Recycled polyurethane foam, its production, and its use

Abstract

Recycled polyurethane ( PU) foam, which contains PU rigid foam basic material, MDI-prepolymer, ion-exchanged water and lignin solution, and does not contain phenolic foam. The object of the invention also relates to a method for the production of this recycled polyurethane ( PU) foam and to its use.

Description

[0001] Recycled polyurethane foam, its production , and its use

[0002] The field of the invention

[0003] The invention relates to recycled polyurethane foam containing rigid polyurethane foam, to a method for the production of such foam, and to its use .

[0004] The state of the art

[0005] The scope of the present invention concerns recycled rigid polyurethane foam .

[0006] On the basis of the widespread use of polyurethanes ( PU) and their considerable share of the market , it may be determined that polyurethane foams have an important role in the urethane and plastics industry . The foaming of PU may be performed using a physical or chemical foaming agent . Physical foaming agents include various pentanes ( such as normal , iso or cyclopentanes ) , while various carboxylic acids , or water, are used most commonly as a chemical foaming agent . As a consequence of the multitude of basic materials available , the characteristics of the foam produced may be altered throughout a broad scale , for example , soft , integral and rigid foams are known of . Rigid PU foams are generally used in the construction industry as thermal insulation elements ; however, these do not conform to strict fire-prevention prescriptions . This fact called for the creation of the family of polyisocyanurate foams (hereinafter abbreviated as PIR) , which, as a consequence of their cyclic structure and greater cross-link density, have greater thermal and fire resistance compared to PU . PIR foams may be viewed as a subtype of rigid polyurethane foams. It is known that the large majority of the volume of the foams are low-density gas, which may create a continuous pore system or consist of separate cells. In accordance with this, we differentiate between open and closed cell foams.

[0007] In 2022 in the EMEA region (Europe, Middle East, Africa) some 6 million tonnes of polyurethane were manufactured, of this amount nearly 2 million tonnes were PU rigid foam. A total of 80% of this was used in the construction industry, mainly in the form of sandwich panels, and thermal insulation foam panels. Additional significant users of PU rigid foams are the sector dealing with the manufacture of refrigerators and the auto industry [ IAL Consultants, PRESS RELEASE, 2023 May, Polyurethane chemicals and products in Europe, Middle East & Africa (EMEA) , 2023 <https : / / www. i al consult ants . com / media / 1104 / pu-emea-press- release-2023 .pdf>] .

[0008] The fact that foams like this are being manufactured in such large volumes also raises the issue of their handling as waste .

[0009] Three main waste formation points may be identified in connection with PU foams:

[0010] 1. the waste created at manufacturers (e.g. manufacturing scrap, waste created during process transition, etc.) ;

[0011] 2. waste formed as a consequence of consumption (e.g. the cutting out of the locations of windows and doors in the field of construction, surplus material, scrap, etc.) ;

[0012] 3. waste source produced at the end of life of products (referred to as End of Life, or abbreviated as EoL in the literature) , e.g. in the remodelling of buildings, their demolition, demolition of cold-storage units, and the wear and tear of household refrigerators.

[0013] The three main sources of waste together in total represent several hundred thousand tonnes of PU rigid foam waste annually in the EMEA region, which is managed in the following ways :

[0014] 1. landfilling;

[0015] 2. incineration for energy recovery;

[0016] 3. recycling.

[0017] From the above it may be concluded that there is a great demand for the recycling of PU foams, as a significant amount of PU foam waste is created every year. This, in the coming decades, is expected to increase exponentially, as a large amount of previously manufactured PU rigid foam-based thermal insulation material will reach the end of its life [Shangwen Zhu et al, 2023, J. Phys. : Conf. Ser. 2553 012001 and Gama, N.V.; Ferreira, A.; Barros-Timmons, A.; Polyurethane Foams: Past, Present, and Future; Materials, 2018, 11, 1841] .

[0018] At present there are two main solutions for the latter that are known of, i.e. for the recycling of PU waste:

[0019] 1. Chemical recycling (e.g. by using glycolysis, aminolysis, hydrolysis, etc.) ;

[0020] 2. Mechanical recycling, which includes the following: a) rebonding; b) recompression using steam or other heat source; c) the use of milled foam as a simple filler material; d) recycling carried out using injection technology.

[0021] Several solutions dealing with the recycling of PU rigid foams are known of according to the state of the art. Patent application number WO23222400A1 concerns a PU rigid foam production method, the product created with which contains a silicone- free surfactant . The patent application mentions recycled polyols , which originate from chemical recycling .

[0022] Patent application number WO2023208946A1 discloses a method with which basic materials originating from polyurethane products containing isocyanurate may be reclaimed . Chemical recycling is used during the method, but physical recycling is also mentioned, however it is noted in connection with this that physical recycling has numerous limits .

[0023] Patent application number WO2022122360A1 relates to the production of rigid polyurethane foams , during which at least one isocyanate component , one polyol component , optionally a catalyser ( catalyses the formation of the urethane or isocyanurate bond) and a foaming agent are used, the product also contains polyester polysiloxane block copolymers .

[0024] Patent application number WO2023194140A1 relates to the value- added recycling of polyurethane foams . The polyurethane rigid foams are chemically depolymerised in such a way that the polyol , the polyamine and the phosphate ester flame retardant are recovered .

[0025] Patent application number W019030071A1 relates to isocyanate functional polymer components , polyurethane obj ects produced from recycled polyurethane plastics and to the production methods in general . General teaching may be read in the application in connection with the recycling of thermoplastic polyurethane articles and PU soft foams . The solution according to patent application number WO2023110753A1 relates to thermoplastic, open-cell , flexible polyurethane foams , which foams may be classed among soft foams .

[0026] Polyurethane soft foams are produced in patent application number W02019023090A1 , in which no mention is made of the use of recycled PU foams .

[0027] The foam product according to patent application number US20200231735A1 partially contains (maximum 50% ) recycled polyurethane .

[0028] As much as 10-30 percent of pure PU materials used during panel production may end up as waste . This scrap PU material may be reused by, for example , being ground into powder and then this powder being used as a filler in the production of PU products , as described in patent application number WO2019219814A1 .

[0029] In patent application number EP3808532A1 thermoplastic polyurethane is produced using recycled cast polyurethane by it being first ground and then added to the new material .

[0030] According to patent application number W009152044A1 recycled polyurethane rigid foam is used as filler material .

