Appeal No. 2000-1832
Application 08/868,736
assistant which has a deplasticizing effect in the ready-to-use mix of the binding mineral building
material with water and which assistant is in the form of a finely divided solid.
33. A process for preparing an addition-polymer powder suitable for modifying a binding
mineral building material by drying an aqueous addition-polymer dispersion whose film has a
glass transition temperature Tg ≤ 30°C and to which a drying assistant has been added, which
comprises adding to the aqueous addition-polymer dispersion before drying only a drying
assistant which has a deplasticizing effect in the ready-to-use mix of the binding mineral building
material with water and admixing the resulting dry addition-polymer powder with at least one
assistant which has a plasticizing effect in the ready-to-use mix of the binding mineral building
material with water and which assistant is in the form of a finely divided solid.
The appealed claims, as represented by claims 32 and 33, are drawn to a process for
preparing an addition-polymer powder which comprises at least the steps of adding a drying
assistant to an aqueous dispersion of a specified addition-polymer, drying the dispersion to obtain
an addition-polymer powder, and then adding a second assistant to that addition-polymer powder
to obtain the specified product. In claim 32, the drying assistant has a plasticizing effect in the
ready-to-use mix of the binding mineral building material with water, and the second assistant
has a deplasticizing effect in the ready-to-use mix of the binding mineral building material with
water. In claim 33, the drying assistant has a deplasticizing effect in the ready-to-use mix of the
binding mineral building material with water, and the second assistant has a plasticizing effect in
the ready-to-use mix of the binding mineral building material with water. Appealed claim 59
encompasses “[a]n addition-polymer powder obtained by the process as claims in Claim 32 or
33,” and appealed claims 61 through 63 encompasses binding mineral building materials
comprising the product of claim 59 and methods of preparing such materials. According to
appellants, the redispersible addition-polymer powder compositions obtained by the claimed
methods make it possible to provide any desired yield value, that is, the “shear stress above
which a material behaves like a fluid, ie. flows, but below which it behaves like a solid, ie. does
not flow,” to ready-to-use mixes with water, wherein “the plasticizing or deplasticizing effect of
the assistant added [to the addition-polymer powder] . . . after the drying has ended is more
pronounced than if added prior to the drying” (specification, e.g., pages 5-6 and 15).
The references relied on by the examiner are:
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