Continuous process for preparation of recycled polyols from polyurethane foams

Abstract

The current invention relates to a continuous process for preparing recycled polyols from polyurethane (PUR) foam and / or polyurethane (PUR) foam waste by glycolysis using an extruder, the process comprising the steps of: mechanically grinding the PUR foams to a particle size of at least 0.2 mm and at most 50 mm; dissolving a cyclotrimerization catalyst in a polyhydric alcohol; mixing the ground PUR foams with said cyclotrimerization catalyst-polyhydric alcohol mixture to form a premixture; continuously feeding the premixture into the extruder to conduct a depolymerization reaction within the extruder to produce a glycolysate comprising polyols; and discharging and collecting said glycolysate comprising recycled polyols. The invention also relates to a method wherein the produced glycosylate is repolymerized with multifunctional isocyanates, preferably selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), cyclic tri-functional isocyanates and combinations thereof.

Description

[0001] CONTINUOUS PROCESS FOR PREPARATION OF RECYCLED POLYOLS FROM POLYURETHANE FOAMS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a continuous process for preparing recycled polyols from polyurethane (PUR) foam and / or polyurethane (PUR) foam waste by glycolysis using an extruder. In a second aspect, the present invention also relates to a use for the production of recycled polyurethane (PUR) or polyisocyanurate (PIR).

[0004] BACKGROUND

[0005] Polyurethane (PUR) foams are widely used in various industries due to their excellent insulation properties, mechanical strength, and versatility. However, the disposal of PUR foam waste poses significant environmental challenges. Traditional disposal methods, such as landfilling and incineration, are not sustainable and contribute to environmental pollution and resource depletion. Recycling of PUR foam waste is a desirable alternative, but existing methods often involve complex, time-consuming, and solvent-intensive processes. These methods may also require high energy consumption and specialized equipment, making them economically unfeasible for large-scale applications. Furthermore, the quality and properties of the recycled polyols produced by conventional methods may not be consistent, limiting their potential for reuse in high-performance applications. There is a growing need for processes that can efficiently recycle polyurethane (PUR) foams into valuable products.

[0006] The present invention aims to resolve at least some of the problems and disadvantages mentioned above.

[0007] SUMMARY OF THE INVENTION

[0008] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates in a first aspect to a continuous process for preparing recycled polyols from polyurethane (PUR) foam and / or polyurethane (PUR) foam waste by glycolysis using an extruder. Preferred embodiments of the device are shown in any of the claims 2 to 14.

[0009] The present invention provides a continuous process for the preparation of recycled polyols from polyurethane (PUR) foam and polyurethane (PUR) foam waste through glycolysis using an extruder. The process is initiated by mechanically grinding polyurethane (PUR) foams to achieve a particle size ranging from at least 0.2 mm to at most 50 mm. This step ensures that the foams are adequately prepared for the subsequent reactions and can be efficiently processed in the extruder.

[0010] Once the polyurethane (PUR) foams have been ground to the desired particle size, the next step involves dissolving a cyclotrimerization catalyst in a polyhydric alcohol. Preferably, the catalyst is dissolved at an elevated temperature, more preferably at least 100°C, more preferably at least 150°C, more preferably at least 180°C, most preferably at between 200°C to 220 °C, to ensure complete dissolution and stability of the solution. The choice of polyhydric alcohol is crucial to the success of the process, and in this invention, the alcohols used include diols, triols, and higher functionality alcohols. A preferred polyhydric alcohol is dipropylene glycol, which has been shown to be particularly effective in facilitating the glycolysis reaction.

[0011] The ground polyurethane (PUR) foams are then mixed with the catalyst-polyhydric alcohol solution to form a premixture. After dissolution, the catalyst-polyhydric alcohol solution remains stable and can be mixed with the ground polyurethane (PUR) foams even at room temperature. This premixture is continuously fed into the extruder, where the depolymerization reaction takes place. The extruder operates under specific conditions, including a temperature range of 150°C to 250°C, with a preferred range of 200°C to 220°C. The pressure within the extruder is maintained at a maximum of 50 bar, with a more preferred maximum pressure of 30 bar. The residence time of the reaction within the extruder is less than 30 minutes, and ideally less than 15 minutes. This short residence time is one of the key advantages of the invention, as it allows for rapid processing while maintaining the quality of the recycled polyols. Upon completion of the depolymerization reaction, the glycolysate comprising polyols is discharged from the extruder and collected. The invention also contemplates the repolymerization of the glycolysate with multifunctional isocyanates to produce new polyurethane (PUR) materials. The isocyanates used in this process are preferably selected from 4,4'-methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), cyclic trifunctional isocyanates and combinations thereof.

[0012] In addition to the main components, auxiliary additives such as stabilizers, flame retardants, plasticizers, fillers, antioxidants, UV stabilizers, and colorants can be mixed into the premixture before the depolymerization reaction. These additives can enhance the properties of the resulting recycled polyols formulation and allow for customization based on the intended end-use applications. The process described in this invention is particularly well-suited for the recycling of rigid polyurethane (PUR) foams. The use of the extruder is a critical aspect of the invention, as it ensures efficient mixing and reaction of the components, leading to a consistent and high-quality product. The screw speed within the extruder can be adjusted based on the specific requirements of the process, with a preferred range of 2 to 600 rpm, and a more preferred range of 5 to 300 rpm.

[0013] A goal of the present invention is to provide a sustainable solution for managing and reusing rigid polyurethane (PUR) foams and - waste.

[0014] A goal of the present invention is to provide a solvent-free process for recycling polyurethane (PUR) foam, thereby reducing environmental impact and simplifying the overall operation while maintaining high product quality.

[0015] A goal of the present invention is to efficiently recycle polyurethane (PUR) foam waste into high-quality polyols.

[0016] A goal of the present invention is to create a continuous process that enhances the scalability of polyurethane (PUR) recycling.

[0017] A goal of the present invention is to reduce the environmental impact of polyurethane (PUR) waste by converting it into reusable materials.

[0018] A goal of the present invention is to optimize the depolymerization reaction within the extruder for maximum efficiency and quality.

[0019] A goal of the present invention is to ensure that the recycled polyols are suitable for producing high-performance polyurethane (PUR) products.

[0020] A goal of the present invention is to facilitate the repolymerization of glycolysate into new polyurethane (PUR) materials using multifunctional isocyanates.

[0021] In a second aspect the present invention relates to a use according to claim 15.

[0022] DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention relates to a continuous process for the preparation of recycled polyols from polyurethane (PUR) foam and polyurethane (PUR) foam waste through glycolysis using an extruder. The invention addresses the environmental and economic challenges associated with polyurethane (PUR) foam waste by providing a process that efficiently recycles this waste into valuable polyols, which can be reused in the production of new polyurethane (PUR) materials. Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0024] As used herein, the following terms have the following meanings:

[0025] "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0026] "About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0027] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

[0028] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0029] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0030] The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation. Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0031] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0032] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0033] The term "continuous process" refers in the present invention to a method that operates without interruption, allowing for the ongoing input of raw materials and output of products.

[0034] The term "polyurethane (PUR) foam" refers to a polymer composed of organic units joined by urethane (carbamate) links. The term "polyurethane (PUR) foam" as used herein includes PIR, a polymer which is linked by both urethane (carbamate) and isocyanurate links. The polyurethane (PUR) foam may be in the form of rigid or flexible foam and preferably rigid.

[0035] The term "Glycolysis" in the context of this invention refers to the chemical breakdown of polyurethane (PUR) foam into its constituent polyols using a polyhydric alcohol in the presence of a catalyst. The process involves the depolymerization of the polyurethane's urethane linkages, leading to the formation of smaller, reusable polyol components.

[0036] The term "extruder" refers to a machine used to process materials by forcing them through a die, in this case, a twin-screw extruder is preferred.

[0037] The term "mechanically grinding" refers to the process of physically reducing the polyurethane (PUR) foam into smaller particles.

[0038] The term "cyclotrimerization catalyst" refers to a type of catalyst that promotes the trimerization of isocyanates, facilitating the breakdown of polyurethane (PUR) foam during the glycolysis process. In the present invention, preferred catalysts include alkali metal salts such as potassium acetate, sodium acetate, and lithium acetate.

[0039] The term "polyhydric alcohol" refers to an alcohol containing more than one hydroxyl group, which in this invention is used to break down polyurethane (PUR) foam into polyols. Examples include diols like dipropylene glycol, ethylene glycol, propylene glycol, and butylene glycol.

[0040] The term "premixture" refers to the mixture of ground polyurethane (PUR) foams with the cyclotrimerization catalyst-polyhydric alcohol solution before being fed into the extruder.

[0041] The term "glycolysate" refers to the product of the glycolysis reaction, which includes polyols.

[0042] The term "repolymerizing" refers to the process of forming new polyurethane (PUR) or polyisocyanurate (PIR) foams from the glycolysate using multifunctional isocyanates.

[0043] The term "multifunctional isocyanates" refers to compounds containing multiple isocyanate groups, which react with polyols to form polyurethane (PUR) or polyisocyanurate (PIR). Examples include 4,4'-methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and cyclic trifunctional isocyanates.

[0044] The term "hydroxyl number" refers to a measure of the hydroxyl group content in the polyhydric alcohol or the resulting polyol, expressed as the amount of potassium hydroxide (KOH) in milligrams equivalent to the hydroxyl content of one gram of substance, measured according to ISO 6796. The term "weight ratio" refers to the proportion of the weight of polyurethane (PUR) foam to the weight of polyhydric alcohol used in the process.

[0045] The term "residence time" refers to the duration for which the mixture remains in the extruder during the depolymerization reaction.

[0046] The term "pressure" refers to the force exerted by the mixture within the extruder, measured in bars.

[0047] The term "temperature" refers to the heat level within the extruder during the process, measured in degrees Celsius (°C). "Room temperature" refers to the ambient air temperature in the surrounding environment, typically ranging from 20°C to 25°C (68°F to 77°F), which serves as the baseline or reference point for the extrusion process. This temperature can influence the starting conditions of the material before it enters the extruder, potentially affecting the overall extrusion performance.

