Crosslinked pulp, cellulose ether products made therefrom, and related methods of making the pulp and cellulose ether products

Abstract

To provide crosslinked pulps and economically efficient methods of making high-viscosity cellulose ether products made therefrom.SOLUTION: Disclosed are pulps including crosslinked cellulose fibers, wherein pulps have pulp R18 value of 93% or over.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 62 / 712,844, filed July 31, 2018, and U.S. Patent Application No. 15 / 999,228, filed August 16, 2018, the contents of each of which are incorporated herein by reference.

[0002] The present disclosure relates to cellulosic products (eg, pulp) and cellulose derivatives (eg, cellulose ethers) and related methods of making the cellulosic products. [Background technology]

[0003] Cellulose ethers (e.g., carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, etc.) form aqueous solutions and are available in a variety of grades, primarily depending on the viscosity of these solutions. High-grade cellulose ethers that form more viscous aqueous solutions tend to be more valuable than low-grade cellulose ethers that form less viscous aqueous solutions under the same conditions (concentration, temperature, etc.). The ability of a given cellulose ether to form a more viscous aqueous solution is closely related to the degree of polymerization, crosslinking, and / or other properties of the cellulose precursor from which the given cellulose ether is produced. High-grade cellulose ethers are typically produced from dissolving-grade pulp (e.g., high-viscosity wood pulp and high-viscosity cotton linter pulp (CLP)), while medium- and low-grade cellulose ethers are typically produced from lower-cost wood pulp. The pulp grades referenced in this disclosure are further discussed in Herbert Sixta, Handbook of Pulp, Wiley-Voch (2006), which is incorporated herein by reference in its entirety. The degree of polymerization of most wood pulps typically does not exceed about 1,500. In contrast, dissolving-grade pulps often have a degree of polymerization of 2,400 or higher. Unfortunately, dissolving-grade pulps tend to be expensive. Previous attempts to modify low-cost pulps for the production of higher-grade cellulosics have met with limited success.

[0004] Several conventional processes have had some success in increasing the ability of kraft pulp to produce cellulose ethers that form high-viscosity aqueous solutions. Unfortunately, the success of these conventional processes has come at the expense of other desirable properties of the resulting cellulose ethers and / or process yield. For example, some conventional processes include a step to increase the removal of hemicellulose from kraft pulp. However, these processes result in low yields due to the removal of hemicellulose-induced clumps. Furthermore, the pulp produced by these processes tends to have low reactivity due to the conversion of the constituent cellulose from cellulose-I to cellulose-II. Conventional crosslinking reactions also typically reduce the reactivity of the pulp. Even taking into account low yields and / or low reactivity, conventional processes for modifying low-cost pulps have still not been able to produce pulps suitable for producing cellulose ethers that form aqueous solutions with viscosities comparable to those of cellulose derivatives produced from high-viscosity dissolving-grade ether pulps.

[0005] Attempts have been made to crosslink cellulose at moderate consistencies to produce pulps of moderately high viscosity. Such moderate consistencies may include, for example, crosslinking at less than 20% or less than 30% consistency. Such processes are limited by the usual processing systems in existing pulp mills. Methods for producing pulp products with high values ​​(e.g., high ether viscosity and viscosity consistency), particularly low-cost methods, have not been explored. As discussed further herein, As has been shown, there is currently a shortage of quality products with consistent product quality. Summary of the Invention [Problem to be solved by the invention]

[0006] Thus, further innovation is needed in this field, particularly with respect to economically efficient methods of making crosslinked pulp and the high viscosity cellulose ether products made therefrom. [Means for solving the problem]

[0007] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. It is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0008] In one aspect, the present disclosure provides a pulp comprising crosslinked cellulose fibers, the pulp having a pulp R18 value of 93% or greater. In one aspect, the present disclosure provides a pulp comprising crosslinked cellulose fibers, wherein the coefficient of variation (COV) of viscosity of carboxymethyl cellulose (CMC) produced from the pulp is less than 30% and the pulp has an R18 value of greater than 92%.

[0009] In one aspect, the present disclosure provides a pulp comprising crosslinked cellulose fibers, the pulp having a water retention value (WRV) in the range of 0.8 g / g to less than 1.0 g / g; and a pulp R18 value greater than 89%.

[0010] In one aspect, the present disclosure provides a cellulose ether product comprising a crosslinked cellulose ether, wherein the crosslinked cellulose ether has a viscosity greater than about 56 centipoise (cP), and the cellulose ether product is formed from a pulp according to any of the embodiments of the present disclosure.

[0011] In one aspect, the present disclosure provides a blended pulp comprising a first pulp according to any of the embodiments of the present disclosure having a first fiber kink value and a second pulp having a second fiber kink value different from the first fiber kink value.

[0012] In one aspect, the disclosure provides a method of making pulp, the method comprising: cooking a cellulosic feedstock to form a pulp; bleaching the pulp to form a bleached pulp; crosslinking cellulose fibers in the bleached pulp with a crosslinking agent to form a crosslinked pulp, wherein upon crosslinking, the bleached pulp has a consistency greater than 30% and the crosslinked pulp has an R18 value greater than 92%; and drying the crosslinked pulp.

[0013] In one aspect, the present disclosure provides a method for making pulp, the method comprising the steps of contacting wood fibers with a crosslinking agent and an alkaline hydroxide, wherein the wood fibers have a moisture content ranging from about 0% to about 50% by weight; heating the wood fibers, the crosslinking agent, and the alkaline hydroxide to obtain crosslinked wood fibers; and washing the crosslinked wood fibers to remove unreacted crosslinking agent, wherein the pulp after crosslinking has an R18 value of 93% or greater.

[0014] In one aspect, the present disclosure provides a method for making crosslinked cellulose pulp, comprising the steps of activating a cellulosic pulp with an alkali hydroxide at a consistency greater than 4% to obtain an activated pulp, removing the alkali hydroxide from the activated pulp, and crosslinking the activated pulp with a crosslinking agent. and crosslinking the pulp at a consistency higher than 20% and at a temperature in the range of 30°C to 95°C to obtain a crosslinked pulp.

[0015] In one aspect, the present disclosure provides a pulp formed according to any of the methods of the present disclosure. The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description when read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a method of making pulp according to an embodiment of the present disclosure. [Figure 2]FIG. 2 is a schematic diagram of an alternative method for making pulp according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a schematic diagram of a further alternative method for making pulp in accordance with an embodiment of the present disclosure. [Figure 4] FIG. 2 is a schematic diagram of an alternative method for making pulp according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present disclosure provides pulp, cellulose ether products, and methods of making the pulp. Method for making crosslinked pulp In certain aspects, the present disclosure provides methods of making crosslinked pulp. As discussed further herein, the methods of the present disclosure are useful in making crosslinked pulp suitable for economically and efficiently producing high viscosity crosslinked ether products.

[0018] In general, it should be understood that other methods, systems, and compositions in addition to those disclosed herein are within the scope of the present disclosure. For example, methods, systems, and compositions according to embodiments of the present disclosure can have different and / or additional operations, components, configurations, etc. than those disclosed herein. Moreover, one of ordinary skill in the art will understand that methods, systems, and compositions according to embodiments of the present disclosure can be without certain operations, components, configurations, etc. disclosed herein without departing from the present disclosure. Modified Kraft process involving high consistency crosslinking Methods for making crosslinked pulp and related systems and compositions according to embodiments of the present disclosure can at least partially address one or more problems associated with conventional techniques, whether or not such problems are described herein. For example, methods according to at least some embodiments of the present disclosure enable low-cost pulp to serve as a precursor in the production of high-grade cellulose ethers and / or other cellulose derivatives (e.g., cellulose esters). For example, kraft pulp is much cheaper and more widely available than certain dissolving-grade pulps. However, when standard kraft pulp is used as a precursor for the production of cellulose ethers, the resulting cellulose ethers tend to be low-grade.

[0019] In conventional kraft processing, the pulp is maintained at a relatively low consistency (e.g., 10% or less consistency). As the consistency of the pulp increases, it becomes more difficult to pipe and mix the pulp. Therefore, any cross-linking in conventional processes for modifying kraft pulp to increase the likelihood of producing high-grade cellulose derivatives is carried out at a relatively low consistency.

[0020] As discussed further herein, it has been discovered that this intimate mixing of, for example, cellulose, caustic, and cross-linking agent can be achieved, for example, by using a high consistency mixer and other high consistency methods. Through the intimate mixing of the cross-linking reaction components, the method of the present disclosure provides a pulp suitable for economically and efficiently producing high viscosity cellulose ether products. Another surprising discovery associated with at least some embodiments is that increasing the consistency of the pulp upon crosslinking can increase the reactivity of the crosslinked pulp relative to certain crosslinked pulps that have a lower consistency upon crosslinking.

[0021] With these and / or other discoveries associated with at least some embodiments of the present disclosure, it is now possible to produce kraft pulp that is a true alternative to and / or a suitable extender of expensive dissolving grade pulp in the production of high grade, high viscosity cellulose derivatives.

[0022] Methods according to at least some embodiments of the present disclosure include cross-linking pulp at a relatively high consistency (e.g., a consistency of 20% or more, 30% or more, or more). Thus, in embodiments of the present disclosure, the method includes cooking a cellulosic feedstock to form a pulp, bleaching the pulp to form a bleached pulp, and cross-linking cellulose fibers in the bleached pulp with a cross-linking agent to form a cross-linked pulp, wherein upon cross-linking, the bleached pulp has a consistency of, for example, greater than 20%, greater than 25%, greater than 30%, or more.

[0023] In one embodiment, the method described herein includes a modified Kraft process for producing crosslinked pulp. Examples of suitable starting materials for producing pulp in a modified Kraft process, such as that according to embodiments of the present disclosure, include wood and recycled paper. In at least some embodiments, the starting material is not dried. In the wood pulping industry, trees are typically classified as hardwood or softwood. Pulp for use as a starting material can be derived from softwood or hardwood tree species. Examples of suitable softwood tree species include fir (e.g., Douglas fir and balsam fir), pine (e.g., white pine and loblolly pine), spruce (e.g., white spruce), larch (e.g., eastern larch), cedar, and hemlock (e.g., eastern and western hemlock). Examples of suitable hardwood species include acacia, alder (e.g., red alder and European black alder), aspen (e.g., quaking aspen), beech, birch, oak (e.g., white oak), rubber trees (e.g., eucalyptus and sweetgum), poplar (e.g., balsam poplar, eastern cottonwood, black cottonwood, and yellow poplar), gmelin, and maple (e.g., sugar maple, red maple, silver maple, and bigleaf maple).

[0024] Wood, whether softwood or hardwood, generally contains three major components: cellulose, hemicellulose, and lignin. Cellulose, which accounts for approximately 50% of the woody structure of plants, is an unbranched polymer of D-glucose monomers. Individual cellulose polymer chains combine to form thicker microfibrils, which in turn combine to form fibrils arranged in bundles. The bundles form fibers, visible under high magnifications under an optical microscope or scanning electron microscope as components of plant cell walls. Cellulose is highly crystalline as a result of extensive intra- and intermolecular hydrogen bonding. Hemicellulose is a group of diverse low-molecular-weight carbohydrate polymers, such as xylans and mannans, that are bound to cellulose in wood. Hemicellulose is an amorphous, branched polymer, in contrast to cellulose, which is a linear polymer. Lignin is a complex aromatic polymer that accounts for approximately 20%–40% of wood and occurs as an amorphous polymer.

[0025] Generally, kraft processing involves chemically cooking cellulosic feedstock (e.g., wood chips) at high temperatures and pressures in white liquor, an aqueous solution of cooking chemicals (e.g., sodium sulfide and sodium hydroxide). The cooking chemicals swell the wood and dissolve the lignin that binds the cellulose fibers together in the feedstock. Once this chemical cooking is complete, pulp is formed. The pulp is then transferred to an atmospheric tank called a "blow tank." The contents of the blow tank are then sent to a pulp washer, where the spent cooking chemicals are separated from the pulp. The pulp then progresses through various stages of washing and bleaching before being pressed and dried into a finished product.

[0026] The Kraft process is designed to recover cooking chemicals and heat from the Kraft process steps. For example, spent cooking chemicals and pulp wash water can be combined to form weak black liquor, which can be concentrated to approximately 55% solids in a multiple-effect evaporator system. The black liquor can then be further concentrated to 65% solids in a direct-contact evaporator or in an indirect-contact concentrator by contacting it with flue gas from the recovery furnace. Strong black liquor can then be calcined in the recovery furnace. Combustion of dissolved organic matter in the black liquor can provide heat for the generation of process steam and the conversion of sodium sulfate to sodium sulfide. Inorganic chemicals present in the black liquor can be recovered as a molten smelt at the bottom of the furnace. The smelt can be dissolved in water to form green liquor, which can then be transferred to a causticizing tank, where quicklime (calcium oxide) can be added to convert the solution back to white liquor and returned to the digester system. Lime mud precipitate from the causticizing tank can be calcined in a lime kiln to regenerate quicklime.

