Method and apparatus for foam forming

The present invention relates to a method of foamed non-woven fabric production and a device for foamed non-woven fabric production. The method and apparatus according to the invention are particularly suitable for the production of various fibrous products from cellulose, glass fiber, aromatic polyamide, sisal or other suitable fibrous material. Particularly suitable for the production of complex, multi-layer laminates used, e.g. for the production of various parts of vehicle bodies, device housings and other, almost countless applications. The method and apparatus of the invention are intended for use in the manufacture of products using long fibers or even continuous fibers, tapes or meshes. The foam as described in the invention means a foam composed primarily of water and a surfactant.

The products of the preferred embodiment of the invention are in many cases intended to replace sheet metal structures, since sheet metal structures and other suitable metal structures need to be supervised and maintained both during manufacture and in use to avoid, for example, rusting. .

Metal surfaces are also sensitive to even light impacts, as impacts can cause either simple aesthetic changes or damage to the paint film. As a consequence, it can cause rusting, especially in applications where structures are exposed to corrosive substances.

Various laminates and sandwich constructions are more durable in the above-mentioned applications, but their price is in some cases slightly higher than the aforementioned sheet metal constructions. One of the reasons for the higher cost is the complicated production technology. The example below relates to the manufacture of a car hood or fender.

It is obvious that the part of the hood or fender of the car, visible from the outside, must be very smooth. Otherwise, the painted surface - another example is the boat hull will reflect light unevenly, which is considered a sign of poor quality and inaccurate workmanship. In other words, laminates must have a surface smoothness similar to that of metal sheets. In practice, this means that if a product is made of, for example, glass fiber, very fine fibers must be used. A characteristic feature of such thin fibers is that the laminate made of them is not sufficiently durable in operation, for example, as a car fender. Therefore, a fiberglass fender has to be manufactured with several different layers. The required strength and durability dictate that there should be a construction layer with relatively coarse fibers, approximately 45-50 mm in length, sometimes more and sometimes less.

As a minimum, said two layers are sufficient to achieve the required appearance and strength, but automation of production causes problems. First, it is obvious that the process requires the use of a mold to accurately reproduce the shape of the product. The easiest way is to make a one-piece mold, in which the surface mat is placed first, and then the resin. A reinforcement mat is then placed on top of which the next layer of resin is applied and the layers are rolled to remove any air bubbles. However, this manufacturing method is entirely manual production, since both the spreading of the resin and the squeezing of the air bubbles must be optically controlled. Moreover, such a laminating process is harmful to health even under good conditions due to the gases generated during production.

Said manual work has been replaced in the industry by a method in which a resin is applied to a surface layer in a mold, after which, for example, a reinforcement mat is applied to the resin. The resulting laminate is thus pressed by the other half of the mold to give the desired shape, which also forces the resin through both layers.

US Patent No. 5,672,309 describes an injection molding process in which a surface layer is first placed in a mold and another layer is placed on top of it. One of the layers has a hole in the right place. The two superposed layers are then pressed against each other with the other mold half so that the mold edges clamp. In this phase, with the help of nozzles, the resin is injected between the layers through an opening in one of the layers, placed opposite the nozzle in one of the mold halves, so that when the mold is fully closed , the resin spreads throughout the mold and impregnates both layers. .

A further improvement of this method is the vacuum injection molding process, in which the mold consists of two parts placed on top of each other, the required

The glass fiber layers are sandwiched therebetween. Such a production technique is mentioned in published Japanese Patent Application No. 58-168510. In addition, holes have been arranged in the part or parts of the mold for injecting resin into the mold and, accordingly, holes have been arranged for removing air replaced by the resin. The term vacuum injection molding is used when suction is used to remove air.

If the said product, i.e. car fender, it is made of the said two layers, that is, the surface layer and the reinforcement layer, it can be quickly seen that the resin does not spread evenly in the glass fiber layers, unless the resin is introduced between the layers when the mold is slightly open, like described in US Patent No. 5,672,309 or holes are made, one very close to each other, at least in the part of the mold facing the reinforcement layer. This is because when compressing the layer of glass fibers, they do not allow the resin to flow freely along the layer and the main flow direction of the resin is perpendicular to the layers. Thus, if it is necessary to produce a two-layer product by vacuum injection molding, either the mold must be partially open or one of the mold halves must be almost completely perforated for the resin to spread evenly inside the mold. The latter option, however, is an unnecessarily costly solution as each resin inlet must in practice include a resin feed pipe with a conduit attached thereto.

A solution to this inconvenience has been suggested by using a special flow layer composed of relatively thick, possibly uniform, hollow fibers which facilitate the flow of the resin along the layer. It would of course be advantageous if the reflow layer could act as a product reinforcement layer, but in practice this is not possible, especially in the surface layer, due to the high thickness of the reflow layer fibers. The smoothness of the surface layer would not meet the requirements of the product. Coarse and / or hollow fibers do not exhibit the maximum strength of the reinforcement layer and therefore cannot be used as reinforcement layers at least in more demanding applications.

Thus, the result is that at least three different layers are needed in this example, unless a partially open mold method is used as described in U.S. Patent No. 5,672,309. In other instances, the following layers are required: surface positioned on the outside of the product, a reinforcement layer positioned inside, and a slump layer between the two layers.

If the production process, analyzing the entire production chain, should be automated, we can describe the product manufacturing method used so far. This is well described in the aforementioned Japanese Published Application No. JP 58-168510, where each layer is put into the mold separately, then the mold halves are pressed against each other and the resin is injected into the mold. In other words, each layer of the laminate is inserted separately into the mold. In practice, this means that each layer is produced separately, handled separately, and each layer is unwound into the mold from its own spool.

The reason for producing each layer separately is that no methods have yet been developed for producing multi-layer products that achieve the desired quality of the final product in terms of both appearance and strength.

Mention should be made of an intermediate production method in which separately produced nonwovens are joined by needling such that at best only one multilayer fibrous mat has to be inserted into the mold. However, it has been found that despite the easier transportation of the fiber mat and the simplification of product manufacturing, the end result is not as good as might be expected. Needling different nonwovens together also creates displacements in the surface layer, with the stitches visible on the surface of the final product, even if the surface itself is smooth. This results in a situation where the reinforcement layer and the flow layer may be needled with each other in the exemplary three-layer product, but the surface layer must be separate. In other words, the additional needling step reduces the number of mats processed separately from three to two. This causes a certain skepticism about the use of needling.

There are several ways to make a nonwoven fabric to be used as a laminate layer. These include the so-called aqueous process, best known from the nonwoven fabrication system used on the paper machine, the foam process developed by Wiggins Teape since 1970, and the so-called

By air. All the mentioned methods can be used as needed to produce multilayer products, but so far none of the methods have been able to produce products of sufficient quality for the products discussed in this application.

