Note: Descriptions are shown in the official language in which they were submitted.
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METHODS OF REDUCING IRRITATION IN PERSONAL CARE COMPOSITIONS
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Application Nos.
10/650,226,
10/650,495, 10/650,573, and 10/650,398, each of which was filed on August 28,
2003, and is
now pending. Each of the aforementioned applications is incorporated herein by
reference.
FIELD OF INVENTION
The present invention relates to methods for reducing the irritation
characteristics
associated with a variety of personal care compositions, and methods of using
such
compositions.
DESCRIPTION OF THE RELATED ART
Synthetic detergents, such as cationic, anionic, amphoteric, and non-ionic
surfactants,
are used widely in a variety of detergent and cleansing compositions. For many
of such
compositions, including, for example, shampoos, it is desirable to use a
surfactant which
imparts or provides to the composition, when incorporated therein, relatively
high foam
volume and foam stability. It is generally recognized that such foam
properties are directly
related to the perceived efficiency with which a shampoo cleans the hair. That
is, the greater
the volume of foam produced and the greater the stability of the foam, the
more efficient the
perceived cleansing action of the shampoo.
Anionic surfactants tend to exhibit superior cleansing and foaming properties,
and
thus are incorporated into many personal cleansing compositions. However,
these anionic
surfactants also tend to be very irritating to the skin and eyes. To produce
more mild
cleansing compositions, it is well-known to replace some of the anionic
surfactant therein
with other surfactants, such as nonionic and/or amphoteric surfactants. See,
e.g. United
States Patent No. 4,726,915. Another approach to producing mild cleansing
compositions is
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to associate the anionic surfactants with amphoteric or cationic compounds in
order to yield
surfactant complexes. See, e.g., United States Patent Nos. 4,443,362;
4,726,915; 4,186,113;
and 4,110,263. Disadvantageously, mild cleansing compositions produced via
both of such
methods tend to suffer from poor foaming and cleansing performance.
In addition, recent literature, Moore, P.; Shiloach, A.; Puvvada, S.;
Blankschtein, D.
Journal of Cosmetic Science, 54, 2003, 143-159 ("Moore et al.") has described
the addition
of polyethylene oxide (PEO) to a solution of water and relatively low
concentrations
(significantly below the levels typical of personal care cleansing
compositions) of sodium
dodecyl sulfate (SDS), a cleansing surfactant, to reduce the penetration of
SDS into the
epidermis skin. Moore et al. postulates that by binding free micelles of the
surfactant thereto,
the PEO forms larger micelles with the SDS, as compared to the free SDS
micelles, which
larger micelles are not able to penetrate the stratum cornea as readily as the
smaller free
micelles. In this manner, Moore et al. asserts that surfactant penetration
into the skin is
mitigated, and that this reduced surfactant penetration may lead to reduced
skin irritation.
Nevertheless, applicants have recognized that PEO does not sufficiently bind
surfactant thereto, and does not provide a significant or sufficient reduction
in irritation, when
added to compositions comprising levels of surfactant higher than those
disclosed in Moore
et al. Because conventional personal care compositions tend to comprise levels
of surfactant
higher than those disclosed in Moore et al., applicants have recognized that
the teachings of
Moore et al. do not significantly overcome the disadvantages associated with
other methods
of mitigating irritation in personal care compositions.
In light of the above, applicants have recognized the need for methods of
producing
personal care compositions having reduced irritation to the skin and/or eye
without adversely
impacting the foam properties and/or other aesthetics associated therewith.
SUMMARY OF THE INVENTION
The present invention provides methods of reducing the irritation associated
with a
variety of personal care compositions which methods overcome the disadvantages
of the prior
art. In particular, according to certain preferred embodiments of the present
invention,
applicants have discovered advantageously that hydrophobically-modified
materials capable
of binding surfactant thereto can be combined with anionic surfactants to
produce personal
care compositions exhibiting relatively low irritation to the skin and/or
eyes, and/or relatively
high-foaming/foam stability properties.
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One aspect of the present invention provides for methods of reducing the
irritation
associated with a personal care composition comprising an anionic surfactant,
the method
comprising combining a hydrophobically-modified material capable of binding a
surfactant
thereto with an anionic surfactant to produce a reduced irritation personal
care composition
comprising from about 3.5 to less than 7.5 weight percent, based on the total
weight of the
reduced irritation composition, of anionic surfactant.
According to another aspect of the present invention, provided are
compositions
produced according to the present invention.
According to yet another aspect of the present invention, provided are methods
of
cleansing skin or hair with reduced irritation thereto comprising the step of
contacting the
skin or hair of a mammal with a reduced irritation composition comprising an
anionic
surfactant and a hydrophobically modified material capable of binding a
surfactant thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graphical depiction of the idealized tensiometry data associated
with the
addition of anionic surfactant to two solutions.
Figure 2 is a graphical depiction of the tensiometry data and CMC measurement
calculated for a composition according to one embodiment of the present
invention.
Figure 3 is a graphical depiction of the tensiometry data and Delta CMC
measurement calculated for a composition according to one embodiment of the
present
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
All percents described herein are weight-by-weight percent based on the total
weight
of composition, unless otherwise indicated.
With regard to reduced irritation, applicants have recognized that the "TEP
value"
associated with a particular composition, which value is measured
conventionally via the
Trans-Epithelial Permeability Test ("TEP Test") as set forth in the Invittox
Protocol Number 86
(May 1994) incorporated herein by reference and described in further detail in
the Examples
below, has a direct correlation to the irritation to the skin and/or eyes
associated with the
composition. More specifically, a higher TEP value of a composition tends to
indicate less
irritation to the skin and eyes associated therewith as compared to a
composition having a
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lower TEP value, which composition tends to cause higher levels of irritation
to the skin
and/or eyes. Applicants have recognized that the present methods are suitable
for producing
personal care compositions having surprisingly high TEP values/lower
irritation associated
therewith. For example, in certain embodiments, the present methods produce
compositions
having a TEP value of at least about 1.5 or greater. In certain more preferred
embodiments,
the composition produced according to the present methods exhibit a TEP value
of at least
about 2 or greater, more preferably, at least about 2.5 or greater, even more
preferably, at
least about 3 or greater, and still more preferably, at least about 3.5 or
greater. In certain
particularly preferred embodiments, the compounds exhibit a TEP value of at
least about 4.0
or greater, and even more preferably, about 4.5 or greater.
Furthermore, to determine when, and to express the degree to which, a
composition
comprising an anionic surfactant and a hydrophobically-modified material
produced via the
present methods exhibits reduced irritation in comparison to a comparable
composition free
of the hydrophobically-modified material, applicants herein define the term
"Delta TEP" of a
composition of the present invention as the value obtained by: (a) measuring
the TEP values
of (i) the composition of the present invention comprising an anionic
surfactant and
hydrophobically-modified material and (ii) the comparable composition for such
composition; and (b) subtracting the TEP value of the comparable composition
from the TEP
value for the anionic surfactant/hydrophobically-modified material
composition. As used
herein, the "comparable composition" of a particular composition comprising
anionic
surfactant and hydrophobically-modified material means a composition which
consists of the
same components in the same relative weight percents as the anionic
surfactant/hydrophobically-modified material composition with the exception
that the
hydrophobically-modified polymer of the anionic surfactant/hydrophobically-
modified
material composition is replaced in the comparable composition with the same
relative
weight percent of water. For example, the comparable composition for an
anionic
surfactant/hydrophobically-modified composition consisting of 7% anionic
surfactant,l5%
amphoteric surfactant, 5% hydrophobically-modified polymer, 5% glycerin, and
68% water
(wherein all percents are by weight based on the total weight of the
composition) is a
composition consisting of 7% anionic surfactant,15% amphoteric surfactant, 5%
glycerin,
and 73% water. In addition, as described hereinbelow, the composition of
Example 10 is a
comparable composition for the anionic surfactant/hydrophobically-modified
polymer
compositions formed in Examples 11-15.
