RU2822575C2 - Cross-linked cellulose masses, cellulose ether-based products obtained therefrom and corresponding methods of producing cellulose masses and cellulose ether-based products - Google Patents

Abstract

FIELD: paper.

SUBSTANCE: invention relates to cellulose-based products. Disclosed is a cellulose mass for producing products based on cellulose ethers, having water-retention capacity WRV in range of 0.8 to less than 1.0 g/g and a R18 value of the pulp of more than 89%, in which the cross-linked cellulose fibres contain a glycidyl ether cross-linking substance containing two or more glycidyl groups, wherein the ratio of the cross-linking substance to the cellulose mass is at least 2:100, the weighted average molecular weight is from 174 to 500, wherein the cellulose mass is a sulphate cellulose mass. Also disclosed is a mixed cellulose mass.

EFFECT: disclosed cellulose mass has high viscosity and, accordingly, high degree of cross-linking, which increases its suitability for producing high-quality ether.

8 cl, 4 dwg, 11 tbl, 14 ex

Description

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 Aug. 16, 2018, the contents of each being incorporated herein by reference.

Field of the present invention

The present invention relates to cellulose-based products (eg, cellulose pulp) and cellulose derivatives (eg, cellulose ethers) and corresponding methods for preparing cellulose-based products.

BACKGROUND OF THE INVENTION

Cellulose ethers (eg carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, etc.) form aqueous solutions, and a variety of grades are available, depending largely on the viscosity of said solutions. High-grade cellulose ethers, which form aqueous solutions of higher viscosity, are generally more valuable than low-grade cellulose ethers, which form aqueous solutions of lower viscosity under the same conditions (concentration, temperature, etc.). The ability of a given cellulose ether to form a higher viscosity aqueous solution is directly related to the degree of polymerization, cross-linking and/or other properties of the original cellulose from which the cellulose ether was obtained. High-grade cellulose ethers are traditionally produced from soluble grade pulp (e.g., high-viscosity wood pulp and high-viscosity cotton lint pulp (CLP)), while mid-grade and low-grade cellulose ethers are traditionally produced from less expensive wood pulp. masses. The pulp grades mentioned herein are further discussed in Herbert Sixta's Pulp Handbook, Wiley-Vch (2006), which is incorporated herein by reference in its entirety. Most wood pulps typically have a degree of polymerization of no more than about 1500. On the other hand, dissolving grade pulps often have a degree of polymerization of 2400 or more. Unfortunately, dissolving grade pulp tends to be expensive. Previous attempts to modify low-cost cellulose pulps to produce high-grade cellulose derivatives have achieved only limited success.

Several traditional processes have been somewhat successful in improving the suitability of kraft pulp for the production of cellulose ethers, which form high-viscosity aqueous solutions. Unfortunately, these traditional processes have achieved these gains at the expense of other desirable properties of the resulting cellulose ethers and/or process yields. For example, some conventional processes involve increasing the removal of hemicellulose from kraft pulp. However, these methods achieve low yields due to the removal of the hemicellulose mass. In addition, pulps produced using these methods typically have low reactivity due to the conversion of the cellulose constituent from cellulose-I to cellulose-II. Traditional crosslinking reactions also tend to reduce the reactivity of the pulp. Even if low yield and/or low reactivity are assumed, traditional methods for modifying low-cost cellulose pulp are still unsuitable for producing cellulose pulp suitable for the production of cellulose ethers, which form aqueous solutions exhibiting viscosities as high as aqueous solutions. solutions of cellulose derivatives obtained from high-viscosity pulps of soluble grade.

Attempts have been made to crosslink pulp at a moderate consistency to produce a pulp having a moderately high viscosity. For such a moderate consistency, crosslinking may be provided at a consistency of, for example, less than 20% or less than 30%. Such methods are limited to traditional process systems in existing pulp mills. To date, methods, in particular low-cost methods for producing a pulp-based product having high value (eg, high ether viscosity and viscosity stability) have not been explored. As also discussed later in this document, there is currently no manufacturing facility that provides a product of consistent quality.

Accordingly, there is a need for further improvement in this area. This is particularly relevant in relation to cost-effective processes for the production of cross-linked cellulose pulps and the high-viscosity cellulose ether products derived therefrom.

Brief Disclosure of the Present Invention

The present summary disclosure is provided to present in simplified form selected concepts that will be further described below in the detailed disclosure of the present invention. This summary is not intended to define the essential features of the claimed subject matter of the present invention, but is intended to serve as a means of defining the scope of the claimed subject matter of the present invention.

According to an aspect of the present invention, there is provided a pulp containing cross-linked cellulose fibers, the pulp having a pulp R18 value of greater than or equal to 93%.

According to an aspect of the present invention, there is provided a pulp containing cross-linked cellulose fibers, the pulp providing a coefficient of variation (COV) of the resulting carboxymethylcellulose (CMC) viscosity of less than 30%; and a pulp R18 value of more than 92%.

According to an aspect of the present invention, there is provided a pulp containing cross-linked 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 an R18 value of pulp of more than 89%.

According to an aspect of the present invention, there is provided a cellulose ether product comprising cross-linked cellulose ether having a viscosity of greater than about 56 centipoise (cP) and produced from cellulose pulp according to any of the embodiments of the present invention.

According to an aspect of the present invention, there is provided a mixed pulp comprising a first pulp according to any embodiment of the present invention having a first fiber break value, and a second pulp having a second fiber break value different from the first fiber break value.

According to an aspect of the present invention, there is provided a method for producing cellulose pulp, comprising: cooking cellulosic raw material to produce pulp; bleaching pulp to produce activated pulp; crosslinking the cellulose fibers in the activated pulp composition using a crosslinking agent and obtaining a crosslinked pulp, wherein during crosslinking the activated pulp has a consistency of more than 30%, and the R18 value of the crosslinked pulp is more than 92%; and drying the cross-linked pulp.

According to an aspect of the present invention, there is provided a method for producing cellulose pulp, comprising: contacting wood fibers with a crosslinking agent and an alkali metal hydroxide, wherein the wood fibers have a water content ranging from about 0 wt. % to approximately 50 wt. %; heating wood fibers, a crosslinking agent and an alkali metal hydroxide to produce crosslinked wood fibers; and washing the crosslinked wood fibers to remove unreacted crosslinker; the R18 value of the pulp after crosslinking is greater than or equal to 93%.

According to an aspect of the present invention, there is provided a method for producing cross-linked pulp, comprising: activating the pulp using an alkali metal hydroxide at a consistency of more than 4% to obtain activated pulp; removing alkali metal hydroxide from the activated cellulose pulp; and cross-linking the activated pulp using a cross-linking agent at a consistency of more than 20% and at a temperature ranging from 30° C. to 95° C. to obtain a cross-linked pulp.

According to an aspect of the present invention, there is provided a pulp produced by any of the methods of the present invention.

Brief description of the figures

The foregoing aspects and many of the corresponding advantages of the claimed subject matter of the present invention will become more apparent upon reading the following detailed description taken in conjunction with the accompanying drawings, wherein:

in fig. 1 is a schematic illustration of a method for producing pulp in accordance with an embodiment of the present invention;

in fig. 2 is a schematic illustration of another method for producing pulp in accordance with an embodiment of the present invention;

in fig. 3 is a schematic illustration of another method for producing pulp in accordance with an embodiment of the present invention;

in fig. 4 is a schematic illustration of another method for producing pulp in accordance with an embodiment of the present invention;

Detailed Disclosure of the Present Invention

The present invention provides pulps, cellulose ether products and methods for producing pulps.

Methods for producing cross-linked cellulose pulps

According to certain aspects of the present invention, methods for producing cross-linked pulps are provided. As discussed later herein, the methods of the present invention are suitable for use in preparing crosslinked pulps suitable for producing high viscosity crosslinked ether products in a cost effective manner.

It should be understood that other methods, systems and compositions that are complementary to those described herein are generally within the scope of the present invention. For example, methods, systems and compositions in accordance with embodiments of the present invention may contain different and/or additional operations, components, configurations, etc. than those described herein. In addition, one of ordinary skill in the art will understand that the methods, systems, and compositions in accordance with embodiments of the present invention may not contain certain operations, components, configurations, etc., described herein without departing from the present invention.

Modified sulfate method, including cross-linking at high consistency

Methods for producing crosslinked pulp and corresponding systems and compositions in accordance with embodiments of the present invention can at least partially solve one or more problems associated with conventional technologies, whether or not such problems are identified herein. For example, methods in accordance with at least some embodiments of the present invention allow that low-cost cellulose pulp can serve as a starting material for the production of high-grade cellulose ethers and/or other cellulose derivatives (eg, cellulose esters). Kraft pulp, for example, is significantly less expensive and more widely available than certain dissolving grade pulp. However, when using standard kraft pulp as a starting material for the production of cellulose ethers, the resulting cellulose ethers are generally of low grade.

In traditional kraft technology, the pulp is kept at a relatively low consistency (eg, a consistency of less than or equal to 10%). As the consistency of the pulp increases, it becomes more difficult for the pulp to flow through the pipes and mix the pulp. Thus, any cross-linking in conventional methods for modifying kraft pulp is also carried out at a relatively low consistency in order to increase its potential for producing high-grade cellulose derivatives.

As discussed later herein, it has been found that through the use of, for example, high consistency mixers and other high consistency methods, thorough mixing of, for example, cellulose, alkali and crosslinking agents can be achieved. By thoroughly mixing the crosslinking reaction components, the methods of the present invention can produce pulps suitable for producing high viscosity cellulose ether products in a cost effective manner. A further unexpected discovery associated with at least some embodiments of the present invention is that increasing the consistency of the pulp during crosslinking can increase the reactivity of the crosslinked pulp compared to certain crosslinked pulps having a lower consistency during crosslinking.

Thanks to these and/or other discoveries associated with at least some embodiments of the present invention, it is now possible to produce kraft pulp that is an effective substitute and/or suitable filler for high-value dissolving grade pulp to produce high-grade cellulose derivatives having high viscosity.

Methods in accordance with at least some embodiments of the present invention include crosslinking the pulp at a relatively high consistency (eg, a consistency of greater than or equal to 20%, 30%, or greater). Accordingly, according to an embodiment of the present invention, the method includes cooking the cellulosic raw material to produce cellulose pulp, bleaching the cellulose pulp to produce activated pulp, and crosslinking the cellulose fibers in the activated pulp using a crosslinker to produce crosslinked pulp, wherein during crosslinking the activated pulp the pulp has a consistency of, for example, greater than 20%, greater than 25%, greater than 30%, or greater.

In an embodiment, the methods described herein include a modified kraft process for producing crosslinked pulps. Examples of suitable starting materials for producing pulp, for example, using a modified kraft process in accordance with embodiments of the present invention are wood and waste paper. In at least some embodiments, the starting material is never dried. For industrial wood processing to produce pulp, tree species are traditionally classified as deciduous or coniferous. Cellulose mass for use as a starting material can be produced from coniferous or deciduous wood. Examples of suitable coniferous tree species include fir (eg, Douglas fir and balsam fir), pine (eg, Weymouth pine and incense pine), spruce (eg, white spruce), larch (eg, American larch), cedar, and hemlock (eg , eastern and western hemlock). Examples of suitable deciduous tree species include acacia, alder (for example, red alder and black alder), aspen (for example, aspen poplar), beech, birch, oak (for example, white oak), gum trees (for example, eucalyptus and liquidambar), poplar (such as balsam poplar, delta poplar, hairy poplar, and tulip lyriodendron), gmelina, and maple (such as sugar maple, red maple, silver maple, and bigleaf maple).

