Reacting polyurethane in a twin-screw extruder

Abstract

The invention relates to a method for reacting a polyurethane-containing plastics material in an extruder designed as a twin-screw extruder, comprising the following steps: providing a reaction mixture, wherein the reaction mixture comprises - a plastics material which is in solid form and contains a polyurethane, - water, and - at least one reaction additive, selected from nitric acid, a carboxylic acid, a dicarboxylic acid, in particular adipic acid, a tricarboxylic acid, in particular citric acid, urea and / or a biological material, transporting the reaction mixture through the transport zone of the extruder, in which two extruder screws extend, wherein the transport zone comprises a reaction zone, in which there is a temperature of 225°C to 260°C, in particular 230°C to 250°C, and the transport zone also comprises downstream of the reaction zone at least one venting zone, in which there is at least the same temperature as in the reaction zone and in which constituents of the reaction mixture that are gaseous at these temperatures and are transported out of the reaction zone can be removed from the extruder by way of at least one venting point.

Description

[0001] CONVERSION OF POLYURETHANE IN A TWIN-SCREW EXTRUDER

[0002] The invention relates to a process for converting a polyurethane-containing plastic material in an extruder and to a corresponding extruder.

[0003] Due to their many adjustable properties, polyurethanes are widely used in industrial and household products. Examples of such products include foams, paints, adhesives, potting compounds, hoses, seals, flooring, mattresses, automotive parts, sports equipment parts, shoe parts, and the like.

[0004] Therefore, a high proportion of polyurethane waste is generated when the corresponding products are damaged or have reached the end of their service life.

[0005] In the past, attempts have therefore been made to recycle polyurethanes. European Patent 01976719 B1, for example, describes a process in which a polyurethane resin is hydrolyzed by contacting it with water at high temperatures.

[0006] The object of the invention is to provide an improved method.

[0007] The invention is based on the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims.

[0008] For the purposes of the invention, a plastic material is understood to mean a material comprising plastic, ranging from pure plastic to plastic-containing mixtures. The term "plastic" is used in the conventional sense and refers to a synthetically produced substance, for example, a substance produced as part of an organic synthesis, such as a polymer produced from one or more different monomers by polymerization, polyaddition, and / or polycondensation. Plastics are commonly classified into thermosets, thermoplastics, elastomers, and thermoplastic elastomers.Known examples of plastics are polyethylene, polycarbonate, polyacrylic, polymethacrylic, polyacrylamide, polystyrene, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, butadiene rubber, and ethylene-propylene-diene rubber, as well as polyurethane. In particular embodiments, the plastic material comprises only hydrolyzable plastics, for example, in addition to polyurethanes, also polyesters, polyamides, and / or polycarbonates. Natural rubber previously used for a technical purpose, for example, obtained in the context of mattress production or chemically processed, such as vulcanized, is also considered a plastic within the scope of the invention. However, lignin, i.e., wood, is not.Depending on their original intended use, the plastics may contain other substances such as plasticizers, microbicidal substances, antioxidants, stabilizers (e.g., against UV light), flame retardants, dyes, or residues of polymerization initiators. Plastics also include those that are not based on petroleum-based starting materials, but rather are produced from renewable raw materials within the framework of a sustainability and renewability concept, either through chemical synthesis or through biotechnological or microbiological processes using appropriately designed enzymes or production organisms. The plastic-containing mixtures mentioned above are either mixtures of pure plastics or mixtures that also include one or more non-plastics, such as metal, ceramic, or glass.Preferably, the plastic(s) in such mixtures, which also comprise non-plastics, represent the relatively largest proportion, based on mass or volume, for example at least 67%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%. Preferably, there are no non-plastics in the plastic material, in particular also to avoid damage to the extruder screws, whereby methods for reducing this are known to the person skilled in the art and include, for example, manual removal of non-plastics, magnetic removal of magnetic metals or metal alloys, or the separation of plastics and optionally other materials of similar density due to density differences between materials of different densities, for example via air classification or shaking or vibrating devices.Within the plastic material, polyurethane makes up the largest mass fraction, preferably more than 60%, for example at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%, and therefore represents the predominant main component. For example, discarded polyurethane mattresses often contain correspondingly small amounts of polyethylene or polypropylene, which usually come from the cover materials.

