Note: Descriptions are shown in the official language in which they were submitted.
_ .. 60285-1031 CA 02144660 2000-10-06
1
HYDROPHILIC POLYMER-COATED
MICROCRYSTALLITES OF BICARBONATE INGREDIENT
CROSS-REFERENCE TO RELATED PATENT APPLICATION
Anhydrous antiperspirant stick systems have good
consumer acceptance primarily due to the ease of application
to the skin, good cosmetic esthetics and an acceptable degree
of effectiveness. Previous to the development of anhydrous
stick systems, numerous water based systems were developed in
which the active astringent salts were solubilized in a
thickened or gelled composition. This is exemplified in
United States Patent Numbers 2,732,327; 2,857,315; 3,255,082
and 3,928,557. The water based systems are difficult to
apply to the skin, and their consistency and effectiveness
are variable.
Many anhydrous stick compositions have been
described in the literature which attempt to improve the
delivery and the effectiveness of their antiperspirant and
deodorant characteristics. Antiperspirant stick systems
consisting of low molecular weight monohydric alcohols in
conjunction with polyhydric alcohols are described in U.S.
4,137,306. These sticks have the advantage of
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quicker drying rates, but the residue of the
polyhydric alcohols in combination with the '
astringent salts produces a high degree of tack,
and their effectiveness is limited to the type and
amount of astringent salts that could be
incorporated in the stick matrix.
Anhydrous stick compositions that suspend
the aluminum salt in a hydrophobic matrix are
described in U.S. 4,049,792. These compositions
employ waxy materials and long chain fatty esters to
form a stick that delivers the active astringent.
salts to the skin.
Cosmetic stick compositions made in
accordance with these embodiments are greasy, and
the active astringent salt is enveloped in a manner
that prevents maximum performance. To alleviate
this inherent negative characteristic, volatile
silicone fluids replacement of the less volatile
long chain fatty esters is described in
U.S. 4,126,679. This disclosure teaches the
advantage of utilizing a volatile non-staining
liquid such as cyclic dimethylpolysiloxanes
(referred to as volatile silicones), in combination
with various types of waxes, as a carrier for the
active astringent salts in an antiperspirant stick
composition. Similar antiperspirant stick
compositions containing volatile silicones are
described in United States Patent Numbers 4,511,554;
4,980,156; and 4,985,238.
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With respect to deodorant activity, sodium
bicarbonate has long been recognized for its
deodorant properties, and has commonly been used as
a household deodorant. Plain powdered sodium
bicarbonate, or sodium bicarbonate diluted with talc
or other filler, has been used as an underarm
deodorant as disclosed in U.S. 4,382,079. Other
publications which describe cosmetic stick
compositions containing a bicarbonate deodorant
include U.S. 4,822,602 and U.S. 4,832,945.
However, the development of a practical
and effective antiperspirant composition in cosmetic
stick or roll-on form which is also capable of
deodorization, and which qualifies for consumer
acceptability, presents many factors which are
unique. Because alkali metal and ammonium
bicarbonate have only limited solubility in water,
alcohol and other solvents, the preparation of a
composition suitable for dispensing in cosmetic
stick or roll-on form has involved many processing
obstacles. In addition to the problem of limited
solubility, a bicarbonate ingredient is incompatible
with the active astringent salts and with other
ingredients of conventional stick compositions.
Also, the dimensional stability of the cosmetic
product containing bicarbonate ingredient, and
the esthetic appearance and the °'feel" on the
skin, are just a few of the additional difficulties
encountered in the preparation of a low residue
antiperspirant-deodorant cosmetic product.
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Another problem associated with the
incorporation of a bicarbonate deodorant ingredient '
in an antiperspirant formulation is the tendency for
the high density bicarbonate salt particles to
settle in the fluid medium during processing. Also,
under the elevated temperature conditions required
for the admixing and blending of ingredients,
bicarbonate degradation and evolution of carbon
dioxide and water occur.
There is continuing interest in the
development of bicarbonate-containing cosmetic
products which exhibit deodorizing activity, and in
improved forms of bicarbonate deodorant ingredients.
