US3652385A - Process for treating cellulosic materials from which metal ions have been removed with alkali and oxygen in the presence of complex magnesium salts - Google Patents

Process for treating cellulosic materials from which metal ions have been removed with alkali and oxygen in the presence of complex magnesium salts Download PDF

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US3652385A
US3652385A US36670A US3652385DA US3652385A US 3652385 A US3652385 A US 3652385A US 36670 A US36670 A US 36670A US 3652385D A US3652385D A US 3652385DA US 3652385 A US3652385 A US 3652385A
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process according
acid
magnesium
pulp
alkali
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Sture Erik Olof Noreus
Hans Olof Samuelson
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Mo och Domsjo AB
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp

Definitions

  • ABSTRACT Cellulosic materials from which metal ions have been removed by acids or complexing agents is delignified with alkali in the presence of oxygen, and particularly air, and in the presence of magnesium compounds such as, for instance, chelates of magnesium and aliphatic alphaand beta-hydroxycarboxylic acids.
  • the invention is of particular application to the reduction of lignin content in cellulose pulps without causing deleterious degradation of the cellulose, the magnesium compounds reducing or entirely preventing attack of oxygen on the hemicellulose and cellulose carbohydrates, without appreciably diminishing the oxidation of the lignin and its dissolution in the course of the process.
  • the process is also useful 7 to obtain a controlled dissolution of the hemicellulose.
  • a further serious disadvantage is that a particularly complicated apparatus is required to carry out the heterogeneous reaction if the process is to be efiected in a reasonable length of time.
  • a process for treating cellulosic materials with alkali in the presence of oxygen, and in the presence of a magnesium compound, such as a magnesium salt of an organic acid having from two to about 12 carbon atoms and either one carboxylic acid group and an alpha or beta hydroxy group such as an aliphatic alphaor beta-hydroxycarboxylic acid, or a mixture of a magnesium salt and an aliphatic alphaor beta-hydroxycarboxylic acid or salt thereof, or two or more carboxylic acid groups and no or from one to hydroxy] groups such as a dicarboxylic acid or a mixture of a magnesium salt and such acid or salt thereof.
  • a magnesium compound such as a magnesium salt of an organic acid having from two to about 12 carbon atoms and either one carboxylic acid group and an alpha or beta hydroxy group such as an aliphatic alphaor beta-hydroxycarboxylic acid, or a mixture of a magnesium salt and an aliphatic alphaor beta-hydroxycarboxylic acid or salt thereof,
  • the cellulose is subjected to a pretreatment in which catalytically active metals and/or metal compounds are removed or deprived of their catalytic activity, and the concentration of cellulose during treatment with oxygen is from about 30 to about 60 percent, preferably from 32 to 40 percent.
  • alkali be added incrementally or continuously, so that, in addition to the amount of alkali present at the beginning of the oxygen treatment, more alkali is added in at least one additional stage during the oxygen treatment.
  • the protective effect obtained when adding magnesium compounds to the system can be increased to such an extent that the process can be effected in practice at high-pulp concentrations if, prior to being treated with oxygen, the cellulose is subjected to a pretreatment step in which metals and/or metal compounds which catalyze the attack on the cellulose and hemicellulose are removed or deprived of their catalytic activity, and if, furthermore, alkali is not added in one single charge,
  • the process of the invention is applicable to unbleached, partially bleached or bleached cellulose pulps, prepared from any cellulose source by any pulping process, for example, sulfate pulp, sulfite pulp and semichemical pulp.
  • the invention is especially applicable to cellulose pulps derived from wood, such as spruce pulp, pine pulp, hemlock pulp, birch pulp, fir pulp, cherry pulp, sycamore pulp, hickory pulp, ash pulp, beech pulp, poplar pulp, oak pulp, and chestnut pulp. or of other ligno-cellulosic material such as bamboo, bagasse straw and reeds.
  • the invention is particularly advantageous in the preparation of any pulp in which it is especially desired to avoid degradation of the cellulose during processing, such as most grades of paper pulp, and when it is desired to obtain a unifonn controlled degradation, such as in the manufacture of viscose pulp of a desired viscosity.
  • the process of the invention can be applied to remove hemicellulose, and/or cause oxidation of end groups of the cellulose, with a regulated diminution of the pulp viscosity.
  • the magnesium compounds have the property of protecting the cellulose and hemicellulose molecules against uncontrolled degradation.
  • the process of the invention is particularly advantageous in the alkaline treatment of lignin-containing wood cellulose in the presence of oxygen, gas or air, for the purpose of removing lignin.
  • This process is referred to in the art as alkaline oxygen gas bleaching. It is also applicable to the controlled dissolution of hemicellulose in cellulose pulps, either during or after delignification.
