EP2841634B1 - Method and device for melt-blowing, forming and plaiting finite fibres to produce a fibrous nonwoven - Google Patents

Description

The invention relates to a method for melt blowing, forming and depositing finite fibers into a nonwoven fabric according to the preamble of claim 1 and to an apparatus for melt blowing, forming and depositing finite fibers into a nonwoven fabric according to the preamble of claim 5.

In principle, two different methods and devices are known in the prior art for the production of fiber webs from synthetic fibers. Both methods differ both in the production of the fibers and in the deposition of the fibers to a nonwoven fabric.

With the variant known in the art as a meltblown process, freshly extruded fibers are drawn off directly from the nozzle openings of the meltblowing die by a hot air stream by means of a hot air stream and fed as a fiber stream to a nonwoven fabric. Essentially finite fibers occur which have a relatively high elasticity. From this variant, the invention proceeds, as will be explained later.

In a second variant, which is referred to in the art as a so-called spunbond process, synthetic filaments are extruded by means of a spinneret and cooled. Subsequently, the filaments are fed by means of a supplied compressed air as a fiber stream to a nonwoven fabric. Here, the nonwoven fabric consists essentially of endless filaments with higher strengths. For depositing the filaments, a compressed air flow generated by the additional extraction device is used, which can be set individually to the respective process.

In contrast, in the meltblown process, the stream of hot air generated at the meltblowing die is used to pull out the extruded fibers and lay down the fibers. The filing of the fibers can be done directly on screen belts or sieve drums, are accumulated on the surfaces of the fiber stream and merged into a fiber composite. In order to produce particularly loosely structured fiber webs, it is also known to receive the fiber stream by means of a Formierspaltes and merge to form a fiber composite. Such a method and such a device are for example from DE 30 41 089 A1 known. Here, two forming elements are arranged below the melt-blowing, which form a forming gap between them. The forming gap is held centrally to the meltblowing die, so that the fiber stream is directed directly onto the forming nip. In such a deposition of the fibers is disadvantageous that a portion of the air flow acts directly on the deposited in the forming gap composite sections. In the conventional shelves of the fiber stream on screen surfaces, the air flow is absorbed and removed by the screen surface. This can be realized in the deposition of the fiber stream in a forming gap only on the laterally arranged forming elements.

Through the publication US 4,375,446 For example, a process is known in which a meltblown web is pressed between two porous rolls. US 2010/266824 A1 discloses a process for making laminates in which fiber streams are compressed to a three-layered structure.

It is an object of the invention to develop a generic method as well as a generic device for melt blowing, forming and depositing finite fibers to a nonwoven fabric such that even the finest fibers can be formed in a forming gap to form a loose fiber composite.

Another object of the invention is to improve the known method and the known apparatus for melt blowing, forming and depositing finite fibers to form a nonwoven fabric such that highly voluminous nonwoven fabrics with small to large basis weights are flexible to produce.

This object is achieved according to the invention in that the fibers are guided essentially vertically vertically from the melt-blowing nozzle to the forming gap via an adjustable blowing line, the setting range of the blowing line being in the range from 100 mm to 2,000 mm.

Advantageous developments are defined by the features and feature combinations of the respective subclaims.

The invention is characterized in that the hot air flow required to produce the fibers can be selected at the melt-blowing nozzle independently of the deposition of the fibers into the forming gap. Around To bring the intensity of the air flow in the tray in a size advantageous for the formation, the blaze can be shortened or extended as required. The blowing line below the melt-blowing nozzle and the forming gap can advantageously be aligned vertically, so that a 3D structure of the fiber composite can be formed during the deposition and formation.

In order to form a fiber composite with high uniformity, it is provided according to the invention that the fibers are blown for forming between two counter-rotating drums with air-permeable drum walls, which drums between them form the forming gap and each with a same peripheral speed in the range of 0, 1 m / min to 50 m / min are driven. By adjusting the peripheral speeds of the drums, the surface densities of the fiber volume can be advantageously influenced. Thus, with an increased peripheral speed of the drum walls in the forming gap very loose fiber webs can be produced.

For both the method according to the invention and for the device according to the invention, it has proved particularly useful that the fiber composite, after being formed by one of the drums, be deposited on the nonwoven fabric on a screen belt which discharges the fiber web tangentially to the drums. Thus, further treatments on the nonwoven fabric can be carried out in a short sequence.

