NL8005799A - FIBER MAT FOR THE PRODUCTION OF SPATIAILY MOLDED PARTS ON A DRY ROAD. - Google Patents

Description

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Fiber mat for the production of spatially pressed molded parts in a dry way.

It is known to produce spatially pressed moldings from lignocellulose fibers by sprinkling the fibers moistened with small amounts of adhesive material loosely on an endless conveyor belt, by flattening the height of the applied fiber layer by means of a scraper roller and finally the fiber layer between pre-reinforce roller ^ pairs. This results in a plate-like endless strand which is cut into separate plates, of which flat blanks are produced after an in-between transport, which are placed in a press mold after a steam treatment and in the press under curing of the binder until the final molded bodies are pressed (German published patent application 12 24 919) · The individual plates formed in this way have, in the first place, a low molding ability and only a low resistance to breakage. After the steam treatment necessary to increase the deformability to produce the spatially pressed molded body, the plates no longer have a significant internal cohesion and must therefore be handled and transported very carefully. Due to the low cohesion of the fibers in the steamed state, they can only deform further to a limited extent, without thinning the areas of material subjected to tensile stress during compression and losing the cohesion of the fibers, which leads to tearing of the fibers. the mat.

To overcome this problem it is known (German patent application 14 53 416 laid open to public inspection) to place on the fiber mat a stretch-deformable reinforcing fabric which is pressed into the fiber layer by the rollers serving for the pre-reinforcement of the mat. Here, too, the bond between the reinforcing fabric and the fiber mat is broken during the steams required for the final deformation, so that during pressing it is forced to effect important relative movements of the individual fibers, which may result in tearing of the fiber mat .

German patent specification 23 64 025 already discloses a fiber mat, which consists of two lignocellulosic fiber layers, between which a deformable support layer is adhered adhesively, the prepressed fiber mat having a large number of evenly distributed zones of smaller cross-section. As a result, the adhesion of 80057002 to the carrier layer is also improved during steaming, so that these tensile forces which occur during pressing are distributed over the mats. Moreover, such a mat strand can be wound on a roll after pre-reinforcement, which facilitates handling and transport.

In particular, in order to be able to manufacture thin-walled, spatially-pressed molded parts, such as are required for the interior lining of cabins of lorries, a method is used (German patent specification 23 38 650), in which the fiber mat is pressed step-by-step into a mold which is equipped with a number of periodically operated stamps. This stepwise pressing is necessary to prevent tearing of the fiber mat.

In this method, the fiber mat draws elastically to the deformation points in steps, without tearing of the fibers. This known method used in the spatial deformation of thin-walled molded parts requires particularly careful treatment due to the sensitivity of the fiber mats and is moreover time-consuming due to the step-by-step pressing.

A further drawback of the known art is that the fiber mats must be manufactured from high-quality wood fiber materials if they are to have satisfactory deformation properties, in particular with a required low wall thickness of the molded parts. A certain lower fiber length limit cannot be exceeded if tearing of the fiber mat is to be avoided during deformation. For these reasons, hitherto the use of short length fibers has been unacceptable, such as those obtained, for example, in the processing of waste materials, eg waste paper, although these waste materials, in particular when added to larger length fibers, usually have satisfactory material properties.

The object of the invention is to eliminate the drawbacks associated with the known fiber mats and the manner of their processing and to provide a fiber mat which can be made into a thin-walled molded part in one go according to the deep-drawing method without step-by-step pressing. are pressed and, with the addition of short-fiber waste materials, a molded part with high strength and less wall thickness is provided.

For example, with a fiber mat for the manufacture of 40 spatially pressed, for example as interior lining for booths, does this task be 8005799? ' * 3 dry vehicle moldings serving dry road consisting of a pre-reinforced cellulose or lignocellulosic fiber layer and of deformable support layers to which the fiber layer is joined lifted because the fiber layer is placed as a middle layer between two support layers and the creep layers of little stretch or none stretchable film materials, e.g., paper, plastic, metal, fabric and the like, exist which are bonded to the surfaces of a center layer while maintaining the crepe's extensibility.

Other preferred embodiments of the invention are discussed below.

