A new method for regenerating polyurethanes.

Abstract

The present invention provides a novel method for the regeneration of polyurethanes, particularly polyurethane foams, by solvolysis, which includes a highly efficient pretreatment method for polyurethanes, which converts them into polyurethane dispersions.

Description

[Technical Field]

[0001] The present invention provides a novel method for the regeneration of polyurethanes, particularly polyurethane foams, by solvolysis. This novel method involves a highly efficient pretreatment of polyurethanes, converting them into polyurethane dispersions.

[0002] Polyurethanes are highly useful materials for the production of rigid and flexible foams, solid and microcellular elastomers, sealants, coatings, and adhesives. Due to their versatility, relatively low cost, and excellent properties, the polyurethane industry has experienced rapid growth over the past 50 years. Currently, thousands of tons of polyurethane are produced annually worldwide. Unfortunately, most polyurethanes are thermoset materials and undergo some degree of crosslinking. Therefore, unlike thermoplastics such as polyethylene, polypropylene, and polystyrene, polyurethane scrap and waste cannot be easily remelted or reprocessed into useful articles. Because of economic and environmental reasons, it is highly desirable to reuse or recover the large amount of scrap or waste polyurethane generated each year rather than incinerating or disposing of it in landfills. Therefore, considerable ingenious efforts have been made to devise processes for recovering useful chemical components from scrap polyurethane materials.

[0003] Glycolysis has been used to regenerate, i.e., depolymerize, PU (polyurethane) waste, including both rigid and flexible types of products.

[0004] Polyurethane foam scrap can also be regenerated by ammonolysis or aminolysis using ammonia, amines or alkanolamines, which recovers the monomer polyols that can be reused in the synthesis of PU. For example, German Patent Application No. 102006036007 describes a method for the regeneration of polyurethanes and polyureas by aminolysis.

[0005] Acid decomposition has also been proposed to regenerate polyurethane into polyol. CN107286369 describes the acid decomposition of flexible polyurethane foam waste to produce polyol. The method includes the steps of: i) producing polyurethane fragments; and ii) feeding the fragments into a reactor by screw feeding or vacuum suction. The foam fragments in CN107286369 have a particle size of 1-20 mm and are produced by crushing. The method in CN107286369 requires a very high reaction temperature of 230-250°C and a long reaction time of 6-12 hours.

[0006] US Patent Application Publication No. 2021 / 0017354 discloses a method for regenerating PU, starting with acidolysis followed by glycolysis. To an acidolysis mixture containing polyether triol, phthalic acid, maleic acid, acrylic acid, and a radical initiator, shredded PU (2 x 2 x 2 cm in size) was added until a reaction mixture containing 40 wt% PU was obtained. The method of US Patent Application Publication No. 2021 / 0017354 is inefficient due to the number of process steps and reactants required. Due to the high PU content, wet PU cannot be pumped like a liquid or dispersion (see Comparative Example 2 below), and the mixture contains a small amount of heat transfer medium. As a result, long reaction times are required, e.g., more than three hours in the examples of US Patent Application Publication No. 2021 / 0017354. Another consequence is incomplete conversion of PU, which leads to poor process productivity.

[0007] US Patent Application Publication No. 2016 / 0347927 describes a chemical degradation reaction for regenerating PU. In the first step, rigid PU is wet-milled to obtain wet PU powder. The PU powder is then subjected to a chemical degradation reaction. Similar to US Patent Application Publication No. 2021 / 0017354, the method of US Patent Application Publication No. 2016 / 0347927 does not allow the wet PU powder to be pumped. Instead, the wet PU powder must be transported by a screw conveyor or other particle transport device. Therefore, metering the powder into the chemical degradation reactor is difficult and inaccurate. Similar to US Patent Application Publication No. 2021 / 0017354, the amount of heat transfer medium is small, resulting in insufficient reaction time and yield.

[0008] Hydrolysis has also been attempted in the prior art for depolymerizing polyurethanes. However, prior art methods using base catalysts to recover polyether polyols suffer from several drawbacks. At relatively low temperatures, the hydrolysis rate is reported to be low and incomplete. At higher temperatures, the hydrolysis rate is high, but certain undesirable side reactions may occur. For example, U.S. Pat. No. 5,208,379 proposes a method for hydrolyzing polyurethanes prepared by reacting an active hydrogen-containing polyether with an organic polyisocyanate. The method comprises contacting the polyurethane with water in the presence of an effective amount of a strong base selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, and alkaline earth metal hydroxides, and an effective amount of an activator selected from the group consisting of quaternary ammonium salts having at least 15 carbon atoms and organic sulfonates having at least 7 carbon atoms, for a time and temperature effective to obtain an active hydrogen-containing polyether and an organic polyamine. In the specification of U.S. Pat. No. 5,208,379, the summary of the invention discloses that the reaction temperature can be selected in the range of 80 to 225°C. However, Example 19 shows that only partial hydrolysis occurs at 120°C, and Example 18 shows that the yield at 140°C is only 70%.

