Appeal 2007-2144
Application 10/147,015
The organopolysiloxane-polyurea block copolymers of this
invention, useful as films or coatings, are prepared in and cast
from solvents. However, for many applications, solvents
cannot be tolerated for reasons of safety, toxicity, flammability
and environmental reasons. Further, many applications for
such films require water dispersibility. In one preferred
embodiment of the invention, the block copolymers of the
invention are rendered water soluble or water dispersible.
...
It has been discovered that these polymers are suitable for use
as release coatings for a variety of pressure-sensitive adhesives.
They have a high degree of difunctionality with little
contamination from monofunctional or nonfunctional siloxane
impurities, virtually eliminating re-adhesion problems. They
have good stability in solution, are film-forming, and have
unusually high strength plus desirable mechanical and
elastomeric properties. In addition, they do not require high
temperature curing or long processing time, a decided
advantage in pressure-sensitive tape manufacturing.
...
As mention previously, the segmented copolymers of this
invention may be prepared with a wide range of useful
properties through variations in the ratio of soft segments to
hard segments, the amount and nature of the chain extenders
employed, and the molecular weight of the polysiloxane
segment. These variations give rise to varying amounts of
release, i.e., from 10g/cm or less, to about 350 g/cm. Certain
copolymers are especially useful as low-adhesion backsizes
(LABs) for removable pressure-sensitive adhesives such as
masking tape.
Given the above teachings, we determine that substantial evidence
supports the Examiner’s finding that one of ordinary skill in the art would
have been led to employ the claimed release coating as the release coating of
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