The thickness of the produced nonwoven fabric is determined essentially by a forming cross section of the forming nip. The setting of the forming gap is done in a simple manner such that a Distance between the drums is adjusted in a range of 1 mm to 100 mm symmetrically or asymmetrically between the drums. In an asymmetric adjustment, the center axis of the formation gap no longer coincides with the center of the meltblowing die. In addition, deposition effects and formations within the formation gap can thereby be generated.

To form an asymmetric formation gap, it is also possible to form the formation gap between two drums having different drum diameters. According to an advantageous development of the device according to the invention, the drums can have identical or different drum diameters with a diameter ratio in the range from 0.5 to 2.0. This can advantageously produce different surface structures on the nonwoven fabric. The drums have for this purpose a drum diameter which is in the range of 100 mm to 800 mm.

On the one hand to influence the deposition of the fibers on the inlet side of the forming gap by receiving the blowing air and on the other hand to carry out the removal of the nonwoven fabric at least one of the drums, the device according to the invention is to be improved such that one of the drums has an inner suction chamber with a negative pressure source is connected and which is shielded by the air-permeable drum wall to the environment. In that regard, additional suction streams can be generated to assist in the generation and guidance of the fibrous web. The effect can be further supported, idem both drums each have a separate suction chamber, which together a vacuum source or separately connected to two vacuum sources.

Particularly advantageous, the development of the invention has been found in which an angular position of the suction chamber on the circumference of the drum is adjustable. Thus, the position of the suction chamber can be freely selected relative to the inlet and outlet of the Formierspaltes.

The method according to the invention and the device according to the invention will be explained in more detail below with reference to some embodiments of the device according to the invention with reference to the attached figures.

Fig. 1

schematisch eine Querschnittsansicht eines ersten Ausführungsbeispiels der erfindungsgemäßen Vorrichtung zum Schmelzblasen, Formieren und Ablegen endlicher Fasern zu einem Faservlies

Fig. 2

schematisch eine Querschnittsansicht eines weiteren Ausführungsbeispiels der erfindungsgemäßen Vorrichtung zum Schmelzblasen, Formieren und Ablegen endlicher Fasern

Fig. 3

schematisch eine Querschnittsansicht eines weiteren Ausführungsbeispiels der erfindungsgemäßen Vorrichtung zum Schmelzblasen, Formieren und Ablegen endlicher Fasern

Fig. 4

schematisch ein weiteres Ausführungsbeispiel der erfindungsgemäßen Vorrichtung zum Schmelzblasen, Formieren und Ablegen endlicher Fasern

They show:

Fig. 1

schematically a cross-sectional view of a first embodiment of the device according to the invention for melt blowing, forming and depositing finite fibers to a nonwoven fabric

Fig. 2

schematically a cross-sectional view of another embodiment of the device according to the invention for melt blowing, forming and depositing finite fibers

Fig. 3

schematically a cross-sectional view of another embodiment of the device according to the invention for melt blowing, forming and depositing finite fibers

Fig. 4

schematically another embodiment of the device according to the invention for melt blowing, forming and depositing finite fibers

In Fig. 1 a first embodiment of the device according to the invention is shown schematically in a cross-sectional view. The exemplary embodiment has a melt-blowing nozzle 1 and a forming element 2 held below the melt-blowing nozzle 1. The forming element 2 is formed by two drums 3 driven in opposite directions, which form a forming gap 6 between them. The forming gap 6 extends between the drums 2.1 and 2.2 in the vertical direction, the drums 2.1 and 2.2 symmetrical to a longitudinal axis of the Schmelzblasdüse 1 are held. The drives of the drums 2.1 and 2.2 are not shown here in detail and can be performed by a group drive or individual drives. The drums 2.1 and 2.2 each have an air-permeable drum wall 3, which rotate in opposite directions in the fiber blowing direction with the predetermined by the drive of the drums 2.1 and 2.2 peripheral speed.

The melt-blowing nozzle 1 is arranged vertically adjustable above the drums 2.1 and 2.2 in a machine frame 13. In this case, the melt-blowing nozzle 1 comprises at least one row of nozzle channels 10 arranged in the center plane and interacting on one outlet side with air nozzles 11.1 and 11.2 for producing a fiber stream 7. The air nozzles 11.1 and 11.2 are each assigned two compressed air chambers 12.1 and 12.2, which are connected to compressed air source, not shown here. The nozzle channels on the melt-blowing nozzle 1 extend over a maximum length of seven meters. Accordingly, the drums 2.1 and 2.2 for forming the formation gap 6 also have a length in the range of seven meters. This is also referred to as a so-called working width, in which a nonwoven fabric is formed continuously from synthetic fibers.

