EP4259686A1

EP4259686A1 - Process for recovering raw materials from polyurethane foams

Info

Publication number: EP4259686A1
Application number: EP21824402.8A
Authority: EP
Inventors: Sebastian Pohl; Friedhelm Steffens
Original assignee: Covestro Deutschland AG
Current assignee: Covestro Deutschland AG
Priority date: 2020-12-14
Filing date: 2021-12-13
Publication date: 2023-10-18
Also published as: WO2022128871A1; US20240101783A1; JP2024501461A

Abstract

The present invention relates to a process for recovering raw materials from a polyurethane foam, comprising step (A), the providing of a polyurethane foam based on an isocyanate component and a polyol component, wherein the polyurethane foam comprises a cell structure containing one or more volatile accompanying substances, namely a component X selected from the group consisting of oxygen, a blowing agent, a disinfectant and a mixture of two or more of the above, wherein component X comprises at least oxygen, step (B), the chemolysis of the polyurethane foam with a chemolysis reagent, wherein the polyurethane foam is degassed before being contacted with the chemolysis reagent, wherein at least oxygen, but preferably all constituents of component X or any gaseous breakdown products thereof that have formed are removed from the chemolysis apparatus in gaseous form via a gas removal device at a pressure of not more than 960 mbar(abs.) and a temperature of not more than 120°C, so as to obtain a degassed polyurethane foam, followed by the reaction of the degassed polyurethane foam with the chemolysis reagent in the presence of a catalyst in an inert gas atmosphere and the workup of the product mixture obtained by the chemolysis, step (C), the obtaining of at least one polyol, and optionally step (D), the obtaining of at least one amine corresponding to an isocyanate of the isocyanate component.

Description

PROCESS FOR RECOVERING RAW MATERIALS FROM POLYURETHANE FOAM

The present invention relates to a method for recovering raw materials from a polyurethane foam, comprising step (A), providing a polyurethane foam based on an isocyanate component and a polyol component, the polyurethane foam having a cell structure containing one or more volatile accompanying substances, namely a component X selected from the group consisting of oxygen, a blowing agent, a disinfectant and a mixture of two or more of the aforementioned accompanying substances, where component X comprises at least oxygen, has step (B), the chemolysis of the polyurethane foam with a chemolysis reagent, the polyurethane foam is degassed before being brought into contact with the chemolysis reagent, with at least oxygen, but preferably all the constituents of component X or any gaseous decomposition products formed thereof, at a maximum pressure of 960 mbar (abs.) and a temperature of v at a maximum of 120 °C in gaseous form via a gas removal device from the chemolysis device, so that a degassed polyurethane foam is obtained, followed by reaction of the degassed polyurethane foam with the chemolysis reagent in the presence of a catalyst in an inert gas atmosphere and the processing of the product mixture obtained by the chemolysis, the step (C), obtaining at least one polyol, and optionally step (D), obtaining at least one amine which corresponds to an isocyanate of the isocyanate component.

Polyurethane foams are used in a wide range of applications in industry and in everyday life. They are usually divided into rigid foams (which are used, for example, as insulating materials) and flexible foams (which are used, for example, in the manufacture of upholstered furniture). Despite such differences, all polyurethane foams have in common the basic polyurethane structure, which is formed by the polyaddition reaction of a polyfunctional isocyanate and a polyol and is suitable, for example, for a polyurethane based on a diisocyanate O=C=N-R-N=C=O and a diol H-O-R'-O-H ( where R and R 'designate organic radicals) as

- [O-R'-O-(O=C)-HN-R-NH-(C=O)] - can be represented.

Precisely because of the great economic success of polyurethane foams, there are also large amounts of polyurethane waste (e.g. from old mattresses or seating furniture), which must be put to sensible use. The technically easiest to implement The type of reuse is incineration using the released combustion heat for other processes, such as industrial manufacturing processes. However, it is not possible to close the raw material cycle in this way. Another type of reuse is the so-called "physical recycling", in which polyurethane waste is mechanically crushed and used in the manufacture of new products. Naturally, there are limits to this type of recycling, which is why there has been no lack of attempts to recover the raw materials on which polyurethane production is based by splitting back the polyurethane bonds (so-called “chemical recycling”). The raw materials to be recovered primarily include polyols (ie HOR'-OH in the above example). In addition, amines can also be obtained by hydrolytic cleavage of the urethane bond (in the above example H2N-R-NH2), which can be phosgenated to isocyanates (in the above example to O=C=NRN=C=O).

Various chemical recycling approaches have been developed in the past. The four most important are briefly summarized below:

1 . Hydrolysis of urethanes by reaction with water to give amines and polyols with evolution of carbon dioxide.

2. Glycolysis of urethanes by reaction with alcohols, with the polyols built into the urethane groups being replaced by the alcohol used and being released in this way. This process is usually referred to in the literature as transesterification (more precisely: 'umurethanization'). This type of chemical recycling is commonly referred to in the literature as glycolysis, regardless of the exact type of alcohol used, although that term really only applies to glycol. Alcoholysis is therefore generally spoken of in connection with the present invention. Hydrolysis can follow glycolysis. If the hydrolysis is carried out in the presence of the still unchanged glycolysis mixture, it is called a

3. Hydroglycolysis of urethane bonds by reaction with alcohols and water. It is of course also possible to add alcohol and water from the beginning, the processes of glycolysis and hydrolysis described above taking place in parallel.

4. Acidolysis of urethane compounds by reaction with carboxylic acids to form acyl urea compounds.

The review article by Simon, Borreguero, Lucas and Rodriguez in l/l/aste Management 2018, 76, 147 - 171 [1] provides a summary of the known polyurethane recycling processes. CN 106 279 760 describes the chemolysis of a polyurethane comprising mechanical comminution, reaction with water and an alcohol in an inert gas atmosphere in the presence of antioxidants at 218° C. to 399° C. and a pressure of 50 to 150 kPa for 3 to 5 hours, with a carbodiimide is used as the catalyst.

DE 32 32 461 A1 describes a process for the continuous glycolytic splitting of polyurethane plastic waste, in particular polyurethane foam waste, in multi-shaft screw machines by adding optionally preheated diols at splitting temperatures of >250° C. while maintaining at least such a pressure that the polyurethane-diol mixture is in the liquid phase is present, discharge of the glycolyzate mixture after a short residence time of 2 to 30 minutes in the reaction screw and rapid cooling of the glycolyzate mixture. In a preferred embodiment, air introduced into the screw machine together with the plastic waste can escape against the conveying direction in front of the feed hopper via a housing bore, to which a slight vacuum is advantageously applied. The application does not disclose that volatile accompanying substances contained in the cell structure of the polyurethane foam, such as in particular oxygen, blowing agents and/or disinfectants, are discharged via the housing bore. With the arrangement described, this is also not to be expected; Rather, it can be assumed that only the air that enters the machine together with the foam waste during the course of the introduction thereof (the air surrounding the foam waste) is actually removed.

DE 24 42 387 A1 describes a process for the continuous hydrolytic decomposition of plastic waste, in which waste made from hydrolyzable plastic material is fed into a screw machine together with water and optionally hydrolysis catalysts, where the mixture of water and plastic waste is placed in a reaction zone with intensive mass and heat exchange of the 2nd is exposed to a temperature of 100 to 300 °C at a pressure of 5 to 100 bar for up to 100 minutes and the liquid-gas mixture produced during the hydrolysis is continuously conveyed into a mouthpiece which is firmly connected to the screw machine, from which the gas is a regulator valve which maintains constant screw machine pressure in the die and the liquid exits via a regulator valve which maintains a constant liquid level within the die. In a preferred embodiment, the air introduced together with the plastic waste is removed through a housing bore located in front of the feed hopper for the plastic material, seen in the conveying direction, to which a slight vacuum is applied. The application does not disclose that volatile accompanying substances contained in the cell structure of the polyurethane foam, such as in particular oxygen, blowing agents and/or disinfectants, are discharged via the housing bore. With just a light vacuum and compression of the foam essentially only after the addition of the chemolysis reagent (here water), this is also not to be expected; Rather, it can be assumed that here—just as in the case of DE 32 32 461 A1—in fact only the air that enters the machine when the plastic waste is fed into the machine (the air surrounding the plastic waste) is removed.

DE 197 19 084 A1 discloses a process for producing polyols from polyurethane waste, in which foam flakes, ground flexible foam or shredded material are fed into a reactor containing waste from the synthesis of polyesters, which has previously been heated to a temperature above 70°C became. The mixture of polyurethane waste and polyester synthesis waste is further heated and reacted by a controlled, catalytic transesterification reaction at a temperature of 120°C to 250°C. In a preferred embodiment, the polyurethane waste is introduced by means of pneumatic conveying through a weak stream of nitrogen. A removal of volatile accompanying substances contained in the cell structure of the polyurethane foam, such as in particular oxygen, blowing agents and/or disinfectants, is not to be expected in this way.

DE 10 2004 014165 A1 describes a process for producing polyols from polyurethane waste and a special device for carrying out this process. The pre-comminuted soft foam is metered in from above via a stuffing screw and a constriction ring, with the gases contained in the foam being removed, according to this document. However, it is doubtful whether oxygen contained in the cell structure of the polyurethane foam can actually be at least essentially completely removed without the use of reduced pressure before the start of the chemolysis. This applies all the more to other accompanying substances that may be contained in the cell structure of the polyurethane foam and potentially impair recycling, as these boil much higher than oxygen, such as blowing agents or disinfectants (which can also be in liquid form).

