Molded bodies containing retrograded popcorn

Abstract

The present invention relates to molded bodies, in particular composite materials or molded parts, containing partially retrograded popcorn.

Description

[0001] The present invention relates to the field of molded bodies or molded parts as well as composite materials containing popcorn.

[0002] Composite materials, especially particleboard or fiberboard, have been known for over a hundred years as a substitute for solid wood in the furniture industry, construction, etc. Several factors play a role in the quality of composite materials, including in particular the density, the tensile strength across the grain, and the thickness swelling.

[0003] The density of the material is particularly important for composite materials, as the advantageous properties of particleboard or fiberboard, such as their strength, generally increase with increasing density. For this reason, wood and / or composite materials consisting (predominantly) of popcorn have been proposed. However, for some of these composites, it is necessary to increase water resistance, especially regarding low swelling and water absorption, through coatings or surface layers, which necessitates a complex manufacturing process.

[0004] Furthermore, it is of interest to create molded bodies or molded parts that are made from renewable raw materials or at least contain them predominantly, and which also have increased water resistance, especially with regard to low swelling values ​​and water absorption.

[0005] The challenge, therefore, is to create a shaped body in which these disadvantages can be at least partially overcome.

[0006] This problem is solved by a molded body according to claim 1. Accordingly, a molded body, in particular a composite material, is proposed, wherein the molded body is retrograded popcorn (popcorn ret ) contains, which in the X-ray spectrum at the 2θ diffraction angle has a peak between 20° and 23° with a higher intensity than in the range between 17° and 20°.

[0007] Surprisingly, it has turned out that in many applications of the invention, a large number of molded bodies with good to excellent properties, especially with regard to improved water resistance, can be produced.

[0008] Depending on the application, one or more of the following advantages can be achieved compared to molded parts made from untreated popcorn: • increased moisture resistance of the molded body • improved transverse tensile strength of the molded body • improved compressive strength of the molded body • increased flexural strength of the molded body

[0009] The expression “the popcorn ret “The X-ray spectrum exhibits a peak between 20° and 23° at the 2θ diffraction angle with a higher intensity than in the range between 17° and 20°” means and / or specifically implies that in the spectrum in question, the signal which has the highest intensity at the 2θ diffraction angle in the range of 17° to 23° lies between 20° and 23°.

[0010] The term "popcorn" as used in the present invention includes, in particular, all materials which, like popcorn (Zea mays, convar. microsperma), expand upon rapid heating to high temperatures—optionally after appropriate greasing—by causing the water present in the seed to evaporate suddenly, thus transforming the starch contained in the seed into a foam-like consistency. Such behavior is known, among other things, from quinoa, amaranth, rice, or wheat. Materials based on these raw materials are explicitly referred to and included as "popcorn" as used in the present invention. The term "popcorn" is not intended to be limited to corn and was chosen particularly for reasons of simplicity, clarity, and readability.

[0011] The term "molded bodies" encompasses in particular all planar and non-planar materials that contain popcorn as their main component, as well as possibly shredded lignocellulosic materials such as wood, cereal straw, hemp or flax, which are shaped after being coated with a synthetic or natural binder and pressed under temperature and pressure.

[0012] The term "composite material" refers in particular to materials that consist mainly of popcorn and possibly of mechanically or thermomechanically crushed lignocellulosic material, which, after being coated with a synthetic or natural binder, are formed and pressed into composite materials under temperature and pressure.

[0013] According to a preferred embodiment, the wood or composite material can be made entirely from popcorn. retThe term "composite material" as used in the present invention is to be understood in the broadest sense and expressly includes materials that consist (only) of popcorn. ret are constructed and no longer contain any wood components.

[0014] The present invention further relates to a molded body, in particular a wood and / or composite material, such as a particleboard and / or fiberboard or a molded part, wherein the molded body contains at least partially retrograded popcorn.

[0015] The term "retrograded" refers to and / or includes in particular popcorn in which the degree of crystallization of the starch contained therein is increased compared to untreated popcorn.

[0016] Furthermore, the term "retrograded" includes and / or refers to popcorn that has been exposed to a temperature of at least 0°C and below 120°C and a relative humidity of at least 80% for such a long time that an increase in bulk density of 10% or more can be observed.