[0009] None of these methods have yet been used on a large industrial scale. They are overly complicated and expensive due to the high reaction temperatures and long reaction times. The recycled polyols and recycled amines are of low quality, meaning only small amounts of recycled raw material can be used with large amounts of virgin polyol to produce new polyurethane foams.

[0010] In addition to the solvolysis itself, problems have been reported in the prior art relating to feeding polyurethane waste to the solvolysis reactor.

[0011] CN109320764 discloses a method for recovering polyurethane foam by alcoholysis and a specific recovery feeding device. CN109320764 addresses the problem of polyurethane foam's low bulk density, making it difficult to transport crushed polyurethane foam agglomerates to a reactor using a conventional screw machine. This is because the alcohol used in alcoholysis evaporates and comes into contact with the polyurethane in the screw. This causes the polyurethane to become sticky and adhere to the feed pipeline. As a solution, CN109320764 proposes a feeding system in which polyurethane foam agglomerates are extruded from a feed hopper onto a screw conveyor and then transported to a double-helix feed conveyor. Finally, the polyurethane is fed into the reactor via a pneumatic gate valve. The feeding system proposed in CN109320764 is quite complex, and the process still requires several hours of reaction time.

[0012] German Patent Application Publication No. 4309288 describes a method for producing granules and pellets from crosslinked polyurethane plastics. Similar to Chinese Patent Application Publication No. 109320764, this method attempts to address the problem of the low bulk density of polyurethane foam clogging the feeding system of thermoplastic processing machines, resulting in very low throughput. As a solution, German Patent Application Publication No. 4309288 proposes cutting the polyurethane foam into particles approximately 6 mm in size using a cutting mill. These particles are then pressed through a flat matrix at a temperature of 160°C to obtain strands. These strands can be further processed into pellets or granules. These pellets and granules can be used as starting materials for PU regeneration processes such as glycolysis, aminolysis, or hydrolysis. The method in German Patent Application Publication No. 4309288 is also complex.

[0013] Therefore, there remains a need for more efficient methods of reclaiming polyurethanes, particularly polyurethane waste and scrap.

[0014] The object of the present invention was to provide a method for the regeneration of polyurethanes which does not have the disadvantages of the prior art methods or which has such disadvantages only to a reduced extent.

[0015] A particular object of the present invention was to provide an effective method for regenerating polyurethanes, which involves efficient feeding of polyurethane to a solvolysis reactor.

[0016] A further specific problem that the present invention seeks to solve was to provide a method for regenerating polyurethane that allows for accurate metering of polyurethane into reactors, particularly reactors operating under elevated or high pressure conditions.

[0017] The next specific problem that the present invention aims to solve was to provide a method for regenerating polyurethanes that is advantageous compared to the prior art methods in terms of reaction time and / or reaction temperature and / or polyol yield.

[0018] Another particular problem that the present invention aims to solve was to provide a method for regenerating polyurethane that allows high polyurethane loads to be charged to the reactor.

[0019] Yet another problem that the present invention aims to solve was to provide a process that makes it possible to produce polyols from polyurethanes, which polyols are of very good quality and can be used in large quantities to produce new polyurethanes.

[0020] Further objects not explicitly mentioned above can be derived from the overall content of the following description, examples, claims and drawings.

[0021] The inventors have surprisingly discovered that the object of the present invention is to a. providing a polyurethane, preferably a polyurethane foam; b. preparing a dispersion from the polyurethane; c. solvolysis of the polyurethane dispersion, preferably by alcoholysis, aminolysis, ammolysis, hydrolysis or acidolysis of the dispersion; a method comprising: It has been found that this problem can be solved by a method in which the polyurethane to be dispersed has an average particle size of 0.1 to 12 mm, and the polyurethane content in the dispersion liquid after step b. and / or the dispersion liquid used in step c. is in the range of 4 to 20% by weight.

