Non-woven material manufacturing machine including glass microfiber and corresponding process

Abstract

A machine for manufacturing nonwoven material comprising glass microfiber, comprising: a forming unit (110, 110') for nonwoven material comprising glass microfiber, on a lower web (120) driven in a forward direction; a smoothing unit (140) comprising an upper web (141) moving in the forward direction and extending so that the nonwoven material is held between the lower and upper webs at the level of the smoothing unit; and a plurality of portions (P1, P2), the plurality of portions defining a lower surface (SI) of the smoothing unit 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 portion. [Fig. 1]

Description

Title of the invention: Machine for manufacturing non-woven material comprising glass microfiber and corresponding method Technical field

[0001] The present disclosure relates to the manufacture of wet-laid nonwoven materials comprising glass microfiber and corresponding manufacturing machines. Prior art

[0002] The expression non-woven materials, well known to those skilled in the art, is for example defined in the ISO 9092 standard in its 2019 version and, according to this standard, refers to "a pre-designed, essentially flat fibrous assembly having a nominal level of structural integrity conferred by means of physical and / or chemical processes, excluding weaving, knitting or papermaking".

[0003] In this document, the term "nonwoven material" is used for both the finished product and the material being manufactured.

[0004] Conventionally, the manufacture of non-woven materials comprising glass microfiber involves the use of a forming unit provided with a moving lower fabric on which a fibrous suspension (comprising a quantity of glass microfiber, for example, greater than 40% by dry weight) is deposited uniformly along the width of the lower fabric (the width being orthogonal to the direction of travel of the fabric).

[0005] Draining of the fibrous suspension is then carried out to remove the liquid phase of the suspension, typically water or foam, in which the fibers were initially suspended, to obtain a nonwoven material.

[0006] It has been observed that the presence of glass microfibers leads to the formation of flocs in the upper part of the nonwoven material, which, during the draining phase, form clumps of microfibers. The surface of nonwoven materials comprising glass microfiber obtained by current techniques is therefore generally very irregular, these clumps being considered as defects degrading the quality of the final product.

[0007] Techniques to avoid the appearance of these clumps may involve slowing down the draining process and therefore the productivity of the manufacturing machine. These techniques are not satisfactory since they have too great an impact on the quantity of nonwoven material produced per minute.

[0008] There is therefore a real need for a machine for manufacturing non-woven material comprising glass microfiber which is free, at least in part, from the drawbacks mentioned above. Statement of the invention

[0009] The present invention relates to a machine for manufacturing non-woven material comprising glass microfiber, comprising: a unit for forming non-woven material comprising glass microfiber, on a lower fabric driven in a running direction (this running direction is followed at least when the non-woven material is on the lower fabric), downstream of the forming unit and above the lower fabric, a smoothing unit comprising an upper fabric running in the running direction and extending so that the nonwoven material is held between the lower fabric (this being the same fabric on which the nonwoven material is formed by the forming unit) and the upper fabric at the smoothing unit, and a plurality of portions arranged consecutively in the running direction, the plurality of portions defining a lower surface of the smoothing unit pressed against the upper fabric at a location where the upper fabric is in contact with the nonwoven material, wherein at least the last portion (i.e. the most downstream portion of the plurality of portions) is provided with a plurality of orifices and is controlled by a suction control system of the smoothing unit to apply suction through the orifices of the last portion,and if the first portion is provided with a plurality of orifices, the suction is stronger through the orifices of the last portion than through the orifices of the first portion (i.e. the most upstream portion of the plurality of portions).

[0010] If the first portion does not have any orifices (it is a solid surface), no suction can be applied to it, and the suction through the orifices of the last portion is non-zero.

[0011] The inventors of the present invention have observed that by using a smoothing unit which comprises several portions, with a weaker or even zero suction at the beginning (for the first portion) and a stronger or at least non-zero suction at the end (for the last portion), a smoothed nonwoven material is obtained with a good reduction, after elimination of the surface liquid phase, of the presence of the resulting clusters of bubbles. In fact, the first portion of the lower surface of the smoothing unit (i.e. the lower surface of the first portion) is in contact with the upper fabric at a location where the nonwoven material is saturated with liquid on its upper face.At this stage, the upper surface of the nonwoven material is more malleable than after suction draining, which facilitates the mechanical flattening of the nonwoven material and in particular of its upper surface (opposite to that supported by the lower fabric) by the first portion. The absence of suction or low suction (compared to the last portion) in the first portion. therefore allows the smoothing unit to shape the upper surface of the nonwoven material to make it smoother.

