BR102014007650A2 - method for producing fibrous carboxylated cellulose, and fibrous carboxylated mercerized cellulose - Google Patents

Abstract

method for producing fibrous carboxylated cellulose, and fibrous carboxylated mercerized cellulose. carboxylated mercerized cellulose fiber having at least 12 meq / 100 g of carboxyl substitution at the c-6 position of the anhydroglucose units, which includes at least 20% cellulose ii, may be produced by catalytically carboxylating the mercerized cellulose fiber to at least two catalytic carboxylation stages in a continuous series where ph is adjusted and a primary oxoammonium salt catalyst (or precursor thereof) and secondary oxidant is added at the beginning of each stage. optionally, carboxylated mercerized cellulose may be made substantially free of aldehyde groups by a stabilizing step following the final carboxylation stage, wherein the aldehyde groups present in the fiber are converted to the carboxyl groups.

Description

“METHOD FOR PRODUCING FIBER CARBOXYLATE CELLULOSE, AND FIBER CARBOXYLATE MERCHANT CELLULOSIS” TECHNICAL FIELD

This description relates to the carboxylation of cellulose, and in particular to stable preparation methods, multistage catalytic carboxylation-mercerized and carboxylated fibrous cellulose, and compositions produced in this manner.

GROUNDS

In a carboxylar cellulose fiber technique, bleached cellulose wood pulp fiber is carboxylated in an aqueous slurry or suspension by the addition of a primary oxidant consisting of a cyclic nitroxide that needs any replaceable hydrogen atoms. at each of the carbon atoms adjacent to the nitrogen nitroxide. Nitroxides having both five- and six-membered rings were found to be satisfactory. Both five- and six-membered rings may have one methylene group or another heterocyclic atom (e.g., nitrogen or oxygen) at position 4 on the ring and both rings may have substituent groups at this location.

A nitride catalyst added to the reaction medium is rapidly converted to the oxoammonium salt (primary oxidant) by a secondary oxidant such as chlorine dioxide. The oxoammonium ion then binds to a primary hydroxyl group or a hydrated C-6 aldehyde hydroxyl group of a cellulose anhydroglucose unit in a cellulose fiber. In a reaction mechanism of the proposed literature, a hydroxide ion then summarizes a proton, thereby breaking a carbon-hydrogen bond at position 6 of the oxidizing anhydroglucose unit. A hydroxylamine form molecule of nitroxide is generated by forming each aldehyde group from a primary alcohol group or forming each carboxyl group from a hydrated aldehyde group. The hydroxylamine form must then be converted to the nitroxide form by a simple electron transfer to a chlorine dioxide molecule. The nitroxide form of the catalyst must then be converted (oxidized) to the oxoammonium salt form (active catalyst and primary oxidant) by a simple electron transfer to chlorine dioxide. In each case the chlorine dioxide is reduced to the chlorite ion.

Nitroxides may be formed in situ by oxidation of the respective hydroxylamines or amines. Oxoammonium salts of nitroxides are generated by the oxidation of nitroxides in situ by the secondary oxidant. The oxoammonium salt of nitroxide is the primary oxidant as well as the active catalyst for cellulose carboxylation. Oxoammonium salts are generally unstable and should be generated in situ from more stable hydroxylamine or amine nitroxide precursors. Nitroxide is converted to an oxoammonium salt, then reduced to a hydroxylamine during cellulose carboxylation reactions. The oxoammonium salt is continuously regenerated by the presence of a secondary oxidant such as chlorine dioxide. In general, since nitroxide is not irreversibly consumed in the oxidation reaction, only a small amount is required. Instead, during the course of the reaction, this is the secondary oxidant that will nullify.

In cellulose carboxylation processes, elements of importance include the length of the reaction time to provide the required carboxylation and the amount of retention storage capacity in the catalytic carboxylation reactor required for that reaction time. A longer reaction time requires more retention storage capacity in the catalytic carboxylation reactor. Other elements of interest include reagent concentrations (eg catalyst, secondary oxidant and so on), optimal reaction conditions (eg pH and temperature) and so on.

If the level of carboxyl added from 2 to 12 milliequivalents (meq) per 100 g of kiln-dried cellulose fiber (OD) is desired, a simple catalytic reaction with short reaction time and minimum retention storage capacity is in general sufficient. However, for many applications of carboxylated fibrous cellulose, high carboxylation levels, for example 20 meq, 40 meq, 100 meq or even higher meq / 100 g, are preferable.

It was thought that only one addition of primary oxidant or catalyst at the beginning of the reaction should be sufficient to achieve a desired level of carboxylation because regeneration of the primary oxidant should allow it to be reused.

However, as described in copending US Patent Application Serial No. 13 / 604,331, the full disclosure of which is incorporated herein by reference, it has been found that it is more difficult to regenerate the active catalyst (i.e. the oxoammonium salt of hydroxylamine precursor) when the carboxylation reaction continues and it is more difficult for the regenerated catalyst to find reactive sites in the cellulose when the carboxylation reaction continues.

Accordingly, in the aforementioned application, carboxylation methods in which both the primary and secondary oxidants are supplied at intervals are described. In particular, high carboxylation levels of native (i.e. non-mercerized) cellulose fibers were achieved in a continuous rapid flow process using multiple catalytic carboxylation reactors with short reaction times (eg, under 5 minutes) and therefore low retention storage volumes.

A continuing challenge, however, is to provide increased levels of carboxylation in a more cost-effective manner.

SUMMARY

Bleached and mercerized cellulose fibers containing both cellulose I and cellulose II forms and lower crystallinity are more reactive with respect to catalytic carboxylation than native (unmerged) bleached cellulose fibers containing only more crystalline cellulose I It is high in and provides highly carboxylated cellulose fibers (greater than 20 meq / 100 g fibers) containing both cellulose I and cellulose II forms more easily with short reaction times.

The multistage catalytic carboxylation methods of mercerized cellulose fibers and compositions produced in this way are described.

In example methods according to the present disclosure, the mercerized cellulose fibers are carboxylated by catalytic carboxylation in an aqueous alkaline suspension in a continuous series of at least two successive carboxylation stages, carboxylation of the mercerized fibers at the C-position. 6 of the anhydroglucose unit, with each last stage still carboxylating the fibers from the previous stage. At each stage, the pH is adjusted to about 8 to 11 and fresh amounts of a precursor of an active oxoammonium salt catalyst and a secondary oxidant adapted to generate sufficient active catalyst to effect carboxylation are added. The precursor is selected from the group consisting of heterocyclic nitroxides in which the carbon atoms adjacent to nitrogen nitroxide need hydrogen substitution, its corresponding amines and hydroxylamines and mixtures thereof and is stable under aqueous alkaline conditions. In some methods, subsequent to the last stage of catalytic carboxylation, mercerized carboxylated fibers are stabilized by treating the fibers with a stabilizing agent under conditions adapted to convert the aldehyde groups present in the fibers to the carboxyl groups, such as in a stabilizing tower under acid conditions at appropriate times and temperatures to achieve stabilization.

Example compositions according to the present disclosure include stable, fibrous, carboxylated, mercerized cellulose having at least 12 meq / 100 g of carboxyl substitution, wherein the carboxyl groups are located at the C-6 position of the units. of anhydroglucose. In some compositions, mercerized cellulose includes at least 20% cellulose II. In some compositions, mercerized cellulose has at least 40 meq / 100 g or at least 80 meq / 100 g of carboxyl substitution. In some compositions, mercerized cellulose is substantially free of aldehyde groups.

