• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    process for making dissolving pulp, liquor, pulp, and using a pulp. the present document relates to processes for making pulp and more specifically to improved processes for making dissolving pulp. the processes were primarily developed to be used in connection with large scale kraft processes, ie they are designed to be incorporated within a facility. a liquor derivable from the process and comprising xylan, lignin, alkali and water is also described, as well as a dissolving pulp produced by the process.
    公开号:BR112014029701B1
    申请号:R112014029701-0
    申请日:2013-05-28
    公开日:2022-01-11
    发明作者:Johannes Bogren；Jim ParkAas；Gabriele Schild；Andrea Borgards
    申请人:Lenzing Aktiengesellschaft；Sodra Skogsãgarna Ekonomisk Forening；
    IPC主号:
    专利说明:

    TECHNICAL FIELD
    [0001] The present invention relates to processes for the manufacture of pulp and more specifically to improved processes for the manufacture of dissolving pulp. The processes are designed to be used in connection with large scale kraft processes, ie they are designed to be incorporated within a facility. A liquor comprising xylan, lignin, alkali and water is also described, as well as a pulp and semi-purified pulp and possible uses for these pulps. BACKGROUND
    [0002] Dissolving pulp, also known as dissolving cellulose, is a bleached wood pulp that has a high cellulose content and is chemically produced from wood using a sulfite process or a kraft process. The kraft process is a commonly used pulping process and in a conventional kraft process, wood is treated with an aqueous mixture of sodium hydroxide and sodium sulfite. This treatment degrades and solubilizes lignin leading to defibration of the wood fibers.
    [0003] Furthermore, the conventional manufacture of dissolving pulps by kraft processes, such as kraft processes comprising a pre-hydrolysis step, suffer from low yields as the hemicelluloses in the wood are degraded during the process, mainly in the step pre-hydrolysis and are transferred into an acid condensate such as low molecular weight hemicellulose, monosaccharides and hemicellulose degradation products. Due to the difficulties in extracting these degradation products from the digester, the degraded material is at best used for energy production by evaporating and burning the components or simply discarded as waste.
    [0004] WO 99/47733 describes a process for producing cellulosic fibers, in which the degree of polymerization of the fibers obtained can be adjusted via oxidative and hydrolytic acid degradation. However, the kraft pulp obtained by this process has high amounts of residual hemicelluloses, which makes the pulp obtained less usable for the production of regenerated cellulose for use in, for example, textile applications as these residual compounds have a negative impact. in the behavior of the process and, as a result of this, also in the textile-mechanical properties of the fibers produced therefrom.
    [0005] US 2009/0312536 describes a process for producing dissolving pulp suitable for textile applications from a cellulosic starting material using a kraft process that has been combined with a cold caustic extraction (CCE) type purification step. The processes described in US 2009/0312536 are not optimized for implementation in a kraft pulp mill, that is, in an industrial scale process.
    [0006] Both WO2011/138633 and WO2011/138634 describe methods for processing pulp including a cold caustic extraction step. However, the methods described describe expensive procedures having a low total yield of dissolving pulp.
    [0007] Accordingly, it is an object of the present description to provide an improved process on an industrial scale to produce high-yield dissolving pulp in an efficient and cost-effective manner. SUMMARY
    [0008] The present invention provides improved processes for manufacturing dissolving pulp comprising a cold caustic extraction (CCE) step in the commonly used kraft process. The processes are highly suitable for use in a plant or mill, i.e. in industrial (large) scale processes and reduce the disadvantages of previously known processes.
    [0009] Therefore, the present description relates to a process for the manufacture of dissolving pulp comprising the steps of: a) selecting a wood-based raw material, wherein said wood-based raw material has a xylan content of 12% by weight or more; b) adding a cooking liquor comprising white and/or black liquor to the wood-based raw material; c) digesting the wood-based raw material composition obtained in step b) in a process kraft cooking process; d) delignify the pulp obtained from step c); e) add industrial white liquor with high ionic strength to the pulp obtained in step d), in which said pulp has a xylan content of 8% by weight or more and in which the temperature is lowered and maintained at 65°C or less for 5 minutes or more and in which the alkali concentration in the liquid phase of the pulp suspension obtained is in the range of 70 g/l to 100 g/l;f ) remove 90% or more of the dissolved alkali and xylan as a liquor stream from the pulp obtained in step e) by removing water from the pulp; and g) subjecting the pulp to washing and pressing in a washing-pressing device 1-5 times.
    [00010] By using an unconventional high concentration of alkali in step e), it is possible to introduce industrial white liquor having high ionic strength into the process and still obtain high quality dissolving pulp. Consequently, the processes described here offer economically viable industrial scale production methods.
    [00011] Removal of xylan from pulp after use of (CCE) cold caustic extraction, as opposed to pre-hydrolysis, yields alkaline liquor comprising a high concentration of high molecular weight xylan, such liquor can be used as is, or the xylan can be isolated therefrom. The processes described here make it possible to obtain valuable added products from the removal of xylan during the process for the manufacture of dissolving pulp. Another advantage is that the total yield obtained from dissolving pulp is higher in processes comprising a CCE step than in processes using a kraft-prehydrolysis process.
    [00012] In previously known dissolving pulp processes, the CCE step is carried out at low temperatures, such as 20°C to 30°C and with reaction times in the order of 30-60 minutes. It has now been shown that the CCE step in a process according to the invention can be carried out at considerably higher temperatures allowing for shorter reaction times. The use of more severe production conditions makes the process described here better suited for industrial scale production as it reduces production time and costs for cooling and reheating process fluids between different process steps. Accordingly, the CCE step in the process of the invention can be carried out at a temperature as high as 65°C, such as 50°C-60°C, and with reaction times of up to 5 minutes such as 5 minutes to 15 minutes. No deterioration in pulp quality due to changes in reaction conditions was observed.
    [00013] Consequently, the process of the invention was developed for use in a facility or a mill, that is, in an industrial environment. The process is highly suitable for integration into a kraft pulping process and is especially adapted for use under the harsh conditions existing in industrial scale mill production using liquids with high ionic strength obtained from industrial processes as opposed to conditions. more ideals and liquors that can be used in laboratory scale processes where cost constraints are of lesser importance. As will be shown here, the difference has a big impact on both process and process conditions. The wood-based raw material used in the process described herein may be in any commonly used physical form, such as chips, sawdust or shavings.
    [00014] The process may comprise a combined bleaching and depolymerization step, wherein the pulp is bleached wherein the pulp is bleached and the pulp viscosity is reduced.
    [00015] The white liquor used in the process is of industrial origin, that is, it is obtained in the mill and comprises Na2CO3, NaHS and NaOH. The presence of these different sodium compounds in the liquor means that the liquor used in CCE step e) has very high ionic strength. A high ionic strength liquor would normally affect the CCE step in a negative way as the xylan content in the resulting pulp would be higher than desired in a dissolving pulp. However, the process as defined herein overcomes this problem, as it has surprisingly been found that this problem can be completely or partially solved by increasing the alkali concentration in CCE step e). The effects of a liquid on the high ionic strength process can be mitigated by lowering the temperature and/or performing a steam activation step prior to the kraft cooking process.
    [00016] A practical upper limit for the alkali concentration in the liquid phase of the pulp suspension in step CCE e) may be approximately 95 g/l. In a process having a wash-press step before the CCE step e) with a dry solids content after the wash-press step of 30%, the amount of alkali in the liquid phase of the pulp suspension when using 117 g/l of white industrial liquor will be up to 83 g/l at a pulp concentration of 10%. This means that the liquid that is removed by the dewatering step f) will have an alkali content in that order. As a comparison, in a conventional process for producing dissolving pulp the amount of alkali in the liquid phase of the pulp suspension is only up to 33 g/l.
