Soil improver

Abstract

A soil improver for increasing the liquid storage capacity of soils, the soil improver consisting of a cured plastic foam, wherein the plastic foam has at least mainly open cells, characterized in that the cured plastic foam has an apparent density of 5 to 15 kg / m³. The invention also relates to a method for producing such a plastic foam of such a soil improver.

Description

[0001] Soil improver

[0002] The invention relates to a soil conditioner for increasing the liquid storage capacity of soils, consisting of a cured plastic foam, wherein the plastic foam has at least predominantly open cells. The invention also relates to a method for producing a plastic foam.

[0003] Often, significantly more liquid is used to irrigate plants than the plants actually need. This poses a major problem, especially in already arid areas. A major reason for inefficient irrigation is the soil's poor liquid storage capacity. Stony and sandy soils, such as those often found in arid and semi-arid regions, in particular, have very low liquid storage capacity, meaning that much of the liquid is lost through runoff, evaporation, or infiltration. Furthermore, this leads to the leaching of nutrients important for plants from the soil.

[0004] Various products are available for increasing the liquid storage capacity of soil. For example, gel-based water storage systems absorb water through a chemical reaction, changing their volume. This change in the gel's volume can lead to unwanted voids in the soil.

[0005] Other water storage systems are based on expanded clay. However, increasing the water storage capacity of a soil by adding expanded clay is ineffective, since even a high input of material into the soil is accompanied by only a comparatively small increase in liquid storage capacity.

[0006] Furthermore, cured, hydrophilic foams are also known to increase the liquid storage capacity. DE 10 2004 004 856 B3 discloses a generic liquid storage device for supplying plants with a porous storage material consisting of a foam formed from a urea resin and a surfactant with a density of 15 kg / m³. 3 - 60 kg / m 3The foam can be in the form of a molded foam body or, preferably, in the form of flakes and can be used to store a liquid, in particular water or an aqueous fertilizer solution. It is intended to be embedded as a layer in the soil or potting soil and essentially absorb the roots of the plant to be supplied. The foam is preferably introduced into the soil as a closed layer, with the layer being formed by the foam flakes or by one or more plate-shaped foam molded bodies. It is also possible to mix the foam in the form of flakes with the soil surrounding the roots of the plant to be supplied, or to distribute it throughout the soil. The foam has open cells, which gives it hydrophilic properties.This allows it to store liquid and gradually release it into its surroundings, for example, into the soil surrounding the root system or directly into the plant roots. This foam is intended to provide a liquid storage medium that can be used over large areas.

[0007] The present invention aims to achieve the object of providing a soil improver with improved properties for storing liquids in soils and with improved suitability for large-scale use.

[0008] This object is achieved by a soil improver made of a hardened plastic foam having the features of claim 1 in that the hardened plastic foam has a bulk density of 5 to 15 kg / m 3 The object is also achieved by a method having the features according to claim 9.

[0009] Whenever reference is made here and below to a plastic foam or a cured plastic foam, the associated terminology refers to the understanding of the structure and composition of a plastic foam set out below. Plastic foams consist of a large number of cells with cell spaces formed by gas inclusions, whereby the cells can vary considerably in size and shape. In so-called open-cell plastic foams, the cells have open cell walls so that the gas inclusions form an interconnected network. The openings in the cell walls are called pores and make the plastic foam permeable to gases and liquids. Open cells consist of a large number of cell webs that are formed around the pores and form the scaffolding of the outer contour of a cell.

[0010] The bulk density of the cured plastic foam of the soil improver according to the invention is 5 to 15 kg / m 3 , so that the cell webs of the individual cells are very thin. In conjunction with the predominantly open cells, a breakdown of the plastic foam into individual fibers, in particular microfibers is made possible. Furthermore, the plastic foam itself has a high liquid storage capacity due to its low bulk density. This means that, provided that it breaks down into fibers and also partially into larger fragments which contain several at least partially intact open cells, it can absorb up to 90% liquid in relation to its own volume. In addition, the intact plastic foam can permanently store large quantities of a liquid, in particular water, once it has been absorbed, for several months. 55 to 65% of the originally absorbed liquid remains in the plastic foam.