[0022] The present applicants have found that when polyurethane foam is pulverized to obtain a dry powder and this dry powder is fed into a solvolysis reactor, the polyurethane powder has such a low density that it floats on the surface of the reaction solution and accumulates in the gas chamber of the reactor. This makes it very difficult to wet the powder and mix it with the reaction solution. This results in delayed feeding, inaccurate metering, and difficulty in controlling the metering, resulting in a long reaction time.

[0023] Prior art has proposed hot-compressing polyurethane waste before grinding to increase powder density. Such a method is applied in U.S. Pat. No. 5,208,379, but it requires a solvolysis reaction time of 8 hours for the compressed and subsequently ground material. U.S. Pat. No. 5,208,379 describes reaction times of 5 minutes to 12 hours, but Examples 20-22 show that shortening the reaction time from 8 hours to 2 hours reduces the polyol yield from 95% to 70%. Therefore, the method of U.S. Pat. No. 5,208,379 cannot be commercially applied at short reaction times.

[0024] The present inventors have discovered that hot pressing reduces the external surface area of ​​the polyurethane powder, which significantly increases reaction times and temperatures.

[0025] In contrast, the process of the present invention achieved very high yields with a reaction time of only 30 minutes for hydrolysis of the polyurethane foam. Without being bound by any theory, this significant improvement is achieved because the process of the present invention opens the pores of the polyurethane, increasing the external surface area of ​​the resulting powder rather than decreasing it, as occurs during hot pressing as disclosed in U.S. Pat. No. 5,208,379.

[0026] The high surface area polyurethane powder of the present invention is converted into a dispersion before being subjected to solvolysis. The preparation of the dispersion can be carried out under mild conditions, such as atmospheric pressure and temperature, and therefore has only a slight adverse effect on the external surface area of ​​the polyurethane powder. The resulting polyurethane dispersion of the present invention can be accurately metered into a reactor, avoiding the aforementioned problem of dry polyurethane powder floating in the reaction solution. In addition to accurate metering, very efficient and rapid mixing of the polyurethane dispersion with the reaction mixture is possible. In summary, the method of the present invention results in short reaction times and high polyol yields, allowing very efficient and accurate feeding of polyurethane into the reactor.

[0027] Another advantage of the method of the present invention is that the polyurethane dispersion obtained in step b. can be easily pumped through a conduit to the reactor. Therefore, conduits and packings with significantly smaller cross sections can be used. This is important for reactors operating under elevated or high pressure, allowing for efficient supply and metering of the inventive dispersion to such reactors. If the reactor is operated under elevated pressure and greater pressure levels must be overcome during metering of the polyurethane, the necessary fittings, such as tight-fitting flaps, must be designed with larger dimensions to allow for flow-free metering of the polyurethane. In contrast to the present invention, if dry polyurethane powder is directly fed into such a reactor, its low density and poor flowability necessitate much larger outlet cross sections, which results in significantly larger fitting dimensions and higher costs.

[0028] The polyurethane dispersion obtained in step b. can be easily pumped through a conduit. As a result, a tubular reactor can be used for the solvolysis reaction, allowing for continuous operation of the process. In addition to continuous operation, a tubular reactor is also beneficial in terms of heat management, i.e., heat transfer to and from the reaction mixture.

[0029] The process of the present invention allows for high polyurethane loadings in the reactor, which have not been achieved in the prior art due to the low bulk density of ground polyurethane foam and the aforementioned flotation problems.

[0030] The process of the present invention is very flexible: the polyurethane dispersion of the present invention obtained in step b. can be used as a feed for different solvolysis processes, preferably aminolysis, ammonolysis, hydrolysis, acidolysis, or alcoholysis processes, such as glycolysis, hydroglycolysis, and methanolysis. Most preferably, hydrolysis is carried out in step c.

[0031] Another advantage of the method of the present invention is the excellent quality of the recycled polyol. The recycled polyol can replace a large amount of virgin polyol when producing new polyurethane foam, preferably flexible PU foam, without adversely affecting the quality of the polyurethane foam. Up to 100% of the recycled polyol of the present invention can be used to obtain high-quality polyurethane foam. The recycled polyol obtained by the present invention can be further used to produce flexible PU foam. In the prior art, recycled polyols adversely affect the physical and mechanical properties of the resulting polyurethane foam, making it impossible to obtain such flexible PU foam from recycled polyol.

