Appeal 2007-2135
Application 10/269,840
used instead of conventional sulphur and carbamate curing
agents.
Such known nitrosamine-free compositions are useful for
products such as pacifier nipples because the products have a
relatively large wall thickness to give the products sufficient
strength and elasticity, and because the increased tackiness of
products resulting from the oxygen-donating curing agents is
acceptable and even desirable for the products. On the other
hand, such nitrosamine-free compositions have not been used
for thin-walled rubber latex products such as gloves, dental
dams, catheters, penrosed drains, etc. because the resulting thin
walled products have insufficient strength characteristics
including tear strength and tensile strength, and because the
increased tackiness of the products causes significant problems
for handling, storing and donning the products. The reduced
strength characteristics and increased tackiness of the oxygen
cured rubber latex compositions results from a decreased cross
linking density of the compositions in comparison to that of
conventional sulfur cured compositions.
(Noecker, col. 3, l. 36 to col. 4, l. 2 (emphasis added)). Fruh also identifies
the problem of nitrosamine generation. According to Noecker, conventional
accelerators such as dithiocarbamates form secondary amines which, in turn,
form nitrosamines, carcinogenic compounds (Fruh, col. 1, ll. 13-42).
Noecker overcomes the problem of nitrosamine generation from the
amine-containing accelerator by using an oxygen-curing system instead of a
sulphur-curing system (Noecker, col. 4, ll. 61-63). In order to overcome the
deficiency in strength resulting from using the oxygen-curing system, a
strength-enhancing agent is used (Noecker, col. 7, l. 62 to col. 8, l. 17).
Noecker also implements a separate solution for the problem of generation
of nitrosamines from amine-antioxidants: The use of non-amine
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