METHOD FOR MANUFACTURING A FIBROUS MATERIAL IMPREGNATED WITH THERMOPLASTIC POLYMER

Abstract

Method for manufacturing a continuous fiber material and a thermoplastic polymer matrix, the material being made from a unidirectional tape, the method comprising a step of pre-impregnating a roving of the material with the matrix and a step of melting the matrix, the melting step being carried out by means of a heat-conducting tension device and a heating system, the tension device being thermostatically controlled at a temperature, for a semi-crystalline thermoplastic polymer, from Tc−30° C. to Tf+50° C., and, for an amorphous polymer, from Tg+50° C. to Tg+250° C., the roving running over the surface of the tension device in the heating system, and the porosity rate in the material being less than 10%.

Claims

1. A method for manufacturing an impregnated fibrous material comprising a fibrous material made of continuous fibers and at least one thermoplastic polymer matrix, wherein said impregnated fibrous material is produced as a single unidirectional ribbon or a plurality of unidirectional parallel ribbons and wherein said method comprises a step of pre-impregnating said fibrous material in the form of a roving or several parallel rovings with said thermoplastic polymer and at least one step of heating the thermoplastic polymer matrix making it possible to melt, or maintain in the molten state, said thermoplastic polymer after pre-impregnation, the at least one heating step being carried out by means of at least one heat-conducting supporting part (E) and at least one heating system, with the exception of a heating calender, said at least one supporting part (E) being temperature-controlled at a temperature, for a thermoplastic semi-crystalline polymer, of Tc−30° C. to Tm+50° C. of said polymer, and for an amorphous polymer, of Tg+50° C. to Tg+250° C. of said polymer, said roving or rovings being in contact with all or part of the surface of said at least one supporting part (E) and partially or wholly passing over the surface of the at least one supporting part (E) present at the level of the heating system, and the porosity level in said pre-impregnated fibrous material being less than 10%.

2. The method according to claim 1, wherein said temperature-controlled supporting part (E) is in controlled rotation.

3. The method according to claim 1, wherein said pre-impregnated fibrous material is not flexible.

4. The method according to claim 1, wherein the pre-impregnation is carried out with a system chosen from a fluidized bed, a spraying using a gun, and the molten route.

5. The method according to claim 4, wherein one or more supporter(s) (E″) is (are) present upstream of said system.

6. The method according to claim 1, wherein a pre-impregnation step and a heating step are carried out, said heating step immediately following the pre-impregnation step.

7. The method according to claim 1, wherein said at least one heating system is selected from an infrared lamp, a UV lamp, and convection heating.

8. The method according to claim 1, wherein said at least one supporting part (E) is a compression roller R′i with a convex, concave or cylindrical shape.

9. The method according to claim 8, wherein said at least one supporting part (E) is made up of 1 to 15 cylindrical compression rollers (R′.sub.1 to R′.sub.15).

10. The method according to claim 8, wherein said roving(s) form(s) an angle α′.sub.1 of 0.1 to 89° with a first compression roller R′.sub.1 and the horizontal tangent to said roller R′.sub.1, said roving(s) expanding in contact with said first compression roller.

11. The method according to claim 8, wherein a second roller R′.sub.2 is present after said first compression roller R′.sub.1, said roving(s) forming an angle α′2 of 0 to 180° with said second compression roller R′.sub.2 and the horizontal tangent to said roller R′.sub.2, said roving(s) expanding in contact with said second compression roller.

12. The method according to claim 9, wherein at least one third roller R′.sub.3 is present after said second roller R′.sub.2, said roving(s) forming an angle α′.sub.3 of 0 to 180° with said third compression roller R′.sub.3 and the horizontal tangent to said compression roller R′.sub.3, said roving(s) expanding in contact with said third compression roller R′.sub.3.

13. The method according to claim 9, wherein six to ten rollers are present and at the same level.

14. The method according to claim 1, wherein the spreading percentage at the outlet of the last compression roller R′.sub.i is about 0 to 300%, relative to that of said roving(s) at the inlet of the first compression roller R′.sub.1.

