US3255071A - Process for production of alkali cellulose in the absence of an aqueous liquid phase - Google Patents

Process for production of alkali cellulose in the absence of an aqueous liquid phase Download PDF

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US3255071A
US3255071A US319405A US31940563A US3255071A US 3255071 A US3255071 A US 3255071A US 319405 A US319405 A US 319405A US 31940563 A US31940563 A US 31940563A US 3255071 A US3255071 A US 3255071A
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alkali
cellulose
impregnated
liquor
liquid phase
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Theodor N Kleinert
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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
    • D21C3/22—Other features of pulping processes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
    • C08B15/08—Fractionation of cellulose, e.g. separation of cellulose crystallites

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  • This invention relates to cellulosic pulps, more especially to pulps of low viscosity and of high tit-cellulose content obtained from fibrous cellulosic material by alkaline treatment and to a process for their production.
  • pulp is produced by delignication of fibrous material upon cooking with low content sodium hydroxidesodium sulfide aqueous solutions, in liquid phase, under relatively mild conditions so as to avoid degradation of cellulose.
  • cellulosic pulp of low viscosity and high tt-cellulose content can be obtained from fibrous cellulosic material by controlled alkaline treatment, with no aqueous liquid phase being present, at a pressure essentially lower than that'of saturated steam at reaction temperature.
  • the present invention in its broadest aspects, consists in a process for producing crystalline cellulosic pulp of low viscosity and high tat-cellulose content having a relatively high purity comprising:
  • the present invention further consists in a stable, crystalline cellulosic pulp having a low viscosity and a relatively high tnt-cellulose content, as will be described hereinafter.
  • Subdivisions of various fibrous cellulosic materials for instance, cotton linters, waste regenerated cellulosic fibers, various woods, straw, bamboo, or bagasse, can be used as Well as small size wood waste materials like the socalled pin chips or the chipper wood dust which are difficult to pulp in conventional pulping operations.
  • alkaline liquor containing hydroxyl ions of sufficient concentration can be used to impregnate the subdivided fibrous cellulosic material.
  • Preferred alkaline liquors are sodium hydroxide solutions of appropriate concentration or the white liquor obtained by causticizing the green liquor resulting from chemical recovery of commercial black kraft liquor.
  • This alkali charge should be in amounts sufficient to result in at least 10% (weight) charge of alkali calculated as Nago and based on the dry fibrous material.
  • fibrous plant material having a high lignin content (before treatment) it may be desirable to obtain a low lignin content in the resultant product and higher amounts of alkali may be used for this purpose, e.g. to provide a l6-30% (weight) charge of alkali (Na20) calculated on the dry wood substance.
  • the low lignin cellulose pulp thus obtained, after recovery, shows good brightness without any further bleaching, e.g. up to 70% Elrepho brightness.
  • Alkali charges higher than 30% can be used but no substantial advantages are noted. Thus 16-30% alkali charge is. preferred, especially for wood.
  • concentration of alkali used is a practical matter. If lower concentrations are used, more liquor has to be retained by the fibrous material to reach a predetermined alkali charge and more Water has to be evaporated. Thus it is preferred to use concentrations corresponding to alkali concentrations expressed e.g. as NaOH of from 8 to 20%, although concentrations as low as 4% and even higher than 20% can be used effectively.
  • concentrations also apply when the alkaline liquor used is obtained from kraft liquor, although, in this case, it is customary to express alkali concentration as effective alkali calculated as NagO.
  • the alkali impregnated fibrous cellulosic material is then subjected to removal of the liquid phase by evaporation of water by any known manner.
  • the impregnated material is treated under such conditions of temperature and time so that water is removed until a water vapour pressure essentially lower than that of saturation is obtained, in other words, until the liquid aqueous phase has disappeared.
  • Removal of a predetermined part of water from the wet, impregnated material prior -to reaction can, for instance, be achieved either by evaporation at a temperature lower than that of reaction or by immediate heating of the wet impregnated material to reaction temperature while withdrawing steam until a predetermined pressure level is reached. In the latter case, the temperature of the impregnated cellulosic material rises as ⁇ the water evaporates. Actually, if the water is removed at a temperature high enough so that substantial reaction can take place, then cellulose degradation will occur as the Water is being removed. However, the rate of reaction increases drastically when the aqueous phase has been removed and the moisture content has dropped beyond the fiber saturation point.
  • heating of the impregnated cellulosic material to a predetermined reaction temperature can take place in any inert, low pressure medium, liquid, vapourous or gaseous.
