Note: Descriptions are shown in the official language in which they were submitted.
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INSECT REPELLENT EMULSIONS
INTRODUCTION TO THE INVENTION
The present invention relates to fluid
formulations containing the insect repellent agent
DEET, and more particularly to emulsion formulations
thereof. -
Man has long used various chemical agents to
reduce attacks by bothersome insects, such as -
mosquitoes, flies, ticks, wasps and bees. The most
widely used insect repellent agent at the present time
-- is N,N-Diethyl-m-toluamide, frequently called "DEET."
------__ DEET is an unctuous, somewhat hygroscopic, light-
sensitive,-oily material having a very high solvency
-- for other water-insoluble materials. It has some
notoriety for being difficult to emulsify, so in-
frequently used in concentrated form or formulated as
an aerosol spray or dilute solution, or in solid or
semi-solid form such as in a stick. To repel insects,
one applies DEET or formulations containing up to about
100o DEET to clothing and exposed skin.
However, humans usually prefer the feel of aqueous
materials on their skin. In the cosmetic and medical
fields, it has been found that oily materials can be
made more pleasing by their incorporation into oil-in-
a 35 water emulsions. Since the droplets of insoluble
material are completely surrounded by the aqueous
phase, the sensation to_--the-skin is essentially one of
applying aqueous materials. Emulsions are also easier
to apply evenly to skin, than are solutions, sprays and
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gelled--materials in stick form. DEET, however, does
not typically form emulsions having commercially
required stability, and it is quite undesirable to
require users to mix the separated phases before using
products. _
SUMMARY OF THE INVENTION
The invention includes a water-in-oil insect
repellent emulsion comprising an effective amount of
N,N-Diethyl-m-toluamide, water, a film-forming polymer
and an emulsifier-emulsion stabilizer.
The emulsion has commercially acceptable storage-
stability and a pleasing feel when applied to the skin.
DETAILED DESCRIPTION OF THE INVENTION
In this application, all references to "percent"
shall mean percent by weight, unless the context
clearly indicates otherwise. Many of the formulation
components (surfactants, emulsion stabilizers, film-
formers, etc.) are identified herein by their names as
given in the monographs of J. A. Wenninger et al.,
Eds., CTFA Cosmetic Ingredient-Handbook, Second
Edition, The Cosmetic, Toiletry and Fragrance
Association, Inc.-, Washington, D.C., 1992.
DEET is commercially available in the form of a
technical concentrate which contains at least about 950
DEET. The remaining 5% or less comprises moisture and
isomers other than the meta-toluic isomer, which other
isomers are considered to also have some insect
repellent activity, plus small amounts of impurities
which are artifacts of the manufacturing process
employed. For simplicity, a recitation herein of DEFT
concentration shall ignore the other components of the
concentrate: "10% DEET" shall indicate that a
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formulation contains 10% of a commercial technical
concentrate.
The emulsions of the present invention contain
DEFT, at about 5 to about 25 percent, together with
water, a film-forming polymer and an emulsifier
emulsion stabilizer. In some instances, a supplemental-
emulsifying agent may be useful as a formulation
component.
Suitable supplemental emulsifiers include, without
l0 limitation, the surfactants sorbitan stearate, stearic
acid, sorbitan oleate, cetyl alcohol, glyceryl oleates,
glyceryl stearates, sorbitan sesquioleate, DEA-cetyl-
phosphate, Oleth-20, PEG-8 distearate, PEG-8-oleate,
PEG-2 stearate, Polysorbate 20, Polysorbate 60,
Polysorbate 80~"~xapylene glycol stearate, sodium
laureth sulfate, sorbitan sesquioleate and many others
known in the art. In general, and keeping in mind that
there are numeroLrs exceptions to this statement, oil-
in-water emulsions are prepared using emulsifiers
having hydrophilic-lipophilic balance ("HLB") values
about 8 to about 18. Combinations of emulsifi-ers may
be used, and frequently will be found to impart a
greater emulsion stability than single emulsifiers.
When combinations a-~e used, all of the individual HLB
values may not always be within the above range, but
the overall HLB value usually will be. In general,
when present, the emulsifier component will amount to
about O.lo to about 10% of the formulation.
