GB2031970A

GB2031970A - Forming fibrous webs

Info

Publication number: GB2031970A
Application number: GB7931997A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-18
Filing date: 1979-09-14
Publication date: 1980-04-30
Also published as: NL7906936A; ES484211A1; DK144426C; BE878828A; FR2436209B1; ES492084A0; FI792895A; LU81691A1; NO792994L; DK144426B; GB2031970B; IT1123717B; IT7925783A0; ES8103228A1; JPS5590662A; FR2436209A1; AU5077779A; DE2937531A1; ZA794918B; SE7907701L

Abstract

A process for the manufacture of fibrous webs comprises passing an endless air-permeable forming wire 13 below a number of fibre distributors, discharging fibres thereon so as to form a fibre layer, the forming wire used having openings of an area exceeding 1 mm<2> and the fibre material passing through the forming wire below a given fibre distributor being passed to one or more of the following fibre distributors. <IMAGE>

Description

SPECIFICATION Process and apparatus for the manufacture of fibrous webs This invention relates to a process for the manufacture of fibrous webs, preferably webs of cellulose fibres, wherein an endless air-permeable forming wire is passed below a number of fib re distributors, discharging fibres which under the influence of one or more suction boxes provided at the opposite side of the forming wire are sucked towards the forming wire so as to form a fibre layer thereon.

When manufacturing fibrous discharging webs by a prior art process of the above mentioned type, the fibre distributors are mounted at intervals along the endless air-permeable forming wire and a suction box is provided at each fibre distributor.

Danish patent application No.4956177 discloses a process, wherein an endless air-permeable forming wire is passed below a fibre distributor consisting of a number of fibre distributor units which are built together and under which there is provided a suction box which is common for these fibre distributor units and which serves to keep the fibrous layer constantly sucked against the wire while its thickness gradually increases.

The invention is based on the discovery that by using a process of the above mentioned type a fibrous product can be obtained having at least one surface layer which mainly consists of relatively long fibres and a central layer mainly consisting of relatively short fibres.

A fibrous product of such a composition is especially soft and has a good feel. Therefore, it is suitable for the manufacture of relatively light fibrous products, especially fibrous products having a weight of less than 100 g/m2. Such products are particularly suitable for use as tissue paper including facial tissue, paper towels, toilet paper etc.

The process of the invention is characterized in that the air-permeable endless wire has openings having an area exceeding 1 mm2 and that the fibre material passing through the wire below a given fibre distributor is passed to one or more subsequent fibre distributors viewed in the direction of movement of said wire.

By using a wire having openings with an area of above 1 mm2 only relatively long cellulosic fibres discharged from the first of the number of fibre distributors are retained by the wire, whereas the relatively short fibres will pass through the wire and down into the suction box.

The relatively long fibres of the fibrous material passing through the forming wire under the first fibre distributor are deposited thereon, whereas the short fibres again will pass through the wire when said fibres are recycled to the following fibre distributor and then are sucked towards the forming wire with the long fibres already deposited thereon.

As the fibre layer becomes thicker, it also becomes more dense and even relatively short fibres will gradually be deposited thereon.

When preparing fibrous products in the form of webs by using several fibre distributors each consisting of a number, for example 6, fibre distributor units and by supplying fresh fibrous material to each fibre distributor, a fibrous product in which both surface layers predominantly consists of relatively long fibres can be obtained.

This is achieved by supplying fibre material consisting of relatively short fibres from the preceding fibre distributor to the rear portion of the last fibre distributor viewed in the direction of movement of the forming wire. In that case the relatively short fibres pass relatively quickly through the bottom of the fibre distributor and are deposited on the layer already formed on the forming wire. The relatively long fibres, however, will be distributed over the whole fibre distributor including its front portion.

Within the front portion they will be subjected to strong influences from the stirring means provided therein because the relatively short fibres already have been discharged from the fibre distributor.

Under these circumstances the likelihood that these fibres will be brought into such a position relatively to the openings of the bottom of the fibre distributor so thatthey can pass through said bottom, is increased.