In the aqueous method, the problems associated with the fibers used in the above-mentioned solutions relate to uncontrolled lumping of the fibers already in the headbox, curling of the fibers, opening of the strand of fibers, etc. The cause of the problems mentioned is the high turbulence used in the aqueous method which, on the one hand, opens up already bonded strands of uniform size and, on the other hand, curls individual strands, and when the suspension is stirred, curly fibers can accumulate and bind other fibers into closed strands of fibers. Moreover, the aqueous method is very sensitive to changes in consistency, which in effect means that the consistency must be carefully kept in order for the process to function properly.

When using the aqueous process to produce multilayer products, the layers of the fibers are mixed too much due to the high level of turbulence in the aqueous process, so that the different layers cannot perform their function optimally. Moreover, it should be noted that the aqueous method was developed from the beginning for the production of nonwovens from cellulose fibers, for which it is very advantageous. In other words, the size and stiffness of cellulose fibers are suitable for aqueous suspensions. Thus, the turbulence present in the aqueous method does not curl the cellulosic fibers and mix them excessively but optimally in view of the formation of the nonwoven fabric and the operation of the headbox. However, since different laminates and sandwich constructions use different fibers, most often starting from glass fibers and ending sometimes, for example, with aromatic polyamide fibers, sometimes carbon fibers, and even sisal or jute fibers, the requirements for the non-woven fabric production process resulting from of different fibers, are often different from the processing requirements of cellulosic fibers. For example, the size and stiffness of the fibers used in laminates and sandwich constructions differ significantly from the size and stiffness of the cellulosic fibers.

The level of turbulence present in the aqueous method is greatly dependent on the viscosity of the water, which in effect means that the level of turbulence is relatively constant, at least with regard to the requirements of the various fibers. This of course means that with certain types of fibers, for example polyester or viscose, the turbulence causes the fibers to bend and twist, which causes the fibers to wrap around one another, creating knots and a large accumulation of fibers that cannot be dispersed in any subsequent step. process.

In a dry process, on the other hand, it is difficult to establish any kind of natural linkage between the fiber layers because there is no mixing turbulence either between individual fibers or strands, or between the layers of fibers. Instead, each layer forms its own easily separable layer which inevitably affects the quality of the end product.

In the air method, the length of the fibers is limited as the fibers are spread over a nonwoven fabric from a screen which cannot work with long fibers. If the fiber layers need to be attached to each other using the air method, the layers have to be needled, which causes changes to the surface of the needled layers, or a special bonding between the layers has to be used. However, this stiffens the product and makes it difficult to roll up. In addition, curling a rigid product can cause interlayer cracks, which can also degrade the quality of the product. Moreover, it is typical of the air method that relatively large local grammage fluctuations occur.

The foam method is situated between the above two nonwoven fabric production methods in terms of the level of turbulence. The turbulence parameters in the foam process are completely different than in the water process. In the foam process, turbulence is typically only used to generate the froth and not after the formation of a uniform foam. In other words, high turbulence is used in the preparation of the foam suspension in the mixing device, although the level of turbulence is, compared to the aqueous method, less by an order of magnitude or several orders of magnitude, which means that in the foam suspension the fibers are not curled or damaged so easy as in the water method. When transferring the froth slurry from the mixing device to the headbox, the flow is virtually completely laminar as in the headbox itself. In the foam suspension, the fibers are bound to the foam bubbles and remain essentially stationary with respect to each other until the foam is removed on the screens of the production device by the action of the suction boxes.

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In the foamed process, consistency is not critical as in the aqueous process, although the consistency of the foamy slurry is an important factor considering the optimal production method for each application. The basic idea in the foam process is to bond individual fibers or fiber bundles of the desired size to the foam bubble or bubbles so that the fibers or fiber bundles do not come into contact with each other before the nonwoven fabric formation step, as this would lead to undesirable fluff formation.

The Applicant has found that in practice the most useful method of producing both monolayer and multilayer products is the foam process, with which each of the different types of fibers can be optimally processed. The froth method is also unlike the method originally developed by Wiggins Teape and described, for example, in US Patent No. 3,938,782. In this method, starting material, e.g. fibers, surfactants, pH regulators and stabilizers etc. are introduced into the mixing device in carefully measured doses, and both foam from e.g. a sieve chamber of the production device and the like is fed into the device. and water, also available from the fluid circulation in the production device. In most cases, all the starting materials needed to make the nonwoven fabric cannot, for various reasons, be mixed together in the same mixing device, but several mixing devices must be used. It is known that, especially when producing a multilayer non-woven fabric, the number of mixing devices must be at least equal to the number of layers of the non-woven fabric. In the device or in the mixing devices, these materials are formed into a foamy suspension which is pumped by a suitably designed pump either into the production device or temporarily into a storage tank.

The foam slurry, introduced into the production equipment, is typically introduced into the inlet tubing of the headbox through the screen chamber. In the sieve chamber, the consistency of the foamy suspension is adjusted to the desired level. Input tubing in the headbox includes a manifold, mating nozzles therewith, and tubing from the nozzles to the manifold. Traditionally, tubing comprises a plurality of flexible pipes made of plastic or rubber arranged to form loops as described in U.S. Patent No. 3,938,782. The purpose of the tubing is to create and maintain turbulence with nozzles positioned in communication between the manifold and the manifold. through the piping so that the foamed slurry remains homogeneous. From the pipes, the foam slurry is introduced into the headbox, the construction of which can be very simple.

The solutions described in US Patent Nos. 6,019,871, 6,136,153 and Canadian Patent Application No. 2301995 may be examples of prior art headbox designs. A headbox is used to dispense foam to produce an even fleece on the wire. The basis weight of the nonwoven fabric can be adjusted, for example, by introducing clean foam into the headbox, depending on the point of introduction, either to dilute the consistency of the original foam slurry or to locally reduce the layer thickness of the original fibrous foam slurry.

In the production of multi-layer products, i.e. the production of so-called multi-layer non-woven material, the headbox may comprise a plurality of compartments each operating independently. An example of such a construction is known from US Patent No. 6,136,153. In some cases, the production of the multilayer nonwoven fabric can also be performed such that the special supply pipes described in U.S. Patent No. 6,238,518 either located inside the headbox or passing through the headbox are used to introduce the foam slurry at the desired location within the nonwoven fabric produced by headbox.

