Fluidized-bed process for manufacturing a fibrous material preimpregnated with thermoplastic polymer

Abstract

The invention relates to a process for manufacturing a preimpregnated fibrous material containing a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein the preimpregnated fibrous material is produced as a single unidirectional tape or of a plurality of parallel unidirectional tapes and wherein the process includes a step of impregnating, in particular fully and homogeneously, the fibrous material that is in the form of a roving or of several parallel rovings with the at least one thermoplastic polymer matrix that is in powder form, the impregnating step being carried out by a dry route in a tank and the control of the amount of the at least one thermoplastic polymer matrix in said fibrous material being achieved by control of the residence time of said fibrous material in the powder, with the exclusion of any electrostatic process with intentional charging.

Claims

1. A process for manufacturing a preimpregnated fibrous material comprising a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein the preimpregnated fibrous material is produced as a single unidirectional tape or as a plurality of parallel unidirectional tapes, wherein the process comprises impregnating a fibrous material, that is in the form of a roving or of several parallel rovings, with the at least one thermoplastic polymer matrix having the form of a powder, the impregnating being carried out by a dry route in a tank comprising a fluidized bed, where control of the amount of the at least one thermoplastic polymer matrix in the fibrous material is achieved by control of residence time of the fibrous material in the powder, with exclusion of any electrostatic process with intentional charging, the volume mean diameter D50 of particles of the powder of the thermoplastic polymer matrix being from 30 to 300 μm, the impregnation being carried out with simultaneous fanning out of the roving or of the rovings between an inlet and an outlet of the fluidized bed, where the fluidized bed comprises at least one tension device, the roving or the rovings being in contact with a portion or the whole of the surface of the at least one tension device, and where the at least one tension device is a compression roller of convex, concave or cylindrical shape, the compression roller having a diameter of from 3 mm to 500 mm, wherein the residence time in the powder is from 0.01 s to 10 s, and wherein the number-average molecular weight Mn of a final polymer present in the thermoplastic matrix is within a range from 10,000 to 40,000.

2. The process as claimed in claim 1, wherein the content of fibers in the impregnated fibrous material is from 45% to 65% by volume.

3. The process as claimed in claim 1, wherein the fanning out of the roving or of the rovings is carried out at least at the at least one tension device.

4. The process as claimed in claim 1, wherein the at least one compression roller is of a cylindrical shape and the percentage of fanning out of the roving or of the rovings between the inlet and the outlet of the fluidized bed is from 1% to 400%.

5. The process as claimed in claim 4, wherein a single compression roller is present in the fluidized bed and the impregnation is carried out at an angle α.sub.1 formed by the roving or the rovings between the start of the compression roller and the vertical tangent to the compression roller.

6. The process as claimed in claim 5, wherein the angle α.sub.1 is from 0 to 89°.

7. The process as claimed in claim 4, wherein two compression rollers R.sub.1 and R.sub.2 are present in the fluidized bed and the impregnation is carried out at an angle α.sub.1 formed by the roving or the rovings between the start of the compression roller R.sub.1 and the vertical tangent to the compression roller and/or at an angle α.sub.2 formed by the roving or the rovings between the start of the compression roller R.sub.2 and the vertical tangent to the compression roller R.sub.2, the compression roller R.sub.1, in the run direction of the process, preceding the compression roller R.sub.2 and the roving or the rovings being able to pass on top of or underneath the roller R.sub.2.

8. The process as claimed in claim 7, wherein the two compression rollers R.sub.1 and R.sub.2 are at a distance of from 0.15 mm to the length equivalent to the maximum dimension of the tank and the difference in height between the two compression rollers R.sub.1 and R.sub.2 is from 0 to the height corresponding to the maximum height of the tank minus the diameters of the two compression rollers, R.sub.2 being the upper compression roller.

9. The process as claimed in claim 1, wherein a single thermoplastic polymer matrix is used and the powder of the thermoplastic polymer powder is fluidizable.

10. The process as claimed in claim 1, wherein the process further comprises shaping the roving or the parallel rovings of the impregnated fibrous material, by calendering with at least one heated calender in the form of a single unidirectional tape or of a plurality of parallel unidirectional tapes with, in the latter case, the heated calender comprising a plurality of calendering grooves, in accordance with the number of the tapes and with a pressure and/or a spacing between the rollers of the calender that are regulated by a servo control system.

11. The process as claimed in claim 10, wherein the calendering is carried out by a plurality of heated calenders, mounted in parallel and/or in series relative to the run direction of the fiber rovings.

12. The process as claimed in claim 10, wherein the heated calender(s) comprise(s) an integrated induction or microwave heating system, coupled with the presence of carbon-based fillers in the thermoplastic polymer or blend of thermoplastic polymers.

