POLYURETHANE DEMOCOLORATION

Description

[0001] The invention relates to a process for degrading polyurethane and a process medium obtainable by this process.

[0002] 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.

[0003] Accordingly, a high proportion of polyurethane waste is generated when the corresponding products are damaged or have reached the end of their service life.

[0004] In the past, several solutions have been proposed for processing polyurethane waste. Several patents concern processes in which polyurethane waste is dissolved in aliphatic diols, for example, US patents 4,044,040, 3,632,530, and 4,162,995, as well as German Offenlegungsschrift 2304444. US patent 4,316,992 proposes dissolving in high-boiling saturated alcohol, and US patent 4,039,568 proposes dissolving in the presence of various alcoholates. A disadvantage of all these processes is the fact that they require hydrocarbons in the form of diols. Motokucho et al. Hydrolysis of aromatic polyurethane in water under high pressure of CO2, Journal of Polymer Science Part A: Polymer Chemistry, 2017, Vol. 55, No. 12, pages 2004-2010, discloses a process for the degradation of polyurethane by hydrolysis under excess pressure and in the presence of carbon dioxide.

[0005] The object of the invention is to provide alternative solutions that preferably use substances that are less harmful to the environment.

[0006] The invention is based on the features of the independent claims. Advantageous further developments and refinements are the subject matter of the dependent claims.

[0007] The object is achieved in a first aspect by a process for the degradation of polyurethane, wherein a polyurethane-containing material is heated at a temperature of 190°C to 250°C in the presence of an aqueous solution containing 1 to 45 mass percent urea under excess pressure. At the start of the process, polyurethane-containing material is present in or together with the aqueous, urea-containing solution. After the selected treatment time has elapsed, the polyurethane portion of the polyurethane-containing material, which was originally in solid form, is partially or completely converted into substances that are present in a liquid process medium, which is attributable to the urea-containing aqueous solution present at the start of the process. The process medium may still contain solids, for example solids that were embedded in the solid polyurethane or deposited thereon, or plastics other than polyurethane.The liquid process medium contains degradation products and / or other byproducts that originate from the original polyurethane. Transferring the product to the liquid process medium advantageously offers the possibility of converting the originally solid polyurethane into a more easily handled form and, if necessary, isolating valuable substances from the resulting liquid process medium or converting them into useful products in further reactions.

[0008] Overpressure is defined as any pressure higher than ambient atmospheric pressure. According to one embodiment, heating takes place at a pressure of 1.05 bar to 100 bar. Examples of pressure ranges are 10 bar to 45 bar, for example, 12 bar to 40 bar, or 25 bar to 35 bar. For the purpose of simplifying the process, overpressure is an equilibrium pressure that develops during heating, for example, the equilibrium pressure that develops when heating in a pressure vessel.

[0009] The process is preferably carried out within a period of 20 minutes to 240 minutes, in particular 45 minutes to 240 minutes, 90 minutes to 240 minutes, for example 120 minutes up to 240 minutes. An example of a preferred period is the period of 30 minutes to 180 minutes, for example the period between 40 minutes and 180 minutes (40 minutes to 180 minutes). The reaction temperature can remain constant at a value within the specified temperature range or assume various values ​​within the specified temperature range, for example in order to achieve a predetermined target value by temperature control. The period is preferably a single continuous period, but can also be cumulatively composed of separate periods during which the specified temperature conditions are maintained.Extensive tests revealed that the first signs of solids formation occurred at a temperature of 245 °C and a duration of 240 minutes. Considering a specified duration of the heat treatment of 240 minutes, a temperature of 250 °C is considered a practical upper limit for the temperature.

[0010] The process opens up the possibility of achieving degradation of polyurethane using urea, a substance that occurs naturally in the environment and is therefore naturally degradable.

[0011] The polyurethane-containing material may be material that, in addition to and distinct from polyurethane, contains a non-polyurethane component, for example, polyurethane in combination with a component made of another plastic, such as styrene-acrylonitrile particles, a metal component, a glass component, or a component made of an inorganic material, for example, calcium carbonate. Non-limiting examples include polyurethane articles that contain metal fasteners or composite materials made of polyurethane and another plastic, for example, refrigerator parts that contain polyurethane as a heat-insulating layer and other plastics as a covering layer. However, polyurethane-containing material may also be considered to be material consisting of polyurethane.The polyurethane itself can be pure polyurethane or a polyurethane containing other substances, such as plasticizers, microbicidal substances, antioxidants, stabilizers (e.g., against UV light), flame retardants, dyes, or residues of polymerization initiators. The term "polyurethane-containing material" can also encompass a mixture of different polyurethane-containing materials, for example, materials that each contain different types of polyurethane.

[0012] The degradation of the polyurethane can occur partially, but depending on the selected process parameters, it can lead to intermediate stages in which the polyurethane is present in crushed form, up to the complete degradation of the polyurethane contained in the material, so that the polyurethane is no longer present as a solid.

[0013] Polyurethane is understood as a polymer having as its characteristic group the urethane group according to the following formula (I):

[0014] Polyurethanes are generally obtainable by the polyaddition of di- or higher-hydric alcohols of the formula (II) HO-R'-OH (II), where R' is a low molecular weight or even polymeric aliphatic or aromatic radical, which optionally comprises at least one further hydroxyl group, with diisocyanates of the general formula (III) O=C=NRN=C=O (III), where R has the same meaning as R'.

[0015] The chemistry and technical production and processing of polyurethanes are generally known to those skilled in the art and are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 6th Completely Revised Edition, Wiley-VHC Verlag GmbH & Co. KGaA, Weinheim, Germany, 2003, Volume 28, pages 667-722. The majority of polyurethane foams (hereinafter also referred to as PUR foams) are produced on the basis of aromatic isocyanates. The most important representatives of this group are mixtures of the isomers 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), as well as mixtures of isomers of diphenylmethane diisocyanate (MDI), of which non-limiting examples are diphenylmethane 2,2'-diisocyanate (2,2'-MDI), diphenylmethane 2,4'-diisocyanate (2,4'-MDI), and diphenylmethane 4,4'-diisocyanate (4,4'-MDI), and prepolymerized MDI. TDI 80 is the most important diisocyanate in flexible foam production.TDI 65 is used in many flexible foams, especially ester foams. In both designations, the number 80 or 65 represents the mass percentage of the highly reactive isomer 2,4-toluene diisocyanate; the difference to 100 mass percent is provided by the isomer 2,6-toluene diisocyanate. Polyethers, polyesters, or diamines are preferably used as polyol components. The properties can also be modified by adding stabilizers such as silicone-polyether copolymers, epoxides, benzophenone, and other substances. Additives can also vary the properties of the foam. For example, phosphoric acid ester is used as a flame retardant. Mechanical reinforcing agents such as carbon fibers can also be incorporated into the foams and are examples of non-polyurethanes that can be included as additional components in the polyurethane-containing material.Fillers such as calcium carbonate can also be used.