[0027] FIG. 1 is a flowchart illustrating a method 100 for making pulp according to an embodiment of the present disclosure. In the illustrated embodiment, the method 100 is based on the Kraft process. In other embodiments, the counterpart of the method 100 can be based on other suitable processes (such as sulfite). Referring to FIG. 1, the method 100 can include a pulping process block 102 and a post-pulping process block 104. Within the pulping process block 102, the method 100 can include adding chips (process block 106) and pre-steaming the chips (process block 108). Steam at atmospheric pressure can be used to preheat the chips and drive off air to increase liquor penetration. After pre-steaming, the method 100 can include adding chemicals (e.g., NaOH, NaS, and / or other suitable chemicals) to the chips (process block 110). For example, the chemicals can be added as a cooking liquor. The wood chips and cooking liquor can then be fed to a digester. Within the digester, cooking liquor can be impregnated into the wood chips, process block 112. Good penetration of the cooking liquor can promote uniform cooking of the wood chips.

[0028] After impregnation, the method 100 can include cooking the wood chips and cooking liquor in cocurrent (process block 114) and countercurrent (process block 116) liquid contact. In either operation, the cooking liquor and chips can be brought to a temperature. Wash liquor can then be introduced into the bottom of the digester in countercurrent flow to the cooked pulp (process block 118). Cooking can be terminated when the pulp encounters the cooler wash liquor. After digester cleaning, the contents of the digester can be blown out (process block 120). Digester blowing can involve expelling the wood and liquor at atmospheric pressure. The expulsion can occur with a sufficient amount of force to cause fiber separation. If desired, the blow tank can be equipped with heat recovery equipment to reduce operating costs. Finally, the pulp can be sent from the blow tank to an external pulp washer to separate the black liquor from the pulp (process block 122).

[0029] Following pulping process block 102, the pulp can be bleached to crosslink the cellulose fibers within the pulp. In standard Kraft processes, bleaching occurs without crosslinking. Bleaching typically does not result in a substantial reduction in the hemicellulose content of the pulp. Instead, bleaching involves the removal of lignin, with a concomitant reduction in pulp fiber length and viscosity. During bleaching, the pulp is treated with various chemicals at different stages in the bleach plant. The bleaching process can be carried out in a variety of ways. The stages can be carried out in vessels or towers of conventional design. Bleaching is typically carried out as a series of operations, including one or more bleaching stages using different bleaching agents (e.g., oxygen, chlorine dioxide, etc.), extraction stages, and other treatment stages. A bleaching sequence can be identified in terms of the order of operations performed in the sequence. For example, one bleaching sequence is ODED. Such a bleaching sequence can include an oxygen-based bleaching stage ("O stage"), then a first chlorine dioxide bleaching stage ("D stage"), then an extraction stage ("E stage," or "EOP stage," in which bleaching chemicals such as peroxide ("P") and / or oxygen ("O") are mixed with caustic to remove lignin), and a second D stage. Several additional examples of bleaching processes are described in U.S. Pat. Nos. 6,331,354 and 6,605,350, which are incorporated herein by reference in their entireties.

[0030] Post-pulping process block 104 can include initially bleaching the pulp with oxygen (process block 124). Bleaching the pulp with oxygen tends to be less specific for lignin removal than bleaching the pulp with chlorine dioxide. Oxygen-based bleaching can be carried out under pressure in an oxygen reactor. Suitable oxygen reactors and related oxygen-based bleaching processes are described in U.S. Patent Nos. 4,295,925, 4,295,926, 4,298,426, and 4,295,927, which are incorporated herein by reference in their entireties. The amount of oxygen added to the pulp can range from 50 to 80 pounds (22.7 to 36.3 kg) per ton of pulp. The temperature during oxygen-based bleaching can range from 100°C to 140°C.

[0031] After oxygen-based bleaching the pulp, the method 100 may include cross-linking the cellulose fibers in the pulp (process block 126). In at least some cases, this involves adding a cross-linking agent and caustic to the pulp to allow the cross-linking reaction to occur before further processing the pulp.

[0032] As discussed further herein, crosslinking the pulp while it is at a relatively high consistency can be useful for increasing the pulp's ability to produce high-grade cellulose derivatives. In that regard, the consistency of the pulp during all or a portion of the crosslinking (e.g., at least 50% of the time) can be at least 30% (e.g., in the range of 30% to 50%) or at least 35% (e.g., in the range of 35% to 50%). In one embodiment, the pulp is mixed in a batch or continuous mixer. In one embodiment, the pulp is mixed in a refiner, extruder, or other high-consistency mixer. In one embodiment, the pulp is mixed using a high-consistency mixer, such as an Andritz™ mixer or a Loedige™ mixer, as further described herein in connection with Example 1. In one embodiment, the pulp is mixed in a system including, for example, a reversing plate to which the pulp and crosslinking agent are added. In one embodiment, the pulp is mixed in a system including one or more rotating plow-like devices, such as a plowshare mixer.

[0033] In one embodiment, a stable flow pump, such as a gear pump or a pump with no or minimal pulses, is used to meter crosslinking reactants, such as a crosslinking agent, an alkali hydroxide, and a catalyst, into the reactor prior to crosslinking. In this way, the crosslinking reactants are uniformly distributed in the reactor for crosslinking. Such uniform distribution of the crosslinking reactants typically results in a uniform and evenly crosslinked pulp, which is suitable for producing crosslinked ethers with a uniform viscosity.

[0034] Such high consistency mixers and mixing result in intimate mixing and contact of the pulp and crosslinking agent, for example, reducing undesirable side reactions of the crosslinking agent with water (and thus increasing the desired reaction of the crosslinking agent with cellulose) and using less reactor space for a given number of useful crosslinking reactions. In this respect, the disclosed method is suitable for using less crosslinking agent than methods that crosslink pulp at lower consistencies. Conversely, methods that crosslink pulp at lower consistencies have a higher moisture content, thus reducing the crosslinker concentration in the water and reducing the interaction between the crosslinker and cellulose. Therefore, for a given degree of crosslinking, more crosslinking agent is required, and more water-crosslinking agent reaction occurs. Furthermore, the disclosed method provides crosslinked pulp using less reactor space and with less capital than methods that crosslink pulp at lower consistencies, particularly due to the greater degree of intimate mixing achieved between the fiber and the crosslinking agent. These advantageous features of the disclosed method result in a crosslinked pulp that is suitable for producing high-viscosity crosslinked ether products at lower cost and with less capital than other lower consistencies.

[0035] Furthermore, due to the relatively high consistency and / or other factors, crosslinking can increase the alkali resistance of the pulp (e.g., as measured by the crosslinked pulp R18 value). In one embodiment, crosslinked wood pulp produced by a method according to the present disclosure has an R18 value of greater than 89%. In one embodiment, crosslinked wood pulp produced by a method according to the present disclosure has an R18 value of greater than 93%, as further discussed herein in connection with Example 1. In one embodiment, crosslinked wood pulp according to the present disclosure has an R18 value ranging from greater than 92% to 100%. In one embodiment, crosslinked wood pulp according to the present disclosure has an R18 value ranging from 93% to 95%. In contrast, crosslinking processes with a crosslinking consistency of less than 30% typically provide wood pulp R18 values ​​of less than 92%. As further discussed herein, such crosslinking processes can produce crosslinked pulp with a WRV of less than 1.0 g / g. In certain embodiments, such pulps have a pulp R18 value of greater than 89% and a WRV of less than 1.0 g / g.

[0036] Furthermore, in one embodiment, upon crosslinking, the pulp in the crosslinking stage has a highly consistent alkali ion concentration due to the high pulp consistency. As discussed further herein, in one embodiment, crosslinking the bleached pulp includes providing an alkali hydroxide to the bleached pulp. Due to the intimate mixing of the cellulose fibers with the alkali hydroxide solution containing, for example, sodium hydroxide upon crosslinking, the pulp in the crosslinking stage has a low coefficient of variation (COV) of sodium ion concentration. In one embodiment, as discussed further herein in connection with Example 12, the pulp described herein has a COV of sodium ion concentration upon crosslinking of less than 10, such as less than 5.

[0037] The crosslinking agent used in the method of the present disclosure can be selected to form relatively strong crosslinks (e.g., ether or ionic crosslinks instead of ester). Relatively strong crosslinks may be preferable, for example, to weaker crosslinks, making them less likely to be disrupted by functionalization reactions (e.g., etherification) used to form cellulose derivatives. The crosslinking agent can be added at a weight ratio to pulp of 2:100 or greater, 3:100 or greater, 5:100 or greater, or another suitable lower threshold. The upper threshold can be the maximum amount of crosslinking agent that can be used without rendering the CMC resulting from the pulp insoluble in water. In at least some cases, a catalyst (e.g., NaOH, zinc tetrafluoroborate Zn(BF4)2) is present during crosslinking. Additionally or alternatively, a surfactant can be present during crosslinking, such as to facilitate crosslinking agent dispersion and penetration. Surfactants can be particularly useful in combination with hydrophobic crosslinking agents.

[0038] Suitable crosslinkers include ethers, such as glycidyl ethers, having two or more glycidyl groups. For example, the crosslinker can include a first glycidyl group, a second glycidyl group, and three or four linear carbon atoms between the first and second glycidyl groups. In one embodiment, the crosslinker includes three or more glycidyl groups. Additionally or alternatively, the crosslinker can have a weight average molecular weight of 500 or less (e.g., in the range of 174 to 500). Furthermore, when the crosslinker is an epoxide, the crosslinker can have a weight average molecular weight of 175 or less (e.g., in the range of 14 The crosslinker may have a weight per epoxide of 0 to 175. The crosslinker may have a viscosity of 500 centipoise (cP) or less at 25°C. In at least some embodiments, the crosslinker is at least partially insoluble in water. This property may be useful for increasing contact between the crosslinker and the cellulosic fibers during the crosslinking reaction. Specific examples of suitable crosslinkers include trimethylolethane triglycidyl ether, 1,4-butanediol diglycidyl ether, glycerol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol polyglycidyl ether, glycerol triglycidyl ether, ethylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether, among others, or mixtures thereof.

[0039] Conventional non-crosslinked kraft pulp tends to have lower reactivity than other chemical pulps, such as sulfite pulp (i.e., pulp made by extracting lignin from wood primarily using sulfite salts). However, in at least some embodiments of the present disclosure, crosslinked kraft pulp has relatively high reactivity. As a theory alone, and without wishing to be limited to such a theory, this is believed to be due to the presence of crosslinks that uniformly add extra space between the cellulose chains. Longer-chain crosslinkers (e.g., polyglycidyl ethers) can produce crosslinked pulps with higher reactivity than shorter-chain crosslinkers (e.g., 1,3-dichloro-2-hydroxypropanol (DCP)) under similar crosslinking conditions. Pulps crosslinked with longer-chain crosslinkers can have a crystallinity lower than that of the starting pulp, and much lower than that of dissolving-grade sulfite wood pulp and cotton linter pulp (CLP). Crosslinking kraft pulp instead of sulfite pulp for high viscosity ether applications can be advantageous in at least some cases because kraft is the dominant pulping process, has higher yields than sulfite pulping processes (at least in part due to its higher hemicellulose content), has lower costs, and is more environmentally friendly.

[0040] In certain embodiments, crosslinking the bleached pulp includes sequentially dosing the bleached pulp with crosslinking reactants, including a mixture containing two or more crosslinking reactants. In this regard, and as further discussed herein with respect to Sample 5A, in certain embodiments, crosslinking the bleached pulp includes sequentially contacting the bleached pulp with an alkaline hydroxide solution, a first portion of water, a crosslinker solution, emulsion, or suspension, and a second portion of water. In certain embodiments, crosslinking the bleached pulp includes multiple applications of a solution containing an alkaline hydroxide and a crosslinker to the bleached pulp. In that regard, in certain embodiments, crosslinking the bleached pulp includes contacting the bleached pulp with a first portion of the alkaline hydroxide and a first portion of the crosslinker, allowing the bleached pulp to react with the first portion of the alkaline hydroxide and the first portion of the crosslinker, and then subsequently contacting the bleached pulp with a second portion of the alkaline hydroxide and a second portion of the crosslinker. In another embodiment, crosslinking the bleached pulp includes contacting the bleached pulp with a mixture comprising a crosslinking agent and an alkaline hydroxide at different times. Multiple doses of the alkaline hydroxide and crosslinking agent can result in increased chemical utilization and / or reduced reaction costs. Furthermore, such sequential doses, including multiple feeds of the alkaline hydroxide and crosslinking agent to the bleached pulp, contemplate a mixer with controlled doses.

