Abstract:
The present invention is directed to a shaving system of the wet shave type comprising a blade member (one or more) and a structure which supports or holds the blade member and which has an external skin engaging portion in proximity to the blade member. The skin engaging portion includes an improved shaving aid composite which comprises a non-volatile cooling agent, such as a non-volatile menthol analog. Preferably the shaving aid composite comprises a matrix of a water-insoluble polymer and, dispersed within the matrix, a skin lubricating water-soluble polymer and a non-volatile cooling agent. Alternatively, the shaving aid composite may comprise a sheath of water-insoluble polymer that surrounds a core which includes a skin-lubricating water-soluble polymer and a non-volatile cooling agent. The improved shaving aid composite (or lubricating strip) is capable of retaining during normal storage conditions substantially all of the cooling agent included during fabrication of the composite and delivering an effective amount of the cooling agent during use.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a shaving system of the wet shave type, more particularly to a shaving system with an improved shaving aid composite. 
     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. Pat. No. 4,170,821 and GB 2,024,082. The shaving aid composite 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 composites suffer from the disadvantage that they release an insufficient amount of the shaving aid, particularly after the first three or four shaves where release of the shaving aid may drop off to negligible quantities. Accordingly, recent efforts have been made to improve shaving aid composites so as to enhance and prolong release of the shaving aid. Such efforts have resulted in improved shaving aid composites which include the following: incorporation of low molecular weight release enhancing agent, such as polyethylene glycol, into the matrix, disclosed in U.S. Pat. No. 5,113,585; the use of ethylene vinyl acetate copolymer as the matrix material, disclosed in U.S. Pat. No. 5,349,750; incorporation of a water-swellable polymer such as Salsorb 84, a cross-linked polyacrylic, disclosed in U.S. Pat. No. 5,626,154, incorporation of a compatibilizer material such as polyethylene oxide-polypropylene oxide copolymer (e.g. Poloxamer 182), disclosed in U.S. Pat. No. 5,454,164; and co-extrusion 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, disclosed in U.S. Ser. No. 08/332,293, now abandoned. All of the aforementioned patents or patent applications are incorporated herein by reference. 
     It has also been suggested in U.S. Pat. No. 5,095,619 that a water-insoluble essential oil, such as menthol, may be advantageously included in a shaving aid composite. However, it has been found in practice that a substantial amount of the essential oil is lost due to volatilization prior to use, rendering the composite unable to deliver an effective amount of the essential oil. It is an object of the present invention to provide a shaving aid composite (i.e. lubricating strip) which is capable of retaining during normal storage conditions substantially all of a cooling agent included during fabrication of the composite and delivering an effective amount of the cooling agent during use. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a shaving system of the wet shave type comprising a blade member (one or more) and a structure which supports or holds the blade member and which has an external skin engaging portion in proximity to the blade member. The shaving system may be a disposable shaving cartridge adapted for coupling to and uncoupling from a razor handle or it may be a shaving head which is integral with a razor handle so that the complete razor is discarded as a unit when the blade or blades become dulled. The blade edge cooperates with the skin engaging portion to define shaving geometry. 
     The skin engaging portion includes an improved shaving aid composite which comprises a non-volatile cooling agent, such as a non-volatile menthol analog. Preferably the shaving aid composite comprises a matrix of a water-insoluble polymer and, dispersed within the matrix, a skin lubricating water-soluble polymer and a non-volatile cooling agent. Alternatively, the shaving aid composite may comprise a sheath of water-insoluble polymer that surrounds a core which includes a skin-lubricating water-soluble polymer and a non-volatile cooling agent. The improved shaving aid composite (or lubricating strip) is capable of retaining during normal storage conditions substantially all of the cooling agent included during fabrication of the composite and delivering an effective amount of the cooling agent during use. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a razor unit in accordance with the invention; 
     FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1; and 
     FIG. 3 is a perspective view of another razor unit in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The shaving unit 10 shown in FIGS. 1 and 2 includes base or platform member 12 molded of high impact polystyrene that includes integral coupling groove structure 14 for attachment to a razor handle and guard structure 16 that defines a transversely extending forward skin engaging surface 18. On the upper surface of platform 12 are disposed steel leading blade 20 having a sharpened edge 22, steel following blade 24 having sharpened edge 26, and aluminum spacer member 28 that maintains blades 20 and 24 in spaced relation. Cap member 30 is molded of high impact polystyrene and has body portion 32 that defines skin engaging surface 34 that extends transversely between forwardly projecting end walls 36 and has a front edge 38 that is disposed rearwardly of blade edge 26. Integral rivet portions 40 extend downwardly from transversely extending body portion 32 and pass through holes in blades 20 and 24, spacer 28, and platform 12 to secure cap 30, blades 20, 24 and spacer 28 on platform 12. Adhesively affixed to skin engaging surface 34 is shaving aid composite 42. 
