JPS61258058A - Method and apparatus for producing dry fiber web containing organic fiber and binder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a method for producing a dry fibrous web comprising organic fibers, preferably cellulose fibers, and a binder, the method comprising applying a liquid binder to a fibrous web. forming a binder-containing web by passing the wet fibrous web through a row of dryers arranged at at least two height positions; The fibrous web is supported by a wire and passes a stream of hot air through the fibrous web in a direction substantially perpendicular to the direction of motion of the web during each dryer pass.

[Conventional technology]

U.S. Pat. No. 3,849,904 describes a dryer system in which a wet fibrous web is passed through four dryers, each divided into an upper chamber and a lower chamber by a perforated wire that supports the web. Disclose. In this prior art system, hot air is supplied to the upper chamber of the dryer, and the air that has passed through the fibrous web is sucked out of the lower chamber and introduced into the upper chamber of the upstream dryer.

Stacking the aforementioned wire dryers one on top of the other, passing the fibrous web from the higher dryer group to the lower dryer group with a rotation of substantially 180°, and finally out of the last dryer at the floor level. By,
Attempts have been made to reduce the floor space required for such dryer systems.

Placing the wet web into the dryer at the highest position and removing the dry web from the dryer at the floor level is recommended for the first turn of the web to prevent fibers from becoming loose from the fibrous web in the turn zone. This is due to the fact that it is desirable to apply a liquid binder to the side of the web which is inverted away from the device in the meantime.

Serious problems can occur when drying fibrous webs made in a dry forming process with the wire equipment described above. That is, the fibers of such a fibrous web are loosely interconnected and the web can withstand mechanical movement only after the web has been dried and the binder has been solidified or optionally cured. The fibrous web therefore easily falls apart during the movement from the point where the binder is applied to the point where the web is initially introduced into the dryer. To break apart like this (bursts:
(hereinafter referred to as looseness) can be a nuisance when a wet fibrous web is passed from the end point, where the binder is preferably applied, to the highest set of dryers in such a dryer system. Ru.

When an aqueous binder is applied to a fibrous web, the fibrous web tends to swell due to absorption of water by the cellulosic fibers, and if the application of the aqueous binder is uneven across the machine, the expansion causes wrinkles. or may result in the formation of folds. The formation of such wrinkles or pleats not only reduces the quality of the finished dry textile product, but also increases the risk of flaking during passage of the web through the dryer.

Because of these problems, there is a zone that can collect considerable lengths of web material in the event of breakage, since there is an inevitable period of time between when breakage of the fibrous web is detected and before the equipment can be shut down. It was necessary to have this in the device.

The risk of such flaking during drying of wet fibrous webs made by dry forming processes has made it impossible to obtain the desired high production rates with such dry forming processes.

In the industrial production of fibrous materials made from dry-formed fibrous webs, it has only been possible to achieve production speeds of 300-500 m/min. On the other hand, the maximum production speed for wet-formed fibrous materials is about 2000 m/min. The differences have considerably reduced the possibility of making dry forming an acceptable alternative to wet forming, which has several advantages over wet forming, for example in terms of quality and pollution control. .

[Purpose of the invention]

It is an object of the present invention to avoid flaking of fibrous webs when such webs are dried in the manner described above.

Another object of the invention is to increase the production rate in the production of dry fibrous materials in which the fibrous web is formatted by dry forming methods by the process in question.

These objects and others which will appear from the description below are achieved by the method of the invention. The present invention provides that the fibrous web is in contact with a support during the movement from one elevational position to another, and that during at least part of this movement the fibrous web is in contact with said support. It is characterized by being attracted to.

[Structure of the invention]

The present invention provides a method for preventing fibers from disintegrating from a fibrous web.
gagement) the danger is essentially reduced by the fact that the fibrous web is suctioned against the support supporting it during the movement from one level position to another; and Based on the discovery that it is not necessary to transport the wet fibrous web from floor level to the top of the dryer - instead, the fibrous web is introduced into a first dryer located at floor level. can be moved from the last dryer in a group of dryers placed at this height to a group of dryers in a higher position, and so on. When the fibrous web passes through the upper group of the dryer, it has achieved a sufficiently high strength that it can be lowered to floor level without support for the fibrous web and without risk of bursting. .