  • Uniform bleaching can be obtained without it being necessary to agitate the cellulose, except possibly when mixing in the alkali, or to subject it to a mechanical treatment other than that necessary in loosening the fibers thereof;
  • the cellulose can be bleached in a continuous process
  • the cellulose is easily, transported, e.g., by means of screw, scraper or gas-carrier conveyor systems, and sluice valves and other valve arrangements;
  • the process is effected at lower oxygen-gas pressure at a given same reaction time
  • the bleaching chemicals used can be recovered in a high concentration, rendering the process more economical.
  • One surprising advantage of the process of the invention is that it gives a cellulose pulp having a very low content of extractive substances, resins, such as fats, sterols, hydrocarbons, waxes and fatty alcohols, in the treated material, even in the case of cellulose material which is very difficult to deresin by other methods.
  • resins such as fats, sterols, hydrocarbons, waxes and fatty alcohols
  • An example of such materials is wood cellulose produced from fresh wood, particularly hardwood, such as birch.
  • the concentration of cellulose during the oxygen treatment should not be less than 30 percent, based on the treating solution. At lower concentrations, the cellulose may adhere to the apparatus, and is liable to dry out, creating, among other things,
  • the concentration of cellulose is here calculated in weight percent of the material impregnated with the alkaline liquid.
  • the lower concentration limit is important, although to some extent dependent on the nature of the cellulosic material and the apparatus used.
  • the alkaline liquid must be completely absorbed by the cellulose and retained by the fiber, so that, consequently, no free coherent liquid phase exists.
  • the concentration must be so high that no liquid droplets are forced out of the material whilst it is in, for example, the bleaching tower or other positions in the apparatus where the pulp is not worked mechanically but can be compressed by its own weight.
  • the oxygen treatment is effected in two or more stages, wherein the alkali-containing liquid is added to the system between and/or during the treatment stages.
  • the alkaline liquid can suitably be added in excess quantities, thereby obtaining uniform liquid impregnation.
  • the excess alkaline liquid is later removed in a known manner, for example, by pressing, to obtain a concentration within the given limits; after which the pulp is disintegrated, e.g., in a shredder, in a manner to provide a porous pulp having a greater surface area. Accessibility to the cellulose during the oxygen gas treatment is in this way increased.
  • the oxygen gas treatment can be effected to advantage during the disintegration process, although the treatment process may be begun instead after the pulp has been disintegrated.
  • the pretreated cellulosic material which may be dry or wet, is loosened by mechanical treatment, whereafter alkaline liquid is added.
  • alkaline liquid is added to the pretreated cellulosic material while the material is being disintegrated by mechanical treatment.
  • the alkaline liquid is added during the oxygen treatment, or simultaneously therewith.
  • the oxygen treatment be effected while the cellulosic material is being disintegrated by mechanical treatment or afterwards.
  • alkaline liquid is added to the cellulosic material while the material is in high pulp concentration
  • the alkaline liquid be added to the system in a finely divided atomized form.
  • the alkaline liquid can be charged to the system by known devices, for instance stationary or rotary jets or nozzles.
  • the liquid can be charged, suitably together with steam and/or with the oxygen necessary for the treatment.
  • the manner in which the liquid is charged is less important when the alkaline liquid is added whilst the cellulosic material is being subjected to mechanical treatment. If the liquid is charged while the material is falling freely, or moving in a stream of gas and/or steam, for example, in a socalled cyclone bed or a blower conduit, atomization of the liquid is desirable, and the liquid is suitably charged to the system in the form of an aerosol.
  • alkaline liquid is supplied to the pretreated cellulosic material, and any surplus of alkaline liquid removed, for instance by pressing, after which the cellulosic material is loosened by mechanical treatment during contemporaneous treatment with oxygen, and atomized alkaline liquid is supplied to the loosened material without or preferably during contemporaneous treatment with oxygen.
  • the alkaline liquid is added to the loosened material suitably in the form of an aerosol, for example while the loosened material is introduced into the upper end of a tower through which it continuously passes, and is subjected to treatment with oxygen.
  • the quantity of alkali necessary to the process depends on the quantity of lignin and hemicellulose which it is desired to remove. Normally, the total alkali addition, calculated as NaOH is within the range from about 0.5 to about 10 percent, based on the dry weight of the cellulosic material. Charges within the range of 7 to 12 percent alkali are used when it is desired to liberate large quantities of lignin and/or hemicellulose. In pulps of low lignin content, the normal total charge lies within the range of l to 7 percent.
  • the alkali normally used is sodium hydroxide, optionally in admixture with sodium bicarbonate. A slurry of calcium hydroxide, so-called lime milk, may also be used as an alkaline medium in the process. This latter medium, however, may cause deposits in the apparatus.