The concepts, features, methods and component configurations briefly described above are clarified with reference to the accompanying drawings and the detailed description below.

BRIEF DESCRIPTION OF DRAWINGS

[00016] FIG. 1 is a partially schematic diagram of an example four-stage carboxylation system suitable for the embodiments and producing compositions according to the present disclosure.

DETAILED DESCRIPTION

The methods of the examples according to the present disclosure achieve high levels of carboxylation (18 to 100 or higher meq / 100 g) of cellulose fiber in the form of bleached and mercerized cellulose wood pulp fiber in a fast flow continuous process using multiple catalytic carboxylation reactors with short reaction times (eg under 5 minutes) and therefore low retention storage volumes.

Various methods of multi-stage catalytic carboxylation of native cellulose fibers are described in the aforementioned copending application, including methods using native cellulose fiber as a starting material, TIME and / or TAA-EGK-NO as the catalyst is chlorine dioxide as a secondary oxidant. The carboxylation rate, however, tends to decrease the higher levels of catalytic oxidation of C-6 hydroxyl groups which occurs, for example, above about 40 meq / 100 g. Without being bound by theory, it is thought that increased reaction times at later carboxylation stages are attributable, at least in part, to a decrease in readily accessible oxidation sites. In particular, carboxylation is thought to occur initially, primarily on the fiber surface, with the active catalyst which then accesses the microfibrils throughout the cellulose fiber wall.

However, it has been found that the mercerization of native cellulose fibers produces a starting material that is more reactive in a continuous catalytic carboxylation process with multiple catalytic stages compared to a starting material composed only of cellulose fibers. native cellulose. Higher reactivity of at least partially mercerized native cellulose fibers (e.g., fibers consisting of more than about 20% cellulose II) results in higher carboxylation rates in catalytic reactors with a retention time less than about 5 minutes.

Cellulose is biosynthesized into a stable meta form, cellulose I, which consists of crystalline microfibrils and amorphous domains. As such, native cellulose consists entirely of cellulose I, which may be made to undergo an irreversible transition to a more thermodynamically stable form, cellulose II, as a result of a chemical process referred to as mercerization. Mercerization requires treatment of the cellulose with a mercerizing agent, such as an aqueous alkaline metal hydroxide solution of sufficient concentration (e.g., aqueous NaOH having a concentration of at least 11% by weight) to perform intracrystalline dilation, followed by recovery, such as by removing or neutralizing the mercerizing agent and washing the mercerized fiber. Variables in the mercerization process (e.g., alkaline concentration, temperature, treatment time, and so forth) can be controlled to produce partially mercerized fiber, i.e. fiber consisting of both cellulose I and cellulose II. Here, mercerization is also referred to as "alkalization," and indicates that at least some of the form of cellulose I has been converted to cellulose II. In other words, "mercerized" is used herein to refer to native cellulose that has been at least partially converted to cellulose II.

Native cellulose pulp fibers below a consistency of about 4% at sodium hydroxide concentrations of about 11 to 25% yields of partially mercerized cellulose pulp fibers which can be catalytically catalyzed have been found. oxidized in a continuous multistage process for the production of partially mercerized and highly carboxylated cellulose fibers. Without being bound by theory, it is thought that the increased reactivity of partially mercerized native cellulose fibers is at least in part attributable to the reduced fiber crystallinity (compared to native cellulose fibers consisting of cellulose I).

Accordingly, the methods according to the present disclosure provide additional carboxyl groups to the targeted and mercerized cellulose wood pulp fiber to provide a carboxylated cellulose wood pulp fiber. For example, in some methods, northern bleached softwood kraft paper pulp (NBSK) which has been pre-mercerized, such as NBSK which has been treated with a suitable mercerizing agent, is used as a starting material. In some methods, pre-mercerized southern softwood kraft paper pulp (SBSK) is used. Bleached cellulose wood pulp fibers typically have a carboxyl content of 5 or below meq / 100 g. As noted above, some uses of carboxylated cellulose wood pulp fiber require higher levels of carboxylation. Accordingly, such methods may be used to provide such high carboxylation levels. In one embodiment the process provides a mercerized cellulose wood pulp fiber that has a total carboxyl content of up to 150 meq / 100 g. In another embodiment the process provides a mercerized cellulose wood pulp fiber having a carboxyl content of up to 100 meq / 100 g. In another embodiment the process provides a mercerized cellulose wood pulp fiber that has a total carboxyl content of up to 70 meq / 100 g. In another embodiment the process provides a mercerized cellulose wood pulp fiber that has a total carboxyl content of up to 50 meq / 100 g. In another embodiment the mercerized cellulose wood pulp fiber has a total carboxyl content of up to 40 meq / 100 g. In another embodiment the mercerized cellulose wood pulp fiber has a total carboxyl content of 25 to 30 meq / 100 g. . Wood for wood pulp fibers can be any softwood or hardwood, including pine, spruce, larch, Douglas pine, pine, hemlock, cedar, redwood, aspen, American linden, beech , birch, canada, latex, maple, ash, chestnut, elm, eucalyptus, mixtures of these and so on. The wood may be pulped by any standard pulping process such as kraft paper or sulfite. The wood pulp fiber can then be bleached by any standard bleaching process.

In the methods according to the present disclosure, the starting material is at least partially mercerized cellulose fiber, such as fiber consisting of at least about 20% cellulose II. The starting material in such methods may be obtained as partially mercerized cellulose pulp fiber having a desired proportion of cellulose II, or may be produced by means of the alkalization process performed on the natural cellulose pulp fiber.

Although in general wood for wood pulp fibers may be as indicated above and any mercerizing agents in any suitable mercerizing procedure may be used, it has been observed that alkalization with natural NBSK cellulose fibers below of about 4% consistency in aqueous sodium hydroxide concentrations of 14-18% at 50 ° C or greater over 15-30 minutes producing partially mercerized pulps (for example with at least about 20% cellulose II) faster reactivity towards catalytic carboxylation. Achieving alkalization at lower temperatures generally requires longer storage times to achieve equivalent mercerization levels. For example, alkalization at 9-18% sodium hydroxide concentrations below about 40 ° C requires about 10-12 hours to obtain partially mercerized pulps exhibiting similarly increased reactivity.

In such methods, the targeted mercerized cellulose wood pulp fiber is carboxylated by means of the multi-stage catalytic carboxylation. This process is generally effected by first oxidizing the mercerized fiber in an aqueous slurry or suspension by the addition of a primary oxidant comprising a cyclic nitroxide that requires any hydrogen substitution of the carbon atoms adjacent to the nitrogen nitroxide. Nitroxides having both five- and six-membered rings were found to be satisfactory. Both five- and six-membered rings may have a methylene group or other heterocyclic atom selected from nitrogen or oxygen in the fourth position on the ring and both rings may have substituent groups at this location. It is important that the chosen nitroxide be stable in an alkaline environment in the range of about pH 8-11.

