Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1993-10-14
1995-05-09
Hoke, Veronica P.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
264205, 604366, D01F 102
Patent
active
054137470
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to fibres or filaments, and it has particular reference to fibres or filaments of water-absorbent water-insoluble material.
Water-absorbent water-insoluble materials are of use in many absorbent products, particularly in products for absorbing aqueous body fluids, such as baby diapers, incontinence pads, sanitary napkins and tampons, and in wiping materials for mopping up spills of aqueous fluids. Most water-absorbent water-insoluble materials are only available in powder form. There are problems in retaining an absorbent powder in the desired position in the absorbent product, for example in diapers. Fibres and filaments can be more effectively retained in position by incorporating them in a fabric.
BACKGROUND ART
EP-A-268498 describes a water-absorbent water-insoluble polymeric fibre, film, coating, bonding layer or foam, made by forming a substantially linear polymer of water-soluble ethylenically unsaturated monomer blends comprising carboxylic and hydroxylic monomers and then reacting the carboxylic and hydroxylic monomers in the linear polymer to form internal crosslinks within the polymer.
EP-A-269393 describes a water-absorbent, water-insoluble crosslinked polymer fibre or film made by dry extrusion of a solution of a substantially linear polymer formed from a water-soluble blend of monoethylenically unsaturated monomers comprising a plasticising monomer and evaporating the solvent. The fibre or film is further plasticised, stretched and then crosslinked.
EP-A-342919 describes film or fibre made by extrusion and stretching from a polymer of water-soluble ethylenically unsaturated monomers that include ionic monomer. A counterionic lubricant compound is absorbed into the surface of the fibre or film before or during the stretching.
EP-A-397410 describes a water-soluble linear polymer of carboxylic acid monomers such as acrylic acid and a hydroxylic monomer which can be crosslinked, after being shaped by extrusion of an aqueous solution of the polymer as fibres or films, to form crosslinks between the carboxyl and hydroxyl groups.
GB-A-2082614 describes a dry, solid, water-swellable absorbent comprising a blend of a water-insoluble absorbent polymer, which may be a covalently crosslinked or ionically complexed anionic polyelectrolyte, and an extender material selected from uncrosslinked derivatives, starch, montmorillonite clay, attapulgite clay, seracite, talc, kaolin, silica and mixtures thereof. It states that the blend may be used as a film, aerated film, powder or fibre, but there is no disclosure as to how a blend of water-insoluble polymer and extender can be made into a fibre.
DISCLOSURE OF THE INVENTION
According to the present invention a fibre or filament of a water-absorbent water-insoluble fibrous material has a matrix of a crosslinked copolymer formed from 50 to 95% by weight of ethylenically unsaturated carboxylic monomer and 5 to 50% by weight of copolymerisable ethylenically unsaturated monomer, the matrix containing dispersed solid water-insoluble particles of a material which is chemically substantially non-reactive with the matrix copolymer.
The dispersed solid particles are generally chosen to improve the properties of the fibre or filament; for example they may modify the absorption/retention characteristics of the fibre or filament, alter the bulk properties of the fibre or filament such as its electrical conductivity or X-ray capacity, or alter the ability of the fibre or filament to absorb chemicals.
The dispersed particles are preferably less than 20 microns in diameter, most preferably less than 5 microns.
The dispersed solid particles may be formed of inorganic salts or oxides or naturally occurring mineral clays, or of any other substantially water-insoluble solids that can be reduced in particle size to a sufficient degree and are chemically substantially non-reactive towards the matrix copolymer.
The fibre or filament may be formed by extruding a dispersion of the solid water-insoluble particles in an aqueous solution of the
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Akers Paul J.
Brunskill William
Courtaulds Fibres (Holdings) Limited
Hoke Veronica P.
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