In order in particular to influence the depositing and the formation of the fibers in the forming gap 6, the melt-blowing nozzle 1 is adjustable on the machine frame 13 at different heights so that a free blowing distance is formed between the melt-blowing nozzle 1 and the forming gap 6. The free blasstrack is in Fig. 1 marked with the letter B and determined by the distance between the bottom of the melt-blowing nozzle 1 and the top of the drums 2.1 and 2.2.

Depending on fiber types and fiber processes, the blowing range can be adjusted in steps of 100 mm to 2,000 mm in steps or steplessly. Thus, the fiber streams arriving directly into the formation gap can be influenced without additional means.

At the in Fig. 1 illustrated embodiment, the nonwoven fabric is discharged immediately after exiting from the forming gap 6 through the drum wall 3 of the drum 2.2. For this purpose, a suction chamber 4 is formed on the outlet side of the drum 2.2, which is coupled to a vacuum source 5. Via the suction flow generated from the environment, a forced guidance of the fiber fleece is achieved so that the fiber fleece can be deflected and removed directly tangentially to the drum 2.2. The blown air forming the fiber stream can advantageously be taken up and removed via the suction chamber 4 and the vacuum source 5. To support the removal of the blowing air could also be formed on the opposite drum 2.1, a second suction chamber, which would be connected to a vacuum source.

In Fig. 1 is shown on the drum 2.1, the possible formation of a second suction chamber in a dashed line. The suction chamber 4 'of the drum 2.1 and the suction chamber 4 of the drum 2.2 each have an offset angular position on the drum 2.1 and 2.2 in order to influence the fiber deposition and the discharge of the blowing air. The angular position of the suction chamber 4 and 4 'could be made adjustable on the circumference of the drums 2.1 and 2.2. This achieves high flexibility for fiber deposition. Thus, the suction chambers 4 and 4 'could be arranged offset from each other to the forming gap 6 - as in Fig. 1 shown - or be set opposite to the drums 2.1 and 2.2.

At the in Fig. 1 illustrated embodiment, in which only the drum 2.1 has a suction chamber 4, the angular position of the suction chamber 4 on the circumference of the drum 2.2 in both clockwise and counterclockwise adjustable. In that regard, in particular, the region at the inlet of the forming gap 6 or the region at the outlet of the forming gap 6 can be sucked.

At the in Fig. 1 illustrated embodiment, the drum 2.1 and 2.2, each with the same size drum diameters are executed. The drum diameter are entered with the code letters D ₁ and D ₂ . In this case, D ₁ = D ₂ . The drum diameter of the drums 2.1 and 2.2 may in this case be in a range of 100 mm to 800 mm. The forming gap 6 formed by the drums 2.1 and 2.2 has a forming cross-section which is determined by the spacing of the two drums 2.1 and 2.2. The distance between the drums is in Fig. 1 marked with the capital letter F. The distance F between the drums 2.1 and 2.2 can be changed by moving one of the drums 2.1 or 2.2 or both drums 2.1 and 2.2. Thus, with simultaneous displacement of both drums 2.1 and 2.2 symmetrical cross-sectional changes of the forming gap 6 can be adjusted. a one-sided displacement of one of the drums 2.1 or 2.2 can also be carried out advantageously asymmetric adjustments in relation to the center axis of the melt-blowing nozzle 1.

An asymmetrical configuration of the formation gap is, for example, in the exemplary embodiment Fig. 3 shown. The embodiment according to Fig. 3 is identical to the embodiment according to Fig. 1 so that only the differences are explained below. At the in Fig. 3 illustrated embodiment, the drum 2.1 is formed with a smaller drum diameter. In that regard, the drum diameter D _{1 of} the drum 2.1 is smaller than the drum diameter D _{2 of} the drum 2.2. The diameter ratio of the drum diameter of the drums 2.1 and 2.2 to form different forming gaps is in the range D ₁ / D ₂ = 0.5 to 2.0. This provides additional flexibility to obtain possible effects in the formation of the fibers.