    [00017] The pulp consistency can be lowered to allow a higher alkali concentration, but then the need for white liquor could increase which is negative from the economic point of view of the process, as it would involve the use of more liquor white, larger vessels, larger process flows, etc. It may be advantageous if streams of alkali coming upstream from the CCE step are used in the washing step preceding the CCE step, as this will mean that the pulp is alkaline upon entering the CCE step.
    [00018] In addition, the white liquor added in step e) may have a suspended solids content of 20 mg/l or less, such as 10 mg/l or less, such as 5 mg/l or less, such as 1 mg/l. The suspended solids content in the white liquor is measured according to Tappi 692 om-08. It was found that maintaining the suspended solid content below 20 mg/l will provide a pure pulp with a low metal ion content. The measurement of solids content can be carried out after final clarification, ie final sedimentation, or after filtration of the white liquor. Sedimentation can be accomplished by, but not limited to, the use of a settling vessel and filtration can be accomplished by, but not limited to, the use of a filter.
    [00019] The present description also refers to a liquor obtainable from the CCE step of the process and comprising xylan, water, lignin and alkali, in which the xylan/lignin ratio is from 2:1 to 20:1, such as such as 3:1 to 15:1, such as 4:1 to 10:1, such as 4.5:1 to 8:1, such as 6:1.
    [00020] The present description also refers to a pulp obtainable from the process and having a twist of 1.3 to 2.0 twists/mm and a form factor of 70 to 82% and to a pulp obtained by the processes as defined here.
    [00021] Furthermore, the present description also relates to the use of a pulp as defined herein for the manufacture of cellulosic products, in particular according to the lyocell process, the modal process or the viscose process. DEFINITIONS
    [00022] As used herein the term "white liquor" implies an industrial white liquor of high ionic strength, i.e. white liquor comprising NaOH, NaHS and Na2CO3.
    [00023] The term "dissolving pulp", as used herein, is intended to define a pulp having high cellulose content and low lignin and hemicellulose content. Dissolving pulps are classified depending on their alpha-cellulose content. Depending on the applications, a different alpha-cellulose content is required.
    [00024] The term "P factor" describes the intensity of the activation step. The calculation and other details are described in, for example, "Handbook of Pulp", vol. 1, Wiley-VCH 2006, pp. 343-345.
    [00025] The term “kraft cooking” refers to a cooking process, in which a wood-based raw material is inserted into a suitable tank or vessel (e.g. a digester), a cooking liquor is added to the wood-based raw material and the cooking is carried out by raising the temperature to a cooking temperature, such as between 140 to 180°C, which is maintained for a time sufficient for delignification to take place, for example, up to 3 hours. Active cooking chemicals are hydroxide and hydrosulfide ions that react and degrade lignin. The purpose of the kraft cooking step is to release the fibers and separate them from each other.
    [00026] The terms “mill” or “facility” are used interchangeably herein and refer to a manufacturing unit that converts wood-based raw materials, such as, but not limited to, wood chips into wood-based products. wood, such as dissolving pulp or pulp.
    [00027] The term “filtrate operating method”, as used here, refers to methods for reducing the amount of fresh water needed in a washing process. One method of achieving reduced fresh water consumption in a washing process is by recirculating filtrate from a downstream washing step and using it as a washing liquid in an upstream washing step.
    [00028] As used herein, the term "hemicellulose" includes different carbohydrates such as, but not limited to, xylan and (galacto)glucomannan.
    [00029] As used herein, the term "xylan" is intended to include arabinoglucuronoxylan and glucuronoxylan, as well as xylan originating from these two.
    [00030] As used here, the expression “industrial scale process” is intended to mean a process that is carried out on a large scale, that is, a process that makes it economically possible for society to use the material obtained by the process in a large scale. scale. An industrial-scale process is distinguished from small-scale processes, such as laboratory-scale processes, pilot plant processes, etc. where cost considerations and other conditions are different from those that govern industrial production.
    [00031] As used herein, the term "alkali" refers to a basic hydroxide ion. The hydroxide ion is present in different compounds such as, but not limited to, NaOH and KOH. In the present context, the alkali concentration is always presented as NaOH, regardless of the counter ion. In this description, this is determined by titrating a sample of the liquor with strong acid to a first inflection point in the procedure specified in SCAN-N 2:88. "The terms effective alkali and alkali are used interchangeably."
    [00032] The term “lignin” refers to the lignin component of wood or any components found in pulp or liquors that originate from lignin.
    [00033] The term “intrinsic viscosity” as used herein, refers to the viscosity of pulp dissolving in a Copper-Ethylene-Diamine solution in accordance with ISO 5351:2010.
    [00034] Xylan was precipitated from the liquid phase of the pulp suspension obtained under acidic conditions following the protocol for isolation of beta-cellulose according to Tappi T 203 om-93: 1993. The molecular weight distribution of the recovered xylan was measured by chromatography size exclusion method (SEC) with multi-angle scattering light detection (MALLS) in LiCl/DMAc (dimethylacetamide) solution according to Schelosky et al., 1999 (Das Papier 53:728-738).
    [00035] The term "kappa index" as used herein is an indication of the residual lignin content or bleachability of wood pulp by a standardized method of analysis. The kappa index is determined by ISO 302:2004. The kappa number is a measurement of the standard potassium permanganate solution that the pulp will consume. The measurement is inflated by the presence of hexenuronic acids in the pulp. These compounds are formed during the chemical pulping process from hemicelluloses. The kappa index estimates the amount of chemicals required during the bleaching of wood pulp to obtain a pulp with a given degree of whiteness. Since the amount of bleaching chemicals needed is related to the lignin content of the pulp, the kappa index can be used to monitor the effectiveness of the lignin extraction phase of the pulping process.
    [00036] As used herein "cellulose II" refers to the most thermodynamically favored allomorph of cellulose as determined by 13C NMR. The method for measuring cellulose II content is described in Wollboldt ET AL. 2010 (Wood Science and Technology, 44, 533-546). Values in % with respect to this description should always be understood as given as % by weight of cellulose.
    [00037] The term “twist(s)” refers to local directional changes greater than 30° in the fibers. In order to be recognized as a twist, the distance between two strains must be at least 200 μm, the unit used is twists/mm. Twists are measured using fiber image analysis and an L&W Fiber Tester - code 912 tester was used in the analyzes in the present description.
    [00038] The term “WRV” as used herein means water retention value and is defined and analyzed by ISO 23714:2007. The WRV values here were obtained from analyzes of once-dried pulp samples.
    [00039] The term “form factor” refers to the ratio of the maximum fiber length length (designed fiber length) to the actual fiber length (along the fiber contour) expressed here in %. Form factor is thus l/Lx100 where l is the projected length and L is the actual length. The form factor is measured using fiber image analysis and an L&W Fiber Tester - code 912 tester was used in the present analyses.
    [00040] The term "lateral fibril aggregate size" or "LFAD" refers to the size of fibril aggregates in cellulose from data received by magic angle cross polarization-spin 13C NMR spectroscopy (CP-MAS). The method was used following that described in Wollboldt ET AL. 2010 (Wood Science and Technology, 44, 533-546).