[0011] It was surprisingly found that the plastic foam according to the invention, with its lower density, can permanently absorb significantly more liquid than the foam known from DE 10 2004 004 856 B3. This allows the liquid storage capacity of a soil to be significantly improved over large areas if the soil improver is incorporated into the soil. Furthermore, it was surprisingly found that the soil improver according to the invention also interacts directly with the soil and the liquid is retained in the soil through this interaction. What is essential for this is that the soil improver at least partially forms a fiber-soil mixture with the soil, in that the plastic foam at least partially breaks down into individual fibers and microfibers over time due to the application of mechanical force before and / or during introduction into the soil and / or as a result of exposure to the soil.By mixing the individual fibers in the soil, the soil conditioner creates a very large contact area with the soil. This large contact area means that the introduction of a liquid into the fiber-soil mixture creates a capillary effect, which allows a large amount of liquid to be retained in the soil. The soil conditioner is particularly suitable for storing water in the soil.

[0012] The liquid reservoir known from DE 10 2004 004 856 B3 stores the liquid exclusively directly in the foam itself, so the liquid storage capacity is defined by the foam volume. Consequently, this liquid reservoir in the floor can only store the total amount of liquid that can be directly absorbed by the liquid reservoir.

[0013] The soil improver according to the invention also has the advantage that it is degraded over time by naturally occurring microfungi and subsequently converted by naturally occurring bacteria into substances that have a fertilizing effect on the soil and can serve as nutrients for plants. The soil improver can advantageously act as a fertilizer until it is completely degraded, which can occur, for example, over a period of 6-8 years.

[0014] Preferably, the cured plastic foam has a density of 8 to 14.5 kg / m 3 , preferably from 9 to 12 kg / m 3 , on.

[0015] The compressive strength of the plastic foam according to the invention is preferably 150 to 350 g / cm 2 , especially 200 to 300 g / cm 2 or particularly preferably 225 to 275 g / cm 2This makes the cured plastic foam relatively unstable, so that even a slight mechanical force causes it to disintegrate into individual fibers and microfibers. The compressive strength of the plastic foam may vary slightly between a surface and an interior area of ​​the same plastic foam sample. The compressive strength data for the soil improver under test refer to all areas of the plastic foam. In this case, the compressive strength is defined as the end of the linear-elastic range under compressive stress at which individual intact cells of the plastic foam fail to such an extent that the soil improver is irreversibly deformed.

[0016] To ensure that the plastic foam breaks down into as many individual fibers and microfibers as possible, thus maximizing the contact area of ​​the soil improver according to the invention with the soil, it is advantageous for the plastic foam to have as many cells as possible with a corresponding number of cell webs, with the proportion of material between the cell spaces being as small as possible. Therefore, the cell density of the plastic foam is preferably 45 to 90 cells / cm, in particular 50 to 75 cells / cm.

[0017] The size of the fibers and microfibers can be influenced by the size of the cell diameter. It is advantageous if the fibers are sufficiently large so that the capillary forces can develop optimally in interaction with the soil. In a preferred embodiment of the soil improver, the cell diameter of all foam cells with a diameter of at least 40 pm is < 80 pm for 5-15% of these cells, 81-100 pm for 25-35% of these cells, 101-140 pm for 35-45% of these cells, 141-200 pm for 10-20% of these cells, 201-600 pm for 1-10% of these cells, and > 601 pm for < 1% of these cells. In a further preferred embodiment of the soil improver, carbon particles are embedded in the plastic foam. By adding carbon particles, the fibers released by mechanical action or exposure to the soil can be longer than fibers from a comparable soil improver without the addition of carbon particles.In addition, the embedded carbon has a fertilizing effect when the soil improver decomposes in the soil.

[0018] The carbon particles can, in particular, be carbon fibers and / or carbon black. They are preferably present in the plastic foam in a proportion of > 0.1 wt.%, in particular > 0.5 wt.%. Furthermore, the proportion of carbon particles in the plastic foam is preferably < 10 wt.%, in particular < 5 wt.%.

