DE102022113375A1 - Implementation of polyurethane in an extruder - Google Patents

Abstract

The invention relates to a method 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, the reaction mixture being - 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, the transport zone being a reaction zone in which there is a temperature of 225 ° C to 260 ° C, in particular 230 ° C up to 250 ° C, and the transport zone further comprises at least one degassing zone after the reaction zone, in which there is at least the same temperature as in the reaction zone 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.

Description

The invention relates to a method for implementing a plastic material containing polyurethane in an extruder and a corresponding extruder.

Due to their many adjustable properties, polyurethanes are widely used in products used in industry and households. Examples of such products are foams, paints, adhesives, casting compounds, hoses, seals, floor coverings, mattresses, car parts, parts of sports equipment, parts of shoes, and the like.

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

Attempts have therefore been made in the past to recycle polyurethanes. The European patent 01976719 B1 for example, describes a process in which a polyurethane resin is hydrolyzed by bringing it into contact with only water at high temperatures.

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

The invention results from the features of the independent claims. Advantageous further developments and refinements are the subject of the dependent claims.

In the context of the invention, plastic material is understood to mean a material comprising plastic, which ranges from pure plastic to mixtures containing plastic. The term “plastic” is used in the usual sense and refers to a synthetically produced substance, for example a substance produced as part of an organic synthesis, such as a polymer produced by polymerization, polyaddition and/or polycondensation from one or more different monomers. Plastics are classified according to a common classification into thermosets, thermoplastics, elastomers and thermoplastic elastomers. Well-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, where in In particular embodiments it is provided that the plastic material only comprises hydrolyzable plastics, for example in addition to polyurethanes also polyesters, polyamides and / or polycarbonates. Natural rubber previously used for a technical task, for example produced or chemically processed in the context of mattress production, such as vulcanized natural rubber, is also considered plastic within the scope of the invention, but lignin, i.e. wood, is not. The plastics can, if appropriate depending on their original intended use, contain other substances such as plasticizers, microbicidal substances, antioxidants, stabilizers, for example against UV light, flame retardants, dyes or residues of polymerization initiators. Plastics also include those that are not based on petroleum-based raw materials, but are created from renewable raw materials as part of a concept of sustainability and renewability, either as part of a chemical synthesis or as part of biotechnological or microbiological processes using appropriately designed enzymes or production organisms. The plastic-containing mixtures mentioned at the beginning 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 or plastics in such mixtures, which also include 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 to avoid damage to the extruder screws, although methods for reducing them are known to those skilled in the art and, for example, manual removal of non-plastics, magnetic removal of magnetic metals or metal alloys, or separation of plastics and possibly other materials of similar density due to differences in density of materials of different densities, for example via wind sifting or shaking or vibration devices. Within the plastic material, polyurethane occupies the largest proportion by mass, 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 is the predominant main component. For example, discarded polyurethane mattresses often have correspondingly small amounts of polyethylene or polypropylene, which usually come from the upholstery materials.

The plastic material used in the process contains polyurethane and optionally one or more hydrolyzable plastics, selected from polyesters, polyamides or polycarbonates, or consists of polyurethanes and optionally also 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 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 hydrolyzable plastics, polyurethane occupies 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%, i.e. accordingly represents the predominant main component. For example, the plastic material is mattresses or waste from mattress production, with the raw material containing polyurethane as a hydrolyzable component. The polyurethane can in particular be in the form of foam, with the particular advantage of the process being that a starting material with a high volume (namely a foam that can be compressed to a certain extent, but always strives to take up a large volume, and therefore requires appropriately dimensioned first lines and reaction vessels) is implemented in the presence of a comparatively small volume of reaction medium, with a significantly smaller volume resulting after appropriate pressure and heat treatment. Essentially, a bulky solid, namely a foam, is converted into an easier-to-handle form with a significantly higher liquid content and a lower volume, thereby solving a major problem in the polyurethane waste and recycling industry.

The invention relates to a method 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, the reaction mixture being selected from a plastic material present as a solid and containing a polyurethane, water, and at least one reaction additive including 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, the transport zone preferably consisting of a reaction zone from at least three kneading zones and a return element - in which a temperature of 225 ° C to 260 ° C, in particular 230 ° C to 250 ° C, such as 235 ° C to 250 ° C or 240 ° C to 250 ° C or 240 ° C to 255 ° C is present, and the transport zone further comprises at least one degassing zone after the implementation zone, in which at least the same temperature as in the implementation zone is present and in which, via at least one degassing point, components of the reaction mixture transported from the reaction zone, which are present in this Temperatures are gaseous and can be removed from the extruder.

