EP3536850A1 - Pulp and lyocell articles with reduced cellulose content - Google Patents

Abstract

The present invention describes special pulp compositions which make it possible to produce a lyocell fiber with a reduced cellulose content in a technically stable manner and the lyocell fiber produced therefrom.

Description

The present invention describes special pulp compositions which make it possible to produce a lyocell fiber with a reduced cellulose content in a technically stable manner and the lyocell fiber produced therefrom.

State of the art

Lyocell fibers are used in a variety of applications. Purified cellulose is often used as a raw material, with a very low content of cellulose endings.

1. a) Aufschluss: Ein Großteil der Hemizellulosen geht in der Sulfit-Kochung verloren; während im alkalischen Aufschluss die Vorhydrolyse speziell zur Entfernung der Hemizellulosen der Kochung vorgeschaltet wird.
2. b) Bleiche: in der Regel zur Eliminierung von Rest-Lignin und/ oder zur optischen Aufhellung, zerstört aber auch Hemizelluloseanteile
3. c) Teilweise Unlöslichkeit von verzweigten Hemizelluloseanteilen im Lyocell-Lösungsmittel
4. d) Abbau im DOPE mit nachfolgender Auflösung im Spinnbad

Pulp is made of wood, which consists only of 40-44% by weight of cellulose. Since a high content of cellulose in the pulp of more than 95 wt.% Is generally required for the production of lyocell moldings, a large part of the raw material for the material utilization is lost during the cooking and bleaching. In this connection, a large number of possibilities are known, in particular to purposefully reduce the proportion of hemicelluloses, both in the pulp production on the way of the wood to the pulp or to the lyocell end product:

1. a) digestion: a large part of the hemicelluloses is lost in the sulphite boiling; while in the alkaline digestion the prehydrolysis is preceded especially for the removal of the hemicelluloses of the cooking.
2. b) bleaching: usually for the elimination of residual lignin and / or for optical brightening, but also destroys hemicellulose components
3. c) Partial insolubility of branched hemicellulose moieties in the lyocell solvent
4. d) DOPE degradation with subsequent dissolution in a spin bath

Although there are strong efforts to use these other ingredients as a by-product as well. However, the reaction takes place only in small quantities due to known technical restrictions. In the waste liquors of pulp extraction, these other wood components are in the form of a variety of different degradation products before, even in mixture with strong acids or alkalis, which makes the separation and processing extremely difficult.

However, in recent years, efforts have been made to broaden the raw material base for lyocell products by using celluloses with an increased level of lignin and / or hemicelluloses. By way of example, US Pat. No. 4,440,523 and US Pat US 6444314 such approaches:

Essentially, the approach followed in these publications consists in describing either the corresponding pulp and / or the lyocell products produced therefrom which, in addition to the cellulose content, also have a hemicellulose content of more than 5% by weight. However, it is considered essential in all of these documents that the higher hemicellulose levels described therein are only possible if a number of other essential conditions are simultaneously met. These are, for example, a certain viscosity of the pulp, a maximum copper number and / or a maximum kappa number.

Although lyocell products are described in these documents, it is noteworthy that developments based on these patent rights have not yet been realized on an industrial scale, although the use, in particular of cellulose with a higher hemicellulose content, should bring significant costs and hence competitive advantages. This may well be due to the difficulties of upscaling from the laboratory scale and the achievable fiber properties, which do not meet the expectations of the textile and nonwovens market.

Object of the invention

In order to maximize resource utilization, it would be desirable to be able to use as much material as possible from the raw material wood to produce a lyocell fiber. The primary goal in the pursuit of maximum sustainability and a truly effective biorefinery concept must be to harness the natural raw material of wood as fully as possible from the outset for the main product, namely lyocell moldings. The extraction of by-products remains of great importance, but overall this remains subordinate. The efforts to date have failed because the reduction of the cellulose content in the fiber either led to a massive change in the material and property parameters of the resulting (lyocell) fiber (or other variants of moldings) or on the other hand, no stable large-scale production was possible. On the contrary, for the large-scale application of a chemical pulp in the lyocell process is required in a variety of patents and publications that the content of lignin, hemicelluloses and accessory components should be extremely low.

For these reasons, it is desirable to use large scale technologies for To provide a reduction in the cellulose content in the finished fiber by increasing the proportion of other wood components, in particular hemicelluloses, but also lignin, without significant restrictions in relation to the resulting material parameters. At present, despite the large number of approaches in the prior art, no industrially useful processes for producing such lyocell products with a reduced cellulose content are known.

Brief description of the invention

The above problems of the prior art are overcome by the present invention. The present invention provides a pulp according to claim 1, a lyocell product according to claim 9, and the methods according to claims 16 and 18. Preferred embodiments of the invention are given in the subclaims and the following detailed description of the invention.

