Purification of of plastic solvolysis mixtures

Abstract

The invention relates to a process for purifying a plastic solvolysis mixture to obtain a mixture of substances. The invention also relates to the use thereof in the production of plastics.

Description

[0001] Purification of plastic solvolysis mixtures

[0002] The present invention relates to a process for purifying a plastic solvolysis mixture to obtain a mixture of substances and its use for producing plastics.

[0003] Plastics are ubiquitous materials and are used extensively as packaging materials, fibers, insulation, components of paints and adhesives, foams, and construction materials, for example, in automotive or furniture manufacturing. Plastics are typically based largely on petrochemical raw materials. Recycling processes are becoming increasingly important, particularly in times of increasing resource scarcity, but also in light of the problem of rising environmental pollution.

[0004] Plastics recycling can involve mechanical, thermal, or chemical degradation. In chemical degradation, the plastics are broken down into their monomers through chemical reactions, which can be reused as reactants in a variety of chemical processes. However, the economic significance of chemical recycling is limited by the process complexity and associated costs. In particular, complex purification processes are required to separate the resulting plastic degradation products from the chemicals used, such as solvents and catalysts.

[0005] The degradation of plastics and plastic waste by solvolysis (such as glycolysis, alcoholysis, acidolysis, aminolysis, and hydrolysis) with the addition of low-molecular-weight degradation reagents such as glycols, alcohols, acids, amines, or water is well known. The degradation reagents are generally used in excess to achieve the most quantitative conversion possible. The resulting plastic solvolysis mixtures are mixtures of various low-molecular-weight plastic degradation products and also contain used and unreacted degradation reagents.

[0006] Plastic solvolysis mixtures are sometimes used as a raw material in their entirety, including excess degradation reagents. For example, polyurethane (PUR) rigid foam waste is solvolyzed using glycols. The resulting mixture of ether polyols, urethanes, and free glycol is added in small quantities as a raw material in PUR rigid foam production. However, the use of these plastic solvolysis mixtures is severely limited because the excess degradation reagents negatively impact the properties of the final product during subsequent use. Other disruptive factors include byproducts of plastic degradation and catalyst, which must usually be added during solvolysis to ensure sufficient plastic degradation.

[0007] Additives such as stabilizers, which are essential for foam stabilization in the production of PU flexible and rigid foam and ensure a uniform, fine-cell foam structure, also remain in the solvolysis mixture after degradation. The stabilizers have, among other things, surface-active properties and can cause significant foam formation in the solvolysis mixture, which makes processing the solvolysis mixture considerably more difficult, if not impossible, especially under reduced pressure (< 1 bar).

[0008] There is therefore a need to improve the recycling of plastics and, in particular, to provide processes in which the plastic degradation products have lower levels of cleavage reagents and by-product residues.

[0009] To reduce the residual cleavage reagent content, the cleavage reagent was sometimes added in substoichiometric amounts. While this slightly reduces the cleavage reagent content in the plastic solvolysis mixture, the resulting mixtures are more viscous and have a high molecular weight, and still contain residual amounts of catalyst and degradation byproducts.

[0010] The plastic solvolysis mixture can also be subjected to conventional distillation to reduce the cleavage reagent content. However, after distillation, the plastic solvolysis mixtures still exist as unfavorable mixtures of plastic degradation products and may contain elevated catalyst contents. Conventional separation processes also have the disadvantage that side reactions occur due to thermal stress. The high distillation temperatures required for the most complete removal of the cleavage reagents and / or by-products have the disadvantage that the formation of polymers with high molecular weights is promoted by side and reverse reactions of the plastic degradation products. The resulting agglomerates lead to phase separation in the plastic solvolysis mixture, which limits the direct use of the plastic solvolysis mixture in the production of new polymers.

[0011] Despite the high relevance of processes for the degradation of plastics, there is currently a lack of processes that enable the separation of plastic solvolysis mixtures into sufficiently pure plastic degradation products and the recovery of cleavage reagent (solvent) under economic conditions.

[0012] It has surprisingly been found that the plastic solvolysis mixture purified according to the process of the invention can be used directly and in high proportions—if not even as the sole starting material—for the production of new plastics. The purification process of the present invention prevents the undesirable back-reaction of the plastic degradation products in the plastic solvolysis mixture, but nevertheless ensures that cleavage reagents and / or by-products are removed almost quantitatively.

[0013] Because cleavage reagents are separated quantitatively by the process according to the invention, the cleavage reagents can also be used in a significant excess and thus the solvolysis processes can be carried out without or with a greatly reduced catalyst content at low reaction times or reaction temperatures, ie more economically.

[0014] The separated cleavage reagent can be used again as a cleavage reagent for the next process (recycling).

[0015] The plastic solvolysis mixtures purified in this way are suitable as polymer raw materials in terms of both quality and technical properties (e.g. homogeneity, viscosity, storage stability, content of low-molecular monomers, by-products).

[0016] The use of the plastic solvolysis mixtures according to the invention for the production of plastics also reduces disposal costs. Overall, this creates a cycle that combines economic and ecological benefits.

[0017] A first aspect of the present invention relates to a process for purifying a plastic solvolysis mixture, comprising the steps:

[0018] (a) providing the plastic solvolysis mixture; (b) treating the plastic solvolysis mixture at a pressure of < 1 mbar and a temperature in the range of 90 to 170 °C; and

[0019] (c) removing at least one compound with a molar mass of < 250 g / mol during step (b) to obtain a mixture of substances.

[0020] The plastic solvolysis mixture provided in step (a) typically comprises plastic degradation product, solvent, in particular cleavage reagent, and optionally at least one catalyst. The plastic solvolysis mixture is preferably liquid at room temperature (20°C) and more preferably in the form of a solution. In one embodiment, the plastic solvolysis mixture provided in step (a) is subjected to solid / liquid filtration prior to step (a).

