1. Field of the Invention
The present invention relates to absorbent composites comprising a fibrous material and a relatively large quantity of a particulate, water-swellable, generally water-insoluble absorbent material.
2. Description of the Related Art
Absorbent composites suitable for use in absorbent products such as diapers, training pants, feminine care products, adult incontinence products, and the like are known. As a general rule, the absorbent composites comprise a matrix of fibers. The fiber matrixes tend to have a relatively low specific absorption capacity. Accordingly, absorbent products requiring a relatively high absorbent capacity, and employing such a fiber matrix, tend to be relatively thick and bulky. In an attempt to increase the absorbent capacity of such fiber matrixes, absorbent materials, known in the art as superabsorbents, have been introduced into the fiber matrixes. As a general rule, the fiber of the matrix and the absorbent material are combined in an airstream and deposited on a porous forming surface. Such structures are generally lofty and soft.
In an attempt to produce thinner absorbent composites and products, higher concentrations of absorbent material have been added to the fibers in an attempt to maintain absorption capacity of the absorbent composites while reducing their overall bulk. Unfortunately, the amount of absorbent material that can be contained within a fibrous matrix, due to fiber entrapment, is limited. When this limit is exceeded, the absorbent material present in the fiber matrix tends to migrate out of the fiber matrix during manufacture and transport of the absorbent product. When this occurs, the absorbent material may contact the skin of a user. This is undesirable.
Various methods have been suggested to overcome the problem of containing absorbent material within a fibrous matrix. For example, European Patent 0 085 729 published Nov. 6, 1985, describes a process wherein a fusion adhesive is used to adhere particles of an absorbent material to a substrate. European Patent Application 0 301 772 published Feb. 1, 1989, describes a particle-bonded, nonwoven fibrous web containing liquid-absorbent polymer particles distributed therein and attached to the fibers by the use of an adhesive binder. European Patent Application 0 255 654 describes a process employing a resin binder to adhere absorbent polymer particles in a cellulose fiber web. Lesniak et al. U.S. Pat. No. 4,826,880 issued May 2, 1989, describes absorbent products containing hydrates of particulate absorbent polymers.
The use of adhesive binders, thermoplastic resins, and the like may be sufficient to adhere particles of absorbent material in a fibrous web but may undesirably affect the flexibility of the web and may prove to be too costly or complicated for use in disposable absorbent products.