| 摘要 |
A coating for a biodegradable article comprises a hydratable coating or a chemically or physically discontinuous coating. Imperfections in the coating, which may comprise pores in the coating, enable water to penetrate to the underlying surface of the water soluble article. The nature and extent of the imperfections permits the rate of penetration of the coating by water to be controlled. Alternatively, the coating is a hydratable coating which swells and tears on hydration to expose the underlying article to moisture. By these means, the article can be protected from premature dissolution during its normal working life, but will degrade on disposal to waste, when the surface coating will degrade to permit water to reach and dissolve the underlying article. Typically, the body of the article comprises water soluble, biodegradable polyvinyl alcohol or polyvinylalcohol/polyvinylacetate copolymer. Chemical/physical discontinuity may be achieved by over-coating a surface already covered with a physically flawed coating with a hydratable coating.
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