A process for making a pulp

The present invention relates to a method of making a pulp from a cellulosic starting material by means of the force method.

In particular, the invention relates to a process for preparing a high-yield pulp which is suitable for further processing into viscose fibers and lyocell fibers.

Chemical pulps are predominantly further processed into cellulose fibers by the viscose and lyocell. In recent years, the cost position of regenerated fibers in relation to competing synthetic fibers has further
deteriorated. A reduction in the cost of pulp, which represent the most important cost factor would significantly improve the cost position of regenerated fibers.

Luo et al. were able to show that conventional kraft pulp by adjusting the
Durchschnittspolymerisationsgrades (DP) by means of säurehydrolytischem or oxidative degradation is suitable for the production of cellulose fibers according to the Lyocell [WO 99/47733]. The kraft pulps produced according to this prior art have a hemicellulose content of at least 7% wt.% On. Lyocell fibers produced from these kraft pulps, have according to WO 99/47733 a hemicellulose content of at least 5 wt.% To 27 wt.% On. The measurement method used to determine the hemicellulose is not revealed.

A disadvantage however, the presence of low molecular weight affects
Hemicellulosenkomponenten on the process behavior (enrichment non-fiber-forming Hemicellulosenanteile in the spinning bath; high chemical expense for depolymerization to adjust the desired DPs) and the textile-mechanical properties (more than 5 cN / tex lower strength under controlled conditions in comparison to
lyocell of prehydrolysis-kraft pulps) the lyocell fibers produced therefrom.

Since the development of "modified kraft cooking" at the beginning of the 1980s, we know that the reduction of the dissolved wood ingredient concentration results in a significant increase in efficiency and selectivity in the final stages of cooking.

To meet this knowledge has been proposed, rich in hemicellulose
waste liquor as such after completion of the concurrent cooking phase in
continuous cooking processes (for example, MCC, EMCC) occur to escape the cooking process to ensure that the concentration level of dissolved hemicelluloses in the further cooking phase to values less than 10 g / l drops [WO 95/00698]. In a further step, the high molecular weight hemicelluloses be further concentrated by means of pressure-driven membrane separation processes, before they are reprecipitated in the final bleaching in the context of an e-step on the surface of the pulp fibers, on the one hand to increase the yield and on the other hand, to increase the static strength.

Although this proposal results in improved pulp yield, the disadvantage, however, that the non-adsorbed portion of the hemicelluloses (equilibrium reaction) inevitably accumulates in the bleaching filtrate, causing increased consumption of bleaching chemicals, and also a part of the effluent.

The present invention has as its object to provide a method for producing pulp available, which solves the problems described pulp production by the kraft process in an improved manner.

This object is comprising the step of cooking the raw material with a cooking liquor, achieved with a process for the preparation of a chemical pulp from a cellulosic starting material by means of the force method, Welch characterized
is in that the starting material is exposed prior to cooking to a steam treatment, and that the pulp obtained by the cooking in the course of
being subjected to a further treatment cold caustic extraction (CCE).

It has been shown that, for a combination of the measures a steam treatment of the starting material prior to cooking, and a CCE stage in the further processing, a pulp can be recovered in high yield and purity that is suitable for the production of viscose and lyocell fibers in an excellent manner ,

The steam treatment is preferably carried out at a temperature of 120 ° C or more and a P-factor of 50 or less. These are much more intensive
conditions than its "low temperature steaming", as described for example in WO 98/15687 of.

Among the preferred conditions according to the invention an increase in the porosity of the decomposition material (wood chips) as well as a partial cleavage of the lignin-carbohydrate bonds is achieved by the steam treatment.

However, it will take place no chemical cleavage of the glycosidic bonds, as would be the case with a prehydrolysis. Typically, P-values ​​exceeding 50 are achieved in a prehydrolysis. The concept of the "P-factor" is described for example in "Handbook of-pulp", Vol. 1, Wiley-VCH 2006, pages 343-345. The intensity of the steam treatment according to the invention is preferably only about one-tenth of a conventional prehydrolysis.

This means that in the erfmdungs provided according to steam treatment in
contrast to prehydrolysis a higher yield of pulp and thus a more economic production can be achieved. Although the pulp obtained also contains a higher proportion of hemicelluloses by the erfmdungs proper combination of the steps of steam treatment and cold caustic extraction is but apparently achieved that the pulp still excellently suited for the production of cellulose fibers.

For the steam treatment the starting material is in particular preferably at a
temperature of 150 to 180 0 treated C with medium-pressure steam.

In known manner, the starting material may be prior to cooking a
are subjected to impregnation. Even though a steam treatment is carried out, the impregnation takes place after steaming.

In the inventive method, the cooking and optionally the steam treatment and / or the impregnation of the starting material can be carried out in the same kettle.

In the inventive process the cooking in the form of a preferably is
continuous batch cooking (CBC) performed. The CBC-technology is for example from EP 0891438 Bl and from Wizani, W., et al. "CBC - Continuous batch cooking The revolution in power cooking." Pulping in process and product quality Conference, 2000, Boston, MA, USA, is known.

When applying the CBC technology the steps of impregnation and correspond
hot displacement (ie the displacement of the impregnating liquor by cooking liquor) the familiar in the CBC technology methods.

The kraft pulps according to the invention can be subjected to achieve the required purity and degrees of whiteness in a conventional manner a TCF or ECF bleaching.

In a further preferred embodiment, a portion of the forming in the cold caustic extraction stage press liquor by means of a membrane separation process, preferably a nano- or ultrafiltration to be cleaned and at least a portion of the retentate of the membrane separation method of the second cooking liquor are admixed.

The cleaning of the press liquor one CCE-V experiencing means of a membrane separation process is described in WO 2005/118923. The retentate accumulating thereby contains the total amount of contained in the press liquor beta-cellulose and more than half of the gamma-cellulose. In the case of hardwood pulps is the beta-cellulose solution of almost pure xylan.

The membrane separation process may be carried out in two stages, wherein a dilution of the retentate of the first stage with water between the two separating stages
is performed.

Here, a nano-filtration of the diluted retentate or dialysis of the retentate of the first stage may be carried out in the second stage. In both cases the NaOH recovery is increased by this step, with a simultaneous concentration of the hemicellulose phase.

Therefore, in addition to the recirculation of the retentate to the second cooking liquor instead of or of at least a portion of the retentate of the membrane separation method, the hemicelluloses contained therein, in particular xylans, are obtained. In
US 2005/0203291 a method for the recovery of xylans from a rich to xylans phase is described.

In contrast to this known method, in a preferred
embodiment of the method according to the invention can be precipitated hemicelluloses, especially xylans, recovered from the retentate of the membrane separation process by means of reverse precipitation.