[0019] If the soil improver according to the invention is to be used in agriculture, it is generally advantageous if it is not toxic itself and if its decomposition in the soil does not produce any toxic substances that have a harmful effect on living organisms and plants.

[0020] A method according to the invention for producing a plastic foam, in particular the soil improver according to the invention described above, is characterized according to claim 9 in that a prefoam A and a prefoam B are formed from a liquid A which contains at least water and a prepolymer, and a liquid B which contains at least water, a surface-active substance and a hardener, by introducing a gas, in particular atmospheric air, into the respective liquid, and both prefoams are then mixed, the mixing ratio of prefoam A and prefoam B being between 40 vol.% to 60 vol.% and 60 vol.% to 40 vol.%, preferably between 45 vol.% to 55 vol.% and 55 vol.% to 45 vol.% or in particular 47.5 vol.% to 52.5 vol.% and 52.5 vol.% to 47.5 vol.%.

[0021] In a particular embodiment of the process according to the invention, the ratio of liquid A to liquid B is between 75 vol% to 25 vol% and 50 vol% to 50 vol%.

[0022] By introducing the gas into the liquids A and B it is possible to

[0023] Number of rows and cell diameter of the resulting mixture

[0024] To control the plastic foam of the soil improver according to the invention and to influence the cell structure. The gas is introduced into liquid A and liquid B, respectively, thereby providing a high number of bubble nuclei in the liquids. In this way, two pre-foams are formed, which, when mixed, form a plastic foam with a high cell density due to the high number of bubble nuclei.

[0025] Pre-foam A and pre-foam B preferably react with one another by mixing in a tubular reaction chamber. The reaction chamber advantageously has at least one open end through which the plastic foam produced by the reaction can exit and subsequently harden. Furthermore, the reaction chamber can have a reaction chamber length in the longitudinal direction and a substantially circular cross-section with a reaction chamber diameter. The ratio of reaction chamber diameter to reaction chamber length is preferably between 1:50 and 1:200, preferably between 1:80 and 1:120, and particularly preferably 1:100. The reaction chamber diameter is in particular less than 200 mm, preferably between 10 and 50 mm.

[0026] The volume flow of the liquids can be between 50 and 150 ml per mm of the reaction chamber diameter, preferably 100 ml per mm of the reaction chamber diameter.

[0027] In a further preferred embodiment of the method, pre-foam A and pre-foam B can each be fed to the reaction chamber via a separate feed channel. The feed channels have a specific channel cross-sectional area, the ratio of which to the reaction chamber cross-sectional area is advantageously between 1.0 to 2.0 and 1.0 to 0.5, preferably 1 to 1. Furthermore, it is advantageous if the ratio of a channel length of the feed channels to the reaction chamber diameter is between 2 to 1 and 4 to 1, preferably 3 to 1. The geometry and dimensions of the reaction chamber and the feed channels ensure that a plastic foam with the required cell diameters and the required cell density is formed before it exits the reaction chamber.

[0028] The mixing of pre-foam A and pre-foam B, as well as the conveying of the reacting pre-foams and the resulting plastic foam, can preferably be carried out automatically by the incoming pre-foams. This is advantageous because no additional devices are required to carry out these processes, which could have an undesirable influence on the production of the soil conditioner. The gas, which is preferably introduced into the liquids using a compressed air device, can be introduced into the liquids at a pressure of 1 to 2.5 bar, in particular 1 to 2.25 bar, or particularly preferably 1 to 2 bar, to ensure stable foam formation.

[0029] The prepolymer contained in liquid A is chemically and / or thermally crosslinkable, so that a soil improver can be formed from a cured plastic foam. In a preferred embodiment of the process according to the invention, the prepolymer can be a urea-formaldehyde, which serves as a carrier material and, in a cured state, ensures that the plastic foam retains its structure. It is advantageous if the proportion of urea-formaldehyde in relation to the water contained in liquid A is preferably > 10 wt.%, in particular > 15 wt.% or particularly preferably

[0030] > 22 wt.%. Furthermore, it is preferred if the proportion of urea-formaldehyde in relation to the water contained in the liquid A is preferably

[0031] < 35 wt.%, in particular < 30 wt.% or particularly preferably < 27 wt.%.