[0031] Patent application number WO12126380A1 states that recycled polyurethane foam is used in the form of powder for the production of PU foams containing a phosphor-containing flame retardant .

[0032] Patent application number WO16028837A1 states that PU products may also be recycled by grinding the PU products into powder and by remixing the powder into the original PU product , then forming it into a new product using a pressing process .

[0033] Patent application number W014047043A1 discloses a polyol production method and PU products ( foam inserts ) made from this .

[0034] Application number US20110212317A1 discloses the production of a multilayer product made by using partially recycled materials ( such as chopped auto industry trim parts ) . The layers are pressed together during heat-treatment .

[0035] The invention disclosed in patent application number DE102006021264A1 relates to composites that contain PU rigid foam flakes , solid isocyanate-based binder materials and inorganic and / or organic additives , the obj ectives of the invention include increasing the flame resistance of composites . The chopped rigid polyurethane foam is mixed with an adhesive and pressed . A temperature of between 100-200 ° C is applied during pressing .

[0036] Patent application number EP1375104A1 relates to a method for the production of cast components , blocks and cylinders , according to which a liquid binder containing reactive NCO groups is added to manufacturing residues originating from polyurethane rigid foam production and / or from polyurethane rigid foam-based components that can no longer be used for their original function and evenly mixed (where this relates to open-cell foam with a density of 5-50 kg / m3) , the mixture obtained in this way is dispensed into a tool , where steam is introduced and, optionally, pressure is applied, then cross-linking of the product takes place , then finally the cast component, block or cylinder is removed from the tool . Patent application number EP0693526A1 discloses a method for the production of urethane rigid foams . In step c ) of the production method in the patent application a powder originating from PU rigid foam is used, the particle si ze of which is preferably between 0 . 3 and 2 mm, more preferably between 0 . 5 and 1 mm . Reference is made in the application to the polyurethane powder as organic filler material , and not as the initial material of urethan rigid foams .

[0037] During the method disclosed in patent application number EP0458261A1 the PU rigid foam powder created during the cutting of PU foams is collected and mixed with linear, low- density polyethylene and high density polyethylene / maleic acid anhydride copolymer . Heat is applied during the production of the product .

[0038] Basic materials similar to those in the present invention are used in patent documents numbers EP3954730A1 and EP3371250B1 . In these documents the reprocessing of PUR / PIR rigid foams is achieved by steps of milling ( a particle si ze typically under 5 mm, preferably under 1 mm and even more preferably between 500 pm and 100 pm is used) , by addition of a binder and activated water and then by pressing . Using both solutions a product may be produced with a density of at least 150 kg / m3, preferably this value is 450 kg / m3, but the finished product may even reach a density of 600 kg / m3, in other words hard, solid panels may be made in this way .

[0039] In the solutions according to the state of the art described in detail above , the PU rigid foams are typically processed in the following way :

[0040] During grinding, chopping or cutting, a polyurethane foam ground material or powder is created, following this the ground material or powder is forti fied with various mixtures , then prepolymers are added to it . Finally, the process is accelerated with steam or heat introduced externally, and then the mixture is pressed . Typically, the polyurethane foam powder is used as a filler (up to an amount of 20% ) and not as a main initial material . The reprocessing, value-added use of soft polyurethanes ( e . g . sponge or rubber ) is more widespread according to the state of the art ( e . g . bed mattresses , playground surfaces , filler, etc . ) . The mechanical reutilisation of closed cell PU rigid foams , i . e . its recycling is a technical field currently being researched, the reprocessing of PU rigid foams in practice is still relatively rare . One market participant is Puren GmbH, which company produces panels from closed cell PU rigid foam following reprocessing .

[0041] BOS IG GmbH also processes polyurethane rigid foams , one may read in detail about the product produced in patent application number WO2022012733A1 . During recycling BOS IG GmbH heats the basic material and uses phenolic foam, among other materials , as an additive .

[0042] Patent document number CN101012332B presents a production method for thermal insulation materials that contain polyurethane rigid foam ground to a powder, lignin in powder form and MDI in one of the embodiments . It is obvious for a person skilled in the art that MDI and the MDI-prepolymer di f fer in terms of their chemical and physical properties .

[0043] Polyurethane panels are produced in patent application number EP4063423A1 , which panels contain plant fibres , polyurethane foam particles and isocyanate .

[0044] Polyurethane rigid foam is produced in patent application number CN113583206A via the degradation of the polyurethane elastomer at a high temperature and then with the addition of reagents .

[0045] The PU product according to patent application number W02018053530A1 contains isocyanate and polyols ( such as lignin) .

[0046] The publication of Xue et al . (ACS Sustainable Chem . Eng . 2014 , 2 , 1474-1480 ) discloses a lignin-based rigid polyurethane foam, which is reinforced with cellulose fibre .

[0047] It may be generally stated that the processing of PU rigid foams is still rare in practice , and instead of recycling the waste created from PU rigid foams it is typically disposed of in waste incinerators , where energy is extracted from the waste via burning, or the waste is disposed of in landfill . Although in a small proportion, the chemical recycling of the aforementioned PU foams also takes place .

[0048] Currently PU rigid foam waste is frequently disposed of in landfill or incinerated, thereby causing a signi ficant environmental load . Although there have been attempts at the mechanical recycling of closed cell PU rigid foams as stated above , the problem can still not be deemed to have been solved .

[0049] The general problem when trans forming waste PU rigid foams into new products is that the experiments performed in connection with reprocessing involve the use of a signi ficant amount of energy, however, i f waste PU rigid foam is not reprocessed then, in addition to the signi ficant environmental burden, this also means that a basic material ( crude oil ) originating from a finite source is not recycled .

[0050] According to the current state of the art , ground PU rigid foam originating from mechanical recycling is only trans formed into a product via the introduction of external heat ( such as heating and / or steam) , this involves the use of signi ficant extra energy .

[0051] In addition to the above the varying particle si ze of particulate PU rigid foam, as initial material , the use of additives di f ferent to the petrochemical additives used to date , such as lignin solution, the method di f ferent to the methods for reprocessing PU rigid foams known of to date ( omitting the use of external heat and / or the use of water spray for wetting) together make it possible to produce high- density, functional rigid foam blocks . In other words , a recycled PU foam product containing PU rigid foam that may be produced in a more energy ef ficient way is not known of according to the state of the art .