[0032] Shortcomings of prior art polyurethane reclaiming methods have prevented widespread commercial implementation. The present invention overcomes these shortcomings, resulting in positive environmental and sustainability impacts, including beneficial life cycle analysis and improved circularity of the PU foam manufacturing process.

[0033] Further advantages can be derived from the following description, examples, figures and claims.

[0034] Before describing the present invention in more detail, some important terms are defined as follows: As used in this specification, examples, and claims, the verb "to comprise" and its conjugations are used in an open-ended sense, meaning that the items following the word are included, but items not specifically mentioned are not excluded. "Comprising" includes "consisting of," which means that the items following the term "comprising" are included, but additional items not specifically mentioned as preferred embodiments are not included.

[0035] The reference to an element by the indefinite article "a" or "an" does not exclude the possibility that a plurality of elements is present, unless the context clearly requires that there be only one element. Thus, the indefinite article "a" or "an" normally means "one or more."

[0036] The terms "catalyst" and "activator" are used interchangeably in this invention.

[0037] In the context of the present invention, polyurethane (PU) is understood to mean, in particular, a product obtained by reacting a polyisocyanate with a polyol or a compound having an isocyanate-reactive group. Polyurethanes that can be used in the process of the present invention are those prepared from active hydrogen-containing polyethers and polyisocyanates. Polyurethanes of this type are well known and are described, for example, in Ulrich, "Urethane Polymers," Encyclopedia of Chemical Technology, Vol. 23, pp. 576-608 (1983) and Backus et al., "Polyurethanes," Encyclopedia of Polymer Science and Technology, Vol. 13, pp. 243-303 (1988). Any known polyurethane can be used in the process of the present invention; preferably, the polyurethane is polyurethane waste.

[0038] The active hydrogen-containing polyether is preferably a polyether polyol (i.e., a polyether having primary and / or secondary end groups, preferably hydroxyl groups), but may also be an amine-functionalized polyether (e.g., "Jeffamine" polyoxypropylamine, available from Texaco Chemical Co.). Such materials are generally prepared by the catalyzed ring-opening polymerization of one or more cyclic ethers, such as epoxides, oxetanes, and oxolanes. To vary the functionality (number of active hydrogens) of the polyether, initiators with two or more active hydrogens, such as polyhydric alcohols, amines, and acids, can be used. When multiple types of cyclic ethers are used, they can be reacted simultaneously (to obtain random copolymers) or sequentially (to obtain block copolymers). Exemplary cyclic ethers include propylene oxide, ethylene oxide, butylene oxide, tetrahydrofuran, and oxetane. Examples of suitable active hydrogen-containing polyethers include polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polytrimethylene glycol, ethylene oxide-capped polypropylene glycol, and random copolymers of ethylene oxide and propylene oxide.

[0039] The present invention provides a method for solvolyzing polyurethane, preferably polyurethane produced by reacting an active hydrogen-containing polyether with an organic polyisocyanate, comprising the steps of: a. providing a polyurethane, preferably a polyurethane foam; b. preparing a dispersion from the polyurethane; c. carrying out solvolysis of the polyurethane dispersion obtained in step b.; The present invention provides a method comprising:

[0040] This method is characterized in that the polyurethane to be dispersed has an average particle size of 0.1 to 12 mm, and the polyurethane content in the dispersion after step b. and / or the dispersion used in step c. is in the range of 4 to 20% by weight.

[0041] The polyurethane provided in step a. of the method of the present invention can be derived from any polyisocyanate reactant (i.e., an organic compound containing two or more isocyanate groups). Suitable polyisocyanates include, but are not limited to, aliphatic diisocyanates, cycloaliphatic diisocyanates, arylalkyl diisocyanates, aromatic diisocyanates (e.g., toluene diisocyanate and diisocyanatodiphenylmethane), aromatic triisocyanates, and isocyanate mixtures such as the isocyanate commonly referred to as "PMDI." Of course, modified polyisocyanates, masked polyisocyanates, and blocked polyisocyanates can also be used.

[0042] The polyurethanes used in the process of the present invention can also contain any of the conventional additional reactants or additives known in the art, such as chain extenders or curing agents (relatively low molecular weight active hydrogen-containing compounds such as glycols and di- or polyamines), physical or chemical blowing agents, flame retardants, surfactants, fillers, stabilizers, antioxidants, colorants, polymers other than polyurethane polymers (e.g., styrene-acrylonitrile copolymers such as found in polymer polyols), catalysts such as catalysts that promote the gelling reaction (isocyanate-polyol), catalysts that promote the blowing reaction (isocyanate-water), and / or catalysts that promote the dimerization or trimerization of isocyanates. Polyurethanes can be in solid, microcellular, or foam form and can range from rubbery, elastomeric, flexible materials to hard, rigid materials.

