US 3575749 A
Description (OCR text may contain errors)
Aprifi m, 171 m K. K. KRYER METHOD FOR MAKING FIBROUS SHEETS 0R WEBS 3 Sheets-Sheet 1 Filed Jan. 4, 1968 ATTORNEY BY M flwm MM Apnl 20, 1971 K. KROtER 3,575,749
I METHOD FOR MAKING FIBROUS SHEETS OR WEBS Filed Jan. 4, 1968 3 Sheets- Sheet 2 INVENTOR A rifi mwm I K. KRQYER 3,575,749
I METHOD FOR MAKING FIBROUS SHEETS OR WEBS Filed Jan. 4., 1968 3 Sheets-Sheet 5 United States Patent O US. Cl. 156--62.2 3 Claims ABSTRACT OF THE DISCLOSURE A method of making fibrous sheets or webs containing a binder by causing a stream of gas containing fibres to pass a gas permeable forming surface so as to form a fibre layer thereon and bonding together the fibres of the fibre layer by means of a binder. Apparatus for making fibrous sheets or webs containing a binder which apparatus comprises means for creating a stream of gas containing suspended fibres through a gas permeable forming surface so as to form a fibre layer thereon, means for applying a binder to the fibres and means for causing the binder to bind together the fibres of said fibre layer. Plate material consisting of a number of embossed fibre sheets which are glued together and which are formed by causing a stream of gas containing suspended fibres to pass through a permeable forming surface so as to form a fibre layer thereon and bonding together the fibres of the fibre layer by means of a binder. Fibrous sheet or web consisting of two outer layers which have been prepared from cellulosic fibres and other fibres, if any, and a binder by causing a stream of gas containing suspended fibres to pass a gas permeable forming surface so as to form a fibre layer thereon and bonding together the fibres of the fibre layer by means of said binder and at least one intermediate cellulosic fibre layer which is bonded to the inner side of the outer layer(s) by means of a binder.
BACKGROUND OF THE INVENTION This invention relates to a method of making fibre sheets or webs containing a binder.
It is Well known to manufacture paper-like sheets and webs consisting of cellulosic fibres and a binder by forming on an endless metal band a binder film and supplying to said binder film cellulosic fibres which are caused to form a uniform fibre layer on said binder film by means of an electrostatic field, the fibres being given an electric charge which is opposite to the electric charge of the metal band.
However, it has been found that the cellulosic fibres behave in the desired manner in the electrostatic field only if their moisture content is kept Within narrow limits viz about 21%. Such a moisture content can be maintained with difficulties only because the cellulosic fibres are very hygroscopic. A higher or a lower moisture content reduces the efficiency of the fibre transport to the metal band. At a higher moisture content than about 21% the fibres tend to form lumps so that a non-uniform product is formed. Other fibre types than cellulosic fibres have another optimum moisture content than about 21% and consequently difiiculties arise when using mixtures of two or more fibre types e.g. cellulosic fibres and synthetic fibres in the above mentioned method.
The object of the invention is to eliminate said difiiculties in the manufacture of fibre sheets and webs.
3,575,749 Patented Apr. 20, 1971 It has now been found that this object can be achieved by the method according to the invention which method is characterized by the fact that a stream of gas containing suspended fibres is caused to pass a gas permeable forming surface to form a fibre layer thereon and that the fibres in said fibre layer are bonded together by means of the binder.
By using a suitable gas permeable forming surface the gas containing suspended fibres passes through said surface and all or essentially all fibres are retained by said surface so as to form said fibre layer thereon.
Since the gas fiow rate through a given area is gradually reduced as more and more fibres are deposited a uniform fibre layer is formed all over the forming surface independent of the point of supply of the fibres.
Due to the fact that the fibres which are supplied to the gas permeable forming surface are suspended in the gas in which they have been able to assume their natural form which as far as natural fibres are concerned means that they are bended and irregular, the fibres will be strongly entangled during the deposition on the forming surface so as to form a very voluminous fibre layer.
'Furthermore, the irregular and bended fibres impart to the products formed a textile-like surface. The voluminous character of the products also facilitates the embossing of said products.