[0016] The polyurethane can be foamed polyurethane or non-porous polyurethane, with non-limiting examples of non-porous polyurethane being polyurethane hoses or polyurethane sealants.

[0017] According to a particular embodiment of the process, the polyurethane (PUR), flexible polyurethane foam (PUR flexible foam), rigid polyurethane foam (PUR rigid foam), shredder light fraction or a mixture of two or more representatives thereof, or consists in particular of these. The term shredder light fraction is familiar to those skilled in the art in waste management and generally describes a heterogeneous mixture that can consist of various plastics, organic and inorganic materials, whereby the specific composition depends on the type of shredded waste. An example of a shredder light fraction arises from the recycling of refrigerators, where the foam filling of cavities consists of PUR rigid foam, possibly with the addition of other plastics, such as plastics that are the result of cable feedthroughs.Shredded light fraction from refrigerator recycling may still contain mineral components, for example due to fillers contained in the polyurethane.

[0018] Non-limiting examples of sources of polyurethane-containing material include production waste from the mattress, automotive, construction, furniture, footwear, electrical, and sports / leisure industries, or defective or no longer used products from these industries, such as mattresses; body or other vehicle parts such as bumpers, dashboards, headrests, armrests, or carpets; wall panels or pipe insulation; furniture or furniture parts; shoes or shoe parts such as soles or toecaps; cable sheathing, plugs, power strips, or parts thereof; or sports equipment such as snowboards or roller skate wheels.

[0019] Within the scope of the process according to the invention, polyurethane foams (hereinafter also referred to as PUR foams) can be used as polyurethane-containing material, which are selected from the following compositions: PUR flexible foams based on non-reactive polyether polyols (so-called standard polyether polyols) with molecular weights of around 3000 g / mol, filled (with SAN copolymers, ie styrene-acrylonitrile copolymers) or unfilled; PUR flexible foams based on reactive high-resilience polyether polyols with molecular weights of more than 3000 g / mol, filled (with SAN copolymers or PHD, iePolyurea dispersion) or unfilled; PUR flexible foams based on reactive 6-functional polyether polyols; PUR flexible foams based on hypersoft polyether polyols; PUR flexible foams based on polyether polyols and mixtures thereof, which lead to viscoelastic foams and may also contain PEG (polyethylene glycol) as a component; PUR flexible foams based on polyester polyols, filled or unfilled; PUR flexible foams based on the aforementioned polyol mixtures in combination with TDI or MDI; and PUR rigid or semi-rigid foams based on the aforementioned polyol mixtures in combination with TDI or MDI, as well as integral rigid foams consisting of the aforementioned components.

[0020] According to special further developments, the PUR foams include one or more representatives from the product family of flexible foams and / or one or more representatives from the product family of rigid foams.

[0021] Flexible foams include plastics such as standard polyether foams, high-resilience polyether foams, combustion-modified polyether foams (CME), combustion-modified high-resilience polyether foams (CMHR), viscoelastic polyether foams, and polyester foams. Exemplary compositions are known to those skilled in the art and are described, for example, in publications DE 3630225 C2, US 3,905,924, and DE 10 2007 051 089 A1.

[0022] These flexible foams preferably comprise the following components or consist of combinations of two or more of them: Isocyanates: 2,4- and / or 2,6-tolylene diisocyanate (TDI) and any mixtures of these isomers; 4,4'- and / or 2,2'-diphenylmethane diisocyanates (MDI) and any mixtures of these isomers; polymer MDI ("crude" MDI) and MDI prepolymerized with polyhydric polyols (preferably di- and / or trihydric polyethers); and / or any mixtures of TDI and MDI from the aforementioned isomers and forms. Polyols: polyether polyols and / or polyester polyols, as are known per se for the production of cellular and homogeneous polyurethane foams and which are described, for example, in DE-A 2 832 253 (pages 11-18).

[0023] Examples include: (Standard) polyethers with hydroxyl groups (functionalities) of preferably 2 and 3; (Standard) polyethers filled with SAN (styrene-acrylonitrile) solids, with hydroxyl groups (functionalities) of preferably 2 and 3; hypersoft polyethers with functionalities of preferably 3; reactive polyethers with primary hydroxyl groups, preferably with functionalities of 3, 5 and 6; reactive polyethers filled with SAN (styrene-acrylonitrile) solids or PHD (polyurea dispersion), with primary hydroxyl groups, preferably with a functionality of 3; reactive polyols prepolymerised with TDI, preferably with a functionality of 3; non-reactive polyols prepolymerised with TDI, also known in the art as so-called "quasi-prepolymers" (QPP), preferably with a functionality of 3, in which the polyols are present in excess of the TDI; polyols based on renewable raw materials and different functionalities.Natural oil products with varying numbers of hydroxyl groups, castor oil being a non-limiting example; compounds with amino groups or hydroxyl groups that serve as chain extenders or crosslinkers and generally contain 2 to 8, preferably 2 to 4, isocyanate-reactive hydrogen atoms, for example diethanolamine, triethanolamine, diisopropanolamine, sorbitol, glycerol, and urea.

[0024] These flexible foams, like the rigid foams mentioned below, optionally comprise one or more additional substances selected from: catalysts of a type known per se, such as tertiary amines and reactive (incorporable) amines; tin(II) compounds and zinc compounds; surface-active additives such as emulsifiers, foam stabilizers, flame retardants, sorbitol, glycerol, diamines, urea, tertiary amines, and siloxane-based or non-siloxane-based stabilizers.

