JP2014533329A - Method for producing a continuous web of fibers comprising natural long fibers, and related apparatus and webs - Google Patents

Abstract

The method of the invention comprises the following steps: knitting a plurality of unconnected ribbons (32) of fibers into at least one parallel ribbon (32) containing natural long fibers; (60) disperse the adjacent ribbons (32) to form parallel fiber strips (62) and, in the tip region (60), relative to the advancing axis (BB '). In parallel, tensioning the strip (62) to stretch the strip (62); and bonding the fibers of the stretched strip (62) to form the web (10); including.

Description

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

  Such webs are particularly intended for use in the production of parts impregnated with a polymer matrix, for example for buildings, automobiles or any other application.

  Natural fibers have many advantages when compared to synthetic fibers.

  In particular, natural fibers generally have a low density and a relatively low cost and are environmentally friendly. Furthermore, natural fibers are renewable and can therefore be produced without exhausting natural resources.

  Under such circumstances, flax fibers are widely cultivated and used in many fields, especially for producing composite materials. Flax fibers are extracted from flax plant stems and can be utilized either in the form of long fiber bundles, in the form of basic fibers, or in the form of microfibrils.

  Long fiber bundles are generally composed of a collection of basic fibers connected to each other by a natural cement and have a length that can be comprised between 2 mm and 1,000 mm.

  These bundles of fibers have interesting mechanical properties because their Young's modulus is advantageously included between 30 GPa and 50 GPa.

  In order to use natural long fibers, it is necessary to produce, for example, a collection of fibers to form a relatively thick ply, fabric, or canvas. These assemblies are complex and expensive to develop, but sufficient machinery to be suitable for subsequent molding operations to obtain parts (eg, including stacking and orientation of the assemblies) Has a strong cohesion.

French Patent Application Publication No. 2705369

  However, the methods for producing these assemblies are complex and relatively expensive. Therefore, in the field of composite materials, it is preferred to use flax tow, ie fibers having a length between 2 cm and 10 cm. Flax tow can be used in connection with conventional so-called “dry” methods, including pre-processing, carding, burring, and optionally needle punching steps. This leads directly to the development of a mat that does not involve such a set of steps.

  However, the mechanical properties of the resulting nonwoven fabric are insufficient for use to make composite materials. In addition, the resulting material is thick, relatively difficult to handle, and its thickness is highly variable.

  French Patent Application 2,705,369 describes a method for forming a non-woven ply of flax fibers from natural segments of flax. The method includes the steps of establishing a fibrous ply and then connecting the fibers of the ply using flax natural conjugate.

  One object of the present invention is a method for forming a web containing natural long fibers, which is easy to implement and enables to obtain a very thin web having a constant basis weight at a low cost. Is to get the way.

To that end, the present invention is a method of the type described above, comprising the following steps:
-Knitting a plurality of unconnected ribbons of fibers into at least one parallel ribbon comprising natural long fibers;
Disperse adjacent ribbons by field of tips to form parallel fiber strips;
-Tensioning the strip in the tip region parallel to the axis of travel;
Bonding the fibers of the stretched strip to form a web.

The method according to the present invention may include one or more of the following features, considered alone or in any technically possible combination.
The step of bonding the fibers of the strip comprises spraying the solution onto the stretched strip, impregnating the solution between the fibers of the strip, and drying the strip; Including.
-Dispersing the solution is done by spraying drops or forming bubbles containing liquid and foaming agent, which bubbles are deposited on the strip.
The tensioning step is preferably carried out between at least one upstream roller having an outer surface of the metal and at least one downstream roller, preferably made of wood, rubber or polymer; The speed at which the strip downstream is driven is at least 2 times, preferably at least 6 times higher than the speed at which the strip is driven by the upstream roller.
The tip region comprises a plurality of bars transverse to the axis of travel, each transverse bar comprising a plurality of tips, the transverse bars advantageously being movable with the strip is there.
The cross bar travel speed is lower than the speed at which the strip is driven by the or each downstream roller.
- surface density of the tip in the tip region includes the 5 chips portions per 1 cm ² during the 23 chips per part 1 cm ^2.
The method includes a step for forming a plurality of ribbons by lining with several single ribbons prior to the knitting step;
The at least one first unitary ribbon contains exclusively natural long fibers, and the at least one second unitary ribbon is advantageously an additional natural, separate from the natural long fibers of the first unitary ribbon. Fibers and / or naturally derived synthetic fibers and / or artificially derived synthetic fibers and / or mixtures thereof.
-The standard deviation of the unconnected ribbon is less than 20%.
-During the knitting step, the unconnected ribbon is positioned in an adjacent chute that emerges upstream from the tip area.
-In the chute, the ribbon is compressed laterally by the chute converging wall.
-At the exit of the chute, the ribbons come into contact with each other and penetrate each other.
- surface density of the web, after the step for bonding the fibers, less than 500 g / ^{m 2,} advantageously less than even 150 g / ^{m 2.}

