HRP921371A2 - Method for the production of a composite structure with an intermediate three dimensional textile, and a structure made by the method - Google Patents

Description

This invention relates to the production process of multi-layer (composite) structures with interspaced three-dimensional textiles, and to the structure obtained by this process, as well as to devices for the production of such structures. Multilayer structures are known, for example, from the appearance of similar ones in the Italian patent filed under no. 12441-A/90, under the title "Procedure for the production of sandwich structures" (for which the author applied for a patent on March 26, 1990), including the so-called a three-dimensional textile product that is made of two sheets of textile fabric, laid face-to-face, which are interconnected by numerous threads that extend between the adjacent surfaces of these fabric sheets.

To obtain such a structure, a three-dimensional textile product impregnated with resin is placed in a mold, and an expanding resin is injected into the space between the fabric sheets, the forces of which spread the fabric sheets, which then come into contact with the mold surfaces. In such a multi-layered structure, the expanding resin determines the mechanical characteristics and thermal insulation properties of the structure itself.

A study was also made of the production of a multilayer structure of the type described above, which is at least partially hollow and made by impregnating a three-dimensional textile with a grain of thermoreactive resin, and instead of an expanding resin, compressed air is blown in order to spread the fabric sheets and create an intermediate space between the sheets themselves.

These procedures, although they have the specifics of creating structures with sculptural geometry, with regard to the construction of flat structures (panels), sometimes give geometric and dimensional irregularities (eg surface undulations and uneven thickness).

The subject of this invention is the formation of a multi-layered structure with an interstitial three-dimensional textile, in a relatively simple and repeatable way, a structure which avoids the above-mentioned disadvantages and which has favorably defined physical, mechanical and dimensional characteristics and which is relatively inexpensive to manufacture.

The following goal is achieved by this invention, which refers to the production process of multi-layer structures with intermediate three-dimensional textile fabrics, and the process itself is characterized by the fact that it includes:

the first stage, in which the layered structure is inserted between the first and second parts of the press mold, a layered structure is obtained, including at least one three-dimensional textile product consisting of two sheets of textile fabric, laid in parallel and interconnected by numerous threads extending from the facing surfaces sheets of fabric; at least one pair of facing layers laid against said fabric sheets, of said structure, at least said three-dimensional textile product also impregnated with resin, the mold having means for attaching said layers to its surface;

the second stage in which the molds are at least partially closed, and the three-dimensional textile product is pressed between the layers and the resin impregnates said sheets of fabric which are placed between the parts in contact, allowing the threads to pass equally;

the third stage, in which the layers are firmly attached to the molds;

the fourth stage, in which the molds are opened again to a certain distance, within the limits of the natural elastic recovery (regeneration) of the three-dimensional textile product, due to the action of the combination of threads that tend to straighten themselves,

the fifth stage, in which at least partial polymerization of the resin between the layers takes place, and the textile end sheets of the three-dimensional textile product are obtained while the resin impregnating the threads remains substantially in a plastic state;

the sixth stage, in which the molds are opened to a predetermined distance, in order to move the sheets of fabric from each other and stretch the threads to the shape when a partially hollow structure is obtained;

the seventh stage, in which the structure remains clamped between the two parts of the mold, until the polymerisation of the resin is finished,

the eighth stage, in which the layers are released from the mold surfaces, the molds are completely opened and the layered structure is removed from the press.

The invention will now be illustrated by a non-limiting example, with special reference to the attached drawings, of which:

Figure 1 provides an exploded and perspective view of the layered structure used to produce a multilayer element, according to the present invention.

Figures 2 to 7 show schematically, in longitudinal section and in successive stages, parts of the device (machine) used for the production of a multilayer structure, according to the method of this invention;

Fig. 8 shows a complete longitudinal section of the press used for the production of the multilayer structure according to this invention,

Fig. 9 represents a detail from Fig. 8, taken on the cross-section IX-IX; And

Figures 10, 11, 12 and 13 show variants of the structure shown in figure 1,

Figures 14 and 15 show a perspective view of a three-dimensional textile in two states, of the type of textile product used in the layered structure shown in Figure 1; and

Figures 16, 17, 18 and 19 show four cross-sections of three-dimensional textiles, which are used in the structure shown in Figure 1, instead of the textiles shown in Figures 14 and 15.

