US3769152A - Digestion of wood with oxygen in the presence of alkali - Google Patents

Digestion of wood with oxygen in the presence of alkali Download PDF

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US3769152A
US3769152A US00119375A US3769152DA US3769152A US 3769152 A US3769152 A US 3769152A US 00119375 A US00119375 A US 00119375A US 3769152D A US3769152D A US 3769152DA US 3769152 A US3769152 A US 3769152A
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digestion
alkali
wood
alkali metal
range
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Hans Olof Samuelson
Sture Erik Olof Noreus
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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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • D21C3/026—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes in presence of O2, e.g. air
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/26—Multistage processes
    • D21C3/263—Multistage processes at least one stage being in presence of oxygen

Definitions

  • ABSTRACT A process is provided for the production of cellulose of high brightness from wood by digestion with alkali and oxygen in aqueous solution under moderate oxygen pressure, limiting the amount of alkali at the start of the digestion to less than that required, and progressively adding alkali as the digestion continues, while maintaining the digestion liquor at a pH within the range from about 9.2 to about 13.
  • cellulose pulp produced today in commerce is prepared by the sulfate or kraft process, in which wood is digested or pulped with alkali and sodium sulfide, and sodium sulfate is used as the make-up chemical to cover losses in the recovery cycle.
  • the greater part of the remainder of the cellulose pulp is produced by the three variants of the sulfite process, in which the active digestion or pulping chemicals comprise acid sulfite, bisulfite, or neutral sulfite.
  • Some pulp is still produced by the so-called soda process, in which sodium carbonate is used instead of sodium sulfate as the make-up chemical, but this process has a number of serious disadvantages, compared to the kraft process, particularly a low pulp yield and a poor pulp quality, and consequently this process is no longer used to any considerable extent.
  • the sulfate process also has a number of disadvantages, the most serious one, from the standpoint of pollution of the environment, being the discharge of sulfur dioxide, hydrogen sulfide and other waste gases, as well as the black liquor effluent, which must be captured, processed for recovery, and recycled to maintain an economical operation.
  • Grangaard and Saunders U.S. Pat. No. 2,926,114, dated Feb. 23, 1960, stated that oxygen prior to 1957 had been used both at low and at high oxygen pressures. However, at low pressures, the pulping was inadequate, and the process had to be used only as a single stage in a multiple stage pulping process, using more conventional pulping chemicals to complete the pulping. At the high pressures, the pressures are so high, large volume batch digesters cannot be readily constructed to withstand them.
  • Grangaard et al. proposed a digestion at pH 7 to 9 over at least a major portion of the cooking time, ranging up to 9.4 at the end of the cook, under oxygen pressures of 40 to 250 psi, using conventional batch digesters.
  • the pH is maintained within the desired range by a buffer such as sodium bicarbonate, or by continuous addition of alkali such as sodium hydroxide or sodium carbonate, to neutralize free acids formed throughout the digestion.
  • a buffer such as sodium bicarbonate
  • alkali such as sodium hydroxide or sodium carbonate
  • a serious problem is that a digestion process using oxygen and alkali tends to produce pulp having a dark color, due to a higher lignin content than is present in pulp obtained using a conventional soda cooking process. It is known, for example, that a soda cook using a charge of 20 percent sodium hydroxide based on the wood, a maximum cooking temperature of 165C., and a reaction time of two hours, is capable of producing a cellulose pulp having a lignin content of 4.2 percent.
  • the brightness of the pulp is deleteriously affected. It is most important that the pH be maintained within the stated range during the first stages and the major portion of the digestion process. With certain types of pulp, particularly viscose pulps and other dissolving pulps, it is possible to permit the pH to drop below 9, down to about 8, during the final stages of the process without seriously affecting the quality of the pulp. Especially, brightness is affected most by chemical reactions occurring during the initial and major part of the digestion reactions.
  • the total amount of alkali that is required for the digestion is determined by the quality and type of the pulp to be produced, and is within the range from about 1 to kilomoles per 1,000 kg. of dry wood. It is well known that certain types of pulp are more digested than others. This is entirely conventional, and does not form a part of the instant invention.
  • Cellulose pulps intended to be used in the production of regenerated cellulose fibers, such as viscose, acetate and cuprammonium pulps are quite fully digested, and should have a low content of lignin and hemicellulose.
  • the amount of alkali can be within the range from about 6 to about 8 kilomoles per 1,000 kg. of dry wood.
  • Semichemical pulps are given an intensive mechanical treatment following their digestion, in order to liberate the cellulose fibers, and in the production of such pulps, using the process of the invention, the amount of alkali can be much less, within the range from about 1 to about 2 kilomoles per 1,000 kg. of dry wood.
  • the amount of alkali used in the process of the invention can be within the range from about 2.5 to about 5 kilomoles.
  • the amount of alkali in the process of the invention is within the range from about 2 to about 6 kilomoles per 1,000 kg. of dry wood.
  • alkali metal hydroxide or alkali metal carbonate can be employed, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate and lithium carbonate.
  • the sodium carbonate obtained in the burning of cellulose digestion waste liquors can be used for this purpose.
  • the use of alkali metal carbonates may be more advantageous than the use of alkali metal hydroxides in maintaining the pH of the digestion liquor within the stated range, because of the buffering properties of the carbonate or bicarbonate present or formed in situ. Consequently, mixtures of alkali metal hydroxides and alkali metal carbonates are particularly satisfactory to obtain the advantages of each, and dilute their disadvantages.