[0043] Preferably, the polyurethane provided in step a. is not subjected to compression above ambient temperature before being used in step b. Preferably, other pretreatments of the polyurethane provided in step a. can be carried out which do not affect or only slightly affect its pore structure, such as heat treatment of PU foams for sterilization.

[0044] In a particularly preferred embodiment of the present invention, a polyurethane foam is provided in step a.

[0045] In step b. of the method of the present invention, a dispersion is prepared from the polyurethane. In a preferred embodiment of the present invention, step b. comprises: b1. shredding, pulverizing, grinding, milling, cutting or otherwise pulverizing the polyurethane provided in step a. to obtain a polyurethane powder; b2. A step of preparing a dispersion from the polyurethane powder obtained in step b1. Includes:

[0046] The method of the present invention, particularly when step b. is carried out as a "two-stage process" including steps b1. and b2., opens the foam structure and destroys the cell walls of the polyurethane foam. As a result, the penetration of the solvolysis liquid and / or dispersion liquid (dispersion medium) is greatly promoted, achieving intensive wetting of the polyurethane powder. Therefore, it is preferred to carry out step b. as a two-stage process.

[0047] In step b1, a cutting mill or other suitable grinding device is preferably used, preferably selected from the group consisting of a roller mill, a crusher, a shredder, and an extruder. Preferred examples of grinding devices using extruders can be found in U.S. Pat. No. 5,769,335 and Japanese Patent Application No. 06-185764. By using a cutting mill, particularly good results were achieved in terms of complete opening of the foam structure and destruction of the cell walls (as can be seen in FIG. 1b).

[0048] If the polyurethane raw material already has a particle size small enough to prepare a dispersion, it is not necessary to carry out step b1. In this case, step b is preferably shortened to a "one-step process" in which step b2 is step b. However, in most cases, it is also preferable to carry out step b1. in order to open the pore structure.

[0049] When step b1. is performed, it may be necessary to pre-crush or coarsely chop the polyurethane raw material in step a. to obtain fragments that can be used in step b1. Whether pre-crushing is necessary depends on the design of the grinding equipment, especially if a cutting mill is used, and the feedstock. Pre-crushing or coarse chopping can be performed manually or using a coarse shredder.

[0050] As mentioned above, the use of a cutting mill is particularly preferred in step b1. Various types of cutting mills can be used, particularly with regard to the arrangement of cutting knives and sieve inserts, which are preferably used to adjust the size of the resulting polyurethane powder. Preferred examples of cutting knives include straight-cut knives, diagonal-cut knives, and cross-cut knives. Sieve layers with round, square, or elongated perforations can be used, with preferred hole sizes ranging from 0.5 to 20 mm. Suitable cutting mill manufacturers include Hosokawa-Alpine, Netzsch-Condux, Pallmann, and Herbold-Meckesheim. The use of such cutting mills results in a "snow-like" fluffy polyurethane powder, where the polyurethane has the appearance of dry, fluffy snow, as shown in Figure 1a.

[0051] To obtain polyurethane dispersions that are particularly stable in terms of particle segregation and / or wetting, the polyurethane powder to be dispersed, i.e., the polyurethane powder dispersed in step b2. of the two-stage process described above or step b. of the one-stage process described above, preferably has an average particle size of 0.2 to 4 mm, more preferably 0.5 to 2 mm. Dispersions obtained from such polyurethane particles have been found to be stable over long periods of storage. Even if segregation occurs after long periods of time, especially in dispersions prepared from polyurethane particles obtained after step b1., i.e., polyurethane particles with a completely open structure, the particles have been found to still be very well wetted.

[0052] The bulk density of the polyurethane powder to be subjected to the dispersion step, i.e., step b2 in the two-stage method or step b in the one-stage method, is 20 to 26 kg / m 3 It is more preferable to adjust the bulk density of the polyurethane powder to be higher than the bulk density of the polyurethane raw material having a bulk density of 30 kg / m or less. 3 Higher, preferably 60 kg / m 3 Higher, even more preferably 90 kg / m 3 ~200kg / m 3 Increasing the bulk density allows for a higher polyurethane loading in the solvolysis reactor. One preferred method for adjusting the bulk density is to use a mill, more preferably a cutter mill, and to select a suitable sieve size. Depending on the selected sieve size, not only the particle size but also the bulk density of the polyurethane snow can be adjusted.