[0041] During crosslinking, the pulp may have a temperature in the range of 30° C. to 90° C. Furthermore, the pulp may have a pH in the range of 9 to 14. In embodiments, the method of the present disclosure includes extracting alkaline hydroxide from the crosslinked pulp after crosslinking the cellulose fibers, as further discussed herein in connection with Examples 2 and 3. Referring now to Figure 2, a method 200 of the present disclosure, including extraction and reuse of caustic, is discussed. In certain embodiments, the method 100 and / or Other methods include one or more aspects of method 200. In embodiments, method 200 begins with process block 202, which includes cooking and bleaching a cellulosic fiber source to obtain a pulp. In embodiments, cooking and bleaching are performed as further discussed herein in connection with FIG. 1. Process block 202 may be followed by process block 204, which includes blending the bleached pulp to a consistency greater than 30%, for example. Process block 204 may be followed by process block 206, which includes crosslinking the bleached high-consistency pulp with an alkaline hydroxide and a crosslinking agent. As discussed further herein, such high-consistency crosslinking reactions offer numerous advantages over lower-consistency crosslinking reactions, including, but not limited to, higher R values, lower crosslinking reagent requirements, and a more consistent pulp, as measured by, for example, CMC viscosity COV, alkali ion COV, among others.

[0042] In embodiments, process block 206 is followed by process block 208, which may include washing the crosslinked pulp and recovering a portion of the alkali hydroxide used to crosslink the bleached high consistency pulp. As shown, the recovered alkali hydroxide may be reused in either or both of cooking and bleaching process block 202 and mixture process block 204. Such recovery and reuse of caustic may provide economic efficiencies through the reuse of reactants and the removal of undesirable organic components in the mixture. Process block 208 may be followed by process block 210, which includes neutralizing the crosslinked washed pulp, such as through the application of an acidic solution to the crosslinked washed pulp. As discussed herein in connection with Examples 2 and 3, washing and neutralizing the crosslinked pulp may reduce pulp component levels, such as extracted organic matter content, metal ion content, ash content, and silica content. In embodiments, process block 210 is followed by process block 212, as further discussed herein in connection with process block 134 of FIG. 1. Process block 212 may include forming market pulp.

[0043] Crosslinking of pulp according to embodiments of the present disclosure can be used in combination with other techniques to increase the pulp's ability to produce high-grade cellulosics. For example, referring again to FIG. 1 , the cooking described above in pulping process block 102 can be relatively mild. A relatively mild cooking may remove less lignin from the pulp than would otherwise be removed. After mild cooking, the pulp may have a kappa number of 25-35 and a high pulp viscosity, indicating the presence of significant residual lignin. As another example, the bleaching and extraction described below in post-pulping process block 104 can be relatively mild. Unlike modifying the kraft process by adding strong caustic extraction and prehydrolysis, the above modifications to the kraft process can incrementally improve the kraft pulp's ability to produce high-grade cellulosics without unduly compromising yield and / or reactivity.

[0044] After crosslinking the cellulose fibers in the pulp, the method 100 can include a step of initially bleaching the pulp with chlorine dioxide (process block 128). Chlorine dioxide bleaching tends to be more selective for lignin removal than oxygen-based bleaching agents. The amount of chlorine dioxide added to the pulp can be in the range of 20-30 pounds per ton of pulp. The temperature during the first chlorine dioxide bleaching can be in the range of 50°C to 85°C. After the first chlorine dioxide bleaching of the pulp, the method 100 can include an extraction step (process block 130) to remove lignin from the pulp. The extraction can include adding hydrogen peroxide or a suitable caustic to the pulp. The amount of hydrogen peroxide added to the pulp can be in the range of 20-100 pounds per ton of pulp. The temperature during the extraction can be in the range of 75°C to 95°C. In contrast to strong caustic extraction, which removes hemicellulose, The extraction to remove the lignin can be relatively mild, for example, the extraction can be one that does not alter the crystalline structure of the cellulose fibers.

[0045] After extraction, the method 100 can include subjecting the pulp to a second bleaching with chlorine dioxide (process block 132). The amount of chlorine dioxide added to the pulp can range from 10 to 30 pounds (4.5 to 13.6 kg) per ton of pulp. The temperature during the second chlorine dioxide bleaching can range from 60°C to 90°C. The method 100 can further include additional operations beyond those specifically identified in FIG. 1. For example, after any of the operations in post-pulping process block 104, the method 100 can include washing the pulp. This can be useful, for example, to remove carryover and increase pulp consistency. After oxygen-based bleaching of the pulp and before crosslinking the pulp, a washing operation can be used to increase pulp consistency.

[0046] While crosslinking in the illustrated embodiment occurs after oxygen-based bleaching and before chlorine dioxide bleaching, in other embodiments, crosslinking can occur at another point in the post-pulping process 104 counterpart described below. The bleaching and extraction operations can also be rearranged or eliminated in other embodiments. Where "X" is defined as a crosslinking operation, post-pulping methods according to embodiments of the present technology can be characterized as OXDED (FIG. 1), ODXED, ODEX, ODEXD, ODEDX, DXEDED, DEXDED, DEDXED, DEDEXD, DEDEDX, DXEED, DEXED, DEEXD, or DEEDX, among many other suitable permutations. Furthermore, crosslinking can occur during oxygen-based bleaching, chlorine dioxide bleaching, and / or extraction. Thus, post-pulping methods according to still other embodiments of the present technology can be characterized as O / XDED, OD / XED, ODE / XD, ODE / X, ODED / X, D / XEDED, DE / XDED, DED / XED, DEDE / XD, DEDED / X, D / XEED, DE / XED, DEE / XD, DEED / X, among many other suitable permutations.

[0047] After bleaching process block 104, method 100 can include processing the pulp for use, sale, and / or transportation (process block 134). For example, the pulp can be dried (e.g., flash dried), pressed, containerized, and / or otherwise processed to make the pulp in a form suitable for use, sale, and / or transportation (e.g., sheets, bales, rolls, etc.). The pulp can be ... 2 ~1200g / m 2 and / or 0.2g / cm 3 ~0.9g / cm 3 In some embodiments, the pulp of method 100 is combined with another pulp before drying. Pulps according to at least some embodiments of the present disclosure are advantageous for use as pulp extenders, reducing the amount of expensive dissolving-grade pulp required to produce a given cellulosic product without compromising the viscosity or other desirable properties of the product. For example, the pulp of method 100 can be blended with another pulp (e.g., a dissolving-grade pulp having a cellulose content greater than 90 wt.% by oven-dry (OD) weight) so that the pulp of method 100 accounts for at least 20 wt.% (e.g., at least 30 wt.%) of the cellulose oven-dry weight of the resulting blended pulp. In other embodiments, the pulp of method 100 can be used without blending with another pulp.

[0048] In embodiments, the dried pulp is further processed or formed into a form suitable for transportation, sale, etc. selected from rolls, bales, and fluff. Dry and semi-dry pulp crosslinking In certain embodiments, the method of the present disclosure comprises: The method includes contacting the wood fibers with an alkali hydroxide solution, wherein the wood fibers have a moisture content ranging from about 0% to about 50% by weight. In embodiments, the moisture content of the wood fibers ranges from about 0% to about 10% by weight. In this case, about 0% by weight refers to a moisture content of 0% to 1% by weight, as determined by detection limits known in the art. While not wishing to be bound by any particular theory, it is believed that by contacting such dry or semi-dry wood fibers with a crosslinking agent and an alkali hydroxide solution, intimate mixing of the crosslinking agent and the wood fibers is achieved, such as by mixing an aqueous suspension or solution in a reaction vessel without actively mixing the pulp. Furthermore, while not wishing to be bound by any particular theory, it is believed that the voids within the dry and semi-dry wood fibers are filled with the alkali hydroxide and crosslinking agent solution. This is in contrast to other methods in which wood fibers are dispersed in a relatively dilute solution of alkali hydroxide and crosslinking agent.

[0049] FIG. 3 schematically illustrates a method 300 according to an embodiment of the present disclosure, which includes contacting dry or semi-dried wood fibers with an alkaline hydroxide and a cross-linking agent. The method 300 may begin at process block 302, which includes contacting dry or semi-dried wood fibers with an alkaline hydroxide and a cross-linking agent. In an embodiment, the dry or semi-dried wood fibers are in the form of a pulp sheet having a moisture content ranging from about 0% to about 50% by weight. The cross-linking agent may be any cross-linking agent discussed herein, such as a glycidyl ether. In an embodiment, the dry or semi-dried wood fibers are saturated with an alkaline hydroxide and cross-linking agent solution. In an embodiment, the wood fibers are contacted with the alkaline hydroxide in a range of about 1% to about 5% by weight. In an embodiment, the wood fibers are contacted with the alkaline hydroxide in a range of about 1% to about 10% by weight.

[0050] In embodiments, process block 302 is followed by process block 304, which includes heating the wood fibers, crosslinking agent, and alkaline hydroxide at a temperature and for a time sufficient to provide crosslinked wood fibers having some crosslinking. In embodiments, heating the wood fibers, crosslinking agent, and alkaline hydroxide includes heating the wood fibers, crosslinking agent, and alkaline hydroxide at a temperature ranging from about 100° C. to about 140° C. In embodiments, heating the wood fibers, crosslinking agent, and alkaline hydroxide includes heating the wood fibers, crosslinking agent, and alkaline hydroxide at a temperature of about 120° C. In embodiments, the wood fibers, crosslinking agent, and alkaline hydroxide are heated for a time ranging from about 5 minutes to about 20 minutes without evaporating all of the water absorbed by the wood fibers.

[0051] Process block 304 may be followed by process block 306, which includes washing the crosslinked wood fibers to remove unreacted crosslinking agent and alkaline hydroxide. In embodiments, the washing step further includes neutralizing the pH of the crosslinked wood fibers, such as with an acidic solution.

[0052] As discussed further herein in connection with Example 5, CMC produced from pulp produced by a method including contacting dry or semi-dried wood fibers with a crosslinking agent and an alkaline hydroxide, such as Method 300, can have a viscosity greater than 80 cP, such as a viscosity greater than 100 cP, greater than 110 cP, or greater than 120 cP. In embodiments, CMC produced from pulp produced according to such methods has a viscosity ranging from about 80 cP to about 140 cP. Furthermore, in embodiments, crosslinked pulp produced by a method including contacting dry or semi-dried wood fibers with a crosslinking agent and an alkaline hydroxide, such as Method 300, has an R18 value greater than 92%. In embodiments, such pulp has an R18 value ranging from 93% to 100%. Moreover, methods including contacting dry or semi-dried wood fibers with a crosslinking agent and an alkaline hydroxide, such as Method 300, are suitable for providing crosslinked pulp for making high-viscosity crosslinked cellulose ether products. Pulp treatment and pulp washing by alkaline extraction In embodiments, the method of the present disclosure includes activating a cellulosic pulp with an alkali hydroxide to obtain an activated pulp, removing the alkali hydroxide from the activated pulp, and cross-linking the activated pulp with a cross-linking agent to obtain a cross-linked pulp. In that regard, attention is directed to Figure 4, which schematically illustrates a method 400 according to an embodiment of the present disclosure.

[0053] The method 400 may begin at process block 402 with activating a cellulosic pulp with an alkali hydroxide to obtain an activated pulp. In an embodiment, the cellulosic pulp is CLP. In an embodiment, the cellulosic pulp is kraft pulp. In an embodiment, activating the cellulosic pulp includes activating the pulp at a consistency greater than 4%, such as greater than 16%.

[0054] Process block 402 may be followed by process block 404, which includes removing the alkaline hydroxide from the activated pulp, such as by filtration. In embodiments, process block 404 is followed by process block 406, in which the removed alkaline hydroxide is recovered and reused in subsequent pulp reactions, as discussed further herein.

[0055] Process blocks 402, 404, or 406 may be followed by process block 408, which includes cross-linking the activated pulp with a cross-linking agent. In embodiments, cross-linking the activated pulp with a cross-linking agent includes cross-linking the activated pulp at a consistency greater than 20%, such as greater than 30%. As further demonstrated herein with reference to Examples 2 and 3, by cross-linking at a higher consistency, such as greater than 20%, and removing the alkaline hydroxide, the viscosity of the CMC produced from such extracted higher consistency pulp is similarly higher. See, for example, the resulting CMC viscosity consistency of Sample 3B vs. Sample 3A and Sample 4B vs. Sample 4A in Table 2.

[0056] In embodiments, crosslinking the activated pulp with a crosslinking agent comprises crosslinking at a temperature ranging from 30°C to 95°C. In embodiments, crosslinking the activated pulp with a crosslinking agent comprises crosslinking at a temperature ranging from 70°C to 95°C. As further demonstrated herein with reference to Examples 2 and 3, crosslinking the pulp at elevated temperatures, such as in the range of 70°C to 95°C, provides a pulp useful in preparing CMC having a high viscosity. See, for example, the viscosities of the CMCs made from Samples 4C and 3C. In embodiments, the viscosity of the resulting CMC ranges from about 100 cP to about 400 cP.