However, it has been found in tests that both the prior art foam production process and the introduction of the foam slurry into the headbox are unnecessarily complicated. Moreover, it has been found that e.g. Both actual processes and tests have shown that these pipes are prone to clogging. In practice, it happens that a single fiber, for example a curled fiber or a strand of strands, is gripped either inside the tube or in the opening of the tube and the held strand or strand then grabs more strands, increasing the size of the strand. Initially, the strand is very porous so that liquid and / or gas can still flow through it, causing fibers and possibly other solids to be trapped in the strand while liquid and / or gas continue to flow through it. As the size increases and the attachment to the pipe or its hole becomes stronger and stronger,

The flock also begins to affect the flow of the liquid and / or gas, eventually blocking the flow through the tube. Clogging of one of the system pipes immediately causes changes to the headbox, which can become large enough to affect the fleece exiting the headbox. Even though clogged pipes can be flushed, if such a possibility has been envisaged in the design of the equipment without completely stopping the production process, it will be labor-intensive at best and will result in relatively large production losses at worst. It has also been noted, which is quite natural, that the longer the fibers of the material, the easier the pipes and manifold are blocked. Naturally, the type of fibers used, mainly the shape and stiffness of the fibers, have an effect both on how quickly the fluff of fibers is formed and on the tendency for the pipes to clog.

Thus, the current foam process, or the practical headbox design used therein, is not always suitable for processing a foam slurry with long fibers. Besides, the fact is that, depending on the type of fibers, traditional headboxes used in the foam process - or rather a pipe system - can process fibers less than 50-100 mm in length.

In some cases, for example when processing thin, soft and / or long fibers, e.g. polyester and 1.7 dtex viscose fibers greater than 30 mm in length, turbulence should not be used at all. In the case of such fibers, even the prior art foaming process cannot be used as even a relatively small turbulence in the mixing device will bend the fibers and mix them so that they wrap one around one another and form fluff which negatively affects both the process and the material. final product. The water method is also completely unacceptable due to the turbulence involved, which is greater than in the traditional froth process.

The addition of certain water-absorbing materials to the non-woven fabric has also proved to be a problem. This is discussed, for example, in US Patent No. 6,019,871. This patent states that the froth process is substantially better than the conventional aqueous process, but since the foam also contains water, the prior froth process also suffers from disadvantages. A disadvantage is, for example, that the water-absorbent polymer used is exposed to foam water for a long time and therefore almost completely loses its property. The above-mentioned publication presents a solution to this problem by, for example, deep freezing or at least cooling the polymer, coating the polymer or simply by introducing the polymer as late as possible into the foam suspension introduced to the screen. All these measures require special equipment, which of course increases the production costs.

While the prior foam process is suitable for the production of multilayer products, such as three-layer products, it has been found impossible to produce long-fiber products with the prior art process, since the aforementioned pipe systems have been found to clog with even shorter fibers. . One of the causes of clogging is that the less stiff fibers are bent, curled and fluff already in the mixing device when forming the foam slurry.

In French Patent Publication No. 1,449,737, the fibers and the liquid from the screen are introduced into a mixer of the type of mixing device located upstream of the screen. The mixing process uses either a mechanical or ultrasonic mixer, which are either not useful or not economical in producing a foam in which, for example, very long fibers or even a mesh are introduced into the headbox. The operation of a mixer of the mixing device type according to the French patent publication mentioned in the discussion of the construction of the headbox for, inter alia, even distribution of the foam suspension on the wire, also remains unclear.

Applicant discusses the manufacturing of the vehicle bumper described in U.S. Patent No. 6,231,094 as another example of the problems associated with traditional stacking materials. The bumper consists of two nonwovens, preferably made of fiber-containing thermoplastic nonwovens that span the entire bumper and of narrower thermoplastic bands, also containing fibers that reinforce the bumper body at appropriate locations. According to the publication, all six nonwovens or tapes are made separately and joined to each other only in the production phase. It is not difficult to imagine how precise and careful laying the nonwovens must be, especially keeping them in place while closing the mold.

The object of the invention is a process for producing foamed nonwoven fabric.

The object of the invention is a device for foaming non-woven fabric production.

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The method of foaming non-woven fabric production in which the fibrous foam suspension is introduced from the headbox of the production equipment into the non-woven fabric section of the production apparatus, and the foam is removed through at least one screen arranged in the non-woven fabric production section to form a non-woven fabric, according to the invention, that at least some of the solids, required to make the foam slurry is introduced into the headbox in a substantially solid state and mixed with the foam in the headbox by introducing the foam under high pressure from the nozzles into the headbox.

Preferably, said foam is produced separately in the foam mixing device.

Preferably, a portion of this foam is taken from the non-woven fabric section of the production device.

Preferably, the chopped fibrous material is mixed with the foam in the headbox and a foam slurry is formed.

Preferably, binders, fillers, dyes, and other materials are added to the headbox foam.

Preferably, the solids are introduced into the headbox with the foam introduced into the headbox to form the foam slurry.

Preferably, the headbox is divided into several parallel or stacked parts for the production of a multilayer non-woven fabric.

Preferably, the continuous fibrous material is introduced into the nonwoven fabric to be produced through the headbox, or through at least one portion thereof.

Preferably, the tape, mesh, mat or other substantially flat material is introduced into the nonwoven fabric to be produced through the headbox or through at least one portion thereof.

Preferably, at least partially different solids are introduced into each part of the headbox.

Preferably, the common solids required in the nonwoven layers produced by the headbox parts are introduced into two or more headbox parts with the foam introduced therein.

Preferably, continuous filaments, threads, cables and the like are introduced into the nonwoven fabric to be produced through the headbox, or at least through a portion thereof.

Preferably, the speed of movement of said material is adjusted to be the same as that of the nonwoven fabric produced.

Preferably, the speed of movement of the material is controlled to be greater than the speed of the nonwoven fabric to be produced.

Preferably, the means for introducing the material directly into the nonwoven fabric to be made in the nonwoven fabricating section is introduced through the headbox through at least part of the headbox.

Preferably, the position of said means is adjusted in the direction of travel of the nonwoven fabric and / or in any direction perpendicular thereto.

Preferably, pipes or channels with nozzles are used as said means.

Preferably, the material used is chopped fiber, a binder, filler or similar solid foam material or slurry.

Preferably, the dry material required for the basic structure of the product is used as said solid material.

A device for foaming non-woven fabric which includes a headbox with outlet openings and a fabric section which also includes one or more screens and means for removing foam placed on the side of the screen opposite to the fabrication, the headbox being provided with means for receiving foam and means for introducing at least one solid material into a headbox according to the invention is characterized by that the headbox is provided with nozzles for introducing the foam under pressure and mixing the at least one dry solid material with the foam to form a foam slurry.

Preferably, the means for receiving foam and the means for mixing the solid material include a headbox reservoir and nozzles for injecting foam into the headbox.

Preferably, the means for receiving foam and the means for mixing solids additionally comprise at least a foam manifold for distributing the foam to the nozzles.

