Use of pith parenchyma from the stem of a plant for the production of a material, material made from pith parenchyma and methods for its production

Abstract

Use of a plant substance to produce a material, wherein the plant substance consists of chemically untreated pith parenchyma of the stem of a plant.

Description

The invention relates to the use of pith parenchyma from the stem of a plant for the production of a material, the material and a method for producing the material. Technical background With regard to climate protection and available raw materials, sustainability and resource conservation are essential considerations in the development of innovative materials. The production of plastics, such as polypropylene, polyethylene, and polyethylene terephthalate, is traditionally based on the use of petroleum as a raw material. Petroleum extraction involves significant environmental impacts and is often very energy-intensive. Furthermore, these plastics do not decompose but rather break down into ever smaller pieces (microplastics), which pose a burden on the environment and thus also on human health. Therefore, there is an urgent need to find alternatives to the use of petrochemical raw materials, particularly in the form of renewable resources. The transition from the use of petrochemical raw materials to biological raw materials, especially those of plant origin, is one of the greatest challenges of our time. The publication EP 3 271 521 B1 describes a method for producing and using an insulating material from a plant-based raw material that has natural cavities. The plant-based raw material, for example miscanthus, is treated with a hydrophobic agent to provide the necessary properties for the insulating material. Chemical treatment of plant material can be environmentally harmful and negatively affect its mechanical properties. Furthermore, shaping the material often requires the addition of binders (e.g., resin), which can lead to recycling difficulties. Additionally, shredded plant material is frequently used as bulk material without any further shaping. The publication DE19817541C2 describes the production of a composite material based on rye, whereby the use of hydrophobizing and binding agents is again mandatory. Further state of the art is represented by the publication DE 10 2015 003 373 A1. As current technology shows, the production and extraction of renewable raw materials is often associated with high energy and material consumption, as well as the use of chemicals. Furthermore, the cultivation of the corresponding plants often requires the conversion of land used for other purposes, and in some cases, the destruction of ecosystems to gain new production areas. The consumption of renewable raw materials, which are essentially foodstuffs, is also questionable. For biological materials to represent a genuine alternative to conventional materials in terms of sustainability, their raw materials must be renewable and cultivated in an environmentally friendly manner. Furthermore, these raw materials should not compete with food production. The challenge lies in providing an environmentally friendly material that incorporates sustainably sourced raw materials. Summary of the invention This problem is solved by a use according to claim 1, a material according to claim 5, and a method according to claim 9. Further advantageous embodiments and configurations of the invention will become apparent from the dependent claims, the figures, and the exemplary embodiments. The embodiments of the invention can be advantageously combined with one another. A first aspect of the invention relates to the use of a plant substance for the production of a material, wherein the plant substance consists of chemically untreated pith parenchyma of the stem of a plant. According to an advantageous embodiment, the pith parenchyma has a pectin content of at least 10 wt%, preferably at least 15 wt%. According to an advantageous embodiment, the plant is selected from the group consisting of plants of the genus Helianthus, plants of the genus Zea, plants of the genus Sambucus, plants of the genus Silphium, and plants of the genus Verbascum. According to an advantageous embodiment, the pith parenchyma is present in the form of particles. Another aspect of the invention relates to a material comprising at least one first plant substance, wherein the first plant substance consists of chemically untreated pith parenchyma of the stem of a plant. According to an advantageous embodiment, the material is free of binders. According to an advantageous embodiment, the material is selected from the group consisting of a nonwoven fabric, a cast fiber material, and a fiber composite material. According to an advantageous embodiment, the pith parenchyma has a pectin content of at least 10 wt%, preferably at least 15 wt%. Another aspect of the invention relates to a method for producing a material comprising at least one plant substance, wherein the at least one plant substance consists of chemically untreated pith parenchyma of the stem axis of a plant, comprising the steps: - providing the stem axis, - separating the pith parenchyma of the stem axis, - comminuting the pith parenchyma into particles, - producing a suspension by mixing the particles with a liquid, - applying the suspension to enable the particles to adhere to one another, - separating at least a part of the liquid. According to an advantageous embodiment of the method, the pith parenchyma is comminuted so that the particles have a size of f 2.0 