STRANDS POWDERED BY ELECTROSTATIC METHOD

Abstract

The invention relates to a method and facility for manufacturing a tape of reinforcement filaments impregnated by a polymer matrix, said tape having a constant width across the entire length thereof, wherein the filaments extend in a direction parallel to the length of the tape, from a strand of filaments coming from a feeding reel, the method including steps and units that make it possible to manage the unwinding tension of the strand, to guide the strand on the axis of the machine, to manage the width of the strand, to deposit the polymer on the strand by electrostatic powdering, with a polymer weight ratio of around 20% to around 75% to melt the polymer, to calibrate the width and thickness of the tape and to collect the tape on the storage reel.

Claims

1. A method for manufacturing a tape from reinforcement filaments impregnated with a thermoplastic or thermosetting polymer matrix, a tape which has a constant width over the whole of its length, wherein the filaments extend along a direction parallel to the length of the tape, from a strand of filaments stemming from a supply coil, the method comprising the following steps, from a coil for supplying strand up to a coil for storing the impregnated and consolidated tape: a) managing the tension between the supply coil and the storage coil, b) guiding the strand so as to obtain a strand moving in translation over a line coinciding with a longitudinal axis, a so called machine axis, extending as far as the proximity of the storage coil, c) optionally transverse spreading of the strand to a predetermined width greater than the rated width of the tape, d) managing the width of the strand, e) optionally pulling the strand, preferably by pinching or with a foulard, f) grounding the strand, g) deposition of the polymer as a powder on the strand, by electrostatic powder coating, with a mass polymer level of about 20% to about 75%, obtaining an impregnated tape, h) melting or softening the polymer, i) calibration in width and in thickness of the tape, j) optionally measuring the width of the tape, k) winding the tape on the storage coil.

2. The method according to claim 1, wherein the electrostatic powder coating is carried out with a polymer powder maintained as a fluidized bed, and then deposited by means of one or several electrostatic powdering guns.

3. The method according to claim 1, wherein in the calibration step h), the tape is calendered and then calibrated transversely.

4. The method according to claim 3, wherein one proceeds with calendering with a cooled calender.

5. The method according to claim 3, wherein calibration is performed both in the transverse direction and in thickness.

6. The method according to claim 5, wherein the calibration is performed by means of at least two antagonistic grooves or with at least one groove and an antagonistic planar surface.

7. The method according to claim 1, wherein calibration is performed to the desired rated width for the tape.

8. The method according to claim 1, wherein the transverse spreading c) of the strand is carried out and it is carried out to a predetermined width greater than the rated width of the tape, by spreading out of the strand, and then the strand is calibrated to a predetermined value.

9. (canceled)

10. A continuous tape impregnated or consolidated and formed with unidirectional fibers of an inorganic material, coated and/or impregnated to the core of a thermoplastic or thermosetting polymer, comprising a polymer level comprised between about 30% and about 75%, based on the weight of the tape, and having a constant width notably comprised between about 2 mm and about 75 mm, with a standard deviation comprised between 0.02 and 0.15 mm, over a length in a single piece greater than or equal to 100, 500, 1,000 or 5,000 m.

11. The tape according to claim 10, which tape it has an average width of about 6.35 mm with a standard deviation comprised between 0.02 and 0.05 mm, over a length of a single piece greater than or equal to 100, 500, 1,000 or 5,000 m.

12. A continuous tape formed with unidirectional fibers of an inorganic material, impregnated with a thermoplastic or thermosetting polymer, comprising a polymer level comprised between about 25% and about 75%, based on the weight of the tape, comprising inside filaments which are not taken in the polymer preferably in an amount of 20, 25 or 30 to about 50% of the total of the filaments of the tape and the polymer forms an outer continuous sheath.

13. (canceled)

14. The tape according to claim 10, wherein the Taber rigidity of the tape with caliber no. 1, a mass of 250 TU and an angle of 7.5° is comprised between about 5 TSU and about 25 TSU, according to the NF ISO 2493-2 standard (Part 2: Taber Tester).

15. The tape according to claim 10, wherein from 80% to 99, 98, 97, 96, 95 or 90% of the filaments are taken in the polymer and sheathed by the latter.

16. The tape according to claim 10, wherein the Taber rigidity of the tape with the caliber no. 1, a mass of 250 TU and an angle of 7.5° is comprised between about 45 TSU and about 65 TSU, compliant with the NF ISO 2493-2 standard (Part 2: Taber Tester).

