Note: Descriptions are shown in the official language in which they were submitted.
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Soap Composition
Field of Invention
The present invention relates to a soap composition, and in particular to a
transparent or translucent soap composition.
Background
A wide range of soap compositions, used to make soap bars or tablets,
particularly
toilet soap tablets for personal washing, are known in the art. There is a
continual
need to improve the properties of the soap composition or soap tablet, such as
ability to lather, hardness, reduction in. mush (softening when left standing
in water),
feel and moisturisation. It can be difficult to obtain a soap composition
having all or
most of the aforementioned properties. Soap compositions can be either opaque,
translucent or transparent, and it can be particularly difficult to achieve
the
aforementioned properties whilst maintaining or improving the translucency or
transparency of a soap composition.
Prior Art
GB-1417183 and GB-1487552 both disclose detergent bars containing a water
soluble lactate salt, which together with a water soluble glutamate salt, act
as
moisturising components.
US-4297230 is directed to a transparent soap bar containing potassium soap and
chloride anions.
WO 99/42554 is directed to a soap bar containing 30-60% by weight of alkali
metal
3o salt of a defined fatty acid mixture, 3-35% by weight of fatty acid, 2-25%
by weight of
structurant and the remainder water.
US-6218348 claims a process of making a soap bar which contains polyalkylene
glycol having a molecular weight in the range from 400 to 25,000.
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Summary of the Invention
We have now surprisingly discovered a soap composition which overcomes or
significantly reduces at least one of the aforementioned problems.
Accordingly, the present invention provides a soap composition comprising (i)
50 to
90% by weight of alkali metal soap of C8 C24 fatty acids, (ii) 3 to 25% by
weight of at
least one polyol, (iii) 0.1 to 10% by weight of the potassium salt of a
carboxylic acid
and/or hydroxy carboxylic acid having 6 or less carbon atoms, and (iv) 5 to
25% by
weight of water.
The invention also provides a soap tablet or bar comprising (i) 50 to 90% by
weight
of alkali metal.soap Of Cg-C~4 fatty acids, (ii) 3 to 25% by weight of at
least one
polyol, (iii) 0.1 to 10% by weight of the potassium salt of a carboxylic acid
and/or
hydroxy carboxylic acid having 6 or less carbon atoms, and (iv) 5 to 25% by
weight
of water.
The invention further provides the use of a soap composition comprising (i) 50
to
90% by weight of alkali metal soap Of C$-C24 fatty acids, (ii) 3 to 25% by
weight of at
least one polyol, (iii) 0.1 to 10% by weight of the potassium salt of a
carboxylic acid
and/or hydroxy carboxylic acid having 6 or less carbon atoms, and (iv) 5 to
25% by
weight of water, to form a transparent and/or translucent soap tablet or bar.
The soap composition according to the present invention may be opaque,
translucent or transparent, and is preferably transparent or translucent. By
"opaque"
is meant having the property of preventing the transmission of light so that
objects
placed behind an opaque soap cannot be seen. By "transparent" is meant having
the property of transmitting light without appreciable scattering, so that
objects
placed behind a transparent soap are entirely visible and can easily be
discerned.
By "translucent" is meant having the property of allowing light to pass
through
partially or diffusely so that objects placed behind a translucent soap tablet
cannot
clearly be distinguished (therefore also called partly transparent or semi-
transparent). The amount of light transmitted is, of course, dependent upon
the
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thickness of the soap, and in the present context soap of 20 mm thickness was
used
as standard.
The soap composition preferably comprises in the range from 55 to 85%, more
preferably 60 to 80%, particularly 63 to 75%, and especially 65 to 70% by
weight of
alkali metal soap of C8-C24 fatty acids, based on the total weight of the
composition,
Fatty acids, suitable for use herein, can be obtained from natural sources
such as,
for instance, plant or animal esters (eg palm oil, palm kernel oil, coconut
ail, babassu
oil, soybean oil, castor oil, tallow, whale or fish oils, grease, lard, and
mixtures
thereof). The fatty acids can also be synthetically prepared (eg, by the
oxidation of
petroleum, or by the hydrogenation of carbon monoxide by the Fischer-Tropsch
process). Resin acids, such as those present in tall oil, may be used.
Naphthenic
acids are also suitable.
