ES2968528T3 - Cellulose pulp and Lyocell molded bodies with reduced cellulose content - Google Patents

Abstract

The present invention describes special cellulose compositions that make it possible to stably produce a lyocell fiber with a reduced cellulose content on a large scale, and the lyocell fiber thus obtained. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Cellulose pulp and Lyocell molded bodies with reduced cellulose content

The present invention describes special cellulose pulp compositions that allow a Lyocell fiber with a reduced cellulose content to be produced stably on an industrial scale, as well as the Lyocell fiber produced therefrom.

State of the art

Lyocell fibers are used in a variety of applications. In this case, purified cellulose is often used as raw material, with a very small proportion of non-cellulose components.

Cellulose pulp is obtained from wood, which is composed of only 40-44% by weight of cellulose. Since, in general, a high cellulose content of more than 95% by weight is required in cellulose pulp for the production of Lyocell molded bodies, a large part of the raw material is lost during cooking and bleaching. material use. In this case, a plurality of possibilities are known to specifically reduce the proportion of hemicelluloses, both in obtaining cellulose pulp on the way from wood to cellulose pulp or to the final Lyocell product:

a) Digestion: A large part of the hemicelluloses are lost in sulfite cooking; while in alkaline digestion prehydrolysis is carried out before cooking specifically to eliminate hemicelluloses.

b) Bleaching: as a general rule to eliminate residual lignin and/or for optical brightening, but it also destroys hemicellulose components.

c) Partial insolubility of the branched hemicellulose portions in the Lyocell solvent

d) Mass degradation with subsequent dissolution in the spinning bath

Certainly, great efforts are being made to utilize these other components as material by-products. However, the reaction is only carried out in small quantities due to known technical restrictions. In the waste liquids from pulp production, these other wood components are present in the form of a plurality of different degradation products, further mixed with strong acids or alkalis, which makes separation and further processing extremely difficult. .

However, in recent years efforts have been made to broaden the raw material base for Lyocell products by using celluloses with a higher proportion of lignin and/or hemicelluloses.

US 6440523 and US 6444314 describe approaches of this type by way of example:

The approach taken in these documents is essentially that they describe the corresponding cellulose pulp (pulp) and/or Lyocell products made from it, which, together with the cellulose portion, also have a hemicellulose content greater than 5% in weigh. However, in all these documents it is considered essential that the higher hemicellulose contents described therein are only possible if a number of other essential conditions are met at the same time. These are, for example, a certain viscosity of the cellulose pulp, a maximum copper number and/or a maximum kappa number.

Although Lyocell products are described in these documents, it should be noted that developments based on these industrial property rights have not yet been implemented on a large scale, although the use, in particular, of cellulose pulp with a higher hemicellulose content should generate significant costs and, therefore, competitive advantages. This could probably be due to the difficulties in moving up from laboratory scale and achievable fiber properties, which do not meet the expectations of the textile and nonwovens market. US 2015/184338 A1 describes compositions containing treated kraft cellulose pulp, useful for producing rayon fibers with a lower degree of polymerization, a high R18, a low hemicellulose content and a high reactivity. Procedures for preparing the compositions are also described.

WO 98/16682 A2 describes a process for upgrading wood pulp from paper grade pulp to dissolving grade pulp suitable for use in the production of viscose rayon, cellulose ethers and cellulose esters such as cellulose acetate. The procedure uses a sequence of caustic extraction, xylanase treatment, and caustic extraction to remove most of the xylan, which can be recovered for use in the production of xylose, xylitol, and furans.

Invention Mission

To maximize resource utilization, it would be desirable to be able to use as many material portions as possible of the raw material wood to produce a Lyocell fiber. The priority objective in the search for the highest possible sustainability and a truly efficient biorefinery concept should be to use wood as a natural raw material to the greatest extent possible from the beginning for the main product, namely Lyocell molded bodies. The obtaining of by-products remains of great importance in this case, but in general it remains of secondary importance. Efforts made so far in this regard have failed because the reduction of the cellulose content in the fiber led to a massive change in the material and property parameters of the resulting (Lyocell) fibers (or other variants of molded bodies) or On the other hand, stable large-scale production was not possible. On the contrary, for the large-scale application of chemical cellulose pulp in the Lyocell process, a large number of patents and publications require that the content of lignin, hemicelluloses and accessory components be extremely low.