[0057] In embodiments, process block 408 is followed by process block 410, which includes drying the crosslinked pulp. Process blocks 408 and 410 may be followed by process block 412, which includes washing and pressing the crosslinked pulp to obtain a pressed pulp. Such washing and pressing may be accomplished, for example, by methods further discussed herein in connection with method 100 and FIG. 1. Process blocks 408, 410, and 412 may be followed by process block 414, which includes diluting and neutralizing the pressed pulp. As further discussed herein in connection with Example 6, such washing and neutralization may be suitable for reducing, for example, levels of organic extractives, metals, ash, and silica in the pulp. pulp In another aspect, the present disclosure provides a pulp comprising crosslinked cellulose fibers. In an embodiment, the pulp is a pulp made according to the methods described herein. Pulp R18 value In embodiments, the pulp of the present disclosure has an R18 value greater than 89%. In this case, the pulp of the present disclosure has an R18 value of greater than 92%. As discussed further herein in connection with the methods of the present disclosure, crosslinking the pulp at a high consistency, such as greater than 20%, greater than 30%, or even greater, generally provides a crosslinked pulp with relatively high alkali resistance, as measured by the pulp R18 value. Conversely, crosslinking at a consistency lower than, for example, 30%, provides a pulp with an R18 value lower than, for example, 93%. For example, as shown in Examples 1-3, such high consistency crosslinking provides a pulp with a pulp R18 value ranging from about 92% to about 100%.

[0058] In an embodiment, the pulp has a pulp R18 value in the range of about 92% to about 100%. In this case, a pulp R18 value of about 100% refers to a pulp R18 value of 99% to 100% when limited by a known detection method such as TAPPI T 235 cm-00. In an embodiment, the pulp of the present disclosure has a pulp R18 value in the range of about 93% to about 97%. In an embodiment, the pulp of the present disclosure has a pulp R18 value in the range of about 93% to about 96%. In an embodiment, the pulp of the present disclosure has a pulp R18 value in the range of about 93% to about 95%. The resulting viscosity of the CMC In an embodiment, the pulp of the present disclosure has a viscosity of the resulting CMC greater than 56 cP. In an embodiment, the pulp of the present disclosure has a viscosity of the resulting CMC greater than 90 cP. In an embodiment, the pulp of the present disclosure has a viscosity of the resulting CMC in the range of about 100 cP to about 400 cP.

[0059] In certain embodiments, the pulp of the present disclosure has a high degree of crosslinking due to a high-consistency crosslinking reaction in certain cases. Moreover, as described above, the resulting CMC of these pulps may have a very high viscosity. As a purely theoretical explanation, and without wishing to be bound by such a theory, the molecular structure of cellulose may change from linear to highly branched at a high degree of crosslinking, such as that achieved by the method of the embodiments of the present disclosure. Cellulose with a highly branched structure can form high-grade ethers, such as high-grade CMC.

[0060] As further discussed herein in connection with Examples 1 and 2 and Tables 1 and 2, pulps crosslinked at high consistency according to embodiments of the present disclosure have such high resulting CMC viscosities. In this regard, in embodiments, pulps of the present disclosure have resulting CMC viscosities in the range of 90 cP to 130 cP as shown in Table 1. In embodiments, pulps of the present disclosure have resulting CMC viscosities in the range of about 100 cP to about 400 cP as shown in Table 2.

[0061] Furthermore, the pulps of the present disclosure produce CMC with a viscosity that contrasts with, for example, conventional CLP. As described in Example 6 and shown in Table 3, pulps according to embodiments of the present disclosure produced by the methods of the present disclosure have a higher resulting CMC viscosity than CLP. As discussed further herein, CLPs are often more expensive than kraft pulps, such as those described in Example 6, at least in part because they are useful in producing high-grade, high-viscosity ethers. However, as shown herein, in certain cases, pulps of the present disclosure, such as pulps produced by the modified kraft process, are suitable for producing CMC with a higher viscosity than more expensive CLPs.

[0062] As used herein, "resulting CMC viscosity" refers to the viscosity of a 0.5 wt. % aqueous solution of CMC obtained according to the resulting CMC test method described herein. Coefficient of variation of the resulting CMC viscosity In embodiments, the pulp of the present disclosure has a coefficient of variation of viscosity of the resulting CMC ( As further discussed herein in connection with Example 9 and Tables 6A-6C, CMC made from the pulp of the present disclosure has a viscosity COV of less than 37%, such as 20% or less, 15% or less. Without wishing to be bound by any particular theory, it is believed that by crosslinking the pulp at a high consistency, the crosslinked pulp is relatively evenly crosslinked, and therefore, CMC made therefrom has a viscosity with a low viscosity COV.

[0063] In that regard, in embodiments, pulps of the present disclosure have a resulting CMC viscosity COV ranging from about 5% to less than 38%. In embodiments, pulps of the present disclosure have a resulting CMC viscosity COV ranging from about 37% to about 20%. As discussed further herein in connection with Table 6B, CMCs made from pulps crosslinked using a plowshare mixer, such as a Loedige™ mixer, have viscosities with a COV ranging from about 37% to about 20%. In embodiments, pulps of the present disclosure have a resulting CMC viscosity COV ranging from about 5% to about 15%. In embodiments, pulps of the present disclosure have a resulting CMC viscosity COV ranging from about 10% to about 12%. As discussed further herein in connection with Table 6C, CMCs made from pulps crosslinked in a reactor containing reversing plates, such as an Andritz™ mixer, have viscosities with a COV ranging from about 5% to about 15%.

[0064] In embodiments, pulps of the present disclosure having a COV of viscosity of the resulting CMC of less than 37% further have a pulp R18 value of greater than 92%. As further discussed herein in connection with Example 9 and Tables 6B, 6C, and 1, such pulps have relatively high alkali resistance in addition to a low COV of viscosity of the resulting CMC. Alkaline ion concentration COV In certain embodiments, the pulp of the present disclosure has a relatively low alkali ion concentration COV. As discussed further herein, the method of the present disclosure crosslinks the pulp at a high consistency. Without wishing to be bound by any particular theory, it is believed that such a high consistency provides a highly uniform crosslinking reaction environment. In this regard, the crosslinking environment and the resulting crosslinked pulp, such as when the pulp is crosslinked but not washed or neutralized, contain certain crosslinking reagents, such as alkali ions, evenly distributed within the pulp. In embodiments, as discussed further herein in connection with Example 12, the pulp described herein has a sodium ion concentration COV of less than 10, such as less than 5, upon crosslinking. The obtained CMC polydispersity index In certain embodiments, the pulps of the present disclosure have a resulting CMC polydispersity index (PDI) of about 3 or greater. In embodiments, the pulps of the present disclosure have a resulting CMC PDI greater than about 4.5. In embodiments, the pulps of the present disclosure have a resulting CMC PDI ranging from 4.5 to about 7. In embodiments, the pulps of the present disclosure have a resulting CMC PDI ranging from about 5.0 to about 6.5. As shown in Table 1, such relatively high PDIs are in contrast to the PDIs of CMCs prepared from commonly available pulps, such as cotton linter pulp, dissolving wood pulp (DWP) sulfite pulp, and conventional crosslinked kraft pulp, which are typically 2 or less. As used herein, the resulting CMC PDI is the ratio of the CMC weight average molecular weight to the CMC number average molecular weight.

[0065] Without being bound by any particular theory, it is believed that the relatively high PDI of the ethers of the present disclosure is due, at least in part, to the addition of higher Mw molecules to smaller molecules due to crosslinking, and not, for example, to degradation of cellulose. Compared to the control pulp PDI (see Tables 1 and 2), the molecules in the crosslinked pulp of the present disclosure have increased molecular length. Upon crosslinking, longer molecules are produced rather than shorter molecules. In this and other respects, a high PDI is advantageous. For example, a higher Mw in the resulting ether makes the final product stronger and more elastic, even at lower concentrations. Furthermore, such a higher weight average Mw resulting ether will tend to exhibit higher shear rates than ethers with lower PDIs. It has excellent shear thinning properties. Water retention value In certain embodiments, the pulp of the present disclosure has a water retention value (WRV) in the range of about 0.8 g / g to about 1.0 g / g. In certain embodiments, the pulp of the present disclosure has a WRV in the range of about 0.8 g / g to less than 1.0 g / g. In embodiments, the pulp of the present disclosure has a WRV in the range of about 0.8 g / g to less than 1.0 g / g and a pulp R18 value in the range of 89% to 94%. In embodiments, the pulp of the present disclosure has a WRV in the range of about 0.8 g / g to less than 1.0 g / g and a pulp R18 value in the range of 92% to 94%. In embodiments, the pulp is a kraft pulp having a WRV in the range of about 0.8 g / g to less than 1.0 g / g and a pulp R18 value in the range of 92% to 94%. As described in Example 10 and Table 7, pulps according to embodiments of the present disclosure prepared in a manner similar to Example 1 have a WRV ranging from about 0.8 g / g to less than 1.0 g / g. Furthermore, such pulps have pulp R18 values ​​of 92% to 94%. As discussed further herein in connection with Example 1, such pulps were kraft pulps prepared at crosslinking consistencies greater than 30%. Such pulps are in contrast to pulps crosslinked at consistencies less than 30%, which typically have R18 values ​​less than 92% and WRVs greater than 1.1 g / g.

[0066] In embodiments, such pulps have a viscosity of CMC ranging from 56 cP to 130 cP. In embodiments, pulps of the present disclosure include linter pulps such as CLPs having an R18 value of 99% or greater and a WRV in the range of 0.6 g / g to 0.8 g / g. As shown in Example 10 and Table 7, crosslinked CLPs prepared as further discussed herein in connection with Samples 3A and 3B according to embodiments of the present disclosure can have relatively high R18 values, such as 99% or greater, and relatively low WRVs, such as in the range of 0.6 g / g to 0.8 g / g.

[0067] A high value pulp product having a high ether viscosity and ether viscosity consistency can have a lower WRV than the starting pulp. As described above, in certain embodiments, the pulps of the present disclosure include pulps suitable for producing high viscosity ethers and, as further discussed herein, highly stable high viscosity ethers, wherein the WRV of the pulp is lower than that of the uncrosslinked feedstock pulp. Surprisingly, it has been discovered that such pulps can produce high viscosity ethers with high viscosity consistency even at relatively low WRVs, such as those lower than that of the feedstock pulp used to produce the crosslinked pulp of the present disclosure. As long as the WRV of the crosslinked pulp is high enough to convert the pulp into a high viscosity ether, the crosslinked pulp can have a relatively low WRV, such as in the range of about 0.6 g / g to about 0.8 g / g. Without being bound by theory, it is believed that crosslinking increases pulp reactivity at the molecular level, as measured by the formation of soluble CMC with the expected DS, due to the introduction of a crosslinking agent between the cellulose molecules and openings in the molecular structure. Hemicellulose content In embodiments, the pulp of the present disclosure has about 6% or more by weight hemicellulose by dry weight (e.g., 10% or more, 15% or more, or 20% or more by weight). In embodiments, the pulp of the present disclosure comprises hemicellulose in a range from about 6% by weight hemicellulose by dry weight to about 30% by weight hemicellulose by dry weight. In embodiments, the pulp of the present disclosure comprises hemicellulose in a range from about 9% by weight hemicellulose by dry weight to about 20% by weight hemicellulose by dry weight. In embodiments, the pulp of the present disclosure comprises about 15% by weight hemicellulose.

[0068] As discussed further herein in connection with the methods of the present disclosure, hemicellulose is one metric of overall pulp processing efficiency. Generally speaking, the higher the hemicellulose content, the better. Pulps with a high hemicellulose content (defined herein as the sum of xylan and mannan) have a higher yield due to the increased bulk provided by hemicellulose. As discussed further herein in connection with Example 11 and Table 8, pulps according to the present disclosure prepared according to the methods of the present disclosure have relatively high hemicellulose contents, such as greater than 6% by weight. As noted, pulps crosslinked at greater than 30% consistency, such as pulps according to the methods further described herein in connection with Example 1, have hemicellulose contents greater than 6% by weight. In particular, the pulp prepared according to the method of Sample 2A has a hemicellulose content of about 16% by weight.

[0069] In an embodiment, the pulp is kraft pulp. As further discussed herein in connection with the methods of the present disclosure, kraft pulp processing generally does not significantly reduce the hemicellulose content from that of the starting feedstock. By utilizing a modified kraft process that includes a high-consistency crosslinking step, the crosslinked pulp of the present disclosure has, for example, a high hemicellulose content (and the associated pulp bulk associated with high hemicellulose content) and a high R18 value. In this regard, such pulp is suitable for producing high-grade cellulose ether products at a relatively low cost.

