Machine for manufacturing nonwoven materials comprising glass microfibers and method thereof

Abstract

A machine for manufacturing a nonwoven material comprising glass microfibers is disclosed, comprising a forming unit (110, 110') for forming the nonwoven material comprising glass microfibers on a lower web (120) driven in a travel direction, a smoothing unit (140) comprising an upper web (141) advancing in the travel direction and extending such that the nonwoven material is held between the lower web and the upper web at the smoothing unit, and a plurality of segments (P1, P2) defining a lower surface (SI) of the smoothing unit which is pressed against the upper web at a location where the upper web is in contact with the nonwoven material, wherein a stronger suction is applied to the last segment.

Description

Technical Field

[0001] This disclosure relates to the wet-laid fabrication of non-woven materials comprising glass microfibers and the corresponding fabrication machinery. Background Technology

[0002] The term “nonwoven material,” as is well known to those skilled in the art, is defined, for example, in the 2019 version of ISO 9092, and according to its standard, refers to “a predominantly flat fibrous assembly that has achieved a design level of structural integrity through physical and / or chemical means (but excluding weaving, knitting, or papermaking processes).

[0003] In this document, the term "nonwoven material" is used to refer to both the finished product and the material used in the manufacturing process.

[0004] Traditionally, the manufacture of nonwoven materials containing glass microfibers involves the use of a forming unit having a movable lower fabric over which a fiber suspension (containing a certain amount (e.g., more than 40% by dry weight) of glass microfibers) is uniformly deposited across the entire width of the lower fabric (the width being perpendicular to the direction of travel of the fabric).

[0005] The fiber suspension is then dehydrated to remove the liquid phase (usually water or foam) from the suspension in which the fibers were initially suspended, thereby obtaining a nonwoven material.

[0006] It has been observed that the presence of glass microfibers leads to the formation of flocs on the upper part of nonwoven materials, which then clump together to form microfiber clusters during the dehydration stage. Therefore, the surface of nonwoven materials containing glass microfibers obtained using existing techniques is often highly irregular, as these clusters are considered defects that impair the quality of the final product.

[0007] Techniques to prevent these clumps from forming might include slowing down the dehydration process, which would reduce the productivity of the manufacturing machines. These techniques are unsatisfactory because they have too much impact on the amount of nonwoven material produced per minute.

[0008] Therefore, there is indeed a need for a machine for manufacturing nonwoven materials containing glass microfibers that at least partially eliminates the aforementioned drawbacks. Summary of the Invention

[0009] This invention relates to a machine for manufacturing nonwoven materials comprising glass microfibers, comprising: A forming unit for forming a nonwoven material containing glass microfibers on a lower fabric that is driven in a direction of travel (at least when the nonwoven material is on the lower fabric). A leveling unit, located downstream of the forming unit and above the lower fabric, includes: an upper fabric that advances and extends in the direction of travel, such that nonwoven material is held at the leveling unit between the lower fabric (the same fabric on which the forming unit shapes the nonwoven material) and the upper fabric; and a plurality of portions arranged continuously in the direction of travel, the portions defining a lower surface of the leveling unit that is pressed against the upper fabric at the point where the upper fabric contacts the nonwoven material. At least the last section (i.e., the most downstream section of the plurality of sections) is provided with a plurality of orifices and is controlled by the suction control system of the leveling unit so that suction is applied through the orifices of the last section, and if the first section is provided with a plurality of orifices, the suction through the orifices of the last section is stronger than the suction through the orifices of the first section (i.e., the most upstream section of the plurality of sections).

[0010] If the first segment has no orifice (i.e., it is a solid surface), suction cannot be applied to it, and suction through the orifice in the last segment is non-zero.

[0011] The inventors of this invention have observed that by using a leveling unit comprising multiple segments, resulting in weak or even zero suction at the beginning (the first segment) and strong or at least non-zero suction at the end (the last segment), a smooth nonwoven material is obtained after removing the surface liquid phase, significantly reducing the presence of clumps caused by air bubbles. More specifically, the first segment of the lower surface of the leveling unit (i.e., the lower surface of the first segment) contacts the upper fabric at the location where the upper surface of the nonwoven material is saturated with liquid. At this stage, the upper surface of the nonwoven material is more elastic than after suction and dehydration, which facilitates mechanical flattening of the nonwoven material, especially its upper surface (opposite to the surface supported by the lower fabric), through the first segment. Therefore, the absence of suction or weak suction (compared to the last segment) in the first segment allows the leveling unit to model the upper surface of the nonwoven material to make it smoother.