The present invention is an apparatus for producing a continuous web of fibers comprising natural long fibers,
An assembly for knitting a plurality of unconnected ribbons of fibers in parallel, the assembly for knitting intended to receive at least one ribbon comprising natural long fibers;
An assembly for forming a strip of fibers comprising an assembly for dispersing a ribbon, including a tip region, and a system for tensioning and stretching the strip in the tip region Assembly of
An assembly for joining the fibers of the strip to form a web;
It also relates to a device including

The device according to the present invention may be considered alone or may include one or more of the following features, in any technically possible combination.
The knitting assembly includes guides delimiting a plurality of chutes positioned side by side, each chute being designed to receive a ribbon;

  The invention further comprises a plurality of continuous webs of fibers comprising at least natural long fibers, wherein the fibers derived from parallel ribbons are dispersed and tensioned to the fibers derived from the parallel ribbons. The parallel fibers relate to a continuous web that includes parallel fibers that are connected together to form a web, the web having a uniform thickness across its width.

A web according to the present invention may be considered alone or may include one or more of the following features, in any technically possible combination.
The web has a surface density of less than 500 g / m2, in particular less than 150 g / m2, and advantageously has a thickness of less than 1 mm.
The web has a length that is 100% greater than its width, and the web is advantageously wound around itself to form a roll;
-Original long fibers are long flax fibers.
-The web contains more than 50 wt% natural fibers.
-The web does not have a synthetic binder that binds the fibers together.

  The invention also relates to a web that can be obtained using the method described above.

  A web according to the present invention may include one or more of the additional features defined above.

FIG. 3 is a flow chart illustrating the main steps of the first method according to the invention. FIG. 2 is a top view of a first device intended to implement the method of FIG. FIG. 3 is a front view of a component with a tip intended for use in the molding assembly of the apparatus of FIG. FIG. 3 is a view similar to FIG. 2 during implementation of the method of FIG. FIG. 5 is a cross-sectional view in the transverse direction along the plane V-V in FIG. 4. FIG. 5 is a cross-sectional view in the transverse direction along the vertical plane VI-VI in FIG. 4. FIG. 3 is an illustration of a web packed in the form of a roll obtained using the method of the present invention. It is a photograph which illustrates the appearance of the 1st web by the present invention. 1 is a side view of an assembly for providing parallel ribbons and an assembly for supplying the ribbons. FIG. 1 is a side view of an assembly for forming a strip obtained from a ribbon. FIG. FIG. 6 is a side view of a joining assembly for joining the fibers of a strip to form a web.

  The present invention will be better understood by reference to the following specification, the merely presented examples, and the accompanying drawings.

  In the following documents, the terms “upstream” and “downstream” are generally understood to be based on the direction of travel of continuously manufactured objects.

  7 and 8 illustrate a first web 10 made using the method according to the present invention. In the example of FIG. 7, the web 10 is advantageously wound around itself to form a roll 12.

  The web 10 according to the present invention comprises natural long fibers positioned parallel to each other and at least one binder that maintains the fibers relative to each other.

  In one embodiment, all of the fibers of the web 10 are composed of natural long fibers. Alternatively, some of the fibers forming the web 10 are composed of additional natural fibers, naturally-derived synthetic fibers, artificially-derived synthetic fibers, or a mixture of these fibers that are different from the natural long fibers. Is done.

  Natural long fibers are advantageously fibers extracted from plants, in particular flax fibers. Alternatively, the natural long fibers are sisal, jute, hemp, kenaf fibers.

  The additional natural fibers are selected, for example, from cotton, wool, silk, sisal, hemp fibers, or mixtures thereof.

  Naturally derived synthetic fibers are selected from, for example, regenerated cellulose fibers, particularly viscose, cupra, and / or modal fibers, alginate viscose fibers, lyocell, PLA (polylactic acid) fibers, and mixtures thereof. The

  Synthetic fibers are formed from petroleum derivatives or molecules from green chemistry (eg, ethylene derived from bioethanol). The synthetic fibers are selected from polyethylene and / or polyolefin fibers such as polypropylene, polyester, polyamide, polyimide fibers, and mixtures thereof. The synthetic fiber may be a bicomponent fiber formed by a polymer and a copolymer, and the polymer and the copolymer have different melting points.

  Advantageously, the proportion of naturally occurring long fibers in the web 10 is greater than 50% of the total weight of the fibers of the web 10.

  Advantageously, the natural long fibers are long natural flax fibers.

  Long flax fibers are derived from flax plants of the "Ama" family. These fibers mechanically break the stem during the crushing operation, and then separate the long fibers, short coarse fibers tow and other components of flax from the periphery of the flax stem. Extracted.

  The long fibers obtained in this way advantageously have a length comprised between 2 mm and 1,000 mm. The meaning of “long fibers” in the present invention means that the fibers are advantageously composed of a longitudinal assembly of elementary fibers joined together by natural cement.

  Long fibers generally constitute bundles that can reach lengths up to 1 meter. Some of the natural long fibers of the web 10 have a length greater than 50 cm, in particular between 50 cm and 80 cm.