17. A consolidated composite part, including a tape according to claim 10.

18. A facility comprising: a) at least one coil-holder pin with a brake. b) an unwinding device and for aligning the thread in the machine axis. c) optionally a transverse spreading device, d) a device for calibration in width, e) optionally a pinching and pulling device, f) optionally a device for measuring the width of the strand, g) at least one metal part grounded, h) at least one electrostatic powder coating device, i) at least one oven, j) optionally, a device for aligning the tape to have it coincide with the machine axis, k) optionally, a calendar, l) a calibration device in the transverse direction and in thickness, m) optionally, a device for measuring the width of the tape, n) at least one storage coil-holder pin.

19. The facility according to claim 18, characterized in that the powder coating device includes a dry fluidizer and one or several guns or nozzles for electrostatic powder coating using the principle of corona discharge.

20. The method according to claim 1, wherein the strand of filaments is made of carbon filaments, and two such carbon filament strands are superimposed before powder coating or are superimposed after powder coating at the time the polymer is melten or soften.

21. The tape according to claim 12, wherein the Taber rigidity of the tape with caliber no. 1, a mass of 250 TU and an angle of 7.5° is comprised between about 5 TSU and about 25 TSU, according to the NF ISO 2493-2 standard (Part 2: Taber Tester).

22. The tape according to claim 15, wherein the Taber rigidity of the tape with the caliber no. 1, a mass of 250 TU and an angle of 7.5° is comprised between about 45 TSU and about 65 TSU, compliant with the NF ISO 2493-2 standard (Part 2: Taber Tester).

23. The tape according to claim 10, wherein the inorganic material is carbon.

24. A consolidated composite part, including a tape produced by the method according to claim 1.

Description

[0104] The invention will now be described in more detail by means of embodiments taken as a non-limiting example and with reference to the drawing wherein:

[0105] FIG. 1 is a schematic illustration of a facility according to the invention.

[0106] FIGS. 2, 3 and 4 are schematic illustrations of different calibration devices according to the invention.

[0107] FIG. 5 is a schematic illustration of a tape produced by the standard method with impregnation in a bath.

[0108] FIG. 6 is a schematic illustration of a tape produced by a first embodiment of the invention.

[0109] FIG. 7 is a schematic illustration of a tape produced by a second embodiment of the invention.

[0110] FIGS. 8 and 9 are graphs representing the width measurements carried out every 1 m of tape according to the metering in m produced.

[0111] FIG. 10 is a schematic illustration of a cross-section of a tape including bundles of filaments.

[0112] The numerical mark 1 refers to a strand coil 2, for example the carbon filament strand. This coil is mounted on a pin (not shown), provided with an adjustable brake. A first bar 3 is parallel to the axis of the coil 1 and oriented at 90° relatively to the running direction of the strand 2, the latter sliding from left to right on the first bar because of the winding effect of the supply coil 2. Subsequently, a second bar 4 is located underneath the first, oriented at 90° relatively to the previous one and perpendicularly to the machine axis. A series of seven spreading bars is illustrated. Four of them referenced as 5 are positioned so that the strand is tangent to their upper portion, the three other referenced as 6 being placed beneath the machine axis and bringing the strand to be tangent with their lower portion by applying to it a stress such that the strand is spread out in width. A calibration device 7 has a groove in which passes the strand, which is calibrated therein to the desired width. A foulard 8 is positioned sequentially to it, this foulard being designed for pinching the strand 2 and forcing it to move in the direction opposite to the supply coil. A Laser device for measuring the width of the strand is illustrated as 9. Two metal bars 10 and 11 connected to the ground are in contact for one, 10 with the lower face of the strand, for the other one, 11 with the upper face. These bars apply a certain pressure on the strand.

[0113] In 12, an electrostatic powdering unit is illustrated comprising two powdering guns 13, supplied with fluidized polymer powder stemming from a fluidization device not shown. One of the guns has its spraying nozzle oriented towards a face of the strand, the other one towards the other face of the strand. The unit is controllable in order to ensure the continuous deposition of a determined amount of thermoplastic or thermosetting material on the strand 2 which runs inside the enclosure.

[0114] The numerical mark 14 designates both infra-red ovens, preferably either short or medium, located one behind the other, which are controlled in temperature and this control is made for power. The impregnated strand with molten polymer then passes into a cooled calender 15. The calender includes two rollers and a device for adjusting the pressure exerted by the rollers on the strand which passes between them. The strand then passes into a calibration device 16, examples of which will be described with reference to FIGS. 2-4. A Laser device for measuring the width of the tape is illustrated as 17, it is connected to a computer or processor allowing the recording of the width and the calculation of the standard deviation. The device carries out one/off measurements, at regular intervals, according to the will of the user. At the stage of the passage in front of the Laser device, the strictly speaking tape 18 is formed. The tape is then managed by a device for winding a tape, comprising two idlers 19 and 20 and a storage coil 21 mounted on a pin (not shown) driven into rotation.

