The present invention relates to a compressed, radially-expanding, generally cylindrical, fibrous tampon. These tampons rapidly expand in environments of high humidity and provide improved early expansion characteristics.
Catamenial tampons are used to absorb, not block the flow of, menstrual fluids to prevent leakage, for example, staining of a user""s garments. Unfortunately, commercial tampons are subject to two major types of failure: a tampon""s inability to continue to absorb fluids once the absorption capacity of the tampon is reached, and a tampon""s inability to immediately expand to fill the vaginal cavity. Thus, until the tampon expands sufficiently to substantially fill the vaginal cavity, menstrual fluid may flow along the tampon""s side and bypass its absorbent portions such as the core.
Generally, tampons are manufactured from absorbent fibers, such as rayon, cotton, or a mixture of both fibers. The volume of absorbent fibers necessary to provide sufficient absorption capacity must be highly compressed to form a cylindrical tampon of sufficiently small size to allow for comfortable insertion into the body. The compression should be adequate to hold the tampon in the cylindrical shape until insertion. As a result the tampon, when first inserted into the body, is often highly compressed into a relatively non-conformable form with a relatively high initial density. Thus, the tampon is not able to immediately conform to the vaginal walls directly after insertion. The initial high density can also inhibit the rapid expansion of the tampon. Expansion, if it occurs at all, occurs only when the tampon comes into contact with a sufficient amount of menstrual fluids to swell the absorbent fibers and to release the expansion energy locked into the tampon when it is compressed. Thus, the tampon is susceptible to early bypass leakage as described above.
There have been several attempts to address the problem of early bypass leakage by providing rapidly expanding tampons. However, these designs suffer from two drawbacks: first, several designs are based upon synthetic materials which are not currently widely accepted for use in internal sanitary-products, and second, many designs have insufficient stability and thus require the use of an applicator; they cannot be used as digital tampons. Designs based upon synthetic materials include those which use foams such as Schaefer, U.S. Pat. No. 3,815,601; Dulle, U.S. Pat. No. 3,794,029; and Fries et al., U.S. Pat. No. 4,341,214; or resilient fibers such as Wolfe et al., U.S. Pat. No. 4,543,098; and Gellert, U.S. Pat. No. 4,475,911. Designs which require applicators include Fries et al. and Gellert.
In addition, Walton et al., U.S. Pat. No. 4,627,849, describes the use of a pre-shortened batt made from natural fibers to obtain a more rapidly expanding compressed tampon. However, this design requires several additional manufacturing steps to form the pre-shortened batt.
There is a desire to avoid premature expansion of these compressed tampons, especially those using more resilient fibers. For example, Courtaulds PLC, EP 0 301 874 B1, discloses a tampon having multi-lobed regenerated cellulose fibers which patentee claims provide high absorbency and a cotton-like handle. These tampons are described as having good stability and absorbency. Longitudinally-expanding tampons having these fibers are described as having less expansion than conventional longitudinally-expanding tampons.
Therefore, what is needed is a radially-expanding tampon having substantial dimensional stability prior to use while rapidly expanding in high humidity environments.
We have developed a tampon which can expand in the presence of high humidity after insertion into a user""s body to prevent early bypass leakage from occurring. This tampon is a substantially cylindrical mass of compressed fibers enclosed within a fluid-permeable cover. The tampon has a stability of at least about 15 N, and is capable of radially expanding upon exposure to a humid environment. The radius increases by at least about 10% after 15 minutes to 90% relative humidity at 40xc2x0 C.