Classifications

• • 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
  • D21C3/222—Use of compounds accelerating the pulping 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
  • D21C1/00—Pretreatment of the finely-divided materials before digesting

Definitions

• This invention relates to a process for the delignification of lignocellulosic material such as wood, straw, bagasse, etc. and in particular relates to an improved vapour phase alkaline pulping process for the production of a chemical cellulosic pulp.
• lignocellulosic material to produce cellulose suitable for the manufacture of paper products involves the removal of lignin and other non- cellulosic components such as gums. Reagents that attack lignin without appreciably affecting the cellulose component are preferred for this purpose. It is still a general practice today to use these reagents in the form of aqueous solutions and to effect the cooking of lignocellulosic material in such solutions under conditions of temperature and pressure chosen to provide an acceptable lignin to cellulose ratio.
• this liquid phase process is known as the soda process wherein the reagent is sodium hydroxide alone, the kraft process wherein the reagents are sodium hydroxide and sodium sulphide, the polysulphide process wherein the reagents are sodium hydroxide, sodium sulphide and polysulphides, or the neutral sulphite semichemical process in which the reagents are an alkali metal base such as sodium hydroxide and an alkali metal sulphite such as sodium sulphite. All these reagents have in common that they give alkaline aqueous solutions and thus constitute alkaline cooking liquors.
• vapour phase process consists in impregnating lignocellulosic material in a suitably divided form with an alkaline cooking liquor, withdrawing any excess of cooking liquor and then cooking the impregnated material under the same time and temperature conditions as in conventional liquid phase pulping.
• An example of this process wherein kraft liquor is used as the impregnating liquor is described by Kleinert in United States Patent No. 3,215,588 issued on 2nd November, 1965.
• the vapour phase process affords an increased pulping rate and lower chemical requirements.
• a cyclic keto compound selected from the group consisting of naphthoquinone, anthraquinone, anthrone, phenanthrenequinone, the alkyl, alkoxy and amino derivatives of these compounds, 6,11-dioxo-1H-anthra[1,2-c] pyrazole, anthraquinone-1,2-naphthacridone, 7,12-dioxo-7,12-dihydroanthra[1,2-b]pyrazine, 1,2-benzanthraquinone, 10-methylene anthrone and the unsubstituted and lower alkyl substituted Diels Alder adducts of naphthoquinone and benzoquinone.
• a cyclic keto compound selected from the group consisting of naphthoquinone, anthraquinone, anthrone, phenanthrenequinone, the alkyl, alkoxy and amino derivatives of these compounds
• this modification which consists in the addition to the cooking liquor of any one of the above cyclic keto compounds results in a increased rate of cooking as well as in a better pulp yield.
• One great advantage of this modification when applied to the soda process is that it makes the latter as efficient as the conventional kraft process in the pulping of soft wood.
• this novel vapour phase process results in higher pulp yields while at the same time requiring lesser amount of caustic and cyclic keto compounds and retaining the advantages of the conventional vapour phase process.
• the cooked lignocellulosic material produced by the above third step is then washed as in the conventional processes with water or an aqueous liquor inert to the lignocellulosic material to obtain a delignified cellulosic material which may be used without further treatment or may be subjected to conventional bleaching steps.
• the lignocellulosic material employed is wood, it is first converted into the form of chips. Of course, this step is not required when the lignocellulosic material is of fibrous form.
• the process of this invention can be used to delignify either coniferous or deciduous species of wood.
• coniferous is meant species such as pine, spruce and balsam fir.
• deciduous is meant species such as birch, aspen, eastern cottonwood, maple, beech and oak.
• Pulping liquors suitable for use in the first step of the process are the soda, kraft, polysulphide and alkaline sulphite liquors.
