| (19) |
 |
|
(11) |
EP 0 790 351 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
06.05.1999 Bulletin 1999/18 |
| (43) |
Date of publication A2: |
|
20.08.1997 Bulletin 1997/34 |
| (22) |
Date of filing: 14.02.1997 |
|
|
| (84) |
Designated Contracting States: |
|
DE FI GB NL SE |
| (30) |
Priority: |
14.02.1996 US 601601
|
| (71) |
Applicant: NALCO CHEMICAL COMPANY |
|
Naperville
Illinois 60563-1198 (US) |
|
| (72) |
Inventor: |
|
- St. John, Michael R.
Chicago, Illinois 60615 (US)
|
| (74) |
Representative: Baillie, Iain Cameron et al |
|
Ladas & Parry,
Altheimer Eck 2
80331 München
80331 München (DE) |
|
| |
|
| (54) |
Papermaking process using multi-polymer retention and drainage aid |
(57) The claimed invention comprises a papermaking process comprising forming an aqueous
cellulosic papermaking slurry, adding to the slurry a mineral filler, adding to the
slurry after the addition of the mineral filler a cationic polymeric coagulant, then
adding to the slurry an effective flocculating amount of a high molecular weight anionic
polymer selected from the group consisting of acrylamide/sodium acrylate copolymers
and copolymers of acrylamide and acrylamido methyl propyl sulfonate (AMPS), adding
a low molecular weight anionic polymer selected from the group consisting of polyacrylic
acid and methacrylic acid, draining the slurry to form a sheet, and drying to form
a paper sheet.