[0009] The plastic material used in the process contains polyurethane and optionally further one or more hydrolyzable plastics selected from polyesters, polyamides, or polycarbonates, or consists of polyurethanes and optionally further polyesters, polyamides, or polycarbonates and / or a mixture thereof. According to a particular embodiment, the plastic material consists of polyurethane or a polyurethane mixture, or consists of polyurethane and polyester or a polyester mixture, for example, of polyethylene terephthalate or a polyethylene terephthalate mixture, or consists of a polyurethane / polyolefin composite material, wherein the polyurethane in the composite preferably has a proportion of at least 50 percent by mass.Within the hydrolysable plastics, polyurethane makes up the largest mass fraction, preferably more than 60%, for example at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%, and therefore represents the predominant main component. For example, the plastic material is mattresses or waste from mattress production, whereby the raw material contains polyurethane as a hydrolysable component.The polyurethane can, in particular, be in the form of a foam. The process offers the particular advantage that a high-volume starting material (namely, a foam that can be compressed to a certain extent but always tends to occupy a large volume and therefore requires appropriately dimensioned initial lines and reaction vessels) is reacted in the presence of a comparatively small volume of reaction medium, resulting in a significantly smaller volume after appropriate pressure and heat treatment. Essentially, a bulky solid, namely a foam, is converted into a more easily handled form with a significantly higher liquid content and a lower volume, thus solving a major problem in polyurethane waste and recycling management.

[0010] The invention relates to a process for reacting a plastic material containing a polyurethane in an extruder designed as a twin-screw extruder, comprising the following steps: providing a reaction mixture, wherein the reaction mixture comprises a plastic material present as a solid and containing a polyurethane, water, and at least one reaction additive selected from nitric acid, a carboxylic acid, a dicarboxylic acid, in particular adipic acid, a tricarboxylic acid, in particular citric acid, urea and / or a biological material, transporting the reaction mixture through the transport zone of the extruder, in which two extruder screws run, wherein the transport zone comprises a reaction zone - preferably consisting of at least three kneading zones and a recirculation element - in which a temperature of 225 °C to 260 °C, in particular 230 °C up to 250 °C,such as 235 °C to 250 °C or 240 °C to 250 °C or 240 °C to 255 °C, and the transport zone further comprises, after the reaction zone, at least one devolatilization zone in which at least the same temperature as in the reaction zone prevails and in which constituents of the reaction mixture transported from the reaction zone, which are gaseous at these temperatures, can be removed from the extruder via at least one devolatilization point.

[0011] The reaction mixture can be prepared outside the extruder or when feeding into the extruder, if necessary with an upstream mixing device.

[0012] For improved implementation, the plastic material can preferably be used in a pre-comminuted state, especially if it comprises plastic that does not swell in water. Standard comminution techniques can be used, for example, the plastic material can be cut, torn, grated into flakes, shredded, granulated, ground, or pulverized, optionally after prior temperature reduction to increase brittleness. Non-limiting examples of the size of the plastic particles used are approximately 0.5 cm. 3 up to 10 cm 3 (0.5 ml to 10 ml), such as 1 cm 3 up to 5 cm 3 , in particular for porous or large-surface-area plastic material, or plastic particles with a diameter, measured at the largest point, of a maximum of approximately 10, 5, 2, 1, 0.5, 0.1, 0.05 or 0.01 millimeters.