For these reasons, it is desirable to provide technologies that can be used on an industrial scale and that allow a reduction of the cellulose content in the finished fibers by increasing the proportion of other wood components, in particular hemicelluloses, but also lignin, without essential restrictions regarding with the parameters of the resulting material. Despite the large number of approaches in the prior art, there are currently no known industrially usable procedures for producing Lyocell products of this type with a reduced cellulose content.

Brief description of the invention

The aforementioned problems of the prior art are overcome with the present invention. The present invention provides a cellulose pulp according to claim 1, a Lyocell product according to claim 9, as well as the methods according to claims 16 and 18. Preferred embodiments of the invention are specified in the subordinate claims and in the detailed description of the invention that follows.

In particular, the present invention provides the following aspects, as well as the preferred embodiments set forth in the secondary claims and description.

1. Cellulose pulp suitable for the production of Lyocell molded bodies, with a cellulose proportion of 85 to 50% by weight and a hemicelluloses proportion of at least 7% by weight, characterized in that the ratio of the C5 fraction /xylan to the fraction of C6/mannan (C5/C6 ratio) present in hemicellulose is in the range of 125:1 to 1:3.

2. Cellulose pulp according to embodiment 1, wherein the C5/C6 ratio is in the range of 25:1 to 1:2.

3. Cellulose pulp according to embodiment 1 and/or 2, wherein the proportion of hemicelluloses is 10% by weight or more.

4. Cellulose pulp according to at least one of the above embodiments, the hemicelluloses of which are present in the native state, have been chemically modified by processing processes or have been chemically modified or functionalized in a separate process step.

5. Cellulose pulp according to at least one of the above embodiments, with a lignin content greater than 1% by weight.

6. Cellulose pulp according to at least one of the above embodiments, wherein the cellulose content is further reduced by the presence of lignin, accessory components of wood and/or the addition of metal compounds.

7. Cellulose pulp according to at least one of the above embodiments, with a xylan content of 9% by weight or more and/or a mannan content of 6% by weight or more.

8. Cellulose pulp according to embodiment 7, with a xylan content of 9% by weight or more and a mannan content of 1% by weight or less.

9. Lyocell molded body, produced using cellulose pulp according to one of embodiments 1 to 8.

10. Lyocell molded body according to embodiment 9, wherein the molded body is selected from fibers, filaments, staple fibers, nonwoven fabrics, films and powders in spherical shape.

11. Lyocell molded body according to at least one of embodiments 9 and/or 10, wherein the molded body is a fiber, a filament or a staple fiber, with a cellulose content of less than 90% by weight, a content of hemicellulose greater than 5% by weight and a C5/C6 ratio of 125:1 to 1:3, preferably 25:1 to 1:2.

12. Lyocell molded body according to at least one of embodiments 9 to 11, wherein the hemicellulose content is greater than 10% by weight.

13. Lyocell molded body according to at least one of embodiments 9 to 12, wherein the molded body is a fiber, a filament or a staple fiber with a WRV greater than 70%, preferably greater than 75%, in particular greater than 80%.

14. Lyocell molded body according to at least one of embodiments 9 to 13, wherein the molded body has a crystallinity of 40% or less.

15. Lyocell molded body according to at least one of embodiments 9 to 14, with a lignin content of more than 0% by weight up to 5% by weight.

16. Procedure for producing a Lyocell molded body, comprising dissolving a cellulose pulp with a proportion of cellulose of 85 to 50% by weight and a proportion of hemicelluloses of at least 7% by weight, characterized in that the ratio of The fraction of C5/xylan to the fraction of C6/mannan (C5/C6 ratio) is in the range of 125:1 to 1:3, in a suitable solvent, and shaping of the solution in a Lyocell molded body.

17. Method according to embodiment 16, wherein the Lyocell molded body is obtained by a Lyocell spinning process.

18. Procedure for producing a cellulose pulp according to one of embodiments 1 to 8, the procedure comprising at least one of the following steps:

a) mix a pure cellulose paste with xylan and/or mannan;

b) treating a cellulose pulp with a hemicellulose content that includes mannan by chemical and/or physical procedures to modify the hemicellulose content and/or the composition of the hemicellulose contained; c) produce a cellulose pulp using wood from conifers and/or deciduous trees;

d) mixing a mannan-free cellulose pulp with a cellulose pulp rich in hemicellulose and optionally a subsequent chemical and/or physical treatment of the mixture to adjust the hemicellulose content and/or the composition of the hemicellulose portion;

e) mixing two cellulose 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. Method according to embodiment 18, in which the different cellulose pulps are selected from cellulose pulp based on coniferous wood and/or deciduous trees.

