Field of the Invention The present invention relates to comfort strips for use with razors and in particular to comfort strips in which the pH level is reduced to avoid certain problems associated with higher pH levels.

Background of the Invention

In order to provide for smoother shaves and to increase the comfort of the user, shaving aids in the form of comfort strips have been mounted on disposable razor heads and in disposable razor systems for many years. For example, U.S. Patent No. 4,170,821, issued to Booth, discloses a solid water soluble shaving aid incorporated as a strip attached to a disposable razor blade cartridge. Razor heads having such comfort strips which are commonly marketed having polyethylene oxide (polyox) as the main lubricant generally have a pH around 8.0. Such comfort strips have been mounted on both men's and women's systems.

While most men use razors together with shaving cream, women are especially likely to use a razor in conjunction with soap of some sort. Generally, most soaps are basic in nature. A drawback associated with the use of razors containing comfort strips in conjunction with soap is that the basic nature of the soap interacts with the polyox and causes the comfort strip to become stringy and uncomfortable to the user.

It would, therefore, be desirable to provide a razor comfort strip which would not become stringy upon exposure to a basic material. It would be especially desirable to provide such a comfort strip which is acidic so that the acidic nature of the comfort strip will not degrade and become stringy upon exposure to soap.

Summary of the Invention

The present invention features a disposable razor cartridge unit or disposable razor system having a shaving aid in the form of a comfort strip mounted on a razor head, wherein the comfort strip is acidified so that the strip does not become stringy upon exposure to a basic material. A water soluble acid or a combination of an acid and other materials may be used to reduce the pH level from that of standard, non-acidified comfort strips. In a preferred embodiment, the comfort strip contains approximately 5% of a water soluble acid such as citric acid.

Detailed Description of the Invention

The embodiments of the present invention are designed to provide a disposable wet shave razor or a disposable wet shave razor system having a shaving aid amounted on the razor head. As used herein, the term "razor head" is meant to include disposable cartridges designed for separate attachment to a razor handle, as well as the operative portion of a razor wherein the cutting portion is integrally formed with the handle portion. For the purpose of this application, "wet shave" refers to razors which are commonly used in conjunction with shaving cream, soap and water and does not include electrically-powered razors.

Most commonly, lubricating strips are affixed to the cap of the razor head which is located just above the blade or blades, however, the comfort strip may be located anywhere on the unit in either a skin engaging or a non- skin engaging position. The comfort strip typically comprises a water soluble phase, with a material such as polyethylene oxide, and a water insoluble phase, such as polystyrene, polypropylene or other suitable polymers. The material or materials chosen for the comfort strip is preferably such that the strip may be formed by a suitable plastic forming process, such as extrusion or molding. Although an entirely water soluble strip may be used, it is

preferable to include a water insoluble phase in that the water insoluble phase provides integrity to the strip and acts as a delivery vehicle for the water soluble phase. According to the present invention, shaving aids in the form of comfort strips are disclosed which contain acid in the water soluble phase in order to reduce stringiness when exposed to basic materials.

Polyethylene oxide (polyox) is widely used as a lubricating material, either alone or in combination with other materials, in the water soluble phase on many comfort strips which are currently commercially available. When in contact with water alone during shaving, such polyox comfort strips generally are at a basic pH of approximately 8.0. Many users of razors containing polyox comfort strips, however, use them in conjunction with soap, which is also basic in nature. The combination of the polyox comfort strip and the basic soap often leads to the comfort strip stringiness during use.

Acids comprise a group of organic and inorganic compounds which, in a water solution are capable of producing hydrogen or hydronium ions and have a pH value of less than 7. Acids may be categorized as mineral acids such as sulfuric, hydrochloric, nitric and phosphoric acid, and organic acids. The organic acids contain carbon and they also usually contain the carboxylic group, -COOH, and are referred to as carboxylic acids. Examples of carboxylic acids are acetic and propionic acids. Carboxylic acids may contain more than one carboxyl group, such as oxalic and malonic acids. Other examples of organic acids include aromatic carboxylic acids such as benzoic acid, phthalic acids, such as ortho phthalic acid, phenols and amino acids. In addition, the acid may be in the form of an acid anhydride which may be reconstituted into an acid by the addition of water. The above are merely set forth as examples.

Further, any combination of acidification agents such that the resulting pH of the soluble phase of the comfort strip is less than 7.0 may also be employed. These agents include materials which are capable of donating a proton, turning blue litmus paper red, reacting with certain metals or bases to give salts, amphoteric compounds (which are capable of acting as either an acid or a base) , metal ions that can function as acids through hydrolysis, acid salts, acid anhydrides and electron acceptors.

The addition of a water soluble acid or a water soluble acid in combination with other materials which reduce pH will aid in producing a more comfortable shave for the user. One method by which the shave quality is improved through the addition of an acid to a comfort strip is by the reduction of the problem of degradation and stringiness in comfort strips. The water soluble acid contained in the comfort strip is liberated from the comfort strip upon contact with soap and water, thereby reducing the pH of the strip and neutralizing the basic nature of the soap. While virtually any acid may be employed in the comfort strip to lower the pH, among the preferred acids are citric acid and other alpha-hydroxy acids. While any alpha-hydroxy acid may be employed in the comfort strip, a preferred alpha-hydroxy acid is glycolic acid. Glycolic acid, also known as hydroxyacetic acid, is the simplest alpha-hydroxy acid and has the formula HOCH2COOH. Glycolic acid has a smaller molecular size than the other alpha-hydroxy acids, such as citric acid. The small molecule size allows the acid to permeate the skin's plasma membranes, allowing the active ingredient to be released in a fat-soluble environment.

In addition to an acid, numerous additional materials may be added, either alone or in combination to the comfort strip. Exemplary materials which have been or may be used

in comfort strips include one or various combinations of the following:

A. A lubricating agent for reducing the frictional forces between the razor head and the skin, e.g., a microencapsulated silicone oil.

B. An agent which reduces the drag between the razor parts and the skin, e.g., a non-ionic polyacrylamide and/or a natural polysaccharide derived from plant materials. C. An agent which modifies the chemical structure of the hair to allow the razor blade to pass through the whiskers very easily, e.g., a depilatory agent is one example.

D. A cleaning agent which allows whiskers and skin debris to be washed more easily from the razor parts during shaving, e.g., a silicone polyethylene oxide block copolymer and detergent such as sodium lauryl sulphate.

E. A medicinal agent for killing bacteria, or repairing skin damage and abrasions. F. A cosmetic agent for softening, smoothing, conditioning or improving the skin.

G. A blood coagulant for the suppression of the bleeding that occurs from nicks and cuts. H. An essential oil, such as menthol.

While not wishing to be bound to any particular formulation, one example of a lubricating strip containing a water soluble acid could be as follows: 47% coagulant grade polyethylene oxide; 25% SWR-N-750 grade polyethylene oxide; 23% medium impact polystyrene (containing 10% titanium dioxide) ; and 5% citric acid. Additional materials, such as aloe and vitamin E may also be incorporated into the lubricating strip as desired.

While there have been described what are presently believed to be the preferred embodiments and methods of the invention, those skilled in the art will realize that

various changes and modifications may be made to the invention without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention.