Technical Field
The present invention relates to an improved mild transparent solid soap composition
including soap bar. The invention also relates to a process of making a mild transparent
solid soap including soap bar comprising a combination of a hydrotrope and soft oil and
its derivatives using a conventional process as well as cast route.
Background and prior art
Traditionally, soaps have been used for cleansing purposes. For effective cleansing,
excess of cleansers and surfactants are used. Due to this, the soaps are invariably harsh on
the skin which eventually results into early aging of skin giving rise to the need for mild
skin cleansing compositions which would act gentle on the skin. US Patent no. 4901851.
US Patent no. 5296159 and US Patent no. 5312559 ha\e addressed this problem and have
disclosed mild soap formulation. However, in case of mild soaps the use life of the soap
has been invariably compromised. Even though use of moisturizers and other benefit
agents that impart mildness to the soap is gentle on the skin, it has undesirable effect on
the bar hardness thus reducing the use life of the soap.
Also, most of the mild soaps in the market are opaque, It is a known fact that translucent
and transparent soaps have for many years held an aesthetic appeal to the consumers.
Thus there exist a need for solid soap compositions that combine all the four attributes in
one i.e. transparency, mildness, bar hardness and cleansing.
US Patent no. 4273684 discloses a transparent detergent bar possessing good foaming
power and detergenc) in hard water, formulated consisting essentially of at least one salt
of a N-long chain acyl 1-optically active acidic amino acid neutralized with a basic amino
acid. Also US Patent no.6730643 includes numerous teachings covering the preparation
and manufacture of transparent soaps through conventional as well as cast methods.
These include the use of 12HSA with and without alcohol, use of monohydric and
dihydric alcohols, use of castor oil. tri-ethanolamines etc. However despite the benefits
offered by hydrotropes. there have been no efforts made in the past to manufacture
personal care transparent soap bar using Hydrotropes. Hydrotropes ha\e been widely used
in liquid cleansing formulations. US Patent no. 6218345 discloses a liquid cleansing
composition which imparts mildness and cleansing attributes to the skin.
US 6479442 teaches liquid detergent compositions containing from about 1% to about
90% of a surfactant selected from anionic, nonionic, and amphoteric surfactants and
mixtures thereof are prepared with a hydrotrope that is a mixture of an alcohol ethoxylate
and a polyethylene glycol ether of glycerin. The hydrotrope provides increased foam
generation. The use of a polyethylene glycol ether of glycerin and an alpha hydroxy acid
in a liquid detergent composition further promotes skin improvement and maintains
healthy skin of the person using the detergent. The composition may comprise soybean oil
as well as foam enhancers. US6130194 teaches granular detergent composition which
includes a hydrotrope such a those commonly used in liquid detergents. It has been
surprisingly found that by enrobing the crystalline calcium carbonate builder with a
hydrotrope, the crystalline calcium carbonate performs well, even when included at
relatively large median particle sizes. Thus there is teaching of granular detergent with
hydrotopes.
However there is no teaching as to the transparent solid soap with mild ness properties
comprising hydrotopes
The present inventors have found that by combining hydrotropes such as sodium cumene
sulphonate and one or more oils such as castor, soybean, sunflower, coconut etc a
transparent solid soap is achieved which has high mildness properties . Thus, this
application disclosed the composition of mild transparent solid soap with four desirable
attributes namely, transparency, mildness, stability and cleansing.
Objects of the present invention
The primary object of the invention is to provide a mild and highly transparent cleansing
solid soap coomprising a hydrotrope such as alkyl/aryl substituted aromatic sulfonates
and vegetable oils (soyabean, castor etc).
Another object of the invention is to provide the mild solid soap imparting attributes like
cleansing, mildness, stability and transparency.
A further object of the invention is to provide a process of manufacture the
aforementioned mild soap by the cast route.
Statement of invention
Thus according to one aspect of the present invention there is provided a transparent solid
soap composition comprising of cleansing agents, soluble and insoluble fatty acids,
hydrotropes, at least one vegetable oil,.
According to one aspect of the present invention there is provided a process of
manufacturing the transparent solid soap composition by the cast route.