[0070] Although kraft pulp is discussed herein, it will be understood that the pulps of the present disclosure include other crosslinked pulps such as CLP, straw pulp, and the like. Weight average molecular weight In embodiments, the pulp of the present disclosure has a resultant CMC weight average molecular weight greater than about 800 kilodaltons (kDa), such as 1,000 kDa or greater, 1,500 kDa or greater, or 2,000 kDa or greater. In embodiments, the pulp has a resultant CMC weight average molecular weight ranging from about 900 kDa to about 4,000 kDa. In embodiments, the pulp has a resultant CMC weight average molecular weight ranging from about 1,000 kDa to about 2,500 kDa.

[0071] As shown in Table 1, CMC made from pulps according to embodiments of the present disclosure have weight average molecular weights greater than 800 kDa, such as greater than 1,000 kDa, greater than 2,000 kDa, etc. This is in contrast to CMC made from commonly available pulps such as CLP, DWP sulfite pulp, and regular kraft pulp. See also Table 1.

[0072] As discussed further herein in relation to the resulting CMC PDI, the resulting increased weight average molecular weight of the CMC produced by the methods according to embodiments of the present disclosure is attributed to crosslinking of the pulp. As also discussed herein in relation to the resulting CMC PDI, such increased weight average molecular weight provides the resulting CMC with greater strength, elasticity, and shear thinning properties compared to CMC prepared from lower molecular weight pulps. Crosslinking agent The pulp of the present disclosure comprises crosslinked cellulose fibers comprising a crosslinking agent coupled to one or more cellulose fibers.

[0073] In embodiments, the crosslinking agent forms ether bonds with one or more cellulose fibers. As discussed further herein in connection with the methods of the present disclosure, such ether crosslinks are typically stronger than certain other crosslinks, such as ionic and / or ester crosslinks. Such stronger crosslinks generally exhibit greater resistance to other pulp processing reactions, such as etherification reactions.

[0074] In embodiments, the crosslinking agent is present in a weight ratio to other pulp components of 2:100 or greater, 3:100 or greater, 5:100 or greater, or another suitable lower threshold. This may be the maximum amount of cross-linking agent that can be used without rendering the CMC obtained from the pulp insoluble in water.

[0075] Suitable crosslinking agents include ethers, such as glycidyl ethers, having two or more glycidyl groups. For example, the crosslinking agent can include a first glycidyl group, a second glycidyl group, and three or four linear carbon atoms between the first and second glycidyl groups. In embodiments, the crosslinking agent includes three or more glycidyl groups. Additionally or alternatively, the crosslinking agent can have a weight average molecular weight of 500 or less (e.g., in the range of 174 to 500). Furthermore, when the crosslinking agent is an epoxide, the crosslinking agent can have a weight per epoxide of 175 or less (e.g., in the range of 140 to 175). The crosslinking agent can have a viscosity of 500 cP or less at 25°C. In at least some embodiments, the crosslinking agent is at least partially insoluble in water. This property can be useful for increasing contact between the crosslinking agent and the cellulose fibers during the crosslinking reaction. Specific examples of suitable crosslinkers include trimethylolethane triglycidyl ether, 1,4-butanediol diglycidyl ether, glycerol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol polyglycidyl ether, glycerol triglycidyl ether, ethylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether, among others. Obtained CMC test method Throughout this disclosure, pulp properties may be characterized in terms of "resulting CMC" properties. These are properties of CMC that can be produced using the pulp, with CMC serving as a representative example of cellulose derivatives. It should be understood that CMC is not the only cellulose derivative that can be produced using pulps according to embodiments of the present disclosure. The resulting CMC properties of a given pulp described herein are determined by the following procedure. Additional details about this procedure can be found in Nevell TP and Zeronian S., Cellulose Chemistry and its Applications, Chapter 15—Cellulose Ethers (1985), which is incorporated herein by reference in its entirety.

[0076] First, determine the degree of substitution (DS) of the CMC. If the DS of the CMC is at least 1.0, proceed as specified below. If the DS of the CMC is 1.0 or less, proceed as specified below, but use 2.73 g of monochloroacetic acid (MCA) (instead of 3.6 g).

[0077] 30 g of (fiberized) pulp with a solids content of approximately 92 wt% is slurried in 80 mL of isopropanol. 8.0 mL of a 30 wt% NaOH (aqueous) solution is added over 3 minutes. The suspension is stirred at 20°C for 1 hour. 2.73 g of MCA (as a 20.7 wt% MCA solution in 15.2 mL of isopropanol) is added over 3 minutes. The temperature is raised to 55°C in 25 minutes and stirring is continued for 3.5 hours. The resulting fibrous CMC is filtered and washed with 100 ml of 70% ethanol (v / v) (aqueous). The sample is neutralized (pH 7.0) using acetic acid and then filtered. The filter cake is washed again with 100 ml of 70% ethanol (v / v) (aqueous) at 20°C and filtered. Wash once more with 100 ml of 70% ethanol (v / v) (aqueous) at 20°C, then wash three more times with 100% denatured ethanol at 20°C. Repeat the washing and filtering. Air-dry the sample to 70-85% solids. Dissolve the air-dried CMC fibers in DI water and mix vigorously (Waring blender, three mixes, 1 minute each) to make a 0.5 wt% solution.

[0078] A 0.5 wt% CMC solution was tested at 20°C according to ASTM method D2196-99 using a Brookfield viscometer with spindle 2 and 50 RPM to determine the resulting CMC Determine the viscosity of the solution. Cellulose Ether Products In another aspect, the present disclosure provides a cellulose ether product comprising a crosslinked cellulose ether having a viscosity greater than about 56 cP. In an embodiment, the cellulose ether product of the present disclosure has a viscosity of 90 cP. In an embodiment, the cellulose ether product of the present disclosure has a viscosity ranging from about 100 cP to about 400 cP. In an embodiment, the cellulose ether product of the present disclosure has a viscosity ranging from 90 cP to 130 cP, as shown in Table 1 and further discussed herein in connection with Example 1. In an embodiment, the cellulose ether product of the present disclosure has a viscosity ranging from about 100 cP to about 300 cP, as shown in Table 2 and further discussed herein in connection with Examples 2 and 3.

[0079] In embodiments, cellulose ether products are formed from the pulp of the present disclosure.As further discussed herein, in certain embodiments, the pulp of the present disclosure is a low-cost pulp such as kraft pulp.As further discussed herein, due to certain aspects of the method of the present disclosure, such as high consistency crosslinking, and as a result of certain properties of the pulp of the present disclosure, such as pulp R18 value, water retention value, etc., this pulp is suitable for making high-grade high-viscosity cellulose ether products.

[0080] In embodiments, the cellulose ether product is crosslinked CMC.Although CMC is discussed herein, it is understood that the cellulose ether product of the present disclosure includes other cellulose ether products.Therefore, in embodiments, the crosslinked cellulose ether product is selected from the group consisting of crosslinked methylcellulose, crosslinked CMC, crosslinked hydroxypropyl methylcellulose, crosslinked hydroxyethyl cellulose, and combinations thereof.

[0081] In embodiments, the cellulose ether products of the present disclosure have a weight average molecular weight greater than about 800 kD, such as greater than 1,000 kDa, greater than 1,500 kDa, or greater than 2,000 kDa. In embodiments, the cellulose ether products have a weight average molecular weight ranging from about 900 kDa to about 4,000 kDa. In embodiments, the cellulose ether products have a weight average molecular weight ranging from about 1,000 kDa to about 2,500 kDa.

[0082] In certain embodiments, the cellulose ether products of the present disclosure have a PDI of about 3 or greater. In embodiments, the cellulose ether products of the present disclosure have a PDI of about 4.5 or greater. In embodiments, the cellulose ether products of the present disclosure have a PDI in the range of 4.5 to about 7. In embodiments, the cellulose ether products of the present disclosure have a PDI in the range of about 5.0 to about 6.5.

[0083] As discussed further herein, the relatively high weight average molecular weight and PDI of the cellulose ether products of the present disclosure provide greater strength, elasticity, and shear thinning than cellulose ethers, such as cellulose ethers prepared from certain conventional pulps, which have lower molecular weights and PDIs.

[0084] In embodiments, the cellulose ether product of the present disclosure comprises about 2 wt. % or more hemicellulose by dry weight (e.g., greater than 6 wt. %, greater than 10 wt. %). In embodiments, the cellulose ether product comprises hemicellulose in the range of about 2.5 wt. % by dry weight to about 20 wt. % by dry weight. In embodiments, the cellulose ether product comprises hemicellulose in the range of about 2 wt. % by dry weight to about 8 wt. % by dry weight. In embodiments, the cellulose ether product comprises about 12 wt. % hemicellulose. As discussed further herein, such a relatively high hemicellulose content can reduce the bulk of the cellulose. This gives rise to the rosin ether product.

[0085] In an embodiment, the cellulose ether product is CMC and has a hemicellulose content ranging from about 10% to about 15% by weight. In an embodiment, the cellulose ether product is CMC and has a hemicellulose content of about 12% by weight.

[0086] In embodiments, the cellulose ether product is a methylcellulose (MC), such as hydroxypropyl methylcellulose (HPMC), and has a hemicellulose content ranging from about 2% to about 8% by weight. Blended pulp In another aspect, the present disclosure provides a blended pulp comprising a pulp according to the present disclosure and a second pulp. In any embodiment, the second pulp is an uncrosslinked pulp.

[0087] In embodiments, the blended pulp comprises greater than 25%, greater than 50%, or greater than 75% by weight of the crosslinked pulp of the present disclosure. In embodiments, the blended pulp of the present disclosure can be characterized by the amount of fibers that remain undissolved after contact with a solvent such as copper ethylenediamine (cuen). In embodiments, the blended pulp remains undissolved by more than 10 wt%, more than 15 wt%, more than 20 wt%, or more than 30 wt% after contact with cuen. See, for example, Table 10 and Example 13.

[0088] As shown in Table 10 and Example 13, the blended pulps of the present disclosure have higher curl and kink than pulps that do not contain the pulp of the present disclosure. Furthermore, such curl and kink tend to be proportional to the proportion of crosslinked pulp of the present disclosure blended therein. Higher curl and kink may be desirable, such as to increase fiber accessibility during the derivatization reaction.

[0089] Thus, in an embodiment, the present disclosure provides a blended pulp comprising a first pulp according to any of the embodiments of the present disclosure having a first fiber kink value and a second pulp having a second fiber kink value different from the first fiber kink value. In an embodiment, the fiber kink value is the number of kinks per meter. See, for example, Table 10. In another embodiment, the kink value is the kink angle. See also Table 10.

[0090] In one embodiment, the first pulp has a first pulp R18 value and the second pulp has a second pulp R18 value that is different from the first pulp R18 value. In another embodiment, the first pulp is partially soluble in cuen. In one particular embodiment, the first pulp is insoluble in cuen. [Example]

[0091] Example 1 High consistency crosslinking of pulp and carboxymethyl cellulose produced therefrom This example demonstrates an improved process for crosslinking pulp, including the use of high consistency mixers such as Andritz™ and Loedige™ mixers to produce extremely high viscosity pulp from both SW and HW pulps. The high viscosity pulp can replace expensive high viscosity CLP or wood pulp in the cellulosic application market. These high consistency reactors can also significantly reduce chemical usage.

[0092] As discussed further herein, experimental samples 2A-2C were prepared using commercially available CLP, as prepared in U.S. Pat. No. 9,771,687, which is incorporated herein by reference in its entirety. The results are compared with a commercially available DWP sulfite pulp and a commercially available NB416 pulp. As shown in Table 1, Samples 2A-2C have higher hemicellulose concentrations, higher weight average molecular weights, higher PDIs, and higher resulting CMC viscosities than commonly available pulps. Sample 2A The starting material for preparing the crosslinked pulp in this example was dried bleached NB416 pulp from New Bern mill, International Paper Company. The pulp was dispersed in water (5% solids) at 90°C (heated by steam) in a pulper to form a slurry, which was then diluted to 4% solids by weight in a feed tank. The resulting slurry was twin-wire pressed to 40% solids by weight. The pulp exited the twin-wire press at approximately 65°C and was subjected to an in-line pin mill. The warm pulp was fed into an Andritz™ high-consistency mixer at a rate of 10 OD kg / min and simultaneously mixed (via a gear pump) with 5% NaOH (aqueous) and an emulsion of 20% Heloxy 48 by weight / 80% water by weight. The Heloxy 48 emulsion was prepared by blending Heloxy 48 with DI water under high-speed mixing (using a lighting mixer or blender). Heloxy 48 was in the form of an emulsion and was prepared by mixing Heloxy 48 in DI water under high-speed mixing. The addition of NaOH and Heloxy 48 to the oven-dried pulp was 2% by weight and 5% by weight, respectively. The pulp mixed with the chemicals was treated with steam to maintain a temperature of approximately 75°C and discharged into a storage tower, where the temperature was maintained at 75°C with steam. The pulp mixture in the tower had a consistency of approximately 30% to 38%, and the pulp residence time in the tower was 60 minutes. After the 60-minute residence time, the pulp was discharged from the tower at a rate of 10 OD kg / min, collected in a tank, and neutralized with acetic acid (pH 4.5-5.0, 3% pulp consistency, and 10-15°C). The neutralized pulp was pressed to a solids content of approximately 40% for further processing (using a paper machine at 0.50 g / cm). 3 ~0.80g / cm 3 (The pulp was formed into rolls at a sheet density of 1000 kJ / cm2 and air-dried as flakes for laboratory testing.) This pulp has a pulp R18 value of 93%.