mm, preferably of 0.3 to 2.0 mm, and more preferably of 0.5 to 1.0 mm. Detailed description of the invention A first aspect of the invention relates to the use of a plant substance for the production of a material, wherein the plant substance consists of chemically untreated pith parenchyma of the stem of a plant. It has surprisingly turned out that chemically untreated pith parenchyma is exceptionally well-suited for providing a material. In particular, materials and components with very good specific properties can be used to substitute petrochemical polymers. The low specific gravity of the material is a particular advantage. For example, nonwovens / woven fabrics with a density of 0.05 g / cm³ to 5.2 g / cm³ have been produced. These densities correspond to those of petrochemical products such as solid polystyrene with a density of 1.04 to 1.09 g / cm³ and expanded polystyrene with a density of 0.02 to 0.06 g / cm³. The tissue in the interior of the shoot axis is referred to here as pith parenchyma. It differs morphologically and functionally from the outer cortical parenchyma (fibrous components) (Fig. 1). In terms of its molecular properties, the pith parenchyma consists of hydrophilic, yet water-insoluble polymers with a three-dimensional network. This network is formed, among other things, by hydrogen bonds between the individual polymer chains, although other interactions between the polymer chain segments are also possible. The present invention allows the pith parenchyma to be used to produce a material, e.g., in the form of a nonwoven fabric, without chemical treatment or additives. Chemically untreated pith parenchyma means, in particular, that the pith parenchyma is not chemically treated during the processing, e.g., with water-repellent agents. The invention also eliminates the need for binders, which are conventionally added to control the material's strength. It is also essential that the pith parenchyma is separated from the other components, especially from the fibers of the plant or shoot axis. In a preferred embodiment, the pith parenchyma is present in a comminuted form. Comminuted production, for example by cutting or grinding, breaks the pith parenchyma down into particles. Accordingly, the pith parenchyma is preferably present in the form of particles. These particles are pith parenchyma fragments of a specific size. Surprisingly, it has been found that the particles have the ability to adhere to one another and thereby aggregate into structures. This results in the formation of a three-dimensional structure, making the material suitable as a material for other applications. Preferably, the particles are flat, meaning their width is greater than their height. These flat particles are also called platelets. Preferably, the particles have a size of essentially 2.0 mm, more preferably 0.3 to 2.0 mm, and further preferably 0.5 to 1.0 mm. These size specifications refer to the diameter of the particles at their width. Particles of this size exhibit optimal adhesion and form a material that, without the addition of binders, possesses high strength and a low specific gravity due to the low density of the pith parenchyma (approximately 0.029 g / cm³). This size is advantageous because platelets larger than 2 mm adhere less effectively. The same applies to sizes below 0.3 mm, although it cannot be ruled out that outliers in terms of size may occur during processing of the material. However, it is also possible that the particles have a significant thickness compared to the platelets. The size specifications mentioned above are used to indicate the cross-sectional area of ​​the particles. The advantages of this size are the same as those of platelets. Uniformly three-dimensional particles can adhere to one another just as flat particles can, although the structure of the resulting aggregates, and thus of the material itself, may differ. This can be advantageous depending on the intended technical application of the material. Preferably, the pith parenchyma used has a pectin content of at least 10 wt%. It has surprisingly been found that, above this amount, the platelets produced during comminution adhere well to one another compared to those with a lower pectin content. Particularly preferably, the pith parenchyma has a pectin content of at least 15 wt%. A high pectin content is advantageous because it influences essential properties of the material, such as the adhesion of the particles to one another. Such a high pectin content particularly facilitates effective particle adhesion. It has been shown that the density and structure of the pith parenchyma depend on its maturity. This is primarily due to the fact that the structural breakdown of the cells during maturation increases the pectin content of the pith parenchyma. Furthermore, the density of the pith parenchyma also increases with increasing maturity. In connection with increasing pectin content and thus increasing density, it has also been shown that material made from fresher pith is more foam-like and lighter in color; material made from more mature pith parenchyma, on the other hand, is rather hard and brownish. In a preferred embodiment, the plant stem consists of at least 10% by weight of pith parenchyma. The weight percentage is calculated as the weight percentage of pith parenchyma in the stem. This allows for efficient harvesting and processing of the starting material. Furthermore, when processing stems with a pith parenchyma content of at least 10% by weight, large quantities of pith parenchyma can be obtained