Consequently, a surface layer of relatively long fibres is formed on top of the fibre layer already formed.

It should be mentioned that the term "distributor" herein is to be understood as comprising also one of the distributor units forming part of a fibre distributor composed of several of such distributor units. In that case the fibre material which has passed the forming surface below such a fibre distributor unit is transported to one or more of the following fibre distributor units which, for example, may be provided within the same housing.

A further advantage of the process described is that the fibre layer initially deposited on the forming surface acts as a filter for the mixture of fibres and air subsequently supplied thereto and consequently reduces the loss of fibre material. The result is that the production economy is improved and that the contamination problems are reduced to a minimum.

When manufacturing fibrous products mainly consisting of cellulosic fibres which ordinarily have a length of 0,5-3 mm, the forming wire used is preferably a wire having openings which in the cross machine direction have dimensions of from 0,5 to 1,5 mm. These openings are preferably elongated in the machine direction and the length of the openings in this direction are for example up to 3 times the width of the openings.

The forming wire preferably consists of a woven metal net in which the warp and weft threads form a plain weave. It is preferable to use a net in which the distance between the weft threads is greater than the distance between the warp threads so as to facilitate the cleaning of said net.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

A particularly suitable metal net is a net in which the metal threads form a plain weave and in which the weft threads are straight, whereas the warp threads form bends atthe crossing points. In such a net the weft threads are surrounded by the warp threads and consequently the risk that fibres accumulate at the crossing points is less than in the commonly used metal nets.

As mentioned above the forming wire preferably is a metal net. However, it can also be prepared from threads of a plastics material and is not necessarily in the form of a woven product. Thus, the wire may be formed of a perforated metal or plastics film.

In a preferred embodiment of the process of the invention several, for example 3, fibre distributors are mounted along the forming wire, said fibre distributors each consisting of several, for example 6, fibre distributor units, each comprising a row of stirrers, said row extending transversely of the forming wire, the fibre material passing through the forming wire below the first fibre distributor being transported to both the second and the third fibre distributor seen in the direction of movement of said wire. In this manner a suitable air balance in the system of fibre distributors is obtained.

The transport of fibre material from the suction box below the first distributor to the second and third fibre distributor is generated partly by means of a fan mounted in a conduit connecting the suction box below the first distributor with the second and third fibre distributors and partly with an exhaustion device which is connected to the suction boxes below the second and third fibre distributors.

As mentioned above the fibre material from the suction box below the first fibre distributor is preferably introduced in the rear portion of the third fibre distributor which is also fed with fresh fibre material so as to obtain a top layer mainly consisting of long fibres.

When manufacturing relatively thin fibrous webs by a process of the type defined in the introductory part of the specification, one or more auxiliary wires are ordinarily used for transporting the fibrous web removed from the forming wire to a drying station.

By using the above mentioned relatively open forming wire, it has been found that it is possible to introduce the thin fibrous web formed on the forming wire directly onto a drying cylinder. This discovery has significantly contributed to making an apparatus for the manufacture of fibrous webs more compact and to reducing the building, initial and operational costs for such an apparatus.

When the forming wire during the transfer of the fibrous web onto the drying cylinder is pressed against said cylinder, e.g. by means of one or more pressure rollers, a surface pattern corresponding to the surface pattern of the wire is formed on both sides of the fibrous web. Consequently, the fibrous web is in contact with the drying cylinder essentially only in a pattern of points or lines and corresponding to the surface pattern of the forming wire.

This is of great importance as far as the subsequent removal of the dried fibrous web from the drying cylinder is concerned. Thus, previously a thin fibrous web which adhering to a drying cylinder over the full contact area can be removed therefrom only in connection with the creping of said fibrous material. However, by utilizing the process of the invention, the fibrous web can be removed from the drying cylinder without simultaneously creping said fibrous web.