The layered structure shown in Fig. 1 is generally denoted by 1, and includes a three-dimensional textile 3 of a known type, which is formed from a pair of woven sheets (Fig. 14) or knitted sheets (Fig. 15) 5 and 6, laid face to face and interconnected by numerous threads 10 that extend between the adjacent surfaces of sheets 5 and 6 and a pair of knitted sheets 12 and 13, laid facing sheets 5 and 6.

The layered structure 1 additionally includes a pair of layers 16 and 17, laid so as to be in contact with the fabric sheets 12 and 13, made of plastic, metal or other materials.

The three-dimensional textile product 3 and the fabric sheets 12 and 13 are also completely impregnated with a thermo-reactive plastic resin 20 (eg, phenolic, epoxy, bismaleic, or polyester resin).

According to the process described in this invention, the layered structure 1 is obtained by well-known methods from continuous flat products of textile fabrics, which are then cut to the required dimensions and inserted between the lower mold 25 and the upper mold 26 (Fig. 2) of the press 28 (best see fig. 8), which has on it accessories for attaching the structure 1 to the molds 25 and 26, as well as accessories for heating the structure 1, thus enabling the resin 20 to polymerize, as will be explained below.

Molds 25 and 26 have respective flat surfaces 29 and 30 having therein rectangular, circumferential grooves 31 and 32 and seals 33 and 34 for fluid tightness 33 and 34, with respective tabs, extending from the flat surfaces 29 and 30 outwardly. Molds 25 and 26 have a large number of channels 40 that extend through the mold, perpendicular to surfaces 29 and 30 and are open to these surfaces 29 and 30, and inside the mold they are connected to cross channels 41 that extend parallel to surfaces 29 and 30 and are connected to the corresponding pump 45 (shown schematically), so that a vacuum suction block is obtained. The structure 1 rests on the lower mold 25 and the layer 17, which has larger transverse dimensions than the three-dimensional textile product 3, which rests on the tongues 35 of the seal 33, so that the air suction from the channel 40 creates a low pressure between the layer 17 and the mold 25, as would ensure firm contact between it and layer 17.

After that (fig. 3) the press 28 is closed, the upper mold 26 is lowered onto the structure 1, during this phase, a controlled pressure is applied to the structure 1, in order to achieve good cohesion between the different layers and to distribute the resin 20 equally between the fabric sheets 5 and 6, of a three-dimensional textile product, as well as between sheets 12 and 13, and between the same and layers 16 and 17.

The pressure acting on the structure 1 also eliminates any air bubbles that exist between all the surfaces in contact and presses the seals 33 and 34 against the plates 16 and 17.

In this phase, the air is extracted using the vacuum pump 45 from the channels 40 in the molds 25 and 26, so that the pressure between them and the layers 16 and 17 is reduced, enough for them to adhere firmly to the surfaces 29 and 30.

After that (fig. 4), the press 28 is opened, the mold 26 is lowered slowly to a distance not greater than the limit of the natural elastic back of the three-dimensional textile product 3, due to the reaction of the combination of threads 10, which tend to be straightened.

This operation should not separate the layers 16 and 17 from the fabric sheets 12 and 13, and these in turn from the fabric sheets 5 and 6, of the three-dimensional textile product 3.

During this phase, the heat produced inside the molds 25 and 26, by the usual means of heating; e.g. by electrical resistance 46, it reaches the end layers of the structure 1, i.e. the fabric layers 12 and 13 of the textile product 1, via the layers 16 and 17, and accordingly it also reaches the layers of the three-dimensional textile product on which the resin 20 has partially solidified, ensuring thus mutual adhesion of all surfaces that are in contact. During this phase, the solidification process in the resin 20 that impregnates the strands 10, is delayed in the area farthest from the heat source; thereby enabling the strands 10 to remain flexible during subsequent stages of the process.

After that (fig. 5), the lower mold 25 is released, so that it can freely "swim" in a plane parallel to the mold 26.