Coniferous or deciduous wood typically contains three main components, cellulose, hemicellulose and lignin. Cellulose makes up approximately 50% of the woody structure of plants and is a straight-chain polymer of D-glucose monomer units. Individual cellulose polymer chains join together to form thicker microfibrils, which in turn join together to form bundles. The bundles form fibers that are visible components of plant cell walls when observed using a high power optical microscope or scanning electron microscope. Cellulose has a high degree of crystallinity as a result of the formation of numerous intramolecular and intermolecular hydrogen bonds. Hemicellulose is a heterogeneous group of low molecular weight carbohydrate polymers, such as xylan and mannan, that are associated with cellulose in wood. Hemicelluloses are amorphous, branched polymers, unlike cellulose, which is a linear polymer. Lignin is a complex aromatic polymer and constitutes approximately 20% to 40% of wood, in which it is present as an amorphous polymer.

Typically, kraft processing involves chemically cooking cellulosic feedstock (such as wood chips) at elevated temperature and pressure in white liquor, which is an aqueous solution containing cooking chemicals (such as sodium sulfide and sodium hydroxide). Cooking chemicals cause the wood to swell and dissolve the lignin that binds together the cellulose fibers in the raw material. When this chemical cooking is complete, the pulp is transferred to an atmospheric pressure tank known as a "blow tank." The contents of the blow tank are then sent to pulp washers where the spent cooking chemicals are separated from the pulp. The pulp is then passed through various washing and bleaching steps, after which it is pressed and dried to obtain the final product.

The sulfate process is designed to recover cooking chemicals and heat from the sulfate process stages. For example, spent cooking chemicals and pulp washing water can be combined to form dilute black liquor, which is concentrated in a multi-effect evaporation system to a solids content of approximately 55%. The black liquor can then be further concentrated to 65% solids in a direct contact evaporator by contacting the liquor with flue gases from the recovery unit or in an indirect contact concentrator. The concentrated black liquor can then be burned in a soda recovery unit. Combustion of organic matter dissolved in black liquor can provide heat to produce process steam and to convert sodium sulfate to sodium sulfide. Inorganic chemicals present in black liquor can collect in the form of a molten mass at the bottom of the furnace. This mass can be dissolved in water to form green liquor, which can then be transferred to an alkalization tank, where quicklime (calcium oxide) can be added to convert the solution back to white liquor, which is returned to the digestion system. The lime slurry sludge from the alkalization tank can be calcined in a lime kiln to regenerate quicklime.

In fig. 1 is a flow chart illustrating a pulp production method 100 in accordance with an embodiment of the present invention. According to the illustrated embodiment, the basis of the process 100 is a sulfate process. In other embodiments, alternatives to process 100 may be based on other suitable processes (such as a sulfite process). As shown in FIG. 1, method 100 may include pulping (process block 102) and a post pulping process (process block 104). As part of pulping (process block 102), process 100 may include chip loading (process block 106) and chip pre-steaming (process block 108). Steam at atmospheric pressure can be used to preheat the chips and displace air to enhance liquor penetration. After the steam pre-treatment, method 100 may include adding chemicals (eg, NaOH, Na ₂ S and/or other suitable chemicals) to the chips (process block 110). For example, chemicals can be added to cooking liquor. The wood chips and cooking liquor can then be sent to the digester. Inside the digester, the cooking liquor can impregnate the wood chips (process block 112). Good penetration of cooking liquor can ensure uniform cooking of wood chips.

After impregnation, method 100 may include cooking wood chips and cooking liquor in contact with liquid in a co-current (process block 114) and counter-current (process block 116) mode. In any mode, cooking liquor and chips can be brought to the specified temperature. The wash liquor may then be introduced into the bottom of the digester such that it flows countercurrently to the pulp being cooked (process block 118). Cooking can be completed when the pulp comes into contact with the lower temperature wash liquor. After washing the digester, the contents of the digester can be purged (process block 120). Blowing down the digester may involve releasing the wood and liquor at atmospheric pressure. Release can occur when a force of sufficient magnitude is applied to cause the fibers to separate. If desired, the blow tank can be equipped with heat recovery equipment to reduce operating costs. Finally, the pulp may be sent from the blow tank to an external pulp washer to separate black liquor from the pulp (process block 122).

After being converted to pulp (process block 102), the pulp may be activated and the cellulose fibers within the pulp may be crosslinked. In the standard sulfate method, bleaching occurs without crosslinking. As a rule, bleaching does not lead to a significant reduction in the hemicellulose content of the pulp. In contrast, bleaching involves the removal of lignin with a corresponding reduction in fiber length and pulp viscosity. During bleaching, the pulp may be treated using a variety of chemicals at various stages in the bleaching plant. These steps can be carried out in tanks or columns of conventional design. Typically, bleaching occurs as a sequence of operations, such as one or more bleaching stages using various bleaching agents (such as, for example, oxygen, chlorine dioxide, etc.), extraction stages, other processing steps, etc. The bleaching sequence can be defined as a series of sequential operations. For example, one whitening sequence is O-D-E-D. This bleaching sequence may consist of an oxygen bleaching stage (“O stage”), followed by a first chlorine dioxide bleaching stage (“D stage”), followed by an extraction stage (“E stage” or “EOP stage”), in which the bleaching chemicals substances such as peroxide (“P”) and/or oxygen (“O”) are mixed with an alkali to remove lignin), and then a second step D. Several additional examples of bleaching processes are described in U.S. Patent Nos. 6,331,354 and 6,605,350, which are incorporated herein by reference in their entirety.

The post-pulp processing (process block 104) may include first bleaching the pulp with oxygen (process block 124). Bleaching of pulp with oxygen appears to be less specific for lignin removal than bleaching of pulp with chlorine dioxide. Oxygen bleaching can occur in a pressurized oxygen reactor. Suitable oxygen reactors and corresponding oxygen bleaching processes are described in US Patent Nos. 4,295,925, 4,295,926, 4,298,426 and 4,295,927, which are incorporated herein by reference in their entirety. The amount of oxygen added to the pulp may range from 50 to 80 pounds per ton of pulp. The temperature during oxygen bleaching may range from 100°C to 140°C.

After oxygen bleaching of the pulp, method 100 may include cross-linking the cellulose fibers within the pulp (process block 126). In at least some cases, this involves adding a crosslinking agent and an alkali to the pulp and causing the crosslinking reaction to occur before subsequent processing of the pulp.

As discussed later herein, crosslinking at relatively high pulp consistency may be useful for improving the applicability of the pulp in the production of high-grade cellulose derivatives. In this regard, the consistency of the pulp during all or part of the time (eg, at least 50% of the time) of crosslinking may be at least 30% (eg, within the range of 30% to 50%) or at least 35% (for example, within the range of 35% to 50%). In an embodiment, the pulps are mixed in a batch or continuous mixer. In an embodiment, a refiner, extruder, or other high consistency mixer is used to mix the pulps. In an embodiment, the pulps are mixed using high consistency mixers, such as an Andritz™ mixer or a Loedige™ mixer, as described later herein, for example, with respect to Example 1. In an embodiment, the pulps are mixed in a system containing counter-rotating plates on which, for example, cellulose pulp and a cross-linking agent are placed. In an embodiment, the pulps are mixed in a system containing one or more rotating plowshare-like tools, such as a plowshare mixer.

In an embodiment, steady flow pumps such as gear pumps or pumps with no or minimal impulse are used to dose crosslinking agents such as crosslinker, alkali metal hydroxide, catalyst, etc. into the reactor before stitching. Thus, a uniform distribution of crosslinking reagents is ensured in the crosslinking reactor. This uniform distribution of cross-linking reagents generally produces stably and uniformly cross-linked cellulosic pulps, which in turn are suitable for producing cross-linked ethers of uniform viscosity.

Such high consistency mixers and mixing methods provide thorough mixing and contact between the pulp and the crosslinkers, resulting in fewer unwanted side reactions, such as between the crosslinker and water (and thus more desirable reactions between the crosslinker and water). and cellulose), and a smaller reactor volume is used for a given number of usable crosslinking reactions. In this regard, the methods of the present invention are suitable for using less crosslinking agent than methods that crosslink the pulps at a lower consistency. On the other hand, in processes that crosslink pulps at a lower consistency, a higher water content is present, and thus the concentration of crosslinking agent in the water is reduced and the number of interactions between the crosslinking agents and the cellulose is reduced. Accordingly, for a given degree of crosslinking, more crosslinking agent is required and the number of reactions between water and crosslinking agent increases. In addition, the methods of the present invention produce cross-linked pulps in a smaller reactor volume and require lower capital costs than processes that cross-link pulps at a lower consistency, due to the higher thorough mixing speed achieved, in particular, between fibers and crosslinking agent. As a result of these advantageous characteristics of the processes of the present invention, crosslinked pulps are produced that are suitable for producing high viscosity crosslinked ether products at a reduced cost and reduced capital expenditure compared to other processes designed for lower consistency.

In addition, due to the relatively high consistency and/or other factors, the alkali resistance (a measure of which is, for example, the R18 value of the crosslinked pulp) of the pulp may be increased by crosslinking. The cross-linked wood pulps produced by the methods of an embodiment of the present invention have an R18 value of greater than 89%. The cross-linked wood pulps produced by the methods of an embodiment of the present invention have an R18 value of greater than 93%, as discussed later herein with respect to Example 1. In an embodiment of the present invention, the cross-linked wood pulps have an R18 value ranging from more than 92% to 100%. According to an embodiment of the present invention, the crosslinked wood pulps have an R18 value in the range of 93% to 95%. On the other hand, crosslinking processes produce wood pulps with a crosslinking consistency of typically less than 30% and an R18 value of less than 92%. As discussed later herein, such crosslinking processes can produce crosslinked pulps having a WRV value of less than 1.0 g/g. In certain embodiments, such pulps have a pulp R18 value of greater than 89% and a WRV value of less than 1.0 g/g.

Moreover, according to an embodiment, during crosslinking, the pulps in the crosslinking step contain alkali metal ions in a concentration that exhibits high stability due to the high degree of consistency of the pulp. As discussed later herein, in an embodiment, crosslinking the activated pulp comprises introducing an alkali metal hydroxide into the activated pulp. Due to the thorough mixing during crosslinking of the cellulose fibers and the alkali metal hydroxide solution, such as sodium hydroxide, the pulp during the crosslinking step has a low coefficient of variation (COV) of sodium ion concentration. In an embodiment, the pulps described herein have a sodium ion concentration coefficient of variation of less than 10 during crosslinking, including less than 5, as discussed later herein with respect to Example 12.

The crosslinker used in the methods of the present invention may be selected to provide relatively strong crosslinkers (eg, ether crosslinkers instead of ester or ionic crosslinkers). Relatively strong cross-links may be preferred over less strong cross-links, for example, because the cross-links should be less likely to be disrupted by functionalizing reactions (eg, ether reactions) used to form cellulose derivatives. The crosslinker may be added at a weight ratio to the pulp of greater than or equal to 2:100, greater than or equal to 3:100, greater than or equal to 5:100, or greater than or equal to another suitable lower threshold value. . The upper threshold value may be the maximum amount of crosslinker that can be used without the resulting pulp CMC becoming water insoluble. In at least some cases, a catalyst (eg NaOH, zinc tetrafluoroborate Zn(BF ₄ ) ₂ ) is present during cross-linking. In addition or alternatively, a surfactant may be present during crosslinking, for example, to aid dispersion and penetration of the crosslinker. The surfactant may be particularly suitable for use in combination with a hydrophobic cross-linking agent.

Suitable cross-linking agents are ethers, such as glycidyl ethers containing two or more glycidyl groups. For example, the crosslinker may contain a first glycidyl group, a second glycidyl group, and a linear chain of three or four carbon atoms between the first and second glycidyl groups. In an embodiment, the crosslinking agent contains three or more glycidyl groups. Additionally or alternatively, the cross-linking agent may have a weight average molecular weight of less than or equal to 500 (eg, within the range of 174 to 500). In addition, when the crosslinker is an epoxy, the crosslinker may have a weight per epoxy group of less than or equal to 175 (eg, within the range of 140 to 175). The crosslinking agent may have a viscosity of less than or equal to 500 centipoise (cP) at 25°C. In at least some embodiments, the crosslinking agent is at least partially water insoluble. This property may be useful, for example, to improve the contact between the crosslinking agent and the cellulose fibers during the crosslinking reaction. Specific examples of suitable cross-linking agents include, but are not limited to, 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, or their mixture.