• the soda liquor is much preferred because it does not contain any sulphur compounds and is therefore considerably less polluting than the three other liquors.
• the soda liquor contains from 8% to 20% by weight of alkali metal base expressed as percent effective alkali, based on the weight of the lignocellulosic material, and normally also contains alkali metal carbonate.
• the kraft liquor contains from 8% to 15% by weight of alkali metal base expressed as percent effective -alkali (TAPPI T-1203 S-6) and from 5% to 40% by weight of alkali metal sulphide expressed as percent sulphidity (TAPPI T-1203 OS-61), based on lignocellulosic material.
• This pulping liquor will normally contain alkali metal sulphate and alkali metal carbonate.
• the polysulphide liquor is essentially a kraft liquor as defined immediately above, containing excess sulphur, i.e. polysulphides.
• the presence of polysulphides results in an improved yield and an amount of 1.0% to 5.0%, preferably 2% thereof (expressed as sulphur and based on weight of lignocellulosic material) in the liquor is therefore a definite advantage.
• the alkaline sulphite liquor is a liquor which contains an alkali metal hydroxide preferably sodium hydroxide and an alkali metal sulphite preferably sodium sulphite.
• Effective alkali is the sum of all alkali hydroxide in solution expressed as Na 2 0 including that formed by hydrolysis of the alkali sulphide, also expressed as Na 2 O.
• Sulphidity is the total sulphide, expressed as Na 2 O, calculated as a percentage of total titrable alkali, including that formed by hydrolysis.
• the compounds which are suitable for use as additives,in the process of the invention are the cyclic keto compounds selected from the group consistings of naphthoquinone, anthraquinone, anthrone, phenanthrenequinone, the alkyl, alkoxy and amino derivatives of these compounds, 6,11-dioxo-1H-anthra[1,2-c]pyrazole, anthraquinone-1,2-naphthacridone, ?,12-dioxo-7,12-dihydroanthra[1,2-b]pyrazine, 1,2-benzanthraquinone, 10-methylene anthrone, 1,2,3,4,5,6,7,8-octahydroanthraquinone and the unsubstituted and lower alkyl substituted Diels Alder adducts of naphthoquinone and benzoquinone.
• alkyl derivatives of these compounds it is meant to include any of the four compounds naphthoquinone, anthraquinone, anthrone and phenanthrenequinone, substituted with one or two alkyl groups containing 1 to 4, preferably 1 to 2, carbon atoms.
• alkoxy derivatives of the same four compounds which are suitable for use as additives are those which have at least one alkoxy substituent containing 1 to 4, preferably one, carbon atoms.
• anthraquinone examples thereof are 1-methyl anthraquinone, 2-methyl anthraquinone, 2-ethyl anthraquinone, 2,6-dimethyl anthraquinone, 2,7-dimethyl anthraquinone, 2,3-dimethylanthraquinone, 1-methoxy anthraquinone and 2-amino anthraquinone.
• the unsubstituted Diels Alder adducts suitable for use as additives in the process of this invention are those obtained by reacting 1 or 2 moles of butadiene with naphthoquinone and benzoquinone respectively.
• lower alkyl-substituted adducts it is meant the adducts obtained where in the above reaction either one or both of the reactants are substituted with the appropriate lower alkyl groups.
• Such lower alkyl groups may range in number from 1 to 4, may each contain from 1 to 4 carbon atoms and may be the same or different.
• Examples of Diels Alder adducts are 1,4,4a,5,8,8a,9a,l0a-octahydroanthraquinone, 2,3,6,7-tetramethyl-1,4,4a,5,8,8a,9a,10a-octahydroanthraquinone, 1,4,4a,9a-tetrahydroanthraquinone, 2-ethyl-1,4,4a,9a-tetra- hydroanthraquinone, 2, 3-dimethyl-l,4,4a,9a-tetrahydroanthra- quinone and 1,3-dimethyl-1,4,4a,9a-tetrahydroanthraquinone,
• the cyclic keto compound as above defined is added to the pulping liquor prior to impregnation of the lignocellulosic material and is employed in proportions of from 0.001% to 10.0%, preferably 0.01% to 1.0% by weight based on the lignocellulosic material.
• alkaline pulping liquor is the soda liquor
• a nitro aromatic compound selected from the group consisting of mono and dinitrobenzenes and the amino, carboxy, hydroxy, and methyl derivatives thereof.
• nitrobenzene examples include nitrobenzene, 2-nitroaniline, 4-nitroaniline, 4-nitrobenzaldehyde, 4-nitrobenzoic acid, 2-nitroresorcinol, 4-nitrostyrene, 2-nitrotoluene, 4-nitrotoluene, 1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 2,4-dinitrotoluene, 3,5-dinitrobenzoic acid, 4,6-dinitro-o-cresol and 2,4-dinitroresorcinol.
