US 6,454,902 C1 (1,639th)
Manufacture of paper and paperboard
Gordon Cheng I Chen, Chesapeake, VA (US)
Filed by Gordon Cheng I Chen, Chesapeake, VA (US)
Assigned to CIBA SPECIALTY CHEMICALS WATER TREATMENTS LIMITED, Bradford (GB)
Reexamination Request No. 95/002,397, Sep. 15, 2012.
Reexamination Certificate for Patent 6,454,902, issued Sep. 24, 2002, Appl. No. 09/704,350, Nov. 2, 2000.
Claims priority of provisional application 60/164,232, filed on Nov. 8, 1999.
Inter Partes Reexamination Certificate issued on Jan. 6, 2021.
Int. Cl. D21H 21/10 (2006.01); D21H 17/28 (2006.01); D21H 17/43 (2006.01); D21H 17/68 (2006.01); D21H 23/14 (2006.01); D21H 23/76 (2006.01)
CPC D21H 21/10 (2013.01) [D21H 17/28 (2013.01); D21H 17/43 (2013.01); D21H 17/68 (2013.01); D21H 23/14 (2013.01); D21H 23/765 (2013.01)]
AS A RESULT OF REEXAMINATION, IT HAS BEEN DETERMINED THAT:
Claims 1-18 are cancelled.
1. A process for making paper or paper board comprising forming a cellulosic suspension, flocculating the suspension, draining the suspension on a screen to form a sheet and then drying the sheet, wherein the cellulosic suspension is flocculated by the addition of a water soluble cationic synthetic polymer of intrinsic viscosity of at least 4 dl/g, wherein the flocculated cellulosic suspension is subjected to mechanical shearing and then reflocculated by a subsequent addition of a reflocculating system, and in which the reflocculating system comprises
i) a siliceous material and
ii) a water soluble anionic polymer of intrinsic viscosity at least 4 dl/g, and in which the siliceous material (i) and water soluble anionic polymer (ii) are added to the cellulosic suspension subsequent to the centriscreen and wherein the cationic polymer is added to a thin stock stream of the cellulosic suspension.