How to decompose polyurethane

Abstract

The present invention relates to a method for decomposing polyurethanes, in which a polyurethane-containing material is heated to 190°C to 250°C under superatmospheric pressure in the presence of an aqueous solution containing 1 to 45% by weight of urea. The present invention also relates to a liquid treatment medium obtained by such a method.

Description

[Technical Field]

[0001] The present invention relates to a method for decomposing polyurethanes and a treatment medium obtained by this method. [Background technology]

[0002] The tunable properties of polyurethanes make them useful in a wide range of industrial and domestic products, including foams, paints, adhesives, pour-in sealing compounds, hoses, seals, floor coverings, mattresses, automotive parts, sporting equipment parts, and shoe components.

[0003] This results in a correspondingly high percentage of polyurethane waste being produced when products break or reach the end of their useful life.

[0004] Therefore, various solutions have been proposed in the past for the reconditioning of polyurethane waste. Many patents relate to the dissolution of polyurethane waste in aliphatic diols, such as U.S. Patents 4,044, 04, 3,632,530, and 4,162,995, and German Unexamined Patent Application 2304444. U.S. Patent 4,316,992 suggests dissolution in high-boiling saturated alcohols, and U.S. Patent 4,039,568 suggests dissolution in the presence of various alcoholates. The drawback of all these methods is the fact that the process requires hydrocarbons in the form of diols. Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that the present invention aims to solve is to provide an alternative solution, in which preferably materials with a less adverse impact on the environment are used.

[0006] The invention results from the features of the independent claims. Advantageous further refinements and variations are the object of the dependent claims. [Means for solving the problem]

[0007] In a first embodiment, this problem is solved by a method for decomposing polyurethanes, in which a polyurethane-containing material is heated to 190°C to 250°C under superatmospheric pressure in the presence of an aqueous solution containing 1 to 45% by weight of urea. At the start of the method, the polyurethane-containing material is present in or together with the aqueous solution containing urea. After a selected treatment period, the polyurethane fraction of the polyurethane-containing material, originally in solid form, is partially or completely converted to the material in the liquid treatment medium, resulting from the aqueous solution containing urea present at the start of the process. The treatment medium may also contain solids, such as solids embedded in or adsorbed onto the solid polyurethane, or plastics other than polyurethane. The liquid treatment medium contains decomposition products and / or other secondary products resulting from the originally present polyurethane. Conversion to a liquid treatment medium advantageously converts the originally solid polyurethane into a more manageable form and, under certain circumstances, provides the ability to separate reusable materials from the resulting liquid treatment medium or to usefully include them in further reactions. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a three-dimensional chart showing the degree of decomposition of polyurethane-containing materials as a function of temperature and time the process was carried out. [Figure 2] FIG. 2 is a three-dimensional chart depicting the effect of urea on the degradation of various polyurethane-containing materials at selected heating times. [Figure 3] Figure 3 is a three-dimensional chart showing the effect of urea on the decomposition of polyurethane-containing materials over time. DETAILED DESCRIPTION OF THE INVENTION

[0009] The term overpressure is understood to mean any pressure greater than atmospheric pressure. According to one variant, the heating is carried out at a pressure between 1.05 bar and 100 bar. Examples of pressure ranges are 10 bar and 45 bar, for example 12 bar and 40 bar, or 25 bar and 35 bar. For the purposes of simple process control, the overpressure is the equilibrium pressure established by heating, for example the equilibrium pressure established by heating in a pressure vessel.

[0010] The process is desirably completed within a period of 20 to 240 minutes, particularly 45 to 240 minutes, 90 to 240 minutes, e.g., 120 to 240 minutes. A preferred period is 30 to 180 minutes, e.g., 40 to 180 minutes (40 to 180 minutes). In this regard, the reaction temperature can remain constant within a specified temperature range, for example, by temperature regulation, or can vary within the specified temperature range. While the period is preferably one continuous period, it can also be cumulatively composed of separate periods during which the intended temperature conditions are maintained. In the course of extensive experimentation, it was found that the first signs of solid formation occurred at a temperature of 245°C and a period of 240 minutes. Therefore, considering the preset 240-minute period of the heat treatment, 250°C is considered the practical upper temperature limit.

[0011] This method makes it possible to carry out the decomposition of polyurethanes using urea, a substance that occurs naturally in the environment and is therefore also naturally decomposed.

[0012] A polyurethane-containing material can also be a material that contains, in addition to polyurethane, non-polyurethane components, such as polyurethanes combined with other plastic components, such as styrene-acrylonitrile particles, metal components, glass components, or inorganic materials, such as calcium carbonate. Non-limiting examples include polyurethane objects containing metal fastening elements, or composites of polyurethane and other plastics, such as refrigerator parts containing polyurethane as an insulating layer and other plastics as a resist coating. However, polyurethane-containing materials can also be understood to mean materials composed entirely of polyurethane. The polyurethane itself can be pure polyurethane, or polyurethane containing other substances, such as plasticizers, fungicides, antioxidants, UV stabilizers, and the like, such as flame retardants, dyes, or polymerization initiator residues. The term "polyurethane-containing material" can also refer to a mixture of various polyurethane-containing materials, each containing a different type of polyurethane.

