Process for the production of pressed parts based on natural biogenic residues

Abstract

The invention relates to a method for producing arbitrarily shaped, flat pressed parts based on natural, biogenic residues from nature, such as leaves in particular. The task is to create a novel, energy-efficient process for the production of pressed parts based solely on natural, biogenic residues, whereby the manufactured products are fully compostable or recyclable after use and disposal. The process for manufacturing pressed parts uses only deciduous tree leaves as its base material. After shredding, the leaves are pre-dried to a moisture content of less than 30 percent. They are then mechanically granulated to a particle size of 0.3 to 8 mm. Following granulation, the granulated leaf material is further dried to a moisture content of 8 to 20 percent. The granulated leaf material is then mechanically pressed to form its desired shape. Depending on the final product, various additives can be incorporated during this stage of the process. The material is then dosed by volume or weight, depending on the specific pressed part being produced. Finally, the part is pressed and cured at temperatures between 100 and 200°C.The moisture necessary for binding, as well as the reactive natural binders contained in the leaves, such as lignin, and any added additives, are the sole components of the starting material until it is shaped. The result is a compostable or easily recyclable, natural, single-use product made from leaves.

Description

[0001] The invention relates to a method for producing arbitrarily shaped, but generally largely planar or spatially simple pressed parts based on natural, biogenic residues from nature, such as in particular leaves from deciduous trees.

[0002] Pressed parts, and especially injection-molded parts, are typically manufactured primarily from petroleum-based thermoplastic polymers. However, it is also known to mix natural fibers with petroleum-based plastic materials to produce pressed parts. In this process, the raw materials are first made flowable and thus injection-moldable through complex processes before being processed into pressed parts or other plastic molded components. A wide variety of biopolymers are now available on the market for the production of disposable products. It is also known to incorporate additional natural fillers to reduce the use of expensive biopolymers and to achieve specific shapes and colors.

[0003] From DE 10 2013 114 774 A1, it is known to produce composite products based on polymers, but especially biopolymers, incorporating natural waste materials such as leaves and / or wood chips. A plastic part, particularly an injection-molded part, is to be produced using a special extrusion process with an injection molding hot runner system. As a rule, the additive (leaves and / or wood chips) is shredded to a particle size of 1 to 3 mm before processing. However, it is also possible to carry out the shredding within the injection molding machine using an integrated knife ring located at the inlet. These composite products made of synthetic polymer-based materials and natural additives are not fully compostable and can cause significant environmental pollution.

[0004] German patent DE 20 2020 004 418 U1 describes single-use products manufactured from the natural raw material leaves using purely mechanical processes such as pressing, rolling, or injection molding. The process begins with suitable thermal or electromagnetic drying to a specific moisture content. The leaves are then ground into small pieces, and a specific quantity of another natural binding agent is added. The resulting single-use products are compostable but meet only very low requirements regarding bending forces, pressure, and / or impact resistance. Furthermore, these single-use products are dimensionally unstable, have low thermal resistance, and a very limited lifespan.

[0005] The invention is based on the objective of creating a novel, energy-efficient process for the production of pressed parts based solely on natural, biogenic residues, wherein the manufactured products, such as disposable products in particular, consist only of this pure natural, biogenic residue and, as a result, are fully compostable or recyclable after use of the disposable product when disposed of, contain no non-biodegradable, artificial, environmentally harmful substances and completely avoid the release of pollutants into nature.