1. 1. Zellstoff, geeignet zur Herstellung von Lyocellformkörpern, mit einem Anteil an Zellulose von 90 Gew.-% oder weniger und einem Anteil an Hemizellulosen von mindestens 7 Gew.-%, dadurch gekennzeichnet, dass das Verhältnis der in der Hemizellulose vorliegenden C5/Xylan- zur C6/ Mannan-Fraktion (C5/C6-Verhältnis) im Bereich von 125:1 bis 1:3 liegt.
2. 2. Zellstoff nach Ausführungsform 1, wobei das C5/C6-Verhältnis im Bereich von 25:1 bis 1:2 liegt.
3. 3. Zellstoff nach Ausführungsform 1 und/oder 2, wobei der Anteil an Hemizellulosen 10 Gew.-% oder mehr beträgt.
4. 4. Zellstoff nach mindestens einer der vorstehenden Ausführungsformen, dessen Hemizellulosen in nativem Zustand vorliegen, durch Verarbeitungsprozesse chemisch verändert oder in einem separaten Prozessschritt chemisch modifiziert bzw. funktionalisiert wurden.
5. 5. Zellstoff nach mindestens einer der vorstehenden Ausführungsformen, mit einem Ligningehalt von mehr als 1 Gew.-%.
6. 6. Zellstoff nach mindestens einer der vorstehenden Ausführungsformen, wobei der Zellulosegehalt durch das Vorhandensein von Lignin, akzessorischen Bestandteilen aus dem Holz und/oder die Zugabe von metallischen Verbindungen weiter reduziert wird.
7. 7. Zellstoff nach mindestens einer der vorstehenden Ausführungsformen, mit einem Xylananteil von 9 Gew.-% oder mehr und/oder einem Mannangehalt von 6 Gew.-% oder mehr.
8. 8. Zellstoff nach Ausführungsform 7, mit einem Xylangehalt von 9 Gew.-% oder mehr und einem Mannangehalt von 1 Gew.-% oder weniger.
9. 9. Lyocellformkörper, hergestellt unter Verwendung des Zellstoffs nach einer der Ausführungsformen 1 bis 8.
10. 10. Lyocellformkörßer nach Ausführungsform 9, wobei der Formkörper ausgewählt ist unter Fasern, Filamenten, Stapelfasern, Nonwoven-Gewirken, Filmen und Pulvern in spherischer Form.
11. 11. Lyocellformkörper nach mindestens einer der Ausführungsformen 9 und/oder 10, wobei der Formkörper eine Faser, ein Filament oder eine Stapelfaser ist, mit einem Zellulosegehalt von weniger als 90 Gew.-%, einem Hemizellulosegehalt von mehr als 5 Gew.-% und einem C5/C6-Verhältnis von 125:1 bis 1:3, bevorzugt 25:1 bis 1:2.
12. 12. Lyocellformkörper nach mindestens einer der Ausführungsformen 9 bis 11, wobei der Hemizellulosegehalt mehr als 10 Gew.-% beträgt.
13. 13. Lyocellformkörper nach mindestens einer der Ausführungsformen 9 bis 12, wobei der Formkörper eine Faser, ein Filament oder eine Stapelfaser ist mit einem WRV von größer als 70%, bevorzugt größer als 75%, insbesondere größer als 80%.
14. 14. Lyocellformkörper nach mindestens einer der Ausführungsformen 9 bis 13, wobei der Formkörper eine Kristallinität von 40% oder weniger aufweist.
15. 15. Lyocellformkörper nach mindestens einer der Ausführungsformen 9 bis 14, mit einem Ligningehalt von mehr als 0 Gew.-% bis zu 5 Gew.-%.
16. 16. Verfahren zur Herstellung eines Lyocellformkörpers, umfassend die Auflösung eine Zellstoffs mit einem Anteil an Zellulose von 90 Gew.-% oder weniger und einem Anteil an Hemizellulosen von mindestens 7 Gew.-%, dadurch gekennzeichnet, dass das Verhältnis der in der Hemizellulose vorliegenden C5/Xylan- zur C6/ Mannan-Fraktion (C5/C6-Verhältnis) im Bereich von 125:1 bis 1:3 liegt, in einem geeigneten Lösungsmittel, und Formung der Lösung zu einem Lyocellformkörper.
17. 17. Verfahren nach Ausführungsform 16, wobei der Lyocellformkörper durch ein Lyocell-Spinnverfahren erhalten wird.
18. 18. Verfahren zur Herstellung eines Zellstoffs nach einer der Ausführungsformen 1 bis 8, wobei das Verfahren mindestens einen der folgenden Schritte umfasst:
    1. a) Mischen eines reinen Zellstoffs mit Xylan und/oder Mannan;
    2. b) Behandeln eines Zellstoffs mit einem Hemizelluloseanteil einschließlich Mannan, durch chemische und/oder physikalische Verfahren, um den Hemizellulosenanteil und/oder die Zusammensetzung der enthaltenen Hemizellulose zu modifizieren;
    3. c) Herstellung eines Zellstoffs unter Einsatz von Nadel und/oder Laubhölzern;
    4. d) Mischen eines Mannan freien Zellstoffs mit einem Hemicellulose reichen Zellstoff und optional anschließende chemische und/oder physikalische Behandlung der Mischung zur Einstellung des Hemizellulosegehalts und/oder der Zusammensetzung des Hemizelluloseanteils;
    5. e) Mischen zweier Zellstoffe mit unterschiedlichem Hemicellulosegehalt und/oder Hemicellulosenzusammensetzung, und optional anschließende chemische und/oder physikalische Behandlung der Mischung zur Einstellung des Hemizellulosegehalts und/oder der Zusammensetzung des Hemizelluloseanteils.
19. 19. Verfahren nach Ausführungsform 18, wobei die unterschiedlichen Zellstoffe ausgewählt werden unter Laub- und Nadelholz basierten Zellstoffen.

In particular, the present invention provides the following aspects, as well as the preferred embodiments recited in the subclaims as well as in the description.

