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AssigneeDomsjö Fabriker AB
InventorsBengt Joensson, Hans Grundberg, Alf Gustafsson
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There is provided a process for improving the quality of lignosulfonate at least partly derived form a spent sulfite cooking liquor in at least two steps, comprising: one step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration using a membrane having a cut-off of 40-150 kD (high cut-off) at the pressure, flow rate and temperature of the step and the permeate is recovered; and another step in which a lignosulfonate-containing fraction at least partly derived from the spent sulfite cooking liquor is subjected to filtration using a membrane having a cut-off of 1-20 kD (low cut-off) at the pressure, flow rate and temperature of the step and the retentate is recovered. Products, uses thereof as well as a system are also provided.
Process for refining lignosulfonate at least partly derived from a spent sulfite cooking liquor in at least two steps, comprising:
A method of improving the strength of paper, comprising adding a lignosulfonate-containing product derived from spent sulfite cooking liquor, wherein the spent sulfite cooking liquor is subjected to membrane filtration and wherein the temperature of the liquor is maintained throughout filtration at a temperature of about 85-140° C., the product comprising less than 4 wt. % sulfate (SO42−) based on dry material obtained, wherein less than 4 wt. % of the lignosulfonate molecules in the product have a molecular weight of more than 60 kD and the amount of resins is below 1 wt. % based on dry material, to paper as a strength-improving agent.
Dependencies are inferred from the claim text.