EP4499369A1 - Process for the manufacture of a filament made of composite material and related system - Google Patents

Abstract

The process for the manufacture of a filament made of composite material comprises at least the phases of: - supply of at least one filament (3) comprising at least one fiber (4) and of at least one resin (6); - application of the resin (6) to the filament (3) to obtain a coated filament (7); - heating of the coated filament (7) to obtain a composite filament (9); wherein the phase of application is performed by gravity distribution of the resin (6) on the filament (3).

Description

PROCESS FOR THE MANUFACTURE OF A FILAMENT MADE OF COMPOSITE MATERIAL AND RELATED SYSTEM

Technical Field

The present invention relates to a process for the manufacture of a filament made of composite material and related system.

Background Art

As is well known, filaments made of composite material are filaments made of a fibrous material, such as e.g. carbon fiber, aramid fiber or other types of fibers, coated with a resin made of polymeric plastic material.

Composite filaments are used in the field of 3D printing in order to give greater strength to manufactured artifacts, compared to the use of plastic material alone. A process for the manufacture of a filament made of composite material is known from document US2020283591A1. The process involves dipping a filament made of a mixture of thermosetting resin in a solvent. The filament is then heated to allow the binder to cure.

The process described by US2020283591A1 has some drawbacks mainly related to the fact that the resin/solvent mixture is contained in a tank which is open at the top to allow the filament to be dipped. However, the application of resin by dipping in the resin/solvent mixture is not always uniform and varies depending on the dipping time of the filament in the mixture itself.

In addition, the described system US2020283591A1 inevitably results in the evaporation of part of the solvent from the mixture contained in the tank. The evaporation of the solvent alters the concentration of the resin in the mixture and, consequently, also the amount of resin which adheres to the filament following dipping, making the coating non-uniform.

It is, therefore, necessary to make frequent adjustments of the process parameters and checks of the mixture concentration and then top up with the missing solvent in order to obtain a homogeneously and uniformly coated composite filament.

In addition, the use of an open tank results in the dispersion of huge amounts of solvent that cause pollution of the surrounding environment, increase the risk of flammability and explosions and can be harmful to the operators.

Description of the Invention

The main aim of the present invention is to devise a process for the manufacture of a filament made of composite material and a related system which allow obtaining a homogeneously and uniformly coated composite filament.

A further object of the present invention is to devise a process for the manufacture of a filament made of composite material and a related system which allow obtaining a composite filament which is robust and not prone to fraying.

Another object of the present invention is to devise a process for the manufacture of a filament made of composite material and a related system which allow minimizing the risk of pollution of the surrounding environment and be safe for the operators.

Another object of the present invention is to devise a process for the manufacture of a filament made of composite material and a related system which allow the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and effective to use as well as affordable solution.

The aforementioned objects are achieved by this process for the manufacture of a filament made of composite material and a related system having the characteristics of claim 1.

The aforementioned objects are further achieved by the present system for the manufacture of a filament made of composite material having the characteristics of claim 20.

The aforementioned objects are further achieved by the present process for the manufacture of a filament made of composite material having the characteristics of claim 26.

The aforementioned objects are further achieved by the present system for the manufacture of a filament made of composite material having the characteristics of claim 27. of the Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a process for the manufacture of a filament made of composite material and a related system, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings in which:

Figure 1 is a schematic representation of a system in the execution of a process according to the invention, in accordance with a first embodiment;

Figure 2 is a schematic representation of a system in the execution of a process according to the invention, in accordance with a second embodiment;

Figure 3 is a schematic representation of a system in the execution of a process according to the invention, in accordance with a third embodiment;

Figure 4 is a schematic representation of a system in the execution of a process according to the invention, in accordance with a fourth embodiment;

Figure 5 is a schematic representation of a system in the execution of a process according to the invention, in accordance with a fifth embodiment;

Figures 6-9 are schematic representations of compaction means according to the invention, in accordance with different embodiments;

Figures 10-11 are schematic cross-sectional representations of a composite filament obtained by means of the present invention, in accordance with different embodiments.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a system for the manufacture of a filament made of composite material.

