JPH0657542A - Apparatus for producing fiber web and production of fiber web - Google Patents

Abstract

PURPOSE:To obtain a producing apparatus of a fiber web and a producing method capable of uniformly opening even if it is a fiber having no stiffness. CONSTITUTION:The apparatus for producing a fiber web is characterized by possessing at least two or more opening devices consisting of a housing 13 for covering opening cylinders 121 and 122, having a first opening cylinder 121 and a second opening cylinder 122 capable of moving a fed fiber while opening, adjacently arranged and capable of mutually rotating in a reverse direction, a delivery part 14 for moving the fiber between the adjacent two opening cylinders 121 and 122 and an open part 15 for releasing the opened fiber on the second opening cylinder 122, a conveyer 17 for receiving the fiber released from the second opening cylinder 122 and a suction box 18 situated under the conveyer 17 and sucking the fiber released from the second opening cylinder 122. The objective production uses this producing apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a fibrous web by a dry method and a method for producing a fibrous web. More specifically, the fibrous web can be opened by opening even non-rigid fibers such as organic fibers. The present invention relates to an apparatus and a manufacturing method capable of manufacturing a resin.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for producing a non-directional fibrous web by a dry method, after opening a fiber-attached cylinder and a walker or stripper,
It was generally known to blow or suck with air.

Further, by adjoining a plurality of cylinders and rotating each cylinder in the same direction, fibers are combed between the cylinders, and excess fibers that cannot move to the adjacent cylinders are blown off by air and laminated. A device for doing so was also known (Japanese Patent Publication No. 3-31807).

On the other hand, the present applicant has provided an apparatus and a method for producing a fiber web according to a principle different from those methods (Japanese Patent Application No. 3-188095). However, although the fiber web manufacturing apparatus and the fiber web manufacturing method have excellent openability with respect to rigid fibers such as carbon fibers, mainly non-rigid fibers such as organic fibers are not contained in the housing. It was likely to stay, and the openability was insufficient.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and a method for producing a fibrous web, which is capable of uniformly opening even non-rigid fibers such as organic fibers.

[0006]

A fiber web manufacturing apparatus of the present invention comprises a feeder 11 for supplying fibers, and a fiber supplied from the feeder 11 for moving while opening the fibers.
A first opening cylinder 12 ₁ and a second opening cylinder 12 ₂ that are arranged adjacent to each other and can rotate in opposite directions and have metallic wires attached to their surfaces, and the two adjacent opening cylinders 12 _1. has a delivery section 14 where the fibers to move between 12 ₂ and the second opening cylinder 12 ₂ side having an opening 15 to release the opened fibers, the open fiber cylinder 12 _1, A housing 13 that covers 12 ₂ , a conveyor 17 that receives the fibers discharged from the second opening cylinder 12 _2, and a fiber that is located below the conveyor 17 and that sucks the fibers discharged from the second opening cylinder 12 _2. And a first opening device including a suction box 18 for moving the fibers supplied from the conveyor 17 of the first opening device while opening the fibers, arranged adjacent to each other, and rotatable in mutually opposite directions, and On the surface The first opening cylinder 22 ₁ Rick wire is attached, and the second opening cylinder 22 _2, the two opening cylinder 22 _1, 22 between ₂ to the adjacent has a transfer unit 24 that the fibers are moved And the second opening cylinder 2
A housing 23 having an opening 25 for discharging the opened fibers on the 2 ₂ side and covering the opening cylinders 22 ₁ and 22 _2.
And a conveyor 27 for receiving the fibers discharged from the second opening cylinder 22 ₂ , and located below the conveyor 27,
At least a second opening device including a suction box 28 for sucking fibers discharged from the second opening cylinder 22 ₂ .

The method for producing a fiber web according to the present invention is a method for producing a fiber web by using the above-mentioned production apparatus, and the first opening cylinders 12 ₁ , 22 ₁ ,.
.... n2 ₁ (n is a natural number) and the second opening cylinders 12 ₂ and 2
2 ₂ ... n2 ₂ (n is a natural number) are reversely rotated with respect to each other. The surface speed (A) of the first opening cylinders 12 ₁ , 22 _1, ..., N 2 ₁ in each opening device.
And the ratio (A / B) of the surface speed (B) of the second opening cylinders 12 ₂ , 22 ₂ ... N2 ₂ is 0.9 or less,
At least one opening cylinder 12 ₁ , 12 ₂ , 22 ₁ ,
22 ₂ ... n2 ₁ and n2 ₂ have a centrifugal acceleration of 9.3 × 10 ⁴ (cm / sec ² ) or more that acts on the fibers, and thus the fibers are more excellent in the spreadability and are uniformly spread. A web is obtained.