Brief description of the Figures

Fig. 1 shows the correlation of crystallinity and water retention capacity of Lyocell fibers of the present invention as well as standard Lyocell fiber.

Fig. 2 shows the ratio of xylan to mannan in sulfite cellulose pulp depending on the H factor when beech wood is used.

Fig. 3 shows the ratio of xylan to mannan in sulfite cellulose pulp depending on the H factor when spruce wood is used.

Detailed description of the invention

If the proportion of cellulose is reduced in the Lyocell process, this means that the savings should be offset by other materials manufactured from the raw material wood. In this case, the problem of process stability or property change arises when the cellulose content is reduced, as already explained above. The essential proportions of the non-cellulosic material in the wood raw material are hemicelluloses (essentially polyose from the sugar monomers xylose, arabinose, mannose, galactose, glucose and rhamnose), lignin and accessory components. Cellulose: Represents the structural substance of the cell walls of wood and mainly provides tensile strength. The long molecular chains formed by glucose units are grouped several times in a helical structure in the so-called fibrils. This helical arrangement in the cell wall provides good bending resistance of the tree, e.g. e.g., in case of exposure to wind, or wood, e.g. e.g., in a roof structure. Cellulose is hydrophilic but not water-soluble due to its high crystallinity.

Lignin: Binding agent for the solid association of cellulose in the form of an amorphous matrix. Thus, lignin is mainly responsible for compressive strength, but on the other hand it is not very flexible and, unlike cellulose, it is hydrophobic. It is responsible for the resistance of the tree. Plants that do not store lignin only reach small heights. Lignin is biologically relatively stable and biodegradable only slowly.

Hemicelluloses in the sense of the present invention are components present in wood in the form of short chain polymers based on C5 and/or C6 sugars. Unlike cellulose, they have side groups and, therefore, can only form crystals to a much lesser extent. Its basic components are mannose, xylose, glucose, rhamnose and galactose. The side groups are preferably composed of arabinose groups, acetyl groups and galactose residues, as well as O-acetyl groups and 4-O-methylglucuronic acid side groups. Mannans are known to preferentially associate with cellulose, while xylans are more associated with lignin. The composition of hemicelluloses varies greatly depending on the type of wood used. During the processing process in cellulose pulp production, the side chains are partially separated and the polymer chains are split. Within the framework of this invention, the term hemicelluloses includes those in their native structure, as well as those that have been modified during processing and also those that have been adapted to the respective intended use through a specific chemical modification. Short-chain celluloses and other polyoses with a DP of up to 500 are also included.

Accessory components: Accessory components are organic and inorganic wood companion substances other than lignin, cellulose and hemicellulose, and generally include salts and low molecular weight organic compounds with up to approximately 100 atoms, such as tannins, resins, fats and waxes. , tanning agents and humic substances, terpenes, terpenoids and phenolic compounds, pectins, suberins, polyphenols and polyose.

If the proportion of cellulose is then reduced as desired in a cellulose pulp material and other components of the wood raw material must compensate for this reduction, it has surprisingly been shown that only by combining different types of sugars in a given proportion is it possible to produce a cellulose pulp which, despite its reduced cellulose content, allows safe large-scale production of Lyocell products, these products also having a reduced cellulose content, but still presenting satisfactory product properties.

According to the invention, it is essential that in the case of a reduced cellulose content in the cellulose pulp of less than 90% by weight, there is a proportion of hemicelluloses of at least 7% by weight, the proportion of sugars having five atoms from C as, e.g. For example, xylan to sugars with six carbon atoms such as mannan (hereinafter referred to as C5/C6 ratio) is in the range of 125:1 to 1:3.

With such a cellulose pulp, surprisingly large-scale production of Lyocell products can be safely achieved, even if the cellulose content in the cellulose pulp is reduced.

The cellulose pulps used here, which are preferably used within the framework of the present invention, show, as already indicated, a relatively high content of hemicelluloses with the composition defined here. Compared to standard cellulose pulps with a low hemicellulose content, used in particular in the state of the art for the production of standard Lyocell fibers, the cellulose pulps preferably used within the framework of the present invention also present other differences. , listed below.