In the context of this disclosure, the term “composite material” means a product composed of two or more different types of materials, e.g., fabric/plastic, metal/plastic, plastic/glass or the like, in which the combination of these materials gives the finished product special physical-mechanical properties.

The system 1 comprises: movement means 2 adapted to move a filament 3 comprising at least one fiber 4 along a direction of work D; application means 5 adapted to apply at least one resin 6 to the filament 3 to obtain a coated filament 7; heating means 8 adapted to heat the coated filament 7 to obtain a composite filament 9.

Specifically, the filament 3 may comprise a single continuous fiber or a plurality of fibers depending on the thickness desired to be imparted to the composite filament 9 and to the required strength.

The filament 3 can be made in the form of a “yarn”, i.e. a set of fibers 4 held together by twisting to form a thread, or in the form of a “tow”, i.e. an untwisted bundle of continuous fibers 4.

The fiber 4 is selected from: carbon fiber, aramid fiber, glass fiber, polymer fiber, boron fiber, basalt fiber, optical fiber, metallic fiber, ceramic fiber, fiber of natural plant origin such as, e.g., flax fiber, hemp fiber, etc.

Preferably, the filament 3 is of the continuous type.

The filament 3 can, e.g., be wound around a spool and unwound during use along the direction of work D to allow the various operational steps to be carried out.

The resin 6 comprises at least one polymeric material and will be described in more detail later in this disclosure.

The application means 5 and the heating means 8 are arranged in succession along the direction of work D.

The system 1 also comprises tensioning means 10 adapted to adjust the tensioning of the filament 3.

The tensioning of the filament 3 allows optimizing and making the application of the resin 6 extremely smooth.

In fact, a predefined and constant tension ensures the utmost precision in the amount of the resin 6 applied to the filament 3 thus making the distribution of the same more uniform. A predefined tensioning also reduces the risk of fiber fraying and tearing and induces minimal deformation of the composite filament 9.

In accordance with the embodiments shown in the figures, the tensioning means 10 coincide with the movement means 2 and comprise a series of pulleys, on which the filament 3 is wound at least partly, adapted both to adjust the tensioning of the filament itself and to determine the movement thereof along the direction of work D.

The tensioning means 10 are provided with a tensioning control system adapted to keep constant tensioning.

Once the filament 3 is tensioned, the resin 6 is applied thereon.

According to the invention, the application means 5 comprise at least one dispensing device 11 adapted to dispense the resin 6 by gravity onto the filament 3.

The dispensing device 11 is arranged on top of the filament 3 and the resin 6 is applied by gravity.

In other words, the filament 3 is not dipped into the resin 6, but rather the latter is applied from above.

The coated filament 7 is then led to the heating means 8 which allow the resin 6 to be heated and made it adhere to the filament 3 to obtain the composite filament 9.

In particular, the heating means 8 may comprise, e.g., an oven. It cannot, however, be ruled out that the heating means 8 may be of a different type.

Advantageously, the system 1 also comprises compaction means 12 arranged downstream of the application means 5 with respect to the direction of work D and adapted to compact the resin 6 on the filament 3.

The compaction means 12 further allow making uniform the amount of resin 6 on the filament 3 and, in addition, allow optimizing the fixation of the resin itself.

Figures 6 to 9 show possible embodiments of the compaction means 12.

In detail, Figures 6 and 7 show embodiments wherein the compaction means 12 are arranged upstream of the heating means 8 with respect to direction of work

D.

Compaction of the coated filament 7 is, therefore, carried out prior to heating.

Figures 8 and 9, on the other hand, show embodiments wherein the compaction means 12 are arranged within the heating means 8.

Compaction of the coated filament 7 is, therefore, carried out, at the same time as heating.

In both cases, the compaction means 12 may comprise, e.g., a pair of rollers 13 through which the coated filament 7 is made to pass.

The rollers 13 are arranged at a predefined distance with each other, depending on the thickness given to the composite filament 9.

The rollers 13 can be of the fixed type or connected to shock- absorbing devices 14 which allow minimal oscillation thereof and optimize compaction, making the composite filament 9 even more uniform.

Possibly, the compaction means 12 may comprise a heating system adapted to heat the rollers 13.