[0013] The reaction mixture is transported via the two extruder rollers, compacted, and subjected to shear forces in preferably at least three kneading zones. A recirculation element is preferably located at the end of a second kneading zone, which significantly controls the fill level and residence time in the extruder. The duration of transport from one end of the extruder to the other end can depend on the length of the extruder, the set rotation speed of the extruder screws, and the consistency of the reaction mixture. Examples of durations are 10 minutes to 2 hours, in particular 0.4 to 1 hour. If necessary, the rotation speed of the extruder screws can be adjusted to increase the residence time in the reaction zone if sampling reveals insufficient conversion, or to decrease it if sufficient conversion is determined.

[0014] The extruder has a transport zone through which the extruder screws run. Within the transport zone there is a conversion zone – preferably consisting of at least three kneading zones and a recirculation element – ​​and, directly or indirectly adjoining the conversion zone, based on the transport direction, at least one venting zone. The temperature in the conversion zone is between 225°C and 260°C, in particular between 230°C and 250°C. The reaction mixture is transported, compacted, and kneaded by the extruder screws. Kneading introduces mechanical energy into the reaction mixture, which is partially converted into thermal energy. However, the heat generated is insufficient, so that appropriate heating elements are provided on the extruder to provide and maintain a desired temperature. Within the conversion zone, the polyurethane is at least partially or completely converted.

[0015] Directly or indirectly, the reaction zone is followed by at least one degassing zone, in which the temperature is at least equal to or higher than the temperature in the reaction zone. At least one degassing point is provided in the at least one degassing zone, with which constituents of the reaction mixture transported through the reaction zone, which are gaseous at the prevailing temperatures, can be removed as gas. If necessary, known cold traps or vacuum traps can be used at the degassing points. The removed gaseous constituents can be used separately.

[0016] After being transported through the extruder, the reaction mixture has a significantly lower volume fraction of solids, or possibly no solids at all, compared to the reaction mixture initially used. Instead, the reaction mixture treated in this way is a liquid or a liquid with solids. One aim of the process is to advantageously reduce the volume of the solid used, consisting of the plastic material present as a solid and, if appropriate, other solids. For example, a reduction of up to 95%, up to 90%, or 4 to 50%, such as 5 to 30%, for example 7 to 25% or 10 to 15%, based on the volume of the solid used is possible. A high reduction is particularly possible with foams.

[0017] To support the reaction, the reaction mixture comprises at least one reaction additive. Non-limiting examples of reaction additives are nitric acid, carboxylic acids, urea, and / or biological material. A good reaction can be achieved with nitric acid. However, if a reaction product with a low proportion of nitrogen-containing components is desired, other reaction additives are preferred, since nitric acid provides additional nitrogen input. In general, mineral acids such as hydrochloric acid or phosphoric acid, or mineral bases such as sodium hydroxide, are less preferred, as they would introduce chlorine, phosphorus, and sodium components into the reaction product, which could have a detrimental effect in the case of downstream pyrolysis or in later uses of the resulting pyrolysis products.Alternative reaction additives with which good conversion can be achieved are carboxylic acids, for example in particular linear, saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid or pentanoic acid, hexanoic acid, heptanoic acid; dicarboxylic acids such as oxalic acid (ethanedioic acid), malonic acid (propanedioic acid), succinic acid (butanedioic acid), glutaric acid (pentanedioic acid), adipic acid (hexanedioic acid), malic acid (2-hydroxybutanedioic acid), tartaric acid (2,3-dihydroxybutanedioic acid); and tricarboxylic acids such as 3-carboxy-2-oxo-pentanedicarboxylic acid (oxosuccinic acid), propane-1,2,3-tricarboxylic acid, citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid) and isocitric acid (1-hydroxypropane-1,2,3-tricarboxylic acid). Another possible reaction additive is urea.Based on the total mass of the aqueous medium, the proportion of urea in the aqueous medium is, for example, 1 to 45 mass percent, in particular 1 to 20 mass percent, for example 1 to 10 mass percent, such as, for example, 1 to 7 mass percent, for example 1.5 to 5 mass percent, 1.5 to 4 mass percent, 2 to 4 mass percent, 2.5 to 3.5 mass percent, or 3 mass percent. Examples of further ranges or further concentrations are 5 to 10 mass percent, 1 mass percent, 5 mass percent, 7.5 mass percent and 10 mass percent. From the point of view of the relationship between the amount of urea to be used and the degree of degradation of polyurethane achieved, a range between 1 mass percent and 10 mass percent is preferred, for example 2.5 to 10 mass percent, 2 mass percent to 7.5 mass percent, such as, for example, 3 mass percent to 5 mass percent. The reaction mixture may in particular contain 2.5 to 10 mass percent urea.The ratio between urea-containing water and polyurethane-containing plastic material can be, for example, 0.2 ml / g to 5 ml / g, in particular 0.4 ml / g to 5 ml / g.