For a reverse precipitation agent is selected from the group consisting of is preferably
mineral acids, CO 2 and mono- or polyhydric alcohols. The sedimentation residue may then (for example, a through appropriate installations
washed wash press) and are mechanically dewatered.

The xylans thus obtained can be at least partially processed into Xylo-oligosaccharides. Xylooligosaccharides have various
applications, such as prebiotic effect food additive.

To prepare these Xylo-oligosaccharides a method selected from the group consisting can be carried out hydrothermolysis and enzymatic hydrolysis are preferred.

A further preferred embodiment of the method according to the invention is characterized in that it is coupled to a process for the preparation of a paper pulp and at least a part of the forming in the cold caustic extraction stage of pressing liquor and / or at least a portion of the retentate of at the press liquor
carried out membrane separation process the cooking liquor for producing an
conducted paper pulp cooking process is supplied.

By coupling the Chemiezellstoff- and paper pulp production and utilization of the costs incurred in CCE-step of the process according proper material flows in the paper pulp production, both a qualitative and economic improvement of the paper pulp manufacturing process is possible.

The filtrate contains the CCE stage or the retentate of the nanofiltered CCE filtrate, as already stated above, a high content of hemicellulose. A cooking liquor which is enriched in hemicellulose, is particularly suitable for the production of high-yield pulps with a higher Hemigehalt.

A further preferred embodiment of the method according to the invention is characterized in that to the pulp obtained by the cooking in the course of
further processing in addition to a bleaching step allfällig carried out a treatment for adjusting the degree of polymerization (DP) is performed.

The treatment is preferably selected from the group consisting of oxidative bleaching process, acid-hydrolytic method and electron beam irradiation method.

The DP-degradation of pulps to a desired DP level can be done either by chemical oxidative manner and by electron irradiation. As
oxidants for the DP degradation are best hypochlorite or
ozone treatments. A disadvantage of chemically-oxidative process that, due to limited accessibility (the oxidizing agent) in the crystalline regions of the
runs very heterogeneous chain degradation, whereby the molecular weight distribution remains significantly wider than would correspond to a statistical degradation.

In contrast, the electron irradiation shows a largely statistical degradation so that the polydispersity of the molecular weight distribution with advancing DP degradation decreases significantly stronger than in the case of chemical-oxidative degradation processes such as the example of
it was shown ozone treatment.

The electron irradiation of pulps for DP setting is well known and has been studied by many groups [eg Kukielka, A., et al., Electron-beam treatment ofcellulose pidps for production derivatives. Zeszyty Naukowe Politechniki Śląskiej, Chemia, 2001. 146: p. 117-120; Here, E., et al., Electron-beam stimulation ofthe reactivily ofcellulose pulps for production of derivatives. Radiation Physics and Chemistry, 2002. 63: p. 253-257; Stepanik, TM, DE Ewing, and R. Whitehouse, Electron treatment of woodpulpfor the viscose process. Radiation Physics and Chemistry, 2000. 57: p. 337-379].

In this work the authors that the electron irradiation is used to replace the alkaline preripening of finished pulps expect. After the
electron beam irradiation in the pulp very reactive groups leaves (carbonyl), but causes a subsequent alkaline treatment another strong DP degradation and the formation of chromophoric structures in the alkali cellulose.

Even worse, the use of irradiated cellulose in lyocell affect. Here, the reactive groups degradation reactions of the solvent NMMO, 'their degradation products induce in turn continue the cellulose degradation. This is one of the reasons why the DP setting is not so far carried out by means of electron irradiation in practice.

The present invention circumvents this problem by providing that the pulps at arbitrary positions of the fiber line, during the manufacturing process of pulp, starting from the unbleached pulp until the last bleaching stage, a
( "treatment ,, e-beam) are exposed to electron irradiation.

The electron irradiation of the pulp may be preferably carried out so that the pulp in a consistency of at least 35%, preferably 40-50% and in a
layer thickness of 2 to 6 mm, preferably 3 to 4 mm, is present as well as an
accelerating voltage of less than 2 , 5 MeV is used.

Layer thicknesses between 2 and 6 mm can also use low
can be irradiated largely homogeneous acceleration voltages. The existing in the pulp mat water content must of course be considered in the choice of the radiation dose. The required for a particular DP-degradation dose increases at a pulp density of 50% roughly doubled.

A further favorable embodiment of the method according to the invention is that after treatment for adjusting the degree of polymerization an alkaline-oxidative treatment, preferably an alkaline peroxide treatment is performed.

In particular, caused by an electron irradiation labile groups be stabilized by these subsequent alkaline peroxide stage, and can therefore can not exert any adverse effect on the further processing processes. In a peroxide (P) stage after a stage EBeam the carbonyl groups are mostly oxidized to carboxyl groups. In this short-chain compounds are formed with strong chromophore groups, which are washed into the bleaching filtrate. The high molecular weight, oxidized residues are mostly present as aldonic acid and thus subsequent alkaline
treatments stable against.

The following are typical process concepts are shown when using an electron irradiation:

TCF-Bleichsequenz:
W-eBeam-OP-AZP; EBeam-W-OP-AP, eBeam-W-OP P, W, OP-AZ-eBeam-P, W-A-OP eBeam-P, W-OP-eBeam-P.

ECF bleaching sequence:
W-EBeam OP-DEP; W-EBeam OP-DED, DED-W-EBeam, WDE-EBeam-P In this case, meanings of the abbreviations used: W ... laundry, OP ... peroxidverstärkte oxygen delignification, E ... alkaline extraction, chlorine dioxide stage D ... , Z ... ozone stage, P ... alkaline peroxide stage.

A further preferred embodiment of the method according to the invention is characterized in that the Kochungsschritt of the pulp is carried out in two stages, where in the first stage, delignification by means of a first cooking liquor to a kappa number of 35 to 70 in the case of coniferous wood as the starting material and to a Kappa No. is carried out from 30 to 60 in the case of hardwood as a raw material, and the boiling is continued until the desired degree of purity of the pulp in the second stage by means of a second cooking liquor.

This embodiment is thus based on the concept of a two-stage kraft cooking.

The task of the first cooking Stufes is to carry out the bulk of the bulk delignification. Here softwoods to a kappa number of 35 to 70 and hardwoods can be delignified to a kappa number of 30 to 60 according to the invention.

The proportion of the H-factor of the first cooking stage, based on the H-factor of both cooking stages together, preferably 40% to 80% in the case of softwoods as
starting material and 20% to 60% in the case of deciduous trees as raw material.

The H-factor defines the relative speed of lignin dissolution and depends on the Kochungszeit and temperature. H-factor of 1 corresponds to a cooking time of 1 hour at 100 ° C. Here, the H-factor expresses the cooking time and the cooking temperature than a single variable. It is a relative reaction rate (with reference to a temperature of 100 0 integrates C, where the reaction rate is defined as 1), which is calculated by means of an Arrhenius rule approach using a specific activation energy, over the time of cooking.