[0021] The term "plastic solvolysis mixture" used herein means that the mixture provided is obtained by solvolysis of plastic. Solvolysis reactions of plastics are known to those skilled in the art and include, for example, glycolysis, alcoholysis, acidolysis, aminolysis, or hydrolysis of plastic. The solvolysis reaction takes place with the addition of solvolysis cleavage reagents such as glycols (in glycolysis), alcohols (in alcoholysis), acids (in acidolysis), amines (in aminolysis), or water (in hydrolysis).

[0022] The plastic can be selected from the group consisting of polyurethane, polyester, polyetherester, polyamide, polycarbonate, polyisocyanurate, or a mixture thereof. In a preferred embodiment, the plastic can be selected from the group consisting of polyurethane and / or polyester, in particular polyurethane, in particular polyester polyurethane and / or polyether polyurethane.

[0023] The plastic solvolysis mixture provided in step (a) preferably comprises at least one solvent, in particular a solvolysis cleavage reagent. The cleavage reagent is preferably selected from alcohols, glycols, amines, water, or mixtures thereof. Suitable solvolysis cleavage reagents are known to the person skilled in the art.

[0024] In one embodiment, in particular in the aminolysis, the cleavage reagent is at least one polyamine, in particular at least one diamine, such as ethanediamine, propanediamine, butanediamine and / or hexanediamine, and / or a triamine, such as ethanediamine, propanetriamine, butanetriamine, pentanetriamine and / or hexanetriamine, and / or hydroxylamines such as ethanolamine, preferably a diamine. In a preferred embodiment, in particular in alcoholysis or glycolysis, the cleavage reagent is selected from at least one monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol and / or hexanol, a diol, in particular ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane, and a tetrol, in particular pentaerythrol, and hydroxycarboxylic acids, in particular ricinoleic acid and lactic acid.

[0025] In a preferred embodiment, in particular in acidolysis, the cleavage reagent is selected from at least one polycarboxylic acid, in particular a dicarboxylic acid, such as succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, heptanedicarboxylic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid and / or phthalic acid, and / or a tricarboxylic acid, such as trimelic acid, and / or at least one polycarboxylic acid anhydride, in particular a dicarboxylic acid anhydride, such as succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, such as trimelic acid anhydride, particularly preferably from at least one polycarboxylic acid, more preferably at least one dicarboxylic acid.

[0026] Hydrolysis is carried out using water as a cleavage reagent.

[0027] In one embodiment, the solvent, in particular the cleavage reagent, has a molecular weight of 15-250 g / mol, preferably 30-180 g / mol.

[0028] The content of solvent or cleavage reagent in the provided plastic solvolysis mixture can be, for example, more than 40 wt.%, preferably 50-95 wt.%, for example 70-90 wt.%, in particular in the case of an alcoholysis mixture, or 40-60 wt.%, in particular in the case of a glycolysis mixture, based on the total weight of the mixture.

[0029] In a further embodiment, the solvolysis is further carried out using at least one catalyst suitable for the degradation of plastics, in particular a basic and / or organometallic catalyst.

[0030] The at least one basic catalyst can be selected from the group consisting of alkali metal alkoxide, in particular sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide and / or potassium butoxide, alkali metal hydroxide, in particular sodium hydroxide and / or potassium hydroxide, and alkali metal acetate, in particular sodium acetate and potassium acetate.

[0031] The at least one organometallic catalyst can be selected from the group consisting of zinc acetate, magnesium acetate, cobalt acetate, tin octoate, dibutyltin dilaurate, titanium tetraisopropoxide, and titanium tetrabutoxide. A metal catalyst such as tetrabutyl titanate is present in particular when the solvent (i.e., the solvolysis reagent) is a glycol, such as diethylene glycol.

[0032] The content of catalyst in the provided plastic solvolysis mixture can be, for example, more than 0 and up to 10 wt.%, preferably 0.1-5 wt.%, in particular 0.5-3 wt.%, based on the total weight of the mixture.

[0033] In one embodiment, the solvolysis is carried out at elevated temperature, in particular at a temperature in the range of 30-300 °C, more preferably 100-250 °C, more preferably 140-220 °C, and optionally at elevated pressure, in particular at a pressure of 1-200 bar, preferably 5-50 bar, more preferably 10-30 bar.

[0034] In a further embodiment, the solvolysis is carried out in a solvolysis reactor, which preferably comprises a stirrer. The stirrer can, for example, convey axially or radially and optionally stir in one or more stages. Furthermore, the solvolysis reactor can be sealed gas-tight. In one embodiment, an oxygen-reduced or oxygen-free atmosphere can be present in the solvolysis reactor. Optionally, an inert gas atmosphere can be present in the reactor. Examples of suitable inert gases are nitrogen and noble gases, such as argon.

[0035] The plastic solvolysis mixture preferably comprises at least one plastic degradation product, at least one cleavage reagent and optionally at least one catalyst.

[0036] The plastic degradation product obtained by solvolysis can be selected from polyamines, polyols, carbamates, polycarboxylic acids, polycarboxylic acid esters, hydroxycarboxylic acids, hydroxycarboxylic acid esters, or mixtures thereof. Preferably, the plastic degradation product is selected from polyamines, polyols, carbamates, polycarboxylic acids, and / or polycarboxylic acid esters. In a preferred embodiment, the plastic degradation product comprises at least one polyol and at least one polyamine.

[0037] The plastic degradation product can have a weight-average molecular weight of 50-50,000 g / mol, preferably 80-10,000 g / mol.

[0038] The content of plastic degradation product in the provided plastic solvolysis mixture can be, for example, up to 70 wt.%, preferably 5-60 wt.%, such as 5-20 wt.%, in particular in a glycolysis mixture, or 40-60 wt.%, in particular in an alcoholysis mixture, based on the total weight of the mixture.

