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Preparation of homogeneous hydrogel copolymers

  • US 5,266,325 A
  • Filed: 12/03/1990
  • Issued: 11/30/1993
  • Est. Priority Date: 09/28/1990
  • Status: Expired due to Term
First Claim
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1. A method for centrifugally casting a biocompatible copolymer having predetermined equilibrium water content (EWC) value formed by the addition polymerization of a mixture containing an ethylenically unsaturated hydrophilic monomer A and an ethylenically unsaturated hydrophilic monomer B copolymerizable therewith, said copolymer being useful as a hydrogen membrane in the diffusion therethrough of a selected active compound in an aqueous medium at a predetermined rate which comprises:

  • a. determining the EWC values of hydrogel homopolymer of monomer A (homopolymer A) and hydrogel homopolymer of monomer B (homopolymer B);

    b. determining the relationship of the EWC values of the homogeneous hydrogel copolymers of mixtures of monomer A and monomer B (copolymers AB) versus the chemical composition of said copolymers AB;

    c. selecting the targeted EWC value and determining the chemical composition of homogeneous copolymer AB having this targeted EWC value;

    d. forming a polymerizable liquid mixture containing said monomer A and said monomer B in amounts sufficient to yield said homogeneous copolymer AB having the targeted EWC value;

    e. filling a tube comprising a core of smooth uniform cylindrical surface and closure means to prevent loss of the mixture during rotation, with a predetermined quantity of the liquid mixture;

    f. rotating the tube while maintaining a longitudinal axis of the tube parallel to the ground and effecting the rotation at a speed sufficient to cause radially outward displacement of the liquid monomers to assume a cylindrically-shaped liquid cartridge shape having a predetermined configuration within said tube;

    g. subjecting the tube to polymerization conditions to convert said liquid state cartridge to a predetermined solid state hollow plastic cartridge; and

    h. recovering a biocompatible, non-degradable, water-swellable, water-insoluble, homogeneous copolymer AB consisting essentially of monomer A units and monomer B units in the form of a cylindrical cartridge having walls of uniform thickness between its smooth external and internal cylindrical surfaces.

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