[0017] During the retrogradation process, the amylose contained in popcorn recrystallizes primarily through the introduction of moisture. The degree of retrogradation achieved can be "frozen" by drying the moist material.

[0018] According to a preferred embodiment, the molded body consists essentially of popcorn as a structuring and dimensionally stabilizing material, i.e., it essentially comprises (only) popcorn. ret and binders or other additives such as hardening accelerators, water repellents, etc.

[0019] The term “essentially” within the meaning of the present invention means >90% (wt / wt), in particular >95% (wt / wt) and most preferably >98% (wt / wt).

[0020] According to a preferred embodiment of the invention, the molded body comprises a binder, preferably selected from thermoplastics, thermosets, aminoplastics, phenolic resins, isocyanates, proteins, tannins, starch, synthetic binders or near-natural / natural binders, or mixtures of binders, such as urea-formaldehyde resin, melamine-formaldehyde resin, melamine-reinforced urea-formaldehyde resin, tannin-formaldehyde resin, phenol-formaldehyde resin, polymeric diphenylmethane diisocyanate or mixtures thereof, as well as mineral binders.

[0021] According to a preferred embodiment of the invention, the binder content in the molded body is from ≥ 0% (wt / wt of the entire molded body) to ≤ 20% (wt / wt of the entire molded body).

[0022] According to a preferred embodiment of the invention, the molded body essentially contains popcorn. ret , which in the X-ray spectrum at the 2θ diffraction angle has a peak between 20° and 23° with a higher intensity than in the range between 17° and 20°.

[0023] According to a preferred embodiment of the invention, the molded body essentially contains retrograded popcorn.

[0024] According to a preferred embodiment, the popcorn has ret (before manufacturing the molded body) a bulk density of ≥ 80 kg / m³ 3 It has been found that the properties of the resulting molded body increase with increasing bulk density. Thus, by controlling the retrogradation and selecting the binder or additives, tailored materials can be produced with regard to strength and hygroscopic properties, depending on the application. The popcorn preferably possesses ret(before manufacturing the molded body) a bulk density of ≥ 100 kg / m³ 3 , preferably ≥ 150 kg / m² 3 and ≤ 450 kg / m² 3 .

[0025] According to a preferred embodiment of the invention, the popcorn ret a grain size distribution in which ≥ 50% and ≤ 90% of the popcorn have a grain size of ≥ 1 mm and ≤ 10 mm.

[0026] This has proven advantageous for many applications within the present invention. Larger grain popcorn is often more difficult to process into molded parts and / or composite materials, while smaller grain popcorn tends to absorb the binder or glue added during the production of the composite material in many applications within the present invention, which can impair the quality of the molded part and / or composite material.

[0027] Popcorn is particularly favored reta grain size distribution in which ≥ 70% and ≤ 90% of the popcorn ret have a grain size of ≥ 1 mm and ≤ 10 mm.

[0028] According to a preferred embodiment of the invention, the popcorn ret a particle size distribution in which ≥ 50% and ≤ 90%, particularly preferably ≥ 70% and ≤ 90% of the popcorn ret have a grain size of ≥ 1 mm and ≤ 10 mm.

[0029] According to a preferred embodiment of the invention, the popcorn ret a grain size distribution in which ≥ 50% and ≤ 80% of the popcorn have a grain size of ≥ 1 mm and ≤ 8 mm.

[0030] According to a preferred embodiment of the invention, the popcorn ret an average particle size distribution of ≥ 1 mm and ≤ 6 mm. This has proven advantageous for many applications within the scope of the present invention.

[0031] Popcorn is particularly favored retan average particle size distribution of ≥ 1.5 mm and ≤ 5 mm.

[0032] According to a preferred embodiment of the invention, the fat content of the popcorn is ret before processing ≤ 10 (wt) %.

[0033] The term "fat content" of popcorn does not refer to the total amount of fat in the popcorn, but rather to the amount of fat used to make the seed epidermis hydrophobic, which leads to better retention of the water contained in the seed.