[0052] Therefore , a method for the production of recycled polyurethane foam containing rigid polyurethane foam is required that may be implemented in a more energy ef ficient way than the current methods and, optionally, may be also implemented more simply and more economically .

[0053] A brief description of the figures

[0054] Figure 1 shows the block diagram of a production line adapted for the production of recycled PU foams .

[0055] A brief description of the invention

[0056] The method according to the present invention is based on recycled PU rigid foams containing PU, to which a speci fic amount of MDI-prepolymer (MDI means methylene diphenyl diisocyanate ) , ion-exchanged water and lignin solution are added . In the course of the method for the production of recycled PU foam according to the present invention, an initial material with a given particle si ze is preferably used and / or the method is implemented without heat treatment and / or during the implementation of the method the wetting step is optionally performed with a water spray . The result of all these method steps is that the energy use of the method is lower than that of the known methods .

[0057] In the course of the method, the steps relating to the preparation of the basic material ( grinding, powder separation, separation of ferromagnetic materials ) are performed in a continuous process , then the basic material prepared in this way is provided with a binder and water in appropriate proportions , and then pressed . The product obtained with the method according to the present invention may typically serve for the production of foam blocks , from which, for example , thermal insulation door inserts , furniture components for the furniture industry, special insulation products for the construction industry and buf fers in parks , public areas and in the logistics sector may be made .

[0058] While searching for initial compositions suitable for the industrial scale production of recycled PU foams , we found that PU rigid foam with a particle si ze greater than 10 mm may also be used for this . It was also recognised that lignin solution may also be used as the additive for the production of recycled PU foams instead of petrochemical substances . It was also recognised that during the production method of recycled PU foams , the desired product may be produced without the use of external energy and / or the water spray used during the wetting step in the method involves additional advantages . Using particulate foam with this particle si ze and / or lignin solution, and also with the implementation of the aforementioned production method steps recycled PU foam may be produced with a lower use of energy.

[0059] Therefore, in accordance with the above, the present invention relates to recycled PU foam that contains PU rigid foam basic material, MDI-prepolymer , ion-exchanged water and lignin solution and that does not contain phenolic foam.

[0060] The invention preferably relates to a recycled PU foam with a relative density of between 60 and 140 kg / m3.

[0061] According to another preferable embodiment the recycled PU foam according to the invention preferably contains at least one additional additive selected from the following group: inorganic fibrous materials (such as: basalt fibre, glass fibre) , plant-based fibres (such as: wood wool, wood powder, sawdust) , natron or potassium water glass solution, vermiculite, thermoplastic polymer fibres (e.g. : polypropylene) , gypsum, calcium sulphoaluminate based cement, other sparsely cross-linked elastomer materials (such as: natural rubber, styrene-butadiene rubber) , where the said additional additive is present in an amount of 0.5 to 55 m / m%.

[0062] The present invention also relates to recycled PU foam where the PU rigid foam basic material was subjected to milling before the production of the recycled polyurethane (PU) foam, and the average particle size of its particles (characteristic largest dimension) is 10 mm or greater, more preferably between 10 and 30 mm.

[0063] The invention preferably relates to a recycled PU foam that contains 30 to 80 m / m% PU rigid foam basic material, 1 to 55 m / m% MDI-prepolymer, 1 to 45 m / m% ion-exchanged water and 0.3 to 20 m / m% lignin solution, more preferably 35 to 75 m / m% PU rigid foam basic material , 15 to 50 m / m% MDI-prepolymer , 2 to 25 m / m% ion-exchanged water and 0 . 3 to 10 m / m% lignin solution .

[0064] In addition, the present invention also relates to a method for the production of recycled PU foams that contains the following steps : a ) the PU rigid foam basic material is milled, optionally to an average particle si ze of between 10 mm and 30 mm, for the purpose of producing chips ; b ) the powder-consistency part of the chips obtained in step a ) is separated, the separation is preferably performed in a rotating drum powder separator ; c ) the particles containing ferromagnetic material are separated from the chips obtained after step b ) on a conveyor belt with the use of a magnet ; dl ) after the separation according to step c ) ion-exchanged water is sprayed onto the accumulated chips for the purpose of producing foam chips or, d2 ) after the separation according to step c ) MDI -prepolymer and lignin solution are added to the dry chips accumulated according to step c ) ; el ) the foam chips according to step dl ) proceed between two conveyor belts , where the MDI-prepolymer and the lignin solution are added to the water-sprayed chips according to step dl ) or, e2 ) in the case that the preliminary water addition has not taken place according to step dl ) , then the chips according to step d2 ) , which also contain MDI-prepolymer and lignin solution, are wetted with a water mist of ion-exchanged water ; f ) the foam chips also containing MDI-prepolymer and obtained in step el ) or e2 ) are collected in a press mold where , optionally, additional additive is mixed with it , g) the foam chips according to step f ) are pressed into foam blocks at a given press pressure without the use of an external heating ef fect , preferably using a hydraulic press for this ; h) for a given period of time the foam blocks are left to rest in the press mold under pressure without the use of any external heating ef fect ; i ) the finished foam block is cut to shape / cut into boards , the foam blocks formed into panels are optionally laminated or coated in accordance with the intended use .

[0065] According to an even more preferable implementation of the method, the pressure applied in step g) is between 0 . 1 and 200 bar, preferably between 50 and 150 bar .

[0066] According to a preferred implementation of the present invention, in step h) the foam blocks are left to rest until the chemical reaction taking place in the blocks i s completed .

[0067] According to a further preferred method of implementation of the invention, steps dl ) and d2 ) are performed in continuous operation with the use of a conveyor belt .

[0068] Furthermore , the present invention also relates to the use of the recycled PU foam according to the above for the production of furniture components , construction industry insulation, construction industry materials , buf fers , and for the reinforcing of furniture components .

[0069] A detailed description of the invention

[0070] I f not mentioned to the contrary, m / m% in the present speci fication is understood to mean mass percent (mass% ) , and ratios are understood to mean the mass ratios of the individual components .

[0071] In the scope of the present speci fication i f a numerical value is given, this is understood to mean that the last digit of the given number shows the precision of the given value according to the rounding-up rules . Therefore , for example , 30 m / m% is understood to mean all values falling within the range of 29 . 5 m / m% to 30 . 4 m / m% .

[0072] In the scope of the present speci fication, i f a range between two values is defined, then the concrete numerical values indicated as the limit values of the range are viewed as constituting parts of the range .

