Cross-linked glycerol based polymers as digestion aids for improving wood pulping processes
The invention provides a method of improving the digestion of wood chips into pulp. The method involves: adding a cross-linked glycerol-based polymer additive to a solution used in the digestion process. This additive is unexpectedly effective at facilitating digestion. The branched and ether structure of the additive allows it to withstand the harsh nature of a high stress environment. In addition, it is more soluble in the harsh condition than other surfactants. The structure, resistance, and particular balance between hydrophobic and hydrophilic regions, causes the additive to increases the interaction between the wood chips and the digestion chemicals. This in turn reduces the costs, the amount of additive needed, and the amount of reject wood chunks that result from the digestion process.
1. A method for enhancing the penetration of cooking liquor into wood chips, the method comprising cooking wood chips in a cooking liquor to form a paper pulp and including at least one cross-linked glycerol-based polymer comprising additive in the cooking liquor, the method so enhances the penetration of pulping liquor into the chips that it reduces lignin such that the resulting pulp has a lower kappa number than if no polymer or if equal amounts of other glycerol based polymers were added to the liquor.
2. The method of claim 1 in which the polymer has a branched structure, the branched structure characterized as having at least three chain segments of the polymer joined at a single joining monomer of the polymer which has an alkoxylate group.
3. The method of claim 2 in which at least one of the chain segments comprises a lipophilic carbon bearing group and this chain segment is engaged to the joining monomer at a location other than the alkoxylate group of the joining monomer.
4. The method of claim 1 wherein the additive is a cross-linked glycerol-based polymer having branched and cyclic structures according to the structure:
wherein m, n, o, and p are each independently between 1 and 700 and q and r are independently a number of 0 and integers of between 1-700, R and R′ are (CH2)n and n can independently be 1 or 0, Z can be 0 or great than 0 and each R1 is independently H, acyl, or a C1-C40 hydrocarbon group, which may be optionally substituted.
5. The method of claim 1 wherein the additive consists essentially of a cross-linked lipohydrophilic polyglycerol solution.
6. The method of claim 1 wherein the additive is selected from the list of crosslinked lipohydrophilic, crosslinked polyglycerols, crosslinked polyglycerol derivatives, and other crosslinked glycerol-based polymers and any combinations thereof.
7. The method of claim 1 wherein the glycerol-based polymers, are branched, hyperbranched, dendritic, cyclic and any combinations thereof.
8. The method of claim 1 wherein the additive is added to the cooking liquor in an amount of less than 1% based on the dried weight of the chips.
9. The method of claim 1 in which the additive reduces the amount of lignin in the produced paper pulp by at least at least 0.5%.
10. The method of claim 1 in which the digestion process is one selected from the list consisting of: Kraft digestion, sulfite pulping, oxygen pulping, semichemical pulping, mechanical pulping, thermal pulping, thermomechanical pulping, pulping designed for conversion into synthetic fibers such as dissolving grade pulps, and any combinations thereof.
11. The method of claim 1 in which the cooking liquor also may comprise additional surfactant(s).
12. The method of claim 1 in which the cross-linked glycerol-based polymers can be used by combining with anthraquinone, anthraquinone derivatives, quinone derivatives, polysulfide and the like and any combinations thereof.
13. The method of claim 1 in which the cross-linked glycerol-based polymers comprises at least one of the structural units illustrated in FIG. 2 .
14. The method of claim 1 in which the cross-linked glycerol-based polymers comprises copolymers containing non-glycerol based structural units.
15. A method for enhancing the penetration of cooking liquor into wood chips, the method comprising cooking wood chips in a cooking liquor to form a paper pulp and including at least one cross-linked lipohydrophilic glycerol-based polymer additive in the white liquor, wherein the polymer has a branched structure, the branched structure characterized as having at least three chain segments of the polymer joined at a single joining monomer of the polymer which has an alkoxylate group, and in which at least one of the chain segments comprises a lipophilic carbon bearing group and this chain segment is engaged to the joining monomer at a location other than the alkoxylate group of the joining monomer, the method so enhances the penetration of pulping liquor into the chips that it reduces lignin, such that the resulting pulp has a lower kappa number than if no polymer or if equal amounts of other glycerol based polymers were added to the liquor.
16. The method of claim 1 wherein the additive consists essentially of a cross-linked polyglycerol solution.
17. The method of claim 1 wherein the cooking liquor is white liquor.
18. The method of claim 1 wherein the crosslinked glycerol-based polymer increases the pulping yield.
19. The method of claim 1 in which the cooking liquor is black liquor.