[0018] The reaction additive can also be a biological material. Within the scope of the invention, biological material is understood to mean plant, animal, or microorganism material, for example, complete plants or plant parts such as wood, leaves, stems, roots, or seeds, such as gardening waste or grass clippings. The biological material is preferably plant material. According to a particular embodiment, the biological material is wood, in particular comminuted wood, for example in the form of sawdust, wood chips, or shredded wood.

[0019] The above-mentioned reaction additives can be used individually or in any mixtures of two or more of the above-mentioned representatives.

[0020] Examples of mixing ratios of the plastic material with water on the one hand and at least one reaction additive on the other hand are 2 to 25 liters of plastic material, which is at least moistened with 0.08 to 1 liter of water / reaction additive. The water to be used can contain 3 to 50 mass percent, in particular 4 to 40 mass percent, for example 4 to 20 mass percent of nitric acid, carboxylic acid, a dicarboxylic acid, a tricarboxylic acid and / or urea. If a biological material is added, it can be provided that the plastic material occupies 55 to 95 volume percent, in particular 67 to 95 volume percent, and the biological material accordingly 5 to 45 volume percent, in particular 5 to 33 volume percent.The biological material can be mixed with the plastic material and then added to the water / reaction additive, or mixed first with water / reaction additive and then with the plastic material, or all three components can be mixed simultaneously.

[0021] If the plastic material and / or the hydrolyzable plastic contained therein is a compressible plastic, in particular a polyurethane foam, the specified volumes refer to the uncompressed plastic. During the process, there is essentially no excess pressure in the extruder. Rather, the process is carried out under ambient pressure. Special pressure-building or pressure-maintaining devices on the extruder are not provided. Momentary local pressure increases within the extruder due to the kneading processes cannot be ruled out; however, it is assumed that a pressure of three bar, in particular two bar, will not be exceeded.

[0022] Given the temperature in the at least one degassing zone, which corresponds at least to the temperature of the reaction zone, at least water can be removed as a gas phase at the at least one degassing point. Accordingly, the reaction product, i.e., the reaction mixture transported through the reaction zone and the at least one degassing zone, has a reduced water content or is anhydrous.

[0023] From the reaction product, i.e. the reaction mixture transported through the transport zone and through the at least one degassing zone, the liquid phase and the solids contained therein can optionally be separated, for example by centrifugation or filtration, and the solids obtained can optionally be dried.

[0024] In one embodiment, the temperature in the at least one degassing zone is the same as in the reaction zone. In this case, essentially gaseous water is withdrawn via the at least one degassing point. The reaction product in this case contains nitrogen-containing components and products with a higher boiling point. The nitrogen-containing components are typically diamines or their degradation products or reaction products.