  • Reactive gases such as carbon dioxide, which would combine with the alkali must not be present in noticeable amounts, if inert gases are used.
  • Oxygen should also be excluded if non-oxidized cellulose degradation products are desired.
  • Heating can be done by any means, for instance, by dielectric heating or by external heating of the reaction vessel.
  • Heating can also conveniently be done by means of unsaturated steam, s-uperheated to appropriate temperature. Because of the heat consumption by water evaporation, to maintain a certain reaction temperature, the superheated steam should be admitted to the impregnated cellulosic material in such a ratio and at such a temperature that, after compensation for the heat losses and after evaporation ⁇ to eliminate the liquid phase, the impregnated material is at reaction temperature. Waste steam from the evaporation or reaction stages, after adjusting to appropriate temperature, can be recycled.
  • agitation effected for example by turbulent movement of the subdivisions of cellulosic material is advantageous.
  • separation from the vapourous phase can be eifected after treatment by known means such as, e.g. centrifugal separators.
  • the impregnated plant material after reaching reaction temperature, in order to undergo reaction over a predetermined period of time, can be deposited for this period in an appropriate retention vessel from which it can be continuously withdrawn at the end of reaction time.
  • the reaction temperature should be between 80 C. and 220 C, while temperatures of ISO-190 C. are preferred. It has been found that most of the cellulose degradation as measured by viscosity-decrease follows approximately a first order reaction pattern. Thus, for a given reaction temperature, the logarithm of said viscosity plotted versus reaction time shows an approximately linear relationship in the ranges of viscosity observed. However, in the range of very low viscosities,
  • the reaction is quenched by cooling. This can, for instance, be achieved by treatment with saturated steam of low temperature or 4by immersion into an aqueous non-.acid liquid of appropriate temperature.
  • the (nonsoluble) crystalline cellulosic pulp produced is then recovered by separating it from the soluble portions. This can appropriately be done by leaching in an aqueous solvent which can also be used -for quenching the reaction.
  • the products of delignication which, if present, are also soluble in aqueous alkaline medium, can also be recovered by known methods from the solution.
  • Leaching out of solubilized portions of treated lignied brous plant material can' also be achieved by first leachdissolution.
  • the unwashed pulps in a dry state as obtained after reaction are fairly brittle and can easily be ground if desired.
  • the process of the present invention is advantageously carried out in a continuous manner.
  • the cellulosic raw material can be impregnated with alkali while in motion and the impregnated material can be continuously transported, for example, in an inclined externally heated rotary kiln or in suspension lin an inert gas, or vapour while lwater is being evaporated and while reaction is being carried out.
  • this 'gas may have to be separated from the treated material before recovery.
  • a most convenient means lof achieving the above is to transport the impregnated material in suspension in a stream of superheated steam at appropriate temperature and pressure.
  • FIGURE 1 represents a -schematic diagram of a preferred embodiment of the process of the invention.
  • FIGURES 2 and 3 represent photographs of X-ray diffraction diagrams of products obtained in accordance with the invention.
  • a storage bin 1 is provided for storing the subdivided fibrous cellulosic material for processing.
  • Storage vessel 2 contains alkaline liquor of appropriate concentration.
  • the subdivided ma terial is conducted through storage bin 1 into impregnation vessel 3, provided with an adequate agitator 3a, wherein it is contacted with the alkaline liquor from storage vessel 2.
  • the impregnation vessel is preferably replaced by a centrifugal pump connected to adequate piping system.
  • the thus disintegrated fibrous cellulosic material is then conducted into a 4separating device, e.g. screw press 5, in which a controlled amount of excess alkali liquor is Withdrawn from the fibrous material. This withdrawn liquor can be recycled to impregnation vessel 3, if desired.
  • reaction stage 7 shown as containing water evaporation section 7A and reactor section 7B. As described, these two sections are not necessarily separate and the water evaporation can be elfected while the librous material is being heated up to reaction temperature.
  • reaction products are then processed to a cooling and recovery section 9 in which the reaction is quenched by cooling and the crystalline cellulosic pulp is separated (and further puried by adequate means) from the portions soluble in aqueous alkali which include decomposition products of carbohydrates as well as lignin conversion products, if lignin is present in the raw material.
  • recovery of some of the lignin decomposition products can be effected in a known manner in lignin recovery section e.g. by solvent extraction .by means of a water-immiscible organic solvent and/ or precipitation after acidification of the resulting black liquor.
