EP2889401A1 - Regenerated cellulose fibre - Google Patents

Abstract

The present invention relates to a regenerated cellulose fiber containing Organosolv lignin. The fiber according to the invention preferably has a content of organosolv lignin of 5% to 90%, preferably 10% to 70%, particularly preferably 20% to 50%, based on fiber. More preferably, the fiber may contain another lignin different from organosolv lignin.

Description

The present invention relates to a regenerated cellulose fiber produced by the viscose process (hereinafter also referred to as "viscose fiber"), to the production and use thereof.

In particular, the present invention relates to a regenerated cellulosic fiber containing lignin.

Viscose fibers are already used in carbonized insulating moldings and nonwovens. In the carbonization carbonaceous starting materials (precursors) are pyrolyzed in an oven at temperatures of 500-1800 ° C with exclusion of oxygen. This foreign atoms such as nitrogen, oxygen and hydrogen are split off in gaseous form. What remains is almost exclusively carbon, which has a graphite-like layer structure. The carbonation yield of viscose is theoretically 44%, but in reality only 15-20%. Thus, 80 to 85% of the fiber mass is lost during the carbonization. By improving the carbon yield, the carbonation process would be much more economical.

From the US 4,177,236 For example, it is known to make viscose fibers containing crosslinked kraft lignin or crosslinked sodium lignosulfonate. According to this document, the incorporation of non-crosslinked lignin into viscose fibers was not possible, which means that virtually no lignin was found in the finished fiber.

As a possible application of the modified viscose fibers described there called the US 4,177,236 the production of carbon fibers.

The WO 2012/156443 A1 describes precursor fibers for producing carbon fibers containing lignin. The fibers are spun from a solution containing a lignin and a fiber-forming polymer from the group of polyacrylonitrile or polyacrylonitrile copolymers. Example 2 of this document describes the spinning of a solution containing chemical cellulose, kraft lignin and polyacrylonitrile.

Also the WO 2013/020919 deals with the production of precursor fibers from carbon fibers. The fiber is a mixture of polyacrylonitrile, a glucan and lignin. Both in the case of WO 2012/156443 A1 as well as the WO 2013/020919 The fibers are spun from a solution in an organic solvent.

The EP 2 524 980 describes the production of precursor fibers from carbon fibers. The fibers contain at least 10% lignin and one or more fiber-forming polymers, such as cellulose, and are spun from an organic solvent.

In the GB 1,111,299 the production of carbon fibers from lignin fibers is described.

Other documents dealing with the use of lignin, especially in lignin fibers or mixed fibers containing lignin, include: US 3,461,082 ; DE 21 18 488 A1 ; Kadla JF et al, "Lignin-based carbon fibers for composite fiber applications", Carbon (40) 15, 2002, 2913-2920 ; Kubo S. et al, "Poly (ethylene oxide) / organosolv lignin blends", Macromolecules (37) 18, 2004. 6904-6911 ; GB 1 500 053 ; US 2,265,563 A ; DE 1 163 654 A ; DE 25 41 220 A and DE 197 34 239 A1 ,

There is still a need for producing lignin-containing cellulosic fibers. Such fibers would be particularly suitable for the production of carbon fibers, which due to the admixture of the cost-effective raw material lignin carbon fiber can be produced more cheaply.

The object underlying the present invention is achieved by a regenerated cellulose fiber containing Organosolv lignin.

Brief description of the figures

• FIG. 1 shows the cross-sections of viscose fibers in which (nominal) 50% Organosolv lignin were incorporated.
• FIG. 2 shows the cross-sections of viscose fibers in which (nominal) 10% Organosolv lignin were incorporated.
• FIG. 3 shows the cross sections of viscose fibers in which (nominal) 35% organosolv lignin and 15% lignosulfonate were incorporated.

Detailed description of the invention

In the production of pulp wood (wood chips) or other plant fibers are chemically digested by the lignin therein is dissolved out while the structure of the cellulose is largely retained. The dissolved lignin differs greatly from its native form, since depolymerizations and derivatizations with the chemicals occur during digestion, depending on the process.
The most important pulping processes are the sulphate process (product: kraft lignin) and the sulphite process (product: lignosulphonates). More than 50 million tonnes of lignin are isolated as a by-product every year.

As a macromolecular natural product, the lignins differ in their monomer composition, type of bonds and their molecular weight depending on the plant species, origin and season. In addition, each digestion process produces lignins with other properties.

By the "Organosolv method" the skilled person understands a wood pulping with the aid of aqueous organic solvents, in particular ethanol, at high pressure and high temperature. The resulting lignin in this process is called Organosolv lignin.

It has now surprisingly been found that contrary to in US 4,177,236 described tendency, according to which (uncrosslinked) lignins can not be spun into viscose fibers, the incorporation of (uncrosslinked) Organosolv lignin in viscose fibers with satisfactory yields is possible.