Preferably, the device also comprises at least a foam mixing device and a pump and a conduit system connecting it to the manifold.

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Preferably, at least one foam manifold is connected by means of a pipe system to the foam removal means.

Preferably, the means for introducing solid material comprises at least a solid material dispensing device.

Preferably, the solid material dispensing device is a conveyor or cutting device connected by a balance.

Preferably, the means for introducing solid material comprises a feeding device by means of which the material is introduced into the space under pressurization, for example a rotary dispenser.

Preferably, the nozzles are arranged on opposite walls of the headbox tank and the nozzles outlets are staggered.

Preferably, the nozzles are arranged on opposite walls of the headbox tank and the nozzles of the nozzles are arranged opposite to each other.

Preferably, the nozzles are arranged at different heights on at least one wall of the headbox tank.

Preferably, the foam mixing device is provided with at least a mixer and means for dispensing surfactants and water to the foam mixing device.

Preferably, the foam mixing device is provided with means for dispensing one or a number of solid materials into the foam mixing device.

Preferably, the headbox comprises a plurality of layering parts adjacent to each other in the nonwoven fabric to be produced.

Preferably, the position in the direction of movement of the web of at least one outlet of at least one part of the headbox is adjustable in relation to the other outlets.

Preferably, the headbox, or at least one of its parts, is provided with means for introducing continuous material through the headbox into the nonwoven fabric to be produced.

Preferably, the material introducing means comprises at least regulating rollers or rollers for adjusting the material introduction speed.

Preferably, the material introducing means also comprises means for adjusting the position of the material in the nonwoven fabric to be produced disposed in the headbox closer to the outlet opening.

Preferably, the headbox or at least one part thereof is provided with means for introducing material into the nonwoven fabric to be produced as far as the nonwoven fabricating section.

Preferably, said material is a chopped fiber, binder, filler, or similar solid foam material or slurry, comprising at least a foam and a solid material.

Preferably, said devices are one or more pipes and the like, either stationary or arranged to slide at least in the longitudinal direction of the nonwoven fabric.

Preferably, the headbox is at atmospheric pressure.

Preferably, the headbox is pressurized and the headbox is equipped with high pressure-resistant supply means.

The method and apparatus according to the invention solves, inter alia, the above-mentioned problems, it being a characteristic feature of the invention that dry materials and foam are not mixed to form a foam slurry until they reach the headbox just prior to the introduction of the slurry onto the production equipment screen by introducing high pressure foam from the nozzles into the headbox.

Thus, in the method according to the invention, no grinding device is needed to mix the fibrous material with the foam. Thus, no foam pumps or manifold tubing are needed, let alone pipes located between the manifold and headbox.

Moreover, the process according to the invention is completely insensitive to the materials used in the foam process. The length or stiffness of the fibers can be freely chosen since the fibers cannot clog the thin tubes as there are no such tubes in the path of the fiber to the screen.

Using the method and devices of the invention, it is possible to incorporate, for example, continuous fibers, yarns, tapes, nets or almost any components required in the final product into one or more layers of the nonwoven fabric to be formed.

Other characteristics of the method and apparatus according to the invention will be apparent from the appended claims.

In the following, the device and the method according to the invention are described in more detail with reference to the accompanying drawings, in which Fig. 1 schematically shows an existing device of the method.

Fig. 2 shows a headbox detail related to the prior foam method, Fig. 3 shows a headbox used in the prior foam method, Fig. 4 shows a headbox used in relation to another prior foam method, Fig. 5 shows a headbox used in connection with the third prior froth method, fig. 6 shows a headbox to be used with a fourth prior art foam method, figure 7 relates to the manufacture of a vehicle bumper body according to the prior method, figure 8 shows a headbox according to a preferred embodiment of the present invention, figure 9 shows a headbox according to another preferred embodiment 10 shows a headbox according to a third preferred embodiment of the invention, fig. 11 Fig. 12 shows a head box according to a fourth preferred embodiment of the invention, Fig. 12 shows a head box according to a fifth preferred embodiment of the invention, Fig. 13 shows a head box according to a sixth preferred embodiment of the invention, Fig. 14 shows a head box according to a seventh preferred embodiment of the invention.

Figure 1 shows a prior art foam process, which can be taken as starting with a mixing device 10, in which foam is produced from at least a liquid, preferably water, gas, preferably air and a surfactant, with fibers, fillers being introduced into the foam. , pH regulators, stabilizers, dyes and binders, and other additives to form the foam slurry. Water is introduced into the mixing device 10 via conduit 14, pump 14, and flow meter 16. The water may come, for example, from the water separation system of the production device or from any other suitable source, including a fresh water source. Surfactants 20 are added to the mixing device 10 by means of a balance 18 or the like, the appropriate fibrous material 24 is introduced by a balance 22 or the like, and fillers, stabilizers, dyes, binders, and pH regulators are dosed by means of a balance or multiple. weight 26. Preferably each component is introduced by means of its own metering system. The gas content of the foam suspension thus produced under normal atmospheric pressure and temperature range should be in the range of 50% to 80%, in some cases even outside this wide range. The solids content of the foam suspension is between 2% and 25%, sometimes even lower, depending on the density of the foam, the type and length of the fibers and the product produced. The foam slurry is then introduced from the mixing device 10 through the headbox 40 onto the screen 30, forming a fleece in the manufacturing device to produce the desired product. In the prior art froth process, solids, including the above-mentioned fibrous material, surfactants and fillers, etc., are introduced into a mixing device 10. The mixing ratio of the materials is determined, for example, by feeding each material through a dedicated insertion device connected to a balance to add the amount necessary to obtain the correct ratio per unit time (kg / min). The necessary amount of water is also introduced into the mixing device through the flow meter 16, so that the water and surfactants form a foam in which the solids are homogeneously dispersed in the mixing device.

In some cases, the material may be introduced into the mixing device only in the step where the quantity can be measured from the foam in the mixing device. This may refer to, for example, a pH regulator. In this case, the pH of the foam in the device is measured and, according to the measurement result, the pH value is modified by introducing either an acidic or an alkaline compound into the mixing device.

In principle, the fiber-free foam may also be introduced into the mixing device 10 via line 38, with the foam being discharged from the suction boxes 32 of the nonwoven fabric section by the pump 36, either directly or through the screen chamber 34.

The foamed slurry exits the mixing device 10 as a constant stream flowing through a pump 42 specially adapted for the purpose. The pump can be either a centrifugal pump or a positive displacement pump. The foam slurry may also be pumped directly into the headbox 40 if the consistency is correct. It can also be pumped into the screen chamber 34 where the consistency of the foam slurry is adjusted to the correct size and from where the slurry is further pumped to the headbox 40, or it can also be pumped to the storage tank 44 if use is desired. From the storage tank 44, the foam slurry is preferably discharged for use by a pump 46.

