Note: Descriptions are shown in the official language in which they were submitted.
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~r~RA~TNG COMPOSITIONS PROVIDING IhL~V~u MnSH
REDUCTION, MTT.nN~ ENHANCEMENT OR BOTH
BACKGROUND TO THE I~v~NllON
Field of the Invention
The invention relates to cleaning compositions
comprising soap, detergent, free fatty acid and further
comprising additives which reduce mush and/or improve
mildness in said compositions.
Prior Art
Soap is mankind's oldest surfactant. Although soap
is efficient at cleaning, it requires formulation to
overcome many physical property defects. Additives have
been discovered which improve soap's lather, fragrance,
visual appeal and other aesthetic properties.
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More recently, attention has been drawn to the
harshness problem of soap toward skin. Eighteen
well-known toilet soaps were evaluated by Frosch &
Kligman, "J. Amer. Acad. Derm.", pp. 35 (1979). Great
differences were noted in their effect upon skin. Most
had an appreciable irritancy. The study revealed that
substantial replacement of soap with an alternative
detergent such as acyl fatty isethionate would provide a
more skin compatible system. Unfortunately, this
alternative is expensive. Less costly solutions to the
harshness problem would be desirable.
US Pat. No. 2,894,912 (Geitz) extols the virtues of
toilet bars containing 30-70% acyl fatty isethionate and
2.5 to 25% soap. As noted above, such large amounts of
acyl fatty isethionate are likely to result in
compositions very expensive to produce.
Accordingly, the art teaches compositions in which
major amounts of soap are combined with lesser amounts
acyl fatty isethionate. US Pat. No. 4,260,507 (Barrett),
for example, teaches compositions with major amounts of
soap, 60-97%, combined with minor amounts, 3-40%, acyl
fatty isethionate. The toilet bars produced are said to
have exceptional lathering properties.
In order to further increase mildness in compositions
with lesser amounts of acyl fatty isethionate,
US Pat. No. 4,695,395 (Caswell et al) teaches the use of
mildness improving salts such as alkali metal
isethionates. Unfortunately, compositions comprising
major amounts of soap and minor amounts of detergents, as
US Pat No. 4,695,395, tend to have higher mush values than
pure fatty acid soap formulations. Reduced mush values
are desirable because of the negative consumer perception
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associated with increased mush (for example, bar melting
easily in tray) and because reduced mush values are also
associated with longer bar use.
US Pat. No. 3,835,057 (Cheng et al) teaches the use
of various potentiator compounds used as solvents to
dissolve anti-bacterial compounds in detergent bar
compositions. Among the compounds which may be used is
included polyethylene glycol. Since this patent is not
concerned with mildness enhancement or mush reduction, the
high-soap, low detergent ranges of the compositions of the
invention are not taught. Moreover, there is no
indication from the reference that the potentiator
compounds can be utilised as anti-mushing agents or that
the potentiator compounds can be used in high
soap-containing, low detergent-containing compositions to
produce enhanced mildness. In addition, the majority of
potentiator compounds described in the patent are either
commercially unavailable, extremely expensive to make or
unsafe for use in consumer products.
Accordingly, it is one object of the invention to
provide relatively high soap-containing, low
detergent-containing compositions with reduced amounts of
mush.
It is a further object of the invention to provide
compositions with enhanced mildness effects.
Finally, it is an object of the invention to provide
low-mush compositions which can be processed using lower
amounts of water than previously possible.
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These and other objects are obtained by the addition
of mush-reducing, mildness-enhancing compounds described
below to compositions of the prior art.