[0053] When carrying out step b1., it is particularly preferred to carry out step b1. in a temperature range of from ambient temperature to 120°C, preferably from ambient temperature to 100°C, more preferably from ambient temperature to 80°C, and most preferably from ambient temperature to 60°C, in order to prevent agglomeration of the product and clogging of the equipment used to produce the polyurethane powder in step b1.

[0054] The pressure applied in step b1. depends on the equipment selected and can be high in the case of extruders. Most other equipment is operated at ambient pressure or a slight vacuum to aid in transport of the powder, depending on the equipment.

[0055] Dispersion step b2 (b. two-stage process) of step b (b. single-stage process) is preferably carried out in a high-speed dispersing device. Preferably, a device selected from the group consisting of colloid mills, more preferably cone mills, and single- or multi-stage rotor-stator systems with various geometries is used. Dispersion can also be achieved in stirred vessels by using high-speed dissolver disks or serrated impellers. The dispersing device used is preferably equipped with tools specially developed for metering solids into liquids, such as a (vertical) feed screw for mechanical feeding or a vacuum for powder suction. The dispersing device can be operated in single-pass, pump-recirculation, or multi-pass modes. Examples of manufacturers of suitable dispersing devices include IKA Prozesstechnik, Cavitron, BWS Technologie, Ytron, or Ystral.

[0056] The dispersion step is preferably carried out at a temperature of 10 to 90°C, preferably 15 to 80°C, more preferably 20 to 60°C.

[0057] Preferably, the liquid or mixture of liquid and other components used as a reactant and / or solvent in the solvolysis step c., or the solvolysis reaction product of step c., such as recycled polyol, is used as a dispersion medium in step b. or b2. More preferably, the liquid or mixture of liquid and other components is one of the following: - water, - organic solvents, preferably selected from the group consisting of polyols, recycled polyols, glycols, glycerin, toluenediamine and mixtures thereof; a mixture comprising a base and water and / or a base and an organic solvent as defined above, preferably an aqueous solution of a base, more preferably an aqueous solution comprising a base and water as further defined below is selected from the group consisting of:

[0058] The dispersion medium may contain one or more additives, preferably selected from the group consisting of wetting agents, silicone surfactants, anionic surfactants, nonionic surfactants and cationic surfactants, such as those available under the trade name Tomadol® from Evonik Industries AG.

[0059] Preferably, polyurethane powder, more preferably a snow-like fluffy powder, is combined with the dispersing medium in a weight ratio of 1:5 to 1:40, more preferably 1:8 to 1:30, and even more preferably 1:10 to 1:25. In a preferred method, the dispersing medium is first charged to the system and circulated. Then, polyurethane snow is gradually added until the desired weight ratio is reached. The dispersion process can then be run as required, for example, in multiple passes or with pump recirculation over a set process time. In a more preferred method, both the liquid and solid components are added simultaneously to the dispersing device and mixed in a single pass.

[0060] In a preferred embodiment, the excess dispersion medium is separated from the finished dispersion, preferably simply mechanically, for example by sieving, and can then be recycled to produce a new dispersion.

[0061] The polyurethane content of the dispersion after step b. and / or the dispersion used in step c. is preferably in the range of 5 to 18 wt. %, more preferably 8 to 15 wt. If the solids concentration is too low, too much liquid will enter the reaction in step c., which may adversely affect the reaction conditions. If the solids concentration is too high, the dispersion process, handling and pumping of the dispersion may be hindered, and the solids distribution may become uneven. As shown in Comparative Example 2 and Figure 3, if the solids content is too high, a wet PU powder is obtained instead of a dispersion.

[0062] Even more preferably, the particle size of the polyurethane particles in the dispersion after step b. and / or in the dispersion used in step c. is in the range of 10 to 2000 μm, preferably 50 to 1500 μm, more preferably 100 to 1000 μm.

[0063] Preferably, the dispersion obtained in step b. is fed to the reactor of step c. In order to avoid possible separation effects, it has proven advantageous to continuously and intensively stir the dispersion, for example by forced pumping, high flow rates, etc. The dispersion obtained in step b. can be fed directly to the reactor of step c. Intermediate buffering of the dispersion can also be carried out, preferably in a stirred vessel or a vessel equipped with an external circulation line and a pump. In principle, this stage can be used for further treatment of the dispersion, for example, adjusting to a specified temperature, purifying and / or disinfecting the polyurethane used. Purification can include additional washing steps, and disinfection can include treatment with hydrogen peroxide, ozone, heat, etc.

