COSMETICS
EMOLL IENTS
M. Mentel*, S. Wiechers, A. Howe, P Biehl, J. Meyer
Senses- A Scientific Tool for the Selection of
The Right Email ient
• Introduction
Face, body and hair care, sun protection, color cosmetics, antiperspirant
and deodorants - the cosmetics market
includes a broad spectrum of different product segments. As diversif ied as
these applications are in terms of their
requ irements, they all share one aspect:
Formulators must take the challenge and
skil lfully select from a wide variety of
ingredients and combine them in perfect
balance. By doing so, they shape the texture, sensory feel, overall performance
and appearance of the emu lsion, creating a targeted cosmetic product.
The choice of the emoll ient, also referred
to as cosmetic oil, is of paramount im-
Abstract
ne of the major challenges for a formulator of cosmetic products
today is the choice out of the overwhelming variety of available
raw materials. The vast majority of cosmetic products are emulsion
systems where the emollient constitutes the second major component
after water. Therefore, the choice of the emollient or emollient mixture
is crucial, as it has the greatest influence on a variety of criteria, by which
the final product will be judged.
In order to guide the formulator in the proper alignment of each individual property, helpful tools were developed based on scientific data.
The data was compiled in a compact format which enables a rapid overview of emollients and their associated characteristics. Among these are
the chemical structure and INCI declaration, physico-chemical properties,
application-technological properties, sustainability criteria and sensory
profile. Application criteria cover UV filter solubility, packaging compatibility and pigment wetting performance.
Here, an introduction into the so-called »Senses« scientific tool will be
given, by discussing some of the most important emollients and criteria
for their selection.
0
8
portance, as it constitutes t he seco nd
maj or component in emu lsion systems
after water. Its basic f unction and ben ef it covers softening, moisturizing, lubricating, protecting, film-fo rmi ng,
condition ing, solubilizing and dispersion
properties. Traditionally, most cosmetics
are f ormu lated w ith a mixture of emollients, carefu lly ch osen based on their
chem ical structu re and INCI declaration,
physico- chemica l properties, sensory
profile as well as origin and ava ilabil ity.
In order to aid t he f ormu lator in the decision for the appropriate emoll ient f or
t heir individual cosmetic product, helpfu l tools have been developed. They are
based on scientif ic data compil ed using a
variety of diffe rent methodologies.
• Emol li ent Cha rt
Ve ry frequently, one of t he fi rst decision criteria for emollient selection is
their physico-chemical properties. To
faci litate the choice and have t he most
importa nt crit eria in one chart, a selection too l was created, which shows at
a glance the five key characteristics of
emollients (Fig. 1) (1 ).
Vi scosity
Viscosity measu rements were conducted
with a fal li ng bal l viscometer (Hoeppler
Viscomet er) following DIN 53015, and
the values we re logarithm ica lly plotted
on t he x- axis. The viscosity of t he emollient strong ly influences the viscosity of
wate r- in-oil (W/0) emulsi ons and thus
t heir spread abil ity. Viscosity also determines the subj ect ive f atty character of
t he f inished cosmetic product.
SOFW-Journal I 140 I 8-2014
.
COSMETICS
EMO LLI EN TS
Surface & interfacial ten sion
Surface tension and interfacial te nsion
were both determined using t he pendant drop method (Data Physics OCA
35). Measurements were co nducted in a
climate chamber after saturation of t he
emoll ient with water. Following equilibration of the emollient/air and emollient/water interface, respectively, the
tension val ue was determined.
The surface te nsion of the emollient drop
aga inst the surrou ndin g air is plott ed on
the y-axis of the emol lient cha rt. This
parameter, together wit h the viscosity
parameter, indicates t he spreadability of
t he fin al emu lsion as wel l as its stickiness,
and can influence wh iteni ng properties.
The relative polarity of the emollient is
derived from the interfacial tension between emollient and water and is rep re-
sented by the circle color in t he emollien t chart. Emollient pol arity is a major
factor influencing emu lsion stabilit y in
both W/0 and oi l-in- water (0/W) systems and solubilit y of li pophilic UV fi lters and active ingred ients.
Spreadabi lity
The size of each circle in t he emollient
chart (Fig. 1) is proportional to the
spreadability, wh ich was measured as
t he sp reading area of emollient saturated wit h water on a commercially available polyac rylamide gel substrate rehydrated in isotonic sali ne solution after 5
mi nutes. The substrate was chosen and
the method developed to closely mimic
spreadability on human skin. Therefore,
spreadability indicates the ability of an
emollient to spread on the skin an d in-
f luences t he subjective absorption behavior.