S SUMMARY OF THE INVENTION
The subject invention provides compositions providing
mush-reduction, mildness-enhancement or both comprising:
(a) a fatty acid soap in an amount greater than 25%
by weight;
(b) 1-50% by weight detergent other than fatty acid
soap;
(c) 1-15% by weight of free fatty acid; and
(d) 1-15% by weight of a mush reducing agent
selected from one of the following groups:
(i) R(OR1)nOR2
wherein R is an alkyl group having from
about 1 to about 22 carbons, a mono- or
disaccharide sugar such as glucose or
sucrose, sorbitol or a sorbitol derivative
such as sorbitan;
R1 is an alkyl group having 1 to 5 carbon
atoms, preferably 2 to 3 carbon atoms;
R2 is hydrogen, an alkyl group having from
about 1 to about 22 carbons, a mono- or
disaccharide sugar such as glucose or
sucrose, sorbitol or a sorbitol derivative
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such as sorbitan or an alkenyl group having
14 to 19 carbon atoms; and
n is at least 1 and is limited only by
practical molecular weight limitations at
which the molecule is no longer soluble;
and
(ii) g
R3C(OR4)nOR5
wherein R3 is an alkyl group having from
about 1 to about 21 carbon or an alkenyl
group having from about 14 to about 19
carbon atoms;
R4 is an alkyl group having 1 to 5 carbon
atoms, preferably 2 to 3 carbon atoms;
R5 is hydrogen, an alkyl group having 1 to
22 carbon atoms, an alkenyl group having
from 14 to 19 carbon atoms, a mono- or
disaccharide such as glucose or sucrose,
sorbitol or a sorbitol derivative such as
sorbitan; and
n is at least 1 and is limited only by
practical molecular weight limitations at
which the molecule is no longer soluble.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, it has been found
that the addition of certain defined compounds to
compositions comprising fatty acid soap, detergent other
than fatty acid soap and free fatty acids results in
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compositions having reduced mush. These compounds also
impart an improved mildness benefit in the form of reduced
skin irritation compared to similar soaps which do not
contain the defined mush-reducing compound.
Soaps
The term "soap" is used herein in its popular sense,
i.e., the alkali metal or alkanol ammonium salts of
aliphatic alkane- or alkene monocarboxylic acids. Sodium,
potassium, mono- di- and tri-ethanol ammonium cations, or
combinations thereof, are suitable for purposes of this
invention. In general, sodium soaps are used in the
compositions of this invention, but from about 1% to about
25% of the soap may be potassium soaps. The soaps useful
herein are the well known alkali metal salts of natural or
synthetic aliphatic (alkanoic or alkenoic) acids having
about 8 to 22 carbon atoms, preferably about 12 to about
18 carbon atoms. They may be described as alkali metal
carboxylates of acyclic hydrocarbons having about 12 to
about 22 carbon atoms.
Soaps having the fatty acid distribution of coconut
oil may provide the lower end of the broad molecular
weight range. Those soaps having the fatty acid
distribution of peanut or rapeseed oil, or their
hydrogenated derivatives, may provide the upper end of the
broad molecular weight range.
It is preferred to use soaps having the fatty acid
distribution of coconut oil or tallow, or mixtures
thereof, since these are among the more readily available
fats. The proportion of fatty acids having at least 12
carbon atoms in coconut oil soap is about 85~. This
proportion will be greater when mixtures of coconut oil
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and fats such as tallow, palm oil, or non-tropical oils or
fats are used, wherein the principal chain lengths are C16
and higher. Preferred soap for use in the compositions of
this invention has at least about 85% fatty acids having
about 12-18 carbon atoms.
Coconut oil employed for the soap may be substituted
in whole or in part by other "high-lauric" oils, that is,
oils or fats wherein at least 50% of the total fatty acids
are composed of lauric or myristic acids or mixtures
thereof. These oils are generally exemplified by the
tropical nut oils of the coconut oil class. For instance,
they include: palm kernel oil, babassu oil, ouricuri oil,
tucum oil, cohune nut oil, murumuru oil, jaboty kernel
oil, khakan kernel oil, dika nut oil, and ucuhuba butter.