[0073] Polymer foams are two-phase systems in which statistically distributed gas bubbles of varying si ze are located in a polymer matrix . The foamed products have numerous preferable characteristics , such as low density, good sound and thermal insulation characteristics , outstanding energy absorption ability, as a consequence of which they may be used in numerous branches of industry .

[0074] From among polymers , the present invention relates to the class of polyurethanes , in which the materials containing the urethane bonding group are classed, and during the production of which a polyaddition reaction takes place between di or polyisocycante and a di or polyol unit . The PIR foams mentioned above may be viewed as a sub-type of PU rigid foams , therefore the term PU foam is understood to mean both PU and PIR foams , and for the sake of simplicity we use the term PU foams for these foams overall . Within the context of the present invention, recycled PU foam is understood to mean that PU rigid foam is used as the basic material for this , in other words with the word recycled we make reference to the reprocessing of PU rigid foam . The PU rigid foam basic material may be open cell or closed cell , and is preferably closed cell PU rigid foam . The PU rigid foam basic material constituting the basis of the recycling typically, but not necessarily, originates from a source of waste , in other words this component should not be understood to originate exclusively from a source of waste .

[0075] The recycled PU foam according to the present invention also contains , in addition to the PU rigid foam basic material , MDI-prepolymer , ion-exchanged water and lignin solution, however, it does not contain phenolic foam .

[0076] According to its composition, the recycled PU foam according to the present invention contains MDI-prepolymer, which, within the scope of the present invention, serves as the binder of the mechanically recycled PU rigid foam basic material ; such urethane prepolymers are , for example , diphenylmethane diisocyanate , a polyether polyol or polyester polyol-based prepolymers . The background of this , on the one part , is that diphenylmethane diisocyanate reacts with the polyurethane molecules of the PU rigid foam basic material , to be more precise with their hydroxyl and amino groups , thereby creating a binder material . On the other part , the reactive isocyanate groups of the diphenylmethane diisocyanate prepolymer also quickly react with water and create urea bonds whilst releasing carbon dioxide . The carbon dioxide generated contributes to the foaming of the recycled PU foam and to the development of its porous structure . It should be noted that the MDI-prepolymer di f fers from MDI in both chemical and physical aspects . The reactivity of MDI-prepolymer is lower than in the case of MDI and its viscosity is higher than that of MDI , and all this has an impact on the composition according to the present invention, on the ability to process this composition and also on the characteristics of the final product . The use of the lower reactivity level MDI-prepolymer in combination with the lignin solution results in such preferable characteristics in the recycled PU foam that were not expected .

[0077] The MDI-prepolymer in the composition according to the present invention is preferable compared to MDI from multiple points of view : as mentioned above , the MDI-prepolymer contains polymeric MDI and polyether-based prepolymer, which results in lower reactivity and higher viscosity in the composition, and these make it possible to better regulate the reaction speed ( the reaction kinetics are also di f ferent ) and ensure a longer processing time . The latter facilitates the even and quality production of larger si zed blocks without the use of external heat . The lower reactivity level also reduces the amount of heat generated during the reaction, therefore there is no need for energy-intensive cooling or heating steps , thereby the production method becomes more energy ef ficient and cost- ef fective .

[0078] Lignin is a large molecular weight polymer that occurs in nature , which reinforces the cell walls of plants and provides them with water resistance , it constitutes one quarter to one third of the dry material content of trees , it is mainly present in the transport and support cells of wood . Along with cellulose and hemicellulose , lignin is a main component of plant biomass , and plays a signi ficant role in the stability of the structure of plant cells and protects plants against pests and disease . The complex, three-dimensional structure of lignin consists of various monomers , which constitute a broad range of bonds . This structural diversity makes lignin exceptionally resistant to biological and chemical degradation [Vanholme et al . , Lignin bios zintezise es s zerkezete [ The biosynthesis and structure of lignin] , Ndvenyelettan [ Plant Biology] , July 2010 , volume 153 , pp . 895- 905 . ] . Lignin solution is a side-product of the cellulose and paper industry and processing . The extraction and refining of lignin is important from the point of view of various industrial applications . Lignin may potentially be used as a replacement of conventional , fossil-based polyols in the production of polyurethane ( PU) foams , thereby reducing the environmental footprint of production . The use of solutions made from lignin as additives has several advantages over fossil-based polyols : They are environmentally friendly, as lignin is a renewable basic material , the use of which may reduce dependence on fossil-based basic materials and facilitate the use of a greater proportion of bio-based materials in industry . They are cost-ef fective , as lignin is created as a sideproduct of cellulose production, and may represent an economical alternative to more expensive , fossil-based polyols .

[0079] The use of lignin-based polyols may modi fy the characteristics of the final PU foam, for example , it may improve its UV resistance , its resistance to fire , and its biodegrading . However, the use of solutions made from lignin in PU foams is still in the research and development phase , and involves numerous challenges , such as the heterogeneity of the basic material , the high viscosity and the quality of the finished product . The purpose of the research and the technological developments is the optimisation of the production process of lignin-based polyols and the improvement of the properties of finished products containing lignin solution . The liquid form of lignin solution enables more even distribution in a mixture than in the case of powder lignin, all this improves the ef ficiency of the reaction and the mechanical properties of the finished product . As mentioned above , the isocyanate groups of the MDI- prepolymer react with the active hydrogen atoms located on the surface of the PU rigid foam chips ( such as with hydroxyl or amino groups ) , as well as with the hydroxyl groups of the lignin in the lignin solution . The cross-linked structure created in this way ef fectively bonds together the particles of the PU foam chips , resulting in a strong and homogenous finished product .

[0080] Within the context of the present speci fication, the lignin solution contains at least 92 mass! lignin and a maximum of 8 mass! water .

[0081] The disadvantages of phenolic foam frequently used in the production of recycled PU foam are as follows :

[0082] The use of phenolic foam is an energy-intensive process , as the polymerisation of phenol formaldehyde resin and its foaming require heat and pressure , and it is obvious for a person skilled in the art that this demands a greater consumption of energy, which raises the production costs and the environmental impacts .

[0083] With the use of phenolic foam, the finished product may be hard and brittle , which may limit the methods used in its processing, such as the cutting and shaping of the product . This may make the customisation of the product dif ficult and increase the amount of waste .