without unwanted fibers getting into the pith parenchyma or requiring laborious fiber removal. Preferably, the stem has a residual moisture content of approximately 50 to 80% by weight, more preferably 54 to 78% by weight, at harvest. The pith parenchyma preferably has a residual moisture content of approximately 65 to 85% by weight, more preferably 68 to 81% by weight, at harvest. The residual moisture content at harvest time is an indicator of the plant's maturity. If the pith parenchyma is white and the residual moisture content of the stem is approximately 50 to 80%, the plant is sufficiently mature but also still sufficiently moist. In this case, the pith parenchyma is particularly suitable for use according to the invention. The residual moisture content is thus an indicator of the material's maturity, which influences the properties of the pith parenchyma. By selecting the harvest time, the material properties (foam-like at lower maturity, wood-like at higher maturity) can also be influenced. The preferred plant is a herbaceous plant. Herbaceous plants are advantageous because several species in this group contain a greater amount of pith parenchyma compared to other plants. The plant from which the pith parenchyma is obtained for use in the production of a material is preferably selected from the group consisting of plants of the genera Helianthus, Zea, Sambucus, Silphium, and Verbascum. Plants of these genera exhibit a particularly high amount of pith parenchyma in the stem compared to other plants. A material derived from plants of the genus Helianthus (sunflowers), especially the common sunflower (Helianthus annuus), is particularly preferred, specifically from pith parenchyma. Sunflowers contain a large amount of pith parenchyma compared to other plants. Furthermore, sunflower pith parenchyma is especially suitable for producing this material. Sunflower pith parenchyma has a pectin content of up to 17.2% by weight. This high pectin content results in exceptionally good adhesion between the pith parenchyma particles. Additionally, sunflower pectin has a methylation level (DM) of < 50% and is therefore classified as a low-methoxyl pectin (LM). LM pectin, such as that of the sunflower, is more stable than high-methoxyl pectin (HM pectin) and can be processed well with tap water and at moderate temperatures (20 ± 5 °C) without the pectin being degraded.Furthermore, the adhesion of the particles is also promoted by a comparatively low hemicellulose and lignin content (compared, for example, to maize, soghum, and kenaf). The chemical composition and content of pectins in sunflower pith depend on the plant's maturity. Sunflowers are also characterized by the fact that their pectin content hardly changes with ripening. As they ripen, the pith parenchyma changes from a watery green to a foamy white, losing water and thus density. The composition of sunflower pith parenchyma is shown as an example in Table 1. Ash 16.6 Protein 0.9 Lipids4 Pectins17.6 Hemicellulose4,4 Lignin3,2 Cellulose 45.4 The porosity of sunflower pith decreases from 59% at the bottom (near the roots) to 53% at the top (near the flower head), while the biochemical composition remains constant. Hygroscopic behavior is higher at the bottom of the stem than at the top, which is due to the altered porosity. This also influences the mechanical properties, which exhibit higher strength at the base than further up. The pith's heat capacity is particularly noteworthy, as at 0.039 W / mK it is superior to that of glass wool at 0.049 W / mK. Its heat capacity is roughly equivalent to that of hemp. Utilizing sunflower stems is also particularly advantageous from an economic perspective. Typically, sunflower stems are not used in the agricultural process and are therefore regularly plowed under after the sunflower seeds are harvested. Using the stems to obtain pith parenchyma thus offers farmers an advantage, as the stems from 3 to 7 tons of dry matter per hectare, which would otherwise be left in the field after harvest, can be economically utilized. This allows pith parenchyma to be provided as a raw material in virtually any desired quantity. Sunflowers are cultivated on a large scale, so there is no need to create new, dedicated fields.Sunflower pith parenchyma is therefore a highly ecological raw material that, as a by-product, does not compete with food production, can be provided cost-effectively, and is also biologically safe and biodegradable. Also particularly preferred is a material which comprises a material obtained from plants of the genus Zea, in particular from Zea mays L., wherein the material consists of pith parenchyma. A second aspect of the invention relates to a material comprising at least one first plant substance, wherein the first plant substance consists of chemically untreated pith parenchyma of the stem of a plant. It has been surprisingly discovered that chemically untreated pith parenchyma is suitable for producing materials with excellent specific properties. These materials are particularly well-suited to replacing conventional materials made from petrochemical polymers. In addition to the low specific gravity of the material mentioned above, it advantageously exhibits damping properties with respect to mechanical and, especially, acoustic vibrations (sound). The vibration transmission can be controlled by the mass, stiffness, and layer structure of a given component. The softer and higher the airflow resistance in the pores, the lower the vibration transmission. Besides the component's structure, the