Note: Descriptions are shown in the official language in which they were submitted.
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ORAL CARE IMPLEMENT COMPRISING AN ELASTOMERIC POLYPROPYLENE-
ETHYLENE COPOLYMER
FIELD OF THE INVENTION
[0001] The present invention is directed to an oral care implement, and more
particularly, to an
oral care implement comprising having one or more components constructed from
elastomeric propylene-ethylene copolymers.
BACKGROUND OF THE INVENTION
[0002] Oral care implements, particularly toothbrush handles, traditionally
have been
manufactured with rigid materials such as polypropylene, polystyrene,
polyethylene,
acrylonitrile-styrene copolymer, or cellulose acetate propionate. Toothbrush
handles
constructed from such rigid materials can be uncomfortable to grip and
difficult to
manipulate during brushing. In addition, the rigid handles can become slippery
in wet
conditions which often are encountered during brushing.
[0003] One approach has been to provide a rigid handle overmolded with an
elastomer to
improve comfort and ease of manipulation of the toothbrush. For example, US
2004/
0025272 to Stvartak et al., incorporated herein by reference, discloses a
toothbrush
having a handle constructed from a rigid base member, such as polypropylene or
polyethylene, overmolded with elastomer, such as urethane,
styrene/ethylene/butylene-
styrene elastomer, metallocene elastomers, e.g., Engage (a polyolefin
elastomer
available from DuPont Dow Elastomers), or fully vulcanized ethylene-propylene-
diene-
monomers in a continuous matrix of polypropylene. However, such elastomers
tend to
be expensive and add significant cost to the manufacture of the toothbrush.
>
[0004] Flexible materials also have been used in portions of toothbrush
handles to increase user
comfort by limiting the amount of force applied to the teeth and gums during
brushing.
For example, US 2004/0128780 to Chan, incorporated herein by reference,
describes an
electric toothbrush having a flexible neck made from a mixture of a first
polymer, such as
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polypropylene, and a second polymer having a lower flexural modulus than the
first
polymer. The second polymer can be a thermoplastic elastomer ("TPE"), a
thermoplastic
olefin ("TPO"), a soft thermoplastic polyolefin, or other elastomeric material
such as
ethylene-vinylacetate copolymer or ethylene propylene rubber.
[0005] There remains a need for alternative materials for constructing
components of oral care
implements, particularly materials which are cost effective while
concomitantly
providing benefits such as non-slip gripping surfaces, enhanced tactile feel
and user
comfort.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to an oral care implement having one
or more
components constructed from an elastomeric propylene-ethylene copolymer
preferably
having a Shore A hardness of less than about 80. Such elastomer can be used to
construct
components including, but not limited to, the handle, or a gripping portion
thereof, a
toothpick section, a head section or portion thereof, a bristle section, a
tongue cleaning
element, elastomeric tooth cleaning element, and/or holding sections, e.g.,
pockets used
for dispersing fragrance or flavor-yielding capsules. Such elastomer can be
overmolded
onto or injection molded with a thermoplastic material, such as polypropylene,
to form a
handle or other component of the oral care implement.
[0007] When used in the handle portion, the elastomer provides a comfortable
and non-slippery
gripping surface in a variety of conditions, including dry environments as
well as the wet
or slurry environments often encountered during brushing. The elastomer also
provides
flexible characteristics which are particularly well suited for flexible heads
or other
hinged handle designs. In addition, the elastomeric material can be
incorporated into
other components such as, but. not limited to, bristles and/or a flexible
pick.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of a toothbrush in accordance with one
embodiment of the
invention;
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[0009] FIG. 2 is a top plan view of the toothbrush of FIG. 1;
[0010] FIG. 3 is a side elevation view of the toothbrush of FIG. 1;
[0011] FIG. 4 illustrates a flexible toothbrush head in accordance with one
embodiment of the
invention;
[0012] FIG. 5 is a bottom plan view of the flexible head shown in FIG. 4;
[0013] FIG. 6 is a perspective view of a toothbrush in accordance with another
embodiment of
the invention; and
[0014] FIG. 7 is a perspective view of a toothbrush in accordance with another
embodiment of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] While the invention is illustrated and described primarily with
reference to manual
toothbrushes, it should be understood that oral care implements are inclusive
of a variety
of other types of devices, such as powered toothbrushes, inter-proximal picks,
flossing
tools, plaque scrapers, tongue and soft tissue cleansers/massagers and the
like.
