EP0144365A1

EP0144365A1 - A method of impregnating a fibrous material

Info

Publication number: EP0144365A1
Application number: EP19840901986
Authority: EP
Inventors: Kjeld Holbek
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-05-24
Filing date: 1984-05-23
Publication date: 1985-06-19
Also published as: FI850292L; NO850280L; AU2969784A; JPS60501400A; WO1984004704A1; FI850292A0

Abstract

On imprègne un matériau poreux et/ou fibreux (10) au moyen d'un milieu d'imprégnation liquide en mettant le matériau en condition sèche et chauffée en contact avec le milieu d'imprégnation, pendant que le matériau est soumis à un vide élevé. On peut ensuite déplacer continuellement un matériau fibreux de préférence en forme de bande à travers une ou plusieurs chambres à vide (57) où le milieu d'imprégnation est appliqué au matériau en bande (10) sous une forme pulvérisée. On effectue de préférence la pulvérisation du milieu d'imprégnation grâce à une pompe d'injection conventionnelle (62) possédant des buses d'injection (68). Si on le désire, le matériau imprégné peut en outre être traité dans un broyeur à marteaux (70).A porous and / or fibrous material (10) is impregnated by means of a liquid impregnation medium by bringing the material in dry and heated condition into contact with the impregnation medium, while the material is subjected to a high vacuum. . A fibrous material, preferably in the form of a strip, can then be continuously moved through one or more vacuum chambers (57) where the impregnation medium is applied to the strip material (10) in a sprayed form. Preferably, the impregnation medium is sprayed using a conventional injection pump (62) having injection nozzles (68). If desired, the impregnated material can further be processed in a hammer mill (70).

Description

A METHOD OF IMPREGNATI NG A FI BROUS MATERIAL

The invention relates to a method of incorporating a liquid impreg¬ nating means to a layer or web-shaped, porous or fibrous material .

The method according to the invention may be used for treating any porous and/or fibrous material to which certain characteristics should desirably be imparted by suitable impregnating means . The material to be treated may contain fibres which may be natu ral fibres with small cavities or cell cavities, such as cellulose fibres - including cotton fibres - or wool fibres or man-made fibres which may each contain inner cavities or which may form spaces or cavities between them. Such man-made fibres may, for example, have cross-sectional shapes with projections promoting the formation of such spaces, or the fibres may have a wavy shape, which also gives rise to the formation of many spaces in a material consisting of such a fibre mass . The ma- terial to be treated may, for example, be fibrous cellulose material made from for example straw, scrap wood, or another wood material, and may be in the form of fibrous sheet or web material, for example composite paper or other paper, paper board or cardboard, or woven or non-woven textile material . The material to be treated may, how- ever, also consist of or comprise non-fibrous materials, such as porous materials formed by sintered or glued particles. As an example, the layer-shaped material may consist of fibres confined within a porous matrix, such as a concrete mass containing reinforc¬ ing fibres which are to be impregnated in situ.

From the Applicant's international patent application No. PCT/DK82/- 00052, publication No. WO 82/04271 , it is known to impart desired characteristics to fibrous materials, such as cellulose and wool fibres or other fibres with inner cavities, by impregnating these fibrous material with a suitable liquid impregnating means . By the known method this is done by passing the fibrous material into the nip formed between a pair of high-pressure rollers, where, in the pre¬ sence of the impregnating means, the fibres are subjected to such high pressure that the cell walls are deformed so that air and gas are expelled from the cell cavities, and when the fibre walls tend to reassume their original shape after the compression, impregnating means will be sucked into the cavities . As the efficiency of this known method is dependent on the circumstance that each single fibre is forcefully compressed and at the same time surrounded by a suffi- cient amount of the liquid impregnating means, only a relatively thin layer of fibrous material may be passed in between the compression rollers, which causes a substantial limitation of capacity, and before the fibrous material is passed in between the rollers, an excessive amount, which is later pressed out of the material by the rollers, must be applied to the material and has to be returned to the reser¬ voir of impregnating means. For some types of impregnating means this may give rise to a decomposition thereof, for example due to oxidation .

