EP0527666B1 - Linen yarn wet production method and linen yarn so obtained - Google Patents

Abstract

According to the invention, the fibres originating from stripping are subjected to the following preliminary operations: a. cutting to a length of between 150 and 400 mm, b. preimpregnation with water, c. action of steam at a pressure of between 10 and 15 bars for a period of between 20 and 60 seconds, d. decompression to atmospheric pressure, e. washing and drying, which are subjected to the preparation stages on any type of material: linen, wool or cotton; the fibre sliver obtained is finally spun wet. The linen yarn obtained has the appearance and the structure of a linen yarn produced by the wet method and has a flexibility which makes it suitable for use in millinery and on a knitting loom.

Description

The present invention relates to flax spinning and more particularly to wet spinning of flax during which the wick or ribbon consisting of substantially parallel fibers is immersed in a bath intended to soften the cements and gums which bind the elementary fibers together. linen inside the technical fibers and to favor their dissociation during the subsequent stretching. The present invention relates to a method aiming to improve the existing technique, in particular in that it makes it possible, under certain conditions, to avoid passing over a bench with pins; on the other hand, it relates to a wet type flax yarn having improved properties, in particular in that it can be used in hosiery, on knitting machine.

The spinning of flax in the wet is well known. It consists of fibers obtained from scutching, either scorched flax itself, or scorched flax, or scutching tows, to subject these fibers to different preparation operations: combing and / or carding, doubling- drawing with the aim of producing a drawing ribbon, that is to say a thin and regular ribbon, of fibers substantially parallelized, and finally carrying out the spinning by passing over a spindle bench where the drawing ribbon is transformed into a wick which is a slightly twisted ribbon, then by passing on a wet spinning bench.

The flax yarn obtained by the wet technique has a natural appearance and a specific apparent structure, which are due to the presence of residual organic cements and to the mode of dissociation and sliding of the elementary fibers with respect to each other during the 'drawing.

However, the presence of these organic cements (pectins, hemicellulose, lignin, etc.), which makes it possible to give the wire better cohesion, has a major drawback which is to increase its rigidity. Thus a traditionally obtained wet linen thread does not have sufficient flexibility to be used in hosiery, on knitting looms, which limits considerably its commercial outlets.

The aim set by the applicant is to propose a process for manufacturing a flax yarn, using the wet technique, which overcomes the aforementioned drawbacks, in that the yarn obtained on the one hand retains the appearance and the structure of a wet linen thread but on the other hand has sufficient flexibility for it to be used in hosiery.

• a. coupe à une longueur comprise entre 150 et 400 mm,
• b. préimprégnation par de l'eau,
• c. action de la vapeur sous une pression comprise entre 10 et 15 bars pendant une durée comprise entre 20 et 60 secondes,
• d. détente à pression atmosphérique,
• e. lavage et séchage.

This object is perfectly achieved by the method of the invention. It is a process for manufacturing a wet linen thread which consists, in a known manner, in the preparation of a fiber ribbon and in its wet spinning. Typically the fibers from scutching have, before the preparation steps, been subjected to the following successive operations:

• at. cut to a length between 150 and 400 mm,
• b. prepreg with water,
• vs. steam action at a pressure between 10 and 15 bars for a period between 20 and 60 seconds,
• d. expansion at atmospheric pressure,
• e. washing and drying.

In addition, the preparation of the fiber ribbon can be carried out on any type of preparation material, linen, wool or cotton.

These preliminary operations have the effect of significantly reducing the amount of organic cements, while retaining a sufficient amount to allow the spinning in the wet and keep the natural appearance of the wire. In addition, the combination of the aforementioned treatment with pressurized steam and wet spinning gives the yarn obtained a very good distribution of residual cements. It is this regularity and the least amount of cement that allows to obtain the desired result, namely improved flexibility while retaining the traditional appearance and structure.

On the other hand, it is thanks to the cut to length between 150 and 400 mm that the preparation of the ribbon can be carried out on preparation materials which are not necessarily of the linen type, but which can be of the wool type or even same cotton.

Thus, thanks to the process of the invention, it becomes possible to produce a wet linen thread, by a simpler and less expensive preparation circuit.

Admittedly, we know, in particular from documents GB-A-388,561, GB-A-476,569 and US-A-2,633,421. treatments in which a fiber plant is subjected to the action of steam under pressure and then relaxed to atmospheric pressure and to a subsequent washing. But it is a high pressure treatment, aiming at the hulling of fiber plants in the form of straw, leaves, grass, that is to say the separation of the bark or the woody part of the fibers proper. The pressures involved are between 38 and 62 bars.

Also known from document EP-A-253.828 is a process for treating a previously stained under-flax flax of the above type, in which the action of steam is at a pressure of the order of 30 bars for one duration of the order of 10 seconds, or at a pressure of the order of 15 bars for a duration of the order of 90 seconds but after the fibers have undergone a pretreatment consisting of impregnation with a basic or acid solution . The aim of this document is to obtain by this process a linen which is substantially free of encrusting materials.

It has been understood that the object of the present invention is quite different and that the conditions for the action of the steam under pressure are precisely determined so that a smaller, but sufficient amount of organic cements remains to allow the smooth spinning at wet.