A preferred soap is a mixture of about 15% to about
20% coconut oil and about 80% to about 85% tallow. These
mixtures contain about 95% fatty acids having about 12 to
about 18 carbon atoms. The soap may be prepared from
coconut oil, in which case the fatty acid content is about
85% of C12-C18 chain length-
The soaps may contain unsaturation in accordance with
commercially acceptable standards. Excessive unsaturationis normally avoided.
Soaps may be made by the classic kettle boiling
process or modern continuous soap manufacturing processes
wherein natural fats and oils such as tallow or coconut
oil or their equivalents are saponified with an alkali
metal hydroxide using procedures well known to those
skilled in the art. Alternatively, the soaps may be made
by neutralising fatty acids, such as lauric (C12),
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myristic (C14), palmitic (C16), or stearic (C18) acids
with an alkali metalhydroxide or carbonate.
Total soap content of the instant compositions must
be greater than 25 wt.%. Usually, from about 30% to 98%
of the composition is soap. Preferably, the concentration
of this component ranges from about 40% to 70%, more
preferably 50% to 65%.
Compositions encompassed by this invention may either
be in liquid or toilet bar form.
Deter~ents
Detergents other than soap are also present in the
formulations of this invention. Examples of these include
anionic, nonionic, cationic, zwitterionic or amphoteric
synthetic detergent materials or mixtures of any of these.
Anionic detergents may be chosen from the alkali
metal, magnesium or ammonium salts selected from the group
consisting of:
C8-C22 hydroxyalkane sulfonates,
C8-C22 acyl isethionates,
C8-C22 N-acyl taurinates,
C8-C22 alkyl sulfates,
C8-C22 alkyl ether sulfates,
C8-C22 alkyl phosphonates and phosphates,
C8-C22 mono-alkyl succinates and maleates,
C8-C22 dialkylsulphosuccinates,
C8-C22 alkylamidosulphosuccinates,
C8-C22 alkane disulfonates,
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C8-C22 alkene sulfonates
C8-C18 alkyl glyceryl ether sulfonates, and
C8-C18 alkyl polyglycosides.
Examples of nonionic synthetic detergents are the
condensation products of ethylene oxide, propylene oxide
and/or butylene oxide with C8-C18 alkylphenols, C8-C18
primary or secondary aliphatic alcohols, C8-C18 fatty acid
amides; further examples of nonionics include tertiary
amine oxides with one C8-C18 alkyl chain and two C1 3
alkyl chains. Further examples are described in "Surface
Active Agents and Detergents" (Vol. I and II) by Schwartz,
Perry and Berch.
The average number of moles of ethylene oxide and/or
propylene oxide present in the above nonionics varies from
1-30; mixtures of various nonionics, including mixtures
of nonionics with a lower and a higher degree of
alkoxylation, may also be used.
Examples of cationic detergents are the quaternary
ammonium compounds such as alkyldimethylammonium
halogenides.
Examples of amphoteric or zwitterionic detergents are
N-alkylamino acids, sulphobetaines, condensation products
of fatty acids with protein hydrolysates, but owing to
their relatively high costs they are usually used in
combination with an anionic or a nonionic detergent.
Mixtures of the various types of active detergents may
also be used, and preference is given to mixtures of
anionic and a nonionic detergent active.
Particular preferred surfactants are the C8-C18 acyl
isethionates. These esters are prepared by reaction
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between alkali metal isethionate with mixed aliphatic
fatty acids having from 6 to 18 carbon atoms and an iodine
value of less than 20. At least 75% of the mixed fatty
acids have from 12 to 18 carbon atoms and up to 25% have
from 6 to 10 carbon atoms.
Acyl isethionates, when present, will generally range
from about 10% to about 40% by weight of the total
composition. Preferably, this component is present from
about 15% to about 30%.