  • alkali metal carbonate such as sodium carbonate is the sole alkali charge, the total amount of sodium is greater, and this imposes a greater load on the sodium recovery system.
  • alkali metal bicarbonate in this case serves as a buffer.
  • Other buffering agents, compounds of alkali metals with nondeleterious acidic anions, can be employed, such as alkali metal acid phosphates, and alkali metal acid or bisulfites, such as potassium dihydrogen phosphate, potassium monohydrogen phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, sodium acid sulfite, and potassium acid sulfite, as well as the lithium salts of these anions.
  • the amount of buffering agent such as alkali metal bicarbonate is usually within the range from about 1 to about 5 kilomoles per 1,000 kg. of dry wood.
  • the alkali metal bicarbonate or other buffering agent should be added to the digestion liquor either initially or at an early stage of the digestion.
  • the addition of the bicarbonate or other buffering agent increases the buffer capacity of the digestion liquor, thereby assisting in avoiding variations in pH outside the prescribed range during the digestion.
  • the buffering agent, particularly a bicarbonate is especially desirable when it is desired to operate at a relatively low pH, for example, from about 9.5 to about 9.7. In this case, bicarbonate or other buffering agent can be added to advantage even if alkali metal carbonate is present.
  • buffering agents and particularly bicarbonates
  • carbon dioxide may be produced in the course of the digestion as the buffer is consumed.
  • the carbon dioxide dilutes the oxygen, and adds an extra load to the chemical recovery system, and is therefore undesirable in large amounts.
  • the addition of minor amounts of the buffering agent within the stated range contribute to pulp uniformity because of their assistance in maintaining pH.
  • Also useful as a buffer are the base liquors from previous digestions and/or the waste liquors from oxygen bleaching processes, such as those described in US. applications Ser. Nos. 869,875 and 36,670 referred to above. In this way, better economy is obtained in chemical recovery, which can be effected after evaporating and burning the waste digestion liquor, using known methods.
  • the sodium compounds are preferred as the alkali metal hydroxide, alkali metal carbonate and alkali metal bicarbonate.
  • the initial charge comprises sodium carbonate, optionally with an addition of sodium bicarbonate as described above, the remainder of the alkali added as the digestion proceeds being sodium hydroxide.
  • the alkali charge initially is alkali metal hydroxide, it is usually important in producing pulps having a low lignin content that the initial charge be low, within the range from about 2 to about percent, of the total molar quantity of alkali.
  • the alkali metal hydroxide and/or alkali metal carbonate can be charged continuously or in increments to the digestion liquor.
  • the wood in a continuous digestion, the wood is caused to move through the digester from one end to the other which thereby constitutes a reaction zone.
  • the wood in a batch process, the wood, usually in the form of chips, is retained in the reaction vessel throughout the digestion.
  • the so-called gas phase digestion procedure can be used to advantage.
  • the wood and the film of digestion liquor present on the wood are kept in continuous contact with the oxygen-containing gas. If the wood is completely or substantially immersed in the digestion liquor, it is important to agitate the wood and- /or the gas and/or atomize the gas or the liquor.
  • the oxygen should be dissolved or dispersed in the digestion liquor to the greatest extent possible. Dissolution or dispersion of the oxygen in the liquor can take place within the digestion vessel and/or externally of the same, such as in nozzles, containers or other known devices used for dissolving or dispersing gases in liquids.
  • Transfer of oxygen to the wood material impregnated with digestion liquor is important in the process, and is controlled by adjusting the oxygen pressure, the digestion temperature and/or the proportion of gas-liquid contact surfaces, including the wood impregnated with digestion liquor.
  • the oxygen is preferably employed as pure oxygen, but mixtures of oxygen with other inert gases can be used, such as, for example, mixtures of oxygen with nitrogen and with carbon dioxide and with both, as well as air. Compressed air can also be used, although this complicates the devices for dissolving or dispersing the oxygen in the reaction mixture.
  • the wood Prior to contact with the oxygen, the wood suitably in the form of chips can be impregnated with an aqueous digestion liquor containing the desired chemicals.
  • the chips are impregnated under vacuum, or under atmospheric pressure or superatmospheric pressure, or by other methods conventional in wood digestion processes.
  • the wood may also be treated with steam before being brought to the digestion zone.
  • the temperature employed during the impregnation can be within the range from about 20 to about 120C., although temperatures within the range from 90 to 120C. would not normally be used except under special circumstances. In the latter case, the highest temperature during the digestion may be the same as the impregnating temperature, as well as the initial digestion temperature. Generally, however, it is to advantage if the digestion temperature is allowed to rise during the digestion process, so that normally the temperature during impregnation would not exceed about 60C.
  • the digestion can be carried out at a temperature within the range from about 60 to about 175C. Usually, it is advantageous if the digestion temperature is permitted to rise during the digestion process from an initial temperature of the order of from 60 to C. to the maximum digestion temperature, of the order of from to or C.
  • a digestion temperature of from 90 to 110C. can be used to advantage when producing semichemical pulps, the fibers of which are not fully liberated until after subjection to a mechanical treatment process, such as in a refiner after the digestion process. These are high yield pulps.