13. The process as claimed in claim 10, wherein the heated calender(s) is/are coupled to a complementary rapid heating device, located before and/or after the/each calender.

14. The process as claimed in claim 1, wherein the impregnating is completed by covering the single roving or the plurality of parallel rovings after impregnation by the powder, the covering being carried out before the calendering, by a molten thermoplastic polymer, which may be identical to or different from the thermoplastic polymer matrix in the form of a powder in the fluidized bed.

15. The process as claimed in claim 1, wherein the thermoplastic polymer matrix further comprises carbon-based fillers.

16. The process as claimed in claim 1, wherein the thermoplastic polymer matrix further comprises liquid crystal polymers or cyclic polybutylene terephthalate, or mixtures containing same as additives.

17. The process as claimed in claim 1, the thermoplastic polymer matrix comprises at least one thermoplastic polymer selected from the group consisting of: polyaryl ether ketones (PAEKs); polyaryl ether ketone ketones (PAEKKs); aromatic polyether imides (PEIs); polyaryl sulfones; polyaryl sulfides; polyamides (PAs); PEBAs; polyacrylates; polyolefins; polylactic acid (PLA); polyvinyl alcohol (PVA); and fluoropolymers.

18. The process as claimed in claim 17, wherein the at least one thermoplastic polymer is a polymer having a glass transition temperature such that Tg 80° C. or a semicrystalline polymer having a melting temperature Tm 150° C.

19. The process as claimed in claim 1, wherein the fibrous material comprises continuous fibers selected from carbon fibers, glass fibers, silicon carbide fibers, basalt fibers, silica fibers, natural fibers, or amorphous thermoplastic fibers having a glass transition temperature Tg above the Tg of the polymer or of the blend of polymers when the latter is amorphous or above the Tm of the polymer or of the blend of polymers when the latter is semicrystalline, or semicrystalline thermoplastic fibers having a melting temperature Tm above the Tg of the polymer or of the blend of polymers when the latter is amorphous or above the Tm of the polymer or of the blend of polymers when the latter is semicrystallin, or a mixture of two or more of the fibers.

20. A unidirectional tape of preimpregnated fibrous material, wherein the unidirectional tape is obtained by a process in accordance with claim 1.

21. The unidirectional tape as claimed in claim 20, where the tape has a width (I) and a thickness (ep) that are suitable for robotic layup in the manufacture of three-dimensional parts, with no need for slitting.

22. The unidirectional tape as claimed in claim 20, wherein the thermoplastic polymer is a polyamide.

23. The process as claimed in claim 1, for the manufacture of calibrated tapes suitable for the manufacture of three-dimensional composite parts, by automated layup of the tapes using a robot.

24. The use of the tape of preimpregnated fibrous material, as claimed in claim 20, in the manufacture of three-dimensional composite parts.

25. The use as claimed in claim 24, wherein the manufacture of the composite parts relates to a field selected from the group consisting of transport, oil and gas; renewable energy; sports and leisure; health and medical; ballistics with weapon or missile parts; and safety and electronics.

26. A three-dimensional composite part, wherein the three-dimensional part results from the use of at least one unidirectional tape of preimpregnated fibrous material as claimed in claim 20.

27. The process as claimed in claim 1, wherein the compression roller has a diameter of from 10 mm to 100 mm.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 presents a diagram of a unit for implementing the process for manufacturing a preimpregnated fibrous material according to the invention.

(2) FIG. 2 presents a cross-sectional diagram of two constituent rollers of a calender as used in the unit from FIG. 1.

(3) FIG. 3 gives details of a tank (20) comprising a fluidized bed (22) with a height-adjustable tension device (82). The edge of the inlet to the tank is equipped with a rotary roller 83a over which the roving 81a runs and the edge of the tank outlet is equipped with a rotary roller 83b over which the roving 81b runs.

(4) FIG. 4 presents describes an having a single compression roller, with a tank (20) comprising a fluidized bed (22) in which a single cylindrical compression roller is present and showing the angle α.sub.1.

(5) The arrows on the fiber indicate the run direction of the fiber.

(6) FIG. 5 presents an embodiment, without being limited to thereto, having two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, with a tank (20) comprising a fluidized bed (22) in which the two cylindrical compression rollers are at different levels relative to the bottom of the tank (R.sub.2 at a height H.sub.2 above R.sub.1 at a height H.sub.1) are present and showing the angles α.sub.1 and α.sub.2.

(7) The arrows on the fiber roving indicate the run direction of the roving.

(8) FIG. 6 presents an exemplary embodiment with a tank (20) comprising a fluidized bed (22) in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side-by-side and showing the angle α.sub.1, and the angle α.sub.2=0° and the roving passing between the two rollers.