From British patent specification No. 1 ,246,806 it is known to impreg- nate textile material by continuously passing a web of the material through a vacuum chamber in which a high vacuum is maintained, and from the vacuum chamber directly out into a succeeding bath of impregnating means. I n practice it is hardly possible to produce a sealing device which makes it possible to pass the web-shaped textile material continously through the vacuum chamber, and which at the same time effectively prevents the impregnating means from the adja¬ cent bath of impregnating means from being sucked into the vacuum chamber. Furthermore, when this knwon apparatus is used, it is not possible to accurately control the amount of impregnating means being applied to the textile material.

From German Auslegeschrift No. 2,452,784 is known a method for applying a liquid layer of material to one side of a paper web. For this purpose the paper web is passed around a roller so that the outer side of the paper web comes into contact with a liquid bath, and the paper web is thereafter moved past a wiper which is main¬ tained pressed against the paper web by means of sub-atmospheric pressure provided within a chamber, in which the wiper constitutes a wall part. This sub-atmospheric pressu re will cause a certain air flow through the paper web tending to remove the coating thereof. The present invention provides a method of incorporating an impreg¬ nating means, by which method it may be ensured that the impregnat¬ ing means penetrates into the fibrous and/or porous material th rough the total thickness of the web-shaped material . Fu rthermore, the method according to the invention makes it possible to accurately control the amount of impregnating means introduced into the web material .

The method according to the invention provides a method of incorpor¬ ating a liquid impregnating means into a layer or web-shaped porous and/or fibrous material by which method the porous and/or fibrous material is subjected to a high vacuum, the impregnating means is applied to at least one side of the web material while it is subjected to a vacuum, and a pressure drop across the layer of material or web material is maintained in a direction from said one side towards the other side after the application of the impregnating means and while the material is subjected to a vacuum. By subjecting the porous and/or fibrous material to a high vacuum, an evacuation of the cavi¬ ties in the porous and/or fibrous material, including the cell cavities of the fibres, is obtained, and the impregnating means may then freely penetrate into and more or less fill these cavities. This pene¬ tration of impregnating means into the cell cavities will be promoted when the material is again subjected to normal pressure and the ambient air tends to penetrate into the evacuated cavities and thereby drives the impregnating means before the air. By maintaining a small pressu re drop across the layer of material or the web material from the side to which the impregnating means is applied towards the other side, the impregnating means may be caused to penetrate into the layer of material to the extent desired . If desired, it may then be ensured that the impregnating means penetrates totally through the layer of material so that complete impregnation is obtained.

The vacuum to which the porous and/or the fibrous material is sub¬ jected, may be more or less complete dependent on the impregnation efficiency desired. I n order to obtain thorough impregnation and almost complete filling of the cavities of the material with impregnating means, a high vacuum for example a 99% vacuum, is preferably used .

OMPI The impregnating means may be applied to the porous and/or fibrous material in any manner, for example by applying, brushing on or by dipping the material into the impregnating means . However, as men¬ tioned above, the impregnating means is preferably applied in an atomized condition, for example by spraying, and the impregnating means may be applied to both sides of the layer of material, if de¬ sired.

When the impregnating means is applied to only one side of the layer of material or web material, this side is preferably the lower side, because impregnating means will then be caused to move in an upward direction through the web under the influence of the pressure differ¬ ence between the two sides of the web.

In order to obtain good penetration of the impregnating means into the cavities of the fibrous and/or porous material it is often of deci- sive importance that the material is subtantϊally free of moisture. Therefore, the material is preferably heated before and/or while the impregnating means in placed in contact therewith . Such heating will remove any moisture from the material and also reduce the viscosity of the impregnating means, whereby its penetration into the cavities of the material is facilitated. The material may, for example, be heated to about 200°C.

The drying of the material need not necessarily be performed by heating, but may, for example, be obtained by passing a dry gas, such as dry nitrogen, through or past the material . Furthermore, it is possible to subject the material to freeze-drying.

The porous and/or fibrous material may, according to the invention, be corona treated before and/or while the impregnating means is brought into contact with the material . Such a corona treatment causes a drastic reduction of the dyne degree of the material, which means that the impregnating means may penetrate into the cavities and pores of the material considerably more easily.