A broad group of nitroxide compounds have been found to be suitable. Examples include 2,2,6,6-tetramethylpiperidinyl-1-oxide (TEMPO) free radical as well as 2,2,2'2 ', 6,6,6,6,6'-octamethyl-4 free di-radical , 4'-bipiperidinyl-1,1'-dioxy (BI-TEMPO, a product bound in a mirror image connection to TIME) and 4-position substituted compounds of TIME, such as free radical 2.2.6.6-tetramethyl- 4-hydroxypiperidinyl-1-oxide, free radical 2,2,6,6-tetramethyl-4-methoxypiperidinyl-1-oxide, free radical 2,2,6,6-tetramethyl-4-benzyloxypiperidinyl-1-oxide, free radical 2,2,6,6-tetramethyl-4-aminopiperidinyl-1-oxide, free radical 2,2,6,6-tetramethyl-4-acetylaminopiperidinyl-1-oxide and free radical 2,2,6,6-tetramethyl-4-piperidone-2 1-oxy. Additional examples include 3.3.5.5-tetramethylmorpholine-1-oxide free radical (TEMMO), a nitroxide with a second 4-position ring heteroatom (relative to the nitrogen atom), 3,4-dehydro-2,2 free radical , 6,6-Tetramethyl-piperidinyl-1-oxide, a nitroxide that does not have a saturated ring and so on. Additionally, 4-position double substituted six-membered ring compounds are suitable and may be preferred in some cases because of their relative ease of synthesis and lower cost. An example of such a compound is triacetoamine ethylene glycol ketal nitroxide (TAA-EGK-NO), 2,2,6,6-tetramethyl-4-piperidone-1-oxide free radical cyclic ethylene; other examples of such compounds include ethylene, propylene and free radical cyclic neopentyl acetal 2,2,6,6-tetramethyl-4-piperidone-1-oxy. An example of suitable five-membered compounds is 2,2,5,5-tetramethyl-pyrrolidinyl-1-oxy free radical.

The compounds named above should only be considered as examples of many representative of nitroxides suitable for use.

Nitroxides suitable for use in the methods described herein may be formed in situ by oxidation of the corresponding hydroxylamines and / or amines representative of any of the free radical nitroxide products. The active form of the catalyst, or primary oxidant, in such catalytic oxidation reactions are oxoammonium (also spelled "oxammonium") nitroxide salts, which are generated from nitroxides (and, as noted above, nitroxides are generated from hydroxylamine / amines), generally by a secondary oxidant such as chlorine dioxide. In general, nitroxide is not irreversibly consumed in the oxidation reaction, and therefore only a minor amount is required. Rather, it is the secondary oxidant that is depleted during the course of the reaction. In one embodiment, the amount of nitroxide required is in the range of about 0.005% to 1.0% based on the amount of cellulose present. In another embodiment, the amount of nitroxide required is about 0.02 to 0.25%. Nitroxide is known to preferentially oxidize the C-6 located primary hydroxyl of the cellulose anhydroglucose moiety.

[00030] In the experiments discussed here, no TIME or TAA-EGK-NO is used as nitroxide.

Nitroxide may first be premixed with a portion of an aqueous chlorine dioxide to form a homogeneous solution prior to addition of the mercerized fiber slurry. Optionally, ultrasonic agitation may be used, for example, to increase the dissolution rate. The carboxylation reaction may be allowed to continue for a period of about 10 seconds to 5 minutes. In one embodiment the temperature is from 0 to 75 ° C. In other embodiments the temperature is 0 ° to 50 ° C. In another embodiment the temperature is room temperature. The reaction temperature will depend on some concurrent considerations. For example, a higher temperature will increase the reaction rate but will reduce the pulp D.P. and may also degrade chlorine dioxide at high alkaline pH.

In general, mercerize fiber slurry passes through various catalytic carboxylation reactors, with a fresh addition of catalyst, secondary oxidizing agent and, if necessary, a pH-adjusting chemical (typically a alkaline buffer) at the inlet of each catalytic carboxylation reactor. The active catalyst is oxoammonium generated from the hindered cyclic amine compound described above. Nitroxide can be obtained by oxidation of the corresponding hydroxylamine or amine. The time at each stage and the size of each stage will depend on the speed of reaction within the stage. The number of stages will depend on the amount of carboxylation required. Based on the experiments, it is estimated that approximately one catalytic carboxylation reactor is required for each 10 meq / 100 g addition of the required carboxyl groups in the mercerized cellulose fibers.

In catalytic carboxylation of the multistage methods of the present disclosure, chlorine dioxide is typically as the secondary oxidant, but sodium hypochlorite or sodium bromide, or combinations thereof, may be used alternatively and still other alternatives include sodium salts. and Caro acid potassium combined with sodium bromide, or sodium peracetic acid or potassium salts combined with sodium bromide, and so on. In the experiments discussed above, chlorine dioxide, a mixture of chlorine dioxide and chlorine, or a mixture of sodium hypochlorite and sodium bromide, are used as the secondary oxidizing agent. The buffer solution is typically a sodium hydroxide solution, but sodium bicarbonate or carbonate, or mixtures thereof, may be used by pH adjustment and control within a narrow pH range. In one embodiment, the pH range is 8-11. In another embodiment, the pEi range is 9.25-10.5.

In practice, the catalytic carboxylation reactor series may be a main tube or a tube series with valve addition tubes that bring chlorine dioxide, catalyst and sodium hydroxide solution to the tubes. Valves in the filler tubes can be used to change the addition of carboxylation chemicals to a catalytic carboxylation reactor to a required carboxylation amount in the catalytic carboxylation reactor. Time spent on each catalytic carboxylation reactor or section may be from 10 seconds to 5 minutes as required. In one embodiment, the pH is adjusted to 8-10 by the addition of a base chemical prior to the near catalytic stage. In another embodiment, the pH is adjusted to 8-9 by the addition of the base chemical.

Following catalytic carboxylation, the fiber is treated with a stabilizing agent adapted to convert substituent groups, such as aldehydes and ketones, to hydroxyl or carboxyl groups. Unstabilized oxidized nitroxide pulps may exhibit objectionably color reversal and are self-cross-drying, thus reducing their ability to redisperse.

Suitable stabilizing agents include reducing agent or one or more additional oxidizing agents. Exemplary reducing agents include alkali metal borohydrides. Sodium borohydride (NaBH4) is favorable from the point of view of cost and availability. However, other borohydrides such as LiBH 3 or alkali metal cyanoborohydrides such as NaBH 3 CN are also suitable. Mixtures are also suitable, such as NaBEL mixed with LiCl to form a reducing agent. When NaBH4 is used for reduction, it is usually in an amount between about 0.1 and 100 g / l. A preferred amount should be about 0.25 to 5.0 g / l and a more preferred amount of about 0.5 to 2.0 g / l. based on the cellulose content, the amount of reducing agent should be in the range of from about 0.1% to 4.0% by weight, preferably from about 1.0 to 3.0%. The reduction may be performed at room temperature or higher for a time between 10 minutes and 10 hours, preferably from about 30 minutes to 2 hours.

Suitable oxidizing agents used as stabilizers include alkali metal chlorides, such as sodium chloride, which may be favorable because of the comparatively lower cost. Other compounds that may serve well as oxidants include permanganates, chromic acid, bromine and silver oxide. A combination of chlorine dioxide and hydrogen peroxide is also a suitable oxideite, as when used in the designated pH range for sodium chloride. Oxidation using sodium chloride may be carried out at a pH in the pH range from about 1.5 to 5.0, preferably from 2.0 to 4.0, at temperatures between about 25 ° and 90 ° C. periods of about 5 minutes to 50 hours, preferably about 10 minutes to 2 hours. One factor that may favor the use of an oxidizing agent as opposed to a reducing agent is the desired end resulting from a stabilizing step. For example, when an oxidizing agent is used, the aldehyde groups in the oxidized cellulose are converted to additional carboxyl groups, thereby resulting in a more highly carboxylated product. Such stabilizing oxidants are sometimes referred to as "tertiary oxidants" to distinguish them from the oxammonium salt of secondary oxidants of primary and secondary chlorine dioxide. Such "tertiary oxidants" are used in a molar ratio of about 1.0 to 15 times the assumed aldehyde content of oxidized cellulose, preferably about 5 to 10 times. In a more convenient way of measuring the required tertiary oxidant, the use of preferred sodium chloride should be within about 0.001 g of sodium chloride / g fiber at 0.2 g / g, preferably 0.01 to 0. 0.9 g / g, the chlorite being calculated on a 100% active material basis.

