid and Interface Science, 40 (1972) 468-474; and "The Behaviour of Minute Oil Droplets Encapsulated in a Water Film", Colloid Polymer Sciences, 2S7 (1979) 392-396.
US-A-4,486,333 to Sebba describes a particular method for the preparation of biliquid foams by agitating a hydrogen bonded liquid containing a soluble surfactant to produce a gas foam and intermittently adding to the gas foam a non-polar liquid'which is immiscible with the hydrogen bonded liquid, the surfactant-containing hydrogen bonded liquid being selected to provide a spreading coefficient equal to or greater than zero.
Known polyaphron dispersions contain a single liquid external phase and a single liquid internal phase. We have now discovered a polyaphron dispersion which can contain additional phases in the internal phase, and a process for the preparation thereof.
Accordingly the present invention provides a polyaphron dispersion comprising an external phase and polyaphrons having an internal phase, the internal phase comprising (i)
a first phase which is liquid and (ii) a second phase which
is liquid or gaseous.
The process for preparing a polyaphron dispersion as defined
above comprises (a) forming the internal phase and (b)
forming a polyaphron dispersion comprising an external phase
and the internal phase prepared in step (a).
The polyaphron dispersion preferably comprises from 70 to
95% by weight of the internal and 5 to 30% by weight of the
external, or continuous phase. The external phase is
preferably an aqueous phase. It may also be composed of a
liquid which has hydrogen bonding such as glycerin,
propylene glycol and/or ethanol or a mixture thereof with
water. A surfactant to stabilise the dispersion may also be
included, for example in an amount of from 0.1 to 3%,
preferably 0.1 to 1%, by weight based on the total weight of
the dispersion. Suitable surfactants are, for example,
anionic, cationic, non-ionic, amphoteric or zwitterionic
surfactants, such as sodium lauryl ether sulphates,
polyethoxylated castor oil, ethoxylated oleyl alcohols or
polyethoxylated hydrogenated castor oils.
The internal phase comprises at least two liquid phases or
at least a liquid phase and a gas phase. The internal phase
may, of course, also comprise additional phases, such as an
additional liquid phase, an additional gas phase or an
additional solid phase.
The internal phase may, for example, comprise an aqueous
phase and a non-aqueous phase, an emulsion or a biliquid
foam (or polyaphron dispersion). The internal phase may
also comprise a aingle aqueous phase and a single nonaqueoua
phase.
When the internal phase comprises an emulsion, the emulsion
is, for example,'a water-in-oil emulsion. The continuous
phase of the emulsion is immiscible with the external phase
of the polyaphron dispersion. The emulsion may, for
example, comprise from 10% to 80% of the non-continuous
phase and from 20% to 90% of the continuous phase. Either
or both of the continuous phase and the non-continuous phase
may comprise one or more additives, particularly additives
which are incompatible with components of the external phase
of the polyaphron dispersion. Examples of suitable oil
phases are those mentioned below with respect to the
international phase when it is a polyaphron dispersion. An
emulsion may be prepared by a standard techniques known in
the art, for example by use of a pair heated vessels in
which the aqueous and non aqueous phases are prepared prior
to final mixing and emulsification by means of a high shear
device such as a rotor stator device of the "Silverson1
type.
When the internal phase comprises a biliquid foam or a
polyaphron dispersion (which may itself be a complex
polyaphron dispersion of the present invention), the
external phase may be aqueous or non-aqueous. The external
phase of this internal phase is different from the external
phase of the polyaphron dispersion of the invention. The
internal phase may comprise from 10% to 80% of the noncontinuous
phase and from 90% to 20% of the continuous
phase. Either or both of the continuous phase and the noncontinuous
phase may comprise one or more additives,
particularly additives which are incompatible with
components of the external phase of the polyaphron
dispersion. Examples of suitable oil phases are oils which
are liquid at room temperature (e.g. 20 degrees C) such as,
for example/ one or more selected from a cyclomethicone,
dimethicone, dimethiconol, dimethicone copolyol, an
emollient ester such as iaopropyl stearate, lanolate,
myristateor palmitate, or octyl palmitate, a glyceride such
as avocado oil, coconut oil, soybean oil or aunflower oil,
or a caprylic/capric triglyceride, a lanolin oil, mineral
oil or natural oil/ or oleyl alcohol, or any other oil known
to be used in emulsions for whatever purpose. Also included
in the definition of oil are water insoluble solvents such
as hexane, toluene, benzene, kerosene, diesel oil and other
like solvents and water-insoluble organic liquids. The
biliquid foam or polyaphron dispersion may be prepared by a
standard techniques known in the art, for example by those
indicated herein.
When the internal phase comprises a single aqueous phase and
a single non-aqueous phase, it may be prepared by forming an
unstable emulsion or polyaphron suspension, which is
subsequently allowed to separate into two components on
standing once the polyaphron suspension of the present
invention is fully formed.