Detailed description of the invention
The invention discloses a mild transparent solid soap composition comprising of
cleansing agents, soluble and insoluble fatty acids, hydrotropes, vegetable oil, , . The
present invention is achieves superior clarity in combination with mildness in presence of
oil/hydrotrope combination.
Further humectants, alkalis, preservatives, colouring agents, perfume and Botanicals may
be present.
Cleansing Agents:
The surface-active agent provides detergent properties to the personal wash rinse off
composition for cleansing the skin. The surface-active agent can be sodium salt of fatty
acid, fatty acid chain length ranging from C8 to CI8, with saturated, mono unsaturated
and poly unsaturated fatty acids. The preferred anionic surfactant or detergent includes
sodium laureth sulfate, sodium lauryl sulfate, disodium oleamido MEA sulfosuccinate,
disodium laureth sulfosuccinate, sodium lauroyl sarcosinate and mixtures thereof.
Preferably, the anionic surfactant is about 5 % by weight or weight percent (wt %) to
about 20 wt % of the total weight of the composition More preferably, the anionic
surfactant is about 10.00 wt % to about 15.00 wt %.
Amphoteric surfactants act as foam boosters and provide thickening and high foam
property to the personal wash rinse off composition. The preferred classes of amphoteric
surfactant are betaines and sultaines. The amphoteric surfactants used in this composition
should preferably be a mixture of sultaine and betaine. Most preferably, the amphoteric
surfactant used should be betaine.
The preferred betaine is cocamidopropyl betaine. Preferably, the total amount of
amphoteric surfactant used in this composition is about 0.25 wt % to about 5-wt % of the
total weight of the composition. More preferably, the total amount of amphoteric
surfactant is about 1.0 wt % to about 2.0 wt % of the total weight of the composition. In
the preferred embodiment, the amphoteric surfactant is about 1.2 wt % to about 1.6 wt %
betaine.
The personal wash rinse off composition, especially a soap, body wash or shower gel
composition may further have a non-ionic surfactant. The non-ionic surfactant is included
to augment the detersive properties of the composition and boost its cleansing action. The
non-ionic surfactant can be any non-ionic compound that has surfactant properties. The
preferred non-ionic surfactants include cocamide MEA, oleaimide MEA, and mixtures
thereof. Preferably, the non-ionic surfactant is about 1 wt % to about 10 wt % of the total
weight of the composition. More preferably, the total amount of the non-ionic surfactant
is about 2 wt % to about 6 wt % of the total weight of the composition.
A significant feature of one of the most preferred embodiments of the present invention is
the surfactant blend that includes sodium laureth sulfate, sodium lauryl sulfate, disodium
oleaimido MEA sulfosuccinate, all of which are anionic surfactant, cocamidopropyl
betaine, which is an amphoteric surfactant and cocamide MEA, which is a non-ionic
surfactant. Besides the surfactant blend, there should also be the nonionic surfactant alkyl
poly glucosides, preferably alkyl glucosides, more preferably alkyl chain length ranging
from C8 to CI6, precisely the alkyl chain length from C8 to CI2. In this most preferred
embodiment, the surfactant blend is about 5 wt % - 20-wt %, while the alkyl glucoside is
about 1.0 wt % to 5.0 wt% of the total weight of the composition.
Insoluble fatty Acids:
The fatty acids employed in making the soaps herein may contain about 6 to 22 or more,
preferably, about 8 to 18 carbon atoms, may be of animal, vegetable, or synthetic origin,
and may be saturated or unsaturated, and straight, mono- or poly-branched chain
hydrocarbon carboxylic acids. As merely illustrative of such acids, there may be
mentioned caproic, caprylic, capric, lauric, myristic, stearic, oleic, elaidic, isostearic,
palmitic, undecylenic, tridecylenic, pentadecylenic, 2-lower alkyl higher alkanoic or other
saturated or unsaturated fatty acids. Dicarboxylic acids may also be used, such as
dimerized linoleic acid. Other higher molecular weight acids as rosin or tall oil acid, e.g.
abietic acid, may be employed. Readily available commercial blends and mixtures of such
blends which may be used include distilled palm and palm kernel oil fatty acids, distilled
coconut oil fatty acids, hydrogenated tallow fatty acids, and commercial stearic acid.