    [00041] Accordingly, the present description relates to a process for manufacturing dissolving pulp comprising the steps of: a) selecting a wood-based raw material, wherein said wood-based raw material has a xylan content of 12 % by weight or more; b) adding a cooking liquor comprising white and/or black liquor to wood-based raw material; c) digesting the wood-based raw material composition obtained in step b) in a cooking process kraft;d) delignify the pulp obtained in step c); e) adding white liquor to the pulp obtained in step d), wherein said pulp has a xylan content of 8% by weight or more and wherein the temperature is lowered and maintained at 65°C or lower for 5 minutes or more and wherein the alkali concentration in the liquid phase of the pulp suspension obtained is in the range of 70 g/l to 100 g/l; ef) removing 90% or more of the dissolved alkali and xylan as a liquor stream from the pulp obtained in step e) by removing water from the pulp; and g) subjecting the pulp to washing and pressing in a washing-pressing device 1-5 times.
    [00042] According to the process as defined herein, step e) may be carried out at a temperature of 60°C or lower, such as at a temperature of 55°C or lower, such as at a temperature of 50°C or lower. Additionally, step e) can also be carried out in the temperature range from 25 to 65oC, such as in the temperature range from 30 to 60oC, such as in the temperature range from 35 to 55oC, such as in the temperature range from 25 to 60oC 50oC, as well as in the temperature range of 30 to 50oC. According to the process as defined herein, the temperature of step e) can be lowered at the same time as the white liquor is added or it can be lowered in steps, i.e. the temperature can be lowered before the white liquor is added and then decreased even after the white liquor is added.
    [00043] The xylan content of the pulp obtained in step c) and used in step d) may be from 8 to 3% by weight, such as from 10 to 0% by weight, such as from 14 to 28% by weight.
    [00044] Furthermore, the treatment of step e) can be carried out for 5 minutes or more, such as from 5 minutes to 3 hours, such as from 5 minutes to 1 hour, such as from 5 minutes to 0.5 h, such as from 5 minutes to 15 minutes.
    [00045] According to the process as defined herein, said wood-based raw material may have a xylan content of from 12% by weight to 35% by weight, such as from 12% by weight to 30% by weight.
    [00046] The alkali concentration of step e) may be in the range of 75 to 100 g/l, such as in the range of 80 to 100 g/l, such as in the range of 85 to 100 g/l, such as in 90 to 100 g/l range, as well as 95 to 100 g/l range. The alkali concentration can be measured using the method described in SCAN N-30:85, ie using potentiometric titration.
    [00047] In addition, the ratio of cooking liquor:raw material based on wood in the digester may be from 2:1 to 6:1, such as 3:1 to 6:1, such as from 3.5:1 to 5.5:1, such as from 4:1 to 5:1, such as from 4.5:1 to 5.5:1, such as from 4:1 to 6:1.
    [00048] Additionally, the process as defined herein may comprise the washing step after step d), that is, between the oxygen delignification step of step d) and the CCE step e) such step comprising washing the pulp obtained in step d) in a washing device. Examples, but not limited to, washing devices are washing presses, screw presses and washing filters, as known in the art.
    [00049] According to the process as defined herein, the xylan and alkali removed by step f) can be completely or partially recirculated as a liquor stream and used as a source of alkali in step d). Optionally, the liquor stream from step f) can be oxidized before being used in step d). Oxidation may be carried out by supplying oxygen either as oxygen gas or as air using methods known to the skilled person. The recirculation of process liquor from step f) having high alkali concentration has the advantage that no external alkali has to be added to the process at step d) as the reused and recycled process liquor contains a sufficient or close to sufficient amount of alkali to satisfy the process requirements of step d). In addition, all or a part of the liquor stream from step f) may be used in another process for pulping, such as in a parallel manufacturing process in the same production facility. With the process as described here, it is possible to obtain a highly concentrated process liquor from the removal of water in step f) going directly to step CCE e). The dewatering liquor of step f) has a high content of xylan as well as a high concentration of alkali. This means that when said liquor stream is used as an alkali source in another pulping process, the alkali concentration in the other process can be maintained in the range of 60 to 90 g/l without any additional alkali addition. Preferably, the liquor stream is added at the last stage of the cooking step in the parallel process and is regulated so that the amount of residual alkali in the process stream leaving the digester is low.
    [00050] According to the present method, 90% or more, such as 95% or more, of alkali and/or xylan can be removed from the pulp obtained in CCE step e) in dewatering step f) and in step wash g).
    [00051] A larger part of the alkali and xylan is removed from the pulp already by the water removal step f). As step f) involves removing water from the pulp of CCE step e) without diluting the filtrate with a washing liquid, the process liquid that is obtained in the dewatering step has the same high xylan content and alkali than the liquid phase in CCE step e).
    [00052] The water removal step f) and the washing step g) can be followed by a filtration step in which the pulp is filtered in a washing filter.
    [00053] The dewatering step directly follows the CCE step and the liquor removed from the pulp by removing water has a very high xylan and alkali content and can be used directly for recycling or to supplement the process liquid in a process parallel pulp production without further concentration and purification steps. Furthermore, the high xylan content in the liquor from the dewatering step makes the liquor highly suitable for further processing and as a source of xylan. The dewatering step may include pressing, applying a vacuum, using a centrifuge, and the like.
    [00054] The process as defined herein may comprise an additional step prior to the addition of the cooking liquor in step b), an additional step comprising activating the wood-based raw material using steam until reaching a P factor of 0 to 200, such as like 25-200, or 50-100.
    [00055] Furthermore, the process may comprise a step after removing water, washing and optionally filtering the pulp, which step is a combined bleaching and depolymerization step. The combined bleaching and depolymerization step can be carried out by adding ozone, or by adding hypochlorite, or by adding chlorine dioxide and sulfuric acid. The step may be carried out by first adding chlorine dioxide to the pulp and then adding sulfuric acid, or by first adding sulfuric acid to the pulp and then adding chlorine dioxide, i.e. said addition may be carried out sequentially in any order. An advantage with the method described here is that the pulp is comparatively easy to depolymerize, which means that the depolymerization step can be carried out under relatively mild conditions requiring less addition of acid, etc.
    [00056] The combined bleaching and depolymerization step can be performed at a temperature of 80 to 99oC and an effective acid load of 5 to 20 kg H2SO4/ADT. In the present description, "effective acid loading" means the amount of sulfuric acid in kg/ton, i.e. it does not include the amount of sulfuric acid needed for neutralization, pulp consistency 10%. If other pulp consistencies are used the acid load must be adjusted accordingly.
    [00057] After the combined bleaching and depolymerization step, the semi-purified pulp obtained may contain 6% by weight of xylan or less, such as from 2 to 6% by weight.
    [00058] The present description relates to a liquor comprising xylan, water, lignin and alkali, wherein the xylan/lignin ratio is from 2:1 to 20:1, such as from 3:1 to 15:1, such as such as 4:1 to 10:1, such as 4.5:1 to 8:1, such as 6:1. The xylan/lignin ratio is the weight ratio between the two components in the liquors using the two defined analyzes described herein, respectively. Liquor is obtainable from dewatering step f) of the process as specified herein. A liquor having particularly high concentrations of xylan and alkali is obtained in dewatering step f) directly following CCE step e), as described herein. It has surprisingly been found that the xylan obtained from the process described here has a higher average molecular weight than the xylan obtainable from previously known processes. Consequently, the liquor obtained from dewatering step f) may comprise xylan having an average molecular weight of from 15 to 40 kg/mol, such as from 20 to 35 kg/mol. A high molecular weight of the xylan obtained is particularly beneficial when the liquor obtained from the dewatering step f) is used as a process liquid in a papermaking process. A higher proportion of added xylan will then be deposited on the pulp fibers in the papermaking process than can be achieved with the lower molecular weight xylan obtainable from a conventional dissolving pulp process.