O PI As mentioned above, the porous and/or fibrous material may be in a loose condition, and efter a possible drying and corona treatment it may then be placed batchwise in a vacuum chamber in which the impregnating means is applied thereto. However, in order to obtain an almost continuous process, the layer of material is preferably in the form of a web material which is continuously or intermittantly passed through a vacuum chamber in which the impregnating means is ap¬ plied. I n order to reduce the viscosity of the impregnating means it may be heated before and/or du ring application within the vacuum chamber.

When an impregnating means has been applied to the porous and/or the fibrous material under vacuum, the material is preferably passed to a hammer mill or another defibrator, in which the fibre material is defibrated, and in which additional impregnating means which will be worked into the material during operation of the hammer mill, may be added .

The invention also relates to a plant for treating a porous and/or fibrous layer or web-shaped material with an impregnating means, said plant comprising a treating chamber adapted to receive the layer or web-shaped material in such a manner that it divides the chamber into first and second spaces, means for generating a high pressu re within the treating chamber, means for applying impregnating means to at least the side of the web material facing said first space, and means for maintaining a lower pressure within the second space than in the first one.

The plant may also comprise a heating tunnel, which extends between a material supply roll and the vacuum chamber, and in which heating means are provided adapted to heat the web material when it is moved from the supply roll th rough the tunnel to the vacuum chamber, and material moving means may be provided after the tunnel and be adapted to pull the web material from the supply roll and through the tunnel while overcoming a torque, which is applied to the supply roll by return winding means connected to the supply roll, and cutting means may be provided between the moving means and the heating

OMPI tunnel for cutting the web rn case of breakdowns . When the web is cut by the cutting means, the torque applied to the supply roll by means of the return winding means will no longer be overcome by the moving means, and therefore the part of the web material positioned within the heating tunnel will rapidly be rolled onto the supply roll by the return winding means and thereby be removed from the heat¬ ing tunnel . It is thereby prevented that this part of the web material is excessively heated in case of breakdown .

The plant may comprise a defibrator which is preferably a hammer mill, the material inlet of which communicates with a material outlet or a material outlet passage formed in the vacuum chamber. The action to which the porous and/or fibrous material is subjected in the defi¬ brator or hammer mill causes a further incorporation of the impreg¬ nating means into the inner cavities of the material .

It is sometimes desirable to reform a coherent material or a coherent layer from the defibrated material . The plant may therefore comprise a particle or fibre separator positioned downstream of the defibrator and including a separator drum, which has a gas permeable peripheral wall, and within which a suction chamber and a pressure chamber are formed in peripheral succession and are defined outwardly by the gas permeable wall of the drum, and the plant may be adapted so that the material from the defibrator is supplied to the peripheral wall of the separator drum opposite to the suction chamber. The defibrated fibrous material supplied from the defibrator will then be passed from the defibrator to the gas permeable peripheral wall of the separator drum opposite to the suction chamber, whereby the fibrous material will form a fibrous layer on the separator drum. When this fibrous layer has been moved to a position opposite to the pressurized air chamber owing to the rotation of the separator drum, the fibrous layer of material is blown off from the separator drum and passed onto a suitable conveyor. I n this manner a web material may be reformed from the defibrated, impregnated material . Alternatively, the impregnated fibres may, however, be passed directly from the hammer mill to a storage site or a place where they are used.

O PI When the method and the plant according to the invention are used, the fibres will be exposed to a certain implosion owing to the vacuum impregnation, whereby the fibres obtain a desired flat shape and a content of impregnating means .

In the following the invention will be explained more in detail with reference to the drawings, wherein

Fig. 1 showns the inlet end of an embodiment of the plant according to the invention with a drying tunnel,

Fig. 2 the succeeding central part of the embodiment shown in Fig . 1 of the plant according to the invention which includes a vacuum chamber, and

Fig . 3 the succeeding last part . of the embodiment shown in Figs . 1 and 2 of the plant according to the invention comprising a hammer mill and a fibre separator.