  • the least amount of cellulose decomposition is obtained when the quantity of alkali present at the beginning of the oxygen treatment is the smallest possible in practice, and when the major portion of the alkali is added incrementally or continuously as the alkali initially charged to the system is totally or partially consumed.
  • the oxygen may be in the form of oxygen and/or air, or mixtures of oxygen with any inert gas, such as nitrogen, argon, helium and krypton.
  • the partial pressure of oxygen at the beginning of the process should be at least one atmosphere.
  • a practical upper limit for the partial pressure of oxygen is 20 atmospheres above atmospheric; the higher the pressure, the more rapid the chemical reactions.
  • the high-pulp concentration and the looseness of the material facilitates dissolution of the oxygen in the cellulose fibers impregnated with alkaline liquid, whereby lower pressures than these used when treating low pulp concentrations can be applied.
  • an oxygen gas pressure within the range of from about two to about 10 atoms is preferred. It is often convenient to charge a further quantity of oxygen gas or air during the process, and to release gas mixtures enriched with respect to inert gas during the process.
  • the reactions take place slowly at low temperatures, e.g., 50 C..
  • the treatment is normally effected at a temperature within the range from about 80 to about 130 C.
  • a somewhat higher temperature can be used, e.g., about 140 C.
  • the treatment process is carried out to advantage at temperatures of between 90 and 1 10 C.
  • a lower temperature is chosen in the case of sulphate paper pulps, provided that a significant reduction in the hemicellulose content is not desired.
  • the temperature may be changed incrementally or continuously during the process. Consequently, it is convenient to start at a low temperature. This is particularly true for pulps containing hemicellulose, which, in nonoxidized state, is attacked by alkali, e.g., sulphite pulps and semichemical pulps.
  • Very short reaction times e.g., in the region of 5 minutes, can be used when working with high-oxygen gas pressures and high temperatures. It has been found relatively simple to control the process under these conditions, since the reaction practically stops when the alkali is consumed. To avoid working at high pressures, it is possible instead to use, for example, oxygen gas at atmospheric pressure, wherewith treatment times of hours and more can be used. Normal reaction times range from 10 to 120 minutes.
  • the magnesium compounds employed in the process of the invention have the important property of reducing or entirely preventing the attack of oxygen on the carbohydrates present in the cellulose and hemicellulose, without to any notably great extend affecting the oxidation of lignin extent its dissolution.
  • This protective effect is most noticeable with regard to the attack of oxygen on the cellulose molecule, and primarily the attack'of oxygen along the anhydroglucose chain of the cellulose molecule, an attack which gives rise to a rapid lowering of pulp viscosity.
  • the treated delignified pulp is found to have a higher viscosity than would be obtained in their absence.
  • the soluble preferred complex or chelate salts contsitutea preerred class of magnesium compounds, because they give most effective protection with a minimum magnesium concentration.
  • n is zero or one.
  • the acid is an alpha-hydroxy acid
  • n is one, the acid is a betahydroxy acid.
  • R in the above formula is hydrogen or an aliphatic radical which may be a hydrocarbon radical having from one to about 10 carbon atoms, or a hydroxy-substituted hydrocarbon radical having from one to nine hydroxyl groups, and from one to about 10 carbon atoms.
  • Exemplary alphaand beta-hydroxy carboxylic acids are glycolic acid, lactic acid, glyceric acid, afl-dihydroxybutyric acid, a-hydroxy-butyric acid, a-hydroxy-isobutyric acid, ahydroxy-n-valeric acid, a-hydroxy-isovaleric acid, fl-hydroxybutyric acid, B-hydroxy-isobutyric acid, B-hydroxy-n-valeric acid, B-hydroxy-isovaleric acid, erythr'onic acid, threonic acid, trihydroxy-isobutyric acid, and saccharinic acids and aldonic acids, such as gluconic acid, galactonic acid, talonic acid, mannonic acid, arabonic acid, ribonic acid, xylonic acid, lyxonic acid, gulonic acid, idonic acid, altronic acid, allonic acid, ethenyl glycolic acid, and ,B-hydroxy-isocrotonic acid.
  • organic acids having two or more carboxylic groups, and no or from one to 10 hydroxyl groups, such as oxalic acid, malonic acid, tartaric acid, malic acid, and citric acid, ethyl malonic acid, succinic acid, isosuccinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, maleic acid,
  • the polyphosphoric acids are also good complexing agents for magnesium, and the magnesium salts of these acids are useful in the process of the invention.
  • Exemplary are disodium-magnesium pyrophosphate, trisodium-magnesium tripolyphosphate and magtesium polymetaphosphate.
  • acids naturally present in waste liquors obtained from the alkaline treatment of cellulosic materials.
  • These acids represent the alkalior water-soluble degradation products of polysaccharides which are dissolved in such liquors, as well as alkalior water-soluble degradation products of cellulose and hemicellulose.