[0039] In one embodiment, the plastic degradation product comprises at least one polyol, particularly when the solvolyzed plastic is a polyurethane and / or polyester. The term "polyol" refers to compounds having at least 2, i.e., 2, 3, 4, or more, hydroxyl groups. A polyol within the meaning of the invention is preferably a polyether polyol, particularly aliphatic, e.g., polyethylene glycol or polypropylene glycol, or aromatic polyether polyol, polyester polyol, particularly aliphatic or aromatic polyester polyol, diethylene glycol, dipropylene glycol, C1-6 alkylene glycol, particularly hexanediol, butanediol, ethylene glycol, and neopentyl glycol, C1-8 alkylene polyol, particularly trimethylolpropane and glycerol, or a mixture thereof.

[0040] In one embodiment, the plastic degradation product comprises at least one polycarboxylic acid, particularly when the solvolyzed plastic is a polyester. A polycarboxylic acid within the meaning of the invention can, for example, comprise an aromatic polycarboxylic acid, preferably phthalic acid or terephthalic acid, or an aliphatic polycarboxylic acid, preferably C1-12 alkylenedicarboxylic acid, more preferably C1-6 alkylenedicarboxylic acid, e.g., adipic acid, succinic acid, or glutaric acid, esters, or mixtures thereof.

[0041] In one embodiment, the plastic degradation product comprises at least one hydroxy-functionalized carboxylic acid, particularly when the solvolyzed plastic is a polyester. A hydroxy-functionalized carboxylic acid within the meaning of the invention can, for example, comprise a hydroxyhexamethylenecarboxylic acid, a hydroxypropyl carboxylic acid such as lactic acid, a hydroxyfatty acid, or hydroxybutyric acid.

[0042] In one embodiment, the plastic degradation product comprises at least one polyamine, particularly when the solvolyzed plastic is a polyamide and / or a polyurethane. The term "polyamine" refers to compounds having at least 2, i.e., 2, 3, 4 or more, preferably 2 or 3, amino groups. A polyamine within the meaning of the invention can, for example, comprise an aromatic diamine, preferably 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, or aniline, an aliphatic polyamine, for example a linear aliphatic polyamine such as hexamethylenediamine and triethylenetetramine, or a cyclic aliphatic polyamine such as isophoronediamine.

[0043] In one embodiment, the plastic solvolysis mixture comprises: i. at least one polyol and / or polyamine, preferably having a molar mass in the range of 50-10,000 g / mol, more preferably 60-6,000 g / mol; and ii. at least one cleavage reagent selected from alcohol, polycarboxylic acid, polycarboxylic anhydride, polyamine, and / or water, having a molar mass of <250 g / mol, preferably in the range of 15 to 180 g / mol.

[0044] The polyol in component i. is preferably an aliphatic polyol, an aromatic polyol, a polyester polyol and / or a polyether polyol, more preferably an aliphatic diol, an aromatic diol, a polyester diol and / or a polyether diol.

[0045] The polyol in component i. can have a molar mass in the range of 50-10,000 g / mol, preferably 60-6,000 g / mol.

[0046] The polyamine in component i. is preferably an aliphatic polyamine, an aromatic polyamine, a polyesterpolyamine and / or a polyetherpolyamine, more preferably an aliphatic diamine, an aromatic diamine, a polyesterdiamine and / or a polyetherdiamine.

[0047] The polyamine in component i. can have a molar mass in the range of 20-1000 g / mol, preferably 60-600 g / mol.

[0048] The at least one alcohol in component ii. is preferably at least one monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol and / or hexanol, hydroxycarboxylic acid, hydroxylamine, a diol, in particular ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane, and / or a polyol, more preferably at least one monoalcohol and / or a diol, more preferably at least one diol.

[0049] The at least one polycarboxylic acid in component ii. is preferably at least one dicarboxylic acid, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid, and / or a tricarboxylic acid, in particular trimelitic acid.

[0050] The at least one polycarboxylic acid anhydride in component ii. is preferably at least one dicarboxylic acid anhydride, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, in particular trimelitic acid anhydride.

[0051] The at least one polyamine in component ii. is preferably at least one diamine, in particular ethanediamine, propanediamine, butanediamine, pentanediamine and / or hexanediamine, and / or a triamine, in particular ethanediamine, propanetriamine, butanetriamine and / or hexanetriamine, more preferably at least one diamine.

[0052] Component i. and component ii. are preferably different.

[0053] In a further embodiment, the plastic solvolysis mixture further comprises: iii. at least one catalyst, particularly suitable for degrading plastics, preferably at least one basic catalyst and / or an organometallic catalyst; and iv. optionally at least one additive, particularly selected from the group consisting of filler, pigment, flame retardant, plasticizer, and stabilizer.

[0054] The at least one basic catalyst in component iii. can be an alkali metal alkoxide, in particular sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide and / or potassium butoxide, alkali metal hydroxide, in particular sodium hydroxide and / or potassium hydroxide, and / or alkali metal acetate, in particular sodium acetate and / or potassium acetate.

[0055] The at least one organometallic catalyst in component iii can be selected from the group consisting of zinc acetate, magnesium acetate, cobalt acetate, zinc acetate, magnesium acetate, cobalt acetate, tin octoate, dibutyltin dilaurate, titanium tetraisopropoxide and titanium tetrabutoxide.

[0056] Component i. preferably makes up 5-80 wt.% of the total mass of the plastic solvolysis mixture.

[0057] Component ii. preferably makes up 20-95 wt.% based on the total mass of the plastic solvolysis mixture.

[0058] Component iii. preferably makes up 0-30 wt.%, more preferably 1-20 wt.%, based on the total mass of the plastic solvolysis mixture.

[0059] Component iv. preferably makes up 0-40 wt.%, more preferably 1-30 wt.% based on the total mass of the plastic solvolysis mixture.

[0060] The pressure in step (b) may be < 1 mbar, preferably < 0.5 mbar, preferably < 0.1 mbar, more preferably from 0.0001 to 0.1 mbar.

[0061] The temperature in step (b) may be in the range of 60-170 °C, preferably 80-150 °C, more preferably 90-130 °C.

[0062] In a further embodiment, the plastic solvolysis mixture is treated in step (b) for 2-10,000 seconds, preferably 5-5,000 seconds, more preferably 10-500 seconds.

