WO2015158483A1

WO2015158483A1 - Method and device for spreading fiber strands

Info

Publication number: WO2015158483A1
Application number: PCT/EP2015/055689
Authority: WO
Inventors: Jürgen Keppel; Andy Rakovac; Thomas Holtmann
Original assignee: C. Cramer, Weberei, Heek-Nienborg, Gmbh & Co. Kg
Priority date: 2014-04-16
Filing date: 2015-03-18
Publication date: 2015-10-22
Also published as: DE102014105464A1; JP2017528606A; EP3132074A1; US20170037545A1; EP3132074B1

Abstract

The invention relates to a method and a device for spreading a fiber strand (2) consisting of continuous multifilament fibers to a strip-type fiber strand (2') of larger final width and smaller final thickness. The fiber strand is spread in the spreader station (5) by means of at least one sonotrode (52) which contacts the fiber strand (2) and passes vibrations in the ultrasonic frequency range into the fiber strand (2). The fiber strand thereby evenly widens transversely to the fiber longitudinal direction.

Description

Method and device for spreading a fiber strand

The invention relates to a method and a device for spreading a fiber strand, which has an initial width and an initial thickness, to a band-shaped fiber strand having a larger end width and with a smaller final thickness, wherein the fiber strand consists of endless multifilament fibers. The spreading of fiber strands has long been known and is used in fiber strands of polymer fibers to improve physical properties, since the spreading, for example, eliminates twists of the filaments in the fiber strand and a fiber strand is achieved with rectified filaments. In the case of fiber strands made of carbon fibers, striving in particular strives to achieve a lower basis weight of the fabrics or scrims produced from these fiber strands. Such fabrics or scrims can be used in particular for composites. Typically, such a composite material is formed by coating a fibrous web or scrim or other fabric of reinforcing filaments, such as carbon fibers, with a thermoplastic matrix and compressing such precursor (prepreg). In order to keep the weight of the resulting composite as low as possible, are used for the textile fabrics, in particular fiber strands with the smallest possible thickness and unchanged good mechanical properties, such as tensile strength. A reduction in thickness and broadening of the fiber strands is obtained by spreading the fiber strands.

In known devices, a spreading of a fiber strand is achieved in different ways. One possibility is to charge the fiber strand in an electric field, whereby the filaments mutually repel and separate in this way. Such a spreading method is energy-intensive and can only be applied to fiber strands which are electrically conductive and thus electrically rechargeable. Glass or textile fibers, for example, must be impregnated before such spreading process.

In another process principle, air is blown into a fiber strand in the longitudinal direction to open the strand. The filaments in a fiber strand are surrounded by a size, which facilitates the handling of the fiber strand in various processing operations, such as in weaving. This sizing glued the fibers and makes it difficult in this Einblasverfahren a uniform spreading of the fiber strand. In addition, removal of sizing is difficult because, on the one hand, different sized sizings are used and, on the other hand, this sizing causes damage, e.g. fracture-endangered carbon fibers prevented during further processing.

In a further variant of the method, vibrations are introduced into the fiber strand for spreading. Thus, the two documents US Pat. No. 5,042,111 and US Pat. No. 3,704,485 describe a method in which sound waves are generated by a loudspeaker and a vibrating air cushion spreads a fiber strand. Such a method is very difficult to control and leads to uneven end widths of the fiber strand. Better transmission of the vibrations to a fiber strand is achieved when the sound is introduced into a liquid, such as water. This is described in the documents US 5,511 1, 395 and EP 1 652 978 B1. A disadvantage of this method, however, is that the sizing surrounding the filaments changes in the water bath. This can also lead to a chemical change depending on the nature of the size. In any case, however, the ratio of fiber to sizing is influenced in the fiber strand, which is not desirable. A further disadvantage of the method is that the spread sliver emerging from the water must be dewatered and dried. Such a drying process is energy-intensive, so that a drying is preceded by a mechanical drainage. To the Dewatering of the tape in the device according to EP 1 652 978 B1, the splayed belts are fed to a squeezing arrangement. It has been shown that with such a squeezing process in addition to the drainage also an additional spreading takes place. Further developments were therefore concerned with the spreading of a dry fiber strand with similar arrangements, in particular a zig-zag guidance of the fiber strand over different rolls and optionally via vibration rods. Also in this method, the fiber strand is heated before, during and after spreading by means of a heater to thermally or chemically break up the sizing existing on the fibers, which on the one hand affects the sizing and on the other hand causes energy costs. However, a change in sizing is not desirable because the sizing in the fiber strand is needed for further processing operations. The object of the present invention is therefore to provide a more cost-effective method of spreading fiber strands, which is applicable to fiber strands of different nature and in particular does not affect the ratio of sizing to fiber in the fiber strand.

