Abstract:
An oral care implement has one or more components, such as a handle or a gripping portion thereof, prepared from an elastomeric propylene-ethylene copolymer. The elastomeric copolymer provides a comfortable and non-slippery gripping surface in a variety of conditions, including both wet and dry environments, and also provides flexible characteristics which are particularly well suited for hinged handle designs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The application claims the benefit of priority of U.S. Patent Application No. 60/702,736, filed Jul. 27, 2005, in which the contents are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     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  
       [0003]     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.  
         [0004]     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.  
         [0005]     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 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.  
         [0006]     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  
       [0007]     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.  
         [0008]     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  
       [0009]      FIG. 1  is a perspective view of a toothbrush in accordance with one embodiment of the invention;  
         [0010]      FIG. 2  is a top plan view of the toothbrush of  FIG. 1 ;  
         [0011]      FIG. 3  is a side elevation view of the toothbrush of  FIG. 1 ;  
         [0012]      FIG. 4  illustrates a flexible toothbrush head in accordance with one embodiment of the invention;  
         [0013]      FIG. 5  is a bottom plan view of the flexible head shown in  FIG. 4 ;  
         [0014]      FIG. 6  is a perspective view of a toothbrush in accordance with another embodiment of the invention; and  
         [0015]      FIG. 7  is a perspective view of a toothbrush in accordance with another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     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.  
         [0017]      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 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 .  
         [0018]     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.  
         [0019]     The head  3  may integral with or permanently attached to the handle  2 , or may be replaceable. One or more other oral surface engaging elements, such as a flossing element, plaque scrapper, and the like, may also be present on the toothbrush  1 .  
         [0020]     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.  
         [0021]     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.  
         [0022]     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. Pat. No. 5,758,383, which is incorporated by reference herein, having first  14  and second  16  sections and an elastomer section or joint  18  located therebetween.  
         [0023]     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 toothbrush heads, as well as examples of other flexible head configurations which can be used, are also described in US 2002-0152570 A1, the disclosure of which is hereby incorporated by reference.  
         [0024]      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.  
         [0025]      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  203   a - b  at the distal end  107  and straddling a longitudinal axis of the toothbrush  100 . The distal cleaning elements  203   a - 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  207   a - c . Any or all of the distal cleaning elements  203   a - b , central cleaning elements  207   a - c , and arcuate cleaning elements  211   a - b , can be formed from the elastomeric propylene-ethylene copolymer.  
         [0026]     The propylene-ethylene copolymer elastomer can be incorporated into the various components of the toothbrush using conventional molding techniques well known to 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.  
         [0027]     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 (M w ) to number average molecular weight (M n ). 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.  
         [0028]     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%.  
         [0029]     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, 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.  
         [0030]     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.  
         [0031]     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 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).  
         [0032]     The presence of TPV in the elastomer improves molding properties without significantly detracting from the desired softness and other properties of the elastomer. Non-limiting examples of TPVs that may be used include Vyram™ and Santoprene™, available from ExxonMobil.  
         [0033]     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.  
         [0034]     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.