degree of disruption and the density of the pith parenchyma are also crucial factors.Furthermore, the material also possesses good thermal properties, although the structure of the pith, especially when it is foam-like and highly porous, promotes poor thermal conductivity. In this respect, the material is suitable for thermal insulation. Another advantage is that the material is easy to prepare and manufacture, namely by processing the pith parenchyma after mixing it with a liquid. The invention provides an inexpensive and technologically simple material to produce, which is an environmentally friendly alternative to conventional, petroleum-based plastics. Preferably, the material is free of binders, i.e., it contains no binder. Conventional materials based on plant materials require the addition of additives, especially binders, to achieve the necessary technical properties. Binders used include, for example, natural or aqueous resins, aqueous synthetic resin dispersions or emulsions, aqueous hybrid dispersions and emulsions, two-component epoxy resin systems, two-component polyurethane systems, mineral mortars based on lime and / or cement, or even natural binders such as clay, loam, or gypsum. In contrast, the properties of the present material can be controlled by the degree of maturity and comminution of the pith parenchyma, the moisture content during processing, and the degree of drying of the product. Preferably, the material is selected from the group consisting of a nonwoven fabric, a cast fiber material, and a fiber-reinforced composite material. These types of materials are advantageously suited for further processing, e.g., into packaging material, containers, and insulation materials. Preferably, the material contains no other plant substance. In other words, the only plant substance contained in the material is preferably pith parenchyma from the stem. According to the invention, pith parenchyma is suitable for the material. Moreover, it is available in large quantities compared to other plant parts, with stems frequently being obtained as a by-product of food production (e.g., in sunflower cultivation). In a particularly advantageous embodiment, the material can also consist specifically, i.e. exclusively, of pith parenchyma. Alternatively, and also preferably, the material may contain one or more additional plant substances. These additional plant substances may originate from a different plant than the first. Furthermore, the additional plant substances may also contain fibers (see, for example, DIN 60000, 60001-1). The addition of foreign fibers can, for example, promote the desired properties of higher elasticity and reduced fracture tendency. A third aspect of the invention relates to a method for producing a material comprising at least one plant substance, wherein the at least one plant substance consists of chemically untreated pith parenchyma of the stem axis of a plant, comprising the steps: - providing the stem axis, - separating the pith parenchyma of the stem axis, - comminuting the pith parenchyma into particles, - producing a suspension by mixing the particles with a liquid, - applying the suspension to enable the particles to adhere to one another, - separating at least a part of the liquid. A method for producing a material comprising at least one plant substance, wherein the at least one plant substance consists of pith parenchyma of the stem of a plant, is also disclosed, comprising the steps of: - providing the stem, - separating the pith parenchyma of the stem, - crushing the pith parenchyma into particles, - producing a suspension by mixing the particles with a liquid, - applying the suspension to enable the particles to adhere to one another, - separating at least part of the liquid. The advantages of the aforementioned processes correspond to the advantages of the material and its use. A particular advantage is that, according to the invention, a purely biological material is processed using a textile method. These processes make it possible, in particular, to produce materials from pith parenchyma without the need for chemical treatment of the pith parenchyma, especially with hydrophobic agents. The particles produced during the comminution of the pith parenchyma are wet-set, i.e., the suspension is applied to a sieve. The pith parenchyma particles then form aggregates through the adhesion described above. This creates a lattice, which is subsequently dried. The suspension is also suitable for fiber casting. Because the process according to the invention can be carried out without the use of chemical additives, it is also particularly environmentally friendly. Furthermore, compared to chemical pulping, the mechanical properties of the material are not negatively affected. Providing the shoot stems means that either freshly harvested or stored shoot stems are fed into the processing process. The preferred parameters mentioned above apply to the provided shoot stems. The pith parenchyma located inside the stem is separated from the surrounding tissue, which contains fibers, among other things, and used for further processing. Preferably, the pith parenchyma is separated by mechanical comminution. Particularly preferably, the pith parenchyma is separated from the fibrous components of the stem. This can be achieved, for example, by mechanically breaking up and comminuting the stem. For this purpose, it can be transferred using a device with rollers, especially three rollers. The process is similar to shredding. A carding machine, which is typically used to