In practice, the oxidized mercerized fiber slurry exiting the late catalytic carboxylation reactor can subsequently enter a single stabilization tower by an acid stabilization step, wherein any of the remaining aldehyde groups in the pulp fibers of oxidized cellulose are converted to carboxyl groups. At the end of the stabilization stage, the fiber slurry is neutralized, washed, water removed and dried.

Optionally, stabilization may be shifted, for example to obtain the carboxyl and aldehyde functional group containing the partially mercerized cellulose fiber.

After stabilization is (optionally) completed, the cellulose is again washed and may be dried if desired. Alternatively, the carboxyl substituents may be converted to salt forms other than sodium; for example potassium, calcium, magnesium or ammonium.

In the experiments using the methods discussed above, catalytic carboxylation of water mercerized cellulose fibers using multiple catalytic carboxylation reactors was used to obtain different levels of carboxylation per 100 g in dried fibers (OD). The catalytic processes used in the hindered nitroxides, and / or their precursor amines or hydroxylamines, to obtain the oxidized oxoammonium salt as the primary catalyst. The secondary catalyst used was chlorine dioxide. In catalytic oxidation processes, the appropriate catalyst levels and required amount of chlorine dioxide are mixed with already made alkaline cellulose fibers. Cellulose fibers may be made alkaline using sodium (or potassium) hydroxide containing buffer solutions containing carbonate or bicarbonate. One embodiment contains the hydroxide mixtures containing the aqueous bases, carbonate and bicarbonate.

[00042] A partially schematic diagram of an embodiment of a carboxylation system in the form of an installation is shown in Fig. 1. Catalytic carboxylation reactors, or stages, are shown as circled because of the oxidation unit. shown in Fig. 1 is, in this embodiment, incorporated into an existing bleach facility (generally indicated at 10) and space is a consideration. However, other configurations of various reactors, connections, and conduits via this and other unit components may take shape and shape. As noted above, the stages should be part of a simple tube in other embodiments consistent with this description.

[00043] The last four stages of bleach installation 10 are shown. These include a first chlorine dioxide unit 12, an extraction stage 14, a second chlorine dioxide unit 16 and a second extraction stage 18. In the acid chlorine dioxide stages 12 and 16, chlorine dioxide reacts with the lignin and hemicellulose in a wood pulp slurry to form a reaction product and in the alkaline extraction stages 14 and 18 the reaction product is removed by treatment with sodium hydroxide. Pulp slurry from extraction stage 18 flows into a scrubber 20 in which soluble reaction products are removed from the pulp. Mercerization of the cellulose fibers may be performed from the extraction stages 14, 18, or at an additional stage not shown in Fig. 1, such as an additional extraction stage / unit or any suitable mercerization stage / unit located upstream or downstream. downstream of washer 20, it can be used for mercerizing the cellulose fibers prior to catalytic carboxylation. Depending on the mercerization method, additional structural components such as reactors, batches and so on may be incorporated into the configuration shown in Fig. 1. Optionally, in some embodiments, mercerized cellulose fibers suitable for catalytic carboxylation are obtained by other methods, by separate systems, and so on.

The slurry of the mercerized pulp then enters the catalytic carboxylation reactors in which the pulp fiber is treated. Four catalytic carboxylation reactors or stages are shown, but here may be as many catalytic carboxylation reactors or stages as are required to obtain the amount of carboxylation required. In general, the volume of each catalytic reactor may be determined by the mass flow rate of the pulp slurry and the retention time required by the complete consumption of the added secondary oxidant. According to the methods of the present disclosure, retention times of less than five minutes are suitable for each catalytic reactor. As noted in Fig. 1, for example "1st Stage," "2nd Stage," etc., the catalytic carboxylation reactors or stages are in series and the pulp slurry flows through it from the first catalytic carboxylation stage to the first stage. catalytic carboxylation solution and then to add processing.

Sodium hydroxide or other base is supplied from the base 22 supply to adjust the pH. Catalyst from catalyst supply 24 and chlorine dioxide from secondary oxidant supply 26 are supplied to each of the catalytic carboxylation reactors 28A, 28B, 28C and 28D at the beginning of each stage. The base is supplied at 30A, 30B, 30C and 30D at the entrance to the catalytic carboxylation reactors 28A, 28B, 28C and 28D, respectively. The primary oxidant, catalyst and secondary oxidant (e.g. chlorine dioxide) are shown to be supplied at 32A, 32B, 32C and 32D at the entrance to the catalytic carboxylation reactors 28A, 28B, 28C and 28D respectively. These can be supplied together as shown or separately from each oxidation stage input.

There is a value between each of the suppliers and the catalytic carboxylation reactors - valve 34 for base 22 supply, valve 36 for catalyst supply 24 and valve 38 for secondary oxidant supply 26 and valves 40A, 40B , 40C and 40D at the inlet of each of the catalytic carboxylation reactors and valve 42 after the catalytic carboxylation reactor.

The carboxylated fibers are then stabilized in a stabilization towers 44. A chlorine dioxide tower is shown being used by the stabilization towers. Sulfuric acid from the supply of sulfuric acid 46 and hydrogen peroxide from the hydrogen peroxide source 48 is supplied to the oxidized pulp fibers before the fibers entering the upstream section 50 of the stabilizing towers 40. Again, there is a valve 52 at the acid supply outlet 46 and a valve 54 at the peroxide supply outlet 48. The carboxylated fibers are then neutralized in the washer 56 where the fibers are washed with a sodium hydroxide solution and subjected to water removal. The mercerized and carboxylated cellulose fibers may be used in wet or dry form as required and may thus be converted to further downstream system components as desired.

The following examples summarize representative experiments of mercerized cellulose pulp fibers according to the methods and concepts discussed above.

Alkalization Example 1: Alkalization of the cellulose pulp fiber at 35 ° C for 30 minutes.

Never dried NBSK cellulose pulp (50.0 g on dry basis) was placed in a 9-18% aqueous solution of sodium hydroxide. Pulp alkalization pulp was made at 3% of fiber consistency. The fiber slurry was kept at 35 ° C with slow mixing for 30 minutes. The fiber slurry was then filtered. The fiber mass was retransformed into slurry in 1.5 liters of deionized water is filtered. The above fiber wash procedure was repeated three times. Alkalization Example 2: Alkalization of the cellulose pulp fiber at 25 ° C for 12 hours.

Never dried NBSK cellulose pulp (50.0 g on dry basis) was placed in a 16% aqueous solution of sodium hydroxide. Pulp alkalization pulp was made at 3% of fiber consistency. The fiber slurry was kept at 25 ° C with slow mixing for 12 hours. The fiber slurry was then filtered. The fiber mass was retransformed into a slurry in 1.5 liters of deionized water and filtered. The above fiber wash procedure was repeated three times.

Alkalization Example 3: Alkalization of; cellulose pulp fiber at 50-70 ° C for 30 minutes.

