RU2617667C2 - Method for producing continious lenght of thin fibres web with long natural fibres, respective device and fibres - Google Patents

Abstract

FIELD: textile, paper.

SUBSTANCE: method comprises the following steps: parallel feeding of a plurality of individual bands (32) of fibres. At least one band (32) comprises long natural fibres; distribution of neighboring bands (32) on the needle field (60) to form a strip (62) of parallel fibres; loading and stretching of the strip (62) on the needle field (60) in parallel to the movement axis (B-B'); binding stretched strip fibres (62) to form a thin fibres web (60).

EFFECT: improved method.

17 cl, 11 dwg

Description

The present invention relates to a method for producing a continuous thin web of fibers containing long natural fibers.

Such a web is intended, in particular, for use in the manufacture of parts impregnated with a polymer matrix, for example, for construction, automobiles, or for any other application.

Natural fibers have many advantages over synthetic fibers.

In particular, natural fibers are usually of low density, they are relatively inexpensive and environmentally friendly. In addition, natural fibers are renewable products and, thus, can be obtained without exhaustion of natural resources.

In this regard, fibers obtained from flax are widely cultivated and used in many fields, in particular, to obtain composite materials. Flax fibers are extracted from the stem of the plant "flax", and they can be used either in the form of bundles of long fibers, or in the form of elementary fibers, or in the form of microfibrils.

Bundles of long fibers usually consist of a set of elementary fibers interconnected by natural cement and have a length that can range from 2 mm to 1000 mm.

These fiber bundles have good mechanical properties, since their Young's modulus is preferably 30 to 50 GPa.

For the use of long natural fibers, it is necessary to connect the fibers to form, for example, a relatively thick sheet, fabric or net. These connected systems are the result of complex and expensive production, but have sufficient mechanical cohesion to succumb to subsequent molding operations of parts, including, for example, overlaying and orienting these systems.

However, methods for producing such systems are complex and relatively expensive. Therefore, in the field of composite materials, it is preferable to use linen flax, that is, fibers from 2 cm to 10 cm long, which can be used in the framework of traditional methods called “dry methods”, including the stages of preparation, scratching, laying and, possibly, needle-piercing, which these steps of fiber bonding would result in a mat.

However, the resulting non-woven material has poor mechanical properties when used in order to obtain composite materials. In addition, the resulting materials are thick, difficult to handle and have a very heterogeneous thickness.

Patent FR 2705369 describes a method for forming nonwoven webs of linen fibers based on natural linen cements. This method includes the step of forming a fibrous sheet, then bonding the sheet fibers with natural linen cements.

The aim of the invention is to develop a method for producing a thin web containing long natural fibers, which would be simple to implement and which would make it possible at low cost to obtain a web of very small thickness with constant surface density.

To this end, the object of the invention is a method of the type indicated above, characterized in that it comprises the following steps:

- parallel supply of many individual ribbons of fibers, and at least one tape contains long natural fibers;

- the distribution of adjacent tapes over the field of needles to form a strip of parallel fibers;

- application of load to the strip in the field of needles parallel to the axis of movement;

- the bonding of the fibers of the elongated strip, forming a thin web.

The method according to the invention may have one or more of the following characteristics, taken individually or in any technically possible combinations:

the step of bonding the strip fibers includes irrigating the elongated strip with a solution, penetrating the solution between the strip fibers and drying the strip to form a thin web;

- solution irrigation is carried out by spraying drops or by forming a foam containing a liquid and a blowing agent, the foam being deposited on a strip;

- the step of applying a load is carried out between at least one front roller, preferably having a metal outer surface, and at least one rear roller, preferably of wood, rubber or polymer, and the speed of entrainment of the strip for the rear roller is at least two times, preferably at least six times the speed of entrainment of the strip by the front roller;

- the needle field contains a plurality of planks transverse to the axis of movement, each transverse plank containing many needles, and the transverse planks can preferably move with the strip;

- the speed of movement of the transverse bars is less than the speed of entrainment of the strip by the specified or each rear roller;

- the surface density of the needles in the field of needles is from 5 needles per cm ² to 23 needles per cm ² ;

- before the filing step, the method includes the step of forming a plurality of tapes by doubling several single tapes;

- at least one first unitary tape contains exceptionally long natural fibers, at least one second unitary tape preferably contains additional natural fibers other than long natural fibers of the first unitary tape and / or synthetic fibers of natural origin and / or synthetic fibers of artificial origin, and / or mixtures thereof;

- the standard deviation of the titer of the divided tapes is less than 20%;

- at the feeding stage, separate tapes are placed in adjacent grooves ending in the needle field;

- in the gutters, the tapes are compressed laterally by the converging walls of the gutters;

- at the exit of the gutters, the tapes come into contact with each other and penetrate each other;

the surface density of the web after the fiber bonding step is less than 500 g / m ² , preferably less than 150 g / m ² .