[0032] Furthermore, the liquid A can contain further substances with which, for example, the density and compressive strength of the cured plastic foam can be influenced. As a preferred example, a urea is added to the liquid A. It is advantageous if the proportion of urea in relation to the water contained in the liquid A is preferably > 0.5 wt.%, in particular > 0.75 wt.% or particularly preferably > 1 wt.%. Furthermore, it is preferred if the proportion of urea in relation to the water contained in the liquid A is preferably

[0033] < 5 wt.%, in particular < 3 wt.% or particularly preferably < 2 wt.%.

[0034] In a further preferred embodiment of the process according to the invention, the surface-active substance in the liquid B is a surfactant that enables foam formation. Suitable surfactants are, in particular but not exclusively, anionic surfactants such as alkylbenzenesulfonates, fatty alcohol ether sulfates or fatty alcohol sulfates. It is advantageous if the proportion of the surfactant in relation to the water contained in the liquid B is preferably > 5 wt.%, in particular

[0035] > 7.5 wt.% or particularly preferably > 10 wt.%. Furthermore, it is preferred if the proportion of surfactant relative to the water contained in the liquid B is preferably < 20 wt.%, in particular < 15 wt.% or particularly preferably < 12 wt.%.

[0036] Furthermore, it is preferred if the hardener contained in liquid B is an acid catalyst which crosslinks the prepolymer and thus stabilizes the plastic foam. Suitable acid catalysts include, for example but not exclusively, phosphoric acid, citric acid and p-toluenesulfonic acid. It is advantageous if the proportion of the acid catalyst in relation to the water contained in liquid B is preferably > 15 wt.%, in particular > 20 wt.% or particularly preferably > 25 wt.% Furthermore, it is preferred if the proportion of the acid catalyst in relation to the water contained in liquid B is preferably < 40 wt.%, in particular < 35 wt.% or particularly preferably < 30 wt.%.

[0037] Furthermore, in a preferred embodiment, liquid B may contain resorcinol as a further catalyst. It is advantageous if the proportion of resorcinol relative to the water contained in liquid B is preferably > 0.5 wt.%, in particular > 1 wt.%, or particularly preferably > 2 wt.%. Furthermore, it is preferred if the proportion of resorcinol relative to the water contained in liquid B is preferably < 10 wt.%, in particular < 5 wt.%, or particularly preferably < 3 wt.%.

[0038] Furthermore, it is advantageous if the process temperature of the method according to the invention is between 30 °C and 55 °C, in particular 35 °C and 50 °C or particularly preferably 40 °C and 45 °C.

[0039] An example of the production of the soil improver according to the invention from the cured plastic foam is described below.

[0040] The properties of the soil improver were determined using the following methods:

[0041] • Determination of bulk density: The bulk density p is the density of the cured plastic foam based on the mass and the total volume, which results from the sum of the volume of the solid material components Vsolid and the volume of the cell spaces Vzei of the plastic foam. The bulk density was calculated using the following formula: p = m / (Vsolid + Vzei).

[0042] • Determination of compressive strength: The compressive strength of the cured plastic foam was determined by subjecting a cuboid-shaped sample of the plastic foam to compressive stress on one of its surfaces until plastic deformation occurred. The foam sample was pressed against a circular punch with a surface area of ​​1 cm 2 loaded, whereby the surface of the plastic foam that was loaded with the stamp was considerably larger than the stamp surface.