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In light of the above, as used herein the term "reduced irritation
composition" refers
generally to a composition comprising an anionic surfactant and one or more
hydrophobically-modified materials capable of binding surfactant thereto,
which composition
has a positive Delta TEP value (i.e. the composition has higher TEP value than
its
comparable composition), measured via the Invittox Protocol incorporated
herein. Certain
preferred reduced irritation compositions of the present invention include
those having a
Delta TEP of at least about +0.5. Certain more preferred reduced irritation
compositions
include those having a Delta TEP of at least about +0.75, and more preferably
at least about
+1. Certain particularly preferred reduced irritation compositions include
those having a
Delta TEP that is at least about +1.2, more preferably at least about +1.5,
and more preferably
at least about +1.8.
As used herein, the term "hydrophobically-modified material" refers generally
to any
material having one or more hydrophobic moieties attached thereto or
incorporated therein.
Examples of certain types of preferred hydrophobically-modified materials
include
hydrophobically-modified polymers. Such polymers may be formed, for example,
by
polymerizing one or more hydrophobic monomers and, optionally, one or more co-
monomers, to form a polymer having hydrophobic moieties incorporated therein,
and/or also
by reacting polymer materials with compounds comprising hydrophobic moieties
to attach
such compounds to the polymers. Certain hydrophobically-modified polymers and
methods
of making such polymers are described in U.S. Patent No. 6,433,061, issued to
Marchant et
al. and incorporated herein by reference.
Any of a variety of hydrophobically-modified materials capable of binding
surfactant
thereto are suitable for use in the present invention. Although applicants do
not wish to be
bound by or to any particular theory of operation, it is believed that the
hydrophobically-
modified materials suitable for use in the instant methods act to reduce the
irritation
associated with personal care compositions, at least in part, by binding
surfactant (free
(unbound) surfactant molecules and/or, especially, surfactant free (unbound)
micelles) thereto
to reduce the concentration of irritation-causing free micelles available in
the composition to
irritate the skin and/or eyes. That is, applicants have recognized that the
relative amounts of
surfactant free micelles contained in a particular composition affect the
relative irritation to
the skin and/or eyes associated with that composition, wherein higher amounts
of free
micelles tend to cause higher levels of irritation and lower levels of free
micelles tends to
cause less irritation. By binding surfactant and/or surfactant micelles
thereto, the
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hydrophobically-modified materials reduce the concentration of unbound
surfactant micelles
in a composition and allow for a higher concentration of surfactant to be
added to the
composition before free micelles are formed and/or before a particular level
of irritation is
achieved. This desirable shift in the concentration of surfactant required
prior to the
formation of free micelles is illustrated further in Figure 1.
Figure 1 is a graph 10 showing the idealized surface tension data curves
associated
with the addition of anionic surfactant to two compositions, a composition
comprising a
hydrophobically-modified material of the present invention and a comparable
composition
composition free of hydrophobically-modified material. Curve 11 shows the
change in
surface tension, measured via conventional tensiometry techniques (examples of
which are
described hereinbelow), of a composition free of hydrophobically-modified
material as
increasing levels of anionic surfactant are added thereto. Curve 1 S shows the
change in
surface tension of a composition comprising hydrophobically-modified material
as increasing
levels of anionic surfactant are added thereto. In curve 11, as surfactant is
added to solution,
the surfactant tends to populate the liquid/air interface, thus reducing the
surface tension of
the solution, until essentially the entire surface area is filled. After this
point, hereinafter the
"critical micelle concentration (CMC)" of surfactant, point 12, essentially
all surfactant added
to the composition forms free micelles in solution, which formation does not
have an
appreciable affect on the surface tension of the solution, but tends to
increase the irritation
associated with the composition. By comparison, as shown in curve 15, as
anionic surfactant
is added to a solution comprising a hydrophobically-modified material, the
surfactant both
aligns itself on the liquid/air interface and binds to the hydrophobically-
modified material
until the CMC, point 16, shifted to a significantly higher surfactant
concentration as
compared to curve 1 l, at which point the surfactant added tends to form free
micelles.
In light of the above, applicants have recognized that one measure of the
efficacy of a
particular hydrophobically-modified material in binding surfactant thereto may
be expressed as
the "Delta CMC" achieved by combining the hydrophobically-modified material
with an anionic
surfactant to form a reduced irritation composition. A "Delta CMC" as used
herein is defined as
the number obtained by: (a) determining the CMC for: (i) a particular
composition of the present
invention comprising anionic surfactant and hydrophobically-modified material,
and (ii) the
comparable composition of the composition in (i), which CMC values are
determined using the
Reverse Titration Tensiomtry Test procedures defined in the Examples below;
and (b)
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subtracting the CMC value obtained for composition (ii) from the value
obtained for
composition (i). In certain embodiments, it is preferred to select a
hydrophobically-modified
material for use in the present methods such that the Delta CMC associated
with the resulting
reduced irritation composition is a positive value. In certain more preferred
embodiments, the
hydrophobically-modified material is selected to achieve a reduced irritation
composition having
a Delta CMC of about +16 or greater, more preferably, about +80 or greater,
and even more
preferably of about +300 or greater.
Examples of hydrophobically-modified materials capable of binding a surfactant
thereto and suitable for use in the present methods include hydrophobically-
modified
polymers, for example, hydrophobically-modified acrylic polymers, as well as,
hydrophobically-modified cellulosics, hydrophobically-modified starches,
combinations of
two or more thereof, and the like.
Hydrophobically-modified acrylic polymers suitable for use in the present
invention
may be in the form of random, block, star, graft copolymers, and the like. In
certain
embodiments, the hydrophobically-modified acrylic polymers are crosslinked,
anionic acrylic
copolymers. Such copolymers may be synthesized from at least one acidic
monomer and at
least one hydrophobic ethylenically unsaturated monomer. Examples of suitable
acidic
monomers include those ethylenically unsaturated acid monomers that may be
neutralized by
a base. Examples of suitable hydrophobic ethylenically unsaturated monomers
include those
that contain a hydrophobic chain having a carbon chain length of at least 3
carbon atoms.
In another embodiment, the hydrophobically-modified, crosslinked, anionic
acrylic
copolymer includes those compositions derived from at least one unsaturated
carboxylic acid
monomer; at least one hydrophobic monomer; a hydrophobic chain transfer agent
comprising
alkyl mercaptans, thioesters, amino acid-mercaptan-containing compounds or
peptide
fragments, or combinations thereof; a cross-linking agent; and, optionally, a
steric stabilizer;
wherein the amount of said unsaturated carboxylic acid monomer is from about
60% to about
98% by weight based upon the total weight of said unsaturated monomers and
said
hydrophobic monomer, as set forth in United States Patent No. 6,433,061, which
is
incorporated by reference herein. In one embodiment, the polymer is an
acrylates copolymer
that is commercially available from Noveon, Inc. under the tradename,
"Carbopol Aqua SF-
1.