The press 28 is still opened, the mold 26 is raised to such a distance that the threads 10 of the three-dimensional textile product 3 are stretched. of this stretching by the vacuum effect, due to the fact that air cannot penetrate through textiles impregnated with partially solidified resin 20.

During this phase, regardless of the free floating of the lower mold 25, the legs 10 do not reposition themselves to become automatically vertical to the planes in which the fabric sheets 5 and 6 lie, thereby necessitating the next phase of manual correction.

In this case (fig. 6), the lower mold is manually moved by the operator (handler), in order to bring the threads 10 to a substantially vertical position and the mold 25 is blocked in this position.

After that (fig. 7), the press 28 is opened again, until the threads 10 are fully stretched and the desired thickness of the structure 1 is reached.

The press is then firmly blocked in this position and the polymerization is completed throughout the resin 20 which solidifies completely even in the area of the thread 10.

After that, after the molds 25 and 26 have probably cooled by means of conventional means not shown, the vacuum pump 45 is disengaged and air enters the channels 40, so that the layers 16 and 17 are separated from the surfaces 29 and 30, the mold 25 and 26, presses 28, finally, the press 28 is completely opened and the layered structure 1 is taken out of the press.

In this structure 1, the threads 10 are completely rigid and extend perpendicular to the fabric sheets 5 and 6, establishing a rigid connection between the sheets 5 and 6 themselves and forming a partially hollow structure due to the space that exists between the threads 10.

This structure can also be filled with an expanding resin, e.g. polyurethane or phenolic foam, which is injected at the end of the phase in which the resin is polymerized, as shown in Fig. 7, in order to improve the mechanical, thermal and acoustic insulation properties. multi-layered structure.

The layers 16 and 17, which in this case represent conveniently detachable films, can then be separated from the structure 1, after it has been removed from the press 28, in this case they serve to release the fabric sheets and define the planar surfaces that are formed after the resin 20 has solidified in the textile fabrics 12 and 13. In fact, it would not be possible to insert into the press 28 a structure formed only by the three-dimensional textile 3, or the textile 3 and the sheets of the textile fabrics 12 and 13, since when pressing the layered structure 1, the resin 20 could enter the channels 40 and block them.

The use of layers 16 and 17 also makes it possible to achieve perfectly flat surfaces, which differ from those obtained by known methods.

In addition, in order to make the difference in the polymerization between the sheets 5 and 6 of the textile product, impregnated with resin 20 and impregnated threads 10, and to make it more significant, it is possible, before arranging the layered structure 1 between the molds 25 and 26, to distribute the catalyst on sides of the layers 16 and 17 that are in contact with the impregnated fabric sheets 5 and 6 or directly on the sheets 5 and 6 themselves. In this way, the greater reactivity of the resin 20 in the contact zones between the sheets 5 and 6 and the layers 16 and 17, already increased by a greater by heat transfer, it continues to increase with respect to the reactivity of the threads 10 that impregnate the resin, by the local presence of a larger amount of catalyst, and accordingly the polymerization time of the resin 20 is reduced, which creates a stable connection between the touching outer surfaces of the three-dimensional textile product 3, thus guaranteeing a safe thread stretching 10 at the later advancing phase of press opening 28.

Methyl ethyl ketone peroxide is recommended as a substance for polyester resin catalysis, in percentages varying up to 3%, for phenolic resins acid solutions can be used in percentages varying up to 15%, while for epoxy resins they can be used as catalysts use amide-based resins, with percentages varying between 30 and 50%, for example.

Figure 8 shows the press 28 in an enlarged cross-sectional drawing, where it rests on a base 99 over a body (housing) 100 which carries a lower mold 25 which is slidably moved by an assembly of rolling balls 110 (of a known type) on the body 100 itself.

These assemblies 110 enable the mold 25 to move in any direction, in a plane parallel to the upper mold 26.