It cannot, however, be ruled out that the compaction means 12 may be of different type and comprise, e.g., systems provided with a plurality of sets of rollers arranged in succession with each other, flat section compaction system and bottleneck compaction systems.

Downstream of the heating means 8, the system 1 then comprises cooling means adapted to reduce the temperature of the composite filament 9.

The cooling means, not shown in detail in the figures, may comprise, e.g., a refrigerated chamber. Alternatively, cooling can take place at room temperature. The composite filament 9 can then be wound back on itself, e.g. in the form of a spool for later use.

In particular, the system 1 may comprise a shifting movement system adapted to allow uniform winding of the composite filament 9 in the spool.

Alternatively, the composite filament 9 may be directly moved to deposition systems, e.g. of the type of 3D printers or a preforming deposition system.

Figures 10 and 11 schematically show in section two possible types of composite filament 9 obtainable by means of the system and of the process according to the invention.

As shown in these figures, the fibers 4 of the filament 3 are homogeneously and evenly coated by the resin 6. In particular, the composite filament 9 may have a rectangular cross section, wherein the fibers 4 are arranged in a plurality of rows and columns (Figure 10). Alternatively, the composite filament 9 may have a curvilinear section, e.g. circular or elliptical (Figure 11).

Again, the composite filament 9 may have an irregular section, not shown in detail in the figures.

The embodiments shown in Figures 1 through 4 will now be described in more detail.

In accordance with the embodiments shown in Figures 1 and 2, the resin 6 is in liquid form.

In more detail, the resin 6 is mixed with at least one solvent to obtain a liquid mixture 15.

Specifically, the solvent is selected from the list comprising: acetone, methyl ethyl ketone, toluene, isopropyl alcohol.

The use of one or more solvents of different type cannot however be ruled out.

In accordance with these embodiments, distribution by gravity is carried out by dripping the mixture 15 onto the filament 3.

The mixture 15 is, then, applied dropwise onto the filament 3 so as to impregnate and coat the filament 3 as a result of the movement of the latter along the direction of work D.

The dispensing device 11 is adapted to determine the drop of mixture 15 drops onto the filament 3.

Conveniently, the dispensing device 11 comprises at least one of a pumping device, a piezoelectric device and a vibration device.

The dispensing device 11 allows precise dispensing of the mixture 15 and allows containing the amount of solvent which may be released into the environment as it evaporates.

In addition, the dispensing device 11 allows dispensing a mixture 15 provided with a predefined and constant concentration at all times so that the composite filament 9 has a uniform and constant coating.

In fact, solvent evaporation occurs, at least partly, only after the deposition of the mixture 15 on the filament 3.

For this purpose, the system 1 may comprise suction means, not shown in detail in the figures and adapted to remove and recover the evaporated solvent. Complete evaporation of the solvent is then carried out by means of the heating means 8.

In accordance with a first embodiment shown in Figure 1 , the resin 6 comprises at least one thermosetting polymeric material selected from the list comprising: epoxy resin, polyvinyl ester, polyester, polyurethane, phenolic resin, polycyclopentadiene, polyimide.

The resin 6 in accordance with such an embodiment cures by heating.

The heating means 8 are, therefore, further adapted to cause the curing of the resin 6.

Figure 2 shows a second embodiment that differs from the previous one by the fact that the resin 6 comprises at least one thermoplastic polymeric material selected from the list comprising: polystyrene, polyethyleneimine, polyether- ether-ketone, polyamide, polyethylene terephthalate, polypropylene, polylactic acid, acrylonitrile butadiene styrene.

The resin 6 in accordance with such an embodiment softens during heating.

In this case, the heating means 8 are further adapted to cause the melting of the resin 6.

In accordance with this embodiment, the cooling means are adapted to cause the resin 6 to cure in order to obtain the composite filament 9.

Figures 3 and 4 show additional embodiments that differ from the previous ones by the fact that the resin 6 is in the powdery form.

Such embodiments do not involve the use of a solvent, thus allow further reducing the environmental impact and eliminating the risk of flammability and explosions and health hazards to operators.

In this case, the distribution by gravity is carried out by means of the dispersion of the powder on the filament 3.