Accordingly, it is an object of this
invention to provide cosmetic products which contain
a novel form of bicarbonate deodorant ingredient.
It is another object of this invention to
provide a powder composition composed of particles
of hydrophilic polymer-coated bicarbonate
microcrystallites.
Other objects and advantages of the
present invention shall become apparent from the
accompanying description and examples.
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1~ESCRIPTION OF THE INVENTION
One or more objects of the present
invention are accomplished by the provision of a
powder composition which is composed of particles
5 having an average particle size between about
5-60 microns, and an average dimensional axial ratio
between about 1-2.5 to 1, and wherein the particles
comprise a hydrophilic polymer surface coating
having an encapsulated core matrix content of at
least two crystallites of water-soluble inorganic
compound selected from alkali metal bicarbonate and
ammonium bicarbonate.
The term "particle size°' as employed
herein refers to the largest size dimension of a
particle.
The term "dimensional axial ratio" as
employed herein refers to the ratio of the largest
axial diameter to the other axial diameters.
The term "water-soluble" as employed
herein refers to a bicarbonate salt which has a
solubility of at least about five grams per
100 grams of water at 25°C.
The terms "crystallite" and
"microcrystallite" as employed herein refer to
micro-size crystalline particles of bicarbonate
salt.
The encapsulated microcrystalline
bicarbonate ingredient of an invention powder
composition is selected from alkali metal and
ammonium bicarbonates, such as sodium bicarbonate,
potassium bicarbonate and ammonium bicarbonate, and
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mixtures thereof. The encapsulated bicarbonate core
matrix can contain up to about 30 weight percent,
based on the weight of bicarbonate ingredient, of an
alkali metal or ammonium carbonate compound in
admixture with the bicarbonate crystallites.
The encapsulated bicarbonate crystallites
in the core matrix have an average particle size
between about 0.5-30 microns. In a typical
embodiment the encapsulated bicarbonate crystallites
have a particle size distribution in which at least
80 percent of the particles have a particle size in
the range between about 0.1-5 microns.
Fig. 1 is a Scanning Electron Microscope
photomicrograph illustrating particles of starch-
coated sodium bicarbonate deodorant. The particle
size distribution substantially is in the range
between about 10-40 microns, and each particle
contains an average of about 2-10 bicarbonate
crystallites in the core matrix.
The bicarbonate crystallites are "sand-
like" and approximately spherical in configuration.
Bicarbonate crystallites which are spheroidal in
shape can be obtained by subjecting particulate
bicarbonate to an air-jet pulverizing treatment, in
which two air-jets containing entrained bicarbonate
particles are impinged at high velocity. The
resultant pulverized bicarbonate is recycled until
the desired crystallite size distribution is
obtained. The pulverized bicarbonate product can be '
sized into fractions as suitable for end-use
purposes.
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The presence of at least two crystallites
of bicarbonate salt in each hydrophilic polymer-
coated core matrix is attributable to the micro-size
of the crystallites. Some of the microcrystallites
aggregate to form crystallite agglomerates
containing between about 2-10 primary crystallites.
Coating of the agglomerates yield particles which
contain between about 2-10 bicarbonate crystallites
in the core matrix of hydrophilic polymer-coated
l0 particles.
Similar coated particles are obtained when
during a coating procedure with a hydrophilic
polymer solution two or more single bicarbonate
crystallites, with a liquid surface coating of
hydrophilic polymer solution, make contact and
coelesce into coated particles containing two or
more bicarbonate crystallites in the core matrix.
The application of the hydrophilic polymer
coating to the core matrix particles is accomplished
by conventional means such as pan coating, fluidized
coating, centrifugal fluidized coating, and the
like. The coating polymer usually is dissolved in a
suitable solvent such as water, methanol, ethanol,
acetone, tetrahydrofuran, ethyl acetate,
dimethylformamide, and the like, as appropriate for
a selected polymer species. A coating polymer also
can be applied in the form of an emulsion or
suspension. After the coating medium is applied to
the particles, the solvent medium is removed by
evaporation, thereby forming a continuous film
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coating which encapsulates the bicarbonate
crystallites as demonstrated in Example I.