More precisely, each assembly 110 contains a plate 101 which is fixed to the body 100 with screws 101a and which is placed as close as possible to the circular recess 102 in the mold 25, facing downwards and having a through opening 103 into which a shaft 104 is inserted which is on its at its lower end firmly attached to the body 100 and at its upper end it has a circular flange 105 inserted into a recess 102. The assembly 110 includes a number of balls 106 arranged circumferentially in the first ring which is coaxial with the shaft 104 and which is located between the plate 101 and the ring plate 108, mounted on the body 100.

The body 100 is also equipped with a stop accessory 120, for tightening the mold 25 on the body 100 and each, including the shaft 122, which can be pneumatically actuated and moved towards the mold 25 and adapted at one end 124, to frictionally press against the mold 25, in the purpose of preventing movement in the mold plane.

The mold 25 also has two pairs of release accessories 130, for releasing the mold 25 within its own plane, as well as for its displacement, i.e. for returning the lower mold 25 to a predetermined position relative to the body 100, after the lower mold has returned in the previous work cycle.

The accessories 130 are suitably arranged on four opposite sides of the mold 25, and each of them includes a corresponding pneumatic actuator 135, mounted so that it protrudes outwards and downwards outside the mold 25, and is equipped with a corresponding movable piston 137 which extends toward the body 100 and terminates with a spherical end 138 facing the body. These ends 138 of the executive organs 135 are placed so as to abut on the supports 140, firmly attached to the body 100.

More precisely, as shown in Fig. 9, each support 40 has a wide V-shaped groove 142, into which the end 132 of the associated piston 137 enters, in the phase of changing the position. In this way, when the end 138 of each piston contacts the surfaces of the groove 142, the lower mold 25 is returned to a defined position relative to the body 100.

From what has been explained above, it will be clear that the process of this invention solves the problems of known processes; in fact, this process gains an advantage, because a layered structure is obtained in a simple and economical way that is partially hollow and has constant geometric and mechanical characteristics (eg uniform thickness) and a specific shape.

Finally, it is clear that modifications and changes can be made to this procedure, without deviating from the protective purpose of the procedure itself.

The thermosetting resin 20 could, for example, be replaced by a thermoplastic resin (for example, with polyamide, polyetherimide, polyester-ketone, polyamide) for impregnating the three-dimensional textile product 3, which is formed into a grain and subsequently cooled inside the press 28.

The structure 1, as shown in Fig. 10, can be without fabric sheets 12 and 13, and includes only three-dimensional textile 3 and panels 16 and 17, thus forming part of the structure itself.

The removable panels 16 and 17 (Fig. 11) may also be covered with a gel resin coating 160 or other surface finish coating that is placed between the three-dimensional textile 3 and the panels 16 and 17. In this way, after removing the panels 16 and 17, the outer surfaces of the structure 1 will be perfectly smooth and pleasant in appearance, thus giving the multi-layered structure an appreciated aesthetic appearance.

Sl. 12 illustrates a structure where the top sheet 16 is formed from a laminate of metal or plastic and is held rigidly attached to the multilayer structure, while the bottom sheet 17 acts as a release sheet and is removed. This bottom sheet 17 may also be covered with a gel coating 160.

Fig. 13 shows a structure which is almost exactly the same as that shown in Fig. 11, but which differs from this only in that it contains a sheet of textile fabric 13 between the three-dimensional textile and the lower release plate.

Threads 10 can also be designed to lie differently from those shown in Figs. 1 2-7, 14 and 15. More precisely (Fig. 16), threads 10 can be inclined towards the sheets of textile fabrics 5 and 6 and they can cross each other, thus forming an X structure (or a V structure). Such a structure (fig. 17), in addition to the threads 10 that together form an X-structure, can also include threads 10A distributed around the sheets of textile fabrics 5 and 6. Finally, the threads 10 (fig. 18) can be curved in relation to sheets 5 and 6.

The sheets 5 and 6 can be additionally connected to each other (Fig. 19) by a piece of textile 200, which extends essentially perpendicular to, and between the facing surfaces of the sheets 5 and 6 and is tightly bound with them, threads 10 also exist in such pieces of textile 200 , next to the threads lying parallel to sheets 5 and 6.