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When the foam slurry is introduced into headbox 40, according to the prior art, it is first introduced into the manifold 50 where the foam slurry is distributed by means of nozzles 52 in a pipe system 54 by which the foam slurry is introduced into the headbox 40. Nozzles 52 and the arrangement of pipes 54 are described in more detail with reference to Fig. 2.

In principle, fiber-free foam may also be drawn, for example, from the screen chamber 34 into the headbox 40 and / or into the supply pipe system to control the consistency of the foam slurry and / or the basis weight of the product.

From the headbox 40, the foam slurry is introduced into the screen 30 in the nonwoven fabrication part, the suction boxes 32 being arranged below that part - or more broadly - on the side opposite the foam slurry, to remove foam from the screen 30 by suction. The foam removed from the nonwoven fabric thus produced is directed to the screen chamber 34 or, alternatively, directly to the mixing device 10, producing the foamed slurry.

The nonwoven fabric produced by the wire 30 is directed to drying and then, optionally, to a coating. The further processing of the nonwoven fabric is of course dependent on the requirements of the respective product, so it does not need to be discussed here.

The inlet nozzles 52 and the tubing 54 shown in Fig. 2 are positioned between the manifold 50 and the headbox 40. A plurality of nozzles 52 have been arranged in a manifold 50 whose inner surface is not cylindrical but contains edges or similar structures to increase the level of turbulence. of the foam slurry upstream of the piping 54. The number of pipes in the piping 54 is equal to the number of nozzles 52 in the manifold 50. The pipes of the piping system 54 are typically arranged in a loop shape as shown in the figure. It is believed that this shape of the pipe and nozzle maintains the uniformity of the foam slurry and maintains uniform turbulence in all the pipes of the piping system 54. The purpose is, of course, to introduce the foam slurry from the pipes into the headbox 40, where the fibers do not form strands but can be readily distributed across the lines. sieving production equipment.

In practice, however, it has been found that the nozzles 52 and the pipework 54 are very easy to clog. Such a danger especially occurs when the length of the fibers in the foam suspension is increased. At present, this becomes a problem when the foam process is introduced into the industry and it has been found that a large number of different products can be produced with it. This also applies, inter alia, to multi-layer products in which one of the layers may be, for example, a reinforcement layer. Reinforcement mats produced by other methods have fiber lengths of about 5 to 50 mm, mainly depending on the type of fibers, so it is also required to use similar fiber lengths in the foam process. However, it has turned out to be difficult in practice, since fibers of such a length, depending on the type of fibers, easily strand and easily clog the entire tube upon penetration into thin tubes.

Moreover, it should be noted that while the description of Fig. 1 mentions only one mixing device, it is clear that in some cases more devices are needed in the production process. For example, when producing a multi-layer product, the required number of mixing devices is usually equal to the number of layers. Furthermore, if the process involves materials that cannot be in contact with each other, it is advisable to make a separate froth slurry from the material and materials neutral to it and add the resulting froth slurry only at the stage of frothing, preferably just before the headbox. In other words, when making a multi-layer non-woven fabric, up to six mixing devices may be required.

Figure 3 shows a schematic view of the existing foam process: headbox 40, upstream pipe system 54, and downstream of headbox 40 a nonwoven fabric production section with its mesh 30 and suction boxes 32. Figure 3 also shows, at 48, a pump corresponding to pump 48 on 1. Downstream of the pump 48 is both the manifold 50 and the piping 54 of Fig. 2. In Fig. 3 it is also shown how the headbox 40 supplies the foam slurry directly to the nonwoven fabricating portion, into the gap between the two screens 30, contrary to Figure 1, which shows a more traditional nonwoven fabricating portion including a Fourdrinier screen. Figure 3 also shows how foam, available in the suction boxes 32, arranged outside the screens 30, or the foam generally available in the nonwoven fabrication section, can be introduced by pump 56 through line 58 to mix with the foam slurry in the area between pump 48 and headbox 40 .

PL 210 100 B1

This is preferably done downstream of the manifold 50 in conjunction with the nozzles 52 or supply pipes 54 or in the headbox 40. Preferably, the amount of foam added can be adjusted.

Figure 4 shows a very similar headbox 140 having foam inlet conduits 158 'cooperating with foam slurry conduits 154 to either dilute the foam slurry or equalize product basis weight by adding foam. Line 158 is functionally similar and supplies foam to the top of the headbox 140 with foam from line 158 being directed along the top of the headbox 40 toward the screen 130. The foam also acts as a lubricant to prevent fibers in the foam suspension from displacing in the direction of flow of the suspension.

Figure 5 shows a third prior art headbox 240 capable of producing a three layer product. As shown in the figure, the headbox 240 is vertically divided into three chambers 242, 244, and 246, each receiving its own foam slurry from sources 248, 250, and 252. It is possible, however, that both the surface layers (produced from the foam slurry in the chambers 242 and 246), or even all layers, are similar, but the technology shown allows the production of three different layers as well. The figure shows how the foam slurry introduced into each chamber 242, 244 and 246 is simultaneously directed to the nonwoven fabrication part between the screens 30. A nonwoven fabric is rapidly formed by removing the foam in two directions by means of the suction boxes 32 and the different layers of the nonwoven fabric are joined to one another by mixing the fibers of the different layers in the interface between the layers.

Figure 6 shows yet another prior art headbox 340. In this case, three chambers 342, 344 and 346 have been placed in the headbox 340 either on top of each other or side by side depending on the orientation of the headbox 340. Each of the chambers 342, 344 and 346 is able to incorporate its own layer into the nonwoven fabric as described with reference to the previous figure. This solution enables yet another method, in addition to the use of chambers, for the production of a separate layer or strip in the nonwoven fabric. This is done by pipes 348 and 350, extending through the chamber 344, introducing the foam slurry which forms its own layers in the fleece if, on the one hand, the feed pipes 348 and, on the other hand, the feed pipes 350 are parallel in the longitudinal direction of the headbox ( perpendicular to the plane of the figure) or own lanes if there is free space between the feed pipes 348 and / or feed pipes 350, where the foam slurry is not introduced from the pipes 348 and 350. According to the preferred embodiment, the feed pipes, in addition to being placed in each chamber, if necessary, may be displaced at least in the longitudinal direction. In practice, the longitudinal position of the feed pipe determines the type of layer or strip that the foam slurry exits the pipe forms. The further the end of the pipe is located from the openings in the chambers, the longer the path of the non-woven fabric formed from the supplied foam slurry and the sharper the boundary with the non-woven fabric produced from the foam suspension supplied from the tube. If the slurry is introduced from the pipes just after the chambers open into the fleece, the foam supplied from the tube is efficiently mixed with the remaining foam and the boundaries of the strip produced from the foam supplied from the tubes are very poorly distinguishable from the rest of the nonwoven.