[0084] Furthermore , the degradation of phenolic foam can take a long amount of time , and as it can contain toxic materials , it cannot be viewed as a sustainable basic material from an environmental point of view . The waste produced during the manufacture of recycled PU foam and the handling of the end- of-li fe products may represent environmental challenges . In summary, by omitting phenolic foam our recycled PU foam product may be produced in a more cost-ef fective and sustainable way . The relative density of the recycled PU foam according to the invention is between 60 and 140 kg / m3. It is obvious for a person skilled in the art that the relative density of a foam product determines its fields of use.

[0085] According to a preferable embodiment the recycled PU foam contains at least one additional additive, which is selected from the following group: inorganic fibrous materials (such as: basalt fibre, glass fibre) , plant-based fibres (such as: wood wool, wood powder, sawdust) , natron water glass solution, or potassium water glass solution; vermiculite; thermoplastic polymer fibres (e.g. polypropylene, polyethylene, polyamide) ; gypsum; calcium sulphoaluminate based cement, other sparsely cross-linked elastomer materials (such as natural rubber, styrene-butadiene rubber) , where the said additional additive is present in an amount of 0.5 to 55 m / m%. By selecting the additives, the properties of the recycled PU foam may be influenced, which are explained in detail below: For example, by adding plant fibres the mechanical properties of the recycled PU foams (e.g. flexural modulus and compressive strength) may be increased.

[0086] Vermiculite may also be used as an additive in the composition of the recycled PU foam according to the present invention. Vermiculite is a mineral that swells on exposure to heat. By using it in the recycled PU foam composition it improves the thermal insulation and mechanical stability of the PU foam. In addition, vermiculite increases the porosity of the foam product, which may influence its thermal and sound insulation properties. Vermiculite does not play any part in the chemical reaction taking place between certain of the components of the recycled PU foam, it only improves the properties of the foam product created. Polypropylene and other thermoplastic fibres may signi ficantly improve the mechanical properties of the material , such as tensile strength, abrasion resistance and resistance to cracking . The addition of thermoplastic polymer fibres increases the resistance of the recycled PU foam to mechanical ef fects . Overall , a recycled PU foam that contains polypropylene fibres as additive is a strong, flexible and durable composite , which may be used widely by the construction industry ( in insulation, for example ) , or special fields of use may enter into consideration where high mechanical strength and resistance are of key importance . The use of gypsum (which may be natural gypsum, power plant gypsum or recycled gypsum) in the composition of the recycled PU foam provides additional rigidity and formability to the finished foam product . Gypsum solidi fies in reaction to water, thereby giving the recycled PU foam stability and a solid structure . Recycled PU foam containing gypsum as additive is a multi function composite that may be used in the construction industry as a special insulation or walling material , for example , furthermore , due to the use of gypsum the foam product may also be suitable for interior design purposes , as well as for thermal insulation solutions for floors . Fast-setting calcium sulphoaluminate based cement , such as Alicem, is a BSAC type ( containing belite ) sulphoaluminate based cement , containing microni zed calcium sulphate , in which C4A3S constitutes the main clinker phase . 85% of the formation of ettringite typically occurs very quickly, even before the development of the aluminates and the silicates , due to this the risk of subsequent , undesired swelling and cracking is very low . [Meselia Hungaria Kft . Kdtesgyorsito cementek [ quick-setting cements ] <https : / / meselia . com / kotesgyorsito- cementek / >]

[0087] According to our assumption the following reaction occurs when the recycled PU foam is produced : the milled PU rigid foam and the MDI-prepolymer react with each other, thereby creating a binder . From among the additives , even several may be used simultaneously . The addition of water to the composition starts the reaction for the actual development of the binder . The MDI-prepolymer and the water react with each other, thereby creating the polyurethane foam . The addition of the calcium sulphoaluminate based cement facilitates the hardening of the binder . The reason for this is that the calcium sulphoaluminate based cement reacts with the water, which starts a so-called hydration process and forms a binder . This binder makes the composition more solid and durable , which composition hardens by the end of the lengthy setting process . Heat is released during the hydration process of the calcium sulphoaluminate based cement , in other words the more calcium sulphoaluminate based cement is added to the composition, the greater the heat production originating from the hydration process . In addition, the MDI-prepolymer and water reaction is also exothermic . In other words , ultimately these two exothermic reactions have a preferable ef fect on the creation of the PU foam . The heat generation is preferable for the MDI - prepolymer foaming and is of critical importance in the foam generation process , and not incidentally the recycling process is also energy-ef ficient , as the heat generated through the addition of the cement makes the use of electric or steam heating frequently used in similar processes ( such as PU rigid foam production) unnecessary .

[0088] The addition of natural rubber or other sparsely cross-linked elastomers to the recycled product enables the production of a durable , flexible finished product , which may be used to excellent ef fect for impact energy absorption, such as in car parks or other similar areas .

[0089] The average particle si ze of the PU rigid foam basic material that has been subj ected to milling, i . e . mechanical grinding according to the present invention, the greatest dimension of the nearly identically si zed elements of all three directions in space , is 10 mm or above , preferably between 10 and 30 mm . In other words , we recognised that it is not necessary to use the PU rigid foam in a format milled into powder, as is done in multiple solutions belonging to the state of the art . It is obvious for a person skilled in the art that during the production process a mixture obtained from an initial material milled to a powder and one in which the average particle si ze of the given starting material is 10 mm or above behave di f ferently during the production process , and the di f ferent behaviour requires di f ferent processing . The production of chips with a particle si ze of 10 mm or greater requires less energy during milling than the production of a fine powder . This results in a signi ficant saving of energy and costs . The use of chips with a greater particle si ze facilitates more open porosity in the finished product and the formation of a special cell structure ( explained in more detail below) , which improves the thermal and sound insulation properties of the foam .

[0090] In the case of the use of chips with a particle si ze of 10 mm or greater technical challenges were overcome , such as ensuring the homogeneity of the mixture , which has an ef fect on the course of the reaction . The greater particle si ze chips have a smaller speci fic surface area as compared to powder, which results in a lower need for binder in order to ef fectively link the particles . It is obvious that finely powdered materials have a large speci fic surface area, and due to this more binder is necessary in order to cover the entire surface . In the case of larger particles , the binder has to cover a smaller total area, in other words the binder is distributed more ef ficiently . This makes it possible for the binder to form a thicker and more uninterrupted layer around the particles , "embracing" them, as it were . The thicker binder better penetrates into the surface unevenness of the particles , thereby creating stronger mechanical and chemical bonds between the particles . As a result of this the bond between the particles will be stronger, which improves the structural integrity and mechanical properties of the finished product .