The object of the invention is also a facility for producing a continuous thin web of fibers containing long natural fibers, characterized in that it contains:

- a parallel feed system for a plurality of individual fiber tapes designed to receive at least one tape containing long natural fibers;

- a system for forming a strip of fibers, including a tape distribution system containing a field of needles, and a system for applying a load and stretching a strip in a field of needles;

- a system for fastening strip fibers to form a thin web.

The installation according to the invention may have one or more of the following characteristics, taken individually or in any technically possible combinations:

- the supply system includes a guide restricting a plurality of troughs arranged side by side, with each trough designed to receive one tape.

In addition, the object of the invention is a continuous thin web of fibers containing at least long natural fibers, characterized in that it contains many parallel fibers obtained by the distribution and application of a load to the fibers of parallel tapes, and the parallel fibers are interconnected, forming a thin the web, the web having a uniform thickness across its width.

The canvas according to the invention may have one or more of the following characteristics, taken individually or in any technically possible combinations:

- it has a surface density of less than 500 g / m ² , in particular less than 150 g / m ² , and preferably has a thickness of less than 1 mm;

- it has a length of more than 100% of its width, and the web is preferably folded to form a roll;

- the original long fibers are long linen fibers;

- the canvas contains more than 50 wt.% natural fibers;

- the web does not contain a synthetic binder that holds the fibers together.

The object of the invention is a thin web, which can be obtained by the above method.

The web of the invention may have one or more additional characteristics as defined above.

The invention will become more clear when studying the following description, given solely as an example and carried out with reference to the attached drawings, in which:

- FIG. 1 is a flowchart showing the main steps of the first method according to the invention;

- FIG. 2 is a schematic top view of a first apparatus for implementing the method of FIG. one;

- FIG. 3 is a front view of a bar containing needles for use in the forming system of the apparatus of FIG. 2;

- FIG. 4 is a view similar to that of FIG. 2, when implementing the method of FIG. one;

- FIG. 5 is a cross section in the plane V-V of FIG. four;

- FIG. 6 is a cross section along the vertical plane VI-VI of FIG. four;

- FIG. 7 is a view of a web obtained by the method of the invention packaged in a roll;

- FIG. 8 is a photograph illustrating the appearance of a first web according to the invention;

- FIG. 9 is a schematic side view of a delivery system and a parallel feed system;

- FIG. 10 is a schematic side view of a strip forming system obtained from tapes;

- FIG. 11 is a schematic side view of a strip fiber bonding system to obtain a web.

Hereinafter, the terms "front" and "rear" are everywhere understood in relation to the direction of movement of an object obtained in a continuous mode.

The first thin web 10 obtained by the method according to the invention is shown in FIG. 7 and 8. In the example of FIG. 7, the web 10 is preferably wound around itself to form a roll 12.

The web 10 according to the invention contains long natural fibers parallel to each other, and at least one binder holding the fibers together.

In one embodiment, all fibers of the web 10 are composed of long, natural fibers. Alternatively, part of the fibers forming the web 10 is formed from additional natural fibers that are different from long natural fibers, from synthetic fibers of natural origin, from synthetic fibers of artificial origin, or from a mixture of these fibers.

Long natural fibers are preferably fibers isolated from plants, in particular flax fibers. Alternatively, long natural fibers are fibers of sisal, jute, hemp, kenaf, etc.

Additional natural fibers are selected, for example, from fibers of cotton, wool, silk, soy, sisal, hemp, or from mixtures thereof.

Synthetic fibers of natural origin are selected, for example, from regenerated cellulose fibers, in particular viscose fibers, cupro and / or modal, alginate viscose fibers, lyocell fibers, PLA fibers (polylactic acid) and mixtures thereof.

Synthetic fibers are formed from derivatives of oil or from molecules obtained biochemically (for example, ethylene derived from bioethanol). They are selected from polyolefin fibers, such as polyethylene and / or propylene fibers, polyester, polyamide, polyimide fibers and mixtures thereof. They can also be bicomponent fibers formed from a polymer and a copolymer, the polymer and its copolymer having different melting points.

Preferably, the mass fraction of long fibers of natural origin in the web 10 exceeds 50% of the total mass of the fibers of the web 10.

Preferably, the long natural fibers are long linen fibers.

Long flax fiber is obtained from a plant called "flax" or "flax plant" from the Linaceae family. These fibers are removed from the periphery of the stem of a flax plant by mechanical destruction of the stem during the grinding operation, and then separation into long fibers, a tow, which is short and coarse fibers, and other components of flax.

The long fibers obtained in this way preferably have a length in the range of 2 mm to 1000 mm. Under the "long fibers" in the framework of the present invention, it is understood that the fibers preferably consist of a longitudinal assembly of elementary fibers interconnected by natural cement.