Figure 7 shows a product manufacturing method used to date. The figure illustrates the manufacture of a vehicle bumper body. According to the figure, the mold includes, of course, two portions 60 and 62 corresponding to the shape of the bumper body. According to the technology described in the publication, a first thermoplastic fibrous mat is placed on the bottom of the mold 62, and two narrower non-woven mats 66 and 68 are placed on the mat 64 at both edges of the mat. The mat corresponding to the lowermost mat is placed on said mats and a thermoplastic material 72 is placed on the last layer 70. When the mold parts 60 and 62 are pressed against each other, said thermoplastic material 72 is spread over all layers of mats 64-70.

It can be readily seen from the manufacturing technique shown in Figure 7 that it requires a high degree of precision and a great deal of preparation work to ensure that all layers 64-70 are placed in their correct positions and remain there during the manufacturing process. In addition, the factory must have separate storage, transport and supply devices for all the required nonwovens, in this case there are six different nonwovens. In addition, the mats must be cut to size either at the factory or by the mat manufacturer. In practice, this means that six nonwovens of a certain width have to be cut somewhere, instead of using just one nonwoven fabric,

If there was a method of combining all the reinforcement nonwovens into one product already at the product manufacturing stage.

Figure 8 shows a fresh foam device 76 and a headbox 78 of a production device according to the invention. As can be seen from the figure, the headbox 78 in this embodiment comprises a predominantly top-open or at least atmospheric reservoir 80, foam nozzles 94, a lower portion 98, and an outlet 100. The foam slurry is produced in the reservoir 80, into which most of the solids needed to produce the product are introduced, in accordance with the principles used in prior art for introducing material into the mixing device. In other words, the amounts of solids introduced into the tank are metered depending on the product to be made, and the fibers or the fibrous mat are cut to the desired length with a cutting device. Fibers may be introduced into the reservoir directly from the cutting device (not shown) if the amount of fibrous material introduced into the cutting device can be accurately controlled. Fibers may also be introduced into the tank by a calibrated conveyor 82 such that a uniform amount of chopped fibers is continuously dropped into the tank 80. Figure 8 also shows how another, calibrated conveyor 83 is used to introduce e.g. filler, binder, dyes, etc. or mixtures thereof into the reservoir 80. It is an essential feature of the invention that at least a portion of said solids are introduced into the reservoir substantially dry and not as a liquid slurry. The solids may, if desired, be wetted, but in any case so that no free water is introduced into the solids tank.

A characteristic feature of a preferred embodiment of the invention is that a significant part of the fibers used in the construction of the product are introduced into the tank in a dry state. The design of the product in this context means the fibrous structure typical of the product and not the components possibly belonging to the product and influencing its properties during use, for example, activated carbon or some liquid-absorbing materials.

In addition, foam produced in a special mixing device 84 is introduced into the tank 80. As already shown in Fig. 1, foam is formed in the mixing device 84 from water, surfactants and a gas, preferably air, with the difference that in this In this manner, no other materials need to be introduced into the mixing device. However, if it is desired to mix solids with foam upstream of the reservoir 80, this may be accomplished with the formation of foam in the mixing device 84. The amounts of water and surfactants are relative to each other when introduced into the mixing device 84 to produce optimal foam. The mixture of water and surfactants is mixed with a mixer such that air is introduced into the mixture in amounts suitable to produce the desired gas content and bubble size.

It is possible and also envisaged to replace at least a portion of the foam with the froth recycled from the manufacturing process by a line 86 as shown in the broken line in Figure 8. Both the foam produced in the mixing device 84 and pumped into the conduit 92 by the pump 90 and the foam returned from the process through the conduit 86 are preferably injected in the desired amounts per unit time into the tank 80 by the nozzles 94 so that the solids are effectively mixed. due to the turbulence caused by the jets of foam forming a homogeneous foam suspension. Once formed, the foam slurry is introduced as a laminar flow through the bottom 98 of the reservoir towards the outlet 100.

The foam is introduced from nozzles 94 preferably at a speed appropriate for each type of fiber; in other words, a speed that produces a uniform foam dispersion, but not so high as to cause too much turbulence in the fibers. Agitation may in some circumstances be enhanced by placing either a mechanical mixer (not shown) in the reservoir, or by using ultrasonic or microwave agitation (not shown).

This embodiment of the invention differs from the prior art mixing devices producing a froth slurry in that the solids must be introduced in a continuous stream, preferably over the entire length of the tank 80, corresponding to the screen width of the production apparatus. Thus, also foam is introduced into the reservoir 80 from nozzles 94 spaced about 10 cm apart. Foam is preferably pumped into manifolds 96 located on both sides of the tank 80 (in some cases, however, a manifold and nozzles are only needed on one side of the tank) from where nozzles 94 lead to the tank, the nozzles obviously having longer nozzle tubes and the actual nozzles are located at the ends of the tubes. According to another embodiment, the manifolds are substantially flush with the top edge of the reservoir 80, while the nozzle tubes with nozzles can be introduced into the reservoir 80 from above without making holes in the reservoir wall. The nozzles 94 may, if desired, be arranged on opposite sides of the reservoir 80, either facing one another or one over the other, depending on the required turbulence. The nozzles 94 may also be arranged in several levels on either one or both sides of the reservoir 80, thereby achieving multi-stage mixing of the fibers and the foam. In addition, all nozzles 94 on one wall of reservoir 80 may be unidirectional, or their directions may be changed as desired. The reservoir 80 according to the preferred embodiment of the invention is tapered downward as shown in Fig. 8, also the bottom 98 of the tank in practice forms a funnel from which the foam suspension is introduced in the form of an essentially laminar flow onto the screen or between the screens of the production device. In some cases, however, the vessel may be uniformly wide up to the outlet 100 located at its bottom 98.

It is important for the nonwoven fabric manufacturing process to keep the surface level of the foam slurry constant in the reservoir 80. The surface level remains constant since all components, ie solids input and line 92 foam, are introduced into the reservoir in precisely measured amounts. Moreover, a level regulating device may of course be arranged in the reservoir to regulate both the solids and foam introduction rates and, if desired, fresh foam generation.