A film-forming polymer is present to provide a
continuous film upon skin application and water
resistance to the formulation. Water resistance may
assist in obtaining an enhanced duration of action for
_ the insect repellent agent. This would be particularly
desirable for users participating in water-related
activities, such as fishing, water skiing, swimming or
activities which may incidentally involve water
contact, or for users who are engaged in strenuous
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sports or work activities and perspire Tzeavily. Useful
film formers include: copolymers of octadecene and
malefic anhydride; copolymers of 1-triacontane and vinyl
pyrrolidone; acrylates/octylacrylamide copolymer;
-5 acrylates/PVP copolymer; acrylates/acrylamide
copolymer; acrylates/VA copolymer; ethylene/maleic
anhydride copolymer; polyisobutene; polyvinyl alcohol;
PVP/eicosane copolymer; starch/acrylates/acrylamide
copolymer; and hexanedioic acid polymers. Such
ingredients will generally be present in a formulation
in amounts about 0 . 1% to about 5% . - '---w-----w
Also required-in the formulation. is an emulsifier-
emulsion stabilizer, such as an acrylates/C10-30 alkyl
acrylate crosspolymer, carbomer, methyl vinyl
ether/maleic anhydride copolymer or a triethanolamine
salt of stearic acid. Suitable acrylates/C10-30 alkyl
acrylate crosspolymer materials are commercially
available from B.F. Goodrich Chemicals, Akron, Ohio
under the trade names PEMULEN~ TR-1 and TR-2, or
CARBOPOL~. The concentration of emulsifier-emulsion
stabilizer in the formulation will typically be about
0.01% to- about 50. In some formulations, it has been
found that the concentration of the emulsion stabilizer
- PEMULEN TR-2 should not exceed about 0.80, to avoid
viscosity increases which adversely affect emulsion
- _. preparation and handling.
Other components, while not required, are commonly
included in skin care products to enhance the feel of
the material upon application, to treat dry skin
conditions and/or to protect the formulation against
microbial contamination. These include emollients,
fragrances, preservatives, vitamins, humectants, skin
conditioners, antioxidants and others. Any of such
- materials may be included as desired, in addition to
35the required components.
Sunscreening ingredients are also useful optional
components of the formulations, when the user desires
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concomitant protection against excessive ultraviolet
radiation exposure. Since the choice of sunscreen
active agents is usually limited to those having
governmental approvals, those skilled in the art will
be aware of acceptable compounds. In the United ,.
States, these currently include: aminobenzoic acid;
cinoxate; diethanolamine p-methoxycinnamate; digalloyl
trioleate; dioxybenzone; ethyl 4-[bis(hydroxypropyl)]
aminobenzoate; 2-et~hylhexyl 2-cyano-3,3-
diphenylacrylate; ethylhexyl p-methoxycinnamate; 2-
ethylhexyl salicylate; glyceryl aminobenzoate;
homosalate; lawsone with dihydroxyacetone; menthyl
anthranilate; oxybenzone,; Padimate A; Padimat-a O-; 2-
phenylbenzimidazole-5-sulfonic acid; red petrolatum;
sulisobenzone; and triethanolamine salicylate. Other
active=sunscreen ingredients, such as avobenzone,
titanium dioxide and phenylbenzimidazole sulfonic acid,
are approved for use in many countries and may also be
incorporated into the insect repellent formulations of
the present invention.
Sunscreening ingredients will be used in sunscreen
effective amounts as needed to provide a desired sun
protection factor (SPF), which may be measured using at
least the essence of the procedure proposed to be
established by the United States Food and Drug
Administration as Title 21, Code of Federal
Regulations, Part 3S2, Subpart D (Sections 352.70-
352.77), which proposal was published in the Federal
Register on May 12, 1993 at pages 28298-28301. In
general, up to about 30 percent sunscreens can be used.
The invention will be further illustrated by the
following examples, which are not intended to limit the
scope of the invention as defined in the appended
claims.