[0012] A portion is here formed of one or more surface elements intended to be in contact with the upper fabric, the portion possibly having orifices (the last one has orifices, the first one optionally has them). The portions extend over the width of the nonwoven material (in a direction orthogonal to the scrolling) and have a given length (in the scrolling direction) which may be the same or different for different portions. The portions, in particular the last portion, may be in fluid communication with the suction control system so that liquid is sucked through the orifices of the portion if they have them. Here, there are at least two portions. The suction control system is configured to control portions independently of each other if both are provided with orifices.

[0013] It can be noted that a portion has a length measured in the direction of movement of the fabric, between 100 mm and 800 mm depending on the type of glass microfibers used.

[0014] Also, an orifice may extend across the entire width of a portion (the orifice is located between surface elements which may be blades which extend on either side of orifices across the entire width of a portion).

[0015] Alternatively, an orifice may be completely surrounded by a surface element, for example, the portion comprises a single surface element and several orifices distributed over the width and length of the portion / single surface element (for example in a uniform distribution). Such orifices may have any shape (circular-based cylinder, oblong-based cylinder, etc.).

[0016] The surface elements of all the portions define the lower surface of the smoothing unit. The upper fabric exerts pressure on the lower surface of the smoothing unit at a location where the upper fabric is in contact with the nonwoven material, which is also in contact with the lower fabric itself exerting pressure on the nonwoven material. The nonwoven material is thus constrained by the lower surface of the smoothing unit, this constraint resulting from the arrangement of the lower surface of the smoothing unit, which itself depends on the arrangement of the portions.

[0017] According to a particular embodiment, the plurality of portions has a given radius of curvature with a center of curvature located above the lower surface.

[0018] As an indication, the radius of curvature may be between 2m and 100m, preferably between 5m and 30m, and for example equal to 15m.

[0019] It has been observed by the inventors that the radius of curvature contributes to the improvement of smoothing.

[0020] According to a particular embodiment, the machine comprises a suction orifice arranged to allow recovery of supernatant liquid upstream of the first portion, the suction orifice being controlled by said suction control system.

[0021] It should be noted that the suction orifice differs from said portions in that it comprises a single orifice whereas the portions comprise a plurality of orifices.

[0022] The suction orifice may be defined by means of a blade extending in the direction of the width of the fabrics from the first portion and configured to brush against the inner face of the upper fabric (i.e. the face of the upper fabric against which the lower surface is in contact) so that the movement of the fabric lifts liquid by means of the blade which is then sucked through the suction orifice. This supernatant liquid does not contribute or contributes little to the malleability of the nonwoven material, it is possible to remove it by suction before smoothing.

[0023] According to a particular embodiment, the machine comprises a draining roller arranged at the outlet of the forming unit and upstream of the smoothing unit, the draining roller being arranged to be in contact with the upper face of the non-woven material.

[0024] The draining roller may comprise a cylinder with a circular base and extending in the direction orthogonal to the movement of the non-woven material. In a manner known per se for draining rollers.

[0025] The inventors of the present invention have observed that the use of a drain roller at the outlet of the forming unit further improves the smoothing of the nonwoven material. The drain roller is in contact with the nonwoven material at a location which is not yet in contact with the upper fabric of the smoothing unit.

[0026] According to a particular embodiment, the draining roller is rotated at a speed different from the speed at which the non-woven material is driven (by drive means of the machine, for example) in the direction of travel.

[0027] By using a different speed (higher or lower than the scrolling speed), shearing occurs in the non-woven material, which facilitates a reorganization of the glass microfibers of the non-woven material and which contributes to the smoothing of the non-woven material.

[0028] According to a particular embodiment, the machine comprises a unit for controlling the thickness of the non-woven material downstream of the location where the lower surface of the plurality of portions is in contact with the upper fabric.

[0029] According to a particular embodiment, the forming unit is configured to deliver a non-woven material comprising a quantity greater than 40% by dry weight of glass microfiber.

[0030] The person skilled in the art will know how to choose the parameters of the fibrous suspension used. in the forming unit as well as the running speed of the lower fabric to obtain a non-woven material having, by dry weight, a quantity greater than 40% of glass microfiber.

[0031] According to a particular embodiment, the machine comprises, on either side of the lower surface (i.e. upstream and downstream of the lower surface), curved lower support surfaces in contact with the inner face of the lower fabric (this inner face being the face of the lower fabric opposite that supporting the non-woven material) and each having a center of curvature which is below the lower fabric.