Preferably, the first cooking liquor replaced during the transition from the first to the second cooking stage through the second cooking liquor. For example, in the case of a continuous
supply of the first cooking liquor are stopped cooking process and at the same time are started from a second leach tank, the supply of the second cooking liquor. The selection of suitable flow rates also enables a substantially complete entry of the cooking liquor during two cooking phases.

The first cooking liquor preferably has an EA (effective alkali) concentration of 10 g / L to 30 g / L, preferably 15 g / L to 25 g / L, particularly preferably 20 g / L, and a sulfidity of 50% to 120% , preferably 100%, based on. The sulfidity S is defined by the test method SCAN-N 30:85 as S = 2 [HS] / ([OH] + [HS]).

In a further preferred embodiment, the composition of the second cooking liquor from that of the first cooking liquor differs.

The composition of the second cooking liquor can be adjusted by admixing a suitable liquor streams to the respective requirements for the pulp quality in particular.

Preferably, the second cooking liquor can be selected from the group consisting of a liquor to be concentrated from the filtrate to a subsequent washing stage, a white liquor from the causticizing and the pressing liquor from a cold caustic extraction stage.

In the inventive process both cooking stages in the form of a continuous batch cooking (CBC) are preferably carried out. This technology offers
particular a higher flexibility in the design of the second cooking stage. In the case of modified continuous cooking processes, the addition of either hemicellulose-rich or hemicellulose-poor cooking liquor has in the counter-current cooking zone (MCC and EMCC / ITC-cooking process) or in the extended cooking zone (EMCC / ITC-cooking process).

The present invention also relates to the use of the chemical pulp according to the invention for the production of viscose and lyocell fibers.

The methods for the production of viscose and lyocell fibers are known to those skilled in the.

Lyocell fibers are obtainable by spinning a chemical pulp according to the invention, characterized in particular by the following features:

Its content H of hemicellulose is preferably more than 3.5 wt.%, Which is slightly higher than the hemicellulose content of lyocell fibers, the (particularly that with a comparatively low yield) produced from high-quality and expensive prehydrolysis-kraft pulps, for example in the WO be prepared 94/12719. The content of H can be present at less than 5.% Are.

In spite of this increased level of hemicellulose, the mercerization of lyocell fiber of the invention (described below in accordance with the measurement method) is 90% or more. Thus, the invention Lyocelllfaser a significantly higher
fastness to mercerization than Lyocell fibers, which are made of a non-inventive kraft pulp, such as described in WO 99/47733 high hemicellulose content,.

The strength of the lyocell fiber according to the invention is in a conditioned state 37 cN / tex or more, and thus is in the same size range was reached so far only by using high-quality and expensive to be manufactured prehydrolysis-kraft pulps.

Lyocell fibers produced from such high quality prehydrolysis-kraft pulps, the Lyocell fiber produced according to the invention also differs in that the average molecular weight of harvestable fiber from the xylans is 20 kDa or more (see the measurement method described below). By contrast, xylans from Lyocell fibers that come from high-quality prehydrolysis kraft pulps (or sulphite pulps) a weight average (Mw) of <10 kDa.

In sum, the fiction, modern lyocell fibers from previously known fibers are thus clearly distinguishable, and have the advantage that they have excellent fiber properties in spite of use of the relatively low obtainable by the process according to Inventive dissolving pulp.

The present invention also relates to a viscose fiber, obtainable by spinning a chemical pulp according to the invention.

The viscose fiber according to the invention is particularly characterized in that its content of hemicellulose H contains more than 2.0.% By its fastness to mercerization, and is 90% or more. The strengths of the inventive viscose are despite high hemicellulose content at the level of the best viscose fibers, which are made from high-quality prehydrolysis kraft pulps (or sulfite pulp).
In particular, the viscose fiber according to the invention may have a tenacity in conditioned state of 23 cN / tex or greater and an elongation in the conditioned state of 18% or more.

The present invention is explained below with reference to the figures and examples.

Figure 1 shows a diagram of the basic concept of the inventive method and its applications.

Figure 2 shows a plot of intrinsic viscosity vs. Kappa number of single and two-stage CBC cookings of spruce.

In Figure 3, temperature and hydroxide are of one and two-stage.
Softwood CBC cookings shown.

Figure 4 shows a plot of total yield vs. Kappa number of single and two-stage Eucalyptus g / OZM / ws-CBC cookings with and without accumulation of hemicellulose.

Figure 5 shows a plot of intrinsic viscosity vs. Kappa number of single and two-stage Eucalyptus globulus CBC cookings with and without accumulation of hemicellulose.

Figure 6 shows the molar mass distribution of Eucalyptus globulus Kτaftzellstof & n.

Figure 7 shows the comparison of the molecular weight distribution of a CBC * -Zellstoffes with a VISCBC pulp.

Figure 8 shows the strengths of prepared from different pulps normal viscose fiber in the conditioned state.

Figure 9 shows the influence of the ozone amount used and the radiation dose to the DP cleardown differently pretreated CBC and LH sulfite pulps.

Figure 10 shows the molecular weight distribution of a means EBeam and ozone on a LVN of 440 ml / g degraded CBC pulp.

Figure 11 shows the molecular weight distribution of a CCE of a filtrate isolated by reverse precipitation in mineral acid xylan.

Figure 12 shows the molar mass distribution of the isolated from pulps and fibers produced therefrom by means of DMSO xylans (Graphical analysis of the GPC analysis)

Figure 13 represents the intensity of the preferred steam treatment (CBC *) according to the
invention a prehydrolysis (VISCBC) opposite. The P-factor of the
invention preferred steam treatment is less than 50; the P-factor of
VISCBC prehydrolysis at 700th

1 shows the basic concept of the method according invention and its various applications are shown schematically.

The variant A shows the preparation of a paper pulp with high strength potential: by a two-stage combustion method (out as a batch or, for example CBC-V) with a TCF or ECF bleaching sequence combined. The two-stage procedure allows optimum adaptation of the cooking conditions to the respective requirements.

The variant B shows the concept of producing a high-yield paper pulp (pulp with increased hemicellulose content): The process proceeds to basically the same as in Variant A. The cooking liquor for the second stage of the cook, but is supplemented here with high molecular weight hemicellulose from hemicellulose liquor. This rich in hemicellulose liquor may in particular originate from a CCE process, which is performed in an input coupled to the process B Process C for preparing a high-yield Lyocellzellstoffes. The hemicellulose liquor can, for example, (a) the CCE filtrate or (b) be the retentate of the nanofiltered CCE filtrate.

