AU2007100308A4 - Improved performance of shaving foams - Google Patents

Description

EDITORIAL NOTE There are 2 pages of description IP AUSTRALIA

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RECE\VEr- Description 17 APR 2007 CANBERRA. FFp t Introduction: The present application relates to the addition of liquid paraffin as a lubricant to shaving foam from aerosol cans so that the foam would contain 15 to 45% by weight of liquid paraffin in it.

Liquid paraffin may be incorporated into the soap slurry inside the container or may be added to the 00 shaving foam at any point in a manner so that it would contain liquid paraffin in the specified O proportion. It may be added to the slurry or the foam as such or as another formulations, such as a C body lotion, containing liquid paraffin as one of its constituents.

On-line search of patents and http//:gb.espacenet.com) failed to find mention of O liquid paraffin as a lubricant in shaving foams. Examination of stated ingredients on shaving foam O containers, currently marketed in Australia, also did not find mention of liquid paraffin amongst the listed ingredients.

Bases for the innovation: Note: The use of the term "razor blade" or "shaving razor" herein includes any type of shaving blade including those of the cartridge type.

Hardness of stainless steel (from which shaving blades are made) is approx. 5.5 while that of hair is approximately 3; on a logarithmic scale this is a difference of over three hundred times in hardness. In theory, therefore, a shaving razor should retain the ability to cut hair and provide a smooth shave for a very very long time, Yet most razor blades last from only a few days to at the most 3-4 weeks depending on their quality. Towards the end of their life razor blades cause too much skin irritation and are, therefore, discarded on the assumption of having become "blunt" and unusable. The culprit infact is an increased skin drag (see below) causing increased scraping of superficial layers of the skin and resulting in increased skin irritation and razor burns.

Lubrication of skin during shaving is widely acknowledged to reduce skin drag exerted by shaving razors and to thereby reduce the scraping of superficial layers of the skin and the skin irritation and razor bums. This is the basis for attaching lubricating strips on shaving cartridges and for the addition of small amounts of lubricants, such as polyethylene oxide and polyvinylpyrollidine, to shaving foams; the very small amounts of lanolin, silicones, mineral oils, vegetable oils etc, contained in some shaving foams as soothing agents, may also exert a slight additional lubricant effect. The total amount of lubricants in shaving foams nonetheless remains small necessitating the addition of lubricating strips to razor blades but these deplete fairly rapidly on use. After just a few shaves lubricating strips have either worn thin or almost disappeared and have become ineffective.

Damage to razor blade edge from use further increases the drag exerted by shaving blades. "Edge decay" is a well known natural phenomenon; edges tend to wear out faster than the main body of a material. This is evidenced in the smoothness of river bed stones which start as jagged pieces of rocks but the edges wear out much faster than the rest of the stone. Polishing semiprecious, opaque gemstone, which are rolled for several days in a barrel full of sand, also exemplifies the phenomenon.

In the case of razor blades this manifests as microscopic spot damage to razor blade edge during shaving which further increases the resistance between the blade and the skin and, therefore, the drag exerted by the blade on the skin. The stainless steel edge, being much harder than the hair, however, still remains quite sharp and retains its ability to cut hair. However, the increased skin drag, from a S combination of "edge decay" and progressively decreasing availability of lubricant from the N lubricating strip, increases skin irritation and razor bums from the use of the razor blade to a point that the razor blade becomes unacceptable by the user and is discarded. Shaving comfort could be Simproved, and the life of the blade prolonged, if the razor blade could glide more easily over the skin.

Predictably, the effect would be more discernible after the razor blade has been used a few time.

Trials conducted by the applicant with several lubricants over a five year period found that addition of increasing amounts of various lubricants to shaving foam reduces skin irritation from razor blades.

00 The improvement was more readily noticeable with razor blades which had been already used for some time (and therefore, were exerting a greater drag on the skin). Consequently, these razor blades a could be used comfortably and effectively for considerably longer durations, for months rather than for O weeks. Liquid paraffin was the most efficient lubricant with maximum improvement in the performance of razor blade being seen in the concentration range of 15 to 45% by weight in the 0 shaving foam. Skin irritation decreased in proportions to the amount of liquid paraffin, in the shaving 0 foam, from 15-35% but only slightly thereafter. Addition of other formulations, such as body lotions S which contain liquid paraffin, was effective in proportion to their liquid paraffin content. Some improvement was also seen with the use of vegetable oils but was not comparable to that achieved with liquid paraffin. Vegetable oils caused a late irritation of facial skin (several hours after the shave) presumably due to oxidation of the thin film of vegetable oil, left on the face after shaving, into irritant fatty acids following exposure to air.

After shaving with a liquid paraffin-containing shaving foam, only a very thin film of liquid paraffin is left on the skin after the shave. This acts like a small amount of cream applied to the face and the skin feels softer and smoother. It also greatly reduces, almost abolishes, irritation caused by the application of after-shave lotions to the face. Like creams, it also exert a small cleansing effect on skin secretions.

The safety of liquid paraffin on application to skin is not in question. Liquid paraffin is the active emollient in most skin and body lotions and creams on the market. It used to be taken orally as a laxative in doses of 45 ml. daily though such use is much less common now because of the availability of alternatives and possible interference with the absorption of fat soluble vitamins from the gut. Its medical uses include use as an emollient in irritant conditions of the skin and to remove crusts. No toxicity attributable to liquid paraffin from skin application has been documented.

Claims (3)

1. Addition of liquid paraffin in a proportion of 15% to 45% by weight to shaving foam reduces 00 irritation, and razor bums, from razor blades.

2. Reduced irritation and easy gliding of the razor blade on the skin allows each razor blade to be used for a considerably longer duration.

3. Irritation caused by the application of after shave lotions is greatly reduced. N4. The skin feels softer and fresher after the shave. This formulation will be of particular use for individuals in whom the skin is not very taut, such as in the elderly. The easy gliding of the razor blades are likely to reduce razor cuts suffered by such individuals.