  • FIGURE 2 represents the X-ray diffraction diagram of a crystalline degraded cellulosic pulp obtained by impregnating black spruce sawdust with a 30% (weight) NaOH charge calculated on oven dry wood, followed by immersing in paratlin oil at 200 C. at atmospheric pressure. Immediate evaporation of water took place in approximately 1 to 2 minutes. Heating was then continued for 10 minutes at the same temperature.
  • the cellulosic pulp recovered was colorless, its lignin content was below 2%, and its tit-cellulose content was labout 92%
  • the X-ray diagram shown in FIGURE 3 represents crystalline cellulosic pulp obtained in the same manner as above except that the impregnated sawdust was heated in the same conditions for thirty minutes, after water was driven out. This diagram shows that, even under such drastic conditions of treatment, crystallinity of the cellulose was still retained to a great extent.
  • the alkali degraded cellulose obtained by the present invention offers little resistance to mechanicall grinding in a dry or wet state. Wet grinding results in the formation of gels of high stability.
  • These new alkali degraded celluloses have been found to contain carboxyl end groups as evidenced by the Ldtke calcium acetate method and by their relatively low copper number (0.5 or lower).
  • a further characteristic of these new celluloses is their improved chemical stability due to the absence of alkali lsensitive groups, e.g. reducing aldehyde or keto groups, which are removed to a great extent during the process.
  • degraded celluloses obtained by acid hydrolysis contain various oligosaccharides, and other degradation products containing such reducinggroups and other alkaline sensitive groups. These groups, particularly those which 'are alkali-sensitive groups, are responsible for the chemical instability of acid hydrolyzed cellulose, especially with regards to yellowing (see Aging and Colour Reversion of Bleached Pulps, part I, L. M. Marraccini and T. N. Kleinert, Svensk Papperstidning, vol. 65 (1962): 4, 126, part II, T. N. Kleinert and L. M. Marraccini, Svensk Papperstidning, vol. 66 (1963): 6, 189).
  • acid degraded celluloses have a relatively low tat-cellulose content.
  • degraded celluloses obtained according to the invention exhibit high a-cellulose content.
  • degraded celluloses obtained from wood according to the present process show an a-cellulose content of 90% or higher.
  • the degraded celluloses of the invention shows a derived intrinsic viscosity of about 6 or less, in some cases as low as 0.5.
  • the products of the invention also show relatively high purity and reactivity in chemical reactions such as, etherification, esterification, saccharification, gratting of polymers on cellulose or even in total acid hydrolysis to glucose.
  • a byproduct of the process consists in alkali-soluble lignin degradation products containing reactive functional groups such as phenolic hydroxyl groups.
  • the formation of these lignin degradation products is especially favoured when the reaction temperature is higher than 180 C. and the alkali charge by impregnation is higher than about 20% by weight, calculated on the O.D. iibrous material.
  • These lignin degradation products can be used for further conversion, for instance, in the production of plastic materials, or as raw material for hydrogenation.
  • EXAMPLE l A 100 gm. charge of air dried spruce wood wafers (moisture content about 30%, dimensions: 1.5 inch x 1 inch x 1&2 inch) contained in a cylindrical nickel wire basket was rst immersed for 30 minutes in a 13% sodium hydroxide solution of about 100 C. After this impregnation, the basket with the material was lifted out froml the liquor, and the excess liquor was drained for five minutes. The resulting alkali charge was about 30% NaOH calculated on O.D. wood material. The basket with the impregnated wood was then immersed into a constant temperature bath of parain oil of 190 C. which was stirred to force circulation of the parain oil through the basket.
  • the basket was then placed into a fitting vessel of slightly larger diameter and enough water was added to fully cover the cellulosic material. Partial cooling and leaching out of residual alkali of relatively high concentration, and of solubilized wood portions took place,
  • the basket containing the cellulosic material was removed and the material was transferred into a glass beaker. There, the material was washed several times with Water of C. by decantation and finally on -a Buchner funnel. After acidifying with N/ 'hydrochloric acid for removing traces of alkali, the cellulose product was washed with distilled water. Then, the material was air-dried, and after drying, it was exhaustively extracted with petroleum ether. The resulting product showed the following analytical data:
  • Coniferous chipper wood dust of about 30% moisture content was used in this example.
  • the wood material was characterized by particle weights from about 0.1 gm. to about 0.001 gm.
  • the wood dust was impregnated at a temperature of about 100 C. and at atmospheric pressure for 30 minutes in white liquor from a commercial kraft mill having an effective alkali content (sulphidity 30%) of about 10% by weight expressed as Na2O. After removal of the impregnated wood material from the liquor, the excess liquor was pressed off resulting in an alkali charge of about 28% NaZO.