The above-mentioned variant C in Figure 1 results in a high yield Lyocellzellstoff for the production of Lyocell fibers with the highest textile-mechanical
strength properties: The basic scheme proceeds according to variant A. The cooked pulp, however, here, either directly after washing and sorting, or after each bleaching or depolymerization ( "DEPOLY"), preferably treated by an O-stage in a CCE-refining stage.

In combination with a to parallel process of paper pulp production, see Scheme B, CCE filtrate to the fortification of white liquor can be preferably used in the second cooking step.

In the absence of or too low paper pulp production, the liquor can be recycled after purification by nanofiltration. The permeate (b) is recycled to the CCE stage, the retentate from (c) hemicelluloses can be obtained.

The variant D in Figure 1 shows a preferred embodiment of the inventive method for the production of high-yield Dissolvingzellstoffen, which is in particular

(a) viscose fibers for textile with high mechanical properties,
(b) all other Dissolvingzellstoffe that are derivatized to cellulose ester or ether.

The basic scheme proceeds according to variant C. To improve the Pulp Reactivity the timber of a steam activation treatment (DA stage) is subjected, in which the
composite structure of the wood is greatly loosened, selectively separate the target in the subsequent alkaline cooking the low molecular weight hemicelluloses.

Examples

Example 1 - Two-stage CBC cooking of spruce

Spruce wood in a 10.8 1 test cooker according to the CBC method
(continuous batch cooking) cooked pulp with Kappa numbers 16-42. The single-stage reference has the following conditions:

Impregnation: [OH-] = 12:37 mol / 1 [HS] = 00:22 mol / 1; mean temperature of 120 0 C,
30 min (fill direction from bottom to top)
heating: Displacement of the impregnating by preset cooking liquor
(displacement direction from top to bottom). After 28 min. which is
target temperature of 160 0 C is reached
cooking stage: cooking liquor is from top to bottom in a flow rate of 2 times the digester volume per hour is pumped through the cooker: 160
0 C, [OH-] = 0.62 mol / 1 [HS] = 00:30 mol / 1, H-factors: 800-1600.

Impregnation and heating of the inventive two-stage CBC cooking were carried out similarly to the single-stage variant.

Cooking step 1: 160 0 C, [OH-] = 00:48 mol / 1 [HS] = 00:48 mol / 1, H-factor = 750 = constant cooking stage 2: 160 0 C, [OH-] = 0.62 mol / 1 [HS-] = 00:32 mol / 1, the H factor was of
100 - 600 varies

There were two variants of the two-stage CBC cooking, the only difference was in the concentration of dissolved substances:

a) DS ~ 80 g/l (Standard)
b) DS ~ 40 g/l (Low Solid-CBC)

The test results are shown in Figure 2 by way of selectivity plots
(vs. intrinsic viscosity kappa number) are summarized. The results show that the already high selectivity of the stage CBC cooking through the two
can be further improved two-stage variants.

In the figure 3, temperature and hydroxide of the incoming and the above-described two-stage Softwood CBC cookings are shown.

As shown in Figure 3, is produced by a two-stage procedure - in case of equal Delignifizierungsgrade - not extend the cooking time. The hydroxide ion concentration in the cooker outlet shows a rapid increase during the second cooking stage and has already achieved half of the cooking time, the target concentration.

Example 2 - Two-Stage CBC Cooking of Eucalyptus globulus

Eucalyptus globulus, in a 10.8 1 test cooker according to the CBC V out (continuous batch cooking) to give pulp with Kappa numbers 13 to 28

The single-stage reference (one-stage) has the following conditions:

Impregnation: [OH-] = 12:38 mol / 1 [HS] = 00:25 mol / 1; average temperature of 120 ° C, 30
min (fill direction from bottom to top)
heating: Displacement of the impregnating by preset cooking liquor
(displacement direction from top to bottom). After 30 min. which is
target temperature of 155 ° C reached
cooking stage: cooking liquor is from top to bottom in a flow rate of 2 times pumped through the cooker of the digester volume per hour: 155
° C, [OH-] = 0.65 mol / 1 [HS] = 12:34 mol / 1, H-factors: 200 - 500th

Impregnation and heating of the two-stage CBC cooking (two-stage) were carried out similarly to the single-stage variant.

Cooking step 1: 155 0 C, [OH J = 12:46 mol / 1 [HS] = 12:37 mol / 1, H-factor = 180 = constant cooking stage 2: 155 0 C, [OH-] = 0.62 mol / 1 [HS-] = 12:37 mol / 1, the H factor was varied from 100 to 400.

In a second variant, the cooking liquor of the second stage was prepared by the hemireichen filtrate of a CCE treatment.

The conditions in the cooking stage 2 were set this as follows: 155 ° C, [OH-] = 12:37 mol / 1 [HS] = 12:16 mol / 1, beta-cellulose concentration (from CCE filtrate) = 10 g / l, H factor = 150 to 400.

As seen from Figure 4, the yield could could both for the "simple" two-step variant ( "two-stage") as well as with the entire Kappa number range
significantly improved reinforced hemicellulose two-step variant ( "hemi-add") compared to the single-stage operation, become.

The advantage of the two-stage process management is also reflected in the
digestion selectivity in Figure 5 as a plot intrinsic viscosity vs. Kappa number is shown.

It is striking that the cooking selectivity, that is the intrinsic viscosity at a given kappa number, after all CBC cookings compared to conventionally produced Eucalyptus g / ozm / ws cookings is very high.

Example 3 - Production of high-yield pulps for further processing to viscose and lyocell

The wood was before the CBC cooking a steam activation (DA) exposed by the digester contents with the aid of medium-pressure steam to a temperature of about 165 0 C was placed. The CBC cooking was carried out in one stage.

The combination of processes DA + CBC is hereinafter referred to for better labeling "CBC *". CB C * -Zellstoff was kaltalkaliextrahiert after O-delignification to remove with the aim of the alkali-soluble hemicellulose, the DP-setting was made in Ralimen. the final bleaching by ozone treatment (Z). the subsequent P-bleaching was used for stabilization of the cellulose and to set the desired Endweissgrades. a prehydrolysis-kraft pulp by means of the "was VISCBC' technology prepared as a reference pulp (modified Visbatch process, see Wizani , W., et al "CBC -. Continuous batch cooking The revolution in power cooking". in Pulping process cmdproditct quality Conference, 2000, Boston, MA, USA).

Table 1 below shows the main characteristics of the unbleached pulp.