[0093] CMC samples were prepared from crosslinked pulp as described elsewhere herein. The 0.5 wt% CMC solution viscosity was 128 cP (DS 0.95 by using 8 ml of 30 wt% NaOH (aqueous) and 2.73 grams of the specified MCA as described elsewhere herein). All CMC viscosities were determined using a Brookfield viscometer using spindle 2 and a speed of 50 RPM. The NB416 starting pulp had a 0.5 wt% CMC (DS 0.95) viscosity of approximately 33 cP.

[0094] For GPC, CMC samples were delivered as aqueous solutions of approximately 0.5 mg / mL. Due to the relatively high viscosity of the solutions, 10 mL of the delivered solution was diluted to 25 mL with ultrapure water. This corresponds to a sample concentration of approximately 2 mg / mL. After dilution, the clear solution was filtered through a 1 μm nylon membrane. Every CMC sample solution was injected twice. The average molar mass, weight-average molecular weight (Mw), and molecular weight distribution (MWD) or PDI of the investigated samples are summarized in Table 1.

[0095] The MWD of the CMC solutions of Sample 2A above, 2B, 2C, 3A to 3C, and 4A to 4C below was analyzed by gel permeation chromatography-multi-angle light scattering (GPC-MALS). The GPC experimental equipment was as follows: Device: Separation module Alliance 2695 (Waters) Refractive Index Detector 2414 (Waters) Laser photometer Dawn-HELEOS (Wyatt Technology Inc.) wavelength λ = 658 nm and K5 flow cell PC-controlled Empower Software 3 (Waters) GPC-MALS evaluation using Astra software 5.3.4.20 (Wyatt Technology Inc.) GPC conditions: GPC column set: Suprema (Polymer Standards Service GmbH PPS) ·GPC-furnace temperature: 30℃ Eluent: Ultrapure water containing 0.2m NaNO3 ·Flow rate: 0.8mL / min Detector: RI (30℃) Laser photometer Dawn Heleos, 658nm ·Injection volume: 100μl Sample concentration: Approximately 0.2 mg / mL, dn / dc, 0.163 mL / g Sample 2B The starting material for preparing the crosslinked pulp in this example was dried bleached NB416 pulp from New Bern mill, International Paper Company. The pulp was dispersed in water (5% solids) at 90°C (heated with steam) in a pulper to form a slurry (4% solids by weight in the feed tank) and then twin-wire pressed to 40% solids by weight. The warm pulp was fed into an Andritz™ high-consistency mixer at a rate of 10 (OD) kg / min and simultaneously mixed (via a gear pump) with 5% NaOH (aqueous) and an emulsion of 20% Heloxy 48 by weight / 80% water by weight. The addition of NaOH and Heloxy 48 to the oven-dried pulp was 1% and 4% by weight, respectively. The pulp mixed with the chemicals was treated with steam to maintain a temperature of approximately 65°C and pumped to a storage tower, where the temperature was controlled at approximately 65°C. The pulp mixture in the tower had a consistency of approximately 30% to 38%, and the pulp residence time in the tower was approximately 60 minutes. After the 60-minute residence time, the pulp was discharged from the tower at a rate of 10 (OD) kg / min, collected in a tank, and neutralized (pH 4.5 to 5.0). The neutralized pulp was pressed or air-dried for further processing. CMC samples were prepared from the pulps described elsewhere herein.

[0096] The 0.5 wt% CMC (DS 0.95) solution viscosity was 71 cP. The NB416 starting pulp had a 0.5 wt% CMC (DS 0.95) viscosity of about 33 cP. Sample 2C The starting material for preparing the crosslinked pulp for this sample was dried bleached NB416 pulp from New Bern mill, International Paper Company. The pulp was dispersed in water at 20°C in a pulper, centrifuged to 40% solids by weight, and fluffed in a pin mill. 26.8 kg (10 OD kg) of wet pulp (20°C) was fed into a Loedige™ high consistency reactor (10 kg / batch), and the temperature was raised to 75°C (while mixing). 0.2 kg of NaOH (aqueous) (50% by weight) was first injected into the pulp in the reactor in 15 seconds, followed by 1 kg of warm water. 2 kg of a 20% by weight Heloxy 48 / 80% by weight emulsion was then injected into the mixture, followed by 1 kg of warm water. The injection time was 15 seconds, with 2 minutes between each injection. The addition of NaOH (aqueous) and Heloxy 48 emulsion to the pulp (OD) was 1% and 4% by weight, respectively (similar results can be achieved by simultaneously mixing / injecting caustic, Heloxy 48, and water). The pulp mixture with chemicals was mixed inside the reactor at 75°C for 5 minutes at high speed and 55 minutes at low speed for a total of 60 minutes. The pulp mixture in the reactor had a consistency of approximately 32%. After a residence time of 60 minutes, the pulp mixture was neutralized with acetic acid, discharged, and washed. The washed pulp was dried, and CMC was prepared from the sample described elsewhere herein. The 0.5 wt% CMC (DS=0.95) solution viscosity from this sample was 95 cP. The NB416 starting pulp had a 0.5 wt% CMC (DS=0.95) viscosity of approximately 33 cP. Sample 2C1 Sample 2C above was repeated, except that undried New Bern mill NB416 was mixed with the chemicals. The final pulp consistency was 32%, and the viscosity of a 0.5 wt% CMC (DS=0.95) solution from the pulp was 110 cP. When the DS was 1.25 (8 ml of 30 wt% NaOH (aqueous) and 3.6 grams of MCA, as described elsewhere herein), the viscosity of a 0.5 wt% CMC solution from the pulp was 298 cP.

[0097] [Table 1]

[0098] Example 2 Method for making crosslinked pulp comprising high consistency crosslinking and alkaline extraction steps This example demonstrates how high-consistency crosslinking of CLP can be used to prepare crosslinked pulp. As shown, the resulting CMC has, for example, high viscosity, molecular weight, and PDI.

[0099] 20 grams of CLP having a SCAN viscosity of 1589 ml / g was placed in a plastic bag and warmed in an oven at 35° C. The warm CLP was then mixed with 480 grams of 8 wt % NaOH (aqueous) (pre-warmed to 35° C.) in a plastic bag for 15 minutes at 35° C. The CLP slurry was divided into three equal parts (A, B, and C) and equal weights of each part (166 grams, containing 6.64 grams of CLP) were stored in plastic bags. Sample 3A (Part A: approximately 166 grams, 6.64 grams of pulp) 2.6 grams of 10 wt% H48 / 90 wt% water emulsion was added to the pulp / caustic mixture (Part A) in the bag (3.92 wt% H48 on the pulp, 4% pulp consistency), the mixture in the bag was mixed thoroughly by hand, and the bag was placed in a 35°C oven and the temperature was raised to 50°C in 5 minutes. The temperature was maintained for 40 minutes (50°C oven). After 40 minutes, the pulp slurry was washed with DI water, neutralized with acetic acid, washed again with DI water, dried in an 85°C oven, and tested. Sample 3B (Part B: approximately 166 grams, 6.64 grams of pulp) Pulp slurry Part B was filtered to remove as much caustic as possible (approximately 141 grams). A portion of the filtrate (6 grams) and 2.6 grams of 10 wt% H48 / 90 wt% emulsion were then mixed and then added to the pulp / caustic mixture in the bag (Part B after filtration) to a final weight of approximately 33 grams (3.92 wt% H48 on the pulp, approximately 20% pulp consistency). The mixture in the bag was thoroughly mixed by hand, and the bag was placed in a 35°C oven, and the temperature was raised to 50°C in 5 minutes. The temperature was maintained for 40 minutes (50°C oven). After 40 minutes, the pulp slurry was washed, neutralized, washed again, and dried and tested as described in 3A. Sample 3C (Part C: approximately 166 grams, 6.64 grams of pulp) The pulp slurry Part C was filtered to remove caustic (133 grams removed). Then, 133 grams of DI water was added to the pulp, and the mixture was mixed. Then, 141 grams of the liquid was filtered again (new filtrate). This time, the mixture had a reduced caustic concentration. A portion of the new filtrate (6 grams) and 2.6 grams of a 10 wt% H48 / 90 wt% water emulsion were mixed and then added to the above pulp / caustic mixture in the bag (reduced caustic Part C) to a final weight of approximately 33 grams (3.92 wt% H48 on the pulp, 20% pulp consistency). The mixture in the bag was thoroughly mixed by hand, and the bag was placed in a 35°C oven, and the temperature was raised to 50°C in 5 minutes. The temperature was maintained for 40 minutes (50°C oven). After 40 minutes, the pulp slurry was washed, neutralized, washed again, and dried, and tested as described in 3A.

[0100] The 0.5 wt% CMC (DS=1.0) solution viscosities (Brookfield viscometer, spindle 2, speed 50 RPM for all tests) from the control, 3A, 3B, and 3C are 55 cP, 79 cP, 150 cP, and 120 cP, respectively, as shown in Table 2.

[0101] Example 3 Method for making crosslinked pulp comprising high consistency crosslinking at high temperature and alkaline extraction steps This example demonstrates how to prepare crosslinked pulp using high consistency crosslinking of CLP at high crosslinking temperatures. As shown, the resulting CMC has, for example, high viscosity, molecular weight, and PDI. Samples 4A to 4C The tests in Example 3 (for Samples 3A, 3B, and 3C) were repeated again to produce Samples 4A, 4B, and 4C, respectively, except that the crosslinking temperature was 75°C instead of 50°C. The 0.5% CMC (DS=1.0) solution viscosities (B The viscosity values ​​of the viscometer (spindle 2, speed 50 RPM) are 109 cP, 124 cP, and 300 cP, respectively.

[0102] The results are shown in Table 2. The CMC solutions were analyzed and the data are shown in Table 2. Conclusion: High consistency crosslinking increased the viscosity of the resulting CMC at a lower cost. See, for example, Sample 3B vs. Sample 3A and Sample 4B vs. Sample 4A. The extraction step improved quality at higher crosslinking temperatures, resulting in higher CMC viscosity. See, for example, Sample 4C vs. Sample 3C. Furthermore, both the CMC from the crosslinked wood pulp (Example 1) and the CMC from the crosslinked CLP (Example 2) using the improved process had much higher solution viscosity, PDI, and Mw than the crosslinked pulp described in U.S. Pat. No. 9,828,725, the entire contents of which are incorporated herein by reference.