  Long fiber bundles generally have a diameter comprised between 10 and 100 microns.

  The binder that binds the different long fibers to one another is advantageously composed of natural zygote from plants, in particular natural flax zygote when the long fibers are long flax fibers.

  Alternatively, the binder is an adhesive or resin, in particular a synthetic binder such as latex, and / or a naturally occurring binder other than flax segments, such as a starch-based binder.

  According to the present invention, the web 10 has a width that is much larger than its thickness and much smaller than its length.

  Thus, the width of the web is for example greater than 30 mm, in particular comprised between 30 mm and 2,000 mm, advantageously comprised between 100 mm and 2,000 mm.

The thickness is less than 0.1 times its width, in particular less than 1 mm, in particular less than 50/100 ^th mm, advantageously less than 10/100 ^th mm.

The web 10 obtained using the method of the present invention has a uniform thickness. Accordingly, the standard deviation of the average thickness of each longitudinal strip of the web 10 formed by longitudinal strips corresponding to 1/10 ^th of the width of the web 10 is 5% based on the average thickness of the web 10 Less than, in particular less than 2%.

  The average surface density of the web 10 is low. This surface density is less than 500 g / m 2, in particular less than 150 g / m 2, or even 100 g / m 2 and is preferably comprised between 30 g / m 2 and 100 g / m 2.

  The surface density is constant as it moves along the width of the web.

  The length of the web 10 is much larger than its width. In particular, the length of the web 10 is greater than 10 m, in particular greater than 100 m. Accordingly, the web 10 can be wound in the form of a roll 12 having a diameter greater than 100 mm, advantageously up to approximately 600 mm.

  As illustrated in FIG. 8 and in light of the manufacturing method according to the present invention, the fibers of the web 10 are substantially aligned in the longitudinal forming direction A-A '.

  Thus, at least 50% of the fibers of the web 10 are parallel to the longitudinal direction A-A ', perpendicular to the winding axis of the web 10 when the web 10 is in the form of a roll 12. Accordingly, the long fibers of the web 10 are generally positioned parallel to each other and connected to each other by a binder to ensure the mechanical binding force of the web 10.

  The web 10 has a sufficient mechanical binding force to allow its handling, particularly during subsequent impregnation and overlay operations, forming a multi-directional mat. Thus, the web 10 is gripped by the user's hand (and once impregnated if not porous) and by a mechanical handler, in particular a suction handler, while maintaining its mechanical strength without undergoing mechanical degradation. obtain. The web 10 is self-supporting.

  The binding force of the web 10 is determined in the transverse direction perpendicular to the preferred orientation direction AA ′ of the fibers, and the average breaking force measured according to the standard ISO 13934-1 for a 50 mm wide sample is advantageously Is a binding force that is greater than 0.1N, in particular between 0.2N and 2N, for example approximately 0.5N. Surprisingly, a web 10 comprising natural long fibers and having both a uniform thickness and a very pronounced orientation of the long fibers but with sufficient cohesiveness to be handled. Is obtained by using the method according to the invention.

  To that end, the web 10 is formed from longitudinal ribbons of fibers that are knitted and distributed in parallel to form strips of parallel fibers, and then the fibers of the strips are combined.

  The “ribbon” in the present invention means a longitudinal member including an aggregate of fibers, particularly long fibers. Ribbons are obtained, for example, by a teaser process or a card process, and then the individual fibers are tensioned and then the individual fibers are grouped together to produce a longitudinal bond.

  The thickness of the ribbon is generally about the same as its width. The thickness is included, for example, between 0.5 and 2 times its width.

  Ribbons may advantageously be obtained from a single ribbon that is aligned by being superimposed on top of each other. In the illustrated embodiment, the width of the ribbon is less than 30 mm, for example. The thickness of the ribbon is comprised between 10 mm and 40 mm, for example greater than 15 mm.

  The length of the ribbon is greater than 800 m, in particular comprised between 850 m and 1700 m.

  The lining operation involves superimposing at least two unitary ribbons having the same or different qualities, then dispersing them in the chip area while keeping them tensioned, and thereafter Consisting of reconstructing a single lined ribbon.

  The number of linings can vary. This number is included between 1 to 15 linings.

  The mass per unit length of a ribbon designed to be used in the method according to the invention is comprised for example between 10 g / m and 40 g / m.

  The flow chart of FIG. 1 summarizes the steps of the first method for producing a web 10 according to the present invention.

  Such a method is implemented, for example, in an apparatus 14 for producing a web 10 which is shown diagrammatically in FIG. 2 or FIG.

  As illustrated in FIGS. 2 and 4, the device 14 is knitted to position a plurality of fiber ribbons including at least one natural long fiber ribbon and the ribbons parallel to each other. Assembly 22 for carrying out the operation.

  With reference to FIGS. 2 and 10, the apparatus 14 further combines an assembly 24 for forming a continuous fiber strip from the ribbon and the fibers of the strip, as shown in FIGS. And an assembly 26 for forming.