Any of a variety of hydrophobically-modified cellulosics or starches are
suitable for
use in the present invention. Examples of suitable hydrophobically-modified
cellulosics
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include hydrophobically-modified hydroxyethyl cellulose (available
commercially, for
example, from Hercules Inc. (Wilmington, DE) as "Natrosol Plus"), and the
like. Examples
of suitable hydrophobically-modified starches include hydrophobically-modified
hydroxylpropyl starch phosphate (available commercially, for example, from
National Starch
(Bridgewater, NJ) as "Structure XL"), and the like.
In certain preferred embodiments of the present invention, the hydrophobically
modified materials comprise hydrophobically-modified acrylic polymers, more
preferably
hydrophobically-modified crosslinked, anionic acrylic copolymers.
Any of a variety of anionic surfactants may be combined with a hydrophobically-
modified material to form a reduced irritation composition according to
preferred
embodiments of the present methods. According to certain embodiments, suitable
anionic
surfactants include those selected from the following classes of surfactants:
alkyl sulfates, alkyl
ether sulfates, alkyl monoglyceryl ether sulfates, alkyl sulfonates, alkylaryl
sulfonates, alkyl
sulfosuccinates, alkyl ether sulfosuccinates, alkyl sulfosuccinamates, alkyl
amidosulfosuccinates, alkyl carboxylates, alkyl amidoethercarboxylates, alkyl
succinates,
fatty acyl sarcosinates, fatty acyl amino acids, fatty acyl taurates, fatty
alkyl sulfoacetates,
alkyl phosphates, and mixtures of two or more thereof. Examples of certain
preferred anionic
surfactants include:
alkyl sulfates of the formula
R'-CHzOS03X';
alkyl ether sulfates of the formula
R'(OCHzCH2)~OS03X';
alkyl monoglyceryl ether sulfates of the formula
R'OCH2~HCHZOS03X' ;
OH
allcyl monoglyceride sulfates of the formula
R'C02CH2t~HCHzOS03X' ;
OH
alkyl monoglyceride sulfonates of the formula
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R'C02CHZ~HCH2S03X' ;
OH
alkyl sulfonates of the formula
R'-S03X';
alkylaryl sulfonates ofthe formula
R'1 S03X
alkyl sulfosuccinates of the formula:
R'02C
~C02X' ;
S03X'
alkyl ether sulfosuccinates of the formula:
R'-(OCHZCH2)~ 02C\ ~
~C02X~ ;
'S03X'
alkyl sulfosuccinamates of the formula:
R~~H~ ~C02X'
503X'
alkyl amidosulfosuccinates ofthe formula
R'-~-NH-CHZCHZ~OCH2CH2- ,~.~ OZC
~COZX' ;
503X'
alkyl carboxylates of the formula:
R'-(OCH2CH2)W-OCH2C02X' ;
alkyl amidoethercarboxylates of the formula:
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R'-~-NH-CHZCHZ~OCHZCHZ-, ,~v OCHZC02X' ;
alkyl succinates of the formula:
R ~O C02X' ;
fatty acyl sarcosinates of the formula:
R'-C-N-CHZC02X' ;
CH3
fatty acyl amino acids of the formula:
R' NH COZX';
fatty acyl taurates of the formula:
~CH CH SO X'
R' N 2 2 3
CH3
fatty alkyl sulfoacetates of the formula:
R O CHZS03X ;
alkyl phosphates of the formula:
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q
R'-(OCHZCHZ)w-O-~-OX';
OH
wherein
R' is an alkyl group having from about 7 to about 22, and preferably fom about
7
to about 16 carbon atoms,
R' 1 is an alkyl group having from about 1 to about 18, and preferably from
about
8 to about 14 carbon atoms,
R'2 is a substituent of a natural or synthetic I-amino acid,
X' is selected from the group consisting of alkali metal ions, alkaline earth
metal
ions, ammonium ions, and ammonium ions substituted with from about 1 to
about 3 substituents, each of the substituents may be the same or different
and
are selected from the group consisting of alkyl groups having from 1 to 4
carbon
atoms and hydroxyalkyl groups having from about 2 to about 4 carbon atoms and
v is an integer from 1 to 6;
w is an integer from 0 to 20;
and mixtures thereof.
According to certain embodiments, the anionic surfactant of the present
invention
preferably comprises one or more alkyl ether sulfates, or mixtures thereof. In
certain more
preferred embodiments, the anionic surfactant of the present invention
comprises sodium
trideceth sulfate. Sodium trideceth sulfate is the sodium salt of sulfated
ethoxylated tridecyl
alcohol that conforms generally to the following formula,
C~3Hz~(OCHzCH2)~OS03Na, where
n has a value between 1 and 4, and is commercially available from Stepan
Company of
Northfield, Illinois under the tradename, "Cedapal TD-403M." Applicants have
recognized
that sodium trideceth sulfate can be used to particular advantage to obtain
compositions
having significantly reduced irritation associated therewith according to the
present
invention.
Any amounts of hydrophobically-modified materials and anionic surfactants
suitable to
produce a reduced irritation composition may be combined according to the
present methods.
According to certain embodiments, sufficient hydrophobically-modified material
is used to
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produced a reduced irritation composition comprising from greater than zero to
about 8% by
weight of active hydrophobically-modified material in the composition.
Preferably, sufficient
hydrophobically-modified material is used to produce a reduced irritation
composition
comprising from about 0.01 to about 5%, more preferably from about 0.01 to
about 4%, even
more preferably from about 0.1 to about 4%, and even more preferably from
about 0.1 to about
3% of active hydrophobically-modified material in the composition. The amount
of anionic
surfactant used in the present invention is preferably an amount sufficient to
produce a reduced
irritation composition comprising from about 0.1 to about 12.5%, more
preferably from about
0.5 to about 8.5%, even more preferably from about 1 to about 8% of total
active anionic
surfactant in the composition. In certain other preferred embodiments, the
amount of active
anionic surfactant is an amount sufficient to produce a reduced irritation
composition comprising
from about 3.5 to about 7.3%, more preferably from 3.5% or greater to 7.3% or
less, more
preferably from 3.5% to 7%, and even more preferably from 4% to 7% of total
active anionic
surfactant in the composition.
The hydrophobically-modified material and anionic surfactant may be combined
according to the present invention via any conventional methods of combining
two or more
fluids. For example, one or more compositions comprising, consisting
essentially of, or
consisting of at least one hydrophobically-modified material and one or more
compositions
comprising, consisting essentially of, or consisting of at least one anionic
surfactant may be
combined by pouring, mixing, adding dropwise, pipetting, pumping, and the
like, one of the
compositions comprising hydrophobically-modified material or anionic
surfactant into or with
the other in any order using any conventional equipment such as a mechanically
stirred
propeller, paddle, and the like. According to certain embodiments, the
combining step
comprises combining a composition comprising anionic surfactant into or with~a
composition
comprising hydrophobically-modified material. According to certain other
embodiments, the
combining step comprises combining a composition comprising hydrophobically-
modified
material into or with a composition comprising anionic surfactant.