Tab. 1: Characterization of unbleached E. globulus pulps: CBC * -Zellstoff

(Paper pulp) and VISCBC cooking process, as a reference for a conventional

Dissolving pulp.
Parameter CBC * VISCBC
Wood # 134 # 141/142
P-factor 0490
Yield,% 100.0 52.9 37.2 sorted
cellulose yield 46.1% wood 41 0 34.9
Kappa number 13.1 6.0
intrinsic viscosity ml / g 1281 963
whiteness 37.7% ISO 42.8
R18-20 ° C% 92.6 96.9 pulp
R18-50 ° C% 84.4 96.2 pulp
xylan% cellulose 16.0 18.4 3 1
% of wood 16.0 9.7 1, 1

The P-factor presses from the intensity of the pre-hydrolysis. The calculation is based on the same concept as in H-factor, wherein a different Aktivierungsenergeie (123 kJ / mol) is used.

The yield (cellulose content) of the CBC * -Zellstoffes was 15.7% points (6.1% points) is higher than compared to the VISCBC reference pulp (see Tab.l).

The CBC * - and VISCBC pulps were then fertiggebleicht using a OZP-TCF sequence. To reduce the low-molecular hemicelluloses were the CBC * - pulps after O-delignification kaltalkaliextrahiert (CCE-stage).

The CCE-treatment was carried out at two different levels of concentration of NaOH, 50 g / l and 100 g / l. As a source of alkalinity white liquor served with a sulfidity of 26%. All other conditions, such as temperature (3O 0 C), residence time (30 min) and mass density (10%) were kept constant in both experiments.

The final bleaching was performed with the aid of a ZP-sequence in all the pulps, the
object of the ozone bleaching consisted primarily therein, the DP to the level for
adjusting Regeneratzellstoffe (DPv 950-1200 corresponds to a limiting viscosity number LVN 420-500 ml / g) , The most important process and pulp data (as part of the pulp bleaching) are listed in Table 2 below.

Tab. 2: Characterization of bleached high-yield E. globulus CBC * -CCE pulps and reference a bleached VISCBC dissolving pulp.
Parameter Units CBC * -reference CBC CCE50 CBC * -CCE100 VISCBC reference
OZPO CCE ZPO CCE ZPOZP
conditions
Temperature • c 110 50 80 110 30 50 70 110 30 50 70 110 50 80

Vetweilzeit 60 240 60 30 120 60 30 120 60 300

Consistency% 12 10 10 12 10 10 10 12 10 10 10 12 10 10

NaOH Emsatz kg / t 25 12 25 6 25 6 25 9 3

NaOH-Konzentration g/ι 50 100
02-Partιaldrιιck bar 10 10 10 10
Ozoneinsatz kg/t 11 87 6 8 3,5 2,8

Peroxidemsatz kg/t 10 5 6

Pulp Parameter
Total yield% / wood 51.7 50.83 50.3 51.7 47.1 46.9 46.6 51.7 45.2 45.1 44.9 36.6 36.4 36.2

Kappazahl 7.7 1 2 0.5 7.7 4.5 0.5 0.3 7.7 2.9 0.4 0.3 1.8 0.4 0.2

Weissgrad %iso 66,4 84 89,0 66,4 90,2 92,5 664 91 ,4 93,6 70,2 88,2 92,4

Intrinsic viscosity ml / g 893 498 470 893 984 490 475 893 1026 490 465 650 490 455

R 18-20% 93.1 96.1 96.4 98.7 97.8 97.0

Xylan % 17,3 9,6 9,3 4,7 4,2 2,9

From Table 2 it is clear that the CCE-treated pulps have a CBC * R18-level high-value in the range of prehydrolysis-kraft pulps (VISCBC reference) is located. The yield on the other hand is the bleached CBC * -CCE materials to 8.7-10.4% points higher than the reference pulp.

The yield advantage is mainly due to the higher cellulose content. The higher xylan content (alkali-resistant) of the CBC * ~ CCE pulps also contributes to the higher yield, this proportion decreases with increasing NaOH concentration in the CCE stage.

A simple balance sheet shows that the CCE treatment highly selective non-cellulosic polysaccharides removed while an intensive prehydrolysis also a massive
causes cellulose degradation.

An important criterion for the assessment of dissolving pulps, especially with regard to their processing properties is the molecular weight distribution.

The molecular weight of Eucalyptus globulus KraΑzQllstoϊfen is shown in FIG. 6

The upper part of Figure 6 shows unbleached CBC pulps, which according to one
was prepared two stage CBC cooking process. Here, the terms "CBC two-stage" "CBC hemi-add" refer with and without the Hemicelluloseanreicherung according to Example 2 pulps produced. The curve "ß-xylan" refers to isolated from the CCE stage isolated xylan.
The lower part of Figure 6 illustrates the following pulps:
(a) CBC *: unbleached CBC pulp by steam activation
(b) CBC * depoly: CBC * after TCF bleaching
(c) CBC * -CCE: CBC * after CCE treatment at 100 g / l NaOH concentration
TCF-bleached (d) (c).

Die Molmassenverteilung wurde mittels GPC in LiCl/DMAc und MALLS Detektion
[Schelosky, N., T. Röder, and T. Baidinger, Molecular mass distribution ofcellulose products by size exclusion chromatography in DMAC/LiCl. Das Papier, 1999. 53(12): p. 728-738] ermittelt.

It is clear from the lower part of Figure 6 that the CCE treatment the low molecular weight carbohydrate fraction very effectively and selectively removed.

A comparison with the molecular weight of conventional highly refined
pulps produced according to a prehydrolysis-kraft process
(VISCBC), shows (see Figure 7) that the CCE treatment with the higher NaOH concentration level of a narrower distribution (lower polydispersity) than in to
allow comparison pulps. In the figure, 7 is a VISCBC pulp with a "CBC * CCElOO Depoly" pulp as a CBC * -Zellstoff, which has undergone a CCE process with 100 g / l NaOH and a depolymerization treatment (TCF) is subjected to was compared.

Further processing into regenerated

1. viscose:

An important criterion for the further processing of dissolving pulps is the achievable viscose identified using the filter value for driver [Sixta, H., et al, Evaluation of new organosob dissυlving pulps. Part I: Preparation, characterization and analytical viscose processability. Cellulose, 2004. 11 (1): p. . 73-83], the average particle content and the distribution of particles in the size range of 3-150 microns (determination by means of the measuring device PAMAS [Sixta et al, Cellulose, 2004, 11 (1):.. P 73-83]) assesses has been.

Table 3 below shows that the steam activation treatment prior to the CBC cooking constitutes the decisive step in order to improve the resulting viscose. The following CCE treatment leads to a further improvement of the viscose, where, as expected, increases the effect with increasing NaOH concentration.