Long fibers usually form bundles, which can have a length reaching one meter. Part of the long natural fibers of the web 10 has a length of more than 50 cm, in particular from 50 cm to 80 cm.

Bundles of long fibers typically have a diameter in the range of 10 microns to 100 microns.

A binder that binds to each other various long fibers is preferably formed from natural cement of plants, in particular from natural flax cements, when the long fibers are long flax fibers.

Alternatively, the binder is a synthetic binder, such as glue or resin, in particular latex, and / or a binder of natural origin, other than flax cements, for example, based on starch.

According to the invention, the width of the web 10 is much greater than its thickness and much less than its length.

Thus, for example, the width of the web is greater than 30 mm, in particular from 30 mm to 2000 mm, preferably from 100 mm to 2000 mm.

The thickness is less than 0.1 of its width, in particular, it is less than 1 mm, preferably less than 0.5 mm, preferably less than 0.1 mm.

The blade 10 obtained by the method according to the invention has a uniform thickness. Thus, the standard deviation of the average thickness of each longitudinal strip of the web 10, consisting of longitudinal strips corresponding to one tenth of the width of the web 10, is less than 5%, in particular less than 2% of the average thickness of the web 10.

The average surface density of the web 10 is low. This surface density is below 500 g / m ² , in particular below 150 g / m ² and even below 100 g / m ^2, and is preferably from 30 g / m ² to 100 g / m ² .

The surface density remains constant across the width of the web.

The length of the blade 10 is much greater than its width. In particular, the length of the web 10 exceeds 10 m, in particular, it is more than 100 m. Thus, the web 10 can be wound in the form of a roll 12, the average diameter of which is more than 100 mm, preferably up to diameters of the order of 600 mm.

As shown in FIG. 8 and taking into account the production method according to the invention, the fibers of the web 10 are substantially aligned in the longitudinal direction of the formation of A-Aʹ.

Thus, at least 50% of the fibers of the web 10 are parallel to the longitudinal direction A-Aʹ, which is perpendicular to the axis of winding of the web 10 when it is in the form of a roll 12. Thus, the long fibers of the web 10 are usually parallel to each other and connected by a binder, to provide mechanical cohesion of the web 10.

The blade 10 has sufficient mechanical cohesion to allow manipulation with it, in particular in later impregnation and application operations, to form multidirectional mats. So, the web 10 can be captured by the user's hand and the manipulators of the machine, in particular, manipulators with vacuum grippers (after impregnation, if it is not porous), without leading to a deterioration in mechanical properties and preserving its mechanical strength. Canvas 10 is self-supporting.

The cohesion of the web 10 is such that the average tensile force applied in the transverse direction perpendicular to the preferred direction of orientation of the fibers A-A ', which is measured according to ISO 13934-1 on a sample with a width of 50 mm, preferably exceeds 0.1 N, in particular is 0.1 N from 0.2 N to 2 N, for example, about 0.5 N. It was unexpectedly found that by the method according to the invention, a web 10 is obtained containing long natural fibers and having at the same time a uniform thickness and a very noticeable orientation of long fibers, while maintaining emya sufficient cohesion to manipulate it.

For this, the web 10 is formed on the basis of longitudinal ribbons of fibers that are fed in parallel and which are distributed to form a strip of parallel fibers, and then the strip fibers are held together.

Under the "tape" in the framework of the present invention refers to a longitudinal element containing a collection of fibers, in particular long fibers. Tapes can be obtained, for example, by combing or carding, and then applying a load to individual fibers, which are then combined again with each other, forming a longitudinal bond.

The thickness of the tape is usually in the same order as its width. For example, it ranges from 0.5 to two tape widths.

Preferably, the tape can be obtained from single tapes, which are doubled by laying on top of each other. In the above example, the width of the tapes is, for example, less than 30 mm. The thickness of the tapes, for example, is more than 15 mm and ranges from 10 mm to 40 mm.

The length of the tapes is more than 800 m, in particular, it ranges from 850 m to 1700 m.

The doubling operations consist of applying at least two single tapes of the same or different nature, and then distributing them in the needle field, supporting them under pressure, until a single double tape is obtained.

The number of doubles may be variable. This number is from 1 to 15 doublings.

The linear density of the tapes intended for use in the method according to the invention is, for example, from 10 g / m to 40 g / m.

The steps of the first method for producing the web 10 according to the invention are shown in the flowchart of FIG. one.

Such a method is carried out, for example, in the installation 14 for obtaining the web 10, schematically shown in FIG. 2 or 4.

As shown in FIG. 2 and 4, the installation 14 comprises a system 20 for delivering a plurality of fiber tapes containing at least one tape of long natural fibers, and a system 22 for supplying tapes for their parallel arrangement.

According to FIG. 2 and 10, the installation 14 further comprises a continuous fiber strip forming system 24 based on the tapes and a strip fiber bonding system 26 to form a thin web 10, as shown in FIG. 2 and 11.