Traditional uncrosslinked kraft pulps tend to be less reactive than other chemical pulps such as kraft pulps (i.e. pulps obtained by extracting lignin from wood, primarily using sulfuric acid salts) . However, according to at least some embodiments of the present invention, the cross-linked kraft pulp has a relatively high reactivity. Purely by theory, and without intending to be limited by such theory, the authors believe that this may be due to the presence of cross-linking bonds that provide additional space evenly distributed between the cellulose chains. Longer chain crosslinkers (eg, polyglycidyl ethers) can produce crosslinked pulp with higher reactivity than shorter chain crosslinkers (eg, 1,3-dichloro-2-hydroxypropanol (DCP)) under similar conditions stitching. Pulps crosslinked with longer chain crosslinkers may have lower crystallinity indices than the original pulps and significantly lower crystallinity indices than dissolving grade sulfite wood pulp and cotton lint pulp (CLP). Crosslinking kraft pulp instead of sulphite pulp in high viscosity ether applications may be advantageous in at least some cases because the kraft process is predominant for conversion to pulp, provides higher yield (due at least in part to higher hemicelluloses) and lower costs, and is also more environmentally friendly than sulfite pulping processes.

In certain embodiments, crosslinking the activated pulp comprises sequentially introducing crosslinking reagents into the activated pulp, including mixtures containing two or more crosslinking reagents. In this regard, as discussed later herein with respect to Sample 5A, in an embodiment, crosslinking the activated pulp comprises sequentially contacting the activated pulp with a solution of an alkali metal hydroxide, a first portion of water, a solution, emulsion or suspension of a crosslinking agent, and a second part of the water. In certain embodiments, crosslinking the activated pulp involves repeatedly introducing a solution containing an alkali metal hydroxide and a crosslinking agent into the activated pulp. In this regard, according to an embodiment, cross-linking the activated cellulose pulp includes contacting the activated cellulose pulp with a first part of an alkali metal hydroxide and a first part of a cross-linking agent and then contacting the activated pulp with a second part of an alkali metal hydroxide and a second part of a cross-linking agent after implementation reacting the activated cellulose pulp with a first part of an alkali metal hydroxide and a first part of a cross-linking agent. According to another embodiment, crosslinking the activated pulp comprises repeatedly contacting the activated pulp with a mixture containing a crosslinking agent and an alkali metal hydroxide. Repeated addition of the alkali metal hydroxide and cross-linking agent may provide greater chemical efficiency and/or reduced reaction cost. In addition, such sequential introduction, including repeated introduction of alkali metal hydroxide and crosslinking agent into the activated pulp allows the use of mixers with controlled dosage.

During crosslinking, the pulp may have a temperature within the range of 30°C to 90°C. In addition, the pulp may have a pH within the range of 9 to 14.

According to an embodiment of the present invention, the methods include extracting alkali metal hydroxide from the cross-linked pulp after cross-linking the cellulose fibers, as discussed later herein with respect to Examples 2 and 3. Consider next FIGS. 2, which shows a method 200 according to the present invention, including extraction and reuse of alkali. In certain embodiments, method 100 and/or other methods of the present invention include one or more aspects of method 200. In an embodiment, method 200 begins with a process block 202 including cooking and bleaching a source of cellulosic fibers to produce pulp. In an embodiment, cooking and bleaching are carried out as discussed later herein with respect to FIG. 1. Process block 202 may be followed by process block 204 which includes mixing the activated pulp to, for example, a consistency of greater than 30%. Process block 204 may be followed by process block 206 comprising cross-linking the high consistency activated cellulose pulp with an alkali metal hydroxide and a cross-linking agent. As discussed later herein, such high consistency crosslinking reactions provide numerous advantages over lower consistency crosslinking reactions, including, but not limited to, increased R18 values, reduced crosslinker consumption, and higher pulp consistencies. which are, among others, COV of CMC viscosity and COV of alkali metal ion content.

In an embodiment, process block 206 is followed by process block 208, which may include washing the crosslinked pulp and recovering a portion of the alkali metal hydroxide used to crosslink the high consistency bleached pulp. As shown in the diagram, the recovered alkali metal hydroxide can be reused for cooking and bleaching (process block 202) and/or blending (process block 204). Such alkali recovery and reuse can provide economic benefits by reusing reagents and removing unwanted organic components in the mixture. Process block 208 may be followed by process block 210 comprising neutralizing the cross-linked washed pulp, for example by exposing the cross-linked washed pulp to an acid solution. As discussed herein with respect to Examples 2 and 3, by washing and neutralizing the cross-linked pulp, the content of pulp components, including extracted organic matter content, metal ion content, ash content, and silica content, can be reduced. In an embodiment, process block 210 is followed by process block 212, which may be the production of market pulp, as discussed later herein in relation to process block 134 in FIG. 1.

Cross-linking of pulp in accordance with embodiments of the present invention can be used in combination with other technologies for improving the suitability of pulp for the production of high-grade cellulose derivatives. For example, consider again FIG. 1, wherein the cooking described above with respect to pulping (process block 102) can be carried out under relatively mild conditions. By cooking under relatively mild conditions, less lignin may be removed from the pulp than would otherwise be removed. After cooking under mild conditions, the pulp may have a permanganate number of 25 to 35, which indicates the presence of a significant amount of residual lignin and high viscosity of the pulp. As another example, bleaching and extraction may be carried out under relatively mild conditions, as described below with respect to post-pulp processing (process block 104). In contrast to the modification of the kraft process by introducing strong alkali extraction and pre-hydrolysis, the above-mentioned modifications of the kraft process can gradually improve the suitability of kraft pulp for the production of high-grade cellulose derivatives without unduly reducing yield and/or reactivity.

After crosslinking the cellulose fibers within the pulp, method 100 may include first bleaching the pulp with chlorine dioxide (process block 128). Chlorine dioxide bleaching generally appears to be more selective for lignin removal than oxygen bleaching. The amount of chlorine dioxide added to the pulp may be in the range of 20 to 30 pounds per ton of pulp. The temperature during the first chlorine dioxide bleaching may range from 50°C to 85°C. After first bleaching the pulp with chlorine dioxide, method 100 may include extraction (process unit 130) to remove lignin from the pulp. Extraction may involve adding hydrogen peroxide or a suitable alkali to the pulp. The amount of hydrogen peroxide added to the pulp may range from 20 to 100 pounds per ton of pulp. The temperature during extraction may range from 75°C to 95°C. Unlike extraction with a strong alkali solution to remove hemicellulose, extraction to remove lignin can be carried out under relatively mild conditions. For example, the extraction may be an extraction in which the crystalline structure of the cellulose fibers is not changed.

After extraction, method 100 may include a second bleaching of the pulp with chlorine dioxide (process block 132). The amount of chlorine dioxide added to the pulp may range from 10 to 30 pounds per ton of pulp. The temperature during the second chlorine dioxide bleaching may be within the range of 60°C to 90°C. Method 100 may further include additional operations that are not those specifically identified in FIG. 1. For example, after any of the steps subsequent to pulping (process block 104), method 100 may include washing the pulp. This can be useful, for example, for removing waste and increasing the consistency of the pulp. The washing operation can be used to improve the consistency of the pulp after bleaching the pulp with oxygen and before cross-linking the pulp.

Although crosslinking in the illustrated embodiment occurs after oxygen bleaching and before chlorine dioxide bleaching, in other embodiments crosslinking may occur in another step of the alternative processing method 104 after pulping, as described below. The bleaching and extraction steps may also be rearranged or eliminated according to other embodiments. If "X" is defined as a crosslinking operation, the post-pulp processing processes in accordance with several embodiments of the present invention can be characterized as O-X-D-E-D (Fig. 1), O-D-X-E-D, O-D-E-X, O-D-E-X-D, O-D-E-D-X, D-X-E-D-E-D, D-E-X-D-E-D, E-D, D-E-D-E-X-D , D-E-D-E-D-X, D-X-E-E-D, D-E-X-E-D, D-E-E-X-D, or D-E-E-D-X, in addition to numerous alternative suitable permutations. In addition, crosslinking may occur during oxygen bleaching, chlorine dioxide bleaching and/or extraction. Thus, post-pulp processing methods in accordance with several additional embodiments of the present invention can be characterized as O/X-D-E-D, O-D/X-E-D, O-D-E/X-D, O-D-E/X, O-D-E-D/X, D/X-E-D-E-D, D-E/X-D-E-D , D-E-D/X-E-D, D-E-D-E/X-D, D-E-D-E-D/X, D/X-E-E-D, D-E/X-E-D, D-E-E/X-D, D-E-E-D/X, in addition to numerous alternative suitable permutations.

After bleaching (process block 104), the method 100 may include processing the pulp for use, sale and/or transportation (process block 134). For example, the pulp may be subjected to drying (eg, flash drying), compression, containerization, and/or other processing to form the pulp into a suitable form (eg, such as sheet, bale, roll, etc.) for use , sales and/or transportation. The pulp may have a surface density of 500 g/ ^m2 to 1200 g/ ^m2 and/or a bulk density of 0.2 g/ ^cm3 to 0.9 g/ ^cm3 . In some embodiments, the pulp produced by method 100 is combined with other pulp before drying. Pulps in accordance with at least some embodiments of the present invention are well suited for use as pulp fillers that reduce the amount of expensive dissolving grade pulp required to make a given cellulose derivative product without compromising viscosity or other desirable properties of the product . For example, the pulp obtained by method 100 may be mixed with other pulp (for example, a dissolving grade pulp having a cellulose content of more than 90 wt.% on an oven dried (OD) weight basis), thus that the pulp obtained by method 100 is at least 20 wt. % (eg at least 30 wt.%) based on the weight of oven-dried pulp in the resulting mixed pulp. In other embodiments, the pulp produced by method 100 can be used without mixing with other pulp.

In an embodiment, the dried pulp is further processed or shaped into a form suitable for shipping, marketing, and other purposes selected from roll, bale, and fluff.

Cross-linking of dry and semi-dry pulp

According to certain embodiments of the present invention, the methods include contacting wood fibers with a cross-linking agent and an alkali metal hydroxide, wherein the wood fibers have a water content ranging from about 0 wt. % to approximately 50 wt. %. In an embodiment, the water content of the wood fibers ranges from about 0 wt. % to approximately 10%. In this case, approximately 0 wt. % means water content ranging from 0 wt. % up to 1 wt. %, which is limited by the detection limits known in the art. Without intending to be limited by theory, the inventors believe that by contacting such dry or semi-dry wood fibers with a crosslinking agent and an alkali metal hydroxide, thorough mixing of the crosslinking agent and wood fibers can be achieved without actively mixing the pulp, such as mixing an aqueous suspension or solution in reaction tank. Furthermore, without intending to be limited by theory, the authors believe that the voids within dry and semi-dry wood fibers are filled with solutions of alkali metal hydroxide and cross-linking agent. This is in contrast to other processes in which wood fibers are dispersed in relatively dilute solutions containing an alkali metal hydroxide and a cross-linking agent.