The reduced irritation compositions produced, as well as any of the
compositions
comprising hydrophobically-modified material or anionic surfactant that are
combined in the
combining step according to the present methods may further comprise any of a
variety of other
components nonexclusively including one or more nonionic, amphoteric, and/or
cationic
surfactants, pearlescent or opacifying agents, thickening agents, secondary
conditioners,
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humectants, chelating agents, and additives which enhance the appearance, feel
and fragrance
of the compositions, such as colorants, fragrances, preservatives, pH
adjusting agents, and the
like.
Any of a variety of nonionic surfactants are suitable for use in the present
invention.
Examples of suitable nonionic surfactants include, but are not limited to,
fatty alcohol acid or
amide ethoxylates, monoglyceride ethoxylates, sorbitan ester ethoxylates alkyl
polyglycosides, mixtures thereof, and the like. Certain preferred nonionic
surfactants include
polyoxyethylene derivatives of polyol esters, wherein the polyoxyethylene
derivative of polyol
ester (I) is derived from (a) a fatty acid containing from about 8 to about
22, and preferably from
about 10 to about 14 carbon atoms, and (b) a polyol selected from sorbitol,
sorbitan, glucose, a-
methyl glucoside, polyglucose having an average of about 1 to about 3 glucose
residues per
molecule, glycerine, pentaerythritol and mixtures thereof, (2) contains an
average of from about
to about 120, and preferably about 20 to about 80 oxyethylene units; and (3)
has an average
of about 1 to about 3 fatty acid residues per mole of polyoxyethylene
derivative of polyol ester.
Examples of such preferred polyoxyethylene derivatives of polyol esters
include, but are not
limited to PEG-80 sorbitan laurate and Polysorbate 20. PEG-80 sorbitan
laurate, which is a
sorbitan monoester of lauric acid ethoxylated with an average of about 80
moles of ethylene
oxide, is available commercially from ICI Surfactants of Wilmington, Delaware
under the
tradename, "Atlas G-4280." Polysorbate 20, which is the laurate monoester of a
mixture of
sorbitol and sorbitol anhydrides condensed with approximately 20 moles of
ethylene oxide, is
available commercially from ICI Surfactants of Wilmington, Delaware under the
tradename
"Tween 20."
Another class of suitable nonionic surfactants includes long chain alkyl
glucosides or
polyglucosides, which are the condensation products of (a) a long chain
alcohol containing from
about 6 to about 22, and preferably from about 8 to about 14 carbon atoms,
with (b) glucose or a
glucose-containing polymer. Preferred alkyl gluocosides comprise from about I
to about 6
glucose residues per molecule of alkyl glucoside. A preferred glucoside is
decyl glucoside,
which is the condensation product of decyl alcohol with a glucose polymer and
is available
commercially from Henkel Corporation of Hoboken, New Jersey under the
tradename,
"Plantaren 2000."
As used herein, the term "amphoteric" shall mean: 1) molecules that contain
both acidic
and basic sites such as, for example, an amino acid containing both amino
(basic) and acid (e.g.,
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carboxylic acid, acidic) functional groups; or 2) zwitterionic molecules which
possess both
positive and negative charges within the same molecule. The charges ofthe
latter may be either
dependent on or independent of the pH of the composition. Examples of
zwitterionic materials
include, but are not limited to, alkyl betaines and amidoalkyl betaines. The
amphoteric
surfactants are disclosed herein without a counter ion. One skilled in the art
would readily
recognize that under the pH conditions of the compositions of the present
invention, the
amphoteric surfactants are either electrically neutral by virtue of having
balancing positive and
negative charges, or they have counter ions such as alkali metal, alkaline
earth, or ammonium
counter ions.
Examples of amphoteric surfactants suitable for use in the present invention
include,
but are not limited to, amphocarboxylates such as alkylamphoacetates (mono or
di); alkyl
betaines; amidoalkyl betaines; amidoalkyl sultaines; amphophosphates;
phosphorylated
imidazolines such as phosphobetaines and pyrophosphobetaines; carboxyalkyl
alkyl
polyamines; alkylimino-dipropionates; alkylamphoglycinates (mono or di);
alkylamphoproprionates (mono or di),); N-alkyl (3-aminoproprionic acids;
alkylpolyamino
carboxylates; and mixtures thereof.
Examples of suitable amphocarboxylate compounds include those of the formula:
A-CONH(CH2)XN+RSR6 R ~
wherein
A is an alkyl or alkenyl group having from about 7 to about 21, e.g. from
about
to about 16 carbon atoms;
x is an integer of from about 2 to about 6;
RS is hydrogen or a carboxyalkyl group containing from about 2 to about 3
carbon atoms;
R6 is a hydroxyalkyl group containing from about 2 to about 3 carbon atoms or
is
a group of the formula:
R$-O-(CHZ)nCO2
wherein
R$ is an alkylene group having from about 2 to about 3 carbon
atoms and n is 1 or 2; and
I4
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R~ is a carboxyalkyl group containing from about 2 to about 3 carbon atoms;
Examples of suitable alkyl betaines include those compounds of the formula:
B-N+R9Ri o(CHz)pCOz
wherein
B is an alkyl or alkenyl group having from about 8 to about 22,
e.g., from about 8 to about 16 carbon atoms;
R9 and R~o are each independently an alkyl or hydroxyalkyl
group having from about 1 to about 4 carbon atoms; and
p is 1 or 2.
A preferred betaine for use in the present invention is lauryl betaine,
available commercially
from Albright & Wilson, Ltd. of West Midlands, United Kingdom as "Empigen
BB/J."
Examples of suitable amidoalkyl betaines include those compounds of the
formula:
D-CO-NH(CHz)q-N+R, ~ R, z(CHz)mC02
wherein
D is an alkyl or alkenyl group having from about 7 to
about 21, e.g. from about 7 to about 15 carbon atoms;
Rl~ and Rlzare each independently an alkyl or
Hydroxyalkyl group having from about I to about 4
carbon atoms;
q is an integer from about 2 to about 6; and m is 1 or
2.
One amidoalkyl betaine is cocamidopropyl betaine, available commercially from
Goldschmidt
Chemical Corporation of Hopewell, Virginia under the tradename, "Tegobetaine
L7."
Examples of suitable amidoalkyl sultaines include those compounds of the
formula
~ Ri4
E ~-NH-(CH2)r-N-R13 S03
RIs
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wherein
E is an alkyl or alkenyl group having from about 7 to about 21, e.g. from
about 7 to about 15 carbon atoms;
R~4 and R,5 are each independently an alkyl, or hydroxyalkyl group
having from about 1 to about 4 carbon atoms;
r is an integer from about 2 to about 6; and
R13 is an alkylene or hydroxyalkylene group having from
about 2 to about 3 carbon atoms;
In one embodiment, the amidoalkyl sultaine is cocamidopropyl hydroxysultaine,
available commercially from Rhone-Poulenc Inc. of Cranbury, New Jersey under
the tradename,
"Mirataine CBS."