Installation 14 contains, in addition, a system 28 for filling the web 10 to store it, in particular, in the form of a roll 12.

As shown in FIG. 9, the delivery system 20 preferably comprises a storage area for comb ribbons (tops) 32.

Tapes 32 are stored, for example, in the form of "tops", or combed tapes, preferably in creel crepes.

Tops are obtained by overturning the tape 32 contained in the tank, for example, from 30 cm to 1 m in diameter, in particular from 40 cm to 60 cm. After filling the tank, the tape 32 is squeezed from above, the tank is removed, and the tape is fastened. Tops then has the dimensions of a tank with a height in the range from 30 cm to 80 cm, in particular about 40 cm. The weight of the tops is, for example, from 15 kg to 40 kg.

To implement the method according to the invention, the tapes 32 supplied to the system 20 are preferably tapes 32, which were obtained by doubling single tapes to obtain tapes 32 that are uniform in linear density. Thus, the linear density of the tapes 32 is preferably from 10 g / m to 40 g / m. The standard deviation between the linear densities of the different tapes 32, intended to produce one web 10, is less than 20%.

In the case where the web 10 consists of long natural fibers, for example long linen fibers, all the tapes 32 are long natural fibers, preferably obtained by doubling single ribbons of long natural fibers.

In the case where the fabric 10 contains additional natural fibers, synthetic fibers of natural origin or synthetic fibers of artificial origin, at least one tape 32 is formed from a single tape consisting of long natural fibers, and from at least one single tape consisting of additional natural fibers, synthetic fibers of natural origin or synthetic fibers of artificial origin.

In all cases, all single tapes are distributed in the field of needles (not shown), then pressure is applied to them and grouped, laying on top of each other. The number of doubling operations is from 1 to 15, preferably from 2 to 4.

Then the tape 32 is stored in the form of combed tapes (or "tops") and placed on the ground or on a support. The collection of tapes 32 is delivered in parallel.

As shown in FIG. 2, 9 and 5, the feed system 22 includes a guide 40 for parallel distribution of the tapes 32, intended for feeding into the forming system 24, and a mechanism 42 for feeding individual tapes 32 into the guide 40.

The feed mechanism 42 includes two guide rollers 44 and a pair of feed rollers 80A and 80B, designed to entrain each tape 32 from the reel 30 to the guide 40.

As shown in FIG. 2 and 5, the guide 40 comprises a plurality of grooves 46 arranged in parallel.

Gutters 46 are preferably located adjacent to each other. Each groove 46 is bounded by two side walls 48, of which at least one is common with the adjacent groove 46, and the bottom wall 49. Each groove 46 is designed to receive one separate tape and distribute it to the forming system 24, having the form of rollers parallel to the axis B-Bʹ web formation.

So, each groove 46 extends in length between the inlet 50 and the outlet 52, which is opposite the formation system 24.

In the example shown in FIG. 4 and 5, the guide 40 comprises a plurality of troughs 46 converging from entrance to exit. The cross section of the groove 46 opposite the inlet 50 is larger than the cross section of the groove 46 at the level of the outlet 52.

Thus, each tape 32 placed in the chute 46 moves in a converging direction to the outlet 52 to contact the side walls 48 on both sides of the tape 32, as shown in FIG. 5, at hole level 52.

The angle of the axis of each groove 46 to the axis B-Bʹ increases from the groove 46 to the groove 46, shifting from the axis B-Bʹ to the outside of the guide 40. The width of each groove 46 at the level of the inlet 50 is at least 10% greater than the width of the groove 46 at the level of the outlet 52. This allows the transverse densification of the fiber bundles to be naturally uniform. At the outlet of the gutters, tapes that were compressed laterally by the converging walls of the gutters, as a rule, have a small expansion, which makes them come into contact with each other and even slightly penetrate each other.

The maximum width of each groove 46 at the level of the outlet 52 is, for example, from 10 mm to 40 mm.

The thickness of the side walls 48 is less than 5 mm to limit the distance between the different tapes 32 when they enter the formation system 24.

As shown in FIG. 2, 4, and 10, the forming system 24 comprises a field of needles 60 designed to distribute the fibers of the tapes to form a continuous strip 62, which can be seen in FIG. 4, and also comprises a system 64 for applying a load and stretching strip 62 to the field of needles 60.

As shown in FIG. 4, 6 and 10, the needle field 60 comprises a plurality of rows of 70 needles 72 parallel and transverse to the axis of movement B-Bʹ. Rows of 70 needles 72 preferably contain from 2 to 16 needles per cm, i.e. from 6 to 40 needles per inch.

Needles 72 have a height greater than the height of the tapes, for example, from 40 mm to 60 mm.

Rows of 70 needles 72 are mounted on separate transverse slats 74 located perpendicular to the B-Bʹ axis. The system formed by each bar 74 and its needles 72 is usually denoted by the English term "gills" (gills).

