WO2006010564A1

WO2006010564A1 - Method for macerating bast fibers

Info

Publication number: WO2006010564A1
Application number: PCT/EP2005/008019
Authority: WO
Inventors: Klaus Sommer; Ralf Jakobi; Dietmar Sommer
Original assignee: Fh Kaiserslautern
Priority date: 2004-07-24
Filing date: 2005-07-22
Publication date: 2006-02-02
Also published as: DE112005001792A5; DE112005001792B4

Abstract

The invention relates to a method for macerating nettle bast by treating the same with aqueous alkaline solutions at an elevated temperature. According to said method, the bast is macerated with ammonia or amine in aqueous or aqueous-alcoholic solution.

Description

Process for breaking up bast fibers

The present invention is an ecologically advantageous method for the digestion of bast fiber, in particular Nesselbast and fibers produced therewith.

Nettle fibers stand out from the diverse group of bast fibers especially by the fact that they have significantly longer elementary fibers than the common bast fibers such as hemp or flax and these fibers are present in a loose fiber composite. For these reasons, the present application is mainly concerned with nettle fibers and the recovery of these fibers. Suitable for fiber extraction are many species of the nettle family (Urticaceae). Particular mention should be made of the species Urtica dioica, U. kioviensis, U. gracile, U. cannabina, Laportea canadensis, Maoutia puya, Girardinia diversifolia, Boehmeria nivea, B. tricuspis and B. tenacissima.

Furthermore, it is found that the method according to the invention is not only suitable for digesting nettle bast but for digesting all common stem and leaf fibers. As other bast fibers supplying plants, which are aufschließbar in this way, to call the silk plants such. Asclepias syriaca and A. incarnata, the common mallow Abutillon theophrastis, the dog's poison species such as e.g. Apocynum venetum and A. canadense, but also the bast of flax species such as textile, oil and Kombilein, as well as hemp, sunnhemp, hops-rod bast, the broom species and kenaf (hibiscus cannabina).

In the case of bast fibers, fiber bundles are found in the bark layer of the stems, which are arranged in a ring and firmly bonded to the bark layer by pectins, xylans and lignin. To obtain the fiber, it is necessary to dislodge the fiber bundles from the bark layer and to elementarize, that is to disassemble into individual fibers. This is done by means of chemical or biochemical digestion processes such as roasting and subsequent mechanical treatment. In nettle plants, individual fibers are often also found in the raffia structure, although a particularly intensive removal of the adhesive substances from the raffia structure is also required for the production of nettle fibers. The dissolution of the pectins and lignin components requires the use of strong bases. Pure biological roasting processes are very time consuming. The chemical treatment processes also require a lot of time and often produce a heavily contaminated by chemicals wastewater from which they are not recoverable. Mostly, fermentation to produce biogas is difficult.

Thus, for example, US Pat. No. 2,725,289 describes a chemical roasting of stem fibers such as ramie, flax or hemp by treating the sliver with alkali several times in the presence of amine palmitates, which is further exposed to oxidizing agents.

US Pat. No. 4,481,355 describes a repeated washing with a surfactant-containing liquor and subsequent treatment with pectinases in an acidic medium.

According to the Indian patent 140829 is decorticated Ramiebast at 93.8 ⁰ C treated for two hours with a 1-2% sodium hydroxide at a liquor ratio of 1: 6 to 1: 7, washed several times, treated with a weak acid and then with quartenären ammonium compounds. After Tappi 48 (1965), 191 the bast material is treated after cutting with ethanol, then boiled with water and then with dilute sodium hydroxide solution, washed several times and bleached. In Cellul.Chem.Technol. 10 (1976) 285 describes a digesting agent of dilute sodium hydroxide solution (2%) in the presence of sodium sulfite. According Fangzhi Xuebao 6 (1985) 755, it is necessary to maintain a 10 to 11% alkali hydroxide concentration in order to achieve a complete fiber pulping.

According to the Chinese Patent 1, 106,080 mixtures of phosphoric acid, ethylenediamine tetraacetate, Nekal BX and sodium hydroxide are recommended as a digesting agent.

In "Biomass for Energy and Industry" Würzburg 1998, p. 516, a method is described in which the nettle straw at 100 ⁰ C treated with a 4% Sodalösung, the bast separated from the wood, calendered and then at 100 ⁰ C with a 2% NaOH solution.