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Example 1
A storage-stable insect repellent lotion is
prepared using the following ingredients:
Name * Percent
Water 4l.89
C12-15 alkyl benzoate C 2l.50
DEFT D 10.00
Sorbitol, 70% aqueous solution B S.00
Sorbitan oleate C 4..00
Sorbitan stearate C 3.00
Glyceryl stearate, self emulsifying C 3.00_
Stearic acid C 2.00
Octadecene/maleic anhydride copolymer C 2.00
Hydrogenated vegetable oil C 2.00
Triethanolamine B 1.80
Benzyl alcohol E 1.00
Propylparaben - C 1.00
Fragrance E 0.70
Dimethicone C 0.40
Methylparaben C :-0.20
Imidazolidinyl urea F -0.20
PEMULEN~ TR-2 A 0.10
Vitamin E - C __~-.10
Jojoba oil C 0.05
Aloe vera lipoquinone C 0.05
Disodium EDTA B 0 a01
* Letter identifies components added during
particular process steps
The emulsion is prepared as follows: (1) a11 but a
small portion of the water and the Pemulen TR-2 are
mixed to form a clear solution and heated to about 60-
65°C; (?) components identified.with a "B" above are
sequentially added to the step 1 solution, with mixing
- to dissolve; (3) a11 components identified as "C" are
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mixed, except for the vitamin E, dimethicone and
octadecene/maleic anhydride copolymer, to form a
solution and heated to about 82-85°C; (4) the
octadecene/maleic anhydride copolymer is added to the
step 3 mixture, and dissolved; (5) the step 4 mixture_
is cooled to about 65-71°C and the remaining "C"
components are added and dissolved; (6) the-warm "D"
component is added to the warm mixture from step 5 and
dissolved; (7) the solution from step 6 is added to the
solution from step 2, with sufficient agitation to form
an emulsion, and mixing is continued until the emulsion
cools to about 49-54°C; (8) the "E" components are
added to the emulsion from step 7, with continued
mixing;(g) the remaining water and the "G"-component
are mixed to form a solution, then added to the
emulsion of step 8; and (10) the emulsion is cooled to
room temperature and water is added to compensate for
evaporative losses during the preparation.
Example - 2
A storage-stable insect repellent lotion,
containing sufficient sunscreen components to provide a
_waterproof sun protection factor (SPF) of 15, is
prepared using the following ingredients and the
general procedure of the preceding example:
Name Percent
Water 42.79
DEET 10.00
Octyl methoxycinnamate 7.50
Octyl salicylate 5.00
Homomenthyl salicylate 5.00
Sorbitol, 70% aqueous solution 5.00
Oxybenzone 4.00
Sorbitan oleate 4.00 _.
Glyceryl stearate, self 'ei~iz~sifying - 3 . 00
Sorbitan stearate 3.00
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Steari:e --acid 2 . 00
Hydrogenated vegetable-oil 2.00
Octadecene/maleic anhydride copolymer 2.00
Triethanolamine 1.80
Benzyl alcohol 1.00
Fragrance 0.70
Dimethicone 0.40
Methylparaben 0.20
Imidazol-idinyl urea 0.20
PEMULEN~ TR-2 0.10
Propylparaben 0.l0
Vitamin E 0.l0
Jojoba oil 0.05
Aloe vera lipoquinone Q.05
Disodium EDTA 0.01
For this emulsion preparation, sunscreen active
ingredients are added as "C" components.
Example 3
A storage-stable insect repellent lotion,
containing sufficient sunscreen components to provide a
waterproof SPF of 30, is prepared using the following
ingredients:
Name - * Percent
Water 57.09
Homomenthyl salicylate B 13.00
DEET D l0.00
Octyl methoxycinnamate B 7.50
Oxybenzone B 6.00
Sorbitol, 70o aqueous solution A 2.00
Octadecene/maleic anhydride copolymer C 2a00
Triethanolamine A Z.00
Dimethicone C 0.40
Pemulen~ TR-2 A 0.30
Fragrance E 0.30
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Imidazolidinyl urea -F' 0.20
Vitamin E acetate B 0.10
Aloe vera lipoquinone B 0.05
Jojoba oil B 0.05
-5 Disodium EDTA A 0.01
* Letter identifies components added during
particular process steps
The emulsion is prepared as follows: (1) the
components identified in the table with an "A" are - ----.~-..-w.,
mixed with a11 but a small portion of the water, while
heating to about 49-55°C to form a solution; (2) the
"B" components are mixed and heated to about 80-82°C,
to form a solution; (3) to the step 2 solution are _
sequentially added the "C" components, with sufficient
mixing after each addition to form a solution; (4) the
step 3 solution is cooled to about 62-68°C; (5) the
DEET is added to the step 4 solution and thoroughly
mixed; (6) the solution of step 1 is agitated to form a -
vortex and the solution of step 5 is slowly added, to
form an emulsion, then mixing is continued as the
mixture cools to about 49-52°C; (7) the fragrance is
_ added to the mixture from step 6 and mixing is
continued as the batch cools to ambient temperature;
- _. (8) the "F" component is dissolved in the remaining
water and added to the mixture of step 7; and (9)
sufficient water is added, with mixing, to compensate
for evaporative losses during the preparation.