[0048] The term "twin-screw extruder" refers to an extruder with two intermeshing screws that rotate to process materials.

[0049] The term "screw speed" refers to the rotational speed of the screws in the twin- screw extruder, measured in revolutions per minute (rpm).

[0050] The term "rigid" refers to polyurethane (PUR) foam that maintains its shape and structural integrity under stress, as opposed to flexible foam. This invention is particularly focused on the recycling of rigid polyurethane (PUR) foams, which are typically used in insulation and structural applications. Typically, rigid polyurethane (PUR) foams comprise both carbamate and isocyanurate functional groups.

[0051] By the term "auxiliary additives" is meant additional substances mixed into the premixture to enhance the properties of the final product, including stabilizers, flame retardants, plasticizers, fillers, antioxidants, UV stabilizers, colorants, and combinations thereof.

[0052] In a first aspect, the invention pertains to a continuous process for preparing recycled polyols from polyurethane (PUR) foam and / or polyurethane (PUR) foam waste by glycolysis using an extruder. This process is distinguished by its speed and solvent- free nature, which collectively ensure a high consistency in the quality of the recycled polyols.

[0053] Present invention relates to a method for the recycling of polyurethane (PUR) foam and / or polyurethane (PUR) foam waste. In a preferred embodiment, present invention relates to a method for the recycling of hard polyurethane (PUR) foams, more preferably polyisocyanurate (PIR) foams. Both PIR and PUR are typically produced by polymerizing polyols and isocyanates. However, PUR is characterized by predominantly urethane (carbamate) linkages; while PIR has both urethane (carbamate) and isocyanurate linkages. Isocyanurate groups are cyclic and provide the polymer foam with significantly increased rigidity and temperature and fire resistance. However, they also make recycling more difficult.

[0054] Advantageously, present invention allows for the recycling of rigid PIR foams which are traditionally more difficult to process, in a single step towards a polyol mixture which can be repolymerized effectively.

[0055] In a preferred embodiment, the polyurethane (PUR) foam and I or polyurethane (PUR) foam waste comprises PIR foam, more preferably rigid PIR foam. In a preferred embodiment, the polyurethane (PUR) foam and I or polyurethane (PUR) foam waste has a isocyanurate to urethane ratio of at least 1:4, more preferably at least 1:3, more preferably at least 1 :2, more preferably at least 2:3, more preferably at least 3:4, more preferably at least 1: 1, more preferably at least 5:4, more preferably at least 4:3, more preferably at least 2: 1. Advantageously, present method is particularly suitable for glycolysis of rigid PIR foams. The ratio of carbamate to isocyanurate groups can be determined with quantitative13C NMR spectroscopy measurements in acetone-de as solvent, using Cr(acac)s as relaxation agent.

[0056] In a preferred embodiment, the feedstock comprises predominantly polyurethane (PUR) and / or polyisocyanurate (PIR) foams. Preferably, the feedstock consists of at least 50 wt.% combined content of PUR and PIR, more preferably at least 60 wt.%, more preferably at least 70 wt.%, more preferably at least 80 wt.%, more preferably at least 85 wt.%, more preferably at least 90 wt.%, more preferably at least 95 wt.%, still more preferably at least 98 wt.%, and most preferably at least 99 wt.%, based on the total weight of the feedstock. Advantageously, the process does not require the addition of any polyethylene terephthalate (PET) or other polyester materials, which are typically employed to facilitate glycolysis, but which complicates downstream processing and reduces the amount of PUR and I or PIR that can effectively be processed. The present invention shows that high yields of recycled polyols can be obtained from PUR and PIR foams alone, including rigid PIR foams, while maintaining efficient depolymerization and product quality. Preferably, the process comprises the step of mechanically grinding the PUR foams to a particle size of at least 0.2 mm and at most 50 mm . Preferably at least 0.4 mm, 0.6 mm, 0.8 mm 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, 8.5 mm, 9.0 mm, 9.5 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm and at most 48 mm, 46 mm, 44 mm, 42 mm, 40 mm, 38 mm, 36 mm, 34 mm, 32 mm, 30 mm, 28 mm, 26 mm, 24 mm, 22 mm, 20 mm, 18 mm, 16 mm, 14 mm, 12 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1 mm or any combination thereof. In a further embodiment, the polyurethane (PUR) foams are mechanically ground to a particle size distribution characterized by a median particle size (d50) of at least 0.2 mm and at most 50 mm. More preferably, the d50 is at least 0.4 mm, more preferably at least 0.6 mm, more preferably at least 0.8 mm, and more preferably at least 1.0 mm; and more preferably at most 30 mm, more preferably at most 20 mm, more preferably at most 15 mm, more preferably at most 10 mm, more preferably at most 8 mm, more preferably at most 6 mm, and more preferably at most 5 mm. In a more preferred embodiment, d50 is between 0.2 and 50 mm, more preferably 0.4-30 mm, more preferably 0.6-20 mm, more preferably 0.8-15 mm, more preferably 1-10 mm, more preferably 1-8 mm, and most preferably 1-5 mm d50. Advantageously, particles having a median size of 1-5 mm d50 have been found to prevent blockage in the extruder and to ensure stable processing, particularly for rigid PIR foams. In a further preferred embodiment, the particle size distribution is defined by the 10th percentile (dlO) and 90th percentile (d90) by weight, wherein dlO corresponds to the particle diameter below which 10 wt.% of the particles fall, and d90 corresponds to the particle diameter below which 90 wt.% of the particles fall, as determined by dry sieving or laser diffraction. Further more preferably, dlO is at least 0.2 mm, more preferably at least 0.4 mm, more preferably at least 0.6 mm, more preferably at least 0.8 mm, and more preferably at least 1.0 mm. Preferably, d90 is at most 50 mm, more preferably at most 30 mm, more preferably at most 20 mm, more preferably at most 15 mm, more preferably at most 10 mm, more preferably at most 8 mm, more preferably at most 6 mm, and more preferably at most 5 mm. Most preferably, dlO is at least 1 mm and d90 is at most 5 mm, thereby ensuring a narrow particle size distribution. Advantageously, such a relatively narrow particle size distribution results in improved process stability in the extruder and consistency of the obtained glycolysate, thereby enhancing the reproducibility and quality of the recycled polyols.

[0057] The process preferably starts with the mechanical grinding of polyurethane (PUR) foams into particles no larger than several millimeters. Said size range has been determined to be optimal for ensuring that the foams can be efficiently processed in the extruder. Grinding the foams to this specific size ensures that the surface area is maximized, allowing for more effective interaction with the catalyst-polyhydric alcohol mixture in the subsequent steps. This step is imperative for ensuring that the foam is adequately prepared for subsequent chemical reactions.

[0058] Preferably, the process comprises the step of dissolving a cyclotrimerization catalyst in a polyhydric alcohol. More specifically, after grinding, the cyclotrimerization catalyst, such as potassium acetate, is dissolved in a polyhydric alcohol— ideally a diol like dipropylene glycol. This dissolution is most effectively carried out at an elevated temperature, preferably approximately 200°C. The choice of polyhydric alcohol is critical to the success of the glycolysis reaction. Dissolving a cyclotrimerization catalyst in a polyhydric alcohol ensures uniform distribution of the catalyst throughout the reaction mixture, enhancing its activity and leading to more efficient and consistent depolymerization of polyurethane (PUR) foams. This step stabilizes the reaction environment, improves the flow characteristics of the mixture within the extruder, and allows for precise control over the catalyst concentration. As a result, the process yields high-quality recycled polyols with uniform molecular weight distribution, essential for producing reliable end products.

[0059] The cyclotrimerization catalyst(s) are preferably dissolved at a temperature above 100°C, more preferably above 150°C, more preferably above 180°C, most preferably about 200°C, this temperature was chosen for its effectiveness in achieving a stable solution. Alternatively, the dissolution temperature might vary slightly depending on the specific polyhydric alcohol used, and other temperatures close to 200°C may also be effective. Preferably, the process comprises the step of mixing the ground PUR foam with said cyclotrimerization catalyst-polyhydric alcohol mixture to form a premixture. Once the catalyst has been dissolved in the polyhydric alcohol, the ground polyurethane (PUR) foams are mixed with this catalyst-alcohol solution to form a premixture. This approach helps to create a homogenous premixture, ensuring that the catalyst is evenly distributed throughout the foam particles. This uniform distribution is crucial for consistent depolymerization during the extrusion process, leading to more efficient breakdown of the polyurethane (PUR) structure. Thus, the premixture must be homogeneous to ensure that the reaction proceeds efficiently within the extruder. Preferably, the mixing occurs at room temperature. By conducting the mixing at room temperature, the process avoids premature reactions that could occur if the temperature were higher, which might lead to partial degradation of the foam before it enters the extruder. This controlled, low- temperature mixing helps maintain the integrity of the premixture, ensuring that the depolymerization reaction only begins under the controlled conditions within the extruder. Additionally, mixing at room temperature simplifies the process, reducing the need for additional heating steps and contributing to the overall energy efficiency of the method.

[0060] Preferably, the process comprises the step of continuously feeding the premixture into the extruder to conduct a depolymerization reaction within the extruder to produce a glycolysate comprising polyols. Continuously feeding the premixture into the extruder ensures a steady and consistent process, which is crucial for maintaining uniform reaction conditions throughout the operation. This continuous mode of operation allows for better control over the reaction parameters, such as temperature, pressure, and residence time, leading to a more efficient and complete depolymerization of the polyurethane (PUR) foam. The continuous feeding also prevents fluctuations in the quality of the output, as the process avoids the startstop issues common in batch processes. As a result, the glycolysate comprising polyols produced in a continuous process has more consistent properties, such as molecular weight distribution, which is critical for the reliability and quality of the final recycled polyols. Moreover, continuous processing increases overall efficiency, reduces processing time, and is more suitable for large-scale industrial applications where high throughput is required.