Recycling all these chemical blends does not make sense, if not impossible, from an economic and ecological point of view.

In addition, in the conventional methods, the fiber is subject to chain length degradation, resulting in the reduction of tear strength.

The present invention is therefore based on the object to provide a method for breaking up bast fibers and especially nettle fibers, in which the chemicals used for digestion can be reused and thus represent no ecological burden and in which additionally fibers are obtained with higher tensile strength.

The solution of this problem is achieved with a method according to the main claim, advantageous embodiments can be found in the subclaims.

In a preferred embodiment, aqueous or aqueous-alcoholic ammonia solution is used for digestion. These are especially good for the digestion of Nesselbast. Depending on the origin of raffia strands ammonia concentrations of 0.5% to 15%, preferably 1 to 15% and temperatures between 8O ⁰ C and 18O ⁰ C, preferably between 125 ⁰ C and 140 ⁰ C, required, which must be worked in pressure vessels , Fleet ratios of 1: 2 to 1: 8 proved to be suitable.

In a further preferred embodiment, aqueous amine solutions or alkanolic aqueous amine solutions are used. Solutions of low boiling point primary, secondary and tertiary amines may be used, not only as an aqueous solution but also dissolved in organic solvents such as e.g. Alcohols may be vor¬ with the addition of water. This results in advantages in the recovery of the amines, since tertiary mixtures of amines, solvents and water have lower boiling points and evaporation energies than water and water-amine mixtures.

It has been found that Bast fiber bundles can be unlocked in a simple manner by that they with aqueous, alcoholic or aqueous-alcoholic solutions of amines at temperatures between 80 ° C and 180 ⁰ C, preferably between 80 ⁰ C and 160 ° C, completely particularly preferably at temperatures between 125 ° C and 140 ⁰ C, treated. If amines with low boiling points are used, they can be recovered almost lossless. The same applies if alcoholic or aqueous-alcoholic pulping liquors with low-boiling amine components are used, both for the alcohol component and for the amine component.

Suitable amines are both primary and secondary amines. also tertiary amines, such as methylamine, dimethylamine, trimethylamine, the corresponding ethylamines, the n-propylamines, the iso-propylamines and the various butyl and Pentylamine. Also amines with different alkyl radicals are suitable, such as methylethylamine or methyl-iso-propylamine, methyldiethylamine or ethyl-iso-propylamine. But also diamines such as 1, 2 diaminoethane, N-methyl-1, 2-diaminoethane, N, N'-dimethyl-1, 2-diaminoethane can be used. It is also possible to use mixtures of the abovementioned amines.

Although amines with higher boiling points also provide good Aufschluss¬ effect, but their recovery requires much higher energy consumption. If the boiling points of the amines are above that of water, the amines remain on the extract side, so that a separation of amine and extract becomes more difficult.

The best results are obtained with secondary amines, e.g. Dimethylamine, diethylamine, di-iso-propylamine, methylethylamine, methyl-iso-propylamine and ethyl iso-propylamine or mixtures thereof.

Depending on the origin of the raffia strands amine concentrations between 0.2 and 10%, preferably between 0.5 and 10% and in particular between 1 and 10% at liquor ratios of 1: 1 to 1: 8 and temperatures between 80 ⁰ C and 180 ⁰ C. used. Particularly suitable are temperatures between 125 ° C and 14O ⁰ C show, as are known in textile finishing as HT-conditions.

The advantages of the amine digestion compared to the ammonia process can be seen in that

1. much lighter fibers are formed,

2. less wash liquor is needed

3. the use of chemicals is lower

4. Low digestion temperatures are sufficient and

5. shorter digestion times are necessary. Furthermore, the digestion process is suitable for all common bast and leaf fibers.

The Bastbänder can be used in the inventive method both in parallelized form as well as in random orientation. Parallel position simplifies a later textile fiber use by spinning.

The use of ammonia or amine as digestion agent allows almost complete recovery by expulsion from the digestion liquor. Digestion problems with prolonged storage, as described in Melliand 43, 1137 (1962), do not occur.

