EP0107603B1 - Method of treating flaxen - Google Patents

Description

The invention relates to a process for treating flax. It will find its application in the textile field, more particularly for the preparation of fibers for scutching, combing or carding and spinning.

The linum usitatissimum, known as common flax, is in the form of a single rod composed by a woody central part surrounded by a Liberian crown of fibers which constitute the textile material and channels in which circulates the sap which feeds the plant. The sap and gummy materials which stick and agglomerate the textile fibers and the channels consist in particular of pectic substances, liquids when the plant is alive, coagulated and dried when the plant dies. The rod is also wrapped in a thin waterproof film when the flax is alive.

To isolate the textile fibers, during a first operation, called retting, we partially remove the pectic substances which stick and agglutinate the fibers to the wood, and during a second operation, known as scutching, we separate the fibers textiles of woody materials to obtain tow which will later be combed or carded and drawn.

The elimination of pectic substances carried out during the retting consists in destroying the agglutinating substances by a so-called "fermentation _{" operation} . The flax fiber which is cellulosic has the property of rotting less quickly than the pectic substances and it is enough to go at the limit of "fermentation to preserve the fiber and eliminate annoying pectic substances. The retting should be carefully monitored because if the" fermentation is insufficient, the fibers do not separate well from the woody central part during scutching and they do not do not divide enough during combing, and flax remains coarse and difficult to spin at the end of the metric number, while prolonged "fermentation" leads to alterations in the cellulose of the fibers.

Retting comes in different forms, the most common being retting on the ground which, after grubbing up, spreads the flax on the ground. Retting takes place under the action of aerobic microorganisms; it requires regular turning of the stems according to the extent of the rains and dews. The operation lasts between four and six weeks, and the quality of the final product largely depends on weather conditions. Excessive retting produces poor quality, poorly colored fibers and requires further bleaching.

There is also retting in water formerly carried out in running water. It consisted in immersing the plants in water for ten to fifteen days depending on the temperature. The "fermentation" then occurs under the influence of anaerobic bacteria. The flax obtained by this process has good qualities of mechanical resistance and has such a beautiful appearance, but it requires strenuous work and requires significant labor. In addition, before retting with water, you have to wait a fortnight for the flax to wilt and dry.

Water retting is currently carried out in reinforced concrete routers in which the stems are immersed in water maintained at a given temperature. "Fermentation takes place very actively there and requires careful monitoring so as not to produce an alteration of the textile fibers. However, this "fermentation gives off foul odors and the water used is polluted.

Aside from retting by "fermentation", there are also various industrial processes which treat dried green flax and act by dissolving pectic substances by various products, for example soda, soap, hot water or steam. These methods, although they give satisfactory results, are complex to implement and require significant handling.

Attempts to replace "fermentation" or the removal of substances by mechanical means have not produced satisfactory results. If it is possible to isolate fibers by mechanical means, these means do not make it possible to free the fibers from the organic substances which surround them and a "fermentation" occurs subsequently.

One of the main difficulties encountered during retting is to carry out a homogeneous operation while the flax stems have a heterogeneous structure since the feet of the plant are clearly more resistant to "fermentation than the rest of the stems. In addition, the feet of under-rotted plants provide coarser flax than that provided by the body and head of the plants. This is disadvantageous because the fineness of a linen is determined by the size of the coarsest fibers. The heterogeneity of the stems gives the reason why the coarse mechanical processes used to accelerate the retting do not give satisfactory results, such as for example the crushing of the flax spread on the ground using the tractor wheels.

Furthermore, it has been observed that the rods have a preferential retting zone which corresponds to the zone in which the mechanical means ensuring lifting are applied. These means, consisting of inclined belts between which the rods engage, cause them to be crushed and it has been found that this location rots faster than the rest of the plant.