Vegetable co ntent and enzymatic
production
The cosmetic oils are listed, in order of
increasing viscosity, in the table with the
INCI declaration, which is indicative of
their chem ical structure class. Two groups
of emollients are highlighted in the chart
(Fig. 1). Circles wit h green outlines indicate ful ly vegetable-based emoll ients,
whi le tu rquois outlines indicat e fully veg etable- based and enzym atically produced
emol lients using
Evonik-proprietary
technology. Great environmental advan tages, like more tha n 60 Ofo en erg y saving
(Fig. 2) and more than 60 Ofo reduction
of green-house gases become apparent
when rep lacing conventio nal chem ical
No.
32
2
Isoamyl Cocoatc
3
Diethylhexyl Carbonate
5
Isopropyl Palmitate
6
Decyl Cocoate
31
Isopropyl Myristate
30
29
28
'E
.......
z
27
..sc:
26
~
25
·~
c:
~
~
:;
"'
INCI
Cyclopentasiloxane
33
24
7
Ethylhexyl Palmitate
8
Phenoxyethyl Caprylate
9
C12·15 Alkyl Benzoate
10
Ethylhexyl Stearate
11
Cetyl Ethylhexanoate
12
Cetearyl lsononanoate
13
Caprylic/Capric Triglyceride
14
Cetyl Dimethicone
23
15
PPG· 3 Myristyl Ether
22
16
Mineral Oil
21
17
Oleyl Erucate
20
18
Octyldodecanol
19
Persea Gratissima (Avocado) Oil
19
20
PPG·15 Stearyl Ether
18
21
Cetyl Dimethicone
17
10
Size of circles:
proportional to spreadability. The smaller/bigger the size of circle the lower/ higher the spreadability.
Colour of circles:
very high polar •
Colour of outline:
0 fully vegetable based; 0 fully vegetable based and enzymatically produced.
<>
22
PPG·14 Butyl Ether
23
Triisostearin
24
Dimethicone
D non polar.
1~~~~~-Emollient Chart with five emollient properties at one glance: surface tension, viscosity, sprea dabi lity, polarity and
~ ble- based origin.
SOFW-Journal l140 I B-2014
9
COSMETICS
EMOLL I ENTS
catalysis with an optimized biocatalytic
process (2) (3).
Several cosmetic oils like e.g. Isoamyl
Cocoate (TEGOSOFT® AC). Oleyl Erucate (TEGOSOFT® OER). Decyl Cocoate
(TEGOSOFT® DC). Cetyl Ricinoleate (TEGOSOFT® CR) and Myristyl Myristate (TEGOSOFT® MM) are produced enzymatically.
d imensiona l landscape. This ca n serve as
a useful tool for a formu lator in selecting
an emoll ient based on the physico-chem ical properties and chemica l synthetic or
enzyma t ic origin. In order to achieve the
desired benefit, however, appl icationtechnological pa rameters have to be
taken into consideration as well.
Emollients based on this technology excellently fulfill today's market needs, in
particular for the formu lation of natura l
and eco-friendly cosmetic products.
The great advantage of t his kind of depiction in the emollient chart is that it
permits simultaneous comparison of
several properties at a glance in a two-
•
22,500
- - ------------------ -
Knowing the capab ility of UV fi lte r solubility is crucial for formu lating ef ficient
sun care products, especially with high
su n protect ion factors. In addition to
sunscreens, other dai ly wear products
often conta in UV fi lters, like facia l care
products, for exampl e. Emol lients help
to achieve the desired skin feel and performance w it hout jeopard izing sun protection. Secondly, formu lators can take
adva ntage of the synergistic effect between emollients and UV f ilters. If proper
solubility of the UV filters is maint ained,
a SPF boosting effect of t he sunscreen
system can be ach ieved (4).
13,800
8,700
Enzymatic
Savings
Conventional
UV f i lte r sol u bil it y - Em o ll ients
for Sun Ca re
Fig. 2 Energy resources (MJ). Generic data of Life Cycle Assessment for Myristyl
Myristate (TEGOSOFT® MM) production on St scale.
• Benzophenone-3
(%)
30
• Butyl Methoxydibenzoylmethane
• Ethylhexyl Triazone
25
• Bis-Ethylhexyloxyphenol Methyoxyphenyl Triazine
20
15
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Fig. 3 Solubility of UV filters at room temperature in various emollients.
10
SOFW-Journal I 140 I 8 -2014
..:.::...
COSMETICS
EMOLLIENTS
The solubi lity of UV filters can be estimated in the fi rst instance from emollient
polarity. However, this aspect was investigated in more detail. Fig. 3 displays the
No.
INCI
solubility of fou r of the most broadly
used, lipoph ilic, crystalline UV filters (4).
Data was collected for the UVA filter Butyl Methoxydibenzoylmethane (BMDM).
