Note: Descriptions are shown in the official language in which they were submitted.
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SHAVING AID STRIP FOR RAZOR CARTRIDGE
This invention relates to a shaving aid strip (or composite) for a razor
cartridge.
It is now well known that shaving comfort can be enhanced by
affixing to a razor cartridge a shaving aid composite, also known as a
lubricating
strip, which continuously releases a shaving aid, typically a lubricant,
during the
shaving process. See, for example, U.S. 4,170,821 and GB 2,024,082. The
shaving
aid strip generally comprises a water-insoluble polymer matrix, typically
polystyrene, and a water-soluble shaving aid, typically polyethylene oxide,
which
leaches out of the composite during shaving to enhance shave comfort.
Unfortunately, conventional shaving aid strips suffer from the
disadvantage that they release an insufficient amount of the shaving aid,
particularly
after the first four or five shaves where release of the shaving aid may drop
off to
negligible quantities. In addition, the amount of shaving aid that may be
included
in the shaving aid strip may be limited because high levels of shaving aid are
difficult to process and can adversely affect the structural integrity of the
strip.
Accordingly, recent efforts have been made to improve shaving aid strips so as
to
enhance and prolong release of the shaving aid.
Such efforts have resulted in improved shaving aid strips which
include the following features: incorporation of a low molecular weight
release
enhancing agent, such as polyethylene glycol, into the matrix (U.S.
5,113,585); the
use of ethylene vinyl acetate copolymer as the matrix material (U.S.
5,349,750);
incorporation of a compatibilizer material such as polyethylene oxide-
TM
polypropylene oxide copolymer (e.g. Poloxamer 182) (U.S. 5,454,164);
TM
incorporation of a water-swellable polymer such as Salsorb 84, a cross-linked
polyacrylic (U.S. 5,626,154); coextrusion of a core comprising a water-
leachable
shaving aid within a sheath of water-insoluble polymer, wherein the sheath has
a
plurality of openings to facilitate release of the shaving aid (WO 96/13360,
which
corresponds to U.S. Ser. No. 08/497,194); and coextrusion of adjacent shaving
aid
portions (U.S. 5,956,848). Also known are shaving aid strips which include an
essential oil (U.S. 5,095,619) or a non-volatile cooling agent (U.S.
5,713,131), and
injection molded strips which include a plasticizer (U.S. 4,850,106). _
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The present invention is directed to a razor cartridge with a solid
polymeric shaving aid strip. The razor cartridge has a blade (one or more) and
a
skin engaging portion in proximity to the blade. The skin-engaging portion
includes
a solid polymeric shaving aid strip having an upper exposed surface which
contacts
the skin during shaving. The shaving aid strip includes a first exposed
lengthwise
extending portion containing a lubricous water-soluble polymer and an
adjacent,
second exposed lengthwise-extending portion containing a lubricous water-
soluble
polymer. The first portion contains a greater amount of the lubricous water-
soluble
polymer than the second portion, and the first portion is adapted to wear at a
faster
rate than the second portion during shaving. This construction enables the
strip to
release more of the lubricous water-soluble polymer for a longer time period
(i.e.,
for more shaves) than conv -:itional shaving aid strips.
The shaving aid strip is typically located at the rear (or cap) portion
of the cartridge (i.e. behind the blade or blades), but may also be located at
the
front (or guard) portion of the cartridge (i.e., in front of the blade or
blades), or a
shaving aid strip may be placed at both positions on the cartridge. The razor
cartridge is generally affixed to a handle for use in shaving. The razor
cartridge
may be designed to be removably affixed to a handle in the case of razor
systems in
which the handle is reused and the cartridge is disposed of after one or more
uses_
Or the razor cartridge may be permanently affixed to a handle (or integral
with the
handle) in the case of disposable razors in which the handle and cartridge are
disposed of together as a wtit after one or more uses. The term razor
cartridge is
thus intended to apply to both types of cartridge.
Fig. 1 is a perspective view of a razor cartridge which includes a
shaving aid strip of the present invention.
Fig. 2 is a sectional view taken along line 2-2 of Fig. 1.
Fig. 3 is a perspective view of the shaving aid strip included in the
razor cartridge depicted in Fig. 1.
Fig. 4 is a side elevation view of the shaving aid strip of Fig. 3.
Fig. 5 is a sectional view of a razor cartridge identical to Fig. 2, but
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depicting a second embodiment of the shaving aid strip of the present
invention.
Fig. 6 is a perspective view of the shaving aid strip depicted in Fig.
5.
Fig. 7 is a side elevation view of the shaving aid strip of Fig. 6.