    [00059] The present description also relates to a process for making pulp comprising a kraft process parallel to the dissolving pulp process as described herein, wherein the liquor obtained from step f) of the process as defined herein is added to the pulping process. kraft cooking in a way that the alkali can be consumed while keeping the liquor in the digester until the end of the cooking process and in which the residual alkali concentration can be from 5 to 15 g/l. Accordingly, 80% or more of the alkali required for digestion of wood-based feedstock in said process can be obtained from a process as defined herein.
    [00060] In order to provide a good result in CCE step e), the composition of wood chemical products must include 12% by weight or more of xylan in addition to lignin and cellulose. Examples of such wood species are hardwoods such as birch, beech, poplar and eucalyptus wood. Birch, beech and poplar are particularly rich in xylan, while eucalyptus wood commonly used in pulping processes has slightly less lower xylan content. Wood species that are less suitable for use in alkali-based pulping processes such as the processes described herein are various conifers, such as spruce and pine. However, these wood species can be used, for example, in a linked process for the manufacture of pulp that can be located in the same mill. Consequently in a linked or parallel process, the wood source may comprise any of the above mentioned wood species as precipitation of alkaline soluble hemicellulose may occur in wood fibers of any origin.
    [00061] Washing step g) comprising one or more washing devices comprised in a process as defined herein can be carried out accordingly: First water is removed from the pulp by passing the pulp through a pressing device in which no dilution of the filtrate of CCE step e) by the washing liquid is performed, indicating that no liquid is added to the pulp. Thereafter, the pulp is passed through two washing-pressing devices where washing is carried out, preferably followed by a washing filter. Washing can be carried out according to the washing method as described. Washing may be carried out in a countercurrent operation as is common in the art. Backwash means that fresh water is added to the last washing device and that washing liquid from a downstream washing step is used in an upstream washing step. In this way, fresh water is efficiently used and the risk of carrying alkali from one step to the next is minimized.
    [00062] The process as defined here has surprisingly proved technically to produce good results without a steam activation step, i.e. at factor P 0. However, if desired, the process can comprise a pre-treatment step prior to addition of the cooking liquor in step b), pre-treatment step that comprises activation of the wood-based raw material by the use of steam. The pre-treatment of wood-based raw material comprises treating the wood-based raw material with steam at a temperature in the range of 150 to 180oC before the kraft cooking step b) in order to facilitate the impregnation of the wood-based raw material in wood and to prepare the wood-based raw material for the cold caustic extraction step e). After steam treatment of the wood-based raw material, a conventional kraft cooking process is carried out. If condensate has been produced in the vessel used for steam treatment, eg a digester, it may be advantageous to remove the condensate so that the pulp quality is not impaired by wood residues remaining in the condensate. As the condensate is acidic, white liquor can be used to remove the condensate. If a digester is used as a vessel for steam treatment, the same vessel can subsequently be used for the kraft cooking process.
    [00063] In the process defined here, step CCE e) will remove most of the xylans from the pulp. Therefore, after the CCE step, the pulp obtained may contain 6% by weight or less of xylan, such as 2-6% by weight of xylan. The alkali concentration measured as effective alkali in step CCE e) is maintained above 90 g/l when the P factor is from 0 to 10 and is maintained in the range of 75 to 90 g/l when the P factor is from 11 to 10. 200. The pulp consistency can be 8 to 12% by weight and the residence time is at least 5 minutes, such as 5 to 30 min.
    [00064] The pulp viscosity will be lowered when applying a combined bleaching and depolymerization step. Depending on the target viscosity, the acidic charge can be from 5 to 20 kg H2SO4/ADT and the temperature can be maintained from 80 to 99°C. The residence time in the downflow tower is precisely controlled so that the target viscosity can be obtained. The combined step has the advantage of decreasing pulp viscosity and at the same time increasing pulp brightness. The heating of this step can be carried out with steam. The advantage of using steam and adding chlorine dioxide before or after adding H2SO4 is that any HS-(hydrogen sulfide) left in the pulp will react with the chlorine dioxide to form sulfate. Therefore, the reaction between acid and HS-, which will provide H2S, is avoided. This step can be performed using an upflow tower as the chlorine dioxide is in gaseous form. In order to control the pulp viscosity, it can be conveyed through a tower with a downflow stream.
    [00065] When the viscosity has been adjusted, a final pulp brightness of above 85% ISO can be obtained by performing a separate bleaching step. When the entire specification of a dissolving pulp is satisfied, the dissolving pulp can be dried and sold as market pulp or transferred directly to an integrated conversion facility.
    [00066] The alkali and xylan removed after the CCE step can be used in another kraft pulping process, said process can be linked to the process as defined here and can be in the same facility. One possibility for such processes is by the use of a tube, the tube is then carrying the liquor from one process to the other. The effective alkali concentration of the transferred liquor is preferably high enough to provide the linked process with the required alkali charge or at least a greater part of the required alkali charge. This requirement can be satisfied by using the washing method as described here, i.e. using a pressing device directly after the CCE step instead of a conventional washing press which thins the filtrate. To maximize the amount of hemicellulose on the wood fibers to be treated in the bonded process, the process liquor as defined here is added to the bonded process after the impregnation of the wood material is completed, so that said liquor will become the residual cooking and so that said liquor will not be displaced before precipitation has taken place.
    [00067] The use of the liquor from washing step e) in a linked process will provide a good economy in the process as the process yield can be increased, which results in a better economy in the process and the resulting mechanical properties of the process. Resulting paper pulp obtained from the bound process are improved by the increased xylan content. The ratio of production speed in the two processes should be on the order of 1:1.5 or 1:2 (dissolving pulp:paper pulp) for optimal process economy and correct alkali balance.
    [00068] If the dissolving pulp obtained by a process as defined here is intended for use in a lyocell process, the dissolving pulp must be pure in terms of high cellulose content and a low content of metal ions and must have a distribution narrow molecular weight. However, if the dissolving pulp obtained by a process as defined here is intended for use in viscose processes, the reactivity and filterability of the pulp are the most important parameters. Dissolving pulp reactivity can be improved by performing steam activation of the wood-based raw material prior to the kraft cooking process and a P factor of 50 and above may be preferred. In the case of dissolving pulp production for solvent processes the P factor should be minimized to such an extent that the steam treatment is limited to the use of a conventional steaming step to improve the impregnation of the liquors, in terms of P factors, i.e. means a range from 0 to 10 units.
    [00069] According to the present description, the CCE step e) is carried out directly after the oxygen delignification, as this will reduce or eliminate the need for fresh alkali addition in the oxygen step as is otherwise, always the case in pulp mills. Furthermore, this order of carrying out the steps will provide a pure dissolving pulp and a high value alkali stream of soluble xylan from the dewatering step f). However, those skilled in the art will appreciate that the CCE step e) can be placed anywhere in the process and that the other parts of the pulp line can be operated in a traditional manner.
    [00070] One of the key aspects in dissolving pulp production is the adjustment of viscosity within a narrow period. Cellulose depolymerization can be carried out according to different methods known to those skilled in the art, such as; oxidative degradation, acid depolymerization and enzymatic depolymerization. It was surprisingly found that by using the CCE step, the resulting pulp is much more sensitive to depolymerization than a regular kraft pulp or a pre-hydrolyzed treated kraft pulp. This provides good process savings due to chipping in acid charge, retention time and/or energy cost (allowing for lower temperature) without detracting from the yield or quality of the resulting pulp. Conditions in the CCE step (eg temperature and alkali charge) determine the kinetics of depolymerization.