The fibres of the final fibrous web are bonded together by a binder. Such a binder may be supplied to the fibrous material in different ways. Thus, a solid binder, for example modified starch which is activated by supplying moisture thereto, can be introduced into the defibrator, for example a hammer mill, which is ordinarily used for preparing the defibrated material supplied to the fibre distributor.

When the binder is supplied to the fibre distributors together with the defibrated material, a significant portion thereof will pass through the forming surface below the first fibre distributor and is therefore primarily deposited in the fibre layer provided on top of the first layer.

In order to activate the binder, moisture, for example water, is sprayed onto the fibre web while it is present on the forming wire. Excessive amounts of water are removed during the contact between the fibrous web and the drying cylinder. During the heating of the fibrous web the binder may be cured.

A binder in the form of a binder solution or suspension may also be sprayed onto the fibrous web while it is present on the forming wire.

By using a thermocuring binder it may be necessary to heat the fibrous web to a higher temperature than the temperature obtained during the contact between the fibrous web and the drying cylinder.

This can be achieved by passing the fibrous web through a curing oven in which hot air is passed through the fibrous web after it has been removed from the drying cylinder.

During such heat treatment with the object of curing the thermocuring binder it is desirable to keep the fibrous web supported.

In a preferred embodiment of the process of the invention such support is provided by using the return run of the forming wire as a support for the fibrous web during the curing process.

Binder may also be supplied by applying to the surface of the forming wire, e.g. by rollers, a binder solution or suspension having a relatively high viscosity. The binder will primarily be deposited on the protruding zones of the wire (the crossing points in a woven metal net) and will consequently be pressed into the fibrous web during the embossing which is effected when the forming wire with the fibrous web located thereon is pressed against the drying cylinder.

In this embodiment of the process of the invention the binder will predominantly be located in the embossed points or lines and the intervening zones are not compressed correspondingly. Therefore, a product having a soft and absorbing surface and being voluminous is obtained.

The removal of the fibrous web from the drying cylinder is preferably effected with a doctor's knife.

Depending on the shape and the mounting of such a knife, the fibrous web is removed in a creped or non-creped state. When the fibrous web is creped, the length thereof will ordinarily be reduced with about 20%. In view of the manner in which the fibrous web is in contact with the surface of the drying cylinder, the fibrous web can be removed from said surface without creping said web. Thus, a fibrous web having a smooth surface and essentially the same surface properties in all directions is obtained.

The invention also relates to an apparatus for the manufacture of fibrous webs made from cellulosic fibres, said apparatus comprising an endless airpermeable forming wire, a number of fibre distributors mounted along said forming wire, one or more suction boxes co-operating with each fibre distributor and mounted on the opposite side of said forming wire.

The apparatus according to the invention is characterized in that the forming wire has openings with an area exceeding 1 mm2 and that it comprises conduits connecting the suction box or suction boxes below a given fibre distributor with one or more subsequent fibre distributors viewed in the direction of movement of the forming wire.

The distributors of the apparatus according to the invention are preferably of the type which comprises one or more rows of stirrers rotating in one or more planes which are essentially parallel to the surface of the forming wire.

It is particularly advantageous to use distributors of the type disclosed in the specification of Danish patent application No. 4956/77. The individual fibre distributor units of such a fibre distributor are preferably provided within the same housing and the stirring zones are separated by separating walls of a type which allows fibre material from passing from one stirring zone to the adjacent one.

In an apparatus comprising three of these fibre distributors, each composed of for example 6 fibre distributor units, the suction box or suction boxes below the first fibre distributor is (are) preferably connected with inlets of the second fibre distributor, said inlets opening in the middle portion of the fibre distributor housing and with inlets of the third fibre distributor opening in the rear portion of the fibre distributor housing.

The suction box or suction boxes below the fibre distributors preferably comprise rollers supporting the forming wire which is passed above said suction box or suction boxes. Such supporting rollers are preferably mounted directly below the shafts of said stirring means because it has been found that an optimum air distribution within the suction box or suction boxes is obtained with such a mounting.