Table 3: viscose measured by the filter value and the average
particle volume of the reference and experimental pulps

Zellstoff # Filterwert Partikelvolumen
ppm
VISCBC-Referenz 73/05 364 28
CBC-Referenz 14/05 34 156
CBC * 74/05 180 58
CBC-223 34 75/05 CCE50
CBC * -CCE100 15/05, 7/06 306 28

Table 3 shows that the quality of viscose produced from the CBC * -CCE100 pulp is almost equivalent to that which had been prepared from the VISCBC reference pulp. The viscoses were filtered and on a laboratory spinning machine having 20 hole (φ 50 microns) at 4 different
spun draw ratios.

The strengths of the produced normal viscose fibers in the conditioned state are summarized in FIG. 8 In this case, fibers are
a) CBC paper pulp
b) CBC * -CCE pulp and
c) VISCBC reference pulp
compared.

The results show that the CBC * pulp -CCE the reference dissolving pulp (VISCBC) with regard to further processing to viscose fibers is equal. The somewhat lower fiber strains are due to a more incomplete filtration, which is recognizable by a slightly increased proportion of small particles in the order of 5-10 microns

The following table lists the physical-chemical properties of the pulps used and the resulting viscose manufactured (after a standard spinning process) are compared:

Table 4: Physico-chemical properties of the pulps and the viscose fibers produced therefrom (standard quality).

The pulp "Solucell" is a VISCBC pulp.

Under the hemicellulose content of the sum of the non-glucose sugar -containing ingredients according to the invention (calculated as anhydro-sugar) after total hydrolysis to understand (two-stage hydrolysis with sulfuric acid) of the pulp or fiber. The measurement is performed by means of anion exchange chromatography combined with pulsed
amperometric detection as a method. The measurement method is in U. corn, H. Sixta,
ACS Symposium Series 2004, 864, 94, and H. Sixta et. al. Proceedings of the 1 lth ISWPC 2001, Vol. 3, pp. Described 655-658.

Method for Determination of Mercerization:

Entavivierung:

The fibers are extracted 3h in a Soxhlet extractor with 96% EtOH and incubated overnight at 50 0 dried C under vacuum.

Mercerisierungsausbeute:

2.00 g entavivierte fiber (initial mass Mi) at 20 0 C with 50 mL of NaOH, having a
concentration of 250 g / L, in a beaker for 3 minutes vigorously stirred with a glass rod (gestösselt). Subsequently, the pulp is filtered off through a G3 frit and washed with deionized water until neutral. After drying the fiber, the fiber is weighed again (final weight M 2 ). The Mercerization is the ratio of M 2 / M [(%).

2. Lyocellfaseπr.

It is known that depolymerized kraft paper pulp is suitable for producing high-quality Lyocell fibers [WO 99/47733]. A (possibly two-stage) kraft cooking with Dampfvoraktivierung creates the basis for the production of lyocell fibers with significantly better textile-mechanical properties. The results of the Ausspinnungen in a Davenport laboratory spinning system show that the cold caustic extraction of
kraft pulps, the textile-mechanical properties to the level of
lyocell fibers from the highest quality dissolving pulps (VISCBC) raises (Table 5).

Table 5: mechanical properties of lyocell fiber manufactured by means of a Davenport- laboratory spinning plant from the CBC paper and chemical pulp
Conditioned fiber data, 1.3 dtex
pulps Strength Elongation
# cN / tex%
VISCBC reference L66 40.7 12.7
9 ?. C "P_ ?.. F ? R - s ? L32 D 30, 0_ 10.1
" C ~ BC * -CCE ~ 5 NC " L53 54 36 ~ ~ ~ Ö Ϊ2 ~, 5 ~ '
CBC * -CCE100 L22 41 0 10.4 the following table shows the results of further testing, for the production of
lyocell fibers from different pulps together:
table 6: Physico-chemical properties of the pulps and lyocell fibers produced therefrom

The pulp "High Hemi" is a teaching of WO 99/47733 the corresponding pulp. The pulp "Solucell" is a VISCBC pulp.

From the table it can be seen that the from inventively produced pulps (CBC * -CCE100) spun Lyocell fibers have, despite favorable production of pulp and higher hemicellulose content in terms of fiber strength and the mercerization excellent, comparable with lyocell fibers of a high quality VISCBC pulp properties.

The lyocell invention significantly exceed the properties of 99/47733 corresponding pulp produced from any of the teaching of WO fibers.

Example 4 - Controlled DP-setting of high-yield pulps

In laboratory tests, the behavior of the ozone bleaching and electron irradiation was ( "EBeam") with respect to the DP degradation of OP (CCE) -A- or OP (CCE) -D
prebleached CBC, CBC * -CCE50- and CBC * -CCE100 pulps compared. For comparison, a hardwood sulfite pulp ( "LH sulfite") was electron.

The ozone bleaching was thereby carried out at 10% consistency and pH 2.0 by mixing in a high-shear mixer under fluidizing conditions.

The EBeam treatment was carried out at 10 MeV -Beschleunigungsspannung by the company IBA SA, Louvain-La-Neuve in a Rhodotron Accelerator for drying the
pulp sheets.

All pulps were determined by the Z or EBeam treatment peroxidgebleicht (70 ° C, 10 kg NaOH / t, 7 kg H2O2 / t, 120 min, 10% consistency, 0.5 kg Mg II ions / t).

The results in Figure 9 show that the degree of chain cleavage (KSP, calculated according of the formula 10 4 / P r 10 4 / P 0 (P ≡ DPv calculated from SCAN LVN values;, ... after removal, 0 • • • from degradation)) as a function of the ozone amount used very strong (on the concentration of hemicellulose and lignin, not shown) in the pulp depends. The higher the hemicellulose content, the higher the ozone applications to achieve a certain KSP.

The hemicellulosenarme CBC CCEL OO pulp requires only 3 kg O 3 / t for a KSP 5.6 (GVZ degradation of 750 ml / g to 420 ml / g), while a CBC pulp with a high xylan content four times as (see Table 2) more than 12 kg of o for the same degradation rate 3 / t required.

In contrast, however, the electron irradiation: The dose required for a particular DP-degradation is largely independent of the type of pulp and here
pulp composition.

Table 7 confirmed from the Kupferzahl- and carboxyl group contents, the
stabilizing effect of a subsequent degradation processes alkaline peroxide treatment. The P-stage causes to both degradation processes an additional KSP of about 0.6 - 1.2, depending on the circumstances.

Table 7: copper number and carboxyl group content of CBC * -CCE100 pulps according Z-, EBeam, or subsequent alkaline peroxide bleaching
OP-CCE100 AZP-
copper number% 0.85 0.72
COOH mmol / kg 34 37
OP-CCE100-D- ebeam ebeam P P
copper number% 0.79 0.65
COOH mmol / kg 33 40

The advantage of electron irradiation manifests itself in the clearly narrower DP distribution of finished pulps. Figure 10 shows that the depolymerized by EBeam CBC paper pulp having a significantly narrower distribution than a degraded with ozone CBC pulp. In a degradation to a LVN of 440 ml / g was the
polydispersity index (PDI) in the case of the Z-treated pulp 4.3, in the case of EBeam-treated pulp only 3.5. The analysis was performed in each case on the finished pulp after a final P-stage.

