Kraft pulp yield by heat treatment of polysulphide liquors...

Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...

Reexamination Certificate

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C162S029000, C423S562000

Reexamination Certificate

active

07371307

ABSTRACT:
Oxidized white liquor is heat treated to increase the concentration of polysulphide measured at 285 or 286 nm (PSUV) or measured at 416 nm (PSVIS) and the PSUV/PSGRor PSVIS/PSGRratio, whereby the content of active polysulphide in the total polysulphide is increased which active polysulphide can be exploited to increase pulp yield in Kraft pulping.

REFERENCES:
patent: 4024229 (1977-05-01), Smith et al.
patent: 5082526 (1992-01-01), Dorris
patent: PCT/US97/05591 (1997-11-01), None
patent: WO 97 42372 (1997-11-01), None
Database Paperchem ‘Online’, The Institute of Paper Science and Technology, Atlanta, GA, US; Database Accession No. AB4701536, Ringley, M.B.: “Laboratory Polysulfide Cooking of Loblolly Pine”, retrieved from Dialog XP002219846, abstract and Southern Pulp Paper MFR. 39, No. 1: 24-26, 28, 30-31 (Jan. 1976).
Multi-Stage Polysulphide Pulping Processes, Part 1, Basic Ideas and Low-Temperature Impregnation Studies on Black Spruce Heartwood, Clayton et al, Pulp and Paper Research Institute of Canada, Pointe Claire, Quebec, Dec. 1967, T-619 to T-630.
Factors Affecting Yield Increase and Fiber Quality in Polysulfide Pulping of Loblolly Pine, Other Softwoods and Red Oak, Sanyer et al, Tappi, vol. 47, No. 10, Oct. 1964, pp. 640-652.
Some Aspects of the Chemistry of Polysulfide Pulping, Ants Teder, Swedish Forest Products Research Laboratory, Stockholm, Sweden, May 1969.
Spectrophotometric Determination of Polysulfide Excess Sulfur in Aqueous Solutions, Ants Teder, The Central Laboratory of the Swedish Cellulose Industry (CCL), Stockholm, Sweden, No. 6, 197-200, Mar. 31, 1967.

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