1. 1. Pulp, suitable for the production of Lyocellformkörpern, with a content of cellulose of 90 wt .-% or less and a content of hemicelluloses of at least 7 wt .-%, characterized in that the ratio of present in the hemicellulose C5 / xylan - to the C6 / mannan fraction (C5 / C6 ratio) in the range of 125: 1 to 1: 3.
2. A pulp according to embodiment 1, wherein the C5 / C6 ratio is in the range of 25: 1 to 1: 2.
3. 3. pulp according to embodiment 1 and / or 2, wherein the proportion of hemicelluloses is 10 wt .-% or more.
4. 4. pulp according to at least one of the preceding embodiments, the hemicelluloses are in the native state, chemically modified by processing processes or chemically modified or functionalized in a separate process step.
5. 5. pulp according to at least one of the preceding embodiments, with a Lignin content of more than 1 wt .-%.
6. 6. Pulp according to at least one of the preceding embodiments, wherein the cellulose content is further reduced by the presence of lignin, accessory constituents from the wood and / or the addition of metallic compounds.
7. 7. pulp according to at least one of the preceding embodiments, with a xylan content of 9 wt .-% or more and / or a Mannangehalt of 6 wt .-% or more.
8. A pulp according to Embodiment 7, having a xylene content of 9% by weight or more and a mannan content of 1% by weight or less.
9. 9. Lyocellformkörper, prepared using the pulp according to one of embodiments 1 to 8.
10. The lyocell mold coater of embodiment 9, wherein the shaped body is selected from fibers, filaments, staple fibers, nonwoven knits, films and powders in spherical form.
11. 11. Lyocellformkörper according to at least one of embodiments 9 and / or 10, wherein the shaped body is a fiber, a filament or a staple fiber, having a cellulose content of less than 90 wt .-%, a hemicellulose content of more than 5 wt .-% and a C5 / C6 ratio of 125: 1 to 1: 3, preferably 25: 1 to 1: 2.
12. 12. Lyocellformkörper according to at least one of embodiments 9 to 11, wherein the hemicellulose content is more than 10 wt .-%.
13. 13. Lyocellformkörper according to at least one of embodiments 9 to 12, wherein the shaped body is a fiber, a filament or a staple fiber with a WRV of greater than 70%, preferably greater than 75%, in particular greater than 80%.
14. 14. Lyocellformkörper according to at least one of embodiments 9 to 13, wherein the shaped body has a crystallinity of 40% or less.
15. 15. Lyocellformkörper according to at least one of embodiments 9 to 14, with a Lignin content of more than 0 wt .-% up to 5 wt .-%.
16. 16. A process for producing a lyocell molding, comprising dissolving a pulp with a content of cellulose of 90 wt .-% or less and a content of hemicelluloses of at least 7 wt .-%, characterized in that the ratio of present in the hemicellulose C5 / xylan to C6 / mannan fraction (C5 / C6 ratio) ranges from 125: 1 to 1: 3, in a suitable solvent, and forming the solution into a lyocell molded article.
17. 17. The method of embodiment 16, wherein the lyocell molded article is obtained by a lyocell spinning process.
18. 18. A process for the production of a pulp according to one of embodiments 1 to 8, wherein the process comprises at least one of the following steps:
    1. a) mixing a pure pulp with xylan and / or mannan;
    2. b) treating a pulp with a hemicellulosic moiety, including mannan, by chemical and / or physical means to modify the hemicellulosic content and / or the composition of the hemicellulose contained;
    3. c) production of a pulp using needle and / or hardwoods;
    4. d) mixing a mannan-free pulp with a hemicellulose-rich pulp and optionally subsequent chemical and / or physical treatment of the mixture to adjust the hemicellulose content and / or the composition of the hemicellulose portion;
    5. e) mixing two pulps with different hemicellulose content and / or hemicellulose composition, and optionally subsequent chemical and / or physical treatment of the mixture to adjust the hemicellulose content and / or the composition of the hemicellulose portion.
19. 19. The method of embodiment 18, wherein the different pulps are selected from foliage and softwood based pulps.

Brief description of the figures

• Fig.1 shows the correlation of crystallinity and water retention of Lyocell fibers of the present invention as well as standard lyocell fiber.
• Fig.2 shows the ratio of xylan to mannan in sulfite pulp as a function of H-factor in the use of beech wood.
• Fig.3 shows the ratio of xylan to mannan in sulfite pulp as a function of H-factor in the use of spruce wood.

Detailed description of the invention

If the proportion of cellulose in the lyocell process is reduced, this means that the savings made by other materials from the wood raw material should be compensated. This raises the problem of process stability or property change when the cellulose content is lowered, as already explained above. The main constituents of non-cellulosic material in the raw material wood are the hemicelluloses (mainly polyoses from the sugar monomers xylose, arabinose, mannose, galactose, glucose and rhamnose), lignin and accessory components.

Cellulose: It is the skeletal substance of the cell walls in the wood and serves mainly the tensile strength. The long molecular chains of glucose units are assembled in so-called fibrils several times in a helical structure. This helical arrangement in the cell wall ensures a good bending strength of the tree, e.g. at a wind load or wood z. B. in a roof construction. Cellulose is hydrophilic but not water-soluble due to its high crystallinity.

Lignin: Binder for the firm bonding of cellulose in the form of an amorphous matrix. Thus, lignin is mainly responsible for the compressive strength, on the other hand, is less flexible and hydrophobic in contrast to cellulose. It is responsible for the stamina of the tree. Plants that do not store lignin only reach low stature heights. Lignin is biologically relatively stable and biologically degradable only slowly.

Hemicellulose for the purposes of the present invention are components present in wood in the form of short-chain polymers of C5 and / or C6 sugars. In contrast to cellulose, they have side groups and can therefore form crystals only to a much lesser extent. Their basic building blocks are mannose, xylose, glucose, rhamnose, galactose. The side groups preferably consist of arabinose groups, acetyl groups and galactose residues as well as O-acetyl groups and 4-O-methylglucuronic acid side groups. It is known that mannans are preferably associated with cellulose, while xylans are more likely to associate with lignin. The composition of hemicelluloses varies greatly depending on the type of wood used. In the process of manufacturing pulp, side chains are partially separated and the polymer chains split. In the context of this invention, the term hemicelluloses includes those in their native structure as well as those modified by their processing and also those which have been adjusted by specific chemical modification for the particular application. Also included are short chain celluloses and other polyoses with a DP of up to 500.