The plant shown in the drawings is adapted to impregnate a web- shaped paper material 10 or another fibrous and/or porous material in a continuous process with one or more liquid . impregnating means imparting desired characteristics to the web-shaped material . The web material 10 to be impregnated is supplied from a supply roll 11 (see Fig. 1 ) , which is mounted on a horizontal shaft 12 which may be locked to the supply roll by means of a mechanism actuated by pres¬ surized air. The shaft 12 is connected to an electric motor 13b, which is preferably an eddy-current motor, via a gear 13a . This motor serves to apply a torque to the shaft 12 in the direction of rolling up, the purpose of which will be further mentioned below. The paper web 10 which has been unrolled from the supply roll 11 is passed between a pair of feeding rollers 14 and thereafter onto a roller table 15. If desired, the roller table 15 may be provided with adjustable side guides, not shown, and cutting means for trimming the free end portion of the web and means for joining the trimmed end portion with an adjacent end portion of a preceding web. The web ends are pre¬ ferably joined by sewing, because the joint must be able to endu re the high temperatures to which the material of the web is subjected when passing through the plant. After the roller table the web 10 is passed between a pair of feeding rollers 16 which may be pressed

OMPI against each other by means of compressed air cylinders 17 at a pressure sufficient to obtain a suitable abutment pressu re between the feeding rollers 16 and the paper web 10. The rollers 16 are driven by means of an electric motor 18 and a gear 19 at a rate corresponding to the desired feeding rate of the paper web 10. The feeding rollers 16 are arranged immediately upstream of a preheating oven 20 ar¬ ranged on a base 21 , and a main oven 22 arranged on a base 23 is positioned immediately downstream of the oven 20. Both ovens 20 and 22 are in the form of tunnel ovens in which the paper web 10 is supported by a number of longitudinally extending, vertically ar¬ ranged rails 24 which are preferably made from metal. Transversely extending wires or rods, not shown, may be arranged between the supporting rails 24 for causing a suitable turbulence in the air pass¬ ing along the underside of the web within the ovens. Fresh air is supplied to the main oven 22 by means of an inlet fan 25, which, via a heat exchanger 26 and a supply conduit 27, blows fresh air pre¬ heated by the heat exchanger 26 into the upper and lower parts of the main oven 22 via branched conduits 27a and 27b, respectively. In the upper part of the oven 22 the fresh air supplied is blown into an upper heating chamber 30 by means of a fan 28 driven by a motor 29. The heating chamber 30 contains electric heating elements 31 to which current is supplied through electric cables 32. The fresh air heated by the heating elements 31 is passed through slots defined between obliquely arranged guide fins 33 into the upper part of the oven tunnel of the main oven 22 through which the web 10 is passed. As indicated by dotted lines, a fan 28 blowing the preheated fresh air supplied through the branched conduit 27b through heating elements 31 and guide fins 33 into the part of the oven tunnel positioned below the paper web 10, is also positioned below the oven tunnel . The heated fresh air having a low relative humidity will then flow through the oven tunnej of the main oven 22 along the upper and lower sides of the web 10 and in the feeding direction of the web as indicated by arrows in Fig . 1 . The main oven 22 may be provided with adjustable dampers, not shown, which in their open positions enable the fans 28 to recirculate the heating, air in the main oven through the heating elements 31 . However, these adjustable dampers are normally closed. The heated air from the main oven 22 continues in counterflow to the

__O pr web 10 into the preheating oven 20, in which the paper web is con¬ sequently preheated by the heating air coming from the main oven 22. Adjustable dampers, not shown , may be arranged between the ovens 20 and 22 to render it possible to adjust the flow of heating air passing from the main oven 22 on both sides of the web 10 into the preheating oven 20. The used heating air is sucked out of the heat¬ ing oven 20 through transverse suction boxes 34 which are arranged immediately downstream of the feeding rollers 16, and which may be provided with suitable coarse filters 35. Both suction boxes 34 are connected to an exhaust conduit 36 leading to the heat exchanger 26 from which the used and now cooled heating air is exhausted into the atmosphere through a conduit 37 and an exhaust fan 38.

A pair of feeding rollers 39, which correspond to the feeding rollers 16, and which may be pressed into and out of engagement with the web 10 by means of compressed air cylinders 40 are arranged down¬ stream of the main oven 22. The feeding rollers 16 and 39 which are preferably totally identical, operate synch ronously, which may, for example, be obtained by mutually connecting the two pairs of feeding rollers by means of a chain drive.