The fibres used are preferably cellulosic fibres but numerous other natural fibres are also suitable. Furthermore, synthetic fibres may be used either alone or in admixture with natural fibres. The strength of the product is generally increased by using increasing amounts of synthetic fibres.
The selection of the binder for use in the method according to the invention depends on the nature of the desired product. If it is desired to make paper or a paperlike product (a relatively rigid product) starch or starch derivatives e.g. dialdehyde starch are preferably used. In the manufacture of textile-like products (soft products) latex binders such as acryl latex emulsions or butadiene styrene emulsions are preferably used. By using relatively great quantities of a water-insoluble binder, a water repellent product can be prepared e.g. a product which is suitable for the manufacture of raincoats.
The binder may be incorporated in the fibre material before the formation of the suspension of fibres in the gas or may be applied to the forming surface simultaneous- 1y with the formation of the fibre layer. However, the application of the binder is preferably effected after the formation of the fibre layer. The binder is preferably applied by spraying or by means of a doctors knife.
Spray application of the binder presents the advantage that the binder is not only applied onto the surface of the fibre layer but also in the interior thereof. This results in the formation of a product in which the fibres are strongly bonded together. By using a suitable forming surface the fibre layer may be removed from said surface without destroying it and may be subjected to a further treatment. The bonder may also be applied to the fibre layer formed by passing said fibre layer through a binder bath. The product may also be subjected to a pressing operation, e.g. by means of rollers, so as to bring the fibres in intimate contact with each other and to bind said fibres together by means of said binder. In order to facilitate the removal of a solvent, if any, and to cause the binder to cure quickly, the product may be heated simultaneously with the pressing or rolling operation. This may be effected by passing the material through the nip of heated rollers.
In order to effect a further strengthening of the product one or more further layers of binder may be applied subsequently and it may then be subjected to further pressing and rolling operations, if desired.
Instead of blowing a stream of gas containing suspended fibres against the gas permeable surface said gas stream is preferably created by removing gas by suction from the down-stream side of the forming surface. In this manner it may be ensured that all the fibres supplied are deposited on the forming surface and that no excessive deposition of fibres takes place at the clearance between the forming surface and the shaft through which the fibres are supplied. This embodiment of the method according to the invention is particularly suitable in the continuous making of fibre webs in which the forming surface in the form of a band is passed through the stream of gas containing suspended fibres.
The forming surface used for making fibre webs is preferably a wire i.e. an endless foraminous metal band. A bronze wire is particularly suitable. Gas permeable bands consisting of other materials than metal, e.g. rubber and plastic, may also be used.
The gas permeable surface may also be a porous scrim in the form of a sheet or a web and in this case said scrim forms an integral part of the final product.
By using a suitable scrim the fibres will not only be interweaved but they will also be entangled in the scrim. By using a net parts of the fibre ends will be drawn through the holes of the scrim so that they will become visible on the other side of the net.
During the subsequent application of binder or binder solution the fibres will be caused to adhere to each other and the fibre layer will be bonded strongly to the net. If the material thus formed is rolled and heated, if desired, to accelerate the curing of the hinder the above men tioned effect will be intensified.
According to a preferred embodiment of the method of the invention the scrim is introduced successively in separate gas streams containing suspended fibres and passing through the scrim from opposite sides. This results in the formation of a product containing a scrim as a reinforcing member and having at both sides fibre layers which cause the product thus formed to assume a textilelike appearance.
In order to strengthen the bonding of the fibres to each other and the bonding between said fibres and the scrim a binder may be applied to the scrim before it is introduced into the gas stream or gas streams.
The scrim is preferably a wide-meshed textile material such as a gauze and particularly preferred is so-called paper gauze in which the size of the meshes is about 0.5 cm. and which is used for reinforcement of envelopes. Also perforated plastic films may be used.
In order to impart a high tear strength to the product formed, the scrim is preferably stretched during the application of the binder and the fibres so that curves, if any, formed by the threads of the scrim are removed. If the product thus formed is subjected to a tension, this tension will be absorbed immediately by the scrim instead of the fibre layer as the case would be without a preliminary stretching of the scrim, 'which fibre layer normally possesses less strength than the textile material. Thus, the strength of the scrim and the fibre layer is combined if the product is stretched.