Overall pigment
wetting capability
Score
3
4
5
Isoamyl Cocoate
Isopropyl Palm1tate
Isopropyl Mynstate
Mynstiyl Myristate
Decyl Cocoate
6
Stearyl Heptanoate
Ethylhexyl Palmitate
8
Ethylhexyl Stearate
9
Cetyl Ethylhexanoate
10
Celearyl lsononanoate
11
Oleyl Erucate
12
Diethylhexyl Carbonate
13
Cetyl Ricinoleate
14
C12·1 S Alkyl Benzoate
15
PPG· 3 Myristyl Ether
16
Caprylic/ Capric Triglyceride
17
Tri1sosteann
18
Phenoxyethyl Caprylate
19
PPG·1 S Stearyl Ether
20
Oimethicone
21
PPG·14 Butyl Ether
• Yellow Iron 0x1de. Ct 77 492
• Red Iron Oxide, Cl 77 491
• Black Iron Ox1de, Cl 77 49Q
_ _ ___• Carbon Black:...
,C
_l _77_2_6_6_ __
• Pigm ent wetting - Emollients for
Color Cosmetics
Totanium Dioxide, Cl 77891
Score values reflect the VIScosity ol the respect1ve pigment/emollient dispersion. The lower the score value, the better the
pigment wetting. Rating ol overall pigment wetting capability:
• • • • • • superior
• • • • • very h1gh
• • • • high
• • • medium
• • low
• very low
• Emollient waxes are measured at elevated temperatures above their melting point.
Fig. 4 Rating of pigment wetting capability of various emollients.
12
th e UVB filters Benzophenone-3 (BP3)
and Ethylhexyl Tria zone (EHT) and the
UVA/UVB filter Bis- Ethylhexyloxyphenol
Methoxyphenyl Triazine (BEMT).
UVfilter solubility was determined by sat uration of emollient with the respective
UV filter, which was added step by step
until the point of saturation. The supernatant solution was then analyzed for the
filter concentration by high performance
liquid chromatography (HPLC).
Phenoxyethyl Caprylate (TEGOSOFf® XC),
for example, is a highly polar ester emollient of Phenoxyethanol and Caprylic Acid
(over 50 Ofo based on vegetable raw materials), which has outstanding solubility properties and can provide a SPF boosting effect
in both US and European sun care formulations (4). This emollient is highly polar and
improves the solubility of lipophilic crystalline structures, compared to the industry
standard C12- 15 Alkyl Benzoate.
Utilizing the solubility data as shown in
Fig. 3, the form ulator is not anymore limited by selecting out of the few emollients
known for use in sun care products, butdepending on the desired sun protection
factor and UV filter - can choose from
a broader palette of emollients, based on
their individual solubilizing properties.
Other criteria which must be kept in
mind by the formulator in the creation
of a targeted cosmetic product are additional application-technological properties like pigment wetting and the sensorial profile of t he cosmetic oil.
Beside traditional foundations a huge
nu mber of classical (make-up) and
emerging market technologies, like
blemish balm (BB) and color control (CC)
formu lations contain pigments. Knowin g
which emollient facil itates pigment wetting helps to formulate color cosmetic
products. This property was evaluated
using some of the most commonly applied metal oxide pigments coated with
Dimethicone. Included in the systematic
evaluation study were Yellow Iron Oxide
Cl 77492). Black Iron Oxide (CI 77499),
Red Iron Oxide (CI 77491), Titanium Dioxide (CI 77891) as well as uncoated Carbon Black (CI 77266) (Fig. 4).
SOFW-Journal l 140 18-2014
COSMETICS
EMOLLIENTS
For each ind ividual pigment the maximum ratio of pigment t o emol lient was
determined and kept constant. Optimized emol lient loadings ranged from
15 Ofo for Carbon Black to 65 Ofo for Red
Iron Oxide. This allowed clear differentiat ion of t he emol lient performance. The
viscosity at 1/ 100 seconds was measured
using a rheometer (Haake RheoStress).
Measu rements were conducted at room
temperatu re, except for waxy emollients, w hich were evaluated at elevated
t emperature above their melting point.
The score values i n Fig. 4 are based on
t he difference of viscosity of the pigment/emol lient dispersion relative to the
viscosity of the pure emollient. The lower
the difference of viscosity, t he higher
the rating of pigment wetting.
Isoamyl Cocoate (TEGOSOFT® AC), for
example, a 100 Ofo vegetable- based
and enzymatically produced emollient
(Fig. 1). showed superior pigment wetting properties for all tested pigments.
This makes it a very su itable emollient
for pigment containing formu lations.