The purpose of the ovens described is to heat the web material 10 and to remove as much humidity as possible therefrom. These ovens may, of cou rse, be replaced by other types of ovens by means of which this purpose may be obtained . As an example, the web material may be passed through a high frequency oven removing the main part of the water contained in the web material, a succeeding oven gener¬ ating infrared radiation, and finally a hot-air oven with great turbu¬ lence for removing the last part of moisture from the web material except water of crystallisation .

As shown in Fig . 2, a cutting device 41 is arranged immediately downstream of the main oven 22 and the feeding rollers 39 and may, for example, be actuated by an impact cylinder driven by compressed air, which permits a very quick cutting of the web material 10. The cutting device, which may be a modified veneer cutter, may sever the web material 10 along a straight cut even when the web is moved at a

^URE

OMPI rate of up to 40 m/minute. The cutting device 41 may, for example, be used for cutting the web material 10 in case of a breakdown . When the web material 10 is cut, the torque generated by the motor 13b causes the part of the web material which is arranged within the ovens to be quickly drawn out and rolled up on the supply roll 11 , whereby it is prevented that the web material is overheated and destroyed in the ovens and possibly gives rise to a risk of fire or explosion . If desired, such risk of fire or explosion may be further reduced by blowing nitrogen or another inactive gas into the ovens . The torque generated by the motor 13b in the direction of rolling up of the supply roll 11 also serves to ensure that the web material 10 is always suitably tightened . For safety reasons, a pair of slave rollers 42, which also function as web guides, are arranged immediately downstream of the cutting device 41 .

After having passed the ovens 20 and 22 and the knife 41 , the web material 10 is then moved past a corona radiating apparatus 43 and thereafter through a vacuum impregnating unit 44 which may conve¬ niently be of the- type which is described in the Applicant's Danish patent application No. 1083/83. A pair of drive rollers 45 and 46, respectively, is arranged upstream of the corona radiating apparatus 43 and downstream of the vacuum impregnating unit 44. These drive rollers are driven by means of a common chain drive 47 and an elec¬ tric motor 48, which is preferably an adjustable eddy-current motor. I n the pairs of drive rollers 45 and 46, only the lower roller is driven by the motor 48, and the upper roller may be pressed against the lower roller at a desired pressure, for example by means of a hand wheel 49 for simultaneously operating two screw spindles 50 as shown in connection with the driving rollers 46. The lowermost of the drive rollers 46 is preferably driven at a peripheral velocity which is slightly greater than the peripheral velocity at which the lower roller of the pair of rollers 45 is driven. This means that the web material between the pairs of driving rollers 45 and 46 is exposed to a slight stretching when these pairs of rollers are clamped sufficiently to¬ gether. This stretching may, however, be controlled by clamping the pairs of rollers more or less forcefully together. Downstream of the driving rollers 45 the web material 10 is passed into a corona treating apparatus 43 which is connected to a high voltage generator 53 via an electric cable 51 and a terminal box 52. I n the corona treating apparatus 43 both sides of the web material 10 are irradiated by ion discharges at a high voltage and high intensity whereby the dyne degree of the material at the surface of the irra¬ diated web is drastically increased . As the corona irradiation involves generation of ozone, the corona irradiation apparatus is combined with an air exhaust nozzle on both sides, which nozzles are connected to an exhaust fan 55 via air exhaust conduits 54. The corona irradiation apparatus may be located within the impregnation unit, if desired, whereby the use of a special exhaust system for the corona apparatus may be avoided .

When the web material 10 has been corona irradiated, it is passed through the vacuum impregnation unit 44 which comprises an inlet passage for sealingly introducing the web material 10 into a pair of vacuum chambers 57, and the web is sealingly passed out from the vacuum chamber through an outlet passage 58. -During operation of the plant an impregnating means is supplied to each of the vacuum chambers 57 in atomized condition from a pair of pressurized con¬ tainers 59, each of which is connected to a high pressure piston pump 62 via tubes or hoses 60 and a liquid indicator 61 . These high pressu re piston pumps 62 are preferably of the type used as fuel injection pumps in certain engines . Each high pressu re piston pump, which contains six cylinders in the embodiment shown, may be con¬ nected to a number - for example twelve - of injection or atomizing nozzles 63 mounted in the upper part of each of the vacuum chambers 57. Thus, each cylinder is connected to two nozzles . Each of the high pressure pumps is driven by a driving motor 64 via a chain drive 65, and the effective stroke length of the high pressure pumps and, consequently, the metering of impregnating means, is adjusted by means of a shaded-pole motor 66 with digital indication associated with each of the pumps, and the function of these shaded-pole motors as well as the other functions of the plant are controlled from a control desk 67.