open wool bales, has proven suitable for this process. Alternatively, the stem breaking process can be carried out using a granulator.The vertical feeding of the stalk to the horizontally rotating cutting blade ensures effective mechanical breaking and shredding of the stalk. The degree of shredding (production fineness) is variable by selecting the appropriate perforated plate. The Tilby method can also be applied to sunflower stalks to separate the bark from the pith. The pith parenchyma of the shredded stem is preferably mechanically separated from the fibrous components of the stem by applying an airflow. Since the pith parenchyma is significantly lighter than the fibrous components of the stem, it can also be spatially separated from the more rapidly settling fibrous components by the airflow. Optionally, a further cleaning step can be included, which involves sieving out the fibrous components using a long sieve. Sieving forms part of the separation process between the bark (fibrous components) and the pith parenchyma. Following the separation of the pith parenchyma, it is ground into particles. This grinding is generally done mechanically, using various methods. The pith parenchyma can be ground into particles in either a dry or wet state. Dry methods include grinding using a cutting mill (also known as a retsch mill), a ball mill, or a cross-flow shredder. Wet methods include grinding using a pulper, a Hollander beater, or a refiner, as used in papermaking. Accordingly, the pith parenchyma is ground into particles using either a cutting tool or a grinding tool. Preferably, in this process, the pith parenchyma is comminuted such that the particles have a size of f 2 mm, preferably 0.3 to 2.00 mm, and more preferably 0.5 to 1.0 mm. As mentioned above, the particles should not be larger than 2 mm because they adhere particularly well up to this size. The same applies to a size of less than 0.3 mm, although it cannot be ruled out that, during processing the material, very small and / or larger particles (= outliers) may also occur. The particulated pith parenchyma is mixed with a liquid to produce a suspension. Water is preferably used as the liquid for preparing the suspension, but this is not the only option. The water can be, for example, demineralized water (DI water). An aqueous solution can also be used. Accordingly, the liquid is preferably selected from the group consisting of water and an aqueous solution. Preferably, the particle content is about 1 to 2 wt%, more preferably 1.0 to 1.5 wt%, and particularly preferably 1.3 wt% of the suspension. The liquid is mixed with the pith parenchyma in a ratio such that the pith parenchyma content is about 1.0 to 2.0 wt%. Advantageously, the suspension achieves a viscosity at this ratio that allows it to flow. The suspension should be stirred to a homogeneous consistency before being suspended on a sieve or in a shaping process. In the next step, the suspension is dispensed, allowing the particles to adhere to one another. This initially occurs as the particles settle, causing them to rest against each other. It is assumed that this direct contact creates mechanical adhesion between the particles. This adhesion can be further promoted by actively separating the liquid, for example, using pressure or a vacuum. Preferably, the suspension is applied to a sieve, preferably in a wet nonwoven process or also preferably in a fiber casting process. In a wet-weave process, the suspension is deposited onto a screen, for example, a long screen, round screen, or inclined screen. It has surprisingly been found that a wet-weave process is suitable for using pith parenchyma to produce a material. The wet-weave technology is similar to papermaking. Essentially, a suspension is formed with the shredded pith parenchyma, which is then suspended on a screen. As it is poured onto the screen, the platelets settle on top of each other. In a fiber casting process, the suspension is poured onto a perforated negative mold (also called a negative tool) of the material to be produced or a corresponding component and dewatered by vacuum. During this process, the aggregated particles of the pith parenchyma are deposited, and the resulting shape can be removed from the negative tool using a counter-mold and vacuum. Alternatively, the suspension can also be processed in a modified thermoforming process and formed into a desired shape. In this process, the wet material is placed as a semi-finished product into a mold and pressed into the component. The mold can be heated, which leads to hardening and a finished component after removal from the mold. In a further step, at least some of the liquid is separated. This can be done by passively draining the liquid. Advantageously, however, the liquid is separated by means of a vacuum or pressure. The removal of the liquid on the one hand, and the pressure applied by the pressure or vacuum on the other, increases the adhesion between the particles. In the wet nonwoven process, the separation of the liquid can be supported, for example, by pressing pressure, causing the particles to move closer together. This creates a structure similar to mother-of-pearl, which consists of many thin layers of platelets. The adhesion of the particles to one another ensures the cohesion of the material. It has been observed that dewatering by pressing can increase the strength of the material. In the fiber casting process, the liquid is separated by both pressing and vacuum. After the liquid is separated, a solid material remains, which forms the