[0034] In many applications within the scope of the present invention, it has proven advantageous to keep the fat content as low as possible, as this facilitates further processing of the popcorn. Preferably, the fat content is ≤ 5% by weight. In a particularly preferred embodiment, no fat is added for the consistency change (conversion) ("puffing"). In this case, it is particularly preferred that the consistency change ("puffing") is carried out using microwaves, as will be explained below.

[0035] According to a preferred embodiment, the molded body contains popcorn. ret as a structuring and / or dimensionally stabilizing material.

[0036] According to a preferred embodiment, the molded body consists of ≥ 50% popcorn. ret , or preferably it consists essentially of this.

[0037] The term "essentially" means in particular > 95% (wt / wt), or preferably > 98%.

[0038] The present invention also relates to a method for manufacturing molded bodies, comprising the steps a) Making popcorn b) Retrogradation of popcorn c) Manufacturing the molded body, whereby steps b) and c) can also be carried out in reverse order.

[0039] The individual steps of the procedure are explained in more detail below, whereby any sub-steps can be combined with others as desired. a) Making popcorn

[0040] Corn kernels can be made to expand using different methods.

[0041] According to a preferred embodiment of the invention, the popcorn used for manufacturing the molded parts is produced by puffing. Depending on the application, unmodified kernels can be used, or suitable seeds, e.g., feed corn kernels, are first crushed, and the kernel fragments are then expanded under pressure and temperature according to the Bichsel process (WO 1999042005A1) in a defined process. Other possibilities for puffing the starchy kernels include, for example, the use of hot plates, hot air machines, and microwaves.

[0042] A preferred embodiment of the invention uses the so-called Cerex process of Cerex AG, CH-3368 Bleienbach. The process can be divided into three sections: a preheating element, a reactor, and an expansion chamber. First, the grain meal is heated uniformly to approximately 100 °C in the preheating element. Then, the grain is treated with hot steam in the reactor, and finally, the grain is fed into an expansion chamber. Here, the corn kernels (corn meal) are expanded by pressure reduction over a specific period of time. At the end, the puffed materials are collected and separated from the unpuffed components (Bichsel, n.d.). The conversion of corn meal to popcorn granules using the Cerex process is almost 100% successful in most applications; only less than 5% of the meal remains unpuffed.

[0043] Furthermore, the popcorn can be crushed again before step b), so that according to a preferred embodiment of the invention the method comprises a step a1) which is carried out between steps a) and b): a1) Crushing the puffed popcorn

[0044] Step a1) can be carried out using all common manufacturing techniques. a) Retrogradation of popcorn

[0045] If the retrogradation of the popcorn is carried out before the production of the molded part, this preferably takes place using a circulation process. This means, in particular, that popcorn granules are placed in a rotating drum and exposed to steam.

[0046] In the case that the molded part is produced first, it is preferably exposed to targeted steam, preferably at an elevated temperature of approximately 100°C for > 0 seconds to 600 seconds. b) Production of the molded body

[0047] In step c), different approaches are chosen depending on whether the desired shaped body is a sheet (such as a chipboard or fiberboard) or a three-dimensional molded part. I) Production of flat pressed boards

[0048] Flat pressed sheets are manufactured under increased pressure and, if necessary, at increased temperature.

[0049] According to a preferred embodiment of the invention, a binder and optionally a hardening accelerator are added in step c).

[0050] In principle, all binders known in the field, such as thermoplastics, thermosets, aminoplastics, phenolic resins, isocyanates, proteins, tannins, starch, synthetic binders or near-natural / natural binders as well as mineral binders, or mixtures of binders, such as urea-formaldehyde resin, melamine-formaldehyde resin, melamine-reinforced urea-formaldehyde resin, tannin-formaldehyde resin, phenol-formaldehyde resin, polymeric diphenylmethane diisocyanate or mixtures thereof, can be preferably used.

[0051] All substances known in the field, especially ammonium sulfate and / or potash, can be used as hardening accelerators.

