Apparatus and process for the production of a non-woven fabric

Abstract

Apparatus for the production of a nonwoven fabric comprising: a spinneret for extruding a plurality of filaments; at least one first cooling device arranged below the spinneret; a first aerodynamic drawing device downstream of the cooling device, to draw the filaments; a mechanical drawing device downstream of the first aerodynamic drawing device; a second aerodynamic drawing device downstream of the mechanical drawing device; a mechanical distributor arranged downstream of the second aerodynamic drawing device to divert the path of the filaments; a filament collecting device arranged below the mechanical distributor, wherein the collecting device comprises a collection surface to collect the filaments and form a nonwoven fabric; a suction element to suction gases below the filament collection surface.

Description

FIELD OF INVENTION

[0001] The present invention relates to an apparatus and process for the production of a nonwoven fabric which is used as reinforcement, typically in the construction field, for example as reinforcement in railways, airports, roads, highways and tunnels, armored concrete columns, or as reinforcement in earthquake-resistant structures, as reinforcement in agricultural areas or forests, as reinforcement in thermally insulating building structures, etc.STATE OF THE ART

[0002] The use of nonwoven fabrics in civil engineering, to build infrastructures such as roads, bridges, railways, dam support works and hydrogeological retaining structures, is well known. These fabrics allow the element in / on which they are placed to be reinforced, for example by distributing loads evenly within the structure.

[0003] However, nonwoven fabrics produced according to the known art have some limitations in terms of characteristics, such as mechanical characteristics.DESCRIPTION OF THE INVENTION

[0004] Thus, object of the present invention is to make a nonwoven fabric which can be effectively used as a reinforcement fabric in the field of civil engineering.

[0005] Further object of the present invention is to make this nonwoven fabric simply and economically.

[0006] The present invention achieves these and other objects by means of an apparatus and process according to the attached independent claims. Preferred aspects are set forth in the dependent claims.

[0007] According to an aspect of the present invention, an apparatus for the production of a nonwoven fabric comprises: a spinneret for extruding a plurality of filaments; at least one first cooling device arranged below the spinneret; a first aerodynamic drawing device downstream of the cooling device, to draw the filaments; a mechanical drawing device downstream of the first aerodynamic drawing device; a second aerodynamic drawing device downstream of the mechanical drawing device; a mechanical distributor arranged downstream of the second aerodynamic drawing device to divert the path of the filaments; a filament collecting device arranged below the mechanical distributor, wherein the collecting device comprises a collection surface to collect the filaments and form a nonwoven fabric; a suction element to suction gases below the filament collection surface.

[0008] The present invention thus introduces drawing carried out in three different steps, by means of two aerodynamic devices (i.e. pneumatic, which draw the filaments by means of air flows), and a mechanical device interposed between the two aerodynamic drawing devices.

[0009] Filament drawing is therefore progressive and allows high tenacity filaments to be formed.

[0010] The mechanical drawing device comprises rollers. The rollers are typically rotatable at progressively increasing speeds in order to draw the filaments. Typically, the rollers comprise primary rollers and secondary rollers, wherein the secondary rollers are movable relative to the primary rollers. Such mobility allows the path of the filaments to be varied, or at any rate allows an easier initial step of spinning, in which the secondary rollers can be arranged so that they do not intercept the path of the filaments, so that the filaments can more easily pass between the rollers and then be arranged in a drawing position, in which the rollers intercept the filaments.

[0011] According to an aspect, the rollers are heatable preferably to a temperature between 60°C and 150° C, in order to adjust the temperature of an element against which the filaments come into contact, thereby preventing, for example, thermal shocks, or otherwise assisting the drawing by means of temporary heating.

[0012] According to an aspect, the apparatus comprises at least one needle-felting device (needle loom) and / or a calender downstream of the filament collection surface. Thanks to this, the newly deposited nonwoven fabric can be consolidated.

[0013] According to an aspect, the apparatus comprises a thermal treatment device and / or a water-jet device which is arranged downstream of the collecting device, preferably downstream of the needle-felting device and / or calender, and which is configured so as to set the nonwoven fabric, i.e., to bond together the filaments of the nonwoven fabric.

[0014] An aspect of the present invention also relates to a process for the production of a nonwoven fabric, comprising the steps of: a) extruding a plurality of filaments by means of a spinneret; b) cooling the filaments by means of at least one first cooling device arranged below the spinneret; c) drawing the filaments by means of a first aerodynamic drawing device; d) drawing the filaments by means of a mechanical drawing device arranged downstream of the first aerodynamic drawing device; e) drawing the filaments by means of a second aerodynamic drawing device arranged downstream of the mechanical drawing device; f) operating a mechanical distributor arranged below the second aerodynamic drawing device so as to divert the path of at least part of the filaments; g) depositing the filaments on a collecting device to form a nonwoven fabric.