Example 5 - Production of high-yield paper pulp

The use of hemicellulose cooking liquor in the second cooking stage primarily causes an increase in pulp yield. As mentioned in Example 2, the average yield increase is (at a Hemikonzentration of about 10 g / l in the cooking liquor) about 2% points compared to the single-stage variant over a wide Kappa number range (see Figure 4).

The reprecipitation of xylan in the pulp surface is significantly increase as the low molecular weight fraction in the molecular weight distribution, see Figure 6 above, recognizable and influences the surface properties and the mechanical strengths. The high Uronsäureanteil (GlcA) of xylan (XY i) GlcA: Xyl ratio about 0.05: 1, increases the hydrophilic nature of the cellulose surface.

Example 6 - Preparation of Xylanprodukten

1. Isolation of Xylan from the CCE filtrate

With the help of a pilot nanofiltration plant (NF), equipped with a
polyether sulfone, Nadir N30 F, cut-off 300, a CCE-filtrate (Profile Star OJ A4007J) was measured using a candle filter pre-filtered to filter off residual fibers and undissolved particles.

The NF was operated at a temperature of 40 ° C, a pressure of 25 bar and a specific flow rate of 5 l / m 2 operated .h. The beta-cellulose (xylan) concentration in the feed was about 15 g / l, the concentration of NaOH 90 g / l. In equilibrium, the flow rates and thus the liquor loads in the permeate to retentate as 0.82: 12:18.

Due to the low cut-offs of the membrane, the total amount of beta cellulose in the retentate was in a concentration of about 85 g / l. The retentate was in a ratio of 1: 1.5 diluted with water, and again supplied to the NF.

The NF-conditions of the second stage were comparable to the first stage, only the permeate dropped to about 70% of the feed amount. The retentate of the second stage, the NF-Beta-cellulose was now in a concentration of about 115 g / l and a NaOH concentration of about 32 g / l (hemi liquor).

This substrate was used for isolation of beta-cellulose (xylan) by reverse precipitation with mineral acid. For this, about 0.1 parts of a 1: 3 water-diluted sulfuric acid with 1 part offset hemi liquor, wherein at the end of a pH 4-5 is established.

After 6-8 hours, a dirty-white precipitate in a consistency of about 10 to 15% by weight forms. This precipitate was then centrifuged, washed and dried. In this solid is a xylan content of 74 wt% was detected. Based on the total carbohydrate content of xylan content was 97.5%. The molecular weight distribution of said xylan powder determined by GPC reveals a weight average molecular weight of 24.4 kg / mol and a number average molecular weight of 10.6 kg / mol (see Figure 11).

2. Further processing of the Xylan Powder into Xylo-oligosaccharides (XOS)

XOS was prepared in two ways from the xylan, (A) hydrothermolytically, (B) enzymatically:

(A) XOS preparation Hydrothermolytic:

318 g dry xylan were in L 9:08 diluted in water (xylan concentration 35 g / L) and treated in a 11 L pressure reactor at 120 ° C for 5 hours under constant agitation. The recirculation rate was 75 L / h. The pH value of the hydrolyzate was after the conclusion of the reaction 3.13.

The solution was then neutralized with 0.3 N NaOH to pH 6.5-7.0. The water-soluble products were centrifuged at 4000 rev / min for 60 min. The isolated amount of XOS was 189.7 g of freeze-dried powder, corresponding to a yield of 59.6% based on the xylan. The XOS mixture hydrothermolytically shows a relatively uniform composition throughout the examined DP-range (see Table 8 below).

(B) Enzymatic hydrolysis:

Has 2 . 10

90 g of moist xylan (equivalent to 40 g dry xylan) were suspended in 900 mL added (44.4 g / L) and 50 mg of Pentopan Mono BG (25.1 mg / g xylan). The mixture was stirred in the fermentor at 50 ° C for 2 h. Thereafter, the enzyme was deactivated by heating for 10 minutes at 99 ° C. The remaining insoluble material was removed by centrifugation, freeze-dried, the aqueous solution. The XOS yield based on the xylan was 75%.

has 2

The reaction was carried out filling in a 7L fermenter containing 6 L, the concentration of xylan amount 20 g / L (120 g Xylan). The preparation was carried out also with the enzyme Pentopan Mono BG, but with increased concentration of 1 g / L (50 mg / g xylan). The fermentation was carried out at 40 0 performed C for 96 h. It was worked up as described above. The XOS yield was 78% based on the amount of xylan used (93.66 g XOS). The product consists predominantly of xylobiose (Table 8).

Table 8: Relative mass fractions of the individual neutral XOS
ProduktHydroEnzymatisch
distribution thermal XOS 2-10 XOS 2
% by weight
X1 11 2 0.1 4.7
X2 9.7 13.0 83.1
X3 10.6 21, 0 12, 2
X4 12.2 16.0
X5 12.5 11 0
X6 7.9 12.0
X7 12.6 7.2
X8 10.3 7.2
X9 9.0 6.9
X10 9.7
XOS 100, 0 100.1 100.0

Example 7 - molecular weight distribution (MMV) of the hemicelluloses (xylans) isolated from Inventive prepared according pulps and fibers

The use of any of the new generation of dissolving pulps category "CBC * -CCE" for the production of high-strength Lyocell textile fibers based on the molecular weight distribution (MMV) isolated from the fibers hemicellulose (In the case of hardwoods, these are almost exclusively xylans) in combination with the clearly demonstrate high strength and high mercerization.

The hemicelluloses are et.al. using DMSO by the method of D. Evtuguin Extracted (carboh. Res. 338 (2003) 597) of the substrates (pulp or fibers) and purified. Fibers or with EtOH before entaviviert (25 g Soxhlet with 1 L EtOH, 6h). The isolated xylan (5 mg) is suspended in DMAc (1 mL) and by adding LiCl (8 mg) at room temperature molecularly. The molecular weight is determined by GPC under the following conditions: eluent: LiCl / DMAc; Temperature:
room temperature; Column: Mixed A Polymer Labs; Detection: MALLS (Wyatt) / RI; Refractive index increment: 0.136 mL / g.

The results of the MMV B DENTIFICATION isolated from pulps and lyocell fibers produced therefrom hemicelluloses are summarized in Table 9 and Figure 12th

Table 9: MMV isolated from pulps derived therefrom, lyocell fibers by DMSO xylans: numerical evaluation of mass and number average

The pulp "Solucell-1772" is a VISCBC pulp.