As a result of the reduced risk of breakage, production rates can be significantly increased. Furthermore, the device in which the method can be carried out can be of small size.

The invention also relates to an apparatus for the production of dry fibrous webs comprising organic fibers and a binder.

The apparatus of the invention includes means for continuously advancing a fibrous web over a support, means for supplying a liquid binder to the web during movement of the fibrous web on the support, and at least two elevational positions. a perforated wire for advancing the fibrous web through the dryer, means for transferring the web from the dryer located at one level to the wire located at another level, and passing through each dryer; The apparatus includes means for generating a flow of hot air through the fibrous web during movement of the web, said airflow being substantially perpendicular to the direction of movement of the web in the dryer.

The apparatus of the invention includes means for supporting a fibrous web during movement from one elevational position to another and for suctioning the web against a support during at least a portion of said movement. It is characterized by including means.

During application of the liquid binder to the fibrous web, the fibrous web is preferably supported by an endless, perforated wire passing through the binder station. During passage through the binder station, a liquid binder;
A liquid binder, for example in the form of a mist, is sprayed onto the upper surface of the fiber web and at the same time air is removed by suction from the lower zone of the perforated endless wire.

Application of the binder is preferably carried out by a row of orifices arranged in a row at right angles to the direction of movement of the fibrous web.

Due to the instability of the liquid binder, it is desirable to avoid mechanical pumping systems for supplying the liquid binder to the orifice and therefore to use a compressed air source connected to a compressed air source with a pressure of e.g. 12 to 15 bar - or two or more hydrophores. (hydrophors) is preferably used. Using hydropores placed in parallel, one of which is filled with binder and the second one can supply binder to the orifice by a conduit that can be connected to one hydrophore or the other through a suitable valve. Particularly advantageous.

The liquid binder is preferably subjected to continuous filtration through a plurality of filters having decreasing mesh sizes, for example from 40 meshes to 15 meshes. The final filtration is preferably performed shortly before the binder is atomized in the orifice.

Application of liquid binder to the fibers makes the web relatively heavy, and since a wet fiber web may stick to the support wire, a liquid binder was used to support the web during application of the binder. The transition from the wire to the perforated wire that supports the web during its passage through the first dryer may be important. This is particularly true in the case of the production of thin fiber webs, for example fiber webs weighing less than 50 g/rd.

If an endless perforated wire is used to support the fibrous web during the application of the binder, the fibrous web after being removed from this wire will support the fibrous web during the first dryer pass. Preferably, it is guided directly onto the wire. Preferably, the air flow is directed against the lower surface of the fibrous web and over the entire width of the zone where the wet web is removed from the wire. Using such airflow facilitates removal of the web from the wire without damaging the web.

The air flow is preferably generated by using perforated rollers and hollow rollers with internal chambers. The internal chamber here has means for supplying compressed air to the chamber and an ejection slot extending over the entire length of the roller and opening in the vicinity of the perforated roller wall.

The perforated wire that supports the fibrous web during the application of the binder is, for example, a wire made of plastic material.

When using such endless wires, it is difficult to prevent the binder from sticking to the wire and causing the web to stick to the wire when the sticky binder contacts the fibrous web. It is therefore preferable to subject the endless wire to a cleaning operation when the fibrous web is removed from the endless wire and before it is contacted again with the fibrous material.

Cleaning of the endless support wire is preferably carried out with high pressure water, optionally containing detergent.

Some water remains in and on the wire after passing below the orifice through which the high pressure water is sprayed onto the wire, and this residual water is preferably sprayed onto the wire from alternate sides of the wire. Compressed air turned on, removed by air. The wire is then contacted with two tips extending across the width of the wire, each lip contacting each side of the wire. The purpose of such contact is to smooth out the remaining droplets, thereby forming a film that can be removed by suction into a suction box provided in association with each lip.

The lips mentioned above preferably consist of a suitable abrasion resistant polyethylene.

The liquid produced during the cleaning operation is preferably collected and purified to avoid environmental contamination with binder residue. The purified liquid can then be flushed down the drain.

Drying of the wet fibrous web is preferably carried out by a group of dryers placed close to each other at the same height. Each dryer preferably consists of two zones, an upper zone and a lower zone, separated by a perforated wire.