Accessory Ingredients: Accessory ingredients are wood-derived organic and inorganic non-lignin, cellulose, and hemicellulose, and commonly include salts and low molecular weight organic compounds of up to about 100 atoms, such as tannins, resins, fats and waxes, tanning agents. and humic substances, terpenes, terpenoids and phenolic compounds, pectins, suberines, polyphenols and polyoses.

Now, if the cellulose content is lowered as desired in a pulp material and other components of the raw material wood to compensate for this reduction, it has surprisingly been found that it is possible only by the combination of different sugars in a certain ratio to specify a pulp, despite its reduced cellulose content safely allows a large-scale production of lyocell products, which products also have a reduced cellulose content, but still have satisfactory product properties.

According to the invention, it is essential that, with a reduced cellulose content in the pulp of less than 90% by weight, a fraction of hemicelluloses of at least 7% by weight is present, whereby the ratio of sugars with five C atoms, such as, for example, B. xylan to sugars with six carbon atoms such. Mannan (hereinafter called C5 / C6 ratio) is in the range of 125: 1 to 1: 3.

With such a pulp, surprisingly, the large-scale production of lyocell products can certainly be realized, even though the cellulose content in the pulp is lowered.

The pulps used here, which are preferably used in the context of the present invention, show, as already stated, a relatively high content of hemicelluloses the composition defined here. In comparison with standard pulps with low hemicellulosic content, used in particular in the prior art for the production of standard lyocell fibers, the pulps preferably used in the context of the present invention also show other differences which are listed below.

In comparison with standard pulps, the pulps preferably used in the context of the present invention show a rather fluffy view. This results after milling (during the preparation of starting materials for the production of spinning solutions for the lyocell process) in a particle size distribution with a high proportion of larger particles. As a result, the bulk density is much lower, compared to standard pulps with a low hemicellulose content. Such a low bulk density requires adaptations with regard to metering parameters (eg metering using at least two storage tanks) in the preparation of the spinning solutions. In addition, the pulps preferably used in the context of the present invention show an impregnation behavior with respect to NMMO, which shows that the impregnation is more difficult in comparison with standard pulps. This can be verified by evaluating the impregnation behavior with the Cobb evaluation. While standard pulps typically exhibit a Cobb value greater than 2.8 g / g (determined in accordance with DIN EN ISO 535 with adaptations for the use of an aqueous solution of 78% NMMO at 75 ° C with a two minute impregnation time ), the pulps preferably used in the context of the present invention show Cobb values of about 2.3 g / g. This requires adaptations during the preparation of spinning solutions, such as increased dissolution time (eg explained in US Pat WO 94/28214 and WO 96/33934 ) and / or temperature adaptation and / or increased shear during dissolution (eg WO 96/33221 . WO 98/05702 and WO 94/8217 ). This allows the production of spinning solutions which make it possible to use the pulps described herein in a standard lyocell method).

In a preferred embodiment of the present invention, the pulp used for the production of lyocell products, preferably fibers as described herein, exhibits a SCAN viscosity in the range of 300 to 440 ml / g, in particular 320 to 420 ml / g, more preferably 320 to 400 ml / g. The SCAN viscosity is determined in accordance with SCAN-CM 15:99 using a Cupriethylendiaminlösung, a method which is known in the art and which can be performed with commercially available devices, such as with the device Auto PulpIVA PSLRheotek, available from the company PSL Reotek. The viscosity of SCAN is an important parameter which influences in particular the processing of pulps in the production of spinning solutions. Even if two pulps show great agreement with respect to their composition, etc., different SCAN viscosities result in completely different behavior during processing. In a direct solution spinning process, like the lyocell method, the pulp is dissolved in NMMO as such. There is no maturation step, comparable for example with the viscose method, where the degree of polymerisation of the cellulose can be adapted to the needs of the process. Therefore, the specifications for the viscosity of a raw pulp are typically for the lyocell process in a small target window. Otherwise problems can occur during production. In accordance with the present invention, it has been found that the pulp viscosity is preferably as previously described. Lower viscosities lead to a deterioration of the mechanical properties of the lyocell products. Higher viscosities can in particular lead to an increased viscosity of the spinning solution, so that spinning is slower overall. With lower spinning speeds, lower draw ratios are obtained, which again can have a significant influence on the fiber structure and the fiber properties ( Cabohydrate Polymers 2018, 181, 893-901 ). This would require process adaptations that would lead to capacity reduction. The use of pulps with the viscosities defined herein, on the other hand, allows for easy processing and the production of high quality products.

• Semi-kommerzielle Pilotanlage: etwa 1 kt/a
• Kommerzielle Einheit größer 30 kt/a

The term "lyocell process", or the terms "lyocell technology" and "lyocell method", as used herein, denotes a direct dissolution process of wood cellulose pulp or other cellulose based feedstocks in a polar solvent (eg N-methylmorpholine n-oxide (NMMO, NMO) or ionic liquids). Commercially, this technology is used to make a group of cellulosic staple fibers, commercially available from Lenzing AG, Lenzing, Austria under the trademark TENCEL® or TENCEL ™), which are widely used in the textile industry or the nonwoven industry. Other cellulose moldings obtained by the lyocell technology were also already manufactured. In accordance with this method, the cellulose solution is usually extruded in a so-called dry-wet-spinning method, using a molding die, and the molded solution obtained, for example, after passing an air-gap into a precipitation bath, where the molded body is obtained Precipitation of the cellulose. The shaped article is washed and optionally dried, after further treatment steps. A process for the production of lyocell fibers is described, for example in US 4246221 . WO 93/19230 . WO 95/02082 or WO 97/38153 , As far as the present invention discusses the disadvantages of the prior art, and discusses the unique properties of the novel products disclosed and claimed herein, particularly in the context of the use of laboratory equipment (especially in the prior art) or in the context of (semi-commercial ) Pilot plants and commercial fiber spinning units, the present invention is to be understood as referring to units that can be defined in terms of their respective production capacities as follows:

• Semi-commercial pilot plant: about 1 kt / a
• Commercial unit greater than 30 kt / a

In the context of the present invention, it has been found that, in particular during fiber production in the context of a lyocell process, an orientation takes place in the direction of production and a stretching of the fibers. From an initial, more or less disoriented mix of different polymers and other ingredients in the dope
is achieved by the strong cross-sectional constriction at the spinneret a first orientation of the polymers in the production direction. The additional stretching in the air gap after the spinneret and during the following process steps results in a stretched oriented fiber structure of the polymers. These processes are well known in the literature.

The fiber properties are strongly influenced by the type and by the assembly of the polymers. It is also known that cellulosic fibers produced by the lyocell process have a very high crystallinity of about 44 to 47%, while fibers from the viscose process have a crystallinity of about 29 to 34%. The crystallinity describes the alignment of the cellulosic polymers to each other and thus, for example, their ability to absorb, swell and store water. In addition, the polymer chains are more ordered in the non-crystalline regions of the lyocell fibers than in the viscose fibers. As a result, ordinary lyocell fibers swell less and are less suitable for highly absorbent products than viscose fibers.

By using the celluloses with reduced cellulose content according to the invention, a completely different type of aggregation of the polymers and thus a different structure of the lyocell fibers is unexpectedly made possible. Their crystallinity is significantly lower, typically 40% or less, such as 39% or less and, for example, in the range of 38% to 30%, such as in the range of 37 to 33%.

The values for WRV for fibers in accordance with the present invention, isolated or in combination with the other preferred embodiments described herein, preferably in combination with the fiber crystallinity values described herein, are preferably 70% or greater, more preferably 75% or greater , like 80% or more, eg from 70 to 85%.

It is known from the literature that xylans also form a crystal structure if their side chains were split off in the course of the production process and precipitated from a pure xylan solution (Fengel, Wegener p. 113; Fengel D, Wegener G (1989): Wood, Chemistry, Ultrastructure, Reactions; Walter de Gruyter Verlag ). The same applies to Mannan (ibid., P.119). In the present invention, however, opposite effects are exhibited. The polymers including the cellulose are present in a mixture in the dope and are thus spun out and precipitated. Furthermore, the hemicelluloses still have side groups, since the glucuronic acid side groups of xylan under the conditions of acid digestion are relatively stable ( Sixta H (Ed.) (2006): Handbook of Pulp Vol. 1; Wiley VCH p. 418 ). The hemicelluloses thus fulfill all conditions to disrupt the crystallization of the cellulose and thus form a more disordered structure compared to standard lyocell fibers. Thus, those skilled in the art would expect that higher hemicellulose content and reduced cellulose content would give useless products, especially fibers. However, it has unexpectedly been shown that the content of hemicelluloses in combination with the C5 / C6 ratio allows targeted control of product properties. By this mixture of different sugar polymers still crystallinity values are reached, which are above the crystallinity values of viscose fibers, nevertheless the accessibility of the fiber as a whole for water increases, so that the water retention capacity (WRV) can be increased significantly. This improved absorbency is crucial for various applications, such. B. for use in the nonwovens sector. This relationship between decreasing crystallinity and increasing water retention for lyocell fibers is in illustration 1 and can be adjusted as described above by the targeted reduction of the cellulose content in the fiber.

As shown in the examples, the grades of the new reduced cellulosic lyocell fibers are similar to those of conventional TENCEL® fibers. It can be seen that the fiber strengths are slightly lower than those of the TENCEL® fibers, measured in the examples as strength and workability. At the same time, the cellulose content could be significantly reduced, recorded in the examples as glucan value. The uptake of other wood constituents reduces the crystallinity by up to 21% and the absorbency increases significantly by up to 27%, measured in the examples as crystallinity index and water retention capacity. Interestingly, the crystallinities of the new lyocell fibers according to the invention lie between those of conventional TENCEL® fibers and nonwovens Lenzing Viscose® fibers; at the same time, WRV is in the Lenzing Viscose® range. Thus, the WRV increases more than would be explained by the decreasing crystallinity of the fibers. This is a clear indication of the unexpected properties that can be realized with the present invention. The other ingredients such as in particular hemicelluloses, but also lignin and accessory Components from the wood therefore not only ensure a significant increase in yield, ie improved sustainability, but also a significant improvement in product properties, such as water retention capacity.

embodiments

As defined in claim 1, the pulp of the invention is characterized by a reduced content of cellulose, a minimum amount of hemicelluloses and a certain C5 / C6 ratio with respect to the composition of the hemicellulose.

In a preferred embodiment, the pulp, which may also be a mixture of different pulps (as long as the essential conditions are met), is a pulp having a hemicellulose content of from 7 to 50% by weight, preferably from 7 to 25% by weight preferably 10 to 20 wt .-%.