    [00071] The process as defined herein may be carried out in the same vessel, such as a digester, when carrying out cooking and/or impregnation of wood-based raw material, such as in the form of batch cooking. The process as defined here can also be carried out as continuous cooking.
    [00072] As mentioned above, it is also possible to use the liquor produced in the dewatering step f) in a process for making pulp comprising a kraft process, wherein said liquor is added to the kraft cooking process in a way that the alkali is consumed while keeping the liquor in the digester until the end of the cooking process and where the residual alkali concentration is 5 to 15 g/l. In addition, at least 80% of the alkali required for the digestion of the wood-based raw material is obtained from the process as defined herein.
    [00073] Other applications for dissolving pulp can be the production of regenerated cellulose, as a raw material for cellulose derivatives, such as carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose ( HEC), etc. paper-related products such as filter paper.
    [00074] The dissolving pulp can be used in processes for the manufacture of viscose or lyocell fibers. Suitable applications for viscose, modal or lyocell fibers are textiles and non-woven products. Other products that can be produced using processes in which dissolving pulp is used as a raw material are cellophane, tire cord and various acetates and other specialty products.
    [00075] The xylan/lignin ratio in a liquor is the weight ratio between the two components in the liquor as determined using the methods of analysis described here. Consequently, the determination of xylan in either wood, pulp or liquor is carried out according to the test method SCAN - SCAN-CM 71:09 and calculated for wood components according to J. Jansson (1974, Faserforschung und Textiltechnik, 25 (9), 375). When the xylan content in a liquor is determined, the first part of the acid hydrolysis using 72% sulfuric acid is omitted.
    [00076] The residual lignin content in the pulp is indicated by the kappa index which is determined by ISO 302:2004 as described here, while the lignin content in a liquor is determined with UV spectrophotometry at 280 nm using the extinction coefficient of wood Birch wood kraft; 20.8 dm 3 /g cm (Alén and Hartus, 1988, Cellulose Chemistry and Technology, 22(6), 613-618).
    [00077] The present description also relates to a pulp obtainable from the process as described herein, said pulp having a twist of 1.3 to 2.0 twists/mm and a form factor of 70 to 82%. Additionally, the pulp obtainable from the process may have a cellulose II content of 7 to 50% by weight in the cellulose, such as from 8 to 35% by weight, and an LFAD of 16 to 40 nm, such as from 17 to 25 no. The coiled fibers defined by the twist and form factor result in a bulky pulp sheet that absorbs liquids in downstream processes much more efficiently than traditional pulp. Additionally, when pulp is used in the process using dry shredding the energy required for shredding this pulp is substantially lower.
    [00078] The present description also relates to a pulp manufactured according to the process as defined hereinabove or in the following parts. Furthermore, said pulp may have the values mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS
    [00079] The processes described here will be described in more detail with reference to the drawings attached here, in which: Figure 1 shows a process diagram of a process as defined here, Figure 2 shows a process diagram of a process for the dissolving pulp manufacturing, Figure 3 shows a process diagram for a process for pulping, comprising a linked process for pulping, and Figure 4 shows the result after working the dissolving pulp samples from the process as defined here. DETAILED DESCRIPTION
    [00080] Figure 1 schematically shows the process for manufacturing dissolving pulp as defined here. The wood-based raw material can be activated by carrying out steam treatment on the wood-based raw material, and after the steam treatment, white liquor can be added to the vessel and a traditional kraft cooking process can be carried out. The kraft cooking process is followed by an oxygen delignification step and a cold caustic extraction step (CCE step). In the CCE step, the pulp delignified with oxygen is treated with alkali. The alkali source is industrial white liquor as specified here. Suitable but not limiting parameters for the CCE step are a temperature of 30 to 50oC, a NaOH concentration of 70 to 95 g/l, and a time interval of 15 to 30 minutes. The CCE step will reduce the xylan content to less than 6% by weight such as from 6% by weight to 2% by weight. Consequently, the process as defined herein comprises the steps of kraft cooking, oxygen delignification and cold caustic extraction, followed by a washing step including an initial dewatering step directly after the CCE step. A steam activation step can optionally be performed before the kraft cooking step. The process may comprise other steps such as depolymerization and bleaching to desired viscosity and gloss level. The liquor removed from the pulp by the dewatering step coupled to the CCE step has a high concentration of alkali and hemicellulose (xylan). As described herein, the alkaline hemicellulose stream from the dewatering step can be recirculated and/or removed and used in other processes and applications.
    [00081] Figure 2 is a schematic representation of a kraft process as defined here, including an optional steam activation step. In the figures, each rectangle represents a process step, and any accompanying washing step.
    [00082] In the depolymerization step (DA), the pulp can be treated with sulfuric acid at a temperature of 80 to 99oC. The effective amount of sulfuric acid can be from 5 to 20 kg/ADT and this step can be carried out for 60 to 180 min. Prior to this treatment, the pulp can be treated with chlorine dioxide (D), which means that there will be chlorine dioxide present in the pulp. The pulp obtained has excellent properties such as low viscosity, high gloss and narrow molecular weight distribution.
    [00083] The DA step can be performed using a chlorine dioxide load in kg/ADT of 1.8 times the kappa index and a temperature around 90oC and a final pH of about 2.0. The DA step can be carried out for about 140 minutes.
    [00084] The alkaline extraction step fortified with oxygen and hydrogen peroxide (EOP) can be performed according to the following but not limiting parameters: pH is about 10.4, O2 is 4 kg/ADT, temperature is about of 80oC.
    [00085] The chlorine dioxide/complexing agent (D/Q) step can be performed according to the following, but not limiting parameters: MgSO4 0.6 kg/ADT, EDTA 1 kg/ADT, temperature 80oC and a pH of 4.5.
    [00086] The pressurized hydrogen peroxide (PO) step can be performed according to the following, but not limiting parameters: pulp consistency 10% by weight, final pH 10.5-11.0, temperature 105°C, O2 is 3 kg/ADT, residual H3O2 3.0 kg/ADT and MgSO4 1.0 kg/ADT.
    [00087] The pulp drying step can be carried out to a dry content of 90-93% and the pulp can be cut into sheets and stacked in bales.
    [00088] Figure 3 describes the basic concept of a kraft process system according to the present description, and including a parallel pulping line in which the liquor containing alkali and xylan removed by the washing step after the CCE step is used in the kraft cooking process. After the cooking step in which the alkali is consumed and the hemicellulose is precipitated onto the wood fiber, the pulp can be bleached in a conventional manner to a desired target brightness.
    [00089] Figure 4 shows that the dissolution pulp as manufactured in accordance with the present description has a higher degree of fibrillation than the reference sample pulp manufactured using a conventional method.ABBREVIATIONS mol/l mol/literH2SO4 sulfuric acidADT tons of dry airEDTA ethylenediamine tetraacetic acidO2 oxygenNa2CO3 sodium carbonateNaHS sodium hydrosulfiteNaOH sodium hydroxideNa+ sodium ionHS- hydrosulfite ionK+ potassium ionOH- hydroxide ionCO32- carbonate ionH2O2 hydrogen peroxideMgSO4 ml/g twists/mm fiber magnesium sulfate milliliter/gramtwist is defined as an abrupt change in the curvature of the D Chlorine DioxideA AcidQ Complexing agent PO Pressurized hydrogen peroxideEOP Alkaline extraction fortified with oxygen and hydrogen peroxide
    [00090] The present description is further illustrated by the following non-limiting examples.Example 1
    [00091] Silver birch wood containing 25% xylan was cooked to pulp according to a Fast Displace Heating (HDR) process to a kappa number of 17 in an industrial digester system. The cooking temperature was 160°C, the H factor was 350 and the residual alkali was 10 g/l. After cooking, the pulp was sieved before delignification with oxygen in a two-step industrial process. The temperature in the first reactor was 85°C and 102°C in the second reactor. The total alkali charge was 23 kg/ADT, the total oxygen charge 15 kg/ADT and the magnesium sulfate charge was 3 kg/ADT. After oxygen delignification, a sample of the pulp was taken from the washing press and further washed in order to proceed with the pulp in the laboratory. The pulp had, after oxygen delignification, a kappa number of 9.3, a brightness of 59.8% ISO and a viscosity of 1008 ml/g.