Drying air is preferably introduced into the upper zone, where the pressure is preferably above atmospheric pressure, and humid air is removed from the lower zone. The air introduced into the first dryer typically has a temperature of 200-220°C and the outlet air preferably has a temperature of 15-120°C. The hot air introduced into the next dryer Optionally, it has a temperature lower than the above-mentioned temperature.

Preferably, perforated plates extending parallel to the perforated wire are provided in both the upper and lower zones in order to make the drying as uniform as possible.

The heating of the air to be supplied to the dryer is preferably
It is carried out by means of a gas burner equipped with a vibrator attached to a supply pipe for hot air. The air that has passed through the fiber web and the wires below it is sucked out and a portion of this air is recycled into the supply pipe for hot air.

The supply pipe for hot air preferably ends at the inlet end of the dryer in the upper zone of the dryer, and the air that has passed through the fibrous web is preferably discharged at the outlet end of the lower zone.

During at least part of the movement of the fibrous web from one height position to a higher position, it is preferably maintained by a hollow rotating cylinder with a perforated cylinder wall and below atmospheric pressure in said cylinder. By this,
Suction is applied to the perforated wire. By this method, the movement of the fibrous web can be effectively controlled.

Preferably, before the fibrous web is introduced into the higher level dryer, the first dryer, a further binder is applied to the side of the fibrous web that has not been previously treated with binder. In this way, the strength of the fibrous web is further increased and the risk of flaking is reduced. An endless perforated wire can be used to support the fibrous web during further application of the binder. This wire is preferably supported by the above-mentioned hollow cylinder with perforated cylinder walls, and the fibrous web is suspended at the time when it is pulled up from the supporting wire in the lower position, and during the application of the dryer, and when it It is in constant contact with the perforated wire until it is guided onto the perforated wire which rides as it is introduced into the dryer at an elevated position.

The drying of the fibrous web at a higher location and the transfer of the dried fibrous web to an even higher location, if any, is preferably carried out as described above. However, when binder is already applied to both sides of the fibrous web, further application of binder is usually unnecessary.

A third set of dryers is preferably used when the binder is heat cured and therefore it is necessary to carry out a final heat treatment of the fibrous web. Such heat treatment is preferably carried out at as high a temperature as possible without risking discoloration of the fibrous web. Temperatures are typically around 180-220
It is ℃.

After heat treatment to harden the binder, the fiber nibs have a strongly reduced moisture content, e.g. less than 2% by weight, and therefore it is customary to readjust the water content of the web, e.g. by spraying water onto the web. is necessary. In this way the water content is increased, for example to about 8% by weight, which is sufficient to obtain a stable product.

During the application of water, preferably by spraying, as described above, and during the movement of the thus treated fibrous web to the winding station, the fibrous web may optionally be supported by an endless wire.

The present invention will be described in more detail with reference to the accompanying drawings.

The apparatus shown in Figure 1 comprises three sections: one section where the fibrous web 1 is brought together and a binder is applied to it, a drying and curing section consisting of a number of dryers, and a conditioning and winding section. .

The first of these three sections was made, for example, by a dry forming process, in which an airborne fiber suspension is directed against an air permeable forming surface and a dry fiber layer is built up onto this forming surface. It has a roller set 2 for gathering the fibrous web 1.

After being brought together, the fibrous web 1 is guided onto an endless perforated wire 3 which is supported by rollers 4 and conveys the fibrous web to a station 5 for the application of binder to the upper surface of the fibrous web 1. be done. Application of the binder is carried out by one or more orifices 6 which emit a stream of binder droplets. The station 5 also has a suction box 7 located below the wire 3 from which air is removed by a fan 8. wire 3
The return portion of the fiber web containing the binder passes through a cleaning station 9 in which the fibers and binder residues are removed to remove the sticking between the fiber web 1 and the wires 3 when they come into contact with each other again. 1 is removed from the wire 3 and an air permeable drying wire 10 supports the fibrous web during passage to dryers 11 and 12 arranged in series.
be led upwards. Wire 10 is supported by roller 12a. The transfer of the binder-containing fibrous web 1 from the wire 3 to the drying wire 10 is shown in FIG.