[0061] In a preferred embodiment, the twin-screw extruder comprises a plurality of temperature zones along its barrel, wherein the temperature is progressively increased from the feeding zone towards the discharge zone. Preferably, the temperature in the first zone is 80-150 °C, more preferably 100-120 °C, followed by one or more intermediate zones maintained at 160-200 °C, and final zones maintained at 200-230 °C, more preferably 210-220 °C, with an optional final cooling zone at 180-200 °C before discharge. In a more specific embodiment, the temperature profile across the extruder comprises: a temperature of at most 150 °C at the feeding zone, followed by one or more zones at 170-190 °C, several consecutive zones at 210-220 °C, and a final zone at 190-200 °C before the die. The use of such temperature zoning provides improved control over the reaction environment, as it allows the premixture to be gradually heated to the depolymerization temperature, thereby limiting the time spent at the highest temperatures. Advantageously, this reduces the occurrence of side-reactions and the formation of undesired byproducts, while ensuring efficient depolymerization. Preferably, the process comprises the step of discharging and collecting said glycolysate comprising polyols. Upon completion of the glycolytic cleavage reaction, said glycolysate comprising polyols are discharged and collected. The glycolysate is a viscous liquid that contains the recycled polyols, which can be directly used in the production of new polyurethane (PUR) materials. The quality of the glycolysate is critical to the success of the subsequent repolymerization process, and the conditions within the extruder are carefully controlled to ensure that the glycolysate has the desired properties. These recycled polyols exhibit excellent solubility in common organic solvents such as acetone, THF, CHCI3, DMF, and DMSO, enabling their comprehensive physico-chemical characterization. This solubility is a significant advantage as it allows for versatile applications and further processing of the recycled polyols.

[0062] In a further embodiment, the process is performed by reintroducing unpurified recycled polyols obtained from a previous depolymerization run into the twin-screw extruder together with flexible polyurethane (PUR) and / or rigid polyisocyanurate (PIR) foam to be recycled, the PUR and / or PIR foam preferably having a particle size within the ranges disclosed herein. In this embodiment, no additional catalyst or virgin polyhydric alcohol is required, since the unpurified recycled polyols still comprise residual catalyst and simultaneously act as polyhydric alcohol. Optionally, small amounts of additional polyhydric alcohol may be included to adjust viscosity or reaction conditions. Preferably, the feed comprises a mixture of PUR and / or PIR foam and recycled polyols in a weight ratio of 30 :70 to 70:30, more preferably 40:60 to 60:40, still more preferably about 50:50. Recycling in this manner advantageously allows operation of the process in a loop, wherein previously obtained recycled polyols are reused in subsequent depolymerization steps, thereby reducing or eliminating the need for fresh input materials, while further optimising the properties of the obtained glycolysate.

[0063] In a further or alternative embodiment of the invention, the process further comprises repolymerizing said produced glycosylate with multifunctional isocyanates, preferably selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), cyclic tri-functional isocyanates and combinations thereof. Preferably the multifunctional isocyanates and glycolysate comprising polyols to produce recycled polyols. This additional step allows for the immediate reuse of the glycolysate, closing the recycling loop and enabling the production of high-quality, fully recycled polyurethane (PUR) products. The repolymerization process allows for the production of high-quality recycled polyurethane (PUR) products, which can be used in various applications, including foams, coatings, and adhesives. Repolymerizing with multifunctional isocyanates, such as 4,4'-methylene diphenyl diisocyanate (MDI), ensures that the resulting polyurethane (PUR) materials retain the desirable mechanical and chemical properties needed for their intended applications. This step not only enhances the value of the recycling process by creating usable end-products but also improves the overall efficiency and sustainability of the process by minimizing waste and reducing the need for virgin materials. Preferably, the cyclic tri-functional isocyanates are chosen from the list of: Polyisocyanurate (PIR) prepolymers, Hexamethylene diisocyanate (HDI) trimer, Isophorone diisocyanate (IPDI) trimer, Toluene diisocyanate (TDI) trimer, Xylylene diisocyanate (XDI) trimer, Bis(isocyanatomethyl)cyclohexane trimer, 1,6- Hexamethylene diisocyanate isocyanurate, Methylenediphenyl diisocyanate (MDI) trimer, Tetramethylxylylene diisocyanate (TMXDI) trimer, Bis(4- isocyanatocyclohexyl)methane (H12MDI) trimer, Cycloaliphatic diisocyanate (CHDI) trimer and combinations thereof.

[0064] Furthermore, the inventors found that the use of combinations of tri-functional and di-functional isocyanates in different ratios to tailor the properties of the resulting polyurethane (PUR) or polyisocyanurate (PIR) materials. This flexibility allows for the production of materials with specific mechanical and thermal properties, depending on the desired application.

[0065] In a further or alternative embodiment of the invention, the polyhydric alcohol is selected from the group consisting of diols, triols, and higher functionality alcohols, more preferably the polyhydric alcohol is a diol, selected from the group consisting of dipropylene glycol, ethylene glycol, propylene glycol, butylene glycol, and combinations thereof. This selection is important because diols and other polyhydric alcohols provide the necessary reactivity for the glycolysis reaction, effectively breaking down the polyurethane (PUR) foam into smaller, usable polyol components.

[0066] Diols, such as dipropylene glycol, are particularly preferred due to their effectiveness in facilitating the depolymerization of the polyurethane (PUR) foams. Diols offer a balanced reactivity that ensures efficient depolymerization without causing excessive degradation of the resulting polyols. This leads to a controlled and predictable reaction, producing high-quality recycled polyols with desirable properties such as appropriate molecular weight and functionality. The choice of specific diols, like dipropylene glycol, further enhances the process by offering compatibility with the polyurethane (PUR) structure, optimizing the reaction conditions, and improving the solubility of the resulting polyols in various applications. Furthermore, the use of diols, such as dipropylene glycol, is particularly preferred due to their balanced reactivity and ability to produce polyols with desirable molecular weight distributions. More preferably, the diols used in the process may have molecular weights ranging from 50 to 500 g / mol, more preferably from 100 to 400 g / mol, more preferably from 150 to 350 g / mol, more preferably from 200 to 300 g / mol, and most preferably from 225 to 275 g / mol.

[0067] Alternatively, triols are used, which provide additional functionality and cross-linking potential in the resulting polyols. Triols such as glycerol and trimethylolpropane are particularly preferred due to their availability and reactivity. The molecular weights of the triols used may preferably range from 90 to 500 g / mol, more preferably from 150 to 450 g / mol, more preferably from 200 to 400 g / mol, more preferably from 250 to 350 g / mol, and most preferably from 275 to 325 g / mol.

[0068] Alternatively, higher functionality alcohols, such as pentaerythritol and sorbitol, are also included in the process to achieve specific properties in the recycled polyols. These higher functionality alcohols may preferably have molecular weights ranging from 120 to 600 g / mol, more preferably from 200 to 550 g / mol, more preferably from 250 to 500 g / mol, more preferably from 300 to 450 g / mol, and most preferably from 350 to 400 g / mol.

[0069] The flexibility in selecting polyhydric alcohols allows for tailoring the properties of the recycled polyols to meet specific application requirements. This adaptability is a significant advantage of the process, enabling the production of recycled polyols with tailored molecular weight distributions, functionality, and reactivity. Consequently, the recycled polyols can be effectively utilized in various polyurethane (PUR) applications, including foams, elastomers, coatings, and adhesives, thereby enhancing the sustainability and circular economy of polyurethane (PUR) materials.

[0070] In a further or alternative embodiment of the invention, the polyhydric alcohol has a hydroxyl number of 200 to 600 mg KOH / g, preferably 250 to 550 mg KOH / g, more preferably 300 to 500 mg KOH / g, even more preferably 325 to 475 mg KOH / g, still more preferably 340 to 460 mg KOH / g, further preferably 350 to 450 mg KOH / g, even further preferably 360 to 440 mg KOH / g, yet more preferably 370 to 430 mg KOH / g, further more preferably 375 to 425 mg KOH / g, still further preferably 380 to 420 mg KOH / g, even more preferably 385 to 415 mg KOH / g, and most preferably 390 to 410 mg KOH / g, to achieve optimal reactivity and product performance. Said range is optimal for achieving the desired balance between reactivity and product quality in the glycolysis reaction. The presence of a hydroxyl number within the specified range ensures that the polyol has sufficient reactive sites to participate in the depolymerization and subsequent repolymerization reactions, resulting in a robust and durable recycled product. The hydroxyl number indicates the amount of hydroxyl groups (-OH) present in the polyhydric alcohol, which directly influences the reactivity of the alcohol during the depolymerization of the polyurethane (PUR) foam. A hydroxyl number within this range ensures that the polyhydric alcohol is sufficiently reactive to effectively break down the polyurethane (PUR) into polyols while maintaining control over the reaction to avoid excessive degradation. This balance is crucial for producing high-quality recycled polyols with consistent molecular weight and functionality, which are necessary for their subsequent use in manufacturing new polyurethane (PUR) products. Additionally, this specific hydroxyl number range provides the right level of functionality to ensure that the resulting polyols are compatible with multifunctional isocyanates in any subsequent repolymerization steps, leading to the production of robust and durable polyurethane (PUR) materials.

[0071] In a further or alternative embodiment of the invention, the polyols, obtained after foam degradation, have a hydroxyl number of at least 300 and at most 900 KOH / g. Preferably at least 350, 400, 450, 500, 550, 600, 610, 620, 635 KOH / g and at most 850, 800, 750, 700, 690, 680, 670, 660, 650, 640, 635 KOH / g. More preferably, the polyols (obtained after foam degradation) have a hydroxyl number of approximately 630 mg KOH / g. Said values are identified as an optimal range or point where the polyols exhibit a balance of reactivity and stability, making them particularly suitable for high-performance applications. The specific hydroxyl number of approximately 630 mg KOH / g is considered optimal because it represents a balanced point in the chemical properties of the polyols, which directly impacts their performance in subsequent reactions, particularly in the production of polyurethane (PUR) or polyisocyanurate (PIR) materials. At this hydroxyl number, the polyols have a sufficient concentration of reactive hydroxyl groups to form strong, durable polyurethane (PUR) networks. This balance ensures the polyols are reactive enough to produce materials with good mechanical properties, such as flexibility and tensile strength, without making the final product too rigid or brittle. Additionally, a hydroxyl number around 630 mg KOH / g typically corresponds to polyols with an ideal molecular weight and functionality for various polyurethane (PUR) applications. These polyols are also easier to handle and process during manufacturing, with a viscosity that is suitable for efficient mixing and reacting with isocyanates. This processing efficiency contributes to consistent, high-quality production of polyurethane (PUR) products. Furthermore, this specific hydroxyl number indicates a controlled and consistent degradation process, leading to uniform polyol properties. This consistency is crucial for producing polyurethane (PUR) products that meet strict performance standards in industrial applications.