EP 0 031 538 A2 describes a method and a device for processing polyurethane obtained from waste materials by alcoholysis or acidolysis. The polyurethane is first mechanically comminuted into a starting material and then treated with solvents at a temperature of more than 120 °C. At least at the beginning of the solvent treatment, which leads to the liquefaction of the starting material and is carried out at a reaction temperature of below 200° C., the mechanical comminution of the starting material that is already undergoing chemical degradation is continued. According to the statements in this document, this method results in a shorter treatment time at a lower temperature until the complete solution of the raw material without quality-reducing discoloration occurring or undissolved residues remaining. The dissolution of the starting material naturally takes place with at least partial reaction of the polyurethane bonds.

The system for carrying out the process has a mixer fed from storage containers, to which a reactor is connected on the outlet side, in which shearing elements exerting shearing forces and which can be rotated in both directions act on the starting material, which are arranged on a hollow, heatable shaft and controlled by a are surrounded by the reactor shell composed of hollow, heatable sectors. In this reactor, the heat transfer to the mass is improved, so that a uniform temperature distribution and thus a relatively short reaction and dissolving time can be achieved. The application discloses an embodiment in which the initial comminution of the starting material takes place while mixing with a proportion of the polyols later used as a solvent component in a heatable kneading mixer with two counter-rotating shafts with sigma blades. According to this document, this achieves good pre-wetting of the polyurethane particle surfaces with solvent, releases part of the gases trapped in the polyurethane cell area, reduces the harmful oxygen content, in particular avoids the agglomeration of the polyurethane particles due to the subsequent mechanical stresses in the subsequent reactor zone and improves the dosability and thermal conductivity of the Mass of the starting material increased significantly. According to this application, the extensive removal of atmospheric oxygen can be effected by subsequent evacuation of the mixture in the same part of the plant and/or by subsequent flushing with protective gas, for example nitrogen, at normal pressure. However, it should be noted that the presence of a solvent (= chemolysis reagent) that wets the polyurethane counteracts effective degassing.

In addition to the processes mentioned of physical recycling (mechanical crushing of the polyurethane products and admixture in the manufacture of new polyurethane products) and chemical recycling (recovery of polyols and preferably also amines through chemical cleavage of the urethane bonds), so-called "upcycling" should also be mentioned, one thing occupies an intermediate position: With upcycling, as with chemical recycling, a chemical change in the polyurethane takes place, but this does not take place until the raw materials originally used in the synthesis (polyol and amine) are recovered, but rather the aim is to convert the polyurethane to be recycled into another polymer to transfer value product. Thus, DT Sheppard et al. in the article Reprocessing Postconsumer Polyurethane Foam Using Carbamate Exchange Catalysis and Twin-Screw Extrusion (ACS Cent. Se. 2020 6 (6), 921-927) describe the treatment of a cross-linked polyurethane foam with dibutyltin laurate in dichloromethane followed by mechanical Processing the foam thus treated in a twin-screw mixer or twin-screw extruder, removing air, to obtain films or fibers.

Only a few of the processes known from the literature for the recycling of polyurethanes are permanently operated on an industrial scale; many have not even reached the pilot scale [1]. In view of the generally increased environmental awareness and increased efforts to make industrial processes as sustainable as possible, this clearly shows that the recycling of polyurethane products is far from mature from a technical and economic point of view. The possibilities of physical recycling are obviously very limited. Although upcycling can open up ways to sensibly recycle polyurethane products and is certainly justified in this respect, it also does not enable the raw material cycles to be closed. The potential for this is only offered by chemical recycling if it is possible to recover the polyols used and preferably also the amines in such a way that they can be used in the manufacture of new polyurethane products of comparable quality to the original polyurethane products. In this respect, there are challenges in particular with regard to the purity of the recovered products. Polyols must be recovered with as little amine contamination as possible so as not to adversely affect foam formation behavior when they are reused in the production of polyurethane foams. If the aim is also to recover amines, these must of course also be obtained in the highest possible purity. Furthermore, an economical recycling process must ensure that the reagents used (for example alcohols used) can be recovered as completely as possible and used again (i.e. recycled).

The polyurethane products to be recycled usually also contain various auxiliaries and additives (stabilizers, catalysts and the like) which have to be separated from the actual target products of recycling and disposed of in an economical and environmentally friendly manner. In the case of polyurethane foams, particular mention should also be made of blowing agents and oxygen, both of which are present in the cell structure of the foams. In addition to these production-related auxiliaries and additives, other foreign substances can get into a polyurethane product to be recycled as a result of preparatory steps that precede the actual chemical recycling. For example, it is common to treat reusable polyurethane foams, which come from old mattresses or seating furniture, with disinfectants. These foreign substances can affect chemical recycling and/or the subsequent use of the recovered raw materials in new manufacturing processes: Oxygen can cause oxidation reactions of the amine in particular. The presence of oxygen is also problematic from a safety point of view, since in alcoholysis, for example, work is often carried out above the flash point of the alcohol used. The blowing agents used, such as pentane, are chemically inert, but this is precisely why they accumulate and have to be discharged regularly, resulting in a loss of product (so-called purge). The presence of propellants can also make the exhaust gas load and the processing of the exhaust gas more difficult. Certain common disinfectants, such as ethanol, can form carbamates during chemolysis, which may be more difficult to split, releasing the amine, than the carbamates of the actual chemolysis reagent (usually glycol or a glycol derivative). Even if the carbamate cleavage is successful, such alcoholic disinfectants then get into the unreacted chemolysis reagent as contamination during work-up, which can make its recovery more difficult. Other common disinfectants such as hydrogen peroxide or sodium hypochlorite can decompose releasing oxygen. The prior art does not yet offer a satisfactory solution to such problems.

There was therefore a need for further improvements in the field of chemical recycling of polyurethane foams. In particular, it would be desirable to remove potentially disruptive accompanying substances such as blowing agents, oxygen or disinfectants from the polyurethane foam to such an extent before the actual chemical recycling begins that they do not interfere with the subsequent steps.

Taking into account the need described, one subject of the present invention is therefore a method for recovering raw materials (i.e. polyols and optionally amines) from a polyurethane foam based on an isocyanate component and a polyol component, having a cell structure containing a component X selected from the group consisting of oxygen , a blowing agent, a disinfectant and a mixture of two or more of the above, where component X comprises at least oxygen, by reacting the polyurethane foam with a chemolysis reagent, the method comprising:

(A) providing the polyurethane foam (1) in a container (100);

(B) chemolysis of the polyurethane foam (1) in a chemolysis device comprising (i) an entry device (200), (ii) a chemolysis reactor connected to the entry device (300), (iii) one with the discharge device (400) connected to the chemolysis reactor and (iv) a gas discharge device (500) arranged in the container and/or in the entry device, wherein the chemolysis comprises:

(B.l) introducing the polyurethane foam from the container into the entry device and from there into the chemolysis reactor, the polyurethane foam being degassed before it is brought into contact with the chemolysis reagent by

(a) at least oxygen (i.e. (i) the oxygen contained in component X and (ii) any oxygen formed by decomposition reactions of constituents of component X), but preferably all constituents of component X or any gaseous decomposition products thereof formed, in one pressure of at most 960 mbar (abs) and a temperature of at most 120° C. are discharged in gaseous form via the gas discharge device from the chemolysis device, so that a degassed polyurethane foam (2) is obtained;

(B.II) reacting the degassed polyurethane foam (2) in the chemolysis reactor (300) with a chemolysis reagent (4) in the presence of a catalyst in an inert gas atmosphere to obtain a product mixture;

(B.l II) discharge of the product mixture from the chemolysis reactor (300) through the discharge device (400); followed by

Processing of the product mixture comprising:

(C) Obtaining (at least) one polyol (from the polyol component or a degradation product of such obtained in the chemolysis); and

(D) optionally, recovering (at least) one amine corresponding to an isocyanate of the isocyanate component.

Surprisingly, it was found that the inventive removal of volatile accompanying substances as defined in component X before the polyurethane foam comes into contact with the chemolysis reagent for the first time leads to a particularly careful depletion of such accompanying substances, thereby overcoming or at least minimizing the problems described above. Oxygen in particular, whether it is present from the outset or, for example, through the decomposition of a disinfectant such as Hydrogen peroxide or sodium hypochlorite formed in situ is successfully removed by the process according to the invention, as a result of which oxidation reactions, in particular of the amine, are avoided. The method according to the invention is characterized in that not only volatile accompanying substances present or adhering on the surface, but also volatile accompanying substances present in the cell structure of the polyurethane foam can be successfully removed.

Because, as is known to the person skilled in the art, a polyurethane foam has a cell structure (also called pore structure) which can be influenced by chemical or procedural parameters during foaming. In the production of polyurethane foams, blowing agents are used which are gaseous under the production conditions of the foaming and lead to the formation of foam cells (also called foam pores) which are connected to one another via so-called webs. Polyurethane foams that are to be recycled regularly contain volatile accompanying substances that can potentially interfere with chemolysis, which are located in the cells (i.e. in the cavities) but can also be present in the ridges (e.g. if the ridges become soaked with a disinfectant).