Alkali metal soaps, such as sodium and potassium soaps, can be made by direct
saponification of the fats and oils or by the neutralisation of the free fatty
acids which
are prepared in a separate manufacturing process. Particularly preferred in
the
present invention are the sodium soaps, but small amounts, suitably less than
10%,
preferably less than 8%, more preferably less than 5%, and particularly less
than 1
by weight of non-sodium soaps, such as potassium soaps, magnesium soaps,
ammonium soaps and/or alkanolamine soaps, and especially potassium soaps, may
also be present. In a particularly preferred embodiment of the invention, the
soap
composition comprises substantially no potassium soaps. Alkali metal salts of
mixtures of fatty acids derived from palm oil and palm kernel oil, eg sodium
palm oil
soaps and sodium palm kernel oil soaps, are preferred.
The term "palm oil" is used herein in to mean fatty acid mixtures having an
approximate by weight carbon chain length distribution of 2.5% C,4, 29% C,6,
23%
C,B, 2% palmitoleic, 41.5% oleic and 3% linoleic acids (the first three fatty
acids
listed being saturated). Other sources having similar carbon chain length
distributions, such as fatty acids derived from various tallows and lard, may
also be
used instead of or in addition to palm oil fatty acids.
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The term "palm kernel oil" is used herein to mean fatty acid mixtures having
an
approximate by weight carbon chain length distribution of: 8% C8, 7%
C,°, 48% C,Z,
17% C,4, 8% C,6, 2% C,B, 7% oleic and 2% linoleic acids (the first six fatty
acids
listed being saturated). Other sources having similar carbon chain length
distributions, such as coconut oil and babassu kernel oil, may also be used
instead
of or in addition to palm kernel oil fatty acids.
The soap component preferably comprises in the range from (i) 10 to 98%, more
preferably 40 to 95%, particularly 60 to 90%, and especially 75 to 85% by
weight of
soaps having in the range from 16 to 20 carbon atoms (preferably derived from
palm
oil fatty acids), and (ii) 2 to 90%, more preferably 5 to 60%, particularly 10
to 40%,
and especially 15 to 25% by weight of soaps having in the range from 8 to 14
carbon
atoms (preferably derived from palm kernel oil fatty acids and/or coconut
oil).
The soap composition may also comprise a minor amount of one or more synthetic
or non-soap detergents, which may be of the anionic, nonionic, amphoteric or
cationic type, or mixtures thereof. Preferably less than 25%, more preferably
less
than 15%, particularly less than 10%, and especially less than 5% by weight,
based
on the total weight of the composition is non-soap detergent. In a
particularly
preferred embodiment of the invention, the soap composition comprises
substantially no non-soap detergent.
Suitable non-soap detergents include (i) anionic detergents such as the alkyl
aryl
sulphonates, such as C,°-C22 alkyl benzene sulphonates; the olefin
sulphonate salts;
the C,°-C~° paraffin sulphonate salts; the C$-C2~ fatty acyl
sarcosinates; the C8 C22
fatty acyl isethionates and C8 C22 fatty acyl N-methyl taurides; and C8 C22
fatty acid
alkanol amides; the C$-CZ° alkyl sulphates and the sulphate esters of
the reaction
product of 1-20 moles of alkylene oxide with 2 to 5 carbon atoms and a
saturated
straight-or branched-chain aliphatic monohydric C8-C~° alcohol, such as
sodium
lauryl ether sulphate, (ii) nonionic detergents such as the reaction products
of 1-50
mole of C2-C4 alkylene oxide with C8 Ca° primary or secondary alkanols,
with dihydric
alcohols, and the like, (iii) amphoteric detergents such as the alkyl-~i-
iminodipropionates, and long-chain imidazole derivatives, such as
imidazolinium
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betaines, and (iv) cationic detergents such as quaternary ammonium compounds,
such as stearyl dimethyl benzyl ammonium chloride, and the like.
The concentration of polyols or polyhydric alcohols in the soap composition
according to the present invention is preferably in the range from 5 to 20%,
more
preferably 8 to 18%, particularly 10 to 16%, and especially 12 to 14% by
weight
based on the total weight of the composition.
The molecular weight of the polyol is preferably less than 300, more
preferably in the
range from 50 to 270, particularly 80 to 220, and especially 90 to 200.
Suitable polyols include sugar alcohols such as sorbitol, mannitol;
(poly)glycols such
as (poly)ethylene glycol, (poly)propylene glycol; and other C3 C6 polyols
containing
from 3 to 6 hydroxyl groups such as trimethylolpropane, trimethylolethane, and
glycerine. Sugar alcohols, particularly sorbitol, are preferred. Mixtures of
any two or
more of the aforementioned materials may also be employed.