A spray cabin having means for spraying water or binder solution onto the fibrous web may be provided adjacent to the last fibre distributor in the row of such fibre distributors.

The transfer of the fibrous web onto the drying cylinder is preferably effected by pressing the fibrous web against said cylinder while it is still in contact with the forming wire.

Thus, the apparatus may comprise one or more rollers which both serve as supporting rollers for the forming wire and as pressure rollers pressing the forming wire and the fibrous web located thereon against the drying cylinder.

The pressure required may be generated by using a forming wire which encircles a substantial portion, for example up to 180 , of the periphery of the drying cylinder.

This embodiment is particularly preferable in case the return run of the forming wire extends above the row of fibre distributors and when it is desired to have that portion of the forming wire on which the fibrous web is to be formed at the floor level.

The drying cylinder used is preferably an internally heated drum. The surface of the drying cylinder is preferably heated to a temperature of 100-200"C and in particular 120-160"C.

The apparatus also comprises means for removing the fibrous web from the drying cylinder. It is preferable to use a doctor's knife having an edge which is pressed against the surface of the drying cylinder. As mentioned above, the means for removing the fibrous web from the drying cylinder may be constructed in a manner so as to simultaneously crepe the fibrous web. As is also mentioned above, the invention permits the removal of the fibrous web without effecting a creping.

The apparatus may also comprise one or more devices for winding up the fibrous web so as to form a roll. If the binder used isathermocuring binder, the apparatus also comprises means for further heating the fibrous web before it is cooled and wound up.

The means for further heating the fibrous web preferably comprise a suction box mounted on one side of an endless support belt and heating elements with air supply means mounted at the opposite side of said support belt.

When the fibrous web is to be subjected to such a further heating, it is introduced on said support belt and it is sucked onto said belt under the influence of the vacuum in the suction box. When the fibrous web is advanced together with the support belt, it is heated by hot air which is generated by the heating elements and which under the influence on the vacuum in the suction box passes through the fibrous web.

In a particularly simple embodiment of the apparatus of the invention, said support belt is a portion of the return run of the forming wire.

The invention will now be described in further detail with reference to the drawings in which Fig. 1 shows a portion of a preferred metal net for use in the process of the invention, Fig. 2 shows the net illustrated in Fig. 1 in perspective, Fig. 3 shows a preferred embodiment of the apparatus according to the invention, and Fig. 4 shows another embodiment of the apparatus according to the invention.

The metal net illustrated in Figs. 1 and 2 consists of warp threads 1 and weft threads 2, the distance between the weft threads being greater than the distance between the warp threads. Therefore, the openings 3 in the net are rectangularly shaped. The warp threads 1 and the weft threads 2 form a socalled plain weave. However, the weft threads 2 are straight, whereas the warp threads 1 form bends at the crossing points with the weft threads. The net illustrated presents the advantage that it is easy to remove fibres, fibre lumps, binder etc. therefrom when a brush rotating about an axis parallel to the longitudinal direction of the weft threads sweep over the net because the weft threads are not adjacent to the surfaces of the net.

The apparatuses illustrated in Figs. 3 and 4 are in principle identical as far as the forming sections and the binder supply sections are concerned and the same components in these sections of the apparatus therefore have the same reference numerals.

The formingsection consists of three firbre distributors 10,11 and 12 which are mounted successively over a forming wire 13 which is advanced in a direction illustrated by an arrow 14. Each fibre distributor consists of six fibre distributor units mounted in a common housing 15. Each fibre distributor unit comprises a number of stirrers mounted in a row perpendicular to the direction of movement of the forming wire 13. The stirrers 16 have impellers which are located a short distance above the bottom of the housing, said bottom having the form of a screen. Separating walls 17 are provided between adjacent rows of stirrers 16. These separating walls 17 do not extend fully to the bottom of the housing 15 and consequently fibres may move from a zone below one row of stirrers 16 to the adjacent zone below another row of stirrers 16.