[0064] In an alternative embodiment, the dispersion can be prepared in the solvolysis reactor. In this embodiment, it is preferable to disperse the entire amount of polyurethane raw materials before initiating the solvolysis reaction. This embodiment avoids the cost of a buffer tank. Internal or external dispersing devices can be used. An external device converts the reaction mixture pumped out of the reactor into a dispersion and then pumps this dispersion back into the reactor. Internal dispersing devices are used to prepare dispersions in the solvolysis reactor, preferably single- or multi-stage rotor-stator systems with various geometries, or high-speed dissolver disks or sawtooth impellers. Unlike the method of feeding dry polyurethane powder into a solvolysis reactor containing a stirred reaction solution, this method uses a dispersing device in addition to or instead of a conventional agitator to produce a homogeneous dispersion. Therefore, the polyurethane is not simply stirred in the reaction medium. If the dispersing medium used to prepare the dispersion in the solvolysis reactor already contains all the reactants for solvolysis, solvolysis is usually initiated by increasing the temperature of the dispersion after the dispersion step is completed. If the dispersion in the solvolysis reactor does not contain all of the reactants necessary for solvolysis, the temperature of the dispersion can be increased to the reaction temperature for solvolysis and the missing reactants can be added to the reactor, or the missing reactants can be added to the dispersion in the reactor and then the temperature of the dispersion can be increased to the reaction temperature for solvolysis, or the missing reactants can be added to the dispersion in the reactor while the temperature of the dispersion is being increased.

[0065] If, preferably during feeding to the solvolysis reactor, conveying against the pressure buildup in the reactor is necessary, this can be carried out, for example, by means of a pump or a pressurized metering vessel, which allows significantly smaller conduit cross-sectional areas and a more compact design in contrast to the metering of dry polyurethane foam.

[0066] When step b. is carried out, particularly as a two-step process b1. and b2., it simultaneously solves two problems associated with the solvolysis reaction in step c. On the one hand, the polyurethane is converted into a compact form that is easily metered and transported, which allows for good and high reactor loading. On the other hand, the polyurethane particles have a small particle size and a large external surface area, which allows for rapid conversion in the reactor despite their compact form.

[0067] In step c., any known solvolysis method can be used, in particular alcoholysis, preferably glycolysis and methanolysis, aminolysis, ammolysis, hydrolysis or acidolysis.

[0068] Preferably, step c. is carried out at a temperature of 80°C to 200°C, preferably 90°C to 180°C, more preferably 95°C to 170°C, and most preferably 100°C to 160°C. If the reaction temperature is too low, the conversion rate and yield will be too low. If the reaction temperature is too high, undesirable side reactions will occur and the energy consumption will be too high.

[0069] As mentioned above, the extremely short reaction time required in step c. is a particular advantage of the method of the present invention. Therefore, the solvolysis is preferably carried out for 1 minute to 14 hours, preferably 1 minute to 12 hours, more preferably 5 minutes to 10 hours, even more preferably 10 minutes to 5 hours, particularly preferably 20 minutes to 2 hours, especially preferably 20 minutes to 1 hour, and most preferably 20 minutes to 50 minutes. The reaction time is defined as the time that begins when the reaction mixture reaches the target reaction temperature and ends when the reaction temperature deviates persistently from the target reaction temperature. "Durably" means that slight fluctuations around the target reaction temperature caused by the temperature control process do not determine the end of the reaction time. Preferably, at the end of the reaction time, the reaction mixture is permanently cooled below the target temperature.

[0070] If the reactions are carried out at different target temperatures, i.e. in different phases at different temperatures, all reaction times in the temperature ranges defined above are summed up.

[0071] The solvolysis is preferably carried out under atmospheric pressure. Depending on the solvolysis method and the starting materials, it may be beneficial to carry out step c. under elevated pressure, in particular at a pressure of 1 to 15 bara, preferably 1 to 10 bara, more preferably 1 to 5 bara, in order to further improve the reaction rate.

[0072] In a preferred embodiment, step c of the method of the present invention is carried out as hydrolysis. More preferably, the polyurethane dispersion obtained in step b is contacted with water in the presence of a base and a quaternary ammonium salt as a catalyst to obtain an active hydrogen-containing polyether, preferably a polyether polyol, and an organic polyamine. The base is preferably used as an aqueous solution, particularly preferably as a saturated aqueous base solution.