Compared to standard cellulose pulps, the cellulose pulps preferably used in the context of the present invention show a rather spongy appearance. After grinding (during the production of starting materials for the production of spinning solutions for the Lyocell process), a particle size distribution with a high proportion of larger particles is obtained. As a result, the bulk density is much lower compared to standard cellulose pulp with a low hemicellulose content. Such a low bulk density requires adaptations regarding the dosing parameters (e.g. dosing with at least two storage containers) during the production of the spinning solutions. Additionally, the cellulose pulps preferably used within the framework of the present invention show an impregnation behavior against NMMO that, compared to standard cellulose pulps, shows that in this case the impregnation is more difficult. This can be verified by evaluating the impregnation behavior using the Cobb evaluation. While standard cellulose pulps typically show a Cobb value greater than 2.8 g/g (determined according to DIN EN ISO 535 with adaptations relating to the use of a 78% NMMO aqueous solution at 75 °C with a impregnation time of two minutes), the cellulose pulps preferably used within the framework of the present invention show Cobb values of approximately 2.3 g/g. This requires adaptations during the production of spinning solutions such as a longer solution time (e.g. explained in WO 94/28214 and WO 96/33934) and/or an adjustment of the temperature and/or an increase of shear during dissolution (e.g. WO 96/33221, WO 98/05702 and WO 94/8217). This allows the production of spinning solutions that allow the cellulose pulps described here to be used in a standard Lyocell process).

In a preferred embodiment of the present invention, the cellulose 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, particularly 320 to 420 ml. /g, more preferably 320 to 400 ml/g. SCAN viscosity is determined in accordance with SCAN-CM 15:99 using a cupryethylenediamine solution, a method known to those skilled in the art and which can be carried out with commercially available devices such as the Auto PulplVA PSLRheotek device available from the company PSL-Reotek. SCAN viscosity is an important parameter that particularly influences the processing of cellulose pulps when producing spinning solutions. Even if two cellulose pulps show a close match in composition, etc., different SCAN viscosities result in completely different behavior during processing. In a direct solution spinning process, such as the Lyocell process, the cellulose pulp is dissolved in NMMO as such. There is no maturation step, comparable to the viscose procedure, for example, where the degree of polymerization of cellulose can be adjusted to the needs of the process. Therefore, specifications for the viscosity of a raw cellulose pulp are generally within a small target window for the Lyocell process. Otherwise problems may arise during production. In accordance with the present invention, it has been discovered that the viscosity of the cellulose pulp is preferably as described above. Lower viscosities lead to a deterioration of the mechanical properties of Lyocell products. Higher viscosities can lead, in particular, to a higher viscosity of the spinning solution, so that spinning generally becomes slower. With lower spinning speeds, lower draw ratios are also obtained, which again can have a significant influence on the fiber structure and fiber properties (Carbohydrate Polymers 2018, 181, 893-901). This would require process adaptations that would lead to a reduction in capacity. The use of cellulose pulps with the viscosities defined here allows easy processing and the production of high quality products.

The term "Lyocell process", or the terms "Lyocell technology" and "Lyocell process", as used herein, designate a process of direct dissolution of cellulose pulp from wood or other cellulose-based starting materials. in a polar solvent (e.g., N-methylmorpholine-n-oxide (NMMO, NMO) or ionic liquids). Commercially, this technology is used to produce a group of cellulose staple fibers, commercially available from Lenzing AG, Lenzing, Austria, under the brand name TENCEL® or TENCEL™), which are widely used in the textile or nonwovens industry. Other molded cellulose bodies obtained using Lyocell technology have also already been produced. According to this method, the cellulose solution is usually extruded in the so-called wet-dry spinning process with the help of a molding tool and the molded solution arrives, e.g. e.g., after passing through an air chamber to a precipitation bath, where the molded body is obtained by precipitation of the cellulose. The molded body is washed and optionally dried after further treatment steps. A procedure for the production of Lyocell fibers is described, e.g. e.g., in documents US 4246221, WO 93/19230, W<o>95/02082 or WO 97/38153. To the extent that the present invention discusses the disadvantages of the prior art and the unique properties of the new products disclosed and claimed herein, particularly in the context of the use of laboratory equipment (particularly in the prior art) or in relation with pilot (semi-commercial) plants and commercial fiber spinning units, it should be understood that the present invention refers to units that can be defined in terms of their respective production capacities as follows:

Semi-commercial pilot plant: around 1 kt/a

Commercial unit greater than 30 kt/a

Within the framework of the present invention, it has been shown that, especially during the production of fibers within the framework of a Lyocell process, an orientation in the production direction and a stretching of the fibers occurs. From a more or less disoriented initial mixture of different polymers and other bulk components, a first orientation of the polymers in the production direction is achieved by strongly narrowing the cross section in the spinneret. Additional stretching in the air space after spinning and during subsequent process steps results in a stretched, oriented fiber structure of the polymers. These processes are well known in the specialized literature.