15. The method according to claim 1, wherein said thermoplastic polymer is a nonreactive thermoplastic polymer.

16. The method according to claim 1, wherein said thermoplastic polymer is a reactive pre-polymer capable of reacting with itself or with another pre-polymer, based on the chain ends borne by said pre-polymer, or else with a chain extender, said reactive polymer optionally being polymerized during the heating step.

17. The method according to claim 1, wherein said at least one thermoplastic polymer is selected from: polyaryl ether ketones (PAEK); polyaryl ether ketone ketones (PAEKK); aromatic polyether imides (PEI); polyaryl sulfones; polyarylsulfides; polyamides (PA); PEBAs, polyacrylates; polyolefins; and mixtures thereof.

18. The method according to claim 1, wherein said at least one thermoplastic polymer is a polymer with a glass transition temperature such that Tg≥80° C., or a semi-crystalline polymer with a melting temperature Tm≥150° C.

19. The method according to claim 1, wherein said at least one thermoplastic polymer is selected from polyamides, PVDF, PEEK, PEKK, PEI and a PEKK and PEI mixture.

20. The method according to claim 1, wherein the fiber level in said impregnated fibrous material is from 45 to 65% by volume.

21. The method according to claim 1, wherein the porosity level in said pre-impregnated fibrous material is less than 10%.

22. The method according to claim 1, wherein it also comprises a step of shaping said roving or said parallel rovings of said impregnated fibrous material, by calendering using at least one heating calender in the form of a single unidirectional ribbon or a plurality of parallel unidirectional ribbons with, in the latter case, said heating calender comprising a plurality of calendering grooves, in accordance with the number of said ribbons and with a pressure and/or separation between the rollers of said calender regulated by a closed-loop control system.

23. The method according to claim 22, wherein the calendering step is carried out using a plurality of heating calenders, mounted in parallel and/or in series relative to the passage direction of the fiber rovings.

24. The method according to claim 22, wherein said heating calender(s) comprise(s) an integrated induction or microwave heating system, coupled with the presence of carbon-based fillers in said thermoplastic polymer or mixture of thermoplastic polymers.

25. The method according to claim 1, wherein a belt press is present between the heating system and the calender.

26. The method according to claim 1, wherein a heating die is present between the heating system and the calender.

27. The method according to claim 1, wherein a belt press is present between the heating system and the calender and a heating die is present between the belt press and the calender.

28. The method according to claim 1, wherein said pre-impregnation and impregnation steps are supplemented by a step of covering said single roving or said plurality of parallel rovings after impregnation by the powder, said covering step being carried out before said calendering step, with a molten thermoplastic polymer, which may be identical to or different from said pre-impregnation polymer.

29. The method according to claim 1, wherein said thermoplastic polymer further comprises carbon-based fillers.

30. The method according to claim 1, wherein said fibrous material comprises continuous fibers selected from carbon, glass, silicon carbide, basalt, silica fibers, natural fibers, or amorphous thermoplastic fibers with a glass transition temperature Tg higher than the Tg of said polymer or said polymer mixture when the latter is amorphous or higher than the Tm of said polymer or said polymer mixture when the latter is semi-crystalline, or the semi-crystalline thermoplastic fibers with a melting temperature Tm higher than the Tg of said polymer or said polymer mixture when the latter is amorphous or higher than the Tm of said polymer or said polymer mixture when the latter is semi-crystalline, or a mixture of two or more of said fibers.

31. A unidirectional ribbon of pre-impregnated fibrous material, wherein the ribbon is obtained by a method as defined according to claim 1.

32. The ribbon according to claim 31, wherein it has a width (I) and thickness (ep) suitable for robot application in the manufacture of three-dimensional workpieces, without the need for slitting.

33. The ribbon according to claim 31, wherein the thermoplastic polymer is an aliphatic polyamide selected from PA 6, PA 11, PA 12, PA 66, PA 46, PA 610, PA 612, PA 1010, PA 1012, PA 11/1010 or PA 12/1010 or a semi-aromatic polyamide or selected from PA 6/6T, PA 61/6T, PA 66/6T, PA 11/10T, PA 11/6T/10T, PA MXDT/10T, PA MPMDT/10T, PA BACT/6T, PA BACT/10T and PA BACT/10T/6T, PA BACT/10T/11, PA BACT/6T/11, a PVDF, a PEEK, PEKK and a PEI or a mixture thereof.