[0013] The decomposition of the polyurethane may be partial or, depending on the processing parameters selected, may involve intermediate stages in which the polyurethane is present in a reduced form until it is completely decomposed and no longer exists as a solid in the material.

[0014] The term "polyurethane" according to the standard technical definition is understood to be a polymer containing as a characteristic group a urethane group according to the following formula (I):

[0015] [ka]

[0016] Polyurethanes are generally prepared by copolymerizing dihydric or higher hydric alcohols represented by formula (II): HO-R´-OH (II) and a diisocyanate having the general formula (III): O=C=NRN=C=O (III) can be obtained by polyaddition with where R' represents a small or already polymeric aliphatic or aromatic radical, optionally further comprising at least one hydroxyl group; R has the same meaning as R'.

[0017] 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, Wiley-VHC Verlag GmbH & Co. KGaA, Weinheim, Germany, 2003, Volume 28, pages 667-722. Most polyurethane foams (hereinafter also referred to as PUR foams) are produced based on aromatic isocyanates. The most important representatives of this group are mixtures of the isomers 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), and mixtures of isomers of diphenylmethane diisocyanate (MDI), of which diphenylmethane-2,2'-diisocyanate (2,2'-MDI), diphenylmethane-2,4'-diisocyanate (2,4'-MDI), and diphenylmethane-4,4'-diisocyanate (4,4'-MDI), as well as prepolymerized MDI. TDI 80 is the most important diisocyanate used in soft foam production. TDI 65 is also used in many soft foams, especially ester foams. In these two designations, the numbers 80 and 65 represent the weight percent of the more reactive isomer 2,4-toluene diisocyanate, with the remainder being supplied by the isomer 2,6-toluene diisocyanate. Polyethers, polyesters, or diamines are preferably used as the polyol component. Properties can also be further modified by adding stabilizers such as silicone-polyether copolymers, epoxies, benzophenones, and other substances. Foam properties can also be modified by additives, such as phosphate esters, which are used as flame retardants. Mechanical reinforcements such as carbon fiber can be incorporated into the foam; these are examples of non-polyurethanes that can be included as additional components in polyurethane-containing materials. Fillers such as calcium carbonate can also be used.

[0018] The polyurethane can be a polyurethane foam or a non-porous polyurethane, non-limiting examples of which are polyurethane hose or polyurethane sealing compound.

[0019] According to a specific variant of the method, the polyurethane (PUR) may comprise or, in particular, consist of polyurethane soft foam (PUR soft foam), polyurethane hard foam (PUR hard foam), light shredder residue, or a mixture of two or more of these. The term light shredder residue is known to those skilled in the art and generally refers to a heterogeneous mixture of various plastics, organic materials, and inorganic materials, the actual composition of which depends on the nature of the shredded scrap. An example of light shredder residue is produced during the recycling of refrigerators in which the foam filling of the voids consists of PUR hard foam, optionally with other plastics, such as plastics derived from cable pass-throughs. Light shredder residue from refrigerator recycling may also contain a mineral fraction, for example, due to fillers contained in the polyurethane.

[0020] Non-limiting examples of sources of polyurethane-containing materials are waste from production and / or rejected or no longer used products from the mattress, automotive, construction, furniture, footwear, electronics, and sports / leisure industries, such as car body or other vehicle parts such as mattresses, bumpers, instrument panels, head supports, armrests, or carpeting; wall panels or pipe insulation; furniture or furniture parts; shoes or shoe parts such as soles or toe caps; cable jacketing; plugs, power strips or parts thereof; or sports equipment such as snowboard or roller skate wheels.

[0021] For the purposes of the method according to the invention, the following may be used as polyurethane-containing materials: In particular, polyurethane foams (hereinafter also referred to as PUR foams) selected from the following compositions: soft PUR foams based on non-reactive polyether polyols ("standard polyether polyols"), filled (with SAN copolymers, i.e., styrene-acrylonitrile copolymers) or unfilled, with molecular weights of the order of 3000 g / mol; filled (with SAN copolymers or PHD, i.e., polyurea dispersions) or unfilled, reactive high-resilience polyether polyols with molecular weights above 3000 g / mol; soft PUR foams based on reactive hexafunctional polyether polyols; soft PUR foams based on hypersoft polyether polyols; soft PUR foams based on polyether polyols and mixtures thereof which act as precursors to viscoelastic foams and may also contain PEG (polyethylene glycol) as a component; soft PUR foams based on filled or unfilled polyester polyols; soft PUR foams based on the above polyol mixtures in combination with TDI or MDI; and hard or semi-hard PUR foams based on the above polyol mixtures in combination with TDI or MDI; and hard integral foams consisting of the above components.

[0022] According to a particular further development, the PUR foam comprises one or more representatives of the product family of soft foams and / or one or more representatives of the product family of hard foams.