The external and/or internal phase of the polyaphron
dispersion may, for example, comprise one or more
surfactants or other additives. Suitable surfactants for
forming and stabilising biliquid foama or polyaphrons can be
selected for example, from the liat given in WO 97/32559 or
will be well-known to those skilled in the art.Methods of
producing biliguid foams are described in US-A-4,486,333
involving the preliminary formation of a gas foam in order
to provide a sufficiently large surface area on which the
biliquid foam can subsequently be formed. It has been found
that the prior formation of a gas foam is not required to
manufacture a stable biliquid foam, provided that a suitable
stirring mechanism is provided in the manufacturing vessel.
Such an apparatus comprises a tank provided with a stirrer
in which the stirrer blade breaks the interface between the
liquid and air and provides low shear mixing throughout the
whole of the volume of the biliquid foam throughout the
whole of the production process. A delivery device is
provided through which the internal phase of the dispersion,
which in this case comprises at least two liquids, is
delivered to the tank. The design of the delivery device ia
such that the rate of addition of the internal phase fluid
can be controlled'and varied during the production process.
A feature of the production process is that the internal
phase is added to the stirred external phase slowly at first
until sufficient droplets have been formed to constitute a
large, additional surface area for the more rapid formation
of new droplets. At this point, the rate of addition of the
internal phase may be increased.
The production process preferably comprises the following
steps:
1. The addition of one or more chosen surfactants to
one or other or both phases (as previously
determined by experiment).
2. The charging of the external phase into the bottom
of a process vessel.
3. The incorporation of the starrer into the vessel
so that it stirs the surface of the external
phase.
4. Adjustment of the stirrer speed to a previously
determined level.
5. The slow addition of the internal phase whilst
continuing to stir at the prescribed speed.
6. The speeding up of the rate of addition of the
internal phase once a prescribed amount (usually
between 5% and 10% of the total amount to be
added) has been added.
The stirring rate and the rate of addition of the internal
phase are variables, the values of which depend upon the
detailed design of the manufacturing plant (in particular,
the ratio of tank diameter to impeller diameter), the
physico-chemical properties of the internal phase and the
nature and concentrations of the chosen surfactants. These
can all be pre-determined by laboratory or pilot plant
experiment.
It will be understood by those skilled in the art that other
manufacturing methods for the polyaphron dispersion may be
used, as appropriate.
Colloidal gas aphrons are known in the art as, for example,
described by Sebba in "Foams and biliquid foams, aphrons",
1987. ISBN: 0471916854. Such colloidal gas aphrons
containing a gas such as air, nitrogen, carbon dioxide or a
reactive gas such as oxygen or hydrogen may constitute the
internal phase of the current invention. Colloidal 'gas
aphrons may be prepared as described in the stated reference
or by a sparging process, which may include the use of a
porous material through, which the gas is injected into a
suitably prepared water insoluble medium containing
surfactants. Alternatively, the gas may be injected into a
water-insoluble medium having a sufficient viscosity and or
yield value to prevent the agglomeration of individual gas
bubbles until the polyaphron dispersion of the present
invention is fully prepared.
In one application of the invention, there is produced a
food product such as a rich and creamy yoghurt type food
product wherein the external phase is aqueous and may
contain water soluble flavours, fruit extracts or particles
of fruit, water-soluble colouring agents and the like,
whereas the internal phase comprises an edible oil
(preferably non fattening) such as olive oil or sunflower
oil or avocado oil and an internal 'water phase which may be
aa high as 80% of the total internal phase concentration.
The total concentration of the complex internal phase may be
as high as 95% but is preferably about 90%, at which
concentration the product has a rich and creamy appearance
and-taste because of the high concentration of the internal
phase. In this manner is produced a low fat, high water
content food product containing about 72 - 80% water phase.
In another application there is produced a self-heating
preparation consisting of two or more chemicals capable of
undergoing an exothermic reaction when mixed where at least
two of the reactants are water-soluble. In this
application, at least one reactant is contained in the
internal phase and another in the external continuous phase.
The composition is such that the reacts do not mix and do
not, therefore, undergo an exothermic reaction until the two
aqueous phases are mixed during use. By this means, a selfheating
composition such as a cosmetic or pharmaceutical
composition, preferably in the form of a cream, may be
produced providing the reactants are not harmful to human
skin.
In a further application there is produced a composition
comprising two or more separate and different complex
polyaphrons comprising different internal phases dispersed
into the same liquid external phase. The external phase
may or may not be polymerised at a later stage. This system
could give rise to a multi functional product, whereby each
complex bi-liquid foam may contain a different active to
perform different tasks upon a different stress. Thus a
aingle formulation could be provided, for example having the
ability to change colour permanently once cooled, and a
different colour once heated and containing two incompatible
drug systems.
We have surprisingly found that at least one of the internal
liquid phases ia in equilibrium with the external phase such
that if the external phase is diluted, the internal phase
will begin to release active components contained in it at a
controlled rate. Thus, for example compositions containing
a hydrogen bonded external phase and at least one hydrogen
bonded internal phase can be caused to release an active
such as an enzyme from the internal phase by diluting the
external phase.
The composition of the present invention can be made, for
example, at room temperature and low shear and can thus be
very useful for enzymes or condition sensitive actives.