34. A use of the method as defined according to claim 1, for the manufacture of calibrated ribbons suitable for the manufacture of three-dimensional composite parts, by the automated laying of said ribbons by means of a robot.

35. A use of the ribbon of pre-impregnated fibrous material, as defined according to claim 31, in the manufacture of three-dimensional composite parts.

36. The use according to claim 34, wherein said manufacture of said composite parts concerns the fields of transportation; renewable energies; thermal protection panels; sports and leisure, health and medical and electronics.

37. A three-dimensional composite part, wherein it results from the use of at least one unidirectional ribbon of pre-impregnated fibrous material as defined according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0554] FIG. 1 shows a diagram of a heating system according to the invention with three rollers.

[0555] FIG. 2 describes a tank (10) comprising a fluidized bed (12) with a supporting part, the height (22) of which is adjustable. The edge of the inlet of the tank is equipped with a rotating roller 23a over which the roving 21a passes and the edge of the tank outlet is equipped with a rotating roller 23b over which the roving 21b passes.

[0556] FIG. 3 describes an embodiment with a single compression roller, with a tank (10) comprising a fluidized bed (12) in which a single cylindrical compression roller (24) is present and showing the angle at

[0557] The arrows at the fiber indicate the passage direction of the fiber.

[0558] FIG. 4 shows, but is not limited to, an embodiment with two compression rollers R.sub.1 and R.sub.2, R.sub.1 preceding R.sub.2, with a tank (10) comprising a fluidized bed (12) in which the two cylindrical compression rollers are at different heights 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 angle α.sub.1 and α.sub.2.

[0559] The arrows at the fiber roving indicate the passage direction of the fiber.

[0560] FIG. 5 shows an exemplary embodiment with the tank (10) comprising a fluidized bed (12) 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 2 rollers.

[0561] FIG. 6 shows an exemplary embodiment with the tank (10) comprising a fluidized bed (12) 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 below R.sub.2.

[0562] FIG. 7 shows an exemplary embodiment with the tank (20) comprising a fluidized bed (12) 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 angle α.sub.1 and α.sub.2 and the roving passing below the roller R.sub.2.

[0563] FIG. 8 shows an embodiment with a tank (10) comprising a fluidized bed (12) with 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.

[0564] FIG. 9 shows a photo taken with scanning electron microscopy of a sectional view of a ¼″ Toray carbon fiber roving, 12K T700S M0E impregnated by a PA11/6T/10T of D50=100 μm polyimide powder according to the method described in WO 2015/121583 (after calendering).

[0565] The method according to WO 2015/121583 shows a lack of homogeneity in several locations of the impregnated roving diagrammed by the white arrows.

[0566] FIG. 10 shows the fluidization as a function of the air flow rate. The air flow rate applied to the fluidized bed must be between the minimum fluidization flow rate (Umf) and the minimum bubbling flow rate (Umf).

[0567] FIG. 11 describes a tank (20) with a supporting part, the height (22) of which is adjustable. The edge of the inlet of the tank is equipped with a rotating roller 23a over which the roving 21a passes and the edge of the tank outlet is equipped with a rotating roller 23b over which the roving 21b passes.

[0568] FIG. 12 shows an embodiment with a single compression roller, with a tank (30) comprising a spray gun (31) for spraying powder (32) in which a single cylindrical compression roller (33) is present and showing the angle α″.sub.1.

[0569] The arrows at the fiber indicate the passage direction of the fiber.

[0570] FIG. 13 shows, but is not limited to, an embodiment with two compression rollers R″.sub.1 and R″.sub.2, R″.sub.1 preceding R″.sub.2, with a tank (30) each comprising a spray gun (31) for spraying powder (32) and in which the two cylindrical compression rollers are at different heights 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 angle α″.sub.1 and α″.sub.2.

[0571] The arrows at the fiber roving indicate the passage direction of the fiber.