This object is achieved by a method having the features of claim 1. For carrying out such a method, a device having the features of claim 8 can be used. The subclaims describe advantageous process or device features.

The inventive method is used for spreading a fiber strand, which has an initial width (extension in the y direction) and initial thickness (expansion in the z direction), to a band-shaped fiber strand with a larger Endbereite and with a lower final thickness, ie a broadening of the fiber strand transverse to his Longitudinal direction (x-direction). The method is applicable to all fiber strands of endless multifilament fibers, ie on Ceramics fibers such as silicate, basalt, glass, silicon carbide, metals such as steel, aluminum, titanium, aramid such as Kevlar, but also for polymer fibers. The aim of the spreading can be solely the improvement of the physical properties or in particular the lower basis weight. Multifilament fibers having a different number of filaments can be used, from 1 K fibers containing 1000 filaments, but also 50,000 filaments having 50,000 filaments, for example. In the present method, the fiber strand to be spread is moved starting from a development in the fiber longitudinal direction, passed through a spreading station, where a spreading takes place and then the spread band-shaped fiber strand is wound or introduced immediately into the further manufacturing process. In accordance with the invention, the fiber strand is exposed to vibrations in the spreading station without the use of a fluid, such as air cushion or a liquid. In this case, ultrasonic waves are used, which are transmitted by a sonotrode. In this case, the sonotrode contacts the fiber strand from above or below. The mechanical vibrations are introduced in the z-direction, ie perpendicular to the longitudinal direction (x-direction) of the fiber strand, whereby this widens in the transverse direction (y-direction). The oscillations used here have a frequency of 15 to 80 kHz, preferably between 20 and 40 kHz. At frequencies less than 20 kHz, very large sonotrodes are to be used, which significantly increase the overall device and make it more expensive. Although the sonotrode decreases for the initiation of frequencies greater than 40 kHz, the process tolerance decreases to the same extent.

The ultrasound transducers are equipped with interchangeable sonotrodes, which initiate the high-frequency mechanical oscillations (ultrasound) into the fiber strand via their end faces. In the spreading station, one or more sonotrodes can be used. As the fiber strands pass through the spreader station, the fiber strands may become sonotrodes wrap around, wherein the angle of attack is changeable to the contact surface of the sonotrode.

In a fiber strand, the individual filaments are surrounded by a size. The composition of the size varies according to the manufacturer of the fibers. Adhesives are known on the epoxy. Such a sizing facilitates the processing of the fiber strands. For example, carbon fibers have a high tensile strength in the longitudinal direction, but can break very easily transversely to the fiber longitudinal direction. Disadvantageously, the sizing causes the fibers to stick together, making it difficult to spread the fiber strand. Advantageously, the sizing does not change on the filaments of the fiber strand in the spreader station. On the one hand, there is no chemical change, since the sizing does not come into contact with any medium. On the other hand, the ratio of fiber to sizing does not change throughout the process. The vibrations induced by the sonotrode lead to friction in the fiber strand, which generates heat and softens the sizing and facilitates spreading of the fiber strand. Conductive fibers, such as carbon fibers, additionally contribute to heat conduction. Since this softening of the size takes place only in the region of the contact surface of the sonotrode and immediately thereafter a cooling of the fiber strand takes place again, the size / fiber ratio does not change.