In fig. 3 schematically illustrates a method 300 in accordance with an embodiment of the present invention comprising contacting dry or semi-dry wood fibers with an alkali metal hydroxide and a cross-linking agent. The method 300 may begin with a process block 302 comprising contacting dry or semi-dry wood fibers with an alkali metal hydroxide and a cross-linking agent. In an embodiment, the dry or semi-dry wood fibers are present in the form of a pulp sheet having a water content ranging from about 0 wt. % to approximately 50 wt. %. The crosslinking agent may be any crosslinking agent discussed herein, such as glycidyl ethers. In an embodiment, dry or semi-dry wood fibers are saturated with solutions of alkali metal hydroxide and a cross-linking agent. According to an embodiment, wood fibers are contacted with an alkali metal hydroxide, the content of which ranges from about 1 wt. % to approximately 5 wt. %. According to an embodiment, wood fibers are contacted with an alkali metal hydroxide, the content of which ranges from about 1 wt. % to approximately 10 wt. %.

In an embodiment, process block 302 is followed by process block 304 that includes heating wood fibers, a crosslinker, and an alkali metal hydroxide at a sufficient temperature and for a sufficient time to produce crosslinked wood fibers containing a number of crosslinkers. In an embodiment, heating the wood fibers, crosslinking agent and alkali metal hydroxide is heating the wood fibers, crosslinking agent and alkali metal hydroxide at a temperature ranging from about 100°C to about 140°C. In an embodiment, heating the wood fibers, crosslinking agent and alkali metal hydroxide is heating the wood fibers, crosslinking agent and alkali metal hydroxide at a temperature of approximately 120°C. In an embodiment, the wood fibers, cross-linking agent and alkali metal hydroxide are heated for a time ranging from about 5 minutes to about 20 minutes without allowing any water absorbed by the wood fibers to evaporate.

Process block 304 may be followed by process block 306 that includes washing the crosslinked wood fibers to remove unreacted crosslinker and alkali metal hydroxide. In an embodiment, the washing further includes neutralizing the pH of the cross-linked wood fibers, for example, with an acid solution.

As discussed later herein with respect to Example 5, CMC produced from pulps produced by a process involving contacting dry or semi-dry wood fibers with a crosslinker and an alkali metal hydroxide, for example, by Process 300, may have a viscosity of more than more than 80 cP, including more than 100 cP, more than 110 cP, more than 120 cP, etc. In an embodiment, CMC produced from pulps produced using such methods has a viscosity ranging from about 80 cP to about 140 cP. Moreover, in an embodiment, crosslinked pulps produced by a process comprising contacting dry or semi-dry wood fibers with a crosslinking agent and an alkali metal hydroxide, such as Method 300, have an R18 value of greater than 92%. In an embodiment, such pulps have an R18 value ranging from 93% to 100%. Accordingly, methods involving contacting dry or semi-dry wood fibers with a crosslinking agent and an alkali metal hydroxide, such as Method 300, are suitable for preparing crosslinked pulps to produce high viscosity crosslinked cellulose ether products.

Processing of pulp using alkaline extraction and washing of pulp

According to an embodiment of the present invention, the methods include activating the pulp using an alkali metal hydroxide to produce activated pulp; removing alkali metal hydroxide from the activated cellulose pulp; and crosslinking the activated pulp using a crosslinker to obtain crosslinked pulp. In this regard, consider FIG. 4, which schematically illustrates a method 400 in accordance with an embodiment of the present invention.

The method 400 may begin with a process block 402 that includes activating the pulp using an alkali metal hydroxide to produce activated pulp. In an embodiment, the pulp is CLP. In an embodiment, the pulp is kraft pulp. In an embodiment, the activation of the pulp is the activation of the pulp at a consistency of greater than 4%, including greater than 16%.

Process block 402 may be followed by process block 404 including removing alkali metal hydroxide from the activated pulp, for example, by filtration. In an embodiment, process block 404 is followed by process block 406 in which the removed alkali metal hydroxide is recovered and reused for subsequent pulp reactions, as discussed later herein.

Process blocks 402, 404, or 406 may be followed by process block 408 that includes cross-linking the activated pulp using a cross-linking agent. In an embodiment, crosslinking the activated pulp using a crosslinking agent comprises crosslinking the activated pulp at a consistency of greater than 20%, including greater than 30%. As presented later herein with respect to Examples 2 and 3, by crosslinking at a higher consistency of, for example, greater than 20%, and by removing the alkali metal hydroxide, the viscosity values of the CMCs obtained from such extracted and increased consistency of cellulose masses. Consider, for example, the consistencies for the viscosity values obtained from CMC of sample 3B versus sample 3A and sample 4B versus sample 4A in Table 2.

According to an embodiment, crosslinking of the activated cellulose pulp using a crosslinking agent is crosslinking at a temperature in the range of 30°C to 95°C. According to an embodiment, crosslinking of the activated cellulose pulp using a crosslinking agent is crosslinking at a temperature in the range of 70°C to 95°C. As presented later herein with respect to Examples 2 and 3, cross-linking pulps at elevated temperatures, such as temperatures in the range of 70° C. to 95° C., produces pulps suitable for use in producing CMC having high viscosity . Consider, for example, the CMC viscosity values obtained from sample 4C and sample 3C. In an embodiment, the viscosity values of the resulting CMCs range from about 100 cP to about 400 cP.

In an embodiment, process block 408 is followed by process block 410 including drying the cross-linked pulp. Process blocks 408 and 410 may be followed by a process block 412 that includes washing and pressing the cross-linked pulp to produce compressed pulp. Such washing and pressing operations can be carried out using methods discussed later herein, for example, with respect to method 100 and FIG. 1. Process blocks 408, 410 and 412 may be followed by process block 414 which includes diluting and neutralizing the pulp. As discussed later herein with respect to Example 6, such washing and neutralization operations are suitable, for example, for reducing the levels of organic extractables and metals, ash and silica content in pulps.

Pulp masses

According to another aspect of the present invention, pulps containing cross-linked cellulose fibers are provided. In an embodiment, the pulps are pulps produced using the methods described herein.

R18 values of cellulose pulps

According to an embodiment of the present invention, the pulps have an R18 value that is greater than 89%. According to an embodiment of the present invention, the pulps have an R18 value that is greater than 92%. As discussed later herein with respect to the methods of the present invention, crosslinking pulps at high consistencies, such as greater than 20%, 30%, or higher, typically results in crosslinked pulps having relatively high alkali resistance. , the measure of which is the R18 value of cellulose pulp. On the other hand, crosslinking at a consistency of, for example, less than 30% results in pulps with R18 values of, for example, less than 93%. As shown in particular in Examples 1-3, this high consistency crosslinking results in pulps having pulp R18 values ranging from about 92% to about 100%.

In an embodiment, the pulps have a pulp R18 value ranging from about 92% to about 100%. In this case, a pulp R18 value of approximately 100% means a pulp R18 value of 99% to 100%, which is limited by known detection methods such as the TAPPI T 235 cm-00 method. According to an embodiment of the present invention, the pulps have a pulp R18 value ranging from about 93% to about 97%. According to an embodiment of the present invention, the pulps have a pulp R18 value ranging from about 93% to about 96%. In an embodiment of the present invention, the pulps have a pulp R18 value ranging from about 93% to about 95%.

Viscosity of the resulting CMC

According to an embodiment of the present invention, the pulps have a resulting CMC viscosity of greater than 56 cP. According to an embodiment of the present invention, the pulps have a resulting CMC viscosity of greater than 90 cP. According to an embodiment of the present invention, the pulps have a resulting CMC viscosity ranging from about 100 cP to about 400 cP.

According to certain embodiments of the present invention, the pulps have high degrees of crosslinking in certain cases due to crosslinking reactions occurring at high consistency. In addition, as stated above, the viscosity of the resulting CMC for these pulps can be very high. Purely by theory, and without intending to be limited by such theory, the inventors believe that the molecular structure of cellulose can vary from linear to highly branched at high degrees of cross-linking, which, for example, can be achieved in the methods according to embodiments of the present invention. Cellulose having a highly branched structure is suitable for producing high grade ether such as high grade CMC.

As discussed later herein with respect to Examples 1 and 2 and Tables 1 and 2, such high viscosities of the resulting CMC are present in pulps crosslinked at high consistencies in accordance with embodiments of the present invention. In this regard, according to an embodiment of the present invention, the pulps have CMC viscosity values ranging from 90 cP to 130 cP, as presented in Table 1. According to an embodiment of the present invention, the pulps have CMC viscosity values ranging from approximately 100 cP to approximately 400 cP, as presented in Table 2.

In addition, the viscosity values of the resulting CMC from cellulosic pulps according to the present invention differ from those of, for example, conventional CLP. As described in Example 6 and presented in Table 3, the viscosity of the resulting CMC from pulps in accordance with embodiments of the present invention using the methods of the present invention is higher than the viscosity in the case of CLP. As discussed later herein, CLPs are often more expensive than kraft pulps, such as the pulps described in Example 6, at least in part because they are suitable for use in producing high-grade ethers having high viscosity. However, as presented herein, in certain cases, the pulps of the present invention, such as modified kraft pulps, are suitable for producing CMCs having higher viscosity than more expensive CLPs.

When used herein, the expression “viscosity of the resulting SMS” means the viscosity of an aqueous solution of 0.5 wt. % resulting CMC when determined by the resulting CMC testing method described herein.

Coefficient of variation of the viscosity of the resulting CMC

According to an embodiment of the present invention, the pulps have a coefficient of variation (COV) of the resulting CMC viscosity of less than 37%. As discussed later herein with respect to Example 9 and Tables 6A-6C, the CMCs produced from the pulps of the present invention have a viscosity COV of less than 37%, including 20% or less, 15% or less, etc. .d. Without intending to be limited by theory, the inventors believe that by cross-linking pulps at high consistency, pulps are obtained that are relatively uniformly cross-linked and, accordingly, the resulting CMCs have viscosity values with low COV viscosities.

In this regard, according to an embodiment of the present invention, the pulps have a COV of the resulting CMC viscosity ranging from about 5% to less than 38%. According to an embodiment of the present invention, the pulps have COV viscosities of the resulting CMC ranging from about 37% to about 20%. As discussed later herein in relation to Table 6B, CMCs produced from pulps crosslinked using a plow mixer, such as a Loedige™ mixer, have COV viscosities ranging from about 37% to about 20%. According to an embodiment of the present invention, the pulps have COV viscosities of the resulting CMC in the range of from about 5% to about 15%. According to an embodiment of the present invention, the pulps have COV viscosities of the resulting CMC in the range of from about 10% to about 12%. As discussed later herein in relation to Table 6C, CMCs produced from pulps crosslinked in a counter-rotating plate reactor, such as an Andritz™ mixer, have COV viscosities ranging from about 5% to about 15%.

According to an embodiment of the present invention, pulps having a resulting CMC viscosity COV of less than 37% also have a pulp R18 value of greater than 92%. As discussed later herein with respect to Example 9 and Tables 6B, 6C and 1, such pulps have relatively high alkali resistance in addition to the low COV viscosity of the resulting CMC.

Coefficient of variation of alkali metal ion concentration

In certain embodiments of the present invention, the pulps have a relatively low concentration of alkali metal ions COV. As discussed later herein, the methods of the present invention crosslink pulps at high consistencies. Without intending to be bound by theory, the authors believe that such high degrees of consistency provide a highly uniform crosslinking reaction environment. In this regard, the crosslinking reaction medium and the resulting crosslinked pulps contain certain crosslinking reagents, such as alkali metal ions, uniformly distributed throughout the pulp, for example, when the pulp has been crosslinked but not washed or neutralized. In an embodiment, the pulps described herein have a sodium ion concentration COV during crosslinking of less than 10, including less than 5, as discussed later herein with respect to Example 12.

Polydispersity coefficient of the resulting CMC

In certain embodiments of the present invention, the pulps have a CMC-resulting polydispersity index (PDI) of greater than or equal to about 3. In an embodiment of the present invention, the pulps have a CMC-resulting PDI of greater than about 4.5. In an embodiment of the present invention, the pulps have a resulting CMC PDI in the range of from 4.5 to about 7. In an embodiment of the present invention, the pulps have a resulting CMC PDI in the range of about 5.0 to about 6.5. As presented in Table 1, these relatively high PDI values are in contrast to the corresponding values for CMC derived from traditionally available pulps such as cotton fluff pulps, sulfite dissolving wood pulps (DWP), and traditional crosslinked kraft pulps, which have values PDI is usually 2 or less. When referred to herein, the PDI of the resulting CMC is the ratio of the weight average molecular weight of the CMC and the number average molecular weight of the CMC.