[0006] The object of the invention is achieved by the features of the first patent claim; further advantageous embodiments are described in the dependent claims. The inventive method for producing pressed parts based on natural, biogenic residues uses as its base material only the leaves of deciduous trees, which, as is known per se, are first shredded. The novel method is primarily used to produce molded parts 11 intended for single-use products. After sorting and / or cleaning, the leaf material is pre-dried 1, unless its moisture content is already less than 30 percent. If this is not the case, storage drying is carried out until this limit is reached or undercut. However, storage drying cannot be carried out indefinitely, as this would lead to mold growth or other decomposition processes.Depending on the type of leaves, it may be necessary to initiate active, time-limited drying to achieve pre-drying (1) to less than 30 percent moisture content. This is followed by mechanical shredding (2) using conventional knives or mills, or a combination of both. Next, the leaves are granulated (3) to particle sizes between 0.3 and 8 mm, depending on the desired disposable product and its performance characteristics. After granulation (3), the granulated leaves undergo a second drying (4) to a moisture content of 8 to 20 percent. The advantage of this process step is that the granulated leaves with this particle size possess a certain flowability and are therefore suitable for transport by pneumatic conveying systems.Transport can therefore also be carried out using conveyor belts, suitable screw conveyor systems, or vacuum conveying via suitable hoses or pipes. The granulated leaf material is then subjected to mechanical pre-compaction 5. Depending on the final disposable product, various other additives 6 may be added before this process phase, if necessary. Following this, depending on the mold used and the specified volume of the compact, mixing and volumetric or weight dosing 7, i.e., mold filling 8, takes place, usually directly depending on the specific compact 12 to be produced. Subsequently, compression molding 9 is carried out at temperatures between 100 and 200°C.The moisture necessary for binding, as well as the reactive natural binders contained in the leaves, such as lignin, and any additives, are the sole components of the starting material until shaping. This material, in granular form, is fed into the mold and processed in a suitably designed molding press without a separate cooling cycle. Surprisingly, the inventive method requires no additional binders, since, due to the technological manufacturing process, the lignin inherent in the leaves, already present in sufficient quantity, is the sole binding agent. Surprisingly, the brief heating process activates this lignin so strongly that it reacts as a binder during thermal curing. Numerous experiments have demonstrated that lignin alone is sufficient as a material binder.The curing process takes place during a specific dwell time of the molded part 12 in the mold, which can be a single or multiple mold. This dwell time depends on the composition of the leaves, the size, weight, and thickness of the molded parts 12 to be produced. The result is a compostable or easily recyclable natural single-use product based purely on leaves. For certain single-use products with specific performance characteristics, however, it may be advantageous to use additional natural binders to adapt or increase the dimensional stability, strength, or lifespan to meet further requirements.

[0007] In the inventive method for producing pressed parts based on natural, biogenic residues, the press forming 9 is carried out by hydraulic pressing with a pressing pressure between 50 and 250 tons for a pressing duration acting on the mold of at least 20 seconds. The pressing duration depends primarily on the wall thickness of the manufactured pressed part and is therefore individually adjustable.

[0008] However, it can be advantageous if, in the process for manufacturing pressed parts based on natural, biogenic residues, additional natural binders and / or other natural additives are added to the leaf material in a measured dose after granulation 3 of the leaves.

[0009] Depending on the desired properties of the disposable product to be manufactured, suitable additional binders include, for example, natural rubber and / or tree resin, and / or birch pitch and / or certain quartz sands and / or clays.

[0010] It is also possible in principle to add further additives, such as natural dyes and / or reinforcing agents, and / or natural biogenic fiber materials, such as hemp fibers in particular, or chopped straw, dried grass or other natural fillers, to the process of manufacturing pressed parts based on natural, biogenic residues.

[0011] It can also be advantageous for certain applications in the process for manufacturing pressed parts based on natural, biogenic residues to inoculate the leaf material with a fungal mycelium after granulation 3 or mechanical pre-compaction 5, whereby the leaf material is stored in a chamber under optimal growth conditions, the growth process of the fungus is specifically controlled, and further processing only takes place after the stored quantity has been colonized by the fungal mycelium.

[0012] During the process of manufacturing pressed parts from natural, biogenic residues, it can be beneficial to add an additional nutrient substrate or solution after inoculation with the fungal mycelium. The degree of dryness can be measured once or several times during or after colonization, and further drying can be carried out if necessary before further processing.