The main object of the invention is to propose a process for treating flax with a view to making it dyeable, combable or cardable and spinnable, which accelerates retting and, even under certain conditions, makes it possible to eliminate this operation. The method also aims to achieve a homogenous retting of the flax stalks. It eliminates the risks of a total or partial excessive “fermentation” which deteriorates the mechanical qualities and the color of the textile fibers, and the risks of an “insufficient fermentation which provides a coarse flax which can possibly ferment later. It is based on the observation that a controlled crushing of the stems causes diffusion and dilution of the sap, pectic substances and other soluble materials throughout the entire stem, which allows aerobic microorganisms to have faster action.

When treating a plant which is still alive, the method according to the invention makes it possible to eliminate and neutralize the non-coagulated pectic substances which agglomerate the fibers with the other components of the stem.

More generally, the method according to the invention makes it possible to reduce the risks during the harvesting of flax. It also ensures a better regularity of finesse of the tow, and in certain cases, it makes it possible to reduce the losses of material during scutching and combing. From a hygienic point of view, it makes it possible to reduce the quantities of dust which are released during the scouring and spinning operations. It also allows savings during laundering.

Another advantage of the process is that it allows the recovery of flax seeds, a by-product used for the production of linseed oil and animal feed.

The process for treating flax used as textile fibers, the flax being in the form of stems, each comprising a body between the foot provided with roots and the head carrying the seeds, and each constituted by a woody central part surrounded by a fibrous crown in which the fiber bundles are glued and agglomerated by pectic substances, and an impermeable film which envelops the stems, is characterized in that the flax is torn off, and immediately afterwards, it is exerted on the whole of the height of the rods a variable pressure and modulated according to the application zones to burst and open the waterproof films.

The invention will be better understood if reference is made to the description which follows.

When the plants reach maturity, they appear in the form of single rods which are most often uprooted using machines known to those skilled in the art. The films that surround the stems are still waterproof and the sap and pectic substances that agglomerate the fibers with the other components are in the liquid state and coagulate when they reach maturity.

The process consists in exerting after pulling a variable pressure over the entire height of the stems until the seeds are born to burst and open the impermeable films. The pressure exerted on the stems varies according to the progress of the cut plant as well as according to the areas of application of the pressure on the stems.

The pressure exerted causes crushing of the stems on themselves and to obtain a better bursting or peeling of the impermeable film, the flax stalks are rolled on themselves during the crushing to cause diffusion of the pectic substances and other soluble matter in the entire stem, which will allow aerobic microorganisms to have a faster action. When the treated plant is still alive, the process ensures a dilution of the pectic substances inside the stems, facilitating the action of aerobic microorganisms.

When the process is used to treat plants which have just reached their maturity stage or have not yet reached it, the sap and the pectic substances which agglomerate the fibers with the other components of the stem, are still in the liquid state. . According to this method, the rods are washed immediately after the bursting of the impermeable films with water washing in order to remove the maximum of soluble non-fibrous substances. This washing dilutes the sap and gummy matter contained in the plant and allows the evacuation of these products out of the stem. It must be accompanied by an energetic mechanical action on the stems to remove sticky matter, because a green flax contains between 20 and 30% of non-cellulosic matter according to the varieties, the degree of maturity and the atmospheric conditions.

This abundant washing of the stems will be done with pure water under ambient temperature conditions, or preferably, with water added with certain products which neutralize the undissolved gums, for example an anti-coagulant. , a non-stick or a wetting agent. These additives improve the elimination of sap and gummy matter. Then, rinse thoroughly and spin to speed up the drying process of the stems.

A few hours after uprooting, the plant, which has been treated before maturity and dried under the combined action of the sun and wind, can be picked up and removed for scouring.

The process used on live plants reduces the volume and weight of the flax to be brought in, thus helping to reduce the costs of transporting the flax.

When the process is used to treat plants that have reached or passed their stage of maturity, that is to say when the sap and pectic substances have started to coagulate, the stems are subjected to waterproofing after the bursting and their crushing, retting on the ground for a period of a fortnight. This accelerated retting makes it possible to be less dependent on atmospheric conditions and to be able to carry out all of the retting during the summer period when the temperatures are relatively high, which promotes the action of microorganisms.