[0103] [Table 2]

[0104] Example 4 Method for producing crosslinked pulp with R18 value higher than 92% This example demonstrates a method of preparing a crosslinked pulp according to an embodiment of the present disclosure, which includes sequentially dosing crosslinking reactants. As shown, the pulp produced according to this example has a high resulting CMC viscosity and a high R18 value. Sample 5A: The starting material for preparing the crosslinked pulp of this example was dried bleached NB416 from New Bern mill, International Paper Company. The pulp was dispersed in water at 20°C in a pulper, dewatered through a 150-mesh screen, centrifuged to 40% solids by weight, and fluffed in a pin mill. 26.8 kg (OD 10 kg) of wet pulp (20°C) was fed into a Loedige™ high-consistency reactor (10 kg / batch), and the temperature was raised to 75°C (while mixing at 80 RPM). 0.6 kg of NaOH (aqueous) (50% by weight) was injected into the pulp in the reactor in approximately 5 seconds, followed by 1 kg of warm water. 2.5 kg of a 20% by weight Heloxy 48 / 80% by weight water emulsion was then injected into the mixture, followed by 1 kg of warm water. There was a 2-minute interval between each injection. The addition of NaOH and Heloxy 48 to the pulp (OD) was 3% by weight and 5% by weight, respectively. The pulp mixture with chemicals was mixed for 5 minutes, then mixed for a total of 55 minutes at 75% by weight and 120 RPM, and the temperature inside the reactor was maintained at approximately 75°C, 25% by weight, and 40 RPM for 55 minutes. The pulp mixture in the reactor had a consistency of approximately 32%. After a residence time of 60 minutes, the pulp mixture was neutralized with 0.45 kg of acetic acid, discharged, and washed with DI water. The washed pulp was dried. The R18 of the pulp was 93.7%, while the starting pulp NB416 had an R18 of 88%. CMC was prepared from this sample. The 0.5 wt% CMC (aqueous) (DS=1.25) solution viscosity from the sample was 313 cP (the calculated pulp SCAN IV is 2304 ml / g, as described further herein). The NB416 pulp had a 0.5% CMC (DS=1.25) viscosity of approximately 40 cP. Sample 5B Sample 5B was prepared as in Sample 5A, except that 4.5 kg of water was added after the pulp addition. The final pulp consistency was 27.5%. The crosslinked pulp had an R18 value of 92.7%. The 0.5 wt% CMC (DS=1.25) viscosity from the pulp was 190 cP. Sample 5C Sample 5C was prepared as in Sample 5A, except that 8.1 kg of water was added after the pulp was added. The final pulp consistency was 25%. The crosslinked pulp had an R18 value of 92.4%. The 0.5 wt% CMC (DS=1.25) viscosity from the pulp was 170 cP. Sample 5D Sample 5B was prepared as in Sample 5A, except that dried eucalyptus pulp from the Mogi mill was mixed with chemicals (1 wt.% NaOH (aqueous) and 4 wt.% H48 (aqueous emulsion) on the pulp). The final pulp consistency was 32%. The crosslinked pulp had an R18 value of 93.8%. The viscosity of a 0.5 wt.% CMC (DS=1.0) solution from this pulp was 65 cP.

[0105] Example 5 A method for producing a crosslinked pulp by application of a caustic and a crosslinking agent, followed by drying and semi-drying the pulp. This example provides a method for preparing a crosslinked pulp that includes applying a crosslinking reactant and drying or semi-drying the pulp. As shown, the pulp produced according to such a method has a relatively high R18 value, and the resulting CMC has a high viscosity without a vigorous mixing step.

[0106] 25 grams of New Bern International Paper Company (OD) NB421 sheet was soaked for 1 minute in a mixture of 6.2 grams of Heloxy 48, 4.8 grams of 50 wt% NaOH (aqueous), and 157 grams of water. The soaked pulp sheet was pressed several times with a stainless steel roller to produce a final pulp sheet consistency of 42%. The NaOH and Heloxy additions to the pulp were approximately 2 wt% and 5 wt%, respectively. The pressed pulp sheet was divided into two pieces, placed in a covered glass beaker (to limit water evaporation), and dried in a 120°C oven for 10 and 20 minutes. The semi-dried pulp sheets were neutralized and washed before being completely dried. The 0.5 wt% CMC solutions from sheets dried for 10 and 20 minutes had viscosities of 82 cP and 130 cP, respectively.

[0107] Example 6 Wash pH and caustic extraction in pulp filtration. This example demonstrates that pulp prepared according to the method of the present disclosure is washed with a low pH solution to reduce the levels of metals, ash, and silica dispersed in the pulp.

[0108] High-viscosity kraft pulp was acid washed at pH <7, <6, <5, or <4 to remove metals (e.g., Ca, Fe, Mn, Ni, Co, Cr, Cu, etc.) and reduce ash (pH can be adjusted using any acid). After acid washing, the pH of the pulp slurry can be adjusted to pH >4, >5, >6, or >7 upon or before entering the headbox to neutralize residual acid. Residual acid in the pulp can cause pulp degradation and viscosity loss during final drying (Table 3). Pulp viscosity was maintained during the crosslinking reaction. In a pilot run, crosslinked pulp prepared as discussed further herein in connection with Sample 2A was dispersed in water at a 3% consistency, and the slurry pH was adjusted to pH 4.5-5 with acetic acid. This washed pulp had a CMC viscosity similar to that of the pulp prepared in the pilot run without acid washing (Table 2). The pilot washed pulp yielded a CMC viscosity higher than the CLP of 2310 ml / g SCAN. These pulps were also low in ash, Ca, Fe, silica, etc., as shown in Table 3. Pilot washed samples were finally formed into rolls at a headbox pH of about 4.8 (using stored permeate water and acetic acid), and these pulps were much lower in ash, Ca, Fe, silica, etc.

[0109] [Table 3]

[0110] [Table 4]

[0111] Example 7 Crosslinked Eucalyptus pulp from high consistency pulp with caustic washing and reuse. Sample 5D above was repeated, except that dried mixed hardwood from Saillat mill, International Paper Company, was mixed with chemicals (1 wt. % NaOH (aqueous) and 4 wt. % H48 (aqueous emulsion) on the pulp). The final pulp consistency was 32%. The crosslinked pulp had an R18 value of 94.1%. The 0.5 wt. % CMC (DS=1.0) solution viscosities from the pulp were approximately 63 cP, 50 cP, and 40 cP when the crosslinked pulp was washed at pH 4, 3, and 2, respectively. It has been recognized that washing the pulp at too low a pH can degrade the pulp.

[0112] To improve pulp washing and effluent treatment, the high-viscosity pulp from the crosslinking reactor can be diluted (with process water or acid water from the mill) from >30% solids by weight to 10% solids or less. The diluted slurry is pressed to a high consistency, releasing the filtrate along with residual caustic, crosslinking agents, etc. The caustic in the filtrate can be reused in pulping and bleaching, and any organic chemicals in the filtrate may be decomposed during reuse. The pressed pulp is again diluted with acid water to a low pH to remove metals (Ca, Fe, Cu, Mn, Mg, etc.) before being recycled to stock. The stock is used to form pulp rolls or bales, with possible pH adjustments during the forming stage, such as in the headbox (e.g., headbox pH can be 4-8).

[0113] Example 8 Methylcellulose from high viscosity pulp. Cellulose (CELL) pulp was ground into powder, suspended in diethyl ether (DEE), and 50 wt% NaOH (aqueous) solution was added. After alkalinization at room temperature, methyl chloride (MeCl) was added to the reactor, and the temperature was raised to 85°C. The reaction time was 2 hours at this temperature. After cooling, the mixture was collected by vacuum filtration, neutralized, and washed four times with hot water. Hydroxylpropylmethylcellulose (HPMC) was also prepared by adding propylene oxide (PO) (Table 5).

[0114] For the determination of DS and distribution of substituents in the AGU of derivatized cellulose, samples were Hydrolyzed with trifluoroacetic acid, dissolved in DO, and purified to a high-resolution liquid 13 The cellulose was analyzed by C-NMR (see Table 5). Measurements were performed at 100 MHz on a 400 MHz spectrometer (Varian) using a quantitative method free of the nuclear Overhauser effect ("Characterization of cellulose and cellulose derivatives in solution by high resolution"). 13 (See "C-NMR spectroscopy", I. Nehls, W. Wagenknecht, B. Philipp, D. Stscherbina, Prog. Polym. Sci., 1994, Vol. 19, pp. 29-78).

[0115] The viscosity of a 2 wt% aqueous solution was measured using a rotational viscometer (VT550, Haake) with a conical cylinder (MV-DIN) at 20 °C. The shear viscosity was measured at a shear rate of 2.55 s ー1 It was decided that.

[0116] [Table 5]

[0117] Example 9 Coefficient of variation of CMC viscosity The present disclosure demonstrates that the methods described herein provide pulps useful in preparing CMCs of viscosities having a low coefficient of variation (COV) compared to commonly available CMCs.

[0118] The preparation and characterization of comparative pulp Kraft B is described in Example 13 and Table 12 of U.S. Patent No. 9,771,687, which is incorporated herein by reference in its entirety. The preparation and characterization of comparative pulp Kraft A is described in Example 8 and Table 8 of U.S. Patent No. 9,771,687.

[0119] [Table 6A]

[0120] The COV of CMC viscosity for samples Kraft A and Kraft B is 38%. Using the equipment and conditions as further described herein for Sample 2C, multiple batches of crosslinked pulp were prepared, and the resulting CMC viscosities had CMC COVs of 20-36%. See Table 6B. In this regard, higher consistency crosslinking results in a more uniform reaction environment, and therefore a much lower CMC viscosity COV.

[0121] [Table 6B]

[0122] Additionally, multiple batches of crosslinked pulp were prepared using the equipment further described herein in connection with Samples 2A and 2B (except that the NaOH and crosslinker were at 2 wt. % and 3.5 wt. % on the pulp, respectively), and the resulting CMC viscosities had even lower CMC COVs of 10%-12%. See Table 6C.

[0123] [Table 6C]

[0124] Example 10 Water retention value of the pulp of the present disclosure Due to process optimization, the crosslinked pulp had a higher crosslink density and reduced WRV.

[0125] [Table 7]

[0126] Example 11 Hemicellulose content of the pulp of the present disclosure The present disclosure reveals the hemicellulose levels of pulps made according to the methods of the present disclosure.

[0127] The crosslinked pulp and CMC were prepared as further described herein in connection with Example 1, Sample 2A. HPLC was used to detect sugar monomers in the hydrolyzed pulp and ether. Major sugars, such as glucose, xylose, and mannose, were detected, allowing the corresponding glucan, xylan, and mannan contents to be calculated. Due to derivatization, the weight percent of sugars in ether was lower than in cellulose pulp. The xylan ratio was calculated as the percentage of xylan in the total of glucan, xylan, and mannan. The mannan ratio was calculated as the percentage of mannan in the total of glucan, xylan, and mannan. The hemicellulose percentage was the sum of the xylan and mannan ratios.

[0128] As shown in Table 8, the crosslinked pulp samples had hemicellulose weight percents ranging from 10 wt% to 20 wt%, the CMCs made therefrom had hemicellulose weight percents of about 12 wt%, and the MCs made therefrom had hemicellulose weight percents ranging from 2 wt% to 8 wt%.

[0129] [Table 8]

[0130] Example 12 Alkali ion coefficient of variation of the pulp of the present disclosure Upon crosslinking, the pulp described herein has a high consistency. Therefore, the alkali ions, such as sodium ions, dispersed therein are more evenly distributed due to the improved mixing method, compared to pulp that is usually crosslinked at a lower consistency due to less thorough mixing. In this example, the sodium is from NaOH, which is mixed with the crosslinking agent and pulp to crosslink. The sodium ion concentration COV is one measure of the effectiveness of the mixing.

[0131] As shown below in Table 9, pulps made according to the methods of the present disclosure have a low sodium ion concentration COV, such as less than 5. Wet pulp samples were removed from the crosslinking reactor, dried, and subjected to metal analysis.

[0132] [Table 9]

[0133] Example 13 Blended pulp A blended pulp containing a crosslinked pulp of the present disclosure was prepared by blending the crosslinked pulp of the present disclosure with an uncrosslinked pulp, in this case NB416.

[0134] As shown in Table 10 below, the blended pulps had a higher kink angle and a higher percentage of insoluble fibers in solvents such as cuen. Additionally, such blended pulps had a higher curl percentage and kink.

[0135] [Table 10]

[0136] Example 14 Multiple crosslinking agent injection Pulps prepared according to the method discussed further herein in connection with Sample 2A (treated with 5 wt. % crosslinker) were crosslinked a second time at a total crosslinker loading of 15-20 wt. As shown in Table 11, these crosslinked pulps (2E, 2F) had much higher viscosities and R18s >94%.

[0137] [Table 11]

[0138] Test Methods and Acronyms About and approximately refer to plus or minus 5% of the stated value. Ash content: Determined by TAPPI T 211 om-07. ASTM: American Society for Testing and Materials CMC: Carboxymethyl cellulose CLP: Cotton linter pulp Coefficient of variation (COV): defined as the ratio of the standard deviation to the mean. Consistency: The consistency of the pulp (C) was calculated by dividing the dry weight of the sample (Wd) by the total weight of the sample (Wt). It is determined by the quotient and expressed as a percentage. Consistency can be expressed as C = (Wd / Wt) x 100. Consistency may be measured by TAPPI / ANSI T 240 om-12. Crystallinity: Determined by the corresponding method of Lionetto et al., "Monitoring Wood Degradation during Weathering by Cellulose Crystallinity," Materials, Vol. 5, pp. 1910-1922 (2012), which is incorporated herein by reference in its entirety. Cuen solubility: Solubility in copper ethylenediamine under the conditions of ASTM-D1795-96. Curl Index: Determined by the corresponding method disclosed in US Pat. No. 6,685,856, which is incorporated herein by reference in its entirety. Degree of polymerization: The number of D-glucose monomers in a cellulose molecule as measured by ASTM-D1795-96. The average degree of polymerization refers to the average number of D-glucose molecules per cellulose polymer in a population of cellulose polymers. Degree of substitution (DS): determined by ASTM D 1439-03. DWP: Dissolving wood pulp Hemicellulose content: The combined mannan and xylan content determined by the method described in Examples 6 and 7 of U.S. Patent No. 7,541,396, which is incorporated herein by reference in its entirety. This test was analyzed by Dionex ion chromatography based on TAPPI T 249 cm00. HPLC: High-performance liquid chromatography ISO: International Organization for Standardization Kink: Determined using a Valmet FS5 fiber image analyzer. Kink angle: Determined using a Valmet FS5 fiber image analyzer. Kappa number: Determined by ISO 302:2004. MCA: Monochloroacetic acid Oven dried (OD): dried to a moisture content of 7% by weight or less. R18:Measured by TAPPI T 235 cm-00. Resulting CMC Viscosity: Refers to the viscosity of a 0.5% solution of the resulting CMC according to the resulting CMC test method described herein. TAPPI: Technical Association for Pulp and Paper Transition Metal Content: Determined by EPA SW-856 Method 3050, 200.8. EPA: United States Environmental Protection Agency Water retention value (WRV): Determined by TAPPI T UM256M (2011).