Free FattY Acids
Free fatty acids of 8-22 carbon atoms are desirably
incorporated within the compositions of the present
invention. Some of these fatty acids are present to
operate as superfatting agents and others as skin feel and
creaminess enhancers. Superfatting agents enhance
lathering properties and may be selected from fatty acids
of carbon atoms numbering 8-18, preferably 10-16, in an
amount up to 25% by weight of the composition. Skin feel
and creaminess enhancers, the most important of which is
stearic acid, are also desirably present in these
compositions. Levels lower than 25% of stearic acid are,
however, necessary in certain formulations where it is
desired to accentuate the performance of the mildness
improving salt disclosed by the present invention. Thus,
stearic acid levels in these formulations must be held
between 4 and 10%, preferably between 5 and 9%, but most
preferably between 6 and 8%.
Fatty acids generally comprise 1 to about 15~ by
weight of the composition.
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Mush-Reducing Agent
The mush-reducing agent hereby disclosed is selected
from one of the following groups:
(i) R(ORl)nOR2
wherein R is an alkyl group having from about 1
to about 22 carbon atoms, a mono- or
disaccharide sugar such as glucose or sucrose,
sorbitol or a sorbitol derivative such as
sorbitan;
R1 is an alkyl group having 1 to 5 carbon atoms,
preferably 2 to 3 carbon atoms;
R2 is hydrogen, an alkyl group having from about
1 to about 22 carbons, a mono- or disaccharide
sugar such as glucose or sucrose, sorbitol or a
sorbitol derivative such as sorbitan or an
alkenyl group having 14 to 19 carbon atoms; and
n is at least 1 and is limited only by practical
molecular weight limitations at which the
molecule is no longer soluble; and
( ii ) 01
R3C(OR4)nOR5
wherein R3 is an alkyl group having from about 1
to about 21 carbons or an alkenyl group having
from about 14 to about 19 carbon atoms;
R4 is an alkyl group having 1 to 5 carbon atoms,
preferably 2 to 3 carbon atoms;
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R5 is hydrogen, an alkyl group having about 1 to
about 22 carbon atoms, an alkenyl group having
from 14 to 19 carbon atoms, a mono- or
disaccharide such as glucose or sucrose,
sorbitol or a sorbitol derivative such as
sorbitan; and
n is at least 1 and is limited only by practical
molecular weight limitations at which the
molecule is no longer soluble.
Examples of compounds selected from group (i) above
include:
(1) polyethylene glycol 6 methyl ether manufactured
by Union Carbide under the trademark Carbowax
Methoxy PEG 350R and having the formula:
CH3(0CH2CH2)60H;
(2) PPG-5 butylether manufactured by Union Carbide
under the trademark UCONLB-65R and having the
formula:
C4Hg(oclHcH2)soH;
CH3
(3) PPG-3 myristyl ether manufactured by Witco under
the trademark Witconol APMR and having the
formula:
CH3(CH2)12CH2(0clHcH2)3
CH3
(4) Methyl gluceth-10 manufactured by Amerchol under
the trademark Glucam-ElOR and having the
formula:
3C6Hl05(cH2cH2)10H; and
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(5) PPG-10 methyl glucose ether manufactured by
Amerchol under the trademark Glucam-P10R having
the formula:
CH3C6Hloos(oclHcH2)lo
CH3
Examples of compounds selected from group (ii) above
include the following:
(1) PEG 100 Laurate manufactured by Lonza under the
trademark Pegosperse 100-LR having the formula:
0~ :
CH3(CH2)l0c-(ocH2cH2)2
(2) PEG 400 Monolaurate manufactured by Lonza under
the trademark Pegosperse 400-MLR having the
formula:
CH3(cH2)l0c-(ocH2cH2)8
(3) Propylene glycol monostearate manufactured by
Goldschmidt under the trademark Tegin P411R
having the formula:
n
CH3(CH2)16C-OCH2CHOH; and
CH3
(4) PPG-26 oleate manufactured by BASF Wyandotte
under the trademark OP-2000 having the formula:
o
CH3(CH2)7CH=CH(CH2)7C-(OCHCH2)26OH
CH3
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These examples are not contemplated to be limiting
examples of the many compounds which can be covered in
each group.