  • a maximum digestion temperature within the range from 110 to 150C. is preferred, at which temperature the digestion can take place in a reasonable time using relatively simple apparatus and under moderate oxygen pressure, with good control of pulp quality, irrespective of whether semichemical pulps are being produced or cellulose pulps whose fibers can be liberated without intensive mechanical treatment, or are simplyliberated when the cooker or digestion vessel is blown.
  • the partial pressure of oxygen during the digestion process should be within the range from about 1 to about 20 atmospheres, preferably from about 3 to about 20 atmospheres. Higher pressures should not be used, from the standpoint of safety, and are definitely unnecessary. At lower pressures, the digestion proceeds more slowly, and such pressures are not economically practical. Normally, a pressure within the range from about 3 to about 12 atmospheres is preferred.
  • Pulps for a certain field of use should have a high degree of strength. In such cases, it is suitable to carry out the digestion in the presence of an inhibitor or mixture of inhibitors which protect the cellulose and hemicellulose molecules against uncontrolled degradation. The effect of the inhibitors is reflected by the viscosity of the pulp, and the degree of polymerization of the cellulose.
  • the inhibitors can to advantage be charged to the digestion liquor during an early stage of the digestion or, preferably, at the beginning, before the digestion heating is begun. Thus, they can be added to the digestion liquor before combination with the wood, or shortly thereafter.
  • Suitable inhibitors are water-insoluble magnesium compounds, such as magnesium carbonate. Magnesium carbonate is known, and is disclosed in U.S. Pat. No. 3,384,533 to Robert et a1. dated May 21, 1968 as useful in the delignification and bleaching of cellulose pulps with alkali and oxygen, but this is not a digestion of wood.
  • Other water-insoluble magnesium compounds such as magnesium oxide and hydroxide are disclosed in South African Pat. No.
  • Aliphatic alpha-hydroxycarboxylic acids of the type RCHOHCOOH and the corresponding beta-hydroxycarboxylic acids RCHOHCH COOH have the property of forming chelates with magnesium. These chelates are of the type:
  • n is zero or one.
  • the acid is an alpha-hydroxy acid
  • n is one
  • the acid is a beta-hydroxy acid
  • R in the above formula is hydrogen or an aliphatic radical, which may be a hydrocarbon radical having from one to about ten carbon atoms, or a hydroxysubstituted hydrocarbon radical having from one to nine hydroxyl groups, and from one to about ten carbon atoms.
  • Exemplary alpha-and beta-hydroxy carboxylic acids are glycolic acid, lactic acid, glyceric acid, :,B-dihydroxybutyric acid, a-hydroxy-butyric acid, a-hydroxyisobutyric acid, a-hydroxy-n-valeric acid, a-hydroxyisovaleric acid, B-hydroxy-butyric acid, B-hydroxyisobutyric acid, B-hydroxy-n-valeric acid, B-hydroxyisovaleric acid, erythronic acid, threonic acid, trihydroxy-isobutyric acid, and sugar 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.
  • sugar acids and aldonic acids such as
  • organic acids having two or more carboxylic groups, and no or from one to ten hydroxyl groups such as oxalic acid, malonic acid, tartaric acid, malic acid, and citric acid, ethyl malonic acid, succini acid, isosuccinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, maleic acid, fumaric acid, glutaconic acid, citramalic acid, trihydroxy glutaric acid, tetrahydroxy adipic acid, dihydroxy maleic acid, mucic acid,
  • oxalic acid, malonic acid, tartaric acid, malic acid, and citric acid ethyl malonic acid, succini acid, isosuccinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, maleic acid, fumaric acid, glutaconic acid, citramalic acid, trihydroxy glutaric acid, tetrahydroxy adipic acid, dihydroxy maleic
  • mannosaccharic acid mannosaccharic acid, idosaccharic acid, talomucic acid, tricarballylic acid, aconitic acid, and dihydroxy tartaric acid.
  • alkali metal salts thereof in which A is the group CH COOH or CH CH OH, where n is an integer from zero to five.
  • A is the group CH COOH or CH CH OH, where n is an integer from zero to five.
  • the mono, di, tri, tetra, penta and higher alkali metal salts are useful, according to the available carboxylic acid groups converted to alkali metal salt form.
  • Examples of such compounds are ethylenediaminetetraacetic acid, ethylene diamine triacetic acid, nitrilotriacetic acid, diethylene-triaminopentaacetic acid, tetraethylenepentamine heptaacetic acid, and hydroxyethylethylenediaminetriacetic acid, and their alkali metal salts, including the mono, di, tri, tetra and penta sodium, potassium and lithium salts thereof.
  • aminocarboxylic acids which can be used to advantage are iminodiacetic acid, 2-hydroxyethyliminodiacetic acid, cyclohexanediaminetetraacetic acid, anthranil-N,N-diacetic acid, and 2-picolylamine- N,N-diacetic acid.
  • complexing agents can be present in rather large quantities, within the range from about two to about 10 times the amount needed to prevent precipitation of magnesium hydroxide during the digestion.
  • the use of waste digestion liquor in combination with complexing agents of this type is particularly advantageous.
  • 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 magnesium polymetaphosphate.
  • acids naturally present in waste liquors obtained from the alkaline treatment of cellulosic materials.