The reaction mixture can be provided outside the extruder or when fed into the extruder, if necessary with an upstream mixing device.

For an improved implementation, the plastic material can preferably be used in an already comminuted state, especially if it comprises plastic that does not swell in water. Customary comminution processes can be used, for example the plastic material can be cut, torn, grated into flakes, shredded, granulated, ground or pulverized, if necessary after previously lowering the temperature to increase the brittleness. Non-limiting examples of the size of the plastic particles used are about 0.5 cm ³ to 10 cm ³ (0.5 ml to 10 ml), such as about 1 cm ³ to 5 cm ³ , especially for porous or large surface 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.

The reaction mixture is transported via the two extruder screws, compressed and exposed to shear forces in preferably at least three kneading zones. There is preferably a return element at the end of a second kneading zone, which significantly controls the degree of filling and the residence time in the extruder. The duration of transport from one end to the other end of the extruder 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, especially 0.4 to 1 hour. Optionally, the rotation speed of the extruder screws may be adjusted to increase a residence time in the reaction zone if sampling reveals insufficient reaction, or to reduce it if sufficient reaction is determined.

The extruder has a transport zone in which the extruder screws run. Within the transport zone there is an implementation zone - preferably consisting of at least three doughs zones and a return element - and directly or indirectly adjoining the implementation zone, based on the transport direction, at least one degassing zone. The reaction zone has a temperature of 225 °C to 260 °C, in particular 230 °C to 250 °C. The reaction mixture is transported, compressed and kneaded through the extruder screws. Kneading introduces mechanical energy into the reaction mixture, some of which is converted into thermal energy. However, the resulting heat is not sufficient, so appropriate heating elements are provided on the extruder to provide and maintain a desired temperature. An at least partial or complete reaction of the polyurethane takes place within the reaction zone.

The reaction zone is directly or indirectly 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 components of the reaction mixture transported through the reaction zone, which are gaseous at the temperatures present, can be withdrawn as gas. If necessary, known cold traps or vacuum traps can be used at the degassing points. The gaseous components removed can be used separately.

After transport through the extruder, the reaction mixture has a significantly lower volume fraction of solids, possibly no solids, compared to the reaction mixture initially used. Instead, the reaction mixture treated in this way represents a liquid or a liquid with solid components. One goal of the process is advantageously to reduce the volume of the solid used, consisting of the plastic material present as a solid and optionally other solid components. 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%, is possible, based on the volume of solid used. A large reduction is particularly possible with foams.

To support the implementation, 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. Good implementation can be achieved with nitric acid. However, if a reaction product with a small proportion of nitrogen-containing components is desired, preference is given to other reaction additives, since nitric acid introduces additional nitrogen. In general, mineral acids such as hydrochloric acid or phosphoric acid, or mineral bases such as sodium hydroxide are less preferred, since chlorine, phosphorus and sodium components would be present in the reaction product and could have a detrimental effect in the event of subsequent pyrolysis or in later uses of the pyrolysis products obtained. Alternative reaction additives with which a good reaction can be achieved, however, 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 (oxalosuccinic 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 1 to 7 mass percent, for example 1 .5 to 5 percent by mass, 1.5 to 4 percent by mass, 2 to 4 percent by mass, 2.5 to 3.5 percent by mass, or 3 percent by mass. 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 ratio 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, for example 2.5 to 10 mass percent, 2 mass percent to 7.5 mass percent, such as about 3 mass percent to 5 mass percent, is preferred.

The reaction mixture can contain in particular 2.5 to 10 percent by mass of urea. The ratio between water containing urea and plastic material containing polyurethane can be, for example, 0.2 ml/g to 5 ml/g, in particular 0.4 ml/g to 5 ml/g.

The reaction additive can also be a biological material. In the context of the invention, biological material is understood to mean plant, animal or microorganism material, for example complete plants or parts of plants such as wood, leaves, stems, roots or seeds, such as gardening waste or cuttings. Preferential wise, the biological material is plant material. According to a special embodiment, the biological material is wood, in particular shredded wood, for example in the form of sawdust, wood chips or shredded wood.