[0016] FIGS. 1-3 illustrate a toothbrush 1 having a handle 2, a head 3
containing cleaning
elements such as bristles 4, a pick 5, a plurality of sockets 6, and a
textured tongue
cleaning element 9. The handle 2 preferably is designed to enable the user to
easily grip
and manipulate the toothbrush. More particularly, the handle 2 preferably is
shaped
and/or includes ergonomic features to provide a higher degree of control for
the user
while maintaining comfort. Examples of ergonomic features include an
overmolded grip
portion 7 that can be segmented and ergonomically sized for users, and the
inclusion of
sections that are angled relative to each other and/or which are wider or
narrower than
other portions of the handle to provide increased control and comfort during
use. In the
embodiment shown in FIGS. 1-3, a textured grip portion 8 is provided in the
center
region of the handle 2 to provide a non-slip surface for the user to grip the
toothbrush
between the thumb and forefinger. The grip portion 8 can, for example, be
provided on
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the same side of the handle 2 as the bristles 4, on the opposite side of the
handle 2 as the
bristles 4, or on both sides as shown in FIG. 3.
[0017] Preferably, the head 3, bristles 4, pick 5, and sockets 6 are
ergonomically sized and
shaped to facilitate tooth cleaning, including interproximal tooth cleaning.
The head 3
can be generally elliptical or rectangular in shape, for example, although
other
configurations are contemplated. The bristles 4 extend from the surface of
head 3 and
can be of conventional size and spacing for effective tooth cleaning. The pick
5 can have
a size and conical shape adapted to promote interproximal cleaning
effectiveness.
[0018] The head 3 may integral with or permanently attached to the handle 2,
or may be
replaceable. One or more otlier oral surface engaging elements, such as a
flossing
element, plaque scrapper, and the like, may also be present on the toothbrush
1.
Although a toothbrush is illustrated in FIGS. 1-3 as having such features as a
pick 5,
sockets 6, grip portions 7 and 8, and a tongue scrape element 9, it should be
understood
that each of these features is optional and merely illustrative. In practice,
the toothbrush
can have these any of these features alone or in any combination with other
features not
illustrated herein. It will also be appreciated that while the cleaning
elements are
illustrated herein as tufts of bristles 4, other cleaning elements of varying
size, shape,
cross-section and material may be used.
[0019] The device may have concave molded portions for holding and dispensing
fragrance,
flavorants, actives or other materials. As illustrated in FIGS. 1-3, for
example, a plurality
of sockets 6 may be located at one or both ends of the handle 2. The sockets 6
can be
sized and shaped to releasably hold fragrance, flavor-yielding capsules, or
other materials
to be dispensed. For example, the sockets 6 can be molded from the elastomeric
material
as concave hemispheres of suitable dimensions to enable flavor-yielding
capsules to be
easily dispensed and replaced. Alternatively, the sockets 6 can be configured
to hold
commercially available fragrance or flavor yielding gel capsules.
[0020] The head 3 may be rigid or flexible. While FIGS. 1-3 show an embodiment
having a
rigid head, FIGS. 4-6 illustrate examples of toothbrush configurations having
flexible
heads. FIG. 4 shows a flexible head 12 of a toothbrush shown in U.S. Patent
5,758,383,
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which is incorporated by reference herein, having first 14 and second 16
sections and an
elastomer section or joint 18 located therebetween.