The results of the GPC measurements of the isolated from pulp and fibers Xylane following conclusions:

• The profile of the xylan-MMV in the pulp is reflected - in spite of degradation - in fiber again.
• Xylane from CBC * -CCE pulps are significantly high molecular weight and
polydisperse than those made of conventional prehydrolysis kraft pulps (PHK).

• xylans from lyocell fibers by using a CBC * -CCE pulp
were prepared, have a weight average (Mw) of> 20 kDa. In contrast, xylans from lyocell fibers derived from commercial today PHK pulps (or Sulfϊtzellstoffen) a weight average (Mw) of <10 kDa.
Claims:

1. A process for the preparation of a chemical pulp from a cellulosic
starting material by the Kraft process, comprising the step of cooking the raw material with a cooking liquor, characterized in that the
starting material prior to cooking to a steam treatment is suspended and that the pulp obtained by the cooking in the the course of further treatment of a cold- alkali extraction (CCE) is subjected.

2. The method according to claim 1, characterized in that the steam treatment at a temperature of 120 ° C or more and a P-factor is carried out of 50 or less.

3. The method according to claim 1 or 2, characterized in that the
steam treatment, the starting material at a temperature of 150 to 180 0 C is treated with medium pressure steam.

4. The method according to any one of the preceding claims, characterized in that the starting material is subjected to an impregnation prior to cooking.

5. The method according to any one of the preceding claims, characterized in that the boiling process, the steam treatment and optionally, the impregnation of the raw material are carried out in the same kettle.

6. The method according to any one of the preceding claims, characterized in that the cooking in the form of a continuous batch cooking (CBC) is performed.

7. The method according to any one of the preceding claims, characterized in that at least a part of the forming in the cold caustic extraction stage
press liquor by means of a membrane separation process, preferably a nano- or ultrafiltration is cleaned.

8. The method according to claim 7, characterized in that the
membrane separation process is carried out in two stages, between the two
, a dilution of the retentate of the first stage is carried out with water separation stages.

9. The method according to any one of claims 7 and 8, characterized in that from at least the therein a portion of the retentate of the membrane separation process
hemicelluloses contained in particular xylans are obtained.

10. The method according to claim 9, characterized in that the precipitable
hemicelluloses, especially xylans from the retentate of the membrane separation process are obtained by an inverse precipitation.

11. The method according to claim 10, characterized in that to the reverse
precipitation, an agent selected from the group consisting of mineral acids, CO 2 and mono- or polyhydric alcohols is used.

12. The method according to any one of claims 9 to 11, characterized in that the xylan obtained are at least partially processed into xylo-oligosaccharides.

13. The method according to claim 12, characterized in that for the production of
xylo-oligosaccharides a method selected from the group consisting of
is performed hydrothermolysis and enzymatic hydrolysis.

14. A method according to any one of the preceding claims, characterized in that it is coupled to a process for the preparation of a paper pulp and at least a part of the forming in the cold caustic extraction stage pressing liquor and / or at least a portion of the retentate carried out one at the press liquor
is supplied to the membrane separation process of the cooking liquor of a process performed for the production of paper pulp cooking process.

15. The method according to any one of the preceding claims, characterized in that to the pulp obtained by the cooking in the course of further processing in addition to a bleaching step allfällig carried out a treatment for
setting the degree of polymerization (DP) is performed.

16. The method according to claim 15, characterized in that a treatment selected from the group consisting of oxidative bleaching process consisting
acid hydrolysis method and electron beam irradiation process is carried out.

17. The method according to claim 16, characterized in that the one
is carried out electron irradiation of the pulp, wherein the pulp in a consistency of at least 35%, preferably 40-50% and in a layer thickness of 2 to 6 mm, preferably 3 to 4 mm, is present, and an accelerating voltage of less than 2.5 MeV is used.

18. The method according to any one of claims 15 to 17, characterized in that after treatment for adjusting the degree of polymerization an alkaline-oxidative
treatment, preferably an alkaline peroxide treatment is performed.

19. A method according to any one of the preceding claims, characterized in that the Kochungsschritt of the pulp is carried out in two stages, where in the first stage, delignification by means of a first cooking liquor to a
Kappa number of 35 to 70 in the case of coniferous wood as a raw material and a Kappa number is carried out from 30 to 60 in the case of hardwood as a raw material, and the boiling is continued until the desired degree of purity of the pulp in the second stage by means of a second cooking liquor.

20. The method according to claim 19, characterized in that the proportion of H-factor of the first cooking stage, based on the H-factor of both cooking stages
together, 40% to 80% in the case of softwoods as starting material and 20% to 60% in the is the case of deciduous trees as raw material.

21. The method according to claim 19 or 20, characterized in that said first cooking liquor is replaced by the second cooking liquor in the transition from the first to the second cooking step.

22. The method according to any one of claims 19 to 21, characterized in that said first cooking liquor an EA concentration of 10 g / L to 30 g / L, preferably 15 g / L to 25 g / L, particularly preferably 20 g / L and a sulfidity of 50% to 120%, preferably 100%, comprising.

23. The method according to any one of claims 19 to 22, characterized in that the composition of the second cooking liquor from that of the first cooking liquor
differs.

24. The method according to claim 23, characterized in that the second cooking liquor having a liquor selected from the group consisting of the filtrate of a
subsequent washing stage, a white liquor from the causticizing, the pressing liquor from a cold caustic extraction stage and the retentate of a at a press liquor from a cold caustic extraction stage carried out the membrane separation process is enhanced.

25. The method according to any one of claims 19 to 24, characterized in that both cooking stages in the form of a continuous batch cooking (CBC) performed
be.

26. The use of a chemical pulp, which by a process according to any one of
prepared claims 1 to 25, for the manufacture of viscose and
lyocell fibers.

27. Lyocell fiber, obtainable by spinning a chemical pulp which has been produced by a process according to any one of claims 1 to 25th

28. Lyocell fiber according to claim 27, characterized in that its content of H of
hemicellulose containing more than 3.5.% By weight and its mercerization is 90% or more.

29. Lyocell fiber according to claim 28, characterized in that the content of H less than 5 wt.% By weight.

30. Lyocell fiber according to claim 28 or 29, characterized in that its
strength in the conditioned state 37 cN / tex or more.

31. Lyocell fiber according to any one of claims 28 to 30, characterized in that the average molecular weight of harvestable fiber from the xylans is 20 kDa or more.

32. Viscose fiber, obtainable by spinning a chemical pulp which, after
been prepared by a process according to any one of claims 1 to 25th

33. Viscose fiber according to claim 32, characterized in that its content of H of
hemicellulose containing more than 2.0.% By weight and its mercerization is 90% or more.

34. Viscose fiber according to claim 32 or 33, characterized in that its
strength in the conditioned state 23 cN / tex or more and its elongation in the conditioned state of 18% or more.