The method according to the invention is particularly suitable for the manufacture of fibrous webs in which the scrim web passes means for applying a binder on both sides of the web. These means preferably consist of rollers. After having passed said rollers the Web is passed through opposite directed gas streams containing suspended fibres. Instead of passing the scrim through separate gas streams a preferred embodiment of the method acording to the invention consists in passing the scrim in a looped path having one run passing below means for supplying a fibre suspension, and another run passing above means, e.g. a suction box, for discharging gas and creating between said supplying means and the suction means a stream of fibres suspended in the gas. This method utilizes only one gas stream containing suspended fibres which primarily are caught by the run passing below the fibre supplying means and which form a fibre layer thereon. The fibres which pass through the scrim and move towards the suction means will be caught by the second run in the looped path and will be deposited on the opposite side of the scrim. Thus, fibres are applied on both sides of the scrim simultaneously and only a small part of the fibres are sucked out through the suction means. The fibres sucked out through the suction means may be recycled to the fibre supplying means. The product thus formed may be subjected to a further treatment, e.g. drying, and may be used for the manufacture of products having a textile-like character, e.g. curtains, table cloths, sheets, slips and napkins. The product prepared by said method may also be embossed and coloured and is then suitable for use in the manufacture of garments such as disposable smocks and dresses.
A flexible thermo insulating fibrous material may be prepared by another embodiment of the invention by using as the gas permeable forming surface a gas permeable foamed plastic layer. When manufacturing such a flexible thermo insulating fiber material a binder is applied upon a thin gas permeable foamed plastic layer in the form of a sheet or a web and a stream of gas containing suspended fibres is then caused to pass the foamed plastic layer so as to form a fibre layer thereon.
The use of a foamed plastic layer as gas permeable forming surface is particularly advantageous because the foamed plastic layer has a very great surface to which the fibres in the fibre layer may be bonded. When the product thus formed is stretched no delamination will take place due to the fact that the bonds between the foamed plastic layer and the fibres are stronger than the bonds between the fibres. Therefore, the fibres will follow the foamed plastic layer if the product is stretched. If the amount of binder or fibres or both are varied within certain limits a desired flexibility may be imparted to the product.
The pores in the foamed plastic layer impart to the product a high insulating power and especially in cases when fibre layers are applied to both sides of the foamed plastic layer. The thickness of the foamed plastic layer is preferably between 0.5 and 2 mm. and the hole or pore size is about 1-5 mm. depending on the thickness of the layer. As mentioned above the foamed plastic layer has to be gas permeable and therefore a material consisting of polyurethane is preferably used. A preferred commercially available product of this type has an open lattice which has been formed during the manufacture of the material by causing the walls between the bubbles formed during the foaming process to disappear.
When using a foamed plastic layer the fibres will be mutually entangled and will also be entangled in the plastic layer. Furthermore, depending on the thickness of said layer a part of the fibres will penetrate said layer and the free fibre ends which will then project from the opposite side of said layer will cause that the final product assumes textile-like character.
In view of the fact that fibres and particularly cellulosic fibres tend to form lumps, the fibre material is preferably subjected to a defibration during which fibre lumps, if any, are dissolved, immediately before the fibres are brought into contact with the forming surface. In order to ensure that all fibre lumps are subjected to such a defibration and to make sure that no lumps are introduced onto the forming surface so as to form a nonuniform prodnct the stream of gas containing suspended fibres is preferably screened immediately before the fibres are introduced onto the forming surface.
In the prior art wet process for the manufacture of paper a fibre layer is formed by removing water from the fibre suspension introduced onto the wire and essentially all fibres in said fibre layer are located in one plane in which the crossing fibres are bonded together by means of so-called hydrogen bonds.
The formation of hydrogen bonds depends on the presence of water and hydrogen bonds are formed only to a limited degree in the above mentioned dry forming process.
However, hydrogen bonds may be formed by the method according to the invention if the fibre layer formed is moistened with water. The moistening does not decrease the softness of the product to any significant degree and does not result in the formation of a product in which the fibres are located in one plane only. The moistening of the fibres may be effected in a separate operation during which water is sprayed onto the fibre material after the application of the binder. The moistening may also be effected by using an aqueous binder solution containing sufiicient water to cause the hydrogen bonds to be formed.
