Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Organic
Patent
1997-03-10
1999-11-02
Bos, Steven
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Organic
604368, 604378, A61F 1315
Patent
active
059770147
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an absorbent composite structure comprising a substrate having an upper and a lower surface and a plurality of hydrogel-forming polymer particles chemically bonded to at least one surface of the substrate, wherein the polymer particles each comprise a plurality of cross-linked molecules. The invention also relates to an absorbent article comprising such an absorbent composite structure and to a method of making such a structure.
BACKGROUND OF THE INVENTION
Particulate, absorbent, polymeric compositions are capable of absorbing large quantities of liquids such as water and body exudates (e.g., urine) and are further capable of retaining such absorbed liquids under moderate pressures. The absorption characteristics of such polymeric compositions make them especially useful for incorporation into absorbent articles such as diapers. See, for example, U.S. Pat. No. 3,669,103 (Harper et al), issued Jun. 13, 1972, and U.S. Pat. No. 3,670,731 (Harmon), issued Jun. 20, 1972, that disclose the use of particulate, absorbent, polymeric compositions (often referred to as "hydrogels", "superabsorbents", or "hydrocolloid materials") in absorbent articles.
Conventional particulate, absorbent, polymeric compositions, however, have the limitation that the particles are not immobilised and are free to migrate during processing and/or use. Migration of the particles can lead to material handling losses during manufacturing as well as non-homogeneous incorporation of the particles into structures in which the particles are being used. Especially when the absorbent polymer particles are incorporated in a fibrous matrix at high concentrations, the particles may sift out of the matrix of may become inhomogeneously distributed in an uncontrolled manner, as for instance described in European application number 94111955.4 (Bogdanski et. al.) Another significant problem occurs when these particulate materials migrate during or after swelling in use. Such mobility leads to high resistance to liquid flow through the material due to the lack of stable interparticle capillary or liquid transport channels. This phenomenon is one form of what is commonly referred to as "gel blocking."
One attempt to overcome the performance limitations associated with absorbent particle mobility during use in absorbent articles is incorporation of the particulate, absorbent, polymeric compositions into tissue laminates, i.e. layered absorbent structures. By encapsulating the particles between tissue layers, and affixation of the particles by water bonding or glue bonding, the overall particle mobility within an absorbent structure is diminished. However, upon liquid contact, the particles within the laminate are often free to move relative to each other resulting in the breakdown of any pre-existent interparticle capillary channels.
Another attempted solution is to immobilise the particulate, absorbent, polymeric compositions by the addition of large quantities of liquid polyhydroxy compounds that act as an adhesive to hold the particles together or attach the particles to a substrate. See, for example, U.S. Pat. No. 4,410,571 (Korpman), issued Oct. 18, 1983. While this approach does limit migration before and, to some extent, during swelling, the particles eventually become detached from each other or from the substrate in the presence of excess liquid, resulting again in the breakdown of any pre-existing capillary channels between the particles.
Another attempted solution to overcome the problem of absorbent particle mobility is to produce a hydrogel-forming film by extrusion of a solution of a linear absorbent polymer and subsequently crosslinking it. See, for example, U.S. Pat. No. 4,861,539 (Allen at al), issued Aug. 29, 1989 (crosslinked with a polyhydroxy compound such as a glycol or glycerol); and U.S. Pat. No. 4,076,673 (Burkholder), issued Feb. 28, 1978 (crosslinked with polyamine-polyamide epichlorohydrin adducts such as Kymene.RTM.). While these hydrogel-forming films may absorb significant qu
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Plischke Manfred
Rezai Ebrahim
Schmidt Mattias
Bos Steven
Hendrickson Stuart L.
Hogg Kevin D.
Rasser Jacobus C.
Roof Carl J.
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