Appeal No. 1999-2808
Application 08/772,351
chloride (col. 1, lines 67-72). Rhodes uses a large amount of
an aryl alkyl phosphite in combination with a small amount of
a zinc salt or soap to retard polyvinyl chloride thermal
degradation, and optionally uses an epoxidized soya oil to
increase the effectiveness of the zinc-phosphite combination
(col. 2, lines 32-44; col. 3, lines 23-40). Ackerman also
teaches that combinations of zinc salts or soaps with
stearates of alkali or alkaline earth metals are not suitable
thermal stabilizers for polyvinyl chloride (col. 1, line 39 -
col. 2, line 9). Ackerman uses combinations of zinc soaps and
potassium soaps, optionally containing additional stabilizers,
one of which can be an epoxide, to stabilize polyvinyl
chloride (col. 2, lines 10-14; col. 3, lines 6-8 and 31-32).
Thus, the applied prior art teaches that alkaline earth
metal stearates or epoxy stabilizers, in combination with zinc
stearate, reduce the rate of thermal degradation of polyvinyl
chloride compared to the rate of thermal degradation when zinc
stearate is used alone, but that a combination of a zinc-
containing stabilizer and either a calcium salt or an
epoxidized oil will not prevent sudden degradation of
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