Another method of invention powder
composition preparation is by slow addition of an
aqueous solution of bicarbonate salt to a water-
miscible organic solvent solution of a hydrophilic
polymer, to form a suspension of precipitated
bicarbonate microcrystallites in the organic solvent
medium. Removal of the solvent medium yields
hydrophilic polymer-coated bicarbonate salt
microcrystallites as demonstrated in Example III.
As an alternative procedure the solvent
component of the suspension admixture is partially
removed, and the remaining concentrated suspension
admixture is blended as a deodorant ingredient with
organic ingredients in the formulation of a cosmetic
stick or roll-on personal care product. The
blending of the diverse miscibility phases serves to
disperse the deodorant ingredient in the form of
hydrophilic polymer-coated bicarbonate
microcrystallites in accordance with the present
invention.
The coating thickness on the particle
surfaces typically will vary in the range between
about 0.1-20 microns. The coating can consist of a
single layer or multiple layers. The polymeric
coating can constitute between about 5-50 weight
percent of the total dry weight of the coated
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particles.
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The hydrophilic polymer employed for
coating the ingredient particles is selected from
water-soluble and water-dispersible organic
polymers. A mixture of polymers can be employed,
and a content of between about 0.5-40 weight percent
of a water-insoluble polymer, based on the coating
weight, can be included.
The term °'hydrophilic" as employed herein
refers to an organic polymer which has a water-
solubility of at least about one gram per
100 grams of water at 25°C.'
Suitable hydrophilic polymers for coating
particles include gum arabic, gum karaya, gum
tragacanth, guar gum, locust bean gum, xanthan gum,
carrageenan, alginate salt, casein, dextran, pectin,
agar, sorbitol, 2-hydroxyethyl starch, 2-aminoethyl
starch, maltodextrin, amylodextrin,
2-hydroxyethyl cellulose, methyl cellulose,
carboxymethyl cellulose salt, cellulose sulfate
salt, polyvinylpyrrolidone, polyethylene glycol,
polypropylene glycol, polyethylene oxide, polyvinyl
alcohol/acetate, polyacrylamide, and the like.
Polyvinyl acetate is illustrative of a water-
insoluble polymer which can be included as an
additional coating component to moderate the
hydrophilicity of the coating.
The rate of particle matrix bicarbonate
release from the particle core under moisture
conditions can be controlled by the quantity and
type of hydrophilic polymer coating on the particle
surfaces.
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Low molecular weight hydrophilic polymers
will release the particle matrix compound at a
relatively fast rate in the presence of moisture.
High molecular weight polymers which are less
5 hydrophilic will release at a relatively slow rate.
Additional rate control is obtained by employing
mixtures of polymer components of varied
hydrophilicity.
Polyethylene glycol (M.W. of 4000) or
10 polyvinyl alcohol will release particle matrix
compound at a relatively fast, rate. Polyethylene
oxide (M. W. of 4,000,000) or partially hydrolyzed
polyvinyl acetate will release at a relatively slow
rate. Polyvinylpyrrolidone will release particle
matrix compound at an immediate rate when in contact
with underarm type of moisture.
In another embodiment a powder composition
of the present invention includes a content of anti-
caking ingredient, in a sufficient quantity to
provide and maintain free-flow properties in the
powder composition.
Suitable anti-caking agents include
magnesium silicate, zinc silicate, calcium silicate,
sodium aluminosilicate, silica aerogel, silica
xerogel, bentonite, attapulgite clay, zinc stearate,
magnesium palmitate, sodium phthalate, zinc sulfide,
magnesium phosphate, zirconium oxychloride, and the
like.
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The present invention also contemplates
the provision of a cosmetic powder such as a
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baby powder formulation. Illustrative of a novel
baby powder~product is a formulation which comprises
a blend of (1) a hydrophilic polymer-coated
bicarbonate crystallite ingredient as described
hereinabove, and (2) between about 5-70 weight
percent of cosmetic grade talc.