The cellulose fiber of the invention may have a content of Organosolv lignin of 5% to 90%, preferably 10% to 70%, particularly preferably 20% to 50%, based on fiber. These figures are also understood below as weight%. Furthermore, the figures relate to the lignin content of a finished viscose fiber, i. the fiber according to the usual in the context of Viskosefaserherstellung aftertreatment and especially washing steps. The contents of Organosolv lignin as well as other lignins are determined by the measurement method given in Example 1.

Preference is given to the highest possible content of lignin, since it has been found in the production of carbon fibers that lignin enables a higher carbon yield. The term "(regenerated) cellulosic fiber" or "viscose fiber" will also encompass fibers containing up to 90% lignin as long as it is made by the viscose process, ie from an alkaline solution containing cellulose xanthate and spun into an acid spin bath , getting produced.

The fiber of the invention may preferably contain another lignin different from organosolv lignin. Because organosolv lignin is less soluble than common lignins, e.g. Kraft-lignin or lignosulfonates is more difficult to obtain by replacing a portion of the Organosolv lignin by another lignin the production of the fiber according to the invention and the carbon fiber resulting therefrom carbonization can be made even more favorable.

The further lignin is preferably selected from the group consisting of kraft lignin, lignosulfonate and mixtures thereof. The further lignin is preferably uncrosslinked.

The content of further lignin in the fiber may be from 5% to 85%, preferably from 10% to 70%, particularly preferably from 20% to 50%, based on fiber.

The ratio of organosolv lignin to further lignin may be from 4: 1 to 1: 4, preferably 3: 1 to 1: 3.

In a preferred embodiment of the present invention, the cellulosic fiber of the present invention is characterized by substantially no further fiber-forming polymer, such as cellulose and lignin. Polyacrylonitrile or polyacrylonitrile copolymers containing.

The cellulose fiber according to the invention may have a titer of 0.5 dtex to 30 dtex, preferably 1 dtex to 4 dtex.

The cellulose fiber according to the invention is preferably used for the production of carbon fibers. Further fields of use are e.g. Hygiene and medical applications (due to the increased water retention capacity of the fiber). A cellulose fiber according to the invention which, in addition to the Organosolv lignin, contains lignosulfonate, is also suitable for ion exchange, for example in water softening or in the setting of concrete, due to the sulfonic acid groups introduced into the fiber (lignosulfonate containing 1.25-2.5% sulfonic acid groups).

The present invention also relates to a process for producing the cellulosic fiber of the invention, comprising the step of adding organosolv lignin and optionally another lignin to a spun viscose or a precursor thereof.

By "precursors" of a spinning viscose are in particular starting substances of the viscose process, such as e.g. Pulp, or intermediates such as e.g. Alkali cellulose or cellulose xanthogenate understood.

Examples: Example 1:

• Kraft-Lignin (Hersteller: Sigma-Aldrich)
• Lignosulfonat (Hersteller: Carl Roth) und
• Organosolv-Lignin (Hersteller: Fraunhofer CBP Leuna Charge K002)

Pilot spinning was carried out to produce viscose fibers into which the following uncrosslinked lignins were spun:

• Kraft lignin (manufacturer: Sigma-Aldrich)
• Lignosulfonate (manufacturer: Carl Roth) and
• Organosolv lignin (manufacturer: Fraunhofer CBP Leuna batch K002)

The lignin was mixed in a proportion of 50% based on the total amount of fiber-forming polymer (cellulose + lignin) in a standard viscose. The lignin was when spinning each in the form of a solution with 30% lignin in 5% NaOH before.

The lignin-containing viscoses were spun according to standard conditions. The target denier of the fibers was 3.3 dtex, the draw was 25%.

The resulting fibers were washed out in a conventional manner.

The lignin contents in the finished fiber were first measured by the Klason method (Tappi Test Methods 2001-2002, T 222 om-02 Tappi Press). According to this method, the acid-insoluble lignin ("Klason lignin") is detected gravimetrically. In addition, the acid-soluble lignin is determined photometrically (Tappi UM 250, wavelength: 205 nm, absorption coefficient: 110 L / (g.cm)). The photometric determination using these parameters is the usual method in the art, although it is known that the results obtained with respect to the different lignin types can vary slightly. For the purposes of the present invention, it is thus defined that the determination of the acid-soluble lignin content must be made using these parameters. The following values represent the total lignin content determined in this way: Kraft lignin lignosulfonate Organosolv lignin Lignin content (nominal) in% 50 50 50 Lignin content found in% 27 11 38 Leaching absolutely in% 23 39 12 Washout in% 45 77 23 Water retention in% * 203% 182% 130% * Certainly according to DIN 53814

The lignosulfonate is thus washed out due to the very good solubility already during the spinning of the fiber and in the subsequent wash to a large extent. Only 11% lignin (absolute) was found in the fiber, so 77% of the lignin offered was washed out. Organosolv lignin shows the highest retention. The fiber contains 38% lignin, while 23% of the offered lignin was washed out. A medium retention shows the force lignin with a content of absolutely 27% lignin in the fiber, while 45% (relatively) were washed out.