[0063] In a further embodiment, the process is carried out in a thin film evaporator or a short path evaporator, more preferably in a short path evaporator.

[0064] The above-mentioned evaporators basically comprise a heated surface as a heating device for transferring the substance to be separated from a mixture from the liquid phase into the gas phase (with formation of vapors) as well as a condensation device at which the separated gas phase (the vapors) can be condensed again.

[0065] In a thin-film evaporator, the mixture to be separated is typically distributed from above onto the heating jacket via a rotating distribution system mounted on a cylindrical heating jacket. Due to gravity, the mixture flows down the inner wall of the heating jacket and forms a liquid film. A mechanical wiping system inside the heating jacket can ensure even distribution and continuous mixing of the mixture on the inner wall of the heating jacket. The lower-boiling component of the mixture evaporates from the liquid film and forms the vapors. The vapors are discharged from the evaporator and fed to a downstream external condenser for condensation. This process is characterized in particular by a short residence time, low operating pressures, and thus low evaporation temperatures.

[0066] In contrast to a thin-film evaporator, the condenser in a short-path evaporator is typically located inside the evaporator's heating jacket. The vapors escaping from the liquid film now only have to travel a short distance within the evaporator before condensing on the surface of the internal condenser. Since the pressure difference required for vapor transport over this short distance is extremely small, very low working pressures can be achieved. The necessary evaporation temperatures are therefore very low.

[0067] The process according to the invention can be a continuous process.

[0068] The at least one compound in step (c) is preferably a cleavage reagent and more preferably has a molar mass of 25-250 g / mol, more preferably of 30-200 g / mol.

[0069] The at least one compound in step (c) preferably comprises a cleavage reagent and is more preferably selected from the group consisting of alcohol, polycarboxylic acid, polycarboxylic anhydride, carboxylic acid ester, polyamine, water and formaldehyde.

[0070] The alcohol in step (c) can be a monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol and / or hexanol, a diol, in particular ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane and / or a polyol, preferably a monoalcohol and / or a diol, more preferably a diol. The polycarboxylic acid in step (c) can be a dicarboxylic acid, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid, and / or a tricarboxylic acid, in particular trimelitic acid.

[0071] The polycarboxylic acid anhydride in step (c) may be a dicarboxylic acid anhydride, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, in particular trimelitic acid anhydride.

[0072] The polyamine in step (c) may be a diamine, in particular ethanediamine, propanediamine, butanediamine, hexanediamine, toluenediamine and / or diaminodiphenylmethane, and / or a triamine, in particular ethanediamine, propanetriamine, butanetriamine and / or hexanetriamine, preferably a diamine.

[0073] The mixture obtained after step (c) is essentially free of the at least one compound in step (c). "Essentially free of the at least one compound in step (c)" preferably means that the mixture obtained after step (c) contains 0.05-50 wt.%, more preferably 0.1-20 wt.%, more preferably 0.5-8 wt.%, of the at least one compound in step (c), based on the total weight of the mixture obtained after step (c).

[0074] In a preferred embodiment, the proportion of the compound in the mixture of substances after step (c) is reduced by 80%, in particular 80% by weight, compared to the proportion of the compound in the plastic solvolysis mixture after step (a). The content of the compound can be determined using methods known in the art for quantifying substances in a mixture, such as GC-MS.

[0075] The mixture obtained after step (c) preferably has a hydroxyl number (OHN) in the range of 20-600 mg KOH, more preferably in the range of 50 to 95 mg KOH, more preferably 60-90 mg KOH. The OHN is a measure of the hydroxyl group content in organic substances. Methods for determining the OHN are known in the art and are described, for example, in DIN 53240.

[0076] The at least one compound removed in step (c) can be reused as a cleavage reagent in a solvolysis reaction. Due to the high cost of cleavage reagents for solvolysis, especially in the case of polyamines, separating unreacted cleavage reagent from a plastic solvolysis mixture is particularly economically advantageous.

[0077] Before or after the process according to the invention, catalyst can be recovered by suitable means known to the person skilled in the art, such as filtration, and optionally subjected to solvolysis.

[0078] The purification process according to the invention is superior to the purification processes known in the prior art.

[0079] Typically, after solvolysis, substances such as cleavage reagents or byproducts are present in the plastic solvolysis mixture, which complicate or even prevent the immediate further processing of the plastic solvolysis mixture for the production of new plastics. The process according to the invention is capable of almost quantitatively removing these substances from the plastic solvolysis mixture. Surprisingly, this simultaneously ensures that the side reactions that occur during conventional purification, leading to polymer or higher molecular weight byproducts, can be largely avoided. As a result, the purified plastic solvolysis mixture remains low-viscosity, homogeneous, and storage-stable, without the need for the addition of stabilizers such as emulsifiers.

[0080] In contrast to conventional recyclates, the substance mixtures obtainable by the process according to the invention can be used in larger concentrations or even as the sole building block for the production of plastics, such as polyurethane, polyester, polycarbonate and / or polyamide, more preferably polyurethane and / or polyester, even more preferably polyurethane.

[0081] A further advantage of the process according to the invention is that the cleavage reagents can easily be used in excess during the solvolysis prior to purification, as effective purification is ensured thereafter. The solvolysis itself can then be carried out quantitatively at low temperatures and with minimal catalyst additions, or even without catalyst.

[0082] A further aspect of the invention therefore relates to the use of the mixture obtained after step (c) for producing a polymer, in particular a polyurethane, polyester, polycarbonate and / or polyamide, more preferably a polyurethane and / or polyester, even more preferably a polyurethane. A further aspect of the invention relates to the mixture obtainable by the process described above.

[0083] The polymer products produced in this way are particularly low in volatile substances. This eliminates the emission of harmful substances from the polymer products and ensures consumer safety.

[0084] Furthermore, the present invention will be explained by the following examples.

