SHAVING UNIT INCORPORATING A SHAVING AID

Abstract: A Disposable shaving unit having one or more razor blades (4) that creates a smooth surface on the skin as a result of friction and contact with water without using other shaving aid materials wherein the production of an entire platform (5) and cap section (7) uses an injection process which defines a skin engaging surface composed of a blend of water insoluble polymer in an amount of 50-90% by weight that is polystyrene, thermoplastic rubber (with or withour filler) with or without polystyrene, polyethylene, polypropylene and polyacetal, water soluble polymer in an amount of 9-40% by weight and polyethylene glycol in an amount of 1-10 % by weight.

Description: This invention relates to shaving units that provide a comfortable shaving whatever the holding position and angle is, as a result of supplying a shaving composition which is water soluble or soluble in shaving foam or soap with the friction of cap and platform sections to the skin. The complete shaving unit or its cartridge is disposable and it comprises one or more razor blades. PRIOR ART Except for the razor blades the whole shaving unit as well as the cartridge section that is engaged with the handle are disposable and made of water insoluble polymer polystyrene based material. These types of shaving units do not consist of a shaving aid material. In the prior art the use of shaving aid material that helps the razor blade to slide smoothly along the skin and facilitates shaving is known. The shaving unit described in the U.S. Patent No. 4 624 051 may be given as example. This patent discloses a shaving aid member (strip) composed of water soluble polymer material having the area of surface in the range of 20-70 mm² and that is disposed through the aperture on the cap protruding at least 0.1 mm above the cap surface. The invention suggests that the polymer blend includes a water soluble polymeric material in an amount of up to 50% by weight selected from the class consisting of polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline and polyhydroxyethylmethacrylate and a water insoluble polymer in an amount of at least 50% by weight selected from the class consisting of polyethylene, polypropylene, polystyrene and polyacetale. The member consisting of water soluble polymer that is present in the shaving units manufactured in accordance with this technique is placed on the cap that is above the razor blade. During shaving as a result of the frictional drag of the razor across the skin the water soluble polymer present in the member is leached and provides a smooth surface. In the prior art shaving units, this smooth surface can only be realized on friction of the razor head on skin. It would be necessary to move the member across the skin in order to enhance the comfort of shaving and to provide smoothness. Also, comfortable shaving is impossible with certain handling positions and angles. The general feature in the prior art shaving units is to manufacture the shaving aid member which consists of shaving aid material separately, placing on top of the blade in form of strip; the blend includes 50% (preferably 80%) water soluble polymer and 50% (preferably 20%) water insoluble polymer. U.S. Patent No. 4, 170, 821 discloses a disposable razor cartridge having a shaving aid containing lubricant as micro-encapsulated silicone oil, polyethylene oxide in the range of molecular weight between 100 000 - 6 000 000, non-ionic polyacrylamide, natural polysaccaride from plants such as guar gum, hair softening agent, cleaning agent, medicinal agent and blood coagulant. This patent does not claim any percentages for mixing of water soluble and insoluble materials in the mixture. In low percentages of water soluble polymer which is polyethylene oxide, the slippery feature will be hardly felt during shaving. The mixture contains non-ionic polymer polyacrylamide which is not a polyethylene oxide plasticizer as a non-ionic polymer. In this patent specification a mixing process is not mentioned therefore homogeneous distribution of water soluble and insoluble polymer in the shaving unit during injection moulding process may not be obtained. United Kingdom Patent No. 2,183,523 discloses a razor cartridge of which one or more of the skin contacting surfaces is/are composed of a self lubricating plastics material comprising a moulded thermoplastics polymer containing a water insoluble migratable slip or lubricating agent, preferably free silicone oil (up to 5 percent by weight) or polytetrafluoroethylene (up to 20 percent by weight). A shaving unit described in the United Kingdom Patent No. 2,024,082 comprises the guard and cap surfaces formed wholly in part of a moulded mixture of at least one hydrophobic material and at least one water leachable hydrophilic polymeric material. The mixture of polymeric materials comprises 85 to 5% by weight of the hydrophobic material(s) and 15 to 95% by weight of the hydrophilic material(s), or from 50 to 60% by weight of the hydrophobic material(s) and 50 to 40% by weight of hydrophilic material(s). The hydrophobic polymeric materials described in the patent are polystyrene, polyethylene, polypropylene or polyacetal. The hydrophilic polymeric materials are polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline or polyhydroxyethyl methacrylate. These hydrophilic materials do not contain polyethylene glycol as being plasticizer of polyethylene oxide and flow modifier. FR-A-2229389 discloses