[0013] Depending on the desired disposable product, the process for manufacturing pressed parts based on natural, biogenic residues can also involve further refinement of the surface of the pressed part 12 with natural colors, varnishes or an additional coating with natural substances such as water glass.

[0014] As an additional intermediate process step in the method for producing pressed parts based on natural, biogenic residues, a layer or a thin layer of uncrushed leaves, or at least larger leaf fragments, can be introduced into the single or multiple mold before filling it. The process then continues according to the invention. The advantage of this solution is that at least one visible surface, or even the entire surface, of the disposable product then acquires the highly decorative appearance of the mold containing the leaves. Furthermore, this results in a pleasant tactile surface.

[0015] The invention is described below with reference to a preferred embodiment according to the Fig. 1. will be described in more detail. Fig. Figure 1 shows a flowchart of the individual required procedural steps.

[0016] To achieve high quality in the disposable product being manufactured, the first step in the process is typically a well-known pre-cleaning procedure. This can be done, for example, using a suitable sieve or a blower system to separate the material mixture. The mixture of collected, delivered leaves, including minor impurities, is exposed to a defined airflow, and the components are largely separated depending on the weight of the leaves and their contaminants. Simultaneously, the strong airflow separates the leaves from any remaining contaminants, such as sand and dust, which are then collected in a separate container. Heavier components of the leaf mixture, such as small stones or metal fragments, are definitively removed, resulting in a high degree of purity for the leaves to be processed.Cleaning with water is also possible in principle, although this entails an increased need for drying.

[0017] The leaves then undergo pre-drying (1) by means of storage drying or active drying to a moisture content of less than 30 percent. Pre-drying (1) can also be carried out, or at least begin, even if, for example, cleaning with an airflow is partially or completely performed, because the airflow can remove moisture from the leaves. This blower drying accelerates the drying process. This primarily takes place at room temperature but can also be done with a temperature-controlled airflow in individual cases.

[0018] After drying, the leaves are mechanically shredded using conventional equipment, such as a single- or multi-stage knife or grinder. Following shredding (2), granulation (3) takes place. Granulation continues until a particle size of between 0.3 and 8 mm is achieved. The size of the individual granules can be within narrow limits or, if required, cover a wider range. This depends on the specific molded part (12) to be produced, i.e., the end disposable product, and the type of leaves used.

[0019] The moisture content is then checked again, followed by further drying, i.e., a second drying process 4, to a degree of dryness between 20 and 8 percent. Depending on the specific end-use product and the type or mixture of leaves used, drying continues until the required degree of dryness is precisely achieved before further processing. It may be beneficial to then perform mechanical pre-compaction 5. Additional materials 6 can be added before or after pre-compaction.

[0020] The granules are then mixed (7) with any additional fillers or additives before being dosed (7), depending on the final volume of the disposable product to be manufactured. For certain applications, especially if the lignin content of the leaf variety or mixture used is insufficient, biologically derived lignin is added during this process step to ensure the desired strength and durability of the disposable product. After filling the mold (8), the granulated leaves are formed and cured by means of a compression molding process (9) involving a defined heating of the mold at temperatures between 100°C and 200°C. After curing (10) in the compression mold, the molded part (12), i.e., the disposable product, is demolded and ejected (11).Heating to a temperature above at least 100°C also reliably kills any harmful microorganisms or small organisms that may still be present in the molded part 12, thus significantly increasing the lifespan of the disposable product. Furthermore, all other pathogens are reliably destroyed, resulting in a largely sterile molded part 12 that is safe for a wide variety of applications.

[0021] The invention is applicable to disposable products, such as decorative stones or panels for use in the construction industry, for example, for wall or ceiling cladding or as flooring elements. It also creates a pleasant indoor climate, accompanied by the natural scent of the leaves used. To produce a decorative stone, dried leaves with a residual moisture content of 20% are granulated to a size of approximately 6 mm. A volumetric dosing system fills an open die cavity directly via a filling chamber. This is followed by compression molding, similar to a thermoset pressing process, at a temperature between 150 and 180°C. The pressing pressure is 200 tons and is maintained for approximately 60 seconds. The cycle time for producing such a decorative stone is 90 seconds.These process parameters can be varied depending on the type of disposable products being manufactured.