In a preferred embodiment, the soap composition according to the present
invention
preferably comprises a polyol mixture of a sugar alcohol, particularly
sorbitol, and
glycerine. The concentration of sugar alcohol in the soap composition
according to
2o the present invention is preferably in the range from 1 to 10%, more
preferably 3 to
8%, particularly 4 to 7%, and especially 5 to 6% by weight based on the total
weight
of the composition. The concentration of glycerine in the soap composition is
preferably in the range from 1 to 15%, more preferably 3 to 12%, particularly
5 to
10%, and especially 6 to 8% by weight based on the total weight of the
composition.
The specific combination of sugar alcohol, particularly sorbitol, and
glycerine polyol
mixture reduces the formation of large opaque white crystals during a normal
soap
neutralisation process, enabling a transparent or translucent product to be
processed on a standard soap finishing line.
The potassium salt of a carboxylic acid and/or hydroxy carboxylic acid having
6 or
less carbon atoms, preferably comprises in the range from 1 to 5, more
preferably 2
to 4, and especially 3 carbon atoms. The potassium salt is preferably the salt
of a
hydroxy carboxylic acid, and preferably comprises 1 or 2, and more preferably
1
carboxyl group(s). The potassium salt also preferably comprises 1 or 2, and
more
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preferably 1 hydroxyl group(s). Suitable materials include the potassium salts
of
formic acid, lactic acid, acetic acid, citric acid, tartaric acid, malic acid,
and alpha
hydroxybutyric acid. In a particularly preferred embodiment of the invention,
potassium lactate is employed.
The concentration of the potassium salt of a carboxylic acid and/or hydroxy
carboxylic acid having 6 or less carbon atoms, preferably potassium lactate,
in the
soap composition according to the present invention is preferably in the range
from
0.3 to 8%, more preferably 0.6 to 6%, particularly 1 to 4%, and especially 1.5
to 2%
1 o by weight based on the total weight of the composition. The presence of
the
aforementioned potassium salt can improve one or more of the translucency,
hardness, lathering, mushing, feel and moisturizing properties of the soap
composition and finished soap bar or tablet.
The concentration of water in the soap composition according to the present
invention is preferably in the range from 10 to 22%, more preferably 12 to
20%,
particularly 14 to 19%, and especially 16 to 1 ~% by weight based on the total
weight
of the composition.
2o The soap composition according to the present invention may optionally
contain free
fatty acids, in addition to the neutralized fatty acids of the actual soap
component.
Preferred free fatty acids are the same types of fatty acids, as defined
above, which
are used to form the soap component, and therefore generally contain from 8 to
20
carbon atoms. The soap composition preferably comprises in the range from 0.5
to
10%, more preferably 1 to 5%, particularly 1.5 to 3%, and especially 2 to 2.5%
by
weight based on the total weight of the composition, of free fatty acids. The
presence of the free fatty acids can improve both the mildness and refitting
properties of the soap composition on the skin.
The soap composition suitably comprises less than 0.5%, preferably less than
0.25%, more preferably less than 0.2%, particularly less than 0.15%, and
especially
less than 0.1% by weight based on the total weight of the composition, of
sodium
chloride. In a particularly preferred embodiment of the invention, the soap
composition comprises substantially no sodium chloride. The presence of sodium
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chloride at such low concentrations, or the complete absence thereof, in a
soap
composition according to the present invention, can result in improved foaming
properties, and faster translucency development in the soap finishing process.
The soap composition may also contain effective amounts of other materials or
functional additives. Suitable functional additives include perfumes,
antioxidants,
such as tocopherols BHA, BHT and the like; chelating agents, such as EDTA and
the like; emulsifiers such as polyglycerol esters, eg polyglycerol
monostearate;
colouring agents; deodorants; dyes; emollients and skin conditioners, such as
dimerized fatty acids, lanolin, cold cream, mineral oil, sorbitan esters,
isopropyl
myristate; enzymes; foam stabilizers; germicides; lathering agents;
moisturizers;
optical brighteners; dyes; pearlescers; sequestering agents; stabilizers;
superfatting
agents; UV absorbers; and mixtures of any two or more of these materials.
