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
  • D21C3/26—Multistage processes
  • D21C3/263—Multistage processes at least one stage being in presence of oxygen

Definitions

• lignocellulosic material to produce cellulose suitable for the manufacture of paper products involves the removal of lignin and other noncellulosic components such as gums. Reagents that attack lignin without affecting appreciably the cellulose are preferred for this purpose.
• lignocellulosic material is cooked with a mixture of sodium hydroxide and sodium sulphide. In the soda process the cooking is carried out with sodium hydroxide alone.
• lignocellulosic material can be delignified effectively in a two stage process, without intermediate defiberization, comprising a first stage cooking with sulphate or caustic liquor at a temperature higher than used in conventional pulping processes, the cooking being adapted to produce a high yield, followed by a second stage treatment in alkaline medium with oxygen or an oxygen-containing gas under pressure.
• the cooking periods of the novel process are of the same order as of conventional kraft processes.
• the novel process provides a pulp in higher yield, of better bleaching response with the production of less pollution than conventional pulping processes.
• the main object of this invention is to provide a pulping process that gives an increased yield of cellulosic pulp.
• a further object is to provide a two stage process that can be carried out as continuous unit operation without an intermediate defiberization step. Ad-' ditional objects will appear hereinafter.
• the process of this invention comprises the steps of l. treating lignocellulosic material in a closed reaction vessel with a pulping liquor containing alkali metal hydroxide with or without admixture of alkali metal sulphide at a temperature in the range 160C to 195C for a period of not greater than 90 minutes and preferably not greater than 60 minutes, the temperature and period of treatment being adapted to provide a pulp yield of 55 to 65 percent by weight.
• the lignocellulosic material employed is wood, this is first converted into the form of chips. This step will not be 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.
• birch is preferred to employ a longer time to reach maximum cooking temperature in the first stage and to add alkali hydroxide in the second stage while the pulp is at low consistency e.g. 2 to 6 percent. It is desirable to remove 40 to 60 percent of the lignin of dense deciduous woods in the first stage.
• the treatment of the first step is carried out with a pulping liquor containing only alkali metal hydroxide, 14 to 24 percent preferably 18 to 22 percent by weight of this, based on the weight of the lignocellulosic material is employed. Normally the liquor will also contain alkali metal carbonate.
• Effective alkali is the sum of all alkali hydroxide in solution expressed as Na O including that formed by hydrolysis of the alkali sulphide, also expressed as Na- O.
• Sulphidity is the total sulphide, expressed as Na O, calculated as a percentage of total titratable alkali, including that formed by hydrolysis of the sulphide, also expressed as Na O.
• the first step treatment is carried out in a closed reaction vessel at a temperature in the range C to C in the presence of water, the reaction will take place at supra atmospheric pressure.
• the yield is increased and delignification is accelerated by the addition to the pulping liquor of 0.02 to 2.0 percent, preferably 0.05 to 1.0 percent, by weight based on the lignocellulosic material, of anthraquinone monosulphonic acid or anthraquinone disulphonic acid, or alkali metal salts of said acids, or mixtures of the aforesaid acids and/or salts.
• the addition of said anthraquinone compounds is most effective when the first step is carried out with a pulping liquor containing alkali metal hydroxide without addition of alkali metal sulphide.
• the resulting pulp yield will be 52 to 65 percent, preferably 58 to 62 percent by weight, based upon the lignocellulosic material.
• the kappa number of the material at the completion of the first step will lie in the range 80-130 for "oniferous woods and in the range 40-90 for deciduous woods.
• the partially delignified material resulting from the first treatment step is discharged from the pulping vessel and the spent liquor displaced by fresh water or spent liquor from the alkaline oxygen treatment step or white water from a later stage of a papermaking process.
• white water is meant process water that has been used for transfer of slush pulp and has been separated from the pulp for re-use in the process.
• alkali metal hydroxide may be provided in the form of pulping liquor or white liquor" such as used in the first stage of the process. This liquor therefore may contain sulphide, sulphate and carbonate in addition to the alkali metal hydroxide.
• magnesium salt such as magnesium chloride or magnesium sulphate.
• the magnesium salt may be added directly as the salt or as a complex formed with the spent liquor from the alkaline oxygen treatment step.
• the alkaline lignocellulosic mateial is then fed without mechanical defiberization into an oxygen treatment vessel.
• the material is then treated with oxygen or an oxygen-containing gas under pressure.
• the product of the oxygen treatment is separated from the spent liquor and washed with water. It will have a residual lignin content of 2 to 6 percent, preferably, 2 to 4 percent of weight of the original lignocellulosic material, corresponding to a yield of 43 to 53 percent by weight.