Serial strips 74 are preferably in contact with each other. Each bar 74 preferably carries at least one row of needles 70, in particular two rows of needles 70, as can be seen in FIG. 3.

The needles 72 of the first row 70 are slightly offset from the needles 70 of the second row in the transverse direction relative to the axis B-Bʹ.

The rows 70 of the needle field 60 can preferably move along the B-Bʹ axis. Each bar 74 is driven by helicoidal screws and carries out movement along a rectangular path.

Thus, the strips 74 move along with the strip 62 to the end of the needle field 60. Then they return to the beginning of the needle field 60.

To this end, as shown in FIG. 10, the needle field 60 comprises a mechanism 75 for longitudinally moving the planks 74 along the B-B оси axis between the extreme forward position and the extreme rear position, by a length L1 along the B-Bʹ axis.

The movement mechanism 75 further comprises means for returning each bar 74 from its extreme rear position to its extreme forward position.

To do this, each bar 74, when it is in its extreme forward position, can move vertically between the allotted return position and the active fiber penetration position in the plane of strip 62.

In the extreme rear position, each bar 74 can move vertically between the active punching position and the retracted position.

The mechanism 75 shifts each bar 74 in the direction of movement of the strip 62 from input to output, holding the bar 74 in its active position, and then moves each bar 74 from the rear position to the front position in the opposite direction to the movement of the strip 62, holding the bar 74 in its allotted position position.

The length L1 of the field of needles 60 exceeds 80 cm, in particular, is from 100 cm to 80 cm in order to accommodate long natural fibers and allow them to be parallel to the B-B 'axis.

As shown in FIG. 2 and 10, the load application system 64 comprises at least one front roller 80A, 80B and at least one rear roller 82A, 82B located laterally on both sides of the needle field 60, respectively between the feed system 22 and the needle field 60 and between needle field 60 and fastening system 26.

In the example shown in FIG. 10, the load application system 64 comprises a pair of front rollers 80A, 80B arranged vertically one above the other. The front rollers 80A, 80B are rotatably mounted about axes perpendicular to the axis B-Bʹ.

The front rollers 80A, 80B preferably have a metal outer surface, in particular chrome. They have a gap with a width less than the height of the tapes 32, in particular less than 20 mm, in order to smooth and compress the tapes 32.

The gap 84 is preferably located horizontally with respect to the needles 70 and horizontally with respect to the outlet openings 52 of the grooves 46 so that the tapes 32 can be sealed and the fibers from the tapes 32 can be distributed into the field of needles 60 through rows of 70 needles 72.

In the example shown in FIG. 10, the load application system 64 comprises at least two rear rollers 82A, 82B located one above the other.

The rollers 82A, 82B are rotatably mounted about axes perpendicular to the axis B-Bʹ.

For example, the roller 82A is a cylinder made of wood, rubber or polymer. Its diameter is preferably larger than the diameter of the roller 82B. The roller 82B has a metal outer surface, such as a chromed outer surface.

The first pair of rollers 80A, 80B and the second pair of rollers 82A, 82B are adjusted so that the speed of the strip 62 formed in the field of needles 60 at the output of the rear rollers 82A, 82B is at least twice, in particular 6 times higher and preferably 6 to 20 times higher than the speed of the strip 62 at the exit of the front rollers 80A, 80B.

This allows you to apply a load and stretch the strip 62 to control its thickness and its surface density.

As shown in FIG. 11, the fastening system 26 comprises an irrigation device 90 for the strip 62 with a liquid solution or a foaming agent, a solution distribution zone 92 over the strip 62, and a strip drying device 94.

The solution is preferably formed as an aqueous solution. In a first embodiment, the aqueous solution consists of water. Alternatively, the aqueous solution contains water and a non-ionic surfactant, such as polyvinyl alcohol, to form a foam.

The content of polyvinyl alcohol in the solution is less than 1%.

Alternatively, the liquid solution may contain a wetting agent.

In the example of FIG. 11, an irrigation device 90 comprises at least one nozzle 96 for ejecting a solution, in particular in the form of droplets, fog or foam, and a transverse chamber 98 for conducting the solution.

Preferably, the nozzles 96 open into the chamber 98. The chamber 98 has a bottom opening opposite the belt conveyor 100 for the strip 62, designed to maintain and entrain the strip 62 between the irrigation device 92 and the drying device 94.

The drying device 94 comprises a heating device 102, for example, a convector provided with hot plates, and a vapor suction system 104, comprising, for example, a fume hood 106.

The intermediate zone 92 is located between the irrigation device 90 and the drying device 94. Its length is, for example, from 0.5 m to 2 m

In this example, the web 10 is packaged in the form of a roll 12. The packaging system 28 thus comprises an axis or mandrel 110 for winding the web and means (not shown) for driving the axis into rotation to allow the winding of the roll 12.

