DE102004036112A1 - Process to macerate bast fibres from a matrix of nettle fibres under pressure in ammonia or amine solution - Google Patents

Abstract

In a process to separate individual bast fibres from a matrix of nettle fibres, the nettles are macerated in an aqueous alkaline solutions at an elevated temperature. The solution is ammonia or amine in aqueous or aqueous-alcoholic solution. The maceration process takes place in a pressure vessel at between 125 and 140C. The ammonia solution is at 0.5 to 15% concentration, or amine solutions at a concentration of 0.2 to 10%. The maceration liquor is in a ratio of between 1:2 and 1:8. In a further embodiment the solution employs primary, secondary and tertiary amines, also as a mixed amine or an amino mixture. The bast fibres are released both in tangled condition or parallel condition. The macerated fibres are subsequently washed in hot ammonia-solution or hot amino-solution.

Description

object The present invention is an ecologically advantageous process for the digestion of nettle bast and thus produced nettle fibers. Nettle fibers stand out from the diverse group of bast fibers in particular, that they have significantly longer elementary fibers than the common ones Bast fibers such as hemp or flax and these fibers in loose fiber composite available. For these reasons The present application is concerned with nettle fibers and the extraction of these fibers. As suitable for fiber extraction many species of the nettle family (Urticaceae). Especially the species Urtica dioica, U. kioviensis, U. graciles, U. cannabina, Laportea canadensis, Maoutia puya, Girardinia diverisfolia, Boehmeria nivea, B. tricuspis and B. tenacissima. For stem fibers can be found in the bark layer of the stems fiber bundles, which are arranged in a ring are and with the bark layer by pectins, xylans and lignin are firmly glued. For fiber extraction, it is necessary to fiber bundles from the bark layer to solve and to elementarize, that is to disassemble into single fibers. This takes place by means of chemical or biochemical digestion processes e.g. the roaster and subsequently mechanical treatment. In nettle plants are often in the raffia also To find individual fibers, nevertheless, is also for the production of nettle fibers a particularly intensive removal of the adhesive substances from the bast fabric required. The dissolution The pectins and lignin components require the use of strong Bases. Pure biological roasting process are very time consuming. The chemical treatment methods also need a lot Time and often produce a heavily contaminated by chemicals Waste water, from which these are not recoverable.

So For example, US Pat. No. 2,725,289 discloses a chemical roasting of Stem fibers like Ramie, flax or hemp by treating the sliver several times with alkalis in the presence of amine palmitates, the one further exposure to oxidizing agents takes place.

In US-P 4,481,355 is a repeated washing with a surfactant-containing Fleet and a subsequent Treating with pectinases in acidic medium.

To Indian Patent 140,829 deals with defastred ramiebast at 93.8 ° C over two Hours with a 1-2% Caustic soda at a liquor ratio of 1: 6 to 1: 7, washes several times, treated with a weak acid and subsequently with quartenary Ammonium compounds. After Tappi 48 (1965), 191 becomes the bast material treated with ethanol after cutting, then with Water and then with diluted Sodium hydroxide cooked, washed several times and bleached. In Cellul.Chem.Technol. 10 (1976) 285, a digesting agent of dilute sodium hydroxide solution (2%) in the presence of sodium sulfite.

To Fangzhi Xuebao 6 (1985) 755 it is necessary a 10 to 11% To maintain alkali liquor concentration to complete fiber pulping to achieve.

To Chinese Patent No. 1,106,080 discloses mixtures of phosphoric acid, ethylenediamine tetraacetate, Nekal BX and caustic soda 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 ° C with a 4% soda solution treated, the bast separates from the wood, calendered and then at 100 ° C with a 2% NaOH solution unlocks.

One Recycling all these chemical blends is among economic and ecological aspects not useful, if not impossible.

Also subject the fiber in the conventional A process of chain length degradation, what for reducing the tensile strength leads.

The The present invention is therefore based on the object, a method to unlock To provide nettle fibers, in which the used for digestion Chemicals can be reused and therefore no ecological Stress and in which additionally fibers with higher tensile strength to be obtained.

The solution This object is achieved with a method according to the main claim, advantageous Embodiments can be found in the subclaims.

ever according to the origin of the bast strands are ammonia concentrations of 1% to 15% and temperatures between 80 ° C and 180 ° C required, being in pressure vessels has to be worked. Fleet ratios proved to be suitable from 1: 2 to 1: 8. The Bastbands can used both in a parallelized form as well as in randomization become. Parallel position simplifies a subsequent textile fiber utilization by Spinning. The use of ammonia as a digestion agent allows a almost complete reclamation by driving out of the digestion liquor.