[0025] The rigid foams of this particular development can be found, for example, in products such as insulation panels (also as sandwich elements with various cover layers), in-situ foams, spray foams, foams produced using the overlay process, foams for solar collector fillings, foams for pipe insulation, filling and assembly foams, and block foams. The compositions are well known to those skilled in the art and are comprehensively described, for example, in EP 0 318 784 A2.

[0026] These rigid foams preferably comprise the following components or consist of combinations of two or more of them: Isocyanates: 2,4- and / or 2,6-toluene diisocyanate (TDI) and any mixtures of these isomers; 4,4'- and / or 2,2'-diphenylmethane diisocyanates (MDI) and any mixtures of these isomers; polymer MDI ("crude" MDI) and MDI prepolymerized with polyhydric polyols (preferably di- and / or trivalent polyethers); any mixtures of TDI and MDI from the aforementioned isomers and forms, but preferably polymer MDI (crude MDI).

[0027] In addition to foams, other examples of polyurethane in the polyurethane-containing material are polyurethane elastomers and polyurethane thermosets.

[0028] The process according to the invention can be carried out batchwise, continuously or semi-continuously.

[0029] In the discontinuous process, also known as the batch process, the starting materials are introduced into a reaction vessel, exposed to the reaction conditions, and then the reaction product is removed after the treatment period has elapsed. The reaction vessel is then loaded with a new batch of starting materials.

[0030] In the continuous process, polyurethane-containing material and urea-containing aqueous solution are not fed into the reaction vessel just once before the start of the reaction, but continuously. Similarly, liquid process medium is also continuously withdrawn. Typically, the feed and withdrawal take place at different points; in particular, the polyurethane-containing material can be pushed together with the urea-containing aqueous solution from the feed point to the withdrawal point or transported by active conveying means within the reaction vessel. Accordingly, there is a low degree of degradation at points close to the feed point, whereby the polyurethane-containing material migrates or is transported together with the urea-containing aqueous solution to the withdrawal point and exhibits a higher degree of degradation with respect to the polyurethane the closer it approaches the withdrawal point.

[0031] Semi-continuous processes represent any possible transitional form between the two processes mentioned above. For example, the removal of the liquid process medium after conducting a batch process may not be essentially complete. As a further example, as a modification of a continuous process, the feeding of new polyurethane-containing material and / or urea-containing aqueous solution may not be continuous, so that new polyurethane-containing material and / or urea-containing aqueous solution is not fed in at all times, but rather only at specific times, for example periodically, or after a certain degree of degradation of the polyurethane in the reaction vessel has been determined.

[0032] For example, any type of conventional device can be used as a reaction vessel, or it can be easily adapted by a person skilled in the art for the purposes of the process according to the invention. Examples include pressure vessels or pressure reactors designed for batch filling and providing reaction volumes from laboratory scale, for example, 0.1 to 10 liters, through intermediate ranges from 10 liters to 1 cubic meter, to large-scale industrial scale in the range from 1 cubic meter to tens or hundreds of cubic meters. Alternatively, the pressure vessels or pressure reactors can be designed for continuous or semi-continuous operation and include pressure locks for feeding polyurethane-containing material or removing the liquid process medium.

[0033] The polyurethane-containing material can be used in its uncomminuted form. For example, a polyurethane foam can be wetted or saturated with the urea-containing aqueous solution and then heated to a temperature in the range of 190°C to 250°C.

[0034] Preferably, however, the polyurethane-containing material is used in a comminuted state. Conventional comminution processes can be used for this purpose; for example, the polyurethane-containing 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 resulting comminution products are approximately 0.5 cm 3 to 10 cm 3 (0.5 ml to 10 ml), such as approximately 1 cm 3 to 5 cm 3 , particularly for porous or large-surface-area polyurethane-containing material, or comminution products with a maximum diameter, measured at the largest point, of approximately 10.5, 2, 1, 0.5, 0.1, 0.05, or 0.01 millimeters.Comminution can be carried out during the process using appropriate devices in the reaction vessel; however, the reaction vessel is preferably filled with polyurethane-containing material in already comminuted form. If the polyurethane-containing material is not merely wetted with the urea-containing solution, but is completely absorbed into it, the resulting material is essentially a suspension of the polyurethane-containing material in the urea-containing aqueous solution.

[0035] Based on the total mass of the aqueous solution, the proportion of urea in the aqueous solution is 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 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 3 mass percent to 5 mass percent.

[0036] The process is preferably carried out under exclusion of air, with optionally small residual amounts of air, for example 20% or 10% of the volume of the reaction vessel in which the degradation process is carried out, being permissible, or is carried out under exclusion of air, or in the presence of an inert gas, for example nitrogen gas. The process is preferably carried out in the presence of an inert gas.

[0037] In a particular embodiment, the aqueous solution comprises 2.5 to 10 mass percent urea, and the heating is carried out over a period of 45 to 250 minutes, in particular over a period of 45 to 240 minutes.

[0038] According to one embodiment, the ratio between urea-containing aqueous solution and polyurethane-containing material is 0.2 ml / g to 5 ml / g, such as 0.4 ml / g to 5 ml / g, for example 0.2 ml / g to 2.5 ml / g, 0.2 ml / g to 2.0 ml / g, 0.2 ml / g to 1.7 ml / g, 0.2 ml / g to 1.2 ml / g or 0.2 ml / g to 1.0 ml / g, or for example 0.4 ml / g to 2.5 ml / g, 0.4 ml / g to 2.0 ml / g, 0.4 ml / g to 1.7 ml / g, 0.4 ml / g to 1.2 ml / g or 0.4 ml / g to 1.0 ml / g. In particular, a low ratio between the volume of the urea-containing aqueous solution used and the amount of polyurethane treated with it results in efficient use of the volume available for carrying out the degradation process.In relation to use with polyurethane foam, an amount of 0.2 ml / , in particular 0.25 ml / g, in particular 0.29 ml / g, and in particular 0.4 ml / g represents a lower limit at which the polyurethane foam is still sufficiently moistened with the aqueous urea-containing solution to enable the desired degradation of polyurethane.