[0023] Soft foams include plastics such as standard polyether foam, high-resilience polyether foam, combustion-modified polyether foam (CME), combustion-modified high-resilience polyether foam (CMHR), viscoelastic polyether foam, polyester foam, etc. Exemplary compositions are known to those skilled in the art and are described, for example, in documents DE 3630225 C2, US 3,905,924 and DE 10 2007 051 089 A1.

[0024] These soft foams preferably contain the following ingredients or consist of a combination of two or more representatives thereof:

[0025] Isocyanates: 2,4- and / or 2,6-toluylene diisocyanate (TDI) and any mixtures of these isomers, 4,4'- and / or 2,2'-diphenylmethane diisocyanate (MDI) and any mixtures of these isomers, polymeric MDI ("neat" MDI) and MDI prepolymerized with polyhydric polyols (preferably dihydric and / or trihydric polyethers), and / or any mixtures of TDI and MDI from the above isomers and products.

[0026] Polyol: Polyether polyols and / or polyester polyols, which are known per se for producing cellular, homogeneous polyurethane foams and are described, for example, in DE-A 2 832 253 (pages 11-18), include, by way of example only: (standard) polyethers, preferably with 2 and 3 hydroxyl groups (functional groups), filled with SAN (styrene acrylonitrile) solids, preferably with 2 and 3 hydroxyl groups; (Standard) polyethers with (functional groups), hypersoft polyethers, preferably with a functionality of 3, reactive polyethers with primary hydroxyl groups, preferably with a functionality of 3, 5 or 6, reactive polyethers with primary hydroxyl groups, trifunctional reactive polyethers, preferably trifunctional, filled with SAN (styrene acrylonitrile) solids or PHD (polyurea dispersions), reactive polyols prepolymerized with TDI, preferably trifunctional, where the polyol is present in greater amounts than the TDI, non-reactive polyols prepolymerized with TDI, also known in the technical community as "quasi-prepolymers" (QPP), polyols based on renewable raw materials and different functional groups, natural oil products with different numbers of hydroxyl groups, such as castor oil as a non-limiting example, amino or hydroxyl compounds that function as chain extenders or crosslinkers, typically with 2 to 8, preferably 2 to 4 hydrogen atoms capable of reacting with isocyanates, such as diethanolamine, triethanolamine, diisopropanolamine, sorbitol, glycerin and urea.

[0027] Like the hard foams described below, these soft foams optionally contained one or more additional substances selected from the following: catalysts of a type known per se, such as tertiary amines or reactive (integrable) amines, tin (II) compounds or zinc compounds, surfactant additives such as emulsifiers, foam stabilizers, flame retardants, sorbitol, glycerin, diamines, urea, tertiary amines, siloxane-based or non-siloxane-based stabilizers.

[0028] Rigid foams of this particular further development can be found, for example, in products such as insulation panels (also as sandwich elements with various covering layers), foams in place, spray-applied foams, foams produced by the overlay method, foams for solar panel fillers, foams for pipe insulation, filled and expanding foams, block foams, etc. These compounds are sufficiently familiar to the skilled person and are comprehensively described, for example, in document EP 0 318 784 A2.

[0029] The hard foam preferably comprises the following components or a combination of two or more of their representatives:

[0030] Isocyanates: 2,4- and / or 2,6-toluylene diisocyanate (TDI) and any mixtures of these isomers, 4,4'- and / or 2,2'-diphenylmethane diisocyanate (MDI) and any mixtures of these isomers, polymeric MDI ("neat" MDI) and MDI prepolymerized with polyhydric polyols (preferably dihydric and / or trihydric polyethers), preferably polymeric MDI (neat MDI), any mixtures of TDI and MDI from the above isomers and products.

[0031] Besides foams, further examples of polyurethanes included in polyurethane-containing materials are polyurethane elastomers and polyurethane duroplasts.

[0032] The process according to the invention can be carried out discontinuously, continuously or semi-continuously.

[0033] In a discontinuous process, also known as a batch process, the feedstock is introduced into a reactor, exposed to reaction conditions, and the reaction products are removed after a processing period, after which the reactor is charged with a fresh batch of feedstock.

[0034] In a continuous process, the polyurethane-containing material and the urea-containing aqueous solution are continuously introduced into the reactor, rather than just once before the reaction begins. Similarly, the liquid treatment medium is continuously removed. Typically, the introduction and removal are performed at different locations, and in particular, the polyurethane-containing material, together with the urea-containing aqueous solution, is pushed or transported through the reactor from the injection point to the removal point via an active transport means. Therefore, the degree of decomposition is low in the region near the introduction point, and the polyurethane-containing material moves or is transported to the removal point together with the urea-containing aqueous solution, and the degree of decomposition of the polyurethane increases as it approaches the removal point.

[0035] A semi-continuous process is any intermediate form possible between the two processes described above. For example, the liquid treatment medium may not be substantially completely removed after the discontinuous process is completed. As a further example, in a continuous process variant, fresh polyurethane-containing material and / or urea-containing aqueous solution may not be continuously supplied, but rather may be supplied only at specific times, for example, periodically, or when a certain degree of decomposition of the polyurethane in the reactor is observed.