In this case, the properties of the fibers are strongly influenced by the type and arrangement of the polymers. It is also known that cellulosic fibers, produced using the Lyocell process, have a very high crystallinity of approximately 44 to 47%, while fibers from the viscose process have a crystallinity of approximately 29 to 34%. Crystallinity describes the orientation of cellulose polymers relative to each other and therefore e.g. e.g., its ability to absorb, expand and store water. Additionally, the polymer chains in the non-crystalline areas of Lyocell fibers are more ordered than in viscose fibers. Thus, ordinary Lyocell fibers expand less and are less suitable for highly absorbent products than viscose fibers.

The use of cellulose pulp according to the invention with a reduced cellulose content unexpectedly allows a completely different type of aggregation of the polymers and, therefore, a different structure of the Lyocell fibers. Its crystallinity is significantly lower, typically 40% or less, such as 39% or less and, for example, in the range of 38% to 30%, for example in the range of 37 to 33%.

The WRV values for fibers according to the present invention, alone or in combination with the other preferred embodiments described herein, preferably in combination with the values for the crystallinity of the fibers described herein, are preferably 70% or more , especially 75% or more, such as 80% or more, for example 70 to 85%.

It is known from the literature that xylans also form a crystalline structure if their side chains have been separated during the production process and are precipitated from a pure xylan solution (Fengel, Wegener p. 113; Fengel D, Wegener G ( 1989): Wood, Chemistry, Ultrastructure, Reactions; Walter de Gruyter Publishing House). The same applies to manano (ibid.; p. 119). However, opposite effects are evident in the present invention. Polymers, including cellulose, are present in a mixture in the dough and are then centrifuged and precipitated. Furthermore, hemicelluloses still present side groups, since the glucuronic acid side groups of xylan are comparatively stable under acid digestion conditions (Sixta H (Ed.) (2006): Handbook of Pulp Vol. 1; Wiley VCH p.418 ). Therefore, hemicelluloses meet all the conditions to interrupt the formation of cellulose crystals and thus form a more disordered structure compared to standard Lyocell fibers. Therefore, one skilled in the art would expect unusable products, in particular fibers, to emerge with a higher hemicellulose content and a reduced cellulose content. However, it has unexpectedly been shown that product properties can be specifically controlled by the hemicelluloses content in combination with the C5/C6 ratio. This mixture of different sugar polymers still achieves crystallinity values that are above the crystallinity values of viscose fibers, but increases the overall accessibility of the fiber to water, so that the water retention capacity (WRV, by its acronym in German) can increase significantly. This improved absorbency is a decisive advantage for various fields of application, e.g. e.g., for use in the nonwovens sector. This relationship between decreasing crystallinity and increasing water holding capacity for Lyocell fibers is depicted in Figure 1 and can be adjusted as described above by specifically reducing the cellulose content in the fiber.

As shown in the Examples, the qualities of the new Lyocell fibers with reduced cellulose content are similar to those of conventional TENCEL® fibers. It is clear that the resistance of the fibers is slightly lower than that of TENCEL® fibers, measured in the examples as resistance and work capacity. At the same time, the cellulose content, which is indicated as the glucan value in the examples, was clearly reduced. By incorporating other wood components, the crystallinity drops to 21% and the absorbency increases significantly 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 are between those of conventional TENCEL® fibers and Viscose® nonwoven fibers from Lenzing, at the same time the WRV is in the range of Viscose® from Lenzing . Therefore, the WRV increases more than could be explained by the decrease in fiber crystallinity. This is a clear sign of the unexpected properties that can be achieved with the present invention. The other components, such as hemicelluloses in particular, but also lignin and other accessory components of wood, not only provide a significant increase in yield, i.e. greater sustainability, but also a significant improvement in the properties of the product. such as water retention capacity.