[0025] In one embodiment, the temperature in the at least one devolatilization zone is in the range from 265°C to 300°C, in particular 265°C to 280°C, wherein constituents of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, can be removed from the extruder via a devolatilization point. At these temperatures, gaseous water can be removed from the reaction mixture transported through the reaction zone. Along with this, however, nitrogen-containing constituents, which are essentially attributable to the diisocyanates used for polyurethane production, can also be removed. In particular, it was found that at a temperature in the devolatilization zone of 265°C to 280°C, diaminotoluenes could be removed in gaseous form from the reaction mixture via the devolatilization point.Reducing the nitrogen content is advantageous if the reaction product, i.e., the reaction mixture transported through the reaction zone and through at least one degassing zone, is subsequently subjected to pyrolysis, for example, and the pyrolysis oils obtained from the pyrolysis are to be subjected to chemical cracking processes for subsequent uses. Without wishing to be bound by any theory, it is assumed that the components with higher boiling points remaining in the reaction mixture are polyols and their degradation and / or conversion products, given the polyurethane present in the initially used reaction mixture.

[0026] In one embodiment, there is a first devolatilization zone in which the temperature is in the range from 225°C to 260°C and in which, via a first devolatilization point, constituents of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, can be removed from the extruder. Furthermore, there is a second devolatilization zone downstream of the first devolatilization zone in which the temperature is in the range from 265°C to 300°C, in particular 265°C to 280°C, and in which, via a second devolatilization point, constituents of the reaction mixture additionally transported through the first devolatilization zone can be removed. In this case, gaseous water can be removed in the first devolatilization zone, whereas in the second devolatilization zone, nitrogen-containing constituents can be removed as a gas phase. Consequently, the water content and the nitrogen-containing constituents can be removed separately from one another as a gas phase.This advantageously makes later reuse easier.

[0027] It can be provided that in the reaction mixture the mass ratio between water on the one hand and polyurethane or polyurethane-containing plastic material on the other hand is not more than 0.6 to 1, in particular not more than 0.5 to 1, for example 0.45 to 1, so that polyurethane or polyurethane-containing plastic material is present in a clear excess based on the mass ratios. Larger amounts of water are possible, but also lead to a reaction product with a higher water content. Accordingly, it is not necessary for the plastic material to be suspended in a coherent aqueous medium; it merely needs to be moistened with it. With the goal of a resource-saving circular economy, reducing water consumption represents a significant advantage.According to one embodiment, the volume ratio between solid and aqueous medium in the reaction mixture for the extruder is 100:1 to 5:1, for example 75:1 to 10:1, 30:1 to 20:1, such as 25:1. In this respect, it is clear that an aqueous medium is not predominantly present in which the plastic material is suspended as a solid (and optionally other solids), but rather the predominant volume fraction is made up of the plastic material, which is merely moistened with a significantly smaller volume of aqueous medium. For example, it can be provided that 0.05 to 0.2 volume fractions of aqueous medium are provided per volume fraction of polyurethane foam or per volume fraction of solid.Accordingly, at the beginning of the reaction, only a plastic material moistened with an aqueous medium is present in the reaction mixture, i.e. essentially a solid moistened with the reaction medium, whereby as the transport progresses in the transport direction, the reaction converts solid with a high volume requirement into a liquid phase with a lower volume requirement.

[0028] In a particular embodiment, the reaction additive is a biological material, in particular a plant material. It has been found that with increasing amounts of plant material, for example, with wood, after appropriate removal of water in the at least one degassing zone, the reaction product develops into a free-flowing solid, which is well suited, for example, for transport via screw conveyors. Subsequent use, for example, transport to and introduction into pyrolysis plants, is thereby significantly facilitated. The presence of plant material in the reaction mixture accordingly leads to a significant improvement.The mass ratio of plastic material to biological material, in particular plant material, can be, for example, 3:1 to 1:1, such as 3:1 to 1.5:1, for example 2:1. In particular, with mass proportions of one third or more, based on the total mass of plastic material and biological material, for example 33 to 50 mass percent, in particular 33 to 45 mass percent, such as 34 to 40 mass percent, free-flowing solids are available.