The present invention is concerned with recycling the polyurethane foams prior to initiating chemical recycling, i. H. prior to the first contact of a polyurethane foam to be recycled with a chemolysis reagent, of such volatile accompanying substances. Under a volatile accompanying substance in this sense, i. H. A component X is understood in the context of the present invention as oxygen, a propellant, a disinfectant or a mixture of two or more of the above, in particular if the volatile accompanying substance (= component X or a component thereof) is at least in a partial area of a is present in gaseous form within a pressure and temperature range defined by a lower pressure limit pu, an upper pressure limit po, a lower temperature limit Tu and an upper temperature limit To or decomposes with the formation of gaseous decomposition products, where the following applies:

Pu = 0.1 mbar(abs);

Po = 960 mbar(abs);

Tu = -20 °C, in particular (namely if the volatile accompanying substances contained in the cell structure are liquid under standard conditions [i.e. at a temperature of 0 °C and a pressure of 1,000 bar(abs)]) 16 °C, and

To = 120°C. The pressures pu and po can be determined using a standard manometer. Of course, this also applies to the pressures p1 and p2, which are described further below. Of course, the presence of other compounds, which could be described purely linguistically as "volatile accompanying substances", but which do not fall under the definition of component X in the context of the present invention, cannot be ruled out, and the recycling of such polyurethane foams with the process according to the invention goes beyond the scope of the invention.

The above condition is met for oxygen; this also regularly applies to blowing agents (e.g. pentane), which are used in the production of polyurethane foam. The large majority of common disinfectants can also be converted into the gas phase or into gaseous decomposition products under the conditions mentioned, so that disruptive substances can be discharged via the gas discharge device. Examples of decomposable volatile impurities are hydrogen peroxide and sodium hypochlorite, both of which decompose to form i.a. tend to oxygen, which can then be drawn off as a "gaseous decomposition product" via the gas discharge device.

In the terminology of the present invention, the term isocyanates includes all isocyanates known to those skilled in the art in connection with polyurethane chemistry, such as in particular tolylene diisocyanate (TDI; can be produced and preferably produced from toluenediamine, TDA), the di- and polyisocyanates of the diphenylmethane series (MDI; can be produced and preferably produced from the di- and polyamines of the diphenylmethane series, MDA),

1,5-pentane diisocyanate (PDI; can be produced and preferably produced from 1,5-pentanediamine, PDA) ^, 1,6-hexamethylene diisocyanate (HDI; can be produced and preferably produced from

1.6-hexamethylenediamine, HDA), isophorone diisocyanate (IPDI; can be prepared and preferably prepared from isophoronediamine, IPDA) and xylylene diisocyanate (XDI; can be prepared and preferably prepared from xylylenediamine, XDA). The expression "an isocyanate" of course also includes embodiments in which two or more different isocyanates (e.g. mixtures of MDI and TDI) were used in the preparation of the polyurethane product, unless expressly stated otherwise, e.g by the formulation "exactly one isocyanate". The entirety of all isocyanates used in the manufacture of the polyurethane product is referred to as the isocyanate component (of the polyurethane product). The isocyanate component includes at least one isocyanate. Analogously, the entirety of all polyols used in the manufacture of the polyurethane product is referred to as the polyol component (of the polyurethane product). The polyol component includes at least one polyol.

In the terminology of the present invention, the term polyols includes all polyols known to those skilled in the art in connection with polyurethane chemistry, such as in particular polyether polyols, polyester polyols, polyether ester polyols and polyether carbonate polyols. Of course, the expression "a polyol" also encompasses embodiments in which two or more different polyols were used in the production of the polyurethane product. If, for example, "a polyether polyol" (or "a polyester polyol" etc.) is mentioned below, this terminology naturally also includes embodiments in which two or more different polyether polyols (or two or more different polyester polyols etc.) are used in the production of the Polyurethane product were used.

In the terminology of the present invention, carbamates refer to the urethanes formed by the reaction with the alcohol in step (B).

An amine corresponding to an isocyanate designates that amine through whose phosgenation the isocyanate can be obtained according to R-NH2+COC/2->R-N=C=O+2HCl. Analogously, a nitro compound corresponding to an amine designates that nitro compound by reduction of which according to R-NO2+3H2->R-NH2+2H2O the amine can be obtained.

All pressure specifications refer to absolute pressures, indicated by the pressure unit being followed by "abs." (e.g. "mbar(abs)").

The invention is therefore concerned with the recycling of polyurethane foams whose cell structure contains oxygen, (at least) one blowing agent and/or (at least) one (volatile or decomposable to form volatile products) disinfectant, i.e. one, several or all of the volatile accompanying substances mentioned , but oxygen is always present. In the terminology of the present invention, the term “component X” is used in this sense as a collective designation for all volatile accompanying substances present.

The method according to the invention removes at least the oxygen present (irrespective of its origin) at least essentially completely. All constituents of component X or gaseous decomposition products thereof are preferably at least essentially completely removed. To this end, the invention provides two alternative solutions, as will be explained in more detail below. What they all have in common is that in (B)(1)(a) oxygen, preferably all components of component X or gaseous decomposition products thereof, “gaseous at a maximum pressure of 960 mbapabs and a maximum temperature of 120 °C [...] be taken away". This means that at least the oxygen present, but preferably also the propellant and the Disinfectants, insofar as they are present (it is not mandatory that all of the volatile accompanying substances mentioned are present; for example, disinfection of the polyurethane foam is not necessary in all cases), are at least essentially completely removed from the polyurethane foam before the actual chemolysis reaction begins.

The first alternative solution is characterized in particular by the fact that the removal of the volatile accompanying substances is essentially effected by a strong pressure reduction followed by a pressure increase. For this purpose, the polyurethane foam is used to carry out the degassing in (B.l)

(1) in a first step at a first temperature (T1) in the range from -20 °C to 120 °C a first pressure (p1) in the range from 0.1 mbar(abs) to 100 mbar(abs) exposed (wherein in particular the first pressure is matched to the first temperature in such a way that all components of component X to be removed in (B)(1)(a) which are not in gaseous form like oxygen anyway, pass into the gas phase or decompose with the formation of gaseous products ), and

(2) exposed in a second step to a second pressure (p2) by supplying an inert gas, which is greater than the first pressure and amounts to a maximum of 2.0 bar(abs).

In this context, a “degassed polyurethane foam (2)” refers to a polyurethane foam that has been freed from volatile accompanying substances of the type mentioned and saturated with an inert gas.

The second alternative solution is characterized in particular by the fact that the volatile accompanying substances are essentially removed by mechanical compression of the polyurethane foam (the volatile accompanying substances are pressed out of the cell structure of the polyurethane foam and into an area of reduced pressure). For this purpose, the polyurethane foam is used to carry out the degassing in (B.l)

(1) in a first step at a first temperature (T1) in the range from -20 °C to 120 °C and a first pressure (p1) in the range from 0.1 mbar(abs) to 960 mbar(abs), in particular 100 mbar(abs) to 960 mbar(abs), to a device for mechanical compression arranged in the entry device (wherein in particular the first pressure is matched to the first temperature such that all in (B)(1)(a) to be discharged Constituents of component X, which are not present in gaseous form like oxygen, pass into the gaseous phase or submerge decompose the formation of gaseous products), the gas removal device being arranged upstream of the device for mechanical compression, and

(2) in a second step in the device for mechanical compression at a second pressure (p2) in the range of 5 bar(abs) to 200 bar(abs) compressed (here the volatile accompanying substances are removed from the cell structure and into the pre the area of the entry device located in the device for mechanical compression and then discharged there via the gas discharge device).

In this context, a “degassed polyurethane foam (2)” refers to a polyurethane foam that has been freed from volatile accompanying substances of the type mentioned and compressed (and is fed in compressed form to the chemolysis carried out in an inert gas atmosphere).

The attached drawings show concrete realization possibilities of these two alternative solutions:

FIG. 1 shows a first variant of the method according to the invention using a flexible lining made of, for example, polyethylene (first alternative solution),

FIG. 2a, b show a second variant of the method according to the invention

Use of a lock system (first alternative solution),

FIG. 3 shows a third variant of the method according to the invention

Use of a mechanical crushing device (first alternative solution) and

FIG. 4 shows a fourth variant of the method according to the invention using a device for mechanical compression (second alternative solution).

First, a brief summary of various possible embodiments of the invention follows.

In a first embodiment of the invention, which corresponds to a first variant and belongs to the first alternative solution, the container and/or the infeed device is provided internally with a flexible lining which, in the first step, is adjusted by adjusting the first Pressure is contracted and so compresses the polyurethane foam, and is expanded again in the second step by supplying an inert gas to set the second pressure.

In a second embodiment of the invention, which is a special configuration of the first embodiment and can be combined with all other embodiments of the first variant, the flexible lining is a film made of polyethylene, polypropylene, aluminum, polyvinyl chloride, polyetheretherketone, polystyrene, polycarbonate, polyester, Polyethylene terephthalate or a composite of the aforementioned materials.

In a third embodiment of the invention, which is a special configuration of the first embodiment and can be combined with all other embodiments of the first variant, the first and the second step are repeated several times, in particular 2 to 5 times.

