Cross-linked glycerol based polymers as digestion aids for improving wood pulping processes

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a Continuation In-Part of U.S. patent application Ser. No. 12 / 720,973 filed on Mar. 10, 2010 and is also a Continuation In-Part of U.S. patent application Ser. No. 13 / 560,771 filed on Jul. 27, 2012 and of U.S. patent application Ser. No. 13 / 848,526.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not Applicable.BACKGROUND OF THE INVENTION[0003]This invention relates to compositions of matter and methods of digesting wood chips used in paper pulping processes. The digestion is often achieved by chemical, mechanical or combined means. Chemical pulping is currently dominated in pulping industry, and among Kraft pulping is the most used pulping process. Chemical digestion is a process in which cellulosic raw materials such as wood chips are treated with chemicals including alkaline and sulfide for Kraft pulping or sulfites / bisulfites for sulfite pulping, usually at high pressure and temperature for the ...

AI Technical Summary

Benefits of technology

[0006]At least one embodiment of the invention is directed towards a method for enhancing the penetration of cooking liquor into wood chips. The method comprises 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. The polymer may have 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. At least one of the chain segments may comprise 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 additive may be a cross-linked glycerol-based polymer having branched and cyclic structures according to the structure:wherein in, 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.

[0007]The additive may consist essentially of a cross-linked lipohydrophilic polyglycerol solution and / or may be selected from the list of crosslinked lipohydrophilic crosslinked polyglycerols, crosslinked polyglycerol derivatives, and other crosslinked glycerol-based polymers and any combinations thereof. The glycerol-based polymers may be branched, hyperbranched, dendritic, cyclic and any combinations thereof. The additive may be added to the cooking liquor in an amount of less than 1% or in an amount of 0.05 to 0.001% based on the dried weight of the chips. The additive may reduce the amount of lignin in the produced paper pulp by at least at least 0.5%.

[0009]The cross-linked glycerol-based polymers may be used by combining with anthraquinone, anthraquinone derivatives, quinone derivatives, polysulfide and the like and any combinations thereof. The cross-links may be formed by reaction between a glycerol-based polymer and diisocyanates, N,N-methylenebis(meth)acrylamide, polyethyleneglycol di(meth)acrylate, glycidyl(meth)acrylate, dialdehydes such as glyoxal, di- or tri-epoxy compounds such as glycerol diglycidyl ether and glycerol triglycidyl ether, dicarboxylic acids and anhydrides such as adipic acid, maleic acid, phthalic acid, maleic anhydride and succinic anhydride, phosphorus oxychloride, trimetaphosphates, dimethoxydimethsilane, tetraalkoxysilanes, 1,2-dichloroethane, 1,2-dibromoethane, dichloroglycerols 2,4,6-trichloro-s-triazine, epichlorohydrin, and any combination thereof. The cross-linked glycerol-based polymers may comprise at least one of the structural units illustrated in FIG. 2. The cross-linked glycerol-based polymers may comprise copolymers containing non-glycerol based structural units. The additive may consist essentially of a cross-linked polyglycerol solution. The cooking liquor may be white liquor. The crosslinked glycerol-based polymer may increase the pulping yield.

[0010]At least one embodiment of the invention is directed towards 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 used polymers were added to the liquor.

Problems solved by technology

Unfortunately the optimal composition of white liquor impairs the effectiveness of the surfactants.

Because white liquor has a high pH, it causes most surfactants to salt out of solution especially in high temperatures and pressures.

Reducing the amount of surfactant causes wood chunks (known as rejects) to survive the digestion process which imposes additional costs and quality control issues in subsequent papermaking stages.

Attempting to overcome this problem by supersaturating the white liquor with surfactant has been shown to offer little improvement and is undesirably expensive.

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