  The device 14 further includes an assembly 28 for packaging the web 10 and storing it in the form of rolls 12 in particular.

  As illustrated by FIG. 9, the providing assembly 20 advantageously includes an area for storing the top of the ribbon 32.

  The ribbon 32 is for example stored in the creel, preferably in the form of a top.

  The top is obtained, for example, by delivering a ribbon 32 contained in a can having a diameter comprised between 30 cm and 1 m, in particular a diameter comprised between 40 cm and 60 cm. Once the can is filled, the ribbon 32 is compressed from the top, the can is removed and the ribbon is joined. The top then has the dimensions of a can with a height comprised between 30 cm and 80 cm, in particular a height equal to approximately 40 cm. The top mass is comprised, for example, between 15 kg and 40 kg.

  To realize the method according to the invention, the ribbon 32 provided in the assembly 20 is advantageously lined with a single ribbon to obtain a homogeneous ribbon 32 in terms of mass per unit length. Is the ribbon 32 obtained by the above. Accordingly, the mass per unit length of the ribbon 32 is advantageously comprised between 10 g / m and 40 g / m. The standard deviation between the mass per unit length of different ribbons 32 intended to form the same web 10 is less than 20%.

  In the case where the web 10 is composed of natural long fibers, such as long flax fibers, all of the ribbons 32 are natural long fiber ribbons that are advantageously obtained by lining a single ribbon of natural long fibers.

  If the web 10 includes additional natural fibers, naturally derived synthetic fibers, or artificially derived synthetic fibers, the at least one ribbon 32 may be a single ribbon composed of natural long fibers and additional natural fibers. It is formed from at least one unitary ribbon composed of fibers, naturally derived synthetic fibers, or artificially derived synthetic fibers.

  In all cases, the single ribbons are grouped by each being dispersed (not shown) in the chip region, then tensioned and overlaid on top of each other. The number of lining operations is comprised between 1 and 15, preferably between 2 and 4.

  The ribbon 32 is then stored in the form of a top and positioned on the ground or on a holder. A plurality of ribbons 32 are provided in parallel.

  As illustrated by FIGS. 2, 9, and 5, the knitting assembly 22 is a guide 40 for delivering ribbons 32 in parallel and is intended to supply the forming assembly 24. , A guide 40 and a supply mechanism 42 for supplying the individual ribbons 32 to the guide 40.

  The supply mechanism 42 includes a guide roller 44 and a pair of supply rollers 80A and 80B, each designed to drive each ribbon 32 from the bobbin 30 toward the guide 40.

  As illustrated by FIGS. 2 and 5, the guide 40 includes a plurality of chutes 46 positioned in parallel.

  The chutes 46 are advantageously arranged next to each other. Each chute 46 is bounded by two side walls 48 and a bottom wall 49. Each chute 46 receives an individual ribbon and toward the forming assembly 24 for forming the web by forming the individual ribbon into a roll parallel to axis BB ′. , Designed to deliver the individual ribbons.

  Thus, each chute 46 extends longitudinally between the inlet opening 50 and an outlet opening 52 positioned opposite the forming assembly 24.

  In the example illustrated in FIGS. 4 and 5, the guide 40 includes a plurality of chutes 46 that converge from upstream to downstream. The cross section of the chute 46 across the inlet opening 50 is larger than the cross section of the chute 46 at the outlet opening 52.

  Thus, each ribbon 32 inserted into the chute 46 converges toward the outlet opening 52 and is guided in contact with the side walls 48 on both sides of the ribbon 32 at the opening 52 as illustrated in FIG. The

  The inclination angle of each chute 46 with respect to the axis BB ′ increases from the chute 46 to the chute 46 while moving from the axis BB ′ toward the outside of the guide 40. go. The width of each chute 46 at the inlet opening 50 is at least 10% greater than the width of the chute 46 at the outlet opening 52. This allows natural homogenization in the transverse compaction of the fibrous bundle. At the exit of the chute, the ribbons compressed laterally by the converging walls of the chute have a tendency to slightly expand, which means that the ribbons are knitted to contact each other or are slightly To penetrate.

  The maximum width of each chute 46 at the outlet opening 52 is included, for example, between 10 mm and 40 mm.

  The thickness of the side wall 48 is less than 5 mm and limits the separation between the different ribbons 32 while entering the molding assembly 24.

  As illustrated in FIGS. 2, 4, and 10, the molding assembly 24 is a tip region intended to disperse ribbon fibers to form a continuous strip 62, as shown in FIG. 4. 60 and a system 64 for tensioning and stretching the strip 62 in the tip region 60.

  As illustrated by FIGS. 4, 6, and 10, the tip region 60 is parallel and includes a plurality of rows 70 of tip portions 72 in the transverse direction with respect to the advancing axis BB ′. Including. Row 70 of tip portions 72 advantageously includes between 2 and 16 tips per cm, or between 6 and 40 tips per inch.