[0043] • Determination of cell density: The cell density was determined by placing a line grid of four horizontal and five vertical lines on ten images of different sections of a foam surface measuring just over 3 x 4 mm, which were taken with a microscope camera with a resolution of 48 megapixels. The distance between these lines corresponds to a distance of 1 mm on the surface of the recorded foam. The recorded foam surfaces are surfaces of foam pieces cut out from the interior of a produced plastic foam. The orientation of the cut surface of the cut out foam piece within the produced plastic foam is irrelevant for determining the cell density. The outer surface of the produced plastic foam is not taken into account when determining the cell density. The cells that at least partially intersected the line were counted along each line.Only cells with a cell diameter greater than or equal to 40 μm were considered. Using the resulting line counts, an average line count was calculated across all lines in all image sections. The average line count was converted into the number of cells per centimeter, defined here as cell density, by adding the known line length. Foam defects, such as cavities that ran through multiple cell walls and cell bridges, were not considered cells.

[0044] • Determination of cell diameter: To determine the cell diameter, the diameter was estimated by calculating the mean of the largest and smallest distances between two opposite cell walls passing through the approximate center of gravity of the cell. The error incurred in estimation is negligible due to the small number of cells, whose average diameter is around 40 pm. Alternatively, the average diameter can be determined by determining the area of ​​a cell using image analysis software and deriving the diameter from the area, assuming that the area is that of an ideal circle. To obtain the soil improver from a cured plastic foam, Liquid A and Liquid B were first prepared separately and kept in containers.

[0045] Liquid A was prepared by mixing distilled water with, in terms of the amount of distilled water, 25 wt% urea-formaldehyde (Basopor® 293) and 1 wt% urea.

[0046] Liquid B was prepared by mixing distilled water with, in terms of the amount of distilled water, 11 wt% of an anionic surfactant, 27 wt% of phosphoric acid and 2 wt% of resorcinol.

[0047] First, a pre-pressurized sample was formed from each liquid by introducing atmospheric air into the liquids using a compressed air device at a flow rate of 90 l / min and 1.5 bar. The liquids were added in a ratio of 50 vol% to 50 vol% and at a flow rate of 3 l / min each.

[0048] Subsequently, prefoam A and prefoam B were fed into a reaction chamber in a ratio of 50 vol% to 50 vol%. Within the reaction chamber, the prefoams were mixed and conveyed out of the reaction chamber for curing. Crucially, liquid B or prefoam B already contained the hardener and surfactant, so that the formation of the plastic foam began immediately upon mixing with prefoam A, with curing starting simultaneously. During production, the process temperature was approximately 42 °C.

[0049] The ratio of the length of the feed channels in which the liquids were prefoamed to the reaction chamber diameter was 3 to 1. Furthermore, the ratio of the feed channel cross-section to the reaction chamber cross-section was 1 to 1, with the feed channel diameter and the reaction chamber diameter each being 20 mm. The ratio of the reaction chamber diameter to the reaction chamber length was 1 to 100. The feed channels and the reaction chamber can be designed as tubes.

[0050] The cured plastic foam of the soil improver according to the invention produced by the process described as an example had a bulk density of 12.3 kg / m 3 , a compressive strength of 249.3 g / cm 2 , measured on a surface of the plastic foam, and a cell density of 59 cells / cm. The inventive method for producing the cured

[0051] Plastic foam, in particular the soil improver according to the invention, can be carried out, for example, with a device shown in Figure 1.

[0052] Fig. 1 shows an apparatus for carrying out the method according to the invention.

[0053] The device 1 shown in Figure 1 has a reaction chamber 2, to which a liquid A is fed from the container 4.1 via the metering pump 3.1 and a liquid B from the container 4.2 via the metering pump 3.2. Between the reaction chamber 2 and the metering pumps 3.1, 3.2 there is arranged a compressed air device 5, which introduces atmospheric air via the gas channel 6.1 into the liquid A and via the gas channel 6.2 into the liquid B and thereby pre-foams the liquids before they are fed into the reaction chamber 2, forming a pre-foam A and a pre-foam B. The pre-foams then flow via the feed channels 7.1 and 7.2 into the reaction chamber 2 due to the pressure of the compressed air device 5 and the inflowing liquids and pre-foams. There the pre-foams mix in such a way that they react with one another, whereby the formation of a plastic foam begins.The resulting plastic foam exits through an open end 8 of the reaction chamber 2 and subsequently hardens. The reacting pre-foams and the resulting plastic foam are automatically moved toward the open end 8 in the reaction chamber 2 by the flowing pre-foams, so no device is required to convey the plastic foam.