Hydrogen bonds formed between fibres applied on opposite sides of a scrim improves the adherence of the fibres to the scrim. Furthermore, the moistening of the fibre reduces the tendency to form dust.
The bonds between fibres applied on opposite sides of the scrim may be further increased by an initial application of thin fibre layers on both sides of the scrim and subsequently, moistening and drying said fibre layers before a further application of fibres and binder 1s effected to obtain the desired thickness. In this manner the fibres applied from both sides of the scrim are entangled in said scrim and consequently both fibre layers become firmly bonded to said scrim.
By moistening a fibre layer to which a binder has been applied the binder may be made plast c. Consequently, the fibres may be easily displaced relative to each other during a subsequent embossing. Therefore, a moistened product may be subjected to a strong embossing so as to form tag. a relief printing. During such an embossing operation the fibres are also brought in intimate contact with each other and during the subsequent drying of the product to cure the partly plasticized binder the fibres will be strongly bonded together and the print Wlll be fixed.
If the product is moistened with the ob ect of facilitating the embossing thereof the binder is preferably of a type which is water soluble or which may be plasticized by water. Examples of such binders are b nders based on starch, e.g. oxidized starch, and polyvinyl alcohol. Other combinations of a moistening agent and binder may also be used. The product prepared by the above mentioned moistening and embossing method can be used e.g. as packing materials. Thus, these products may be used instead of corrugated paper and for the manufacture of moulded packings. Furthermore, these products may be used for the manufacture of stamped wall paper and as products for construction purposes.
The embossing of the product prepared by the method according to the invention is preferably carried out in such a manner that the fibres within the embossed areas are pressed strongly together so as to form a reinforcing network. The intermediate areas which consist of relatively loosely bonded fibres present a textile-like character.
A product which has been suitably embossed, e.g. w th a pattern corresponding to that of a loosely woven textile fabric to form a reinforcing network possesses a considerable burst strength. The strength properties are 1mproved as the embossing area is increased. However, at the same time the volume of the product is decreased. A satisfactory burst strength and a textile-like appearance and feel may be obtained with an embossed area of up to 50% of the total area. The product is preferably embossed in an esthetic pleasant pattern. .Such products are particularly suitable for the manufacture of garments, curtains and bed linen.
The invention also relates to an apparatus for carrymg out the above mentioned method. This apparatus is characterized by the fact that it comprises means for creating 6 a stream of gas containing suspended fibres through a gas permeable forming surface so as to form a fibre layer thereon, means for applying a binder onto the fibres and means for causing the binder to bind together the fibres of the fibre layer.
In a preferred embodiment of the apparatus according to the invention the means for creating a stream of gas containing suspended fibres through the forming surface consist of a suction box located at the down-stream side of the forming surface. As mentioned above the use of a suction box ensures that all fibres are deposited on the forming surface and eliminates a deposition at leaks between the forming surface and the supply shaft for the gas stream.
The apparatus according to the invention may also comprise means for subjecting the fibres contained in the gas to a defibration treatment immediately before they are brought into contact with the gas permeable forming surface. A screen for separating fibre lumps, if any, is preferably located between the means for subjecting the fibres to a defibration treatment and the forming surface.
The apparatus according to the invention may also comprise means for subjecting the fibre layer to a pressing operation before it is removed from the forming surface. Furthermore, means for spraying a binder onto the fibre layer may be provided.
The gas permeable surface in the apparatus according to the invention is preferably an endless gas permeable band. As mentioned above the forming surface may also consist of a scrim in the form of a web. When employing such a forming surface the apparatus used preferably comprises means for introducing the scrim in gas streams containing suspended fibres and passing in opposite directions. The apparatus may also comprise means for applying binder on both sides of the scrim before it is introduced into said gas streams.
A preferred embodiment of the above mentioned apparatus comprises means for passing the porous scrim through a looped path having one run passing below a means for supplying a suspension of fibres in a gas and another run passing above a means for discharging gas and means for creating a stream of gas containing suspended fibres between the supply means and the suction means.