Hydro tropes
The mild transparent solid soap composition disclosed may contain from about 1 to about
10 weight percent of a hydrotrope selected from the group consisting of sodium cumene
sufonate, sodium xylene sulfonate, potassium xylene sulfonate, ammonium xylene
sulfonate, sodium toluene sulfonate, potassium toluene sulfonate, ammonium toluene
sulfonate and combinations thereof, the most preferred hydrotrope being Sodium Cumene
Sulfonate. -
Vegetable oil:
Vegetable oils employed in making the soaps herein may contain sunflower oil, Soybean
oil, castor oil, corn oil, palm oil, almond oil, rice bran oil and palm oil among others. The
most preferred vegetable oil used in the disclosed composition is castor oil and soybean
oil. The vegetable oils are present in amount of from about 0.1% to about 10%
Humectants:
The bar soap composition includes a high level of humectant solvent to provide desired
skin-moisturization and mildness attributes and to provide a vehicle in which to solubilize
the fatty acid soap content of the bar soap. Suitable humectant solvent levels include from
about 38% to about 96%, preferably greater than 50%, more preferably between 50% and
about 96%, and most preferably between 50% and about 70%. Humectant solvents are
superb skin moisturizers. However, at extremely high levels, humectant solvents may tend
to reduce the foam production and contribute to the sweating phenomenon.
"Humectant solvents" include water-soluble organic polyols, such as glycerin, propylene
glycol, dipropylene glycol, butylene glycol, and ethylene glycol, 1,7-heptane-dioI,
polyethylene and propylene glycols of up to 8,000 molecular weight, and mono-C.sub.1-4
alkyl ethers thereof, sugar alcohols such as sorbitol, mono- di- and triethanolamine, 2-
amino-1-butanol, and mixtures thereof. Preferred humectant solvents are glycerin,
propylene glycol, butylene glycol, and sorbitol.
As previously discussed, the humectant solvent also provides a vehicle for solubilizing
the fatty acid soap content, in particular the insoluble fatty acid soap content, which is less
soluble in humectant solvent than is soluble fatty acid soap. The ratio of humectant
solvent to insoluble fatty acid soap preferably ranges from about 3:1 to about 23:1, more
preferably from about 4:1 to less than about 14:1.
Other ingredients
The mild transparent solid soap composition of the present invention can further include
one or more additives that are commonly used in such products. Such additives include a
a preservative, a fragrance, a colorant, benefit agents, botanicals, alkali and a pH adjuster.
Aqueous medium
Water is used as an aqueous carrier in the present invention. It helps in producing
optimum viscosity to the product. Water also helps in producing plasticity for the bar
soap.
Water is one of the most suitable and economical medium that can be used for this
composition. The present invention comprises from about 60% to about 90% by weight of
deionized water in case of the liquid formulation, more precisely about 70% to 80% by
weight of deionized water and about 5 % to 20 % by weight of deionized water in case of
solid formulations, more precisely 8 % to 12% by weight of deionized water for solid
formulations.
The fatty acids and selected oils, humectants were taken in a homogenizing/stirring
vessel and heated to about 70C. Alkali was dosed to neutralize the fatty acids and
saponify the oil. The hydrotrope was added subsequently., continuing the stirring for
about 1 hour. Selected surface active agents are then added and stirred continuously. The
temperature of the liquid was reduced to about 60C and fragrance oil was dosed. The
liquid was poured into moulds and cooled in a continuous manufacturing cooling tunnel
or in a deep freezer. After complete solidification the soap was taken out and stretch
wrapped and packed.
Experimental data:
In order to determine the effect of the disclosed composition in terms of conferring the
Mildness, bar hardness and transparency, several experiments were conducted. Solid
soaps A-F with compositions indicated in Table 1 was prepared using the cast route.

Transparency:
Transmittance measurements were carried out using a Minolta Spectrophotometer 3500.