In a fourth embodiment of the invention, which is a special configuration of the first embodiment and can be combined with all other embodiments of the first variant, the second pressure is a maximum of 1.8 bar(abs) and is in particular equal to the ambient pressure.

In a fifth embodiment of the invention, which is a special configuration of the first embodiment and can be combined with all other embodiments of the first variant, the first temperature is in the range from 0° C. to 80° C., preferably from 16° C. to 80° C

In a sixth embodiment of the invention, which is a special configuration of the first embodiment and can be combined with all other embodiments of the first variant, the second step is carried out at a second temperature (T2), which is in the range from -20 °C to 120 °C, preferably 0 °C to 80 °C, particularly preferably 16 °C to 80 °C, and in particular corresponds to the first temperature (i.e. there is no specific change in temperature during the transition from the first to the second step).

In a seventh embodiment of the invention, which corresponds to a second variant and also belongs to the first alternative solution, the entry device has a first lock area (upstream of the chemolysis reactor) having a lockable feed device for the polyurethane foam provided in step (A) and a lockable discharge device for the degassed polyurethane foam, the following steps being run through in step (B1): (BIIa) blocking off the discharge device of the first lock area, introducing polyurethane foam into the first lock area and blocking off the feed device of the first lock area;

(B.l.2.a) Carrying out the first step of (B.l) in the first lock area;

(B.l.3.a) Carrying out the second step of (B.l) in the first lock region by supplying the inert gas to obtain degassed polyurethane foam;

(B.l.4.a) Transferring the degassed polyurethane foam obtained in (B.l.3.a) into the chemolysis reactor.

In an eighth embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, the entry device has a second lock area in addition to the first lock area, which has a lockable feed device for the in step (A) provided polyurethane foam and a closable discharge device for the degassed polyurethane foam, wherein in step (B.I.I.a) a first subset of the polyurethane foam is introduced into the first lock area, so that in step (B.l.3a) a first subset of the degassed polyurethane foam is obtained, wherein in Step (B.l) the following steps are also run through:

(B.l.1.b) blocking off the discharge device of the second lock area, entering a second partial quantity of the polyurethane foam into the second lock area and blocking off the feed device of the second lock area;

(B.l.2.b) Carrying out the first step of (B.l) in the second lock area;

(B.l.3.b) Carrying out the second step of (B.l) in the second lock region by supplying the inert gas to obtain a second portion of the degassed polyurethane foam;

(Bl4.b) transferring the second portion of the degassed polyurethane foam to the chemolysis reactor; wherein steps (BII.a) to (Bl4.a) are matched to steps (BII.b) to (Bl4.b) in such a way that continuously degassed polyurethane foam is transferred to the chemolysis reactor. In a ninth embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, the first temperature is in the range from 0°C to 80°C, preferably 16°C to 80°C .

In a tenth embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, the polyurethane foam is only brought into contact with the chemolysis reagent in the chemolysis reactor.

In an eleventh embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, the second step is carried out at a second temperature (T2), which is in the range from -20 °C to 120 °C, preferably 0 °C to 80 °C, particularly preferably 16 °C to 80 °C and in particular corresponds to the first temperature (i.e. there is no specific change in temperature during the transition from the first to the second step).

In a twelfth embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, provided these are not limited to the addition of the chemolysis reagent in the chemolysis reactor, the polyurethane foam is still in the second step first and/or second lock area with chemolysis reagent (optionally already with the catalyst) brought into contact, in particular wetted.

In a thirteenth embodiment of the invention, which is a special configuration of the twelfth embodiment, the chemolysis reagent has a temperature in the range from 120° C. to 240° C., in particular > 120° C. to 240 °C, on.

In a fourteenth embodiment of the invention, which is a special configuration of the seventh embodiment and can be combined with all other embodiments of the second variant, the second pressure is a maximum of 1.8 bar(abs) and is in particular equal to the ambient pressure.

In a fifteenth embodiment of the invention, which corresponds to a third variant and also belongs to the first alternative solution, during the first step of (Bl) the polyurethane foam is conveyed and crushed by a mechanical crushing device arranged in a first part of the feeding device, the second step is carried out in such a way that the present after the mechanical comminution polyurethane foam by a second, downstream of the first, part of Entry device is promoted in an inert gas atmosphere which is under the second pressure.

In a sixteenth embodiment of the invention, which is a special refinement of the fifteenth embodiment and can be combined with all other embodiments of the third variant, the polyurethane foam is conveyed in the first and second part of the entry device by means of

(at least) one worm shaft,

(at least) one piston,

(at least) one conveyor belt, vibration and/or gravity.

In an eighteenth embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant, the device for mechanical comminution comprises a cutting mill, a knife mill, an impact crusher and/or a hammer mill.

In a nineteenth embodiment of the invention, which is a special refinement of the eighteenth embodiment, the device for mechanical comminution comprises an impact crusher and/or a hammer mill, the first temperature being in the range from <0°C to -20°C.

In a twentieth embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant except the nineteenth, the first temperature is in the range from 0 °C to 80 °C, preferably 16 °C to 80℃

In a twenty-first embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant, the polyurethane foam is only brought into contact with chemolysis reagent in the chemolysis reactor.

In a twenty-second embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant, the second step is carried out at a second temperature (T2), which is in the range from -20 °C to 120 °C, preferably 0 °C to 80 °C, particularly preferably 16 °C to 80 °C, and in particular the first temperature (ie there is no intentional change in temperature during the transition from the first to the second step).

In a twenty-third embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant, provided these are not limited to the addition of the chemolysis reagent only in the chemolysis reactor, the polyurethane foam is still in the second step second part of the entry device with chemolysis reagent (optionally already with the catalyst) brought into contact, in particular wetted.

In a twenty-fourth embodiment of the invention, which is a special configuration of the twenty-third embodiment, the chemolysis reagent has a temperature in the range from 120 °C to 240 °C, in particular >120 °C to 240 °C, when brought into contact with the polyurethane foam in the second part of the entry device C, on.

In a twenty-fifth embodiment of the invention, which is a special configuration of the fifteenth embodiment and can be combined with all other embodiments of the third variant, the second pressure is a maximum of 1.8 bar(abs) and is in particular equal to the ambient pressure.

In a twenty-sixth embodiment of the invention, which corresponds to a fourth variant and is a special configuration of the second alternative solution and can be combined with all other embodiments of the fourth variant, the gas discharge device is arranged in the entry device.

In a twenty-seventh embodiment of the invention, which is a special configuration of the twenty-sixth embodiment and can be combined with all other embodiments of the fourth variant, the device for mechanical compression comprises an extruder (also including multi-zone screws and single and multi-screw extruders), a roller or a flask.

In a twenty-eighth embodiment of the invention, which is a special configuration of the twenty-sixth embodiment and can be combined with all other embodiments of the fourth variant, the polyurethane foam is still in the entry device with the Chemolysis reagent brought into contact, especially wetted.

In a twenty-ninth embodiment of the invention, which is a particular refinement of the twenty-eighth embodiment, the chemolysis reagent when brought into contact with the polyurethane foam in the feed device, a temperature in the range from 120 °C to 240 °C.

In a thirtieth embodiment of the invention, which is a special configuration of the twenty-sixth embodiment and can be combined with all other embodiments of the fourth variant, the first temperature is in the range from 0°C to 80°C, preferably 16°C to 80°C .

In a thirty-first embodiment of the invention, which is a special configuration of the twenty-sixth embodiment and can be combined with all other embodiments of the fourth variant, the second step is carried out at a second temperature (T2), which is in the range from -20 °C to 120 °C, preferably 0 °C to 80 °C, particularly preferably 16 °C to 80 °C, and in particular corresponds to the first temperature (i.e. there is no specific change in temperature during the transition from the first to the second step).

In a thirty-second embodiment of the invention, which can be combined with all embodiments of all four variants, step (B.ll) is carried out at a temperature in the range from 140° C. to 240° C., preferably from 160° C. to 240° C., particularly preferably 180 °C to 220 °C.

In a thirty-third embodiment of the invention, which can be combined with all embodiments of all four variants, step (B.II) is carried out at a pressure in the range from >960 mbar(abs) to 1.8 bar(abs), in particular at ambient pressure. carried out.

In a thirty-fourth embodiment of the invention, which can be combined with all embodiments of all four variants, component X contains at least one component which, under standard conditions (i.e. at a temperature of 0° C. and a pressure of 1,000 bar(abs)) is liquid, the first temperature being at least 16°C.

In a thirty-fifth embodiment of the invention, which can be combined with all embodiments of all four variants, the blowing agent comprises (in particular is) pentane, a chlorofluorocarbon, dichloromethane or a mixture of two or more of the aforementioned blowing agents; and includes (particularly is) the disinfectant hydrogen peroxide, chlorine dioxide,

Formaldehyde, peracetic acid, an alkali metal hypochlorite (especially sodium hypochlorite), ethanol, isopropanol, 1-propanol or a mixture of two or more of the aforementioned disinfectants.

In a thirty-sixth embodiment of the invention, which can be combined with all embodiments of all four variants, the isocyanate component contains an isocyanate selected from tolylene diisocyanate (TDI), the di- and polyisocyanates of the diphenylmethane series (MDI), 1,5-pentane diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI) or a mixture of two or more of the aforementioned isocyanates. Particular preference is given to polyurethane foams which, with regard to the isocyanate component, are based on a mixture of TDI and MDI. Very particular preference is given to polyurethane products which, with regard to the isocyanate component, are based only on TDI.