the use of polyethylene glycol in shaving aids (e.g. shaving creams). OBJECTS OF THE INVENTION The objective of this invention is to provide comfortable and easy shaving by making the surface smooth during shaving before the friction of the blade with the skin and keeping it smooth afterwards. This smoothness is defined as coating the whisker or hair by gel type of water soluble polymer so as not to feel cutting action during shaving. This objective of the invention can be reached by the manufacture of platform and cap portions of the shaving units that can be totally or partly disposable with the addition of polyethylene glycol that makes the dissolving easier and that is surface active during the injection process into the mixture prepared with water soluble and insoluble polymers because it is a plasticizer for polyethylene oxide and non-ionic polymer. Subject matter of the present invention is a disposable shaving unit according to claim 1. Preferred embodiments of this shaving unit are subject matter of claims 2 to 9. A further subject matter of the present invention is a method of manufacturing a shaving unit according to the present invention. DETAILED DESCRIPTION OF THE INVENTION The invention will be clearly understood by the following description and accompanying drawings, in which FIGURE 1, is a front view of the disposable shaving unit. FIGURE 2, is a side view of the disposable shaving unit. FIGURE 3, is a bottom view of the platform section of the shaving unit FIGURE 4, is the top view of the platform of the shaving unit FIGURE 5, is the bottom view of the cap section of the shaving unit FIGURE 6, is a top view of the cap section of the shaving unit. FIGURE 7, is a view of the cartidge of the shaving units that can be attached to the handle. THE PARTS 1. Handle 2. The portion that engages the platform to the handle 3. Cap 4. Razor blade 5. Platform 6. The pins on the cap 7. The protection bar in front of the platform This invention discloses an improved technique that uses polyethylene glycol in addition to the water soluble and insoluble polymers in the blend used in the manufacture of platform 5 and cap 3 as being plasticizer of polyethylene oxide and flow modifier for the injection moulding process. The composition of the blend that forms the cap 3 and platform structure may be summarized as follows: 1. Water insoluble polymer material : polystyrene, thermoplastic rubber (with or without filler) mixed with polystyrene or not, all types of plastics that can be used in the injection process such as polyethylene, polypropylene and polyacetal. 2. Water soluble polymer material : WRPA 5769® compound containing plasticizer, antibacterial, anti oxidant and heat stabilizer. WSR-301® polyethylene oxide coagulant to reduce melt flow, increase slippery and pituity feature. The blend used in this invention was examined by size exclusion chromatography. The samples (from TSK Toyo Sodo monufacturing Co. Ltd., Japan) having following properties: The log M is plotted against retention volume (Vr) in ml. Among the chromatographic solvents including THF, Toluene and Dimenthyl formamide used in the system PEO polymer dissolved only in chloroform and the dissolved polymer was in the form of a gel with a fully crosslinked appearance. On the other hand, PEO sample was fully dissolved in THF by gentle heating. The results obtained from the evaluation of chromatogram were Mn= 94 000, Mw=416 000 and heterogeneity index (Mw/Mn)= 4.43 for the soluble portion of this PEO in THF. The results obtained by heating the same sample to 90°C and injecting to the system under the identical conditions were Mn=164.000, MW= 483.000 and Mw/Mn=2.94 for the soluble part of this commercial PEO in THF. 3. Non-ionic water soluble polymer: polyethylene glycol (PEG) with a molecular weight of 3000 to 30 000, preferably polyethylene glycol (PEG 6000) with a molecular weight of 6000. This non-ionic polymer acts as a plasticizer for polyethylene oxide, flow modifier for mixture. The preferred weight percentages of the blend used in the manufacture of the platform and cap are as follows: 60% water insoluble polymer 35% water soluble polymer 5% polyethylene glycol Water soluble polymer is prepared by mixing 80% by weight WRPA 5769® and 20% by weight WSR 301®. This water soluble polymer is mixed with polyethylene glycol with the weight percentage ratio 7:1. Water insoluble polymer which is polystyrene is humidified with a plasticizer dibutyl phatalat. 50-100 ml of dibutyl phatalat is used per 100 kilogram of polystyrene as premix. Then 60% by weight of humidified polystyrene is mixed with 40% by weight of water soluble polymers. As the final mixture for injection moulding process, the weight percentages of the polymers become 60% polystyrene, 35% water soluble polymer and 5% polyethylene glycol. The cap 3 and platform 5 of the shaving unit is manufactured by injection moulding process at 190-200°C temperature, under 5 to 10 MPa (50-100 bar) injection pressure with screws that have a diameter of 35-45 mm. The cap 3 and platform 5 that were taken out of the mould as hard pieces at 30-40°C would become the main shaving part of the shaving unit after inserting the razor blade(s) 4 between them and riveting the pins 6 on the cap 3 by cold riveting process. Since polyethylene glycol is not compatible with polystyrene and being plasticizer for polyethylene oxide, after the injection moulding process it tends to take place at the surface of polystyrene component