Without being limited by theory, we believe that the relatively high PDIs of the ethers of the present invention are due at least in part to the addition of high molecular weight substances to low molecular weight substances due to cross-linking and do not arise, for example, from cellulose decomposition. Compared to the control pulp (see Table 1 and Table 2), the molecules in the crosslinked pulp according to the present invention have an increased molecular chain length. During cross-linking, longer rather than shorter molecules are formed. In this regard, all other things being equal, a high PDI is preferable. For example, increasing the molecular weight of the resulting ether makes the final product stronger and more resilient even at lower concentrations. In addition, such resulting ethers having a higher weight average molecular weight exhibit a decrease in viscosity at higher shear rates than ethers having a lower PDI.

Water holding capacity values

In certain embodiments of the present invention, the pulps have a water retention value (WRV) ranging from about 0.8 g/g to about 1.0 g/g. In certain embodiments of the present invention, the pulps have a WRV ranging from about 0.8 g/g to less than 1.0 g/g. According to an embodiment of the present invention, the pulps have a WRV ranging from about 0.8 g/g to less than 1.0 g/g and a pulp R18 value ranging from 89% to 94%. According to an embodiment of the present invention, the pulps have a WRV ranging from about 0.8 g/g to less than 1.0 g/g and a pulp R18 value ranging from 92% to 94%. In an embodiment, the pulp is a kraft pulp having a WRV ranging from about 0.8 g/g to less than 1.0 g/g and a pulp R18 value ranging from 92% to 94%. As described in Example 10 and Table 7, the pulps in accordance with embodiments of the present invention produced in Example 1 have a WRV ranging from about 0.8 g/g to less than 1.0 g/g. In addition, such pulps have a pulp R18 value ranging from 92% to 94%. As discussed later herein with respect to Example 1, such pulps are kraft pulps produced by crosslinking at a consistency of greater than 30%. Such pulps differ from pulps crosslinked at a consistency of less than 30%, which typically have an R18 value of less than 92% and a WRV value of greater than 1.1 g/g.

In an embodiment, such pulps have a CMC viscosity ranging from 56 cP to 130 cP.

According to an embodiment of the present invention, the pulps are cotton fluff pulps such as CLP having an R18 value of 99% or more and a WRV ranging from 0.6 g/g and 0.8 g/g. As presented in Example 10 and Table 7, cross-linked CLPs prepared as discussed later herein with respect to Samples 3A and 3B in accordance with embodiments of the present invention may have a relatively high R18 value of, for example, 99% or more, and a relatively low WRV value, for example in the range of 0.6 g/g to 0.8 g/g.

A high value pulp product with high ether viscosity and stable ether viscosity may have a lower WRV than the original pulp,

As stated above, in certain embodiments of the present invention, the pulps are pulps suitable for producing high viscosity ethers and, as discussed later herein, having high stability of high viscosity ethers, wherein the pulp has a lower WRV value, than the original material based on uncrosslinked cellulose pulp. Surprisingly, it has been found that such pulps can produce high viscosity ethers with high viscosity stability even at a relatively low WRV, such as a WRV below the WRV of the pulp starting material used to prepare the crosslinked pulps of the present invention. Provided that the WRV of the crosslinked pulp is high enough to convert the pulp to a high viscosity ether, the crosslinked pulp may have a relatively low WRV, for example, in the range of about 0.6 g/g to approximately 0.8 g/g. Without being limited by theory, we believe that crosslinking increases the reactivity of the cellulose pulp, as measured by, for example, the formation of soluble CMC with the expected degree of substitution (DS) at the molecular level due to the introduction of a crosslinker between the cellulose molecules and the opening of the molecular structure.

Hemicellulose content

According to an embodiment of the present invention, the pulps have a hemicellulose content of approximately 6 wt. on a dry weight basis. % or more (for example, greater than or equal to 10 wt. %, 15 wt. %, or 20 wt. %). According to an embodiment of the present invention, the pulps have a hemicellulose content ranging from about 6 wt. % based on dry weight to approximately 30 wt. % in terms of dry weight. According to an embodiment of the present invention, the pulps have a hemicellulose content ranging from about 9 wt. % based on dry weight to approximately 20 wt. % in terms of dry weight. According to an embodiment of the present invention, the pulps have a hemicellulose content of approximately 15 wt. %.

As discussed later herein in relation to the methods of the present invention, hemicellulose content is one parameter of the overall efficiency of pulp processing. Generally speaking, pulps having higher hemicellulose content (defined herein as the sum of xylan and mannan) exhibit higher yields due to the increased volume provided by the hemicellulose. As discussed later herein with respect to Example 11 and Table 8, the pulps of the present invention, produced by the methods of the present invention, have a relatively high hemicellulose content, for example, greater than 6 wt. %. As described, pulps crosslinked at a consistency of greater than 30%, for example, using the methods described later herein with respect to Example 1, have a hemicellulose content of greater than 6 wt. %. In particular, the pulps obtained using the methods for sample 2A have a hemicellulose content of approximately 16 wt. %.

In an embodiment, the pulp is kraft pulp. As discussed later herein with respect to the methods of the present invention, kraft processing of pulp generally does not result in a significant reduction in hemicellulose content compared to the hemicellulose content of the starting material. By using a modified kraft process involving high consistency crosslinking, the crosslinked pulps of the present invention have, for example, a high hemicellulose content (and corresponding pulp volume, which is associated with a high hemicellulose content) as well as a high R18 value. In this regard, such pulps are suitable for producing high-grade cellulose ether products at relatively low cost.

Although kraft pulps are discussed herein, it should be understood that the pulps of the present invention include other cross-linked pulps such as CLP, straw pulps, etc.

Weighted average molecular weight

According to an embodiment of the present invention, the pulps have a weight average molecular weight of the resulting CMC of greater than about 800 kilodaltons (kDa), including greater than or equal to 1000 kDa, 1500 kDa, 2000 kDa. In an embodiment, the pulp has a weight average molecular weight of the resulting CMC ranging from about 900 kDa to about 4000 kDa. In an embodiment, the pulp has a weight average molecular weight of the resulting CMC ranging from about 1000 kDa to about 2500 kDa.

As presented in Table 1, CMCs obtained from pulps in accordance with embodiments of the present invention have weight average molecular weights of greater than 800 kDa, including greater than 1000 kDa and greater than 2000 kDa. This is in contrast to CMCs derived from traditional available pulps such as CLP, DWP kraft pulps and traditional kraft pulps. See also Table 1.

As discussed later herein with respect to PDI resulting from CMC, the increase in the weight average molecular weight of CMC produced using methods in accordance with embodiments of the present invention occurs due to cross-linking of the pulps. As also discussed herein with respect to the PDI of the resulting CMC, this increase in weight average molecular weight provides higher strength, resiliency, and shear loss for the resulting CMC compared to CMCs derived from lower molecular weight pulp. mass.

Crosslinkers

The pulps of the present invention contain crosslinked cellulose fibers containing a crosslinking agent associated with one or more cellulose fibers.

In an embodiment, the crosslinker forms an ether linkage with one or more cellulose fibers. As discussed later herein with respect to the methods of the present invention, such ether crosslinks are generally stronger than other specific crosslinks, such as ionic crosslinks and/or ester crosslinks. These stronger cross-links tend to be more stable in reactions during subsequent pulp processing, such as ether formation reactions.

In an embodiment, the crosslinking agent is present in a weight ratio to other components of the pulp that is greater than or equal to 2:100, greater than or equal to 3:100, greater than or equal to 5:100, or greater than or equal to another suitable lower threshold value or equal to it. The upper threshold value may be the maximum amount of crosslinker that can be used without the resulting pulp CMC becoming water insoluble.

Suitable cross-linking agents are ethers, such as glycidyl ethers containing two or more glycidyl groups. For example, the crosslinker may contain a first glycidyl group, a second glycidyl group, and a chain of three or four carbon atoms between the first and second glycidyl groups. In an embodiment, the crosslinking agent includes three or more glycidyl groups. Additionally or alternatively, the cross-linking agent may have a weight average molecular weight of less than or equal to 500 (eg, within the range of 174 to 500). In addition, when the crosslinking agent is an epoxy, the crosslinking agent may have a weight per epoxy group of less than or equal to 175 (eg, within the range of 140 to 175). The crosslinking agent may have a viscosity of less than or equal to 500 cP at 25°C. In at least some embodiments, the crosslinking agent is at least partially water insoluble. This property may be useful, for example, to improve the contact between the crosslinking agent and the cellulose fibers during the crosslinking reaction. Specific examples of suitable cross-linking agents include, but are not limited to, 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.

Methods for studying the resulting CMC

Throughout this specification, the properties of the pulp may be characterized in terms of the properties of the “resulting SMS”. These represent the properties of CMC to which cellulose pulp may be used, CMC being used here as a representative example of a cellulose derivative. It should be understood that CMC is not the only cellulose derivative for which pulps may be used in accordance with embodiments of the present invention. The properties of the CMC obtained from a given pulp described herein are determined through the following procedure. Additional details regarding this procedure can be found in T. P. Nevell and S. Zeronian, Cellulose Chemistry and Applications, Chapter 15, Cellulose Ethers (1985), which is incorporated herein in its entirety. via link.

First, the degree of substitution (DS) is determined for the CMC. If the CMC's DS is at least 1.0, perform the operations below. If the DS of CMC is less than or equal to 1.0, perform the steps below, but use 2.73 g (instead of 3.6 g) monochloroacetic acid (MCA).

Suspend 3 g of oven-dried (fluff) pulp containing approximately 92 wt. % solids, in 80 ml isopropanol. Add 8.0 ml of an aqueous solution of 30 wt. % NaOH over a three minute period. Stir the suspension for 1 hour at 20°C. Add 2.73 g of MSA (in the form of a 15.2 ml solution of 20.7 wt.% MSA in isopropanol) over a three-minute period. Raise the temperature to 55°C for 25 minutes and continue stirring for 3.5 hours. The resulting fibrous CMC is filtered and washed using 100 ml of a 70 vol aqueous solution. % ethanol. The sample is brought to a neutral state (pH 7.0) with acetic acid and then filtered. The filtered precipitate is washed again using 100 ml of an aqueous solution of 70 vol. % ethanol, at 20°C and filter. Repeat washing and filtering, using once more 100 ml of a 70 vol aqueous solution. % ethanol, at 20°C, and then carry out three more washes using 100% denatured ethanol, at 20°C. Air dry the sample to 70 to 85% solids. Dissolve the air-dried CMC fibers in deionized water with vigorous stirring using a Waring mixer and performing three stirring cycles, each stirring lasting one minute, to obtain a solution of 0.5 wt. %.

A solution of 0.5 wt. is examined. % CMC using a Brookfield viscometer equipped with a No. 2 spindle at 50 rpm and 20°C according to ASTM Standard Method D2196-99 to determine the viscosity of the resulting CMC.

Cellulose ether products

According to another aspect of the present invention, there is provided a cellulose ether product that is a cross-linked cellulose ether and has a viscosity of greater than about 56 cP. In an embodiment, the cellulose ether products of the present invention have a viscosity of 90 cP. In an embodiment, the cellulose ether products of the present invention have a viscosity ranging from about 100 cP to about 400 cP. In an embodiment, the cellulose ether products of the present invention range from 90 cP to 130 cP, as presented in Table 1 and discussed later herein with respect to Example 1. In an embodiment, the cellulose ether products of the present invention The invention have a viscosity ranging from about 100 cP to about 300 cP, as presented in Table 2 and discussed later herein in relation to Examples 2 and 3.