  • the chemical nature of these degradation products are complex, and they have not been fully identified.
  • saccharinic and lactic acids are present in such liquors, and that other hydroxy acids are also present.
  • C -isosaccharinic and C metasaccharinic acids has been demonstrated, as well as C,- and C metasaccharinic acids.
  • Glycolic acids and lactic acid are also probable degradation products derived from the hemicelluloses, together with beta-gamma-dihydroxy butyric acid.
  • Carbohydrate acid-containing cellulose waste liquors which can be used include the liquors obtained from the hot alkali treatment of cellulose, liquors from sulfite digestion processes, and liquors from sulfate digestion processes, i.e., kraft waste liquor.
  • the waste liquors obtained in alkaline oxygen gas bleaching or alkaline peroxide bleaching processes can also be used. In this instance, the alkaline liquor can be taken out from the process subsequent to completing the oxygen gas treatment stage, or during the actual treatment process.
  • the complex magnesium salts can be formed first, and then added to the cellulose pulp. They can also be formed in situ from a water-soluble or water-insoluble magnesium salt, oxide or hydroxide, in admixture with the complexing acid, and this mixture can be added to the pulp.
  • the waste liquor employed as the source of complexing acid or anhydride or salt thereof can be mixed with a magnesium salt, oxide or hydroxide, before being introduced to the process. It is also possible to add the magnesium salt, oxide or hydroxide to the pulp, and then bring the pulp into contact with the complexing acid or anhydride or salt thereof. It is also possible to combine the complexing acid or anhydride or salt thereof with the pulp, and then add the magnesium salt, oxide or hydroxide, but this method may be less advantageous in practice.
  • magnesium is added, whether as salt, oxide, hydroxide, or complex salt, the amount of magnesium is calculated as MgO.
  • a noticeable improvement is obtained when as little magnesium as 0.005% MgO, calculated on the dry weight of the pulp, is added.
  • a high proportion of magnesium, up to 1% MgO, calculated on the dry weight of the pulp, has been employed without disadvantageous effect.
  • the alkaline liquid contains a solid magnesium compound, e.g., magnesium carbonate, magnesium oxide and magnesium hydroxide.
  • a solid magnesium compound e.g., magnesium carbonate, magnesium oxide and magnesium hydroxide.
  • large amounts of magnesium compounds are required, and the process becomes less satisfactory economically.
  • the addition and distribution of solid compounds also involves technical complications.
  • the amount of magnesium compounds should in this instance be within the range from about 0.5 to 2.0% calculated as MgO on the dry weight of the pulp.
  • a negligible shielding efiect is obtained when practicing the process of the invention using magnesium silicate in solid form.
  • an alkaline silicate for example, sodium silicate, or other compounds which stop free radical reactions, for example, aromatic organic substances such as benzene
  • the quantity of sodium silicate or benzene introduced to the system is within the range from about 0.05 to about 3.0 percent, estimated on the dry weight of the cellulosic material, preferably from 0.1 to 1.0 percent.
  • magnesium-containing waste liquor Upon conclusion of the alkaline-oxygen gas treatment, it is possible to separate the magnesium-containing waste liquor and recycle it for reuse.
  • the consumption of magnesium salts is negligible, and usually it is not even necessary to replenish the magnesium content before recycling.
  • additional magnesium compound can be added before recycling, if necessary, to restore the magnesium content, as MgO, and maintain a high enough level, for instance, to prevent oxidative degradation of the cellulose or hemicellulose.
  • the consumption of magnesium salt has been noted to be particularly low when waste liquor from a part of the alkaline-oxygen gas treatment process is employed as the source of complexing acid, and recycled for continued treatment of new batches of pulp.
  • waste liquors are particularly high in magnesium ion because of the nature of the pulp or of the pulping process.
  • waste pulping liquors from unbleached pulps produced by the cooking of wood with magnesium bisulfite or magnesium sulfite usually contain enough magnesium ion so that no addition of magnesium compound need be made.
  • Such waste liquors can be used per se, in the process of the invention, inasmuch as they already contain the complexing acids, and a sufficient proportion of magnesium ion as well.
  • magnesium salts, oxide or hydroxide either to regenerate a spent treatment liquor, or to prepare a waste liquor or other material for use in the process.
  • Any water-soluble magnesium compound can be used, such as, for example, magnesium sulfate, magnesium chloride, magnesium bromide, magnesium chlorate, magnesium potassium chloride, magnesium formate, magnesium oxide, magnesium hydroxide, and magnesium nitrate. If it is desired to recover the liquor after the treatment, then it is usually preferable to employ magnesium sulfate, so as to avoid the introduction of foreign anions into the system.