    [00092] The pulp was then treated with industrial white liquor with high ionic strength at a consistency of 10%, effective alkali concentration of 95 g/l, at a temperature of 40°C for 15 minutes. The liquors and pulp were preheated to process temperature before mixing and treated in plastic bags. After the treatment, the free liquor was pressed and the pulp was subsequently washed with diluted filtrate with alkali concentrations of 13 g/l, 3 g/l and with water in a sequence in order to simulate an industrial washing sequence. The resulting pulp had a xylan content of 5.5% by weight and an R18 value of 97.8%. The filtrate, which was pressed directly after the CCE treatment, had an effective alkali concentration of 83 g/l and a dissolved xylan concentration of 28.8 g/l.
    [00093] The pulp, after treatment with white liquor, had great potential as a dissolving pulp, however the viscosity and brightness needed to be adjusted. This was carried out in a combined acidic and chlorine dioxide step. In an industrial process, it is important that the pH in the step does not drop too far below 2.0, as this increases the risk of severe corrosion in the equipment. Instead, parameters other than the acidic charge were adjusted in order to satisfy the demands of a dissolving pulp. The DA step was conducted at 95°C with an active chlorine load of 6.1 kg/ADT and a sulfuric acid load of 10 kg/ADT. The residence time was 165 min. and the treatment resulted in a pH of 1.9. After the DA step, an extraction step was performed at 80°C, alkali charge of 5.5 kg/ADT and a hydrogen peroxide charge of 2 kg/ADT for 120 minutes. This resulted in a pulp with a brightness of 85.7% ISO and an intrinsic viscosity of 390 ml/g.
    [00094] The final step was a Q PO treatment with an alkali charge of 20 kg/ADT and a hydrogen peroxide charge of 10 kg/ADT. The temperature was 110°C and the residence time 150 minutes. The pulp was analyzed thereafter and a good dissolving pulp was obtained with an R18 value of 97.6%, xylan content of 4.4% by weight and a viscosity of 383 ml/g.
    [00095] The final pulp was also analyzed for other relevant parameters and the results are shown in Table 1. The metal ion content is an important property for a dissolving pulp and this content is very low and one reason for this is the treatment acidic acid to a pH of approximately 2 in the combined DA step, which protonizes the pulp acids and therefore decreases the metal ion content. Table 1 Pulp characterization after the different treatments
    Example 2: Mill process
    [00096] In this example a kraft mill using 4 batch digesters at 325 m3 each were used. The raw material comprised 93% silver birch and 7% other hardwoods, mainly poplar. The woodchips were steamed to a P factor of 100 and the activation was terminated with the addition of white liquor to the bottom of the digester, followed immediately by a mixture of white and black liquor until a cooking liquor:raw material ratio with wooden base of 3.7:1 was achieved. The cooking step was carried out with liquor circulation at 160°C until an H factor of 400 was reached. Typical properties after digestion were; viscosity: 1100 ml/g, gloss: 45% ISO, kappa index: 13.
    [00097] The oxygen delignification was performed in a two-step reactor, using a total oxygen charge of 23 kg/ADT, without any additional alkali charge. A load of 1 kg of MgSO4/ADT was used to minimize degradation reactions. The temperature in the two steps was 86°C for 30 minutes and 105°C for an additional 60 minutes. After this treatment, the pulp properties were: gloss: 56% ISO, kappa index: 9.
    [00098] Since the wood was activated using steam, the alkali charge in the CCE step can be decreased. White liquor was charged so that the effective alkali concentration was 85 g/l at a temperature of 45°C for 20 minutes. The resulting slurry water was removed in a press before dilution and treatment in two washing presses and a washing filter in a sequence. After washing the pulp properties were: viscosity: 770 ml/g, gloss: 61.9% ISO.
    [00099] The filtrate after the press was analyzed and the xylan content was 24.3 g/l, lignin content was 4.6 g/l resulting in a xylan/lignin ratio of 5.3:1. The weight average molecular weight of xylan was determined to be 30.0 kg/mol, corresponding to a degree of polymerization of 227.
    [000100] Since the pulp still contained some hydrosulfite ions after washing, chlorine dioxide was charged first and then shortly afterwards, sulfuric acid was charged. The DA stage was performed in a small upflow tower coupled with a larger downflow tower. The temperature was 91°C, the chlorine dioxide loading was 21 kg/ADT and the sulfuric acid loading was 24 kg/ADT. About 9 kg of sulfuric acid filler was used for neutralization and the remainder was used as active filler. After washing, the pulp was treated in an extraction step at 80°C, 4 kg of O2/ADT, 2 kg of H2O2/ADT and an alkali charge to reach a final pH of 10.4. The pulp properties after this treatment were; viscosity: 420 ml/g, gloss: 86% ISO.
    [000101] To achieve a target gloss, the pulp was treated in a Q PO sequence. The chelation step was performed with 0.5 kg/ADT of EDTA with 0.6 kg/ADT of magnesium sulfate at a temperature of 80°C. After washing, the PO step was conducted with 10 kg of H2O2/ADT, 20 kg of NaOH/ADT, 1 kg of MgSO4/ADT and 3 kg of O2/ADT. The temperature at the bottom of the reactor was 95°C. After this final treatment, the pulp was dried in a drying machine to a dry content above 90% as specified above, cut into sheets and stacked in bales. Table 2 Characterization of the pulp after the different treatments in the mill.
    Example 3: Comparison with commercial dissolving pulps
    [000102] Different commercial pulps (paper pulps and dissolution pulps) were collected and analyzed using the L&W FiberTester tester and CP-MAS 13C NMR spectroscopy [Wollboldt ET AL. 2010 (Wood Sci. Technol. 44:533-546 )]. The uniqueness of the dissolving pulp produced using the method as defined here is illustrated in the measured data as shown in Tables 3 and 4 below. Table 3. Data from fiber dimension analyzes with L&W Fiber Tester tester and WRV measurements.
    Kraft birch paper pulp 1 Kraft eucalyptus paper pulp 2 Birch dissolving pulp prepared according to Example 23 Commercial pre-hydrolysis eucalyptus dissolving kraft pulp 4 Commercial beech sulphite dissolving pulp 5 Table 4. Data from analysis with 13 C NMR spectroscopy CP- BUT.
    Birch paper kraft pulp 1 Birch dissolving pulp prepared according to Example 22 Commercial pre-hydrolysis eucalyptus dissolving kraft pulp 3 Commercial beech sulphite dissolving pulp 4
    [000103] As is evident from Table 3, a major difference between dissolving pulp produced according to the method as defined here and commercial dissolving pulps is the high tensile value and low form factor of the pulp. produced according to the invention. Furthermore, from Table 4 it is evident that the pulps which were produced according to the present method have high contents of cellulose II as a result of the high alkali loading in the CCE step and that the dimensions of lateral fibril aggregates are significantly higher than for the commercial pulps analyzed.