[0021] The handle and head sections are preferably molded from a plastic or
resin such as
polypropylene, while the joint 18 can be formed from the propylene-ethylene
copolymer
elastomer of the invention. From the view shown in FIG. 5, it can be seen that
the
elastomer-containing section 18 spans the width of the head sections 14 and 16
between
its lateral sides. Other details of flexible tootllbrush heads, as well as
examples of other
flexible head configurations which can be used, are also described in US 2002-
0152570
Al, the disclosure of which is hereby incorporated by reference.
[0022] FIG. 6 illustrates another embodiment of a toothbrush 80 having a head
87 that can be
rigid or flexible as described in connection with the embodiment of FIGS. 4-5
. The head
87 has cleaning elements in the form of bristles 86 and a plurality of
elastomeric
massaging elements 94 disposed around a perimeter portion. The elastomeric
massaging
elements 94 can be molded from the propylene-ethylene copolymer elastomer. The
elastomeric massaging elements 94 typically are slightly longer than the
bristles 86 and
can be used to massage the gums during brushing. Other portions of the
toothbrush, such
as grip portions 91, 97, also can incorporate the propylene-ethylene copolymer
elastomer.
[0023] FIG. 7 shows another embodiment of a toothbrush 100 having a support
101 including a
handle 103 and a head 105, and tooth cleaning elements 200 as shown in US 2005-
0000048, which is incorporated herein by reference. The head 105 also includes
distal
cleaning elements 203a-b at the distal end 107 and straddling a longitudinal
axis of the
toothbrush 100. The distal cleaning elements 203a-b typically protrude higher
from the
base surface 109 than the tips of the other tooth cleaning elements. The tooth
cleaning
elements 200 also can include arcuate cleaning elements 211 a-b and central
cleaning
elements 207a-c. Any or all of the distal cleaning elements 203a-b, central
cleaning
elements 207a-c, and arcuate cleaning elements 21 la-b, can be formed from the
elastomeric propylene-ethylene copolymer.
[0024] The propylene-ethylene copolymer elastomer can be incorporated into the
various
components of the toothbrush using conventional molding techniques well known
to
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those of ordinary skill, such as overmolding or co-injection molding
techniques. The
elastomer can be used to form a handle or a portion thereof, a flexible joint
in the head, a
flexible pick, elastomeric cleaning elements, bristles, a tongue cleaning
element, other
components of an oral care implement, or any combination thereof.
[0025] Suitable propylene-ethylene copolymer elastomers which can be used the
practice of the
present invention are commercially available, such as Versify which is
available from
Dow Chemical Company. The elastomeric propylene-ethylene copolymer can be
prepared using metallocene polymerization, such as by using Group 4 metal
complex
catalysts as described in US 2004/0087751 to Tau et al., the disclosure of
which is hereby
incorporated by reference. The copolymer preferably has a molecular weight
distribution
of about 2 to 3. Molecular weight distribution is the ratio of weight average
molecular
weight (Mw) to number average molecular weight (Mõ). Other preferred physical
properties of the propylene-ethylene copolymers include a comonomer content of
from
about 5 to about 15 wt%; a density of about 0.8 to 0.9 g/cc, preferably from
about 0.858
to 0.888 g/cc; a Shore A hardness (ASTM D-2240) of from 30 to 80, preferably
from
about 50 to about 75; a glass transition temperature (ASTM E1356-98) of from
about -15
to about -35 C; and a flexural modulus (ASTM D-790A) of from about 1,000 to
about
40,000 psi.
[0026] Another example of a commercially available elastomer which can be used
is
Vistamaxx , a metallocene catalyst-based elastomer available from ExxonMobil.