The pulp to be used according to the invention is furthermore preferably a pulp which has a xylan content of at least 9% by weight, preferably a fraction of at least 10% by weight. The proportion of mannan can, in combination or independently, be chosen within a wide range, as long as the ratio defined according to the invention is fulfilled. Suitable mannan contents are in the range of 0.1 to 10% by weight, such as from 0.1 to 9% by weight and in embodiments from 0.1 to 6% by weight, from 0.1 to 4% by weight. %, from 5 to 10% by weight, from 6 to 10% by weight, etc. In embodiments, the Mannangehalt in the range of 0.1 to 1 wt .-%, preferably in combination with a xylan content of at least 9 wt. -%, preferably at least 10 wt .-%. In other embodiments, the Mannangehalt is higher, preferably in the range of 6 wt .-% or more.

In a preferred embodiment, isolated or in combination with the embodiments described above and below, the cellulose content in the pulp is in a range of equal to or less than 90% by weight to 50% by weight, preferably in the range of 90% by weight. % to 60 wt%, such as from 85 wt% to 70 wt%.

The weight ratio of cellulose to hemicellulose may range from 1: 1 to 20: 1. The level of accessory constituents may be more than 0.05% by weight, preferably more than 0.2% by weight, more preferably more than 0.5% by weight. It has unexpectedly been found that with such proportions of accessory constituents in the pulp according to the invention, the effect can be promoted that the C5 / C6 ratio is also stable in the prepared lyocell products, in particular fibers, and the hemicellulose content does not change significantly (ie the content does not decrease in the lyocell product or only slightly in comparison to the pulp).

In a further preferred embodiment, the inventive C5 / C6 ratio achieves such a high retention capacity that at the same time a proportion of metal compounds, generally present as their oxides and hydroxides of up to 25% by weight, based on the weight of the lyocell product (eg, Mg (OH) ₂ or Al (OH) ₃ for flame retardancy purposes), which further substantially reduces the cellulose content. Such metal compounds are in particular TiO ₂ , Al ₂ O ₃ , MgO, SiO ₂ , CeO ₂ , Mg (OH) ₂ , Al (OH) ₃ , BN, ZnO and originate in part from the mineral constituents of the wood or can be used as the cellulose solution functional additives (flame retardant, matting agent, biocide ...) are added.

In a further preferred embodiment, lyocell fibers having a cellulose content reduced to less than 70% can be prepared which not only meet the practical requirements in comparison with the known lyocell fibers (mechanical strengths, etc.), but also due to the novel properties resulting for some applications even better. The investigations have shown that fibers in the proposed composition have, in particular, an increased water retention capacity and a rapid biodegradability during composting.

According to the invention, the ratio of C5 / C6 sugars of the non-cellulosic polymers has been shown to be an important factor in adjusting the fiber composition and its resulting properties. Through targeted adjustment of this ratio, also in combination with the content of hemicelluloses, desired product properties can be adjusted in a targeted manner.

The person skilled in the art is aware of how he / she can control or adjust the C5 / C6 ratio. This can be achieved by a mixture of different pulps such. As softwood pulps with a higher Mannananteil be achieved with hardwood pulps with a higher xylan content. Attempts have confirmed another very effective way to adjust accordingly. By a targeted adjustment of cooking parameters such. As the H-factor, the ratio of C5 to C6 sugars can be controlled. This is shown in Figures 2 and 3. The H factor is considered to be an essential parameter for the control of sulfite boiling (Sixta (Vol. 1 2006) p. 432). He summarizes cooking temperature and cooking time as one size.

Figure 2 shows the influence of the H-factor in sulfite boiling on the hemicellulose ratio in hardwood using the example of beech. For deciduous trees, xylan content is inherently higher. As H-factor increases, xylan degrades more than mannan. The ratio C5 / C6 decreases.

When using softwood, the hemicellulose ratio is the other way round. The proportion of mannan in wood and pulp is higher. Contrary to expectation, Mannan breaks down faster than Xylan does FIG. 3 is apparent.

Another way to adjust the pulp composition according to the invention, is the admixing of C5 and / or C6 sugars, which were previously obtained in other processes or process steps, such as. B. in an alkaline extraction, be it a cold-alkali extraction or an E-stage or the like. For the production of viscose, the addition of hemicelluloses in dissolved form to the spinning mass and the subsequent co-spinning are known ( WO2014086883 ). As a result, viscose fibers can be produced with a reduced cellulose content. This is only possible because the viscose process takes place in the aqueous medium and the hemicelluloses are correspondingly alkali-soluble, so the cellulose xanthogenate and the dissolved hemicelluloses can be mixed together and spun together. In contrast, the solution of the pulp in the lyocell process takes place in NMMO or similar solvents, so here no alkaline or aqueous solutions can be added. You would dilute the solvent and reduce the solubility or even lead to unwanted precipitation. Thus, the hemicelluloses can not be added in the form of solutions in spinning solution production, but must be introduced differently in the process. One possibility is the addition in the pulp manufacturing process, so that the mixture can then be dried with the pulp.

It has surprisingly been found that careful consideration of the hemicellulose composition is a decisive factor for the industrial production of lyocell molded articles, in particular fibers. A co-utilization of hemicellulose in the fiber structure is only possible if the proportion of the C5 fraction is correlated with the proportion of the C6 fraction. Preferably, the ratio of xylan to mannan is between 18: 1 to 1: 3, preferably 9: 1 to 1: 2. At the same time, such a mixing ratio allows the incorporation of 0.5-5% by weight of lignin (and / or other accessory Constituents) into the fiber structure without adversely affecting the desired properties.