(9) FIG. 7 presents an exemplary embodiment with a tank (20) comprising a fluidized bed (22) in which the two compression rollers R.sub.1 and R.sub.2 are cylindrical, at the same level relative to one another and side-by-side and showing the angle α.sub.1, and the angle α.sub.2=90° and the roving passing underneath R.sub.2.

(10) FIG. 8 presents an exemplary embodiment with a tank (20) comprising a fluidized bed (22) in which two compression rollers R.sub.1 and R.sub.2. R.sub.1 preceding R.sub.2, at different levels are present and showing the angles α.sub.1 and α.sub.2 and the roving passing under the roller R.sub.2.

(11) FIG. 9 presents an embodiment with a tank (20) comprising a fluidized bed (22) having two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, and a compression roller R.sub.3 and showing the angles α.sub.1, α.sub.2 and α.sub.3.

(12) FIG. 10 represents a photo taken with a scanning electron microscope of a cross-sectional view of a carbon fiber (¼′ Toray 12K T700S M0E carbon fiber) roving, impregnated by a PA11/6T/10T polyamide powder with D50=100 μm according to the process described in WO 2015/121583 (after calendering).

(13) The process according to WO 2015/121583 reveals a lack of homogeneity at several locations of the preimpregnated roving depicted by the white arrows.

(14) FIG. 11 represents a photo taken with a scanning electron microscope of a cross-sectional view of a ¼″ carbon fiber (Toray 12K T700S M0E fiber) roving, impregnated by a PA MPMDT/10T polyamide powder with D50=115 μm according to the process of the invention (as described in example 2, after calendering).

(15) Image analysis gives a degree of porosity of 5% excluding the edges of the tape.

(16) FIG. 12 represents a photo taken with a scanning electron microscope of a cross-sectional view of a ¼″ carbon fiber (Toray 12K 1700 fiber) roving, impregnated by a PA 11/6T/10T polyamide powder with D50=132 μm according to the process of the invention (as described in example 2, after calendering).

(17) FIG. 13 represents a photo taken with a scanning electron microscope of a cross-sectional view of a 3B HiPer Tex 2400 tex glass fiber roving, impregnated by a PA 11 polyamide powder with D50=120 μm according to the process of the invention (as described in example 3, before calendering).

(18) FIG. 14 represents a photo taken with a scanning electron micro cope of a cross-sectional view of a 3B HiPer Tex 2400 tex glass fiber roving, impregnated by a PA 11/6T/10T polyamide powder with D50=132 μm according to the process of the invention (as described in example 3, after calendering).

(19) FIG. 15 represents a photo taken with a binocular microscope of a cross-sectional view of a ½″ carbon fiber (SGL grade AA, 50K) roving, impregnated by an MPMDT/10T polyamide powder with D50=115 μm according to the process of the invention (as described in example 4, after calendering).

(20) FIG. 16 presents the fluidisation as a function of the flow rate of air. The flow rate of air applied to the fluidized bed must be between the minimum fluidizing flow rate (Umf) and the minimum bubbling flow rate (Umf).

(21) FIG. 17 presents the impregnation of flax fibers by PA11 (D50=15 to 34 μm) obtained by a molten route as a comparative example with the process of the invention (example 3).

(22) FIG. 18 presents the impregnation of Toray T700 S 24K 60E carbon fibers by MPMDT/10T (D50=115 μm) obtained by a molten route as a comparative example with the process of the invention (example 3).

(23) The following examples nonlimitingly illustrate the scope of the invention.

EXAMPLE 1 (COMPARATIVE EXAMPLE)

(24) A 12K carbon fiber roving was impregnated with PA 11/6T/10T as described in WO 2015/121583.

(25) D50=100 μM.

(26) Results:

(27) The results are presented in FIG. 10 and show a lack of homogeneity at several locations of the preimpregnated roving depicted by the white arrows.

EXAMPLE 2

General Procedure for Impregnating a (Carbon Fiber) Fibrous Material with a Polyamide Powder in a Fluidized Bed with a Single Roller

(28) The following procedure was carried out: A cylindrical compression roller in the tank (L=500 mm, W=500 mm, H=600 mm), diameter 25 mm. Residence time of 0.3 sec in the powder Angle α.sub.1 of 25° Fanning out of around 100% (i.e. a width multiplied by 2) for a ¼″ Toray, 12K T700S M0E carbon fiber roving D50=115 μm, (D10=49 μm, D90=207 μm) for the MPMDT/10T powder. D50=132 μm, (D10=72 μm and D90=225 μm) for the 11/6T/10T powder. edge of the tank equipped with a fixed roller.

(29) The fibrous material (¼″ carbon fiber roving) was preimpregnated by various polyamides (MPMDT/10T and PA 11/6T/10T of particle size defined above) according to this procedure and are presented in FIGS. 11 and 12. FIG. 11 corresponds to MPMDT/10T, FIG. 12 to PA 11/6T/10T.