After calibrating the spectrophotometer using a black and fully transparent plates for 0
and 100% transmittance at 700nm, a 1cm thickness soap block, prepared using a standard
mould was mounted on the path of the light source. Transmittance values were recorded
for samples A-F.
Mild ness:
In order to assess the property of mildness of the soaps, the corresponding protein damage
using standard Zein Test Method was used. About 0.3-0.5 gm of Zein protein (Fluka)
having molecular weight of about 25000-29000 is weighed accurately. Using the Zein so
weighed, prepare tablets using a tableting machine and record the tablet weights
individually.A 1% solution of Test formulations as the case may be is prepared with
distilled water.
The respective solution as mentioned above is taken in individual stoppered conical flasks
along with a tablet of Zein prepared as mentioned above. The flask containing the said
ingredients is kept in an orbital shaker @ 200 rpm for 2hrs at room temperature, allowing
the dissolution of the tablet by the surfactant/formulation. After completion of 2hrs, the
contents of the flask are filtered using a vacuum set up through a pre-weighed Whatman
No.41 or Whatman No.4 filter paper. The weight of undissolved tablet along with the
filter paper after drying overnight (constant weight at 45 deg C) is recorded and from the
initial tablet weight and final tablet weight, the percent Zein dissolved is calculated. The
lower the percentage dissolution of protein ( The Zein protein dissolution of l%Sodium
Lauryl sulphate is considered to be 100% damage)from the tablet due to its interaction
with soap solution, the milder the soap formulation.
Bar Hardness:
For bar hardness measurement, a standard Dial penetrometer was used. A standard
weight of 50 gm is placed on the load arm of the instrument. The solid soap of which the
hardness is to be measured is kept at the bottom of the penetration needle of the
instrument. The position of the needle is adjusted so as to just touch the surface of soap.
Care is to be taken that the dial pointer is at null point. The knob is pressed and released
after 30 seconds. The penetration level is evaluated by the pressing of the needle on the
surface of the soap. The Hardness Value is reported in mm, which is l/10thof the dial
reading. The lower the penetration value, higher is the hardness of the solid soap.
Observations:
All the soaps have been evaluated for their cleansing properties and were observed to
clean to the same degree as measured using an expert panel by established sensorial
protocols.

Note: During the development of this composition, it was observed that the absence of
humectants resulted in affected the transmittance value and hence the optical clarity of
the bar.
Castor and soya both improve transparency and mildness in presence of Sodium cumene
sulphonate. Based on the above data that has been reproduced in triplicate, it is clear that
a combination of hydrotrope and oil impart significantly improved transparency to bars
with comparable hardness( Samples B-F), while enhancing the mild property of the solid
soaps (Samples E&F).
Although the invention has been described with reference to specific embodiments, this
description is not meant to be construed in a limiting sense. Various modifications of the
disclosed embodiments, as well as alternate embodiments of the invention, will become
apparent to persons skilled in the art, upon reference to the description of the invention. It
is therefore contemplated that such modifications can be made without departing from the
spirit or scope of the present invention as defined.
We claim:
1. A transparent solid soap composition comprising cleansing agents, fatty acids,
hydrotropes and at least one vegetable oil.
2. The transparent solid soap composition as claimed in claim 1 wherein the
transparent solid soap composition is a mild transparent solid soap composition.
3. The transparent solid soap composition as claimed in claim 1 wherein the
hydrotrope selected from sodium cumene sufonate, sodium xylene sulfonate,
potassium xylene sulfonate, ammonium xylene sulfonate, sodium toluene
sulfonate, potassium toluene sulfonate, ammonium toluene sulfonate and
combinations thereof, preferably Sodium Cumene Sulfonate.
4. The transparent solid soap composition as claimed in claim 3 wherein the
hydrotope is present in amount of from about 1 to about 10 weight %.
5. The transparent solid soap composition as claimed in any one of preceding claims
wherein the vegetable oil is selected from sunflower oil, soybean oil, castor oil,
corn oil, palm oil, almond oil, rice bran oil, palm oil and mixtures thereof.