Achievements

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

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

The cellulose pulp to be used according to the invention is, furthermore, preferably a cellulose pulp having a xylan portion of at least 9% by weight, preferably a portion of at least 10% by weight. The mannan portion can be selected within a wide range, in combination or independently, as long as the ratio defined according to the invention is met. Suitable mannan levels are in the range of 0.1 to 10% by weight, such as 0.1 to 9% by weight and in embodiments of 0.1 to 6% by weight, 0.1 to 4% by weight. weight, 5 to 10% by weight, 6 to 10% by weight, etc. In embodiments, the mannan content is in the range of 0.1 to 1% by weight, preferably in combination with a xylan content of at least 9% by weight, preferably at least 10% by weight. In other embodiments, the mannan content is higher, preferably in the range of 6% by weight or more.

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

The weight ratio of cellulose to hemicellulose may be in the range of 1:1 to 20:1. The proportion of accessory components 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 been unexpectedly shown that with proportions of accessory components of this type in the cellulose pulp according to the invention the effect can be favored that the C5/C6 ratio is also stable in the manufactured Lyocell products, in particular fibers, and the hemicellulose content does not change significantly (i.e. the content in the Lyocell product does not decrease or only decreases to a small extent compared to cellulose).

In another preferred embodiment, the C5/C6 ratio according to the invention reaches 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% can be obtained. by weight, referred to the weight of the Lyocell product (e.g., Mg(OH<)2>or Al(OH)3 for flame retardant purposes), which further substantially reduces the cellulose content. Metal compounds of this type are, in particular, TiO<2>, Al2O3, MgO, SiO<2>, CeO<2>, Mg(OH)<2>, Al(OH)3, BN, ZnO and in part they come from of the mineral components of the wood or they can be added to the cellulose solution as functional additives (flame retardants, mattifying agents, biocides...).

In another preferred embodiment, the Lyocell fibers can be produced with a cellulose content reduced to less than 70%, which not only meets the practical requirements compared to known Lyocell fibers (mechanical strengths, etc.), but Also due to the new properties resulting from the invention for some applications they are even more suitable. The corresponding studies have shown that the fibers of the proposed composition have, in particular, a greater water retention capacity and rapid biodegradability during composting.

According to the invention, it has been shown that the C5/C6 sugar ratio of non-cellulosic polymers is an important factor in adjusting the composition of the fibers and their resulting properties. By specifically adjusting this ratio, also in combination with the hemicelluloses content, the desired product properties can be specifically adjusted.

In this context, the person skilled in the art knows how to control or adjust the C5/C6 ratio. This can be achieved by mixing different cellulose pulps such as e.g. e.g., cellulose pulps from coniferous wood with a higher proportion of mannan with cellulose pulps from deciduous trees with a higher proportion of xylan. Experiments have confirmed another very effective option for corresponding adjustment. By specifically adjusting cooking parameters such as e.g. For example, the H factor, the ratio of C5 to C6 sugars can be controlled. This is represented in Figures 2 and 3. The H factor is considered an essential parameter to control sulfite cooking (Sixta (Vol. 12006) p. 432). Combines cooking temperature and cooking time as a single quantity.

Figure 2 shows the influence of the H factor in sulfite cooking on the hemicellulose ratio in the case of deciduous trees using beech as an example. In the case of deciduous trees, the xylan content is naturally higher. As the H factor increases, xylan is broken down more than mannan. The C5/C6 ratio decreases.

When softwood is used, the hemicellulose ratio is the other way around. The proportion of mannan in wood and cellulose pulp is higher. Here, contrary to expectations, mannan decomposes faster than xylan, as can be seen in Figure 3.

Another possibility of adjusting the cellulose pulp composition according to the invention is to add by mixing C5 and/or C6 sugars that were previously obtained in other processes or process steps such as, e.g. e.g. in an alkaline extraction, whether a cold alkaline extraction or an E stage or similar. For the production of viscose, the addition of hemicelluloses in dissolved form to the spinning mass and subsequent joint spinning is known (WO2014086883). This can produce viscose fibers with a reduced cellulose content. This is only possible because the viscose process takes place in an aqueous medium and the hemicelluloses are correspondingly soluble in alkalis, so that the cellulose xanthogenate and the dissolved hemicelluloses can be mixed and centrifuged together. On the contrary, in the Lyocell process the cellulose pulp is dissolved in NMMO or similar solvents, so alkaline or aqueous solutions cannot be added here. They would dilute the solvent and reduce solubility or even cause unwanted precipitation. Therefore, hemicelluloses cannot be added in the form of solutions during the production of spinning solution, but must be introduced into the process in another way. One possibility is to add it in the cellulose pulp production process so that the mixture with the cellulose pulp can then be dried.