In a thirty-seventh embodiment of the invention, which can be combined with all embodiments of all four variants, the polyol component contains a polyol selected from a polyether polyol, a polyester polyol, a polyether ester polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols. The polyol component preferably contains a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., does not contain any other polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is encompassed and does not depart from the scope of this embodiment).

In a thirty-eighth embodiment of the invention, which can be combined with all embodiments of all four variants, the isocyanate component contains toluylene diisocyanate (TDI) and di- and polyisocyanates of the diphenylmethane series (MDI) (in particular only TDI), and the polyol component contains a polyether polyol (and is in particular a polyether polyol, i.e. it does not contain any other polyols different from polyether polyols, but a mixture of two or more different polyether polyols is included and does not go beyond the scope of this embodiment).

In a thirty-ninth embodiment of the invention, which can be combined with all embodiments of all four variants, the chemolysis reagent comprises an alcohol selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol or one Mixture of two or more of the aforesaid alcohols.

In a fortieth embodiment of the invention, which is a particular aspect of the forty-second embodiment, the chemolysis reagent comprises water. In a forty-first embodiment of the invention, which can be combined with all embodiments of all four variants, the catalyst is selected from an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal salt of a carboxylic acid (especially an acetate), an alkaline earth metal salt of a carboxylic acid (especially an acetate), a Lewis acid (especially dibutyltin dilaurate, tin octoate, monobutyltin oxide or tetrabutyl titanate) and/or an organic amine (especially diethanolamine, 1,1,3,3-tetramethylguanidine, 1,8-diazabicyclo(5.4.0)undec- 7-ene or 1,4-diazabicyclo[2.2.2]octane).

In a forty-second embodiment of the invention, which can be combined with all embodiments of all four variants, the chemolysis reagent has a temperature in the range from 120° C. to 240° C., in particular >120° C. to 240° C., when brought into contact with the polyurethane foam .

The embodiments of the invention briefly described above and other possible embodiments are explained in more detail below. All of the embodiments and further configurations of the invention can be combined with one another as desired, unless otherwise stated or clearly evident from the context.

PREPARATION OF THE POLYURETHANE FOAM FOR CHEMICAL RECYCLING

In step (A) of the method according to the invention, the polyurethane foam to be chemically recycled is provided.

In principle, this can be any type of polyurethane foam; in particular, both flexible foams and rigid foams are suitable, with flexible foams (for example from old mattresses, upholstered furniture or car seats) being preferred. Such polyurethane foams are produced using a blowing agent. Apart from water-blown foams (in which carbon dioxide is released by hydrolysis in situ), pentane is a particularly common blowing agent nowadays. When recycling old polyurethane foams, it is conceivable that chlorofluorocarbons, which were previously used as blowing agents, were also used. Another conceivable blowing agent is dichloromethane.

Furthermore, preference is given to those polyurethane foams which, with regard to the isocyanate component, are based on an isocyanate selected from tolylene diisocyanate (TDI), the di- and polyisocyanates of the diphenylmethane series (MDI), 1,5-pentane diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI) or mixtures of two or more of the aforementioned isocyanates. Particular preference is given to polyurethane foams which, with regard to the isocyanate component, are based on a mixture of TDI and MDI. Very particular preference is given to polyurethane products which, with regard to the isocyanate component, are based only on TDI.

With regard to the polyol component, preference is given to those polyurethane foams which are based on a polyol selected from a polyether polyol, a polyester polyol, a polyether ester polyol, a polyether carbonate polyol or a mixture of two or more of the aforementioned polyols. The polyol component preferably contains a polyether polyol. More preferably, the polyol component is a polyether polyol (i.e., does not contain any other polyols other than polyether polyols; however, a mixture of two or more different polyether polyols is encompassed and does not depart from the scope of this embodiment).

The polyurethane foam is very particularly preferably a foam whose isocyanate component contains toluylene diisocyanate (TDI) and di- and polyisocyanates of the diphenylmethane series (MDI), in particular only TDI, and whose polyol component contains a polyether polyol (and is in particular a polyether polyol i.e. does not contain any other polyols other than polyether polyols, although a mixture of two or more different polyether polyols is included and does not go beyond the scope of this embodiment.)

Step (A) preferably already comprises preparatory steps for the cleavage of the urethane bonds in step (B.II). In particular, this involves mechanical comminution of the polyurethane foams. Such preparatory steps are known to those skilled in the art; reference is made, for example, to the literature cited in [1]. Depending on the nature of the polyurethane foam, it can be advantageous to "freeze" it before mechanical shredding to facilitate the shredding process.

Before, during or after the mechanical comminution, the polyurethane foam can be treated with (aqueous or alcoholic) disinfectants. Such disinfectants are preferably hydrogen peroxide, chlorine dioxide, formaldehyde, alkali metal hypochlorites (in particular sodium hypochlorite) and/or peracetic acid (aqueous disinfectants) or ethanol, isopropanol and/or 1-propanol (alcoholic disinfectants). In particular when carrying out such a disinfecting treatment, the compounds contained in the cell structure can also include those which are liquid under standard conditions, ie at a temperature of 0° C. and a pressure of 1,000 bar(abs). In this case, it is preferable to select a value of 16° C. as the minimum value for the first temperature. The foam thus prepared is finally transferred to the container (reference number 100 in the figures) connected to the feeding device. This container can be a conventional container known in the art, such as solid silos or containers.

It is also conceivable to carry out the preparatory steps described above at a location which is spatially separate from the location of the chemolysis. In this case, the prepared foam is filled into suitable transport vehicles, such as silo vehicles, for onward transport. The prepared foam can also be compressed for onward transport in order to achieve a higher mass-to-volume ratio. The foam is then filled into the container at the site of the chemolysis reactor. It is also conceivable to connect the transport vehicle used directly to the infeed device, in which case the transport vehicle is to be regarded as a container within the meaning of the terminology of the present invention.

CHEMOLYSIS OF POLYURETHANE FOAM

Step (B) of the method according to the invention includes the chemolysis of the polyurethane foam provided in step (A). This step is performed in a chemolysis device, the

(i) an entry device (reference number 200 in the figures),

(ii) a chemolysis reactor (reference number 300 in the figures) connected to the feed device,

(iii) a discharge device connected to the chemolysis reactor (reference number 400 in the figures) and

(iv) has at least one gas discharge device (reference number 500 in the figures) for discharging the compounds contained in the cell structure. Step (B) comprises the sub-steps (B.l), the introduction of the polyurethane foam from the container into the entry device and from there into the chemolysis reactor, the polyurethane foam being degassed before it is brought into contact with the chemolysis reagent by

(a) at least oxygen (i.e. (i) the oxygen contained in component X and (ii) any oxygen formed by decomposition reactions of constituents of component X), but preferably all constituents of component X or gaseous decomposition products thereof, at a pressure of a maximum of 960 mbapabs and a maximum temperature of 120 °C are removed in gaseous form from the chemolysis device via the gas removal device, so that a degassed polyurethane foam is obtained, (B.ll), reacting the degassed polyurethane foam in the chemolysis reactor with a chemolysis reagent in the presence of a catalyst in a Inert gas atmosphere to obtain a (first) product mixture, and (B.lll), the discharge of the (first) product mixture from the chemolysis reactor by the discharge device.

As part of step (B.l), the polyurethane foam is degassed, i. H. the volatile accompanying substances present in the cell structure are removed from the cells and/or the webs of the cell structure of the polyurethane foam and discharged via the at least one gas discharge device (500). There are various implementation options for this:

In a first variant of step (B.l) belonging to the first alternative solution and shown in FIG. 1, the container (100 in FIG. 1) and/or the feeder (not shown in FIG. 1, but also possible) is provided internally with a flexible liner (600) which in the first step is adjusted by adjusting the first pressure (p1) is contracted to a value in the range from 0.1 mbar(abs) to 100 mbar(abs) and thus compresses the polyurethane foam, and in the second step, by supplying an inert gas (3) to set the second pressure (p2 ) is extended again. The second pressure is preferably a maximum of 1.8 bar (abs.) and corresponds in particular to ambient pressure (i.e. in the second step, the pressure is reduced to ambient pressure). “M” here and in the other figures stands for motor and designates a motor-driven device, in this case a device for opening and closing the entrance to and exit from the container (100).

In FIG. 1 the filling of the container (100) with polyurethane foam (1) is shown on the left. The valve in the lower area of the container (110), the connection to the inlet device (200) and the gas discharge device (500; valve 510 in the "closed" position) are closed.

In the middle of FIG. 1 shows the implementation of the first step. The filling opening of the container (100), the valve 110 and the connection to the entry device (200) are closed. A vacuum (valve 510 in the “open” position) is applied via the gas discharge device (500) and the pressure inside the flexible lining (600) is reduced to p1.