• the alkali metal hydroxide employed as reagent in the process of this invention may be sodium hydroxide or potassium hydroxide.
• the alkali metal sulphide reagent may be sodium sulphide or potassium sulphide.
• the oxygen treated material may be subjected to a bleaching treatment.
• a conventional bleaching sequence comprising chlorination, alkaline extraction and treatment with chlorine dioxide is sufficient to provide a product having a brightness of approximately 90 units (Elrepho).
• the first bleaching stage may comprise treatment with chlorine dioxide followed sequentially, without intervening washing, by chlorination.
• the process of this invention has the advantage that no defiberization is required between the treatment with pulping liquor and the treatment with oxygen. This reduces the amount of equipment required for the process.
• conventional soda pulping which requires cooking periods of several hours the cooking periods of the present invention are of the same order as a conventional kraft process.
• Employing the process of the present invention wherein the first stage utilizes kraft pulping liquor it is possible to obtain a product in yield which is 6 to 7 percent greater than the yield of a conventional kraft process.
• the present process is followed by a conventional bleaching sequence the decrease in yield caused by bleaching is equivalent to the decrease in yield that occurs in bleaching pulp of the same kappa number prepared by the kraft process.
• the lessened usage of sulphur-containing reagents results in lessened pollution potential.
• the chips were cooked with kraft liquor containing 12 percent by weight of effective alkali expressed as sodium oxide and 25% sulphidity and 1.0% of anthraquinone- 2-mono-sulphonic acid based on the weight of wood, the ratio of liquor to wood being 4.
• the maximum temperature of the cook was 180C and was reached after 60 minutes. The cook was maintained at 180C for 10 minutes. The yield of the cook was 60.9 percent, the product having a kappa number of 104.
• the partially delignified wood was impregnated at room temperature with an aqueous solution containing 9.5% sodium hydroxide and magnesium sulphate in an amount containing 0.2% magnesium ion, based on the weight of the partially delignified wood.
• the alkaline wood was treated in a closed reactor in the presence of water at a consistency of 27 percent, at 1 15C for 50 minutes with oxygen under a partial pressure of 80 psi.
• the delignified product was obtained with a yield of 51.9 percent based on the starting material, and a kappa number of 30 and a viscosity of 13.1 centipoise.
• step 4 The oxygen-treated product of step 4 was subjected to three bleaching steps: chlorination, caustic extraction and chlorine dioxide treatment.
• Chlorination Pulp at 3 percent consistency by weight treated with 6 percent by weight of chlorine for 1 hour at 24C.
• Caustic extraction Pulp at 10 percent consistency by weight treated with 2.9 percent by weight of sodium hydroxide for 2 hours at C.
• Chlorine dioxide treatment Pulp at 6 percent consistency by weight treated with 0.6% chlorine dioxide by weight for 3 hours at 70C.
• the pulp was washed with water at the completion of each of the bleaching steps.
• the product had a brightness of 88.4 (Elrepho) and a viscosity of 11.8 centipoise.
• the physical properties of the product are shown in the following Table I.
• Example 1 was subjected to the following treatment sequence. 3. Without defiberization, the partially delignified wood was impregnated at room temperature with an 1. The chips were cooked with soda liquor containing aqueous sohltion Containing 50% sodium hYdr9Xde percent by weight of sodium hydroxide based on and magneslllm S u1phate m an amolmt contammg the weight of wood, the ratio of liquor to wood being 9 magnslum based on the Welght of the 4. Maximum temperature of the cook was 180C and dehgmfied Wood was reached after 60 minutes. The cookwas maim 20 4. The alkalme wood was treatedln a closed reactor in tained at 180C for 60 minutes.
• the yield was 53.2 the Presence of Wafer at FOHSISteIICY of 27 percelfltl percent and the kappa number 106 at l 15C for 50 mlnutes with oxygen under a partial 2.
• the partially delignified wood was washed with fresh Pressure of 80 P
• the delignified Product was water tained with a yield of 48.4 percent based on the start- 3.
• the oxygen'tl'eated P P p of p 4 was The pulp was washed with water at the completion jected to three bleaching steps: chlorination, caustic f h f the bleaching steps. extraction and chlorine dioxide treatment. 40
• Chlorination Pulp at 3 Percent consistency by The product had a brightness of 87.5 (Elrepho) and weight treated'with 5.6% chlorine for 1 hour at 24C.