[0032] These curved support surfaces facilitate the pressing of the lower surface of the smoothing unit against the lower fabric.

[0033] The invention also relates to a method for manufacturing non-woven material comprising glass microfiber, comprising: a formation by a non-woven material forming unit comprising glass microfiber, on a lower fabric driven in a running direction, smoothing carried out downstream of the forming unit and above the lower fabric, by means of a smoothing unit comprising an upper fabric running in the running direction and extending so that the nonwoven material is held between the lower fabric and the upper fabric at the smoothing unit, and a plurality of portions arranged consecutively in the running direction, the plurality of portions defining a lower surface pressed against the upper fabric at a location where the upper fabric is in contact with the nonwoven material, wherein at least the latter portion is provided with a plurality of orifices and is controlled to apply suction through the orifices of the latter portion, and if the former portion is provided with a plurality of orifices, the suction is stronger through the orifices of the latter portion than through the orifices of the former portion.

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

[0035] According to a particular embodiment, the non-woven material moves at a speed greater than 5 m / min and preferably greater than 25 m / min.

[0036] The use of the smoothing unit makes it possible to obtain a non-woven material which is acceptable in terms of the absence of clumps for these speeds. Brief description of the drawings

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

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

[0039] [Fig. 1] [Fig.l] is a schematic representation of a machine according to an example.

[0040] [Fig.2] [Fig.2] is a schematic representation of a machine according to another example.

[0041] [Fig.3] [Fig.3] shows a smoothing unit in more detail.

[0042] [Fig.4A] [Fig.4A] is a photograph of a nonwoven material obtained without a smoothing unit.

[0043] [Fig.4B] [Fig.4B] is a photograph of a non-woven material obtained using a drip roller.

[0044] [Fig.4C] [Fig.4C] is a photograph of a nonwoven material obtained with the use of a smoothing unit. Description of the embodiments

[0045] We will now describe a machine for the manufacture of non-woven materials comprising glass microfiber.

[0046] The term “glass microfiber” refers to fibers having average diameters between 0.2 pm and 10 pm, and preferably between 0.26 pm and 5.5 pm.

[0047] The manufacturing process of this non-woven material will be described simultaneously.

[0048] The machine and the method described in the present description make it possible to obtain a smooth non-woven material or at least a smoother one than according to the techniques of the prior art, that is to say for which the presence of clusters of glass microfibers is limited. Also, the machine and the method described below make it possible to obtain this smooth non-woven material with a production of several meters per minute (greater than 5 m / min and preferably greater than 25 m / min).

[0049] The non-woven materials obtained by means of this machine and this method can be used in "AGM" type storage batteries. The invention therefore makes it possible to obtain more desirable non-woven materials for the manufacture of these storage batteries. In fact, lead storage batteries designated by the English acronym "AGM: Absorbent Glass Mat" comprise electrodes which are not bathed in an acid but separated by porous separating layers, made of non-woven material comprising glass microfiber and in which an electrolyte / acid is stored.

[0050] The invention is not limited to non-woven materials usable for “AGM” type accumulator batteries. For example, the non-woven materials obtained by means of this machine and this method can also be used in the manufacture of HVAC filters (“Heating, Ventilation, and Air Conditioning”, according to an English acronym meaning heating, ventilation, and air conditioning), these filters which can be used for air filtration, and be pre-filters, fine filters, HEPA filters ("High-Efficiency Particulate Air" or high efficiency air filters), ULPA filters ("Ultra-Low Penetration Air" or filters with very low air penetration)), cryogenic insulation papers, or any other material which must contain at least 40% glass microfibers.

[0051] [Fig. 1] shows a first example of a machine for manufacturing nonwoven material in side view. This machine 100 comprises a forming unit 110 known per se and configured to deposit a fibrous suspension, comprising glass microfiber on a moving lower fabric 120. The forming unit of the type shown in [Fig. 1], comprises a cylinder 111 around which the lower fabric moves. The forming unit 110 further comprises a module 112 for depositing the fibrous suspension on the lower fabric which is on the cylinder. For information purposes, the forming unit may be of the type marketed by the French company ALLIMAND under the trade name ROTOFORMER. Although such means are not shown in the figure, the machine may comprise means for driving the cylinder 111.

[0052] For reasons of simplicity, the non-woven material is not visible in this figure.