[0012] Here, a segment is formed by one or more surface elements intended to contact the upper fabric, and the segment optionally has an orifice (i.e., the last segment includes an orifice, and the first segment optionally includes an orifice). These segments extend across the width of the nonwoven material (in a direction orthogonal to the direction of travel) and have a given length (in the direction of travel), which may be the same or different for different segments. The segments (particularly the last segment) may be in fluid communication with a suction control system to draw liquid through the orifice of the segment, if the segment includes any orifice. Here, there are at least two segments. If both segments are provided with orifices, the suction control system is configured to control the two segments independently of each other.

[0013] It should be noted that, depending on the type of glass microfiber used, the length of a segment measured in the direction of fabric travel ranges from 100 mm to 800 mm.

[0014] Furthermore, the orifice can extend across the entire width of the section (the orifice is located between surface elements, which can be scrapers extending across the entire width of the section on either side of the orifice).

[0015] Alternatively, the orifice can be completely surrounded by the surface element; for example, the segment includes a single surface element and multiple orifices (e.g., in a uniformly distributed manner) distributed along the width and length of the segment / single surface element. This type of orifice can have any shape (a cylinder with a circular base, a cylinder with an elliptical base, etc.).

[0016] The surface elements of all segments define the lower surface of the leveling unit. The upper fabric applies pressure on the lower surface of the leveling unit at the points where it contacts the nonwoven material. The nonwoven material also contacts the lower fabric itself, and the lower fabric, in turn, applies pressure to the nonwoven material. Therefore, the nonwoven material is constrained by the lower surface of the leveling unit, a constraint created by the arrangement of the lower surface, which itself depends on the arrangement of these segments.

[0017] According to a specific embodiment, multiple segments have a given radius of curvature, with the center of curvature located above the lower surface.

[0018] For example, the radius of curvature can be between 2 m and 100 m, preferably between 5 m and 30 m, and for example equal to 15 m.

[0019] The inventors have observed that the radius of curvature helps improve flatness.

[0020] In a specific embodiment, the machine includes a suction port arranged to recover the supernatant upstream of the first section, the suction port being controlled by the suction control system.

[0021] It should be noted that the suction orifice differs from the section in that the suction orifice comprises a single orifice, while the section comprises multiple orifices.

[0022] The suction orifice can be defined by a scraper extending across the width of the fabric from the first section and configured to scrape the inner surface of the upper fabric (i.e., the surface of the upper fabric that the lower surface contacts). The movement of the fabric, aided by the scraper, lifts the liquid, which is then drawn away through the suction orifice. Since this supernatant contributes little or no to the stretchability of the nonwoven material, it can be removed by suction before leveling.

[0023] According to one embodiment, the machine includes a dandy roll disposed at the exit of the forming unit and upstream of the leveling unit, the dandy roll being arranged to contact the upper surface of the nonwoven material.

[0024] Finishing rollers may include a cylinder having a circular base that extends in a direction orthogonal to the direction of travel of the nonwoven material. This is a known manner for finishing rollers.

[0025] The inventors of this invention have observed that using a finishing roller at the exit of the forming unit further improves the smoothness of the nonwoven material. The finishing roller contacts the nonwoven material at a point where it has not yet come into contact with the upper fabric of the smoothing unit.

[0026] According to a specific embodiment, the finishing roller is driven to rotate at a speed different from that of the nonwoven material being driven in the direction of travel (e.g., by the machine's drive unit).

[0027] By using different speeds (higher or lower than the travel speed), shear stress is induced within the nonwoven material, which facilitates the recombination of glass microfibers in the nonwoven material and contributes to the smoothness of the nonwoven material.

[0028] According to a specific embodiment, the machine includes a unit downstream of the location where the lower surface of multiple sections contacts the upper fabric for controlling the thickness of the nonwoven material.

[0029] According to a specific embodiment, the forming unit is configured to convey a nonwoven material comprising glass microfibers in an amount greater than 40% by dry weight.

[0030] Those skilled in the art will know the parameters of the fiber suspension used in the forming unit and the travel speed of the lower fabric in order to obtain a nonwoven material having a quantity of glass microfibers greater than 40% by dry weight.

[0031] According to a specific embodiment, the machine includes a curved lower support surface on either side of the lower surface (i.e., upstream and downstream of the lower surface), the curved lower support surface contacting the inner surface of the lower fabric (the inner surface being the surface of the lower fabric opposite to the surface supporting the nonwoven material), and the center of curvature of each lower support surface is located below the lower fabric.