Surprisingly, precise attention to the hemicellulose composition was found to be a crucial point for the technical production of Lyocell molded bodies, especially fibers. A commercially viable use 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. The ratio of xylan to mannan is preferred between 18:1 and 1:3, preferably between 9:1 and 1:2. At the same time, such a mixing ratio allows the incorporation of 0.5 to 5% by weight of lignin (and/or other accessory components) into the fiber structure without negatively affecting the desired properties.

The fibers provided according to the invention have common fiber titers such as 7 dtex or less, for example 2.2 dtex or less, such as 1.3 dtex or less, optionally even lower such as 0.9 dtex or less, depending on the desired application. Titers of 1.5 to 1.8 dtex are particularly typical for applications in the nonwovens sector, while lower titres, such as 1.2 to 1.5 dtex, are suitable for textile applications. However, the present invention also includes fibers with even lower titers, as well as fibers with significantly higher titers such as 10 dtex or less, such as 9 dtex or less, or also 7 dtex or less. Suitable lower limits for fiber titers are values of 0.5 dtex or more, such as 0.8 dtex or more and in embodiments 1.3 dtex or more. The upper and lower limits disclosed herein may be combined and resulting ranges such as, for example, 0.5 to 9 dtex are also included. Surprisingly, the present invention enables the production of fibers with titers that allow their use across the entire spectrum of fiber applications, including textile applications as well as nonwoven applications.

Regarding the parameters referenced in this application, they are determined as described here. In this case, it is essential that these parameters are obtained with the fibers as such, comprising a maximum of 1% by weight of additives, such as mattifying agents, etc. However, the fibers described here may, of course, contain conventional additives in the usual amounts, unless this impairs the production of spinning solutions and/or the fiber manufacturing process.

The following Examples illustrate aspects of the present invention.

Methods

Determination of crystallinity index [%]

The determination of the crystallinity index takes place by Raman spectroscopy. This method is calibrated with data from the wide-angle X-ray (WAX) method and was described by Roderet al. (2009)(Roder T, Moosbauer J, Kliba G, Schlader S, Zuckerstatter G and Sixta H (2009): Comparative Characterization of Man-Made Regenerated Cellulose Fibers. Lenzinger Reports, Vol. 87, p. 98 et seq.) .

Determination of water retention capacity [%]

The sample is allowed to expand at 20 ± 0.1 °C overnight. After further dilution, the sample is centrifuged in a centrifuge at 3000 times the gravitational acceleration according to Zellcheming Bulletin IV/33/57. The water retention capacity is then calculated as follows:

WRV (Wet sample weight - sera sample weight)

dry sample weight

Examples

Example for adjusting the xylan-mannan ratio

Table 1 shows the results of adjusting the C5/C6 ratio for two types of wood, using the example of the variation of the H factor in cellulose pulp with magnesium bisulfite.

Table 1: Adjustment of the xylan-mannan ratio in the magnesium bisulfite cooking of Fagus sylvatica (beech) and Picea abies (fir) with the help of the H factor.

Example of a eucalyptus kraft pulp

In the technical center, a new kraft chemical pulp according to the invention was produced from eucalyptus wood using the VisCBC process. The H factor was 1200, the effective alkali in the cooking liquor was 25 g/l. Bleaching was carried out according to a TCF sequence. Relevant process information and product characteristics are shown in Table 2.

Table 2: Properties from wood through cellulose pulp to finished cellulose-reduced Lyocell fiber.

In the case of this new chemical cellulose pulp with reduced cellulose content, the ratio of xylan to mannan increased enormously, i.e. to 121 in the finished fiber, while at the same time the cellulose content remained very low, around of 85%. This new cellulose pulp meets in all aspects the requirements of the Lyocell process to produce the new Lyocell fiber with reduced cellulose content.

Example of fiber properties when using new cellulose-reduced pulps

Table 3 compiles the sugar monomer content of the starting cellulose pulps for the production of Lyocell fibers.

Table 3: Sugar contents of cellulose-reduced pulps compared to a standard Lyocell pulp

Table 4 shows the mechanical characteristics of standard fibers (Lyocell and viscose) in comparison with the characteristics achieved with Lyocell fibers produced with cellulose pulps according to the invention. The results clearly demonstrate the advantages of the present invention.