As it passes through the spreading station, the fiber strand is kept under tension. This state of tension is adjustable and preferably the same over the entire process in order to achieve the most uniform possible spreading. The achievable spread width is dependent on this state of stress. The higher the tension, ie the firmer the fiber strand is held, the lower the spread width. When the voltage state is kept constant and the oscillation frequency is constant, the spread width can be changed with the change in the oscillation amplitude. By means of the method described above, fiber strands can be moved at a high speed, preferably of at least 20 m / min, and spread apart uniformly. By this method, a fiber strand can be spread reliably to a band-shaped fiber strand with at least twice the final width, preferably, the end width changes at least by 5 times. For example, a 12K carbon fiber strand having a width of 2 mm was spread at a frequency of 30 kHz to a uniform ribbon-like 12 mm wide fiber strand. By appropriate Bandbreitenbegrenzer the final width can be set to a predetermined Endbreitenwert.

Advantageously, the process according to the invention represents a cost-effective process, since the fiber strand is processed dry, no energy for dewatering, heating or drying of the fiber strand is necessary. In addition, the nature of the fiber strand does not change with respect to its composition, namely the proportion of multifilament fibers and size in the process. It is intended, a band-shaped fiber strand with uniform and greater final width and achieved with lower final thickness, which is desirable to a low basis weight and in the application of the fiber strand for fabric or scrim to lighter composites with equally good mechanical properties, such as tensile strength leads.

For this method, a device is used which has an angling device for the fiber strand to be spread, a spreading station for spreading the inserted fiber strand into a band-shaped fiber strand, a controllable tensioning device for uniform tensioning of the fiber strand during its movement through the spreading station and a winding device of the spread band-shaped fiber strand includes. In accordance with the invention, the spreading station contains at least one sonotrode for contacting and spreading the fiber strand, wherein the sonotrode via their contact surface oscillations of a frequency between 15 kHz and 80 kHz from above and / or below (z-direction) in the fiber strand initiates, which leads to a spreading of the fiber strand in the y direction. In this case, preferably two or three sonotrodes act successively on the fiber strand. The more sonotrodes the spreader station contains, the better the spreader result, but the more expensive the device will be. For this reason, spreading stations with two to three sonotrodes are preferred. The ultrasonic vibrators are preferably equipped with interchangeable sonotrodes, which have contact surfaces for contacting the fiber strand on their front side. These contact surfaces can be flat, concave or curved in the direction of movement of the fiber strand, ie in the fiber longitudinal direction. The width of the contact surfaces, ie the extent of the contact surface transverse to the movement of the fiber strand is chosen so that it is greater in any case than the attainable by spreading end width of the band-shaped fiber strand.

If, for example, at least two sonotrodes are provided in the spreading station, two adjacent sonotrodes are arranged at a preset distance. This depends on the nature of the fiber strand material. Adjacent sonotrodes are furthermore preferably provided in different orientations with respect to each other so that a first sonotrode, for example, contacts the fiber strand from above and the second sonotrode contacts the fiber strand from below. This has led to more consistent process results. The contact surfaces of the sonotrodes are preferably located in one plane. In tensile fiber strands, such as carbon fiber strands, however, a looping of the sonotrodes is desired. For the spreading of such fiber strands, the contact surfaces are preferably arranged at different heights in relation to the continuous fiber strand, so that this fiber strand is guided as possible in a zig-zag line through the spreading station. In order to achieve a desired angle of attack of the fiber strand to the contact surface of the sonotrode, deflection rollers can be provided in front of and behind the expansion station. Additionally, in addition, a bandwidth limiter may be installed behind the spreader station to provide a uniform end width of the spread ribbon fiber strand. The invention is illustrated by means of embodiments in the drawing is a. Show it:

1 is a schematic diagram of a device according to the invention,

2a, 2b, 2c different forms of sonotrodes,

3a, 3b, 3c different Anornungen of sonotrodes,

Fig. 4 schematic diagram of another invention

Contraption.