Another apparatus for carrying out the method according to the invention comprises a first endless gas permeable band having an upper run serving as a forming surface and a suction box located below said upper run, a second perforated band which is mounted above that part of the first band at which the suction box is located, means for supplying a fibre material to one end of the lower run of the upper band, means for removing fibre material from the other end of said lower run and intermediate means for performing a defibration of the fibre material.
In said apparatus only that part of the fibre material which has been sufiiciently defibrated to pass the holes in the upper band reaches the forming surface and that part of the fibre material which has not been sufficiently defibrated under the influence of the defibration means will be removed from the lower run of the upper band. The material thus removed may be subjected to a more severe defibration, if desired, and recycled to the supply means to the lower run of the upper band.
The apparatus according to the invention may also comprise means for moistening the fibre layer with water. Means for subjecting the fibre material to an embossing may also be provided. The embossing means are preferably embossing rollers which may be heated, if desired.
The invention also relates to a fibrous material in the form of plates which fibrous material is characterized by the fact that it comprises several embossed fibrous sheets which are glued together and which are prepared by the above mentioned method.
As mentioned above the fibre layers prepared by the method according to the invention may be strongly embossed especially when moistened without rupturing the material because the fibres may be displaced relative to one another. The embossing is preferably effected when the fibre sheets have been rolled to produce a smooth and even surface but before they are subjected to a drying process to cure the binder. The height of the printed pattern in the fibrous sheets prepared by said method may be several times the thickness of the fibre sheets. By gluing such fibrous sheets together a product is formed having a high rigidity and also high insulation power which is due to the cavities formed between the projections of the embossed sheets.
The shape of the products consisting of relatively thin paper-like sheets of fibres and binder does not change significantly when they are subjected to changes in temperature and moisture content of the surrounding air. The plate material according to the invention is, therefore, particularly suitable for use as a binding material, e.g. as lining plates and plates for construction of partition walls and outer walls. The low weight of the product is very important when the product is used for these purposes.
It it is desired to obtain a surface other than the one obtained by using an embossed fibre sheet as outer layer the material according to the invention may be provided with non-embossed covering layers consisting of the material forming the embossed fibre sheets or other materials, e.g. metals, such as aluminum foil, plastic foil or textiles.
Furthermore, the product may be made water-proof and fire-resistant by using a suitable binder.
The fibrous plate material according to the invention which combines a high strength, stability, and insulation power as well as a low weight and which is prepared from commercially available and reltaively inexpensive raw materials may be used for many purposes.
For hygenic reasons and in order to save labour in washing, cleaning and disinfecting operations it would be desirable at, for example, hospitals, rest homes and hotels to dispose of bed linen after the use thereof. However, the relatively high costs of woven textiles have made such a disposal of bed linen uneconomic. Therefore, many attempts have been made to manufacture less expensive materials having the properties of woven textile products.
A primary requirement to such materials is that they have a relatively soft and smooth surface so that they feel pleasant when they are brought into contact with the skin. Furthermore, these products should be capable of absorbing moisture both in vapour form and in liquid form. Finally, in some instances it would be desirable if the product was thermo insulating.
According to the invention there is provided a fibrous material in the form of sheets or webs which fufils these requirements and the characteristic feature of said material is that it consists of two rolled outer layers which have been prepared from cellulosic fibres and other fibres, if desired, and a binder by a dry process and one or more intermediate fibre layers which are glued to the interior side of the outer layers by means of a binder.
As mentioned above fibre layers prepared by a dry process are voluminous and if such fibre layers are rolled a smooth and even surface is created without losing the textile-like character of said product. The material according to the invention presents the advantage of having such outer layers with a pleasant feel and also of having relatively good strength properties.
The layers of cellulosic fibres glued to the interior side of said outer layers are capable of absorbing great amounts of moisture and consequently the material according to the invention becomes strongly water-absorbing. Furthermore, by using several fibre layers applied on top of each other and glued together by means of a binder a resilient and heat insulating material may be obtained.
The presence of one or more fibre layers between the outer layers also facilitates the embossing of the material according to the invention.