[0008]

The fiber web manufacturing apparatus of the present invention comprises at least a first opening device and a second opening device, and each opening device has only two opening cylinders.
Even fibers having no rigidity do not stay and are subjected to at least two opening operations by the first opening device and the second opening device, so that uniform opening can be achieved.

In the method for producing a fibrous web of the present invention, since the fibers are opened by the above-mentioned apparatus for producing a fibrous web, the fibers do not stay and can be uniformly opened.
Since the first opening cylinder and the second opening cylinder rotate in opposite directions to each other, the carding action does not work between the opening cylinders, and the fibers are opened mainly when the fibers collide with the housing, resulting in damage to the fibers. Less is. Therefore, there is a feature that even a fiber that can be mechanically divided can be opened without splitting to obtain a fiber web.

Below, the first opening device and the second opening device 2
Detailed description will be given based on FIG. 1 illustrating a cross-sectional view of a fiber web manufacturing apparatus including a pair of opening devices, but the present invention is not limited thereto.

The feeder 11 in the first opening device of the present invention supplies the fibers to the first opening cylinder 12 _1. When the fibers supplied from the feeder 11 are opened to a certain extent, Although a uniformly opened fiber web can be obtained, it may be unopened.
Further, although the rotation direction of the feeder 11 is not particularly limited, as shown in FIG. 1, when the fiber is rotated so that the fiber can be supplied from below, the fiber can be supplied without reversing.

In the first opening device of the present invention, the fibers are collided with the housing 13 to open the fibers. Therefore, the first opening cylinder 12 ₁ and the second opening cylinder 12 ₂ are rotated in opposite directions. . That is, the first opening cylinder 12 ₁ and the second opening cylinder 12 ₁
When the fiber-spreading cylinders 12 ₂ rotate in the same direction, a carding action is exerted between the fiber-spreading cylinders to weaken the force of collision of the fibers with the housing 13, resulting in insufficient fiber-spreading and friction. This is not preferable because the force is increased and the fibers are damaged.

Even if the first opening cylinder 12 ₁ and the second opening cylinder 12 ₂ rotate in opposite directions, the first opening cylinder 12 ₁ is faster than the second opening cylinder 12 _2. Since the fibers are difficult to deliver when rotating at ₁ , the fibers are likely to stay in the first opening cylinder 12 ₁ and the opening of the fibers tends to be insufficient, so that the first opening cylinder 12 ₁ It is preferable to rotate at a lower speed than the second opening cylinder 12 ₂ . More specifically, the first opening cylinder 12 ₁
The ratio (A / B) between the surface speed (A) of the above and the surface speed (B) of the second opening cylinder 12 ₂ is preferably 0.9 or less, and more preferably 0.7 or less.

Further, even if the first opening cylinder 12 ₁ is rotated at a lower speed than the second opening cylinder 12 ₂ , if the force acting on the fiber is small, it is difficult to open the fiber even if it collides with the housing 13. Therefore, the first opening cylinder 1 of the first opening device
2 ₁ , the second opening cylinder 12 ₂ or the first of the second opening device
The centrifugal acceleration of at least one of the opening cylinders 22 ₁ and the second opening cylinders 22 ₂ is 9.3 × 10 ^4.
It is preferably cm / sec ² or more. The “centrifugal acceleration acting on the fiber” means the radius r rotating at an angular velocity w.
This means the acceleration component of the centrifugal force F = mrw ² , that is, rw ² that acts when the fiber of mass m is conveyed by the opening cylinder.

Since the opening cylinders 12 ₁ and 12 ₂ rotate at high speed, the radius is preferably 50 cm or less.
In order to efficiently open the fibers, it is preferably 5 cm or more. In the case of an opening cylinder with a radius of 5 cm, the rotation speed is 1
At 300 (times / min) or more, the centrifugal acceleration is 9.3 × 10 ⁴ cm / sec ² (= 5 × (1300 × 2π /
60) ² ), the preferred number of revolutions is 1300 (revolutions / minute) or more.