Never dried NBSK cellulose pulp 50.0 g in the dry base was placed in a 14-18% aqueous solution of sodium hydroxide. Pulp alkalization pulp was made at 3% of fiber consistency. The fiber slurry was kept at 50-70 ° C with slow mixing for 30 minutes. The fiber slurry was then filtered. The fiber mass was retransformed into a slurry in 1.5 liters of deionized water and filtered. The above fiber wash procedure was repeated three times.

The following examples summarize representative catalytic carboxylation experiments using the methods and concepts discussed above.

Example 1 (CBXY-387): Catalytic carboxylation of the mercerized NBSK cellulose pulp fiber using TAA-EGK-NO chlorine dioxide / catalyst, 8 catalytic stages and one stabilization stage.

Catalytic Stage 1 [00054] NBSK pulp fibers mercerized in 14.65% sodium hydroxide solution at 50 ° C for 30 minutes, 50.0 g OD 10% consistency was added 300 ml deionized water containing 8 0.0 g sodium bicarbonate and 2.0 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 32 ° C. The initial pH was 10.17. Pulp consistency 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% CIO 2 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 27 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.49 and the final temperature was 33 ° C. Pulp consistency 5.3%. Water volume 900 ml. Catalyst concentration 0.0775 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.25 g of sodium hydroxide and mixed as well. The initial pH was 10.06 and temperature was 33 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% of the C102 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 29 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.33 and the final temperature was 32 ° C. Pulp consistency 4.5%. Water volume 1050 ml. Catalyst concentration 0.1328 meq / liter.

Catalytic Stage 3 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.10 and temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% of solution C102 containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 25 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.35 and the final temperature was 32 ° C. Pulp consistency 4.0%. Water volume 1200 ml. Catalyst concentration 0.1744 meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.02 and temperature was 34 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml 1.01% CIO 2 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for the depletion of d 10 x. 1 d of chlorine was 29 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.28 and the final temperature was 32 ° C. Pulp consistency 3.6%. Water volume 1350 ml. Catalyst concentration 0.2067 meq / liter.

Catalytic Stage 5 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.11 and temperature was 33 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% of the C102 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 34 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.40 and the final temperature was 32 ° C. Pulp consistency 3.2%. Water volume 1500 ml. Catalyst concentration 0.2025 meq / liter.

Catalytic Stage 6 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.09 and temperature was 29 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% of the C102 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 47 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.50 and the final temperature was 31 ° C. Pulp consistency 2.9%. Water volume 1650 ml. Catalyst concentration 0.2536 meq / liter.

Catalytic Stage 7 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.34 and temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml 1.01% CIO 2 solution containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 70 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.63 and the final temperature was 31 ° C. Pulp consistency 2.7%. Water volume 1800 ml. Catalyst concentration 0.2731 meq / liter.

Catalytic Stage 8 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.41 and temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.01% of solution C102 containing 0.28% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 96 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.64 and the final temperature was 32 ° C. Pulp consistency 2.5%. Water flow 1950 ml. Catalyst concentration 0.2862 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for 12 hours at 25 ° C.

Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium bicarbonate solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salt. Carboxyl determination gives 96.14 meq carboxyl / 100 g of pulp fibers.

Example 2 (CBXY-350): Catalytic carboxylation of mercerized NBSK cellulose pulp fiber using chlorine dioxide / chlorine / TAA-EGK-NO catalyst, 4 catalytic stages and one stabilization stage.

Catalytic Stage 1 [00072] NBSK pulp fibers mercerized in 16% of sodium hydroxide solution at 50 ° C for 30 minutes, 50.0 g 10% consistency OD from above procedure 300 ml of water was added deionized powder containing 8.0 g sodium bicarbonate and 1.75 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 29 ° C. The initial pH was 10.15. Pulp consistency 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 220 ml 0.80% of the CIO2 solution containing 0.24% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 35 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.40 and the final temperature was 30 ° C. Pulp consistency 4.9%. Water volume 970 ml. Catalyst concentration 0.0719 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.14 and temperature was 31 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 220 ml 0.80% solution C102 containing 0.24% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 36 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.25 and the final temperature was 31 ° C. Pulp consistency 4.0%. Water volume 1190 ml. Catalyst concentration 0.1172 meq / liter.

Catalytic Stage 3 The pulp slurry maintained at 28-34 ° C was added 1.70 g of sodium hydroxide and mixed as well. The initial pH was 10.17 and temperature was 31 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 220 ml 0.80% of the CIO2 solution containing 0.24% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 37 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.26 and the final temperature was 31 ° C. Pulp consistency 3.4%. Water volume 1410 ml. Catalyst concentration 0.1484 meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.17 and temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 220 ml 0.80% of the C102 solution containing 0.24% chlorine and mixed with a slurry of pulp. The time taken for chlorine dioxide depletion was 45 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.22 and the final temperature was 31 ° C. Pulp consistency 3.0%. Water flow 1630 ml. Catalyst concentration 0.1712 meq / liter.

Stabilization Stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for 12 hours at 25 ° C.

Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 71.06 meq carboxyl / 100 g of pulp fibers.

Example 3 (CBXY-352): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / chlorine / TAA-EGK-NO catalyst, 3 catalytic stages and a stabilization stage.

Catalytic Stage 1 [00082] NBSK pulp fibers mercerized in 14% sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD 10% consistency of procedure above was added 300 ml ionized water containing 8.0 g sodium bicarbonate and 1.5 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 31 ° C. The initial pH was 10.19. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% CIO 2 solution containing 0.20% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 36 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.43 and the final temperature was 28 ° C. The consistency of pulp 5.0%. Water volume 955 ml. Catalyst concentration 0.0730 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.26 and temperature was 30 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% C102 solution containing 0.20% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 30 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.37 and the final temperature was 31 ° C. The consistency of pulp 4.0%. Water volume 1200 ml. Catalyst concentration 0.1162 meq / liter.

Catalytic Stage 3 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 10.06 and temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% of the C102 solution containing 0.20% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 30 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.18 and the final temperature was 31 ° C. The consistency of pulp 3.4%. Water volume 1405 ml. Catalyst concentration 0.1489 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 50 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 57.94 meq carboxyl / 100 g of pulp fibers.

Example 4 (CBXY-353): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / chlorine / TAA-EGK-NO catalyst, 2 catalytic stages and a stabilization stage.

Catalytic Stage 1 [00090] NBSK pulp fibers mercerized in 14% of sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD 10% of the above procedure consistency was added to 300 ml of ionized water containing 8.0 g sodium bicarbonate and 1.5 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 31 ° C. The initial pH was 10.28. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% of the CIO2 solution containing 0.21% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 21 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.71 and the final temperature was 30 ° C. The consistency of pulp 5.0%. Water volume 955 ml. The catalyst concentration is 0.0730 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 0.75 g of sodium hydroxide and mixed as well. The initial pH was 10.07 and the temperature was 31 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% of the CIO2 solution containing 0.21% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 22 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.46 and the final temperature was 31 ° C. The consistency of pulp 4.0%. Water volume 1200 ml. Catalyst concentration 0.1162 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 50 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 36.18 meq carboxyl / 100 g of pulp fibers.

Example 5 (CBXY-354): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / chlorine / TAA-EGK-NO catalyst, 1 catalytic stage and one stabilization stage.

