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US 5,212,219 AGranted
Degradable plastics
AssigneeEpron Industries Limited
InventorGerald J. L. Griffin
Life of this patent
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AssigneeEpron Industries Limited
InventorGerald J. L. Griffin
Estimating the term…
A degradable polymer composition is disclosed which comprises a blend of a normally stable chemically saturated polymer, such as polyethylene, a less stable chemically unsaturated polymer or copolymer, such as a styrene/butadiene block copolymer, or natural rubber, an antioxidant active over a limited period and a latent pro-oxidant, such as an organic salt of a transition metal, e.g. cobalt naphthenate. The presence together of the anti-oxidant and the pro-oxidant give rise to a period of induction before a sharp loss of physical strength occurs, whereby the period of induction can be exploited as the effective working life of the polymer composition. The polymer composition preferably also includes filler particles of a directly biologically sensitive material such as natural starch, a derivative of natural starch, a natural protein or a natural cellulose product or a powdered sugar of melting point higher than the processing temperature of the host polymer composition, whereby, the biological breakdown, in natural environments or in the especially biologically active surroundings of composting urban garbage, of the molecular fragments created by the onset of oxidative scission of the molecular chains of the chemically saturated polymer is accelerated by the presence of said filler particles.
A polymer composition for preparing degradable articles having as essential ingredients a blend of:
A composition as claimed in claim I where the stable chemically saturated polymer is a copolymer of ethylene.
A composition as claimed in claim I where the unstable chemically unsaturated polymer is a synthetic elastomer of the type made by the polymerization of a 1:4 diene.
A composition as claimed in claim I where the unstable chemically unsaturated polymer is a copolymer of butadiene and isoprene.
A composition as claimed in claim I where the unstable chemically unsaturated polymer is a terpolymer of styrene, butadiene and isoprene.
A composition as claimed in claim I where the antioxidant is of the sacrificial type being an organic compound more readily oxidized than the host polymer blend.
A composition as claimed in claim I where the pro-oxidant is at least one transition metal salt.
A composition as claimed in claim I in which the stable polymer is selected from the group consisting of polyethylene, polypropylene, polystyrene, and their copolymers with other monomers;
A degradable article prepared from a composition comprising a blend of a stable polymer selected from the group consisting of polyethylene, polypropylene, polystyrene, and their copolymers with other monomers;
The polymer composition of claim I which incorporates a biologically active filler, and the unsaturated polymer does not include butadiene-styrene copolymer and is selected from the group consisting of (a) natural rubber, (b) synthetic rubber, (c) polymer of styrene, butadiene, or isoprene, (d) copolymer of butadiene and acrylic acid, acrylonitrile or isoprene, copolymer of isoprene and isobutylene, (e) terpolymer of ethylene, propylene and 1-6-hexadiene or norbornene, and (f) a terpolymer of styrene, butadiene and isoprene.
A polymer composition for preparing degradable articles having as essential ingredients a blend of:
Dependencies are inferred from the claim text.