Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1997-05-09
1999-01-12
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 57, 521 64, 604358, 604367, 604369, C08J 9236, C08J 924
Patent
active
058590749
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This application relates to porous, absorbent macrostructures that comprise flexible interparticle bonded aggregates which are surface crosslinked. This application particularly relates to porous absorbent macrostructures in which an effective amount of latex is coated on a portion of the particles comprising the bonded aggregates so as to impart increased flexibility to the macrostructure.
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. 3,699,103 (Harper et al), issued Jun. 13, 1972, and U.S. Pat. No. 3,770,731 (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 immobilized 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 nonhomogeneous incorporation of the particles into structures in which the particles are being used. A more significant problem, though, 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, 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 immobilize 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 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 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 superabsorbent 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 et 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 superabsorbent films may absorb significant quantities of liquids, they have limited liquid transport properties because they are essentially nonporous, i.e. lack internal capillary channels. Indeed, due to the lack of internal capillary channels, these superabsorbent films are especially prone to gel blocking.
Moreover, the crosslinking reaction between the hydroxy groups of the glycerol and the carboxy groups of the polymers present in the absorbent particles is relatively slow. Indeed, the glycerol treated absorben
REFERENCES:
patent: 3669103 (1972-06-01), Harper et al.
patent: 3670731 (1972-06-01), Harmon
patent: 4076673 (1978-02-01), Burkholder
patent: 4410571 (1983-10-01), Korpman
patent: 4861539 (1989-08-01), Allen et al.
patent: 5102597 (1992-04-01), Roe et al.
patent: 5124188 (1992-06-01), Roe et al.
patent: 5149344 (1992-09-01), Lahrman et al.
patent: 5324561 (1994-06-01), Rezai
patent: 5372766 (1994-12-01), Roe
Hsueh Kesyin
Rezai Ebrahim
Shimizu Motohiro
Foelak Morton
Linman E. Kelly
Rasser Jacobus C.
Roof Carl J.
The Procter & Gamble Co.
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