The aforementioned reaction additives can be used individually or in any mixtures of two or more of the respective aforementioned representatives.

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 that is at least moistened with 0.08 to 1 liter of water/reaction additive. The water to be used can contain 3 to 50 percent by mass, in particular 4 to 40 percent by mass, for example 4 to 20 percent by mass 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 percent by volume, in particular 67 to 95 percent by volume, and the biological material accordingly occupies 5 to 45 percent by volume, in particular 5 to 33 percent by volume. 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.

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.

When carrying out the process, there is essentially no excess pressure in the extruder. Rather, the process is carried out under ambient pressure. There are no special pressure-building or pressure-maintaining devices on the extruder. Current local pressure increases within the extruder due to the kneading processes cannot be ruled out, but it is assumed that a pressure of three bar, in particular two bar, will not be exceeded.

Given the temperature present in the at least one degassing zone, which corresponds at least to the temperature of the conversion zone, at least water can be withdrawn 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.

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 can optionally be separated, for example centrifugation or filtration, and optionally the solids obtained can be dried.

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

In one embodiment, the at least one degassing zone has a temperature in the range from 265 ° C to 300 ° C, in particular 265 ° C to 280 ° C, with components of the reaction mixture transported through the reaction zone being gaseous at these temperatures via a degassing point , can be removed from the extruder. At these temperatures, gaseous water can be withdrawn from the reaction mixture transported through the reaction zone. At the same time, however, nitrogen-containing components, which are essentially due to the diisocyanates used for polyurethane production, can also be removed. In particular, it was found that at a temperature in the degassing zone of 265 ° C up to 280 ° C, diaminotoluenes could be withdrawn from the reaction mixture in gaseous form via the degassing point. The reduction in the nitrogen content is advantageous if the reaction product, i.e. the reaction mixture transported through the reaction zone and through the at least one degassing zone, is subsequently to be subjected to pyrolysis, for example, and the pyrolysis oils obtained from the pyrolysis are to be subjected to chemical cracking processes in later uses should. Without wishing to be bound to a theory, it is assumed that the components with a higher boiling point remaining in the reaction mixture are polyols and their degradation products and/or conversion products in view of the polyurethane present in the initial reaction mixture.

In one embodiment, there is a first degassing zone in which the temperature is in the range from 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 are. Furthermore, after the first degassing zone, there is a second degassing 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 components of the material additionally transported through the first degassing zone are transported via a second degassing point Reaction mixture can be removed. In this case, gaseous water can be drawn off in the first degassing zone, whereas nitrogen-containing components can be drawn off as a gas phase in the second degassing zone. Consequently, the water content and the nitrogen-containing components can be removed separately as a gas phase. This advantageously makes later reuse easier.

It can be provided that in the reaction mixture the mass ratio between water on the one hand and polyurethane or plastic material containing polyurethane 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, based on the mass ratio, is present in a significant excess. Although larger amounts of water are possible, they also lead to a reaction product containing more water. Accordingly, it is not necessary for the plastic material to be suspended in a coherent aqueous medium, but rather it simply needs to be moistened with it. With the aim of a resource-saving circular economy, reducing water consumption represents a significant advantage.

According to one embodiment, in the reaction mixture for the extruder, the volume ratio between solid and aqueous medium 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 can be seen that there is not predominantly an aqueous medium in which the plastic material is suspended as a solid (and possibly other solids), but rather the majority of the volume is made up of the plastic material, which merely moistens with a significantly smaller volume of aqueous medium is. For example, it can be provided that 0.05 to 0.2 parts by volume of aqueous medium are provided per volume of polyurethane foam or per volume of solid. Accordingly, at the beginning of the reaction there is only a plastic material moistened with an aqueous medium in the reaction mixture, i.e. essentially a solid moistened with the reaction medium, with the solid material with a high volume requirement being converted into a liquid phase with a lower volume requirement as the transport progresses in the transport direction.

In a particular embodiment, the reaction additive is a biological material, in particular a plant material. It was found that with increasing amount of plant material, for example with wood, after appropriate withdrawal of water in the at least one degassing zone, the reaction product develops in the direction of a free-flowing solid, which is, for example, well suited to be transported via screw conveyors. This makes subsequent use, for example transport to and introduction into pyrolysis plants, much easier. 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. Particularly in 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, easily free-flowing solids are available.