All the opening cylinders 12 ₁ , 12 ₂ ,
It is not necessary for 22 ₁ and 22 ₂ to act on the fiber at a centrifugal acceleration of 9.3 × 10 ⁴ (cm / sec ² ) or more, and at least one of these may act on the fiber at the centrifugal acceleration described above. The first opening cylinder 12 ₁ and the second opening cylinder 12 ₂ in the first opening device have the same radius, and the first opening cylinder 22 ₁ and the second opening cylinder 22 ₂ in the second opening device have the same radius. Therefore, it is preferable to increase the rotational speed of the second opening cylinders 12 ₂ and 22 ₂ so that the centrifugal acceleration falls within the above range.
Further, if the second opening device can open the fibers more uniformly than the first opening device, the finally obtained fiber web will be more uniform, so at least the second opening device of the second opening device. The fiber cylinder 22 ₂ preferably acts on the fiber with a centrifugal acceleration of 9.3 × 10 ⁴ (cm / sec ² ) or more.

Considering that it is preferable that the feeder 11 supplies the fibers from the lower side with respect to the rotation direction of the first opening cylinder 12 ₁ adjacent to the feeder 11 of the present invention, the first opening cylinder 12 ₁ includes the feeder 11. It is preferable to rotate the fibers in the same direction as the above so as to prevent the fibers from reversing, and the second opening cylinder 12 ₂ rotates in the opposite direction to the first opening cylinder 12 ₁ so that the fibers can be discharged downward from above. Preferably.

Metallic wires having a saw-shaped cross section are attached to the surfaces of the opening cylinders 12 ₁ and 12 _{2 so} that the fibers can easily fly.

The opening cylinders 12 ₁ and 12 ₂ are surrounded by the housing 13, and the opening cylinders 12 ₁ and 12 ₂
The fibers blown off by the centrifugal acceleration due to the collision with the housing 13 open the fibers. Therefore, the opening cylinders 12 ₁ and 12 ₂
Is a portion for supplying fibers to the first opening cylinder 12 ₁ .
Opening part 15 for discharging fibers from the second opening cylinder 12 _2.
And the second opening cylinder 12 ₂ and the first opening cylinder 12 ₁ are connected to each other, and the transfer section 14 for moving the fibers is removed,
It is covered by the housing 13.

Since the housing 13 collides with the fibers to open the fibers, it may be easier to open the fibers if the inside of the housing 13 has a sawtooth shape like a metallic wire. In this case, the fibers are caught. It is preferable that the inside of the housing 13 is smooth because the fibers are likely to stay and uniform opening cannot be performed.

If the gauge between the apex of the metallic wires attached to the opening cylinders 12 ₁ and 12 ₂ and the housing 13 is less than 0.1 mm, the fibers tend to stay and it is difficult to open the fibers uniformly. On the other hand, when it exceeds 5.0 mm, the force of collision with the housing 13 due to the centrifugal acceleration is reduced, and opening is insufficient, so the gauge is 0.1 to 5.
It is preferably 0 mm, more preferably 0.5 to 3.0 mm.

The fibers discharged from the second opening cylinder 12 ₂ successively fall onto the conveyor 17 to form a fiber web. At this time, the suction box 18 located below the conveyor 17 sucks the fibers, The web is given some strength.

[0023] Since the fibers are released by the centrifugal acceleration of the second opening cylinder 12 _2, the second opening cylinder 12
_{Since the} fibers may be concentrated only in the tangential direction at a certain point of 2, the fibers are diffused by disposing the air shower device 16 above the portion of the second opening cylinder 12 ₂ which discharges the fibers. Is preferred. In addition, when the air shower is directly applied to the fibers, a turbulent flow occurs and a uniform fiber web cannot be obtained. Therefore, by indirectly acting the air shower on the fibers, a pressure difference is generated, It is preferable to attract the fibers close to the air shower and diffuse the fibers.

When the distance between the second opening cylinder 12 ₂ and the conveyor 17 becomes long, the fibers tend to clump, so that the centrifugal acceleration of the second opening cylinder 12 ₂ becomes large and small.
It may be appropriately adjusted depending on the presence or absence of the air shower device 16.