Catalytic Stage 1 [00096] NBSK pulp fibers mercerized in 14% of sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD 10% of the above procedure consistency was added to 300 ml of ionized water containing 8.0 g sodium bicarbonate and 1.5 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 30 ° C. The initial pH was 10.16. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 205 ml 0.86% of the C102 solution containing 0.21% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 21 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.71 and the final temperature was 30 ° C. The consistency of pulp 5.0%. Water volume 955 ml. Catalyst concentration 0.0730 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 50 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 22.44 meq carboxyl / 100 g of pulp fibers.

Example 6 (CBXY-326): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO catalyst, 2 catalytic stages and a stabilization stage.

Catalytic Stage 1 [000100] NBSK pulp fibers mercerized in 14.75% of sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD of 10% of above procedure consistency was added 300 ml of water ionized solution containing 8.0 g of sodium bicarbonate and 1.5 g of sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 29 ° C. The initial pH was 9.99. The consistency of pulp 6.3%. Water volume 750 ml. - Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 56 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.97 and the final temperature was 29 ° C. The consistency of pulp 5.1%. Water volume 920 ml. Catalyst concentration 0.0758 meq / liter.

Catalytic Stage 2 [000102] The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.09 and temperature was 30 ° C. Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% CIO 2 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 35 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.22 and the final temperature was 29 ° C. The consistency of pulp 4.4%. Water volume 1090 ml. Catalyst concentration 0.1280 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 60 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 30.11 meq carboxyl / 100 g of pulp fibers.

Example 7 (CBXY-300): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO catalyst, 4 catalytic stages and a stabilization stage.

Catalytic Stage 1 [000106] NBSK pulp fibers mercerized in 15.8% sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD 10% consistency was added 300 ml ionized water containing 8 0.0 g sodium bicarbonate and 1.0 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 29 ° C. The initial pH was 9.71. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 160 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 80 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.50 and the final temperature was 28 ° C. The consistency of pulp 5.2%. Water volume 910 ml. Catalyst concentration 0.0766 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.50 g of sodium hydroxide and mixed as well. The initial pH was 9.92 and temperature was 28 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 160 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 45 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.81 and the final temperature was 28 ° C. The consistency of pulp 4.4%. Water volume 1070 ml. Catalyst concentration 0.1304 meq / liter.

Catalytic Stage 3 [000110] The pulp slurry maintained at 28-34 ° C was added 1.5 g of sodium hydroxide and mixed as well. The initial pH was 9.97 and temperature was 28 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 160 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 36 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.02 and the final temperature was 28 ° C. The consistency of pulp 3.9%. Water flow 1230 ml. Catalyst concentration 0.1701meq / liter.

Catalytic Stage 4 The slurry of pulp maintained at 28-34 ° C was added 1.25 g of sodium hydroxide and mixed as well. The initial pH was 9.88 and temperature was 28 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 160 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 47 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.61 and the final temperature was 28 ° C. The consistency of pulp 3.5%. Water volume 1390 ml. Catalyst concentration 0.2007 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour 35 ° C.

Neutralization Stage A. Acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 55.66 meq carboxyl / 100 g of pulp fibers.

Example 8 (CBXY-288): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO catalyst, 4 catalytic stages and a stabilization stage Catalytic stage 1 [000116] NBSK pulp fibers Mercerized in 18% sodium hydroxide solution at 35 ° C for 30 minutes, 50.0 g OD 10% consistency was added 300 ml ionized water containing 10.0 g sodium bicarbonate and 2.0 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 32 ° C. The initial pH was 10.16. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 24 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pEl was 9.52 and the final temperature was 31 ° C. The consistency of pulp 5.3%. Water volume 900 ml. Catalyst concentration will be 0.0775 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.23 and temperature was 31 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 20 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.74 and the final temperature was 31 ° C. The consistency of pulp 4.5%. Water volume 1050 ml. Catalyst concentration 0.1328 meq / liter.

Catalytic Stage 3 The pulp slurry maintained at 28-34 ° C was added 1.25 g of sodium hydroxide and mixed as well. The initial pH was 10.22 and the temperature was 31- ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% of the C102 solution and mixed with the slurry pulp. The time taken for chlorine dioxide depletion was 20 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.73 and the final temperature was 32 ° C. The consistency of pulp 4.0%. Water volume 1200 ml. Catalyst concentration 0.1744 meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.25 g of sodium hydroxide and mixed as well. The initial pH was 10.14 and the temperature was 33 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% CIO2 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 20 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.68 and the final temperature was 32 ° C. The consistency of pulp 3.6%. Water volume 1350 ml. Catalyst concentration 0.2067 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 35 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 46.29 meq carboxyl / 100 g of pulp fibers.

Example 9 (CBXY-290): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO catalyst, 4 catalytic stages and a stabilization stage.

Catalytic Stage 1 NBSK pulp fibers mercerized in 9.4% sodium hydroxide solution at 35 ° C for 30 minutes, 50.0 g OD 10% consistency was added 300 ml ionized water containing 14 0.0 g sodium bicarbonate and 3.0 g sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 31 ° C. The initial pH was 10.08. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% CIO 2 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 25 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.63 and the final temperature was 32 ° C. The consistency of pulp 5.3%. Water volume 900 ml. Catalyst concentration 0.0775 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.0 g of sodium hydroxide and mixed as well. The initial pH was 10.00 and the temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 22 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.56 and the final temperature was 30 ° C. The consistency of pulp 4.5%. Water volume 1050 ml. Catalyst concentration 0.1328 meq / liter.

Catalytic Stage 3 The pulp slurry maintained at 28-34 ° C was added 1.0 g of sodium hydroxide and mixed as well. The initial pH was 9.83 and the temperature was 33 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% solution 002 and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 23 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.45 and the final temperature was 30 ° C. The consistency of pulp 4.0%. Water volume 1200 ml. Catalyst concentration 0.1744meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.00 g of sodium hydroxide and mixed as well. The initial pH was 9.76 and the temperature was 31 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 150 ml of 1.2% CIO2 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 23 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.45 and the final temperature was 30 ° C. The consistency of pulp 3.6%. Water volume 1350 ml. Catalyst concentration 0.2067 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for one hour at 35 ° C. Neutralization Stage A. Acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 46.73 meq carboxyl / 100 g of pulp fibers.

Example 10 (CBXY-312): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO catalyst, 4 catalytic stages and a stabilization stage.

Catalytic Stage 1 [000136] NBSK pulp fibers mercerized in 16% sodium hydroxide solution at 25 ° C for 12 hours, 50.0 g OD 10% consistency was added 300 ml ionized water containing 8.0 g of sodium bicarbonate and 1.25 g of sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 29 ° C. The initial pH was 9.95. The consistency of pulp 6.3%. Water volume 750 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 50 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.93 and the final temperature was 27 ° C. The consistency of pulp 5.1%. Water volume 920 ml. Catalyst concentration 0.0758 meq / liter.

Catalytic Stage 2 The pulp slurry maintained at 28-34 ° C was added 1.5 g of sodium hydroxide and mixed as well. The initial pH was 10.01 and the temperature was 29 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% of the C102 solution and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 38 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.07 and the final temperature was 29 ° C. The consistency of pulp 4.4%. Water volume 1090 ml. Catalyst concentration 0.1280 meq / liter.