Examples of suitable amphophosphate compounds include those of the formula:
O+R~6 ~ O
G-C-NH~CH2)S N-R~gO-P-O
Rl~ OH
wherein
G is an alkyl or alkenyl group having about 7 to about 21, e.g. from about
7 to about 15 carbon atoms;
s is an integer from about 2 to about 6;
R,6 is hydrogen or a carboxyalkyl group containing from about 2
to about 3 carbon atoms;
RI~ is a hydroxyalkyl group containing from about 2 to about 3
carbon atoms or a group of the formula:
RI9-OOCH2)rCOZ
wherein
R,9 is an alkylene or hydroxyalkylene group
having from about 2 to about 3 carbon atoms
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and
t is 1 or 2; and
Rl8 is an alkylene or hydroxyalkylene group having from about 2 to
about 3 carbon atoms.
In one embodiment, the amphophosphate compounds are sodium lauroampho PG-
acetate phosphate, available commercially from Mona Industries of Paterson,
New Jersey under
the tradename, "Monateric 1023," and those disclosed in U.S. Patent 4,380,637,
which is
incorporated herein by reference.
Examples of suitable phosphobetaines include those compounds of the formula:
R1
E-~-NH-(CH2) ~N-R-O-~ O
3
R2 OH
wherein E, r, Rl, RZ and R3, are as defined above. In one embodiment, the
phosphobetaine
compounds are those disclosed in U.S. Patent Nos. 4,215,064, 4,617,414, and
4,233,192, which
are all incorporated herein by reference.
Examples of suitable pyrophosphobetaines include those compounds of the
formula:
Rt
E ~-NH-(CH ) ~N-R-O-~-O-~ OH
2 R2
wherein E, r, R,, Rz and R3, are as defined above. In one embodiment, the
pyrophosphobetaine compounds are those disclosed in U.S. Patent Nos.
4,382,036,
4,372,869, and 4,617,414, which are all incorporated herein by reference.
Examples of suitable carboxyalkyl alkylpolyamines include those of the
formula:
I N-R21 N~R22
R22
R22
a
wherein
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I is an alkyl or alkenyl group containing from about 8 to about 22, e.g.
from about 8 to about 16 carbon atoms;
R22 is a carboxyalkyl group having from about 2 to about 3 carbon
atoms;
Rzl is an alkylene group having from about 2 to about 3 carbon atoms
and
a is an integer from about 1 to about 4.
Classes of cationic surfactants that are suitable for use in this invention
include alkyl
quaternaries (mono, di, or tri), benzyl quaternaries, ester quaternaries,
ethoxylated
quaternaries, alkyl amines, and mixtures thereof, wherein the alkyl group has
from about 6
carbon atoms to about 30 carbon atoms, with about 8 to about 22 carbon atoms
being
preferred.
Any of a variety of commercially available pearlescent or opacifying agents
which are
capable of suspending water insoluble additives such as silicones and/or which
tend to
indicate to consumers that the resultant product is a conditioning shampoo are
suitable for use
in this invention. The pearlescent or opacifying agent may be present in an
amount, based
upon the total weight of the composition, of from about 1 percent to about 10
percent, e.g.
from about 1.5 percent to about 7 percent or from about 2 percent to about 5
percent.
Examples of suitable pearlescent or opacifying agents include, but are not
limited to mono or
diesters of (a) fatty acids having from about 16 to about 22 carbon atoms and
(b) either
ethylene or propylene glycol; mono or diesters of (a) fatty acids having from
about 16 to
about 22 carbon atoms (b) a polyalkylene glycol of the formula: HO-(JO)a-H,
wherein J is an
alkylene group having from about 2 to about 3 carbon atoms; and a is 2 or
3;fatty alcohols
containing from about 16 to about 22 carbon atoms; fatty esters of the
formula: KCOOCHzL,
wherein K and L independently contain from about 15 to about 21 carbon atoms;
inorganic
solids insoluble in the shampoo composition, and mixtures thereof
The pearlescent or opacifying agent may be introduced to the mild cleansing
composition as a pre-formed, stabilized aqueous dispersion, such as that
commercially available
from Henkel Corporation of Hoboken, New Jersey under the tradename, "Euperlan
PK-3000."
This material is a combination of glycol distearate (the diester of ethylene
glycol and stearic
acid), Laureth-4 (CH3(CHZ),oCHz(OCHZCHz)40H) and cocamidopropyl betaine and
may be in a
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weight percent ratio of from about 25 to about 30: about 3 to about 15: about
20 to about 25,
respectively.
Any of a variety of commercially available thickening agents, which are
capable of
imparting the appropriate viscosity to the personal cleansing compositions are
suitable for use in
this invention. If used, the thickener should be present in the shampoo
compositions in an
amount sufficient to raise the Brookfield viscosity of the composition to a
value of between
about 500 to about 10,000 centipoise. Examples of suitable thickening agents
nonexclusively
include: mono or diesters of 1) polyethylene glycol of formula: HO-
(CH2CH20)ZH, wherein z is
an integer from about 3 to about 200; and 2) fatty acids containing from about
16 to about 22
carbon atoms; fatty acid esters of ethoxylated polyols; ethoxylated
derivatives of mono and
diesters of fatty acids and glycerine; hydroxyalkyl cellulose; alkyl
cellulose; hydroxyalkyl alkyl
cellulose; and mixtures thereof. Preferred thickeners include polyethylene
glycol ester, and
more preferably PEG-150 distearate which is available from the Stepan Company
of Northfield,
Illinois or from Comiel, S.p.A. of Bologna, Italy under the tradename, "PEG
6000 DS".
Any of a variety of commercially available secondary conditioners, such as
volatile
silicones, which impart additional attributes, such as gloss to the hair are
suitable for use in this
invention. In one embodiment, the volatile silicone conditioning agent has an
atmospheric
pressure boiling point less than about 220 C. The volatile silicone
conditioner may be present in
an amount of from about 0 percent to about 3 percent, e.g. from about 0.25
percent to about 2.5
percent or from about 0.5 percent to about 1.0 percent, based on the overall
weight of the
composition. Examples of suitable volatile silicones nonexclusively include
polydimethylsiloxane, polydimethylcyclosiloxane, hexamethyldisiloxane,
cyclomethicone fluids
such as polydimethylcyclosiloxane available commercially from Dow Corning
Corporation of
Midland, Michigan under the tradename, "DC-345" and mixtures thereof, and
preferably include
cyclomethicone fluids.
Any of a variety of commercially available humectants, which are capable of
providing
moisturization and conditioning properties to the personal cleansing
composition, are suitable
for use in the present invention. The humectant may be present in an amount of
from about 0
percent to about 10 percent, e.g. from about 0.5 percent to about 5 percent or
from about 0.5
percent to about 3 percent, based on the overall weight of the composition.
Examples of
suitable humectants nonexclusively include: 1) water soluble liquid polyols
selected from the
group comprising glycerine, propylene glycol, hexylene glycol, butylene
glycol, dipropylene
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glycol, and mixtures thereof; 2)polyalkylene glycol of the formula: HO-(R"O)b-
H, wherein R"
is an alkylene group having from about 2 to about 3 carbon atoms and b is an
integer of from
about 2 to about 10; 3) polyethylene glycol ether of methyl glucose of formula
CH3-C6H~o05-
(OCHZCHZ)~ OH, wherein c is an integer from about 5 to about 25; 4) urea; and
5) mixtures
thereof, with glycerine being the preferred humectant.