Below each fibre distributor 10, 11 and 12 there is provided a suction box 18, 19 and 20, respectively, containing several rollers 21 supporting the forming wire 13. The fibre distributors 10,11 and 12 are con nected with supply pipes 22,23 and 24, respectively, for freshly defibrated fibre material. The suction box 18 is connected with the middle portion of the fibre distributor 11 and the rear portion of the fibre distributor 12 via a pipe 25 comprising an air pump 26.

The supply pipes for freshly defibrated fibre material also open into the rear portion of the fibre distributor 12.

The suction box 19 is connected with an exhaust pump 29 via a connecting pipe 27 and the suction box 20 is connected with the exhaust pump 29 via a connecting pipe 28. The apparatus shown also comprises a spraying cabin 30 mounted adjacent to the fibre distributor 12 and above the forming wire 13.

In the apparatus illustrated in Fig. 3 the return run of the forming wire 13 is located below the fibre distributors 10, 11 and 12 and the spraying cabin 30 and the forming wire is supported by rollers 31-36 of which the roller 34 is a guide roller and the roller 35 is a tension roller.

The apparatus illustrated in Fig. 3 further comprises a rotatable drying cylinder 37, a doctor's knife 38 and rollers 39,40,41 and 42 for supporting a fibrous web 43 formed in the apparatus before it is wound up so as to form a roll 44.

In the apparatus illustrated in Fig. 4 the forming wire 13 extends around a drying cylinder 45 and the return run is supported by the rollers 46-50 of which the roller 47 is a guide roller.

The apparatus illustrated in Fig. 4 also comprises a doctor's knife 51 and rollers 52, 53 and 54 for a fibrous web 55 which, when wound up, forms a roll 56.

A suction box containing some support rollers 58 for the forming wire 13 is mounted above the forming wire 13 between the drying cylinder 45 and the roller 52. On the opposite side of the forming wire 13 there is mounted a drying oven 59 and conduits (not shown) for air.

When supplying freshly defibrated cellulosic fibrous material optionally containing a minor amount of synthetic fibres, for example thermoplastic fibres, to the fibre distributors 10-12 and by discharging air with the exhaust pump 29 and transporting air containing relatively short fibres from the suction box 18 to the fibre distributors 11 and 12, a fibrous layer is gradually formed on the forming wire 13 of the apparatus illustrated in Figs. 3 and 4, the bottom and top layers of said fibrous layer predominantly consisting of relatively long fibres.

When the fibrous layer has attained a desired thickness in the fibre distributor 12, it passes through the spraying cabin in which a binder solution can be applied to the fibrous layer.

In the apparatus illustrated in Fig. 3 the fibrous layer is contacted with the drying cylinder 37 which e.g. is heated to a temperature of 1600C and at the same time it is strongly compressed.

The fibrous layer is then removed from the forming wire 13 and during the rotation of the drying cylinder 37 it is contacted with the doctor's knife 38.

At this stage the binder is cured and a self-supporting fibrous web 43 is obtained. The web 43 is then wound up to form a roll 44.

A brush (not shown) is mounted along the return run of the forming wire 13 and between the rollers 32 and 36 in order to remove remaining fibres or binder from the forming wire 13.

The fibrous layer prepared by the apparatus illustrated in Fig. 4 is contacted with the drying cylinder 45 while it is compressed between said cylinder and the forming wire 13. During this contact a sufficient curing is initiated even when using a thermocuring binder to provide a fibrous web which, when it has been removed from the drying cylinder by means of the doctor's knife 51, is self-supporting.

After being removed from the drying cylinder the fibrous web 55 is brought into contact with the forming wire 13 under the influence of the vacuum within the suction box 57.

During its passage above the suction box 57 hot air generated in the drying oven 59 passes through the fibrous web so as to completely cure the binder.

The fibrous web 55 thus formed can subsequently be wound up in the form of a roll 56.

The return run of the forming wire 13 is cleaned in the same manner as discussed in connection with Fig.3.