  • the impregnated wood was continuously fed into a small externally rheated inclined rotary kiln, Whereit was heated at atmospheric pressure to 185-188 C. while moving and simultaneously being subjected to the action of countercurrently owing unsaturated steam of the same temperature.
  • the steam was produced in a steam generator, free of O2 and CO2.
  • the total time of the heat treatment in the kiln was minutes.
  • the cellulose produced had a lignin content of about 1.2% and an alpha cellu lose content of about 94%.
  • the apparent 0.5% CED viscosity was about 1%.
  • the lcellulose showed without any bleaching an Elrepho brightness of about 68%.
  • Intrinsic viscosity of this material was low, corresponding to an apparent 0.5% CED viscosity of about 11.2. Elrepho brightness was 69% Without any bleaching treatment. Wet grinding of the cellulose in a ratio of 1:25 for half an hour resulted in the formation of a stable gel.
  • the alkali charge calculated 4on wood was 25-26% expressed as NazO.
  • the material was mechanically treated to break down agglomerations and was thenuidized in superheated steam of 220 C. and l30 p.s.i. pressure in a reactor column which was kept at this temperature by external heating. Total time of treatment was 40 seconds. After recovery, the cellulose had a lignin content of 3%. Its Elrepho brightness was 58%.
  • EXAMPLE 6 Surgical cotton was impregnated for 30 minutes at room temperature in 17.5% sodium hydroxide solution and the excess liquor was pressedl out. Part a of this material was subjected to azeotropic distillation at C. in
  • the product obtained after recovery had a brightness of about 60% G.E. and had a copper viscosity of about ,5 centipoises. Its -cellulose content was 88% and the yield calculated on initial material was about 54%.
  • EXAMPLE 8 Air dry coniferous sawdust was impregnated with a 10% sodium hydroxide solution at 100 C. in a slurry yhaving a ratio of 1:20 of sawdust to solution and the Vmixture was' stirred for 3 minutes. The impregnated sawdust was separated from the residual liquor by pressing to obtain a ratio of wood to liquor of about 1:2 and the ⁇ alkali charge was found to be about 24% expressed as Na20 and calculated on the O.D. wood residue. The wet sawdust, after mechanical treatment to break down agglomerations, was subjected at atmospheric pressure to superheated steam at 190 C. in a container which was externally heated to 190 C. The total treatment for water removal and reaction at 1,90c C, took 61/2 minutes.
  • the product thus obtained was dumped in hot water (about 90 C.) to leach out solubilized wood portions, was subsequently acidiiied with N/ 100 HCl to neutralize traces of residual alkali and was iinally washed with distilled water.
  • the degraded cellulose obtained had the following properties:
  • Process for producing crystalline cellulosic pulp of low viscosity and high nr-cellulose content having a rela- ⁇ tively high purity which comprises:
  • Process for producing crystalline cellulosic pulp of low viscosity and high -cellulose content having a relatively high purity which comprises:

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US319405A 1963-10-25 1963-10-28 Process for production of alkali cellulose in the absence of an aqueous liquid phase Expired - Lifetime US3255071A (en)

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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3887426A (en) * 1969-09-26 1975-06-03 Brev Ind Et Chimiques Soc Gen Process for producing cellulose pulp by digestion with a diol or triol solvent and an aniline or phenol salt
US4135967A (en) * 1969-09-26 1979-01-23 Societe Generale De Brevets Industriels Et Ohimiques Process for producing cellulose pulp by solid phase digestion
US4226982A (en) * 1970-09-11 1980-10-07 Blount David H Process to break down cellulose polymers and produce cellular solid or solid reaction products
US4244778A (en) * 1978-03-31 1981-01-13 Modo-Chemetics Ab Process for the chemical refining of cellulose pulp
WO1981003176A1 (en) * 1980-04-28 1981-11-12 D Blount Process to break down cellulose polymers and produce cellular solid or solid reaction products
US4339573A (en) * 1979-07-18 1982-07-13 Henkel Kommanditgesellschaft Auf Aktien Preparation of cellulose derivatives using highly reactive alkali cellulose
US4339574A (en) * 1979-07-18 1982-07-13 Henkel Kommanditgesellschaft Auf Aktien Preparation of alkyl cellulose
WO1984003527A1 (fr) * 1983-03-02 1984-09-13 Nivelleau Bruniere Patrick M F Procede de traitement de matieres ligno-cellulosique pour l'obtention de cellulose.