These esters and ethers comprise from about 1% to
about 15% by weight of the cleaning composition,
preferably 1% - 10~, most preferably 2% - 8%.
Other Ingredients
A preferred optional ingredient which may be used in
the compositions of the invention is a skin mildness
lmprover .
Skin mildness improvers which may be used include,
for example, salts of isethionate. Effective salt cations
may be selected from the group consisting of alkali metal,
alkaline earth metal, ammonium, alkyl ammonium and mono-,
di- or tri-alkanolammonium ions. Specifically preferred
cations include sodium, potassium, lithium, calcium,
magnesium, ammonium, triethylammonium,
monoethanolammonium, diethanolammonium or
triethanolammonium ions.
Preferred as a mildness improver, when such agents
are used, are compounds of the general formula:
HO-CHRCH2-SO3M
where R is a hydrogen or C1 to Cg alkyl or alkenyl
radical; and M is action selected from alkali metal,
alkaline earth metal, ammonium, alkyl ammonium or mono-,
di- or tri-alkanolammonium ions.
A particularly preferred compound is simple,
unsubstituted sodium isethionate of the general formula
above wherein R is hydrogen.
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The skin mildness improver may be present from about
0% to about 50% by weight of the composition. Preferably,
the mildness improver is present from about 0.5% to about
25%, more preferably from about 2% to about 15%, optimally
from 5% to 10%, by weight of the total composition.
Other performance chemicals and adjuncts may be
needed with these compositions. The amount of these
chemicals and adjuncts may range from about 1% to about
40% by weight of the total composition. For instance,
from 2 to 10% of a suds-boosting detergent salt may be
incorporated. Illustrative of this type additive are
salts selected from the group consisting of alkali metal
and organic amine higher aliphatic fatty alcohol sulfates,
alkyl aryl sulfonates, and the higher aliphatic fatty acid
taurinates.
Adjunct materials including germicides, perfumes,
colourants, pigments such as titanium dioxide and water
may also be present.
The addition of the mush-reducing agent not only
reduces mush but also allows soap bars to be readily
processed at low moisture levels. Specifically, the agent
allows processing to occur at levels as low as 5%-6%
moisture without major splitting and cracking. In
addition, although relatively high mush values would be
expected at these moisture levels, the mush reducing
compounds keep the mush level down even at these low
moisture values.
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Mush Immersion Test
The mush immersion test is used as a relatively quick
method of measuring a cleaning tablet's ability to absorb
water and therefore disintegrate (mush). A cleaning
tablet is shaved to a rectangular shape approximately
7 x 4 x 2 cm. A horizontal line is scribed across one
face about 3.5 cm from the bottom. The block will be
immersed in water up to this line. The dimensions below
the line are measured. The surface area of the portion to
be immersed is calculated. The block is weighed and then
suspended in a beaker. The beaker is filled with 72F
(22.2C) deionized water until it reaches the scribed
line. The beakers sit in a constant temperature bath kept
at 72F (22.2C). The block is allowed to sit in water
for exactly two hours. The block is removed from the
water, carefully shaken to remove any excess water and
weighed. The difference between the net weight and the
initial weight represents the water weight gained during
the two hour period. The mush is then carefully removed
from the block with a plastic utensil or blunt knife. The
block is then wiped gently with a soft cloth to remove any
excess mush not scraped off previously. The block is
dried overnight and weighed. The difference between the
final dry weight and the initial weight represents the
block weight lost. The final mush value is calculated by
adding the weight of water gained and the weight of block
lost. An average of five blocks is used to assign a mush
number to any composition. It is important to note that
both weights, the water gained and the block lost, are
important. Compositions can gain water readily without
loosening the mass enough to be scraped off. Conversely,
some formulations can lose large masses with only a slight
water gain. Therefore the sum of both weights is
necessary to accurately compare formulations.