In FIG. 1 shows the second step or the conveying of the degassed polyurethane foam (2) into the feed device (200) that follows the second step. In the second step, the pressure inside the flexible lining is increased to p2 by adding an inert gas (3) through the valve 110, which is now open. After opening the connection to the entry device, the degassed polyurethane foam (2) is conveyed to the entry device (200) (or simply falls down into it due to the force of gravity). In the first variant, there is preferably no specific change in temperature during the transition from the first to the second step, so that the temperature for both steps is in the range from −20° C. to 120° C. Both the first and the second step are preferably carried out at a temperature in the range from 0°C to 80°C. If the compounds to be removed are liquids under standard conditions (which does not exclude the possibility that a significant vapor pressure may be present), a lower temperature limit of 16 °C has proven useful. It has proven advantageous to repeat the first and the second step several times, in particular 2 to 5 times, before the polyurethane foam degassed in this way is fed to the reaction of step (B.II).

The flexible lining used in this variant is preferably a film made of polyethylene, polypropylene, aluminum, polyvinyl chloride, polyether ether ketone, polystyrene, polycarbonate, polyester, polyethylene terephthalate or a composite of the aforementioned materials.

By lowering the pressure to a maximum of 100 mbar(abs) in the first step, the flexible lining contracts and compresses the polyurethane foam. In the process, volatile accompanying substances are pressed out of the cell structure of the foam and discharged via the gas discharge device. After setting the second pressure by supplying an inert gas (in particular nitrogen, argon or helium), the degassed polyurethane foam can be conveyed to the chemolysis reactor by vibration, mechanically or pneumatically or simply by gravity. In this variant, the chemolysis reagent and the catalyst are only added after the polyurethane foam has left the area of the chemolysis reactor provided with the flexible lining; in particular, the chemolysis reagent and the catalyst are only added in the chemolysis reactor. The chemolysis reagent is preferably added at a temperature which is in particular higher than the first temperature and is preferably in the range from 120°C to 240°C.

In a second variant of step (B1), which also belongs to the first alternative solution and which is shown in FIG. 2a, b is shown graphically, the entry device has a first lock area (121) (upstream of the chemolysis reactor), having a lockable feed device for the polyurethane foam (1) provided in step (A) and a lockable discharge device for the degassed polyurethane foam (2) , where in step (Bl) the following steps are run through: (BII.a) blocking off the discharge device of the first lock area, introducing polyurethane foam into the first lock area and blocking off the feed device of the first lock area;

(B.l.2.a) Carrying out the first step of (B.l) in the first lock area while adjusting the first pressure to a value in the said range of 0.1 mbar(abs) to 100 mbar(abs);

(B.l.3.a) Carrying out the second step of (B.l) in the first lock area while adjusting the second pressure to a value in the said range of > p1 to 2.0 bar(abs) by supplying an inert gas to obtain degassed polyurethane foam;

In the simplest configuration of this embodiment, there is only one lock area; the wording "first lock area" therefore does not imply the inevitable presence of several lock areas.

However, the use of at least two lock areas opens up the possibility of continuously transferring polyurethane foam into the chemolysis reactor by operating them alternately. In this embodiment of the second variant of the invention, the entry device has, in addition to the first lock area, a second lock area, which has a lockable feed device for the polyurethane foam provided in step (A) and a lockable discharge device for the degassed polyurethane foam, wherein in step (B.I.I.a ) a first subset of the polyurethane foam is introduced into the first lock area, with the following steps also being run through in step (B.l):

(Bl2.b) carrying out the first step of (Bl) in the second lock area with the setting of the first pressure to a value in the said range of 0.1 mbar(abs) to 100 mbar(abs); (Bl3.b) Carrying out the second step of (Bl) in the second lock area while adjusting the second pressure to a value in the said range from >p1 to 2.0 bar(abs) by supplying an inert gas to obtain a second subset of the degassed polyurethane foam ;

(B.l.4.b) transferring the second portion of the degassed polyurethane foam to the chemolysis reactor; wherein steps (B.I.I.a) to (B.l.4.a) are matched to steps (B.I.I.b) to (B.l.4.b) in such a way that continuously degassed polyurethane foam (2) is transferred to the chemolysis reactor.

In the left half of FIG. 2a shows a lock (220) with a first (221) and a second lock area (222). The second lock area (222) is constructed like the first; this is no longer shown in detail in the figure. Access to the second lock area (222) is closed. Polyurethane foam (1) is being filled into the first lock area (221). The first lock area (221) is closed towards the bottom (i.e. towards the chemolysis reactor). After completion of the filling process, as shown in the right half of FIG. 2a, the entrance to the first lock area (221) is closed. The valve (510) associated with the gas discharge device (500) is opened and the pressure p1 is set by reducing the pressure (first step). At the same time, polyurethane foam (1) can be introduced into the second lock area (222). After the pressure p1 has been reached in the first lock area (221), the valve 510 is closed and the pressure p2 is set by adding an inert gas (3) through the valve 210 (left half of FIG. 2b). Chemolysis reagent can also be supplied through the valve 210 . After the pressure p2 has been reached, the valves 210 and 510 are closed and the polyurethane foam (2), which has now been degassed and possibly wetted with chemolysis reagent, can be conveyed on to the chemolysis reactor (right half of FIG. 2b).

With regard to the temperatures and pressures, what was said above for the first variant also applies accordingly to the second variant.

In this variant, the chemolysis reagent can be added to the polyurethane foam not only in the chemolysis reactor, but also immediately after the second step (ie after the end of the degassing process), ie in the first and/or second lock area. In both cases, the added chemolysis reagent has a temperature which is in particular higher than the first temperature and is preferably in the range from 120.degree. C. to 240.degree. It is also possible to add the catalyst at this point (in particular as a solution in the chemolysis reagent). When the chemolysis reagent is added in the first and/or second lock area, the Polyurethane foam preferably wetted with this. The addition of chemolysis reagent in the first and/or second lock area naturally does not preclude the addition of further chemolysis reagent and/or further catalyst in the chemolysis reactor.

In this variant, the polyurethane foam can be introduced into the first or second lock area by vibration, mechanically or pneumatically. The lock area fills with the polyurethane foam and is then closed. Vacuum is applied and the exhaust air valve is then closed again. By reducing the pressure in the first step to a maximum of 100 mbar(abs), volatile compounds are sucked out of the cell structure of the foam and discharged via the gas discharge device. After the second pressure has been set by supplying an inert gas (in particular nitrogen, argon or helium), the degassed polyurethane foam can be conveyed to the chemolysis reactor. Again, this can be done by vibration, mechanically or pneumatically, or simply as a result of gravity. If the polyurethane foam comes into contact with chemolysis reagent in the first or second lock area, the apparent density of the polyurethane foam increases, as a result of which it can easily fall down into the reactor. In addition, mixing of the polyurethane foam into chemolysis reagent already present in the chemolysis reactor is facilitated if the cell structure of the polyurethane foam already contains chemolysis reagent.

In a third variant of step (B.l), which also belongs to the first alternative solution and which is shown in FIG. 3 is shown graphically, the polyurethane foam is during the first step of (B.l) with adjustment of the first pressure (p1) to a value in the said range of 0.1 mbar (abs.) To 100 mbar (abs) by a in a first Part of the entry device (201) arranged device for mechanical comminution (230) and comminuted there, the second step being carried out in such a way that the polyurethane foam (11) present after the mechanical comminution is passed through a second part of the entry device ( 202) in an inert gas atmosphere (particularly in a nitrogen, argon or helium atmosphere) which is under the second pressure. This promotion can take place by means of (at least) a screw shaft, (at least) a piston, (at least) a conveyor belt, vibration and/or gravity.

The device for mechanical comminution (230) can be, for example, a cutting mill, a knife mill, an impact crusher and/or a hammer mill. The use of an impact crusher or a hammer mill is particularly preferred when the polyurethane foam is introduced into the chemolysis device in a frozen state becomes. In particular, this embodiment of the third variant of the present invention makes it possible to include the mechanical comminution of the polyurethane foam, which is preferably to be carried out, at least partially in step (B). In this case, the above-described mechanical comminution of the polyurethane foam in step (A) can be limited to coarse comminution of the polyurethane foam into pieces of manageable size, or can even be omitted entirely.

With the exception of the previously described embodiment involving freezing of the polyurethane foam, what was said above for the first and second variants also applies correspondingly to the third variant with regard to the temperatures and pressures. The pressures are also preferred in this embodiment of the third variant as described for the first and second variant, but the mechanical compression naturally takes place at a temperature below 0°C, in particular at temperatures of down to -20°C.

As in the second variant, the chemolysis reagent can also be used in the third variant not only in the chemolysis reactor, but also immediately after the second step (i.e. after the end of the degassing process), i. H. are still given here in the second part of the entry device to the polyurethane foam. In both cases, the added chemolysis reagent has a temperature which is in particular higher than the first temperature and is preferably in the range from 120.degree. C. to 240.degree. It is also possible to add the catalyst at this point (in particular as a solution in the chemolysis reagent). If the chemolysis reagent is already added in the second part of the feed device, the polyurethane foam is preferably wetted with it. The addition of chemolysis reagent in the second part of the feed device naturally does not preclude the addition of further chemolysis reagent and/or further catalyst in the chemolysis reactor.