[0039] The process optionally includes a further process step for at least partially recovering the liquid process medium obtained after heating. Accordingly, the liquid process medium is removed entirely or partially from the reaction vessel. This allows for optional subsequent steps, for example, fractionation into individual substances or groups of substances that can be disposed of more specifically or, ideally, become available as raw material sources.

[0040] According to one embodiment, any solids contained in the obtained liquid process medium are removed, if present. These may be, for example, metal particles, particles of other plastics, or particulate reaction or degradation products of the polyurethanes or polyurethane components. Methods for removing solids are known to those skilled in the art and include, for example, sedimentation, centrifugation, or filtration.

[0041] According to a preferred embodiment, the aqueous solution containing 1 to 45 mass percent urea is free of polyol, for example, free of diol, and / or free of carboxylic acids and / or free of ammonia. This advantageously avoids environmentally harmful substances. According to a particular embodiment, the aqueous solution consists of water and 1 to 45 mass percent urea.

[0042] During the degradation process, the polyurethane is partially or completely transferred into the liquid process medium. Accordingly, polyurethane-containing materials originally in solid form, which require a large volume, particularly when the polyurethane is in the form of a foam, can be converted into more easily handled liquids, namely the liquid process medium, with a lower volume requirement. Furthermore, it is possible to fractionate and / or isolate the substances contained in the liquid process medium and / or, if necessary, to further use or reuse them.

[0043] The present invention accordingly relates to a process medium obtainable or obtained by a process described herein, wherein the heating is carried out at a temperature of 190°C to 250°C for a period of 20 minutes to 240 minutes, wherein the aqueous solution contains 1 to 10 mass percent urea and the ratio between urea-containing aqueous solution and polyurethane-containing material is 0.4 ml / g to 5 ml / g. It particularly relates to such a process medium which contains polyols used to prepare the polyurethane degraded by the process, or modifications of such polyols, and / or diamines or modifications of such diamines, wherein the diamines are precursors of the diisocyanates used to prepare the polyurethane degraded by the process. Non-limiting examples of modifications are ring formations or deaminations.Such a process medium thus contains valuable raw materials for the chemical industry, in particular for the polyurethane recycling industry, which can be reused - if necessary after isolation from the process medium.

[0044] Further advantages, features and details emerge from the following description, in which - if necessary with reference to the figures - at least one embodiment is described in detail. Figure 1 shows a three-dimensional diagram illustrating the degree of degradation of polyurethane-containing material as a function of temperature and duration of the process. Figure 2 shows a three-dimensional diagram illustrating the influence of urea on the degradation of various polyurethane-containing materials at a selected heating time. Figure 3shows a three-dimensional diagram illustrating the influence of urea on the degradation of a polyurethane-containing material in a time series. Example 1 - Polyurethane flexible foams

[0045] Two flexible polyurethane foams based on TDI and MDI (product names: R 4030 and R 5535, source: Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) were taken up with 20.0 g and 19.6 g, respectively, in 32.2 ml and 35.7 ml of 7.5% urea solution and treated for 180 minutes at 190 °C in a closed pressure vessel. Table 1: Weight of polyurethane flexible foam [g] Urea content of the aqueous solution [mass%] volume of aqueous solution used [ml] Reduction [%] 20,0 (R 4030) 7,5 32,2 50 19,6 (R 5535) 7,5 35,7 90 180 min at 190°C

[0046] After cooling, the samples taken were semi-quantitatively classified by visual inspection with regard to the degree of degradation of solid polyurethane and the corresponding disappearance of detectable solid material and transfer into the liquid process medium. As in all other subsequent tests, "0%" represents that no degradation of polyurethane had yet taken place and, accordingly, the originally used amount of solid polyurethane was still present, whereas "100%" represents complete degradation and corresponding transfer of the polyurethane into the liquid process medium.

[0047] In both cases, partial degradation occurred, with varying amounts of solids in the form of apparently compacted foam residues still present in the liquid process medium. Example 2 - Polyurethane integral foam

[0048] Two samples of flexible ether-based polyurethane integral skin foam and a cast elastomer marketed under the brand name Colo-Fast ®< (BASF, SE, Ludwigshafen, Germany) were taken up with initial weights of 25 g and 35 g, respectively, in 40 ml of 3% urea solution and treated for 240 minutes at 245 °C in a closed pressure vessel that was 80% full. Table 2: Weight of polyurethane integral foam [g] Urea content of the aqueous solution [mass percent] volume of aqueous solution used [ml] Reduction [%] 25 (ether base) 3 40 100 35 (Colo-Fast) 3 40 100 240 min at 245°C

[0049] The polyurethane materials used were completely degraded, but a small amount of particles was detected, which could possibly be attributed to polymerization. Example 3 - non-foamed polyurethane

[0050] In a series of experiments, solid, non-foamed polyurethanes were used for the degradation process. Blue polyurethane plastic tubing of the "PUN" type (Festo Gesellschaft mbH, Vienna, Austria) was crushed and 1 g each was heated in 25 ml of an aqueous urea solution with a urea content of 1% by mass, 5% by mass, 7.5% by mass, or 10% by mass, for a period of 150 minutes at 210 °C in a closed pressure vessel. The series of experiments primarily served to determine the influence of urea concentration and to determine the degradability of solid polyurethanes. Table 3: Weight of polyurethane hose [g] Urea content of the aqueous solution [mass percent] volume of aqueous solution used [ml] Reduction [%] 30 1 25 100 30 5 25 100 5 7,5 20 100 5 7,5 20 100 30 7,5 25 100 30 10 25 100 150 min at 210°C

[0051] As a result, it was found that in all batches, no trace of the originally used solid polyurethane was detectable in the resulting liquid process medium. Thus, non-foamed polyurethanes are degradable under the stated test conditions. Example 4 - thermosetting polyurethane

[0052] As another example of non-foamed polyurethanes, a thermoset polyurethane core with a density of 165 g / l, used in skis, was used for the degradation process. The core was crushed and 15 g was heated to 210 °C in 40 ml of an aqueous urea solution with a urea content of 3 mass percent for 150 minutes in a closed pressure vessel filled to 80% of the available volume (remaining volume 20%: air). Table 4: Weight of polyurethane ski core material [g] Urea content of the aqueous solution [mass percent] Volume of aqueous solution [ml] Reduction [%] 15 3 40 100 150 min at 210°C