Referring to Figs. 1, 2 and 5, the razor cartridge 14 includes housing
16, which carries three blades 18, a finned elastomeric guard 20, and a solid
polymeric shaving aid strip 22 (or 22') located on a skin-engaging portion (in
this
case the cap) of the cartridge. The shaving aid strip (or composite) is locked
in an
opening in the rear of the cartridge and includes a lubricous water-soluble
polymer
shaving aid that is released by the strip during shaving to improve shave
attributes. While shown at the rear portion of this particular razor
cartridge, the
shaving aid strip may be located at any skin-engaging portion of the cartridge
and
may be fabricated in any size or shape deemed appropriate. For example, the
strip
can be incorporated into razor cartridges such as the Mach 3 , Sensor Excel ,
Atra
Plus and Custom Plus razors sold by The Gillette Company, as well as in
other
commercial razor cartridges.
Referring to Figs. 3 and 4, shaving aid strip 22 includes a first
exposed lengthwise-extending portion 24 and an adjacent, second exposed
lengthwise-extending portion 26, each portion being approximately in the shape
of a
rounded lobe with a lengthwise-extending exposed surface. Second portion 26
preferably extends at least partially under first portion 24 and provides
support for
first portion 24. The boundary between first portion 24 and second portion 26
may
approximate an inclined plane as shown. Strip 22 also includes connecting
portion
28, which extends below portions 24 and 26 and also optionally serves to lock
the
strip into a mating receiving portion of the cartridge. Second portion 26 and
connecting portion 28 preferably have the same composition. The upper surface
of
first portion 24 preferably comprises about 55% to about 85%, more preferably
about 60% to 80%, of the surface area of the upper surface of the shaving aid
strip.
In addition, the uppermost surface of first portion 24 preferably extends
slightly
above the uppermost surface of second portion 26. It is also preferred that
first
portion 24 comprises a greater amount (in percent by weight) of shaving aid
than
second portion 26. The shaving aid strip typically may be about 2.5 cm to
about
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3.7 cm in length, and about 0.15 cm to about 0.35 cm in width.
A second embodiment of the shaving aid strip of the present
invention is depicted in Figs. 6 and 7. In this embodiment, like the one
previously
described, shaving aid strip 22' includes a first exposed lengthwise-extending
portion 24' and an adjacent, second exposed lengthwise-extending portion 26',
each
portion being approximately in the shape of a rounded lobe with a lengthwise-
extending exposed surface. Second portion 26' extends substantially under
first
portion 24' and provides support for first portion 24'. The boundary between
first
portion 24' and second portion 26' is curvilinear (approximately S-shaped) as
shown. Of course, the boundary may also be arcuate, either convex or concave.
Strip 22' also includes connecting portion 28', which extends below portions
24' and
26' and also optionally serves to lock the strip into a mating receiving
portion of the
cartridge. Second portion 26' and connecting portion 28' preferably have the
same
composition. The upper surface of first portion 24' preferably comprises about
55%
to about 85%, more preferably about 60% to 80%, of the surface area of the
upper
surface of the shaving aid strip. In addition, the uppermost surface of first
portion
24' preferably extends slightly above the uppermost surface of second portion
26'.
It is also preferred that first portion 24' comprises a greater amount (in
percent by
weight) of shaving aid than second portion 26'. The shaving aid strip
typically may
be about 2.5 cm to about 3.7 cm in length, and about 0.15 cm to about 0.35 cm
in
width.
A shaving aid strip constructed as described above may be inserted
into a razor cartridge with first portion 24 (or 24') facing forward (i.e., in
the
direction of shaving) as shown in Fig. 2. Alternatively, the strip may be
inserted
with first portion 24 (or 24') facing rearward as shown in Fig. 5. Since first
portion
24 (or 24') contains a greater proportion of shaving aid than the rest of the
strip,
and optionally contains other ingredients that may contribute to its faster
wear
characteristics, it will tend to wear away slightly faster than second portion
26 (or
26'). This faster wear tends to present a fresh surface of shaving aid, which
is
present in high proportion in that portion, and thus provides more lubrication
over a
longer period of time. At the same time, portion 26 (or 26') wears more slowly
and
maintains the proper shaving geometry.
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Each portion of the shaving aid strip will include a lubricous water-
soluble polymer as the main shaving aid and, optionally, a water-insoluble
polymer
to serve as a matrix in which the water-soluble polymer is dispersed.
Preferably,
the first portion will comprise about 0% to about 30%, more preferably about
10%
to about 25%, by weight water-insoluble polymer, and about 65% to about 95%,
more preferably about 65% to about 90%, lubricous water-soluble polymer. The
second portion will preferably comprise about 10% to about 40%, more
preferably
about 20% to about 35%, water-insoluble polymer, and about 50% to about 80%,
more preferably about 55% to about 75%, lubricous water-soluble polymer.
Typical lubricous water-soluble polymers include polyethylene oxide,
polyvinyl pyrrolidone, polyacrylamide, modified hydroxyalkyl cellulose,
polyvinyl
imidazoline, polyvinyl alcohol, polysulfone and polyhydroxyethylmethacrylate.