[0085] Example 1 (comparison example)

[0086] An excess of 500 g of dipropylene glycol (decomposition reagent) is added and heated to 200°C. 500 g of polyurethane flexible foam residue (standard foam based on TDI and ether polyols for mattress production) are added to the 200°C heated mixture over a period of 1 h while stirring and under a nitrogen atmosphere.

[0087] After a further reaction time of 2 h, a homogeneous, brown, clear polyol mixture (plastic solvolysis mixture) with a hydroxyl number of 434 mg KOH / g and a viscosity of 340 mPas / 25°C is formed.

[0088] Due to the high proportion of cleavage reagent and the associated high hydroxyl number, this mixture cannot substitute the standard polyols used in flexible foam production (hydroxyl number 28-56 mg KOH / g).

[0089] Even with the addition of 1-5% of this mixture in flexible foam formulations (substitution of the ether polyol), the flexible foam properties (e.g. compression hardness) change drastically, so that a return of the mixture to the flexible foam production is not possible.

[0090] Example 2 (comparison example)

[0091] To reduce the hydroxyl number of the plastic solvolysis mixture, the decomposition reagent dipropylene glycol is reduced. To achieve sufficient reaction times, the temperature is increased and a catalyst is added. 200 g of dipropylene glycol (decomposition reagent) are mixed with 0.1% catalyst (titanium butylate) and heated to 210°C.

[0092] 400g of polyurethane flexible foam residues (standard flexible foam based on TDI and ether polyol) are added to the 210°C hot feed under N2 (inertization) within 4 hours.

[0093] After a further reaction time of 4 h, a highly viscous, agglomerated plastic solvolysis mixture with a hydroxyl number of 278 mg KOH / g is formed.

[0094] Even a small reduction of the cleavage reagent leads to longer reaction times due to the equilibrium reaction and to coarsely agglomerated, particle-containing and highly viscous plastic solvolysis mixture, which is not usable for foam production.

[0095] Example 3 (comparison example)

[0096] 500 g of dipropylene glycol and 500 g of flexible polyurethane foam are reacted according to Example 1.

[0097] After a post-reaction of 2h, a vacuum is applied at 200°C and the cleavage reagent is distilled off under vacuum.

[0098] After a distillation time of 10 hours at a final vacuum of 50 mbar absolute, 240 g of dipropylene glycol were distilled off. Due to the long distillation time at elevated temperatures, the thermal stress increased the concentration of undesirable, toxic byproducts such as TDA (toluenediamine). The equilibrium shift during the distillation of the cleavage reagent resulted in an increase in molecular weight, resulting in increased viscosity and phase separation.

[0099] Due to the reduction / distillation of the cleavage reagent, the solubility / miscibility of the mixture changes, and at higher temperatures, the components of the mixture tend to agglomerate / phase separate. The original, clear, and homogeneous dispersion becomes a highly agglomerated, highly viscous dispersion with agglomerates larger than 100 μm, which is unsuitable as a polyol component for foam production.

[0100] Example 4: (Comparison example)

[0101] 500 g of dipropylene glycol and 500 g of flexible polyurethane foam are reacted according to Example 1.

[0102] To reduce the hydroxyl number, the cleavage reagent is distilled off under vacuum. To avoid molecular weight buildup and agglomeration / phase separation (Example 3), distillation is carried out at low temperatures: The plastic solvolysis mixture was cooled, and the cleavage reagent was distilled off at 120°C and 13 mbar.

[0103] After 1 hour of distillation, the distillation stopped. Only 3% of the cleavage reagent could be distilled off, and the hydroxyl number of the mixture was reduced to only 425 mg KOH / g. The bottom temperature was increased to 130°C, and the distillation continued at 13 mbar. The bottom temperature was further increased. After 4 hours of distillation at 130°C bottom temperature and 13 mbar vacuum, the distillation stopped after 3.5 hours. Only 22.6% of the cleavage reagent could be distilled off. The hydroxyl number was reduced to only 369 mg KOH / g. The mixture is homogeneous and clear.

[0104] The bottom temperature was increased again by 10°C to 140°C to distill off more cleavage reagent. After a further 1.5 hours of distillation at 140°C, a further 35.7% of cleavage reagent was distilled off before distillation stopped. The hydroxyl number decreased to only 282 mg KOH / g. The mixture is no longer clear, but contains coarse agglomerates >100 pm.

[0105] The cleavage reagent could not be separated quantitatively. Only 61.2% of the cleavage reagent could be distilled off, thus reducing the hydroxyl number to only 282 mg KOH / g. Therefore, this mixture cannot be used as a raw material for flexible foam production, or only to a significant extent.

[0106] To distill at all, higher bottom temperatures were necessary, which in turn led to the detrimental formation of higher molecular weights, agglomerates / phase separations, and byproducts. Example 5:

[0107] 5000 g of dipropylene glycol and 5000 g of flexible polyurethane foam are reacted according to Example 1. After a post-reaction of 2 h, the resulting plastic solvolysis mixture with a hydroxyl number of 436 mg KOH / g is cooled and continuously fed into a short-path evaporator as feed.

[0108] At an evaporator jacket temperature of 90°C and a pressure of 0.04 mbar, 42.6 wt.% was continuously distilled off (85.2% of the cleavage reagent).

[0109] The remaining mixture (57.4%) is liquid, finely dispersed (disperse fractions <10 pm), and absolutely stable in storage. The hydroxyl number of the product is 132 mg KOH / g.

[0110] The mixture can be used directly as a polyol component for the production of polyurethane plastics. Due to the low distillation temperatures, the resulting mixtures are liquid, homogeneous, and phase-stable and storage-stable. At these low temperatures, the reverse reaction (molecular mass buildup) is significantly inhibited kinetically. Likewise, the mixtures are phase-stable at these low temperatures, meaning agglomeration / separation does not occur.

[0111] Due to the low hydroxyl number, higher additions of the mixture of substances in the range of at least 20-50% are also easily possible in the production of PUR flexible foam.

[0112] Due to the ideal process conditions in the thin-film / short-path evaporator, the cleavage reagent can be distilled quantitatively (>85%) and economically even at advantageous low temperatures.