[0072] In an embodiment, the cyclotrimerization catalyst may be chosen from the list of:

[0073] - alkali metal-based catalysts more preferably potassium acetate, potassium 2-ethylhexanoate, sodium p-toluenesulfonate (p-TolSChNa) and zinc octoate;

[0074] - quaternary ammonium salts more preferably tetramethylammonium chloride (TMAC), benzyltrimethylammonium hydroxide (BTMAH), tetrabutylammonium acetate (TBAA);

[0075] - tertiary amines and lewis basic salts, more preferably triethylamine (TEA),

[0076] N,N-dimethylcyclohexylamine (DMCHA), 2-{[2-

[0077] (dimethylamino)ethyl]methylamino}ethanol (DMAEMAE),

[0078] Tris(dimethylaminopropyl)hexahydrotriazine (TDMAPHT), [HTBD][OAc] (a conjugate between 1,5,7-triazabicyclo [4.4.0] dec-5-ene and acetic acid) and l,4-diazabicyclo[2.2.2]octane (DABCO).

[0079] Cyclotrimerization catalysts primarily promote the cyclotrimerization of isocyanates, thereby forming cyclic polyisocyanurate (PIR) structures within PIR foams. These cyclic structures contribute significantly to the thermal stability and fire resistance of PIR foams, particularly in comparison with PUR foams. The addition of cyclotrimerization catalysts for the glycolysis process aids in reducing undesirable byproducts, thereby stabilizing the reaction mixture.

[0080] In a further embodiment, the cyclotrimerization catalyst is preferably chosen from the list consisting of : 2,4,6-Tris(dimethylaminomethyl)phenol (TDMAMP), tetrabutylammonium acetate (TBAA), potassium 2-ethylhexanoate, 2-{[2- (dimethylamino)ethyl]methylamino}ethanol (DMAEMAE), sodium p-toluenesulfinate (p-TolSO2Na), potassium acetate, N,N',N"-tris(3-dimethylaminopropyl)hexahydro- 1,3,5-triazine (TDMAPHT).

[0081] In a particular embodiment, the cyclotrimerization catalyst is chosen from tetrabutylammonium acetate (TBAA), potassium 2-ethylhexanoate, 2-{[2- (dimethylamino)ethyl]methylamino}ethanol (DMAEMAE). These cyclotrimerization catalysts show highest activity. However, their particularly high activity makes it difficult to control the reaction conditions. In a particular embodiment, the cyclotrimerization catalyst is chosen from potassium acetate and 2,4,6-Tris(dimethylaminomethyl)phenol (TDMAMP). These catalysts were found to be particularly suitable due to the mildness of the activity providing additional control over the reaction conditions within the twin screw extruder. In addition, these catalysts had sufficient solubility and processability to be suitable for use in the extruder-glycolysis process. Among these, potassium acetate is especially preferred due to its high solubility in polyhydric alcohols and its ability to maintain a stable and controlled reaction environment. This stability helps in achieving consistent and predictable reaction outcomes, resulting in high-quality recycled polyols with desirable properties. Moreover, alkali metal catalysts like potassium acetate are relatively mild, which minimizes the risk of unwanted side reactions that could degrade the quality of the polyols. The use of these catalysts ensures that the process is efficient, producing polyols that are suitable for further use in the production of new polyurethane (PUR) materials, while also maintaining the overall economic and environmental efficiency of the recycling process.

[0082] Moreover, the use of polyhydric alcohols with a hydroxyl number of 200 to 600 mg KOH / g is preferably combined with the use of an alkali metal catalyst, such as potassium acetate, to facilitate the glycolysis reaction. This combination is effective in breaking down the rigid polyurethane (PUR) foam waste into smaller oligomeric units, which can then be repolymerized into new polyurethane (PUR) foams with desirable properties. The optimized hydroxyl number range ensures that the polyol maintains a balance between viscosity and reactivity, making it suitable for various industrial applications, including the production of flexible and rigid foams, coatings, adhesives, and elastomers.

[0083] In a further or alternative embodiment of the invention, a weight ratio of PUR or PIR foam to polyhydric alcohol is from 1 : 10 to 1: 1, more preferably from 1:5 to 1 : 1.2, even more preferably from 1 :2.5 to 1 : 1.4, still more preferably from 1 :2 to 1 : 1.5, further preferably from 1: 1.8 to 1: 1.6, even further preferably from 1 : 1.7 to 1: 1.6, yet more preferably from 1 : 1.6 to 1: 1.55, still further preferably from 1 : 1.55 to 1: 1.5, even more preferably from 1: 1.52 to 1: 1.5, still more preferably from 1 : 1.5 to 1: 1.45, even further preferably from 1: 1.5 to 1: 1.4, yet more preferably from 1: 1.5 to 1 : 1.35, still more preferably from 1: 1.5 to 1 : 1.3, and most preferably about 1: 1.5, to achieve optimal mixing and performance. This range of ratios has been found to provide the best balance between reaction efficiency and product yield, ensuring that the polyhydric alcohol is neither in excess nor deficient, which could otherwise affect the quality and properties of the recycled polyols. These optimal ratios provide an optimal balance between effective depolymerization and manageable process conditions and ensures that there is sufficient polyhydric alcohol to facilitate the depolymerization reaction, while also maintaining the viscosity and flow characteristics of the premixture within the extruder. A ratio within said range ensures that there is sufficient polyhydric alcohol available to fully interact with and break down the polyurethane (PUR) foam during the glycolysis reaction. This amount of alcohol is necessary to dissolve the cyclotrimerization catalyst properly and to create a homogenous reaction mixture, which promotes consistent depolymerization throughout the foam. Using too little polyhydric alcohol could lead to incomplete depolymerization, resulting in a lower yield of recycled polyols and potentially leaving unreacted foam particles. Conversely, using too much polyhydric alcohol could dilute the reaction mixture, reducing the efficiency of the process and potentially requiring additional energy to evaporate or remove the excess alcohol after the reaction. The preferred ratio range from 1:2.5 to 1: 1.4 is particularly effective because it ensures that the reaction proceeds efficiently, producing high-quality polyols with consistent molecular weights and desirable properties. This range also helps to maintain a manageable viscosity of the reaction mixture, which is important for smooth processing in the extruder and for maintaining the overall efficiency of the continuous process.

[0084] In a further or alternative embodiment of the invention, the residence time of the depolymerization reaction in the extruder is less than 90 minutes, preferably less than 75 minutes, more preferably less than 60 minutes, still more preferably less than 45 minutes, and further preferably less than 30 minutes, more preferably, more preferably less than 25 minutes, even more preferably less than 20 minutes, still more preferably less than 18 minutes, further preferably less than 15 minutes, even further preferably less than 12 minutes, yet more preferably less than 10 minutes, still further preferably less than 8 minutes, even more preferably less than 6 minutes, still more preferably less than 5 minutes, yet further preferably less than 4 minutes, still more preferably less than 3 minutes, and most preferably less than 2 minutes, to ensure efficient processing and optimal product quality. In a more preferred embodiment, suitable residence times are found to be between 1 and 45 minutes, more preferably between 2 and 45 minutes, more preferably between 5 and 45 minutes, more preferably between 5 and 30 minutes, more preferably between 10 and 35 minutes, still more preferably between 12 and 28 minutes, even more preferably between 15 and 25 minutes, yet more preferably between 16 and 22 minutes, and most preferably about 18 to 20 minutes. Residence time refers to the duration that the polyurethane (PUR) foam and the polyhydric alcohol mixture remain inside the extruder while undergoing the depolymerization reaction. More preferably, the residence time is the mean residence time which can be estimated from the extruder free volume divided by the extruder volumetric throughput during operation. This time is crucial because it determines how long the materials are exposed to the reaction conditions, such as temperature, pressure, and catalyst activity. The residence time must be carefully controlled to ensure that the depolymerization reaction is complete but not excessive, which could affect the quality of the final product. Said optimal residence time allows for rapid processing of the polyurethane (PUR) foam, which is essential in a continuous industrial process. This shorter reaction time maximizes the output of recycled polyols, making the process more economically viable and suitable for large-scale operations. By limiting the residence time, the process minimizes the risk of over-depolymerization, which can degrade the quality of the resulting polyols. Over-exposure to heat and catalysts can lead to unwanted side reactions, producing polyols with lower molecular weights or inconsistent properties. A controlled, shorter reaction time helps produce high- quality polyols with the desired molecular characteristics. A shorter residence time reduces the energy required to maintain the reaction conditions within the extruder. This contributes to the overall energy efficiency of the process, lowering operational costs and reducing the environmental impact. Said short residence time ensures that the polyhydric alcohol and the catalyst do not excessively react with the polyurethane (PUR), preserving the integrity of the final polyol product. This controlled reaction environment is key to achieving a consistent and high-quality product. Sufficiently high residence times are required to avoid the product having a viscosity too high to effectively repolymerize.