The invention will now be illustrated further with reference to the following examples: EXAMPLE 1 Cellulose pulp (type "Korsnass Marma") and oxidized starch (type "Viscosol 220") in a proportion of 95% cellulose pulp and 5% oxidized starch were introduced into a hammer mill. After forming a fibrous web in an apparatus as illustrated in Fig. 3 and comprising a metal net having mesh openings with an area of 1,5 mm2, water containing 4% dissolved oxidized starch (type "Viscosol 220") was sprayed onto the fibrous web. Measurements showed that when fresh defibrated material is supplied to the three fibre distributors in equal amounts, about 20% of the total amount of starting material passed through the metal net below the first fibre distributor and are transferred to the second and third fibre distributor.After transferring the fibrous layer from the metal net to the drying cylinder having a temperature of 1200C, a product was obtained which, before it was removed from the drying cylinder with a creping knife, contained about 25% water. The product, the length of which had been reduced by about 25%, was wound up to form a roll. The fibrous product obtained weighed 30 g/m2 and was suitable for the manufacture of toilet paper and tissue paper.

EXAMPLE 2 A fibrous product was prepared from the same starting materials and by using the same technique as described in Example 1 with the exception that the temperature of the drying cylinder was 150 C and that the final product was wound up without any reduction of its length. Due to the use of the increased temperature of the surface of the cylinder, the fibrous layer could be removed from the drying cylinder without creping the product. Therefore, the fibrous product obtained could be wound up with a speed corresponding to the rate at which it was formed on the forming wire.

EXAMPLE3 A fibrous product was prepared in the same man neras described in Example 1, exceptthatthe amount of cellulose pulp was 93% and that also 2% thermocuring melamin binder (of the type "Cymell 411") were used. The product obtained weighted 25 g/m2. In order to obtain a sufficiently high wet strength, the fibrous product removed from the heating cylinder was heated to a temperature of 160 C for 1-2 seconds.

EXAMPLES 4-6 Fibrous products having different weights were prepared by the methods described in Examples 1-3.

Thus, a fibrous product having a weight of 75 g/m2 (Example 4) was prepared by the method according to Example 1, a fibrous product having a weight of 75 g/m2 (Example 5) was prepared by the method according to Example 2 and a fibrous product having a weight of 80 g/m2 (Example 6) was prepared by the method according to Example 3. The products having weights of 75 g/m2 and 80 g/m2 were suitable for the manufacture of kitchen rolls and papertowels.

The product containing the melamin binder had an increased wet strength.

EXAMPLE 7 The method according to Example 3 was repeated but by using a melamin binder of the type "Cymell 430". Preliminary investigations of the product obtained showed no significant differences compared to the product prepared according to Example 3.

EXAMPLE8 Afibrous product was prepared as described in Example 1 but with the exception that part of the cellulose pulp was replaced by thermoplastic polyethylene in fibre form. The polyethylene fibres had essentially the same length as the cellulosic fibres of the pulp material. The material introduced onto the forming wire had the following composition: 80% cellulosic fibres, 15% polyethylene fibres and 5% oxidized starch. After the formation of the fibrous layer, a solution of oxidized starch in water was sprayed thereon.

The product formed was more yellowthan the product obtained according to Example 1 but the quality of the product was such that it was suitable for use for the manufacture of toilet paper.

EXAMPLE 9 A product was prepared by the method according to Example 1 with the exception that a 15% starch solution was applied to the forming wire by rollers before the fibrous layer was formed thereon. The product obtained was stronger but not as soft as the product according to Example 1.

EXAMPLE 10 A fibrous product was prepared by the method described in Example 9 with the exception that the concentration of the solution containing oxidized starch which was sprayed onto the fibrous layer before the latter was contacted with the drying cylinder, only was 2%. The product obtained was suitable for the manufacture of kitchen rolls and the weight of the product was 60 g/m2.