Catalytic Stage 3 [000140] The pulp slurry maintained at 28-34 ° C was added 1.5 g of sodium hydroxide and mixed as well. The initial pH was 10.05 and the temperature was 29 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% solution 002 and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 40 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.01 and the final temperature was 29 ° C. The consistency of pulp 3.8%. Water volume 1260 ml. Catalyst concentration 0.1661 meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.25 g of sodium hydroxide and mixed as well. The initial pH was 9.88 and the temperature was 28 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 170 ml of 1.2% solution 002 and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 48 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 8.74 and the final temperature was 29 ° C. The consistency of pulp 3.4%. Water volume 1430 ml. Catalyst concentration 0.1951 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for three hours at 30 ° C. Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 57.76 meq carboxyl / 100 g of pulp fibers.

Example 11 (CBXY-376): Catalytic carboxylation of mercerized NBSK cellulose pulp fibers using sodium hypochloride / sodium bromide / time catalyst, 4 catalytic stages and a stabilization stage.

Catalytic Stage 1 - [000146] NBSK pulp fibers mercerized in 14% sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD 10% consistency was placed in 2400 ml aqueous buffer solution containing 9.0 g of sodium bicarbonate and 7.5 g of sodium carbonate maintained at 50 ° C and pH 9.5-10. Time catalyst 0.04 g, sodium bromide 0.15 g and 50.0 ml of 3.5% sodium hypochloride were added and mixed for 2 minutes Catalytic stage 2 The pulp slurry maintained at pEI 9 5-10 A second addition of the 0.04 g time catalyst, 0.15 g sodium bromide and 50.0 ml of 3.5% sodium hypochloride was performed and mixed for 2 minutes.

Catalytic Stage 3 [000148] The pulp slurry maintained at pH 9.5-10 a third addition of the time catalyst 0.04 g, sodium bromide 0.15 g and 50.0 ml of 3.5% hydrochloride hypochloride. Sodium was held and mixed for 2 minutes.

Catalytic Stage 4 [000149] The pulp slurry maintained at pH 9.5-10 a fourth addition of the time catalyst 0.04 g, sodium bromide 0.15 g and 50.0 ml of 3.5% sodium hypochlorite. Sodium was held and mixed for 2 minutes.

Stabilization Stage The pulp slurry was acidified to pH 2.5-3.5 and kept at 50 ° C. Sodium chloride 12.0g and 5.0ml of 50% hydrogen peroxide was added to the slurry and mixed as well. The slurry was mixed for one hour at 50 ° C.

Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 71.06 meq carboxyl / 100 g of pulp fibers.

Example 12 (CBXY 400): Catalytic carboxylation of mercerized SBSK cellulose pulp fibers using chlorine dioxide / TAA-EGK-NO, 4 catalytic stages and a stabilization stage.

Catalytic Stage 1 [000152] SBSK pulp fibers mercerized in 14.2% of sodium hydroxide solution at 70 ° C for 30 minutes, 50.0 g OD of 10% of above procedure consistency was added 200 ml of water ionized solution containing 8.0 g of sodium bicarbonate and 2.25 g of sodium hydroxide. The pulp slurry was kept at 28-34 ° C. The initial temperature of the pulp slurry was 31 ° C. The initial pH was 10.10. The consistency of pulp 7.1%. Water volume 650 ml.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 215 ml 0.81% of the CIO2 solution containing 0.23% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 28 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.22 and the final temperature was 31 ° C. The consistency of 5.5% pulp. Water volume 865 ml. Catalyst concentration 0.0806 meq / liter.

Catalytic Stage 2.

The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.13 and the temperature was 32 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 215 ml of 0.81% of solution C102 containing 0.23% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 26 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.20 and the final temperature was 32 ° C. The consistency of pulp 4.4%. Water flow 1080 m. Catalyst concentration 0.1291 meq / liter.

Catalytic Stage 3 [000156] The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pH was 10.10 and the temperature was 3 2 o C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 215 ml 0.81% of the CIO2 solution containing 0.23% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 37 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.26 and the final temperature was 31 ° C. The consistency of pulp 3.7%. Water volume 1295 ml. Catalyst concentration 0.0268 meq / liter.

Catalytic Stage 4 The pulp slurry maintained at 28-34 ° C was added 1.75 g of sodium hydroxide and mixed as well. The initial pEI was 10.05 and the temperature was 33 ° C.

Then the TAA-EGK-NO catalyst, 0.015 g was mixed with 215 ml 0.81% solution C102 containing 0.23% chlorine and mixed with the pulp slurry. The time taken for chlorine dioxide depletion was 40 seconds. The yellow color of chlorine dioxide fades indicating depletion. The final pH was 9.02 and the final temperature was 33 ° C. The consistency of pulp 3.2%. Water volume 1510 ml. Catalyst concentration 0.1848 meq / liter.

Stabilization stage The pulp slurry was acidified to pH 2.0-3.0 and kept at 60 ° C. Hydrogen peroxide (50%) 5.0 ml was added to the slurry and mixed as well. The slurry was mixed for 12 hours at 25 ° C.

Neutralization Stage The acid pulp slurry was neutralized and made alkaline at pH 8-9.5 by the addition of 10% of the sodium hydroxide solution with mixing. The pulp slurry was subjected to water removal by filtration under reduced pressure. The pulp was again dispersed in 2 liters of deionized water and filtered again to remove excess salts. Carboxyl determination gives 61.24 meq carboxyl / 100 g of pulp fibers.

Tables 1-3 present the results of representative catalytic carboxylation experiments using the methods and concepts discussed above. Table 1 presents the results of representative experiments in which TAA-EKG-NO is used as the precursor and in which chlorine dioxide is used as the secondary oxidant. Each experiment includes a stabilization step, using one or more of hydrogen peroxide and sulfuric acid as the stabilizing agent. Table 1 includes examples 7-10 presented above.

Table 1

Catalytic carboxylation of C102-bleached and mercerized cellulose fibers using TAA-EGK-NO. _______________________________________ [000163] Table 2 presents the results of representative experiments in which TAA-EKG-NO is used as the precursor and in which a mixture of chlorine dioxide and chlorine is used as the secondary oxidant. Each experiment includes a stabilization step using one or more of hydrogen peroxide and sulfuric acid as the stabilizing agent. Table 2 includes Examples 1-5 and 12 set forth above.

Table 2

Catalytic carboxylation of mercerized and chlorinated C102-bleached cellulose fibers using TAA-EGK-NO.

[000164] Table 3 presents the results of representative experiments in which TIME is used as the precursor and in which a mixture of sodium hypochloride and sodium bromide is used as a secondary oxidant. Each experiment includes a stabilization step, using one or more of hydrogen peroxide and sulfuric acid as the stabilizing agent. Table 3 includes Example 11 presented above.

Table 3

Catalytic carboxylation of mercerized cellulose fibers bleached with sodium hypochloride and sodium bromide using TEMPO.

Non-exclusive examples illustrating descriptions of some compositions and methods within the scope of the present disclosure are set forth in the following numbered paragraphs. The following paragraphs are not intended to be an exhaustive series of descriptions and are not intended to define the maximum or minimum scope, or required elements or steps, of this description. Rather, these are provided as illustrative examples of selected compositions and methods that are within the scope of the present disclosure, with other descriptions of the broader or narrower scopes or combinations thereof not specifically listed herein within the scope of the present disclosure.