In the in the Fig. 1 and 3 illustrated embodiments, a polymer melt is applied by means of a melt source not shown here the melt blowing nozzle. By one or more pumps, the melt is passed under pressure through the nozzle channels 10 of the melt-blowing nozzle 1. On the outlet side of the melt-blowing nozzle 1, a hot air flow is generated by the air nozzles 11.1 and 11.2, which together with the fibers emerging from the nozzle channels 10 blown into the blowing line. The generated fiber stream 7 is aligned vertically and meets at the end of the blowing line B on the forming gap 6 and the drum walls 3 of the drums 2.1 and 2.2. About the rotational movement of the drums 2.1 and 2.2, the fibers are guided into the forming gap 6 and formed into a fiber composite 8. The formation takes place essentially through the forming cross section of the forming gap 6, so that a finished nonwoven fabric 9 is already present on the outlet side of the drums 2.1 and 2.2. The fiber fleece 9 is taken from the drum 2.2 after leaving the Formierungsspaltes 6 and discharged. The drum speeds of the drum 2.1 and 2.2 are set synchronously and can be in a range of peripheral speed of 0.1 to 50 m / min. be adjusted continuously.

In Fig. 2 a further embodiment of the device according to the invention for melt blowing, forming and depositing synthetic fibers is shown schematically in a cross-sectional view. The exemplary embodiment is essentially identical to the exemplary embodiment according to FIG Fig. 1 , so that at this point only the differences will be explained and otherwise reference is made to the above description.

At the in Fig. 2 illustrated Ausführungsbespiel the meltblowing 1 is identical to the embodiment according to Fig. 1 , Below the melt-blowing nozzle 1, the drums 2.1 and 2.2 are arranged in a guide frame 15 as forming element 2. The drums 2.1 and 2.2 can be continuously adjusted together in position on the guide frame 15 wherein on the one hand a blow line B formed between the melt blowing nozzle 1 and the forming gap 6 and on the other hand a stacking height A formed between a wire 4 and the drum 2.2. The storage height is in Fig. 2 entered with the code letter A. The screen belt 14 below the drums 2.1 and 2.2 is guided over a plurality of guide rollers 16 such that the nonwoven fabric tangentially from drums 2.1 and 2.2 can be removed. Due to the adjustment between the drums 2.2 and the screen belt 14, it is additionally possible to form an additional forming zone for the nonwoven fabric.

The drums 2.1 and 2.2 are driven in opposite directions together via an electric motor 19. For this purpose, the drive axes of the drums 2.1 and 2.2 are connected to each other via a belt 20 and pulleys 21. The direction of rotation of the drums 2.1 and 2.2 is rectified to the fiber stream 7, which arrives in the forming gap 6. in this respect can be controlled via the peripheral speed of the drum 2.1 and 2.2, the absorption of the fibers in the forming gap.

The function of in Fig. 2 illustrated embodiment of the device according to the invention is identical to the aforementioned embodiment according to Fig. 1 , Only the filing of the nonwoven fabric takes place on the below the drums 2.1 and 2.2 arranged screen belt. In this case, larger storage heights A can be adjusted so that the fiber composite emerging from the forming gap 6 initially separates from the drums and is then deposited freely on the wire belt. For receiving and removing the blast air, one or both drums could be equipped with a suction chamber, as in the exemplary embodiment Fig. 1 is described.

This in Fig. 2 illustrated embodiment of the device according to the invention is particularly suitable for producing composite nonwovens. So goes out of the Fig. 4 a further embodiment of the device according to the invention, in which a plurality of melt blowing nozzles are arranged side by side to merge several nonwoven fabrics to form a composite nonwoven. At the in Fig. 4 illustrated embodiment, a total of three blowing stations 17.1, 17.2 and 17.3 are shown, each showing a Schmelzblasdüse. In the first two blowing stations 17.1 and 17.2, the fiber streams are taken up by a forming gap and formed and then deposited on the wire 14. In this case, 17.1 and 17.2 different blown sections are set between the forming columns 6 and melt blowing nozzles 1 of the blowing stations. The second blowing station 17.2 is identical to the first blowing station 17.1, so that a second nonwoven fabric is deposited on the surface of the screen belt 14 which forms a composite with the first nonwoven fabric. The third blowing station 17.3 shows a melt-blowing nozzle 1, which is arranged at a short distance above the sieve belt 14. On the opposite side of the screen belt 14, a suction device 18 is formed, which serves to receive the fiber flow on the surface of the screen belt 16. In that regard, the nonwoven fabric produced by the blowing station 17.3 is deposited directly on the surface of the screen belt 14 and forms a composite nonwoven with the already existing fiber webs.

The inventive method and apparatus are suitable for all spinnable materials such as polyolefins (eg polyethylene, polypropylene, polyoctene, polymerized cycloalkenes), aliphatic, cycloaliphatic and partially aromatic polyesters, aliphatic and aromatic polyamides, polyarylene sulfides and polyarylene oxides, polyoxymethylene, polycarbonates, thermoplastics Polyurethanes or reactive resins (such as melamine resin, phenolic resin, epoxy resin) to process. Due to the adjustability of the blowing line, these materials can advantageously be produced at very different fiber strengths to very loose fiber webs. The formation within the formation gap can be carried out with high uniformity and constancy.