  The tip part 72 has a height larger than the height of the ribbon, and has a height included between 40 mm and 60 mm, for example.

  Rows 70 of tip portions 72 are supported by individual transverse bars 74 positioned parallel to axis B-B '. The assembly formed by each bar 74 and its tip 72 is commonly referred to as a “gil”.

  The continuous bars 74 are advantageously arranged in contact with each other. Each bar 74 advantageously carries at least one row of tip portions 70, in particular two rows of tip portions 70, as shown in FIG.

  The tip portions 72 of the first row 70 are slightly biased in the transverse direction with respect to the axis B-B ′ with respect to the tip portions 72 of the second row.

  The row 70 of tip regions 60 is advantageously movable along the axis B-B '. Each bar 74 is moved by a helical screw to perform a square movement.

  Accordingly, the bar 74 advances with the strip 62 to the end of the tip region 60. The bar 74 then returns to the starting point of the chip area 60.

  To that end, as illustrated by FIG. 10, the tip region 60 spans a length L1 along the axis BB ′ and between the upstream end position and the downstream end position, the axis B− It includes a mechanism 75 for moving the rod 74 longitudinally along B ′.

  The moving mechanism 75 further includes means for returning each bar 74 from the downstream end position to the upstream end position.

  To that end, each bar 74, when positioned at the upstream end position, is vertically between the retracted return position and the active stitching position of the fibers in the face of the strip 62. It is movable.

  At the downstream end position, each strip 74 is movable vertically between an active stitching position and a retracted position.

  The mechanism 75 moves each strip 74 from the upstream to the downstream in the direction of travel of the strip 62 while keeping the bar 74 in its operating position, and then keeps the bar 74 in its retracted position. Each bar 74 is moved from the downstream position to the upstream position in the direction opposite to the travel of the strip 62.

  The length L1 of the tip region 60 is greater than 80 cm, in particular from 100 cm to 80 cm, in order to accommodate natural long fibers and to allow the natural long fibers to be arranged parallel to the axis BB ′. Included between.

  As illustrated by FIGS. 2 and 10, the tensioning system 64 includes a tip region between the feeder assembly 22 and the tip region 60 and between the assembly 26 that couples to the tip region 60, respectively. 60 includes at least one upstream roller 80A, 80B and at least one downstream roller 82A, 82B positioned transversely on either side of 60.

  In the example illustrated in FIG. 10, the tensioning system 64 includes a pair of upstream rollers 80A, 80B, one positioned vertically above the other. The upstream rollers 80A and 80B are attached so as to rotate around an axis perpendicular to the axis B-B '.

  The upstream rollers 80A, 80B advantageously have a metal outer surface, in particular a chromium outer surface. The upstream roller has a gap having a height smaller than the height of the ribbon 32, particularly a height smaller than 20 mm, and flattens the ribbon 32 so as to be pinched.

  The gap 84 is advantageously arranged horizontally across the tip portion 70 and horizontally across the outlet opening 52 of the chute 46 to crush the ribbon 32 and in the tip region 60 the tip portion. Allows distribution of fibers from the ribbon 32 via 72 rows 70.

  In the example shown in FIG. 10, the tensioning assembly 64 includes at least two downstream rollers 82A, 82B positioned on top of each other.

  The rollers 82A and 82B are mounted so as to rotate around an axis perpendicular to the axis B-B '.

  The roller 82A is formed of, for example, a cylinder of wood, rubber, or polymer. The roller 82A advantageously has a diameter that is larger than the diameter of the roller 82B. Roller 82B has a metal outer surface, eg, a chromium outer surface.

  The first pair of rollers 80A, 80B and the second pair of rollers 82A, 82B are such that the speed determined at the outlet of the downstream rollers 82A, 82B of the strip 62 formed in the tip region 60 is the upstream roller 80A. , Driven to be at least twice, especially 6 times, preferably between 6 and 20 times the speed of the strip 62 at the outlet of 80B.

  This allows the strip 62 to be tensioned and stretched to adjust its thickness and basis weight.

  As illustrated by FIG. 11, the joining assembly 26 dries the strip 90 with a device 90 for spreading a liquid or foaming solution, a space 92 for diffusing the solution onto the strip 62, and the strip. Device 94 for.

  The solution is advantageously formed by an aqueous solution. In the first embodiment, the aqueous solution is composed of water. Alternatively, the aqueous solution contains water and a nonionic surfactant such as polyvinyl alcohol to form bubbles.

  The proportion 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, the dispensing device 90 comprises at least one nozzle 96 specifically designed to eject the solution in the form of drops, mist or bubbles, and a transverse body 98 for guiding the solution. Including.

  Advantageously, the nozzle 96 appears in the body 98. The body 98 has a lower opening positioned opposite the conveyor belt 100 of the strip 62, designed to support and drive the strip 62 between the spreading device 90 and the drying device 94. .

  The drying device 94 includes a heating device 102, such as a convector provided with a heating plate, and a steam suction assembly 104, including a hood 106, for example.