[0113] The separated cleavage reagent (here dipropylene glycol) has a purity of >97% and can be used as a redistillate again as a cleavage reagent.

[0114] Example 6:

[0115] 5000 g of dipropylene glycol and 5000 g of PUR flexible foam are reacted analogously to Example 5, cooled and added as feed to a short-path evaporator at 80°C.

[0116] In contrast to Example 5, the evaporator temperature is increased to 170°C and then cooled to 80°C. Higher distillation temperatures, as in Examples 3 and 4 (already at 140°C), lead to detrimental agglomeration and molecular weight buildup with longer distillation times.

[0117] At an evaporator jacket temperature of 170°C and a pressure of 0.04 mbar, 48.4 wt.% (96.8% of the cleavage reagent) was continuously distilled off. The remaining mixture (51.6%) is liquid, finely dispersed, and absolutely stable in storage. The hydroxyl number of the mixture is 92 mg KOH / g. The viscosity is 3605 mPas / 25°C.

[0118] Due to the extremely short residence time in the evaporator of only 2 min, the negative effects such as molecular weight buildup and / or agglomeration / separation could be avoided even at higher distillation temperatures.

[0119] Example 7:

[0120] A plastic solvolysis mixture made from 500g diethylene glycol and 500g PUR integral foam contains 0.12% 1,4-dioxane, which is formed as a by-product by the acid-catalyzed reaction of diethylene glycol.

[0121] 1,4-Dioxane is classified as carcinogenic and therefore detrimental to plastic solvolysis products. After distillation in the short-path / thin-film evaporator according to Example 5, the 1,4-dioxane content is reduced to <0.01%. This means that in addition to distilling off the cleavage reagent, byproducts or fractions are also advantageously separated, thus obtaining purer and low-emission mixtures.

[0122] Example 8:

[0123] 500 g of polyurethane foam (containing foam stabilizer) are reacted with catalyst and 500 g of diethylene glycol as described in Example 1 (glycolysis). The resulting solvolysis mixture is subjected to low temperatures and decreasing pressure in a conventional distillation apparatus to distill off free diethylene glycol. At a pressure of 160 mbar (absolute) and a bottom temperature of 141 °C, slight foam formation is observed. With decreasing pressure (110 mbar) and increasing bottom temperature (150 °C), foam formation increases significantly. At pressures below 106 mbar and a bottom temperature of 150 °C, foam formation was so severe that distillation of diethylene glycol from the solvolysis raw mixture was no longer possible. Increasing the stirrer speed did not provide any relief. The addition of defoamers is not possible, as these prevent the subsequent polyurethane foam production with the solvolysis mixture according to the invention.

[0124] The solvolysis mixture can only be distilled extremely slowly (>48 h) at pressures > 100 mbar. The long distillation times lead to undesirable polymer degradation.

[0125] Example 9:

[0126] The purification of a solvolysis mixture according to Example 8 was carried out using a thin-film evaporator.

[0127] Even at temperatures of 150°C and pressures < 1 mbar, no significant foam formation occurs in the thin-film evaporator. Compared to Example 8, the purification time in the thin-film evaporator can be reduced by a factor of 8-12 for the same volume of solvolysis raw mixture and identical diethylene glycol content in the purified product.

[0128] The solvolysis mixture thus produced can be used for foam production.

[0129] The following points are the subject of the invention:

[0130] 1. A process for purifying a plastic solvolysis mixture, comprising the steps:

[0131] (a) providing the plastic solvolysis mixture;

[0132] (b) treating the plastic solvolysis mixture at a pressure < 1 mbar and a temperature in the range of 90 to 170 °C; and

[0133] (c) removing at least one compound with a molar mass of < 250 g / mol during step (b) to obtain a mixture of substances.

[0134] 2. The process according to point 1, wherein the plastic solvolysis mixture is obtainable by solvolysis of at least one polymer selected from the group consisting of polyurethane, polyester, polyetherester, polyamide, polycarbonate, polyisocyanurate, preferably polyurethane and polyester, more preferably polyurethane, in particular polyester polyurethane and / or polyether polyurethane. 3. The process according to point 2, wherein the solvolysis is a glycolysis, alcoholysis, acidolysis, aminolysis, or hydrolysis, preferably an alcoholysis or an aminolysis, more preferably an alcoholysis.

[0135] 4. Process according to point 3, wherein the alcoholysis is carried out using at least one monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol and / or hexanol, a diol, in particular ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane, and / or a tetrol, in particular pentaerythrol and / or hydroxycarboxylic acid, in particular ricinoleic acid and lactic acid, preferably using at least one monoalcohol and / or a diol, more preferably using at least one diol, as cleavage reagent.

[0136] 5. The process according to point 3, wherein the acidolysis is carried out using at least one polycarboxylic acid, in particular a dicarboxylic acid, such as succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, heptanedicarboxylic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid and / or phthalic acid, and / or a tricarboxylic acid, such as trimelic acid, and / or using at least one polycarboxylic acid anhydride, in particular a dicarboxylic acid anhydride, such as succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, such as trimelic acid anhydride, particularly preferably using at least one polycarboxylic acid, more preferably using at least one dicarboxylic acid, as cleavage reagent.