In an embodiment, a cellulose ether product is formed from the pulp of the present invention. As discussed later herein, in certain embodiments of the present invention, the pulps are inexpensive pulps, such as kraft pulps. As discussed later herein, due to certain aspects of the methods of the present invention, such as high consistency crosslinking, and as a result of certain properties of the pulps of the present invention, such as pulp R18 values, water holding capacity, and other parameters, such pulps are suitable for the production of high-grade, high-viscosity products based on cellulose ethers.

In an embodiment, the cellulose ether product is cross-linked CMC. Although CMC is discussed herein, it should be understood that the cellulose ether products of the present invention may be other cellulose ether products. Accordingly, in an embodiment, the crosslinked cellulose ether product is selected from the group consisting of crosslinked methyl cellulose, crosslinked CMC, crosslinked hydroxypropyl methylcellulose, crosslinked hydroxyethylcellulose, and combinations thereof.

In an embodiment, the cellulose ether products of the present invention have a weight average molecular weight of greater than about 800 kDa, including greater than or equal to 1000 kDa, 1500 kDa, 2000 kDa. In an embodiment, the cellulose ether product has a weight average molecular weight ranging from about 900 kDa to about 4000 kDa. In an embodiment, the cellulose ether product has a weight average molecular weight ranging from about 1000 kDa to about 2500 kDa.

In certain embodiments, the cellulose ether products of the present invention have a PDI of greater than or equal to about 3. In an embodiment, the cellulose ether products of the present invention have a PDI of greater than or equal to about 4.5. In an embodiment, the cellulose ether products of the present invention have a PDI in the range of 4.5 to about 7. In an embodiment, the cellulose ether products of the present invention have a PDI in the range of about 5.0 to about 6.5 .

As discussed later herein, the relatively high weight average molecular weight and PDI of the cellulose ether products of the present invention provide increased strength, resilience, and reduced shear viscosity compared to cellulose ethers, such as cellulose ethers derived from certain traditional pulps having lower molecular weight and PDI values.

According to an embodiment of the present invention, cellulose ether products have a hemicellulose content of approximately 2 wt. % based on dry weight or more (for example, more than 6 wt.%, more than 10 wt.%, etc.). In an embodiment, the cellulose ether product has a hemicellulose content ranging from about 2.5 wt. % based on dry weight to approximately 20 wt. % in terms of dry weight. In an embodiment, the cellulose ether product has a hemicellulose content ranging from about 2 wt. % based on dry weight to approximately 8 wt. % in terms of dry weight. In an embodiment, the cellulose ether product has a hemicellulose content of approximately 12 wt. %. As discussed later herein, this relatively high hemicellulose content imparts bulk to the cellulose ether product.

In an embodiment, the cellulose ether product is CMC and has a hemicellulose content ranging from about 10 wt. % to approximately 15 wt. %. In an embodiment, the cellulose ether product is CMC and has a hemicellulose content of approximately 12 wt. %.

In an embodiment, the cellulose ether product is methylcellulose (MC), such as hydroxypropylmethylcellulose (HPMC), and has a hemicellulose content ranging from about 2 wt. % to approximately 8 wt. %.

Mixed pulps

According to another aspect of the present invention, mixed pulps are provided comprising pulp according to the present invention and a second pulp. In any embodiment, the second pulp is uncrosslinked pulp.

According to an embodiment, the mixed pulp contains cross-linked pulp according to the present invention in an amount of more than 25 wt. %, more than 50 wt. % and more than 75 wt. %.

In an embodiment, the blended pulps of the present invention can be characterized by the amount of fiber remaining undissolved after contact with a solvent such as copper ethylenediamine complex (CuEn). According to an embodiment, the mixed pulps contain more than 10 wt. %, more than 15 wt. %, more than 20 wt. %, more than 30 wt. % of material remaining undissolved after contact with CuEn. Consider, for example, table 10 and example 13.

As also presented in Table 10 and Example 13, the blended pulps of the present invention have a higher degree of crimp and fracture than pulps that do not contain the pulps of the present invention. Moreover, this degree of crimp and fracture will generally be proportional to the content of the crosslinked pulp of the present invention present in the mixture. A higher degree of crimp and kink may be desirable, for example, to increase the accessibility of the fibers during derivatization reactions.

Accordingly, according to an embodiment of the present invention, there is provided a mixed pulp comprising a first pulp according to any one of the embodiments of the present invention having a first fiber break value; and a second pulp having a second fiber break value that is different from the first fiber break value. In an embodiment, the fiber kink amount is the number of kinks per meter. See, for example, Table 10. According to another embodiment, the value is a kink angle. See also table 10.

In an embodiment, the first pulp has a first pulp value R18, and the second pulp has a second pulp value R18 that is different from the first pulp value R18. According to a further embodiment, the first cellulose pulp is partially soluble in CuEn. In certain embodiments, the first pulp is insoluble in CuEn.

Examples

Example 1

Cellulose masses cross-linked at high consistency and carboxymethylcellulose obtained from them

This example demonstrates an improved process for crosslinking pulps that involves the use of high consistency mixers, such as Andritz™ and Loedige™ mixers, to produce very high viscosity pulps from softwood and hardwood pulps. High viscosity pulp can replace expensive high viscosity CLP or wood pulp in the cellulose derivative applications market. In addition, for suitable high-consistency reactors, the consumption of chemical reagents can be significantly reduced.

As discussed later herein, commercially available CLP, DWP sulfite pulp produced by U.S. Patent No. 9,771,687, which is incorporated herein by reference in its entirety, and commercially available pulp were compared to Experimental Samples 2A-2C NB416. As presented in Table 1, Samples 2A-2C have high hemicellulose concentrations, high weight average molecular weights, high PDIs, and high resulting CMC viscosities compared to conventionally available pulps.

Sample 2A

The crosslinked pulp starting material in this example was dried activated pulp NB416 from New Bern (International Paper Company). The pulp was dispersed in water using a pulper at 5% solids and 90° C. (steam heating) to produce a slurry which was diluted to 4 wt. % solids in feed tank. The resulting suspension was pressed on a double-grid press to a content of 40 wt. % solids. After a double screen press at a temperature of approximately 65° C., the pulp was subjected to in-line pin milling. The warm pulp was fed into an Andritz™ high consistency mixer at a speed of 10 kg dry pulp per minute and simultaneously mixed with an aqueous solution of 5 wt. % NaOH (20 wt.%) and aqueous emulsion Heloxy 48 (80 wt.%) using a gear pump. Heloxy 48 emulsion was prepared by mixing Heloxy 48 with deionized water while mixing at high speed using a mixer or mixer). The emulsion form of Heloxy 48 was prepared by mixing Heloxy 48 with deionized water while stirring at high speed. The additions of NaOH and Heloxy 48 to the oven-dried cellulose mass were 2 wt. % and 5 wt. % respectively. The pulp mixed with chemicals was treated with steam while maintaining the temperature at approximately 75°C and discharged into a cylindrical storage tank in which the temperature was maintained at 75°C using steam. The pulp mixture in the cylinder had a consistency of approximately 30% to 38%, and the residence time of the pulp in the cylinder was 60 minutes. After a residence time of 60 minutes, the pulp was released from the cylindrical storage tank at a rate of 10 kg dry pulp per minute and collected in a tank for neutralization with acetic acid at a pH of 4.5 to 5.0, a pulp consistency of 3% and a temperature of 10 to 15°C. The neutralized pulp was compressed to approximately 40% solids for subsequent processing (paper machine rolls at a sheet density of 0.50 g/ ^cm3 to 0.80 g/ ^cm3 and air dried into flakes for laboratory testing) . This pulp had a pulp R18 value of 93%.

The CMC sample was prepared from crosslinked pulp as described elsewhere in this document. Solution viscosity 0.5 wt. The % CMC was 128 cP (DS 0.95 using 8 mL aqueous solution of 30 wt % NaOH and 2.73 g MSA as described elsewhere in this document). All CMC viscosity values were determined using a Brookfield viscometer equipped with a No. 2 spindle at 50 rpm. The original cellulose mass NB416 provided a solution viscosity of 0.5 wt. % CMC (DS 0.95) of approximately 33 cP.

CMC samples for gel permeation chromatography (GPC) were prepared in the form of aqueous solutions with a concentration of approximately 0.5 mg/ml. Due to the relatively high viscosity of the solutions, 10 ml of the resulting solutions were diluted to 25 ml with ultrapure water. This corresponded to a sample concentration of approximately 2 mg/mL. After dilution, clear solutions were filtered through 1-μm nylon membranes. Each CMC sample solution was injected twice. The average molecular weight, weighted average molecular weight ( _Mw ) and molecular weight distribution (MWD) or PDI of the studied samples are presented in Table 1.

The MWD of the CMC solution for sample 2A described above and samples 2B, 2C, 3A-3C and 4A-4C described below were analyzed by gel permeation chromatography coupled with multi-angle light scattering (GPC-MALS).

The experimental GPC setup had the following composition:

Equipment:

• Alliance 2695 separator module (Waters)

• Refractive Index Detector 2414 (Waters)

• Laser photometer Dawn-HELEOS (Wyatt Technology Inc.), wavelength % = 658 nm and flow cell K5

• Control from a personal computer with Empower 3 (Waters) software

• Evaluation of GPC-MUSR using Astra 5.3.4.20 software (Wyatt Technology Inc.)

GPC conditions:

• GPC column system: Suprema (Polymer Standards Service GmbH PPS)

• GPC oven temperature: 30°C

• Eluent: solution of 0.2 M NaNO ₃ in ultrapure water

• Flow rate: 0.8 ml/min

• Detector: refractive index (30°C)

• Laser photometer Dawn Heleos, 658 nm

• Injection volume: 100 µl

• Sample concentration: approximately 0.2 mg/ml, refractive index increment dn/dc at 0.163 ml/g

Sample 2B

The crosslinked pulp starting material for this sample was dried activated pulp NB416 from New Bern (International Paper Company). The pulp was dispersed in water using a pulper at 5% solids and 90° C. (steam heating) to produce a slurry which was diluted to 4 wt. % solids in the feed tank and pressed on a double-grid press to a content of 40 wt. % solids. The warm pulp mass was sent to an Andritz• high consistency mixer at a speed of 10 kg dry mass per minute and was simultaneously mixed with an aqueous solution of 5 wt. % NaOH (20 wt.%) and aqueous emulsion Heloxy 48 (80 wt.%) using a gear pump. The additions of NaOH and Heloxy 48 to the oven-dried cellulose mass were 1 wt. % and 4 wt. % respectively. The pulp mixed with chemicals was steamed while maintaining the temperature at approximately 65°C and discharged into a cylindrical storage tank in which the temperature was maintained at 65°C. The pulp mixture in the cylinder had a consistency of approximately 30% to 38%, and the residence time of the pulp in the cylinder was 60 minutes. After residence for 60 minutes, the pulp was discharged from the cylindrical storage tank at a rate of 10 kg dry pulp per minute and collected in a tank for neutralization with acetic acid at a pH of 4.5 to 5.0. The neutralized cellulose mass was pressed for further processing or dried in air. The CMC sample was prepared from pulp as described elsewhere in this document.

Solution viscosity 0.5 wt. % CMC (DS 0.95) was 71 cP. The original NB416 pulp had a solution viscosity of 0.5 wt. % CMC (DS 0.95) of approximately 33 cP.