  The intermediate space 92 is positioned between the spreading device 90 and the drying device 94. The length is included between 0.5 m and 2 m, for example.

  In this example, the web 10 is packed in the form of a roll 12. Accordingly, the packaging assembly 28 includes an axle or mandrel 110 for wrapping the web and means (not shown) for rotating the axle to allow formation of the roll 12.

  In one alternative, the packaging assembly 28 includes a device for delivering a separator sheet that is wound together with the web 10 and designed to separate two successive layers of the web 10 in the roll 12. .

  A method for manufacturing the web 10 according to the present invention will now be described.

  As illustrated by FIG. 1, the method first includes a step 120 for providing an uncoupled ribbon 32 and then a step 122 for knitting the ribbon 32 in parallel in a knitting assembly 22. Including.

  The method then forms the continuous strip 62 by dispersing the ribbon 32 in the forming assembly 24 and then forms the web 10 in the assembly 26 where the strip 62 is locked and joined. Step 126 is included.

  The method finally includes a step 128 for packing the web 10.

  This method is advantageously carried out continuously, i.e., steps 122 to 128 are carried out continuously from one to the next without interruption.

  In step 120, a plurality of parallel ribbons 32 are formed, for example, by winding them in the form of a top 30 of a teasered ribbon positioned on the holder or on the ground, preferably on the creel. .

  As specified above, the ribbon 32 is advantageously obtained by lining a single ribbon, the ribbon 32 comprising, for example, a single ribbon of natural long fibers, Alternatively, it is composed of a mixture of a single ribbon of natural long fibers and at least one single ribbon of additional natural fibers, naturally derived synthetic fibers, or artificial synthetic fibers.

  The size of the ribbon 32 is substantially constant so that the standard deviation between the sizes of the ribbons 32 is less than 20%.

  Then, during the knitting step, a plurality of uncoupled ribbons 32 are conveyed in parallel from the providing assembly 20 toward the forming assembly 24 via the knitting assembly 22.

  The number of parallel ribbons 32 is comprised between 2 and 100, in particular between 8 and 15 ribbons, to produce a web having a width comprised between 10 mm and 2,000 m.

  Each ribbon 32 is then driven by a supply roller 44 and directed toward the inlet opening 50 of the chute 46.

  Thus, the guide 40 receives a plurality of parallel ribbons 32 and each ribbon 32 is received in a respective chute 46. Next, the ribbon 32 is driven through the chutes 46 by the upstream rollers 80 </ b> A and 80 </ b> B up to the outlet opening 52.

  During the forming step 124, the different ribbons 32 are initially pinched in the gap 84 between the upstream rollers 80A and 80B to reduce the ribbon thickness and distribute the ribbons laterally.

  Then, the fibers derived from different adjacent ribbons 32 are inserted into the chip region 60 while being stretched by the downstream rollers 82A and 82B.

  To that end, the rod 74 positioned at the upstream end position is such that the tip portion 72 of each ribbon 32 is viewed as passing through a parallel array of fibers and viewed vertically. From its retracted position to its vertically deployed position so as to form a uniform strip 62 having a thickness less than the thickness.

  The rod 74 then moves longitudinally with the fibers of the strip 62 along the tip region 60 to the downstream tip portion.

  During this transition, the fibers form a strip 62 having a uniform thickness across its width.

  Further, in light of the relative speed of rotation of the upstream rollers 80A, 80B and downstream rollers 82A, 82B, in the tip region 60, the strip 62 is tensioned to stretch the strip 62 and the length of the fiber in a single direction. This produces directional alignment.

  By providing fibers in the form of uncoupled ribbons 32, dispersion in the upstream rollers 80A, 80B, passage in the tip region 60, and tension by the downstream rollers 82A, 82B, a substantially uniform thickness is achieved. A strip having a low basis weight, in particular a basis weight of less than 150 g / m 2 and having a substantially parallel alignment of at least 50% of the number of fibers or 80% of the number of fibers. It becomes possible to form.

  At the exit of the tip region 60, the strip 62 is clamped between the downstream rollers 82A and 82B and conveyed toward the assembly 26 to be joined.

  The stretched strip 62 is not transversely cohesive before passing through the assembly 26 to be joined. Thus, the different fibers making up the stretched strip 62 can be separated from each other by simple, manual pressure when exiting the downstream rollers 82A, 82B upstream of the assembly 26 to be joined.

  Thus, the stretched strip 62 reinforces its transverse binding force through the joining assembly 26.

  First, the strip 62 is sprayed with a solution designed to promote bonding between fibers in the dispersion device. In the first embodiment, the aqueous solution is sprayed in the form of droplets, for example in the form of a mist guided via the body 98.

  In one alternative, the solution is in the form of bubbles that are deposited on the strip 62 via the body 98.

  The strip 62 then passes through the intermediate space 92 and allows the solution to diffuse between the fibers by capillary action. When the solution is formed by bubbles, the bubbles are broken and the liquid thus formed diffuses through the fibers.