[0137] 6. The process according to item 3, wherein the aminolysis is carried out using at least one polyamine, in particular at least one diamine, such as ethanediamine, propanediamine, butanediamine and / or hexanediamine, and / or a triamine, such as ethanediamine, propanetriamine, butanetriamine, pentanetriamine, hexanetriamine and / or hydroxylamine, such as ethanolamine, preferably using at least one diamine, as the cleavage reagent. The process according to item 3, wherein the hydrolysis is carried out using water as the cleavage reagent. The process according to any one of items 2 to 7, wherein the solvolysis is further carried out using at least one catalyst suitable for the degradation of plastics, in particular a basic and / or organometallic catalyst.The process according to item 8, wherein the at least one basic catalyst is selected from the group consisting of alkali metal alkoxide, in particular sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide and / or potassium butoxide, alkali metal hydroxide, in particular sodium hydroxide and / or potassium hydroxide, and alkali metal acetate, in particular sodium acetate and potassium acetate. The process according to item 8, wherein the at least one organometallic catalyst is selected from the group consisting of zinc acetate, magnesium acetate, cobalt acetate, tin octoate, dibutyltin dilaurate, titanium tetraisopropoxide and titanium tetrabutoxide. The process according to any one of items 2-10, wherein the solvolysis is carried out at elevated temperature, in particular at a temperature in the range 30-300°C, preferably 100-250°C, more preferably 140-220°C; and optionally.at elevated pressure, in particular at a pressure of 1-200 bar, preferably 5-50 bar, more preferably 10-30 bar. Process according to one of the preceding points, wherein the plastic solvolysis mixture comprises at least one plastic degradation product, at least one cleavage reagent and optionally at least one catalyst. Process according to one of the preceding points, wherein the plastic solvolysis mixture comprises: i. at least one polyol and / or polyamine, preferably having a molar mass in the range of 50-10,000 g / mol, more preferably 60-6,000 g / mol; and ii. at least one cleavage reagent selected from alcohol, polycarboxylic acid, polycarboxylic anhydride, polyamine and / or water, having a molar mass of < 250 g / mol, preferably in the range of 15 to 180 g / mol. 14. Process according to point 13, wherein the polyol in component i.an aliphatic polyol, an aromatic polyol, a polyester polyol and / or a polyether polyol, preferably an aliphatic diol, an aromatic diol, a polyester diol and / or a polyether diol.

[0138] 15. Process according to any one of items 13-14, wherein the polyol in component i. has a molar mass in the range of 50-10,000 g / mol, more preferably 60-6,000 g / mol.

[0139] 16. Process according to any one of items 13-15, wherein the polyamine in component i. is an aliphatic polyamine, an aromatic polyamine, a polyesterpolyamine and / or a polyetherpolyamine, preferably an aliphatic diamine, an aromatic diamine, a polyesterdiamine and / or a polyetherdiamine.

[0140] 17. Process according to any one of items 13-16, wherein the polyamine in component i. has a molar mass in the range of 20-1000 g / mol, more preferably 60-600 g / mol.

[0141] 18. Process according to any one of items 13-17, wherein the at least one alcohol in

[0142] Component ii. at least one monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol and / or hexanol, hydroxycarboxylic acid,

[0143] Hydroxylamine, a diol, especially ethylene glycol, diethylene glycol,

[0144] Polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane, and / or a polyol, preferably at least one monoalcohol and / or one diol, more preferably at least one diol.

[0145] 19. The process according to any one of items 13-18, wherein the at least one polycarboxylic acid in component ii is at least one dicarboxylic acid, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid, and / or a tricarboxylic acid, in particular trimelitic acid.

[0146] 20. Process according to any one of points 13-19, wherein the at least one polycarboxylic acid anhydride in component ii. is at least one dicarboxylic acid anhydride, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, in particular trimelitic acid anhydride. Process according to any one of points 13-20, wherein the at least one polyamine in component ii. is at least one diamine, in particular ethanediamine, propanediamine, butanediamine, pentanediamine and / or hexanediamine, and / or a triamine, in particular ethanetriamine, propanetriamine, butanetriamine and / or hexanetriamine, preferably at least one diamine. Process according to any one of points 13-21, wherein component i. and component ii. are different. Process according to any one of points 13-22, wherein the plastics solvolysis mixture further comprises: iii.at least one catalyst, particularly suitable for degrading plastics, preferably at least one basic catalyst and / or an organometallic catalyst; and iv. optionally at least one additive, particularly selected from the group consisting of filler, pigment, flame retardant, plasticizer, and stabilizer. The process according to item 23, wherein the at least one basic catalyst comprises at least one alkali metal alkoxide, particularly sodium methoxide.

[0147] Potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide and / or potassium butoxide, alkali metal hydroxide, in particular sodium hydroxide and / or potassium hydroxide, and / or alkali metal acetate, in particular sodium acetate and / or potassium acetate. Process according to item 23, wherein the at least one organometallic catalyst is selected from the group consisting of zinc acetate, magnesium acetate, cobalt acetate, tin octoate, dibutyltin dilaurate, titanium tetraisopropoxide and titanium tetrabutoxide. Process according to any one of items 13 to 25, wherein component i. makes up 5-80 wt.% based on the total mass of the plastic solvolysis mixture. 27. Process according to any one of items 13 to 26, wherein component ii. makes up 20-95 wt.% based on the total mass of the plastic solvolysis mixture.

[0148] 28. Process according to any one of items 23 to 27, wherein component iii. constitutes 0-30 wt.% based on the total mass of the plastic solvolysis mixture.

[0149] 29. Process according to any one of items 23 to 28, wherein component iv. constitutes 0-40 wt.% based on the total mass of the plastic solvolysis mixture.

[0150] 30. A process according to any one of the preceding points, wherein the pressure in step (b) is < 1 mbar, preferably < 0.5 mbar, preferably < 0.1 mbar, more preferably from 0.0001 to 0.1 mbar.

[0151] 31. A process according to any one of the preceding points, wherein the temperature in step (b) is in the range of 60-170 °C, preferably 80-150 °C, more preferably 90-130 °C.

[0152] 32. Process according to one of the preceding points, wherein the plastic solvolysis mixture is treated in step (b) for 2-10,000 seconds, preferably 5-5,000 seconds, particularly preferably 10-500 seconds.

[0153] 33. Process according to one of the preceding points, wherein the process is carried out in a thin-film evaporator or a short-path evaporator, preferably in a short-path evaporator.

[0154] 34. A process according to any one of the preceding points, wherein the process is a continuous process.

[0155] 35. Process according to one of the preceding points, wherein the at least one compound in step (c) has a molar mass of 25-250 g / mol, preferably of 30-200 g / mol.

