EP0221811A1 - Process for the biochemical setting of plants containing bast fibres - Google Patents

Abstract

The process for biochemical retting of phloem-fiber plants such as hemp, flax, ramie, jute, kenaf, etc. permits separation of the fibers of the bundle for subsequent utilization in the textile or paratextile industry. The process comprises treating the fibrous plants with at least one SPS-ase enzyme and preferably a mixture of enzymes comprising beta -glucanase, pectinase and SPS-ase.

Description

The present invention relates to a biochemical retting process for Liberian fibrous plants such as hemp, flax, ramie, jute and kenaf.

The invention relates in particular to a biochemical process, the application of which is intended to allow the use, by the textile or para-textile industry or the rope industry, of liberian, cellulosic and similar fibrous plants, which have not undergone the natural retting which makes it possible to separate the fibers in the bundle.

In the prior art, the Liberian fibrous plants, after their harvest, are subjected to natural retting, either on land by exposure to the weather, or in water for the natural development of microorganisms whose effect is disintegration and "digestion" of the natural cements which bind the fibers within the bundle in the Liberian fibrous plants. This technique, directly linked to atmospheric and hydrographic conditions, requires a duration of action of the order of 2 to 5 weeks and the intervention of labor and important equipment.

Hemp is one of the so-called Liberian fiber plants, in which the cellulosic fibers are bundled in the liber surrounding the stem of the plant.

Flax, ramie, jute and kenaf are the main other fiber plants belonging to this family of Liberian plants.

To be usable in the textile industry, the cellulosic fibers of these plants must be separated from the bast, then from them in bundles. This separation is made possible by natural retting. It is then carried out mechanically using specially adapted textile material.

Natural retting, an operation known and practiced for centuries, consists in immersing the stems in the water of certain rivers for relatively long periods, immersion which results in the natural development of bacteria, anaerobes which generate micro-organisms capable of degrading the plant macromolecules which weld the beams together in the liber and the fibers between them in the beams.

This retting, known as water, while still being practiced on a small scale, is more and more replaced by retting - called earth - which consists in leaving on earth, after mowing or uprooting, the stems of Liberian plants in order to cause the bacterial action developed by the soil microflora thanks to the alternation of periods of rain and humid heat.

During the whole duration of this exposure (several weeks) of the stems to bad weather, it is of course essential to turn over the swaths so that all the stems undergo an action as regular as possible.

This operation, relatively easy in the case of flax whose stems measure approximately 80 cm to 1 meter, is very difficult to achieve for hemp whose stems reach 2.50 m to 3 m long.

In addition, the harvest of hemp being later than that of flax: at the end of August - mid-September, the climatic conditions governing the retting "earth", become more and more random, due to the reduction of sunshine and increased precipitation.

For these reasons and as a result of the abandonment of retting with water, the hemp workers were led to abandon the exploitation of hemp for textile use in order to keep only the paper industry.

Thus the applicants, in search of new outlets for the exploitation of hemp and similar Liberian plants, sought the possibility of artificially retting these plants.

The applicants have thus sought to separate the fibers from the bundles by degradation of the cements connecting them.

All purely chemical approaches have negative since the degradation of the cements by these means was always accompanied by a significant deterioration of the cellulose fibers.

The object of the invention is therefore to provide an industrial process for the retting of Liberian fibrous plants in order to solve the reliability and reproducibility problems posed by the natural retting processes due to meteorological hazards.

According to the invention, the biochemical retting process of fibrous Liberian plants, in particular hemp, in order to obtain the degradation of cements aggregating the fibers in the bundles and thus allow their physical separation for their use in spinning or cordage in view of the manufacture of yarns or rovings usable in the textile or paratextile industry, or cordage, is characterized in that the fibrous plants are treated by means of at least one SPS-ase enzyme.

The process which is the subject of the invention is based on the main use of this SPS-ase enzyme which makes it possible to break the macromolecular chains of the cements which link together the cellulosic fibers in the fibrous plants of Liberia such as hemp, linen, ramie, jute, kenaf, etc. while not touching, or as little as possible, the cellulose constituting the fibers of interest for the textile or paratextile industry.

The SPS-ase enzyme used for this purpose is specific to the non-cellulosic constituents of fibers, which weld the fibers together within the fiber bundle.

In the remainder of this description, the non-cellulosic constituents of the fibers will be designated "cements".

The chemical nature of these cements is not yet really known.