It is usually necessary to subject the digested fiber material to a washing process. For this purpose, according to a preferred embodiment, a hot amine or ammonia solution is used, which is used in the next digestion process as a digestion liquor and was obtained by condensation of the evaporated ammonia or amine of the liquor of the previous digestion. Thus, the ammonia or the amine is almost completely circulated. Small amounts of unrecovered ammonia or amine remain in the digestion liquors and must be supplemented. These waste liquors are either fed to biogas production or used as liquid fertilizer.

When used by fermentation in a biogas plant, the small amount of amine or ammonia serves as nitrogen source for the microorganisms. It may be necessary to lower the pH of the waste liquors by adding acids. Particularly suitable for this are fermentable, ie biodegradable acids such as formic acid, acetic acid, lactic acid, tartaric acid, citric acid or - if the biogas waste products are used as fertilizer - nitric acid, sulfuric acid or phosphoric acid. In direct utilization of the waste liquors as fertilizer, it makes sense to make any necessary pH adjustment with the above-mentioned mineral acids. Precipitates of lignin and pectins which precipitate on evaporation of the ammonia or amine can be separated by filtration and added as reactive fillers to conventional phenol-formaldehyde resin mixtures.

In the case of nettle fibers from the amine or ammonia digestion, a lesser chain degradation is observed than during the digestion with alkali liquors, ie. H. the tear strength is less affected. Conventional bleaching requires less hydrogen peroxide to produce equal degrees of whiteness.

example 1

In a 1 l autoclave 225 g of nettle bast with 600 g of 6% ammonia are heated to 160 ⁰ C for one hour. After cooling, the fiber material is spun off and washed twice with 500 g of 6% ammonia solution and then with

Washed 500 ml of water at 90 to 95 ° C. There are obtained 147 g of raw fiber material.

Example 2

150 g of dry bast material from Laportea canadenis are heated to 152 ° C. for 1.5 hours together with 280 g of 5% ammonia in a 500 ml autoclave. After cooling, the fiber material is pressed and washed twice with 200 g of 5% ammonia at 90 ⁰ C and then with 200 ml of hot water and dried. There are obtained 62 g of dry crude fiber, which are then bleached. Digestion liquor and first washing liquid are combined and expelled ammonia by heating and recovered, wherein evaporating ammonia is collected in wash liquor 3 and additional water. Washing liquor 2 serves as digestion solution for a further approach. Example 3

160 g of dry rape strips from Boehmeria nivea are heated to 16O ⁰ C in an autoclave with 300 g of 6% ammonia (for example from washing solution 2 of Example 1) for 100 minutes. After cooling, the fiber material is spun off and washed with 6% ammonia, for example, from wash liquor 2, again pressed and washed with 200 ml of 8% ammonia and then with 250 ml of water. After centrifuging, it is bleached with hydrogen peroxide without drying. This gives 92 g of dry fiber material. The washing liquors are used as in Example 1.

Example 4

1, 6 kg parallelized ramie bast strips are heated in a 5 l autoclave with 3.6 l of 7% ammonia for 1, 2 hours at 158 ° C. After cooling to 75 ⁰ C, the digestion liquor is drained off and the bast material is spun off. It is washed twice with 2 l of 7% ammonia at 11O ⁰ C, each centrifuged and then washed out the fiber material again with 2 l of water. This gives 1.912 g of dry crude fiber.

Example 5

120 g of bast of the nettle are added with 300 g of 4% ammonia for 50 min

155 ° C open-minded. After cooling to 80 ⁰ C, the mixture is passed through

Centrifuging separately and the fiber residue 2 times with 250 ml 4% each

Washed ammonia and then washed with 250 ml of water and dried.

Example 6

140 g bast of broilers are kept in an Ahiba pressure vessel with 280 g of 4% methylamine solution for one hour at 135 ° C. After cooling to 75 ° C. to 80 ° C., the material is spun off and treated with 300 ml of 4% strength Washed methylamine solution at 85 ° C, spun off again and washed with 2 x 350 ° hot water and dried. 89 g of light gray fibers will be obtained. The methylamine from the digestion solution is evaporated and collected in water. The amine-containing wash solution serves as a digestion liquor in a further batch.

Example 7

In a pressure vessel 125 g of the bast Milkweed Asclepias domestic carnata be with 300 ml of a 3.5% solution of trimethylamine for 1.5 hours at 135 ⁰ C. After pressing off the pulp and 300 ml of 3.5% trimethyl-amine solution at 125 ° C then washed twice with the same amount of water and dried. There are obtained 72 g of gray fiber material.