[0054] The reaction chamber 2 has a reaction chamber cross-sectional area, which can, for example, correspond to the respective channel cross-sectional area of ​​the feed channels 7.1, 7.2. Furthermore, the reaction chamber 2 has a reaction chamber length L, wherein the ratio of a reaction chamber diameter RD to the reaction chamber length L can be, for example, 1 to 100. The ratio of a feed channel length ZKL to the reaction chamber diameter RD can also be, for example, 3 to 1. In this way, a plastic foam with a cellular structure can form in the reaction chamber 2, which leads to the soil improver according to the invention. Reference numeral hste

[0055] 1 device

[0056] 2 reaction chamber

[0057] 3.1 Dosing pump

[0058] 3.2 Dosing pump

[0059] 4.1 Container

[0060] 4.2 Container

[0061] 5 Compressed air device

[0062] 6.1 Gas duct

[0063] 6.2 Gas duct

[0064] 7.1 Feed channel

[0065] 7.2 Feed channel

[0066] 8 open ending

[0067] L Reaction chamber length

[0068] RD reaction chamber diameter

[0069] ZKL feed channel length

Claims

Patent claims 1. Soil improver for increasing the liquid storage capacity of soils made of a cured plastic foam, wherein the plastic foam has at least predominantly open cells, characterized in that the cured plastic foam has a bulk density of 5 to 15 kg / m³ 3 exhibits.

2. Soil improver according to claim 1, characterized in that the cured plastic foam has a bulk density of 8 to 14.5 kg / m³ 3 , preferably from 9 to 12 kg / m² 3 , exhibits.

3. Soil improver according to claim 1 or 2, characterized in that the cured plastic foam has a compressive strength of preferably 150 to 350 g / cm². 2 , especially 200 to 300 g / cm² 2 or especially preferably 225 to 275 g / cm² 2 exhibits.

4. Soil improver according to one of the preceding claims, characterized in that the plastic foam has a cell density of 45 to 90 cells / cm, in particular 50 to 75 cells / cm.

5. Soil improver according to one of the preceding claims, characterized in that the cell diameter of the cells of the plastic foam has a cell diameter of at least 40 pm. 5-15% of these cells < 80 pm 25-35% of these cells 81-100 pm 35-45% of these cells 101-140 pm 10-20% of these cells 141-200 pm 1-10% of these cells 201-600 pm < 1% of these cells are > 601 pm.

6. Soil improver according to one of the preceding claims, characterized in that carbon particles are embedded in the plastic foam, wherein the carbon particles are preferably embedded in the plastic foam as carbon fibers and / or soot. Soil improver according to claim 6, characterized in that the proportion of carbon particles in the plastic foam is > 0.1 wt.%, in particular > 0.5 wt.%. Soil improver according to claim 6 or 7, characterized in that the proportion of carbon particles in the plastic foam is < 10 wt.%, in particular < 5 wt.%. Method for producing a cured plastic foam, in particular for producing a soil improver for increasing the liquid storage capacity of soils from a cured plastic foam according to one of the preceding claims, characterized in that a precursor A and a precursor B are formed from a liquid A, which contains at least water and a prepolymer, and a liquid B, which contains at least water, a surfactant and a hardener, by introducing a gas, in particular atmospheric air, into the respective liquid, and both precursors are subsequently mixed, wherein the mixing ratio of precursor A and precursor B is between 40 vol% to 60 vol% and 60 vol% to 40 vol%.A method according to claim 9, characterized in that the mixing ratio of preview A and preview B is preferably between 45 vol% to 55 vol% and 55 vol% to 45 vol%, or more preferably between 47.5 vol% to 52.5 vol% and 52.5 vol% to 47.5 vol%. A method according to claim 9 or 10, characterized in that the ratio of liquid A to liquid B is between 75 vol% to 25 vol% and 50 vol% to 50 vol%. A method according to any one of claims 9 to 11, characterized in that the gas is introduced into the respective liquid by means of a compressed air device. A method according to claim 12, characterized in that the gas is introduced by means of the compressed air device at a pressure of 1 to 2.5 bar, more preferably 1 to 2.25 bar, or more preferably 1 to 2 bar. Method according to one of claims 9 to 13, characterized in that the preview A and the preview B are in a tubular reaction chamber. They are mixed together, with the resulting plastic foam escaping from at least one open end of the reaction chamber.