It In most cases, the pulped fiber material is necessary for a washing process to subjugate. For this purpose, a hot ammonia solution is used, the next Digestion process used as digestion liquor and by condensation of evaporated ammonia of fleet of the previous digestion was obtained. So the ammonia is almost completely in the Guided circles. Small amounts not recovered Ammonia remains in digestion liquors and must be supplemented. These waste liquors are either fed to a biogas production or used as liquid fertilizer. When used by fermentation In a biogas plant, the small amount of ammonia serves as a source of nitrogen for the Microorganisms. It may be necessary for this, the pH of the waste liquors by adding acids lower. Particularly suitable for this purpose are fermentable, i. Biodegradable acids such as for example, formic acid, Acetic acid, Lactic acid, Tartaric acid, citric acid or when the biogas waste products as fertilizer be recycled - nitric acid, sulfuric acid or Phosphoric acid. With direct utilization of the waste liquors as fertilizer it makes sense, one make any necessary pH adjustment with the mineral acids mentioned above. Upon evaporation of the ammonia precipitating precipitates of lignin and pectins can separated by filtration and conventional as reactive fillers Phenol-formaldehyde resin mixtures added become. For nettle fibers from the ammonia digestion is a lesser Chain degradation observed when digested with caustic lye, d. H. the tear resistance is less affected. In conventional Bleaching requires less hydrogen peroxide to achieve equal degrees of whiteness produce.

example 1

In In a 1 liter autoclave, 225 g of nettle bast with 600 g of 6% ammonia one hour at 160 ° C heated. After cooling The fiber material is spun off and washed twice with 500 g of 6% each ammonia solution and then washed with 500 ml of water at 90 to 95 ° C. It will be 147 g of raw fiber material receive.

Example 2

150 g dry bast material from Laportea canadenis are put together with 280 g of 5% ammonia in a 500 ml autoclave for 1.5 hours at 152 ° C heated. After cooling The fiber material is pressed off and twice with 200 g of 5% ammonia at 90 ° C and subsequently with 200 ml of hot water washed and dried. There are obtained 62 g of dry crude fiber, the following to be bleached. Digestion liquor and first wash liquor are combined and ammonia is driven off by heating and recovered, wherein evaporating ammonia in wash liquor 3 and additional Water is caught. Wash liquor 2 serves as a digestion solution for a another approach.

Example 3

160 g dry bast strips from Boehmeria nivea are mixed with 300 g of 6% Ammonia (for example, from washing solution 2 of Example 1) in one Autoclave for 100 minutes at 160 ° C heated. After cooling The fiber material is thrown off and with 6% ammonia, for example washed from wash liquor 2, again pressed and with 200 ml 8% Ammonia and then washed with 250 ml of water. After centrifuging, without drying bleached with hydrogen peroxide. This gives 92 g of dry fiber material. The washing liquors are used as in Example 1.

Example 4

1.6 kg of ramie bast of parallelized racks are placed in a 5 liter autoclave heated with 3.6 l of 7% ammonia for 1.2 hours at 158 ° C. After cooling to 75 ° C is the pulping liquor is drained and the bast material is thrown off. It is washed twice with 2 l of 7% ammonia at 110 ° C, each spun off and then the fiber material still once washed with 2 liters of water. This gives 1.912 g of dry crude fiber.

Example 5

120 g Bast of the nettles are mixed with 300 g of 4% ammonia 50 min at 155 ° C open minded. After cooling at 80 ° C the mixture is separated by centrifuging and the fiber residue Washed twice with 250 ml of 4% ammonia and then with Washed 250 ml of water and dried.

Claims (12)

A process for the digestion of Nesselbast by treatment with aqueous alkaline solutions at elevated temperature, characterized in that the digestion is carried out with an aqueous ammonia solution. Method according to claim 1, characterized in that that the digestion in pressure vessels at temperatures of about 80-180 ° C performs. Method according to claim 1 or 2, characterized that ammonia solutions be used in concentrations between 1 and 15%. Method according to claims 1-3, characterized that fleet conditions between 1: 3 and 1: 8. Process according to claims 1-4, characterized in that that the Bastbänder be open-minded as well as in parallelized form. Process according to claims 1-5, characterized in that that the digested fiber material then similar with hot ammonia solution Concentration (1 to 15%) is washed. Method according to claims 1-6, characterized that the washing solutions for the further digestion operations are used. Method according to claims 1-7, characterized that the ammonia from the digestion solution by heating as much as possible expelled and the watery Condensate is used as a wash liquor. Method according to claims 1-8, characterized that the most liberated from ammonia digestions to the Production of fertilizers neutralized with nitric, sulfuric or phosphoric acid or mixtures thereof become. Method according to claim 9, characterized in that that precipitated during neutralization lignin separated and used in the production of phenolic resins. Method according to claims 1-10, characterized that the digestion acids such as nitric, sulfuric or phosphoric acid or mixtures thereof or fermentable, i.e. biodegradable acids like formic acid, Acetic acid, lactic acid, tartaric acid, citric acid neutralized or partially neutralized and fed to a biogas production. Nettle fibers are obtained by digestion with an aqueous Ammonia solution.