• Caustic extraction Pulp at 10 percent consistency by weight treated with 2.2% sodium hydroxide for 2 a viscosity of 10.7 centipoise. The physical properties of the product are shown in Table III.
• hOLlIS at 65C. TABLE In Chlorine dioxide treatment: Pulp at 6 percent consistency by weight treated with 0.7% chlorine dioxide Freeness Breaking Burst Tear Bulk y Weight for 3 hours at 700C C.S.F. Lelnllgth Factor Factor cc/gm The pulp was washed with water at the completion e leachin ste s. .500 2,700 84 107 1.37 of each ofth b g p 300 13,300 93 98 1.35
• the product had a brightness of 88.5 (Elrepho) and a viscosity of 7.3 centipoise.
• the physical properties of the product are shown in Table II.
• EXAMPLE 4 TABLE II A mixture of spruce and balsam wood chips was subjected to the following sequence of treatment. Freeness Breaking Burst Te Bulk l. The chips were cooked with kraft liquor containing g Factor Factor cc/gm 12 percent by weight effective alkali expressed as sodium oxide and 25 percent sulphidity based on the 588 i238 3g 3g lg? weight of wood, the ratio of liquor to wood being 4. The maximum temperature of the cook was 180C and was reached after 60 minutes. The cook was maintained at 180C for 15 minutes. The yield of the EXAMPLE 3 cook was 60.4 percent, the product having a kappa The same mixture of spruce and balsam wood chips number of 103.
• Example 2 As in Example 1 was subjected to the following treat- 2. The partially delignified wood was washed with fresh ment sequence. water.
• the partially delignified wood was impregnated at room temperature with an aqueous solution containing 9.0% sodium hydroxide and magnesium sulphate in an amount containing 0.2% mag-
• the chips were cooked with a kraft liquor containing 15.5 percent effective alkali expressed as sodium oxide and 25 percent sulphidity based on wood, the ratio of liquor to wood being 4.
• the maximum temperature of As comparison to the results obtained in Examples 1,
• Chlorine dioxide treatment Pulp at 6 percent consisorma p a per n e y tency by weight treated with 1.0% chlorine dioxide weight treated with percent by weight of chlorlne by weight for 3 hours at 0 i 1 h at t t t b
• Caustic extraction Pulp at 10 percent consistency by 3 extractlohu p a percen (fonsls Y y weight treated with 0.5 percent by weight of sodium weight treated w1th 2.4 percent by weight of sodium hydroxide for 1 1 hours at o hydroxide for 2 hou at 65
• Chlorine dioxide treatment Pulp at 6 percent consis- Chlorme dioxide treatment: Pulp at 6 percent consrstency by Weight trgated with 03% Chlorine dioxide tency by weight treated with 0.7% chlorine dioxide by weight for 3 hours at I o y Weight for 3 hours 7 The pulp was washed with water at the completion of The pulp was washed with water at the completion each of the bleaching Steps.
• the product was obtained in 41.2 percent yield based
• the Product was Obtamed 4725 Percent yleld on wood, and had a brightness of 89.0 (Elrepho) and based on wood and had a brightness of 88.5 (Elrepho) a viscosity f 1&8 i i and a Viscosity of cehtipolse-
• the strength properties of the product are shown in The strength properties of the product are shown in T bl ⁇ I Table IV.
• Adjustment of the yield of the control to a yield corresponding to kappa number of Examplesl to 4 was carried out by interpolation of a plot of kappa number against yield for the wood species in question.
• the plot was based upon the relationship Percent lignin 0.15 (Kappa Number) 0.24 disclosed in Some Fundamental Aspects of Oxygen Pulping" by R. Marton, 4th Canadian Wood Symposium, Quebec City, July 4-6, 1973.
• the initial lignin content of the wood was obtained from Pulpwoods of United States and Canada, I. H. lsenberg, 2nd edition, Institute of Paper Chemistry, Appleton Wisconsin 1951.
• the slope of the plotted values was 0.332 percent yield per kappa numand25.0 percent sulphidity at a liquor to wood ratio of 4:1.
• the maximum temperature of the was 180C and was reached in 2 hours. The treatment was terminated when 180C was reached.
• the yield was 58.1 percent of wood at a kappa number of 42.9.
• Portion A had a yield of 93.9 percent with 9.8 per- TABLE II cent of screen rejects based on pulp weight or a yield of 54.6 percent with 4.9 percent of screen rejects based fC fBl h Ch I on wood.
• the kappa number of the product was 1 1.1, Comparison 0 omposition o eac ing emicas by the Product of this Invention the v1scos1ty 22.2 cps.