    [000104] In order to obtain comparative values, for example when measuring LFAD in pulp using NMR, it is important that the analyzed pulps are dried to the same extent. All commercial pulps tested were therefore dried in a drying machine to a dry content above 90%. Example 4FE-SEM
    [000105] After coating with a thin layer of Au/Pd, the pulp samples were examined by high resolution scanning electron microscopy at a magnification of 350 with a Hitachi S4000 SEM (FE-SEM) applying an accelerating voltage of 6 kV. To preserve the surface structure of the wet pulps, the method of rapid freezing in liquid N2 and normal freeze-drying described by Okamoto and Meshitsuka, 2010 (Cellulose 17:1171-1182) was applied.
    [000106] The result of the SEM analysis is shown in Figure 4. Figure 4 shows that the dissolving pulp fibers made according to the process of the invention are rolled and have a high twist as measured by image analysis as described herein. Coiled pulp fibers can be formed into bulky pulp sheets that absorb liquids easily and are easy to disintegrate in a dry state.
    权利要求:
    Claims (23)
    [0001]
    1. Process for manufacturing dissolving pulp, characterized in that it comprises the steps of: a) selecting a wood-based raw material, said wood-based raw material having a xylan content of 12% by weight or more; b) adding a cooking liquor comprising white and/or black liquor to the wood-based raw material; c) digesting the wood-based raw material composition obtained in step b) in a kraft cooking process; d) delignifying with oxygen to the pulp obtained in step c);e) adding industrial white liquor with high ionic strength to the pulp obtained in step d) in which said pulp has a xylan content of 8% by weight or more and in which the temperature is lowered and maintained at 65°C or less for 5 minutes or more and wherein the alkali concentration in the liquid phase of the pulp suspension obtained is in the range of 70 g/l to 100 g/l; ef) removing 90% or more of alkali and dissolved xylan as a liquor stream from the pulp obtained in step e) by removing water from the pulp; and g) subjecting the pulp to washing and pressing in a washing-pressing device 1-5 times.
    [0002]
    2. Process according to claim 1, characterized in that said white liquor comprises Na2CO3, NaHS and NaOH.
    [0003]
    3. Process according to claim 1 or 2, characterized in that said white liquor added in step e) has a suspended solids content of 20 mg/l or less.
    [0004]
    4. Process according to any one of claims 1 to 3, characterized in that said white liquor has a combined concentration of Na+ and K+ of 3 to 5 mol/l, OH concentration of 2.25 to 3.5 mol /l, HS- concentration from 0.2 to 1.0 mol/l, and a CO32- concentration from 0.10 to 0.60 mol/l.
    [0005]
    5. Process according to any one of claims 1 to 4, characterized in that the pulp obtained in step g) is filtered through a washing filter.
    [0006]
    6. Process according to any one of the preceding claims, characterized in that the temperature in step e) is 60°C or lower.
    [0007]
    7. Process according to any one of the preceding claims, characterized in that the alkali concentration in step e) is in the range of 85 to 100 g/l.
    [0008]
    Process according to any one of the preceding claims, characterized in that said process comprises a washing step between step d) and step e), said washing step comprising washing the pulp obtained in step d) in a device wash.
    [0009]
    A process according to any one of the preceding claims, characterized in that xylan and alkali removed in step f) are recirculated as a liquor stream and used as an alkali source in step e) and/or wherein xylan and alkali are removed as a liquor stream and used as an alkali/xylan source in another pulping process.
    [0010]
    Process according to any one of the preceding claims, characterized in that xylan and alkali removed in step f) are recirculated as a liquor stream and used as an alkali source in step d).
    [0011]
    11. Process according to claim 10, characterized in that said liquor flow is oxidized before being used in step d).
    [0012]
    12. Process according to any one of claims 9 to 11, characterized in that the alkali concentration of said liquor stream is in the range of 60 to 90 g/l without any additional alkali addition.
    [0013]
    13. Process according to claim 12, characterized in that said liquor stream is used as a source of alkali in another process for making pulp.
    [0014]
    14. Process according to any one of the preceding claims, characterized in that said process comprises a step before step b), step comprising activating the wood-based raw material using steam until a P factor of 0 to 200 has been achieved, such as a P factor of 25 to 200, or a P factor of 50 to 100.
    [0015]
    15. Process according to any one of the preceding claims, characterized in that said process comprises a step after step g), step which is a combined bleaching and depolymerization step.
    [0016]
    16. Process according to claim 15, characterized in that said combined bleaching and depolymerization step is carried out by the addition of ozone, or by the addition of hypochlorite or by the addition of chlorine dioxide and sulfuric acid.
    [0017]
    17. Process according to claim 15 or 16, characterized in that said combined bleaching and depolymerization step is carried out at a temperature of 80 to 99 °C and an effective acid charge of 5 to 20 kg H2SO4/ADT .
    [0018]
    Process according to any one of claims 15 to 17, characterized in that the pulp obtained after the combined bleaching and depolymerization step comprises 6% by weight or less of xylan, such as from 2 to 6% by weight of xylan.
    [0019]
    19. Process according to any one of the preceding claims, characterized in that the pulp obtained is further processed into a cellulosic product by a lyocell process, modal process or viscose process.
    [0020]
    20. Liquor obtained or obtainable from the process as defined in any of the preceding claims, characterized in that it comprises xylan, water, lignin and alkali, in which the xylan/lignin ratio is from 2:1 to 20:1.
    [0021]
    21. Liquor according to claim 20, characterized in that said liquid comprises xylan having a weight average molecular weight (Mw) of 15 to 40 kg/mol.
    [0022]
    22. Pulp obtained or obtainable from the process as defined in any one of claims 1 to 18, characterized in that said pulp has a twist of 1.3 to 2.0 twists/mm and a form factor of 70 at 82%.
    [0023]
    23. Pulp according to claim 22, characterized in that said pulp has a cellulose II content of 7 to 50% by weight based on the total amount of cellulose and a dimension of lateral fibril aggregates (LFAD) of 16 at 40 nm, the size of lateral fibril aggregates being the size of the fibril aggregates in the cellulose calculated from the data received by cross-polarization-spin spectroscopy at magic angle.