with some of the polyethylene oxide. This feature makes the water soluble polymer dissolve easier and create a thin gel layer on the skin to provide a comfortable and smooth shaving. During shaving using this type of shaving unit the protection bar 7 in front of the platform 5 made of the above described blend is moved along the skin just before the razor blade(s) 1 touch(es) the skin. Also, after the contact of the razor blade(s) 1 to skin, the cap 3 made of the same blend that is disposed on the blade(s) 4 continues to contact the skin and it makes the skin smooth that may be required for blade(s)'s second pass from the same spot by dissolving the platform 5 as well as the protection bar 7. Thus all surfaces of the shaving unit will dissolve in water as a result of friction and provides the skin with a continuous smoothness and a very comfortable shaving. Although the section 2 on the platform 5 of the shaving unit that provides the engagement with the handle 1 consists of water soluble polymer blend material and It contacts with water since it is not exposed to water there would be no slippery surface on the handle 1. The same applies to the handle because the water soluble polymer and polyethylene glycol is not present in the blend of the handle 1. The forming of the smoothness on the skin during shaving is first started with the contact of the platform 5 with skin and continues with the contact of the cap the parts that are made of the said blend may continue to contact with the skin whatever the handling position and angle may be so it provides the user with the opportunity to enjoy a very comfortable shaving. The compounds of the blend of which platform and cap is consisted of the lowest and highest limits of weight percentages and the characteristics of the blend will be defined below. When the blend is composed of 50-90% water soluble polymer, 9-40% water soluble polymer and 1-10% polyethylene glycol, it provides the manufacture of the platform 5 and cap 3 for a comfortable shaving. 9-40% presence of water soluble polymer, polyethylene oxide with high molecular weight, 1-30% coagulant polyethylene oxide (WSR - 301)® and minor amounts of additives such as colorants, odorants, in the blend ensures a comfortable shaving. There is a loss of material from the platform and cap during each shaving operation which is approximately between 7,2 x 10⁻⁴ and 10,5 x 10⁻⁴ (7.2 and 10.5 ppm) because of the solution of water soluble polymer in the blend and polyethylene glycol on the surface however these losses are not as much as to impair the mechanical features and structural quality of the platform and cap and to limit the useful life of the shaving unit. That means there would always be enough water soluble polymer in the structure of platform and cap during the shaving operations over the useful life of the shaving unit.

Claims: 1. Disposable shaving unit having one or more razor blades (4), comprising injection molded platform (5) and cap (3) sections, wherein the sections engaging the user's skin surface are composed of a blend of a water insoluble polymer in an amount of 50 to 90 % by weight and a water soluble polymer in an amount of 10 to 50% per weight, characterized in, that the water soluble polymer comprises polyethylene glycol in an amount of 1 to 10 % by weight of said blend. 2. Shaving unit according to claim 1, characterized in, that the water insoluble polymer is selected from polystyrene, thermoplastic rubber, polyethylene, polypropylene and/or polyacetal. 3. Shaving unit according to claim 1 or 2, characterized in, that it has a disposable cartridge unit with one or more razor blades (4) and that may be engaged with a handle (1). 4. Shaving unit according to any of claims 1 to 3, characterized in, that the water soluble polymer blend contains polyethylene oxide coagulant, odorant and bactericid. 5. Shaving unit according to claim 4, characterized in, that polyethylene oxide coagulant is present in the water soluble polymer blend in an amount of 1 to 30 % by weight. 6. Shaving unit according to any of claims 1 to 5, characterized in, that the polyethylene glycol has a molecular weight in the range of from 3000 to 30000. 7. Shaving unit according to any of claims 1 to 6, characterized in, that the platform (5) has a protection bar (7) that contacts with skin directly and that the platform (5) includes blade or blades in it. 8. Shaving unit according to any of claims 1 to 7, characterized in, that the cap (3) is placed on the blade or blades (4). 9. Shaving unit according to any of claims 1 to 8, characterized in, that cap (3) and platform (5) are manufactured in one piece. 10. A method of manufacturing a shaving unit according to any of claims 1 to 9, comprising the steps of: preparing a mixture of water insoluble polymer in an amount of 50 to 90 % by weight, water soluble polymer in an amount of 9 to 40 % by weight and polyethylene glycol in amount of 1 to 10 % by weight; injection molding the platform (5) and cap (3) within a temperature range of 190 to 200°C, using an injection pressure of 50 to 10 MPa (50 to 100 bar) and injection screws having a diameter of 35 to 45 mm; removing the platform and cap from the injection mold at a temperature range of 30 - 40°C; and inserting a razor blade (4) between the platform (5) and cap (3).

Inventors: AMRAM, JAK IKITELLI KOEYUE, Amram, Jak Ikitelli Köyü
Applicants: PERMATIK CELIK VE PLASTIK SANAYI A.S.
Application year: 1989
Main classification: B26B21
IPC codes: B26B21