[0053] As a result, it was found that no portions of the originally used non-foamed polyurethane could be detected in the resulting liquid phase. Example 5 - elastomeric polyurethanes

[0054] Examples of elastomeric polyurethanes used included springs made of microcellular polyurethane, marketed under the brand Cellasto® (BASF SE, Ludwigshafen, Germany), and the cast elastomer Colo-Fast® (BASF SE, Ludwigshafen, Germany). The samples were crushed and heated in separate batches in 40 ml of an aqueous urea solution with a urea content of 3 mass percent for 150 minutes at 210 °C in a closed pressure vessel filled to 80% of the available volume (remaining volume 20%: air). Table 5: Weight of elastomeric polyurethane [g] Urea content of the aqueous solution [mass percent] volume of aqueous solution used [ml] Reduction [%] 35 (Cellasto ®< (Sample 1) 3 40 100 40 (Cellasto ®< (Sample 2) 3 40 100 35 (Colo-Fast ®< ) 3 40 100 150 min at 210 °C

[0055] As a result, it was found that in all batches, no portions of the originally used elastomeric polyurethane could be detected in the resulting liquid phase. Example 6 - Time series

[0056] In a series of tests, the aforementioned polyurethane foams R 4030 and R 5535 were heated in an aqueous urea solution with a urea content of 7.5 mass percent at a temperature of 230 °C in a closed pressure vessel for 60 minutes, 90 minutes or 120 minutes. Table 6: Weight of polyurethane foam [g] Urea content of the aqueous solution [mass percent] volume of aqueous solution used [ml] Duration [min] Reduction [%] 9,98 (R 4030) 7,5 25 60 50 10,47 (R 5535) 7,5 25 60 50 9,93 (R 4030) 7,5 25 60 50 10,36 (R 5535) 7,5 25 60 50 10,08 (R 4030) 7,5 25 90 90 10,04 (R 5535) 7,5 25 90 90 10,15 (R 4030) 7,5 25 120 100 10,23 (R 5535) 7,5 25 120 100 different times at 230°C

[0057] At a degradation rate classified as 50%, the foam structures dissolved and resulted in a pasty consistency; at a degradation rate classified as 90%, the foam structure was almost completely liquefied; at 100% degradation, it was 100% liquefied. Example 7 - Time series and temperature series

[0058] After the previous tests had shown that in principle any type of polyurethane-containing material can be degraded by means of the process, a new series of tests was carried out with the aim of systematically determining the temperature and time dependence of the degradation, using a mixture of different polyurethane-containing materials, namely a mixture of equal weight proportions with a weight of 4.15 g each. a) Standard foam (standard foam grade TDI 80-based) with filler (calcium carbonate) and SAN polymer particles (N 4045 WS), b) high resilience polyurethane foam [HR (high resilience) foam grade TDI 80 / TDI65-based] with filler (calcium carbonate) and SAN polymer particles (R 4040 WS), c) high resilience polyurethane foam [HR (high resilience) foam grade MDI-based] with filler (calcium carbonate) and SAN polymer particles (R 5535 WS), and d) viscoelastic foam (viscoelastic foam grade MDI-based - V5018 WS, Eurofoam Deutschland GmbH Schaumstoffe) without fillers.

[0059] The resulting polyurethane-containing material was shredded and mixed with a 3% urea solution at a ratio of 0.582 ml of urea solution per gram of polyurethane-containing material. Temperature series were conducted by heating samples in sealed pressure vessels to 190 °C, 210 °C, 230 °C, and 245 °C in a heating cabinet at equilibrium pressure. Samples were removed after a residence time of 60 minutes, 90 minutes, 120 minutes, 180 minutes, and 240 minutes at the respective temperature, respectively. Three samples were prepared and analyzed in parallel for each time point.

[0060] After cooling, the samples taken were semi-quantitatively classified by visual inspection, with the average value of the three samples being calculated, with regard to the degree of degradation of solid polyurethane and the corresponding disappearance of detectable solid material and transfer into the liquid process medium. The result is shown in Figure 1 The horizontal x-axis represents the duration of the heat treatment at a given temperature in minutes, the vertical z-axis represents the semi-quantitative degree of degradation in percent, and the three selected temperatures of 190 °C, 210 °C, 230 °C, and 245 °C are plotted on the y-axis leading into the image plane. It can be seen that with increasing temperature up to 245 °C, faster degradation rates can be achieved. Example 8 - Control test without overpressure

[0061] In a control experiment, 2 g of TDI polyurethane foam (product name: R 4030; source: Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) and 2 g of MDI polyurethane foam (product name: R5535; source: Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) were each mixed with 40 ml of a 7.5% urea solution in two separate batches and treated in a glass flask at a temperature of 100 °C to 110 °C at ambient pressure in a heating cabinet, with the fluid loss being replenished by adding water. After 4.5 hours, no degradation was observed. Example 9 - first control test without urea at overpressure

[0062] As a further control experiment, four different approaches were used, namely 16.6 g of black PUR integral foam (window insulation material) in 9.66 ml of H 2 O, 16.6 g of white PUR integral foam (component of a shoe) in 9.66 ml of H 2 O, 14.0 g of PUR semi-rigid foam (BASF) in 8.15 ml of H 2 O, and 16.0 g of PUR elastomer (Cellasto ®< from BASF) in 9.66 ml of H 2 O were each heated for 30 min at 245 °C in sealed pressure vessels, whereby the stated amounts of water were either free of urea or contained 3 mass percent urea.