[0053] A parameter of the forming unit may be the quantity of glass microfibers contained in the fibrous suspension which feeds it. As an indication, the quantity of glass microfibers in the fibrous suspension may be chosen so that the nonwoven material obtained comprises a quantity greater than 40% by dry weight of glass microfiber.

[0054] In [Fig.l], the lower fabric 120 runs from left to right on the side supporting the nonwoven material being formed. For information purposes, the running speed of the lower fabric (and therefore of the nonwoven material) may be greater than 5 m / min, as indicated above, and preferably greater than 25 m / min. The lower fabric and the nonwoven material supported by this fabric are driven by rollers 130 on which the lower fabric is mounted to circulate continuously in a clockwise direction and allow continuous running here from left to right where the nonwoven material is supported by the lower fabric. Some of these rollers may be driven in rotation by motors, not shown for reasons of simplicity.

[0055] Downstream of the forming unit 110, a smoothing unit 140 is shown partly above the lower fabric. The smoothing unit comprises an upper fabric 141 which runs in the direction of travel of the lower fabric where it is in contact with the nonwoven material (more precisely with the upper face of the nonwoven material). For this purpose, the upper fabric is mounted to run continuously in the counterclockwise direction on rollers 142 and to allow continuous travel here from left to right. the right where the top fabric is in contact with the nonwoven material. Some of these rollers may be rotated by motors, not shown for simplicity.

[0056] It is understood that in one area, the non-woven material is held between the lower fabric 120 and the upper fabric 141. This holding will be described in more detail below with reference to [Fig.3].

[0057] To smooth the nonwoven material, the smoothing unit comprises a plurality of portions arranged consecutively in the direction of travel. Here, a first portion PI is shown, followed by a second portion P2. The portion PI is upstream of the portion P2. The invention is not limited to the presence of only two portions and also applies to machines comprising, for example, three or four portions.

[0058] The first portion PI here comprises a plurality of orifices 144 which are openings allowing the water to be sucked through (in the case where suction is applied; at the very least, they allow suction). Alternatively, the first portion may not comprise orifices or a single orifice (this is not the case for the second portion which comprises several orifices).

[0059] The orifices are delimited by surface elements 143, which are solid portions serving as a support surface for the upper canvas. For a first portion not comprising orifices, the first portion only comprises a solid surface element.

[0060] It may be noted that a portion may have a plateau structure with solid areas and possibly empty areas.

[0061] The second portion P2 is here analogous to the portion PI provided with several orifices.

[0062] The lower surfaces of portions PI and P2 define a lower surface of the smoothing unit referenced SI in the figure. The lower surface SI may typically consist of perforated plates or a succession of spaced blades, as shown in [Fig.l], which extend in a direction orthogonal to the direction of travel of the nonwoven material / webs. Between these blades referenced 143, orifices 144 are defined.

[0063] The lower surface SI of the smoothing unit is pressed by its arrangement against the upper fabric of the smoothing unit, at a location where the upper fabric is in contact with the non-woven material, as will be seen in [Fig. 3]. This pressing leads to a deformation of the lower fabric (and the non-woven material) visible in [Fig. 1].

[0064] Within the smoothing unit, at least the second portion is controlled by a suction system of the machine, not shown in [Fig.l] for reasons of simplicity. That being said, in the illustrated example, each portion PI or P2 is connected to a 145 line of its own and in fluid communication with the machine's suction control system.

[0065] When suction is applied to a portion, a vacuum is obtained at the portion to suck in particular liquid through the orifices 144.

[0066] Here, the suction control system is configured to apply a stronger suction through the orifices of the second portion P2 than through the orifices of the first portion PI. In [Fig.l], this is represented by means of an arrow emerging from the conduit 145 associated with the second portion P2 longer than the arrow emerging from the conduit 145 associated with the first portion PI.

[0067] It has been observed by the inventors that the nonwoven material obtained at the outlet of the forming unit 110, which always circulates on the lower fabric 120 which is that of the forming unit, is particularly malleable when it is saturated with water. Thus, it is advantageous to apply low or no suction through the orifices of the first portion PI. This makes it possible to obtain mechanical smoothing of the upper surface of the nonwoven material while this nonwoven material is then easily deformable.

[0068] Through the second portion P2 and its orifices, a stronger suction is applied to remove liquid from the nonwoven material. The nonwoven material remains in contact with the lower surface SI under the second portion, which also contributes to its smoothing by freezing the effect obtained in the portion PL

[0069] For information purposes, the suction pressure of the first portion may be between 0 and -5 kPa. The suction pressure of the second portion may be of the order of several tens of kPa, preferably between -20 kPa and -40 kPa.

