Stock material or miscellaneous articles – Hollow or container type article – Cellular material derived from plant or animal source
Patent
1984-02-21
1986-03-25
Michl, Paul R.
Stock material or miscellaneous articles
Hollow or container type article
Cellular material derived from plant or animal source
428500, 428515, 428913, 524 81, 524297, 264345, B27N 502
Patent
active
045782938
ABSTRACT:
A method and apparatus for improving the service life of thermoplastic resin articles exposed on one side to a fluid, such as heated water or air. The thermoplastic resin article, such as a pipe or tank liner, contains a minor proportion of an additive such as an anti-oxidant, an ultraviolet stabilizer, a plasticizer, or a heat stabilizer. During exposure to the fluid, the additive tends to migrate toward the exposed surface and be leached from the resin setting up a concentration gradient throughout the thickness of the resin article. A layer containing a quantity of the additive is applied to the outer unexposed surface of the thermoplastic article, and the concentration gradient causes the additive from the outer layer to diffuse inwardly through the wall of the article to replace the additive lost by exposure to the fluid, thereby substantially increasing the service life of the thermoplastic article and providing additional amounts of additive by an effective time release mechanism.
REFERENCES:
patent: 4167597 (1979-09-01), Yoshida et al.
patent: 4179432 (1979-12-01), Molt
patent: 4289815 (1981-09-01), Lee
patent: 4421805 (1983-12-01), Prader
patent: 4456660 (1984-06-01), Colombo
B. D. Gesner, "Stabilization Against Chemical Agents" in W. L. Hawkins, ed., Polymer Stabilization, J. Wiley & Sons, Inc., pp. 353 and 371-374, (1972).
Plastics Engineering, Aug. 1978, "A New Primary Antioxidant for Polypropylene and ABS", Schurdak et al.
"Zinc Oxide Stabilization of PP Against Weathering", D. S. Carr et al., Modern Plastics, May 1980.
"Zinc Oxide/Synergist Systems Provide Improved UV Control" D. S. Carr et al., Modern Plastics, Jul. 1981.
A. O. Smith Corporation
Michl Paul R.
Teskin Fred M.
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