[0091] The use of less binder does not only reduce the materials costs , but also contributes to the sustainability of the production process , as less chemical material is used . Furthermore , the use of chips with a larger particle si ze makes it possible for the cross-link structure formed during the reaction taking place between the MDI-prepolymer , the lignin solution and the water to optimally fill the space between the components . It is obvious that there are greater cavities remaining between the larger particles , which the cross-linked polymer matrix only partially fills . As a result of this a more open cell structure is formed that contains larger pores , thereby creating a strong and homogenous structure . The structure created improves the mechanical properties of the finished product , for example , it increases strength and resistance to impact , as the binder developing during the cross-linking process does not only connect to the surface of the particles , but also fills the space between them, thereby reinforcing the entirety of the recycled PU foam .

[0092] Due to the cell structure of the product created in this way it is able to bind more air, which reduces heat conduction and so it ensures better insulation, in other words it preferably influences the thermal and sound insulation properties of the product as well . The carbon dioxide released during the crosslinking process contributes to the foaming, thereby creating an even cell structure , which optimises the insulating capability . The combination of the larger particles and the optimal space filling results in porosity that improves the thermal insulation properties of the product without undermining mechanical strength .

[0093] In the course of experimental production, we came to the conclusion that the PU rigid foam chips also contain an amount of powder fraction, however, this is undesirable throughout the entire volume of the finished product and a factor that may signi ficantly influence the quality . Within the scope of the present speci fication powder is understood to mean the fraction with an average particle si ze of under 5 mm .

[0094] According to a preferable embodiment of the recycled PU foam according to the invention it contains 30 to 80 m / m% PU rigid foam basic material , 1 to 55 m / m% MDI-prepolymer , 1 to 45 m / m% ion-exchanged water and 0 . 5 to 55 m / m% additive , more preferably 35 to 75 m / m% PU rigid foam basic material , 15 to 50 m / m% MDI-prepolymer, 2 to 25 m / m% ion-exchanged water and 0 . 5 to 55 m / m% additive . It should be noted that additives should be understood to not only mean those materials mentioned above , instead lignin solution may also be listed here , according to a preferable embodiment of the recycled PU foam it contains 0 . 3 to 10 m / m% lignin solution .

[0095] The method for the production of recycled PU foams contains the following steps , which may also be followed in figure 1 schematically depicting the production line : a ) the PU rigid foam basic material is milled in the miller 1 , optionally to an average particle si ze of between 10 mm and 30 mm, for the purpose of producing chips ; b ) the powder-consistency part of the chips obtained in step a ) is separated in the powder separator 2 , which is preferably a rotating drum powder separator :

[0096] As it was explained further above , after milling the PU rigid foam also contains a powder fraction, which, however, is undesirable in the present method from the point of view of the production of the finished product , as it may signi ficantly influence the quality of the finished product . A rotating drum powder separator contains a cylindrical external and a perforated internal drum, centri fugal force is exploited in the separation of the particles according to si ze , the separated powder fraction is transported to a central collection bin via a suction process . The proportion of the separated particles is between 5 and 40% , depending on the quality of the incoming rigid foam . c ) The chips obtained after step b ) are transported further on a conveyor belt 3a, in the meantime the particles containing ferromagnetic material are separated with the magnet 4 , which step is of key importance due to the subsequent cutting up of the product at a later point in time : During our experiments we came to the conclusion that the milled PU rigid foam may contain a signi ficant amount of metal shavings , as a unique characteristic of the collected PU rigid foam is that metal shavings get into the foam waste itsel f during the cutting and chopping process . Therefore , a metal-separation magnet has been interposed into the production line at several points , with which the undesirable particles may be removed . One of these has been indicated in the schematic figure 1 . dl ) after the separation according to step c ) ion-exchanged water is sprayed onto the accumulated chips on the conveyor belt 3a for the purpose of producing foam chips or, d2 ) after the separation according to step c ) MDI -prepolymer and lignin solution are added to the dry chips accumulated according to step c ) , it should be noted that i f additive is added to the combination, it is added at this part of the production line ( the unit for adding the water or the MDI - prepolymer and lignin solution or the additive has been marked in figure 1 with reference sign 5 ) ; el ) the foam chips according to step dl ) proceed between two conveyor belts ( 3c and 3d) , where the MDI-prepolymer and the lignin solution are added to the water-sprayed chips according to step dl ) or, e2 ) in the case that the preliminary water addition has not taken place , then the chips according to step d2 ) , which also contain MDI-prepolymer and lignin solution, are wetted with a water mist of ion-exchanged water ; ( in other words reference sign 6 serves for the addition of the MDI - prepolymer and lignin solution or the ion-exchanged water mist ) :

[0097] The cooling ef fect achieved with the use of the water mist makes it possible for the chemical reaction to start in the lower section of the foam block after a delay . All this represents a signi ficant di f ference compared to the known solutions , as the mixture provided with binder is heated in the solutions according to the state of the art . In the method according to the present invention the use of the water mist does precisely the opposite , it cools the starting mixture , thereby there is suf ficient cycle time for the pressing of the foam block . The use of the water mist may be viewed as an energy-saving solution, as the physical ef fect of evaporation is used for cooling . By slowing down the chemical reaction larger si zed foam blocks may be produced, panels are generally produced in those cases where the cycle time is shorter, in other words the range of products in the latter case is limited . During the method according to the present invention, the delayed chemical reaction results in an extended cycle time , which makes a broader range of products possible , and in a cost-ef fective way . f) the foam chips also containing the MDI-prepolymer , lignin solution and ion-exchanged water are collected in a press mold 7 where, optionally, additional additive is mixed with it (the unit with reference sign 8 serves for dispensing this) , if necessary, the subsequent mixing of this may take place with the unit marked with reference sign 9 ; g) the foam chips according to step f) are pressed into foam blocks at a given press pressure without the use of an external heating effect, preferably using a hydraulic press 10 for this:

[0098] If 2,160,000 cm3of chips is filled into the press mold, then after pressing a product with a volume of approximately 624,000 cm3is obtained. A thicker block may be produced if 3,720,000 cm3of chips is pressed, then a block with a volume of approximately 1,248,000 cm3is obtained .