[0032] These curved support surfaces help press the lower surface of the flattening unit against the underlying fabric.

[0033] This invention relates to a method for manufacturing a nonwoven material comprising glass microfibers, the method comprising: A nonwoven material containing glass microfibers is shaped on a lower fabric driven in the direction of travel by a forming unit. A leveling process is performed downstream of the forming unit and above the lower fabric. The leveling unit includes: an upper fabric that advances and extends in the travel direction such that nonwoven material is held between the lower and upper fabrics at the leveling unit; and a plurality of segments arranged continuously in the travel direction, the plurality of segments defining a lower surface that is pressed against the upper fabric at locations where the upper fabric contacts the nonwoven material. At least the last segment is provided with multiple orifices and is controlled to apply suction through the orifices of the last segment, and if the first segment is provided with multiple orifices, the suction through the orifices of the last segment is stronger than the suction through the orifices of the first segment.

[0034] This process can be adapted to implement each embodiment of the machine described above.

[0035] According to a specific implementation, the nonwoven material travels at a speed greater than 5 m / min, and preferably greater than 25 m / min.

[0036] The use of leveling units makes it possible to obtain acceptable nonwoven materials without lumps at these speeds. Attached Figure Description

[0037] The accompanying drawings are schematic and are primarily intended to illustrate the principles of this disclosure.

[0038] In these accompanying figures, from one figure to another, the same elements (or parts of elements) are identified by the same reference numerals.

[0039] [ Figure 1 ] Figure 1 It is based on a schematic diagram of an example machine.

[0040] [ Figure 2 ] Figure 2 This is a schematic diagram based on another example of a machine.

[0041] [ Figure 3 ] Figure 3 The leveling unit is shown in more detail.

[0042] [ Figure 4A ] Figure 4A These are photographs of nonwoven materials obtained without the use of leveling units.

[0043] [ Figure 4B ] Figure 4B This is a photograph of nonwoven material obtained using finishing rollers.

[0044] [ Figure 4C ] Figure 4C These are photographs of nonwoven materials obtained using a flattening unit. Detailed Implementation

[0045] A machine for manufacturing nonwoven materials containing glass microfibers is now described.

[0046] The term "glass microfiber" refers to fibers with an average diameter between 0.2 µm and 10 µm, preferably between 0.26 µm and 5.5 µm.

[0047] The method for manufacturing this nonwoven material will also be described.

[0048] The machines and methods described in this specification are capable of producing smooth nonwoven materials, or materials that are at least smoother than those produced by prior art, i.e., materials in which the presence of clumps in the glass microfibers is limited. Furthermore, the machines and methods described below are capable of producing such smooth nonwoven materials at a production rate of several meters per minute (greater than 5 m / min, preferably greater than 25 m / min).

[0049] The nonwoven material obtained using this machine and method can be used in AGM batteries. Therefore, this invention makes it possible to obtain nonwoven materials more suitable for manufacturing these batteries. More specifically, lead-acid batteries, referred to by the abbreviation "AGM: Adsorbed Glass Fiber Separator," include electrodes that are not immersed in acid but are separated by a porous separator made of a nonwoven material containing glass microfibers, within which the electrolyte / acid is stored.

[0050] This invention is not limited to nonwoven materials suitable for use in “AGM” rechargeable batteries. For example, nonwoven materials produced using this machine and method can also be used to manufacture HVAC filters (for heating, ventilation and air conditioning; these filters can be used for air filtration and can be pre-filters, fine filters, HEPA filters (high efficiency particulate air filters), ULPA filters (ultra-low penetration air filters)), cryogenic insulation paper, or any other material that needs to contain at least 40% glass microfibers.

[0051] Figure 1 A first example of a machine for manufacturing nonwoven materials is shown, viewed from the side. The machine 100 includes a forming unit 110, which is known in itself, and is configured to deposit a fiber suspension containing glass microfibers onto a traveling lower fabric 120. Figure 1 The forming unit of the type shown includes a cylinder 111 around which a lower fabric passes. The forming unit 110 also includes a module 112 for depositing a fiber suspension onto the lower fabric located on the cylinder. For example, the forming unit could be of the type sold by the French company ALLIMAND under the trademark ROTOFORMER. Although such a device is not shown in the figures, the machine may include means for driving the cylinder 111.

[0052] For the sake of simplicity, nonwoven materials are not shown in this figure.