The invention is not limited to these embodiments. The schematic diagram in FIG. 1 shows the basic passage of a fiber strand 2 to be spread starting from the bending device 1, through the spreading station 5, to the winding device 8. The fiber strand 2 in this case is a 12K fiber strand, ie Fiber strand consists of 12,000 filaments, which are arranged endlessly in the fiber strand 2 side by side and are each surrounded by a size. This sizing prevents the fiber strand 2 from being damaged during its movement. The inserted and delivered on a coil of the bending device 1 fiber strand 2 is unwound from this coil. Due to the development of the fiber strand 2 from the spool, different unwinding positions would result with each revolution. So that this fiber strand 2 is always fed at the same position of the following dancer device 3, which forwards it to the spreading station 5 and thus the fiber strand 2 is moved in an unchanged plane starting from the bending device 1 towards the spreading station 5, the coil is in the unwinding device. 1 rotatable in the direction of movement and transversely to the direction of movement of the fiber strand 2, that is arranged displaceably in the y-direction. Thus, for example, the unwinding position of the fiber strand 2 can be determined by a sensor and the unwinding reel can be displaced correspondingly to the desired unwinding position. The fiber strand 2 then passes into the front dancer unit 3, which serve together with the rear dancer unit 7 as tensioning devices, wherein the front dancer unit 3 in the direction of movement of the fiber strand 2, 2 'in front of the spreading station 5 and the rear dancer unit 7 in the direction of movement of the fiber strand 2, 2 'is provided behind the spreader 5. This causes the fiber strand 2, 2 'in the spreading station 5 is stretched uniformly throughout the process. In accordance with the unwinding process of the fiber strand 2 from the unwinding device 1 and the winding process of the spread fiber strand 2 'onto the winding device 8, the dancer units 3, 7 can counteract changed conditions which influence the tension of the fiber strand 2, 2'. In the apparatus shown, the dancer units 3, 7 each comprise three rollers. For a uniform tensioning of the fiber strand 2, 2 ', two rollers would be sufficient. Depending on the desired fiber strand guide towards the spreading station 5, a third roller of the dancer unit 3 can serve as an additional deflection roller for the fiber strand 2. Further deflection rollers 4 in front of the spreading device 5 and further deflection rollers 6 behind the spreading station 5 are used in particular for setting a desired angle of attack of the fiber strand 2 when entering the spreading station 5.

Each ultrasonic transducer 51 has a replaceable sonotrode 52 with a frontal contact surface 53. In an ultrasonic generator, not shown, the vibrations are generated by the sonotrodes 52 via the contact surface 53 from above or from below, ie in the z-direction, are introduced into the fiber strand 2. In this example, the three sonotrodes 52 are arranged one behind the other in the direction of movement of the fiber strand 2, 2 ', with adjacent sonotrodes 52 being provided in different orientation in the spreading station 5 in such a way that the contact surfaces 53 of the first and third sonotrode 52 vibrate from above down into the fiber strand 2 and the second, arranged therebetween sonotrode 52, which initiates vibrations from the contact surface 53 from bottom to top in the fiber strand 2. at In this example, the sonotrodes 52 introduce mechanical vibrations at a frequency of 30 kHz into the fiber strand 2, 2 '. Already at the first sonotrode 52 there is a spreading of the inserted fiber strand 2, ie a spreading of the fiber strand in the lateral direction (y-direction). This spreading increases during the passage of the fiber strand 2 in contact with the subsequent sonotrodes 52. The passage of the fiber strand 2, 2 'by the spreading station 5 is carried out in the example shown horizontally, ie without deflection up or down. Such a course is chosen in particular for sensitive or elastic fiber strands.

The spread strip-shaped fiber strand 2 'emerging from the spreading station 5 is fed via the rear dancer unit 7 to the winding device 8, where the spread fiber strand 2' is wound onto a spool with the appropriate winding tension. For this purpose, the coil can be configured in the winding device 8 as a torque-driven take-up reel.