Examples of suitable chelating agents include those which are capable of
protecting and
preserving the compositions of this invention. Preferably, the chelating agent
is ethylenediamine
tetracetic acid ("EDTA"), and more preferably is tetrasodium EDTA, available
commercially
from Dow Chemical Company of Midland, Michigan under the tradename, "Versene
100XL"
and is present in an amount, based upon the total weight of the composition,
from about 0 to
about 0.5 percent or from about 0.05 percent to about 0.25 percent.
Suitable preservatives include Quaternium-15, available commercially as
"Dowicil 200"
from the Dow Chemical Corporation of Midland, Michigan, and are present in the
composition
in an amount, based upon the total weight of the composition, from about 0 to
about 0.2 percent
or from about 0.05 percent to about 0.10 percent.
The methods of the present invention may further comprise any of a variety of
steps for
mixing or introducing one or more of the optional components described
hereinabove with or
into a composition comprising a hydrophobically-modified material and/or an
anionic surfactant
either before, after, or simultaneously with the combining step described
above. While in
certain embodiments, the order of mixing is not critical, it is preferable, in
other embodiments, to
pre-blend certain components, such as the fragrance and the nonionic
surfactant before adding
such components into a composition comprising a hydrophobically-modified
material and/or an
anionic surfactant.
The reduced irritation compositions produced via the present invention are
preferably
used as or in personal care products such as shampoos, washes, baths, gels,
lotions, creams,
and the like. As discussed above, applicants have discovered unexpectedly that
the instant
methods allow for the formulation of such personal care products having
reduced irritation to
the skin and/or eyes and desirable foaming characteristics.
According to certain other preferred embodiments, the present invention
provides
methods for cleansing skin or hair with reduced irritation thereto comprising
the step of
contacting the skin or hair of a mammal with a reduced irritation composition
comprising an
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anionic surfactant and a hydrophobically-modified material capable of binding
the anionic
surfactantthereto.
Any conventional means for contacting mammalian skin and/or hair can be used
according to the present invention. In certain preferred embodiments, the
contacting step
comprises applying a reduced irritation composition of the present invention
to human skin
and/or human hair.
The cleansing methods of the present invention may further comprise any of a
variety
of additional, optional steps associated conventionally with cleansing hair
and skin including,
for example, lathering, rinsing steps, and the like.
EXAMPLES
The following Trans-Epithelial Permeability ("TEP") and Tensiometry tests are
used
in the instant methods and in the following Examples. In particular, as
described above, the
TEP test is used to determine when a composition is a reduced irritation
composition
according to the present invention, and the Tensiometry test may be used to
determine the
suitability of a particular hydrophobically-modified material for binding
surfactant thereto.
Trans-Epithelial Permeability Test ("TEP Test"):
Irritation to the eyes and/or skin expected for a given formulation is
measured in
accordance with the Invittox Protocol Number 86, the "Trans-epithelial
Permeability (TEP)
Assay" as set forth in Invittox Protocol Number 86 (May 1994), incorporated
herein by
reference. In general, the ocular and/or skin irritation potential of a
product can be evaluated
by determining its effect on the permeability of a cell layer, as assessed by
the leakage of
fluorescein through the layer. Monolayers of Madin-Darby canine kidney (MDCK)
cells are
grown to confluence on microporous inserts in a 24-well plate containing
medium or assay
buffer in the lower wells. The irritation potential of a product is evaluated
by measuring the
damage to the permeability barrier in the cell monolayer following a 15 minute
exposure to
dilutions of the product. Barrier damage is assessed by the amount of sodium
fluorescein that
has leaked through to the lower well after 30 minutes, as determined
spectrophotometrically.
The fluorescein leakage is plotted against the concentration of test material
to determine the
ECSO (the concentration of test material that causes 50% of maximum dye
leakage, i.e., 50%
damage to the permeability barrier). Higher scores are indicative of milder
formulas.
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Exposure of a layer of MDCK cells grown on a microporous membrane to a test
sample
is a model for the first event that occurs when an irritant comes in contact
with the eye. In vivo,
the outermost layers of the corneal epithelium form a selectively permeable
barrier due to the
presence of tight junctions between cells. On exposure to an irritant, the
tight junctions separate,
thereby removing the permeability barrier. Fluid is imbibed to the underlying
layers of
epithelium and to the stroma, causing the collagen lamellae to separate,
resulting in opacity. The
TEP assay measures the effect of an irritant on the breakdown of tight
junctions between cells in
a layer of MDCK cells grown on a microporous insert. Damage is evaluated
spectrophotometrically, by measuring the amount of marker dye (sodium
fluorescein) that leaks
through the cell layer and microporous membrane to the lower well.
Tensiometry Titration Test:
A well-known method to measure the surface tension of surfactant solutions is
the
Wilhelmy plate method (Holmberg, K.; Jonsson, B.; Kronberg, B.; Lindman, B.
Surfactants and
Polymers in Aqueous Solution, Wiley & Sons, p. 347). In the method, a plate is
submerged into
a liquid and the downward force exerted by of the liquid on the plate is
measured. The surface
tension of the liquid can then be determined based on the force on the plate
and the dimensions
of the plate. It is also well known that by measuring the surface tension over
a range of
concentrations the critical micelle concentration (CMC) can then be
determined.
There are commercially available Wilhelmy plate method instruments. In the
following examples, a Kruss K12 Tensiomter (Kruss USA, Mathews, NC) with a
platinum
Wilhelmy plate used to determine the surface tension of each sample over a
range of
concentrations. The test can be run either forward or reverse. In either case,
a sample vessel
contains some initial solution in which the Wilhelmy plate measures the
surface tension.
Then a second solution is dosed into the sample vessel, stirred, and then
probed again with
the Wilhelmy plate. The solution initially in the sample vessel before the
titration begins,
into which the second solution is dosed, will be referred to hereinafter as
the initial solution,
and the solution that is dosed into the sample vessel during the titration
will be referred to
hereinafter as the dosing solution, in accordance with the convention used by
Kruss USA.
In the forward titration, the concentration of the initial solution is lower
than the
concentration of the dosing solution. In this example during forward titration
tests, the initial
solution was HLPC grade water (Fischer Scientific, NJ), with no sodium
trideceth sulfate. The
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dosing solution was a solution of sodium trideceth sulfate and HLPC grade
water (Fischer
Scientific, NJ) with a concentration of 5750 mg/L of sodium trideceth sulfate.
A large stock
solution, 4L, of the dosing surfactant solution was prepared before hand;
sodium trideceth
sulfate (Stepan Company, Northfield, IL) was added to HLPC grade water
(Fischer Scientific,
NJ) to a concentration of 5750 mg/L.
At the beginning of the forward titration, 50 ml of initial solution was added
to the
sample vessel. The surface tension of this initial solution was measured, and
then a volume of
the dosing solution was added to the sample vessel. The solution was stirred
for at least 5
minutes, before the next surface tension measures was taken. All titrations
were run from 0
mg/L to at least 3500 mg/L of sodium trideceth sulfate, which is well beyond
the CMC of all
samples. A test run according to this procedure is here after referred to as a
Forward Titration
Tensiomtry Test.