The reaction mixture obtained at the end of the extruder and previously transported through the reaction zone and the at least one degassing 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 with the exclusion of external oxygen, usually in a temperature range of 150°C to 800°C. In the context of the process described herein, the highest temperature present in the reaction zone or the at least one degassing zone is preferred as the lower limit of the temperature range, such as a temperature range of 265 ° C to 800 ° degrees. 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 a calcium carbonate-poor or calcium carbonate-free pyrolysis to provide coke as a product of pyrolysis. The pyrolysis treatment is preferred over using the pressure- and heat-treated reaction medium obtained. Assuming that it essentially contains polyols as well as given If conversion products are present, additional cleaning steps or separation steps are required to ensure sufficient quality for their further use. On the other hand, pyrolysis can advantageously obtain polyol monomers which are assumed to have a higher qualitative purity compared to polyols.

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 and which is introduced directly or indirectly into a pyrolysis plant, is a reaction mixture which previously contains gaseous components with a boiling temperature below that in a degassing zone prevailing temperature of 265 ° C to 300 ° C, in particular 265 ° C up to 180 ° C, were 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 components or is free of such components. This makes pyrolysis products available, which in turn can be used advantageously. In particular, liquid, gaseous and solid pyrolysis products can be obtained during pyrolysis. With regard to the liquid products, these are pyrolysis oils, which in turn can be subjected to chemical cracking, in which high proportions of nitrogen-containing components would, however, be disruptive. Pyrolysis gas obtained can be used to generate electricity, with small proportions of nitrogen-containing components reducing the problem of nitrogen oxides. Solid pyrolysis products, which represent a type of pyrolysis coke, can be used for various purposes, for example as a replacement for carbon black or as petroleum coke that is also to be converted into electricity, so that lower or missing proportions of nitrogen-containing components are also advantageous here.

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 reaction zone - preferably consisting of at least three kneading zones and a return element - and after the reaction zone at least one degassing zone, wherein a temperature of 225 ° C to 260 ° C, in particular 230 ° C to 250 ° C, can be specified in the reaction zone, and a temperature can be specified in the at least one degassing zone which corresponds at least to the temperature in the reaction zone.

According to one embodiment, the extruder has a degassing zone in which the same temperature is present as in the reaction zone.

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

According to one embodiment, there is a first degassing zone in the extruder, in which the temperature is in the range from 225 ° C to 260 ° C and in which components of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, are removed from the via a first degassing point Extruder can be removed, with a second degassing zone being present after the first degassing 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 components of the additional through the can be removed from the reaction mixture transported to the first degassing zone.

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

Further advantages, features and details emerge from the following description, in which at least one exemplary embodiment is described in detail - if necessary with reference to the figures. Identical, similar and/or functionally identical parts are provided with the same reference numerals.

• 1: eine schematische Schnittdarstellung eines Extruders mit einer Entgasungszone,
• 2: eine schematische Darstellung eines Extruders mit zwei Entgasungszonen.

Show it:

• 1 : a schematic sectional view of an extruder with a degassing zone,
• 2 : a schematic representation of an extruder with two degassing zones.

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

Examples

Example 1: Extruder

In a pilot test, a laboratory extruder was used, which was designed as a twin-screw extruder and had three kneading blocks of different lengths. The diameter of the sealing combs The extruder screws were 24 mm and the length was 1.2 m. The extruder had a cooling zone and then nine heating zones that were evenly distributed over its length. Shortly before the exit in the area of the last zone there was a connection for a vacuum suction. Condensates were collected in a cold trap.

Example 2: Provision of a reaction mixture

A polyurethane mattress, including its cover, was shredded using a shredder and the shredded material was compacted into small balls. 1 kg of this plastic material containing polyurethane was sprayed and moistened with 200 ml of water and 200 ml of 53 percent nitric acid. This moistened mixture was added to a metering unit (a rotary valve) above the feed of the extruder, with a dosage of 1 kg/h being set.

Example 3: Implementation 1

The temperature zones were set to the following values: cooled; 180; 230; 230; 230; 230; 230; 250; 250; 250°C.

Initially, essentially undegraded brown foam flakes were ejected.