  • These acids represent the alkali-or water-soluble degradation products of polysaccharides which are dissolved in such liquors, as well as alkali-or 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 acid and lactic acid are also probable degradation products derived from the hemicelluloses, together with betagamma-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 processes for example, those disclosed in Ser. Nos. 869,875 and 36,670, or alkaline peroxide bleaching processes can also be used.
  • 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 digestion liquor. They can also be formed in situ from a water-soluble or waterinsoluble magnesium salt, oxide or hydroxide, in admixture with the complexing acid, and this mixture can be added to the digestion liquor.
  • the waste liquor employed as the source of complexing acid or lactone 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 digestion liquor, and then being the liquor into contact with the complexing acid or lactone or salt thereof. It is also possible to combine the complexing acid or lactone or salt thereof with the liquor 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 0.01 percent MgO, calculated on the dry weight of the wood, is added.
  • a high proportion of magnesium, up to 1 percent MgO, calculated on the dry weight of the wood, has been employed without disadvantageous effect.
  • magnesium salts are 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 wood.
  • waste liquors are particularly high in magnesium ion because of the nature of the pulp or of the pulping process.
  • liquors from 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 chlorate, magnesium formate, magnesium oxide, magnesium acetate, 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 corrosive 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 digestion liquor, or before commencing the alkaline oxygen gas digestion. Any other waterinsoluble magnesium compounds can be used in this way, for instance, magnesium phosphate, magnesium silicate and magnesium sulfide.
  • alkali-soluble silicic acids or silicates preferably the alkali metal silicates, such as sodium silicate and potassium silicate.
  • the amount usually is within the range from about 0.01 to about 2 percent, calculated as SiO by weight of the dry wood, but preferably the amount is within the range from about 0.05 to about 1 percent by weight of the dry wood.
  • the protective effect is particularly great if both magnesium compounds and silicic acid are used as the inhibitors.
  • the liquor can be fortified by adding alkali metal hydroxide and/or alkali metal carbonate and/or inhibitor before or after pressureheating.
  • the pretreatment can be carried out with such solutions at lower temperatures, from about 30 to about C, preferably using an acid solution such as a 0.1 to l percent aqueous solution of sulfuric acid, nitric acid, or
  • the oxygen digestion process of the present invention Before carrying out the oxygen digestion process of the present invention, it is particularly suitable to pretreat the wood with an aqueous solution containing sulfur dioxide, sodium bisulfite and/or sodium sulfite or other alkali metal sulfite such as potassium bisulfite or sulfite.
  • the treatment causes some dissolution and modification of the wood material, which has been found to be favorable during the oxygen digestion, particularly in the case of wood material which is difficult to pulp without any form of pretreatment, such as softwood.
  • the pulp By pretreating the wood in this manner with water or aqueous solutions, the pulp can be modified to any desired degree, and by suitably selecting the conditions according to trial-and-error experimentation (which can be carried out on a small sample) to suit the wood used, the treating conditions can be optimized for different fields of use of the pulp product.
  • the pretreatment causes a reduction in the consumption of alkali during the oxygen digestion process of the invention.
  • the pretreatment stage or part thereof is preferably carried out in the presence of a complexing agent for bivalent and/or polyvalent metal ions, such as copper, iron, manganese, cobalt and vanadium.
  • a complexing agent for bivalent and/or polyvalent metal ions such as copper, iron, manganese, cobalt and vanadium.
  • suitable complexing agents are chelating salts of nitrogencontaining polycarboxylic acids of the class set forth above in conjunction with the magnesium complex as well as polyphosphates and ethylenediamine and ethylenediamine derivatives, although other complexing agents of an inorganic or organic nature can also be used to advantage.
  • the effect can be increased if mixtures of different complexing agents are used, since certain complexing agents having more of an affinity for certain polyvalent metal ions than others, and a blend is better capable of chelating a mixture of polyvalent metal ions for this reason.
  • the use of complexing agents in connection with the pretreatment has been found to promote uniformity of the pulp during digestion.
  • This washing step may be desirable in the case of any of the pretreatment processes described above.
  • the washing increases the cost of the processing, and also increases the risk of water contamination of the pulp with metal ions and metal compounds, and consequently it may often be more practical to omit the washing step, unless it can be carried out with deionized water, at low cost. Omission of the washing is usually disadvantageous.
  • complexing agents for bivalent and/or polyvalent metal ions present during the oxygen digestion process.
  • Any complexing agents which are stable and not deleteriously affected by the digestion liquor can be used.
  • Suitable complexing agents include those mentioned above.
  • a surface-active agent can be added to the digestion liquor, and contributes to a reduction in the resin content of the wood cellulose produced from the wood. This also surprisingly contributes to a reduction in the lignin content, and a more uniform delignification.
  • the surface-active agent is suitably added at the beginning of the digestion process, or during an early stage of the digestion, and may be present during all or only a part of the digestion.
  • Cationic, anionic, and nonionic surface-active agents and mixtures thereof can be used. If liquor is circulated during the digestion process, it is suitable to use agents which do not produce foam.
  • suitable surface-active agents are polyalkylene glycol ethers of fatty alcohols and alkyl phenol polyoxyalkylene glycol ethers. Sulfonated anionic surface-active agents such as the alkylbenzene sulfonates can also be used.