-gTJRE »

OMPI The nozzle 63 may, for example, have an angle of dispersion of 60°, and when the pressure within the vacuum chambers is very low, for example a pressure of only about 10 mb, the pressure drop occurring when the impregnating means is sprayed through the nozzles will be so big that the liquid impregnating means is not only atomized, but almost gasified, as it may obtain a particle size of 50-200 Angstrøm.

In a preferred embodiment of the plant according to the invention four pressurized containers 59 are used, and they are all supplied with nitrogen or another inactive gas at a pressure of 5-6 atm. One of the containers may then be su rrounded by a thermostatically con¬ trolled heating jacket, and the container may, for example, be adapt¬ ed to contain methyloxide acylates or alkydketene di ers or isocyan- ates. The two first mentioned impregnating means may be paste-like or viscous at room temperature and require heating in order to be sprayed onto the web material . Therefore, a temperature of about 120°C may be maintained in this container. The hose 60 connected thereto may also be heated so as to maintain the contents thereof at a temperature of 180°C, and as shown in Fig . 2, the high pressure pumps 62 may be enclosed in a jacket 68 which is also heated so that the impregnating means here attains a temperature of about 200°C. The nitrogen atmosphere in the pressurized container and the gradual heating of the impregnating means as it is consumed reduces the risk of degradation which would otherwise occur at longlasting, high temperature influences. The impregnating means from the above mentioned first pressurized container may, for example, be supplied to the first one of the vacuum chambers 57 through its nozzles 63, and the desired temperature within the jacket 68 may be obtained by means of a separate, thermostatically controlled heater fan .

The other of the pressurized containers 59 may be intended for silicon oligomers and so-called coupling agents which are liquid at room temperature, wherefore the other pressurized container need not be heated .

The third pressurized container may contain kerosene or a similar solvent and may be connected to feeding hoses, and by means of a multiway cocks the third container may be connected to the feeding

O PI hoses of the first as well as of the second pressu rized container and be directly connected to the pressure pumps so that the system may quickly be cleared of impregnating means by breakdown and by change of impregnating means .

When the heated, dried, and corona treated web material 10 is passed through the vacuum chambers 57, in which impregnating means is applied thereto in atomized condition , the impregnating means will penetrate into the pores, spaces, and cavities of the fibrous and/or porous material, whereby an effective impregnation is obtained.

The fourth one of the above mentioned pressurized containers may contain water, water glass or polyelectrolytes, which may, for example, be applied to the web material 10 in a manner not shown , immediately after the web has passed th rough the vacuum impregna¬ tion unit 44. The application of such a liquid may have at least one of the following th ree purposes : (1 ) to cool the material , (2) to react chemically with any excessive silane or isocyanates for environmental reasons, and (3) to complete the impregnation process, because the silane as well as the oligomers must react with water whether the water stems from the atmospheric air or is supplied separately.

The vacuum in the vacuum chamber is obtained by means of an air suction arrangement 69 comprising vacuum blowers or vacuum pumps .

When the web material 10 has passed the vacuum impregnation unit 44, as indicated in Fig . 3, it may be rolled onto a stock roll 70 which may be driven by an eddy-cu rrent motor, not shown , and the web material may be introduced between a pair of rollers 71 and passed around a web roll 72. The rotational speed of the rolling-up motor may be controlled by a diameter sensor, and a hydraulically damped sensor 73 which is actuated by pressurized air, ensures that the web is transversely controlled so as to obtain an accu rate rolling on when the rollers 71 are rotated . Any tears or breakage of the web is detected by a third sensor which stops the rolling on in case of tears of the web material . I n case a defibration of the web material 10, which has been impregnated in the vacuum chamber, is desired, the