material, e.g. as a fleece. Preferably, the resulting material is dried in a further step. Depending on the manufacturing process, only a portion of the liquid is initially removed, and the resulting material still contains liquid. For example, water molecules may be trapped between the aggregated particles or may have formed at least a partial molecular bond with molecules of the particles. Drying can be carried out, for example, under reduced pressure, with heat, with radiation (infrared), or in a convection dryer. The drying of the material is influenced by various factors. The maturity of the pith parenchyma plays a role in both the separation of the liquid and the subsequent drying process. Pith parenchyma with a lower degree of maturity dehydrates significantly better and therefore requires a shorter drying time than pith parenchyma with a higher degree of maturity. In pith parenchyma with a lower degree of maturity, the platelets have a smaller contact area with each other, which allows water to escape more quickly. Mature pith parenchyma dehydrates more slowly due to the trapping of water between the smoother platelets. In this context, the ripening-dependent structure of the particles is a factor influencing drying, as it affects the surface and thus the contact area of ​​the platelets to each other. Furthermore, the drying process can be accelerated by adding foreign fibers to the pith parenchyma. These foreign fibers, i.e., fibers originating from a different plant than the pith parenchyma, increase moisture transport. The dried material can be stored or put to use. Examples The invention is explained in more detail using the figures. Character description Fig. 1 shows a graphic representation of a sunflower and a cross-section through its stem axis. Fig. 2 shows a flow diagram of an embodiment of the method according to the invention. Fig. 3 shows finely comminuted plant pith parenchyma (1 mm). Fig. 4 shows coarsely comminuted plant pith parenchyma (4 mm). Fig. 5 shows aggregates formed from comminuted pith parenchyma. Fig. 6 shows a material produced from pith parenchyma by fiber casting (Fig. 6a) and wet nonwoven processes (Fig. 6b). Example 1 The flowchart in Fig. 2 shows the steps of an embodiment of the process according to the invention, in which a material is produced from the pith parenchyma of the sunflower. In the first step, S1, 130 kg of sunflower stems (also known as sunflower stalks) are prepared. The sunflower stalks are approximately 1 m long each. They are harvested directly after the flower heads, which are separated from the stalks to obtain the sunflower seeds, have been harvested. The stalks are dried (residual moisture content f 20%) and then used. Drying fixes the chemical structure, and the material subsequently degrades very little. Alternatively, the stalks can be processed immediately after harvesting. In a second step (S2), the pith parenchyma is separated from the stem. The material is first mechanically broken up. For this purpose, the stems are pulled lengthwise through a granulator or a cutting mill. The material is then separated from the fibrous components of the stem by applying an airflow. For this purpose, the material is transferred to a container into which an airflow generated by a blower or fan is directed. The sections of sunflower stems are separated from each other by mechanical forces caused by air turbulence. The pith parenchyma and the fibrous components are sorted as the heavier fibrous components sink to the bottom, while the lighter, foam-like parts of the pith parenchyma are held aloft and carried by the airflow into another container. In this way, the pith parenchyma is spatially separated from the fibrous components. At a pith content of 10% by weight, approximately 13 kg of separated pith parenchyma are obtained. In a third step, S3, the pith parenchyma is comminuted. A retting mill, or possibly another comminution device with a cutting mechanism, is used for this purpose. The process yields platelet-shaped particles. The target particle size is 0.2 to 1.9 mm, based on the diameter. Smaller particle sizes are achieved through fine comminution (Fig. 3), while larger particle sizes are achieved through coarser comminution (Fig. 4). In a fourth step, S4, the particles, i.e., the comminuted pith parenchyma, are mixed with water. For the resulting 13 kg of pith parenchyma, the material is mixed with 1000 l of water, resulting in a pith parenchyma content of 1.3% by weight. Besides ordinary tap water, distilled water, double-distilled water, or deionized water can be used, for example. The material is mixed with the water by stirring or swirling until a homogeneous suspension is obtained. In a fifth step, S5, the suspension is applied to an inclined sieve. In a further step, S6, some of the liquid is separated by dripping from the sieve under negative pressure. Reducing the liquid volume brings the particles into closer contact with each other. The particles then begin to adhere to one another, forming aggregates (Fig. 5). The separation of the liquid and the aggregation of the particles result in a fleece (Fig. 6b). In a further, subsequent step of the process (S6), the nonwoven fabric is passed through a flow-through dryer. This dryer transfers heat to the nonwoven fabric and absorbs and removes the resulting water vapor. Additionally, after the flow-through dryer, the nonwoven fabric can be fed into a contact dryer in the form of a cylinder dryer. This provides further drying of the nonwoven fabric, and the pressure between the