• nitrobenzene is particularly preferred because of its favourable cost:benefit ratio.
• the nitro aromatic compound is employed in proportions of from 0.01% to 10.0%, preferably 0,10% to 2.0%, by weight, based on the lignocellulosic material.
• nitro aromatic compound as second additives in combination with cyclic keto compounds is optional and only applicable to the case where the pulping liquor is soda liquor. All combinations formed from any one of the above defined cyclic keto compounds with any one of the above defined nitro aromatic compounds are suitable for use in this particular embodiment of the invention. Preferred, however, is the combination comprised of anthraquinone and nitrobenzene.
• the alkali metal base employed as reagent in the alkaline pulping liquors may be sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.
• the process of the invention is carried out in a closed vessel to which lignocellulosic material in subdivided form, pulping liquor containing the above-defined additive or additives, and, if necessary, dilution water are fed in the amounts required to give the desired effective alkali. Impregnation is effected under gas or mechanical pressure and at a temperature of 25°C or higher. Once full impregnation has taken place, excess pulping liquor, if any, is drained off and the impregnated lignocellulosic material is heated either directly with steam or indirectly by e.g. electrical heating to a temperature of 150°C to 200°C for a period of 0.5 to 480 minutes.
• the material resulting from step (3) of the process may be bleached by any conventional bleaching process.
• a conventional sequence comprising chlorination, alkaline extraction, chlorine dioxide treatment, alkaline extraction, chlorine dioxide treatment (C-E-D-E-D) will provide a product having a brightness of approximately 85-90 units (Elrepho).
• Runs 1 to 4 and 9 to 12 illustrate pulping by the conventional liquid phase process with (runs 2, 4, 10 and 12) or without (runs 1, 3, 9 and 11) anthraquinone as an additive and are provided for comparison purposes.
• Runs 5 and 13 illustrate pulping by the conventional vapcur phase process and are also provided for comparison purposes.
• Runs 6 to 8 and 14 to 16 illustrate pulping by the process of the present invention employing kraft or soda liquors containing varying amounts of anthraquinone as an additive.
• Impregnating of the chips for the vapour phase cooking was made as follows:
• This treatment was intended to simulate mill scale processes of presteaming to remove air followed by pressure impregnation. The procedure was carried out at 22°C.
• Liquid phase cooks were carried out with the effective alkali, sulphidity and additive levels listed in Table II under the heading "Impregnated Liquor”.
• Liquid phase cooks were carried out with the effective alkali and additive levels shown in Table III under the heading "Impregnated Liquor”.
• Impregnation of the chips for the vapour phase cooking was effected by the same technique as used for runs 5 and 6 of Example 3, except that the one hour preheating operation (to form the polysulphide solution) and the subsequent impregnation were carried out at 50°C instead of 80°C.
• Impregnation of the chips for the vapour phase pulping was effected by the same technique as used for runs 5 and 6 of Example 3.

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Cited By (3)

Citations (4)

• 1979
  • 1979-10-05 CA CA337,139A patent/CA1132763A/en not_active Expired
  • 1979-10-10 NZ NZ191815A patent/NZ191815A/xx unknown
  • 1979-10-17 ZA ZA00795541A patent/ZA795541B/xx unknown
  • 1979-10-18 NO NO793363A patent/NO793363L/no unknown
  • 1979-10-18 AU AU51898/79A patent/AU528368B2/en not_active Withdrawn - After Issue
  • 1979-10-24 FI FI793317A patent/FI793317A/fi not_active Application Discontinuation
  • 1979-10-24 EP EP79302316A patent/EP0010451A1/en not_active Withdrawn
  • 1979-10-24 PT PT70365A patent/PT70365A/pt unknown
  • 1979-10-24 BR BR7906873A patent/BR7906873A/pt unknown
  • 1979-10-25 JP JP13709479A patent/JPS5562289A/ja active Pending
  • 1979-10-25 ES ES485352A patent/ES485352A1/es not_active Expired

Patent Citations (4)

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