The SPS-ase enzyme used in the process according to the invention is a broad spectrum polyactive enzyme acting on polysaccharides. This SPS-ase enzyme has been described in British patent 2,115,820. It is marketed by the Danish company NOVO INDUSTRI A / S under the reference SP 249. This enzyme has the following four main activities:
- pectolytic activity
- cellulolitic activity
- hemicellulolitic activity
- proteolytic activity.

The pectolytic activity of this enzyme would appear, according to the research carried out by the applicants, to be more at the level of the reduction in viscosity of pectins, water-soluble parts of pectic materials essentially consisting of polygalacturonic acid comprising various amounts of methyl ester groups or at the level of the depolymerization of water-soluble protopectins with a high degree of esterification.

The cellulolitic activity is observed especially at the level of the natural carboxy-methyl-celluloses of plants. This activity is interesting in the retting of hemp due to the degradation of C.M.C. which constitute a very resistant "glue" with high adhesive power.

This cellulolitic activity is supplemented by a gluconic fungal activity and above all by a tiny cellubiase activity, which makes it possible to avoid degradation of the cellulose fibers, the only ones which are interesting and the aim of the whole operation.

The hemicellulolitic activity, the aim of which is the degradation of hemicelluloses, xylans, as well as polyoses such as arabinase and α galactoses.

This broad spectrum polysaccharidase also has proteolytic activity on plant proteins.

The applicants have found that the action of SPS-ase is enhanced when the treatment is carried out by means of a mixture of this enzyme with beta-glucanase and / or pectinase.

Β-glucanase acts by hydrolysis of β glucans at the level of the β 1-3 and β 1-4 bonds into oligosaccharides and soluble dissaccharides.

This hydrolysis is also accompanied by a marked reduction in the viscosity of the baths.

Pectinase has a double activity on pectic matters, namely:
- a non-depolymerizing activity,
- depolymerizing activity.

Thanks to the non-depolymerizing activity of this enzyme, there is no reduction in the length of the pectin chains but reduction in their degree of esterification by opening the ester bridge between the carboxyl groups of unitary galacturonic acid. and methanol groups.

This reduction in the degree of esterification results in a reduction in viscosity and easier elimination of the water-soluble pectins during retting.

The three types of enzymes above thus have complementary activities and in addition the important characteristic of having application conditions compatible with the treatment of bast fibers, namely an optimal pH zone located between pH 4 and pH 6 and an optimal temperature range between 40 and 60 ° C.

The treatment of Liberian plants is carried out by impregnation and then maceration of the straws or tows in an aqueous medium containing the above enzyme (s).

The maceration time should be between one hour and forty eight hours, preferably between three and thirty six hours.

Furthermore, the maceration temperature must be between 20 ° C and 70 ° C, preferably between 40 ° C and 60 ° C and this maceration is carried out at a pH between 3 and 7, preferably between 4 and 6, this pH being adjusted using an organic acid.

The applicants determined the application of the enzymes empirically, defining as the progress of their study the quality of the retting obtained by the carding ability of the hemp tows treated according to the invention.

These carding tests were systematically carried out on a laboratory card on the handles of tows treated according to the invention.

A first series of tests consisted in determining, on paper tows, the action of broad spectrum polysaccharidase (SPS-ase) by subjecting to the action of an enzyme bath of a defined concentration of the quantities identical tows in order to define the optimal duration of the enzymatic action.

For this purpose, enzymatic macerations were carried out hour by hour from 1 to 12 hours and then at 6 p.m. - 12:30 p.m. - 36 - 48 - 60 - 72 - 84 and 96 hours.

Thus, by comparison of the separation of the beams at carding, an optimal period of between 18 and 30 hours has been defined. Within 12 hours, poor separation of the beams was observed with breaking of the beams during carding.

Beyond the 36 hours, good separation of the bundles was observed, but numerous breaks in the fibers.

Systematic tests on hemp samples different from each other by their coloring, blond-green hemp or dark brown hemp, were carried out. In all cases, the best carding test results were found with a duration of 22 to 26 hours.

In all cases, whatever the type of hemp, a very good separation of the bundles and the fibers was found at the end of this period.

It is commonly accepted that the action of an enzyme is proportional to its concentration. On the other hand, it is often claimed that the speed of the enzymatic action is directly linked to the concentration of enzymes.

To determine the optimum concentration, the applicants subjected hemp samples for 8 to 12 hours, then 18 - 24 and 30 hours, to hemp samples of SPS-ase enzyme of increasing concentration and at pH and constant temperature.

Using the carding test as an element of appreciation of the enzymatic retting, it has been found that at high concentration of the enzyme, macerations for less than 18 hours were less effective than macerations for 20 to 30 hours for higher concentrations. weak.