This
polymer has a Shore A hardness ranging from about 30 to about 65; a specific
gravity of
0.86-0.99; a melt flow rate (ASTM D-1238) of 1-20 g/10 min; a glass transition
temperature of from about -20 to about -30 C; a melting temperature of from
about 40 to
about 160 C; a tensile strength (ASTM D-638) of about 2200-400 p.s.i.; a
flexural
modulus of from about 1,000 to about 3,000 psi; and an elongation at break
(ASTM D-
638) of about 100-1500%.
[0027] The propylene-ethylene copolymer elastomers described in this invention
are inherently
elastomeric in the as-polymerized form. Other Thermoplastic Elastomers (TPE)
commonly used are either a compound of copolymers (e.g., Styrenic block
copolymers,
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fillers, mobilizers (e.g., paraffin oil, paraffin wax, etc.) and other
additives; or a
compound of polypropylene, particles of vulcanized or non-vulcanized synthetic
elastomers and other additives. In comparison, the propylene-ethylene
copolymer
elastomers described in this invention are inherently and consistently lower
in
manufacturing cost since the more cumbersome blending and compounding steps
are
generally not required. Moreover, the propylene-ethylene copolymer elastomers
avoid
the need for various fillers and additives found in many Thermoplastic
Elastomers (TPE)
that can result in non-compliance with food contact requirements as regulated
by the
FDA or its equivalence.
[0028] The propylene-ethylene copolymer elastomer preferably is blended with a
polyolefin
such as polypropylene homopolymer and/or polypropylene copolymers. Non-
limiting
examples of other blending polyolefins include high density polyethylene
(HDPE) and
low density polyethylene (LDPE). The amount of polyolefin blended with the
elastomer
depends on such factors as the desired physical properties of the molded
section and the
specific molding operation employed. Most often, the amount of polyolefin used
ranges
from about 5 to about 20 wt%. In general, higher levels of polyolefin (and/or
nucleating
agents) reduce molding time and improve molding properties, but also detract
from the
desirable properties imparted by the elastomer, e.g., softness, non-slip grip,
etc.
Polypropylene is a preferred material for blending, particularly for
compatibility purposes
when the blend is overmolded onto a polypropylene substrate base.
[0029] In an alternative embodiment, an oral care implement has one or more
components
constructed from a propylene-ethylene copolymer elastomer having a Shore A
hardness
of from about 30 to about 80, blended with a thermoplastic vulcanizate (TPV).
The
elastomer/TPV blend can be used to construct the handle, or a gripping portion
thereof, a
toothpick section, a head section or portion thereof, a bristle section, a
tongue cleaning
element, elastomeric tooth cleaning element, and/or holding sections, e.g.,
pockets used
for dispersing fragrance or flavor-yielding capsules. One preferred propylene-
ethylene
copolymer elastomer for this embodiment is Versify available from Dow
Chemical,
although other propylene-ethylene copolymer elastomers as described above also
can be
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used. The elastomer/TPV blend can be used to construct one or more components
of an
oral care implement as described with reference to the previous embodiment(s).
[0030] The presence of TPV in the elastomer improves molding properties
without significantly
detracting from the desired softness and otller properties of the elastomer.
Non-limiting
examples of TPVs that may be used include VyramTM and SantopreneTM, available
from
ExxonMobil.
[0031] The propylene-ethylene copolymer elastomers also can be blended with
one or more
additives, non-limiting examples of which include organic or inorganic
fillers, light
stabilizers, plasticizers, processing aids (such as oils or stearic acid),
colorants or
pigments. Appropriate loadings of such additives will be apparent to persons
of ordinary
skill in the art with the aid of no more than routine experimentation. The
additives
should not interfere with the desired physical properties of the elastomer.
[0032] It will be understood that while the invention has been described in
conjunction with
specific embodiments thereof, the foregoing description and examples are
intended to
illustrate, but not limit the scope of the invention. While specific
toothbrush
configurations have been illustrated, the present invention is not limited to
any of the
aesthetic aspects shown and, in practice, may differ significantly from the
illustrated
configurations.
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