[0029] The reaction mixture obtained at the end of the extruder and previously transported through the reaction zone and the at least one devolatilization zone can be fed directly or indirectly to pyrolysis. The principle of pyrolysis itself is known and is based on a thermochemical conversion of substances in the absence of external oxygen, typically in a temperature range of 150°C to 800°C. In the process described herein, the highest temperature present in the reaction zone or the at least one devolatilization zone, such as a temperature range of 265°C to 800°C, is preferred as the lower limit of the temperature range. For example, this is a temperature range of 265°C to 500°C or 300°C to 500°C.Another example of a temperature range is the range from 700°C to 800°C, in particular from 750°C to 800°C, which is advantageously suitable for decomposing calcium carbonate present in the plastic material into calcium oxide and carbon dioxide and thus providing a calcium carbonate-poor or calcium carbonate-free pyrolysis coke as the pyrolysis product. The pyrolysis treatment is preferred over the use of the resulting pressure- and heat-treated reaction medium. Assuming that it essentially contains polyols and, if applicable, conversion products, additional purification or separation steps are required to ensure sufficient quality for their further use. On the other hand, pyrolysis can advantageously produce polyol monomers, which are assumed to have a higher qualitative purity compared to polyols.

[0030] According to a preferred embodiment, the reaction product, i.e. the reaction mixture transported through the reaction zone and the at least one degassing zone, which is introduced directly or indirectly into a pyrolysis plant, is a reaction mixture from which gaseous constituents having a boiling point below the temperature prevailing in a degassing zone of 265°C to 300°C, in particular 265°C to 180°C, have previously been partially or completely removed. In particular, according to the embodiments described herein, it is possible to feed such a reaction mixture to pyrolysis which has a lower proportion of nitrogen-containing constituents or is free of such constituents. This makes it possible to provide pyrolysis products which, in turn, can be advantageously used further. In particular, liquid, gaseous, and solid pyrolysis products can be obtained during pyrolysis.The liquid products are pyrolysis oils, which can themselves be subjected to chemical cracking, although high levels of nitrogenous components would be detrimental. The resulting pyrolysis gas can be used to generate electricity, with low levels of nitrogenous components reducing the problem of nitrogen oxides. Solid pyrolysis products, which are a type of pyrolysis coke, can be used for various purposes, for example, as a substitute for carbon black or as petroleum coke, which can also be converted into electricity. Therefore, lower or no levels of nitrogenous components are advantageous here as well.The invention further relates to an extruder designed as a twin-screw extruder for carrying out a process as described herein, wherein the extruder has a transport zone which comprises a conversion zone - preferably consisting of at least three kneading zones and a return element - and at least one devolatilization zone after the conversion zone, wherein a temperature of 225 °C to 260 °C, in particular 230 °C to 250 °C, can be predetermined in the conversion zone, and a temperature which corresponds at least to the temperature in the conversion zone can be predetermined in the at least one devolatilization zone.

[0031] According to one embodiment, the extruder has a venting zone in which the temperature is the same as in the reaction zone.

[0032] According to one embodiment, the extruder has a devolatilization zone in which a temperature in the range from 260 °C to 300 °C, in particular 265 °C to 280 °C, is present, wherein and via at least one devolatilization point, constituents of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, can be removed from the extruder.

[0033] According to one embodiment, a first devolatilization zone is present in the extruder, in which the temperature is in the range from 225 °C to 260 °C and in which constituents of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, can be removed from the extruder via a first devolatilization point, wherein after the first devolatilization zone there is a second devolatilization zone in which the temperature is in the range from 265 °C to 300 °C, in particular 265 °C to 280 °C and in which constituents of the reaction mixture additionally transported through the first devolatilization zone can be removed via a second devolatilization point.

[0034] Reference is made to implicit disclosures regarding the device made in connection with the method and vice versa.