LIST OF REFERENCE NUMBERS

1

meltblowing

2

forming component

2.1, 2.2

drum

3

drum wall

4, 4 '

suction chamber

5, 5 '

Vacuum source

6

forming gap

7

fiber stream

8th

fiber composite

9

non-woven fabric

10

nozzle channel

11.1, 11.2

air nozzles

12.1, 12.2

Compressed air chamber

13

machine frame

14

screen belt

15

guide frame

16

leadership

17.1, 17.2, 17.3

blowing station

18

suction

19

engine

20

belt

21

pulley

Claims (10)

1. A method for melt-blowing, forming, and depositing finite fibers to form a fibrous non-woven, in which the fibers produced by a melt-blow nozzle are blown by a hot air stream into a forming gap, and in which the fiber composite formed by the forming gap is conveyed away as a fibrous non-woven on an outlet side of the forming gap,
   characterized in that
   from the melt-blow nozzle to the forming gap, the fibers are substantially freely guided in a vertical manner via an adjustable blowing section, wherein the adjustment range of the blowing section is in the range from 100 mm to 2000 mm, wherein for forming, the fibers are blown between two counter rotating drums which have air-permeable drum walls and which between them form the forming gap and which are in each case driven at an identical circumferential speed in the range from 0.1 m/min to 50 m/min, and wherein for adjusting a forming cross section on the forming gap, a distance between the drums in a range from 1 mm to 100 mm, which is symmetrical or asymmetrical between the drums, is readjusted.
2. The method as claimed in claim 1,
   characterized in that
   after forming, the fiber composite, to form the fibrous non-woven, is deposited by one of the drums onto a sieve band which conveys away the fibrous non-woven in a tangential manner in relation to the drums.
3. The method as claimed in one of claims 1 or 2,
   characterized in that
   the fibers are blown into a symmetrical or asymmetrical forming gap, wherein, to this end, the drums display identical or different drum diameters having a diameter ratio in the range from 0.5 to 2.0.
4. The method as claimed in claim 3,
   characterized in that
   the drum diameter of the drums is in the range from 100 mm to 800 mm.
5. A device for melt-blowing, forming, and depositing finite fibers to form a fibrous non-woven, having a melt-blow nozzle (1) for producing a fiber stream and having at least one forming element (2) for forming a forming gap (6) in which the fibers are formed to a fiber composite and conveyed away,
   characterized in that
   an adjustable free blowing section (B) is configured between the melt-blow nozzle (1) and the forming gap (6), wherein the blowing section (B) is vertically oriented and is readjustable by way of a height readjustment of the melt-blow nozzle (1) and/or of the forming element (2) in the range from 100 mm to 2000 mm, wherein the forming gap (6) between two drums (2.1, 2.2) is formed by air-permeable drum walls (3) which are drivable in counter rotating manner at a circumferential speed in the range from 0.1 m/min to 50 m/min, and wherein for adjusting a forming cross section (F) on the forming gap (6), a distance between the drums (2.1, 2.2) in a range from 1 mm to 100 mm, which is symmetrical or asymmetrical between the drums (2.1, 2.2), is configured so as to be readjustable.
6. The device as claimed in claim 5,
   characterized in that
   a moving sieve band (14) is disposed below the drums (2.1, 2.2), wherein the sieve band (14) conveys away the fibrous non-woven in a tangential manner in relation to the drums (2.1, 2.2).
7. The device as claimed in one of claims 5 or 6,
   characterized in that
   for forming a symmetrical or asymmetrical forming gap (6), the drums (2.1, 2.2) display identical or different drum diameters (D₁, D₂) having a diameter ratio in the range from 0.5 to 2.0.
8. The device as claimed in claim 7,
   characterized in that
   the drums (2.1, 2.2) display a drum diameter in the range from 100 mm to 800 mm.
9. The device as claimed in one of claims 5 to 8,
   characterized in that
   one of the drums (2.1, 2.2) or both drums (2.1, 2.2) displays/display an inner suction chamber (4, 4') which is connected to a negative-pressure source (5, 5') and which is shielded toward the environment by the air-permeable drum wall (3).
10. The device as claimed in claim 9,
    characterized in that
    an angular position of the suction chamber (4, 4') on the circumference of the drum (2.1, 2.2) is adjustable.

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