Preferably, the wet spinning is carried out with a stretching ratio of between 50 and 140 from a ribbon which has not undergone passage on the spindle bench. Thus, it is possible to avoid the first stage of spinning, which consists in switching to a spindle bench, by purely and simply increasing the rates of drawing during spinning without prejudice to the regularity of the yarn obtained.

Advantageously, prior to wet spinning, the ribbon is subjected to an alkaline pretreatment, which makes it possible to improve the sliding of the elementary fibers during the stretching and the homogeneity of distribution of the cements.

Advantageously, before the wet spinning, the ribbon has undergone a bleaching operation, for example with hydrogen peroxide.

It is another object of the invention to claim a linen thread obtained according to the above-mentioned process, characterized in that it has the appearance and structure of a wet thread and in that it has flexibility sufficient to be used in hosiery on knitting loom.

The invention will be better understood on reading the description which will be given of an example of the manufacture of a wet linen thread for knitted or crocheted use.

The starting material consists of scutching tows from the scouring of an undercooked linen. It is for example a flax that was prematurely picked up in the case of retting on the ground. Compared to normally rotted flax, under-rotted flax always contains more encrusting materials, since the cements which bind the fibers together could not be sufficiently degraded by the bacteriological agents of retting.

These tows undergo a preliminary cleaning treatment on a finishing card, which moreover presents them in the form of a ribbon. This ribbon is cut in sections of 300mm.

The material thus cut is introduced into a reactor where it is impregnated with pure water, then subjected to a hydrolysis treatment in steam at 15 bars of pressure for a period of 40 seconds; at the expiration of this period, the opening of the discharge port of the reactor causes a sudden expansion by passing the pressure from 15 bars to atmospheric pressure and therefore the ejection by said orifice of the flax in a container containing slightly alkaline water where it is washed and then rinsed.

The flax fibers thus treated, after drying, are transformed into a ribbon of 4 g / m per passage through the preparation machines, namely successively a passage through a finishing card, a passage in the GN4 double-stretching machine, two passages in a small combing machine , a passage in GN4 double-stretching machine and two passages in GN5 double-stretching machine without passage on a bench with spindles.

At the end of the preparation, the fineness of the ribbon is characterized by an IFS of 16.74 and a CV% of 5.07. It should be noted that with a linen not treated according to the process the IFS is normally greater than 20, which clearly shows an increase in the fineness of the fibers in the ribbon according to the invention.

The ribbon undergoes a light degumming treatment using a solution of 2.5 g / l of sodium carbonate.

Wet spinning is carried out on a continuous spinning machine with two drawing zones. The pressure of the stretching cylinders is obtained using a counterweight system. The ribbon goes into a tub filled with cold water; it is guided at the entrance and at the exit of the drawing train by ceramic guides.

In a specific, but not limiting, embodiment, the spacing of the cylinders was 80 mm for the rear zone and 60 mm for the front zone; the twist was 410 rpm and the reception speed of the order of 13 m / mm. The wet flax yarn obtained had a metric number of 23, a resistance Rkm of 17 (CV% 20 to 25), an elongation of 1.6 to 1.8%.

This yarn, the appearance and structure of which are that of a traditional wet linen yarn, has a very great flexibility compared to a yarn obtained by the traditional process which makes it suitable for use under acceptable operating conditions on knitting looms, especially circular, and therefore suitable for use in hosiery.

The invention is not limited to the embodiment which has been described by way of nonlimiting example. In particular, the length of the cut must be determined by the skilled person depending on the preparation circuit, linen, wool or cotton, which he has chosen. On the other hand, the ribbon, before wet spinning, can undergo various treatments, for example a bleaching treatment, which leads to the manufacture of a bleached linen thread.

Claims (6)

1. Process for the manufacture of a wet-spun linen yarn, consisting in the preparation of a fibre sliver and in its wet spinning, characterized in that the fibres produced by the scutching have been subjected to the following successive operations before the preparation steps:

   a. cutting to a length of between 150 and 400 mm,

   b. preimpregnation with water,

   c. action of steam at a pressure of between 10 and 15 bars for a period of between 20 and 60 seconds,

   d. decompression to atmospheric pressure,

   e. washing and drying

   and in that the preparation of the sliver is carried out on preparation equipment of any type: linen, wool or cotton.
2. Process according to Claim 1, characterized in that the wet spinning is carried out with a draw ratio of between 50 and 140 from a sliver which has not been subjected to passing over the fly frame.
3. Process according to either of Claims 1 and 2, characterized in that, the fibres produced by the scutching being scutching tows, the latter are subjected to cleaning on a finishing card before the cutting operation.
4. Process according to Claim 1, characterized in that, before the wet spinning, the fibre sliver is subjected to an alkaline pretreatment, especially with a solution of sodium carbonate.
5. Process according to Claim 1, characterized in that, before the wet spinning, the fibre sliver is subjected to a bleaching treatment, especially with agueous hydrogen peroxide.
6. Linen yarn obtained by the process of Claim 1, characterized in that it has the appearance and the structure of a wet-spun linen yarn and in that it has a flexibility making it suitable for utilization in hosiery, on a knitting loom.