[0035] Further advantages, features, and details will become apparent from the following description, in which at least one embodiment is described in detail—possibly with reference to the figures. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0036] Shown are: Fig. 1 : a schematic sectional view of an extruder with a degassing zone,

[0037] Fig. 2: a schematic representation of an extruder with two venting zones.

[0038] The representations in the figures are schematic, not necessarily to scale and show only essential components.

[0039] Examples

[0040] Example 1 : Extruder

[0041] In a pilot test, a laboratory extruder was used. It was designed as a twin-screw extruder and featured three kneading blocks of different lengths. The diameter of the closely meshing extruder screws was 24 mm, and the length was 1.2 m. The extruder featured a cooling zone followed by nine heating zones, evenly distributed along its length. A connection for a vacuum extraction system was located just before the exit of the last zone. Condensate was collected in a cold trap.

[0042] Example 2: Preparation of a reaction mixture

[0043] A polyurethane mattress, including its cover, was shredded using a shredder, and the shredded material was compacted into small pellets. 1 kg of this polyurethane-containing plastic material was sprayed and moistened with 200 ml of water and 200 ml of 53% nitric acid. This moistened mixture was fed into a dosing unit (a rotary valve) above the extruder inlet at a rate of 1 kg / h.

[0044] Example 3: Implementation 1

[0045] The temperature zones were set to the following values: cooled; 180; 230; 230; 230; 230; 230; 250; 250; 250; 250°C. Initially, essentially undegraded brown foam flakes were emitted.

[0046] Example 4: Implementation 2

[0047] The temperature zones were set to the following values:

[0048] Chilled; 180; 250; 250; 250; 230; 230; 250; 250; 250 °C

[0049] This resulted in a soft, black, pasty mass that was very soft.

[0050] Example 5: Reaction with adipic acid as reaction additive in water

[0051] 1 kg of the polyurethane-containing plastic material was mixed with 50 g of powdered adipic acid and then sprayed and moistened with 200 ml of water. This moistened mixture was fed into a dosing unit (a rotary valve) above the extruder inlet, with a dosing rate of 1 kg / h set.

[0052] The temperature zones were set to the following values: chilled; 180; 250; 250; 250; 250; 265; 265; 265; 265; °C.

[0053] The speed of the twin screw was 120 rpm.

[0054] The heat-treated, degassed and dewatered reaction product at the end of the screw was creamy brown.

[0055] Brown deposits were collected in the cold trap, which, after analytical examination, turned out to be diamines,

[0056] Example 6: Reaction with 3% water-urea solution

[0057] 1 kg of the polyurethane-containing plastic material was sprayed and moistened with 400 g of a 3% water-urea solution. This moistened mixture was fed into a dosing unit (a rotary valve) above the extruder inlet, with a dosage rate of 1 kg / h set.

[0058] The temperature zones were set to the following values: chilled; 180; 250; 250; 250; 250; 265; 265; 265; 265; °C.

[0059] The rotational speed of the twin screw was 110 rpm. The heat-treated, degassed, and dewatered reaction product at the end of the screw was creamy gray-brown.

[0060] Brown deposits were collected in the cold trap, which, after analytical examination, turned out to be diamines.

[0061] Character description

[0062] Figure 1 shows a schematic longitudinal section through an extruder 10, which is designed as a twin-screw extruder and accordingly has an extruder screw 14a and an extruder screw 14b. The extruder 10 has a transport zone 12, which is indicated in Figure 1 by a dotted bracket. Extruder screws 14a and 14b run through the transport zone 12, by means of which a reaction mixture can be introduced into the extruder 10 via an inlet device (not described in more detail and indicated without reference numeral). Extending within the transport zone 12 are a conversion zone 16 and a devolatilization zone 18. In the conversion zone 16, at a temperature of 220°C to 260°C, the transported reaction mixture is converted. A devolatilization zone 18 adjoins the conversion zone 16.This has a degassing point 20, via which components of the reaction mixture transported from the reaction zone, which are gaseous at the temperatures present in the degassing point 20, can be removed.