15. Method according to claim 14, characterized in that the reaction chamber has a substantially circular cross-section with a reaction chamber diameter, wherein the ratio of the reaction chamber diameter to a reaction chamber length of the reaction chamber is between 1 to 50 and 1 to 200, preferably between 1 to 80 and 1 to 120 and particularly preferably 1 to 100.

16. Method according to claim 14 or claim 15, characterized in that preview A and preview B are each supplied to the reaction chamber via a feed channel with a channel cross-sectional area, wherein the ratio of channel cross-sectional area to reaction chamber cross-sectional area is between 1.0 to 2.0 and 1.0 to 0.5, preferably 1 to 1.

17. Method according to one of claims 9 to 16, characterized in that the mixing of the preview material A and the preview material B and the conveyance of the reacting pre-foams and the resulting plastic foam in the reaction chamber are carried out automatically by the incoming pre-foams.

18. A method according to any one of claims 9 to 17, characterized in that the prepolymer of liquid A is a urea-formaldehyde, wherein the proportion of the urea-formaldehyde in liquid A in relation to the water contained in liquid A is preferably > 10 wt.%, in particular > 15 wt.% or particularly preferably > 22 wt.%, and / or wherein the proportion of the urea-formaldehyde in liquid A in relation to the water contained in liquid A is preferably < 35 wt.%, in particular < 30 wt.% or particularly preferably < 27 wt.%.

19. A method according to any one of claims 9 to 18, characterized in that urea is added to the liquid A, wherein the proportion of urea in the liquid A in relation to the water contained in the liquid A is preferably > 0.5 wt.%, in particular > 0.75 wt.% or particularly preferably > 1 wt.%, and / or wherein the proportion of urea in the liquid A in relation to the water contained in the liquid A, preferably < 5 wt.%, in particular < 3 wt.% or particularly preferably < 2 wt.%. A process according to any one of claims 9 to 19, characterized in that the surface-active substance of liquid B is a surfactant, wherein the proportion of the surfactant in liquid B relative to the water contained in liquid B is preferably > 5 wt.%, in particular > 7.5 wt.% or particularly preferably > 10 wt.%, and / or wherein the proportion of the surfactant in liquid B relative to the water contained in liquid B is preferably < 20 wt.%, in particular < 15 wt.% or particularly preferably < 12 wt.%. A process according to any one of claims 9 to 20, characterized in that the hardener of liquid B is an acid catalyst, wherein the proportion of the acid catalyst in liquid B relative to the water contained in liquid B is preferably > 15 wt.%, in particular > 20 wt.% or particularly preferably > 25 wt.%.-%, and / or wherein the proportion of the acid catalyst in liquid B in relation to the water contained in liquid B is preferably < 40 wt.%, particularly < 35 wt.% or most preferably < 30 wt.%. A process according to any one of claims 9 to 21, characterized in that liquid B contains resorcinol, wherein the proportion of resorcinol in liquid B in relation to the water contained in liquid B is preferably >. 0.5 wt.%, in particular > 1 wt.% or particularly preferably > 2 wt.%, and / or wherein the proportion of resorcinol in liquid B relative to the water contained in liquid B is preferably < 10 wt.%, in particular < 5 wt.% or particularly preferably < 3 wt.%. A process according to any one of claims 9 to 22, characterized in that the process temperature is between 30 °C and 55 °C, in particular 35 °C and 50 °C or particularly preferably 40 °C and 45 °C.

Images