6. The transparent solid soap composition as claimed in claim 5 wherein the
vegetable oil is selected from castor oil, soybean oil and mixture thereof.
7. The transparent solid soap composition as claimed in claim 5 wherein the amount
of the at least one vegetable oil is from about 0.1% to about 10% by weight.
8. The transparent solid soap composition as claimed in any one of preceding claims
wherein the fatty acid is selected from those having 6 to 22 or more, preferably,
about 8 to 18 carbon atoms, natural o, or synthetic origin, and may be saturated or
unsaturated, and straight, mono- or poly-branched chain hydrocarbon carboxylic
acids.
9. The transparent solid soap composition as claimed in claim 8 wherein the fatty
acid is selected from caproic, caprylic, capric, lauric, myristic, stearic, oleic,
elaidic, isostearic, palmitic, undecylenic, tridecylenic, pentadecylenic, 2-lower
alkyl higher alkanoic or other saturated or unsaturated fatty acids, dicarboxylic
,higher molecular weight acids and blends thereof.
10. The transparent solid soap composition as claimed in any one of preceding claims
wherein the cleansing agent is selected from anionic, amphoteric, non ionic
surfactants and blends thereof.
11. The transparent solid soap composition as claimed in claim 10 wherein the anionic
surfactant is selected form sodium laureth sulfate, sodium lauryl sulfate, disodium
oleamido MEA sulfosuccinate, disodium laureth sulfosuccinate, sodium lauroyl
sarcosinate and mixtures thereof
12. The transparent solid soap composition as claimed in any one of claims 8 or 9
wherein the anionic surfactant is present in an amount of about 5 wt % to about 20
wt % of the total weight of the composition., preferably, about 10.00 wt % to
about 15.00wt%.
13. The transparent solid soap as claimed in claim any preceding claim wherein the
amphoteric surfactant are selected from betaines and sultaines.
14. The transparent solid soap as claimed in claim 12 wherein the amount of
amphoteric surfactant is about 0.25 wt % to about 5wt %, preferably about 1.0 wt
% to about 2.0 wt % more preferably about 1.2 wt % to about 1.6 wt % of the total
weight of the composition .
15. The transparent soap as claimed in any one of preceding claim wherein the non-
ionic surfactants are selected from cocamide MEA, oleaimide MEA, and mixtures
thereof.
16. The transparent solid soap as claimed in claim 14 wherein the non-ionic
surfactant is present in amount of about 1 wt % to about 10 \vt % , preferably
about 2 wt % to about 6 wt % of the total weight of the composition.
17. The transparent solid soap composition as claimed in one of preceding claims
optionally comprising suitable humectant solvent levels selected from water-
soluble organic polyols, such as glycerin, propylene glycol, dipropylene glycol,
butylene glycol, and ethylene glycol, 1,7-heptane-diol, polyethylene and
propylene glycols of up to 8,000 molecular weight, and mono-C.sub.1-4 alkyl
ethers thereof, sugar alcohols such as sorbitol, mono- di- and triethanolamine, 2-
amino-1-butanol, and mixtures thereof.
18. The transparent solid soap composition as claimed in claim 16 wherein the
humectant solvents are selected from glycerin, propylene glycol, butylene glycol,
and sorbitol
19. The transparent solid soap composition as claimed in claim 16 or claim 17
wherein the amount of humectant is present from about 38% to about 96%,
preferably between 50% and about 96%, and most preferably between 50% and
about 70%.
20. The transparent solid soap composition as claimed in any one of preceding claim
optionally comprising additives selected from preservative, fragrance, colorant,
benefit agents, botanicals, alkali and pH adjuster.
21. A process for manufacture of a transparent solid soap as claimed in claim 1, said
process comprising saponification of the fatty acids with the oils, addition of the
hydrotope, and cooling to form the transparent soap.

A transparent solid soap composition comprising cleansing agents, fatty acids,
hydrotropes and at least one vegetable oil. The said solid soap composition is a mild soap.
A process for preparing the transparent solid soap comprising saponification of the fatty
acids with the oils, addition of the hydrotope, and cooling to form the transparent soap.