[0036] Any type of equipment commonly used in this field can serve as a reactor, or can be easily adapted by those skilled in the art for the purposes of the method according to the present invention. Examples of such equipment are pressure vessels or pressure reactors designed for batch loading, with reaction volumes ranging from, for example, 0.1 liters to 10 liters on a laboratory scale, through intermediate volumes ranging from 10 liters to 1 cubic meter, to large industrial scale volumes of 1 cubic meter to tens or hundreds of cubic meters. Alternatively, the pressure vessel or pressure reactor can be designed for continuous or semi-continuous operation and can include pressure locks for supplying polyurethane-containing material and / or removing liquid treatment medium.

[0037] The polyurethane-containing material can be introduced in unreduced form, for example, by wetting or fully saturating the polyurethane foam with an aqueous urea-containing solution and then heating to a temperature in the range of 190°C to 250°C.

[0038] However, it is desirable to introduce the polyurethane-containing material in a reduced state. In this process, standard technical grinding methods can be implemented, for example, the polyurethane-containing material can be cut, torn, grated into flakes, shredded, granulated, powdered or ground, optionally after prior cooling to increase its brittleness. Non-limiting examples of the size of the ground product thus obtained are about 0.5 cm, especially for polyurethane-containing materials that are porous or have a large surface area. 3 ~10 cm 3 (0.5 ml to 10 ml), for example, about 1 cm 3 ~5 cm 3 or a ground product having a diameter measured at its widest point not exceeding about 10, 5, 2, 1, 0.5, 0.1, 0.05, or 0.01 millimeters. The grinding can be carried out in the reactor during the process using corresponding equipment, but it is preferred that the reactor is already filled with ground polyurethane-containing material. When the polyurethane-containing material is not merely wetted with the urea-containing solution but is completely immersed therein, the resulting material is essentially a suspension of the polyurethane-containing material in the urea-containing aqueous solution.

[0039] The urea content of the aqueous solution is 1 to 45% by weight, particularly 1 to 20% by weight, for example 1 to 10% by weight, for example 1 to 7% by weight, for example 1.5 to 5% by weight, 1.5 to 4% by weight, 2 to 4% by weight, 2.5 to 3.5% by weight, or 3% by weight, based on the total weight of the aqueous solution. Further examples of ranges or concentrations include 5 to 10% by weight, 1% by weight, 5% by weight, 7.5% by weight, and 10% by weight. A range of 1% to 10% by weight, for example 2.5 to 10% by weight, 2% to 7.5% by weight, or about 3% to 5% by weight, is preferred in terms of the ratio between the amount of urea used and the degree of decomposition of the polyurethane.

[0040] The process is preferably carried out with the exclusion of air, optionally allowing a small residual amount of air, for example 20% or 10% of the volume of the reactor in which the decomposition process is carried out, or is carried out in the absence of air, or in the presence of an inert gas, for example nitrogen gas, preferably in the presence of an inert gas.

[0041] In a particular variation, the aqueous solution contains 2.5 to 10% by weight of urea and heating is carried out for a period of 45 to 250 minutes, particularly 45 to 240 minutes.

[0042] According to one variant, the ratio of the urea-containing aqueous solution to the polyurethane-containing substance is 0.2 ml / g to 5 ml / g, for example about 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, when the ratio between the volume of the urea-containing aqueous solution and the amount of polyurethane to be treated therein is small, the volume available for carrying out the degradation process can be efficiently utilized. For use in polyurethane foams, an amount of 0.2 ml / g, especially 0.25 ml / g, especially 0.29 ml / g, especially 0.4 ml / g is a lower limit, in which case the polyurethane foam can still be sufficiently wetted with the urea-containing aqueous solution to allow the desired degradation of the polyurethane.

[0043] In the context of the method, recovery of at least a portion of the liquid treatment medium obtained after heating is optionally provided as a further process step, so that the liquid treatment medium is partially or completely removed from the reactor, allowing it to be used in any further subsequent steps, such as fractionation into individual substances or groups of substances that can be more selectively discarded or, in the best case, used as a source of raw materials.

[0044] According to one variant, if the recovered liquid treatment medium contains solids, they are removed. These are, for example, metal parts, particles of other plastics, or particulate products of reaction or decomposition of polyurethane or polyurethane components. Methods for removing solids are known to those skilled in the art and include, for example, sedimentation, centrifugation, or filtration.

[0045] According to a preferred variant, the aqueous solution containing 1 to 45% by weight of urea is free of polyols, such as diols, and / or free of carboxylic acids and / or free of ammonia. This advantageously helps to avoid environmentally harmful substances. According to a particular variant, the aqueous solution consists of water and 1 to 45% by weight of urea.

[0046] During the degradation process, the polyurethane is partially or completely converted into a liquid treatment medium. Thus, the originally solid polyurethane-containing material, which may have a large volume requirement (especially if the polyurethane is in a foam state), can be converted into a liquid, i.e., a liquid treatment medium, which has a smaller volume requirement and is more easily processable. There is also the possibility of fractionating and / or separating the substances contained in the liquid treatment medium and / or delivering them for optional further use or reuse.