[0063] The results are in Figure 2The above-listed approaches are referred to as "PUR-Integral Window," "PUR-Integral Shoe," "PUR-Semi-Rigid," and "PUR-Elastomers," respectively. The degree of conversion is indicated on the y-axis in percent. It was shown that in all cases, a significant increase in degradation could be achieved by adding urea. In the case of the integral foams and the elastomer, this triggered complete or almost complete degradation of the solid material used. Even in the case of the PUR-Semi-Rigid foam, which was completely degraded with a heating time of 30 minutes less, a significant increase in the degradation rate was still observed with the addition of urea.The impaired degradation of the semi-rigid foam could be due to impaired heat transfer in the foam material, as the semi-rigid foam used, with a density of 133 g / L, has a significantly lower density than the "PUR-Integral Window" (850 g / L), "PUR-Integral Shoe" (790-830 g / L), and "PUR-Elastomer" (400-550 g / L). As a result, the PUR semi-rigid foam filled the pressure vessel much more completely, making it less wettable with the urea-free or urea-containing aqueous solution, and hindering heat transfer due to the higher air volume in the pores. Example 10 - second control test without urea at overpressure

[0064] In a further control experiment, multiple batches of a mixture of flexible polyurethane foams (either 16.6 g in 9.66 ml of water or 16.6 g in 9.66 ml of water containing 3% by mass of urea) were heated at 245 °C in sealed pressure vessels and removed at different times (40, 60, 90, 120, 180, or 240 min). Compared with the samples used in Example 9, the mixture of flexible polyurethane foams most closely resembled the PUR semi-rigid foam in terms of its material properties. The results are shown in Figure 3The graphs are shown in Table 1. The x-axis represents the time in minutes and the y-axis represents the degree of conversion in percent. It was shown that in the presence of 3 mass percent urea, complete degradation was observed after a heating time of just 40 minutes, whereas in urea-free water, only partial degradation occurred after 40 minutes. Although this degradation also increased with increasing heating time, it was always below the degradation achievable by treatment with urea-containing water. Example 11 - Test with a simple flexible foam system (single polyol foam), analysis of the degradation products

[0065] To determine the degradation products formed after application of the method, a flexible polyurethane foam with the simplest possible chemical structure was produced in the laboratory (Table 7). To limit the influencing factors, only a standard ether polyol with a molecular weight of 3500 MW was used, and toluene diisocyanate TDI 80 was used as the isocyanate. The density of the foam was 22 kg / m³. Table 7: raw material parts by weight Polyol Standard Ether (3500 MW) 100 Amine BDE - Dabco BL 11 (Evonik Industries, Essen, Germany 0,1 Amin TEDA - Dabco 33 LV Evonik Industries, Essen, Germany) 0,22 Silicone Niax L 620 (Momentive Performance Materials, D-Leverkusen 0,48 Water dosed 4,48 Tin octoate pure 0,15 TDI 80 50,81

[0066] This flexible PUR foam was crushed and treated with the process in an 11.5-liter Büchi reactor (Büchi AG, Uster, Switzerland). 400 grams of foam were pre-moistened with 236 milliliters of a 3% water-urea solution and poured into a stainless steel digestion vessel (also known as an inliner vessel) with a volume of approximately 10.2 liters. The bottom of the vessel was lined with aluminum foil with a rim height of 5 cm to collect the resulting liquid process medium. 200 ml of water was added beneath the inliner vessel inserted into the reactor to rapidly generate steam. The process according to the invention was carried out over a period of 240 minutes, with the reactor jacket temperature initially set at 260°C for 60 minutes and then at 250°C for 180 minutes. The reactor interior ultimately reached a temperature of almost 230°C (229.3°C).

[0067] To chemically analyze the resulting process medium, 1 ml of it was dissolved in 99 ml of acetonitrile and mixed for 24 h on a laboratory shaker plate. The acrylonitrile-sample mixture was then filtered using a syringe filter (e.g., Chromafil Xtra, RC, 25 mm, 0.45 µm) before 1.5 microliters of the sample were introduced directly into an Agilent 8890 GC gas chromatography system (Agilent, Santa Clara, USA). The GC column was initially held at 40°C for 2 minutes and then heated from 40°C to 250°C at 10 Kelvin per minute. A hold time of 5 minutes followed. The total measurement time was 28 minutes. The measurement was performed using a 1:10 split. The method name is Ramp40-250_28min_1.5ml_split1-10.M. The spectrum, measured with the coupled Agilent 5977B GC / MSD mass spectrometer system, shows two distinct peaks at retention times 1.37 to 1.75 minutes and 13.71 minutes.The spectra were analyzed using the "NIST17" software package (National Institute of Standards and Technology, Gaithersburg, USA), which was included in the scope of delivery of the TG / STA-GC-MS system described in more detail in Example 12. It also included the "AMDIS32" software for qualitative GC-MS analyses, the ALKANES, NISTCW, NISTDRUG, NISTEPA, NISTFAD, NISTFF, NISTTOX, and PESTPLUS databases, and the MSSEARCH software. The latter software allows for the targeted comparison of individual measured scans with the databases used. The peak analysis is shown in Table 8, where MF (Match Factor) represents the match between the measured spectrum and the spectra in the databases, and RFM (Reverse Match Factor) represents the match between the available database spectra and the measured spectrum. In both cases, a special algorithm is used, which is stored in the software. These factors are normalized in the NIST software to 1000 = 100% agreement. Table 8: Retention time [min] substance MF RMF 1.37 Acetonitrile (CAS 75-05-8) 897 900 1.75 Acetonitrile (CAS75-05-8) 912 914 13.71 1,3-Benzenediamine, 4-methyl-(CAS 95-80-7) 962 963

[0068] The acetonitrile peak is due to the solvent used, acetonitrile. A synonym for 1,3-benzenediamine, 4-methyl- (CAS 95-80-7) is 2,4-diaminotoluene. The 2,4-diaminotoluene peak indicates that this compound can be obtained within the scope of the process according to the invention. 2,4-Diaminotoluene is a precursor of toluene diisocyanate TDI 80, into which it can be converted via phosgenation, and thus represents an industrially valuable, reusable raw material, particularly in the polyurethane industry.

[0069] The process medium was also subjected to GPC (gel permeation chromatography) analysis to determine the molecular weight (external measurement at BASF Lemförde - Central Analytic Lemförde, BASF Polyurethanes GmbH, Elastogranstr 60, 49448 Lemfoerde, Germany).

[0070] A molar mass distribution with a clear main peak at 3700 g / mol was measured. The viscosity of the process medium was also determined, and it was 1100 mPas. The OH number of the process medium was also determined, and it was 325 mg KOH / g.