The fibers provided according to the invention have typical fiber titers, such as 7 dtex or less, for example 2.2 dtex or less, such as 1.3 dtex or less, possibly even lower, such as 0.9 dtex or less, depending on the desired application. For applications in the nonwoven sector, titres of 1.5 to 1.8 dtex are typical, while for textile applications lower titers, such as 1.2 to 1.5 dtex are suitable. However, the present invention also includes fibers having even lower titers, as well as fibers having significantly higher titers, such as 10 dtex or less, such as 9 dtex or less, or even 7 dtex or less. Suitable lower limits for fiber titers are values of 0.5 dtex or greater, such as 0.8 dtex or greater and, in embodiments, 1.3 dtex or greater. The upper and lower limits disclosed herein may be combined and the regions formed thereby, such as from 0.5 to 9 dtex, are also included. Surprisingly, the present invention enables the production of fibers with titers, which allows use in the entire spectrum of fiber applications, including textile applications as well as nonwoven applications.

As far as parameters are referred to in this application, they are determined as described herein. It is essential that these parameters are obtained with the fibers as such, comprising a maximum of 1 wt .-% additives, such as matting agent, etc. However, the fibers described here can of course conventional additives in conventional amounts, unless this is the production of spinning solutions and / or affects the manufacturing process of the fibers.

The following examples illustrate aspects of the present invention.

methods Determination of the crystallinity index [%]

The determination of the crystallinity index is carried out by means of Raman spectroscopy. This method is calibrated with data from the X-ray wide-angle method (WAX) and was used by Röder et al. (2009) ( Röder T, Moosbauer J, Kliba G, Schlader S, Zuckerstätter G, and Sixta H (2009): Comparative Characterization of Man-Made Regenerated Cellulose Fibers. Lenzinger Berichte Vol. 87, p. 98 ff .).

Determination of water retention [%]

The sample is allowed to swell at 20 ± 0.1 ° C overnight. After further dilution, the sample is centrifuged in a centrifuge according to Zellcheming leaflet IV / 33/57 at 3000 times the gravitational acceleration. The water retention capacity is then calculated as follows: $$\mathrm{WRV}=\frac{\left(\mathrm{Weight\; wet\; Pr}\mathit{obe}-\mathrm{Weight\; dry\; sample}\right)}{\mathrm{Weight\; dry\; sample}}\times 100$$

Examples Example for setting the xylan-mannan ratio

Table 1 shows the results of setting the C5 / C6 ratio for two species of wood, using the example of H-factor variation in magnesium bisulfite digestion. <b> Table 1: </ b> Setting of the xylan-mannan ratio in the magnesium bisulfite boiling of Fagus sylvatica (beech) and Picea abies (spruce) using the H factor. test number H-factor Xyl / Man Xylan /% Mannan /% Fagus sylvatica Wood 0 17.7: 1 19.5 1.1 Mg433 eighteen 13.1: 1 14.5 1.1 Mg434 37 8.5: 1 9.4 1.1 Mg435 60 7.6: 1 6.9 0.9 Mg436 90 6.4: 1 5.1 0.8 Mg437 130 6.6: 1 4.0 0.6 Mg438 160 6.4: 1 3.2 0.5 Mg439 180 5.8: 1 2.9 0.5 Mg420 210 5.8: 1 2.3 0.4 Mg408 249 4.3: 1 1.3 0.3 Picea abies Wood 0 1: 2.4 5.6 13.6 Mg673 78 1: 1.6 4.1 6.7 Mg674 116 1: 1.5 3.4 5.2 Mg675 166 1: 1.4 2.9 4.0 Mg678 180 1: 1.4 2.5 3.4 Mg676 193 1: 1.4 2.0 2.8 Mg677 201 1: 1.6 1.7 2.7

Example of a eucalyptus kraft pulp

In the pilot plant, a new Kraft-Chemie pulp of eucalyptus wood according to the invention was produced by the VisCBC process. The H-factor was 1200, the effective alkali in the cooking liquor was 25 g / l. Bleaching was done after a TCF sequence. Relevant process information and product properties are given in Table 2. <b> Table 2: </ b> Wood-pulp properties for the finished cellulosic-reduced lyocell fiber. analysis unit Eucalyptus wood Raw pulp Bleached pulp Cellulose-reduced lyocell fiber pilot plant trial test number Clone "D" Ka_CBC689698 BI438 E33_2017_0572 Klason lignin % 24.9 - - - Acid-soluble lignin % 3.4 - - - Kappa number - - 9.6 0.3 - whiteness % ISO - 40.8 92.2 - Intrinsic viscosity ml / g - 1025 385 - R ₁₀ % - 92.7 88.3 - R ₁₈ % - 94.9 94.0 - Acetone extract % 0.76 0.19 0.04 0.46 ash % 0.20 0.33 0.20 - Fe ppm 6.4 6.3 6.9 - Mn ppm - 0.8 <0.38 - Cu ppm - 1.0 <1.3 - Ni ppm - 0.7 <1.2 - mg ppm - 12.0 130.0 - Si ppm - 24.7 31.3 - Ca ppm - 78.0 12.0 - SiO2 ppm - 52.8 67.0 - CaO ppm - 109.1 16.8 - glucan % 44.3 79.8 82.3 85.4 xylan % 13.1 15.1 14.0 12.1 mannan % 0.8 <0.2 <0.2 0.1 Xylan / mannan - 16.4 - - 121 arabinan % 0.3 <0.1 <0.1 <0.1 rhamnan % 0.2 <0.1 <0.1 <0.1 galactan % - <0.1 <0.1 <0.1 Crl % - - - 39 WRV % - - - 78

With this new chemical pulp with reduced cellulose content, the xylan-to-mannan ratio has been pushed extremely high, namely to 121 in the finished fiber and at the same time the cellulose content is kept very low at about 85%. This new pulp meets in every respect the requirements of the Lyocell process for the production of the new lyocell fiber with reduced cellulose content.