Cyclopentasi loxane, an emollient which
is commonly employed in make-up formulations, did not show favorable wetting performance. It might influence
the skin feel as such but would not help
for pigment wetting. Isoamyl Cocoate
(TEGOSOFT® AC). t he ester of Isoamyl
Alcohol and vegetable based fatty acid
has a medium spreadability, good absorption and a light and non-oily skin
feel. Other emol lients with very high
pigment wetting capability are Isopropyl Pa lmitate (TEGOSOFT® P), Isopropyl
Myristate (TEGOSOFT® M), Myristyl Myristate (TEGOSOFT® MM) and Decyl Cocoate (TEGOSOFT® DC).
•
Sensory map
The sensory profile of cosmetic con sumer products is essentially influenced
by the formulator's choice of emoll ien ts.
An overview was developed that directly
maps the effect of different oil components on skin feel, enab ling the formulator to create the sensory profile t hat is
desired.
A wide range of cosmetic oils has been
comp rehensively eva luated by sensory
analysis. The pure emol lients were analyzed in a descriptive panel. Five in- use
(spreadability, oi liness, absorption, stickiness, slipperiness) and two after-feel attributes (greasy feel, silicone feel) were
classified.
Sensory eva luation data was ana lyzed
by principle component analysis and
cluster analysis and structured in six
different clusters with similar sensory
properties. The position of the clusters
is schematically depicted in a sensory
map spanned by ax is result ing f rom
the principal component analysis. The
result ing dimensions are skin feel characte ristics (light skin fee l to rich skin
feel) on the x-axis and oily residue (no
o ily residue to oily residue) on t he y-axis
(Fig. 5) . Th e bubble size correlates to
the area over which the emollients of
the cluster are d istributed. Th e smal ler
the bu bble of the cl uster and the closer
the bu bbles are located in the sensory
map, the more sim ilar t he pe rceived
skin feel. This importan t tool supporls
Oily
residue
jTh""""i'r.
Mineral Oil
Cyclopentasiloxane
No oily
residue
Light skin feel
• Rich skin feel with medium oily residue
• Medium rich skin feel with oily residue
• Rich and smooth skin feel
Rich skin feel
• Light skin feel with low oily residue
• Light and smooth skin feel
• Medium light skin feel with low oily residue
• high viscosity, medium polarity
-very high viscosity, nonpolar
Fig. 5 Sensory map displaying a variety of cosmetic emollients in six skin feel clusters. Reference emollients were included in
the evaluation and are given in black letters in the map.
14
SOFW·Journal l 140 I 8-2014
~
.
COSMETICS
EMO LLIE NTS
the formulator in choosing the right
combi nation of emollients and creating
the cosmetic product with the req uired
sensory aspects.
Isoamyl Cocoate (TEGOSOFf® AC), for
example, imparts a light and non-oi ly
skin feel with low residu e, and is clustered togeth er with Phenoxyethyl Caprylate (TEGOSOFf® XC). This cosmet ic oil
for sun care formulations absorbs better
and provides a less oily skin feel than
the industry sta ndard C12-15 Alkyl Benzoate, which is found in the adjacent
cl uster, ch aracterized by medium light
skin feel with low oily residue. In comparison, natural oils and Oleyl Erucate
(TEGOSOFf®OER), a 100 Ofo natural-based
and enzymatically produced emollient
made by enzymatic esterification, with
structure and properties similar to Jojoba Oil, imparts a rich skin feel with
medium oily residue.
• Summary
(3) 0. Thurn, •Enzymatic Emollients - Sustainability t hat gets under t he skin• COSSMA
All of the above-mentioned factors influence the final texture, sensory feel,
and overall performance of a cosmetic
product. When utilized together, the
Senses scientific tool sup ports the formulator in the proper alignment of each
individual property. It is to be taken as
supporting tool in the selection of emollients, to create products with improved
sensory and emotional appeal.
1-2/2010.
(4) A. Howe, D. Adkins, M. So/data, B. Jha, 0.
Springer, •Phenoxyethyl Caprylate - A New
Polar Emollient for Organic UV Fil ters« SOFWJournal 137 (7), 2011.
References
(1)
"Au thor's address:
T. Dietz, »Basic properties of cosmetic oils and
their relevan ce to emulsion
preparations«
SOFW- Journal125 (7). 1999.
(2) 0. Thurn, K.
M. Oxenbe/1, • Biocatalysis- A Sus-
Dr. Matthias Mentel
Evonik Industries AG
Goldschmidtstr. 100
45127 Essen
Germany
Email: [email protected]
tainable Method for the Production of Emol-
•
lien t Esters« SOFW-Journa l1 34 (1/2). 2008.
pro
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W HERE EXPERTS ARE COMMITTE D.
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