[0156] 36. The method according to any one of the preceding points, wherein the at least one compound in step (c) comprises a cleavage reagent and is preferably selected from the group consisting of alcohol, polycarboxylic acid, polycarboxylic anhydride, carboxylic acid ester, polyamine, water, and formaldehyde. 37. The method according to point 36, wherein the alcohol in step (c) is a monoalcohol, in particular methanol, ethanol, propanol, butanol, pentanol, and / or hexanol, a diol, in particular ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, pentanediol, and / or hexanediol, a triol, in particular glycerol and / or trimethylolpropane, and / or a polyol, preferably a monoalcohol and / or a diol, more preferably a diol.

[0157] 38. The process according to item 36, wherein the polycarboxylic acid in step (c) is a dicarboxylic acid, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid, and / or a tricarboxylic acid, in particular trimelitic acid.

[0158] 39. The process according to item 36, wherein the polycarboxylic acid anhydride in step (c) is a dicarboxylic acid anhydride, in particular succinic acid, glutaric acid, adipic acid, hexanedicarboxylic acid, azelaic acid and / or phthalic acid anhydride, and / or a tricarboxylic acid anhydride, in particular trimelitic acid anhydride.

[0159] 40. Process according to item 36, wherein the polyamine in step (c) is a diamine, in particular ethanediamine, propanediamine, butanediamine, hexanediamine,

[0160] Toluenediamine and / or diaminodiphenylmethane, and / or a triamine, in particular ethanetriamine, propanetriamine, butanetriamine and / or hexanetriamine, preferably a diamine.

[0161] 41. Process according to any one of the preceding points, wherein the mixture of substances obtained after step (c) contains 0.05-50 wt.%, preferably 0.1-20 wt.%, more preferably 0.5-8 wt.%, of the at least one compound in step (c), based on the total weight of the mixture of substances obtained after step (c).

[0162] 42. Process according to one of the preceding points, wherein the proportion of the compound in the mixture of substances after step (c) is reduced by 80% compared to the proportion of the compound in the plastic solvolysis mixture after step (a).

[0163] 43. Process according to one of the preceding points, wherein the mixture obtained after step (c) has a hydroxyl number (OHN) in the range of 20-600 mg KOH, preferably in the range of 50 to 95 mg KOH, more preferably 60-90 mg KOH. Use of the mixture obtained according to point 1 (c) for producing a polymer, in particular a polyurethane, polyester, polycarbonate and / or

[0164] Polyamide, more preferably a polyurethane and / or polyester, even more preferably a polyurethane. A mixture of substances obtainable by a process according to any one of items 1-43.

Claims

Claims 1. A method for purifying a polymer solvolysis mixture, comprising the steps of: a. Providing the polymer solvolysis mixture obtainable by solvolysis of at least one polymer selected from the group consisting of polyurethane, polyester, polyether esters, polyamide, polycarbonate, and polyisocyanurate; b. Treating the polymer solvolysis mixture at a pressure < 1 mbar and a temperature in the range of 90 to 170 °C; and c. Removing at least one compound with a molar mass of < 250 g / mol during step (b) to obtain a mixture.

2. The method according to claim 1, wherein the solvolysis is glycolysis, alcoholysis, acidolysis, aminolysis or hydrolysis, preferably alcoholysis or aminolysis, more preferably alcoholysis, and is preferably carried out at elevated temperature, in particular at a temperature in the range of 30-300 °C, preferably 100-250 °C, more preferably 140-220 °C; and optionally at elevated pressure, in particular at a pressure of 1-200 bar, preferably 5-50 bar, more preferably 10-30 bar.

3. A method according to claim 1 or 2, wherein the plastic solventy mixture further comprises: v. at least one catalyst, in particular suitable for the degradation of plastics, preferably at least one basic catalyst and / or one organometallic catalyst; and vi. optionally at least one additive, in particular selected from the group consisting of filler, pigment, flame retardant, plasticizer and stabilizer.

4. A method according to any of the preceding claims, wherein the pressure in step (b) is < 1 mbar, preferably < 0.5 mbar, preferably < 0.1 mbar, more preferably from 0.0001 to 0.1 mbar, and wherein the temperature in step (b) is preferably in the range of 60-170 °C, preferably from 80-150 °C, more preferably from 90-130 °C, and wherein the plastic solventization mixture is treated in step (b) for 2-10,000 seconds, preferably 5-5,000 seconds, more preferably 10-500 seconds.

5. Method according to one of the preceding claims, wherein the method is carried out in a thin-film evaporator or a short-path evaporator, preferably in a short-path evaporator.

6. A method according to any of the preceding claims, wherein the method is a continuous method.

7. Method according to any of the preceding claims, wherein the at least one compound in step (c) has a molar mass of 25-250 g / mol, preferably of 30-200 g / mol.

8. Method according to any of the preceding claims, wherein the at least one compound in step (c) comprises cracking reagent and is preferably selected from the group consisting of alcohol, polycarboxylic acid, polycarboxylic anhydride, carboxylic ester, polyamine, water and formaldehyde.

9. Method according to any of the preceding claims, wherein the mixture obtained after step (c) contains 0.05-50 wt.%, preferably 0.1-20 wt.%, more preferably 0.5-8 wt.%, at least one compound in step (c), based on the total weight of the mixture obtained after step (c).

10. Method according to any of the preceding claims, wherein the proportion of the compound in the mixture after step (c) is reduced by 80% compared to the proportion of the compound in the polymer solventization mixture after step (a).

11. Method according to one of the preceding claims, wherein the mixture of substances obtained after step (c) has a hydroxyl number (OHZ) in the range of 20-600 mg KOH, preferably in the range of 50 to 95 mg KOH, more preferably 60-90 mg KOH.

12. Use of the mixture obtained according to claim 1 (c) for the production of a polymer, in particular a polyurethane, polyester, polycarbonate and / or polyamide, more preferably a polyurethane and / or polyester, even more preferably a polyurethane.