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The following examples will more fully illustrate the
embodiments of this invention. These examples are
intended to be of illustrative value only and are not
intended to limit applicants' invention in any way. All
parts, percentages and proportions referred to herein and
in the appended claims are by weight of the total
composition unless otherwise stated.
Basic Formulation
The basic formulations employed for this study were
as follows:
COMPONENTS CONTROL (%) EXPERIMENTAL (~)
Soap about 51 parts/100 about 51 parts/100
Sodium Cocoyl
Isethionate about 21 parts/100 about 21 parts/100
Sodium Isethionate about 6 parts/100 about 6 parts/100
Fatty Acid about 2 parts/100 about 2 parts/100
Water about 10 parts/100 about 10 parts/100
Mush Reduction
Agent --- about 4 parts/100
*Miscellaneous
Compounds about 10 parts/100 about 10 parts/100
___ _____
Total 100.0 100.0
*Miscellaneous compounds include various preservatives,
fragrances and antimicrobial agents.
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ExamPles 1 - 16
Various mush reduction compounds were placed into the
composition set forth in the basic formulation over
various batch moisture ranges. The results of these runs
are set forth below:
- Batch Mush
Content
Moisture Mush Reducing (Grams
Mush~
Example Content_ Compound 50cm_)
1 (Comparative) 11% - lS.17
2 (Comparative) 11% - 15.45
3 (Comparative) 11% - 14.87
4 (Comparative) 11% - 14.97
11% 4% PEG 6 Methyl Ether 13.12
6 11% 4% Prop. Glycol
Monostearate 11.14
7 (Comparative) 8-9% - 17.23
8 5-6% 4% PEG 100 Monolaurate 13.14
9 5-6% 4% PEG 400 Monolaurate 13.34
5-6% 4% PPG-3 Myristal Ether 13.62
11 5-6% 2% PPG-26 oleate 14.04
12 5-6% 4% Methyl Gluceth-10 14.35
13 5-6% 4% PPG-10 Meth. Glucose
Ether 13.64
14 5-6% 4% PEG-6 Methyl Ether 14.69
5-6% 4% Propylene Gly. Mono-
stearate 12.59
16 5-6% 4% PPG-5 Butyl Ether 14.61
In general, batches prepared according to the Basic
Formulation described above are best processed at moisture
levels between 9-12%. At moisture levels about 12% the
mush values decrease but the formulation is very sticky
and impossible to process. At moisture levels below 8 or
9%, bar processing properties (e.g. plodding and stamping)
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become highly unmanageable. At these low moisture levels,
the extruded plodder log tends to split and crack and the
finished bar tends to develop surface deformities (cracks)
as well as general sandiness. Accordingly, it would be
greatly beneficial to find a compound or agent which would
allow processing of low moisture batches in addition to
providing mush reduction. Precisely such advantage is
provided by the compounds of the invention described in
the following pages.
As seen from comparative examples 1-4, when no mush
reducing compound is used, the average mush value is 15.12
and mush values range between 14.8 and 15.5. Mush values
can approach as high as 17 or 18 at lower batch moisture
levels (comparative example 7). When the mush reduction
compounds of the invention are added to batches having the
same batch moisture content (examples 5 and 6), average
mush value drops to 12.13. This represents a reduction
in average mush value of about 20%:
Without Mush With Mush
Reducing Reducing
Compound _ Compound_
Average mush value at 15.2 12.13
11% moisture content
As seen from the table above, dropping the batch
moisture content to 5-6% (moisture levels associated with
increased mush content in the prior art), produced an
average mush value (average of examples 8 to 16) of 13.78.