The term "crepe" is understood to mean all shapes of the carrier layer which, when pulled out in at least one direction, allow enlargement of the surface of the carrier layer without stretching or stretching the material itself. Such shapes may consist of parallel folds such as a pleated, which is effective if a substantially groove-shaped spatial deformation is desired. In a nap-like deformation, intersecting folds are recommended. For example, the term "crepe" also includes annular pleats or indentations, and in fabrics also those yarns which are crimped or twisted.

The advantage of the mats according to the invention is in the first place that the fiber layer itself no longer comes into contact with the pressing tools. As a result, the sliding properties of the mats according to the invention during pressing are improved to the same extent as the separating properties after pressing. This improves the surface area of the finished parts clearly.

Moreover, during the closing of the tool, thermal insulation of the fiber layer with respect to the tool surfaces can be achieved, thereby preventing the surfaces of the fiber layer from hardening prematurely. This improves the strength properties of the fiber layer.

Covering the fiber layer with support layers on both sides increases the effective interface between the fiber layer and the support-55 layer. This alone can significantly improve the reciprocal effect of the favorable deformation behavior of the carrier layers on the fiber layer. Creating the carrier layers according to the invention hereby represents an extra important advantage. The prior art elastically deformable carriers are stretched to fail, i.e., $ 7 # 7 qo 4, they cover the "surface requirement" required for spatial deformation from their volume and are during the deformation they are first of all arbitrarily stretchable in view of their elasticity, the elongation is distributed uncontrollably over the entire surface 5. Because local stretches in the fiber material must be greater than the overlap length of the fibers. avoided, co-operation between the prior art elastic, support layers and the fiber layer means that local exhausts of the tensile strength of the fiber layer can still occur, thereby opening up the possibility of forming fiber mats with support layers according to the prior art is significantly limited In contrast to this, creped carrier layers have the pre-molding properties necessary surface reserve in the crepe itself and need not be covered by a loss of thickness. If the surface reserve of the crepe is locally exhausted, then tensile forces are transferred to the surrounding area and the surface reserve thereof is also used. The shape and intensity of the crepe can be chosen in such a way that, on the one hand, the local stretching capacity required for shaping is ensured and, on the other hand, the local stretching capacity of the carrier layer can be adapted to the overlapping length of the fibers.

This avoids local failure of the fiber layer itself. The large surface area of the carrier layers in the creped state also favors the transfer of force at the interfaces between the fiber and the carrier layer. This results in a total mat, which is capable of transmitting tensile forces of notable magnitude also in the outer region during the deformation without local failure of the fibrous layer.

The return of the stretch stretch portion to the overall deformation of the mat means a more even thickness distribution in the finished piece. This gives the particularly advantageous possibility of manufacturing parts whose wall thickness is clearly less than the parts hitherto manufactured. In the current state of the art, a thickness of 2 mm of the finished part is regarded as the lower limit of the technological possibility. With the mats according to the invention, still finished parts with wall thicknesses of about 1 mm can be manufactured with satisfactory quality.

Since the surface enlargement of creped carrier layers during molding has only small forces, carrier layers of increased strength can be used for the mats according to the invention.

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The pressed part then has a "sandwich" structure consisting of a medium-strength core and very strong coatings. "The resulting improvement in the strength and stiffness of the finished parts allows finished parts with the same usage properties to be more thin-walled and thus more favorable in material consumption and cost to be produced than in the prior art.

Covering the fiber mat with closed carrier layers on both sides also reduces the risk of damage to the mats during transport and handling.

This point of view is then particularly important if thin-walled finished parts are to be pursued and the fiber mats consequently have only a small thickness and thus little inherent stability. In particular, the risk of breaking of thin fiber mats during transport is significantly reduced by the carrier layer applied on both sides.

The advantageous possibility of reducing the wall thickness of finished parts in case this is necessary by using mats according to the invention by about half, is explained in its total meaning 20 once more.

Above the weight and material savings of 50%, the necessary pressing time is reduced by about half. The pressing time when pressing wood fiber materials is mainly determined by the poor thermal conductivity of this material group. A reduction in thickness means a correspondingly faster heating (in practice, fixed pressing times per mm of material are used). Thus, the amount of utilization of the large presses, which require a great deal of investment, can also be increased proportionately as the number of the necessary high-cost press tools can be reduced. The gains resulting from rationalization, which can be achieved with the mats according to the invention, are therefore important.