Sample 2C

The crosslinked pulp starting material for this sample was dried activated pulp NB416 from New Bern (International Paper Company). The cellulose mass was dispersed in water using a pulper at 20°C and centrifuged to a content of 40 wt. % solids and fluffed in a pin mill. 26.8 kg (10 kg dry weight) of wet pulp (20°C) was introduced into a high consistency Loedige™ reactor (10 kg batch size) and the temperature was raised to 75°C (during the kneading process). First, 0.2 kg of an aqueous solution of 50 wt. % NaOH was introduced into the pulp in the reactor for 15 seconds, then 1 kg of warm water was introduced. After this, 2 kg of emulsion of 20 wt. was introduced into the mixture. % Heloxy 48/80 wt. %, and then 1 kg of warm water. The interval between each two injections was two minutes, and the duration of the injection was 15 seconds. The additions of an aqueous NaOH solution and Heloxy 48 emulsion to the cellulose mass, calculated on a dry basis, were 1 wt. % and 4 wt. %, respectively (you can mix/introduce lye, Heloxy 48 and water at the same time to achieve similar results). The mixture of pulp and chemicals was mixed inside the reactor for 5 minutes at high speed and for 55 minutes at low speed at 75°C (60 minutes in total). The pulp mixture in the reactor had a consistency of approximately 32%. After remaining in the reactor for 60 minutes, the pulp mixture was neutralized with acetic acid and released for washing. The washed pulp was dried and CMC was obtained from the sample as described elsewhere in this document. Solution viscosity 0.5 wt. The % CMC (DS=0.95) from the sample was 95 cP. The original NB416 pulp had a solution viscosity of 0.5 wt. % CMC (DS=0.95) of approximately 33 cP.

Sample 2S1

Sample 2C described above was replicated except that undried NB416 pulp from the New Bern mill was mixed with chemicals. The final consistency of the pulp was 32%, and the solution viscosity was 0.5 wt. The % CMC (DS=0.95) of the pulp was 110 cP. Solution viscosity 0.5 wt. The % CMC from the pulp was 298 cP when the DS was 1.25 (8 mL aqueous solution of 30 wt % NaOH and 3.6 g MSA as described elsewhere herein).

Example 2

Method for producing crosslinked cellulose pulp, including crosslinking at high consistency and alkaline extraction

This example demonstrates a method for producing crosslinked pulp using high consistency crosslinking CLP. As presented, the resulting CMCs have, for example, high viscosity, molecular weight and PDI values.

20 g of CLP with a SCAN viscosity of 1589 ml/g were placed in a plastic bag and heated in an oven at 35°C. Warm CLP was then mixed with 480 g of an aqueous solution of 8 wt. % NaOH (preheated to 35°C) in a plastic bag at 35°C for 15 minutes. The CLP suspension was divided into three equal parts (A, B and C) and each part of the same max (166 g with 6.64 g CLP) was stored in a plastic bag.

Sample 3A (Part A: - 166 g. 6.64 g pulp)

2.6 g of aqueous emulsion 10 wt. % H48/90 wt. % was added to the mixture of pulp and alkali (part A) in the bag (3.92 wt.% H48 on the pulp, pulp consistency 4%), the mixture in the bag was thoroughly mixed by hand, and the bag was placed in an oven at a temperature of 35 ° C , which was increased to 50°C for five minutes. The temperature (50°C) in the oven was maintained for 40 minutes. After 40 minutes, the pulp suspension was washed with deionized water, neutralized with acetic acid, washed again with deionized water and oven dried at 85°C for testing.

Sample 3B (Part B: ~166 g. 6.64 g pulp)

The pulp suspension (Part B) was filtered to remove as much alkali as possible (~141 g). After this, some part of the filtrate (6 g) and 2.6 g of emulsion 10 wt. % H48 and 90 wt. % water was mixed and then added to the pulp/lye mixture (Part B after filtration) in the bag to a final weight of approximately 33 g (3.92 wt % H48 on pulp, pulp consistency ~20%). The mixture in the bag was thoroughly mixed by hand and the bag was placed in an oven at 35°C, which was increased to 50°C for five minutes. The temperature (50°C) in the oven was maintained for 40 minutes. After 40 minutes, the pulp suspension was washed with deionized water, neutralized with acetic acid, washed again and dried for testing as described in Example 3A.

Sample 3C (Part C: ~166 g. 6.64 g pulp)

The pulp suspension (Part C) was filtered to remove alkali (133 g was removed). Thereafter, 133 g of deionized water was added to the pulp and the mixture was stirred. Then 141 g of liquid was filtered again (new filtrate). After this, the concentration of alkali in the mixture decreased. Then some part of the new filtrate (6 g) and 2.6 g of 10 wt. emulsion. % H48 and 90 wt. % water was mixed and then added to the above pulp and alkali mixture (Part C with lower alkali concentration) in the bag to a final weight of approximately 33 g (3.92 wt.% H48 on pulp, pulp consistency 20% ). The mixture in the bag was thoroughly mixed by hand and the bag was placed in an oven at 35°C, which was increased to 50°C for five minutes. The temperature (50°C) in the oven was maintained for 40 minutes. After 40 minutes, the pulp suspension was washed with deionized water, neutralized with acetic acid, washed again and dried for testing as described in Example 3A.

Solution viscosity 0.5 wt. % CMC (DS=1.0) (Brookfield viscometer equipped with No. 2 spindle, speed 50 rpm for all tests) of the control sample and samples 3A, 3B and 3C were 55 cP, 79 cP, 150 cP, 120 cP, respectively , as presented in Table 2.

Example 3

A method for producing cross-linked cellulose pulp, including cross-linking at high consistency and alkaline extraction at elevated temperatures

This example demonstrates a method for producing crosslinked pulp using crosslinking at high CLP consistency and elevated crosslinking temperature. As presented, the resulting CMCs have, for example, high viscosity, molecular weight and PDI values.

Samples 4A-4C

The study described in Example 3 (for samples 3A, 3B and 3C) was repeated to obtain samples 4A, 4B and 4C, respectively, except that the crosslinking temperature was 75°C instead of 50°C. Solution viscosity 0.5 wt. The % CMC (DS=1.0) (Brookfield viscometer equipped with No. 2 spindle, speed 50 rpm) of samples 4A, 4B and 4C was 09 cP, 124 cP and 300 cP, respectively.

The results are presented in Table 2. The CMC solutions were analyzed and the data are presented in Table 2.

Conclusion: Crosslinking at high consistency increased the viscosity of the resulting CMCs at lower costs. Consider, for example, sample 3B versus sample 3A and sample 4B versus pattern 4A. The extraction step improved the quality at elevated crosslinking temperature resulting in higher viscosity CMC. Consider, for example, sample 4C versus sample 3C. In addition, crosslinked wood pulp CMC (Example 1) and crosslinked CLP (Example 2) produced using the improved process exhibited significantly higher solution viscosity, PDI, and _Mw values than the crosslinked wood pulp described in U.S. Patent No. 9,828,725, which is incorporated herein by reference in its entirety.

Example 4

Method for producing cross-linked cellulose pulps having R18 values. making up more than 92%

The present example demonstrates a method for producing crosslinked pulp in accordance with an embodiment of the present invention, including the sequential addition of crosslinking reagents. As presented, the pulps produced according to the present example have high CMC viscosity values and high R18 values.

Sample 5A

The crosslinked pulp starting material for this sample was dried activated pulp NB416 from New Bern (International Paper Company). The pulp mass was dispersed in water using a pulper at 20°C, dewatered on a 150 mesh screen, and centrifuged to a content of 40 wt. % solids and subjected to fluffing in a pin mill. 26.8 kg (10 kg dry weight) of wet pulp at 20° C. was loaded 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 aqueous solution of 50 wt. % NaOH was introduced into the pulp in the reactor for approximately 5 seconds, and then 1 kg of warm water was introduced. After this, 2.5 kg of 20 wt. emulsion was introduced into the mixture. % Heloxy 48 and 80 wt. % water, and then 1 kg of warm water. The interval between each two injections was two minutes. The additions of NaOH and Heloxy 48 to the cellulose mass (based on dry weight) were 3 wt. % and 5 wt. %, respectively. The mixture of pulp and chemicals was stirred for 5 minutes at 75 rpm and for 55 minutes and 120 rpm, with the temperature inside the reactor being maintained at approximately 75°C for 55 minutes at 25 wt. % and 40 rpm. The pulp mixture in the reactor had a consistency of approximately 32%. After remaining in the reactor for 60 minutes, the pulp mixture was neutralized using 0.45 kg of acetic acid and released for washing with deionized water. The washed cellulose mass was dried. The R18 value of the pulp was 93.7%, while the original NB416 pulp had an R18 value of 88%. CMC was obtained from the sample. The viscosity of the aqueous solution is 0.5 wt. The % CMC (DS=1.25) from the sample was 313 cP (calculated SCAN IV pulp value was 2304 ml/g, as described later herein). The viscosity of the 0.5% CMC (DS=1.25) solution from NB416 pulp was approximately 40 cP.

Sample 5B

Sample 5B was prepared in the same manner as Sample 5A, except that 4.5 kg of water was added after the addition of pulp. The final pulp consistency was 27.5%. The crosslinked pulp had an R18 value of 92.7%. Solution viscosity 0.5 wt. The % CMC (DS=1.25) of the pulp was 190 cP.

Sample 5C

Sample 5C was prepared in the same manner as Sample 5A, except that 8.1 kg of water was added after the addition of the pulp. The final pulp consistency was 25%. The crosslinked pulp had an R18 value of 92.4%. Solution viscosity 0.5 wt. The % CMC (DS=1.25) of the pulp was 170 cP.

Sample 5D

Sample 5B was prepared in the same manner as Sample 5A except that dried eucalyptus pulp from the Mogi plant was mixed with chemicals (1 wt% NaOH aqueous solution 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%. Solution viscosity 0.5 wt. The % CMC (DS=1.0) of the pulp was 65 cP.

Example 5

A method for producing cross-linked cellulose pulp by exposing dry and semi-dry cellulose pulp to alkali and a cross-linking agent

This example presents a method for producing cross-linked cellulose pulps, including the action of cross-linking reagents on dry or semi-dry cellulose pulps. As presented, pulps produced using such processes have relatively high R18 values, and the resulting CMCs have high viscosity values without active mixing steps.

25 g (dry weight) of NB421 pulp sheet from New Bern (International Paper Company) was impregnated with a mixture of 6.2 g Heloxy 48, 4.8 g aqueous solution of 50 wt. % NaOH and 157 g water for one minute. The impregnated pulp sheets were compressed several times using a stainless steel roller to obtain a final pulp sheet having a consistency of 42%. The additions of NaOH and Heloxy to the pulp were approximately 2 wt. % and 5 wt. %, respectively. The pressed sheet pulp was divided into two samples, which were placed in glass beakers with lids (to limit water evaporation) and dried in an oven at 120°C for 10 and 20 minutes. The semi-dried pulp sheets were neutralized and washed before being completely dried. A solution of 0.5 wt. The % CMC from sheets dried for 10 minutes and 20 minutes had viscosities of 82 cP and 130 cP, respectively.

Example 6

pH value during washing and alkaline extraction for pulp filtration

This example demonstrates the washing of pulps produced by the methods of the present invention using low pH solutions to reduce the metal content, ash content and silica content dispersed in the pulp.

Having a high viscosity, kraft pulp was washed with acid at pH below 7, below 6, below 5, below 4 to remove metals (Ca, Fe, Mn, Ni, Co, Cr, Cu, etc.) and reduce ash content (to regulate pH, any acid can be used) and silica content. After acid washing, the pH of the pulp slurry can be adjusted during or prior to introduction into the headbox to above 4, above 5, above 6 or above 7 to neutralize residual acid. Residual acid in the pulp may cause pulp decomposition and a decrease in viscosity during final drying (Table 3). The viscosity of the pulp was maintained during the crosslinking reaction. In pilot production, the crosslinked pulp obtained as discussed later herein with respect to Sample 2A was dispersed in water at a consistency of 3% and the pH of the suspension was adjusted using acetic acid at a level of 4.5 to 5. This washed pulp provided the same CMC viscosity as pulp without acid washing in pilot production (Table 2). The experimental washed pulp produced higher CMC viscosity than CLP with a SCAN value of 2310 ml/g. These pulps also had low ash content and content of Ca, Fe, silica, etc., as shown in Table 3. The experimental washed sample was ultimately obtained in the form of rolls, with a pH value in the headbox of approximately 4.8 (reverse osmosis purified water and acetic acid were used), and the specified cellulose mass had even lower ash content and content of Ca, Fe, silicon dioxide, etc.