[0052] Through targeted retrogradation in an area of ​​approximately 60 kg / m³ 3 and 450 kg / m² 3The precisely adjustable bulk density of the popcorn granules makes it possible to produce highly compression-resistant core layers for rigid sandwich panels, allowing the full potential of highly rigid facing layers made of materials such as HDF, HPL, etc., to be utilized in sandwich construction. It is also possible to press sandwich panels with a fiberboard or particleboard coating in a single step. II) Manufacturing of molded parts

[0053] The molded part is preferably produced from retrograded popcorn granules under slightly elevated pressure and / or temperature. During this step, electromagnetic radiation in a frequency range of ≥ 30 kHz to ≤ 300 GHz is selectively used.

[0054] Preferred pressures are ≥ 0.1 bar and ≤ 10 bar, preferably ≤ 5 bar, and most preferably ≤ 2 bar.

[0055] Alternatively, the molded part can also be manufactured under vacuum. Preferred vacuum levels are ≥ 0.1 bar and ≤ 1 bar.

[0056] Preferred pressing times are ≥ 0.5 s / mm molded part and ≤ 24 s / mm molded part per minute, preferably ≤ 8 s / mm molded part.

[0057] Two techniques are preferably used to manufacture the molded part itself: 1) Compression molding

[0058] This process is particularly well-suited for slightly curved or flat components. Its primary applications are typically in the automotive and packaging industries, where it is used to produce larger components with two-dimensional or three-dimensional structures.

[0059] At the beginning of the process, the molding compound, i.e., the popcorn surrounded by polymer, is retThe molding compound, possibly with additional binding agent, is placed into a cavity and closed using a pressure piston. The pressure gives the molding compound the shape defined by the tool. The molding compound in the cavity is heated under pressure and temperature, optionally by irradiation with electromagnetic radiation in a frequency range of ≥ 30 kHz to < 300 GHz.

[0060] When using thermosetting plastics as polymers, the temperature serves, among other things, to influence the curing process; with thermoplastics, it is used to melt the plastic. Afterwards, the finished part can be removed from the mold and, if necessary, further processed, coated, or laminated (e.g., with starch-based films or PU films). 1) Use of molding machines

[0061] This technique typically uses specialized molding machines that can operate at higher pressures and / or temperatures. The first process step involves pneumatically compressing the molding compound (i.e., the optionally polymer-coated popcorn with any additional binder) and filling the closed, specialized molding machine with the compressed compound. Alternatively, the molding compound can be conveyed into the cavity using a vacuum.

[0062] Using targeted electromagnetic radiation in a frequency range of ≥30 kHz to ≤ 300 GHz and, if necessary, pressure, the molding compound is brought to the desired curing temperature and, depending on the application, the polymer is completely cross-linked.

[0063] After the popcorn particles are cross-linked or fused together, the molded part is removed from the mold in the final process step. The molded parts can then be coated or laminated (e.g., with starch-based films, PU films, PLA films, or flocking).

[0064] The molded parts according to the invention and / or the molded parts produced according to the method according to the invention can be used in a variety of applications, including (but not limited to): Packaging materials (e.g., cooler boxes, protective packaging for electrical appliances, spice tins, etc.), building materials, furniture, automotive parts (e.g., headrests, sun visors, child car seats, soundproofing mats for door panels and motorhome cabin linings), insulation materials (e.g., for electrical appliances), dishes, sporting goods (e.g., yoga rollers, neck rolls), toys (e.g., dice, board games, puzzles), picture frames, gift baskets, acoustic composite molded parts, motorhome parts, etc.

[0065] The aforementioned components, as well as those claimed and described in the exemplary embodiments, to be used according to the invention are not subject to any special exceptional conditions with regard to their size, shape, material selection and technical conception, so that the selection criteria known in the field of application can be applied without restriction.

[0066] Further details, features, and advantages of the subject matter of the invention will become apparent from the dependent claims and from the following description of the accompanying drawings, in which several exemplary embodiments are shown. The drawings show: Fig. 1 the X-ray spectrum of popcorn as used in the present invention Fig. 2 the X-ray spectrum of ordinary popcorn Fig. 3 the two spectra from Fig. 1 and Fig. 2 stacked on top of each other Fig. 4 a diagram showing the change in relative humidity (rH) during the conditioning of test specimens Fig. 5 a diagram showing the change in the bulk density of the test specimens Fig. 4 shows. Fig. 6 a diagram showing the transverse tensile strength of the test specimens before and after air conditioning. Fig.7 a diagram showing the change in bulk density of popcorn granules during air conditioning.