[0071] The results support the assumption that a significant component of the process medium is polyol. It is very similar in molar mass to the originally used polyol and has (possibly due to treatment experienced in the process) a slightly higher viscosity (Polyol Standard Ether -3500 MW = 700-900 mPa•s, OH 48) and a higher OH number.

[0072] Accordingly, polyols can be obtained using the process according to the invention and reused as valuable raw materials. Example 12 - Test with PUR flexible foam mixture, analysis of degradation products via TG - GC / MS

[0073] In this example, an attempt was made to detect polyols formed during the process according to the invention in the resulting process medium. For this purpose, the process medium was to be thermally decomposed at temperatures of approximately 380 °C, and the presence of polyols in the process medium was to be determined from the resulting decomposition products. For this purpose, coupled TG / STA-GC-MS measurements were used (coupling of gas chromatography and mass spectrometry with thermal analysis, where TG stands for thermogravimetry and STA for "simultaneous thermal analysis"). The measuring instruments used were an STA 449 F3 Jupiter (Netzsch, Selb, Germany), which was connected via a heated transfer line to the Agilent 8890 GC gas chromatography system (Agilent, Santa Clara, USA) and the Agilent 5977B GC / MS mass spectrometer system.

[0074] First, in a preparatory step, a reference database was created as follows.

[0075] For this purpose, the polyols listed in Table 9 below were used, as these represent constitutional components of the flexible foams used in the mixture actually tested later using the reference database (see Table 10). Table 9: Polyol Additional designation in the AMDIS database Standard 3500 MW STD_POLYOL Standard 45% SAN Polyol SAN_45% HR 6000 MW Polyol HR_6000 HR 25% SAN Polyol HR_SAN HR high functional polyol HR_HF Hypersoft Polyol HYPERSOFT Viscoelastic polyol VE8420

[0076] These were each decomposed individually at 380°C in the thermal degradation stage of the aforementioned TG / STA-GC-MS system. The main peaks were determined using the NIST and AMDIS databases (see Example 11), and the name of the assigned compound according to these databases and the GC retention times of the decomposition products were stored in the reference database. Each decomposition product was assigned the respective additional designation according to Table 9. If the same decomposition products occurred with different polyols, the respective additional designation was added. These decomposition products, along with the corresponding identifying product abbreviation, can then be found in Table 11 (where Table 11 shows the decomposition products of the mixture according to Table 10).

[0077] After the reference database was created, a mixture of flexible foams was subjected to the process according to the invention in order to clarify the extent to which polyols occur in the process medium after carrying out the process according to the invention.

[0078] For this purpose, 400 grams of a mixture of flexible foams were treated with the inventive process in an 11.5-liter Büchi reactor. The mixture contained the following flexible foam grades (purchased from Neveon Holding GmbH, Ebersbach-Fils, Germany): Table 10: Soft foam Class Quantity [g] N 3045 TDI 80 - Standard 100 R 4040 TDI 80 - high resilience 100 R 5535 MDI - high resilience 100 V 5018 MDI - Viscoelastic 100

[0079] The 400 grams of foam mixture were pre-moistened with 236 milliliters of a 3% water-urea solution and poured into a stainless steel digestion vessel (volume approximately 10.2 liters). The bottom of the vessel was lined with aluminum foil with a rim height of 5 cm to collect the resulting liquid process medium. 200 ml of water was added beneath the liner vessel to quickly generate steam.

[0080] The process was carried out over a period of 240 minutes, with the reactor jacket temperature initially set at 260°C for 60 minutes and then at 250°C for 180 minutes. The reactor interior ultimately reached a temperature of just under 236°C.

[0081] The obtained process medium was again analyzed using coupled TG / STA-GC-MS measurements.

[0082] The spectrum at 379°C was analyzed using AMDIS and the reference database created in the preliminary step, with a default minimum match factor (MF) of 80%. The match factor represents the percent agreement between the measured spectrum and the spectra from the AMDIS databases. This factor is calculated using algorithms embedded in the software. The main peaks correspond to the peaks measured for the individual polyols according to Table 9.