Alternatively in the reverse titration, the concentration of the initial
solution is higher
than the concentration of the dosing solution. During the reverse titration
tests of the following
examples, the dosing solution was HLPC grade water (Fischer Scientific, NJ),
which had no
surfactant, 0 mg/L. The full concentration formulas (for example, those in
Table 1) were diluted
with HLPC grade water (Fischer Scientific, NJ) to a dilution of approximately
5% wt. This 5%
diluted solution was then added to the sample vessel and was the initial
solution. The surface
tension of this initial solution was measured, and then a volume of the dosing
solution was
added to the sample vessel. The solution was stirred for at least 5 minutes,
before the next
surface tension measures was taken. This dosing, stirring, and then measuring
was repeated
until the dilution reached at least 0.0008%. A Test run according to this
procedure is here after
referred to as a Reverse Titration Tensiomtry Test.
From the raw tensiomtry data, the CMC was determined for each sample in the
following manner. First, the equation for a horizontal line was fitted to the
portion of the data at
high concentrations, i.e. concentrations above the nadir of the graph and well
into the region
where the surface tension is essentially constant, as shown, for example, in
Figure 2 as line 21.
Then, the equation for a straight line is fit to the data at lower
concentrations having a surface
tension above the horizontal line derived previously, as shown, for example,
in Figure 2 as line
22. The intersection of these two lines/equations 23 was then defined as the
CMC for that
sample. Figure 3 is a example graph showing two tensiometry data curves 31 and
32 for a
composition comprising an anionic surfactant and hydrophobically-modified
material (curve 31)
and its comparative composition comprising anionic surfactant (curve 32). The
CMC for curve
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31 is shown at point 33 and the CMC for curve 32 is shown at point 34. The
Delta CMC 35 is
CMC 33 minus CMC 34.
Examples 1- 4: Preparation of Cleansing Compositions
The cleansing compositions of Examples 1 through 4 were prepared according to
the
materials and amounts listed in Table 1.:
Table 1*
Tradename INCI Name 1 2 3 4
PEG 8000 (100%) PEG 8000 1.800 ---------------
POlyox WSR 205 (100%)PEG-14M ----- 1.800----------
Carbopol ETD 2020 Carbomer ----- -----1.800-----
(100%)
Carbopol AQUA SFl Acrylates Copolymer----- ----------6.000
(30%)
Tegobetaine L7V Cocamidopropyl9.330 9.3309.3309.330
(30%) Betaine
Monateric 9497 (30%)Disodium 2.000 2.0002.0002.000
Lauroamphodiacetate
Cedepal TD403LD Sodium Trideceth10.00010.00010.00010.000
(30%) Sulfate
Glycerin 917 (99%) Glycerin 1.900 1.9001.9001.900
Polymer JR-400 Polyquaternium-100.140 0.1400.1400.140
Dowici1200 Quaternium-15 0.050 0.0500.0500.050
Versene 100XL Tetrasodium 0.263 0.2630.2630.263
EDTA
Sodium Hydroxide Sodium Hydroxide----- 0.5000.5000.500
solution (20%)
Citric Acid solutionCitric Acid 0.500 ---------------
(20%)
Water Water qs Qs qs qs
*expressed in %w/w
The compositions of Table 1 were prepared as follows:
Water (50.0 parts) was added to a beaker. The polymer, (PEG 8000 in Example
#1, Polyox
WSR 205 in Example #2, Carbopol ETD 2020 in Example #3 and Carbopol Aqua SF1
in
Example #4) was added to the water with mixing. The following ingredients were
added
thereto independently with mixing until each respective resulting mixture was
homogenous:
Tegobetaine L7V, Monateric 9497, Cedepal TD403LD, Glycerin 917, Polymer JR400,
Dowicil 200, and Versene 100XL. The pH of the resulting solution was then
adjusted with
either a 20% Citric Acid solution (Example 2) or a 20% Sodium Hydroxide
solution
(Examples 1, 3, 4) until a final pH of about 6.3 to 6.6 was obtained. The
remainder of the
water was then added thereto.
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Mildness Comparison of Cleansing Compositions: The compositions prepared in
accordance with Examples 1 - 4 were tested for mildness in accordance with the
above TEP
Test . The results of these tests are listed below in Table 2:
Table 2: Mildness Comparison
Example TEP value
Example 1 3.64 + I .OI
Example 2 3.69 + 0.98
Example 3 4.08 + O.I8
Example 4 4.93 + 0.32
* = Statistically Significantly Different (95% CI)
This Example demonstrates that not all materials are capable of mitigating
skin and eye irritation of a cleansing surfactant composition equally.
Examples 5 - 8: Preparation of Tensiometry Titration Compositions
The compositions of Examples 5 through 9 were prepared according to the
materials and
amounts listed in Table 3:
Table 3*
Tradename INCI Name 5 6 7 8 9
PEG 8000 PEG 8000 -----0.050 ---------------
(100%)
Polyox WSR PEG-14M ---------- 0.050----------
205
(100%)
Carbopol Carbomer ---------- -----0.050-----
ETD 2020
(100%)
Carbopol Acrylates ---------- ----------0,167
AQUA SF1 Copolymer
(30%)
Sodium HydroxideSodium Hydroxide---------- ------As As
solution neededneeded
(20%)
DI Water DI Water Qs Qs Qs Qs Qs
I ( I I I I
*expressed in %w/w
The compositions of Table 3 were prepared as follows:
HPLC grade water (50.0 parts) was added to a beaker. The polymer, (PEG 8000 in
Example
#1, Polyox WSR 205 in Example #2, Carbopol ETD 2020 in Example #3 and Carbopol
Aqua
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SF1 in Example #4) was added to the water with mixing. The pH of the resulting
solution
was then adjusted with a 20% Sodium Hydroxide solution (as needed) until a
final pH of
about 7.0 was obtained. The remainder of the water was then added thereto.
Critical Micelle Concentration Values: The compositions prepared in accordance
with Examples 5-9 were tested for Critical Micelle Concentration (CMC) values
using the
forward titration tensiomtry experiment. The initial solution was 50 ml of one
of the
Examples 5 through 9. The dosing solution was 5750 mg/L of sodium trideceth
sulfate in
HPLC grade water. 42 dose were prefonned, which increased the sodium trideceth
concentration from 0 mg/L in the initial solution up to 3771 mg/L at the final
measurement.
The results of this test are listed below in Table 4:
Table 4 Critical Micelle Concentration Comparison
Example CMC value (m,~lL)Delta CMC
(mQlL)
Example 5 125 -
Example 6 83 -42
Example 7 122 -3
Example 8 169 44
Example 9 400 275
The CMC is the surfactant concentration (in this example sodium trideceth
sulfate) at
which free micelles begin to form. At surfactant concentration below the CMC,
no surfactant
exist as free micelles, while at concentrations above the CMC free micelles
are present in
solution. In Example 5, the CMC was measured without any polymer and found to
be 125
mg/L. Also shown in Table 4 is the Delta CMC associated with the composition
of Example
(without additional material). In Example 6, with PEG 8000, the measured CMC
was 83,
which is below the CMC of that in Example 5, only surfactant no polymer.
In Example 7, the addition of Polyox WSR 205 to the solution resulted an
insignificant change in the CMC compared to the solution without additional
material,
Example S. However the addition of Carbopol ETD 2020 did have a significant
effect on the
CMC, increasing the CMC from 124 mg/L without additional material up to 169
mglL; this
represents the second largest Delta CMC. Example 8, Carbopol SF-l, possess the
highest
CMC, and the largest Delta CMC.