  • Magnesium compounds which have no deleterious anion or which have an anion which is destroyed in the course of the process are also advantageous. Since these are water-insoluble, it is desirable, however, to combine these with the complexing agent in the presence of water, and await their dissolution, indicating that the complex has been formed, before combining with the pulp, or before commencing the alkalineoxygen gas reaction. Any other water-insoluble magnesium compounds can be used in this way, for instance, magnesium phosphate, magnesium silicate and magnesium sulfide.
  • the pretreatment of the cellulose can be effected to advantage with an acid aqueous solution containing one or more acids, e.g., mineral acids such as hydrochloric acid, nitric acid, phosphoric acid, or sulphurous acid.
  • acids e.g., mineral acids such as hydrochloric acid, nitric acid, phosphoric acid, or sulphurous acid.
  • the use of sulphurous acid is particularly advantageous in the case of cellulose containing iron compounds, while sulphuric acid is preferred with cellulose containing copper and copper compounds.
  • Progressive treatment with several acid aqueous solutions provides an increased effect if for example, both iron and copper compounds are present in the material.
  • the solution may have a pH of l or thereover, for example, from 1.5 to 4, preferably 2 to 3.5.
  • Mixtures of different mineral acids may also be used, for example, mixtures containing hydrochloric acid, sulphuric acid, and organic acids such as formic, acetic, and
  • the pretreatment is effected with acid bleaching liquids used in the bleaching process, or washing water obtained from acid bleaching stages.
  • the cellulosic material is subjected to a pretreatment process in the presence of a complex builder for catalytically active heavy metal compounds, such as those which contain copper, cobalt, iron and manganese.
  • a complex builder for catalytically active heavy metal compounds such as those which contain copper, cobalt, iron and manganese.
  • complexing agents are ethylene diaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylene-triaminepentaacetic acid (DTPA), hydroxyethylimindiacetic acid, hydroxyethylethylenediaminetriacetic acid (HEDTA) and polyphosphoric acid and salts of said acids.
  • Amines for example, ethylene-diamine
  • the complex builders can be used at pH values of, for example, from 4 to 10, preferably 5 to 8.
  • complexing agents having a low pH, e.g., from 2 to 5, preferably 3 to 4, and then to raise the pH, e.g., by adding alkali. It is also suitable when practicing this type of pretreatment to wash the material prior to charging to the system the alkali necessary for the oxygen treatment.
  • the pretreatment step can be carried out at any pulp concentration whatsoever, for example, concentrations within the range from about lto about 20 percent. For practical reasons, however, a concentration of 5 to 10 percent is preferred.
  • the temperature may be room temperature, although an elevated temperature within the range from 40 to C., for example, gives a more rapid treatment. ln the presence of certain metal compounds, the treatment time may be very short, for example, 2 minutes. A longer reaction time from about 10 to about 60 minutes, is often preferred, however, in order that an acceptable result can be obtained. If high temperatures and/or long reaction time are used, a pH of less than 1.5 should be avoided when pretreating with acid solutions.
  • surface tension reducing substances for example, nonionic or anionic wetting agents, or mixtures thereof can be used during the oxygen treatment.
  • the process can also be applied to materials which have previously been treated in a known manner with, for example, chlorine, hydrochlorite or chlorine dioxide or a combination of such bleaching agents.
  • the process can be applied with particular advantage to a weakly chlorinated cellulose pulp.
  • the pulp treated in accordance with the process of the invention can be further processed in accordance with known methods, as desired. It can, for example, be bleached with chlorine and/or sodium hydrochlorite and/or chlorine dioxide, and it may also be subjected to continued refinements, in accordance with known procedures.
  • sulphate pulp it has been shown to be particularly advantageous to treat the pulp with a mixture of chlorine and chlorine dioxide, followed by alkali extraction and final bleaching with, for example, chlorine dioxide.
  • EXAMPLE 1 a 1.4 l 192 crnfl/g. according to SCAN I77 amendin TAPPI Kappa number Viscosity Viscosity ing to TAPPl
  • the pulp was pretreated with an acid residual liquid ob tained from a bleaching stage in which a mixture of chlorine and chlorine dioxide had been used to bleach an acid alkalitreated pulp having a kappa number of 17.
  • the conditions in this bleaching stage were as follows:
  • the unbleached pulp was treated with theresidual acidic liquid, under the following conditions:
  • the pulp which contained NaOH and magnesium complex, was then loosened in peg shredder, after which it was introduced into a pressure vessel which was heated by direct steam contact to 100 C.
  • the pressure vessel was then connected to an oxygen gas tube, and the pressure adjusted to 8 kg/cmF. After 20 minutes reaction time, the pulp was washed with water.