• Portion B had a yield of 90.3 per (Example 1 cent w1th 16 percent screen re ects based on pulp and gzzfiqgg Pmcess weight or a yield of 52.5 percent with 7.7 percent mangle 1 Example 5 screen rejects based on wood.
• the kappa number was (Control) 12.3, the viscosity 16.6 cps.
• Chlorine 6 6 It can be seen that low consistency 1mpregnation is Sodium hydroxide 2.9 3.3 o e effectlve.
• hydroxlde an percent e85 c 40 Four additional samples were delignified using the process with first stage cooking with soda liquor. One sample serving as control was delignified by a conventional kraft cookin rocedure. The details of the deli nifi- EXAMPLE 6 g P g cation procedures are shown in Table IX, the bleachlng A sample of birch wood chips was treated with kraft response in Table X and strength properties in Table cooking liquor containing 13.0 percent effective alkali X1.
• a mixture of spruce and balsam fir wood chips was subjected to the following treatment sequence.
• the chips were cooked with soda liquor containing sponding to the kappa number of Samples 1, 2, 5 and percent by weight of sodium hydroxide based on 8 was carried out as in in Examples 1 to 4.
• the slope the weight of wood, the ratio of liquor to wood being of the plot of percent yield against kappa number was 4:1.
• the cook contained 0.1 percent by weight based 0.415 percent yield per kappa number.
• the adjusted on wood of anthraquinone-2-monosulphonic acid. yield values for the control (Sample 9) are as follows.
• the maximum temperature of the cook was 180C and was reached after 1 hour.
• the cook was main- TABLE XIII tained at 180C for 50 minutes.
• the kappa number of the product was 82.4.
• the alkaline wood was treated in a closed reactor in the presence of water at a consistency of 27 percent at 1 C for 50 minutes with oxygen under a partial pressure of 80 pounds per square inch.
• the deligni- 14 treated additionally with 0.1 percent by weight of -anthraquinone-2-monosulphonic acid (AMS). In all samples the liquor to wood ratio was 4:1. The maximum temperature of the cooks was in all cases 170C.
• AMS -anthraquinone-2-monosulphonic acid
• the oxygen-treated product pulp of step 4 was sub- The products of Samples 1, 3 and 4 were treated, at jected to three bleaching steps: chlorination, caustic a consistency of 3 percent in water, with sodium hyextraction and chlorine dioxide treatment. droxide and magnesium sulphate in amount equal to Chlorination: Pulp at 3.0 percent consistency by 0.2% magnesium ion. The products were then pressed weight treated with 7.14 percent by weight chlorine to a consistency of 27 percent and treated in an oxygen for 1 hour at 25C. reactor with oxygen under a partial pressure of 80 psi Caustic Extraction: Pulp at 12 percent consistency for 50 minutes at 115C.
• EXAMPLE 9 Five portions of eastern cottonwood chips were subjected to differing delignification treatments. Eastern All 5 samples were next subjected to bleaching secottonwood is a low density deciduous wood, in distincquences. All samples were subjected to the sequence; tion to birch, a high density deciduous wood. In the first chlorination, caustic extraction with sodium hydroxide, step all portions were treated in a 3 liter digester with and treatment with chlorine dioxide. Samples 2 and 5 cooking liquor at a liquor to wood ratio of 4:1. The were subjected to the additional sequence; caustic exmaximum temperature of the cooks was 170C.
• lignocellulosic material is a coniferous species of wood. there is added to said pulping liquor 0.02 to 2.0 45 3.
• the lignopercent, preferably 0.05% to 1.0% by weight, cellulosic material is a deciduous species of wood. based on the weight of the lignocellulosic material 4.
• magnesium salt is magnesium chloride or magnesium sulphate.
• alkali metal hydroxide is sodium hydroxide or potassium hydroxide.

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• 1973
  • 1973-12-31 GB GB6030373A patent/GB1449828A/en not_active Expired
• 1974
  • 1974-04-04 CA CA196,893A patent/CA1035508A/en not_active Expired
  • 1974-04-08 US US459112A patent/US3888727A/en not_active Expired - Lifetime
  • 1974-04-24 SE SE7405516A patent/SE407816B/xx unknown
  • 1974-04-25 JP JP49046070A patent/JPS5029801A/ja active Pending
  • 1974-04-26 DE DE2420381A patent/DE2420381A1/de active Pending
  • 1974-04-26 BR BR3415/74A patent/BR7403415D0/pt unknown
  • 1974-04-26 ES ES425711A patent/ES425711A1/es not_active Expired

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