- - - ^-gtlRE g

( OMPI W web material is introduced into a hammer mill 74 which is driven by an electric motor 75, and which is preferably of the type described in Danish patent application No. 1084/83. The material defibrated in the hammer mill 74 is passed through a transport passage 75 to a fibre separator 76 having a net drum 77 which is driven by an electric motor 78, which is preferably an eddy-current motor by means of which the drum 77 may be driven at a controllable rotational speed . The net drum may, for example, be made from stainless steel and have a mesh size of 550 meshes/cm², and the fibrated material is supplied thereto along its total axial length through a transport passage 75 which is provided with an inspection glass 79. A rubber roller 80 which is swingably mounted on the outlet end of the trans¬ port passage is pressed resilϊently against the net drum 77. At the location at which the fibre material 81 is supplied to the net drum 77, a stationary suction chamber is arranged within the drum. The strong suction which is thereby established from the inner side of the net drum causes dust and any chemical residues, etc. , to be sucked into the drum and be removed, while the fibres are retained against the peripheral surface of the net drum, whereby the fibres are caused to . form a smooth layer. When the fibres have been moved a quarter of a revolution together with the drum they pass another rubber roller 82 and are thereafter directed over a stationary compressed air chamber which is arranged within the drum and contains a series of com¬ pressed air nozzles. The strong air flow generated by the nozzles releases the fibre layer from the net drum, and the freshly formed web material 81 , which has been released from the net drum 77 is passed onto a conveyor 84 via a profiled rail 83. The air sucked from the suction chamber in the net drum 77 is passed through a tube 85 to a cleaning or filtering plant 86 which may include bag filters.

The conveyor 84 may be a conveyor belt which is made from em¬ bossed, reinforced rubber sheeting and which has transverse guides made from nylon . The conveyor belt passes the impregnated fibrous material to a collecting container 87 or another collecting site.

If, for example, the material treated in the plant is cellulose fibres, the pile web formed on the conveyor 84 may be treated in various manners:

-gtJRE ~» OMPI (a) by heat treatment of coated fibres, where a special film forming polymer has been used, the fibres may be bound together into a rockwool-Iike mat,

(b) by heat rolling of the specially coated fibres a paper web may be made directly, and

(c) by pressing the conditioned fibres, structural plates with all degrees of density and variants may be obtained.

It should be understood that various changes and modifications of the embodiment shown in the drawings may be made within the scope of the invention . Thus, the material to be impregnated need not be web-shaped, but when it has been subjected to a suitable heating and drying treatment it may be introduced into a vacuum impregnating chamber batchwise. Furthermore, the material to be treated may be in the form of rigid plates, such as fibre reinforced porous concrete, in which it is desired to have the reinforcing fibres impregnated.

EXAMPLE

Unbleached recycled paper (400 g/m²) having a web width of 1200 mm was passed through the ovens 20 and 22 shown in Fig . 1 at a rate of 11 m/minute, and a temperatu re of 300°C was maintained in the ovens . The temperatu re of the paper was dete^'rmined to be 175°C while the room temperature was 23°C.

The corona irradiating apparatus 43 shown in Fig . 2 was adjusted to a setting of 3, while the high pressure piston pumps 62 were adjusted so as to supply impregnating means in an amount of 36 kg/h into the first vacuum chamber and 3.6 kg/h to the second vacuum chamber. This caused application of amounts of the impregnating means of 10.2% by weight and 1% by weight, respectively, in the two vacuum cham¬ bers. I n the first vacuum chamber a mixture of TES 40 (an ethyloxy- silane with 1 -9 silicon atoms per molecule from Wacker Chemie, West Germany) , and Silane A-1100 (a silane coupling agent consisting of y-aminoproρyl triethoxysilane, from Union Carbide, USA) at a ratio

OMPI of 96:4 was applied, while LUDOX HS40 (an aqueous colloid dispersion of silica particles from DuPont, USA) was supplied to the second vacuum chamber. The pressure within the vacuum chamber was measured to be 550 mb .

I n the fibre separator 76 shown in Fig . 3, the velocity of the net drum 77 was 14 m/minute, while the velocity of the conveyor 84 was 16 m/minute.

The plant was in operation for a total of 35 minutes under the condi¬ tions stated above, which yielded an amount of defibrated fibres of 177.7 kg, which corresponds to a capacity for the plant of 307 kg/h .