Further, the conveyor 1 is designed so that the fibers discharged from the second opening cylinder 12 ₂ are not affected by the outside.
It is more preferable to cover 7 and the periphery of the second opening cylinder 12 ₂ .

As described above, the fiber web that has been opened by the first opening device and accumulated on the conveyor 17 is sent to the second opening device and opened evenly. Since the first opening device and the second opening device have exactly the same structure, details of the device and the opening mechanism are omitted.

Also in the second opening device, it is preferable to make the surface speed of the first opening cylinder 22 ₁ slower than the surface speed of the second opening cylinder 22 ₂ , and more specifically, the first opening cylinder. The ratio (A / B) between the surface speed (A) of the cylinder 22 _{1 and} the surface speed (B) of the second opening cylinder 22 ₂ is preferably 0.9 or less. When the surface speed ratio exceeds 0.9, the first opening cylinder 22 ₁ to the second opening cylinder 22 ₂
Since the fibers cannot be efficiently moved to the fiber and the fibers are accumulated, the surface speed (A) of the first opening cylinder 22 _{1 and} the surface speed (B) of the second opening cylinder 22 ₂ are increased. )
The ratio (A / B) is preferably 0.9 or less, and more preferably 0.7 or less.

Further, as described above, if the second opening device can be opened more uniformly than the first opening device, the finally obtained fiber web will be more uniform. The centrifugal acceleration of the second opening cylinder 22 ₂ of the device is 9.3 × 10.
^It is preferable to act on the fiber at ⁴ cm / sec ² or more. For example, when the radius of the second opening cylinder 22 ₂ is 5 cm, the number of rotations is preferably 1300 (times / minute) or more.

The above description is based on FIG.
The manufacturing apparatus of the present invention does not need to be two sets of opening devices,
It is possible to arrange 3 sets of opening devices or 4 sets of opening devices, but if too many opening devices are placed, it is disadvantageous in terms of economical efficiency. It is enough.
Also, when three or more sets of opening devices are arranged, as in the case of the description of two sets of opening devices, the first of the opening devices of each
The ratio of the surface speed of the opening cylinder to the surface speed of the second opening cylinder is preferably 0.9 or less, and the centrifugal acceleration acting on the fibers of at least one opening cylinder is 9.
It is preferably 3 × 10 ⁴ cm / sec ² or more.

Each of the fiber-spreading devices of the fiber web manufacturing apparatus of the present invention comprises two fiber-spreading cylinders, so that fibers are retained and the fiber that can be fiber-split by the fiber-web manufacturing device is like asbestos. Not only rigid inorganic fibers such as mineral fibers, glass fibers and carbon fibers, but also recycled fibers such as rayon fibers, semi-synthetic fibers such as acetate fibers, plant fibers such as cotton, wool, etc. Animal fiber,
Even non-rigid fibers such as synthetic fibers such as polyamide fibers, polyester fibers and polypropylene fibers can be opened.

In the fiber web manufacturing apparatus of the present invention, the fibers are hooked on the metallic wire attached to the fiber-opening cylinder to be blown, and the fiber is collided with the housing to open the fiber.
If the fiber has a large number of crimps or a long fiber length, it is easy to be entangled with the metallic wire. Therefore, it is more preferable to use a fiber having no crimp and a short fiber length.

Since the first opening cylinder and the second opening cylinder of the present invention rotate in opposite directions to each other, when the fibers move between the opening cylinders, the fibers are not carded, but simply move, and by centrifugal acceleration. Since fibers are opened by colliding with the housing, there is little damage to the fibers, and even fibers that can be mechanically divided that could not be opened without splitting with a conventional card machine are divided. It can be opened without doing.

Examples of the fiber web manufacturing apparatus and the fiber web manufacturing method of the present invention are shown below, but the present invention is not limited to these examples.