When products are prepared by the methods described in the above examples 1-10, the thickness of the material depends on the pressure under which the fibrous layer is pressed against the drying cylinder with the metal net and on the temperature of the cylinder. As a rule, however, products having a weight of 30 g/m2 generally have a thickness of 0,3-0,4 mm, and products having a weight of 75 g/m2 have a thickness of about 0,8-0,9 mm.

All the products prepared according to the above examples showed a clear embossed pattern corresponding to that of the metal net. The fibres were strongly bonded together within the embossed zones and the product obtained had a considerable strength and were voluminous, thus making such products suitable for the manufacture of toilet paper and paper tissue.

Claims

1. A process for the manufacture of fibrous webs, wherein an endless air-permeable forming wire is passed below a number of fibre distributors discharging fibres which under the influence of one or more suction boxes mounted at the opposite side of the forming wire are sucked towards the forming wire so as to form a fibre layer thereon, characterized in that the air-permeable endless forming wire has openings having an area exceeding 1 mm2 and that fibre material passing through the forming wire below a given fibre distributor is passed to one or more subsequent fibre distributors viewed in the direction of movement of the forming wire.

2. A process according to claim 1, characterized in using several fibre distributors, each consisting of a number of fibre distributor units and in supplying fresh fibre product to each of said fibre distributors.

3. A process according to claim 1 for the manufacture of cellulosic fibre products, characterized in that the openings of the forming wire have a dimension in the cross machine direction of from 0,5 to 1,5 mm.

4. A process according to claim 3, characterized in that the dimension of the openings in the machine direction is 2-3 times the dimension of said openings in the cross machine direction.

5. A process according to claim 1, characterized in using a woven metal net in which the warp and weftthreadsform a plain weave.

6. A process according to claim 5, characterized in that the distance between the weft threads is higher than the disance between the warp threads.

7. A process according to claim 6, characterized in that the weft threads are straight and the warp threads form bends at the crossing points.

8. A process according to claim 1, characterized in that the fibrous web formed on the forming wire is directly introduced onto a drying cylinder.

9. A process according to claim 8, characterized in that the forming wire is pressed against the drying cylinder during the transfer of the fibrous web onto said drying cylinder.

10. A process according to claim 9, characterized in that a binder is applied to the forming wire before the formation of the fibrous layer thereon.

11. A process according to claim 8, characterized in that the drying cylinder is heated to a temperature of 1 00-2000C.

12. A process according to claim 8, characterized in that the fibrous web is removed from the drying cylinder without reduction of length.

13. A process according to claim 12, characterized in that the fibrous web is further heated after being removed from the drying cylinder.

14. A process according to claim 13, characterized in that the fibrous web is supported bythe return run of the forming wire during said further heating.

15. An apparatus for manufacturing cellulosic fibre webs comprising an endless air-permeable forming wire, a number of fibre distributors mounted along said forming wire, one or more suction boxes co-operating with each of said fibre distributors and mounted at the opposite side of the forming wire, characterized in that the forming wire have openings having an area exceeding 1 mm2 and that it comprises conduits connecting the suction box or suction boxes below a given fibre distributor with one or more following fibre distributors viewed in the direction of movement of the forming wire.

16. An apparatus according to claim 15, characterized in that it comprises means for supplying fresh fibre material to each fibre distributor and that the suction box of a given fibre distributor is connected with the rear end of the last fibre distributor in the series of fibre distributors, each consisting of a number of fibre distributor units built together.

17. An apparatus according to claim 15, characterized in that it further comprises a drying cylinder mounted in direct connection with the forming wire.

18. An apparatus according to claim 17, characterized in that it comprises one or more rollers which apart from serving as support rollers for the forming wire serve as pressure rollers pressing the forming wire and the fibrous web located thereon against a drying cylinder.

19. An apparatus according to claim 17, characterized in that the forming wire is mounted so as to encircle a significant portion of the drying cylinder.

20. An apparatus according to claim 19, characterized in that the return run of the forming wire passes above the fibre distributors.

21. An apparatus according to claim 17, characterized in that it has means for further heating the fibrous web after its removal from the drying cylinder.