  This operation results in partial dissolution of the natural cement that binds the fibers together.

  The liquid-impregnated strip 62 then enters the heating device 94. The strip 62 is heated to a temperature above 70 ° C., in particular to a temperature comprised between 100 ° C. and 180 ° C., allowing the liquid part of the solution to evaporate.

  This evaporation is convenient for the suction generated by the device 104. The solubilized natural cement is re-solidified, thereby increasing the binding force between the fibers, and in particular, securing the binding force in the transverse direction to form the web 10.

  If the web 10 is composed of less than 50% long flax fibers, the natural flex joint quality does not necessarily provide sufficient transverse cohesion for the web 10. In that case, as described above, a small proportion of additional binder may be added to the solution.

  In the packaging step, the web 10 is rolled onto itself to form a roll around the mandrel 110. In one alternative, an intermediate sheet is inserted between different layers of the web 10 to avoid degradation of the web 10.

  As specified above, the set of steps described above continues from the knitting of the ribbons 32 in parallel until the web 10 is packaged after the web 10 is formed. The speed of web travel in all operations is greater than 1 m / min, in particular comprised between 1 m / min and 50 m / min.

  When a sufficiently long web 10 is wound around the mandrel 110 in the form of a roll 12, the roll 12 can be easily and economically produced, for example, to produce impregnated panels. Can be transported.

  According to the present invention described above, a web 10 containing high quality natural long fibers, especially long flax fibers, can be formed very economically. This web 10 has a small thickness and has a basis weight that is below 500 g / m2, in particular below 150 g / m2, or even comprised between 30 g / m2 and 100 g / m2. The web 10 further has a uniform thickness across its width and a very pronounced orientation of fibers that are substantially aligned and parallel to each other.

  In particular, in contrast to flax fiber fabrics, these fibers are not twisted or entangled. Thereafter, the web 10 does not have any uprights, which limits the thickness of the web 10 and allows a minimum amount of resin to be used during panel manufacture.

  Furthermore, this manufacturing method is very easy to implement because it does not include a spinning step and can therefore be performed at a competitive price. The web 10 obtained after the bonding step is cohesive and self-supporting so that it can be transported without risk of degradation, which is also from a cost and handling standpoint. Represents an advantage.

  Furthermore, since the formed web 10 is made mainly from natural fibers, especially long flax fibers, or exclusively as a base, the web 10 is completely biodegradable and uses artificial binders. Without, it can be made using only natural conjugates formed from natural fibers, for example by hemicellulose and lignin.

  The invention described above makes it possible to produce a web 10, i.e. a planar collection of fibers, having a uniform thickness and excellent uniformity in both the longitudinal and transverse directions.

  This web 10 is obtained from ribbons 32 or long fiber tufts, in particular flax tufts, having a length that is much greater than its width and can be considered as infinite.

  Ribbon 32 results from a complex pretreatment process that allows long fibers to be extracted and separated from tows, which are short and coarse fibers. These ribbons 32 are obtained by, for example, a cheeseer process or a card process.

  As specified above, in order to obtain good transverse uniformity, a ribbon 32 having a thickness approximately close to its width and having a circular or pseudo-elliptical cross section is uniformized. There is a need. These ribbons 32 are arranged side by side in a guide 40 that delimits a plurality of converging chutes 46 so that the ribbons 32 are knitted to contact each other or the ribbons 32 slightly penetrate each other. Let

  As a result, the ribbon 32 is flattened and meshed, thereby eliminating the wrinkles generated by the ribbon 32 and obtaining a flat set that is uniform in the transverse direction.

  The nature of the chutes 46, in particular the degree of convergence and the optimum distance between the chutes 46, are optimized based on the ribbon size to ensure a lateral expansion effect.

  As specified above, the mass per unit length of the ribbon 32 is high, for example comprised between 10 g / m and 40 g / m. To obtain good longitudinal uniformity, the molding assembly 24 includes a system 64 for tensioning and stretching the strip and a tip region 60 having a length greater than the maximum length of the long fibers. And both.

  Therefore, since the pair of downstream rollers 82A and 82B has a driving speed larger than the driving speed of the upstream rollers 80A and 80B, each tip portion of the fiber squeezed between the downstream rollers 82A and 82B is captured by the intake assembly. Driven at a speed faster than the speed of the strip 62 formed at the 22 outlets.

  Although the tip of the fiber has not yet reached the downstream rollers 82A and 82B, the fiber drives the adjacent fiber that is in contact with itself, which is extremely In order to prevent the occurrence of a non-uniform web, the tip portion 72 of the tip region 60 blocks the fibers adjacent to the driven fibers. In this respect, the row 70 of tip portions 72 supported by the bar 74 and parallel to the tip region 60 moves at substantially the same speed as the driving speed of the strip 62 by the upstream rollers 80A, 80B.

  Furthermore, when each downstream roller 82A, 82B has an outer surface of wood, rubber, or polymer, the fibers pinched between the rollers 80A and 80B held upstream in the tip region 60 are driven. And can slide between the downstream rollers 82A and 82B without breaking.