[0053] One parameter of the forming unit can be the amount of glass microfibers contained in the fiber suspension supplied to it. As an example, the amount of glass microfibers in the fiber suspension can be selected such that the obtained nonwoven material contains more than 40% glass microfibers by dry weight.

[0054] exist Figure 1 In this process, the lower fabric 120 moves from left to right on the side supporting the nonwoven material being formed. As an example, as described above, the travel speed of the lower fabric (and therefore the nonwoven material) can be greater than 5 m / min, and preferably greater than 25 m / min. The lower fabric and the nonwoven material supported by it are driven by rollers 130, on which the lower fabric is placed and continuously circulates clockwise, and is capable of continuous travel (here from left to right), with the nonwoven material supported by the lower fabric. Some of these rollers can be driven rotatably by motors, which are not shown for simplicity.

[0055] Downstream of forming unit 110, a leveling unit 140 is shown, partially located above the lower fabric. The leveling unit includes an upper fabric 141 that moves in the direction of travel of the lower fabric, wherein the upper fabric contacts the nonwoven material (more specifically, the upper surface of the nonwoven material). For this purpose, the upper fabric is positioned to continuously circulate counterclockwise on rollers 142, allowing continuous left-to-right movement where it contacts the nonwoven material. Some of these rollers may be rotatably driven by a motor, which is not shown for simplicity.

[0056] It should be understood that, within a given area, the nonwoven material is held between the lower fabric 120 and the upper fabric 141. (Refer to the following...) Figure 3 This retaining mechanism will be described in more detail.

[0057] To smooth the nonwoven material, the smoothing unit comprises multiple segments arranged continuously in the direction of travel. Here, a first segment P1 is shown, followed by a second segment P2. Segment P1 is upstream of segment P2. The invention is not limited to having only two segments, but is also applicable to machines comprising, for example, three or four segments.

[0058] The first section P1 includes a plurality of orifices 144, which are openings that allow water to be pumped through (at least these orifices allow pumping when pumping is applied). Alternatively, the first section may not include orifices or may include a single orifice (unlike the second section, which includes a plurality of orifices).

[0059] These openings are defined by surface elements 143, which are solid segments that serve as a support surface for the upper fabric. For the first segment without openings, the first segment consists of only a single solid surface.

[0060] It should be noted that the segment may have a plate-like structure, which has a solid area and an optional empty area.

[0061] Here, the second segment P2 is similar to the segment P1 which has multiple orifices.

[0062] The lower surfaces of segments P1 and P2 define the lower surface of the flattening unit, denoted by the reference numeral SI in the figure. For example... Figure 1 As shown, the lower surface S1 may typically consist of multiple perforated plates or a series of spaced-apart blades extending in a direction orthogonal to the direction of travel of the nonwoven material / fabric. Orifices 144 are defined between these blades, indicated by reference numeral 143.

[0063] The lower surface S1 of the leveling unit is pressed against the upper fabric of the leveling unit at the point where the upper fabric contacts the nonwoven material, as shown in the image. Figure 3As shown. This pressure causes deformation of the underlying fabric (and non-woven materials), such as... Figure 1 As shown.

[0064] Within the leveling unit, at least the second section is controlled by the machine's suction system; for the sake of simplicity, Figure 1 The suction system is not shown. That is, in the illustrated example, each segment P1 or P2 is connected to its own conduit 145 and is in fluid communication with the machine's suction control system.

[0065] When suction is applied to the section, a vacuum is created in that section so that liquid can be drawn through orifice 144.

[0066] Here, the suction control system is configured to apply stronger suction through the orifice of the second section P2 than to apply suction through the orifice of the first section P1. Figure 1 This is indicated by the fact that the arrow extending from the catheter 145 associated with the second segment P2 is longer than the arrow extending from the catheter 145 associated with the first segment P1.

[0067] The inventors have observed that the nonwoven material formed by the forming unit, obtained at the outlet of the forming unit 110, and continuously circulated on the lower fabric 120, is particularly ductile when saturated with water. Therefore, it is advantageous to apply weak suction or no suction at all through the orifice of the first section P1. This allows for mechanical smoothing of the upper surface of the nonwoven material while it is still easily deformable.

[0068] A stronger suction is applied through the second section P2 and its orifice to remove liquid from the nonwoven material. The nonwoven material remains in contact with the lower surface S1 below the second section, which also helps to smooth it by consolidating the effect achieved in section P1.

[0069] As an example, the suction pressure in the first section can range from 0 to -5 kPa. The suction pressure in the second section can be on the order of tens of kPa (preferably between -20 kPa and -40 kPa).