[0070] It may be noted that the portions and their associated conduits may be implemented by means of suction boxes known per se in machines for manufacturing non-woven materials.

[0071] As indicated above, the invention applies to smoothing units comprising more than two portions. That being said, the last portion, i.e. the most downstream, must have a stronger suction than that applied to the first portion. Also and preferably, the suction level must increase from upstream to downstream, between each consecutive portion.

[0072] To facilitate the pressing of the lower surface SI against the upper fabric, the non-woven material, and the lower fabric, the machine further comprises, on either side of the lower surface SI (i.e. upstream and downstream), a curved lower bearing surface 146 upstream of the lower surface SI, and a curved lower bearing surface 147 downstream of the lower surface SL.

[0073] Preferably the curved lower bearing surface 147, the one located downstream, is controlled by the suction control system of the machine to apply an as piration. This can help keep the fabrics and nonwoven material together. The two curved lower support surfaces have centers of curvature located below the lower fabric (where it supports the nonwoven material).

[0074] Also, in the example of [Fig.l], a drip roller 150 (“dandy roll” in English) is shown arranged at the outlet of the forming unit and upstream of the smoothing unit, this drip roller being arranged to be in contact with the upper face of the non-woven material. This drip roller can be driven in rotation by drive means not shown in [Fig.l]. Preferably, the drip roller is driven in rotation at a speed different from the speed at which the non-woven material is driven in the running direction: it has been observed by the inventors that this creates shear and reorganizes the fibers of the non-woven material, which makes it possible to further avoid the presence of clumps to obtain a smoother non-woven material.

[0075] The machine of [Fig.l] and more precisely the smoothing unit 140 comprises another optional element, a unit 160 for controlling the thickness of the non-woven material arranged downstream of the location where the lower surface SL The unit 160 for controlling the thickness of the non-woven material here comprises a roller. Other units known per se can be used, for example using several rollers in a rolling mill configuration.

[0076] In [Fig. 2], another example of a manufacturing machine 100' is shown which differs from that of [Fig. 1] in particular in that its forming unit 110' does not deposit a fibrous suspension on a fabric mounted on a cylinder but a forming unit of the inclined table type. The forming unit 110' also comprises a module 112' for depositing the fibrous suspension on the lower fabric which runs on an inclined table 111'. In the inclined table 111', a set of suction boxes 113' sucks the liquid from the non-woven material which has just been deposited. For information, the forming unit may be of the type marketed by the French company ALLIMAND under the trade name HYDROFIBER.

[0077] In the same way as for [Fig.l] and although this has not been shown, the machine shown in [Fig.2] may include a thickness control unit downstream of the surface SI and upstream of the curved surface 147.

[0078] It is understood that the invention applies to any type of forming unit capable of forming on a lower fabric a non-woven material comprising glass microfiber. For example, the forming unit may also be of the round shape type also called "vat former" in English. For information purposes, the forming unit may be of the type of the unit marketed by the French company ALLIMAND under the trade name CAISSE DE TÊTE FP or SFP or S4 or E-BOX.

[0079] It should be noted that the lower web of the forming unit on which is deposited the fibrous suspension is the same as that on which the nonwoven material is at the level of the passage in the smoothing unit. Indeed, the smoothing unit preferentially treats a nonwoven material saturated with liquid, which is not yet transferable to another fabric, and which is therefore on the same lower fabric as that on which the forming unit forms the nonwoven material.

[0080] [Fig. 3] shows in more detail the smoothing unit, which may be that of the machine 100 of [Fig. 1] or of the machine 100' of [Fig. 2] or of any other machine equipped with a forming unit. In this [Fig. 3], the lower fabric 120, the non-woven material 200, and the upper fabric 141 are shown spaced apart from each other, these three elements being in fact in contact at least along a portion, contrary to what is shown. As can be seen, this portion extends between the two lowest drive rollers 142 of the smoothing unit.

[0081] To obtain good smoothing and avoid deterioration of the nonwoven material 200, the lower surface SI has a radius of curvature R, with a center of curvature C which is located above the lower surface SI. As an indication, a radius of curvature well suited for smoothing the nonwoven material may be between 2m and 100m, preferably between 5m and 30m, for example equal to 15m. This radius of curvature is obtained by the relative position of each of the surface elements 144 of the portions PI and P2, to define a curve.