[0115] According to a significant feature, the active surfaces (in contact with the strand or the tape) of the elements 4, 5, 7, 8, 14, 15, and 16 are perfectly aligned on the machine axis, so that the strand, and then the tape when it is formed, does not undergo any lateral or sensitive height movement.

[0116] In FIG. 2, a first embodiment is illustrated of a calibration device which may be used, notably as a device 16 in the facility of FIG. 1. It comprises a plate 22 dug with a groove 23 formed of a flared portion 24 and of a rectilinear portion 25. The width of the groove is equal to the width of the tape to be produced. The numerical mark 26 designates a roulette having a planar axisymmetrical surface with a width slightly less than that of the rectilinear portion 25 of the groove in which it will be inserted in part. During operation, it is understood that the strand passes at the bottom of the groove 23 and that the roulette will apply a pressure on it inside the portion 25 of the groove 23. A device (not shown), for example a vernier, gives the possibility of carrying out this operation. This gives the possibility of adjusting the pressure exerted on the strand.

[0117] In FIG. 3, the same plate 22 is again found. At the place of the roulette 26, downstream from the plate, a roulette 27 is positioned including a peripheral groove 28 with a flat bottom, the width of which is equal to the width of the tape to be produced. When operating, it is understood that the strand 2 passes at the bottom of the groove 23, and then in the groove 28 of the roulette 27, which will apply a pressure on it. A device, for example a vernier, not shown, gives the possibility of positioning the flat bottom of the groove in height relatively to the machine axis in order to adjust the pressure exerted on the strand.

[0118] In FIG. 4, a succession of three roulettes 29 are used each including a peripheral groove 30 with a flat bottom, the width of which is equal to the width of the tape to be produced. The first and third roulettes are placed above the machine axis, the second one below. When operating, it is understood that the strand 2 passes into contact with the bottoms of the groove 30, at the lower portion of the first roulette, and then at the upper portion of the second roulette, finally at the lower portion of the third roulette. A device, for example a vernier, not shown, gives the possibility of positioning the flat bottom of the grooves in height relatively to the machine axis in order to adjust the pressure exerted on the strand.

EXAMPLE 1

Obtaining a Carbon/PEEK Tape with a Mass Polymer Level of 34% and with a Width of 6.35 mm by Using the Facility of FIG. 1

[0119] One starts with a flat strand of carbon filaments HR HTS45 E23 from Toho Tenax, a titer comprised between 810 tex and 780 tex, the strand width varying between 3 and 7 mm, wound and crossed.

[0120] A PEEK 150PB powder from Victrex, grain size d.sub.10=30 μm, d.sub.50=60 μm, d.sub.90=100 μm.

[0121] The strand of carbon fiber is heated and then spreaded out to a width comprised between 8 mm and 12 mm by bar spreading, under a tension after bar spreading comprised between 4.5 kg and 2.5 kg. The fibers then pass into a groove with a width of 10 mm, and then in the foulard which gives the possibility of pulling the fiber. Before entering the powdering cabin, the fiber passes into the contact of two bars connected to ground.

[0122] The powdering coating step is carried out by means of an SAMES facility comprising a fluidization pan, 2 guns and a controlled central unit. In order to obtain the targeted powder level, a single gun is used, its adjustments are shown in the following table:

TABLE-US-00002 Parameter Adjustment Voltage (kV) 70 Intensity (μA) 70 Injection pressure 12 Dilution pressure 5

[0123] The pressure of the fluidization pan is adjusted to 2 bars, which gives the possibility of having a homogeneous and regular fluidization conditions.

[0124] Next, the melting of the polymer is carried out by having the tape pass between two infrared radians rollers with a tape (average IR) SOPARA, adjusted between 50% and 70% of their power. These are IR tape radians of the brand SOPARA with a length of 75 cm and each with a power of 2.3 kW.

[0125] The calibration is carried out by calendering in a first phase the tape, and then having it pass into a groove with a rated width of 6.35 mm+/−0.05 mm.

[0126] The measurement of the width is carried out with a LASER Mike Model 911 (measurement accuracy of 0.003 m), the data collected every 1 m during the production of a coil of 1,000 m are illustrated in FIG. 8.