The
preferred lubricous water-soluble polymer is polyethylene oxide. The more
TM
preferred polyethylene oxides generally are known as POLYOX (available from
TM
Union Carbide Corporation) or ALKOX (available from Meisei Chemical Works,
Kyoto, Japan). These polyethylene oxides will preferably have molecular
weights
of about 100,000 to 8 million daltons, most preferably about 300,000 to 5
million
daltons. It is preferred to use a blend of polyethylene oxides, typically a
blend
having at least one polyethylene oxide having a molecular weight in the range
of
100,000 to 500,000 and at least one polyethylene oxide having a molecular
weight
in the range of 3 million to 8 million. The most preferred polyethylene oxide
comprises a blend of about 40% to 80% by weight of polyethylene oxide having
an
TM
average molecular weight of about 5 million (e.g. POLYOX COAGULANT) and
about 60% to 20% of polyethylene oxide having an average molecular weight of
TM
about 300,000 (e.g. POLYOX WSR-N-750). A 60:40 blend of these two poly-
ethylene oxides (5 million: 300,000) is especially preferred.
Suitable water-insoluble polymers which can be used include
polyethylene, polypropylene, polystyrene, butadiene-styrene copolymer (e.g_
medium
and high impact polystyrene), polyacetal, acryionitrile-butadiene-styrene
copolymer,
ethylene vinyl acetate copolymer, polyurethane and blends thereof such as
polypropylene/polystyrene blend or polystyrene/impact polystyrene blend. The
more
preferred water-insoluble polymer is polystyrene, preferably a general purpose
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polystyrene, such as NOVA C2345ATM, or a high impact polystyrene (i.e.
polystyrene-butadiene), such as BASF 495F KG21 TM. The strip of any portion
should contain a sufficient quantity of water-insoluble polymer to provide
adequate
mechanical strength, both during production and use.
The first portion of the shaving aid strip will also preferably include a
material
which allows it to wear more quickly than the second portion and/or which
facilitates
the inclusion of relatively high levels of water-soluble polymer. One such
material
is polycaprolactone, as described in U.S. Patent No. 6,301,785 of October 16,
2001.
Preferably, the polycaprolactone will be included in an amount of about 1% to
about
10% by weight. Polycaprolactones are available from Union Carbide Corporation
under the name TONED polymers (e.g., P-737, P-767, P-787, and polyol 1270).
Preferably, the polycaprolactone will have a molecular weight between about
1000
and about 80,000 daltons, more preferably between about 30,000 and 60,000
daltons,
and most preferably about 50,000 daltons.
The shaving aid strip, or any portion, also may contain other conventional
shaving aid ingredients, such as low molecular weight water-soluble release
enhancing agents such as polyethylene glycol (MW<10,000; e.g., 1-10% by weight
PEG- 100), water-swellable release enhancing agents such as cross-linked
polyacrylics
(e.g., 2-7% by weight), colorants, antioxidants, preservatives, botanical
oils, vitamin
E, aloe, cooling agents, essential oils, beard softeners, astringents,
medicinal agents,
etc. Portions that contain a colorant can be designed to release the colorant
(e.g., by
leaching or abrasion), and thereby cause the strip to change color during
shaving. A
portion may contain, for example, between about 0.1 % and about 5.0%
(preferably
between about 0.5% and 3%) colorant by weight. Preferably, the first portion
contains a colorant so as to contrast with the second portion, whereby wear of
the first
portion during shaving provides a visual indication to the user that the
shaving aid
strip and/or the razor cartridge has reached the end of its effective life or
the end of
its optimum performance.
Shaving aid strips of the present invention may be fabricated by any
appropriate method, including injection molding and extrusion, the latter
being
preferred. All of the components of the strip are blended prior to molding or
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extrusion. For best results, it is preferred that the components are dry.
The blended components may be extruded through a Haake System
90, 3/4 inch diameter extruder with a barrel pressure of about 1000-2000 psi,
a rotor
speed of about 10 to 50 rpm, and a temperature of about 150 -185 C and a die
temperature of about 170 -185 C. Alternatively, a 1 1/4 inch single screw
extruder
may be employed with a processing temperature of 175 -200 C, preferably 185 -
190 C, a screw speed of 20 to 50 rpm, preferably 25 to 35 rpm, and an
extrusion
pressure of 1800 to 5000 psi, preferably 2000 to 3500 psi. The extruded strip
is air
cooled to about 25 C. To injection mold the strips it is preferred to first
extrude
the powder blend into pellets. This can be done on a 1 1/4 or 1 1/2 inch
single
screw extruder at a temperature of 120 -180 C, preferably 140 -150 C, with a
screw speed of 20 to 100 rpm, preferably 45 to 70 rpm. The pellets are then
molded in either a single material molding or multi-material molding machine,
which may be single cavity or multi-cavity, optionally equipped with a
hotrunner
system. The process temperature can be from 165 to 250 C, preferably from 180
to 225 C. The injection pressure should be sufficient to fill the part
completely
without flashing. Depending on the cavity size, configuration and quantity,
the
injection pressure can range from 300 to 2500 psi. The cycle time is dependent
on
the same parameters and can range from 3 to 30 seconds, with the optimum
generally being about 6 to 15 seconds.