[0047] The present invention therefore relates to a treatment medium obtained or obtainable via the method described herein, in particular a treatment medium of the type that contains the polyol used to prepare the polyurethane decomposed by this method, or a modification of such a polyol, and / or that contains a diamine or a modification of such a diamine, where the diamine is a precursor of the diisocyanate used to prepare the polyurethane decomposed by this method.

[0048] Non-limiting examples of modifications are ring formation or deamination. These types of process media contain valuable raw materials for the chemical industry, especially for the recycling economy of polyurethanes, which can in some cases be reused after separation from the process media.

[0049] Further advantages, features and particularities can be discerned from the following description, in which at least one exemplary embodiment will be described in detail, optionally with reference to the figures. [Example]

[0050] (Example 1) Polyurethane soft foam

[0051] Two TDI-based and MDI-based polyurethane soft foams (product names: R 4030 and R 5535, source: Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) weighing 20.0 g and 19.6 g, respectively, were imbibed with 32.2 ml and 35.7 ml of a 7.5% urea solution, respectively, and treated at 190°C for 180 minutes in a sealed pressure vessel.

[0052] [Table 1]

[0053] The collected samples were cooled and then semi-quantitatively classified by visual assessment of the degree of decomposition of the solid polyurethane and the corresponding disappearance of observable solid material and conversion to the liquid treatment medium, where (as in all subsequent experiments) "0%" indicates that no decomposition of the polyurethane has yet occurred and therefore the amount of solid polyurethane initially used was still completely present, and "100%" means that the polyurethane has been completely decomposed and correspondingly converted to the liquid treatment medium.

[0054] In both cases, partial decomposition had taken place and varying amounts of solids were still present in the liquid treatment medium, apparently in the form of condensed foam residues.

[0055] (Example 2) Polyurethane integral foam

[0056] Two samples of polyurethane integral foam, one ether-based and one flexible cast elastomer sold under the trade name Colo-Fast® (BASF, SE, Ludwigshafen, Germany), with original weights of 25 g and 35 g, respectively, were absorbed in 40 ml of a 3% urea solution and treated at 245°C for 240 min in a closed pressure vessel filled to 80% of its capacity.

[0057] [Table 2]

[0058] The polyurethane material used was completely decomposed, although a few particles were observed, possibly due to polymerization.

[0059] (Example 3) Non-foamed polyurethane

[0060] A series of tests on the degradation method used solid, non-foamed polyurethane. In these tests, blue plastic polyurethane hoses of the "PUN" type (Festo Gesellschaftm.bH, Vienna, Austria) were crushed and 1 g of each was heated to 210 °C for 150 min in 25 ml of aqueous urea solutions with urea contents of 1, 5, 7.5, or 10% by weight in a sealed pressure vessel.

[0061] This series of tests was conducted primarily to determine the effect of urea concentration and to calculate the degradability of solid polyurethanes.

[0062] [Table 3]

[0063] As a result, no fraction of the solid polyurethane originally used was observed in any of the samples, and therefore, non-foamed polyurethane is decomposable under the experimental conditions described above.

[0064] Example 4: Duroplastic Polyurethane

[0065] As a further example of non-foamed polyurethane, a Duroplast polyurethane core with a volume weight of 165 g / L, such as that used in skis, was used in the decomposition method. The core was crushed, and 15 g of the crushed core was heated to 210 °C for 150 min in 40 ml of an aqueous urea solution with a urea content of 3% by weight in a sealed pressure vessel filled to 80% of the usable volume (the remaining 20% ​​volume was air).

[0066] [Table 4]

[0067] As a result, it was found that the fraction of non-foamed polyurethane that was originally used was no longer observed in the resulting liquid phase.

[0068] (Example 5) Elastomer polyurethane

[0069] Examples of elastomeric polyurethanes used were microcellular polyurethane springs sold under the trade name Cellasto® (BASF, SE, Ludwigshafen, Germany) and the cast elastomer Colo-Fast® (BASF, SE, Ludwigshafen, Germany). Samples were ground and heated in separate batches to 210 °C for 150 min in 40 ml of an aqueous urea solution with a urea content of 3% by weight in a sealed pressure vessel filled to 80% of the usable volume (the remaining 20% ​​volume was air).

[0070] [Table 5]

[0071] The results showed that in the resulting liquid phase, fractions of the elastomeric polyurethane originally used were no longer observed.

[0072] (Example 6) Time series

[0073] In a series of tests, the aforementioned R 4030 and R 5535 polyurethane foams were heated in an aqueous urea solution containing 7.5% urea by weight at 230°C for 60, 90, or 120 minutes in a closed pressure vessel.

[0074] [Table 6]

[0075] At a decomposition rate classified as 50%, the foam-like structures transformed into a solution with a paste-like consistency, at a decomposition rate classified as 90%, the foam-like structures were almost completely liquefied, and at a decomposition rate of 100%, they were completely liquefied.