To obtain a uniform retting, a modulated pressure is exerted over the entire height of the rod such that the pressure exerted on the feet is greater than that exerted on the bodies and the head. The rolling of the stems on themselves during the crushing improves the fineness of the textile fibers provided by the base of the plant, and it is no longer necessary to remove the feet thereof to obtain flax yarns end number.

In addition, the crushing pressure will be adjusted according to the state of maturity, a dry and very ripe flax requires a higher pressure than young and tender flax.

The crushing of the rods is obtained using a series of pressure rollers whose axes of rotation are parallel to the longitudinal direction of the rods which arrive parallel to each other. Then, the stems are deposited on the ground so as to constitute a layer with a thickness of the order of a few centimeters, the width of which corresponds to the height of the plants. The layer of flax thus obtained is subject to either retting on the ground in the case of very ripe dry flax, or to rapid drying on the field for pressed flax and washed with its sap. .

The modulation of the pressure on the height of the rod can be obtained by the use of independent pressing cylinders arranged according to the location of the rods, such that the rollers which apply to the feet are adjusted to a pressure higher than that of the rollers that apply to the rest of the stems.

Preferably, the stems are routed so that their upper zones which contain the seeds are aligned with each other, and the method proposes to pass this zone outside of the pressure rollers so that the seeds remain intact . As a result, the seeds, which are ripe and dried ten days after being uprooted, can be harvested when the flax is picked up after the accelerated retting which lasts fifteen days. This process, which coincides with the end of accelerated retting and the favorable moment for harvesting seeds, allows the recovery of a by-product of good market value.

In the case of ripe flax, water can be used to facilitate crushing and to wash the pressure rollers. Water prevents sticking of the stems due to the presence of sticky substances within the plant. This washing requires a reduced amount of water, much lower than that required by washing the stems for the complete elimination of pectic substances in the case of a flax not yet mature.

Claims (10)

1. Process for the treatment of flax used as textile fibre, with said flax in the form of stalks, each with a body section between the foot carrying roots and the head supporting the seeds, each stalk with a ligneous central section enveloped by a fibrous ring in which the fibre bundles are glued and massed together by pectic substances and with an impermeable membrane that envelops the stalks, characterized in that the flax is pulled out and immediately afterwards, variable pressure adjusted according to the areas of application is brought to bear on the entire length of the stalks in order to have the impermeable membranes burst and open up.

2. Flax treatment process according to claim 1, characterized in that while pressure is being applied to the stalks, these are made to rotate in order to obtain improved bursting open of the impermeable membranes.

3. Flax treatment process according to claim 1 or 2, in particular for the treatment of flax that has not yet fully ripened characterized in that immediately after the impermeable membranes have been made to burst and open up, the stalks are washed in water to remove the pectic substances and other water-soluble substances.

4. Flax treatment process according to claim 1 or 2, in particular for the treatment of ripe or overripe flax, characterized in that this flax, after having made the impermeable membranes burst and open up, is left to ret for about fifteen days on the ground.

5. Flax treatment process according to any one of the claims above, characterized in that the pressure applied to the stalks is stronger at foot level than at body section or head level.

6. Flax treatment process according to any one of the claims above, characterized in that the pressure applied to the stalks will vary according to the degree of ripeness of the flax, and that dry and ripe flax requires stronger pressure as compared to young and tender flax.

7. Flax treatment process according to any one of the claims above, characterized in that the flax stalks are arranged parallel one to another and fed between pressure rollers, the rotation axes of which are parallel to the stalks.

8. Flax treatment process according to claim 7, characterized in that the stalks are fed through several pressure rollers set up independently along the stalks and the pressure rates of which are variable and adjusted according to the area of application and the degree of ripeness attained by the plant.

9. Flax treatment process according to claim 4, characterized in that the seeds carried by the stalks are not crushed and that the seeds are collected after the accelerated retting operation.

10. Flax treatment process according to claim 3, characterized in that the stalks are washed in pure water or in water to which a product neutralizing the pectic and rubber substances has been added, e.g. an anticoagulant, an anti- adhesive, an enzyme or a wetting agent.