[0085] In a further or alternative embodiment of the invention, the pressure in the extruder is at most 50 bar, more preferably at most 45 bar, even more preferably at most 40 bar, still more preferably at most 35 bar, further preferably at most 32 bar, even further preferably at most 30 bar, yet more preferably at most 28 bar, still further preferably at most 25 bar, even more preferably at most 22 bar, still more preferably at most 20 bar, even further preferably at most 18 bar, yet more preferably at most 15 bar, still further preferably at most 12 bar, even more preferably at most 10 bar, still more preferably at most 8 bar, and most preferably at most 5 bar, to achieve optimal processing conditions and product quality. Said pressure level optimizes the balance between promoting efficient depolymerization of the polyurethane (PUR) foam and maintaining safe, manageable operating conditions. A pressure of up to 50 bar ensures that the materials within the extruder, including the polyurethane (PUR) foam, polyhydric alcohol, and catalyst, are thoroughly mixed and maintained in close contact. This facilitates the effective penetration of the polyhydric alcohol and catalyst into the foam particles, enhancing the depolymerization process and leading to a more complete breakdown of the polyurethane (PUR) into polyols. At the same time, limiting the pressure to at most 50 bar helps to prevent the risk of over-depolymerization or degradation of the polyols, which could compromise the quality of the recycled product. Higher pressures, while potentially accelerating chemical reactions, can lead to unwanted side reactions and reduce the overall quality of the final product. Moreover, operating at or below this pressure level ensures that the process remains within a safe and reliable operating range, reducing the risk of equipment failure and maintaining the integrity of the extruder over time. Additionally, keeping the pressure at or below 50 bar optimizes energy consumption, making the process more energy-efficient and cost-effective for continuous industrial applications. This preferred pressure range also decreases mechanical stress on the twin-screw extruder equipment, thereby enhancing its longevity. Operating at reduced pressures minimizes the wear and tear on the extruder components, which is particularly advantageous for continuous processes where equipment durability is crucial. These pressure ranges are chosen to optimize the balance between effective depolymerization of the polyurethane (PUR) foam and the mechanical integrity of the extruder. Operating within these pressure limits also contributes to the safety of the process, as lower pressures reduce the risk of equipment failure and potential hazards associated with high-pressure operations. Additionally, maintaining lower pressures can lead to energy savings, as less force is required to drive the extrusion process, making the overall process more energy-efficient.

[0086] In a further or alternative embodiment of the invention, the mixture of ground PUR foams and catalyst solution is fed into the feeding zone of the extruder at room temperature. This allows for controlled and stable processing conditions as the material enters the extruder. Introducing the mixture at room temperature prevents any premature reactions or thermal degradation of the components before they reach the optimal reaction environment within the extruder. This approach ensures that the depolymerization reaction begins only when the mixture is exposed to the specific temperature and pressure conditions inside the extruder, where these parameters can be precisely controlled. Starting at room temperature also simplifies the process by eliminating the need for additional heating steps before the mixture enters the extruder, making the process more energy-efficient. Additionally, feeding the mixture at room temperature helps maintain the integrity of the feed components, ensuring a consistent and homogeneous reaction mixture, which is critical for achieving uniform depolymerization and producing high-quality recycled polyols.

[0087] In a further or alternative embodiment of the invention, a temperature in the extruder is between 150°C and 250 °C, more preferably between 200°C and 220°C. Said temperature range is optimal for promoting the efficient depolymerization of polyurethane (PUR) foams into polyols. Temperatures within this range are high enough to facilitate the breaking of chemical bonds within the polyurethane (PUR) structure, allowing the glycolysis reaction to proceed effectively. At the same time, this temperature range is carefully chosen to avoid excessively high temperatures that could lead to undesirable side reactions, such as over-depolymerization or degradation of the resulting polyols. Maintaining the temperature within 150°C to 250°C ensures that the reaction is both effective and controlled, producing high- quality recycled polyols with consistent molecular weight and functionality. Additionally, this range is suitable for continuous industrial processing, providing a balance between reaction speed and energy efficiency, while ensuring the longevity and safety of the equipment used in the process.

[0088] Preferably, the temperature in the extruder is at least 150°C, more preferably at least 180°C, even more preferably at least 190°C, and still more preferably at least 200°C and at most 250°C, more preferably at most 240°C, even more preferably at most 230°C, still more preferably at most 225°C, and most preferably at most 220°C, or any combination thereof. Preferably between 180°C and 240°C, even more preferably between 190°C and 230°C, still more preferably between 200°C and 225°C, further preferably between 200°C and 220°C, even further preferably between 205°C and 218°C, yet more preferably between 210°C and 215°C, and most preferably between 212°C and 214°C, to ensure optimal reaction conditions and product consistency and to balance efficiency and material stability.

[0089] In a further or alternative embodiment of the invention, the extruder is a twin-screw extruder. A twin-screw extruder is a type of extruder that uses two intermeshing screws to move, mix, and process materials through the extruder barrel. The screws rotate, either in the same direction (co-rotating) or in opposite directions (counterrotating), to convey and knead the material, ensuring thorough mixing and processing. A twin-screw extruder offers superior mixing and control over the process compared to single-screw extruders. The twin-screw design allows for more efficient and homogeneous mixing of the ground polyurethane (PUR) foams with the catalyst-polyhydric alcohol mixture, which is critical for ensuring consistent and complete depolymerization. The intermeshing screws also provide better control over the residence time, pressure, and temperature within the extruder, which are essential for optimizing the reaction conditions and producing high-quality recycled polyols. The extruder is equipped with co-rotational screws that include standard feed screw elements, several feed conveying and reverse feeding elements, conveying mixing elements, long helix feed screws, and extrusion discharge elements. These components are meticulously designed to facilitate the continuous flow and thorough mixing of the reactants, thereby ensuring a consistent and high- quality output of recycled polyols.

[0090] In a further or alternative embodiment of the invention, the screw speed of the twin- screw extruder is adjusted to ensure sufficient residence time for the depolymerization reaction. The inventors have found that the suitable screw speed range depends on the screw diameter of the twin-screw extruder, as the residence time is a function of both throughput and free volume of the extruder. In a general embodiment, the screw speed is between 2 rpm and 600 rpm, which ensures sufficient residence time across typical extruder sizes. In a preferred embodiment employing a small-scale twin-screw extruder with a screw diameters of between 8 and 14 mm, preferably about 11 mm (i.e. Extruder 1), the screw speed is between 3 rpm and 5 rpm, more preferably about 3 to 4 rpm, and most preferably about 3 rpm. These reaction conditions lead to strong depolymerisation while minimizing side reactions.

[0091] In an alternative preferred embodiment employing a larger twin-screw extruder with a larger screw diameter, such as between 15 and 25 mm, preferably about 18 mm (i.e. Extruder 2), the screw speed is between 50 rpm and 500 rpm, more preferably between 60 and 500 rpm, more preferably 80 rpm and 400 rpm, still more preferably between 100 rpm and 350 rpm, and most preferably about 300 rpm. Within this embodiment, the reaction proceeds successfully at all screw speeds between 60 rpm and 500 rpm. Speeds above 600 rpm reduce residence time below the required minimum, whereas speeds below 50 rpm do not allow continuous operation of the extruder. The choice of screw speed within this range directly affects the molecular mass and viscosity of the resulting recycled polyols. Higher screw speeds (e.g., 500 rpm) tend to yield polyols of slightly higher molecular mass and viscosity, whereas moderate screw speeds (e.g., 300 rpm) balance product quality and throughput.

[0092] In a further or alternative embodiment of the invention, both screws in the twin- screw extruder rotate in the same direction (co-rotating), this configuration enhances the mixing and conveying efficiency of the materials through the extruder. When both screws rotate in the same direction, they create a consistent and smooth flow of the material, which is particularly beneficial for processes like depolymerization where uniform mixing and consistent shear are critical. Co-rotating screws intermesh and provide a high degree of mixing, which ensures that the polyurethane (PUR) foam, polyhydric alcohol, and catalyst are thoroughly combined. This uniformity in the mixture is essential for achieving consistent depolymerization and producing high-quality polyols. Additionally, co-rotating screws help in maintaining stable pressure and temperature conditions throughout the extruder, reducing the likelihood of material degradation and ensuring that the reaction proceeds efficiently. Moreover, co-rotating screw extruders are generally easier to control and adjust, making them more suitable for the precise processing required in continuous industrial applications. This configuration thus contributes to the overall reliability, efficiency, and quality of the recycling process described in the invention.

[0093] In a preferred embodiment, the screws of the twin-screw extruder comprise sections of differing pitch. The term "pitch" refers to the axial distance between two consecutive screw flights, and the term "pitch ratio" as used herein refers to the ratio of the pitch in a middle or reaction section to the pitch in a feeding section of the screw. Preferably, the pitch ratio is at least 1.5, more preferably at least 2, still more preferably at least 2.5, and most preferably at least 3. By employing a coarser pitch in the feeding section, efficient intake and conveyance of the ground PUR and / or PIR foams into the extruder is ensured, whereas a finer pitch in the middle or reaction section increases shear, residence time, and mixing intensity with the catalyst- polyhydric alcohol mixture. This variation in pitch optimizes the depolymerization reaction by enhancing contact between the foam particles, the catalyst, and the polyhydric alcohol, thereby improving the efficiency of the process and the quality of the recycled polyols obtained.

[0094] In a further or alternative embodiment of the invention, the polyurethane (PUR) foam and / or polyurethane (PUR) foam waste is rigid. Rigid PIR foams present particular challenges in recycling that the invention is specifically designed to address. Rigid polyurethane (PUR) foams are characterized by a dense, cross-linked structure that makes them more difficult to break down and recycle compared to flexible foams. This dense structure requires a more robust and controlled process to effectively depolymerize the foam into usable polyols. The present invention is optimized for rigid foams because it employs specific process conditions, such as controlled temperature, pressure, and catalyst concentration, to ensure efficient depolymerization. By targeting rigid polyurethane (PUR) foams, the invention addresses a significant need in the recycling industry, where rigid foams are commonly used in applications like insulation and construction but are challenging to recycle due to their toughness and stability. Focusing on rigid foams also allows the present invention to contribute to sustainability efforts by providing a viable method for recycling these materials, which might otherwise be landfilled or incinerated. The ability to effectively recycle rigid polyurethane (PUR) foams into high-quality polyols expands the range of materials that can be sustainably managed and reused, aligning with environmental goals and industry needs.