[0076] (Example 7) Time series and temperature series

[0077] Since previous experiments had shown that in principle any type of polyurethane-containing material could be decomposed in this way, a new series of experiments aimed at systematically calculating the temperature and time dependence of decomposition used mixtures of different polyurethane-containing materials, specifically mixtures of equal weight proportions and each with an original weight of 4.15 g. a) Standard foam grade TDI 80 based on filler (calcium carbonate) and SAN polymer particles (N 4045 WS), b) High resilience (HR) polyurethane foam grade TDI 80 / TDI65 based on filler (calcium carbonate) and SAN polymer particles (R 4040 WS) c) High resilience (HR) polyurethane foam grade MDI based on filler (calcium carbonate) and SAN polymer particles (R 5535 WS), and d) unfilled viscoelastic foam grade MDI (V 5018 WS, Eurofoam Deutschland GmbH Schaumstoffe).

[0078] The resulting polyurethane material was reacted in shredded form with a 3% urea solution in a ratio of 0.582 ml of urea solution per gram of polyurethane material. To perform the temperature series, samples in a sealed pressure vessel were heated in a heat cabinet to 190°C, 210°C, 230°C, and 245°C to establish equilibrium pressure and removed after residence times of 60, 90, 120, 180, and 240 minutes at each temperature. Three samples were tested and evaluated in parallel at each time point.

[0079] The removed samples were cooled and semi-quantitatively classified by visual assessment to obtain an average value for each set of three samples for the degree of decomposition of the solid polyurethane and the corresponding loss of observable solid material and conversion to liquid processing medium. The results are shown in Figure 1, where the heat treatment time at a given temperature is plotted in minutes along the horizontal x-axis, the semi-quantitative degree of decomposition is shown in percent on the vertical z-axis, and three selected temperatures—190°C, 210°C, 230°C, and 245°C—are plotted on the y-axis, progressing relative to the image plane. It is clear that faster decomposition rates can be achieved with increasing temperatures up to 245°C.

[0080] Example 8: Control experiment without overpressure

[0081] In a control experiment, two separate samples consisting of 2 g of TDI polyurethane foam (trade name: R 4030; obtained from Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) and MDI polyurethane foam (trade name: R 5535; obtained from Eurofoam Deutschland GmbH Schaumstoffe, Wiesbaden, Germany) were each reacted with 40 ml of 7.5% urea solution in a glass flask at temperatures between 100 and 110 °C under ambient pressure in a heat cabinet; liquid loss was compensated for by the addition of water. After 4.5 h, no decomposition of any kind was observed.

[0082] Example 9: First control experiment without urea under overpressure

[0083] As a further control experiment, four different samples were tested: 16.6g black PUR integral foam (window insulation) in 9.66ml H2O 16.6g of white PUR integral foam (shoe part) in 9.66ml H2O 14.0 g of PUR semi-rigid foam (BASF) in 8.15 mL H2O, and 16.0 g of PUR elastomer (BASF Cellasto®) in 9.66 ml H2O were each heated at 245°C for 30 minutes in a sealed pressure vessel, and the amounts of water shown here contained either no urea or 3% by mass of urea.

[0084] The results are shown in Figure 2, where the samples are identified as "PUR Integral Window," "PUR Integral Shoe," "PUR Semi-Hard," and "PUR Elastomer." The degree of conversion is shown as a percentage on the y-axis. In all cases, a significant increase in decomposition was achieved by adding urea. In the case of integral foams and elastomers, this method was able to initiate complete or near-complete decomposition of the solid material. Even in the case of PUR Semi-Hard foam, which was not completely decomposed after 30 minutes of heat treatment, a clear increase in decomposition rate was still recorded after the addition of urea. Because the semi-hard foam, with a volume weight 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), the less efficient decomposition of the semi-hard foam may be due to poor heat conduction within the foam material. In this case, the PUR semi-rigid foam takes up more space in the pressure vessel and therefore is not effectively wetted by the urea-free and urea-containing aqueous solutions, which results in a larger volume of air in the pores, making heat transfer more difficult.

[0085] Example 10: Second Control Experiment Without Urea Under Overpressure

[0086] In further control experiments, samples of polyurethane soft foam mixtures (16.6 g in 9.66 ml of water or 16.6 g in 9.66 ml of water containing 3% urea by weight) were heated at 245 °C in a sealed pressure vessel and removed at different time points (40, 60, 90, 120, 180, and 240 minutes). Compared to the samples used in Example 9, the polyurethane soft foam mixtures were most similar to the PUR semi-rigid foam in terms of material properties. The results are shown in Figure 3, with time in minutes on the x-axis and percent conversion on the y-axis. In the presence of 3% urea by weight, complete decomposition was recorded after only 40 minutes of heating, whereas with water without urea, only partial decomposition occurred after 40 minutes, which also increased as heating time progressed, but in all cases was found to be below the decomposition obtained with water containing urea.