The material in question may be used not only for the manufacture of bed linen such as sheets, slips, etc. but also for the manufacture of diapers, sanitary towels, dishcloths, towels, dish-towels and similar absorbing materials. By gluing several layers together a thermo insulating material is obtained which material may be used instead of blankets. When using a thermo plastic binder several layers may be glued together by placing the layers on top of each other and generating an electric heating, e.g. a dielectric heating, in the area in which the layers con tact each other.
BRIEF DESCRIPTION OF THE DRAWING The invention will now be further described with reference to the drawings, in which FIG. 1 is a schematic view of a preferred embodiment of the apparatus according to the invention,
FIG. 2 is a schematic view of another preferred embodiment of the apparatus according to the invention,
FIG. 3 shows a horizontal view of a plate material according to the invention,
FIG. 4 shows a cross section along the line IV-IV of the plate material shown in FIG. 3 on an enlarged scale,
FIG. 5 shows a cross section through an embodiment of a sheet fibre material according to the invention, and
FIG. 6 shows the surface of another embodiment of a sheet material according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 of the drawings 1 is a roll of a textile net 2 having a mesh size of about 0.5 cm. This textile net is passed through a looped path in which the lower run passes through the nip between two rollers 3, 4 for the application of a binder solution contained in containers 5, 6 on said net. The binder solution is transferred from the container 5 to a roller 3 by means of three intermediate rollers 7, 8 and 9. In a similar manner binder solution is transferred from the container 6 to the roller 4 by means of an intermediate roller 10. When the net has passed the nip between the rollers 3, 4 it is passed above a suction box 11 and around a roller 12 from which it passes in an upper run in a direction which is opposite to the direction of movement in the lower run.
In the upper run the net 2 is passed below a shaft 13 through which a suspension of fibres in a gaseous medium is supplied. During the continued movement in the upper run the net 2 passes two nozzles 14, 15 from which a binder solution is sprayed on both sides of the net. Then the net passes through the nip of two drying rollers 16, 17 and to a roll 18 on which the final web material is wound. The apparatus shown in FIG. 1 also comprises a casing 19 which is located between the lower and upper run of the net 2 and which forms a compartment between said two runs.
The apparatus shown operates in the following manner:
When the net 2 is advanced in the above mentioned path binder solution is applied on both sides thereof by means of the rollers 3, 4 which by exerting a pressure on the net impregnate the net with binder solution.
The application of fibres on the net impregnated with the binder solution is effected by supplying a suspension of fibres in a gas through the shaft 13 and by discharging gas through the suction box 11. The major part of the suspended fibres will be caught by the upper run of the net and will form the primary fibre layer on the side of the surface which in the upper run of said net is upside. The fibres passing through the upper run will fall through the compartment formed by the casing 19 and reach the upper side of the net in the lower run and will be caught by the net. After the application of fire layers on each side of the net it is passed between the nozzles 14 and 15 which serve to spray a further amount of binder on the fibre layers. After the application of said binder the material thus formed is passed through the nip of the rollers 16 and 17 which serve to press the binder into the material and to bond the fibres together. Furthermore, the rollers may be heated so that the material is dried when passing the rollers. The product thus formed is finally wound on the roll 18.
-The roller 12 may be rotated with a peripheral speed different from that of the net so that during the movement of the net the fibre layer applied to that side of the net facing the roll is smoothened. 1
In FIG. 2 of the drawings 21 is an endless gas permeable band mounted on two rollers 22, 23 of which at least one is driven by a motor (not shown). A suction box 24 having a considerable length in the direction of movement of the band is mounted below the upper run of said band 21. The band 21 passes through the nip of a net of rollers 25, 26 and below a nozzle 27 to which binder is supplied. Another endless band 28 which is perforated in such a manner that single fibres may pass said band is mounted above the band 21. The band 28 is mounted on a roller 29 and a drum consisting of two end plates 30 which are connected with horizontal rods 31. The apparatus shown in FIG. 2 also comprises a supply means 32 for fibres and a suction means 33 which opens into the interior of the above mentioned drum. Three rakes 34 which may be caused to rotate around a vertical axis immediately above the band 28 are mounted above the lower run of said band.