[0070] It should be noted that these sections and their associated conduits can be achieved using suction boxes, which are known in machines used to manufacture nonwoven materials.

[0071] As described above, the present invention applies to leveling units comprising more than two sections. That is, the last section (i.e., the downstream section) must have a stronger suction than that applied to the first section. Furthermore, preferably, the suction intensity should increase from upstream to downstream between each consecutive section.

[0072] To facilitate pressing the lower surface SI against the upper fabric, nonwoven material, and lower fabric, the machine also includes a curved lower support surface 146 located upstream of the lower surface SI and a curved lower support surface 147 located downstream of the lower surface SI on either side (i.e., upstream and downstream).

[0073] Preferably, the downstream curved lower support surface 147 is controlled by the machine's suction control system to apply suction. This allows the fabric and nonwoven materials to be firmly held together. The center of curvature of the two curved lower support surfaces is located below the lower fabric (where the nonwoven material is supported).

[0074] In addition, Figure 1 In the example, a finishing roller 150 is shown positioned at the exit of the forming unit and upstream of the leveling unit, arranged to contact the upper surface of the nonwoven material. This finishing roller can be driven by a drive device ( Figure 1 (Not shown in the image) rotates. Preferably, the finishing roller is driven to rotate at a speed different from that of the nonwoven material in the direction of travel: the inventors have observed that this generates shear force and rearranges the fibers of the nonwoven material, which further prevents the formation of clumps, resulting in a smoother nonwoven material.

[0075] Figure 1 The machine (more specifically, the leveling unit 140) includes another optional element: a nonwoven material thickness control unit 160 disposed downstream of the lower surface S1 position. Here, the nonwoven material thickness control unit 160 includes rollers. Other units known per se may be used, such as multiple rollers in a rolling mill configuration.

[0076] Figure 2 Another example of manufacturing machine 100' is shown, which is different from Figure 1 The manufacturing machine is unique in that its forming unit 110' does not deposit the fiber suspension onto the fabric placed on a cylinder, but rather onto an inclined table forming unit. The forming unit 110' also includes a module 112' for depositing the fiber suspension onto the lower fabric as it passes over the inclined table 111'. On the inclined table 111', a set of suction boxes 113' draws the liquid from the recently deposited nonwoven material. As an example, the forming unit could be a model sold by the French company ALLIMAND under the trade name HYDROFIBER.

[0077] and Figure 1 Similarly, although not shown, but Figure 2 The machine shown may include a thickness control unit located downstream of the SI surface and upstream of the curved surface 147.

[0078] It should be understood that the present invention is applicable to any type of forming unit capable of shaping nonwoven materials containing glass microfibers on an underlying fabric. For example, the forming unit can also be a circular forming type, also known as a "vatformer". As an example, the forming unit can be a model sold by the French company ALLIMAND under the trade names CAISSE DE TÊTE FP, SFP, S4, or E-BOX.

[0079] It should be noted that the lower fabric of the forming unit on which the fiber suspension is deposited is the same fabric on which the nonwoven material rests as it passes through the leveling unit. In fact, the leveling unit preferably processes liquid-saturated nonwoven material that has not yet been transferred to another fabric, and is therefore on the same lower fabric as the fabric on which the forming unit shapes the nonwoven material.

[0080] Figure 3 The leveling unit is shown in more detail. This can be... Figure 1 The leveling unit of machine 100, or Figure 2 The leveling unit of machine 100', or the leveling unit of any other machine equipped with a forming unit. Figure 3 In the figure, the lower fabric 120, the nonwoven material 200, and the upper fabric 141 are shown as spaced apart from each other; in reality, these three elements are in contact at least along one section, contrary to what is shown in the figure. It can be seen that this section extends between the two lowest drive rollers 142 of the leveling unit.

[0081] To achieve good flatness and prevent damage to the nonwoven material 200, the lower surface SI has a radius of curvature R, with the center of curvature C located above the lower surface SI. For example, a radius of curvature well-suited for flattening nonwoven materials can be between 2 m and 100 m, preferably between 5 m and 30 m, and, for example, equal to 15 m. This radius of curvature is obtained by the relative position of each surface element 144 of segments P1 and P2 to define the curve.

[0082] exist Figure 3 Within the leveling unit, a suction port 180 has been formed, which is arranged to allow the recovery of the supernatant upstream of the first section P1.