The invention may be further described by the following examples in
which all parts and percentages are by weight.
EXAMPLES 1 TO 4
Shaving aid strips with a cross-section like that of strip 22 shown in
Fig. 4 are fabricated from the blends of components indicated below by
coextruding
the blends in the following manner. The components for each portion (portion
24
and portion 26,28) may be supplied by two separate melting/pumping (plastics
extruders), each consisting of a heated barrel, a pumping screw, a motor drive
for
that screw and a control system for the entire system. The materials are
fed in powder form into their respective extruders (e.g., single screw type
manufactured by Davis Standard). The extruders can operate at the same or
different speeds and the same or different temperatures. The barrel
temperature for
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each extruder can be ramped in three zones from 165 C to 190 C; a fourth
heater at
the die/barrel connection can also be set to 190 C, and a fifth heater at the
die can
range from 190 C to 205 C. Via rugged weldments the molten streams of the
components are brought together to form the strip. Portion 24 can be precisely
located on portion 26,28 through accurately machined pathways in the die head.
Because they have different compositions, the two molten materials are brought
together at the last possible moment before exiting the die. Both materials
exit the
die head in a size and shape approximating that of the final product. The
final
dimensions are achieved using a series of forming rollers as the extrudate is
cooled.
The strip is typically extruded at a rate of about 50 feet per minute. The
combined
molten materials are drawn from the die head into the sizing/cooling device at
a
constant speed such that its cross section is always constant. Under a bath of
cool
dry air the molten material is cooled until no longer pliable. Once cooled,
the strips
can be cut to the appropriate length and attached to razor cartridges like
cartridge
14.
Component Weight Percent
Example 1 Example 2
Portion 26,28 Portion 24 Portion 26,28 Portion 24
Polyethylene oxide' 60.0 75.0 60.0 70.0
Polystyrene2 10.2 15.2
H.I. Polystyrene3 32.5 32.5
PEG-100 5.0 5.0 5.0 5.0
White Color4/Preserv. 1.5 1.5
Blue Color4/Preserv. 4.0 4.0
Vitamin E 0.8 0.8
Polycaprolactone5 1.0 5.0 1.0 5.0
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Component Weight Percent
Example 3 Example 4
Portion 26,28 Portion 24 Portion 26,28 Portion 24
Polyethylene oxide' 58.0 77.0 60.0 80.0
Polystyrene 2 14.0 8.2
H.I. Polystyrene3 35.5 33.5
PEG-100 5.0 5.0 5.0
White Color4/Preserv. 1.5 1.5
Blue Color4/Preserv. 4.0 4.0
Vitamin E 0.8
Polycaprolactone5 7Ø
60:40 blend of Coagulant: WSR-N-750 (mol. wt. 5 million:300,000)
2 NOVA C2345A
3 BASF 495F KG21
4 Color concentrate contains 65-95% polystyrene
Tone P-767, P-737, polyol 1270, or P-787 (Union Carbide
EXAMPLES 5 AND 6
Shaving aid strips with a cross-section like that of strip 22' shown in
Fig. 7 are fabricated from the blends of components indicated below by
coextruding
the blends in the manner described above with respect to Examples 1 to 4. Once
cooled, the strips are cut to the appropriate length and attached to razor
cartridges
like cartridge 14.
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Component Weight Percent
Example 5 Example 6
Portion Portion Portion Portion
26',28' 24' 26',28' 24'
Polyethylene oxide' 63.0 69.0 63.0 74.0
Polystyrene 2 16.0 11.0
H.I. Polystyrene3 30.5 30.5
PEG-100 5.0 5.0 5.0 5.0
White Color4/Preserv. 1.5 1.5
Blue Color4/Preserv. 4.2 4.2
Vitamin E 0.8 0.8
Polycaprolactone5 5.0 5.0
60:40 blend of Coagulant: WSR-N-750 (mol. wt. 5 million:300,000)
2 NOVA C2345A
3 BASF 495F KG21
4 Color concentrate contains 65-95% polystyrene
Tone P-767 (Union Carbide
While particular embodiments of the invention have been shown and
described for illustrative purposes, it will be apparent to those skilled in
the art that
various changes and modifications may be made without departing from the
spirit
and scope of the invention, which is defined by the claims which follow.