    类似技术:
    公开号 | 公开日 | 专利标题
    BR112014029701B1|2022-01-11|PROCESS FOR MANUFACTURING DISSOLUTION PULP, LIQUOR, AND, PULP
    EP2895653B1|2019-03-13|Method of producing dissolving pulp, dissolving pulp and use of method
    WO1998016682A2|1998-04-23|Process for the co-production of dissolving-grade pulp and xylan
    Gabov et al.2013|Hydrotropic fractionation of birch wood into cellulose and lignin: a new step towards green biorefinery
    US6245196B1|2001-06-12|Method and apparatus for pulp yield enhancement
    BRPI0810975B1|2018-12-26|Method for Removing Hemicellulose from Cellulosic Fibers Using Ammonia and Hydrogen Peroxide Solution
    JP6474897B2|2019-02-27|Process for producing treated pulp
    CN105339544B|2017-08-25|The method for producing the cellulose and hemicellulose of regeneration
    CN101967764B|2013-04-03|High-whiteness cotton pulp product for banknote paper and production method thereof
    US20110073264A1|2011-03-31|Kraft-Pulping of Hot Water Extracted Woodchips
    CA1188686A|1985-06-11|Method of producing celluloses having a low lignincontent
    WO2009117402A2|2009-09-24|Methods of pretreating comminuted cellulosic material with carbonate-containing solutions
    EP3559340A1|2019-10-30|A method for manufacturing dissolving pulp
    Martinsson et al.2021|Hardwood kraft pulp fibre oxidation using acidic hydrogen peroxide
    Hertzberg2019|Cellulose acetate production from Finnish hardwood and softwood dissolving pulp
    BRPI1100723B1|2020-10-20|xylan deposition process during pre-bleaching of cellulosic pulp
    JP4380968B2|2009-12-09|Ozone bleaching method for lignocellulosic materials
    BR102013033663A2|2015-09-22|Reversible process of converting paper pulp production to soluble pulp and process for soluble pulp production
    Hutterer et al.2017|Pulps
    Tripathi et al.2011|Quality improvement of rayon grade bamboo pulp by modified bleaching
    WO2018204061A1|2018-11-08|Treatment of brown stock
    BR112020025159A2|2021-03-09|GROSS PULP, CELLULOSE Ether PRODUCTS MADE FROM THE SAME, AND RELATED METHODS FOR MANUFACTURE PULP AND CELLULOSE ETHER PRODUCTS
    同族专利:
    公开号 | 公开日
    US20150136346A1|2015-05-21|
    CA2874901A1|2013-12-05|
    PT2855765T|2017-02-06|
    EP2855765B1|2016-11-02|
    CN104379833A|2015-02-25|
    CA2874901C|2020-04-07|
    EP2855765A1|2015-04-08|
    BR112014029701A2|2017-06-27|
    WO2013178608A1|2013-12-05|
    CN104379833B|2016-05-11|
    ZA201408103B|2015-12-23|
    US10023995B2|2018-07-17|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US5143702A|1990-10-22|1992-09-01|A. H. Lundberg Associates, Inc.|Two stage white liquor oxidation apparatus|
    AT398588B|1992-12-02|1994-12-27|Voest Alpine Ind Anlagen|METHOD FOR THE PRODUCTION OF VISCOSE CELLS|
    WO1995000698A1|1993-06-25|1995-01-05|Kamyr, Inc.|Hemicellulose recovery during kraft pulping|
    US6210801B1|1996-08-23|2001-04-03|Weyerhaeuser Company|Lyocell fibers, and compositions for making same|
    US7812153B2|2004-03-11|2010-10-12|Rayonier Products And Financial Services Company|Process for manufacturing high purity xylose|
    AT503610B1|2006-05-10|2012-03-15|Chemiefaser Lenzing Ag|METHOD FOR PRODUCING A PULP|
    CN101457494B|2008-12-24|2012-01-11|宜宾长毅浆粕有限责任公司|Production method of bamboo chemical dissolving pulp|
    EP3124501A1|2009-03-09|2017-02-01|TreeToTextile AB|Shaped cellulose manufacturing process|
    JP5808795B2|2010-05-04|2015-11-10|バイーア スペシャルティ セルロース ソシエダッド アノニマ|Method and system for the production of high alpha dissolving pulp|
    CN104379833B|2012-05-28|2016-05-11|索德拉细胞公司|New technology and the dissolving pulp of manufacturing by this technique|CA3085086A1|2011-12-06|2013-06-13|Delta Faucet Company|Ozone distribution in a faucet|
    CN104379833B|2012-05-28|2016-05-11|索德拉细胞公司|New technology and the dissolving pulp of manufacturing by this technique|
    AT515174B1|2013-10-15|2019-05-15|Chemiefaser Lenzing Ag|Cellulose suspension, process for its preparation and use|
    AT515180B1|2013-10-15|2016-06-15|Chemiefaser Lenzing Ag|Three-dimensional cellulosic molding, process for its preparation and its use|
    AT515152B1|2013-11-26|2015-12-15|Chemiefaser Lenzing Ag|A process for pretreating recovered cotton fibers for use in the manufacture of regenerated cellulose moldings|
    JP6398388B2|2014-07-02|2018-10-03|王子ホールディングス株式会社|Dissolving pulp and method for producing the same|
    CN107075799B|2014-11-05|2019-10-08|双子科技有限责任公司|The preparation method of cellulose|
    SE538752C2|2014-11-21|2016-11-08|Innventia Ab|Process for the production of a treated pulp, treated pulp, and textile fibres produced from the treated pulp|
    AT517020B1|2015-02-06|2020-02-15|Chemiefaser Lenzing Ag|Recycling of cellulosic synthetic fibers|
    WO2017044030A1|2015-09-07|2017-03-16|Domsjö Fabriker Ab|Novel dissolving pulp|
    CN106436420B|2016-11-02|2019-02-22|湖南佰霖生物技术股份有限公司|A kind of activator and preparation method thereof for producing dissolving pulp|
    SE540778C2|2016-12-23|2018-11-06|Soedra Skogsaegarna Ekonomisk Foerening|A method of manufacturing dissolving pulp using coniferous wood material|
    TW201938591A|2018-03-06|2019-10-01|奧地利商蘭仁股份有限公司|Dissolving pulp|
    FI20185213A1|2018-03-07|2019-09-08|Andritz Oy|Method of producing dissolving pulp|
    CN108867130A|2018-04-26|2018-11-23|天津科技大学|The pulping process of high yield pulp1 needlebush dissolving pulp and its dissolving pulp of preparation|
    SE1850733A1|2018-06-15|2019-12-16|Valmet Oy|Method and assembly for optimizing filtrate circulation in a kraft process|
    CN108914669B|2018-07-10|2020-01-03|亚太森博（山东）浆纸有限公司|Dissolving pulp and preparation method thereof|
    CN114096711A|2019-06-14|2022-02-25|布拉塞尔巴伊亚特种纤维素公司|High alpha and high intrinsic viscosity pulp production apparatus, method and system|
    US11142589B2|2019-06-14|2021-10-12|Bracell Bahia Specialty Cellulose SA|High alpha and high intrinsic viscosity pulp production apparatuses, methods and systems|
    CN110629576A|2019-08-27|2019-12-31|齐鲁工业大学|Method for preparing dissolving pulp by completely chlorine-free bleaching of poplar sulfate pulp|
    法律状态:
    2017-07-11| B25A| Requested transfer of rights approved|Owner name: LENZING AKTIENGESELLSCHAFT (AT) , SOEDRA SKOGSAEGARNA EKONOMISK FOERENING (SE) Owner name: LENZING AKTIENGESELLSCHAFT (AT) , SOEDRA SKOGSAEGA |
    2018-03-06| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2018-03-13| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2018-03-20| B06I| Publication of requirement cancelled [chapter 6.9 patent gazette]|Free format text: ANULADA A PUBLICACAO CODIGO 6.6.1 NA RPI NO 2462 DE 13/03/2018 POR TER SIDO INDEVIDA. |
    2019-09-10| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-06-01| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2021-09-08| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2021-11-03| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2022-01-11| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 28/05/2013, OBSERVADAS AS CONDICOES LEGAIS. |
    2022-02-08| B16C| Correction of notification of the grant [chapter 16.3 patent gazette]|Free format text: REFERENTE AO DESPACHO 16.1 PUBLICADO NA RPI 2662 DE 11.01.2022, QUANTO AO NOME DE UM DOS INVENTORES |
    优先权:
    申请号 | 申请日 | 专利标题
    SE1250540.0|2012-05-28|
    SE1250540|2012-05-28|
    PCT/EP2013/060926|WO2013178608A1|2012-05-28|2013-05-28|New process and a dissolving pulp manufactured by the process|
    [返回顶部]