FIGS. 2a, 2b, 2c show different sonotrodes 52 ', 52 ", 52"'. In order to prevent damage to a fiber strand 2 during the contacting of the sonotrodes 52 ', 52 ", 52"', the respective contact surface 53 ', 53 ", 53" may have a radius in the direction of movement of the fiber strand 2, for example as the contact surface 53 "in FIG This makes it possible to easily wrap these sonotrodes 52 "during the spreading process without the fiber strand 2 being damaged in such a looping, see FIG. The sonotrode 52 "'according to FIG. 2 a also has a curved contact surface 53"', which additionally has the advantage that such sonotrodes 52 "'can be arranged in one another in a spreading device 5, as shown in FIG. 3 a. 2c further shows a sonotrode 52 'which also has a radius at the outer edge 54 of the contact surface 53' and a recessed plane 55 at the center. When such a sonotrode 52 'is used in a spreading device, the fiber strand 2 is stretched over the edge 54 and has a freedom to oscillate upon introduction of the vibrations by the low recessed plane 55. One possible arrangement of a plurality of such sonotrodes 52 'is shown in Fig. 3c. A looping of the sonotrodes 52, as shown in Fig. 3a, 3b, 3c, is preferred in carbon fiber strands. The fiber strand 2 is supplied at a steep angle of attack of the contact surface 53 ', 53 ", 53"' of the sonotrodes 52 ', 52 ", 52"'. This is also possible if, in the example of FIG. 1, the first and third sonotrode 52 are lowered relative to the second sonotrode 52, so that the contact surfaces 53 are no longer arranged at the same height but the first and third contact surfaces 53 in comparison to FIG second contact surface 53 are positioned deeper.

A further exemplary embodiment is shown in FIG. 4. In this example, a plurality of fiber strands 2 are spread out simultaneously, ie several fiber strands 2 are guided side by side in the y direction through the spreader 5 and a plurality of spread fiber strands 2 ', ie widened in the y direction, leave the spreader 5. In order to produce a single wide fiber strand 2 "'from these several spread fiber strands 2', the individual spread fiber strands 2 'are fed to a delivery mechanism 9 which combines the fiber strands 2' into a common fiber strand 2". In addition, in order to standardize and / or further widen the bundled fiber strand 2, it can pass through another spreading device 5. Such broad fiber strands 2 "produced in this way can advantageously be used for the production of knits or loops.

LIST OF REFERENCE NUMBERS

handling facility

Fiber strand, unspread

Fiber strand, spread

Fiber strand, from several spread, merged single strands

Fiber strand, unified from single strands

front dancer unit

idler pulley

spreading station

ultrasonic vibrator

sonotrode

contact area

edge

level

idler pulley

rear dancer unit

takeup

delivery mechanism

Claims

claims

A method of spreading a fiber strand having an initial width and having an initial thickness into a band-shaped fiber strand having a greater end width and a smaller final thickness, wherein the fiber strand consists of endless multifilament fibers,

in which the fiber strand is moved starting from a development towards a winding in the longitudinal direction (x direction),

- Wherein the fiber strand between the settlement and the winding passes through a spreading station and is held in this pass under an adjustable state of tension,

characterized in that

- In the spreading of the fiber strand at least one sonotrode contacted and by means of the sonotrode from above and / or below (z-direction) introduced into the fiber strand vibrations of this fiber strand is widened uniformly transversely to the longitudinal direction and in the lateral direction (y-direction),

- These oscillations have a frequency that are between 15 kHz and 80 kHz.

2. The method according to claim 1, characterized in that the multifilament fibers of the fiber strand are surrounded by a size and the amount ratio of multifilament fibers to size in the resulting ribbon-shaped fiber strand relative to the unspreaded fiber strand does not change.

3. The method according to claim 1 or 2, characterized in that when spreading fiber strands of tensile fibers, these fibers are supplied in an angle of attack of a contact surface of the sonotrode or sonotrodes.

4. The method according to any one of claims 1 to 3, characterized in that the fiber strand, starting from the settlement towards the winding in the fiber longitudinal direction at a speed of at least 20 m / min is moved.

5. The method according to any one of claims 1 to 4, characterized in that the fiber strand, starting from the settlement towards the spreading station and preferably to the winding, continuously in an unchanged plane (xz plane) is moved, although in the fiber longitudinal direction up or down is deflected, but apart from the spread no lateral deflection transversely (y-direction) experiences the fiber longitudinal direction.