[0572] FIG. 14 shows an exemplary embodiment with the tank (30) comprising a spray gun (31) for spraying powder (32) 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 2 rollers.

[0573] FIG. 15 shows an exemplary embodiment with the tank (30) each comprising a spray gun (31) for spraying powder (32) and 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 below R″.sub.2.

[0574] FIG. 16 shows an exemplary embodiment with a tank (30) each comprising a spray gun (31) for spraying powder (32) and 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 angle α″.sub.1 and α″.sub.2 and the roving passing below the roller R″.sub.2.

[0575] FIG. 17 shows an embodiment with a tank (30) with two compression rollers R″.sub.1 and R″.sub.2, R″.sub.1 preceding R″.sub.2, each comprising a spray gun (31) for spraying powder (32) and a compression roller R″.sub.3 comprising a spray gun (31) for spraying powder (32) and showing the angles α″.sub.1, α″.sub.2 and α″.sub.3.

[0576] FIG. 18 shows a photo taken with a scanning electron microscope of a sectional view of a ¼″ Toray carbon fiber roving, 12K T700S 31E impregnated by a D50=120 μm PA MPMDT/10T powder according to the method with non-temperature-controlled supporters.

[0577] The diameter of a fiber represents 7 μm.

[0578] FIG. 19 shows the view of the fouled supporter, since it was not temperature-controlled, after 2 h of use.

[0579] FIG. 20 shows a photo taken with a scanning electron microscope of a sectional view of a ¼″ Toray carbon fiber roving, 12K T700S 31E impregnated by a D50=120 μm PA MPMDT/10T powder according to the inventive method described in example 2.

[0580] The diameter of a fiber represents 7 μm.

[0581] FIG. 21 shows the view of the unfouled supporter, since it was temperature-controlled and in controlled rotation, after 1 day of use

EXAMPLES

[0582] The following examples provide a non-limiting illustration of the scope of the invention.

Comparative Example 1: General Procedure Comprising a Step of Pre-Impregnation of a Fibrous Material (Carbon Fiber) with an MPMDT/10T (67/33 Mol %) Powder in a Tank Comprising a Fluidized Bed Provided with a Single Roller and a Step of Infrared Heating with a Non-Temperature-Controlled Roller

[0583] The following procedure was carried out:

Pre-Impregnation Step

[0584] A cylindrical compression roller R.sub.1 in the tank (L=500 mm, I=500 mm, H=600 mm), diameter 25 mm. [0585] Residence time of 0.3 s in the powder

[0586] Angle α.sub.1 of 25°

[0587] Spreading about 100% (that is a width multiplied by 2) for a carbon fiber roving of Toray ¼″ carbon, 12K T700S 31E PA MPMDT/10T (67/33 mol %): Tc=230° C., Tm=272° C.

MPMDT/10T (67/33 mol %) powder: D50=120 μm, (D10=45 μm, D90=280 μm).

[0588] edge of the tank equipped with a stationary roller.

[0589] The fibrous material (¼″ carbon fiber roving) was pre-impregnated with a polymer (MPMDT/10T with particle size defined hereinabove) according to this procedure.

Heating Step

[0590] The heating system used is that described in FIG. 1, but with eight stationary cylindrical metal rollers R′.sub.1 to R′.sub.8 with diameter 15 mm.

[0591] The speed of advance of the roving is 10 m/min.

[0592] The infrared used has a power of 25 kW, the height between the infrared and the upper roller is 4 cm and the height between the infrared and the lower rollers is 9 cm.

[0593] After 30 min of operation, the supporters reached a temperature of 340° C. (measurement by thermocouple)

[0594] The angles α′.sub.1 to α′.sub.8 are identical and 25°.

[0595] The height h is 20 mm.

[0596] The length l is 1000 mm.

[0597] The eight rollers are each separated by 43 mm.

[0598] Calendering using two calenders mounted in series equipped with an IR of 1 kW each after the heating step.

[0599] FIG. 18 shows the impregnated fibrous material obtained with PA MPMDT/10T under these method conditions without a temperature-controlled supporter: a good impregnation quality was obtained.

