Plastic and nonmetallic article shaping or treating: processes – With twining – plying – braiding – or textile fabric formation
Patent
1995-02-07
1996-12-10
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
With twining, plying, braiding, or textile fabric formation
264143, 264146, 26417113, 264205, 2642104, 2642108, 26421113, 26421114, 26421117, 2642112, 264232, 264236, 427379, B29C 4700, B32B 3130, D01D 504, D02G 302
Patent
active
055827861
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to methods of producing water-absorbent shaped articles such as fibre or film, including free-standing film and film coated on a surface.
It is known to produce fibre or film of polymeric material which is capable of absorbing large quantities of water or other liquids. One method of manufacturing such fibre or film is to use as a starting material a water-soluble polymer which can be crosslinked under the action of heat. The polymeric material is dissolved in water to form an aqueous solution which is then extruded into a heated gaseous environment. This produces fibre or film of the water-soluble polymer, which is dried by the heated gaseous environment into which the material is extruded. The extruded fibre or film is subsequently heated to crosslink the polymer to such a degree that it is water-insoluble but water-absorbent.
Without the crosslinking step the fibre or film will redissolve should it ever encounter water subsequently. The crosslinking step, therefore, stabilises the fibre or film so that on encountering water it absorbs the water without dissolving. The more the material is heated and crosslinked the less capable the product is of absorbing water, but in general terms the more stable the material is and the more it retains its structure on absorbing water, that is to say the more the fibre retains its fibrous nature. The exact amount of crosslinking and heating can be varied depending upon the uses to which the water-absorbent fibre or film is to be put.
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 by polymerisation 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, evaporating the solvent and forming polymeric fibre or film plasticised by an external plasticiser, stretching the fibre or film while the external plasticiser remains in the fibre or film, and then crosslinking the polymer.
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 fibre or film, to form crosslinks between the carboxyl and hydroxyl groups.
FR-A-2355929 describes a process for manufacturing yarns and fibres having a water-retention capacity of more than 80% by weight, in which process aqueous solutions containing water-soluble polymers of acrylic acid, distributed homogeneously, and aliphatic, cycloaliphatic, araliphatic or aromatic compounds that contain at least two hydroxyl and/or primary or secondary amino groups in their molecule are spun, and the yarns spun in this way are heated at temperatures of between 100.degree. and 200.degree. C.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention, a method of producing water-absorbent water-insoluble fibre or film, by extruding an aqueous solution of a water-soluble polymer into a gaseous medium to form fibre or film and crosslinking the fibre or film at a temperature in the range 125.degree. to 250.degree. C. to a degree sufficient that the crosslinked fibre or film is water-insoluble, is characterised in that the extruded fibre or film is collected at a moisture content of 8 to
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patent: 4997714 (1991-03-01), Farrar et al.
patent: 5147956 (1992-09-01), Allen
Akers Paul J.
Brunskill William
Carefull John F.
Courtaulds Fibres Limited
Tentoni Leo B.
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