[0099] The omitting of the use of external heat during the pressing procedure may, according to our calculations, even result in a 20 to 40% lower use of energy during the production of the recycled product. h) for a given period of time the foam blocks are left to rest in the press mold under pressure without the use of any external heating effect; i) the finished foam blocks are cut to shape (see reference sign 11 in figure 1) / cut into boards, the shaped foam blocks are optionally laminated or coated in accordance with the intended use (see the unit with reference sign 12 in figure 1 ) .

[0100] In the method according to the invention the pressure applied in step g) is between 0.1 and 200 bar, preferably between 50 and 150 bar. According to a preferred implementation of the present invention, in step h) the foam blocks are left to rest until the chemical reaction taking place in the blocks in completed . According to our measurements the duration of the chemical reaction depends on the composition of the foam block and the si ze of the foam block, and may take as long as 12 to 24 hours . Within the scope of the present speci fication the endpoint of the chemical reaction is understood to mean when the exothermal processes have come to an end in the produced foam block . The completion of the exothermal processes is indicated by the temperature of the foam block dropping to under 30 ° C, which is monitored by a core thermometer . The working of the foam block ( chopping, milling, shaping) may only be started after the completion of the chemical reaction . During the exothermal chemical reaction, the MDI-prepolymer reacts with the water and the lignin solution .

[0101] In the method according to the invention steps dl ) and d2 ) are performed in continuous operation with the use of a conveyor belt .

[0102] As a consequence of the composition of the recycled PU foam according to the present invention, it is suitable for the production of furniture components , door and window components ( such as thermally insulated door and window inserts ) , construction industry insulation, construction industry materials , buf fers ( in car parks and public areas , for example ) , as well as for the reinforcing of furniture components .

[0103] Higher resistance to fire

[0104] In connection with construction industry insulation it should be noted that the recycled PU foam according to the present invention has a higher resistance to fire , on the basis of measurements it may be classed in EN ISO 11925 Burn behaviour class "B" , or class "A2" .

[0105] Buf fers are understood to mean various three-dimensional

[0106] 5 bodies that are made from the recycled PU foam according to the present invention and that are suitable for guiding car and goods vehicle traf fic as well as pedestrian traf fic . 0 Example 1 : General insulation material recipe

[0107] Table 1 a ) 65 m / m% PU rigid foam basic material is milled in a miller, in a given case to an average particle si ze of between 10 mm and 30 mm in order to make chips ; 5 b ) the powder consistency part is separated from the chips obtained in step a ) using a powder separator, which preferably is a rotating drum powder separator ; c ) the chips obtained after step b ) are transported onwards on a conveyor belt , meanwhile the particles containing 0 ferromagnetic material are separated using a magnet ; d) following the separation according to step c) 20 m / m% MDI- prepolymer and 10 m / m% lignin solution are added to the accumulated dry chips; e) the chips according to step d) , which now contain MDI- prepolymer and lignin solution, are wetted with 5 m / m% ion- exchanged water mist; f) the foam chips containing MDI-prepolymer , lignin solution and ion-exchanged water are collected in a press mold and subsequent mixing takes place in the collection bin; g) the foam chips according to step f) are pressed into foam blocks using a hydraulic press without the use of an external heat effect, applying a pressure of 150 bar; h) the foam blocks are left to rest for 12 hours without the use of an external heat effect in the press mold under pressure; i) the finished foam blocks are cut into boards; the panels are optionally laminated or given a coating corresponding with their function.

[0108] The characteristics of the products produced on the basis of the compositions according to table 1:

[0109] Relative density: 60 - 90 (kg / m3) ;

[0110] Heat transfer factor: 0.028 - 0.034 ( (W / (m-K) ) ;

[0111] Compressive strength for 10% deformation (kPa) : 30 - 100 (kPa) ; Flexural modulus (E) : 700 - 1700 (kPa) .

[0112] Example 2 : Furniture industry basic material recipe

[0113] Table 2 a ) 52 m / m% PU rigid foam basic material is milled in a miller, in a given case to an average particle si ze of between 10 mm and

[0114] 5 30 mm in order to make chips ; b ) the powder consistency part is separated from the chips obtained in step a ) using a powder separator, which preferably is a rotating drum powder separator ; c ) the chips obtained after step b ) are transported onwards on

[0115] 10 a conveyor belt , meanwhile the particles containing ferromagnetic material are separated using a magnet ; d) following the separation according to step c ) 35 m / m% MDI- prepolymer and 10 m / m% lignin solution are added to the accumulated dry chips ;

[0116] 15 e ) the chips according to step d) , which now contain MDI- prepolymer and lignin solution, are wetted with 3 m / m% ion- exchanged water mist ; f ) the foam chips containing MDI-prepolymer , lignin solution and ion-exchanged water are collected in a press mold and its

[0117] 20 subsequent mixing takes place in the collection bin ; g) the foam chips according to step f ) are pressed into foam blocks using a hydraulic press without the use of an external heat ef fect , applying a pressure of 150 bar ; h) the foam blocks are left to rest for 12 hours without the use of an external heat effect in the press mold under pressure; i) the finished foam blocks are cut to shape, or given a coating corresponding with their function.

[0118] 5 The characteristics of the products produced on the basis of the compositions according to table 2: Relative density: 70 - 110 (kg / m3) ;

[0119] Compressive strength for 10% deformation (kPa) : 100 - 200 (kPa) ; Flexural modulus (E) : 1300 - 2700 (kPa) ;

[0120] 10 Burn behaviour: class "C".

[0121] Example 3: Transport buffer recipe

[0122] Table 3

[0123] 15 a) 60 m / m% PU rigid foam basic material is milled in a miller, in a given case to an average particle size of between 10 mm and 30 mm in order to make chips; b) the powder consistency part is separated from the chips obtained in step a) using a powder separator, which preferably

[0124] 20 is a rotating drum powder separator; c) the chips obtained after step b) are transported onwards on a conveyor belt, meanwhile the particles containing ferromagnetic material are separated using a magnet; d) following the separation according to step c) 25 m / m% MDI- prepolymer and 8 m / m% lignin solution are added to the accumulated dry chips; e) the chips according to step d) , which now contain MDI- prepolymer and lignin solution, are wetted with 7 m / m% ion- exchanged water mist; f) the foam chips containing MDI-prepolymer , lignin solution and ion-exchanged water are collected in a press mold and its subsequent mixing takes place in the collection bin; g) the foam chips according to step f) are pressed into foam blocks using a hydraulic press without the use of an external heat effect, applying a pressure of 150 bar; h) the foam blocks are left to rest for 12 hours without the use of an external heat effect in the press mold under pressure; i) the finished foam blocks are cut to shape and given a coating corresponding with their function.