A headbox structure suitable for producing a three-layer non-woven fabric is shown with reference to a preferred embodiment in Fig. 9. In practice, in an embodiment, the headbox is merely divided into three parallel portions 78 '78 and 78' according to Fig. 8. in view of a finished three-layer product, the portions 78 ', 78 and 78' may also be placed one above the other. Here, the outlets 101, 102 and 103 of the lower portions of the tanks 80 ', 80 and 80' of the headbox portions 78 ', 78 and 78' are parallel and each introduces its own foam slurry into the nonwoven fabric forming section between the screens 30. One or more openings Outlets 101, 102 and 103 may be arranged so that they do not open between the screens 30 simultaneously with the other openings, but somewhat earlier or later. This makes it possible to control how much the different layers of the nonwoven fabric mix with each other. For example, the later the central outlet 102 opens in the nonwoven fabric forming section, the longer it takes for the surface layers to form and less middle layer fibers will be mixed with the surface layer fibers.

By means of the apparatus shown in Fig. 9, it is possible to manufacture a three-layer non-woven fabric from even three different materials. Different solids may be introduced into each of the tanks 80 ', 80 and 80' using, for example, the apparatus described in Fig. 8. However, it is preferred to introduce the same fresh foam into all of the tanks 96, making it possible to using only one foam maker. In this context, it can be stated that in some cases it is advantageous to mix, with respect to the production of the foam, the solids in the foam generator, the solids being added uniformly to all the layers of the non-woven fabric. An example would be a binder or a fibrous component common to all layers.

However, it should also be mentioned that in some cases the materials used in the different layers of the nonwoven fabric are so different from each other that it is not preferable to use exactly the same foam in all the layers. In this case, the different foams are of course produced in different mixing devices and are introduced into the tanks of the head boxes through the respective pipe systems. This arrangement allows, for example, some adhesive to be incorporated into certain layers of nonwoven fresh foam, the adhesive being only suitable for the fibers used in these layers.

It should be noted, however, that the apparatus may be used to produce single, double, triple or multiple layer products. Thus, the foregoing description should only be considered as an example of many variations of the invention. In the embodiment shown in Figs. 8 and 9, the tanks are arranged substantially vertically. The nonwoven fabrication section, including the two opposing screens 30 and suction boxes 32 disposed outside the screens 30, is also substantially vertical.

Figure 10 also shows how the screen 30 and the suction boxes 32 can be arranged horizontally, if more preferably, due to the inclination of the lower parts 98 ', 98' and 98 'of the headbox, even though the headbox or at least the top parts 80', 80 thereof and 80 ', used to mix the foam slurry, are vertical.

PL 210 100 B1

The headbox structures according to the invention, shown above in Figures 8-10 clearly illustrate that the headbox is fully open at the top in these embodiments. This allows the incorporation of various materials and facilitates the fabrication of the nonwoven fabric. It is entirely possible to incorporate, for example, glass fibers, metal fibers, rubber or the like into one or more layers of the product. Other suitable materials that can be introduced into the product according to the invention by means of the above headbox, for example, various tapes of textiles, carbon fibers, aromatic polyamide fibers and polyester fibers, etc., electrically conductive threads, tapes or cables, optical fibers, etc., various resistance wires or meshes, other meshes, materials that change color as a function of temperature, etc.

This is shown in Fig. 11 which shows the production of a product according to a preferred embodiment of the invention using a device of the basic structure as shown in Fig. 8. The figure shows that continuous filament, yarn, tape, etc. are introduced into the nonwoven fabric through the reservoir. 80. In the embodiment shown in the figure, continuous filament 106, etc. it is unwound from a spool or similar device (not shown) or, in some cases, even directly from a manufacturing device, from a deflection roll 108 between two adjusting rollers 110. Adjusting rollers 110 regulate the speed of yarn 106 introduction so that it corresponds to the speed of the nonwoven fabric in the device production. It is therefore a characteristic of this embodiment that the yarns etc. are arranged along a line parallel to the nonwoven fabric. Even in such a basic headbox structure, the erect form of the yarn is maintained in that the turbulence needed to produce the foam slurry is so weak that it cannot significantly deflect the yarn from the desired direction. It is not possible to introduce yarns in this way in the water method, since in the water method the turbulence in the headbox causes the yarn to swing so strongly that its end point in the product is random. A way to ensure that the yarn reaches exactly the right place in the product is to direct the yarn, etc., through the turbulence zone in the headbox to a laminar flow location using suitable tubing.

In addition to the yarn 106, the embodiment shown in Fig. 11 can be used to introduce a product much wider in the width direction of the nonwoven fabric or manufacturing device. An example would be a netting extending substantially the full width of the product to be manufactured, and the netting may be made of almost any material. An example is a resistance wire mesh used to connect the final product to an electrical system for alerting purposes. Another alternative among the numerous possibilities is a pre-fabricated reinforcement mat which, for some reason, cannot be produced simultaneously with the product produced by the method. The mat is directed from the spool through the regulating rollers to the reservoir and from there to the fleece. A third alternative is, for example, inserting a perforated thin steel plate or narrow steel strip through a receptacle into the fleece. The bonding of the steel plate to the non-woven fabric is ensured by bonding the fibers and resin through the holes in the plate.

The solution employing regulating rollers 110 to introduce yarn, tape, net or the like first into the nonwoven fabric at the same speed as the nonwoven is advanced may be given here as an additional embodiment. After starting production, said regulating rollers may slightly inhibit yarn advance, etc. This helps to provide tension to the yarn, etc., so that it is directed towards the correct location in the product and cannot be shifted in any other direction. Another way to prevent the yarn or the like from shifting in a direction perpendicular to the insertion direction is to place guides relative to the exit port 100 to guide the yarn or the like to the desired location in the nonwoven fabric. It is of course also possible to introduce yarns, tapes, nets etc. by means of the guide only to the laminar flow area in the lower part of the tank, or if necessary quite deep in the nonwoven fabrication section between the screens.

Figure 12 shows a preferred headbox structure according to the invention in which continuous filaments, yarns 112, etc. are introduced through the central reservoir 80 into the nonwoven fabric to be produced. The figure shows how the regulating rollers 110 feed the yarn 112 etc. at a speed exceeding that of the nonwoven fabric. The idea is to form a separate layer of yarns 112, etc., preferably, for example, glass fiber, with the yarns, fibers, etc. being evenly distributed in this layer. The introduction of loose yarns or the like into the nonwoven fabric cannot be carried out in the aqueous method, since in the aqueous method the fibers in the suspension would be trapped by the yarns due to the high turbulence, so that a homogeneous distribution of the fibers in the product would be impossible. Also in this embodiment, introduction devices 82 and 83 are also used to introduce other solids into the reservoir 80, such as fillers, binders, and / or some discontinuous fiber components.