  • the pulp had the following analysis:
  • the pulp obtained had the following analysis:
  • EXAMPLE 3 The same EDTA-treated pulp as that used in Example 2 was used in this experiment.
  • the pulp was dewatered to a pulp concentration of 34 percent, after which the pulp was enclosed in a pressure vessel, and heated with direct steam contact to C.
  • the pressure vessel was then connected to an oxygen gas tube, and the pressure set at 8 kg./cm.
  • the quantity of magnesium complex was 0.1 percent, calculated as MgO, and the quantity of sodium silicate was 0.3 percent, based on the amount of dry pulp.
  • After 5 minutes reaction time more alkali solution was introduced to the system, corresponding to 2.0% NaOH in atomized liquid form. The reaction was then continued for another 20 minutes, after which the pulp was washed with water.
  • the pulp had the following analysis:
  • the improvement which comprises pretreating the cellulosic material with a compound selected from the group consisting of acids and complexing agents for catalytically active heavy metal compounds to remove or inactivate catalytically active metals or metal compounds, bringing the concentration of cellulosic material to within the range from about 30 to about 60 percent, and then delignifying the cellulosic material with alkali in the presence of oxygen and a soluble complex magnesium compound selected from the group consisting of a magnesium salt of organic acids having from two to about 12 carbon atoms and one carboxylic acid group and an alpha or beta hydroxyl group or at least two carboxylic acid groups and no or from one to about hydroxyl groups, and a magnesium salt of polyphosphoric acids, and charging the alkali in at least two increments during the oxygen treatment, the complex magnesium compound being in an amount sufficient to reduce entirely prevent attack of oxygen on the hemicellulose and cellulose carbohydrates, without appreci
  • silicate is an alkali metal silicate.
  • magnesium compound is a chelate of magnesium and an aliphatic alphaor beta-hydroxycarboxylic acid.
  • magnesium compound is a magnesium salt of a dicarboxylic aliphatic acid.
  • a process according to claim 1, wherein the magnesium compound is a chelate of magnesium and an aliphatic hydroxy acid having from two to about l2 carbon atoms and from one to about 10 dlhydroxy-butyric hydroxyl groups.
  • cellulosic material is an unbleached, partially bleached or bleached cellulose sulfate pulp, sulfite pulp or semichemical pulp derived from wood.

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US36670A 1969-05-13 1970-05-12 Process for treating cellulosic materials from which metal ions have been removed with alkali and oxygen in the presence of complex magnesium salts Expired - Lifetime US3652385A (en)

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Cited By (29)

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US3769152A (en) * 1970-05-13 1973-10-30 Mo Och Domsjoe Ab Digestion of wood with oxygen in the presence of alkali
US4004967A (en) * 1972-06-22 1977-01-25 Billeruds Aktiebolag Bleaching cellulose pulp with oxygen in the presence of formaldehyde
US4172006A (en) * 1976-08-26 1979-10-23 Weyerhaeuser Company Method of delignifying wood chips with oxygen by adding cooking liquor under pressure
US4181516A (en) * 1977-08-22 1980-01-01 Gray Kenneth R Products for correcting iron chlorosis in plants
US4182648A (en) * 1972-02-07 1980-01-08 Sterling Drug Inc. Oxygen pulping process
US4187141A (en) * 1975-02-24 1980-02-05 Alf Societe Anonyme Method of producing bleached mechanical pulp
US4222819A (en) * 1978-02-17 1980-09-16 Mo Och Domsjo Aktiebolag Process for the acid bleaching of cellulose pulp with peroxides
US4238282A (en) * 1979-07-23 1980-12-09 Nalco Chemical Company Chemical treatments in bleaching stages which increase pulp brightness
US4594130A (en) * 1978-11-27 1986-06-10 Chang Pei Ching Pulping of lignocellulose with aqueous alcohol and alkaline earth metal salt catalyst
US5593544A (en) * 1993-07-12 1997-01-14 Kvaerner Pulping Aktiebolag Pulp production
US5755926A (en) * 1992-02-24 1998-05-26 Kimberly-Clark Worldwide, Inc. Integrated pulping process of waste paper yielding tissue-grade paper fibers
WO2000047812A1 (en) * 1999-02-15 2000-08-17 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US6210801B1 (en) * 1996-08-23 2001-04-03 Weyerhaeuser Company Lyocell fibers, and compositions for making same