In a further embodiment this invention
provides a powder composition which comprises a
blend of (1) a hydrophilic polymer-coated
bicarbonate crystallite ingredient, and
(2) between about 0.05-10 weight percent of a
biocidal ingredient, such as 2,4,4'-trichloro-2'-
hydroxydiphenyl ether (Triclosan). A preferred
biocidal ingredient is zinc oxide having an average
particle size less than about one micron.
Other advantages are achieved by the
practice of the present invention. As noted in the
Background section of the specification, the
relative densities of liquid and solid phases in a
cosmetic stick or roll-on product directly affects
the stability and esthetics of the formulations.
Density matching of inorganic and organic phases is
a significant factor in cosmetic stick and roll-on
products. The present invention provides a
hydrophilic polymer-coated bicarbonate deodorant
ingredient of lower density which more closely
matches the density of the organic matrix of a
cosmetic stick or roll-on product than does uncoated
bicarbonate ingredient.
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When there is density matching of organic
matrix and dispersed hydrophilic polymer-coated '
bicarbonate particle phases, a cosmetic stick or
roll-on product has improved dimensional stability,
and better esthetic appearance and "feel" when
applied to human skin.
An antiperspirant-deodorant cosmetic stick
or roll-on product in accordance with the present
invention has exceptional properties for treating or
preventing perspiration and malodor associated with
human underarm perspiration. A present invention
cosmetic stick or roll-on product can be applied
effectively with safety and comfort for reduction of
underarm perspiration and offensive odors.
The following Examples are further
illustrative of the present invention. The
components and specific ingredients are presented as
being typical and various modifications can be
derived in view of the foregoing disclosure within
the scope of the invention.
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EPLE I
This Example illustrates a fluidized bed
procedure for coating a particulate bicarbonate
compound with a hydrophilic polymer in accordance
with the present invention.
A fluidized bed vessel is utilized which
is equipped with a Wurster air-suspension coater
system (WARF) as described in U.S. 4,568,559 and
U.S. 4,877,621.
A coating solution is prepared by
dissolving polyethylene glycol (45 g, Poly-G 2000,
Olin Corp.), and propylene glycol butyl ether
(10 g, PPG 14, Americol) in ethanol (500 g)/water
(75 g) .
Sodium bicarbonate is utilized as the core
matrix particles. The sodium bicarbonate (Particle
Size Technology, Inc.) has an average particle size
of about 5 microns, and 90 percent of the particles
have a diameter less than 20 microns.
The sodium bicarbonate powder is charged
into the coating chamber of the coater system.
Compressed air is introduced into the
coating chamber, and the polymeric coating solution
is sprayed on the air-suspended bicarbonate core
matrix particles, until the coating weight is about
30~ of the total dry weight of the coated particles.
The procedure is repeated, except that
Hydroxypropylmethylcellulose (Methocel 60 HG,
Dow Chemical Co.) is employed as the hydrophilic
polymer.
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The procedure is repeated, except that
multiodextrin (Lodex 10; Durkee Foods) or
amylodextrin is employed as the water-soluble
polymer, and 0.5 g of a surfactant is included in
the solution (polyoxyethylenesorbitan monolaurate;
Tween 20; ICI Americas, Inc.)
The coated particles consist of a
hydrophilic polymer coating on an inner core of
2-10 crystallites of sodium bicarbonate. The coated
particles have an average particle size of about
35 microns.
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EXAMPLE II
This Example illustrates a procedure for
the preparation of an antiperspirant-deodorant
cosmetic stick product in accordance with the
5 present invention.
A stainless steel tank is provided which
is equipped with turbine agitation.
Silicone oil DC 245 (400 lbs, Dow Corning)
and Dow DC 200 (37.50 lbs, Dow Corning) are charged
10 to the mixing tank. Agitation (55-65 RPM) is
initiated, and heating the liquid medium to 176°F is
commenced.
During the heating period, the following
ingredients are added to the stirred liquid medium:
15 lbs.