Thus, it is possible to obtain a substantially parallel alignment with a low basis weight, in particular less than 150 g / m ² and at least 50% by number of fibers and thus 80% by number of fibers.

  The resulting stretch is uniform and avoids fiber breakage.

Advantageously, the surface density of the tip 72 in the chip area, 1 contains a square inch per 36 pieces of the tip between the tip of 144 per square inch, or, cm ² from the tip of five per cm ² It is included between 23 tips.

It should be noted that the method according to the invention is advantageously applied to ribbons comprising at least a part with long fibers whose length is greater than 20 cm, in particular greater than 50 cm.

Claims (17)

A method for producing a continuous web (10) of fibers comprising natural long fibers having a length at least partly greater than 20 cm, in particular greater than 50 cm, comprising the following steps:
-Knitting a plurality of unconnected ribbons (32) of fibers into at least one parallel ribbon (32) containing natural long fibers;
-Dispersing adjacent ribbons (32) by means of tip regions (60) to form parallel strips of fibers (62);
-Tensioning the strip (62) in the tip region (60) parallel to the axis of travel (BB ');
-10 steps of bonding the fibers of the stretched strip (62) to form the web (10).   -The step for bonding the fibers of the strip (62) comprises spreading a solution on the stretched strip (62); impregnating the solution between the fibers of the strip; The method of claim 1, comprising drying the strip (62) to form a web (10).   The spraying of the solution is carried out by spraying drops or by forming bubbles containing liquid and foaming agent, the bubbles being deposited on the strip (62); The method according to claim 2.   The tensioning step is preferably at least one upstream roller (80A, 80B) having an outer surface of metal and preferably at least one downstream roller (82A) made of wood, rubber or polymer; The speed at which the strip (62) is driven downstream of the downstream roller (82A) is higher than the speed at which the strip (62) is driven by the upstream rollers (80A, 80B). 4. A method according to any one of the preceding claims, wherein the method is at least 2 times, preferably at least 6 times higher.   The tip region (60) includes a plurality of bars (74) transverse to the advancing axis (BB '), each transverse bar (74) comprising a plurality of tip portions ( 72), wherein the transverse bar (74) is advantageously movable with the strip (62).   The method according to any one of the preceding claims, comprising the step of forming the plurality of ribbons (32) by lining with several unitary ribbons prior to the knitting step. The method described.   The at least one first unitary ribbon comprises exclusively natural long fibers, and the at least one second unitary ribbon is advantageously distinct from the natural long fibers of the first unitary ribbon. The method according to claim 6, comprising additional natural fibers and / or naturally derived synthetic fibers and / or artificially derived synthetic fibers and / or mixtures thereof.   A method according to any one of the preceding claims, wherein the standard deviation of the unconnected ribbon (32) is less than 20%.   -In the knitting step, the unconnected ribbon (32) is positioned in an adjacent chute (46) that emerges upstream from the tip region (60). The method according to claim 1. - wherein the surface density of the web (10), after said step of coupling said fibers, less than 500 g / ^{m 2,} advantageously less than 150 g / ^{m 2,} one of claims 1 to 9 one The method according to item.   The method according to any one of claims 1 to 10, wherein the length of the tip region (60) is greater than or equal to the maximum length of the natural long fibers. An apparatus (14) for producing a continuous web (10) of fibers comprising natural long fibers having a length at least partly greater than 20 cm, in particular greater than 50 cm,
An assembly (22) for knitting a plurality of unconnected ribbons (32) of fibers in parallel, the knitting intended to receive at least one ribbon (32) comprising natural long fibers An assembly (22) for
An assembly (24) for forming a strip of fiber (62), comprising a tip region (60), for dispersing the ribbon (32), and said strip (60) in said tip region (60); An assembly (24) for molding comprising a system (64) for tensioning said strip (62) to stretch said strip (62);
An assembly (26) for bonding the fibers of the strip (62) to form the web (10);
A device (14) comprising:   The knitting assembly (22) includes a guide (40) delimiting a plurality of chutes (46) positioned side by side, each chute (46) being designed to receive a ribbon (32); The apparatus according to claim 12.   A continuous web (10) of fibers comprising at least natural long fibers, wherein a plurality of parallel webs obtained by dispersing fibers originating from parallel ribbons and tensioning the fibers originating from said parallel ribbons; Including parallel fibers, connected to each other, having a uniform thickness across its width, and at least a portion of the long fibers having a length greater than 20 cm, in particular greater than 50 cm. A continuous web (10) having:   The web (10) according to claim 14, having a surface density of less than 500 g / m2, in particular less than 150 g / m2, advantageously having a thickness of less than 1 mm.   16. A web (10) according to claim 14 or claim 15, having a length that is 100% greater than its width, and advantageously wound around itself to form a roll (12). The web (10) according to any one of claims 14 to 16, wherein the original long fibers are long flax fibers.

Images