The functional additives may be used in any desired quantity to effect the
desired
functional characteristics, and usually minor amounts in the range from 0.01
to 5%
by weight based on the total weight of the composition are used. For example,
if
present, (i) anti-bacterial agents and sanitizers generally comprise in the
range from
0.5 to 4% by weight, (ii) emollients and skin conditioning agents generally
comprise
in the range from 0.5 to about 5% by weight, and (iii) perfumes, dyes and
coloring
agents comprise in the range from 0.2 to about 5% by weight, all based on the
total
weight of the composition.
In a preferred embodiment, the soap composition according to the present
invention
is translucent, preferably having a translucency value, measured as described
herein, of greater than 15%, more preferably in the range from 20 to 80%,
particularly 30 to 70%, and especially 40 to 60%.
fn addition, the soap composition preferably has a total mush value, measured
as
described herein, of less than 30, more preferably in the range from 5 to 25,
particularly 10 to 20, and especially 15 to 20 g/50 cm2.
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The soap composition preferably has,.a lather volume, measured as described
herein, of greater than 30, more preferably in the range from 40 to 150,
particularly
50 to 120, and especially 60 to 100 ml.
The soap composition according to the present invention may be converted into
flakes, noodles, pellets, or any other suitable form or shape by methods known
in
the art. The converted soap composition, preferably in the form of noodles,
can be
mixed with other components, such as perfumes, colorants and other functional
additives in an amalgamator for at least 5 minutes. The resultant mixture may
be
plodded or extruded into an endless bar that, after cutting into billets, can
be
stamped into a final soap tablet.
The invention is illustrated by the following non-limiting examples.
The following test procedures were employed;
(i) Translucency
Translucency was evaluated by measuring the light transmission of a slice of
soap
having a thickness of 20 mm using a reflectometer according to Dr B Lange,
Type
LMG 008. The result is expressed as a percentage of the light transmission of
a
matted glass standard. The transmission of the glass standard compared to air
was
8.3% and the transmission of this standard was taken as 100%.
Translucency: >40% = excellent
20 to 40% = good
<20% = moderate
ii Mush
Mush was determined by immersing a well defined portion of a soap tablet
(approximate weight = 45 g, and approximate surface area = 70 cm2) in
demineralised water at 20°C for 2 hours. Before immersion, the weight
of the soap
block was measured (= W,). After removal from the water, excess water was
3o allowed to drip from the soap block for 1 minute, and the weight of the
soap block
was measured again (= W~). All of the mush was scraped off the soap block with
a
plastic spatula and the soap block again reweighed (= W3). The amount of mush
is
expressed in 3 different parameters, which were calculated according to the
following equations (based on an immersed surface area of 50 cm2);
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Total mush - (WZ-W3)x50/immersed area
Water uptake = (W,-WZ)x50/immersed area
Mushed soap = (W,-W3)x50/immersed area
Total mush is a measure of the resistance against slime formation when the
soap
bar is in contact with water. Water uptake and mushed soap quantity is an
indication
of measure of the structure of the mush.
Total mush: <15 g/50 cm~ = excellent
15-25 g/50 cm2 = good
>25 g/50 cm2 = moderate
iii Lather
Lather volume was measured by using a handwash method which closely
approximates normal consumer habits. The test was carried out using a pair of
surgeon's disposable latex gloves which were rinsed to remove talc. The soap
tablets (approximate weight of tablets = 85 g, dimensions 8 cm x 5.5 cm x 2.5
cm
(cushion model)) to be tested were washed for 10 minutes before the test by
twisting
the tablet 20 times through 180° under running water at approximately
14°C. The
soap tablet was then immersed in water at a temperature of 20°C,
twisted 15 times
through 180°, and placed back in the soap dish. Lather was than
generated by
rubbing the tips of the fingers of one hand against the palm of the other hand
10
times. As much lather as possible was removed from the hands by alternately
gripping one hand with the other and forcing lather towards the fingertips.
Accumulated lather was dislodged into a 150 ml beaker calibrated at 10 ml
intervals.
The whole procedure was repeated twice and the total volume of lather recorded
as
lather volume. Before measuring the lather volume, the lather was gently
stirred to
release large air pockets. The test was done in triplicate using 3 different
soap
tablets made from the same composition. Lather volume was calculated as an
average value of the three results.
Lather volume: >100 ml = excellent
50-100 ml = good
<50 ml = moderate
(iv) Rate of wear
The soap tablets used in the lather volume test were weighed both before and
after
the test. Weighing after the test was done after the soap had dried at ambient
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temperature (approximately 23°C) for at least for 24 hours. The weight
difference
was recorded as rate of wear and expressed in grams.