[0015] According to an aspect, in order to increase the mechanical properties of the filaments, they are filled, that is, they comprise one or more filler materials.

[0016] According to an aspect, the process comprises the step of consolidating the nonwoven fabric by a needle-felting device and / or by a calender.

[0017] According to an aspect, the process comprises the step of thermally setting the nonwoven fabric, preferably following the step of consolidating the nonwoven fabric.

[0018] Process according to one of claims 7 to 10, wherein at least part of the rollers, preferably all except the last one met by the filaments in their own path, is heated to a temperature between 60°C and 150°C.BRIEF DESCRIPTION OF THE FIGURES

[0019] Hereinafter, referring to the appended figures, exemplary and non-limiting embodiments of the present invention will be described, in which: Figure 1 is a schematic view of a possible embodiment of an apparatus according to the present invention; Figures 2 and 3 are schematic views of the mechanical drawing device of the apparatus of Figure 1; Figures 4 and 5 are schematic views of possible embodiments of a mechanical di stributor. DETAILED DESCRIPTION OF THE INVENTION

[0020] An apparatus 1 for the production of a nonwoven fabric comprises a spinneret 2 for extruding a plurality of filaments 3, and at least one first cooling device 4 arranged below the spinneret 2.

[0021] The spinneret is formed, in a known way, to extrude the filaments 3, which can be mono-component or bi-component filaments.

[0022] Preferred materials for the production of filaments are olefin polymers (polypropylene and / or polyester), polyamides, polyesters, PBT (polybutylene terephthalate), monopolymers or copolymers.

[0023] The spinneret, or otherwise the material supplied to it, can be configured to provide a filler to the filaments, for example a metal filler. Preferred fillers are calcium carbonate or titanium oxide.

[0024] The extruded filaments can be bi-component, preferably in side-by-side or core-sheath configuration with, for example, round or trilobate section. In trilobate section, the filament is preferably made of SBS material, or styrene-butadiene-styrene.

[0025] The cooling device 4 is typically configured to direct against the filaments 3 a cooled, or otherwise room-temperature, gas (typically air).

[0026] The apparatus 1 also comprises three drawing devices 5, 6, 7 arranged in series.

[0027] Specifically, the apparatus comprises a first aerodynamic drawing device 5.

[0028] The first aerodynamic drawing device 5 is configured to draw the filaments by one or more flows of gas, typically air. Typically, the filaments pass through a duct into which also high-speed gas, which draws the filaments, flows. The gas flow can be formed passively (e.g., by venturi effect) or actively, such as by compressors or similar elements. Preferably, air with pressure between 0.2 and 2 bars is injected into the first aerodynamic drawing device 5.

[0029] The apparatus further comprises a mechanical drawing device 6 arranged downstream of the first aerodynamic drawing device 5, typically below the latter.

[0030] The mechanical drawing device 6 preferably comprises a plurality of rollers 61 - 65 which are arranged in series and generally have tangential speeds different from each other. Typically, the tangential speeds of the rollers 61 - 65 are progressively increasing, considering the order in which, in use, the rollers 61 - 65 come into contact with the filaments 3 during their fall from the spinneret 2.

[0031] The rollers 61 - 65 are rotatable about their own axis of rotation A61 - A65, preferably at a speed between 400 meters / minute and 2000 meters / minute.

[0032] According to an embodiment, at least part of the rollers is configured so that it can be heated, for example by means of an oleodynamic circuit. The heated rollers are configured to have a temperature preferably between 60°C and 150°C when in use. Preferably all the heated rollers are upstream of all the unheated rollers. Specifically, according to a preferred aspect, all the rollers are heated except for the roller immediately upstream of the crimping device 6 (i.e., except for the roller furthest downstream in the path of the filaments 3). This last roller, i.e., the roller 65 in the embodiment shown in the figures, is configured to have a temperature between 20°C and 50°C. This can be done by means of a dedicated device adapted to cause the roller to reach the desired temperature or, more preferably, such a roller has no heating / cooling means, so that it remains basically at room temperature.

[0033] According to a preferred aspect, the mechanical drawing device 6 comprises primary rollers 61, 63, 65 and secondary rollers 62, 64, in which the secondary rollers 62, 64 are movable relative to the primary rollers 61, 63, 65.

[0034] In other words, the primary rollers 61, 63, 65 and the secondary rollers 62, 64 are constrained to the frame of the apparatus (not shown herein in detail) so as to allow a relative movement between the primary and secondary rollers so that to alternately engage and disengage the filaments 3. The secondary rollers 62, 64 and the primary rollers 61, 63, 65 are preferably arranged alternately with each other so that, in use, the filaments 3 alternately meet a primary roller and a secondary roller.