[0063] Figure 2 also shows a schematic longitudinal section through an extruder 10, which, however, in contrast to the extruder shown in Figure 1, has a first devolatilization zone 18a with an associated first devolatilization point 20a and a second devolatilization zone 18b with an associated second devolatilization point 20b. The temperatures in the first devolatilization zone 20a are equal to or higher than the temperatures in the reaction zone 16, preferably in a range from 225°C to 260°C. The temperatures are preferably sufficient to remove gaseous water. The temperature in the second devolatilization zone 20b is above the temperature of the first devolatilization zone 20a, preferably in a range from 265°C to 300°C, in particular 265°C to 280°C, and is preferably sufficient to remove nitrogen-containing constituents in gaseous form. List of Reference Symbols

[0064] 10 extruders

[0065] 12 Transport zone

[0066] 14a, b Extruder screw

[0067] 16 Implementation zone

[0068] 18 Degassing zone

[0069] 18a first degassing zone

[0070] 18b second degassing zone

[0071] 20 Degassing point

[0072] 20a first degassing point

[0073] 20b second degassing point

Claims

Patent claims: Method for converting a polyurethane-containing plastic material in an extruder designed as a twin-screw extruder, comprising the following steps: Preparation of a reaction mixture, wherein the reaction mixture - a plastic material in solid form containing polyurethane, - Water, and - comprising at least one reaction additive selected from nitric acid, a carboxylic acid, a dicarboxylic acid, in particular adipic acid, a tricarboxylic acid, in particular citric acid, urea and / or a biological material, Transporting the reaction mixture through the transport zone of the extruder, in which two extruder screws are located, wherein the transport zone comprises a reaction zone in which a temperature of 225 °C to 260 °C, in particular 230 °C to 250 °C, is present, and the transport zone further comprises at least one degassing zone downstream of the reaction zone in which at least the same temperature as in the reaction zone is present and in which components of the reaction mixture transported from the reaction zone, which are gaseous at these temperatures, can be removed from the extruder via at least one degassing point, a method according to claim 1, characterized in that the same temperature as in the reaction zone is present in the at least one degassing zone, a method according to claim 1, characterized in that the temperature in the at least one degassing zone is in the range of 265 °C to 300 °C,especially 265 °C to 280 °C and components via at least one degassing point, The process according to claim 1, characterized in that a first degassing zone is present in which the temperature is in the range of 225 °C to 260 °C and in which components of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, can be removed from the extruder via a first degassing point, and a second degassing zone is present after the first degassing zone in which the temperature is in the range of 265 °C to 300 °C, in particular 265 °C to 280 °C, and in which components of the reaction mixture additionally transported through the first degassing zone can be removed via a second degassing point.A process according to any one of the preceding claims, characterized in that the mass ratio between water on the one hand and polyurethane or polyurethane-containing plastic material on the other hand in the reaction mixture is no more than 0.6 to 1. A process according to any one of the preceding claims, characterized in that the volume ratio between solid and material is 100:1 to 5:

1. A process according to any one of the preceding claims, characterized in that the reaction additive is a biological material, in particular a plant material. A process according to any one of the preceding claims, characterized in that the reaction mixture obtained at the end of the extruder and previously transported through the reaction zone and the at least one degassing zone is directly or indirectly subjected to pyrolysis.An extruder (10) designed as a twin-screw extruder for carrying out a process according to one of the preceding claims, characterized in that the extruder (10) has a transport zone (12) with two extruder screws (14a, 14b) running therein, which comprises a conversion zone (16) and, after the conversion zone (16), at least one degassing zone (18), wherein a temperature of 225 °C to 260 °C, in particular 230 °C to 250 °C, can be specified in the conversion zone (16) and in the at least one degassing zone (18). a temperature can be specified that is at least equal to the temperature in the conversion zone.

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