Example 7

Cross-linked eucalyptus pulps from high consistency pulps with lye washing and reuse

Sample 5D described above was replicated except that dried mixed hardwood pulp from Saillat (International Paper) was mixed with chemicals (1 wt% NaOH aqueous solution and 4 wt% H48 aqueous emulsion on pulp). The final pulp consistency was 32%. The crosslinked pulp had an R18 value of 94.1%. Solution viscosity 0.5 wt. The % CMC (DS=1.0) of the pulp was approximately 63 cP, 50 cP and 40 cP when the cross-linked pulp was washed at a pH of 4, 3 and 2, respectively. It should be noted that washing pulp at an excessively low pH may result in pulp decomposition.

To improve pulp washing and wastewater treatment, the high-viscosity pulp from the crosslinking reactor can be diluted from more than 30 wt. % up to 10 wt. % or less solids content (using process water or acidic aqueous solution from the plant). The dilute suspension was pressed to a high consistency, releasing a filtrate containing residual alkali, cross-linking agent, etc. The alkali in the leachate can be reused in the pulping and bleaching process, and any organic chemicals in the leachate can also be degraded during the reuse process. The pressed pulp was re-diluted with an aqueous acid solution to a low pH in order to remove metals (Ca, Fe, Cu, Mn, Mg, etc.) before being sent for storage. This material has been used to produce rolls or bales of pulp with possible pH adjustment at the manufacturing stage, for example in a headbox (the pH value in the headbox can be, for example, from 4 to 8).

Example 8

Methylcellulose from high viscosity cellulose pulp

The cellulose mass (CELL) was ground into powder and suspended in diethyl ether (DEE) and an aqueous solution of 50 wt. was added. % NaOH. After alkalinization at room temperature, methyl chloride (MeCl) was added to the reactor and the temperature was increased to 85°C. The reaction time was 2 hours at this temperature. After cooling, the mixture was vacuum filtered, neutralized, and washed four times with hot water. In addition, hydroxypropyl methylcellulose (HPMC) was obtained by adding propylene oxide (PO) (Table 5).

To determine DS and the distribution of substituents in the anhydroglucose unit (AGU) of the cellulose derivative, samples were hydrolyzed with trifluoroacetic acid, dissolved in D ₂ O and analyzed by high-resolution liquid-phase ¹³ C NMR. See Table 5. Measurements were carried out at a frequency of 100 MHz in a Varian 400 MHz spectrometer using a quantitative method without using the nuclear Overhauser effect (see the work “Study of cellulose and cellulose derivatives in solution using high-resolution ¹³ C NMR spectroscopy”, I. Nehls, W. Wagenknecht, V. Philipp, D. Stscherbina, Prog. Polym. Sci., 1994, 19, 29-78).

The viscosity of the aqueous solution is 2 wt. % was measured using a rotational viscometer (VT550, Haake) with a conical cylinder (MV-DIN) at 20°C. Shear viscosity was determined at a shear rate of 2.55 s ^-1 .

Example 9

Viscosity variation coefficient CMC

The present invention provides methods described herein for producing pulps suitable for use in producing CMC having low coefficients of variation (COV) viscosity compared to conventionally available CMC.

The preparation and characteristics of Comparative Kraft Pulp B are described in Experimental Example 13 and Table 12 of US Pat. No. 9,771,687, which is incorporated herein by reference in its entirety. The preparation and characteristics of comparative kraft pulp A are described in Experimental Example 8 and Table 8 of US Pat. No. 9,771,687.

The coefficient of variation in CMC viscosity from Kraft Pulp A and Kraft Pulp B samples is 38%.

Using the equipment and conditions that are detailed herein for Sample 2C, multiple batches of crosslinked pulp were produced and the resulting CMC had a COV of 20 to 36% COV. See Table 6B. In this regard, crosslinking at a higher consistency provides a more homogeneous reaction environment, and accordingly the COV of the CMC viscosity is significantly lower.

In addition, using the equipment that is described in detail herein with respect to samples 2A and 2B (except that NaOH and cross-linking agent are 2 wt.% and 3.5 wt.% pulp, respectively), were obtained several batches of crosslinked pulp, and the resulting CMC still had a reduced COV of 10% to 12%. See Table 6C.

Example 10

Water-holding capacity of cellulose pulps according to the present invention

Due to technological optimization, the cross-linked cellulose pulp had an increased cross-link density and a reduced water-holding capacity.

Example 11

Hemicellulose content in cellulose masses according to the present invention

The present disclosure demonstrates the hemicellulose content of pulps produced using the methods of the present invention.

Crosslinked pulps and CMC were prepared as described in detail herein with respect to Sample 2A in Example 1.

HPLC was used to detect monomeric sugars in hydrolyzed cellulose pulp and ether. Basic sugars such as glucose, xylose and mannose can be detected and the corresponding glucan, xylan and mannan contents can be calculated. Due to the formation of derivatives, the weight percentage of sugar in the ether is less than its content in the pulp. The xylan content is calculated as a percentage of the total content of glucan, xylan and mannan. Mannan content was calculated as a percentage of mannan from the total content of glucan, xylan and mannan. The percentage of hemicellulose is the sum of xylan and mannan.

As presented in Table 8, the crosslinked pulp samples had a hemicellulose weight percentage ranging from 10 wt. % up to 20 wt. %, the CMC obtained from them had a hemicellulose weight percentage of approximately 12 wt. %, and the MS obtained from them had a mass percentage of hemicellulose in the range of 2 wt. % up to 8 wt. %.

Example 12

Coefficient of variation of the content of alkali metal ions in cellulose masses according to the present invention

During crosslinking, the pulps described herein have a high consistency. Accordingly, the alkali metal ions dispersed therein, such as sodium ions, are more evenly distributed due to improved mixing methods compared to cellulose pulps traditionally cross-linked with lower consistency and poorer mixing quality. In the present example, the sodium source is NaOH, with which the crosslinking agent and crosslinking pulp are mixed.

The coefficient of variation of sodium ion concentration is a measure of the efficiency of mixing.

As presented below in Table 9, pulps produced using the methods of the present invention have a low coefficient of variation in sodium ion concentration, for example, less than 5. Samples of wet pulp were removed from the crosslinking reactor and dried for metal content analysis.

Example 13

Mixed pulps

Mixed pulps containing pulps according to the present invention were prepared by mixing crosslinked pulp according to the present invention and non-crosslinked pulp, here NB416.

As presented in Table 10 below, the blended pulps exhibited a higher angle and a higher content of fibers undissolved in a solvent such as CuEn. In addition, such blended pulps exhibited higher percentages of crimp as well as fracture.

Example 14

Repeated injection of crosslinker

The pulp produced using the methods discussed in detail herein with respect to Sample 2A (treated with 5 wt.% crosslinker) was re-crosslinked using the full amount of crosslinker, ranging from 15 to 20 wt. %. As presented in Table 11, said crosslinked pulps (2E, 2F) exhibited even higher viscosity and an R18 value greater than 94%.

Research methods and reductions

The terms "about" and "approximately" mean plus or minus 5% of the stated value.

Ash content: determined by the TAPPI T 211 cm-07 method.

ASTM: American Society for Testing and Materials.

CMC: carboxymethylcellulose.

CLP: Cotton lint pulp.

Coefficient of Variation (COV): Defined as the ratio of the standard deviation to the mean.

Consistency: The consistency (C) of the pulp is determined by dividing the dry weight ( _Wd ) of the sample by the total weight ( _Wt ) of the sample and is expressed as a percentage. The consistency can be expressed as C=(W _d /W _t ) × 100. The consistency can be measured by the TAPPI/ANSI T 240 cm-12 method.

Crystallinity index: determined by the appropriate method described in Lionetto et al., “Observation of wood degradation during weathering by cellulose crystallinity,” Materials, 5, 1910-1922 (2012), which is incorporated herein in its entirety by links.

Solubility in CuEn: solubility in copper-ethylenediamine complex under ASTM-D1795-96 method conditions.

Torsion Ratio: Determined by the appropriate method described in US Pat. No. 6,685,856, which is incorporated herein by reference in its entirety.

Degree of Polymerization: The number of D-glucose monomer units in a cellulose molecule as measured by ASTM-D1795-96. The average degree of polymerization means the average number of D-glucose units per molecule of cellulose polymer in a variety of cellulose polymers.

Degree of Substitution (DS): determined by ASTM D 1439-03 method.

DWP: dissolving wood pulp.

Hemicellulose Content: The sum of mannan and xylan content determined by the method described in Examples 6 and 7 of US Pat. No. 7,541,396, which is incorporated herein by reference in its entirety. The basis of this study is the TAPPI T 249 cm-00 method, which includes analysis using a Dionex ion chromatography column.

HPLC: High Performance Liquid Chromatography.

ISO: International Organization for Standardization.

Fracture: determined using a ValmetFS5 fiber image analyzer.

Break angle: determined using a Valmet FS5 fiber image analyzer.

Permanganate number: determined by ISO 302:2004 method.

MCA: monochloroacetic acid

Oven Dried (OD): Dried to a moisture content of less than or equal to 7% by weight.

R18: measured by TAPPI T 235 cm-00 method.

Resultant CMC Viscosity: means the viscosity of a 0.5% resulting CMC solution as determined by the resulting CMC test method described herein.

TAPPI: Technical Association of the Pulp and Paper Industry.

Transition metal content: determined by EPA method SW-856 3050, 200.8.

EPA: US Environmental Protection Agency.

Water holding capacity (WRV): determined by TAPPI T UM256M method (2011).

While exemplary embodiments have been presented and described, it should be understood that various changes may be made thereto without departing from the spirit or scope of the present invention.

Claims (13)

1. Cellulose mass for the production of products based on cellulose ethers, wherein the cellulose mass has: water holding capacity of WRV in the range from 0.8 g/g to less than 1.0 g/g, determined by the TAPPI T UM256M method; And pulp R18 value of more than 89% measured by TAPPI T 235 cm-00 method, wherein the crosslinked cellulose fibers comprise a glycidyl ether crosslinker containing two or more glycidyl groups, wherein the ratio of crosslinker to cellulose pulp is at least 2:100, and the weight average molecular weight is from 174 to 500 kDa, and wherein the cellulose the mass is a sulfate cellulose mass. 2. The pulp according to claim 1, wherein the pulp contains hemicellulose in an amount of approximately 6 wt. % or more on a dry weight basis. 3. The pulp of claim 1, wherein the R18 value of the pulp is in the range of 93% to about 99.9%. 4. The pulp according to claim 1, wherein the pulp has a water retention value (WRV) of more than 0.8 g/g. 5. Pulp mass according to paragraphs. 1-4, wherein the pulp contains hemicellulose in the range of about 6 wt. % based on dry weight to approximately 30 wt. % in terms of dry weight. 6. Mixed cellulose mass for the production of products based on cellulose ethers, containing: the first cellulose mass according to any one of paragraphs. 1-4, having a first fiber fracture value; And a second pulp having a second fiber break value different from the first fiber break value. 7. The mixed pulp according to claim 6, wherein the first pulp has a first pulp R18 value, and the second pulp has a second pulp R18 value different from the first pulp R18 value, wherein R18 is measured by the TAPPI T 235 cm method -00. 8. The mixed pulp of claim 6, wherein the first pulp is partially soluble in the copper-ethylenediamine (CuEn) complex solution, optionally wherein the first pulp is insoluble in the CuEn solution.