According to the invention, the point-or-line fixed joining of the layer layers with each other at preferably regular distances 55 further improves the overall properties of the mat. This defines regions of the fiber layer relative to one another, which are only slidable on their own, but are fixed over a larger surface relative to each other. To this end, the danger of large-area shifts of the fiber mats 40 during pressing is avoided, so that a total uniform distribution of material is achieved during the deformation of 8 n n n 7 o 6 6 of the mazermeer.

This effect is somewhat comparable to the behavior of modern point or line-stitched feather or down beds, whereby even distribution of the spring or down filling is ensured even when the bed is shaken or rolled.

An advantageous further embodiment of the invention consists in that the creping of the carrier layer is a cross creping. As a result, these layers obtain an improved deformation capacity.

It may further be advantageous if the carrier layers (for example 10 are pierced by needle pricks). The perforation makes the carrier layers permeable to gas, so that mats according to the invention can be thermally released, for example steamed, without difficulty. In addition, the gas permeability caused by the perforation favors the removal of moisture from the mat during the pressing itself.

Since the deformation properties of carrier layers no longer have to be provided by the material itself, but are determined by the crepe formation, all materials capable of creping can be used as carrier layers for the mats according to the invention.

Creped fabrics of synthetic fibers or natural fibers can be used as well as creped plastic films. Carrier layers of creped metal foils are also possible, in particular if the finished object must have a high resistance to moisture penetration. A particular advantage is the carrier layers of creped paper, because this material can be obtained inexpensively and can be processed easily. In addition, fiber mats according to the invention can also have carrier layers of different materials creped on the underside and the top of the mat.

This makes it possible, for example, to provide the visible side of the finished object with a carrier layer, which is chosen from a decorative point of view, while the invisible side of the carrier layer is chosen on the basis of costs.

If water-resistant carrier layers are used, it may be particularly advantageous if these carrier layers have a heat-resistant duroplastic resin. For example, they can be pre-soaked with phenolic or melamine resins. In this way, during hot pressing, a highly refined, very strong surface layer is formed, which imparts properties to the finished part "sandwich". A particular advantage is this when pressing thin-walled objects 8005799 7.

Contrary to the prior art underlying the invention, in which the carrier layers used therein are always bonded to the fiber layer over the entire surface, it is not always necessary with the mats according to the invention that the carrier layers are designed to be adhesive over the entire surface.

Areas in which the fibrous layer is sufficiently well fixed between the carrier layers are created by the point or line-shaped fixed connection of the carrier layers with each other. Such a mat design can be advantageous for special design problems. As a rule, however, it is better to fix the carrier layers on the fiber layer in an adhesive manner over the entire surface. When bonded over the entire surface of the carrier layers, the force initiation conditions for the required transforming forces improve.

The adhesives used for this purpose can be adhesives acting thermoplastic, but it is also possible to use contact adhesives or a solvent adhesive. It is particularly economical and from the point of view of manufacture it is advantageous if the carrier layers are previously provided with a layer of the adhesive to be used.

The point-or-line joining of the carrier layers according to the invention can take place in a manner known per se by means known in the textile industry, for example by sewing or stitching. With regard to the manufacturing technique, however, it is more favorable if the point or line-shaped connection of the carrier layers is mutually bonded. In this case, the corresponding adhesions of the carrier layers can be effected with the aid of the adhesive, with which the adhesion across the entire surface of the carrier foil on the fiber layer is also creamed.

This is the most favorable solution from the viewpoint of manufacture and cost.

Donkey mats according to the invention, such as fiber mats belonging to the present state of the art, are preferably provided with heat-setting binders and are predominantly hot pressed into molded parts. In hot pressing, it has a particular advantage if the point or line-shaped connections of the carrier layers are mutually designed in such a way that the connection points or connection lines are releasable in the press heat.

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During the closing of the press mold the connection points then still execute the functions described so far, however after intensive contact with the press surfaces during the build-up of the press pressure, the connection points become loose and allow material exchange in these local areas, so that the connecting points or connecting lines no longer mark on the finished part. When the carrier layers are joined together by a method known in the textile industry, the loosening in the heat can be obtained by using thermoplastic sewing threads. With adhesive bonds, the bond strength in the heat can be eliminated by using adhesives whose adhesive strength is lost in the heat.