In one embodiment, the filling system 28 comprises a distribution sheet distribution device for winding together with the web 10 to separate two successive layers of the web 10 in the roll 12.

Next, a method for producing a web 10 according to the invention will be described.

As shown in FIG. 1, the method first includes a step 120 for delivering the separate tapes 32, and then a step 122 for feeding the tapes 32 in parallel to the feed system 22.

The method then includes forming a continuous strip 62 by distributing the tapes 32 in the forming system 24, then a step 126 of fixing the strip 62 to form the web 10 in the fastening system 26.

Finally, the method includes the step 128 of filling the web 10.

The method is preferably implemented in continuous mode, that is, steps 122-128 are carried out sequentially one after another in continuous mode, without an intermediate stop.

At step 120, a plurality of parallel ribbons 32 are delivered, for example, coiled in the form of tops 30 of combed ribbons, located on a support or on the ground, preferably in crevasses.

As specified above, the tapes 32 were preferably obtained by doubling single tapes, and tapes 32 are formed, for example, from single tapes of long natural fibers or consist of a mixture of single tapes from long natural fibers with at least one single tape from additional natural fibers, synthetic fibers natural origin or synthetic fibers of artificial origin.

The title of the tapes 32 is substantially constant, so that the standard deviation between the titles of the tapes 32 is less than 20%.

Then, at the feeding step, a plurality of separate tapes 32 are conducted in parallel from the delivery system 20 to the forming system 24 through the feeding system 22.

The number of parallel tapes 32 is from 2 to 100, in particular from 8 to 15 tapes, in order to obtain paintings with a width of 10 mm to 2000 mm.

Then each tape 32 is carried away by the feed rollers 44 and is directed to the inlet 50 of the groove 46.

Thus, the guide 40 receives a plurality of parallel tapes 32, with each tape 32 being received into a corresponding trough 46. The tapes 32 are then entrained through each trough 46 via the front rollers 80A, 80B to the outlet 52.

In the forming step 124, various tapes are first compressed in the gap 84 between the front rollers 80A, 80B to reduce their thickness and lateral distribution.

Then, fibers from different adjacent ribbons 32 are introduced into the field of needles 60, being extended with the rear rollers 82A, 82B.

To this end, the strap 74, in its most forward position, moves from its retracted position to its vertically extended position so that its needles 72 intersect the lines of parallel fibers and form a strip 62 with a uniform thickness determined vertically, which is less than the thickness of each tape 32 .

Then the straps 74 are displaced in length along with the fibers of the strip 62 along the field of needles 60 to the back needle.

With this passage, the fibers form a strip 62 with a thickness uniform in width.

In addition, given the relative rotation speed of the front rollers 80A, 80B and the rear rollers 82A, 82B, a load is applied to the strip 62 and it is pulled into the field of needles 60, leading to a longitudinal alignment of the fibers in a single direction.

The delivery of fibers in the form of separate tapes 32, their distribution in the front rollers 80A, 80B, passage into the field of needles 60 and the application of load by the rear rollers 82A, 82B allow, acting together, to form a strip of essentially uniform thickness, with a low surface density, in particular less than 150 g / m ² , with substantially parallel alignment of at least 50% of the number of fibers, even 80% of the number of fibers.

At the exit from the field of needles 60, the strip 62 is compressed between the rear rollers 82A, 82B and is conducted to the fastening system 26.

Before it passes into the fastening system 26, the elongated strip 62 does not have transverse cohesion. Thus, the various fibers forming the elongated strip 62 can be removed from each other as a result of a simple hand pressure when they exit the rear rollers 82A, 82B above the fastening system 24.

Thus, the elongated strip 62 is conducted into the bonding system 24 to enhance lateral cohesion.

First, the strip 62 is sprayed in the irrigation device with a solution designed to activate the connection between the fibers. In the first embodiment, the aqueous solution is sprayed in the form of droplets, for example in the form of a mist, which is directed through the chamber 98.

In one embodiment, the solution is in the form of foam, and the foam is deposited on strip 62 through chamber 98.

Then, the strip 62 passes into the intermediate zone 92, which allows the diffusion of the solution between the fibers under the action of capillary forces. In the case where the solution is formed from foam, the bubbles of the foam are quenched and the resulting liquid diffuses through the fibers.

The purpose of this operation is the partial dissolution of natural cements that bind the fibers to each other.

Then, the strip 62, impregnated with liquid, enters the heating device 94. The strip 62 is heated to a temperature above 70 ° C, in particular, the heating temperature is from 100 ° C to 180 ° C to allow evaporation of part of the liquid from the solution.

This evaporation is facilitated by the absorption created by the device 104. The solubilized natural cements harden again, which enhances the cohesion between the fibers and provides, in particular, transverse cohesion to form a thin web 10.