[0125] The characteristics of the products produced on the basis of the compositions according to table 3:

[0126] Relative density: 110 - 140 (kg / m3) ;

[0127] Compressive strength for 10% deformation (kPa) : 110 - 150 (kPa) ; Flexural modulus (E) : 1500 - 2000 (kPa) .

[0128] Example 4 : Flame retardant insulation material recipe

[0129] Table 4

[0130] 5 a ) 57 m / m% PU rigid foam basic material is milled in a miller, in a given case to an average particle si ze of between 10 mm and 30 mm in order to make chips ; b ) the powder consistency part is separated from the chips obtained in step a ) using a powder separator, which preferably 0 is a rotating drum powder separator ; c ) the chips obtained after step b ) are transported onwards on a conveyor belt , meanwhile the particles containing ferromagnetic material are separated using a magnet ; d) following the separation according to step c ) 25 m / m% MDI- 5 prepolymer and 10 m / m% lignin solution are added to the accumulated dry chips , 5 m / m% aqueous potassium water glass solution is added at this section of the production line ; e ) the chips according to step d) , which now contain MDI- prepolymer and lignin solution, are wetted with 3 m / m% ion- 0 exchanged water mist ; f ) the foam chips containing MDI-prepolymer , lignin solution, potassium water glass solution and ion-exchanged water are collected in a press mold, here 3 m / m% vermiculite is added. The subsequent mixing of this takes place in the collection bin; g) the foam chips according to step f) are pressed into foam blocks using a hydraulic press without the use of an external heat effect, applying a pressure of 150 bar; h) the foam blocks are left to rest for 12 hours without the use of an external heat effect in the press mold under pressure; i) the finished foam blocks are cut to shape, the foam blocks cut to shape are optionally laminated or given a coating corresponding with their function.

[0131] The characteristics of the products produced on the basis of the compositions according to table 4:

[0132] Relative density: 60 - 110 (kg / m3) ;

[0133] Heat transfer factor: 0.030 - 0.034 ( (W / (m-K) ) ; Compressive strength for 10% deformation (kPa) : 100 - 250 (kPa) ;

[0134] Flexural modulus (E) : 1800 - 3000 (kPa) ;

[0135] Burn behaviour: class "B".

Claims

Claims1. Recycled polyurethane (PU) foam, characterised by that it contains polyurethane (PU) rigid foam basic material, MDI-prepolymer , ion-exchanged water and lignin solution and does not contain phenolic foam.

2. Recycled polyurethane (PU) foam according to claim 1, characterised by that its relative density is between 60 and 140 kg / m3.

3. Recycled polyurethane (PU) foam according to either of claims 1 to 2, characterised by that it contains at least one additional additive selected from the following group : inorganic fibrous materials, plant-based fibres, natron water glass solution, or potassium water glass solution; vermiculite; thermoplastic polymer fibres; gypsum; calcium sulphoaluminate based cement, cross-linked elastomer materials, preferably where the said additional additive is present in an amount of 0.5 to 55 m / m%.

4. Recycled polyurethane (PU) foam according to any of claims 1 to 3, characterised by that the PU rigid foam basic material was subjected to milling before the production of the recycled polyurethane (PU) foam, and the average particle size of its particles, characteristic largest dimension, is 10 mm or greater, more preferably between 10 and 30 mm.

5. Recycled polyurethane (PU) foam according to any of claims 1 to 4, characterised by that it contains 30 to 80 m / m% polyurethane (PU) rigid foam basic material, 1 to 55 m / m% MDI-prepolymer, 1 to 45 m / m% ion-exchanged water and0.3 to 20 m / m% lignin solution, more preferably 35 to 75 m / m% PU rigid foam basic material, 15 to 50 m / m% MDI- prepolymer, 2 to 25 m / m% ion-exchanged water and 0.3 to 10 m / m% lignin solution.

6. Method for the production of recycled polyurethane (PU) foam according to claims 1 to 5, characterised by that it contains the following steps: a) the polyurethane (PU) rigid foam basic material is milled, optionally to an average particle size of between 10 mm and 30 mm, for the purpose of producing chips; b) the powder-consistency part of the chips obtained in step a) is separated, the separation is preferably performed in a rotating drum powder separator; c) the particles containing ferromagnetic material are separated from the chips obtained after step b) on a conveyor belt with the use of a magnet; dl) after the separation according to step c) ion-exchanged water is sprayed onto the accumulated chips for the purpose of producing foam chips or, d2 ) after the separation according to step c) MDI-prepolymer and lignin solution are added to the dry chips accumulated according to step c) ; el) the foam chips according to step dl) proceed between two conveyor belts, where the MDI-prepolymer and the lignin solution are added to the water-sprayed chips according to step dl) or, e2) in the case that the preliminary water addition has not taken place according to step dl) , then the chips according to step d2 ) , which also contain MDI-prepolymer and lignin solution, are wetted with a water mist of ion-exchanged water; f) the foam chips also containing MDI-prepolymer and obtained in step el) or e2) are collected in a press moldwhere, optionally, additional additive is mixed with it, then g) the foam chips according to step f) are pressed into foam blocks at a given press pressure without the use of an external heating effect, preferably using a hydraulic press for this; h) for a given period of time the foam blocks are left to rest in the press mold under pressure without the use of any external heating effect; i) the finished foam block is cut to shape / cut into boards, the foam blocks formed into panels are optionally laminated or coated in accordance with the intended use.

7. Method according to claim 6, wherein the pressure applied in step g) is between 0.1 and 200 bar, more preferably between 50 and 150 bar.

8. Method according to claim 6 or 7, wherein in step h) the foam blocks are left to rest until the chemical reaction taking place in the blocks in completed.

9. Method according to any of claims 6 to 8, wherein steps dl) and d2 ) are performed in continuous operation with the use of a conveyor belt.

10. The use of the recycled polyurethane (PU) foam according to any of claims 1 to 5 as furniture components, construction industry insulation, construction industry materials, buffers, or as elements for the reinforcing of furniture components.

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