As can be seen in FIG.
It passes over a roller 4 having an axially extending internal chamber 13 with an axially extending slot 14 provided in the vicinity of the roller. The internal compartment 13 is connected to a fan 16 that can set a pressure higher than atmospheric pressure in the internal compartment 13 . The roller 4 is placed close to the roller 12 that supports the drying wire 10 so that the fibrous web 1 is unsupported for only a short distance.

The fan 16, which generates a superatmospheric pressure in the chamber 13 and an air flow in the slot 14, contributes to removing the fibrous web 1 from the wire 3. This air flow
When oriented against the underside of wire 3, the fibrous web
lifted up from

As mentioned above, the angular position of the chamber 3 is adjustable so that the optimum position of the slot 14 can be determined under given operating conditions.

The dryer 11 is divided by wires 10 into an upper section and a lower section, hot drying air being supplied to the upper section and humid air being discharged from the lower section.

The structure of the dryer will be explained in conjunction with FIG.

In the illustrated embodiment, a portion of the air is recycled. That is, a portion of the humid air exiting the lower section is recycled through the pipe 17 and fan 18 to the upper section of the dryer after being reheated in the burner 19. A relatively small amount of humid air is removed by fan 2
The air is discharged through a branch pipe 20 connected to a common outlet vibe 21 through which the air can be discharged into the ambient atmosphere.

After passing through a second dryer 12, which is constructed similarly to dryer 11, the fibrous web is brought into contact with an endless wire 23 supported by a roller 24 and a number of additional rollers 25. While the fibrous web 1 is in contact with the wire 23, it is raised to a higher position and in this higher position is passed through two dryers 26 and 27 placed in series, configured similarly to the dryer 11. .

During the movement of the fibrous web through the dryers 26 and 27, it is placed on an uncut air permeable drying wire 28 supported by rollers 29.

Roller 24 is preferably configured as shown in FIGS. 3 and 4. As can be seen from these figures, it has a perforated cylinder wall and the interior of this roller is divided by a partition plate 32 into two chambers 30 and 31.

The chamber 31 is located near the portion of the cylinder wall that supports the wire 28 and the fibrous web during vertical movement of the web;
It is connected to a fan 33 via a suction pipe 34 provided at the center. Subatmospheric pressure is maintained within chamber 31 by fan 33, and this subatmospheric pressure draws the fibrous web against wire 28 during the significant turning movement of the fibrous web from a lower position to a higher position. As a result of this suction arrangement, deflection movements can be carried out even at very high speeds of the wire 28.

After reaching the higher position, the binder is applied to the side of the fibrous web that was opposite the orifice(s) 6 during the initial application of the binder. This additional application of binder takes place in one or more orifices located in a chamber 36 which functions as a suction box and has a lower part connected to a fan 37. The return of the endless wire 23 passes through three cleaning stations to remove sticky binder and fibers. After passing through the dryer 27, the fibrous web is guided into a chamber 40 in which it is transported to a higher position and at which point it is passed through a series of three dryers 4.
2. is contacted with another endless air permeable wire 41 through which 43 and 44 pass. Wire 41 is roller 4
5, this roller has a perforated cylindrical wall like the roller 24, inside which is a fan 4.
6 and a number of additional support rollers 47. The air sucked out from the interior of the rollers 45 by the fan 46 is reintroduced into the chamber 40, and the heat content of this air is such that the heat content in the dryers 42-44 (in which the temperature is preferably higher than in the other dryers) is is used for heating the fibrous web 1 before it is introduced into the fibrous web 1 (which can carry out the curing of the binder).

A perforated distribution plate 50 is provided within the chamber 40 to evenly distribute the air reintroduced into the chamber.

A series of dryers 42 in which the binder is cured
After passing through ~44, the fibrous web has a low moisture content. It is therefore guided onto another endless air-permeable wire 51 which is supported by rollers 52 and conveys the fibrous web 1 past to a conditioning station 53. In the conditioning station, water is sprayed onto the fibrous web from one or more nozzles and air is sucked out from below by a fan 55. After being conditioned to obtain the desired moisture content, the fibrous web is wound at 56.

The dryer shown in Figures 5 and 6 has an upper section with means for supplying hot drying air to the upper section, and a lower section from which the humid air is discharged. Air is supplied through a duct 60 provided at the upstream end, and air is discharged through another duct 61 provided at the downstream end. The dry air is thus forced to move in both directions along and at right angles to the fiber web 1.