[0022] Another huge area of ​​application is simple, three-dimensional molded parts, which are used particularly for fireworks such as rockets or firecrackers, either as casings for the explosives inside or at least as protective caps at the tips of rockets or other molded parts used in large firework containers. If these were no longer made from petroleum-based materials, as is currently the case, but from leaves, there would be no need for complex collection and disposal, and these parts or fragments could remain in nature without harming it, because these types of molded parts or their remnants decompose completely and without pollutants in a relatively short time through natural processes.

[0023] Another important and very large potential application is in flowerpots, or any kind of plant container, or their use as design elements for temporary displays in garden centers. Once these single-use products are introduced into nature, they can remain there without requiring a complex collection and expensive recycling process. Typically, plants offered in hardware stores or garden centers are sold in petroleum-based flowerpots or other containers, from which the plants must be removed and planted. These containers are then disposed of in a costly manner and only partially recycled. Reference symbol list 1. Pre-drying 2. First granulation 3. Crushing 4. Night drying 5 Additives 6 Mixture 7 Second granulation 8 Filling 9 Press forming 10 Thermal curing 11 Eject 12 Molded part QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2013 114 774 A1

[0003] DE 20 2020 004 418 U1

[0004]

Claims

[1] Method for the production of pressed parts based on natural, biogenic residues using leaves from deciduous trees, which are shredded, in particular for the production of molded pressed parts, characterized by , that the leaves are pre-dried by means of storage drying or active drying (1) to a moisture content of less than 30 percent, that a mechanical shredding (2) and granulation (3) of the leaves is carried out to a particle size of 0.3 to 8 mm, that a second drying (4) of the granulated leaf material takes place to a moisture content of 8 to 20 percent, that the granulated leaf material is subsequently subjected to mechanical pre-compaction (5), then, if necessary, additives (6) are added, that a mixture and / or dosage (7) is carried out depending on the molded parts (12) to be produced, a filling (8) of a single or multiple form is carried out, subsequently a press forming (9) takes place at temperatures between 100° and 200°, a curing (10) is carried out in single or multiple form, then the ejection (11) of the molded parts (12) takes place. [2] Method for producing pressed parts based on natural, biogenic residues according to claim 1, characterized by , that the press forming (9) is carried out by hydraulic pressing with a pressing pressure between 50 and 250 tonnes and a pressing duration of 20 seconds or more. [3] Method for producing pressed parts based on natural, biogenic residues according to claim 1, characterized by , that after granulation (3) of the leaves, further additional binder and / or further natural additives are mixed into the leaf material. [4] Method for producing pressed parts based on natural, biogenic residues according to claims 1 and 3, characterized by that further additives, such as natural dyes and / or reinforcing agents, and / or natural fiber materials and / or natural fillers, are added. [5] Method for producing pressed parts based on natural, biogenic residues according to claims 1, 3 and 4, characterized by , that after granulation (3) or mechanical pre-compaction (5) the leaf material is inoculated with a fungal mycelium, stored in a chamber under optimal growth conditions, the growth process of the fungus is specifically controlled and further processing takes place after colonization. [6] Method for producing pressed parts based on natural, biogenic residues according to claim 5, characterized by , that a nutrient substrate or nutrient solution is added to the mushroom mycelium, The degree of dryness is measured after the plants have grown through the soil. If necessary, further drying is carried out before further processing. [7] Method for producing pressed parts based on natural, biogenic residues according to claim 1, characterized by , that the surface of the molded part (11) is finished with natural colors, varnishes or coated with natural substances such as water glass. [8] Method for producing pressed parts based on natural, biogenic residues according to claim 1, characterized by , that prior to filling (8) a single or multiple mold, a layer or a thin layer of uncrushed leaves or at least larger leaf parts is placed into the single or multiple mold.

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