For this purpose, the dispensing device 11 comprises at least one of a vibration device, a compressed air device, a worm screw device. The dispensing device 11 allows dispensing predefined amounts of powder in a way that enables precise and uniform coating.

In particular, Figure 3 shows a third embodiment wherein the resin 6 comprises at least one thermosetting polymeric material.

Similarly to what has been described for the first embodiment, therefore, the resin 6 cures by heating.

In this case, the heating means 8 are configured to determine the curing of the resin 6 only.

Figure 4, on the other hand, shows a fourth embodiment wherein the resin 6 comprises at least one thermoplastic polymeric material.

Similarly to what has been described for the second embodiment, therefore, the resin 6 softens during heating.

In this case, the heating means 8 are configured to determine the melting of the resin 6 only.

The operation of the system 1, in accordance with the aforementioned embodiments, in the execution of the process according to the invention is as follows.

The process comprises at least the phases of: supply of at least one filament 3 comprising at least one fiber 4 and of at least one resin 6; application of the resin 6 to the filament 3 to obtain a coated filament 7 ; heating of the coated filament 7 to obtain a composite filament 9.

Advantageously, the phases are carried out continuously by means of the movement of the filament 3 along a direction of work D.

The filament 3 is moved along the direction of work D in order to carry out the various phases of the process. This operation is carried out by means of the movement means 2.

The process also comprises a phase of tensioning the filament 3, which is carried out by means of the tensioning means 10.

Once the filament 3 is tensioned, the resin 6 is applied onto it by means of the application means 5. According to the invention, the phase of application is carried out by distribution by gravity of the resin 6 on the filament 3.

In other words, the filament 3 is not dipped into the resin 6, but rather the latter is applied from above.

The distribution by gravity is carried out by means of the dispensing device 11. Following the application of the resin 6, the process then comprises the phase of heating, carried out by the heating means 8, through which the resin 6 is heated and adheres to the filament 3 to obtain the composite filament 9.

Advantageously, the process also comprises a phase of compaction of the resin 6 on the filament 3.

The phase of compaction, carried out by means of the compaction means 12, allows further equalizing the amount of resin 6 on the filament 3 and, in addition, allows optimizing the fixation of the resin itself.

Figures 6 and 7 show possible embodiments wherein the phase of compaction is carried out prior to the phase of heating.

Figures 8 and 9, on the other hand, show alternative embodiments wherein the phase of compaction is carried out at the same time as the phase of heating.

Subsequently to the phase of heating, the process comprises a phase of cooling the composite filament 9.

The phase of cooling allows the temperature of the composite filament 9 to be reduced, which can then be wound onto itself again, e.g., in the form of a coil.

In accordance with the embodiments shown in Figures 1 and 2, the resin 6 is mixed with at least one solvent to obtain a liquid mixture 15.

In accordance with these embodiments, the distribution by gravity is carried out by dripping the mixture 15 onto the filament 3.

The mixture 15 is, then, applied dropwise onto the filament 3 so as to impregnate and coat the filament 3 as a result of the movement of the latter along the direction of work D.

The subsequent phase of heating then comprises a sub-phase of evaporation of the solvent.

The solvent is, therefore, moved away by heating the deposited mixture 15 leaving only the resin 6 applied onto the filament 3.

In accordance with a first embodiment shown in Figure 1 , the resin 6 comprises at least one thermosetting polymeric material.

The resin 6 in accordance with such an embodiment cures by heating.

For this purpose, the phase of heating also comprises a sub-phase of curing the resin 6.

The sub-phase of evaporation and the sub-phase of curing are usefully carried out at the same temperature.

It cannot however be ruled out that the sub-phase of evaporation and the subphase of curing can be carried out at different temperatures.

In other words, the heating means 8 can operate at a single temperature or at different temperatures.

A second embodiment is shown in Figure 2, which differs from the previous one by the fact that the resin 6 comprises at least one thermoplastic polymeric material.

The resin 6 in accordance with such an embodiment softens during heating.

The phase of heating comprises a sub-phase of melting the resin 6.

The sub-phase of heating is carried out so as to cause the melting of the resin 6 and the coating of the filament 3.

In accordance with this embodiment, the subsequent phase of cooling causes the curing of the resin 6 to obtain the composite filament 9.