[0034]

【Example】

(Example 1) Polyamide fiber having a fineness of 1.5 denier and a fiber length of 10 mm was used as a feeder 1 for a manufacturing apparatus as shown in FIG.
1 to open the first opening cylinder 12 _{1 of} the first opening device
And, after the fibers are opened by the second opening cylinder 12 ₂ , the fibers discharged from the opening cylinder 12 ₂ are received by the conveyor 17, and the fibers received by the conveyor 17 are transferred to the first opening cylinder 22 ₁ of the second opening device. Supply and first open cylinder 22 ₁
The fibers opened by the second opening cylinder 22 ₂ were received by the conveyor 27 to form a fiber web, and the limit supply amount was measured. In this manufacturing apparatus, in FIG. 1, the feeder 11 and the first opening cylinders 12 ₁ and 22 ₁ are rotated in the same direction as the timepiece, and the second opening cylinders 12 ₂ and 22 ₂ are rotated in the opposite direction to the timepiece. In addition, the opening cylinders 12 ₁ , 12 ₂ , 22 ₁ ,
The gauge of the top of the metallic wire attached to 22 ₂ and the housings 13 and 23 is 1.5 mm, and the opening cylinder 1
The radii of 2 ₁ , 12 ₂ , 22 ₁ and 22 ₂ are all 5 cm, and the rotation speeds of the opening cylinders 12 ₁ , 12 ₂ , 22 ₁ and 22 ₂ are 495 rotations / minute and 2,701 rotations / minute, respectively. 495 times / minute and 2,701 times / minute. The shortest distance between the centers of the second opening cylinders 12 ₂ and 22 ₂ and the conveyors 17 and 27 is 30 cm, and the conveyors 17 and 27 are as shown in FIG.
It was moved to the left at a speed of 2 m / min. Also, the air showers 16 and 26 are 1 kgf / cm in the direction along the cover.
Acted indirectly with ² . The first opening cylinder 1
2 ₁ , 22 ₁ centrifugal acceleration, 2nd opening cylinder 12 ₂ , 2
2 ₂ of the centrifugal acceleration, the first opening cylinder 12 ₁ of each opening device, 22 ₁ and the second opening cylinder 12 _2, 22 ₂ and the surface velocity ratio, limit the feed rate shown in Table 1. The limit supply amount is a value obtained as follows.

[0035]

[Table 1]

(Limited amount of supply) While the amount of fibers supplied from the feeder 11 is increased in order, the fiber webs opened by the first opening device and the second opening device are visually inspected to prevent reaggregation of fibers. The maximum fiber supply amount per 1 m width is defined as the limit supply amount.

(Examples 2 to 6) The rotation speeds of the _first opening cylinders 12 ₁ and 22 ₁ of the _first opening device and the second opening device were set to 1,170, 1,485, 1,784, respectively. 2,332,
The limiting supply rate was measured in exactly the same manner as in Example 1 except that the rate was 2,778 times / min (in order, Examples 2, 3, 4, 5, and 6). The results are also shown in Table 1.

(Examples 7 to 11) First spreader and second spreader
The rotation speed of each of the second opening cylinders 12 ₂ and 22 ₂ of the opening device is set to 539, 936, 1,267, 1,552, 2,1.
The limit supply rate was measured in exactly the same manner as in Example 1 except that the rate was 18 times / minute (in order, Examples 7, 8, 9, 10, and 11). The results are also shown in Table 1.

Example 12 A chrysanthemum-type easy-dividable fiber (fineness: 2 denier, fiber length: 3) having a fiber cross section in which a polyamide component is radially arranged between polystyrene components and capable of being divided into 13 parts.
8 mm) and the number of rotations of the first opening cylinder and the second opening cylinder in each opening device is 2, 30 respectively.
The limit supply rate was measured in exactly the same manner as in Example 1 except that the rate was 0, 3,340 times / minute. The results are also shown in Table 1. Further, the opened web was observed with an electron microscope, and it was confirmed that the easily split fibers were not split.

(Comparative Example) The same easily split fibers as in Example 12 were supplied to a roller card at a supply amount of 100 g / min to open the fiber, to obtain a fiber web. The rotation speed of the main cylinder at this time was 920 rotations / minute. The fiber web thus obtained had a nep (group of entangled fibers), and when observed with an electron microscope, easily split fibers were split and entangled.

[0041]

The fiber web manufacturing apparatus of the present invention comprises at least a first opening device and a second opening device, and each opening device has only two opening cylinders. Therefore, even non-rigid fibers do not stay, and
Since the opening operation is performed at least twice by the opening device and the second opening device, the opening can be performed uniformly.