[0095] In a further or alternative embodiment of the invention, one or more auxiliary additives are mixed into the premixture before the depolymerization reaction, said additives being selected from the group consisting of stabilizers, flame retardants, plasticizers, fillers, antioxidants, UV stabilizers, colorants and combinations thereof. Preferably, one or more auxiliary additives are mixed into the premixture before the depolymerization reaction to customize and enhance the properties of the recycled polyols and the final polyurethane (PUR) products. These additives play a role in improving the performance, stability, and application-specific qualities of the resulting materials.

[0096] Stabilizers such as phosphites or hindered amine light stabilizers (HALS) are used to prevent degradation of the polyurethane (PUR) during both processing and the lifecycle of the final product. Phosphites can protect against thermal degradation during extrusion, ensuring that the polyols maintain their desired molecular weight and functionality, while HALS can safeguard the final polyurethane (PUR) products from UV light exposure, thus enhancing durability and extending their lifespan.

[0097] Flame retardants, such as phosphorus-based compounds or mineral fillers like aluminum hydroxide, are added to increase the fire resistance of the recycled polyols and the final polyurethane (PUR) materials. By incorporating these flame retardants, the material becomes more resistant to ignition and reduces flame spread, making it suitable for applications where fire safety is a concern, such as in building insulation or automotive interiors.

[0098] Plasticizers, such as phthalates or adipates, are included to improve the flexibility and workability of the recycled polyols and the resulting polyurethane (PUR) products. For instance, the addition of a plasticizer like dioctyl phthalate can make the polyurethane (PUR) foam more pliable, which is advantageous for uses in cushioning materials or flexible insulation. Fillers like calcium carbonate or silica are introduced to improve the mechanical properties, reduce cost, or adjust the density of the final polyurethane (PUR) products. For example, calcium carbonate can enhance the rigidity and strength of the polyurethane (PUR), making it more suitable for structural applications, while also reducing the overall material cost.

[0099] Antioxidants, such as butylated hydroxytoluene (BHT) or hindered phenols, are added to prevent oxidative degradation of the polyols during processing and in the final product. BHT, for example, helps maintain the integrity of the polyols by preventing oxidation, which could otherwise lead to discoloration, loss of flexibility, or a reduced lifespan of the polyurethane (PUR) products.

[0100] UV stabilizers, including benzotriazoles or benzophenones, are used to protect the final polyurethane (PUR) products from degradation due to ultraviolet light. These stabilizers absorb UV radiation and dissipate it as heat, preventing the breakdown of polymer chains within the polyurethane (PUR), which helps maintain the material's color, strength, and flexibility over time.

[0101] Colorants, such as pigments or dyes are incorporated to impart specific colors to the recycled polyols or the final polyurethane (PUR) products. The use of colorants can be important for aesthetic reasons, branding, or functional purposes such as colorcoding materials in manufacturing processes.

[0102] Overall, the inclusion of these auxiliary additives allows the process to produce recycled polyols and polyurethane (PUR) products that meet specific performance criteria, enhancing their durability, safety, and suitability for a wide range of applications. This customization through additives increases the commercial and functional value of the recycled materials, making them more competitive and versatile in various industries.

[0103] In a particularly preferred embodiment, the process is carried out in a twin-screw extruder, more preferably a co-rotating twin-screw extruder, wherein the screws optionally comprise sections of differing pitch, preferably with a coarser pitch in the feeding section to facilitate intake of polyurethane (PUR) and / or polyisocyanurate (PIR) foams and a finer pitch in the reaction section to increase shear and residence time. Preferably, the extruder comprises a plurality of temperature-controlled zones, wherein the temperature is optionally progressively increased from at most 150 °C at the feeding zone to at least 200 °C in the reaction zones, more preferably 210- 220 °C, and optionally followed by a cooling zone at 180-200 °C before discharge. The residence time of the depolymerization reaction is preferably less than 20 minutes, more preferably less than 15 minutes, even more preferably less than 10 minutes, and most preferably less than 5 minutes. Preferably, the feedstock consists predominantly of PUR and / or PIR foams, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, 95 wt.% or 98 wt.%, and most preferably at least 99 wt.% of the total feedstock, optionally with substantially no polyethylene terephthalate (PET), paper, aluminium foil, plastic film or other contaminants. The weight ratio of PUR and / or PIR foam to polyhydric alcohol is preferably from 1 : 1.0 to 1 : 1.5, more preferably from 1:2.0 to 1: 1.5. The cyclotrimerization catalyst is preferably an alkali metal catalyst selected from potassium acetate, sodium acetate and lithium acetate, more preferably potassium acetate, most preferably potassium acetate. The process optionally further comprises repolymerizing the glycolysate with multifunctional isocyanates, preferably selected from methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and combinations thereof, wherein the repolymerization is preferably carried out either directly with 100% recycled polyols obtained from the process or with a blend of recycled polyols and virgin polyols, more preferably in a ratio of 30:70 to 70:30, and most preferably about 50:50.

[0104] In a preferred embodiment of the invention, the recycled polyols exhibit a hydroxyl index, as determined by KOH titration, in the range of 10% to 20%. Preferably, the hydroxyl index is in the range of 12% to 20%, more preferably in the range of 13% to 20%, more preferably in the range of 14% to 20%, more preferably in the range of 14% to 19%, and more preferably in the range of 14% to 18%, more preferably in the range of 14 to 15%. Such hydroxyl index values ensure that the recycled polyols maintain the necessary reactivity for subsequent polyurethane (PUR) or polyisocyanurate (PIR) production. Advantageously, hydroxyl indices in this range provide a balance between reactivity and stability, yielding polyols that are particularly suitable for high-performance applications requiring precise material specifications, while lower hydroxyl indices after purification may be used where reduced functionality is advantageous.

[0105] In an embodiment emphasizing the molecular characteristics of the recycled polyols, the invention produces polyols with a more homogeneous molecular mass distribution, featuring a peak molecular mass (Mp) of approximately 3000. This uniformity is essential for producing high-quality recycled polyols suitable for applications where consistent material properties are critical, such as in the manufacturing of foams, coatings, and adhesives. In a preferred embodiment, the recycled polyols exhibit a peak molecular mass (Mp) of at least 1000 and at most 5000, more preferably at least 2000 and at most 4000, more preferably at least 2500 and at most 3500, more preferably at least 2800 and at most 3200, and most preferably about 3000, as determined by GPC. This range has been found optimal to balance reactivity with processability in subsequent repolymerization reactions. In a further preferred embodiment, the recycled polyols obtained according to the process of the invention exhibit a substantially unimodal molecular mass distribution as determined by gel permeation chromatography (GPC). Preferably, the recycled polyols are characterized by the presence of a single main peak (Mp) without evidence of polymodal distributions. Such a unimodal distribution advantageously ensures reproducible viscosity and facilitates direct use of the recycled polyols in polyurethane (PUR) and polyisocyanurate (PIR) formulations.

[0106] In a preferred embodiment, the recycled polyols are characterized by a number average molecular mass (Mn) of at least 500 and at most 10 000, preferably at least 800 and at most 5000, more preferably at least 900 and at most 4000, even more preferably at least 1000 and at most 3000, and most preferably at least 1200 and at most 2500. In a further embodiment, the recycled polyols are characterized by a weight average molecular mass (Mw) of at least 1000 and at most 20 000, preferably at least 1500 and at most 10 000, more preferably at least 1800 and at most 7000, even more preferably at least 2000 and at most 5000, and most preferably at least 2200 and at most 4000. Preferably, the ratio Mw / Mn (polydispersity index, PDI or D) is less than 3.0, more preferably less than 2.5, still more preferably less than 2.0, and most preferably less than 1.8, indicating a narrow molecular mass distribution and enhanced homogeneity of the recycled polyols.

[0107] In a further embodiment, the recycled polyols exhibit a viscosity at 25 °C of at least 100 mPas and at most 20 000 mPas, preferably at least 200 mPas and at most 10 000 mPas, more preferably at least 300 mPas and at most 8000 mPas, even more preferably at least 400 mPas and at most 6000 mPas, still more preferably at least 500 mPas and at most 5000 mPas, more preferably at least 600 mPas and at most 4000 mPas, and most preferably at least 800 mPas and at most 3000 mPas. These viscosity values are particularly advantageous to ensure compatibility with conventional polyurethane production equipment, while maintaining desirable reactivity and processability of the recycled polyols.

[0108] In an embodiment, the polyols obtained directly from the depolymerization process, prior to or absent of purification, exhibit a hydroxyl number of at least 300 mg KOH / g and at most 700 mg KOH / g, preferably at least 350 mg KOH / g and at most 650 mg KOH / g, more preferably at least 360 mg KOH / g and at most 630 mg KOH / g. Within this range, rigid PIR foams such as insulation panels typically yield values around 480-630 mg KOH / g, while flexible PUR foams yield values around 530 mg KOH / g. These hydroxyl numbers ensure that the non-purified polyols maintain high reactivity suitable for polyurethane (PUR) and polyisocyanurate (PIR) repolymerization.

[0109] In a further embodiment, the polyols may be subjected to purification, which results in a reduction of the hydroxyl number. Purified recycled polyols typically exhibit hydroxyl numbers of at least 80 mg KOH / g and at most 300 mg KOH / g, preferably at least 90 mg KOH / g and at most 240 mg KOH / g, more preferably between 90 and 150 mg KOH / g. For example, rigid PIR foam-derived polyols show values of about 92-236 mg KOH / g after purification, while flexible PUR foam-derived polyols show values around 95 mg KOH / g. This adjustment of hydroxyl functionality provides additional control over viscosity and reactivity, enabling the purified polyols to be tailored for specific polyurethane formulations where lower hydroxyl numbers are advantageous.

[0110] In a further embodiment, the process has been demonstrated on both pilot-scale and industrial-scale extruders. Preferably, when using a small-scale extruder with a screw diameter of about 11 mm, a continuous production rate of about 30-40 g / h and a residence time of less than 10-12 minutes are achieved. More preferably, when using a larger extruder with a screw diameter of about 18 mm, the process achieves a production rate of about 1.5 kg / h with a residence time of less than 10, more preferably less than 5 minutes, thereby maintaining the homogeneous molecular mass distribution of the recycled polyols. This demonstrates scalability of the invention from laboratory to industrial conditions without loss of product quality.