The fibres produced showed good defibration and distribution of the impregnating materials.

UR£4

^' OMPI

Claims

1 . A method of incorporating a liquid impregnating means in a layer- or web-shaped porous and/or fibrous material , by which method the porous and/or fibrous material is subjected to a high vacuum, the impregnating means is applied to at least one side of the web material while it is subjected to a vacuum, and a pressure drop across the layer of material or web material is maintained in a direction from said one side towards the other after the application after the application of the impregnating means and while the material is subjected to a vacuum.

2. A method according to claim 1 , wherein the impregnating means is applied to the material in an atomaized condition .

3. A method according to claim 1 or 2, wherein the material is sub¬ jected to a 99% vacuum.

4. A method according to any of the claims 1 -3, wherein the layer or web-shaped material extends substantially horizontally during the application of impregnating means, said one side of the web-shaped material to which the impregnating means is applied being the lower side.

5. A method according to any of the claims 1 -4, wherein the material comprises natural fibres, such as cellulose fibres or wool fibres .

6. A method according to any of the claims 1 -5, wherein the material is heated before and/or while the impregnating means is applied .

7. A method according to claim 6, wherein the material is heated to about 200°C.

8. A method according to any of the claims 1 -7, wherein the material is corona-treated before and/or while the impregnating means is applied to the material .

9. A method according to any of the claims 1 -8, wherein the layer of material or the web material is continuously or intermittantly passed through a vacuum chamber in which the impregnating means is ap¬ plied.

10. A method according to any of the claims 1 -9, wherein the web material is defibrated in a hammer mill after the application of the impregnating means, in which hammer mill additional impregnating means are added, if desired .

11 . A plant for treating a porous and/or fibrous layer or web-shaped material with an impregnating means, said plant comprising a treating chamber adapted to receive the layer or web-shaped material in such a manner that the material divides the chamber into first and second spaces, means for providing a high vacuum within the treating cham¬ ber, means for applying an impregnating means to at least the side of the web material facing said first space, and means to maintain a pressure which is lower within the second space than in the first one.

12. A plant according to claim 11 , wherein the means for applying the impregnating means comprise one or more atomizing nozzles within the first space of the vacuum chamber.

13. A plant according to claim 11 or 12, wherein the atomizing nozzles are of the type used as fuel injection nozzles in combustion engines .

14. A plant according to any of the claims 11 -13, wherein the means for maintaining the lower pressure within the second space comprise a vacuum sou rce communicating with said space.

15. A plant according to any of the claims 11-14, wherein the treating chamber is provided with inlet and outlet passages adapted to sealing¬ ly receive the web-shaped material in such a manner that it may be passed through the treating chamber continuously or intermittantly.

^ JREA OMPI _

16. A plant according to any of the claims 11 -15, wherein the layer or web-shaped material is received in the treating chamber so that it extends substantially horizontally, and wherein the fi rst space is positioned below the layer or web-shaped material .

17. A plant according to any of the claims 11 -16, wherein a corona discharging apparatus for corona treating the material to be treated is arranged upstream of and/or within the treating chamber.

18. A plant according to any of the claims 15-17, and comprising a heating tunnel extending between a material supply roll and the treating chamber and containing heating means adapted to heat the web material when it is passed from the supply roll, th rough the tunnel, and to the treating chamber, and material moving means arranged downstream of the tunnel and adapted to pull the web material from the supply roll and th rough the tunnel by overcoming a torque which is applied to the supply roll by return winding means, and cutting means positioned between the moving means and the heating tunnel for cutting the web in case of breakdowns .

19. A plant according to any of the claims 11 -18 and comprising a defibrator, preferably a hammer mill, the material inlet of which communicates with a material outlet or a material outlet passage formed in the vacuum chamber.

20. A plant according to claim 19 and comprising a particle or fibre separator, which is positioned downstream of the defibrator, and which includes a separator drum having a gas permeable peripheral wall and a suction chamber and a pressurized air chamber formed therein in succession and being defined outwardly by the gas per¬ meable wall of the drum, the plant being adapted so that material from the defibrator is supplied to the peripheral wall of the separator drum opposite to the suction chamber.

₂, ^jREΛ^'» OMPI