Example of fiber properties when using the new cellulosic reduced pulps

In Table 3, the contents of the sugar monomers of the starting pulps for lyocell fiber production are summarized. <b> Table 3: </ b> Sugar content of cellulosic reduced pulps compared to standard lyocell pulp sugar Pulp for standard lyocell fiber Pulp for cellulosic lyocell fiber Pulp for cellulose-reduced lyocell fiber "Technikumsversuch" Glucan (%) 95.5 82.2 82.3 Xylan (%) 2.3 8.3 14.0 Mannan (%) 0.2 5.7 <0.2

Table 4 shows mechanical characteristics for standard fibers (lyocell and viscose) compared with characteristics obtained with lyocell fibers made with pulps of the invention. The results clearly demonstrate the advantages of the present invention.

Both pilot plant and large scale lyocell fibers in accordance with the present invention show that acceptable levels of strength and workability can be realized for commercially relevant titers, despite substantially reduced cellulose levels. At the same time, the WRV is drastically increasing, so that such fibers are interesting for new applications, which are so far occupied by viscose fibers. In comparison with commercially available viscose fibers, however, significantly higher mechanical characteristics can be achieved with the lyocell fibers according to the invention.

The new lyocell fibers according to the invention thus combine the respective advantageous properties of hitherto commercially available lyocell or viscose fibers. <b> Table 4: </ b> Properties of conventional and cellulosic reduced lyocell fibers compared to a standard viscose fiber. sample Titre [dtex] Strength [cN / tex] Working capacity [cN / tex *%] Crystallinity [%] Glucan [%] WRV [%] TENCEL® NW (standard) 1.8 32.1 408 47 94.3 65.3 TENCEL® textile (standard) 1.3 36.1 455 44 95.8 69.6 Cellulose-reduced lyocell 1.8 28.1 323 40 85.6 82.5 Cellulose-reduced lyocell fiber 1.7 28.9 370 39 - 81.6 Cellulose-reduced lyocell fiber 1.3 30.9 374 37 86.6 82.8 Lenzing Viscose® NW (standard) 1.7 22.0 429 33 - 78-85 Cellulose-reduced lyocell fiber pilot plant trial 1.7 27.6 315 39 85.4 78.0

Claims (19)

Pulp suitable for the production of lyocell moldings, with a cellulose content of 90% by weight or less and a content of hemicelluloses of at least 7% by weight, characterized in that the ratio of C5 / xylan present in the hemicellulose to C6 / mannan fraction (C5 / C6 ratio) ranges from 125: 1 to 1: 3. Pulp according to embodiment 1, wherein the C5 / C6 ratio is in the range of 25: 1 to 1: 2. Pulp according to embodiment 1 and / or 2, wherein the proportion of hemicelluloses is 10 wt .-% or more. Pulp according to at least one of the preceding embodiments, the hemicelluloses are in the native state, chemically modified by processing processes or chemically modified or functionalized in a separate process step. Pulp according to at least one of the preceding embodiments, with a lignin content of more than 1 wt .-%. Pulp according to at least one of the preceding embodiments, wherein the cellulose content is further reduced by the presence of lignin, accessory constituents from the wood and / or the addition of metallic compounds. Pulp according to at least one of the preceding embodiments, having a xylan content of 9% by weight or more and / or a mannan content of 6% by weight or more. A pulp according to Embodiment 7, having a xylene content of 9% by weight or more and a mannan content of 1% by weight or less. Lyocell molding produced using the pulp according to any of embodiments 1 to 8. A lyocell granulator according to embodiment 9, wherein the shaped body is selected from fibers, filaments, staple fibers, nonwoven knitted fabrics, films and spherical powders Shape. Lyocellformkörper according to at least one of embodiments 9 and / or 10, wherein the shaped body is a fiber, a filament or a staple fiber having a cellulose content of less than 90 wt .-%, a hemicellulose content of more than 5 wt .-% and a C5 / C6 ratio of 125: 1 to 1: 3, preferably 25: 1 to 1: 2. Lyocellformkörper according to at least one of embodiments 9 to 11, wherein the hemicellulose content is more than 10 wt .-%. Lyocellformkörper according to at least one of embodiments 9 to 12, wherein the shaped body is a fiber, a filament or a staple fiber with a WRV of greater than 70%, preferably greater than 75%, in particular greater than 80%. Lyocellformkörper according to at least one of embodiments 9 to 13, wherein the shaped body has a crystallinity of 40% or less. Lyocellformkörper according to at least one of embodiments 9 to 14, with a lignin content of more than 0 wt .-% up to 5 wt .-%. A process for producing a lyocell-shaped body comprising dissolving a pulp with a cellulose content of 90% by weight or less and a hemicellulosis content of at least 7% by weight, characterized in that the ratio of C5 present in the hemicellulose Xylan to C6 / mannan fraction (C5 / C6 ratio) in the range of 125: 1 to 1: 3, in a suitable solvent, and forming the solution into a lyocell mold. The method of embodiment 16, wherein the lyocell molded article is obtained by a lyocell spinning process. A process for producing a pulp according to any one of embodiments 1 to 8, said process comprising at least one of the following steps: f) mixing a pure pulp with xylan and / or mannan; g) treating a pulp with a hemicellulosic moiety, including mannan, by chemical and / or physical means to modify the hemicellulosic content and / or the composition of the hemicellulose contained; h) production of a pulp using needle and / or hardwoods; i) mixing a mannan-free pulp with a hemicellulose-rich pulp and optionally subsequent chemical and / or physical treatment of the mixture to adjust the hemicellulose content and / or the composition of the hemicellulose portion; j) mixing two pulps of different hemicellulose content and / or hemicellulosic composition, and optionally subsequent chemical and / or physical treatment of the mixture to adjust the hemicellulose content and / or the composition of the hemicellulose portion. The method of embodiment 18, wherein the different pulps are selected from deciduous and softwood based pulps.

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