[0067] The present invention will be further explained below by means of examples which are to be regarded as purely descriptive and not as limiting. Example 1: X-ray spectrometric analysis of popcorn

[0068] The following two samples, “A” and “F”, were examined and prepared as follows: Sample A: Untreated popcorn granules (55.9 kg / m³) 3 The material was coated with a binder (UF resin) of 8% and pressed at 180°C with a pressing time factor of 10 s / mm to form a 20 mm thick flat-pressed sheet. Samples measuring 50 mm x 50 mm were cut into and examined radiographically. Sample F: Popcorn granules were exposed to steam in a recirculating process for approximately 120 seconds and then retrograded. The resulting retrograded popcorn granules had a bulk density of 209.3 kg / m³. 3 The material was processed into a 20 mm thick flat-pressed plate as described above and also examined using X-ray diffraction.

[0069] Subsequently, both samples “A” and “F” were examined radiographically as follows: Sample preparation

[0070] To prepare a powdered sample, the samples were embrittled in liquid nitrogen and then ground in a Retsch centrifugal mill (ZM-100) using a 1 mm mesh sieve. The powder was then hermetically sealed with silicone between two PET films in a 2 mm thick sample carrier (Ø opening = 2.5 cm). X-ray wide-angle examination on the dual-circuit diffractometer

[0071] The wide-angle X-ray examinations were performed using a Bruker-AXS D5000 dual-circle diffractometer in symmetrical transmission using monochromatic (Ge (111) -Primary monochromator) Cu-K α - Radiation (λ = 0.15406 nm) performed at 30 mA and 40 kV.

[0072] Diffractograms were recorded in the 20-angle range of 3°–29° (step size Δ2θ = 0.1°) and 29.5°–104° (step size Δ2θ = 0.5°), measurement time / Δ2θ = 60 s. The sample rotated at 15 rpm around the sample normal during the measurement. The entire angular range was measured three times to improve statistical accuracy. The total measurement time per sample was 20.3 h. For background correction, a diffractogram was prepared in the same manner from the empty sample holder and the two PET cover sheets.

[0073] Fig. Figure 1 shows the X-ray spectrum of the resulting popcorn (sample “F”), Fig.2 the X-ray spectrum of the untreated popcorn (sample “A”) as well as Fig. 3. A representation of both spectra in overlap.

[0074] As in the Fig. While the signal is clearly visible in images 1 to 3, the untreated popcorn (sample "A") shows a strong signal at approximately 18.3° (2θ diffraction angle), whereas this signal is no longer visible in sample "F," which instead shows a signal at approximately 21° (2θ diffraction angle). Without committing to a specific theory, the inventors assume that this is due to the increased degree of crystallization of the starch, particularly the amylose, in the popcorn. Example 2: Production of shaped bodies (subsequent retrogradation)

[0075] The following section described plate-shaped composite materials with a target bulk density of 200 kg / m³. 3The product was manufactured using both a urea-formaldehyde resin and a hemoglobin-based adhesive made from natural raw materials. The pressing time and temperature were 10 seconds per millimeter and 200 °C, respectively.

[0076] Square specimens with an edge length of 50 mm were cut from these slabs, measured, and weighed. For further investigations, those specimens were selected that met the target density of 200 kg / m³. 3 corresponded.

[0077] These were then deliberately exposed to water (air-conditioned) as follows:

[0078] The test specimens were climate-controlled in a climate chamber at an ambient temperature of 20 °C. The relative humidity was increased from 65% RH to 90% RH in 10% increments and then reduced again. This cycle was repeated twice and is described in Fig. 4 shown again graphically.

[0079] The bulk density of the test specimens was examined with each change in humidity ( Fig. 5) As can be clearly seen, the bulk density of the test specimens changed in the first cycle and subsequently remains constant with further changes in the climate - except for a few measurement fluctuations.

