Appeal 2007-2135
Application 10/269,840
vulcanization accelerators, such as zinc thiocarbamate and sodium
diethylcarbamate (Fruh, col. 1, ll. 13-35; Noecker, col. 1, ll. 33-46). When
those of ordinary skill in the art speak of sulphur-cured natural rubber, they
are referring to a system including accelerators such as the above carbamate
amine compounds.
“Although products formed from such sulphur-cured natural rubber
exhibits some very good qualities, including strength, toughness, elasticity,
etc. and are used very effectively in many applications, there are some areas
or applications where compatibility problems arise due to the chemicals
incorporated into the rubber which react undesirably with foreign materials
contacted by products formed from the rubber during the products'
subsequent use.” (Noecker, col. 1, l. 61 to col. 2, l. 1.) For instance,
chemicals in latex examination gloves may react with dental impression
materials preventing proper curing of the material (Noecker, col. 2, ll. 21-
53).
According to Noecker,
Another problem encountered with conventional sulphur
cured, natural rubber latex products are the nitrosamines
contained therein. The nitrosamines, which are often generated
from the antioxidants used in natural rubber compositions or by
other amine compounds used in the rubber latex, are believed to
be carcinogenic. Hence it is undesirable to use the conventional
compounds having a high nitrosamine content, where products
formed from the rubber composition are likely to be contacted
by humans, such as with their skin, body fluids, or in their
mouths or other body cavities. For this reason, some natural
rubber products namely baby pacifier nipples have been formed
from substantially nitrosamine-free rubber compositions in
which oxygen-donating curing agents such as peroxides are
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Last modified: September 9, 2013