WO2001059204A1 (en) * 2000-02-14 2001-08-16 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US6306334B1 (en) 1996-08-23 2001-10-23 The Weyerhaeuser Company Process for melt blowing continuous lyocell fibers
US6331354B1 (en) 1996-08-23 2001-12-18 Weyerhaeuser Company Alkaline pulp having low average degree of polymerization values and method of producing the same
US6398908B1 (en) 1991-04-30 2002-06-04 Eka Nobel Ab Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound
US6440547B1 (en) 1996-08-23 2002-08-27 Weyerhaeuser Lyocell film made from cellulose having low degree of polymerization values
EP1244840A1 (de) * 1999-06-08 2002-10-02 Eastern Pulp and Paper Corporation Sauerstoff-hochdruck-bleichung einer pulpe
US20030025252A1 (en) * 1996-08-23 2003-02-06 Weyerhaeuser Company Process for making lyocell fiber from sawdust pulp
US20030183351A1 (en) * 1999-02-24 2003-10-02 Sealey James E. Use of thinnings and other low specific gravity wood for lyocell pulps method
US6685856B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell products method
US6686039B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell pulps
US6686040B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell products
WO2010139589A1 (en) * 2009-06-02 2010-12-09 Akzo Nobel Chemicals International B.V. Process for producing mechanical pulp
WO2015155788A3 (en) * 2014-04-07 2015-12-10 Praj Industries Limited Method for efficient enzymatic hydrolysis of lignocellulosic materials
WO2017055504A1 (en) * 2015-09-30 2017-04-06 Imerys Minerals Limited Methods for bleaching aqueous pulps and compositions for use in these methods
US10407830B2 (en) 2012-04-18 2019-09-10 Gp Cellulose Gmbh Use of surfactant to treat pulp and improve the incorporation of kraft pulp into fiber for the production of viscose and other secondary fiber products
US11512427B2 (en) 2017-09-08 2022-11-29 Dte Materials Incorporated Selectively depolymerizing cellulosic materials for use as thermal and acoustic insulators

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SE373896B (de) * 1972-07-05 1975-02-17 Mo Och Domsjoe Ab
FI58360C (fi) * 1974-06-14 1981-01-12 Mo Och Domsjoe Ab Foerfarande foer delignifiering av lignocellulosahaltigt material med hjaelp av syreinnehaollande gas och apparatur foer utfoerande av detta foerfarande
SE417114B (sv) * 1977-07-25 1981-02-23 Mo Och Domsjoe Ab Forfarande for forebyggande av inkrustbildning i cellulosafabriker
DE2841013C2 (de) * 1978-09-21 1984-06-07 Degussa Ag, 6000 Frankfurt Verfahren zur Vollbleiche von Zellstoff
SE470065C (sv) * 1991-04-30 1996-01-15 Eka Nobel Ab Behandling av kemisk massa med en syra och därefter en magnesium- och kalciumförening vid klorfri blekning
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US3769152A (en) * 1970-05-13 1973-10-30 Mo Och Domsjoe Ab Digestion of wood with oxygen in the presence of alkali
US4182648A (en) * 1972-02-07 1980-01-08 Sterling Drug Inc. Oxygen pulping process
US4004967A (en) * 1972-06-22 1977-01-25 Billeruds Aktiebolag Bleaching cellulose pulp with oxygen in the presence of formaldehyde
US4187141A (en) * 1975-02-24 1980-02-05 Alf Societe Anonyme Method of producing bleached mechanical pulp
US4172006A (en) * 1976-08-26 1979-10-23 Weyerhaeuser Company Method of delignifying wood chips with oxygen by adding cooking liquor under pressure
US4181516A (en) * 1977-08-22 1980-01-01 Gray Kenneth R Products for correcting iron chlorosis in plants
US4222819A (en) * 1978-02-17 1980-09-16 Mo Och Domsjo Aktiebolag Process for the acid bleaching of cellulose pulp with peroxides
US4594130A (en) * 1978-11-27 1986-06-10 Chang Pei Ching Pulping of lignocellulose with aqueous alcohol and alkaline earth metal salt catalyst
US4238282A (en) * 1979-07-23 1980-12-09 Nalco Chemical Company Chemical treatments in bleaching stages which increase pulp brightness
US6398908B1 (en) 1991-04-30 2002-06-04 Eka Nobel Ab Process for acid bleaching of lignocellulose-containing pulp with a magnesium compound
US5755926A (en) * 1992-02-24 1998-05-26 Kimberly-Clark Worldwide, Inc. Integrated pulping process of waste paper yielding tissue-grade paper fibers
US5593544A (en) * 1993-07-12 1997-01-14 Kvaerner Pulping Aktiebolag Pulp production
US6692827B2 (en) 1996-08-23 2004-02-17 Weyerhaeuser Company Lyocell fibers having high hemicellulose content
US6514613B2 (en) 1996-08-23 2003-02-04 Weyerhaeuser Company Molded bodies made from compositions having low degree of polymerization values