In this variant, the polyurethane foam is conveyed via a - preferably sealed as possible - conveyor, in particular a screw conveyor, to the device for mechanical comminution, which is under a maximum pressure of 100 mbar (abs), with volatile compounds largely being released during the mechanical comminution Compression processes are removed during shredding. By conveying the polyurethane foam comminuted in this way into the second part of the feed device, which is under an inert gas atmosphere, the cell structure of the polyurethane foam is filled with the inert gas and is thus effectively protected against the penetration of other gases. The mechanical comminution in step (B1) can optionally replace a mechanical comminution in step (A). In a fourth variant of step (B1), which represents the second alternative solution and which is shown in FIG. 4, the polyurethane foam is conveyed during the first step to a mechanical compression device (240) arranged in the infeed device, wherein in the second step the polyurethane foam is transported in this mechanical compression device at a value for the second pressure p2 in the range of 5 bar(abs) to 200 bar(abs) is compressed. The pressure p2 can be determined by means of a manometer (connected to a capillary protruding into the area of the feeding device where the device for mechanical compression is arranged). Making the polyurethane foam inert prior to mechanical compression is preferred, but not essential. After the second step has been carried out, the pressure is at least S hares.), which is higher than the pressure preferred for step (B.II) (see the explanations further below). The expansion to the pressure of step (B.II) preferably takes place when the polyurethane foam treated in step (B1) enters the chemolysis reactor. In this variant, chemolysis reagent (4) can be added, for example, after passing through the device for mechanical compression (ie after the end of the degassing process) and before entry into the chemolysis reactor (300) (see further below for further details).

In this variant, the gas discharge device (500) is preferably arranged in the entry device (200). A device (600) for discharging reaction gases formed during the chemolysis, such as in particular carbon dioxide, can be arranged in the chemolysis reactor (300).

A suitable device for mechanical compression is, for example, an extruder (also including multi-zone screws and single- and multi-screw extruders), a roller or a piston. Multi-zone screws are extruders whose spiral has, for example, different diameters or pitches of the spiral windings. This promotes compression.

As in the second and third variants, the chemolysis reagent can also be used in the fourth variant not only in the chemolysis reactor, but also immediately after the second step (i.e. after the end of the degassing process), ie here still in the entry device, but after passing through the device for the mechanical Compression to be given to the polyurethane foam. In both cases, the chemolysis reagent added has a temperature which is preferably in the range from 120.degree. C. to 240.degree. C., in particular in the range >120.degree. C. to 140.degree. In contrast to the second and third variants, however, it is preferred not to add any catalyst at this point. If the chemolysis reagent is already added in the feed device, the polyurethane foam is preferably wetted with it. The additions of chemolysis reagent of course, already in the entry device does not rule out that further chemolysis reagent and/or further catalyst is added in the chemolysis reactor.

As in the other variants, the temperature for the second step is preferably in the range from -20 °C to 120 °C and corresponds in particular to the first temperature (i.e. there is no deliberate change in temperature during the transition from the first to the second step). The first temperature is preferably in the range of 0°C to 80°C. This also applies to the second temperature. If the compounds to be removed are liquids under standard conditions (which does not preclude a significant vapor pressure), a lower temperature limit of 16 °C (in both steps) has proven useful.

In the device for mechanical compression, which is used in this variant, the polyurethane foam is compressed, as a result of which gases and volatile compounds present in the cell structure of the polyurethane foam are forced out.

In step (B.ll) of the method according to the invention, the actual chemical recycling, the cleavage of the urethane bonds, takes place (which does not rule out that the reaction can already begin in part in the entry device, provided that the degassing is complete; see the above explanations Step (B.l)). The chemolysis is carried out in an inert gas atmosphere (particularly in a nitrogen, argon or helium atmosphere). The chemolysis reagent used is preferably also saturated after being freed of oxygen by inert gas saturation (regardless of whether this is added for the first time in the chemolysis reactor or already in the feed device).

In principle, step (B.ll) can be carried out by any method known in the art. To carry out the reaction, the chemolysis reactor in particular is partially filled with chemolysis reagent (and catalyst). The polyurethane foam to be converted is introduced into this "bath" of chemolysis reagent. The polyurethane foam can be fed in both above and below the liquid level.

Preferred embodiments of this step are alcoholysis (usually referred to as glycolysis in the literature; cf. No. 2 above) and hydroalcoholysis (usually referred to as hydrog/yo/ysis in the literature; cf. No. 3 above). Regardless of the exact type of configuration, step (B.II) is preferably carried out at a temperature in the range from 140° C. to 240° C., preferably from 160° C. to 240° C., particularly preferably from 180° C. to 220° C. The pressure in step (B.II) is preferably >960 mbar(abs) to 1.8 bar(abs) and is in particular equal to ambient pressure (ie the reaction in step (B.II) is carried out). in particular operated without pressure). The pressure in step (B.II) means the pressure prevailing in the gas space of the chemolysis reactor.

If the chemolysis is carried out as an alcoholysis, the addition of the chemolysis reagent (in this case an alcohol) occurs without the addition of significant amounts of water. In this context, without the addition of significant amounts of water means that water is not deliberately added in such quantities that would bring about hydroalcoholysis to a significant extent. This does not rule out the entry of small amounts of water, which may be contained dissolved in the alcohol used in step (B.II), are introduced via the polyurethane foam or can be used as a solvent for the catalyst.

If the chemolysis is carried out as hydroalcoholysis, an alcohol and water are used as the chemolysis reagent, and these two components can, but do not have to, be premixed. In particular, it is also possible first to add only the alcohol (and possibly a small portion of the water) and to dissolve the polyurethane foam in it before the water (or the remaining water) is added. In the case of the hydroalcoholysis, it is preferable not to add all the water to be used all at once, but gradually, as water is chemically consumed in the reaction.

Regardless of whether the chemolysis is carried out as an alcoholysis or as a hydroalcoholysis, the chemolysis reagent preferably contains an alcohol selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl glycol, triethylene glycol, glycerol, 2-methyl-1,3-propanediol or a mixture of two or more of the aforementioned alcohols. Diethylene glycol is particularly preferred.

Although alcoholysis and hydroalcoholysis are preferred, other chemolysis methods such as hydrolysis or aminolysis can of course also be used.

A particularly suitable catalyst for step (B.II) is an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal salt of a carboxylic acid (especially an acetate), an alkaline earth metal salt of a carboxylic acid (especially an acetate), a Lewis acid (especially dibutyltin dilaurate, tin octoate, monobutyl tin oxide or tetrabutyl titanate) and/or an organic amine (especially diethanolamine, 1,1,3,3-tetramethylguanidine, 1,8-diazabicyclo(5.4.0)undec-7-ene or 1,4-diazabicyclo[2.2 .2]octane). The catalyst is added at the latest in the chemolysis reactor; however, it can also, see the above statements, already be added to the feed device beforehand, in particular dissolved in the chemolysis reagent. Step (B.II) can be carried out in any reactor known in the art for such a purpose. Stirred tanks (stirred reactors) and tubular reactors are particularly suitable as chemolysis reactors.

Step (B.ll) provides a first product mixture which contains unreacted chemolysis reagent (because it is used superstoichiometrically), polyols (originating from the polyol component and/or newly formed as degradation products during the reaction with the chemolysis reagent) and (depending on the chemolysis reagent used) carbamates and /or contains amines. In the preferred embodiments, when the chemolysis is carried out as an alcoholysis or hydroalcoholysis, the excess chemolysis reagent comprises at least the alcohol used in the chemolysis and optionally (when the chemolysis is carried out as a hydroalcoholysis) water pure alcoholysis may be present in small amounts; see the explanations above.

This first product mixture is discharged from the chemolysis reactor in step (B.III) and then fed to further work-up (step (C), preferably step (C) and step (D)). As a discharge device to be used for this purpose, all devices known in the art for fluid delivery, such as in particular pumps, can be used.

RECOVERY OF THE POLYOLS

In step (C) of the process according to the invention, the first product mixture obtained in step (B) is worked up to obtain the polyols. In principle, this work-up can be carried out as known from the prior art. An organic solvent is preferably first added to the first product mixture. Various possible configurations are available for this:

In a possible embodiment of step (C), in the preferred embodiments, with the chemolysis being carried out as an alcoholysis or hydroalcoholysis, this comprises the steps:

(Cl) Mixing the first product mixture obtained in step (B.III), in particular without prior separation of any water present in the first product mixture, with an organic solvent which is not completely miscible with the alcohol used in step (B) (in particular a aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, or a mixture of two or more of the foregoing organic solvent) and phase separation into a first alcohol phase and a first solvent phase;

(C.II) Working up the first solvent phase to obtain the polyols.

Step (C.II) comprises work-up steps known to those skilled in the art, such as washing and distillation in particular.

In another possible embodiment of step (C), in the preferred embodiments, with the chemolysis being carried out as an alcoholysis or hydroalcoholysis, this comprises the steps:

(C.l*) mixing the first product mixture obtained in step (B.III) with an organic solvent which is miscible with the alcohol used in step (B) (in particular a halogen-substituted aliphatic hydrocarbon, a halogen-substituted alicyclic hydrocarbon, a Halogen-substituted aromatic hydrocarbon or a mixture of two or more of the aforesaid organic solvents), optionally followed by a separation of solid components to give a second product mixture;

(C.ll*) Washing of the second product mixture obtained in step (C.l*) with an aqueous washing liquid (whereby any carbamates present in the second product mixture are partially hydrolyzed with release of amines and alcohol) and phase separation into a first solvent phase containing in step (C.l *) organic solvents and polyols used, and a first aqueous phase containing water, alcohol, carbamates and amines;

(C.III*) Work-up of the first solvent phase to obtain the polyols.