In the method for producing a fiber web of the present invention, since the fibers are opened by the above-described apparatus for producing a fiber web, the fibers do not stay and the fibers can be uniformly opened.
Since the first opening cylinder and the second opening cylinder rotate in opposite directions, the carding action does not work between the first opening cylinder and the second opening cylinder, and mainly when the fibers collide with the housing. Since the fiber is opened, there is little damage to the fiber. Therefore, even mechanically dividable split fibers, which could not be opened without splitting with a conventional card machine, can be opened without splitting.

Further, the ratio of the surface speed of the first opening cylinder to the surface speed of the second opening cylinder of each opening device is 0.
When the number is 9 or less, the delivery between the fiber-opening cylinders is efficiently performed, so that the problem that the fibers stay in the housing does not occur.

Furthermore, when the centrifugal acceleration acting on the fiber of at least one opening cylinder of the fiber web manufacturing apparatus is set to 9.3 × 10 ⁴ (cm / sec ² ) or more, the fiber is sufficiently and uniformly distributed. It can be opened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a fiber web manufacturing apparatus of the present invention.

[Explanation of symbols]

11 Feeder 12 ₁ First Opening Cylinder 12 ₂ Second Opening Cylinder 13 Housing 14 Transfer Part 15 Opening Part 16 Air Shower Device 17 Conveyor 18 Suction Box 22 ₁ First Opening Cylinder 22 ₂ Second Opening Cylinder 23 Housing 24 Delivery part 25 Opening part 26 Air shower device 27 Conveyor 28 Suction box

Claims (4)

[Claims] 1. A feeder 11 for supplying a fiber, and a fiber 11 fed from the feeder 11 for moving while opening the fibers, arranged adjacent to each other, rotatable in opposite directions, and having a metallic wire attached to the surface thereof. The first opening cylinder 12 ₁ , the second opening cylinder 12 ₂ and the adjacent 2
Between the individual opening cylinders 12 ₁ and 12 ₂ there was a delivery section 14 through which the fibers move, and on the second opening cylinder 12 ₂ side there was an opening section 15 for discharging the opened fibers. A housing 13 that covers the opening cylinders 12 ₁ and 12 ₂ ;
A conveyor 17 for receiving the fibers released from the opening cylinder 12 _2, positioned below the conveyor 17, the first open consisting of the suction box 18 for sucking the fibers released from the second opening cylinder 12 ₂ Fiber device and the first
The first fiber-opening cylinder 22 ₁ , which is arranged adjacent to each other and which is capable of rotating the fibers supplied from the conveyor 17 of the fiber-opening device while being fiber-opened, can rotate in mutually opposite directions, and has a metallic wire attached to the surface thereof. A two-spreading cylinder 22 ₂ and a delivery section 24 through which fibers move are provided between the two adjacent spreading cylinders 22 ₁ and 22 ₂ , and the spreader is opened on the side of the second spreading cylinder 22 _2. Housing 2 covering the opening cylinders 22 ₁ and 22 ₂ having an opening 25 for discharging
3, a conveyor 27 that receives the fibers discharged from the second opening cylinder 22 ₂ , and a suction box 28 that is located below the conveyor 27 and that sucks the fibers discharged from the second opening cylinder 22 _2. And a second fiber-spreading device comprising: 2. A method for producing a fiber web using the production apparatus according to claim 1, wherein the first opening is provided in each opening device.
Opening cylinders 12 ₁ , 22 ₁ ... n2 ₁ (n is a natural number)
And a second opening cylinder 12 ₂ , 22 ₂ ... n2 ₂ (n is a natural number) are reversely rotated with respect to each other. 3. The surface velocity (A) of the first opening cylinders 12 ₁ , 22 ₁ ... N2 ₁ in each opening device, and the second opening cylinder
The method for producing a fiber web according to claim 2, wherein the ratio (A / B) of the open cylinders 12 ₂ , 22 ₂ ... N2 _{2 to} the surface speed (B) is 0.9 or less. 4. At least one opening cylinder 12 ₁ , 1
The centrifugal acceleration acting on the fibers of 2 ₂ , 22 ₁ , 22 ₂ ... n2 ₁ , n2 ₂ is 9.3 × 10 ⁴ (cm / sec ² ) or more, The claim 2 or claim Item 4. A method for producing a fiber web according to Item 3.