[0127] The average width of the tape is 6.37 mm with a standard deviation of 0.04 mm.

[0128] The winding is carried out in tension, at a value comprised between 15 m/min and 20 m/min with a winding device SAHM.

[0129] FIG. 6 is a schematic view of the surface of the tapes observed with a binocular magnifying glass with a magnification of 0.6×3. The numerical mark 104 designates the polymer coating, relatively continuous, and only shows the carbon filaments on discrete areas designated by the numerical marks 105.

EXAMPLE 2

Obtaining a Carbon/PEEK Tape with a Mass Polymer Level of 34% and a Width of 6.35 mm by Using the Facility of FIG. 1

[0130] One starts with a round strand of carbon filaments HM M46JB 12K 50B from Toray, a titer of 445 tex, a strand width varying between 2 and 5 mm, wound and crossed.

[0131] PEEK powder 150PB from Victrex, grain size d.sub.10=30 μm, d.sub.50=60 μm, d.sub.90=100 μm.

[0132] The strand of carbon fiber is heated in order to spread it out at a width comprised between 5 mm and 8 mm by bar spreading, under a tension after bar spreading comprised between 4.5 kg and 2.5 kg. The fibers then pass into a groove with a width of 8 mm, and then into the foulard which gives the possibility of pulling the fiber. Before entering the powdering cabin, the fiber passes into the contact of two bars connected to ground.

[0133] The powdering coating step is carried out like in Example 1. The pressure of the fluidization pan is adjusted to 2 bars, which gives the possibility of having a homogeneous and regular fluidization conditions. Next, the melting of the polymer is carried out by having the tape pass under two infrared radians with a lamp SOPARA (length of 75 cm and each with a power of 3 kW), adjusted between 50% and 70% of their power.

[0134] The calibration is carried out by calendering in a first phase of the tape, and then by having it pass into a groove with a rated width of 6.35 mm+/−0.05 mm.

[0135] The measurement of the width is carried out with the LASER Mike, like in Example 1, the collected data every 1 m during the production of a coil of 150 m are illustrated in FIG. 9.

[0136] The average width is 6.16 mm with a standard deviation of 0.13 mm.

[0137] The winding is carried out in tension, at a velocity comprised between 5 m/min and 20 m/min with a winding device SAHM.

[0138] FIG. 7 is a schematic view of the surface of the tapes observed with a binocular magnifying glass with a magnification of 0.6×3. The numerical mark 106 designates the carbon filaments and this time, the polymer having remained at the surface does not form a quasi continuous coating, but discrete areas 107.

[0139] By comparison with FIGS. 6 and 7, FIG. 5 shows what one obtains with the standard impregnation method by immersion in a bath. The numerical mark 101 designates continuous areas of polymer at the surface, the mark 102 designates discrete clusters of polymer and the mark 103 designates naked filaments.

EXAMPLE 3

Production of a Composite Article

[0140] An automated fiber placement automaton (AFP) is programmed for depositing the tape according to Example 1 or according to Example 2 on a support, until the blank of the part to be manufactured is formed. The automaton places the tape edge to edge in order to thereby form a fold, and then superpose another fold on the preceding one, the superposition being able to be accomplished according to adapted angle(s) according to the production program for the blank. The formed blank is then placed according to a first sub-example in an oven and according to a second sub-example in an autoclave. The consolidation is conducted to its end and the consolidated composite part is obtained.

[0141] Composite parts were formed successfully with the tape according to Example 1.

EXAMPLE 4

Production of a Tape with Bundles of Filaments

[0142] In the powdering device 12, a bar with circumferential grooves is installed, the grooves having a width which depends on the targeted width of the bundles; typically, this width may be comprised between about 0.25 and about 2 mm. The tape is brought into contact with this bar, in a permanent or intermittent way, in order to ensure the separation of the strand into bundles. The first powdering gun projects the powder on the strand separated into bundles, notably immediately downstream from the bar. The second gun is positioned a little downstream, notably a few centimeters further on, in a location where the bundles are brought closer to each other. The impregnated product stemming from this application, schematically visible in FIG. 10, is characterized by a distribution of the filaments as bundles 108 with a width comprised between 200 μm and 6,000 μm and a height comprised between 50 μm and 250 μm for which the spacing (polymer area 109) is comprised between 25 μm and 100 μm. Further, this product retains a thin sheath 110 of polymer with a thickness comprised between 25 μm and 100 μm. This product has good cohesion in the direction transverse to the filaments. Its surface condition may be similar to the one observed with the hollow product.