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This example shows that the addition of certain materials to the solution can
change
the CMC of the surfactant in solution. An increase in the CMC of the solutions
suggests that
the onset of free micelles formation occurs at higher concentrations. In
Example 5, free
micelles begin to form at 124 mg/L of trideceth sulfate, while in Example 9
free micelle do
not begin to form until 400 mg/L of trideceth sulfate.
We believe that the shift in the CMC to higher concentration with the addition
of
certain materials (i.e., Example 8 and 9) occurs because surfactant associates
with said
material, thereby reducing the free monomer concentration. The free monomer
concentration
is reduced proportional to the amount of surfactant associated with the
material. The
magnitude of the Delta CMC suggests the amount of surfactant that the material
is capable of
associating with, or the efficiency of the material in associating surfactant.
The addition of PEG 8000 (Example 1 and 6) resulted in the lowest TEP score,
most
irritating, and the lowest CMC. The addition of Polyox WSR 205 (Example 2 and
7) resulted
in the second lowest TEP score, and the second lowest CMC. The addition of
Carbopol ETD
2020 (Example 3 and 8) resulted in the second highest TEP score, and the
second largest shift
in the CMC. The addition of Carbopol Aqua SF-1 (Example 4 and 9) resulted in
the highest
TEP score, and the largest shift in the CMC. Surprisingly, we discovered a
relationship/correlation between the magnitude of the CMC shift caused by the
addition of a
material and the mildness of the composition. The addition of a material or
materials that
results in a larger shift of the CMC results in improved mildness of the
composition. The
addition of a material that causes a sufficient increase in CMC results in a
composition with
reduced irritation.
In Example 9, the concentration of Carbopol Aqua SF-1 was 500 mg/L, and the
CMC
was 400 mg/L of sodium trideceth sulfate, while the CMC of sodium trideceth
sulfate without
SF-1 was 125 mg/L. Therefore, the material of Example 9 associated with 275 mg
of sodium
trideceth sulfate per every 500 mg of material, or 0.183g of sodium trideceth
sulfate per 1.0 g
of Aqua SF-1. The efficiency of a material to associate surfactant is the
Delta CMC per mass
of the material. A material with a higher efficiency will associate more
surfactant and will
produce a larger Delta CMC.
Examples 10 -15: Preparation of Cleansing Compositions
The cleansing compositions of Examples 10 through 15 were prepared according
to
the materials and amounts listed in Table 5.
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Table 5*
INCI Name 10 11 12 13 14 15
Carbopol Acrylates Copolymer-----0.9002.7003.6004.5006.000
Aqua SF-1
(30%)
Atlas G-4280PEG-80 Sorbitan4.5804.5804.5804.5804,5804.580
(72%) Laurate
Tegobetaine Cocamidopropyl 11.3311.3311.3311.3311.3311.33
L7V Betaine 0 0 0 0 0 0
(30%)
Cedepal TD403LDSodium Trideceth20.0020.0020.0020.0020.0020.00
(30%) Sulfate 0 0 0 0 0 0
Glycerin Glycerin 1.9001.9001.9001.9001.9001.900
917 (99%)
Polymer JR-400Polyquaternium-100.1400.1400.1400.1400.1400.140
Dowici1200 Quaternium-15 0.0500.0500.0500.0500.0500.050
Versene 100XLTetrasodium 0.2630.2630.2630.2630.2630.263
EDTA
Water Water qs qs Qs qs qs qs
*expressed in %w/w
Each of the compositions of Table 5 was independently prepared as follows:
Water (50.0 parts) was added to a beaker. For examples 1 I through 15,
Carbopol Aqua SF-1
was added to the water with mixing. (For Example 10, this step was omitted.)
The Atlas G-
4280 was then added thereto with mixing. For examp1es10-15, the following
ingredients
were then added thereto independently with mixing until each respective
resulting mixture
was homogenous: Tegobetaine L7V, Cedepal TD403LD, Glycerin 917, Polymer JR400,
Dowicil 200, and Versene I OOXL. The pH of the resulting solution was then
adjusted with
either a 20% Sodium Hydroxide solution or a 20% Citric Acid solution until a
final pH of
about 6.3 to 6.6 was obtained. The remainder of the water was then added
thereto.
Mildness Comparison of Cleansin-positions: The compositions prepared in
accordance with Examples 10-15 were then tested for mildness in accordance
with the above
TEP Test. Table 6 lists the TEP value of the composition of each Example:
Table 6: Mildness Comparison
Example TEP value Delta TEP Value
Example 10 1.46 + 0.26 -
Example 11 2.68 +0.28 1.22
Example 12 2.85 + 0.51 1.39
Example 13 2.74 + 0.18 1.28
Example 14 3.34 + 0.83 1.88
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Attorney Docket No. JBP-5017
Example 15 ~ 3.26 + 0.39 1.80
As shown in Example 10, the composition containing a relatively high amount of
anionic surfactant (6.0% active) without the Carbopol Aqua SF 1 recorded a
relatively low
TEP value and thus was considered to be irritating. However, upon the addition
of the
Carbopol Aqua SF1 thereto as shown in Example 1 l, the TEP score was improved.
Examples 12 to 15 further showed that as the amount of Carbopol Aqua SF-1
added to the
composition was increased, the TEP values for those respective compositions
were generally
concomitantly improved. Also shown in Table 6 is the Delta TEP score relative
to the
comparable composition, Example 10 (without any Carbopol Aqua SF-1).
These Examples indicated that the presence of the Carbopol Aqua SF 1
significantly
improved the skin and eye mildness of the compositions via binding of
surfactant thereto, and
that such mildness generally improved as the amount of the copolymer was
increased. The
majority of the increase in the TEP score (68%) occurs with the addition of
only 0.9%
Carbopol Aqua SF-1, Example 10.
Critical Micelle Concentration Comparison of Cleansing Compositions: The
compositions prepared in accordance with Examples 10-15 were then tested for
Critical
Micelle Concentration in accordance with the above Reverse Titration
Tensiometry Test.
Table 7 lists the CMC values of the composition of each Example:
Table 7: Critical Micelle Concentration Comparison
Example CMC value fmElL)Delta CMC fmplLJ
Example 10 48 -
Example 11 65 17
Example 12 136 88
Example 13 377 329
Example 14 370 322
Example 15 398 350
This series of examples, 10-15 shows that as the amount of Carbopol Aqua SF-1
was
increased from 0 to 6% (0 to 1.8% active), the Delta CMC increased to higher
values. While
not bound by any particular theory, we attribute this increase in the Delta
CMC that results by
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Attorney Docket No. JBP-5017
increasing concentration of Carbopol Aqua SF-1 to the ability of the Carbopol
Aqua SF-1 to
bind surfactant thereto. As more Carbopol Aqua SF-1 is added to the
composition (from
Example 10 to 15) more surfactant is bound thereto. Since surfactant that is
bound to the
Carbopol Aqua SF-1 does not contribute to the free monomer concentration, the
CMC is
shifted to higher values.
Similarly, as shown in Table 6, the mildness (TEP values) of the composition
generally increases with increasing concentrations of Carbopol Aqua SF-1.
Again with
Examples 10-15, we find a correlation between the increase in CMC and Delta
CMC and the
improved mildness (TEP/Delta TEP scores) of the composition.