The structure 1 can also be made of numerous superimposed layers of three-dimensional textile 3; the catalyst can be previously spread between the facing surfaces of these layers, e.g. between sheets 5 and 6, in order to locally accelerate the polymerization process of the resin, which results in a stable bond between the facing surfaces of the different layers, so that the stretching of the strands 10 of the various internal layers is guaranteed, during the progressive opening of the press.

The stage of centering the two molds 25 and 26 could be eliminated as unnecessary, and both molds could be moved in parallel planes.

Finally, the press 28 could be equipped with accessories other than those shown to float the lower mold 25 relative to the upper mold 26. For example, it could be equipped with off-the-shelf ball bearings or pneumatic suspension slides (air cushions).

Likewise, the means 46 for electric heating of the molds 25 and 26 could be replaced with some other means, thereby speeding up the polymerization process.

Claims (31)

1. The production process of multi-layer structures with non-spatial three-dimensional textiles, characterized by the fact that it includes: the first stage, in which the layered structure (1) is inserted between the first and second molds (25, 26) of the press (28); a layered structured product (1) containing at least one three-dimensional textile (3) which again consists of two sheets of fabric (5, 6) laid parallel and interconnected by numerous threads (10) that extend between the facing surfaces of the sheets (5, 6) ; at least one pair of layers (16, 17) laid facing said sheets (5, 6) on the outside of said structure (1); at least said three-dimensional textile (3) which is also impregnated with resin (20); molds (25, 26) are equipped with means (40, 45) for attaching said layers (16, 17) to their surfaces; the second phase, in which the molds (25, 26) are at least partially closed, and the three-dimensional textile (3) is pressed between the layers (16, 17), and the felt (20) that impregnates the mentioned sheets is distributed between the parts that are in contact , equally permeable threads (10); the third phase, in which the layers (16, 17) are firmly attached to the molds (25, 26); the fourth stage, in which the molds (25, 26) are opened again to a certain distance, within the limits of the natural elastic return of the three-dimensional textile (3), due to the action of the combination of threads (10) which tend to straighten themselves; the fifth phase, in which at least partial polymerization of the resin (20) is achieved between the layers (16, 17} and the end sheets (5, 6) of the three-dimensional textile, while the resin (20) that impregnates the threads (10) remains substantially in a plastic state; the sixth stage, in which the molds (25, 26) are opened again to a predetermined distance, in order to move the sheets (5, 6) away from each other and to stretch the threads (10) to the shape of a partially hollow structure; the seventh stage, in which the structure (1) remains clamped between the two molds (25, 26) until the polymerization of the resin (20) is completed; the eighth stage, in which the plates (16, 17) are released from the surfaces of the molds (25, 26), the molds (25, 26) are completely opened, and the layered structure (1) is removed from the press (28). 2. The method according to claim 1, characterized in that in the sixth stage at least one of the molds (25, 26) appears to be movable relative to each other, in a plane perpendicular to the space between the molds (25, 26), and after that the molds (25, 26) are again moved away from each other by a distance of 100 m, in order to stretch said threads (10) at least partially, where it is possible that the movable mold (25) will swim in the sixth stage, whereby the threads (10) are placed in the direction which is substantially perpendicular to the planes of the sheets (5, 6) of the three-dimensional textile; the molds (25, 26) are further moved away from each other in a blocked position in their planes to another predetermined distance, for the purpose of fully stretching the aiti (10), in order to achieve the overall desired thickness of the structure (1). 3. The method according to claim 1 or 2, characterized in that said molds (25, 26) are heated in order to accelerate the polymerization process of said resin (20); in the mentioned fifth phase, in the mentioned molds (25, 26) by heating mainly the self-edge (end) parts of the mentioned structure, only the mentioned partial polymerization of the resin (20) occurs on the outer sheets (5, 6) of the mentioned three-dimensional textile (3). 4. The method according to some of the previous patent claims, characterized in that said resin (20) is a thermoreactive resin. 5. The method according to patent claim under 4, characterized in that a catalyst is placed between the aforementioned layers (16, 17) and the aforementioned fabric sheets (5, 6) of the aforementioned three-dimensional textile in order to locally accelerate the polymerization process of the aforementioned resin. (20). 