Absorbent gelling material comprising a dry mixture of at least

Details Absorbent gelling material comprising a dry mixture of at least Absorbent gelling material comprising a dry mixture of at least

1997-01-06

1998-02-03

Page, Thurman K.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Wearing apparel, fabric, or cloth

424484, 424486, 424487, A61K 914

Patent

active

057141568

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/US95/08379 filed Jul. 03, 1995.


FIELD OF THE INVENTION

The invention relates to an absorbent gelling material comprising a dry mixture of at least a first type of hydrogel-forming particles and a second type of hydrogel-forming particles. The invention also relates to a method for making such a material.


BACKGROUND OF THE INVENTION

Such absorbent gelling materials are described in many prior art references.
EP-A-0 407 838 discloses a gel-forming material for use in foodstuffs, which comprises a mixture of a crosslinked polymer and a non-crosslinked polymer for lump-free solution in water.
EP-A-0 278 601 discloses a mixture of an absorbent gelling polymer, such as formed from water-soluble, ethylenically unsaturated monomers or crosslinked products thereof, including acrylic acid or a salt of acrylic acid as the main component, and inorganic material such as aluminia, or silica. The polymers in the mixture may be comprised of any combination of two or more chemically different types. The disclosed absorbent mixture is suited to absorb both low-viscosity and high-viscosity liquids.
WO 91/12029 discloses an odor control composition comprising aggregated absorbent gelling material particles and zeolite material. The absorbent gelling material is made of hydrolized acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylates, malice anhydride-based copolymers and combinations thereof.
U.S. Pat. No. 4,333,464 discloses a sanitary napkin having water absorbent polymer which may comprise a mixture of two types of absorbent gelling material from the group consisting of starch, .beta.-hydroxyethylacrylate, acrylonitrile, acrylic acid and acrylamide, carboxymethylcellulose, hydrophilic copolymers of acrylates, copolymers of a vinyl ester and an ethylenically unsaturated carboxylic acid and their saponification products, polyvinyl alcohol, and its derivatives.
U.S. Pat. No. 4,902,544 discloses a flexible tubular casing comprising a crosslinked hydrocolloid and naturally occurring cellulose such as saw dust, crushed corncobs, cottonlinters, wood pulp and the like, ion-exchange resins or clay minerals.
GB-B-1 544 002 discloses a mixture of a salt of an acrylic acid polymer and either guar gum, alginates or xanthan gum to provide an absorbent material with good absorbent properties, irrespective of the presence of an electrolyte in the liquid to be absorbed. Polyvalent ions may be incorporated in the absorbent composite.
U.S. Pat. No. 4,411,660 discloses in an absorbent product two layers of absorbent material of different types, such that the upper layer gels slower than the first layer.
European Patent Specification EP-B-0 401 189 discloses that favourable properties of absorbent products can be achieved by using two different types of absorbent gelling material in separate layers, rather than as a mixture of the two absorbent gelling materials in a single layer.
Absorbent gelling materials are extensively used in absorbent hygiene articles such as diapers or sanitary napkins, due to their high absorption capacity for liquids, which may typically range from 15 g per gram to about 50 g/g. The gelling material is most often applied in particulate form in particle sizes ranging from 20 to 2000 micrometers. The particles that are used in absorbent hygiene articles can be mixed with hydrophilic fibers or can be employed in layers solely consisting of the hydrogel-forming particles.
An important parameter which describes the ability of the absorbent gelling material to take in liquids under in-use conditions, i.e. when applied in an absorbent product such as a baby diaper or a sanitary napkin, is the Absorption Against Pressure value, further referred to as the AAP-value, of the material. The absorbent gelling materials most useful in absorbent products have AAP-values of 15 g/g or higher at a confining pressure of 49.2 gcm.sup.-2 (0.7 psi). Absorbent gelling materials having a relatively high AAP value, will show relatively little gel blocking and tend to maintain an open s

REFERENCES:
patent: 4333464 (1982-06-01), Nakano
patent: 4411660 (1983-10-01), Dawn et al.
patent: 4902544 (1990-02-01), Kim et al.
patent: 5505718 (1996-04-01), Roe et al.

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