For batches containing no mush reducing compound, when a
batch moisture value of only 8-9% is used (comparative
example 7), the mush value was 17.23. Thus, batches with
the mush reduction compound showed an average mush
reduction of about 20%:
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Without Mush With Mush
Reducing Reducing
Compound _ Compound _
S Average mush value 17.23* 13.78**
* at 8-9% batch moisture content
** at 5-6% batch moisture content
Since the prior art indicates that even higher mush
values are expected at lower moisture content, it would be
expected that mush values of prior art soaps having a S-6%
moisture content (if they could be processed at all at
this low moisture level) would have been even higher than
17.23. Accordingly, if a direct comparison could be made,
it would be appreciated that the reduction in average mush
value would be higher than even 20%.
Example 17
A soap bar produced using the mush-reducing compound
of the invention was compared to a similar bar, i.e. a
Lever 2000 bar similar in composition except for the
absence of the mush-reducing compound, to determine the
effect of this compound on mildness. The comparison was
made according to the following test procedure:
The Flex Wash
The flex wash procedure consists of three daily two
minute washes of the ante-cubital fossa (flex area of the
elbow). This is an "exaggerated use" method which has
been designed to differentiate mild products. Erythema
response varies only slightly with temperature and
humidity fluctuations making the protocol suitable for
year round testing.
- 2043~7~)
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Approximately 15 panellists are used as the test
population. Panellist flex areas must be free of any skin
condition (eczema, dryness, irritation, cuts or
abrasions). Anyone taking antihistamines,
anti-inflammatory drugs (more than 8 per week) or topical,
oral or injectable cortisone on a regular basis is
excluded from the study. The panel is divided into two
subgroups which are balanced for left handedness. Group I
is assigned the control composition for the left flex and
the experimental for the right flex. Group II reversed
the order.
Following an evaluation, the panellist is instructed
to moisten the left flex area. Sponge and test
compositions (formulated as toilet bars) are dampened with
tap water (100 ppm calcium/magnesium ions). The sponge is
then stroked over the test bar 10 times by the evaluator.
The "dosed" sponge is placed in the panellist's right
hand. The panellist then washes the left flex area for
exactly two minutes. Thereupon, the flex area is rinsed
and patted dry. This washing procedure is repeated on the
right arm with the appropriate composition. Washing by
this procedure is repeated three times daily for five
consecutive days for a total of 15 washes. Treatment
times are scheduled 1.5 hours apart. Each test site is
evaluated immediately prior to washing and 4 hours after
the third daily wash.
One trained assessor evaluates test sites prior to
each wash and four hours after the third wash each day for
a total of 15 evaluations. The grading scale is as
follows:
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0 - no erythema
0.5 - barely perceptible erythema
1 - mild spotty erythema/no edema
1.5 - mild/moderate erythema/with or
without edema
2 - moderate confluent erythema/with or
without edema or vesiculation
Each test site is treated in the prescribed method
until a grading of "2" or greater is attained or 15 washes
are completed. When a score of "2" or greater is attained
the treatment is discontinued on that flex area. The
final score is then carried through for all remaining
evaluations. The remaining flex area is washed until
either a grading of at least "2" or 15 treatments are
attained, whichever is first. In the example of this
specification, the final grading, Mean Rank Scores, is the
sum total of grade scores for 15 assessments per panellist
averaged over the scores from all panellists. Thus, the
average score can range from 0 to 30; the lower score
indicating absolutely no skin irritation, and the "30"
score the most severe. Mean Endpoint Erythema scores are
the mean of the valuation scores, for each panellist, at
which the first arm received a grade of "2" or greater
erythema score or at the completion of fifteen washes.
The following example illustrates the difference in
mildness between Lever 2000 and a toilet bar employing
PEG 400 monolaurate as a mush reduction agent.
Mean Endpoint Mean Rank
Erythema Score
Bar with 4% PEG 400 1.71 16.39
Monolaurate
Control Bar 1.95 22.61
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Statistical Analysis of Rank Scores p=0.05
(Wilcoxon 2 sample)
It can be seen from the results that these mush
reduction agents offer a significant improvement in
mildness relative to the control.