  • nonsurface-active quaternary ammonium lower alkyl and/or lower alkanol and/or polyoxyalkylene alkanol salts which have the formula:
  • R R R and R are saturated aliphatic hydrocarbon radicals having from one to about four carbon atoms; and/or from one to four of R R R and R are hydroxyalkyl or polyoxyalkylene radicals terminating in a hydroxyl group, and having a formula selected from the group consisting of (C H O),,,H, (C H O),,l-l and (C H O),,H, wherein m is an integer from zero to five, p is an integer from zero to five, and q is an integer from zero to two; and mixtures of two or more thereof.
  • all of the R radicals are either saturated lower aliphatic hydrocarbon radicals or hydroxyalkyl or hydroxyalkylene polyoxyalkylene radicals of these types.
  • X is an inorganic anion, and is preferably selected from the group consisting of H CH SO C H SO Cl and Br.
  • the nature of X is not critical, provided it is inert in the cellulose pulping liquor.
  • these compounds are quaternary lower hydrocarbon amines having methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tertbutyl groups, in any combination of the same and different groups; quaternary alkanol amines, and quaternary hydroxyalkylene amines having polyoxyethylene, polyoxypropylene, and/or polyoxybutylene groups; or quaternary hydrocarbon alkanol amines having mixed combinations of such groups.
  • Exemplary quaternary ammonium compounds are tetramethyl ammonium chloride, trimethylethyl ammonium bromide, monopropyl dimethyl ethyl ammonium chloride and ammonium dibuty] methyl monomethyl sulfate.
  • the preferred compounds are quaternary methyl triethanolamines having the formula:
  • the quaternary hydrocarbon amines are known, and are available commercially. Where not available, they are readily obtainable by known methods.
  • the quaternary triethanolamines, tripropanolamines and tributanol amines also are known, and they and their polyoxyalkylene derivatives can be prepared in known manner by the condensation of ethylene oxide, propylene oxide or butylene oxide with ammonia or a mono, di or trialkanolamine.
  • the reaction mixture thus can contain mixtures of mono-, diand trialkanolamines, together with higher polyoxyalkylene derivatives.
  • This mixture can be subjected to quaternization, but it is preferable to distill the product, so as to remove the trialkanolamine fraction in the form of a product having from 98 to 99 percent trialkanolamine.
  • the quaternary ammonium nonsurface active resin control agent can be prepared from the alkanolamine such as 98-99 percent triethanolamine by quaternizing with the quaternizing agent, such as dimethyl sulfate, in known manner.
  • the oxygen digestion process of the invention is applicable to any kind of wood.
  • hardwood such as beech and oak can be pulped more easily than softwood, such as spruce and pine, but both types of wood can be pulped satisfactorily using this process.
  • Exemplary hardwoods which can be pulped include birch, beech, poplar, cherry, sycamore, hickory, ash, oak, chestnut, aspen, maple, alder and eucalyptus.
  • Exemplary softwoods include spruce, fir, pine, cedar, juniper and hemlock.
  • the processing conditions including the particle size of the wood fragments, the digestion temperature, the alkali concentration, and the oxygen pressure, should be carefully determined and controlled during the digestion.
  • the wood should be in particulate form. Wood chips having dimensions that are conventionally employed in the sulfate process can be used. However, appreciable advantages with respect to uniformity of the digestion process under all kinds of reaction conditions within the stated ranges can be obtained if the wood is in the form of nonuniform fragments of the type of wood shavings or chips having an average thickness of at most 3 mm., and preferably within the range from about 0.2 to about 2 mm. Other dimensions are not critical. Sawdust, wood flour, wood slivers and splinters, wood granules, and wood chunks, and other types of wood fragments can also be used. It is important, particularly in the case of softwood, that the wood fragments be thin, since otherwise the digestion may be nonuniform, and the process may be more difficult to control.
  • the pulped wood may optionally be subjected to a mechanical treatment in order to liberate the fibers. If the pulping is brief or moderate, a defibrator, disintegrator, or shredder may be appropriate. After an extensive or more complete pulping or digestion, the wood can be defibrated in the same manner as in other conventional cellulose cooking processes, such as sulfate pulping, by blowing off the material from the digester, or by pumping.
  • the pulped wood cellulose that is obtained in accordance with the process of the invention is of such whiteness that it can be used to advantage directly for producing tissue paper, light cardboard and magazine paper.
  • tissue paper light cardboard and magazine paper.
  • the pulp can easily be bleached in accordance with known methods by treatment with chlorine, chlorine dioxide, chlorite, hypochlorite, peroxide, peracetate, oxygen or any combinations of these bleaching agents in one or more bleaching sequence as described in for example US. application Ser. No. 882,812, now US. Pat. No. 3,652,388.
  • Chlorine dioxide has been found to be a particularly suitable bleaching agent for the oxygen digested cellulose pulp obtained in accordance with this invention.
  • the consumption of bleaching chemicals is generally markedly lower in bleaching oxygen digested pulps of the invention than when bleaching sulfate cellulose.
  • the chemicals used for the digestion process can be recovered after the waste liquor is burned and subsequent to optionally causticizing all or part of the carbonate obtained when burning the liquor.
  • EXAMPLE 1 Birch chips about 1 mm. thick and having a lignin content of 21.1 percent were used in this example. a. As a reference control, the chips were treated in an alkaline aqueous solution under the following conditions:
  • the alkali addition was conducted in four stages. 1.25 kmol of NaOH based 1,000 kg of dry wood was charged in the dirst stage, and in each of the three following stages 0.75 kmol of NaOH was charged. The digestion was otherwise carried out as before, with the exception that the alkali charge was reduced in accordance with the aforegoing.