6. Process in accordance with the patent claim under Ido3, characterized by the fact that the mentioned resin (20) is a thermoplastic resin. 7. The method according to some of the previous patent claims characterized in that the resin (20), with at least partial polymerization in the mentioned second phase, firmly fixes the fabric sheets (5, 6) to the plates (16, 17). 8. The method according to patent claims 1 to 6 characterized in that it includes a ninth phase in which the plates (16, 17) are mechanically separated and removed from the layered structure (1). 9. A process in accordance with some of the mentioned patent claims, characterized in that the plates (16, 17) have larger dimensions than those of the layered structure (I), so that they could be separated from the mold surfaces (25, 26). 10. The method in accordance with some of the previous patent claims, characterized in that it includes a further phase after the seventh phase, in which the three-dimensional textile (3) in a layered structure is filled with expanding resin. 11. A method in accordance with some of the previous patent claims, characterized in that the mentioned layered structure includes at least one larger number of superstructure layers, the mentioned three-dimensional textile (3). 12. The method according to patent claim under 11, characterized in that before the mentioned first stage, a catalyst is placed between the facing surfaces of the mentioned layers, which locally accelerates the polymerization process of the mentioned resin (20). 13. A multi-layered structure with a non-spatial three-dimensional textile (3), characterized in that it is produced by a process in accordance with one of the patent claims under 1 to 12. 14. Structure according to claim 13, characterized in that the layered structure (1) contains at least one sheet of textile fabric (12, 13) laid between one of the panels (16, 17) and the three-dimensional textile (3). 15. A structure in accordance with claim 13 or 14, characterized by the fact that the layered structure (1) contains at least one layer of fleece coating (160) in the form of a gel, placed between the three-dimensional textile (3) and one of the panels (16, 17) ). 16. Structure according to one of the patent claims under 13 to 15, characterized in that the plates (16, 17) are made of plastic material. 17. Structure according to one of the patent claims under 13 to 15, characterized in that the plates (16, 17) are made of metal. 18. Device for the production of a multi-layered structure with an interstitial three-dimensional textile (3), characterized in that it is equipped with means for carrying out the procedure in accordance with some of the patent claims under 1 to 12. 19. Device characterized in that the means for attaching the plates (17, 17) to the molds (25, 26) are based on the principle of pneumatics. 20. Device according to claim 19, characterized in that the pneumatic fastening means include a large number of channels (40) that extend inside the molds (25, 26) and are open to the surfaces of the molds themselves and arranged in such a way that they can be connected to vacuum pump (45) and at least one circumferential seal (33, 34) which extends around each mold (25, 26) and is adapted to participate together with the plates (26, 17) in achieving a liquid-tight joint. 21. Device according to one of the patent claims under 18 to 20, characterized in that at least one of the molds (25) has means that enable it to move at least along two vertical axes, parallel to the plane of the other mold (25, 26). 22. Device according to patent claim under 21, characterized in that these means include at least an assembly of rolling balls (110). 23. Device according to patent claim under 21, characterized in that these means include pneumatic support slides. 24. Device according to patent claims under 18 to 23, characterized in that it contains means (122) for fixing the relative positions of the molds (25, 26). 25. Device according to claim 24, characterized in that the fastening means (122) contain clamping elements knii difiliiiii on the principle of friction. 26. A device according to claim 18 to 25, characterized in that it contains means (130) for releasing at least one of the molds (25, 26). 27. The device according to claim 18 to 26, characterized in that it contains means (130) for centering the relative positions of the molds (25, 26). 28. Device according to patent claim under 27, depending on patent claim under 26, characterized in that the release means (130) when they act in reverse represent the centering means (130). 29. Device according to patent claims under 18 to 28, characterized in that it contains means (46) for heating the mold (25, 26) in order to accelerate the polymerization of the resin (20). 30. Device according to claim 29, characterized in that the heating means contain electric resistors (46). 31. The method of manufacturing a multilayer structure with an interspaced three-dimensional textile, the multilayer structure obtained by this process itself, and the device for carrying out the mentioned process, as described, with reference to the attached drawings.