     The shaving unit 50 shown in FIG. 3 is of the type shown in Jacobson, U.S. Pat. No. 4,586,255, and includes body 52 with front portion 54 and rear portion 56. Resiliently secured in body 52 are guard member 58, leading blade unit 60 and trailing blade unit 62. A shaving aid composite in the form of elongated insert member 64 is frictionally locked in opening 66 of rear portion 56. The shaving aid composite incorporates a shaving aid which, upon contact with water, leaches out of the composite onto the skin of the user during shaving to improve the shave attributes. While shown at the rear portion of this particular shaving unit, the shaving aid composite may be located at any skin-engaging portion of the shaving unit and may be fabricated in any size or shape deemed appropriate. 
     The shaving aid composite comprises a non-volatile cooling agent, such as a non-volatile menthol analog. Preferably the shaving aid composite comprises a matrix of a water-insoluble polymer and, dispersed within the matrix, a skin lubricating water-soluble polymer and a non-volatile cooling agent. Alternatively, the shaving aid composite may comprise a sheath of water-insoluble polymer that surrounds a core which includes a skin-lubricating water-soluble polymer and a non-volatile cooling agent, the sheath having a plurality of openings to facilitate release of the water-soluble polymer and cooling agent. The shaving aid composite may also optionally include low molecular weight water-soluble release enhancing agents such as polyethylene glycol (e.g. 1-10% by weight), water-swellable release enhancing agents such as cross-linked polyacrylics (e.g. 2-7% by weight), colorants, antioxidants, preservatives, microbiocidal agents, beard softeners, astringents, depilatories, medicinal agents, conditioning agents, etc. 
     Suitable water-insoluble polymers which can be used for the matrix (or sheath) include polyethylene, polypropylene, polystyrene, butadiene-styrene copolymer (e.g. medium and high impact polystyrene), polyacetal, acrylonitrile-butadiene-styrene copolymer, ethylene vinyl acetate copolymer and blends such as polypropylene/polystyrene blend. 
     Preferably the water-insoluble polymer comprises about 10 to 50%, more preferably about 15 to 40%, and most preferably about 20 to 35% by weight of the shaving aid composite. The more preferred water-insoluble polymer is polystyrene, preferably a general purpose polystyrene such as Dow STYRON (Dow Chemical Company) or a high impact polystyrene (i.e. polystyrene-butadiene), such as Mobil 4324 (Mobil Corporation). The composite should contain a sufficient quantity of water-insoluble polymer to provide adequate mechanical strength, both during production and use. 
     Suitable skin lubricating water-soluble polymers include polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline, and polyhydroxyethylmethacrylate. Preferably the water-soluble polymer comprises about 20 to 80%, more preferably about 40 to 75%, by weight of the shaving aid composite. 
     The more preferred water-soluble polymers are the polyethylene oxides generally known as POLYOX (available from 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 6 million, most preferably about 300,000 to 5 million. The most preferred polyethylene oxide comprises a blend of about 40 to 80% of polyethylene oxide having an 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 about 300,000 (e.g. POLYOX WSR-N-750). The polyethylene oxide blend may also advantageously contain up to about 10% by weight of a low molecular weight (i.e. MW&lt;10,000) polyethylene glycol such as PEG-100. 
     The non-volatile cooling agent will generally comprise about 1% to about 25%, preferably about 2% to about 20%, most preferably about 10% to about 17%, by weight of the shaving aid composite. By non-volatile cooling agent is meant an agent which has a physiological cooling effect on the skin and which is appreciably less volatile than menthol. Preferably, the non-volatile cooling agent will be one which when subjected to thermogravimetric analysis (e.g. using a 951 Thermogravimetric Analyzer from Dupont with a 20° C. temperature rise per minute) will retain at least 50% of its initial weight at a temperature of 160° C., more preferably at least 80% of its initial weight at a temperature of 160° C., and most preferably at least 50% of its initial weight at a temperature of 175° C. 