In the case where the web 10 contains less than 50% of the long flax fibers, natural flax cements are not always sufficient to give the web 10 sufficient transverse cohesion. In this case, a small amount of an additional binder can be added to the solution, as described above.

In the packaging step, the web 10 is wound into a roll around the mandrel 110. In this embodiment, an intermediate sheet is introduced between the different layers of the web 10 to prevent damage.

As indicated above, all previous steps are carried out in a continuous mode, from the parallel feed of the tapes 32 to the packaging of the web 10 after receiving it. The speed of the web during all operations is above 1 m / min, in particular, it ranges from 1 m / min to 50 m / min.

After a sufficient length of the web 10 has been wound into a roll 12 around the mandrel 110, the roll 12 can be easily and economically transported to its place of use, for example, to obtain impregnated panels.

Thus, thanks to the above-described invention, it is very economical to obtain a thin web 10 containing an increased amount of long natural fibers, in particular long linen fibers. This web 10 has a small thickness and a surface density below 500 g / m ² , in particular below 150 g / m ² , even in the range from 30 g / m ² to 100 g / m ² . In addition, it has a uniform thickness along its width and a very noticeable orientation of the fibers, which are essentially aligned in one line and parallel to each other.

In particular, unlike linen fabric, the fibers are neither twisted nor crossed. Therefore, the fabric 10 has no reliefs, which reduces its thickness and allows the use of a minimum of resin in the manufacture of panels.

In addition, the production method does not include a spinning step, it is very simple to implement and therefore has a competitive price. The web 10 obtained after the bonding step has a grip and is self-supporting, so that it can be transported without danger of damage, which is also beneficial in terms of cost and handling.

In addition, since the resulting fabric 10 is implemented mainly or solely on the basis of natural fibers, in particular long linen fibers, it is completely biodegradable and can be obtained without the use of an artificial binder, using only natural cements of natural fibers, for example, formed from hemicellulose and lignin .

Thanks to the above invention, it is possible to obtain a thin web 10, that is, a collection of flat fibers, with a uniform thickness, excellent ordering, both in the longitudinal and transverse directions.

The canvas 10 is obtained from tapes 32 or bundles of long fibers, in particular linen, whose length is much greater than their width, which can be considered as an infinite length.

Tape 32 is obtained by a complex method of preparation, which allows you to extract long fibers, separating them from tow, which is a short and coarse fiber. Tapes 32 are obtained, for example, by combing or carding.

As specified above, in order to obtain good transverse homogeneity, it is necessary to order ribbons 32, the thickness of which usually has the same order as their width, and which have a circular or pseudo-elliptical cross-section. These tapes 32 are placed next to each other in a guide 40 defining a plurality of converging troughs 46 to bring them into contact with each other, and even with little penetration into each other.

This allows you to smooth and layer the tape 32 to glue the edges that they form, obtaining a flat system, uniform in the transverse direction.

The characteristics of the grooves 46, in particular, the degree of convergence and the optimal distance between the grooves 46 are optimized depending on the title of the tapes in order to guarantee this lateral expansion effect.

As specified above, the mass of the unit length of the tapes 32 is increased, for example, it is from 10 g / m to 40 g / m. In order to obtain good uniformity in length, the forming system 24 simultaneously comprises a system 62 for applying a load and stretching the strip and a needle field 60 with a length greater than or equal to the maximum length of the long fibers.

Thus, a pair of rear rollers 82A, 82B has a drag speed greater than that of the front rollers 80A, 80B, each upper end of the fiber sandwiched between the rear rollers 82A, 82B is carried away with a speed greater than the speed of the strip 62 formed at the output of the feed system 22 .

In order to avoid that this fiber will entrain adjacent fibers with which it is in contact, but whose upper ends have not yet reached the rear rollers 82A, 82B, which would lead to stretching in packets and to a very inhomogeneous web, needles 72 of the needle field 60 block the fibers, adjacent to trapped fiber. Therefore, the rows 70 of parallel needles 72 of the needle field 60, which are located on the strips 74, move at substantially the same speed as the drag speed of the strip 62 by the front rollers 80A, 80B.

In addition, when each rear roller 82A, 82B has an outer surface of wood, rubber or polymer, the fiber sandwiched between the rollers 82A, 82B, which will be held up to the needle field 60, can slide between the rear rollers 82A, 82B without being caught and not bursting.

Thus, it is possible to obtain essentially parallel alignment of at least 50% of the number of fibers, even 80% of the number of fibers at low surface density, in particular below 150 g / m ² .

The resulting hood is regular and does not lead to fiber breakage.

Preferably, the surface density of the needles 72 in the needle field is from 36 needles per square inch to 144 needles per square inch, that is, from 5 needles per cm ² to 23 needles per cm ² .

