Absorbent article comprising chitosan material.(Hygiene)

Breathable absorbent articles that include chitosan material have been developed by Procter & Gamble. Disclosed in US Patent 6 867 287, items such as sanitary napkins, panty liners, nursing pads and baby diapers have been designed to effectively control odour as well as providing effective breathability and high protection levels.

According to the company of Cincinnati, Ohio, USA, the use of chitosan material unexpectedly maintains breathability during prolonged usage conditions. Chitosan is believed to reduce fluid diffusion once it is contacted with bodily fluids, thereby concentrating the storage of acquired fluid in close proximity. This, says Procter & Gamble, results in a larger area of dry article that is not soiled by bodily fluids, such as menses.

The positively charged cationic groups of the chitosan material interacts with negatively charged anionic groups present in bodily fluids, such as the carboxylic groups of proteins or hydroxylic groups of short chain acids (e.g. butyric acid). This results in the formation of a tri-dimensional net, which traps most molecules, such as lipids and acids, thereby retaining fluid and odour.

It is further believed that the chitosan material acts as an antimicrobial agent. The chitosan with its positively charged cationic groups is thought to interfere with negatively charged surfaces of microorganism walls, thereby inhibiting their growth or even killing them. The chitosan also interferes with negatively charged surfaces of enzymes, thereby inactivating enzymatic activity, which is largely responsible for the formation of malodorous components.

The chitosan material is located either in the absorbent core of the absorbent article but closer to the backsheet than the topsheet, or in the secondary backsheet itself, Procter & Gamble points out.

Preferred chitosan materials are water-soluble chitosan salts, which have the ability to chelate most of the metals, such as calcium and zinc, necessary for bacterial growth. They should also have a pH of 5, which corresponds to the skin pH. Alternatives include cross-linked chitosans and modified chitosans.

Optionally, the absorbent article can contain an anionic absorbent gelling material (a so-called "super-sorber"), such as polyacrylate, and/or additional odour control agents.

The chitosan material may be incorporated in particle form as a powder or granulate. It can also be applied by spraying a solution containing the chitosan onto the desired layer and leaving it to dry.

Procter & Gamble notes that the use of highly breathable backsheets in absorbent articles not only increases the propensity for leakage onto the wearer's garments, but malodorous compounds may also be more readily exchanged with, and escape into, the environment, thereby causing embarrassment to the wearer.

Further, the breathable properties, particularly air-transmission abilities, of breathable absorbent articles, which may function well upon initial use, are often drastically reduced upon initial loading with bodily fluids.

The breathable absorbent article described in the Patent is said to overcome these problems, offering:

* maintained breathability above a critical level, even after loading;

* high performance without impairing the basic absorption and liquid retention functions;

* high initial comfort and effective comfort upon prolonged wearing time;

* effective odour control to a broad range of malodorous components.

For further information, see US Patent 6 867 287, or contact: The Procter & Gamble Company, One Procter & Gamble Plaza, Cincinnati, OH 45202, USA; tel: +1-513-983-1100; fax: +1-513-983-9369; Internet:www.pg.com