cylinder drum and the belt can also improve its mechanical strength. Alternatively, the fleece can be dried, for example, by a so-called microwave drying process. In this process, the fleece is irradiated with high-energy microwaves, which cause the water molecules inside the fleece to move. The resulting frictional heat dries the fleece from the inside out. Another option for drying the nonwoven fabric is the use of an infrared dryer, which can be connected in series with the flow-through dryer, preferably before the material (nonwoven fabric) is transported into the flow-through dryer. Finally, after passing through the flow dryer, the fleece can be wound up or compacted with the drying cylinder. Example 2 - Experimental Procedure Degree of exposure of the pith parenchyma In an initial experiment, the refinement of the pith and its influence on the specimen's properties were investigated. For this purpose, the biomass was pulverized in a mixer over three different time periods (90 sec. / 180 sec. / 270 sec.), with a biomass content of 2%. Dewatering was performed using the Dynamic Drainage Analyzer (DDA), allowing its determination to be carried out simultaneously. A clear difference was observed between the wet samples (P1) after 90 seconds and those after 180 seconds. The second sample (P2) was considerably finer than P1. The difference between P2 and P3, however, was minimal. The average shrinkage after drying was 39.7%. Interestingly, all three samples were very hard after hardening and could not be broken by hand. The DDA analysis from Experiment 1 showed that the degree of digestion had no significant effect on the dehydration behavior of the samples. The dehydration curves indicated that the material was dehydrated up to 50 ml using vacuum, but no further dehydration could be achieved beyond that point. This could be due to small particles settling on the sieve and blocking further dehydration. Fiber composite production by adding fibers The addition of fibers was used to explore the possibility of using pith as a matrix material in composites. In fiber composite production, the pith parenchyma is used as a matrix that encloses the fibers or the tissue. The added fibers are intended to interlock with each other and with their surroundings, thereby giving the matrix improved tensile strength and reduced brittleness. The aim was to investigate whether matrix-fiber adhesion occurs and to what extent this positively influences fracture brittleness. For this purpose, 1 g each of hemp fibers and nettle fibers were dispersed in a 2% solution and pressed into a specimen. Upon addition of fibers, fiber embedding in the pith was observed. Fiber separation was less successful, resulting in the formation of specks. The samples had a foam-like character. It was demonstrated that it is possible to embed natural fibers in the pith parenchyma matrix. Interim observation 3: Variance of the dry specimens Based on the previous experiments, a variance of the dry test specimens could be determined, ranging from foam-like to foam-like / compressed (SCH / K) to compressed. A comparison of the dry biomass concentration as a percentage of weight, the location where the sunflower was harvested, and the mixer used to prepare the suspension is shown in Table 2: Table 2 Determination of the influencing parameters of the different sample characteristics Table 2 Determination of the influencing parameters of the different sample characteristics Pre-production 123004 Holzmaden, RG1 Blend-Tec foam V163002Holzmaden,RG2Blend-TecCompressed V263002Holzmaden,RG2WMFSch / K 2.3 V2_233001Holzmaden,RG2NordicaSch / K Material control63002Kfurt, RG3WMFSch / K V363002Holzmaden,RG1Nordica Foam F133001Kfurt, RG3NordicaSch / K F133001Holzmaden,RG2NordicaSch / K 1 Ripeness level (RG): RG1 = fresh from stem, RG2 = moist ripe pith, RG3 = dried pith 2 Sch = foam, K = compressed. Sch / K = lies between the two properties. 3 The exception is the test with baking powder, which is highly compressed. The comparisons showed that the foam-like texture correlates with the maturity of the pith. The fresher pith parenchyma exhibits a pronounced 3D structure, and the cells are still intact. In the dried, mature pith parenchyma, the cell walls have degraded, and the structure is rather flat. When the pith parenchyma lies flat on top of each other, this results in a compressed specimen. The cells did not disintegrate during digestion but remained as platelets. This could be examined microscopically. The difference in structure affects the way the material is deposited. If the material is more branched, the distance between the layers increases, resulting in a more foam-like appearance. Drainage analysis according to maturity level In a further step, the dewatering behavior according to maturity level (RG) was examined. For this purpose, a suspension was prepared for both RG2 and RG3, and the dewatering of three samples each was measured using the DDA. The dewatering time of 80 seconds is particularly noteworthy, as the material was sufficiently dewatered during this period, at a minimum screen speed of 1 m / min for processing on the NVLA, to have enough strength to be transported undamaged from the headbox table to the oven.Very rapid dewatering was observed for RG2. During the DDA (Dewatering Diagram), air suction was audible. This, together with the analysis of the dewatering diagram, allows conclusions to be drawn about the material's processing behavior. The particles in the dispersion are so large that they do not adhere to the sieve and