(30) This demonstrates the effectiveness of the process of impregnation by a dry powder in a fluidized bed with a compression roller and control of the residence time in the powder.

EXAMPLE 3

General Procedure for Impregnating a (Glass Fiber) Fibrous Material with a (PA11 and 11/6T/10T) Polyamide Powder in a Fluidized Bed with a Single Roller

(31) The following procedure was carried out: A fixed compression roller in the tank with a diameter of 6 mm Residence time of around 5 sec Angle α.sub.1 of 45° D50 of the PA11 powder of 120 μm (D10=60 μm and D90=210 μm). D50 of the PA11/6T/10T powder of 132 μm (D10=60 μm and D90=210 μm). Edge of the tank equipped with a fixed roller.

(32) The fibrous material (2400 tex glass fiber roving) was preimpregnated by various polyamides (PA11 and 11/6T/10T) according to this procedure and are presented in FIGS. 13 and 14. FIG. 13 corresponds to PA11 and FIG. 14 to PA 11/6T/10T.

(33) This demonstrates the effectiveness of the process of impregnation by a dry powder in a fluidized bed with a compression roller and control of the residence time in the powder.

EXAMPLE 4

General Procedure for Impregnating a Fibrous Material with a Polyamide Powder in a Fluidized Bed with Two Rollers

(34) Two cylindrical compression rollers having a height difference H.sub.2-H.sub.1=2 cm, in the tank (L=500 mm, W=500, H=600), both having a diameter of 25 mm. Distance between rollers around 1 cm (as represented in FIG. 5) Residence time of 2 sec in the powder Angle α.sub.1 of 25° and angle α.sub.2 of 30° Fanning out of around 100% (i.e. a width multiplied by 2) for a ½″ SGL grade AA carbon fiber roving D50 of the powder of 98.9 μm. edge of the tank equipped with a rotary roller.

(35) The fibrous material (½″ carbon fiber roving) preimpregnated by a MPMDT/10T polyamide) was prepared according to this procedure and is presented in FIG. 15 (binocular microscope view).

(36) The degree of impregnation is 40%.

(37) This demonstrates the effectiveness of the process of impregnation by a dry powder in a fluidized bed with two compression rollers and control of the residence time in the powder.

EXAMPLE 5

Determination of the Degree of Porosity Bu Image Analysis

(38) The porosity was determined by image analysis on a ½″ carbon fiber roving impregnated by MPMDT/10T). It is 5%.

EXAMPLE 6

Determination of the Degree of Porosity—the Relative Deviation Between Theoretical Density and Experimental Density (General Method)

(39) a) The data required are: The density of the thermoplastic matrix The density of the fibers The basis weight of the reinforcement: linear density (g/m) for example for a ¼ inch tape (derived from a single roving) surface density (g/m.sup.2) for example for a wider tape or a woven fabric

(40) b) Measurements to be performed:

(41) The number of samples must be at least 30 so that the result is representative of the material studied.

(42) The measurements to be performed are: The size of the samples taken: Length (if linear density is known). Length and width (if surface density is known). The experimental density of the samples taken: Measurements of mass in air and in water. Measurement of the content of fibers is determined according to ISO 1172: 1999 or by thermogravimetric analysis (TGA) as determined for example in document B. Benzier, Applikationslabor, Mettler Toledo, Giesen, UserCom 1/2001.

(43) The measurement of the content of carbon fibers may be determined according to ISO 14127: 2008.

(44) Determination of the theoretical weight content of fibers:

(45) a) Determination of the theoretical weight content of fibers:

(46) $\%{\mathrm{Mf}}_{\mathrm{th}}=\frac{m_l.Math.L}{{\mathrm{Me}}_{\mathrm{air}}}$

(47) with

(48) m.sub.l the linear density of the tape,

(49) L the length of the sample and

(50) Me.sub.air the mass of the sample measured in air.

(51) The variation in the weight content of fibers is assumed to be directly linked to a variation in the content of matrix without taking into account the variation in the amount of fibers in the reinforcement.

(52) b) Determination of the theoretical density:

(53) $d_{\mathrm{th}}=\frac{1}{\frac{1-\%{\mathrm{Mf}}_{\mathrm{th}}}{d_m}+\frac{\%{\mathrm{Mf}}_{\mathrm{th}}}{d_f}}$

(54) with d.sub.m and d.sub.f the respective densities of the matrix and of the fibers.

(55) The theoretical density thus calculated is the accessible density if there is no porosity in the samples.

(56) c) Evaluation of the porosity;

(57) The porosity is then the relative deviation between the theoretical density and the experimental density.