[0600] FIG. 19 shows the fouling of the supporters after 2 h of production: the accumulation of small carbon fibrils is observed, bonded together by the PA MPMDT/10T resin which has accumulated over time.

Example 2: General Procedure Comprising a Step of Pre-Impregnation of a Fibrous Material (Carbon Fiber) with an MPMDT/10T (67/33 Mol %) Powder in a Tank Comprising a Fluidized Bed Provided with a Single Roller and a Step of Infrared Heating with a Roller Temperature-Controlled at 245° C.

[0601] The same protocol is used as for example 1, with the difference that the rollers under infrared are temperature-controlled at 245° C.

[0602] The rollers are heated by IR radiations, and the temperature at the surface of the rollers is measured using pyrometers. Cooling is provided by cold air (20° C.) pulsed into the rollers. Regulation is provided by a PID which triggers the pulses of air (it controls the appearance and duration thereof) to the core of the bars.

[0603] FIG. 20 shows the impregnated fibrous material obtained with PA MPMDT/10T of comparative example 1 and rollers temperature-controlled at 245° C.

[0604] The impregnation of the fibrous material is identical to that obtained without temperature-controlled rollers.

[0605] FIG. 21 shows that, in this case, the fouling of the supporters is greatly reduced.

[0606] This demonstrates the effectiveness of the method for impregnation by a dry powder in fluidized bed with a compression roller and the control of the residence time in the powder combined with a heating step using temperature-controlled rollers.

Example 3: Determination of the Porosity Level by Image Analysis

[0607] The porosity was determined by image analysis on a ¼″ carbon fiber roving impregnated by MPMDT/10T in fluidized bed with upstream supporters followed by a heating step as defined hereinabove.

[0608] It is less than 5%.

Example 4: Determination of the Porosity Level the Relative Deviation Between Theoretical Density and Experimental Density (General Method) a)

[0609] The required data are:

[0610] The density of the thermoplastic matrix

[0611] The density of the fibers

[0612] The grammage of the reinforcement:

[0613] linear mass (g/m) for example for a ¼ inch tape (coming from a single roving)

[0614] surface density (g/m.sup.2) for example for a wider tape or a fabric

b) Measurements to be Carried Out:

[0615] The number of samples must be at least 30 in order for the result to be representative of the studied material:
The measurements to be carried out are:

[0616] The size of the samples taken:

[0617] Length (if linear mass is known).

[0618] Length and width (if surface density is known).

[0619] The experimental density of the samples taken:

[0620] Mass measurements in the air and in water.

[0621] The measurement of the fiber level is determined according to ISO 1172:1999 or by thermogravimetric analysis (TGA) as determined for example in the document B. Benzler, Applikationslabor, Mettler Toledo, Giesen, UserCom 1/2001.

[0622] The measurement of the carbon fiber level is determined according to ISO 14127:2008.

[0623] Determination of the theoretical mass fiber level:

a) Determination of the Theoretical Mass Fiber Level:

[0624] [00001]$\begin{array}{cc}\%{\mathrm{Mf}}_{\mathrm{th}}=\frac{m_I.Math.L}{{\mathrm{Me}}_{\mathrm{air}}}& \left[\mathrm{Math}1\right]\end{array}$

With

[0625] m.sub.l the linear mass of the tape,
L the length of the sample, and
Me.sub.air the mass of the sample measured in the air.
The variation of the mass fiber level is presumed to be directly related to a variation of the matrix level without taking into account the variation of the quantity of fibers in the reinforcement.

b) Determination of the Theoretical Density:

[0626] [00002]$\begin{array}{cc}{d}_{\mathrm{th}}=\frac{1}{\frac{1-\%{\mathrm{Mf}}_{\mathrm{th}}}{d_m}+\frac{\%{\mathrm{Mf}}_{\mathrm{th}}}{d_f}}& \left[\mathrm{Math}2\right]\end{array}$

With d.sub.m and d.sub.f the respective densities of the matrix and the fibers.
The theoretical density thus calculated is the accessible density if there is no porosity in the samples.

c) Evaluation of the Porosity:

[0627] The porosity then is the relative deviation between theoretical density and experimental density.