[0080] Fig. Figure 6 shows the transverse tensile strength (QZ) of the specimens before and after air conditioning. An increase in transverse tensile strength of 3.8 times (hemoglobin-bound specimens) and 8.9 times (UF resin-bound specimens) can be observed.

[0081] For comparison: A chipboard with a comparable density of approximately 650 kg / m³ 3 According to EN 312, it achieves a minimum transverse tensile strength of 0.35 N / mm². 2 . Example 3: Processing of treated popcorn granules

[0082] Instead of conditioning the molded body for retrogradation, tests were carried out with popcorn granules, unglued granules, and granules glued with the binders from Example 2, with the conditions chosen analogously to Example 2.

[0083] The change in bulk density during the conditioning of the samples is in Fig.Figure 7 illustrates this. It can be observed that the bulk density also increases in the first cycle and then hardly changes further. From this, it can be concluded that popcorn granules, after the initial increase in relative humidity and corresponding increase in bulk density, remain dimensionally stable even under further climate changes. If composite materials are manufactured from these granules, they often exhibit significantly more favorable properties regarding dimensional stability under changing climates. The degree of retrogradation can be measured based on the bulk density of the granules. While untreated granules of the 2 mm - 4 mm size fraction have a bulk density of approximately 57 kg / m³, 3 This increases to approximately 350 kg / m³ after complete retrogradation. 3 to. Example 4: Production of shaped bodies from treated popcorn granules

[0084] 10,000 g of popcorn granules of size fraction 2 - 4 mm with a bulk density of approx. 55 kg / m³ 3 The granules were sprayed with 3 kg of water using a spray device in a rotating drum and then dried for 6 hours at a temperature of 100°C in a drying cabinet. This increased the bulk density of the granules from 55 kg / m³. 3 to 150 kg / m 3 The treated popcorn was then used to produce a composite material. For this purpose, 2500 g of popcorn containing 8% (based on dry weight) urea-formaldehyde resin was applied. Subsequently, 1920 g of the coated material (dry weight) was weighed out and pressed into a 2 cm thick sheet in a hot press at a temperature of 180°C. These parameters resulted in a sheet density of 400 kg / m³. 3 .

[0085] Ten test specimens measuring 50 mm x 50 mm were cut from the plate and used to test the transverse tensile strength according to EN 319. A transverse tensile strength of 0.81 N / mm² was obtained. 2 . Standard particleboard of type P2 (EN 312) has a density of 650 kg / m³ 3 - 680 kg / m 3 a transverse tensile strength of 0.35 N / mm 2 The water absorption, determined according to DIN EN ISO 29767:2019, also yielded a value of 2.1 kg / m² for the manufactured panels. 2 after 24 hours of immersion in water. It should be noted that the use of water-repellent agents was initially completely omitted.

[0086] Comparable slabs made from conventional popcorn granules exhibit a water absorption of 7.8 kg / m² after 24 hours of water storage. 2 Here too, a significant improvement in the hygienic properties of the resulting molded body can be observed. Example 5: Investigation of the properties of shaped bodies according to the invention

[0087] 10,000 g of untreated popcorn granules of size fraction 2 - 4 mm with a bulk density of approx. 55 kg / m³ 3 The samples were exposed to steam for varying durations in a rotating drum and then dried. After steaming for 10 s, 60 s, and 100 s and subsequent drying, bulk densities of 75 kg / m³ were achieved. 3 / 113 kg / m 3 / 150 kg / m 3 (see Table 2). Significant retrogradation occurs, as evidenced by the fact that the bulk density of the granules is 55 kg / m³. 3 to 150 kg / m 3 rises. From Fig. It is evident that this treatment achieves partial, though not complete, retrogradation. Flat-pressed boards with densities of 200 kg / m³ were produced from these retrograded granules. 3 / 300 kg / m 3 / 400 kg / m 3A reference plate was also produced from untreated granules. For this, 2500 g to 5000 g of granules were coated with urea-formaldehyde resin (8% based on the dry weight of the granules). Subsequently, 960 g to 1920 g of the respective coated material were weighed out and pressed into 2 cm thick plates in a hot press at a temperature of 180°C. Based on these parameters, plate densities of 200 kg / m³ were obtained with input weights of 960 g, 1440 g, and 1920 g, respectively. 3 / 300kg / m 3 / 400 kg / m 3 .