  • the digestion time at each stage was 240 minutes.
  • the cellulose material was washed with water between each treatment stage. Subsequent to impregnating the wood with cooking liquor, the pH was 13, but fell to 10 in the liquor which was withdrawn the first time at 120 C.
  • the pH of the liquors withdrawn in the latter stages was within the range from 10 to 11. i
  • the lignin content of the pulp after the digestion was 1.5 percent, the pulp yield was 51.5 percent, and pulp brightness 75 percent SCAN.
  • the wood was digested as in b), but not under oxygen pressure. After the digestion, the burnt chips residue had a lignin content of 22.1 percent, and the yield was 71 percent. The chips residue was dark brown in colour.
  • EXAMPLE 2 Beech chips were treated in accordance with Example lb) but with the addition of a magnesium complex prepared from MgSO and ethylene-diaminetetraacetic acid (EDTA).
  • the magnesium complex was added prior to the heating.
  • the quantity of magnesium (as MgO) corresponded to 0.1 percent based on the dry wood.
  • the amount of EDTA was 0.5 percent based on the dry wood.
  • the pH values during the oxygen digestion were approximately 0.5 unit higher than in Example lb). This is related to the fact the yield of carbohydrates was higher, due to the presence of the magnesium complex.
  • the lignin content of the pulp was 2 percent, pulp yield was 57.5 percent, and the brightness of the pulp was the same as that in Example lb). The results show that the yield is greatly improved by the addition of magnesium complex.
  • EXAMPLE 3 a Birch chips having a lignin content of 2 0.9% and a thickness of 1.5 mm were digested using sodium carbonate as the alkali under the following conditions: Pretreatment: waste digestion liquor from Example lb).
  • the wood Prior to being digested, the wood was impregnated with cooking liquor. The digestion was effected in a rotary autoclave. After each digestion stage, the pulp was washed with water. Subsequent to impregnating the wood with cooking liquor at C, the pH was 1 1.0. During the major portion of the oxygen cooking process, the pH remained within the range 9.5 to 10. The lignin content of the pulp was 3 percent, the pulp yield 56.4 percent, and the pulp brightness 64 percent SCAN. The results show that a good delignification is obtained if sodium carbonate is used. b. The process was repeated exactly as in a), but without washing the wood between the different digestion stages. The same results were obtained.
  • Oxygen partial pressure atmospheres 8 Initial temperature, C 80 Initial pH 11 Time for temperature to rise from 80C to 120C,
  • EXAMPLE Spruce chips having a lignin content of 27.6 percent and a thickness of 1.6 mm were pretreated with an aqueous bisulphite solution containing 20 grams of sodium bisulphite per liter and disodium salt of ethylendiaminetetraacetic acid in a quantity corresponding to 0.4 percent based on the dry weight of the wood:
  • Pretreatment temperature C 120 Pretreatment time, minutes 90 Wood-to-liquid ratio, kg/ 1 1:4
  • the process for the digestion of wood in a digestion liquor comprising a mixture of aqueous alkali and oxygen the improvement which results in the obtention is high yield of a cellulose pulp having a high brightness and a low lignin content, which comprises limiting the amount of alkali at the beginning of the digestion to at most 75 percent of the total molar quantity of alkali required for the digestion, and adding the remainder of the required alkali progressively, during the digestion, while maintaining the pH of the digestion liquor in the course of the digestion within the range from about 9.5 to about 13 during the first stages and the major portion of the digestion process.
  • the cellulose pulp produced is a viscose, acetate or cuprammonium pulp, and the amount of alkali is within the range from about 6 to about 8 kilomoles per 1,000 kg. of dry wood.
  • the cellulose pulp produced is a pulp for use in making fine paper, plastic fillers, and soft paper or tissue paper, and the amount of alkali is within the range from about 2 to about 6 kilomoles per 1,000 kg. of dry wood.
  • alkali is any alkali metal hydroxide or alkali metal carbonate.
  • the alkali is a mixture of alkali metal hydroxide or alkali metal carbonate with an alkali metal bicarbonate which serves as a buffer.
  • aqueous alkali includes a buffering agent which increases the buffer capacity of the digestion liquor, and assists in maintaining the pH within the prescribed range during the digestion.
  • the buffering agent is a waste liquor selected from the group consisting of waste liquor from a previous alkaline oxygen digestion and waste liquor from an alkaline oxygen bleaching process.
  • aqueous alkali comprises an inhibitor inhibiting attack on the hemicellulose and cellulose.
  • the magnesium compound is a magnesium complex selected from the group consisting of an inorganic or organic acid complex of polyhydroxy acids, organic acids containing at least two carboxylic acid groups, and polyphosphoric acids.
  • the aqueous solution comprises a sulfite precursor selected from sulphur dioxide, an alkali metal bisulphite, or an alkali metal sulphite.
  • the wood is a hardwood selected from birch, beech, poplar, aspen, maple, alder and eucalyptus.