It is obvious that in the case of the solutions shown in Figures 11 and 12 there may be one or more threads etc. along the width of the product. As already mentioned above, yarns etc. may be included in an amount sufficient to form an entire layer in the laminate. It is also possible to individually insert fibers, yarns, etc. between two or more layers without foam or foam slurry. It is also possible to introduce continuous filament, yarn, mesh, non-woven material, etc. to the nonwoven fabric produced as shown in Fig. 11 through reservoirs 80 'and / or 80', using e.g. the structure shown in Fig. 12. Accordingly, it is evident that continuous yarns etc. can be incorporated into any nonwoven layer as well at a speed greater than that of the nonwoven fabric. Thus, the outlet of the reservoir 80 shown in Fig. 12 can be positioned in conjunction with other openings 80 'and / or 80' if desired.

Figure 13 shows another preferred embodiment of a headbox and method of producing a nonwoven fabric according to the invention. The figure shows the manufacture of a bumper body, already discussed with reference to Fig. 7, using the new foam method, so that all the layers required in the bumper body are incorporated in the same non-woven fabric, so that the bumper body can be manufactured simply in one production phase from one laminate mat by simply adding resin.

Figure 13 shows how two feed pipes 114 and 116 have been led through the center of the headbox reservoir 80, slightly past the headbox outlet 100, to the nonwoven fabric making section. For the product shown in Figure 7, the material for the surface layer 64 is discharged from the reservoir 80 'and the material for the surface layer 70 is discharged from the chamber 80'. Moreover, it is possible to introduce a so-called flow layer between the surface layers 64, 70 from the central chamber 80, in this layer the resin is evenly distributed throughout the product. On the other hand, pipes 114, a number of which are preferably arranged transversely to the width of the product, i.e. in the longitudinal direction of the headbox, are used to introduce the other foam slurry needed to produce a nonwoven fabric composed of the narrower nonwovens 66 and 68 indicated by reference numeral 66 in Fig. 7, sandwiched between the surface layers 64 and 70. A feed pipe 116 is suitably used to introduce foam slurry, forming mat 68 in the whole product. The figure shows the situation where the feed pipes 114, 116 are used to introduce the fiber suspension in the form of foam. The same end result can be achieved by inserting a narrow web or tape into the above-mentioned locations in the web as shown in Fig. 11. Nonwoven fabric with a plurality of blanks arranged side by side can be produced by arranging the feed pipes 114, 116 shown in the figure at appropriate intervals along the entire length of the headbox. The semi-finished products may later be cut into separate, narrower nonwovens, for example when winding the product.

Even though it has been shown above that the same foam slurry is introduced through the feed pipes 114, 116, it is of course possible to introduce a different foam slurry into each of the pipes. Accordingly, it is possible to make one of the narrow layers with the foam suspension and the other with the finished non-woven fabric. The headbox according to the invention allows any choice of production method depending on the requirements and capabilities of the product.

It is of course possible that if a product according to Fig. 7 is required having reinforcement layers in the edge regions between the two surface layers, the product can be made not only with the device of Fig. 13, but also by forming the end of one feed pipe such that the thickness of the injected foam suspension changes. In such a case, the thicker portion of the spray corresponds to the two superposed webs or tapes, and the thinner portion corresponds only to the wider of the webs or tapes.

Figure 13 also shows how the foam slurry is introduced into the headbox through the supply pipes 114, 116. In other words, the foam slurry has been separately formed, in a small mixing device adapted for this purpose if necessary. Another possibility is to provide a small reservoir for the foam slurry, the slurry being produced in the reservoir and introduced therefrom into the interlayer formed nonwoven fabric.

In addition, the pipes leading through the headbox chamber or chambers may be used to introduce into the nonwoven fabric, in addition to the finished nonwoven fabric or foam slurry, also solids required in the product. The solids can be, for example, plain, chopped fibers, a binder,

A mixture of binder and chopped fibers or some other material not related to layer formation. For example, the material may be SAP (Superabsorbent Polymer) which is used to absorb the liquid, or e.g. a belt with seeds attached to it at predetermined intervals.

Moreover, it is evident that the feed pipes 114 and / or 116 can be replaced by channels with flat nozzles running along the width of the nonwoven fabric which can form a wide strip in the nonwoven fabric. And, as described in previous publications, the pipes or flow channels can be moved longitudinally so that the point of introduction of the material into the nonwoven fabric forming section can be adjusted according to the application. The pipes and / or ducts with nozzles can of course also be movable in the perpendicular direction and / or in the thickness direction of the non-woven fabric, if for some reason it is desired to make undulating stripes in the longitudinal direction of the non-woven fabric.

Figure 14 also shows another headbox 178 design corresponding to a preferred embodiment of the invention. The main difference to the headboxes described above is that in this embodiment the headbox is closed, i.e. pressure is generated therein, while in other embodiments the headbox is at atmospheric pressure. In practice, the only difference between the embodiment shown in Fig. 14, and the embodiment shown in FIG. 8, for example, is that chopped fibers and other solids are now introduced through headbox lid 179 178 using rotary dispensers 182 and 183 or other suitable high pressure injection devices. Accordingly, if the application requires continuous yarn, tether, filament, etc. to be introduced through the headbox into the yarn to be formed, the material must be introduced through a high pressure resistant conduit. Sealing spools pressed air-tight against the headbox cover may be examples of pressure-resistant conduits with yarn, tape, etc. passing from atmospheric pressure to the headbox at elevated pressure. Another solution is, of course, to place the entire material spool in a pressurized space.

The above-mentioned embodiments show that this new variation of the foam process enables the production of almost any type of product made of nonwovens. Thus, both inorganic and organic fibers can be used as fibrous materials either alone or with each other. Various glass fibers, carbon fibers, quartz fibers, ceramic fibers, zirconium fibers, boron fibers, tungsten fibers, molybdenum fibers, beryllium fibers, and various steel fibers may be examples of inorganic fibers. Examples of organic fibers include polyamide fibers, polyester fibers, polyethylene fibers, acetate fibers, acrylic fibers, melamine fibers, nylon fibers, modacrylic fibers, olefin fibers, cellulose lyocell fibers, rayon fibers, aromatic polyamide fibers and various natural fibers. such as sisal or jute. The above-mentioned fibers can be used either as separate single fibers or as different bundles of fibers. Fibers of various lengths can also be used, ranging from very short ones, only a few millimeters long, to continuous filaments.

As is evident from the above, new types of series of products have been developed which can only be produced with the new variation of foamed non-woven fabric described above. It should be noted that in the above, the term foam is used in the text in the sense of either fresh foam made of water and surfactants, or reused foam, collected from the suction boxes of the production equipment, as a result of a significant part of the solids being retained in the product on the screen . Thus, the foam can be essentially a fiberless foam. The term foam suspension, on the other hand, means a foam containing fibers and / or solids, i.e. essentially the foam being fed into the production equipment to deliver a substantial portion of the solids to the screen.