Figures 3 and 4 show additional embodiments that differ from the previous ones by the fact that the resin 6 is in the powdery form.

In this case, distribution by gravity is carried out by means of the dispersion of the powder on the filament 3.

In particular, a third embodiment is shown in Figure 3 wherein the resin 6 comprises at least one thermosetting polymeric material.

Similarly to what has been described for the first embodiment, therefore, the resin 6 cures by heating.

In this case, the phase of heating comprises only the sub-phase of curing the resin 6. Figure 4, on the other hand, shows a fourth embodiment wherein the resin 6 comprises at least one thermoplastic polymeric material.

Similarly to what has been described for the second embodiment, therefore, the resin 6 softens during heating.

In this case, the phase of heating comprises only the sub-phase of melting the resin 6.

Figure 5 shows a system 1 for the manufacture of a filament made of composite material in accordance with an additional embodiment.

Similarly to the above, the system 1 comprises: movement means 2 adapted to move a filament 3 comprising at least one fiber 4 along a direction of work D; application means 5 adapted to apply at least one resin 6 to the filament 3 to obtain a coated filament 7; and heating means 8 adapted to heat the coated filament 7 to obtain a composite filament 9.

According to the invention, the resin 6 is in the powdery form and the application means 5 comprise at least one application device 16 adapted to contain the resin 6 and to receive the filament 3 by dipping.

The application device 16 is of the type, e.g., of a tank or the like.

The movement means 2 are configured to lead the filament 3 inside the application device 16 and to dip it into the powdery resin 6 to obtain the coated filament 7.

Once out of the application device 16, the coated filament 7 is then moved towards the heating means 8.

Similarly to the above, the system 1 may comprise compaction means 12 in accordance with one of the described embodiments.

Also in this case, moreover, the resin 6 may comprise a thermosetting polymeric material or a thermoplastic polymeric material.

The powdery resin 6 is, then, cured by heating or by melting and subsequent cooling, respectively.

The operation of the system, in accordance the fifth embodiment, in the execution of the process according to the invention is as follows.

The process comprises the phases of: supply of at least one filament 3 comprising at least one fiber 4 and at least one resin 6; application of the resin 6 to the filament 3 to obtain a coated filament 7 ; heating of the coated filament 7 to obtain a composite filament 9.

According to the invention, the resin 6 is in the powdery form and the phase of application is carried out by dipping the filament 3 in the resin 6.

During the phase of application, the filament 3 is coated with the powdery resin and later subjected to heating.

The absence of solvent allows application by dipping, reducing the environmental impact and avoiding the risk of fire formation and health hazards to operators, compared with known solutions.

It has in practice been ascertained that the described invention achieves the intended objects, and in particular, the fact is emphasized that the process and the system according to the invention enable a homogeneously and uniformly coated composite filament to be obtained.

In addition, the process and the system allow obtaining a strong composite filament that is not prone to fraying.

Finally, the distribution by gravity of the resin and/or the use of a powdery resin allow minimizing the risk of polluting the surrounding environment and make the process and the system remarkably safe for the operators.

Claims

1) Process for the manufacture of a filament made of composite material, comprising at least the phases of: supply of at least one filament (3) comprising at least one fiber (4) and of at least one resin (6); application of said resin (6) to said filament (3) to obtain a coated filament (7); heating of said coated filament (7) to obtain a composite filament (9); characterized by the fact that said phase of application is performed by gravity distribution of said resin (6) on said filament (3).

2) Process according to claim 1, characterized by the fact that said phases are performed continuously by means of the movement of said filament (3) along a direction of work (D).

3) Process according to one or more of the preceding claims, characterized by the fact that said filament (3) is of a continuous type.

4) Process according to one or more of the preceding claims, characterized by the fact that said fiber (4) is selected from: carbon fiber, aramid fiber, glass fiber, polymer fiber, boron fiber, basalt fiber, optical fiber, metallic fiber, ceramic fiber, fiber of natural plant origin.

5) Process according to one or more of the preceding claims, characterized by the fact that said resin (6) is in the powdery form.

6) Process according to one or more of the preceding claims, characterized by the fact that said gravity distribution is performed by means of the dispersion of said powder on said filament (3).