The effectiveness of the other two enzymes, namely β glucanase and pectinase, was determined under the same conditions as the SPS-ase polysaccharidase.

The results obtained with regard to the separation of the bundles and the fibers were less convincing than with polysaccharidase (SPS-ase), but it was noted a more important action of β glucanase on the degradation of the shives which become more brittle and more brittle as well as a very clear improvement in the detachment of strips or bundles of fibers from shives and pieces of stems.

With regard to pectinase, a more specific action appeared at the level of the colored "cuticle" surrounding the fiber bundles, as well as at the level of the silky and softness of the fibers, no doubt as a result of the degradation and of the solubilization of this cuticle.

In order to seek the greatest efficiency for the enzymatic retting, the applicants have resumed their systematic tests using mixtures of the above three enzymes until carding is obtained with a ribbon having long fibers, although separated - without going to unitary separation, however - silky and containing the least amount of shives or shea waste.

• a) pour la pectinase comprises entre 0,01% et 2% et de préférence entre 0,05% et 1%,
• b) pour la béta-glucanase comprises entre 0,10% et 3% et de préférence entre 0,25% et 2%,
• c) pour l'enzyme à spectre d'action plus large, entre 0,25% et 5%, et de préférence entre 0,5% et 3%.

The tests thus made it possible to determine that the quantities of enzymes used relative to the dry weight of straws or tows of fibrous liberian plants must be as follows:

• a) for pectinase of between 0.01% and 2% and preferably between 0.05% and 1%,
• b) for beta-glucanase of between 0.10% and 3% and preferably between 0.25% and 2%,
• c) for the enzyme with a wider action spectrum, between 0.25% and 5%, and preferably between 0.5% and 3%.

The three enzymes degrading the polymers as a result of their activity specific to the cleavage of well defined bonds, would also seem to improve the solubilization and the reduction in the viscosity of the degradation products thus leading to their better elimination by rinsing at the end of maceration. In fact, the tows treated with the ternary mixture have a much less tendency to "stick" together during drying following a brief rinsing than the tows treated with the only polysaccharidase.

The applicants have always obtained, during their tests, resistant and good tenacity hemp fibers. This is no doubt due to the fact that the three enzymes retained have little or no action on the cellulose, but also to the fact that all the degradation reactions result in the formation of reducing sugars. There is therefore practically no risk of hydrocellulose formation, and therefore reduction of the D.P. of the cellulose by acid oxidation.

It goes without saying that numerous modifications can be made to the implementation of the method described without thereby departing from the scope of the invention.

Claims (10)

1. Process for the biochemical retting of liberian fibrous plants, in particular hemp, in order to obtain the degradation of the cements aggregating the fibers in the bundles and thus allow their physical separation for their use in spinning or cordage for the manufacture of yarns or rovings usable in the textile or paratextile industry, or cordage, characterized in that the fibrous plants are treated with at least one SPS-ase enzyme. 2. Method according to claim 1, characterized in that the fibrous plants are treated by means of a mixture of SPS-ase and β-glucanase. 3. Method according to claim 1, characterized in that the fibrous plants are treated by means of a mixture of enzymes comprising SPS-ase, β-glucanase and pectinase. 4. Method according to one of claims 1 to 3, characterized in that the treatment is carried out by impregnation and then maceration of the straws or tows in an aqueous medium containing the enzyme (s). 5. Method according to claim 4, characterized in that the maceration time is between one hour and forty eight hours, preferably between three and thirty six hours. 6. Method according to one of claims 4 or 5, characterized in that the maceration temperature is between 20 ° C and 70 ° C, preferably between 40 ° C and 60 ° C. 7. Method according to claim 6, characterized in that the maceration is carried out at pH between 3 and 7, preferably between 4 and 6, this pH being adjusted using an organic acid. 8. Method according to one of claims 3 to 7, characterized in that the quantities of enzymes used for the treatment relative to the dry weight of straws or tows of fibrous plants are included: a) for pectinase, between 0.01% and 2%, preferably between 0.05% and 1%, b) for β-glucanase, between 0.10% and 3%, preferably between 0.25% and 2%, c) for SPS-ase, between 0.25% and 5%, preferably between 0.5% and 3%. 9. Method according to one of claims 1 to 8, characterized in that it is applied to the retting of the Liberian fibrous plants chosen from the group comprising hemp, flax, ramie, jute, kenaf and their mixtures. 10. Fibers of Liberian plants obtained by applying the method according to one of claims 1 to 9.