6. The method according to any one of claims 1 to 5, characterized in that the resulting by spreading strip-shaped fiber strand is compared to the initial width by at least 2 times, preferably at least 5 times, larger end width receives, preferably the final width of the band-shaped fiber strand is limited to a predetermined value.

7. The method according to any one of claims 1 to 6, characterized in that the plurality of fiber strands are spread simultaneously and combined to form a common particularly broad spread fiber strand.

8. A device for spreading a fiber strand (2) with an initial width and with an initial thickness to a band-shaped fiber strand (2 ') with greater final width and with a smaller final thickness, wherein the fiber strand (2, 2') consists of endless multifilament fibers comprising

a unwinding device (1) for the fiber strand (2) used for unwinding in the fiber longitudinal direction (x direction),

a spreading station (5) for lateral (y-direction) spreading of the inserted fiber strand (2) into a band-shaped fiber strand (2 '), - A controllable tensioning device (3, 7) for uniform clamping of the fiber strand (2, 2 ') in the fiber longitudinal direction in its movement through the spreading station (5) and

a winding device (8) of the spread band-shaped fiber strand (2 '),

characterized in that

the spreading station (5) contains at least one sonotrode (52) for contacting and spreading the fiber strand (2),

- Wherein the sonotrode (52) via its contact surface (53) vibrations of a frequency between 15 kHz and 80 kHz from above and / or below (z-direction) in the fiber strand (2, 2 ') can initiate.

Apparatus according to claim 8, characterized in that the contact surface (53) of the sonotrode (52) has a width which is greater than the recoverable by spreading end width of the strip-shaped fiber strand (2 ').

Apparatus according to claim 8 or 9, characterized in that at least 2 sonotrodes (52, 52 ', 52 ", 52"') are provided in the spreading station (5), wherein two adjacent sonotrodes (52, 52 ', 52 ", 52 "') are arranged at a preset distance and in a preset, different orientation to each other, so that fiber strands (2) of different nature with an adjustable wrap the sonotrodes (52, 52', 52", 52 "') can contact.

Device according to one of claims 8 to 10, characterized in that for adjusting an angle of incidence of the fiber strand (2, 2 ') to the contact surface (53) of the sonotrode (52) additional deflection rollers (4, 6) in front of and behind the spreading station (5). are provided.

Device according to one of claims 8 to 1 1, characterized in that the controllable tensioning device for uniform tensioning of the fiber strand (2, 2 ') of two dancer units (3, 7) with at least two Rolls, wherein a front dancer unit (3) in the direction of movement of the fiber strand (2, 2 ') in front of the spreading station (5) and a rear dancer unit (7) in the direction of movement of the fiber strand (2, 2') provided behind the spreading station (5) is.

Device according to one of claims 8 to 12, characterized in that for limiting and setting a uniform end width of the spread band-shaped fiber strand (2 ') a Bandbreitenbegrenzer is provided, in the direction of movement of the fiber strand (2, 2') behind the spreading station (5). is arranged.

Device according to one of claims 8 to 13, characterized in that for the continuous movement of the fiber strand (2) in an unchanged plane (xz plane) starting from the unwinding device (1) towards the spreading station (5) the unwinding device (1) as a rotatable and as a transversely (y-direction) to the direction of movement of the fiber strand (2) displaceable supply reel is configured.

Apparatus according to claim 14, characterized in that the front dancer unit (3) controls the rotational speed of the supply reel and the take-up device (8) is designed as a torque-driven take-up reel. 16. Device according to one of claims 8 to 15, characterized in that the spreader (5) is designed so that a plurality of fiber strands (2) next to each other can pass through the spreader (5) and to bring together the individual spread fiber strands (2 ') a wide fiber strand (2 ") in the direction of movement of the fiber strands (2, 2 ') behind the spreader (5) arranged delivery mechanism (9) and, if necessary, a further spreading device (5') to standardize this wide fiber strand (2") is provided.