Example 8

125 g of bast of the plant A. syriaka are digested in 300 ml of a liquor containing 1, 5% ethylamine and 1, 5% di-ethyl-amine at 130 ⁰ C for one hour. After centrifuging the liquor is washed with the same amount of amine solution at 90 °, centrifuged again and then washed again with 500 ml ge. After separating the wash liquor and drying, 82 g of fibers are obtained.

Example 9

950 g Ramiebast be in an oblique rotary autoglaves with 500 ml of ethanol and 1, 4 I of a 4% di-ethylamine solution for 1.5 hours at 130 ⁰ C. After cooling to 80 ⁰ C is spun off, the fiber material with amine solution and then washed with water and dried.

Example 10

165 g of hop bast become with 320 g of a 2.8% di-i-propylamine solution

Hour open at 130 ⁰ C, centrifuged after cooling to 85 ° C, with wash the same amount and the same concentration of the isopropylamine solution ge, again centrifuged and washed with water and dried.

Example 11

125 g Bast the Canadian nettle (Laportia canadense) are mixed with a Lö¬ solution of 100 g of methanol and 160 g of a 4% solution of methyl-ethyl-amine at 150 ⁰ C 1, open for 5 hours. The procedure is as described in the previous examples 6 to 10.

Example 12

100 g bast fibers of the Nepalese nettle (Girardinia diversifolia) are opened in a pressure vessel with 260 g of a diisopropylamine solution for one hour. After centrifuging, washing with di-isopropylamine solution of the same concentration, again centrifuging off and washing with water, 62 g of a slightly gray fiber material are obtained.

All% data are by weight unless otherwise specified.

Claims

claims

1. A method for the decomposition of bast materials by treatment with aqueous alkaline solutions at elevated temperature, characterized in that the digestion with ammonia or amine in aqueous or aqueous-alcoholic solution is performed.

2. The method according to claim 1, characterized in that the digestion in pressure vessels at temperatures of about 80 to 180 ⁰ C, preferably from 125 to 140 ⁰ C, performs.

3. The method according to claim 1 or 2, characterized in that ammonia solutions are used in concentrations between 0.5 and 15% or amine solutions in concentrations of 0.2 to 10%.

4. The method of claim 1 - 3, characterized in that liquor ratios between 1: 1 and 1: 8, preferably 1: 2 to 1: 8 are applied.

5. The method according to claim 1 - 4, characterized in that solutions of primary, secondary and tertiary amines are used, which may also be present as mixed amines or amine mixtures.

6. The method according to claim 1-5, characterized in that low sie¬ dende diamines such as 1, 2-diaminoethane, 1,2-diaminopropane, 1, 3-diaminopropane and their methyl derivatives are used.

7. The method according to claim 1-6, characterized in that the Bastbands are digested both in random orientation and in a parallelized form.

8. The method of claim 1-7, characterized in that the digested fiber material is then washed with hot ammonia solution of similar concentration (0.5 to 15%) or hot amine solution of similar concentration (0.2 to 10%).

9. The method according to claim 1-8, characterized in that the washing solutions are used for the further digestion operations.

10. The method according to claim 1-9, characterized in that the ammonia or amines and .sowhere present, the alcohol, expelled from the digestion solution by heating as much as possible and the aqueous condensate is used as a wash liquor.

11. The method according to claim 1-10, characterized in that the ammonia or amines largely liberated digestion liquors are neutralized for the production of fertilizers with nitric, sulfuric or phosphoric acid or mixtures thereof.

12. The method according to claim 11, characterized in that the precipitated in the neutralization lignin is separated and used in the production of phenolic resins.

13. The method according to claim 1-12, characterized in that the digestion liquors are fed to a biogas production.

14. The method according to claim 13, characterized in that the digestion liquors with acids such as nitric, sulfuric or phosphoric acid or mixtures thereof or fermentable, ie biodegradable acids such as formic acid, acetic acid, lactic acid, tartaric acid, citric acid neutralized or partially neutralized and then fed to a biogas production.

15. Fibers, especially nettle fibers obtained by a decomposition of bast material with ammonia or amine in aqueous or aqueous-alcoholic solution.