upon performance properties of the product.
The references relied upon by the examiner are:
Del Pico (Del Pico) 4,160,726 Jul. 10, 1979
Kuhls et al. (Kuhls) 4,369,266 Jan. 18, 1983
Claims 22 and 23 stand rejected under 35 U.S.C. ' 112, second paragraph. The
claims also stand rejected under 35 U.S.C. ' 103. As evidence of obviousness, the
examiner relies on Del Pico and Kuhls. We reverse both grounds of rejection.
Background
The equipment for making a polymer latex product must be cleaned on a regular
basis. The cleaning operations result in the dilution of the polymer latex product with water,
producing a whitewater with a solid concentration of about normally 5% by weight or less,
although it may be higher.1 Typical whitewaters may contain emulsion-sized particles of
polymers and are generated by combining batches of different polymer types, with the
entire mixture treated as a single waste stream.1
The whitewater emulsion often presents a waste-disposal problem.
Semipermeable membrane filtration, particularly ultrafiltration, is used to concentrate the
whitewater emulsion. Solids are recovered, along with various cleaning agents and
miscellaneous contaminants, and typically buried in land-fills or used as a filler in asphalt or
as a dust-control agent on roadways.2
The membrane in the ultrafiltration process is subject to fouling by coagulum which
is formed when the whitewater emulsion is sheared and the latex destabilized. The
destabilized latex does not retain the performance properties found in the originally
1 Specification, p. 2, lines 18-29.
2 Specification, paragraph bridging pp. 2 and 3.
2
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