Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1997-10-02
2000-03-07
Copenheaver, Blaine
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
524041, 138141, 427197, 427244, 427448, 428 17, 4283179, 4283193, 428913, 604369, A61L 1542, A61L 1560, B32B 518, C08J 518
Patent
active
060337699
DESCRIPTION:
BRIEF SUMMARY
The invention relates to bodies which absorb water and aqueous liquids and consist of foamed, soluble polymer layers and superabsorbent polymers, a production process for said bodies and their use as absorbing agents, particularly in the field of hygienics for absorbing body fluids such as blood, sweat, urine and other liquid excretions. Furthermore, the invention relates to the use of said bodies as components in wound protections, in packaging and insulation means, in textiles for clothing and cleaning purposes, and the use in the field of plant cultivation and as depot material.
Today, superabsorbent polymers are used in the form of a powder. For process simplification, it is desired to employ the superabsorbers in a fixed form, i.e., to integrate them in a matrix. According to prior art, there are a number of suggested solutions, all of which, however, suffer from drawbacks.
Bodies of layered structure, which are capable of absorbing aqueous liquids, are well-known. U.S. Pat. No. 4,000,028 describes bodies made of latex foam and fluffy cellulose which, however, do not contain any superabsorbent polymerizates, so that they have a quite limited absorptive capacity for liquids.
U.S. Pat. No. 5,128,082 describes absorbent bodies which are produced using mixtures of fluffy materials and superabsorbent polymerizates, and an enclosing latex forming the exterior layer. The polymerizate ratio in these bodies is not distributed uniformly, giving rise to the well-known problems in absorption of liquids and the associated disadavantages with respect to the wearing comfort of these hygiene articles.
EP 212,618 B1 describes diaper constructions wherein, in order to avoid these drawbacks, polymerizates having a specific grain size distribution are distributed in a layer of cellulose fibers, using a gradient. However, such constructions are not sufficiently stable; in particular, the distribution of the materials is altered during transportation.
Mixing superabsorbent polymerizates with polymeric foams containing water normally results in foam breakdown with dehydration, the open-cell structure being destroyed, so that subsequently, only SAP particles located at the surface are capable of absorbing liquids immediately. The remaining SAP particles can bind water only in a delayed fashion after the surrounding water-soluble polymer layer has dissolved.
According to EP 427,219 A2, mixtures of superabsorbent polymers and latex foams are known, which are obtained by incorporating the polymerizates as a powder spray in the foamed latex. This procedure does not permit a defined structure of those bodies; in particular, accurate distribution of the polymerizates is not possible.
The use of a tape as a component of the insulation of electric cables is known from EP 577,233 A1, which tape consists of a layer of nonwovens and a layer of foamed material and contains particles of a swelling powder affixed within the region of the layer of nonwovens.
The U.S. Pat. No. 4,649,164 describes water-absorbing foamed materials produced frbm CO.sub.2 -liberating foaming agents and acrylate-(meth)acrylic acid latices, the foamed latex itself constituting the absorbing material. As a resuit of the hydrophobic character of the acrylate component, the absorptive capacity of these foams is limited compared to the well-known superabsorbers.
Likewise, biocompatible open-cell polyurethane foams having guar gum as an incorporated hydrogel, which may be used as wound protections, are known from DE 4,242,015 A1, the gel component being introduced by foaming in situ during production. The water-absorbing capacity of these products is said to be limited to a value below three times the initial weight.
EP 340,945 A1 describes mixtures of elastomers and cationic water-swellable hydrocolloids, preferably chitosan salts, for use as wound protections, which have absorption values of at least 180 wt.-%, wherein the colloid particles are randomly integrated in the elastomer, and the absorptive capacity for aqueous liquids likewise is low.
Similarly, hydrophil
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Brueggemann Helmut
Dahmen Kurt
Lehwald Dieter
Theilmann Roland
Copenheaver Blaine
Stockhausen GmbH & Co. KG
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