FR2639370A1 (fr) * 1988-11-21 1990-05-25 Tag Pulp Ind Sa Procede et installation de cuisson en phase solide de matieres lignocellulosiques
US6210801B1 (en) 1996-08-23 2001-04-03 Weyerhaeuser Company Lyocell fibers, and compositions for making same
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
US6440547B1 (en) 1996-08-23 2002-08-27 Weyerhaeuser Lyocell film made from cellulose having low degree of polymerization values
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
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
US6773648B2 (en) 1998-11-03 2004-08-10 Weyerhaeuser Company Meltblown process with mechanical attenuation

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2267087A (en) * 1937-06-07 1941-12-23 Dreyfus Henry Manufacture of cellulose
FR1129642A (fr) * 1955-08-01 1957-01-23 Perfectionnements aux dispositifs pour le traitement continu des produits en bande, notamment des tissus
GB828909A (en) * 1956-03-20 1960-02-24 Walter Philip Williams Steaming and pulping fibrous material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2267087A (en) * 1937-06-07 1941-12-23 Dreyfus Henry Manufacture of cellulose
FR1129642A (fr) * 1955-08-01 1957-01-23 Perfectionnements aux dispositifs pour le traitement continu des produits en bande, notamment des tissus
GB828909A (en) * 1956-03-20 1960-02-24 Walter Philip Williams Steaming and pulping fibrous material

Cited By (35)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3887426A (en) * 1969-09-26 1975-06-03 Brev Ind Et Chimiques Soc Gen Process for producing cellulose pulp by digestion with a diol or triol solvent and an aniline or phenol salt
US4135967A (en) * 1969-09-26 1979-01-23 Societe Generale De Brevets Industriels Et Ohimiques Process for producing cellulose pulp by solid phase digestion
US4226982A (en) * 1970-09-11 1980-10-07 Blount David H Process to break down cellulose polymers and produce cellular solid or solid reaction products
US4244778A (en) * 1978-03-31 1981-01-13 Modo-Chemetics Ab Process for the chemical refining of cellulose pulp
US4339573A (en) * 1979-07-18 1982-07-13 Henkel Kommanditgesellschaft Auf Aktien Preparation of cellulose derivatives using highly reactive alkali cellulose
US4339574A (en) * 1979-07-18 1982-07-13 Henkel Kommanditgesellschaft Auf Aktien Preparation of alkyl cellulose
WO1981003176A1 (en) * 1980-04-28 1981-11-12 D Blount Process to break down cellulose polymers and produce cellular solid or solid reaction products
WO1984003527A1 (fr) * 1983-03-02 1984-09-13 Nivelleau Bruniere Patrick M F Procede de traitement de matieres ligno-cellulosique pour l'obtention de cellulose.
US4790905A (en) * 1983-03-02 1988-12-13 Societe Tag Pulp Industries S.A. Process for the pulping of lignocellulose materials with alkali or alkaline earth metal hydroxide or salt and a solvent
FR2639370A1 (fr) * 1988-11-21 1990-05-25 Tag Pulp Ind Sa Procede et installation de cuisson en phase solide de matieres lignocellulosiques
US6471727B2 (en) 1996-08-23 2002-10-29 Weyerhaeuser Company Lyocell fibers, and compositions for making the same
US6706237B2 (en) 1996-08-23 2004-03-16 Weyerhaeuser Company Process for making lyocell fibers from pulp having low average degree of polymerization values
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
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
US6210801B1 (en) 1996-08-23 2001-04-03 Weyerhaeuser Company Lyocell fibers, and compositions for making 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
US6514613B2 (en) 1996-08-23 2003-02-04 Weyerhaeuser Company Molded bodies made from compositions having low 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
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
US7090744B2 (en) 1996-08-23 2006-08-15 Weyerhaeuser Company Process for making composition for conversion to lyocell fiber from sawdust
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
US6861023B2 (en) 1996-08-23 2005-03-01 Weyerhaeuser Company Process for making lyocell fiber from sawdust pulp
US6306334B1 (en) 1996-08-23 2001-10-23 The Weyerhaeuser Company Process for melt blowing continuous lyocell fibers
US6692827B2 (en) 1996-08-23 2004-02-17 Weyerhaeuser Company Lyocell fibers having high hemicellulose content
US6706876B2 (en) 1996-08-23 2004-03-16 Weyerhaeuser Company Cellulosic pulp having low degree of polymerization values
US6773648B2 (en) 1998-11-03 2004-08-10 Weyerhaeuser Company Meltblown process with mechanical attenuation
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
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
US20030183351A1 (en) * 1999-02-24 2003-10-02 Sealey James E. Use of thinnings and other low specific gravity wood for lyocell pulps method

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AT260006B (de) 1968-02-12
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