  • HOC H --N CH SO HOC H CHJ
  • line 53 "dirst” should be first 9
  • Column 16 line 36 "-35" should be -45 7
  • Column 17 line 63 is high yield” should be in high yield Signed and Sealed this Twenty-eighth Day Of September 1976 [SEAL] Altest:

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Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2523191A1 (de) * 1974-06-14 1975-12-18 Mo Och Domsjoe Ab Verfahren zur delignizifierung von lignocellulosischem material
US3944463A (en) * 1972-12-19 1976-03-16 Mo Och Domsjo Aktiebolag Pulping of lignocellulosic material with oxygen in two stages at increasing pH
US3951732A (en) * 1972-11-16 1976-04-20 A. Ahlstrom Osakeyhtio Delignification and bleaching of wood pulp with oxygen in the presence of triethanolamine
US3963561A (en) * 1973-08-27 1976-06-15 Kamyr Aktiebolag Recirculation of unconsumed oxygen pulp bleaching gas
US4119486A (en) * 1975-08-14 1978-10-10 Westvaco Corporation Process for bleaching wood pulp with ozone in the presence of a cationic surfactant
US4141786A (en) * 1976-09-13 1979-02-27 International Paper Company Manganic ion delignification of lignocellulosic material
US4152197A (en) * 1974-09-23 1979-05-01 Mo Och Domsjo Ab Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion
US4162188A (en) * 1977-05-18 1979-07-24 Honshu Seishi Kabushiki Kaisha Process for producing pulp
US4172006A (en) * 1976-08-26 1979-10-23 Weyerhaeuser Company Method of delignifying wood chips with oxygen by adding cooking liquor under pressure
US4295927A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen and storing the treated pulp
US4295926A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen
US4295925A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Treating pulp with oxygen
US4298426A (en) * 1979-06-15 1981-11-03 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen in a multi-stage bleaching sequence
US4303470A (en) * 1979-06-15 1981-12-01 Weyerhaeuser Company Method and apparatus for mixing gases with a wood pulp slurry
WO1982001019A1 (en) * 1980-09-22 1982-04-01 Nardi F Process to produce pulps
US4338158A (en) * 1976-04-09 1982-07-06 Weyerhaeuser Company Pulping in the presence of a protector
WO1983000816A1 (en) * 1981-09-04 1983-03-17 Weyerhaeuser Co Method and apparatus for mixing pulp with oxygen
US4431480A (en) * 1981-10-27 1984-02-14 The Black Clawson Company Method and apparatus for controlled addition of alkaline chemicals to an oxygen delignification reaction
US4622100A (en) * 1984-10-01 1986-11-11 International Paper Company Process for the delignification of lignocellulosic material with oxygen, ferricyanide, and a protector
US4622101A (en) * 1984-10-01 1986-11-11 International Paper Company Method of oxygen bleaching with ferricyanide lignocellulosic material
US4664832A (en) * 1984-09-28 1987-05-12 State Of South Dakota As Represented By The Department Of Transportation Deicing chemicals and their preparation from polysaccharide sources
US5073301A (en) * 1989-07-18 1991-12-17 Degussa Aktiengesellschaft Process for stabilization of the viscosity of wood pulps
US5350493A (en) * 1992-02-18 1994-09-27 Domtar, Inc. Oxygen delignification of old corrugated containers
US5858021A (en) * 1996-10-31 1999-01-12 Kimberly-Clark Worldwide, Inc. Treatment process for cellulosic fibers
WO2000047812A1 (en) * 1999-02-15 2000-08-17 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
WO2001059204A1 (en) * 2000-02-14 2001-08-16 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US20050061460A1 (en) * 2003-09-24 2005-03-24 Martin Ragnar Method and arrangement for oxygen delignification of cellulose pulp
US20050106071A1 (en) * 2002-05-29 2005-05-19 Masaaki Minamoto Bottomed tube for blood examination, stopper of bottomed tube for blood examination and blood examination container
US20060060315A1 (en) * 2003-11-28 2006-03-23 Cheng Xiang W Catalyzer for clean pulping and process for using the same
CN103492050A (zh) * 2011-04-29 2014-01-01 吉奥森泰克咨询公司 减小有机液体体积的方法

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US3652386A (en) * 1968-10-29 1972-03-28 Mo Och Domsjoe Ab Process for treating cellulosic materials with alkali and oxygen in the presence of complex magnesium salts
DE2022866A1 (de) * 1969-05-13 1970-12-23 Mo Och Domsjoe Ab Verfahren zur Behandlung von zelluloseartigem Material
US3652385A (en) * 1969-05-13 1972-03-28 Mo Och Domsjoe Ab Process for treating cellulosic materials from which metal ions have been removed with alkali and oxygen in the presence of complex magnesium salts

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Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3951732A (en) * 1972-11-16 1976-04-20 A. Ahlstrom Osakeyhtio Delignification and bleaching of wood pulp with oxygen in the presence of triethanolamine
US3944463A (en) * 1972-12-19 1976-03-16 Mo Och Domsjo Aktiebolag Pulping of lignocellulosic material with oxygen in two stages at increasing pH
US3963561A (en) * 1973-08-27 1976-06-15 Kamyr Aktiebolag Recirculation of unconsumed oxygen pulp bleaching gas