A special advantage of the mats according to the invention consists in that the deformation properties thereof are no longer largely determined by the quality of the fiber materials used. For example, it is not or only to a very limited extent possible to reuse production waste in mats belonging to the prior art, because when the waste is prepared the fiber length becomes shorter and their addition of released production waste reduces the deformation properties of the mats badly affected. In mats according to the invention, the deformation property of the carrier layers dominates. It is thus possible to supply the production waste together with the prepared carrier layers for the manufacture of the mats completely and thus to realize a cost-effective and material-saving waste-free production.

The middle layers of these mats are pre-reinforced, but have a considerably lower density in the initial state than in the pressed state. The deformability of these middle layers 50 is improved before pressing by thermal decomposition, for example steaming, their moisture content, if they are sufficiently deformable, must be more than 10%. This is a technical drawback in that it has the drawback that the removal of moisture during hot pressing requires extra pressing time.

The moisture content can give rise to the formation of steam bubbles during pressing, in particular when steam-impermeable carrier layers are used. Nor does the perforation of the support layers proposed in the above-mentioned patent application to overcome this drawback completely avoid the danger of steam blow formation, because the degree of perforation 80057999 over the total area of the support layers is, of course, small.

The formation of steam blowers either gives rise to an increased amount of waste or requires a correspondingly complicated pressing technique to avoid it (intermediate relief of the press 5 during the pressing). Both tax the efficiency of the total working method.

An advantageous further embodiment of the invention therefore lies in that the density of the pre-reinforced middle layer for the press material corresponds approximately to its density in the finished article and that the moisture in this middle layer is less than 10%.

In the first place, the low moisture content has the advantage that the pressing time can be further shortened and that steam blowing in the pressing part no longer occurs. Since the density of the pre-reinforced middle layer already corresponds approximately to the density of the finished article, the tendency of this layer to have uncontrolled moisture absorption during intermediate storage is also small, so that its preconditioning can be maintained over a longer period of time. Further advantages are obtained because mats with such highly compacted middle layers are less bulky and therefore require less storage space, and because the stability during handling and transport thereof relative to the hitherto known mats is significantly improved.

The middle layers of the mats according to the invention must also still be deformable in a correspondingly highly compacted state.

25 This usually requires additional measures. For example, an advantageous embodiment of such mats consists in that the middle layer consists of at least one layer of creped thermoplastic or duroplastic adhesives soaked paper or cardboard.

In the case of creped paper, cardboard, fabric or nonwovens, the total surface area thereof is evenly finely folded. Thus, such structures have a total area that is a multiple of the area corresponding to the outer dimension of the corresponding webs. They are therefore able to cover the surface enlargement necessary to form the spatial shape from the "surface stock" of the crimp. In a suitable shape of the pleats of the crepe (crêpe crepe), in which the corresponding web is finely pleated in two directions perpendicular to each other, the corresponding material has a great ability to change shape in all eligible spatial directions, the surface enlargement is always made possible by smoothing the pleats, for example 10, without the material being subjected to greater tensile loads resulting from the deformation. The creping of the middle layer thereby allows the necessary shape change thereof, creped papers, which already have a final density, can be pretreated and soaked without problems. In addition to the cellulose fibers, they can also contain powdery fillers.

Middle layers with texal construction can also be used to make the mats according to the invention. For example, it is possible for the middle layer to consist of at least one layer of creped fabric or fleece, which has duroplastic or thermoplastic adhesives. In this case, too, the required shape-changing ability of the middle layer is obtained because the fabrics or fleeces which are in themselves only insufficiently deformable are creped.

If the middle layer of the mats according to the invention is sufficiently deformable with regard to the material, particularly favorable results are obtained. This is then the case, for example, if the middle layer is a thermoplastic material which is preferably filled and / or reinforced with cellulose or lignocellulosic materials.

Such a mat can be hot deformed without further measures. Shaped articles which are exposed to thermal loads in later use are then obtained with particular advantages if the creped carrier layers consist of metal. This improves both the dimensional stability of the parts in the heat and the heat absorption by the favorable back-blasting conditions of the carrier layer.

Creped adhesives-soaked papers, cartons, fabrics, or webs as proposed for the mats of the invention as a midlayer material are capable of creping only in limited thickness. It may therefore be advantageous in the practice of the inventive concept to use middle layers which consist of a number of bonded layers of one or more materials of the type described. The connection of the individual layers 55 of the middle layer can then take place by sewing, stitching or needle pricking.