[0035] The secondary rollers 62, 64 are typically translatable alternately along a curve or, more preferably, a straight line. According to an embodiment, considering a condition of use, the secondary rollers 62, 64 are movable horizontally, as schematically shown for example in Figure 3 where the initial position of the rollers is shown schematically by dashed lines. It should be noted that Figure 3 is only a schematic illustration, so that proportions and distances traveled are not to scale.

[0036] The apparatus 1 comprises an additional aerodynamic drawing device 7 downstream of the mechanical drawing device 6.

[0037] Similarly to the first aerodynamic drawing device 5, the second aerodynamic drawing device 7 is configured to draw the filaments 3 by one or more flows of gas, typically air.

[0038] The air pressure in the second aerodynamic drawing device is preferably between 0.2 and 2 bars.

[0039] The apparatus 1 further comprises a mechanical distributor 8 arranged below said second cooling device 7 in order to divert the path of said plurality of filaments, so as to direct them towards a collecting device 9. Specifically, the mechanical distributor 8 allows the filaments 3 to be separated and distributed over the deposition surface 91 of the collecting device 9, in order to form the voluminous nonwoven fabric 150.

[0040] According to an embodiment, the mechanical distributor 8 comprises a movable shelf 101 on which the filaments 3 leaving the second aerodynamic drawing device 7 are laid. The movement of the movable shelf diverts the fall path of the filaments 3, which are deposited on a collecting device 9 comprising a surface 91 on which a first nonwoven fabric 150 is formed.

[0041] According to an alternative embodiment, the mechanical distributor comprises a fixed shelf 102 and a swinging rod 30. The filaments leaving the cooling device 7 are laid on the fixed shelf 102 by deflecting the fall path in the direction of the swinging rod 30, which causes the filaments 3 to swing / vibrate before being deposited on a collection surface 91 of the collecting device 9.

[0042] A further embodiment (not shown in the figures) provides a mechanical distributor comprising alternately moving blades which allow the crimped filaments 3 to be separated and distributed on the deposition surface 91, in order to form the first voluminous nonwoven fabric 150.

[0043] In general, the mechanical distributor 8 typically comprises a movable element 101, 30 adapted to deflect the filaments 3 in a time-varying way. Preferably, such a movable element moves at a movement frequency of between 100 and 1000 movements (oscillation) / minute.

[0044] The collecting device 9 can take various forms and typically comprises a movable belt. Furthermore, the apparatus typically comprises a suction element 92 to suction gases below the filament collection surface 91, in order to promote the formation of a first nonwoven fabric 150.

[0045] According to a possible embodiment, the apparatus 1 further comprises at least one needle-felting device 13 downstream of the collecting device 9, that is, downstream of the region where the filaments 3 meet the collecting device 9. The needle-felting device 13 allows the filaments 3 of the nonwoven fabric 150 to be bonded, thereby allowing the first nonwoven fabric 150 to be consolidated. As an alternative or in addition, the apparatus 1 may comprise a calender 11, possibly heated, to consolidate the nonwoven fabric 150.

[0046] If both elements are present, the calender 11 is typically downstream of the needle-felting device 13.

[0047] Preferably, the apparatus comprises a thermal treatment device 12, which is typically adapted to heat the nonwoven fabric 150 and which is arranged downstream of the collecting device and of either the needle-felting device 13 or calender 11, if any. The thermal treatment device can heat the nonwoven fabric 150 according to various methodologies, typically by convection and / or radiation, preferably by a flow of air heated between 80°C and 150°C.

[0048] The thermal treatment device 12 allows the nonwoven fabric to be thermally set.

[0049] The nonwoven fabric can also be hydro-treated, typically with a water-jet device, for further consolidation.

[0050] After the various treatments, the nonwoven fabric 150 is typically collected by means of special devices, typically is wound into bobbin form.

[0051] In use, a plurality of filaments 3 are extruded from the spinneret 2.

[0052] Following the extrusion step, the extruded filaments are cooled by means of the cooling device 4 arranged below the spinneret 2.

[0053] After the cooling step, the filaments 3 are drawn by means of the three drawing devices 5, 6, 7, which are arranged in series downstream of the cooling device 4.

[0054] As described above, the aerodynamic drawing devices 5, 7 draw the filaments by one or more gas (air) flows, while the mechanical drawing device 6 preferably comprises primary rollers 61, 63, 65 and secondary rollers 62, 64 in which the secondary rollers are movable relative to the primary rollers.