The dryer also has two perforated tents 62 and 63 placed a short distance above and below the endless wire 10 to provide an even distribution of air both longitudinally and laterally of the dryer.

- The adjacent zone of the duct 60 and the upper section is
It has angular guides 64 which divide the ducts into smaller ducts 65 to further improve the distribution of the drying air over the width of the fibrous web. Each of these small ducts has a damper 66 which can be rotated on a vertical axis so that the opening can be adjusted as desired.

The duct 61 and the adjacent zones of the lower section have similar angular guide plates 67 forming four small ducts 68, each of the ducts having an adjustable damper 69.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of a preferred embodiment of the device according to the invention. Figure 2 shows a vertical passage through a portion of the endless wire for support of the fibrous web during binder application, near the forward end of the endless wire for support of the fibrous web during the first dryer pass; FIG. FIG. 3 is a vertical section through part of the endless wire and rollers for the support of the fibrous web during its movement from one height position to a higher position. FIG. 4 is a side view of the endless wire and roller shown in FIG. 3. FIG. 5 is a schematic diagram of the dryer with certain parts removed. FIG. 6 is a plan view of the dryer shown in FIG. 5. ' Procedural amendment 61.5. -1 Showa year month day 2・'''J1(7)S4 $3 difference g crystal difference ≦13
iK Dry 3, Person making the amendment Relationship with the case Applicant 4, Agent 5, Date of amendment order Self Correct the following errors in the invention specification.

Claims (9)

[Claims] (1) A method for producing a dry fibrous web comprising organic fibers and a binder, the method comprising: applying a liquid binder to a fibrous web to form a wet binder-containing web; drying the wet fibrous web by passing it through a series of dryers; supporting the fibrous web by perforated wire during each dryer pass; directing a stream of hot air through the fibrous web during each dryer pass; the fibrous web is in contact with the support during movement from one height position to another in a method comprising the step of passing in a direction substantially perpendicular to the direction of movement of the web; and a method characterized in that it is suctioned against said support during at least part of said movement. (2) The fibrous web is supported by an endless foraminous wire during the application of the liquid binder, and immediately after being removed from said wire, the fibrous web is supported by an endless foraminous wire that supports the fibrous web during passage through the first dryer. 2. The method of claim 1, wherein the method is transferred to a wire. 3. The method of claim 2, in which one or more air streams are directed against the lower surface of the endless wire in the zone where the web is removed from the wire. (4) using a perforated wire supported by at least one intermediate rotatable roller with a perforated surface to transfer the fibrous web from one height position to another; The method according to claim 1, wherein the pressure within the roller is maintained below atmospheric pressure. (5) The method of claim 1, wherein the binder is applied to opposite sides of the web at two different height positions. (6) Apparatus for producing a dry fibrous web comprising organic fibers and a binder, comprising means for continuously advancing the fibrous web over a support: applying a liquid binder to the web during movement of the fibrous web over the support; Feeding means: a dryer placed at at least two levels, a wire with small holes for passing the fibrous web through the dryer, from the dryer at one level to the wire at another level; and means for generating a flow of hot air through the fibrous web during movement of the fibrous web through each dryer, wherein the air flow is directed substantially in the direction of movement of the web in the dryer. means for supporting the fibrous web during its movement from one elevational position to another in an apparatus at right angles to said support during at least part of said movement; A device characterized in that it has means for suctioning the web. (7) During the application of the binder, the support for the fibrous web is an endless perforated wire supported by rollers, the endless wire having a perforated surface at the end where the fibrous web is removed from the endless wire. and the device further comprises means for generating one or more air streams directed against the underside of the fibrous web in the zone where the fibrous web is removed from said endless wire. Range 6th
Apparatus described in section. 8. The device of claim 7, wherein the means for generating one or more air flows against the underside of the fibrous web comprises a chamber with an angularly adjustable exit slot. (9) The device has an endless perforated wire supporting the fibrous web during its movement from one height position to another, the perforated wire having a perforated surface. 7. The device of claim 6, wherein the device is supported by a rotatable roller having a rotatable roller, and the device further includes means for reducing pressure within said roller.