Example 4: Implementation 2

• Gekühlt; 180; 250; 250; 250; 230; 230; 250; 250; 250 °C

The temperature zones were set to the following values:

• Chilled; 180; 250; 250; 250; 230; 230; 250; 250; 250°C

This resulted in a soft black pasty mass that was very soft.

Example 5: Reaction with adipic acid as a reaction additive in water

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 added to a metering unit (a rotary valve) above the feed of the extruder, with a dosage of 1 kg/h being set. The temperature zones were set to the following values: cooled; 180; 250; 250; 250; 250; 265; 265; 265; 265; °C.

The speed of the twin screw was 120 rpm.

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

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

Example 6: Reaction with 3% water-urea solution

1 kg of the plastic material containing polyurethane was sprayed and moistened with 400 g of 3% water-urea solution. This moistened mixture was added to a metering unit (a rotary valve) above the feed of the extruder, with a dosage of 1 kg/h being set.

The temperature zones were set to the following values: cooled; 180; 250; 250; 250; 250; 265; 265; 265; 265; °C.

The speed of the twin screw was 110 rpm.

The heat-treated and degassed and dewatered reaction product at the end of the screw was gray-brown creamy.

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

Character description

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 the 1 is marked by a dotted bracket. Extruder screws 14a and 14b run through the transport zone 12, by means of which a reaction mixture can be transported, which can be introduced into the extruder 10 via an insertion device which is not specified in detail and is not given a reference number. A reaction zone 16 and a degassing zone 18 extend within the transport zone 12. In the reaction zone 16, in which there is a temperature of 220 ° C to 260 ° C, a reaction of transported reaction mixture takes place. A degassing zone 18 adjoins the implementation 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.

2 also shows a schematic longitudinal section through an extruder 10, which, however, in contrast to that in 1 The extruder shown has a first degassing zone 18a with an associated first degassing point 20a and a second degassing zone 18b with an associated second degassing point 20b. The temperatures in the first degassing zone 20a are equal to or higher than the temperatures in the reaction zone 16, preferably in a range of 225 ° C to 260 ° C. Preferably the temperatures are sufficient to draw off gaseous water. The temperature in the second degassing zone 20b is above the temperature of the first degassing 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 components in gaseous form to deduct.

Reference symbol list

10

extruder

12

Transport zone

14a, b

extruder screw

16

Implementation zone

18

Degassing zone

18a

first degassing zone

18b

second degassing zone

20

degassing point

20a

first degassing point

20b

second degassing point

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 01976719 B1 [0004]

Claims (9)

Process for implementing 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 - a plastic material that is present as a solid 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 run, 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 further comprises, after the reaction zone, at least one degassing 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. Procedure according to Claim 1 , characterized in that the same temperature is present in the at least one degassing zone as in the conversion zone. Procedure according to Claim 1 , characterized in that in the at least one degassing zone there is a temperature in the range from 265 ° C to 300 ° C, in particular 265 ° C to 280 ° C, and via at least one degassing point, components of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures can be removed from the extruder. Procedure according to Claim 1 , characterized in that there is a first degassing zone in which the temperature is in the range from 225 ° C to 260 ° C and in which components of the reaction mixture transported through the reaction zone, which are gaseous at these temperatures, are removed from the extruder via a first degassing point can be removed, and after the first degassing zone there is a second degassing 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 components of the additionally through the first via a second degassing point Degassing zone transported reaction mixture can be removed. Method according to one of the preceding claims, characterized in that in the reaction mixture the mass ratio between water on the one hand and polyurethane or plastic material containing polyurethane on the other hand is not more than 0.6 to 1. Method according to one of the preceding claims, characterized in that the volume ratio between solid and is 100:1 to 5:1. Method according to one of the preceding claims, characterized in that the reaction additive is a biological material, in particular a plant material. Method according to 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 fed directly or indirectly to pyrolysis. Extruder (10) designed as a twin-screw extruder for carrying out a method 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 have a conversion zone (16 ) and after the implementation zone (16) at least one degassing zone (18), wherein in the implementation zone (16) a temperature of 225 ° C to 260 ° C, in particular 230 ° C to 250 ° C, can be specified, and in the at least one Degassing zone (18) a temperature can be specified which corresponds at least to the temperature in the conversion zone.

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