[0088] Ten 50 mm x 50 mm test specimens were cut from the slab and used to test the transverse tensile strength according to EN 319. Surprisingly, a significant increase in transverse tensile strength was observed with increasing bulk density of the granules, reaching up to 0.81 N / mm². 2 (see Table 1). Sheets made from unretrograded popcorn exhibit a transverse tensile strength of 0.26 N / mm². 2on; standard particleboard type P2 (EN 312) with a density of 650 kg / m³ 3 - 680 kg / m 3 a transverse tensile strength of 0.35 N / mm 2 .

[0089] The water absorption, determined according to DIN EN ISO 29767:2019, also yields a value of 1.1 kg / m² for the manufactured panels. 2 up to 2.1 kg / m² 2 After 24 hours of water immersion (Table 1). It should be noted that no water-repellent agents were used initially. Comparable slabs made from conventional popcorn granules exhibit a water absorption of 7.8 kg / m² after 24 hours of water immersion. 2 Even with incomplete retrogradation of the popcorn granules, a significant improvement in the hygroscopic properties of the composite material made from partially retrograded popcorn granules can be observed.

[0090] The results are shown in Table 1 below. Table 1: Properties of popcorn flat pressing plates according to the invention and comparative example Flat pressboard (20 mm) transverse tensile strength Flexural strength Bulk density of granules Bulk density of the flat pressed panels Water absorption after 24 hours, water storage untreated popcorn granules 0,26N / mm 2 1,32N / mm 2 58,5 kg / m 3 200 kg / m 3 7,8 kg / m 2 Retrograded popcorn granules 0.41 N / mm" 1,6N / mm 2 75,0 kg / m 3 200 kg / m 3 1,1 kg / m 2 Retrograded popcorn granules 0.61 N / mm" 2,4N / mm 2 113 kg / m 3 300 kg / m 3 1,6 kg / m 2 Retrograded popcorn granules 0.81 N / mm" 3,20N / mm 2 150,0 kg / m 3 400 kg / m 3 2,1 kg / m 2 Example 6: Investigation of the increase in bulk density during retrogradation.

[0091] 3000 g of popcorn granules were placed in a drum and then exposed to steam (100°C) while rotating at 60 rpm. The amount of steam and the duration of the steaming are given in the following table. After the retrograded popcorn granules were removed, they were subsequently dried in a drying chamber at approximately 100°C for about 24 hours, and then the bulk density was determined.

[0092] Table 2 below shows the resulting increase in bulk density as a function of the steaming time and the amount of steam. Table 2: Influence of steaming on the bulk density of the popcorn. Time of steaming [S] Steam quantity [l] Initial bulk density of popcorn granules [kg / m³] 3 ] achieved bulk density of popcorn granules [kg / m³] 3 ] 15 117,45 58,3 84,3 30 234,9 58,3 102 45 352,35 57,9 104 60 469,8 57,9 111,5 75 587,25 58 111 90 704,7 58 139,8 105 822,15 58,2 165,4 120 939,6 58,2 191,8 135 1057,05 58,3 199,7 150 1174,5 56,9 204,3 165 1291,95 56,8 258 180 1409,4 58,1 280,4 195 1526,85 56,3 335

[0093] The individual combinations of components and features of the embodiments already mentioned are exemplary; the exchange and substitution of these teachings with other teachings contained in this publication and with the cited publications are also expressly considered. The person skilled in the art will recognize that variations, modifications, and other embodiments described herein may also occur without deviating from the inventive concept and scope of the invention.

[0094] Accordingly, the above description is exemplary and not to be considered limiting. The word "comprise" used in the claims does not exclude other components or steps. The indefinite article "a" does not preclude the meaning of a plural. The mere fact that certain measures are cited in mutually different claims does not clarify that a combination of these measures cannot be used to advantage. The scope of the invention is defined in the following claims and their equivalents. 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] WO 1999042005A1

[0041] Cited non-patent literature

[0000] DIN EN ISO 29767:2019 [0085, 0089]

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