[0083] The correlation of these data is shown in Table 11. The analysis results show that the process medium includes originally used polyols as well as conversion products and / or degradation products formed during the degradation process. Table 11: Retention time [min] substance MF 2.4464 Ethanol, 2-methoxy-, acetate _ HOURS _ POLYOL (CAS#:110-49-6) 83 IUPAC: 2-methoxyethyl acetate 3.9042 1-Propene, 2-(1-methylethoxy) _HR_6000 (CAS#:4188-63-0) 93 IUPAC: ( E )-1-propan-2-yloxyprop-1-ene 6.5138 Diisopropylether_HR_SAN (CAS#: 108-20-3) 99 6.9436 2-Propanone, 1-(1-methylethoxy)- _STD_POLYOL_HR_HF_VE8420 ( CAS#:42781-12-4) 100 1-Isopropoxyacetone IUPAC: 1-propan-2-yloxypropan-2-one 7.4102 Oxirane, trimethyl- _HR_6000 (CAS#:5076-19-7) 98 Trimethyloxirane IUPAC: 2,2,3-trimethyloxiranes 7.6279 Carbonic acid, allyl 2-ethoxyethyl ester _HR_6000 (NIST#: 357377) (ID#:2-87-3) 93 8.3387 Styrene _SAN_45%HR_SAN (CAS#:100-42-5) Styrol 97 9.4547 Diisopropyl ether _HR_6000_HR_HF (CAS#:108-20-3) 99 9.5666 3-Pentanol, 2-methyl- _HR_6000_HR_HF (CAS#:565-67-3) 98 IUPAC: 2-methylpentan-3-ol 9.9325 2-Pentanone, 5-methoxy- _ STD_POLYOL _ HR_HF_VE8420 (CAS#: 17429-04-8) IUPAC: 5-methoxypentan-2-one 89 10.1310 Ethanol, 2-(2-ethoxyethoxy)- _HYPERSOFT (CAS#:111-90-0) 98 Diethylene glycol monoethyl ether 11.3633 1-Propanol, 3-[3-(1-methylethoxy)propoxy]- _STD_POLYOL_HR_SAN_HR_HF (CAS#:54518-03-5) 99 IUPAC: 3-(3-Isopropoxypropoxy)propan-1-ol 11.4137 1-Propanol, 2-(2-hydroxypropoxy)- _VE8420 (CAS#:106-62-7) 94 IUPAC: 2-(2-hydroxypropoxy)propan-1-ol 11.5686 Propane, 1,1-dipropoxy- _STD_POLYOL_HR_HF (CAS#:4744-11-0) 98 Dipropylpropylal 11.9289 1-Butoxypropan-2-yl isobutyl carbonate _HR_6000_HR_HF (NIST#:378276) (ID#:26899) 98 13.0548 1-Propanol, 2,2'-oxybis- _STD_POLYOL_VE8420 (CAS#:108-61-2) 96 2,2'-Oxydipropanol 13.2251 Ethanol, 2-[2-(2-ethoxyethoxy)ethoxy]- _HR_6000_HR_HF (CAS#:112-50-5) 83 Triethylene Glycol Monoethyl Ether 13.3345 12-Crown-4 _HR6000_VE8420 (CAS#:294-93-9) 94 1,4,7,10-Tetraoxacyclododecan 13.9039 Diethyl carbitol _HYPERSOFT (CAS#:112-36-7) 83 Diethylenglycoldiethylether 14.2187 Tri(propylene glycol) propyl ether _STD_POLYOL (CAS#:96077-04-2) 81 14.5563 2-Propanol, 1-[1-methyl-2-(2-propenyloxy)ethoxy]- _STD_POLYOL_VE8420 (#:55956-25-7) 94 15.5887 Tripropylene glycol monomethyl ether_STD_POLYOL_VE8420 ( CAS#:20324-33-8) 81 16.5011 Benzene, 1,1'-(1,3-propanediyl)bis- _SAN_45% (CAS#:1081-75-0) 89 1,3-Diphenylpropan 17.6774 4,8,12,16-tetraoxaeicosan-1-ol _HR_6000_HR_HF (NIST#:397636) (ID#:32-16-4) 96 IUPAC: 3-[3-[3-(3-butoxypropoxy)propoxy]propoxy]propan-1-ol 17.8010 Pentaethylene glycol _HR_SAN (CAS#:4792-15-8) 92 19.5699 3,6,9,12-Tetraoxatetradecan-1-ol _HYPERSOFT (CAS#:5274-68-0) 85 IUPAC: 2-[2-[2-(2-dodecoxyethoxy)ethoxy]ethoxy]ethanol Tetraethyleneglycol monododecyl ether 19.5699 Tetraethylene glycol diethyl ether _HYPERSOFT (CAS#:4353-28-0) 85 IUPAC: 1-ethoxy-2-[2-[2-(2-ethoxyethoxy)ethoxy]ethoxy]ethane 3,6,9,12,15-Pentaoxaheptadecane 19.5988 1,4,7,10,13,16-Hexaoxacyclooctadecane _HYPERSOFT_HR_6000 ( CAS#: 17455-13-9) 18-Crown-6 ether 84 19.6542 3-Phenylpropanol _SAN_45% (CAS#:122-97-4) 81 IUPAC: 3-phenylpropan-1-ol Benzenepropanol 19.9315 (1-Benzyl-2-O-tolyl-ethyl)-isonitrile _SAN_45% (NIST#:287385), (ID#:88-42-6) 82 IUPAC: N -[1-(2-methylphenyl)-3-phenylpropan-2-yl]methanimine

[0084] The spectrum at 265°C was analyzed using AMDIS and the AMDIS and NIST databases with a default match factor (MF) of 90%. Preliminary tests had determined that at a temperature of 265°C, the components in the process medium that are attributable to the diisocyanate in the polyurethane are thermally degraded, whereas components in the polyurethane that are attributable to the polyols are not degraded at this temperature.

[0085] The main peaks correspond to the diamine precursors of the diisocyanates used in the flexible foams (Table 12). The liquid process medium obtained after carrying out the process according to the invention thus contains the precursors before the industrial phosgenation step of the diisocyanates. Table 12: Retentionszeit [min] Substanz MF 9.7657 Aniline 99 14.2512 1,3-Benzenediamine, 4-methyl- 98 14.2727 1,3-Benzenediamine, 4-methyl- 98 18.9949 Benzenamine, 4,4'-methylenebis- 92 19.4296 Benzenamine, 4,4'-methylenebis- 100 19.8471 Benzenamine, 4,4'-methylenebis- 98

[0086] The described process enables the degradation of polyurethane and is therefore commercially applicable. Furthermore, raw materials can be extracted from the resulting process medium, which can be reused in the chemical industry, particularly in the polyurethane recycling industry.

Claims

1. Process for the decomposition of polyurethane, wherein a polyurethane containing material is heated at excess pressure to a temperature of 190°C to 250°C in the presence of an aqueous solution containing 1 to 45 mass percent urea.

2. Process according to claim 1, wherein the heating is performed at a pressure of 1.05 bar to 100 bar.

3. Process according to any one of the preceding claims, wherein the excess pressure is an equilibrium pressure resulting from heating.

4. Process according to any one of the preceding claims, wherein the heating is performed for 20 minutes to 240 minutes.

5. Process according to any one of the preceding claims, wherein the aqueous solution comprises 2.5 - 10 mass percent urea and wherein the heating is performed for 45 - 250 min, in particular for 45 - 240 min.

6. Process according to any one of the preceding claims, wherein the ratio between urea containing aqueous solution and polyurethane containing material is 0.4 ml / g to 5 ml / g.

7. Process according to any one of the preceding claims, wherein the liquid process medium obtained after heating is at least partially recovered.

8. Process according to claim 7, wherein solids are removed from the recovered aqueous process medium.

9. Process according to any one of the preceding claims, wherein the aqueous solution is polyol-free and / or carboxylic acid-free and / or ammonia-free.

10. Process according to any one of the preceding claims, wherein the aqueous solution consists of water and urea.

11. Liquid process medium, obtainable by a process according to one of the preceding claims, wherein the heating is performed at a temperature of 190°C to 250°C for 20 minutes to 240 minutes, wherein the aqueous solution contains 1 to 10 mass percent urea and wherein the ratio between urea containing aqueous solution and polyurethane containing material is 0.4 ml / g to 5 ml / g.