Lanette 18 DEO«~ 175.00
Castorwax MP-80~z~ 31.25
ICI G-2162~3~ 6.25
«~ Stearyl alcohol; Henkel.
Hydrogenated castor oil; RTD.
PEG 25 PG stearate; ICI.
The mixture is stirred at 176°F for about
minutes until the ingredients are melted and the
25 liquid medium is homogeneous. The stirring speed is
reduced to about 35 RPM, then Cyprus Supra A Talc
1625 (18.75 lbs, Cyprus) and Reach AZP 908 aluminum-
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zirconium tetrachlorohydrex glycine (312.50 lbs,
Reheis) are added. The temperature is maintained
at 176°F for about 40 minutes until the fluid medium
is uniform, and then the temperature is lowered
to 154°F.
Polymer-coated sodium bicarbonate
(140 lbs.) and Sobica F41 fragrance (6.25 lbs,
Takasago) respectively are added with stirring to
Silicone oil DC 245 (200 lbs, Dow Corning) in a
second mixing tank at a temperature of 154°F to
form a homogeneous suspension medium. The sodium
bicarbonate particles are pre-coated with
amylodextrin as described in Example I.
The contents of the two mixing tanks which
contain heated fluid medium are transferred to
separate fill tanks through a Greer mill, and the
fill tanks are connected to a mixing and dispensing
nozzle device, of the type described in
U.S. 5,094,276. The nozzle device is adapted for
homogeneously blending the two separate streams of
fluid media, and dispensing a predetermined quantity
of the blended fluid.
Plastek 2 oz. bottom-fill stick containers
are filled with the blended fluid. The container
contents are cooled to a room temperature solid
stick over a period of about 45 minutes. The
average hardness value of the solid sticks is
7 (ASTM Method D5).
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~~AMPLE III
This Example illustrates a precipitation
procedure for forming microcrystallites of potassium
bicarbonate, and coating the microcrystallites with
a hydrophilic polymer in accordance with the present
invention.
A coating solution is prepared by
dissolving polyethylene glycol (10 g, Poly-G 2000,
Olin Corp.), propylene glycol butyl ether
l0 (5 g, PPG 14, Americol), and polyoxyethylenesorbitan
monolaurate (1.0 g; Tween 20; ICI Americas, Inc.) in
1-propanol (300 g).
A solution of potassium bicarbonate (30 g)
in water (100 g) is prepared. The potassium
bicarbonate solution is added dropwise to the
coating solution with high speed stirring.
The admixture which forms is a suspension
of potassium bicarbonate microcrystallites in the
liquid medium. The liquid medium is concentrated to
dryness by removal of water/1-propanol azeotrope
under vacuum at 60°C in a rotating evaporator.
The resultant dry powder is composed of
particles which consist of a 33% by weight coating
on an inner core of 2-10 microcrystallites of
potassium bicarbonate. The microcrystallites have a
particle size distribution substantially in the
range of 0.1-5 microns.
In another embodiment, the potassium
bicarbonate suspension admixture is concentrated
until all of the water is removed azeotropically.
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The remaining liquid concentrate is utilized as a
deodorant ingredient in a cosmetic stick or roll-on
formulation. The blending of the liquid concentrate
with the other formulation ingredients disperses the
deodorant ingredient in the form of hydrophilic
polymer-coated potassium bicarbonate particles,
which are similar to the encapsulated bicarbonate
crystallites described in Example I.
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EXA~~PLE IV
This Example illustrates the preparation
of an antiperspirant-deodorant roll-on product in
accordance with the present invention.
A roll-on formulation is prepared by
blending the following proportions of ingredients:
lbs.
Silicone oil DC 245 60.90
Quaternium-18 hectorite
clay (Rheox) ' 10.00
Reach AZP 908 23.00
Encapsulated potassium
bicarbonatez~ ~ 5 .
0 0
Cab-o-Sil fumed silica
(Cabot) 0.60
Sobica F41 0.50
The roll-on formulation exhibits excellent
dimensional stability when packaged and maintained
under storage conditions for six months.
Prepared by an Example III type of precipitation
procedure.