A. A method of producing fibrous carboxylated cellulose, the method including: Obtaining mercerized cellulose fibers;

Carboxylating the mercerized cellulose fibers by catalytic carboxylation of said fibers in an aqueous alkaline suspension in at least two stages of catalytic carboxylation in which said stages are in series and each further stage additional to carboxylates in the fibers from the previous stage; Where the first stage of at least two stages of catalytic carboxylation includes adjusting the fiber pH to 8-11, followed by supplying the amounts of an active oxoammonium salt catalyst precursor and a secondary oxidant adapted to generate the active catalyst. sufficient to effect carboxylation;

Wherein each subsequent stage of at least two stages of catalytic carboxylation includes adjusting the fiber pH to 8-11, followed by the provision of additional precursor amounts and sufficient secondary oxidant to effect additional carboxylation; and wherein the precursor is selected from the group consisting of heterocyclic nitroxides in which the carbon atoms adjacent to nitrogen nitroxide require the replacement of hydrogen, its corresponding amines and hydroxylamines and mixtures thereof and is stable under aqueous alkaline conditions. A.l. The method of paragraph A, wherein the precursor is one or more of TIME and TAA-EGK-NO. A.2. The method of paragraph A or A.l, wherein the secondary oxidant is one or more chlorine dioxide, chlorine, sodium hypochloride and sodium bromide. A.3. The method of any of paragraphs A through A.2, wherein the time in each of at least two stages of catalytic carboxylation is about 10 seconds to 5 minutes. A.4. The method of any of paragraphs A through A.3 further including: following the late stage of at least two stages of catalytic carboxylation, stabilizing the carboxylated fibers by treating the fibers with a stabilizing agent under conditions adapted to convert the aldehyde groups present in the fibers to the carboxyl groups. A.4.1 The method of paragraph A.4, wherein the stabilizing agent includes one or more tertiary oxidants selected from the group consisting of a peroxide, a chloride and an acid. A.4.2. The method of paragraph A.4 of A.4.1, wherein the stabilizing agent includes one or more of sodium chloride, hydrogen peroxide and sulfuric acid. A.4.3. The method of any of paragraphs A.4 through A.4.2, wherein stabilization is performed at a pH of about 1.0-3.5. A.4,4. The method of any of paragraphs A.4 through A.4.3, wherein stabilization is performed at about 40-70 ° C. A.4.5. The method of any of paragraphs A.4 through A.4.4, wherein stabilization is performed over a period of about 30 minutes to 2 hours. A.5. The method of any of paragraphs A.4 through A.4.5, wherein it additionally obtains and includes mercerized natural cellulose fibers to obtain mercerized cellulose comprising at least 20% cellulose II.

A.5.1. The method of paragraph A.5, wherein mercerization includes treating one or more of the natural NBSK and natural SBSK cellulose fibers at aqueous sodium hydroxide concentrations of about 14-18%. A.5.2. The method of paragraph A.5 or A.5.1, wherein mercerization is performed at a temperature of at least 50 ° C over a period of about 5-30 minutes. A.5.3. The method of any of paragraphs A.5 to A.5.2, wherein the natural cellulose fibers are below 4% consistency. A. 6. The fibrous carboxylated mercerized cellulose produced by the method of any of paragraphs A to A.5,3. B. A stable fibrous carboxylated mercerized cellulose having at least 12 meq / 100 g of carboxyl substitution, wherein the carboxyl groups are located at the C-6 position of the anhydroglucose units. B.l. The carboxylated mercerized cellulose of paragraph A.6 or B, wherein the mercerized cellulose includes at least 20% cellulose II. B.2. The carboxylated mercerized cellulose of any of paragraphs A. 6, B, or B.1, having at least 40 meq / 100 g of carboxyl substitution. B. 3. The carboxylated mercerized cellulose of any of paragraphs A. 6 and B to B.2, having at least 80 meq / 100 g of carboxyl substitution. B. 4. The carboxylated mercerized cellulose of any of paragraphs A.6 and B to B.3, wherein the cellulose is substantially free of the aldehyde groups.

Although the present invention will be shown and described with reference to the foregoing operating principles and illustrated examples and embodiments, it will be apparent to one skilled in the art that various forms in form and detail can be made without departing from spirit and scope. of the invention. The present invention is intended to encompass all such alternatives, modifications and differences which differ within the scope of the appended claims.

Claims (20)

Method for producing fibrous carboxylated cellulose, characterized in that it comprises: obtaining mercerized cellulose fibers; carboxylating the mercerized cellulose fibers by catalytically carboxylating said fibers in an aqueous alkaline suspension at least two catalytic carboxylation stages wherein said stages are in series and each last stage further carboxylates the fibers of the previous stage; wherein the first stage of the at least two catalytic carboxylation stages include adjusting the fiber pH from 8 to 11, followed by supplying amounts of a precursor of an active oxoammonium salt catalyst and a secondary oxidant adapted to generate the active catalyst. sufficient to carry out carboxylation; wherein each subsequent stage of the at least two catalytic carboxylation stages includes adjusting the fiber pH from 8 to 11, followed by the provision of additional amounts of the precursor and sufficient secondary oxidant to perform the additional decarboxylation and wherein the precursor is selected from the precursor. A group consisting of heterocyclic nitroxides in which the carbon atoms adjacent to nitrogen nitroxide require the replacement of hydrogen, its corresponding amines and hydroxylamines and mixtures thereof and is stable under aqueous alkaline conditions. A method according to claim 1, characterized in that the obtaining further comprises mercerizing native cellulose fibers to obtain mercerized cellulose comprising at least 20% cellulose II. Method according to claim 2, characterized in that the mercerization includes treating one or more of the native NBSK and native SBSK cellulose fibers at aqueous sodium hydroxide concentrations of about 14 to 18%. Method according to claim 3, characterized in that the mercerization is carried out at a temperature of at least 50 ° C over a period of about 5-30 minutes. Method according to claim 3, characterized in that the native cellulose fibers are below about 4% consistency. Method according to claim 1, characterized in that the precursor is one or more of the TIME and TAA-EGK-NO. Method according to claim 1, characterized in that the secondary oxidant is one or more of chlorine dioxide, chlorine, sodium hypochlorite and sodium bromide. Method according to claim 1, characterized in that the time in each of the at least two catalytic carboxylation stages is from about 10 seconds to 5 minutes. A method according to claim 1, further comprising: following the last stage of the at least two catalytic carboxylation stages, stabilizing the carboxylated fibers by treating the fibers with a stabilizing agent under conditions adapted to convert the aldehyde groups present in the fibers to the carboxyl groups. Method according to claim 9, characterized in that the stabilizing agent includes one or more tertiary oxidants selected from a group consisting of a peroxide, a chlorite and an acid. Method according to claim 9, characterized in that the stabilizing agent includes one or more of sodium chloride, hydrogen peroxide and sulfuric acid. Method according to claim 9, characterized in that the stabilization is carried out at a pH of about 1.0 to 3.5. Method according to claim 12, characterized in that the stabilization is carried out at about 40 to 70 ° C. Method according to claim 12, characterized in that the stabilization is carried out over a period of about 30 minutes to 2 hours. Fibrous carboxylated mercerized cellulose, characterized in that it is produced by the method as defined in claim 1. 16. Stable fibrous carboxylated mercerized cellulose, characterized in that it has at least 12 meq / 100 g of carboxyl substitution, wherein the carboxyl groups are located at the C-6 positions. Carboxylated mercerized cellulose according to claim 16, characterized in that the mercerized cellulose comprises at least 20% cellulose II. Carboxylated mercerized cellulose according to claim 16, characterized in that it has at least 40 meq / 100 g of carboxyl substitution. Carboxylated mercerized cellulose according to claim 16, characterized in that it has at least 80 meq / 100 g of carboxyl substitution. Carboxylated mercerized cellulose according to claim 16, characterized in that the cellulose is substantially free of aldehyde groups.