[0139] While exemplary embodiments have been illustrated and described, it will be recognized that various changes can be made therein without departing from the spirit and scope of the invention. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: [Mode of the invention] [1] 1. A pulp comprising crosslinked cellulose fibers, Pulp with a pulp R18 value of 93% or greater. [2] 1. A pulp comprising crosslinked cellulose fibers, a coefficient of variation (COV) of the viscosity of the resulting carboxymethyl cellulose (CMC) of less than 30%, and Pulp R18 value higher than 92% Pulp having [3] 1. A pulp comprising crosslinked cellulose fibers, Water retention value (WRV) in the range of 0.8g / g to less than 1.0g / g, and Pulp R18 value higher than 89% Pulp having [4] An R18 value of 99 or greater, and Water retention value in the range of 0.6g / g~0.8g / g Crosslinked linter pulp having [5] 5. The pulp of claim 1, comprising at least about 6% by weight of hemicellulose by dry mass. [6] 6. The pulp of claim 1, having a resulting CMC viscosity higher than 56 centipoise (cP). [7] 7. The pulp of any one of claims 1 to 6, having a resulting CMC viscosity in the range of about 100 cP to about 400 cP. [8] 8. The pulp of any one of claims 1 to 7, having a resulting CMC weight average molecular weight of greater than about 800 kilodaltons (kDa). [9] 9. The pulp of any one of claims 1 to 8, having a resulting CMC weight average molecular weight in the range of about 900 kDa to about 4,000 kDa.

[10] 4. The pulp according to claim 1, wherein the pulp R18 value is in the range of 93% to about 100%.

[11] 11. The pulp of any one of claims 1 to 10, having a resulting CMC polydispersity index (PDI) of about 3 or greater.

[12] 12. The pulp of any one of claims 1 to 11, wherein the crosslinked cellulose fibers comprise a glycidyl ether crosslinker having two or more glycidyl groups.

[13] 4. The pulp according to any one of claims 1 to 3, having a water retention value (WRV) higher than 0.8 g / g.

[14] 3. The pulp according to claim 1 or 2, having a WRV in the range of 0.8 g / g to less than 1.0 g / g.

[15] 15. The pulp of any one of claims 1 to 14, comprising hemicellulose in the range of about 6% by weight dry mass to about 30% by weight dry mass.

[16] 4. The pulp according to claim 1, which is a kraft pulp.

[17] 4. The pulp according to any one of claims 1 to 3, which is straw pulp.

[18] 16. The pulp of any one of claims 1 to 15, which is cotton linter pulp.

[19] A cellulose ether product comprising a crosslinked cellulose ether, the crosslinked cellulose ether comprising: having a viscosity greater than about 56 cP; 19. A material formed from the pulp of any one of claims 1 to 18. Cellulose ether products.

[20] 20. The cellulose ether product of claim 19, selected from the group consisting of crosslinked methyl cellulose, crosslinked CMC, crosslinked hydroxypropyl methyl cellulose, crosslinked hydroxyl ethyl cellulose, and combinations thereof. [twenty one] 20. The cellulose ether product of claim 19, having a PDI of about 3 or greater. [twenty two] 20. The cellulose ether product of claim 19, having a weight average molecular weight greater than about 800 kD. [twenty three] 20. The cellulose ether product of claim 19, having a weight average molecular weight in the range of about 900 kDa to about 4,000 kDa. [twenty four] 20. The cellulose ether product of claim 19, comprising at least about 2% by weight hemicellulose by dry mass. [twenty five] 20. The cellulose ether product of claim 19, comprising hemicellulose in the range of about 2.5% by weight dry weight to about 20% by weight dry weight.

[26] A first pulp according to any one of claims 1 to 18, having a first fiber kink value; a second pulp having a second fiber kink value different from the first fiber kink value; Blended pulp containing

[27] 27. The blended pulp of claim 26, wherein the first pulp has a first pulp R18 value and the second pulp has a second pulp R18 value that is different from the first pulp R18 value.

[28] 27. The blended pulp of claim 26, wherein the first pulp is partially soluble in a copper ethylenediamine (cuen) solution.

[29] 27. The blended pulp of claim 26, wherein the first pulp is insoluble in cuen solution.

[30] 1. A method of making pulp, comprising: cooking the cellulosic feedstock to form a pulp; bleaching the pulp to form a bleached pulp; Crosslinking the cellulose fibers in the bleached pulp with a crosslinking agent to form a crosslinked pulp, wherein upon crosslinking, the bleached pulp has a consistency greater than 30% and the crosslinked pulp has an R18 value greater than 92%; and Drying the crosslinked pulp A method comprising:

[31] 31. The method of claim 30, wherein cross-linking the bleached pulp comprises providing an alkaline hydroxide to the bleached pulp, the method further comprising extracting the alkaline hydroxide from the cross-linked pulp after cross-linking the cellulose fibers.

[32] 32. The method of claim 31, wherein cross-linking the bleached pulp comprises providing the alkaline hydroxide and the cross-linking agent to the bleached pulp multiple times.

[33] 31. The method of claim 30, wherein the coefficient of variation of the alkali ion concentration is less than 10%.

[34] 31. The method of claim 30, further comprising forming the crosslinked pulp into a form selected from the group consisting of a roll, a bale, and a fluff.

[35] 31. A crosslinked pulp formed according to the method of claim 30.

[36] 1. A method of making pulp, comprising: contacting wood fibers with a crosslinking agent and an alkaline hydroxide, wherein the wood fibers have a moisture content in the range of about 0% to about 50% by weight; Heating wood fibers, a crosslinking agent, and an alkaline hydroxide to obtain crosslinked wood fibers; Washing the crosslinked wood fiber to remove unreacted crosslinker and alkaline hydroxide. and the R18 value of the pulp after crosslinking is 93% or more. method.

[37] 37. The method of claim 36, further comprising recovering the alkaline hydroxide.

[38] neutralizing the crosslinked pulp to obtain a neutralized pulp; washing the neutralized pulp to obtain washed pulp; Drying the washed pulp 37. The method of claim 36, further comprising:

[39] 37. A pulp formed according to the method of claim 36.

[40] 1. A method for making crosslinked cellulose pulp, comprising: activating a cellulosic pulp with an alkali hydroxide at a consistency higher than 4% to obtain an activated pulp; removing the alkali hydroxide from the activated pulp; and Crosslinking activated pulp with a crosslinking agent at a consistency higher than 20% and at a temperature ranging from 30°C to 95°C to obtain crosslinked pulp. A method comprising:

[41] 41. The method of claim 40, further comprising washing and pressing the crosslinked pulp to obtain a pressed pulp.

[42] 42. The method of claim 41, further comprising diluting and neutralizing the pressed pulp.

[43] 41. The method of claim 40, further comprising recovering the alkali hydroxide removed from the activated pulp.

[44] 41. The method of claim 40, further comprising drying the crosslinked pulp.

[45] 41. A pulp formed according to the method of claim 40.

Claims

1. 1. A pulp comprising crosslinked cellulose fibers, a coefficient of variation (COV) of the viscosity of the resulting carboxymethyl cellulose (CMC) of less than 30%; a pulp R18 value greater than 92%, and Water retention value (WRV) in the range of 0.8 g / g or more and less than 1.0 g / g Pulp having

2. 10. A pulp comprising crosslinked cellulose fibers according to claim 1, wherein the pulp has a pulp R18 value of 93% or greater.

3. 3. The pulp of claim 1 or 2, which contains at least about 9% by weight of hemicellulose on a dry basis.

4. 4. The pulp of any one of claims 1 to 3, having a viscosity of the resulting CMC greater than 56 centipoise (cP).

5. 5. The pulp of any one of claims 1 to 4, having a resulting CMC viscosity in the range of about 100 cP to about 400 cP.

6. 6. The pulp of any one of claims 1 to 5, having a resulting CMC weight average molecular weight greater than about 800 kilodaltons (kDa).

7. 7. The pulp of any one of claims 1 to 6, having a resulting CMC weight average molecular weight in the range of about 900 kDa to about 4,000 kDa.

8. 3. The pulp of claim 1 or 2, wherein the pulp R18 value is in the range of 93% to about 100%.

9. 9. The pulp of any one of claims 1 to 8, having a resulting CMC polydispersity index (PDI) of about 3 or greater.

10. 10. The pulp of claim 1, wherein the crosslinked cellulose fibers comprise a glycidyl ether crosslinker having two or more glycidyl groups.

11. 3. The pulp of claim 1 or 2 having a water retention value (WRV) higher than 0.8 g / g.

12. 12. The pulp of any one of claims 1 to 11, comprising hemicellulose in the range of about 6% by weight dry mass to about 30% by weight dry mass.

13. 3. The pulp according to claim 1 or 2, which is kraft pulp.

14. 3. The pulp according to claim 1 or 2, which is straw pulp.

15. A method for producing a cellulose ether product comprising a crosslinked cellulose ether having a viscosity greater than about 56 cP, comprising: The crosslinked cellulose ether is formed from the pulp of any one of claims 1 to 14. method.

16. The method of claim 15, wherein the cellulose ether product is selected from the group consisting of cross-linked methylcellulose, cross-linked CMC, cross-linked hydroxypropyl methylcellulose, cross-linked hydroxyl ethyl cellulose, and combinations thereof.

17. The method of claim 15, wherein the cellulose ether product has a PDI of about 3 or greater.

18. The method of claim 15, wherein the cellulose ether product has a weight average molecular weight greater than about 800 kD.

19. The method of claim 15, wherein the cellulose ether product has a weight average molecular weight in the range of about 900 kDa to about 4,000 kDa.

20. The method of claim 15, wherein the cellulose ether product contains at least about 2% by weight hemicellulose by dry mass.

21. The method of claim 15, wherein the cellulose ether product comprises hemicellulose in the range of about 2.5% by weight dry mass to about 20% by weight dry mass.

22. A first pulp according to any one of claims 1 to 14, having a first fiber kink value; a second pulp having a second fiber kink value different from the first fiber kink value; Blended pulp containing

23. 23. The blended pulp of claim 22, wherein the first pulp has a first pulp R18 value and the second pulp has a second pulp R18 value that is different from the first pulp R18 value.

24. 23. The blended pulp of claim 22, wherein the first pulp is partially soluble in a copper ethylenediamine (cuen) solution.

25. 23. The blended pulp of claim 22, wherein the first pulp is insoluble in the cuen solution.

26. 10. The pulp of claim 1, wherein the pulp comprises at least about 6% by weight hemicellulose on a dry mass basis.

27. 10. A method for making the pulp of claim 1, comprising: cooking the cellulosic feedstock to form a pulp; bleaching the pulp to form a bleached pulp; Crosslinking the cellulose fibers in the bleached pulp with a crosslinking agent to form a crosslinked pulp, wherein upon crosslinking, the bleached pulp has a consistency greater than 30% and the crosslinked pulp has an R18 value greater than 92%; and Drying the crosslinked pulp A method comprising:

28. 10. A method for making the pulp of claim 1, comprising: contacting wood fibers with a crosslinking agent and an alkaline hydroxide, wherein the wood fibers have a moisture content ranging from about 0% to about 50% by weight; Heating wood fibers, a crosslinking agent, and an alkaline hydroxide to obtain crosslinked wood fibers; Washing the crosslinked wood fiber to remove unreacted crosslinker and alkaline hydroxide. and the R18 value of the pulp after crosslinking is 93% or more. method.

29. 10. A method for making the crosslinked cellulose pulp of claim 1, comprising: activating a cellulosic pulp with an alkali hydroxide at a consistency higher than 4% to obtain an activated pulp; removing the alkali hydroxide from the activated pulp; and Crosslinking the activated pulp with a crosslinking agent at a consistency higher than 20% and at a temperature ranging from 30°C to 95°C to obtain a crosslinked pulp. A method comprising:

Images