This can be particularly advantageous if the separate layers consist of paper, cardboard, fabric or fleece.

If textile bonding operations are used, the target is useful if the bonding threads are made of thermoplastic materials, 8005799 11 which become readily deformable during hot pressing. A further advantageous possibility of designing the core layer as a plurality of layers consists in that this core layer is formed by adhesives which escape under the influence of heat.

This has the advantage that middle layers of any thickness are built up from individual layers with good deformability, the interconnection of which becomes flexible during hot pressing, so that the shape-changing properties of the individual layers can be fully utilized.

Because in this layered layer the materials can be combined practically arbitrarily, a further leeway is obtained for adapting the properties of the pressing part.

In the present state of the art, middle layers according to the invention can be wholly or partly manufactured from reclaimed materials. The creped papers or cartons of the middle layers can be, for example, reclaimed paper or reclaimed cardboard, the quality of which is not sufficient for other applications. The same applies to fabrics or non-woven fabrics made of synthetic fibers and / or natural fibers. In both cases, pre-products for manufacturing mats according to the invention can be obtained from the industry concerned.

Middle layers of filled and / or reinforced thermoplastic plastics can also be produced from inexpensive waste of thermoplastic plastics, such as obtained in the form of coated paper waste and waste from the cable industry, which waste cannot otherwise be used. Color differences and impurities do not play an important role in the use according to the invention, insufficient mechanical strength properties, such as can occur in the use of mixed waste, can be compensated by suitable choice of carrier layers.

The mats according to the invention are manufactured in accordance with the known prior art.

The middle layer is placed on the bottom carrier layer serving as the conveyor belt, after which the top carrier layer is fed from a supply roll and the assembly formed of carrier layers and middle layer is guided between the pairs of rollers serving as pre-reinforcement and connected to each other. To obtain a piercing perforation, different 40-roller pairs can be used with corresponding needles, the needles of which always penetrate a carrier layer and partially penetrate the middle layer.

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Claims (12)

Fiber mat for the production of spatially pressed, for example as an inner lining for, the cab of a truck, dry parts, molded parts consisting of a pre-reinforced layer containing cellulose or lignocellulose fibers and of deformable carrier layers with which the fiber layer is connected, characterized in that the fiber layer is placed as a middle layer between two carrier layers and that the carrier layers consist of creped low-stretch or non-stretch film materials, for example paper, plastic, metal, fabric and the like, which layers maintain the retractability of the crepe with the surfaces of the middle layer are connected. Fiber mat according to claim 1, characterized in that the crepe consists of parallel folds arranged side by side. Fiber mat according to claim 1, characterized in that the crepe consists of intersecting pleats. Fiber mat according to any one of claims 1 to 3, characterized in that the depth of the crepe is adapted to the length of the fibers of the middle layer such that the center layer is not interrupted after the crepe of the fiber assembly has been pulled out, for which the shape and intensity of the crepe is adapted to the overlapping length of the fibers. Fiber mat according to any one of claims 1 to 4, characterized in that the creped carrier layers with their surfaces facing the middle layer are bonded to the middle layer by bonding or gluing. Fiber mat according to any one of claims 1 to 4, characterized in that the carrier layers are joined to each other by adhering or sewing through the middle layer in a pointed or linear manner, preferably at equal distances. Fiber mat according to claim 6, characterized in that the point or line-shaped connections are releasable under the influence of heat. Fiber mat according to one of claims 1 to 7, characterized in that the creped carrier layers are provided with piercing perforations. Fiber mat according to any one of claims 1 to 8, characterized in that the middle layer has a high content of short 8005799 waste fibers and is creped in the same manner as the carrier layers. 10. The donkey mat according to claim 9, characterized in that the middle layer consists of at least one layer of paper or cardboard soaked from paper waste recovered with thermoplastic or duroplastic adhesives. 11. The donkey mat as claimed in claim $, characterized in that the middle layer consists of at least one layer of fabric or fleece 10 impregnated with thermoplastic or duroplastic adhesives. The donkey mat according to claim 9, characterized in that the middle layer consists of a thermoplastic plastic filled with cellulose or lignocellulose. The donkey mat according to any one of claims 9 to 12, characterized in that the middle layer consists of a number of layers joined together by suturing or sewing. 8005799