[0087] (Example 11) Experiments on a simple structure soft foam system (single polyol foam), analysis of decomposition products

[0088] To determine the decomposition products formed after carrying out this method, polyurethane soft foams with the simplest possible chemical structure were produced in the laboratory (Table 7). To maintain a distinction between the influencing factors, only one standard ether polyol with a molecular weight of 3500 MW was used, and toluene diisocyanate TDI 80 was used as the isocyanate. The volume weight of the foam was 22 kg / m. 3 was

[0089] [Table 7]

[0090] This PUR soft foam was crushed and processed using the present method in an 11.5-liter Büchi reactor (Büchi AG, Uster, Switzerland). 400 grams of foam was pre-wetted with 236 milliliters of a 3% water-urea solution and poured into a stainless steel digester (also called an inliner) with a volume of approximately 10.2 liters. A 5-cm-high rim of aluminum foil was placed at the bottom of the digester to capture the liquid treatment medium produced. To rapidly generate steam, 200 ml of water was placed under the inliner inserted into the reactor. The method was run for 240 minutes, with the reactor shell temperature initially set at 260°C for 60 minutes and then at 250°C for 180 minutes. This process resulted in the reactor's internal chamber reaching a temperature just below 230°C (229.3°C).

[0091] To perform chemical analysis of the resulting treatment medium, 1 ml of the medium was dissolved in 99 ml of acetonitrile and mixed for 24 hours on a laboratory vibrating plate. The acrylonitrile sample mixture was then filtered through a syringe filter (e.g., Chromafil Xtra RC, 25 mm, 0.45 μm), after which 1–5 μL of sample was directly injected into an Agilent 8890 GC-type gas chromatography system (Agilent, Santa Clara, USA). The GC column was initially maintained at 40°C for 2 minutes, then heated from 40°C to 250°C at a heating rate of 10 Kelvin / min. A final 5-minute hold time was added. The total measurement time was 28 minutes. The measurement was performed with a 1:10 split. The method was named Ramp40-250_28min_1.5ml_split1-10.M. The spectrum measured on a coupled Agilent 5977B GC / MSD mass spectrometer system shows two prominent peaks at retention times of 1.37–1.75 min and 13.71 min. The spectrum was analyzed using the "NIST17" software package (National Institute of Standards and Technology, Gaithersburg, USA), which is included in the scope of the TG / STA-GC-MS system described in more detail in the context of Example 12. It also includes the "AMDIS32" software for qualitative GC-MS analysis, the databases ALKANES, NISTCW, NISTDRUG, NISTEPA, NISTFAD, NISTFF, NISTTOX, and PESTPLUS, and MSSEARCH software. This last software program can be used to selectively compare individual measurement scans with the database used. The peak analysis is shown in Table 8. Here, MF (Match Factor) refers to the comparison of the measured spectrum with the database spectrum, and RFM (Reverse Match Factor) refers to the comparison of the measured spectrum with the available database spectra. In both cases, a special algorithm stored in the software is used, and these elements are standardized to a 1000=100% match in the NIST software.

[0092] [Table 8]

[0093] The acetonitrile may be due to the solvent used. 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 during the process of the present invention. 2,4-diaminotoluene is a precursor to toluene diisocyanate TDI 80, which can be converted to it by phosgenation, making it an industrially valuable, recyclable raw material, especially in the context of polyurethane production.

[0094] Gel permeation chromatography (GPC) analysis of the treatment medium was also carried out to determine the molecular weight (external measurement at BASF Lemfoerde-Central Analytic Lemfoerde, BASF Polyurethanes GmbH, Elastogranstr 60, 49448 Lemfoerde, Germany).

[0095] During this analysis, a molar mass distribution was measured with a pronounced main peak at 3700 g / mol. The viscosity of the treatment medium was also determined. It has a value of the order of 1100 mPas. The OH number of the treatment medium was also determined and was found to be 325 mgKOH / g.

[0096] The results supported the theory that a substantial component of the treatment medium was a polyol: its molar mass was very similar to that of the polyol originally used, it had a slightly higher viscosity (Polyol Standard Ether - 3500 MW = 25 700-900 mPa·s, OH 48) (probably due to the treatment it underwent during the process) and it had a higher OH number.

[0097] Therefore, the method of the present invention can be used to recover polyols and reuse them as valuable raw materials.

[0098] (Example 12) Experiment on PUR soft foam mixture, analysis of decomposition products by TG-GC / MS

[0099] This example attempts to prove that the polyols produced during the process according to the invention were present in the resulting process medium. For this purpose, the process medium was pyrolyzed at a temperature of approximately 380°C, and the resulting decomposition products could indicate the presence of polyols in the process medium. To achieve this, a combined TG / STA-GC-MS measurement (gas chromatography-mass spectrometry combined with thermal analysis, where TG stands for thermogravimetry and STA stands for "simultaneous thermal analysis") was chosen. The measuring instrument used was a STA 449 F3 Jupiter (Netzsch, Selb, Germany), which was connected via a heated transfer line to an Agilent 8890 GC-type gas chromatography system (Agilent, Santa Clara, USA) and an Agilent 5977B GC / MSD mass spectrometer system.

[0100] First, in the preparatory stage, a reference database was created as follows:

[0101] For this, the polyols shown in Table 9 below were used, as they are the soft foam constituents used in the mixtures that were subsequently analyzed by reference to the database (see Table 10).