     Suitable cooling agents which can be utilized include non-volatile menthol analogs such as menthyl lactate, menthyl ethoxyacetate, menthone glycerinacetal, 3-l-menthoxypropane-1,2-diol, ethyl l-menthyl carbonate, (1S,3S,4R)-p-menth-8-en-3-ol, menthyl pyrrolidone carboxylate, N-substituted-p-menthane-3-carboxamides (as described in U.S. Pat. No. 4,136,163, which is incorporated herein by reference) including, for example, N-ethyl-p-menthane-3-carboxamide, acyclic carboxamides of the formula ##STR1## where R&#39; and R&#34;, when taken separately, are each hydrogen, C 1  -C 5  alkyl or C 1  -C 8  hydroxyalkyl and provide a total of no more than 8 carbon atoms, with the proviso that when R&#39; is hydrogen R&#34; may also be alkylcarboxyalkyl of up to 6 carbon atoms; R&#39; and R&#34;, when taken together, represent an alkylene group of up to 6 carbon atoms thereby forming a nitrogen heterocycle, the alkylene chain being optionally interrupted by oxygen; R 1  is hydrogen or C 1  -C 5  alkyl; and R 2  and R 3  are each C 1  -C 5  alkyl (such acyclic carboxamides being described in U.S. Pat. No. 4,153,679, which is incorporated herein by reference)including, for example, N,2,3-trimethyl-2-isopropylbutanamide, and ketal coolants (as described in WO 93/23005, which is incorporated herein by reference) including, for example, l-menthon-ld-isomenthon glycerin ketal. 
     Shaving aid composites 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 composite are blended prior to molding or 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 11/4 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 11/4 or 11/2 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 multimaterial 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 illustrated by the following examples in which all pads and percentages are by weight. 
     EXAMPLE 
     Shaving aid composites similar to insert member 64 shown in FIG. 3 are fabricated from the blends indicated below by extruding the blends 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. The extruded strip of composite is cooled and sliced to appropriate lengths for securing into openings 66 of shaving units 50. In the blends listed below, the polystyrene is Dow STYRON or Mobil 2824, the high impact polystyrene (&#34;Hips&#34;) is Mobil 4324, the polyethylene oxide (60/40) is a blend of 60% POLYOX COAGULANT (M.W. 5 million) and 40% POLYOX WSR-N-750 (M.W. 300,000), and the polyethylene glycol (&#34;PEG&#34;) is Dow 4500 PEG (MW=4500). The cooling agents used are 3-l-menthoxypropane-1,2-diol (Cooling Agent 10), N-ethyl-p-menthane-3-carboxamide (WS-3), N,2,3-trimethyl-2-isopropylbutanamide (WS-23), menthyl lactate (Frescolat ML), menthone glycerinacetal (Frescolat MGA) and menthyl ethoxyacetate (Menglytate). 
     
         ______________________________________Blend A28.5%          Hips46.8%          polyethylene oxide8.5%           PEG15.0%          Cooling Agent 101.2%           colorant/antioxidantBlend B30.2%          Hips49.5%          polyethylene oxide9.0%           PEG10.0%          Cooling Agent 101.3%           colorant/antioxidantBlend C31.9%          Hips52.3%          polyethylene oxide9.5%           PEG5.0%           Cooling Agent 101.3%           colorant/antioxidantBlend D32.9%          Hips53.9%          polyethylene oxide9.8%           PEG2.0%           Cooling Agent 101.4%           colorant/antioxidantBlend E28.5%          Hips46.8%          polyethylene oxide8.5%           PEG15.0%          WS-31.2%           colorant/antioxidantBlend F30.2%          Hips49.5%          polyethylene oxide9.0%           PEG10.0%          WS-31.3%           colorant/antioxidantBlend G28.5%          Hips46.8%          polyethylene oxide8.5%           PEG10.0%          WS-35.0%           Poloxamer 1821.2%           colorant/antioxidantBlend H29.5%          Hips48.4%          polyethylene oxide8.8%           PEG10.0%          WS-32.0            Na dodecylbenzene sulfonate1.3%           colorant/antioxidantBlend I31.2%          Hips51.2%          polyethylene oxide9.3%           PEG5.0%           WS-32.0%           Na dodecylbenzenesulfonate1.3%           colorant/antioxidantBlend J31.9%          Hips52.3%          polyethylene oxide9.5%           PEG5.0%           WS-31.3%           colorant/antioxidantBlend K24.0%          polystyrene59.4%          polyethylene oxide5.3%           Salsorb 8810.0%          WS-31.3%           colorant/antioxidantBlend L28.5%          Hips46.8%          polyethylene oxide8.5%           PEG15.0%          WS-231.2%           colorant/antioxidantBlend M31.9%          Hips52.3%          polyethylene oxide9.5%           PEG5.0%           WS-231.3%           colorant/antioxidantBlend N30.2%          Hips49.5%          polyethylene oxide9.0%           PEG10.0%          Frescolat ML1.3%           colorant/antioxidantBlend O30.2%          Hips49.5%          polyethylene oxide9.0%           PEG10.0%          Frescolat MGA1.3%           colorant/antioxidantBlend P30.2%          Hips49.5%          polyethylene oxide9.0%           PEG10.0%          Menglytate1.3%           colorant/antioxidant______________________________________ 
    
     Each of the foregoing strips retains a substantial portion (i.e. &gt;50%) of the cooling agent (i.e. menthol analog) included during fabrication when stored at 45° C. for four days. In addition, each of the foregoing strips releases cooling agent when contacted with water.