[0082] Within the smoothing unit of [Fig.3], a suction orifice 180 has been formed, arranged to allow recovery of supernatant liquid upstream of the first portion PI.

[0083] The suction port allows suction controlled by the suction control system of the machine. The suction port is defined by a conduit 181 (in fluid communication with the suction control system of the machine) and at the port by a blade 182 which is flush with the surface of the upper screen to lift the supernatant liquid. The blade 182 extends in the upstream direction from the first portion PL

[0084] The suction port 180 is optional.

[0085] [Fig.4A] is a photograph of a nonwoven material obtained without a smoothing unit being used. This photograph shows reliefs that show the presence of glass microfiber clumps, which result from the presence of fiber flocs directly at the outlet of the forming unit.

[0086] [Fig.4B] is a photograph of a non-woven material manufactured by a machine which also does not include a smoothing unit, but which includes a drip roller similar to the drip roller 150 described for example with reference to [Fig.1]. This non-woven material always has reliefs and its appearance is not satisfactory for use in a battery.

[0087] [Fig.4C] is a photograph of a nonwoven material manufactured by a machine which includes a smoothing unit of the type of those of Figures 1 to 3 described above. As can be seen, the nonwoven material has a smoother appearance and does not include clumps which have a significant relief, as do the nonwoven materials of Figures 4A and 4B.

[0088] From Figures 4B and 4C, it is understood that the draining roller alone is not sufficient to avoid defects in nonwoven materials. On the other hand, it has been observed that the draining roller combined with a smoothing unit improves smoothing.

[0089] The invention is not limited to the examples described and shown because various modifications can be made thereto without departing from its scope.

Claims

Claims

1. Machine for manufacturing nonwoven material (200) comprising glass microfiber, comprising: a forming unit (110, 110') of a nonwoven material comprising glass microfiber, on a lower web (120) driven in a running direction, downstream of the forming unit and above the lower web, a smoothing unit (140) comprising an upper web (141) running in the running direction and extending so that the nonwoven material is held between the lower web and the upper web at the smoothing unit, and a plurality of portions (PI, P2) arranged consecutively in the running direction, the plurality of portions defining a lower surface (SI) of the smoothing unit pressed against the upper web at a location where the upper web is in contact with the nonwoven material,wherein at least the last portion is provided with a plurality of orifices and is controlled by a suction control system of the smoothing unit to apply suction through the orifices of the last portion, and if the first portion is provided with a plurality of orifices, the suction is stronger through the orifices of the last portion than through the orifices of the first portion.,

2. A machine according to claim 1, wherein the lower surface of the plurality of portions has a given radius of curvature (R) with a center of curvature (C) located above the lower surface.

3. Machine according to claim 1 or 2, comprising a suction orifice (180) arranged to allow recovery of supernatant liquid upstream of the first portion, the suction orifice being controlled by said suction control system.

4. Machine according to any one of claims 1 to 3, comprising a draining roller (150) arranged at the outlet of the forming unit and upstream of the smoothing unit, the draining roller being arranged to be in contact with the upper face of the non-woven material.

5. Machine according to claim 4, in which the drip roller is rotated at a speed different from the speed at which the nonwoven material is driven in the running direction.

6. Machine according to any one of claims 1 to 5, comprising a unit (160) for controlling the thickness of the non-woven material downstream of the location where the lower surface of the plurality of portions is in contact with the upper web.

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

8. Machine according to any one of claims 1 to 7, comprising, on either side of the lower surface, curved lower bearing surfaces (146, 147) in contact with the lower fabric and each having a center of curvature which is below the lower fabric.

9. A method for manufacturing nonwoven material (200) comprising glass microfiber, comprising: forming by a forming unit (110, 110') nonwoven material comprising glass microfiber, on a lower web (120) driven in a running direction, smoothing carried out downstream of the forming unit and above the lower web, by means of a smoothing unit (140) comprising an upper web (142) running in the running direction and extending so that the nonwoven material is held between the lower web and the upper web at the smoothing unit, and a plurality of portions (PI, P2) arranged consecutively in the running direction, the plurality of portions defining a lower surface (SI) pressed against the upper web at a location where the upper web is in contact with the nonwoven material,wherein at least the latter portion is provided with a plurality of orifices and is controlled to apply suction through the orifices of the latter portion, and if the former portion is provided with a plurality of orifices, the suction is stronger through the orifices of the latter portion than through the orifices of the former portion.,

10. Method according to claim 9, in which the non-woven material moves at a speed greater than 5 m / min and preferably greater than 25 m / min.

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