[0111] In another embodiment, the process utilizes a larger-capacity extruder equipped with an enhanced feeder system, allowing for a significantly higher production rate of recycled polyols. In this embodiment, the continuous production rate is at 10 g / hour, more preferably at least 15 g / hour, more preferably at least 20 g / hour, more preferably at least 50 gram per hour, preferably at least 60, 70, 80, 90, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900 or even more gram per hour. This embodiment is designed to meet the demands of large-scale industrial applications, offering increased throughput while maintaining the quality and consistency of the recycled polyols.

[0112] In an embodiment, the recycled polyols obtained are miscible and preferably mixed with virgin or commercially available polyols in all proportions. Preferably, the recycled polyols are blended with virgin polyols in a ratio of 10:90 to 50:50, more preferably 20:80 to 40:60, even more preferably about 30:70, and still more preferably at least 50:50 or 100% recycled polyols. Such blends yield polyurethane products with excellent expansion, cell morphology, durability, and strength, thereby enabling the production of high-quality foams for industrial applications. While inclusion of virgin polyol is not required to produce PUR or PIR from the recycled glycosate; the inclusion of virgin polyol provides additional control to finetune the material quality.

[0113] The larger feeder system facilitates the continuous and efficient introduction of greater quantities of the premixture into the extruder, optimizing the depolymerization process. The process parameters, such as screw speed, temperature, and pressure, can be adjusted to accommodate the increased feed rate, ensuring that the reaction proceeds efficiently without compromising the integrity of the final product.

[0114] In one embodiment of the invention, the process is adapted to accommodate extruders with different screw diameters, reflecting the varying capacities and operational requirements of different equipment. Preferably, the extruder used in the process has a screw diameter of at least 11 mm, more preferably at least 18 mm, and even more preferably at least 35 mm. By accommodating a range of screw diameters, this embodiment ensures that the process is versatile and can be scaled effectively for various industrial applications. This flexibility allows the process to be optimized based on the specific equipment available, making it applicable to a wide range of manufacturing environments.

[0115] In another embodiment, the process is designed to offer flexibility in how the mixture of ground polyurethane (PUR) foam, catalyst, and polyhydric alcohol is introduced into the extruder. This flexibility is essential for optimizing the depolymerization reaction depending on the specific extruder used and the desired outcome.

[0116] The process may involve a one-step introduction method, wherein the entire mixture of ground foam, catalyst, and polyhydric alcohol is introduced directly into a feeding zone of the extruder. This method ensures that the mixture is homogeneously combined and that the residence time within the extruder remains less than 15 minutes.

[0117] Alternatively, the process can employ a two-step introduction method. In this approach, the ground polyurethane (PUR) foam is first introduced into the extruder, followed by the separate introduction of the liquid mixture containing the catalyst and polyhydric alcohol into an adjacent feeding zone. This two-step process also maintains a residence time of less than 15 minutes and may provide additional control over the reaction conditions, potentially leading to further optimization of the depolymerization process.

[0118] Preferably, the one-step introduction method has been predominantly used, with the mixture being introduced at the very first feeding zone of the extruder. This method has proven effective in ensuring a smooth and efficient depolymerization process. However, the inclusion of the two-step introduction method as an alternative embodiment allows for flexibility in process design, catering to different operational requirements and enabling further fine-tuning of the reaction parameters.

[0119] In a further embodiment of the invention, the feeding rate of the mixturecomprising ground polyurethane (PUR) foam, cyclotrimerization catalyst, and polyhydric alcohol— into the extruder, preferably the twin-screw extruder, is at least 200 mg / min. Preferably, the feeding rate is at least 300 mg / min, more preferably at least 350 mg / min. In a further preferred embodiment, the feeding rate may be at most 1000 mg / min, more preferably at most 800 mg / min, more preferably at most 600 mg / min, more preferably at most 500 mg / min. Most preferably, the feeding rate is approximately 400 mg / min. Controlling the feeding rate within this specified range ensures optimal interaction between the reactants inside the extruder, leading to efficient and consistent depolymerization of the polyurethane (PUR) foam. A feeding rate of at least 200 mg / min guarantees a sufficient supply of material to sustain a continuous process, preventing interruptions and ensuring steady production. Keeping the rate at most 600 mg / min prevents overloading the extruder, which could lead to insufficient mixing, incomplete reactions, or thermal inconsistencies. By fine- tuning the feeding rate within the preferred ranges, the process achieves a balanced residence time and effective heat transfer, resulting in high-quality recycled polyols with uniform properties. A most preferred rate of approximately 400 mg / min has been identified as delivering optimal results in terms of product quality and process efficiency. This rate allows for thorough mixing and adequate reaction time while maintaining a manageable throughput suitable for both laboratory-scale experiments and scalable industrial applications. Adjusting the feeding rate within these parameters also provides flexibility to accommodate different types of polyurethane (PUR) foams, varying degrees of foam particle sizes, and specific production requirements. This adaptability ensures that the process can be tailored to meet diverse operational needs while consistently producing recycled polyols suitable for high-performance applications. In a second aspect, the invention pertains to a use of multifunctional isocyanates to produce recycled polyols from glycolysate comprising polyols for the production of recycled polyurethane (PUR) or polyisocyanurate (PIR).

[0120] The use of these multifunctional isocyanates is crucial because they enable the formation of new polymer chains from the recycled polyols, thereby creating high- quality PUR or PIR materials with properties comparable to those made from virgin polyols. This process not only enhances the sustainability of polyurethane (PUR) production by allowing the reuse of materials that would otherwise be discarded, but it also ensures that the recycled products retain the mechanical strength, chemical resistance, and thermal stability necessary for demanding applications.

[0121] Moreover, the ability to produce recycled PUR or PIR using this approach expands the utility of the recycled polyols, making them suitable for a wide range of industrial applications, including insulation, automotive parts, and construction materials. By utilizing multifunctional isocyanates in this manner, the invention provides a practical and efficient method for integrating recycled materials into high-performance polyurethane (PUR) products, contributing to both environmental sustainability and economic efficiency.

[0122] Preferably, the recycled polyols are used to produce 100% recycled polyurethane (PUR) foams. This process is notably conducted without the addition of external blowing agents, activators, cell regulators, or emulsifiers, relying solely on components present in the initial waste material. This approach simplifies the repolymerization process, reduces costs, and maintains the purity of the final product while achieving high-quality foams with the necessary physical properties for their intended applications. In some embodiments, minimal quantities of these agents may be optionally included to fine-tune the properties of the final foam product, depending on specific application requirements.

[0123] The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.

[0124] EXAMPLES

[0125] The present invention will now be further exemplified with reference to the following examples. The present invention is in no way limited to the given examples.

[0126] For experimental validation of the present invention, two types of twin-screw extruders were employed: Extruder 1: a small-scale twin-screw extruder with screw diameter of 11 mm, suitable for laboratory and pilot-scale operations, configured for operation at controlled temperatures and pressures.

[0127] Extruder 2: a larger twin-screw extruder with screw diameter of 18 mm, equipped with multiple heating zones for controlled temperature profiling along the barrel, suitable for industrial-scale operation.

[0128] Both extruders were equipped with screw elements comprising sections of varying pitch. The screws included a feeding section with a relatively coarse pitch to facilitate effective intake and conveyance of the foam particles, a middle section with a finer pitch to increase shear, residence time, and mixing intensity, and a final section with a coarser pitch to support discharge of the depolymerized material. This configuration was found to promote efficient depolymerization by combining smooth feeding and discharge with enhanced mixing in the reaction zone.

[0129] Unless otherwise indicated, the pressure within the extruder was maintained below 30 bar, and the resulting glycolysate was collected directly at the discharge.

[0130] Example 1.

[0131] A continuous process for preparing recycled polyols from rigid polyurethane (PIR) foam waste was conducted. The rigid PIR foams, sourced from building and construction material, were mechanically ground to a particle size of approximately 5 mm. A cyclotrimerization catalyst, potassium acetate, was dissolved in dipropylene glycol at a temperature of 200°C. The ground PIR foams were then mixed with the catalyst-alcohol mixture to form a premixture with a weight ratio of 1: 1.5. This premixture was continuously fed into extruder 1 at a controlled temperature range of 210°C and a pressure of less than 30 bar. The screw speed was maintained at 5 rpm. The depolymerization reaction occurred within the extruder with a residence time of less than 12 minutes. The resulting glycolysate, comprising recycled polyols, was discharged and collected. The recycled polyols exhibited good solubility in common organic solvents such as acetone and THF, indicating successful depolymerization.

[0132] Example 2.

[0133] In another experiment, flexible polyurethane (PUR) foam waste was used. The flexible PUR was sourced from matrasses and pillows, as well as soft foam packaging. The flexible PUR foams were ground to a particle size of approximately 10 mm. Potassium acetate was used as the cyclotrimerization catalyst, dissolved in propylene glycol at 200°C. The ground PUR foams were mixed with the catalyst-alcohol mixture to form a premixture with a weight ratio of 1 : 1.5. This premixture was continuously fed into extruder 1 at a temperature of 210°C and a pressure of less than 30 bar. The screw speed was set to 5 rpm. The depolymerization reaction occurred within the extruder with a residence time of 10 minutes. The glycolysate was collected and analyzed, showing a uniform molecular mass distribution and high-quality recycled polyols.

[0134] Example 3.

[0135] To demonstrate the versatility of the process, a mixture of rigid and flexible polyurethane (PUR) foam waste was processed. The foams were ground to a particle size of approximately 8 mm. Lithium acetate was dissolved in ethylene glycol at 200°C, and the ground foams were mixed with this catalyst-alcohol mixture to form a premixture with a weight ratio of 1 : 1.2. The premixture was fed into a extruder 1 at a temperature of 200°C and a pressure of less than 30 bar. The screw speed was maintained at 5 rpm. The depolymerization reaction occurred within the extruder with a residence time of 10 minutes. The resulting glycolysate was collected and displayed enhanced polyol quality, suitable for various applications.