In both pilot plant tests and on large scale Lyocell fibers produced in accordance with the present invention, it has been shown that acceptable values of strength and workability can be achieved for commercially relevant grades, despite a significantly higher cellulose content. reduced. At the same time, the WRV increases drastically, so that this type of fibers are interesting for new fields of application that until now were occupied by viscose fibers. However, compared to commercially available viscose fibers, significantly higher mechanical characteristics can be achieved with the Lyocell fibers according to the invention.

Therefore, the new Lyocell fibers according to the invention combine the advantageous properties of the commercially available Lyocell or viscose fibers until now.

Table 4: Properties of conventional and cellulose-reduced Lyocell fibers compared to a standard viscose fiber.

Claims (19)

1. Cellulose pulp suitable for the production of Lyocell molded bodies, with a cellulose proportion of 85 to 50% by weight and a hemicelluloses proportion of at least 7% by weight, characterized in that the ratio of the C5 fraction /xylan to the fraction of C6/mannan (C5/C6 ratio) present in hemicellulose is in the range of 125:1 to 1:3. 2. Cellulose pulp according to claim 1, wherein the C5/C6 ratio is in the range of 25:1 to 1:2. 3. Cellulose pulp according to claim 1 and/or 2, wherein the proportion of hemicelluloses is 10% by weight or more. 4. Cellulose pulp according to at least one of the preceding claims, whose hemicelluloses are present in the native state, have been chemically modified by processing processes or have been chemically modified or functionalized in a separate process step. 5. Cellulose pulp according to at least one of the preceding claims, with a lignin content greater than 1% by weight. 6. Cellulose pulp according to at least one of the preceding claims, wherein the cellulose content is further reduced by the presence of lignin, accessory components of wood and/or the addition of metal compounds. 7. Cellulose pulp according to at least one of the preceding claims, with a xylan content of 9% by weight or more and/or a mannan content of 6% by weight or more. 8. Cellulose pulp according to claim 7, with a xylan content of 9% by weight or more and a mannan content of 1% by weight or less. 9. Lyocell molded body, produced using the cellulose pulp according to one of claims 1 to 8. 10. Lyocell molded body according to claim 9, wherein the molded body is selected from fibers, filaments, staple fibers, nonwoven fabrics, films and powders in spherical shape. 11. Lyocell molded body according to at least one of claims 9 and/or 10, wherein the molded body is a fiber, a filament or a staple fiber, with a cellulose content of less than 90% by weight, a content of hemicellulose greater than 5% by weight and a C5/C6 ratio of 125:1 to 1:3, preferably 25:1 to 1:2. 12. Lyocell molded body according to at least one of claims 9 to 11, wherein the hemicellulose content is greater than 10% by weight. 13. Lyocell molded body according to at least one of claims 9 to 12, wherein the molded body is a fiber, a filament or a staple fiber with a WRV greater than 70%, preferably greater than 75%, in particular greater than 80%. 14. Lyocell molded body according to at least one of claims 9 to 13, wherein the molded body has a crystallinity of 40% or less. 15. Lyocell molded body according to at least one of claims 9 to 14, with a lignin content of more than 0% by weight up to 5% by weight. 16. Procedure for producing a Lyocell molded body, comprising dissolving a cellulose pulp with a proportion of cellulose of 85 to 50% by weight and a proportion of hemicelluloses of at least 7% by weight, characterized in that the ratio The C5/xylan fraction to the C6/mannan fraction (C5/C6 ratio) is in the range of 125:1 to 1:3, in a suitable solvent, and shaping the solution into a Lyocell molded body. 17. Method according to claim 16, wherein the Lyocell molded body is obtained by a Lyocell spinning process. 18. Procedure for producing a cellulose pulp according to one of claims 1 to 8, the procedure comprising at least one of the following steps: a) mix a pure cellulose paste with xylan and/or mannan; b) treating a cellulose pulp with a hemicellulose content that includes mannan by chemical and/or physical procedures to modify the hemicellulose content and/or the composition of the hemicellulose contained; c) produce a cellulose pulp using wood from coniferous and/or deciduous trees; d) mixing a mannan-free cellulose pulp with a cellulose pulp rich in hemicellulose and optionally a subsequent chemical and/or physical treatment of the mixture to adjust the hemicellulose content and/or the composition of the hemicellulose portion; e) mixing two cellulose 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. Method according to claim 18, in which the different cellulose pulps are selected from cellulose pulp based on coniferous wood and/or deciduous trees.