[0055] At first, at the initial operating step of the spinneret 2, the secondary rollers are typically arranged in the disengaged condition to allow the filaments 3 to pass between the rollers 61 - 65. Next, the secondary rollers are brought to the drawing position, so as to engage the filaments and cause them to be drawn.

[0056] The filaments passing around the rollers alternately meet the first and second secondary rollers. In other words, the filaments are laid alternately on a surface portion of a primary roller and then are laid on a surface portion of a secondary roller. Typically, the filaments 3 exhibit a basically S-shaped pattern in the transition from a primary roller to a secondary roller.

[0057] As discussed, according to a possible aspect, at least part of the rollers can be heated, preferably between 60° C and 150° C, so as to affect the temperature of the filaments 3. The last roller to meet the filaments is preferably unheated, at a temperature between 15°C and 25°C.

[0058] Following the drawing step, the filaments 3 are diverted and scattered in their fall path by the mechanical distributor 8 in order to increase the surface where the filaments 3 are deposited on the deposition surface 91 of the collecting device to form the nonwoven fabric 150.

[0059] Below the collecting device 9, the suction element 92 suctions air so as not to disperse the filaments deposited on the deposition surface 91 and ensure the proper formation of the nonwoven fabric 150.

[0060] Subsequently, the nonwoven fabric 150 can undergo different treatments.

[0061] For example, the nonwoven fabric 150 can be consolidated by a needle-felting device 13 and / or a calender 11.

[0062] The first nonwoven fabric 150 can also be heated to set the filaments 3, and possibly hydrotreated to perform further consolidation or bonding. Specifically, the fabric can be hydrotreated, typically by a water-jet device. In possible embodiments, water-jet treatment can be used instead of thermal treatment to set and bond the filaments together.

[0063] Finally, the nonwoven fabric 150 is typically collected, typically wound, according to known methods.

Claims

1. Apparatus (1) for producing a nonwoven fabric (150), comprising: - a spinneret (2) for extruding a plurality of filaments (3); - at least one first cooling device (4) arranged below said spinneret (2); - a first aerodynamic drawing device (5) downstream of said cooling device (4), to draw the filaments; - a mechanical drawing device (6) downstream of said first aerodynamic drawing device (5); - a second aerodynamic drawing device (7) downstream of said mechanical drawing device (6); - a mechanical distributor (8) arranged downstream of the second aerodynamic drawing device (7) to divert the path of said plurality of filaments; - a collecting device (9) to collect the filaments arranged below said mechanical distributor (8), said collecting device (9) comprising a collection surface (91) to collect the filaments and form a nonwoven fabric (150); - a suction element (10) to suction gases below the filament collection surface (91).

2. Apparatus according to claim 1, wherein the mechanical drawing device comprises rollers.

3. Apparatus according to claim 2, wherein said rollers comprise primary rollers (61, 63, 65) and secondary rollers (62, 64), said secondary rollers being movable relative to said primary rollers.

4. Apparatus according to one of the preceding claims, wherein at least part of the rollers are heatable, preferably to a temperature between 60°C and 150° C.

5. Apparatus according to claim 1 or 2, comprising at least one needle-felting device (13) and / or a calender (11) downstream of the filament collection surface (91).

6. Apparatus according to any one of the preceding claims, comprising a thermal treatment device (12) and / or a water-jet device which is arranged downstream of the collecting device, preferably downstream of said needle-felting device and / or said calender, and which is configured to set the nonwoven fabric.

7. Process for producing a nonwoven fabric (150) comprising the steps of: a) extruding a plurality of filaments (3) by means of a spinneret (2); b) cooling said filaments (3) by means of at least one first cooling device (4) arranged below the spinneret; c) drawing said filaments by means of a first aerodynamic drawing device (5); d) drawing the filaments by means of a mechanical drawing device (6) arranged downstream of the first aerodynamic drawing device (5). e) drawing said filaments by means of a second aerodynamic drawing device (7) arranged downstream of the mechanical drawing device (6); f) operating a mechanical distributor (8) arranged below the second aerodynamic drawing device (7) so as to divert the path of at least part of the filaments; g) depositing said filaments on a collecting device (9) to form a nonwoven fabric (150).

8. Process according to claim 7, any of the preceding claims, wherein the filaments are filled.

9. Process according to claim 7 or 8, comprising the step of consolidating the nonwoven fabric (150) by a needle-felting device and / or by a calender.

10. Process according to one of claims 7 to 9, comprising the step of thermally setting the nonwoven fabric (150), preferably following the step of consolidating the nonwoven fabric (150).

11. Process according to one of claims 7 to 10, wherein at least part of the rollers, preferably all except the last one met by the filaments in their own path, is heated to a temperature between 60°C and 150°C.

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