Example 2:

An uncrosslinked Organosolv lignin of the type lignin 139OL (manufacturer: Fraunhofer Institute CBP) was mixed in a proportion of 10% based on the total amount of fiber-forming polymer (cellulose + lignin) of a viscose and spun the resulting solution into fibers ,

In the finished fiber, a total of 7.7% lignin was found by the method described above.

The fiber had a titer of 3.24 dtex. The maximum tensile force in cN was 6.71, the elongation 18.79%.

Example 3:

An uncrosslinked organosolv lignin of the type lignin 151OL (manufacturer: Fraunhofer Institute CBP) was mixed in a proportion of 10% based on the total amount of fiber-forming polymer (cellulose + lignin) a viscose and spun the resulting solution into fibers ,

In the finished fiber, a total of 7.3% lignin was found by the method described above.

The fiber had a denier of 3.66 dtex. The maximum tensile force in cN was 5.72, the elongation 17.95%.

Example 4:

Analogously to Example 1, a mixture of 35% uncrosslinked Organsolv lignin of the type batch K002 (manufacturer: Fraunhofer Institute CBP) and 15% of the lignosulfonate used in Example 1, in each case based on the total amount of fiber-forming polymer (cellulose + lignin), a viscose blended and the resulting solution spun into fibers.

The mixture showed very good spinning stability.

In the finished fiber, a total of 35.4% lignin was found by the method described above. The leaching of lignin was thus only about 15% (absolute).

The fiber had a titer of 2.72 dtex. The maximum tensile force in cN was 2.78, the elongation 17.12%. The water retention was 123%.

Properties of Organosolv lignin-containing fibers

The fibers are distinguished by a dark brown color.

The fibers prepared according to Example 1 with (nominal) 50% addition of lignin show a very smooth surface with mainly C-shaped cross-sections. These cross sections are in the FIG. 1 shown.

In contrast, in the case of the nominal incorporation of 10% organosolv lignin prepared according to Example 2, the typical viscous cloud form is found, see FIG. 2 ,

The fibers prepared according to Example 3 with a nominal incorporation of 35% organosolv lignin and 15% lignosulfonate also show the typical viscous cloud form, see FIG. 3 ,

All of the lignin-containing fibers show a significantly higher absorption (higher water retention capacity) compared to a normal viscose fiber, making them ideal for use in hygiene products.

The (inter alia) containing lignosulfonate fiber according to Example 4 contains sulfonic acid groups which act as ion exchangers.

Carbonisierungsversuche

The organosolv lignin or a mixture of organosolv lignin and lignosulfonate-containing viscose fibers prepared according to Examples 1, 2 and 4 were carbonized (Gero oven, 20 ° C. to 1800 ° C., heating rate 10 K / min under a nitrogen atmosphere). The carbon yield was compared to that of a standard viscose fiber.

The results are shown in the following table: reference 10% Organosolv lignin 50% Organosolv lignin 35% Organosolv lignin + 15% lignosulfonate Carbon yield in% 15.8 to 16.7 17.8 30.17 31.02

By incorporating 10% (7.8% in real terms) Organosolv lignin into viscose, the carbon yield can be increased by about 2%. Purely arithmetically, this results in a real carbon yield of 40% for the lignin.

The 50% Organosolv lignin fiber and the mixed viscose fiber of 35% Organosolv lignin and 15% lignosulfonate both show carbon yields of around 30%. Compared with normal viscose, the carbon yield can be significantly increased (by 80%) through the incorporation of larger amounts of lignin. In this case, the calculated yield for pure lignin is just under 60%. This means that for the manufacturer of Carbon fiber large savings in the amount of fiber with the same carbon yield are possible.

Claims (10)

Regenerated cellulose fiber containing Organosolv lignin. Cellulose fiber according to claim 1, characterized in that the content of Organosolv lignin from 5% to 90%, preferably 10% to 70%, particularly preferably 20% to 50%, based on fiber. Cellulosic fiber according to claim 1 or 2, characterized in that the fiber contains another, different from Organosolv lignin lignin. Cellulosic fiber according to claim 3, characterized in that the further lignin is selected from the group consisting of kraft lignin, lignosulfonate and mixtures thereof. Cellulose fiber according to claim 3 or 4, characterized in that the content of further lignin from 5% to 85%, preferably 10% to 70%, particularly preferably 20% to 50%, based on fiber. Cellulose fiber according to one of claims 3 to 5, characterized in that the ratio of Organosolv lignin to further lignin of 4: 1 to 1: 4, preferably 3: 1 to 1: 3. Cellulosic fiber according to one of the preceding claims, characterized in that , apart from cellulose and lignin, it contains substantially no further fiber-forming polymer. Cellulose fiber according to one of the preceding claims, characterized by a titer of 0.5 dtex to 30 dtex, preferably 1 dtex to 4 dtex. Use of a cellulose fiber according to one of the preceding claims for the production of carbon fibers. A process for producing a cellulosic fiber according to any one of claims 1 to 8, comprising the step of adding organosolv lignin and optionally another lignin to a spun viscose or a precursor thereof.

Images