The apparatus shown also comprises two sets of rollers 35, 36 and 37, 38 respectively and a nozzle 39 which is mounted between said sets of rollers and to which binder is supplied. Furthermore, the apparatus comprises a roll 40 for winding the final product and a screen 41 which is mounted between the upper band 28 and the lower band 21.
The apparatus shown in FIG. 2 operates in the following manner:
A fibre material 42 is introduced on the lower run of the band 28 through the supply means 32. The band which is moved in the direction shown in FIG. 2 moves the fibre material which does not pass through the holes of the band 28 to the rakes 34 at which point the fibre material is subjected to a defibration. Thereby, the major part of the fibre material becomes defibrated so that it can pass through the holes of the band 28. The remaining part of the fibre material passes into the drum and is sucked away through the suction means 33. The material removed from the drum may be subjected to a more severe defibration and may then be recycled to the supply means 32.
The fibre material which passes the holes of the band 28 and which are not retained by the screen 41 falls down on the band 21 on which it is moved in the direction shown in FIG. 2 and forms a fibre layer when air is sucked away through the suction box 24. The fibre layer thus formed is rolled when passing the nip of the roller set 25, 26 and a binder is then applied by means of the nozzle 27. The material thus formed has such a strength that it can be removed from the band 31 and passed through the set of rollers 35, 36 and past the nozzle 39 at which binder is applied on the side of the material facing downward on the band 21. When the material has passed the set of rollers 37, 38 it is wound on the roll 40. The rollers 36 and 38 are preferably heated so as to remove the moisture supplied together with the binder.
The fibre material, if any, retained by the screen 41 is removed continuously or discontinuously and recycled to the supply means 32.
The plate material shown in FIGS. 3 and 4 of the drawing consists of a number of fibre sheets 51 which on both sides are provided with raised areas 52 prepared by embossing the sheet material. The raised areas 52 on one sheet are glued together with the raised areas 52 on another sheet. The product thus formed which has a great number of inner voids is thermo insulating and sound-absorbing.
In FIGS. 5 and 6 of the drawing 61 and 62 are rolled fibre layers of cellulosic fibres which layers have been prepared by a dry process. Cellulosic fibre layers 63 and 64- are glued to the inner side of the outer layers 61 and 62 which are connected at 65. The bond between the outer layers 61 and 62 can be effected for example by subjecting a folded material to an embossing.
The product shown in FIG. 6 of the drawings is formed in a similar manner as that shown in FIG. 5 but is provided with another embossing pattern.
What I claim is:
1. In a method of making fibrous sheets or webs containing a binder by causing a stream of gas containing suspended fibres to pass through a gas-permeable foamed resin layer so as to form a fibre layer thereon and bonding together the fibres of the fibre layer by means of a binder, characterized in screening the fibre-containing stream of gas and subjecting any fibre lumps contained therein to a defibration treatment immediately before introducing said fibres onto the gas-permeable foamed resin layer.
2. The method according to claim 1, characterized in that the foamed resin layer is of a thickness of between 0.25 and 2 mm. and a pore size of between 1 and 5 mm.
3. In a method of making fibrous sheets or webs containing a binder by causing a stream of gas containing suspended fibres to pass through a porous reinforcing web so as to form a fibre layer thereon and bonding together the fibres of the fibre layer by means of a binder, characterized in screening the fibre-containing stream of gas, subjecting any fibre lumps contained therein to a defibration treatment immediately before introducing said fibres onto the porous reinforcing web, moving the gas-permeable forming surface through a looped path having one run passing below means for supplying a suspension of fibres in the gas and a second run passing above a means for discharging gas by suction and creating a stream of gas containing suspended fibres between said supply means and said suction means.
References Cited UNITED STATES PATENTS 2,152,901 4/1939 Manning 156-370X 2,755,215 7/1956 Talalay et al l56-62.4 3,081,207 3/1963 Fox 156-62.4X 3,150,215 9/1964 Houghton 156-370X SAMUEL W. ENGLE, Primary Examiner I. J. DEVITI, Assistant Examiner US. Cl. X.R. 156-370, 377