[0083] The suction orifice enables suction controlled by the machine's suction control system. The suction orifice is defined by a conduit 181 (which is in fluid communication with the machine's suction control system) and further defined at the orifice by a scraper 182 flush with the surface of the upper fabric to lift the supernatant. The scraper 182 extends upstream from the first segment P1.

[0084] The suction port 180 is optional.

[0085] Figure 4A This is a photograph of nonwoven material obtained without using a leveling unit. The photograph shows raised areas, indicating the presence of clumps of glass microfibers, due to the presence of fibrous flocs directly at the outlet of the forming unit.

[0086] Figure 4B It consists of units that do not include flattening elements but include, for example, references. Figure 1 The image depicts a machine-manufactured nonwoven material similar to the finishing roller 150. This nonwoven material still exhibits raised areas, and its appearance is unsatisfactory for use in batteries.

[0087] Figure 4C It is composed of including Figures 1 to 3 The photograph shows a machine-manufactured nonwoven material of the type of flattening unit described above. It can be seen that the nonwoven material has a smoother appearance and is not included in... Figure 4A and Figure 4B Clumps with distinct raised areas seen in nonwoven materials.

[0088] Figure 4B and Figure 4C It has been shown that finishing rollers alone are insufficient to prevent defects in nonwoven materials. However, it has been observed that when finishing rollers are combined with leveling units, the leveling process is improved.

[0089] This invention is not limited to the examples described and illustrated, as various modifications can be made thereto without departing from the scope of the invention.

Claims

1. A machine for manufacturing a nonwoven material (200) comprising glass microfibers, comprising: Forming units (110, 110') are used to form a nonwoven material containing glass microfibers on a lower fabric (120) that is driven in the direction of travel. A leveling unit (140), located downstream of the forming unit and above the lower fabric, includes: an upper fabric (141) that advances and extends in the direction of travel such that the nonwoven material is held between the lower and upper fabrics at the leveling unit; and a plurality of segments (P1, P2) arranged continuously in the direction of travel, defining a lower surface (SI) of the leveling unit, the lower surface being pressed against the upper fabric at the point where the upper fabric contacts the nonwoven material. At least the last section is provided with multiple orifices and is controlled by the suction control system of the leveling unit so that suction is applied through the orifices of the last section, and if the first section is provided with multiple orifices, the suction through the orifices of the last section is stronger than the suction through the orifices of the first section.

2. The machine according to claim 1, wherein the lower surface of the plurality of sections has a given radius of curvature (R) and the center of curvature (C) is located above the lower surface.

3. The machine according to claim 1 or 2, comprising a suction port (180) arranged to recover supernatant upstream of the first section, the suction port being controlled by the suction control system.

4. The machine according to any one of claims 1 to 3, comprising a finishing roller (150) arranged at the outlet of the forming unit and upstream of the leveling unit, the finishing roller being arranged to contact the upper surface of the nonwoven material.

5. The machine of claim 4, wherein the finishing roller is driven to rotate at a speed different from the speed at which the nonwoven material is driven in the direction of travel.

6. The machine according to any one of claims 1 to 5, comprising a unit (160) downstream of the position where the lower surface of the plurality of sections contacts the upper fabric for controlling the thickness of the nonwoven material.

7. The machine according to any one of claims 1 to 6, wherein the forming unit is configured to convey a nonwoven material comprising glass microfibers in an amount greater than 40% by dry weight.

8. The machine according to any one of claims 1 to 7, wherein each side of the lower surface includes a curved lower support surface (146, 147) in contact with the lower fabric, and the center of curvature of each curved lower support surface is located below the lower fabric.

9. A method for manufacturing a nonwoven material (200) comprising glass microfibers, the method comprising: The nonwoven material containing glass microfibers is shaped on the lower fabric (120) driven in the direction of travel by the forming units (110, 110'). Downstream of the forming unit and above the lower fabric, a leveling unit (140) is performed, comprising: an upper fabric (142) that advances and extends in the travel direction such that the nonwoven material is held between the lower and upper fabrics at the leveling unit; and a plurality of segments (P1, P2) continuously arranged in the travel direction, the plurality of segments defining a lower surface (SI) that is pressed against the upper fabric at the location where the upper fabric contacts the nonwoven material. At least the last segment is provided with a plurality of orifices and is controlled to apply suction through the orifices of the last segment, and if the first segment is provided with a plurality of orifices, the suction through the orifices of the last segment is stronger than the suction through the orifices of the first segment.

10. The method of claim 9, wherein the nonwoven material travels at a speed greater than 5 m / min, preferably greater than 25 m / min.

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