[0102] [Table 9]

[0103] These were individually decomposed at 380 °C in the pyrolysis stage of the TG / STA-GC-MS system described above. The main peaks were determined from the NIST and AMDIS databases (see Example 11). The compound names and GC retention times of the decomposition products assigned according to these databases were stored in a reference database, and appropriate suffixes according to Table 9 were assigned to each decomposition product. When the same decomposition product occurred in different polyols, the respective suffixes were added. These decomposition products and their corresponding identification product codes are then listed in Table 11 (Table 11 shows the decomposition products of the mixture according to Table 10).

[0104] After the reference database had been created, a soft foam mixture was subjected to the method according to the invention in order to answer the question of to what extent polyol appears in the treatment medium after carrying out the method according to the invention.

[0105] For this purpose, in an 11.5 liter Büchi reactor, 400 grams of a soft foam mixture was processed according to the method of the invention, the mixture having the following soft foam properties (obtained from Neveon Holding GmbH, Ebelsbach-Fils, Germany):

[0106] [Table 10]

[0107] 400 grams of the foam mixture was pre-wetted with 236 milliliters of a 3% water-urea solution and poured into a stainless steel digester vessel (volume approximately 10.2 liters). The bottom of the vessel was lined with aluminum foil with a 5 cm rim to catch the liquid treatment medium produced. 200 ml of water was placed under the inliner vessel to rapidly generate steam.

[0108] The process was carried out for 240 minutes, with the reactor shell temperature initially set at 260°C for 60 minutes and then at 250°C for 180 minutes. This process resulted in the reactor's inner chamber reaching a temperature just below 236°C.

[0109] The recovered treatment medium was analyzed again by coupled TG / STA-GC-MS measurements.

[0110] The spectrum at 379 °C was analyzed in AMDIS using a reference database created in the preliminary step with a default minimum match factor (MF) of 80%. The match factor is the percentage of agreement between the measured spectrum and the spectra in the AMDIS database. This factor is calculated by an algorithm stored in the software. The main peaks correspond to those measured for the single polyols according to Table 9.

[0111] The correlation of this data is shown in Table 11. Analysis revealed that the treatment medium contained the polyol originally used as well as conversion and / or decomposition products formed during the cracking process.

[0112] [Table 11] TIFF0007803949000013.tif244167TIFF0007803949000014.tif46159

[0113] The spectra at 265°C were analyzed using the AMDIS and AMDIS-NIST databases with a default minimum match factor (MF) setting of 90%. Previous experiments have found that at a temperature of 265°C, components in the processing medium that can be traced back to the diisocyanates in the polyurethane are thermally decomposed, while components that can be traced back to the polyols in the polyurethane are not decomposed at this temperature.

[0114] The main peak corresponds to the diamine precursor of the diisocyanate used in the soft foam (Table 12). Thus, the liquid treatment medium obtained after the method according to the invention is carried out contains the precursor from before the industrial process of phosgenation of diisocyanates.

[0115] [Table 12]

[0116] The described method allows for the decomposition of polyurethanes and is therefore commercially viable. Furthermore, raw materials can be recovered from the resulting treatment medium, which can be reused in the chemical industry, and are particularly useful for the polyurethane recycling economy.

[0117] Although the present invention has been illustrated and described in more detail with the help of its preferred embodiments, the present invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of protection of the present invention. Therefore, it is clear that multiple variations exist, and that the identified variations or elements thereof can be combined with each other. It is also clear that the variations identified for illustrative purposes actually represent only examples that should not be interpreted in any way as constituting a limitation on the scope of protection, applicability, or configuration of the invention. Rather, the foregoing description and the illustrations are designed to enable those skilled in the art to specifically reproduce the exemplary embodiments, so that those skilled in the art, having knowledge of the disclosed inventive idea, can introduce many changes, for example, with regard to the function or arrangement of the individual elements identified in the exemplary variations, without departing from the scope of protection of the invention as defined by the claims and their legal counterparts, such as the more detailed description in the specification.

Claims

1. A method for decomposing polyurethane, comprising heating a polyurethane-containing material to a temperature of 190°C to 250°C under superatmospheric pressure in the presence of an aqueous solution containing 1 to 10% by weight of urea; wherein the heating is carried out for 20 to 240 minutes, and the ratio of the aqueous solution containing urea to the polyurethane-containing material has a value of 0.4 ml / g to 5 ml / g. method.

2. 2. The method of claim 1, wherein the heating is carried out under a pressure of 1.05 bar to 100 bar.

3. 3. The method of claim 1, wherein the overpressure is an equilibrium pressure established by heating.

4. 4. The method according to claim 1, wherein after heating, at least a portion of the liquid treatment medium obtained is recovered.

5. 5. The method of claim 4, wherein solids are removed from the recovered liquid treatment medium.

6. 6. The method according to claim 1, wherein the aqueous solution is polyol-free and / or carboxylic acid-free and / or ammonia-free.

7. 7. The method according to claim 1, wherein the aqueous solution consists of water and urea.

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