Modification of the viscosity profiles of the internal
phases and external phase by viscosity modifiers, known to
those skilled in the art, can be adjusted to influence the
droplet size and aphron strength during manufacture.
Further examples of use of reacting species separated in the
two aqueous phases until used include the formulation of
adhesive products wherein at least one hydrogen bonded phase
such as an aqueous phase contains a suitable adhesive
precursor such as a polymer and the other at least one
initiator species.
In a similar manner, the present invention allows there to
be used a colour change reaction (such as, for example, a
reaction using a pH sensitive dye, such as bromothymol blue
on the one hand and an acid or base solution on the other),
In yet a further application, the two aqueous phases may be
used to keep separate two materials which are mutually
incompatible until the moment of use. An example would be
the delivery vehicle for two drugs which would precipitate
out of solution when combined together-(as might be the
case, for example, is one drug was anionic in character and
the other cationic) .
The present invention is now further described in the
following Examples.
EXAMPLES
PREPARATION OF WATER IN OIL EMULSIONS
Preparation Example 1
A *water in oil" emulsion was prepared from the following
ingredients.
Ingredients Weight (g) %
Aqueous Phase
1% Sodium chloride in 50 50
demineralised water
Oil Phase
Dow Corning 5200 formulation aid 4.0 4.0
Medium viscosity white mineral oil 46 46
Total 100 100
The water in oil emulsion was prepared in a 250ml Beaker
with a diameter of 6.5cm. The aqueous phaae.was added to
the oil phase while being stirred at approximately 2000rpm
for 15 minutes with an impeller of diameter 5.5cm.
Preparation Example 2
A "water in oil" emulsion was prepared from the following
ingredients.
Ingredients Weight (g) %
Aqueous Phase
1% Sodium chloride in 100 50.0
detnineralised water
Oil Phase
Dow Corning S225C formulation aid 7.40 3.70
Phenyl trimethicone 92.6 4N6.3
Total 200 100
The water in oil emulsion was prepared in a 500ml Beaker
with a diameter of 6.5cm. The aqueous phase was added to
the oil phase while being stirred at approximately 4500rpm
for 10 minutes with a rotor stator.
Preparation of Complex Biliquid foams
Example 1
Ingredients Weight (g) %
Preparation 1 90 . 90
PEG 40 Castor Oil 1.0 1.0
Demineraliaed water 8.9 8.9
Methyldibromo Glutaronitrile 0.1 0.1
(and) Phenoxyethanol (preservative)
Total ' 100 100
The PEG 40 castor oil and the preservative were dissolved
into the water in a 250ml Beaker. Preparation 1 was then
added to the beaker dropwise, at first, with a stirrer speed
of 350rpm and an impeller of diameter 5.5cm. As more of
preparation 1 was added, the impeller speed was reduced and
the rate of addition increased, until total addition of
preparation 1 and a stirrer speed of 15 Orpin.
Example 2
Ingredients Weight (g)
Preparation 2 180 90
Laureth-7 1.8 .0.9
Sodium Laureth sulphate 0.2. 0.1
Demineralised water 17.8 8.9
Diazolidinyl urea, iodopropynyl 0.2 0.1
butylcarb.amate, Propylene glycol (preservative)
Total 200 100
The Laureth-7, sodium laureth sulphate and preservative were added to the water and mixed, gently in a 500ml beaker with a flat bladed stirrer. Preparation 2 was then added to the beaker dropwise, at first, with a stirrer speed of 200rpm. The stirrer speed was reduced as more of preparation 2 was added.

We Claim:
1. A polyaphron dispersion comprising an external phase and polyaphrons having an internal phase, the internal phase comprising (i) a first phase which is liquid and (ii) a second phase which is liquid or gaseous.
2. A polyaphron dispersion as claimed in claim 1 wherein the external phase is aqueous.
3. A polyaphron dispersion as claimed in claim 1 or 2 wherein the internal phase comprises at least two liquid phases.
4. A polyaphron dispersion as claimed in any one of claims 1 to 3 wherein the internal phase comprises an aqueous phase and a non-aqueous phase.
5. A polyaphron dispersion as claimed in claim 4 wherein the internal phase comprises a single aqueous phase and a single non-aqueous phase.
6. A polyaphron dispersion as claimed in any one of claims 1 to 4 wherein the internal phase comprises an emulsion.
7. A polyaphron dispersion as claimed in any one of claims 1 to 4 wherein the internal phase comprises polyaphrons.
8. A polyaphron dispersion as claimed in any one of the preceding claims wherein the internal phase additionally comprises a solid phase.
9. A polyaphron dispersion as claimed in any one of the preceding claims wherein the internal phase comprises at least 60 wt% of an aqueous phase.
10. A polyaphron dispersion as claimed in any one of the preceding claims wherein a component of the external phase is capable of reacting with a component of the internal phase upon the polyaphrons being disrupted or destroyed.

11. A process for preparing a polyaphron dispersion as claimed in any one of the preceding claims which comprises:
a. forming the internal phase; and
b. forming a polyaphron dispersion comprising an external phase and the internal phase prepared in step a.