7) Process according to one or more of the preceding claims, characterized by the fact that said resin (6) is mixed with at least one solvent to obtain a liquid mixture (15).

8) Process according to claim 7, characterized by the fact that said solvent is selected from the list comprising: acetone, methyl ethyl ketone, toluene, isopropyl alcohol.

9) Process according to claim 7, characterized by the fact that said gravity distribution is performed by dripping said mixture (15) onto said filament (3).

10) Process according to claim 7, characterized by the fact that said phase of heating comprises a sub-phase of evaporation of said solvent.

11) Process according to one or more of the preceding claims, characterized by the fact that said resin (6) comprises at least one thermosetting polymeric material selected from the list comprising: epoxy resin, polyvinyl ester, polyester, polyurethane, phenolic resin, polycyclopentadiene, polyimide.

12) Process according to claim 11, characterized by the fact that said phase of heating comprises a sub-phase of curing said resin (6).

13) Process according to one or more of claims 1 to 10, characterized by the fact that said resin (6) comprises at least one thermoplastic polymeric material selected from the list comprising: polystyrene, polyethyleneimine, polyether- ether-ketone, polyamide, polyethylene terephthalate, polypropylene, polylactic acid, acrylonitrile butadiene styrene.

14) Process according to claim 13, characterized by the fact that said phase of heating comprises a phase of melting said resin (6).

15) Process according to one or more of the preceding claims, characterized by the fact that, subsequently to said phase of heating, it comprises a phase of cooling said composite filament (9).

16) Process according to one or more of the preceding claims, characterized by the fact that it comprises a phase of tensioning said filament (3).

17) Process according to one or more of the preceding claims, characterized by the fact that, subsequently to said phase of application, it comprises a phase of compaction of said resin (6) on said filament (3).

18) Process according to claim 17, characterized by the fact that said phase of compaction is performed prior to said phase of heating.

19) Process according to claim 17, characterized by the fact that said phase of compaction is performed concurrently with said phase of heating.

20) System (1) for the manufacture of a composite filament, comprising: movement means (2) adapted to move a filament (3) comprising at least one fiber (4) along a direction of work (D); application means (5) adapted to apply at least one resin (6) to said filament (3) to obtain a coated filament (7); heating means (8) adapted to heat said coated filament (7) to obtain a composite filament (9); characterized by the fact that said application means (5) comprise at least one dispensing device (11) adapted to dispense said resin (6) by gravity onto said filament (3).

21) System (1) according to claim 20, characterized by the fact that said dispensing device (11) comprises at least one of a pumping device, a piezoelectric device, a vibration device, a compressed air device or a worm screw device.

22) System (1) according to claim 20 or 21, characterized by the fact that it comprises tensioning means (10) adapted to adjust the tensioning of said filament (3).

23) System (1) according to one or more of claims 20 to 22, characterized by the fact that it comprises compaction means (12) arranged downstream of said application means (5) with respect to said direction of work (D) and adapted to compact said resin (6) on said filament (3).

24) System (1) according to claim 23, characterized by the fact that said compaction means (12) are arranged upstream of said heating means (8) with respect to said direction of work (D).

25) System (1) according to claim 23, characterized by the fact that said compaction means (12) are arranged within said heating means (8).

26) Process for the manufacture of a composite filament, comprising at least the phases of: supply of at least one filament (3) comprising at least one fiber (4) and at least one resin (6); application of said resin (6) to said filament (3) to obtain a coated filament (7); heating of said coated filament (7) to obtain a composite filament (9); characterized by the fact that said resin (6) is in the powdery form and that said phase of application is performed by dipping said filament (3) in said resin (6).

27) System (1) for the manufacture of a composite filament, comprising: movement means (2) adapted to move a filament (3) comprising at least one fiber (4) along a direction of work (D); - application means (5) adapted to apply at least one resin (6) to said filament (3) to obtain a coated filament (7); heating means (8) adapted to heat said coated filament (7) to obtain a composite filament (9); characterized by the fact that said resin (6) is in the powdery form, and by the fact that said application means (5) comprise at least one application device (16) adapted to contain said resin (6) and to receive said filament (3) by dipping.