DE2523191A1 (de) * 1974-06-14 1975-12-18 Mo Och Domsjoe Ab Verfahren zur delignizifierung von lignocellulosischem material
US4152197A (en) * 1974-09-23 1979-05-01 Mo Och Domsjo Ab Process for preparing high-yield cellulose pulps by vapor phase pulping an unpulped portion of lignocellulosic material and a partially chemically pulped portion
US4119486A (en) * 1975-08-14 1978-10-10 Westvaco Corporation Process for bleaching wood pulp with ozone in the presence of a cationic surfactant
US4338158A (en) * 1976-04-09 1982-07-06 Weyerhaeuser Company Pulping in the presence of a protector
US4172006A (en) * 1976-08-26 1979-10-23 Weyerhaeuser Company Method of delignifying wood chips with oxygen by adding cooking liquor under pressure
US4141786A (en) * 1976-09-13 1979-02-27 International Paper Company Manganic ion delignification of lignocellulosic material
US4162188A (en) * 1977-05-18 1979-07-24 Honshu Seishi Kabushiki Kaisha Process for producing pulp
US4295927A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen and storing the treated pulp
US4295926A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen
US4295925A (en) * 1979-06-15 1981-10-20 Weyerhaeuser Company Treating pulp with oxygen
US4298426A (en) * 1979-06-15 1981-11-03 Weyerhaeuser Company Method and apparatus for treating pulp with oxygen in a multi-stage bleaching sequence
US4303470A (en) * 1979-06-15 1981-12-01 Weyerhaeuser Company Method and apparatus for mixing gases with a wood pulp slurry
WO1982001019A1 (en) * 1980-09-22 1982-04-01 Nardi F Process to produce pulps
WO1983000816A1 (en) * 1981-09-04 1983-03-17 Weyerhaeuser Co Method and apparatus for mixing pulp with oxygen
US4431480A (en) * 1981-10-27 1984-02-14 The Black Clawson Company Method and apparatus for controlled addition of alkaline chemicals to an oxygen delignification reaction
US4664832A (en) * 1984-09-28 1987-05-12 State Of South Dakota As Represented By The Department Of Transportation Deicing chemicals and their preparation from polysaccharide sources
US4622100A (en) * 1984-10-01 1986-11-11 International Paper Company Process for the delignification of lignocellulosic material with oxygen, ferricyanide, and a protector
US4622101A (en) * 1984-10-01 1986-11-11 International Paper Company Method of oxygen bleaching with ferricyanide lignocellulosic material
US5073301A (en) * 1989-07-18 1991-12-17 Degussa Aktiengesellschaft Process for stabilization of the viscosity of wood pulps
US5350493A (en) * 1992-02-18 1994-09-27 Domtar, Inc. Oxygen delignification of old corrugated containers
US5486268A (en) * 1992-02-18 1996-01-23 Domtar Inc. Oxygen delignification of old corrugated containers
US5858021A (en) * 1996-10-31 1999-01-12 Kimberly-Clark Worldwide, Inc. Treatment process for cellulosic fibers
WO2000047812A1 (en) * 1999-02-15 2000-08-17 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US6770168B1 (en) 1999-02-15 2004-08-03 Kiram Ab Process for oxygen pulping of lignocellulosic material and recorvery of pulping chemicals
WO2001059204A1 (en) * 2000-02-14 2001-08-16 Kiram Ab Process for oxygen pulping of lignocellulosic material and recovery of pulping chemicals
US20080274540A1 (en) * 2002-05-29 2008-11-06 Sekisui Chemical Co., Ltd. Blood testing bottomed tube, stopper for blood testing bottomed tube and blood testing container
US20050106071A1 (en) * 2002-05-29 2005-05-19 Masaaki Minamoto Bottomed tube for blood examination, stopper of bottomed tube for blood examination and blood examination container
US8685713B2 (en) 2002-05-29 2014-04-01 Sekisui Chemical Co., Ltd. Blood testing bottomed tube, stopper for blood testing bottomed tube and blood testing container
US7595028B2 (en) * 2002-05-29 2009-09-29 Sekisui Chemical Co., Ltd. Bottomed tube for blood examination, stopper of bottomed tube for blood examination and blood examination container
US20050061460A1 (en) * 2003-09-24 2005-03-24 Martin Ragnar Method and arrangement for oxygen delignification of cellulose pulp
US7156952B2 (en) * 2003-09-24 2007-01-02 Kvaerner Pulping Ab Method and arrangement for oxygen delignification of cellulose pulp
US7264690B2 (en) * 2003-11-28 2007-09-04 Xiang Wu Cheng Catalyzer for clean pulping and process for using the same
US20060060315A1 (en) * 2003-11-28 2006-03-23 Cheng Xiang W Catalyzer for clean pulping and process for using the same
CN103492050A (zh) * 2011-04-29 2014-01-01 吉奥森泰克咨询公司 减小有机液体体积的方法
CN103492050B (zh) * 2011-04-29 2016-08-17 吉奥森泰克咨询公司 减小有机液体体积的方法

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AT304251B (de) 1972-12-27
DE2123542B2 (de) 1973-10-25
JPS5025042B1 (en, 2012) 1975-08-20
SE355614B (en, 2012) 1973-04-30
BR7102728D0 (pt) 1973-06-07
FR2091515A5 (en, 2012) 1972-01-14
CA935957A (en) 1973-10-30
DE2123542C3 (de) 1974-05-22
NO134563B (en, 2012) 1976-07-26
SU574164A3 (ru) 1977-09-25
NO134563C (en, 2012) 1976-11-03
ZA712744B (en) 1972-01-26
FI54343C (fi) 1978-11-10
DE2123542A1 (de) 1971-11-25

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