Rate of Wear: <3 g = excellent
3-5 g = good
5 >5 g = moderate
(v) Hardness
A "cheese wire" with an attached weight was cut into the corner of a soap
tablet,
until an equilibrium position was reached. The area over which the force acts
increases as the depth of the cut increases, and therefore the stress being
exerted
10 decreases until it is exactly balanced by the resistance of the soap and
the wire
stops moving. The stress at that point is equal to the yield stress of the
soap. The
time taken to reach this point was 60 seconds. After this time the weight was
removed and the length of the cut measured. The yield stress was calculated
from
the semi-empirical formula:
Yield stress = 3/8(Wx98.1 )/LxD N/mz
where L and D are the length of the cut and diameter of the wire in cm. W is
the
weight applied on the wire to obtain the cut and is given in grams.
Hardness: >7x105 Nlm2 = hard
>4<7x105 N/m2 = moderate
< 4x105 N/m2 = soft
Hardness is strongly dependent upon temperature and moisture content, and
therefore measurements need to be performed under strictly controlled
conditions of
temperature and moisture.
Example 1
A soap formulation was prepared containing 53.5% by weight of sodium soap of
palm oil fatty acids, 13.5% by weight of sodium soap of palm kernel oil fatty
acids,
2% by weight of free fatty acids, 7.5% by weight of glycerin, 5% by weight of
sorbitol,
1.5% by weight of potassium lactate, and 17% by weight of water.
The soap composition was passed 6 times through a laboratory Mazzoni M-100
duplex refiner/plodder with refining sieves of 0.5 mm and provided with a
rectangular
extrusion die of 45 mm x 19 mm at the end of the conical outlet. The cylinder
temperature was set at 30°C and the cone temperature was 57°C.
The speed of the
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plodder screw was fixed at 13 rpm. Soap tablets were made from the soap
composition produced after each passage through the plodder. The translucency
of
each cycle soap tablet was measured from the corresponding billets and the
results
are given in Table 1.
The soap tablet made from the soap composition produced after 6 passages
through the plodder, was subjected to the test procedures described herein and
the
results are given in Table 2.
1 o Example 2
This is a comparative example not according to the present invention. The
procedure of Example 1 was repeated except that the soap formulation contained
no
potassium lactate. The results are given in Tables 1 and 2.
Table 1
Translucency of Soap Tablet (%)
Cycle Example 1 Example 2 (Comp.)
1 4.4 4.0
2 6.6 4.4
3 12.9 6.9
4 27.2 13.4
5 42.2 29.5
6 54.1 52.1
Table 2
Properties Example 1 Example 2 (Comp
(i) Translucency (%) 54.1 52.1
(ii) Mush
Total mush (g/50 cm~) 21.9 29.2
3o Water uptake (g/50 18.8 24.7
cm~)
Mushed soap (g/50 cm2) 3.1 4.6
(iii) Lather (ml) 58 48
(iv) Rate of wear (g) 5.3 7.7
(v) Hardness (x105 N/m2)6.6 4.7
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Example 3
The procedure of Example 1 was repeated except that 1.5% by weight based on
the
total weight of the composition of perfume oil (Green Apple (ex Fragrance Oils
Ltd))
was added to the soap composition. The results are given in Tables 3 and 4.
Example 4
This is a comparative example not according to the present invention. The
procedure of Example 2 was repeated except that 1.5% by weight based on the
total
weight of the composition of perfume oil (Green Apple (ex Fragrance Oils)) was
added to the soap composition. The results are given in Tables 3 and 4.
T..L.1... n
Translucency of Tablet (%)
Soap
Cycle Example 3 Example 4 (Comp.)
1 6.6 2.0
2 8.3 4.5
3 17.8 9.0
4 35.2 17.0
5 41.4 34.5
6 50.9 43.7
Table 4
Properties Example 3 Example 4 (Comp.)
(i) Translucency (%) 50.9 43.7
(ii) Mush
Total mush (g150 cm2) 17.1 20.0
Water uptake (g/50 cm~)12.2 14.9
Mushed soap (g/50 cm~) 4.9 5.1
(iii) Lather (ml) 87 40
(iv) Rate of wear 5.3 4.6
(g)
(v) Hardness (x105 N/m2)5.7 4.4
The above examples illustrate the improved properties of a soap composition
according to the present invention.