[0136] Example 4.

[0137] A test was conducted using butylene glycol as the polyhydric alcohol and potassium acetate as the catalyst. Rigid PIR foam waste was ground to a particle size of approximately 2 mm. The rigid PIR foam was sourced from post-industrial waste. The catalyst was dissolved in butylene glycol at 200°C, and the ground foams were mixed with this catalyst-alcohol mixture to form a premixture with a weight ratio of 1: 1. The premixture was fed into extruder 1 at a temperature of 210°C and a pressure of less than 30 bar. The screw speed was set to 5 rpm. The depolymerization reaction occurred within the extruder with a residence time of 10 minutes. The glycolysate was collected and exhibited high consistency in quality, demonstrating the versatility of using different polyhydric alcohols.

[0138] Example 5.

[0139] A repolymerization post-reaction was performed using the glycolysate obtained from Example 1. The glycolysate was mixed with 4,4'-methylene diphenyl diisocyanate (MDI) at 80°C and 100 rpm. The reaction was conducted for less than 30 minutes, resulting in the formation of 100% recycled foams with cell-like morphology. No additional blowing agents, activators, or emulsifiers were added during the post- reaction. The resulting recycled foams demonstrated good durability and strength, showcasing the potential for creating high-quality recycled products.

[0140] Example 6

[0141] Rigid polyurethane (PIR) foam waste representative of insulation panel applications was mechanically ground to a particle size of approximately 5 mm. A cyclotrimerization catalyst, potassium acetate, was dissolved in dipropylene glycol at a temperature of 200 °C. The ground PIR foams were then mixed with the catalyst-alcohol mixture to form a homogeneous premixture with a weight ratio of 1: 1.5. The feed rate was 1.5 kg / h of premixture (including foam waste, catalyst and DPG).

[0142] The premixture was continuously fed into extruder 2, which was equipped with multiple heating zones to allow gradual heating of the material. The temperature profile of the zones, measured sequentially from the feeding zone to the die, was controlled as follows: 100 °C, 170 °C, 190 °C, 210 °C, 210 °C, 210 °C, 210 °C, 210 °C, 210 °C, and 190 °C.

[0143] The screw speed was maintained at 300 rpm. Under these conditions, the depolymerization reaction occurred with a residence time of less than 2 minutes. The resulting glycolysate, comprising recycled polyols, was discharged and collected. The recycled polyols showed good solubility in common organic solvents such as acetone and THF, demonstrating effective depolymerization. However, during this test, difficulties were encountered with the feeding of the foam into the extruder. The screw profile employed in Example 6 comprised standard conveying elements in the introduction zone. Under these conditions, foam tended to accumulate in the feed section rather than being conveyed smoothly into the reaction zone, leading to poor material throughput and incomplete or absent depolymerization. This highlighted the importance of optimizing the screw profile to achieve efficient processing.

[0144] Example 7

[0145] Rigid polyurethane (PIR) foam waste, ground to approximately 5 mm, was premixed as in Example 6 using potassium acetate dissolved in dipropylene glycol at 200 °C, at a weight ratio of 1 : 1.5. The feed rate was 1.2 kg / h of premixture (including foam waste, catalyst and DPG).

[0146] The premixture was continuously fed into extruder 2, which was equipped with multiple heating zones. The temperature profile across the zones, measured sequentially from the feeding zone to the die, was: 100 °C, 170 °C, 190 °C, 210 °C, 210 °C, 210 °C, 210 °C, 220 °C, 220 °C, and 200 °C. The screw speed was maintained at 300 rpm, and the depolymerization reaction occurred with a residence time of less than 2 minutes. In this test, the twin-screw profile was modified compared to Example 6. Larger conveying elements with a lower pitch were introduced in the feeding zone to improve the intake and transport of foam particles into the machine. This adjustment was critical, as it prevented accumulation of foam in the introduction zone and ensured that the premixture was properly conveyed to the reaction zone. With this improved screw profile, continuous feeding and efficient depolymerization were achieved.

[0147] The resulting glycolysate was discharged and collected, showing good solubility in acetone and THF. The results demonstrate that the screw profile plays a key role in enabling successful recycling of rigid polyurethane foams. For all subsequent tests, this improved screw profile was employed.

[0148] Example 8

[0149] The glycolysates obtained from Example 7 (extruder 2, using the improved screw profile with larger conveying elements in the feeding zone) and Example 4 (extruder 1) were evaluated for miscibility and reactivity with commercially available polyols. In both cases, the glycolysate presented good miscibility with commercial polyols, irrespective of whether the glycolysate was obtained from extruder 1 or extruder 2.

[0150] Blends were prepared in a ratio of 30:70 (recycled polyols : virgin polyols) and reacted with 4,4'-methylene diphenyl diisocyanate (MDI). The resulting foams, containing both recycled and virgin polyols, displayed excellent expansion and well- developed cell-like morphology. The foams further exhibited good durability and mechanical strength.

[0151] These results confirm that the recycled polyols of the invention are highly compatible with conventional polyol formulations and can be used in combination with virgin polyols to produce foams meeting industrial quality requirements. The successful outcome also demonstrates that, with the improved screw profile, high-quality recycled polyols are consistently obtained and suitable for blending at different scales of operation.

[0152] Example 9

[0153] Rigid polyurethane foam (PIR) waste representative of air filtration applications was mechanically ground to a particle size of approximately 5 mm. A cyclotrimerization catalyst, potassium acetate, was dissolved in dipropylene glycol at a temperature of 220 °C. The ground PIR foams were then mixed with the catalyst-alcohol mixture at a weight ratio of 1: 1.

[0154] The premixture was continuously fed into extruder 1, operated at 220 °C and a screw speed of 5 rpm. For this test, the extruder was equipped with the improved screw profile described in Example 7, comprising larger conveying elements in the feeding zone to ensure smooth intake and transport of foam particles. Under these conditions, the depolymerization reaction proceeded reliably, with a residence time of less than 12 minutes.

[0155] The resulting glycolysate, comprising recycled polyols, was discharged and collected. The glycolysate exhibited good solubility in acetone and THF, confirming effective depolymerization. This example further demonstrates that the improved screw profile is applicable across different foam types and extruder scales, and plays a decisive role in the successful recycling of polyurethane foams.

[0156] Example 10 The recycled polyols obtained in examples 6, 7, 8 and 9 exhibited a hydroxyl number of approximately 480-630 mg KOH / g; with a corresponding mean OH-index 14.0 to 19.0. The recycled polyols obtained in example 4 showed a relatively hydroxyl number of 363 mg KOH / g; with a corresponding mean OH-index of 11.

Claims

1. CLAIMS1. A continuous process for preparing recycled polyols from polyurethane (PUR) foam and / or polyurethane (PUR) foam waste by glycolysis using an extruder, the process comprising the steps of: mechanically grinding the PUR foams to a particle size of at least 0.2 mm and at most 50 mm; dissolving a cyclotrimerization catalyst in a polyhydric alcohol; mixing the ground PUR foams with said cyclotrimerization catalyst- polyhydric alcohol mixture to form a premixture; continuously feeding the premixture into the extruder to conduct a depolymerization reaction within the extruder to produce a glycolysate comprising polyols, wherein the residence time is at most 30 minutes; and discharging and collecting said glycolysate comprising recycled polyols.

2. Process according to claim 1, further comprising repolymerizing said produced glycosylate with multifunctional isocyanates, preferably selected from the group consisting of 4,4'-methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), cyclic trifunctional isocyanates and combinations thereof, preferably the multifunctional isocyanates and glycolysate comprising polyols to produce recycled polyols.

3. Process according to claim 1 or 2, wherein the polyhydric alcohol is selected from the group consisting of diols, triols, and higher functionality alcohols, more preferably the polyhydric alcohol is a diol, selected from the group consisting of dipropylene glycol, ethylene glycol, propylene glycol, butylene glycol, and combinations thereof.

4. Process according to any of the claim 1 to 3, wherein the polyhydric alcohol has a hydroxyl number of 200 to 600 mg KOH / g.

5. Process according to any of the claim 1 to 4, wherein the cyclotrimerization catalyst as an alkali metal catalyst selected from the group consisting of potassium acetate, sodium acetate, lithium acetate, and combinations thereof.

6. Process according to any of the claim 1 to 5, wherein a weight ratio of PUR foam to polyhydric alcohol is from 1 : 10 to 1 : 1 and more preferably from 1 :5 to 1 : 1.2, more preferably from 1:2.5 to 1 : 1.4.

7. Process according to any of the claim 1 to 6, wherein a residence time is less than 15 minutes.

8. Process according to any of the claim 1 to 7, wherein a pressure in the extruder at most 50 bar, preferably at most 30 bar.

9. Process according to any of the claim 1 to 8, wherein the mixture of ground PUR foams and catalyst solution is fed into the feeding zone of the extruder at room temperature.

10. Process according to any of the claim 1 to 9, wherein a temperature in the extruder is between 150°C and 250 °C, more preferably between 200°C and 220°C.

11. Process according to any of the claim 1 to 10, wherein the extruder is a twin- screw extruder.

12. Process according to claim 11, wherein a screw speed of the twin-screw extruder is between 2 and 600 rpm, preferably between 5 and 50 rpm, preferably both screws rotate in the same direction.

13. Process according to any of the claims 1 to 12, wherein the polyurethane (PUR) foam and / or polyurethane (PUR) foam waste is rigid.

14. Process according to any of the claims 1 to 13, wherein one or more auxiliary additives are mixed into the premixture before the depolymerization reaction, said additives being selected from the group consisting of stabilizers, flame retardants, plasticizers, fillers, antioxidants, UV stabilizers, colorants and combinations thereof.

15. Use of multifunctional isocyanates to produce recycled polyols from glycolysate comprising polyols for the production of recycled polyurethane (PUR) or polyisocyanurate (PIR).