US6306334B1 (en) 1996-08-23 2001-10-23 The Weyerhaeuser Company Process for melt blowing continuous lyocell fibers
US6331354B1 (en) 1996-08-23 2001-12-18 Weyerhaeuser Company Alkaline pulp having low average degree of polymerization values and method of producing the same
US6210801B1 (en) * 1996-08-23 2001-04-03 Weyerhaeuser Company Lyocell fibers, and compositions for making same
US6440523B1 (en) 1996-08-23 2002-08-27 Weyerhaeuser Lyocell fiber made from alkaline pulp having low average degree of polymerization values
US6440547B1 (en) 1996-08-23 2002-08-27 Weyerhaeuser Lyocell film made from cellulose having low degree of polymerization values
US6444314B1 (en) 1996-08-23 2002-09-03 Weyerhaeuser Lyocell fibers produced from kraft pulp having low average degree of polymerization values
US7090744B2 (en) 1996-08-23 2006-08-15 Weyerhaeuser Company Process for making composition for conversion to lyocell fiber from sawdust
US6471727B2 (en) 1996-08-23 2002-10-29 Weyerhaeuser Company Lyocell fibers, and compositions for making the same
US6491788B2 (en) 1996-08-23 2002-12-10 Weyerhaeuser Company Process for making lyocell fibers from alkaline pulp having low average degree of polymerization values
US6706237B2 (en) 1996-08-23 2004-03-16 Weyerhaeuser Company Process for making lyocell fibers from pulp having low average degree of polymerization values
US20030025252A1 (en) * 1996-08-23 2003-02-06 Weyerhaeuser Company Process for making lyocell fiber from sawdust pulp
US20030025251A1 (en) * 1996-08-23 2003-02-06 Weyerhaeuser Company Process for making cellulose solution from sawdust pulp
US6528163B2 (en) 1996-08-23 2003-03-04 Weyerhaeuser Company Lyocell fiber from sawdust pulp
US7083704B2 (en) 1996-08-23 2006-08-01 Weyerhaeuser Company Process for making a composition for conversion to lyocell fiber from an alkaline pulp having low average degree of polymerization values
US6605350B1 (en) 1996-08-23 2003-08-12 Weyerhaeuser Company Sawdust alkaline pulp having low average degree of polymerization values and method of producing the same
US6861023B2 (en) 1996-08-23 2005-03-01 Weyerhaeuser Company Process for making lyocell fiber from sawdust pulp
US6706876B2 (en) 1996-08-23 2004-03-16 Weyerhaeuser Company Cellulosic pulp having low degree of polymerization values
US6770168B1 (en) 1999-02-15 2004-08-03 Kiram Ab Process for oxygen pulping of lignocellulosic material and recorvery of pulping chemicals
WO2000047812A1 (en) * 1999-02-15 2000-08-17 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US20030183351A1 (en) * 1999-02-24 2003-10-02 Sealey James E. Use of thinnings and other low specific gravity wood for lyocell pulps method
US6686040B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell products
US6686039B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell pulps
US6685856B2 (en) 1999-02-24 2004-02-03 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell products method
US6797113B2 (en) 1999-02-24 2004-09-28 Weyerhaeuser Company Use of thinnings and other low specific gravity wood for lyocell pulps method
EP1244840A4 (de) * 1999-06-08 2003-04-16 Eastern Pulp And Paper Corp Sauerstoff-hochdruck-bleichung einer pulpe
EP1244840A1 (de) * 1999-06-08 2002-10-02 Eastern Pulp and Paper Corporation Sauerstoff-hochdruck-bleichung einer pulpe
WO2001059204A1 (en) * 2000-02-14 2001-08-16 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
WO2010139589A1 (en) * 2009-06-02 2010-12-09 Akzo Nobel Chemicals International B.V. Process for producing mechanical pulp
US10407830B2 (en) 2012-04-18 2019-09-10 Gp Cellulose Gmbh Use of surfactant to treat pulp and improve the incorporation of kraft pulp into fiber for the production of viscose and other secondary fiber products
WO2015155788A3 (en) * 2014-04-07 2015-12-10 Praj Industries Limited Method for efficient enzymatic hydrolysis of lignocellulosic materials
WO2017055504A1 (en) * 2015-09-30 2017-04-06 Imerys Minerals Limited Methods for bleaching aqueous pulps and compositions for use in these methods
US11512427B2 (en) 2017-09-08 2022-11-29 Dte Materials Incorporated Selectively depolymerizing cellulosic materials for use as thermal and acoustic insulators

Also Published As

Publication number Publication date
DE2022866A1 (de) 1970-12-23
AT295997B (de) 1972-01-25
FR2047420A5 (de) 1971-03-12
DE2022866C3 (de) 1974-11-14
FI45575B (de) 1972-04-04
DE2022866B2 (de) 1974-03-28
FI45575C (fi) 1972-07-10
NO128372B (de) 1973-11-05
SE335053B (de) 1971-05-10

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