1. Field of the Invention
This invention relates to an absorbent material, an absorbent body, and a method for the production thereof. More particularly, it relates to an absorbent material which, in its independent form, possesses excellent absorbing characteristic and molding property and, in the form incorporated in a fiber matrix, manifests preeminently excellent effect and to a method for the production thereof. It further relates to an absorbent body which is soft, stable, and incapable of causing exfoliation of an absorbent polymer and a method for the production thereof.
2. Description of the Prior Art
Heretofore, absorbent polymer particles coated with a hydrophilic cellulose and an absorbent article containing them have been disclosed U.S. Pat. No. 3,901,236 and JP-A-58-163,438(1983)). As means aimed at enabling an absorbent article to manifest improved strength while in a wet state, a method which comprises dry mixing thermoplastic fibers into the absorbent article (JP-A-56-89,839(1981), JP-A-58-8,175(1983), and JP-A-63-122,452(1988)). and an absorbent material having a hydrophobic fiber web partly embedded in an absorbent polymer and an absorbent article using the absorbent material U.S. Pat. Nos. 4,354,487 and 4,235,237 have been taught.
In the case of the method mentioned above, however, an absorbent article to be obtained by dispersing an absorbent polymer coated with a hydrophilic cellulose in a hydrophilic fiber matrix exhibits an improved ability for absorption of a liquid as compared with the absorbent polymer used in its independent form. The absorbent article wetted with the absorbed liquid, however, is deficient in strength. Particularly on account of the molding strength, the absorbent polymer concentration in the matrix has its own limit.
In the case of the absorbent material mentioned above, the incorporation of a thermoplastic fiber by dry mixing results in improving the stability of the web in the wet form and yet induces no sufficient solidification of the absorbent polymer. When the absorbent material is compressed to a high degree enough to ensure solidification of the absorbent polymer, the absorbent article consequently obtained is unduly rigid and the absorbent article's capacity for absorption is unduly low because of the inevitable decrease in the content of the absorbent polymer's voids available for swelling within the web. Thus, an attempt to increase the absorbent polymer concentration in the web or densify the absorbent polymer is difficult to fulfil. The partial embedment of the fiber web in the absorbent polymer indeed improves the wet strength and the molding strength of the produced absorbent material and yet induces the fibers to restrict the swelling of the absorbent material. Moreover, it has the disadvantages that the absorbing characteristic is inferior, the swelled absorbent polymer exhibits unduly low gel strength, and the production of the absorbent material consumes much time and labor.
An object of the present invention, therefore, is to provide a novel absorbent material, an absorbent body, and a method for the production thereof.
Another object of the present invention is to provide an absorbent material which, in the independent form, possesses excellent absorbing characteristic and molding property and, in the form incorporated in a fiber matrix, manifests preeminently excellent effects (wet stability, shape-retaining property, dispersibility, and absorbing characteristic) and a method for the production thereof.
Yet another object of the present invention is to provide a thin absorbent body which is soft, stable in the wet form (shape-retaining property), and incapable of causing exfoliation of an absorbent polymer and which is made chiefly of an absorbent polymer and enabled to manifest a highly satisfactory absorbing property and a method for the production thereof.
USPTO Backgrounds
USPTO Backgrounds