Step (C.III*) in turn comprises work-up steps known to those skilled in the art, such as, in particular, washing and distillation.

An extraction of the first product mixture with an organic solvent can of course also be carried out when carrying out the chemolysis as a pure hydrolysis.

RECOVERY OF THE AMINES

The process according to the invention preferably comprises a step (D) for obtaining at least one amine which corresponds to an isocyanate of the isocyanate component. The starting point for this part of the work-up is the alcohol phase or first aqueous phase obtained from the first product mixture in step (C).

The way in which step (D) is carried out depends in particular on the way in which step (B.II) is carried out. If step (B) is carried out as an alcoholysis, the first alcohol phase or the first aqueous phase will regularly still contain substantial proportions of carbamates which have to be hydrolyzed in step (D). Such a hydrolysis is advantageously carried out catalytically, with the same catalysts as described above being suitable for the chemolysis.

If step (B.II) is carried out as a hydroalcoholysis, then at this point in the process there are no longer any carbamates present (or at most in insignificant trace amounts), so that a separate hydrolysis step can be dispensed with.

Regardless of this, step (D) comprises work-up steps, such as in particular a distillation, in order to purify the amine obtained by cleaving the urethane bonds. It is particularly advantageous here to integrate the insulation of amines recovered from a polyurethane foam into a process for producing new amines, as described in WO 2020/260387 A1 and the as yet unpublished patent application PCT/EP2021/075916.

The invention is explained in more detail below using examples.

Examples:

Example 1 (according to the invention, first variant):

250 g of polyurethane flakes (toluylene diisocyanate-based flexible foam) were filled into a flexible polyethylene (PE) bag (30 L), sealed and connected to a vacuum pump. By starting the vacuum pump, the pressure inside the PE bag was reduced to a value below 10 mbar^s). The interior of the PE bag was then expanded to ambient pressure by adding nitrogen. This process was repeated 2 more times. An oxygen probe was then inserted into the outlet of the bag. By exerting pressure on the inerted bag, the gas in it flowed past the oxygen probe for 1 minute. At no time did the oxygen content in the exhaust air exceed 0.5% by volume.

A glycolysis was then carried out with the inerted foam flakes as follows:

250 g of diethylene glycol and 2.5 g of bismuth trineodecanoate were placed in a 1 L 3-neck round bottom flask and heated to 200.degree. The polyurethane flakes were then added, dissolved and kept at 200° C. for a further 3 hours. During the addition and reaction, a nitrogen purge was switched on continuously (at 10 NL/h). After the reaction time, the mixture was cooled to room temperature.

Example 2 (comparison test):

The chemolysis of polyurethane flakes was carried out analogously to Example 1, but without the degassing according to the invention. Here, too, a nitrogen purge was permanently connected during metering and reaction.

In Example 2, the reaction mixture was clearly black, while the previously degassed polyurethane foam (Example 1) was only slightly brown. This clearly shows the influence of the oxygen contained in the cell structure of the polyurethane foam through significantly increased oxidation of the toluenediamine compounds released during glycolysis.

Claims

Patent Claims:

1. Process for the recovery of raw materials from a polyurethane foam based on an isocyanate component and a polyol component, having a cell structure containing a component X selected from the group consisting of oxygen, a blowing agent, a disinfectant and a mixture of two or more of the aforementioned, the component X comprises at least oxygen, by reacting the polyurethane foam with a chemolysis reagent, the method comprising:

(A) providing the polyurethane foam in a container;

(B) Chemolysis of the polyurethane foam in a chemolysis device having (i) an entry device, (ii) a chemolysis reactor connected to the entry device, (iii) a discharge device connected to the chemolysis reactor and (iv) one arranged in the container and/or in the entry device Gas removal device, wherein the chemolysis comprises:

(a) at least oxygen, but preferably all components of component X or gaseous decomposition products thereof, are removed in gaseous form via the gas removal device from the chemolysis device at a maximum pressure of 960 mbar (abs.) and a maximum temperature of 120 °C, so that a degassed polyurethane foam is obtained;

(B.II) reacting the degassed polyurethane foam in the chemolysis reactor with a chemolysis reagent in the presence of a catalyst in an inert gas atmosphere to obtain a product mixture;

(B.l II) discharge of the product mixture from the chemolysis reactor through the discharge device; followed by

Processing of the product mixture comprising: (C) recovering a polyol; and

(D) optionally, recovering an amine corresponding to an isocyanate of the isocyanate component. Process according to Claim 1, in which the degassing of the polyurethane foam in (B.l) is carried out by

(1) in a first step, the polyurethane foam is exposed to a first pressure in the range from 0.1 mbar(abs) to 100 mbar(abs) at a first temperature in the range from -20 °C to 120 °C, and

(2) in a second step, the polyurethane foam is subjected to a second pressure by supplying an inert gas, which pressure is greater than the first pressure and amounts to a maximum of 2.0 bar(abs). Method according to claim 2, in which the container and/or the infeed device is provided internally with a flexible liner which in the first step is contracted by adjusting the first pressure and so compresses the polyurethane foam, and which is expanded again in the second step by supplying the inert gas becomes. The method according to claim 2, in which the entry device has a first lock area, having a lockable feed device for the polyurethane foam provided in step (A) and a lockable discharge device for the degassed polyurethane foam, the following steps being carried out in step (B.l):

(B.I.I.a) Blocking off the discharge device of the first lock area, entries of polyurethane foam into the first lock area and blocking off the feed device of the first lock area;

(B.l.2.a) Carrying out the first step of (B.l) in the first lock area;

(Bl4.a) Transferring the degassed polyurethane foam obtained in (Bl3.a) into the chemolysis reactor. Method according to Claim 4, in which the entry device has, in addition to the first lock area, a second lock area which has a lockable feed device for the polyurethane foam provided in step (A) and a lockable discharge device for the degassed polyurethane foam, wherein in step (BII .a) a first subset of the polyurethane foam is introduced into the first lock area, so that in step (Bl3a) a first subset of the degassed polyurethane foam is obtained, with the following steps also being run through in step (Bl):

(B.l.1.b) blocking off the discharge device of the second lock area, entering a second subset of the polyurethane foam into the second lock area and blocking off the feed device of the second lock area;

(B.l.2.b) Carrying out the first step of (B.l) in the second lock area;

(Bl4.b) transferring the second portion of the degassed polyurethane foam to the chemolysis reactor; steps (BII.a) to (Bl4.a) being matched to steps (Bl1.b) to (Bl4.b) in such a way that continuously degassed polyurethane foam is transferred to the chemolysis reactor. Method according to claim 2, wherein during the first step of (Bl) the polyurethane foam is conveyed and comminuted by a mechanical comminution device arranged in a first part of the input device, the second step being carried out in such a way that the one present after the mechanical comminution Polyurethane foam is conveyed through a second part of the entry device, downstream of the first, into an inert gas atmosphere which is under the second pressure. Method according to one of Claims 2 to 6, in which the second pressure is a maximum of 1.8 bar(abs). The method of claim 1, wherein the degassing of the polyurethane foam in (Bl) is carried out by (1) the polyurethane foam in a first step at a first temperature in the range from -20 °C to 120 °C and a first pressure in the range from 0.1 mbar(abs) to 960 mbar(abs), in particular 100 mbar(abs ) to 960 mbar(abs), to a device for mechanical compression arranged in the intake device, the gas discharge device being connected upstream of the device for mechanical compression, and

(2) the polyurethane foam is compressed in a second step in the mechanical compression device at a second pressure ranging from 5 bar(abs) to 200 bar(abs).

9. The method as claimed in claim 8, in which the gas discharge device is arranged in the entry device.

10. The method according to any one of claims 2 to 9, wherein the second step is carried out at a second temperature which is in the range of -20°C to 120°C.

11. The method according to any one of claims 2 to 10, in which the component X contains (at least) one component which is liquid at a temperature of 0 ° C and a pressure of 1, 000 bar (abs), and in which the first temperature is at least 16 °C.

12. The method according to any one of the preceding claims, in which step (B.II) is carried out at a temperature in the range from 140°C to 240°C.

13. A method according to any one of the preceding claims wherein the blowing agent comprises pentane, a chlorofluorocarbon, dichloromethane or a mixture of two or more of the foregoing; and the disinfectant comprises hydrogen peroxide, chlorine dioxide, formaldehyde, peracetic acid, an alkali metal hypochlorite, ethanol, isopropanol, 1-propanol, or a mixture of two or more of the foregoing.

14. The method according to any one of the preceding claims, wherein the isocyanate component is an isocyanate selected from toluylene diisocyanate, the di- and polyisocyanates of the diphenylmethane series, 1, 5-pentane diisocyanate, 1, 6-hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate or a mixture of two or contains more of the aforementioned isocyanates, and/or wherein the polyol component comprises a polyol selected from a polyether polyol, a polyester polyol, a polyetherester polyol, a polyethercarbonate polyol, or a mixture of two or more of the foregoing polyols. A method according to any one of the preceding claims, wherein the chemolysis reagent is ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,

Methyl glycol, triethylene glycol, glycerol, 2-methyl-1, 3-propanediol or a mixture of two or more of the aforementioned alcohols.