can therefore be dewatered effectively, but at the same time, air is drawn in, resulting in an uneven vacuum. The vacuum level dropped during the measurement from an initial 250 mbar to as low as 130 mbar. This is always observed when the material is dewatered to such an extent that its circumference decreases within the DDA and air can be drawn in laterally. Simultaneously, the strongly fluctuating curves indicate that the water was not being extracted uniformly from the sample.This can be attributed to the water retention capacity of the medulla, whereby the water is only released under a certain force. During the dehydration of the suspension from the RG3 chamber, it was observed that the water flowed into the DDA dehydration chamber in bursts. Nevertheless, the dehydration process was more consistent than with the RG2 suspension (see error! Reference source not found). The vacuum level also remained constant at 250 mbar. Overall, the RG3 suspension took significantly longer to dehydrate. Furthermore, the samples were still very moist when removed from the DDA. A direct comparison of the drainage curves according to maturity further highlights the difference. As observed, the 3D structure of the parenchyma decreases with increasing maturity. This also alters the drainage process. In fresher material, the platelets have a smaller contact area with each other, allowing water to escape more easily, while the smoother, more mature platelets tend to retain the water. The average moisture content of the samples is 90.27% for RG2 and 95.97% for RG3. The material strength required for further processing is achieved with a residual moisture content of 91% (measured using a moisture analyzer). RG2 is dry after 4 hours in the oven at 60°C, while RG3 requires more than 8 hours. Table 3: Data collected from the dewatering test after RG: Consistency 1%11 Average sample wet g 25.9167.41 Average sample dry g 2.522.71 Variance % 1,572.83 1 Percentage by weight of dry BM in the suspension The samples from the DDA differ in terms of fineness and color in appearance, as well as in strength. Example 3 - Evaluation of the investigation of the manufacturing processes of fiber composites Composite materials consist of two main components. The finite or continuous fibers transmit tensile forces, while the matrix fixes the fibers and provides support against compressive and shear stresses, as well as protecting them from environmental influences. This allows for the achievement of superior properties. For the material in question, a modified thermoforming process is suitable. The starting material is provided as a semi-finished product. This semi-finished product is then placed directly into the mold and pressed into the component. The press can be heated during this process, resulting in curing and a finished component after removal from the press (similar to the process used with thermosetting resins). The possibility of forming a composite with the pith parenchyma as a matrix has been investigated (see above). Wet fleece process In wet nonwoven technology, a solution or dispersion is suspended on an inclined screen, through which the material is dewatered by means of a vacuum. What remains are the fibers, which form a nonwoven fabric. Any fibers that are dispersible in liquid can be used. The DDA application can be considered as a representative example of the wet nonwoven process. Based on the preceding DDA, it can be stated that a primary material can be produced by creating a fiber suspension and dewatering it on a screen using a vacuum. The results from fiber composite production with fibers can be transferred to wet nonwoven technology.

Claims

Use of a plant substance to produce a material, wherein the plant substance consists of chemically untreated pith parenchyma of the stem of a plant. Use according to claim 1, wherein the pith parenchyma has a pectin content of at least 10 wt%, preferably at least 15 wt%. Use according to claim 1 or 2, wherein the plant is selected from the group consisting of plants of the genus Helianthus, plants of the genus Zea, plants of the genus Sambucus, plants of the genus Silphium, and plants of the genus Verbascum. Use according to any of the preceding claims, wherein the pith parenchyma is in the form of particles. Material comprising at least one first plant substance, wherein the first plant substance consists of chemically untreated pith parenchyma of the stem of a plant. Material according to claim 5, wherein the material is free of binders. Material according to claim 5 or 6, wherein the material is selected from the group consisting of a nonwoven fabric, a cast fiber material, and a fiber composite material. Material according to claim 5, 6 or 7, wherein the pith parenchyma has a pectin content of at least 10 wt%, preferably at least 15%. Method for producing a material comprising at least one plant substance, wherein the at least one plant substance consists of chemically untreated pith parenchyma of the stem of a plant, comprising the steps: - providing the stem, - separating the pith parenchyma of the stem, - comminuting the pith parenchyma into particles, - producing a suspension by mixing the particles with a liquid, - applying the suspension to enable the particles to adhere to one another, - separating at least part of the liquid. Method according to claim 9, wherein the pith parenchyma is comminuted so that the particles have a size of ≤ 2.0 mm, preferably 0.3 to 2.0 mm, and more preferably 0.5 to 1.0 mm.

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