It should be noted that the method according to the invention is preferably applied to tapes containing at least a portion of long fibers having a length of more than 20 cm, in particular more than 50 cm

Claims (27)

1. A method of producing a continuous thin web (10) of fibers containing long natural fibers, wherein at least a portion of the long fibers of the web has a length of more than 20 cm, in particular more than 50 cm, comprising the following steps: - parallel supply of many individual tapes (32) of fibers, at least one tape (32) contains long natural fibers; - the distribution of adjacent tapes (32) over the field (60) of needles, containing many rows (70) of needles (72) parallel and transverse to the axis (B-B ') of the advancement of the tapes, to form a strip (62) of parallel fibers; - application of the load and stretching of the strip (62) in the field (60) of needles parallel to the axis of advancement (B-B '); - fastening the fibers of the elongated strip (62) to obtain a thin web (60), wherein the step of bonding the fibers of the strip (62) includes irrigating the elongated strip (62) with an aqueous solution, penetrating the aqueous solution between the fibers of the strip and drying the strip (62) to form a thin web (60), moreover, the surface density of the web (10) after the step of bonding the fibers is less than 500 g / m ² , preferably less than 150 g / m ² . 2. The method according to p. 1, characterized in that the fabric (10) consists of at least 50 wt.%, Long linen fibers. 3. The method according to p. 1, characterized in that the aqueous solution consists of water, with the possible addition of a non-ionic surfactant, for example polyvinyl alcohol. 4. The method according to PP. 1-3, characterized in that the irrigation of the solution is carried out by spraying drops or by forming a foam containing a liquid and a blowing agent, the foam deposited on the strip (62). 5. The method according to PP. 1-3, characterized in that the step of applying the load is carried out between at least one front roller (80A, 80B), preferably having a metal outer surface, and at least one rear roller (82A), preferably of wood, rubber or polymer, moreover, the capture speed of the strip (62) behind the rear roller (82A) is at least two times higher, preferably at least six times higher than the capture speed of the strip (62) by the front roller (80A, 80B). 6. The method according to one of paragraphs. 1-3, characterized in that the field of needles (60) contains a plurality of planks (74) transverse to the axis of advancement (B-B '), each transverse plank (74) containing a plurality of needles (72), while the transverse planks (74 ) can preferably move with the strip (62). 7. The method according to one of paragraphs. 1-3, characterized in that before the filing step, it includes the step of forming a plurality of tapes (32) by doubling several single tapes. 8. The method according to p. 7, characterized in that at least the first single tape contains only long natural fibers, while at least the second single tape contains preferably additional natural fibers other than the long natural fibers of the first single tape, and / or synthetic fibers of natural origin, and / or synthetic fibers of artificial origin, and / or mixtures thereof. 9. The method according to one of paragraphs. 1-3, characterized in that the standard deviation of the titer of separate tapes (32) is less than 20%. 10. The method according to one of paragraphs. 1-3, characterized in that at the feeding stage, separate tapes (32) are located in adjacent grooves (46), opening at the entrance to the field of needles (60). 11. The method according to one of paragraphs. 1-3, characterized in that the field length of the needles (60) is greater than or equal to the maximum length of long natural fibers. 12. Installation (14) to obtain a continuous thin web (10) of fibers containing long natural fibers, and at least part of the long fibers of the web has a length of more than 20 cm, in particular more than 50 cm, containing: - a system (22) for parallel supply of a plurality of separate tapes (32) of fibers, intended for receiving at least one tape (32) containing long natural fibers; - a tape distribution system (32) containing a needle field (60) containing a plurality of rows (70) of needles (72) parallel and transverse to the axis (B-B ') of the tape advancement, - a system (64) for applying loads and stretching strips (62) in the field (60) of needles; and - a bonding system (26) of strip fibers (62) for forming a thin web (10), wherein the bonding system (26) comprises a device (90) for irrigating the strip (62) with an aqueous solution, liquid or foaming, a solution distribution zone (92) along strip (62) and device (94) for drying the strip. 13. Installation according to claim 12, characterized in that the feed system (22) comprises a guide (40) defining a plurality of troughs (46) located side by side, each trough (46) designed to accommodate one tape (32). 14. A continuous thin web (10) of fibers containing at least long natural fibers, wherein the fiber contains a plurality of parallel fibers obtained by distributing and applying a load to the fibers of parallel tapes, the parallel fibers being bonded together by natural cements of natural fibers, partially dissolved and cured again to form a thin web (10), the thickness of the web (10) being uniform in width, and at least a portion of the long fibers has a length greater than 20 cm, in particular more than 50 cm, the web (10) having a surface density below 500 g / m ² , preferably below 150 g / m ² . 15. The canvas (10) according to claim 14, characterized in that it has a thickness of less than 1 mm. 16. Cloth (10) according to claim 14 or 15, characterized in that it has a length 100% greater than its width, and the web (10) is preferably wound into a roll (12). 17. Cloth (10) according to claim 14 or 15, characterized in that the initial long fibers are long linen fibers.

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