[0073] The method of this embodiment of the invention results in the efficient hydrolytic cleavage of urethane and urea linkages present in polyurethanes, which are treated to produce active hydrogen-containing polyethers, particularly polyether polyols, polyamines, and, if the polyurethane is prepared using chain extenders or curing agents, low molecular weight glycols, diols, and diamines.

[0074] The structure of the active hydrogen-containing polyether, preferably polyether polyol, recovered by the process of the present invention is a function of the structure of the polyether polyol used in preparing the polyurethane treated by the process of the present invention.

[0075] The structure of the polyamine recovered in this embodiment of the process of the present invention correlates with the structure of the polyisocyanate used to prepare the polyurethane treated in the process of the present invention. "Polyamine" includes diamines, and preferably includes amines having two or more primary amino groups in the molecule.

[0076] In a first particularly preferred embodiment, the hydrolysis in step c. is carried out by contacting the polyurethane dispersion obtained in step b. with water in the presence of a combination (I) of a base and a catalyst, wherein the base contains an alkali metal cation and / or an ammonium cation and has a pKb value at 25°C of 1 to 10, and the catalyst is selected from the group consisting of quaternary ammonium salts containing ammonium cations having 6 to 30 carbon atoms and organic sulfonates having at least 7 carbon atoms.

[0077] The base used in this first particularly preferred embodiment contains an alkali metal cation and / or an ammonium cation and has a pK at 25°C of 1 to 10, preferably 1 to 8, more preferably 1 to 7, and most preferably 1.5 to 6. b The base has a value of 0.01. Both organic bases, i.e., bases containing one or more C-H bonds, and inorganic bases, i.e., bases without C-H bonds, can be used. Preferably, a low-corrosive or non-corrosive base is used. Particularly preferably, a base selected from the group consisting of alkali metal phosphates, alkali metal hydrogen phosphates, alkali metal carbonates, alkali metal silicates, alkali metal hydrogen carbonates, alkali metal acetates, alkali metal sulfites, ammonium hydroxide, and mixtures thereof is used in the process of the present invention. The ammonium cation in the base of the present invention is NH4 + , NHR3 + , NH2R2 + , NH3R + For example, ammonium hydroxide includes NH4OH, NHR3OH, NH2R2OH, and NH3ROH, where R represents an organic group and the groups R in the ammonium cations may be the same or different. Preferably, the ammonium cation of the base is NH4 + Particularly preferred bases of the present invention do not contain alkaline earth metal cations.

[0078] Even more preferably, a base selected from the group consisting of alkali metal phosphates, alkali metal carbonates, alkali metal silicates, ammonium hydroxide and mixtures thereof is used.

[0079] Most preferably, a base selected from the group consisting of alkali metal carbonates, alkali metal silicates and mixtures thereof is used.

[0080] Preferred alkali metals are selected from the group consisting of Na, K and Li and mixtures thereof, most preferably Na and K and mixtures thereof.

[0081] The use of the base allows the process of the present invention to be carried out in standard equipment, preferably steel reactors, without special corrosion protection, and therefore the use of the base contributes significantly to reducing the investment costs of the plant. It also allows the use of very cheap bases, which contributes to reducing the operating costs.

[0082] The amount of base in the reaction mixture must be sufficient to catalyze the desired hydrolysis of the polyurethane at a practical rate. Preferably, the weight ratio of base to polyurethane is in the range of 0.01 to 50, more preferably 0.1 to 25, and most preferably 0.5 to 20. Preferably, the base is used in the form of a base solution containing base and water, and even more preferably as a saturated base solution. When a saturated base solution is used, the weight ratio of saturated base solution to polyurethane, calculated at 25°C, is preferably in the range of 0.5 to 25, more preferably 0.5 to 15, even more preferably 1 to 10, and most preferably 2 to 7.

[0083] In a second particularly preferred embodiment, the hydrolysis in step c. is carried out by contacting the polyurethane dispersion obtained in step b. with water in the presence of a combination of a base and a catalyst (II), wherein the base is a strong inorganic base having a pKb value at 25°C of <1, and the catalyst is a quaternary ammonium salt containing an ammonium cation having 6 to 14 carbon atoms, preferably 6 to 12 carbon atoms when the ammonium cation contains a benzyl group.

[0084] The bases preferably used in this second particular preferred embodiment have a pK at 25°C of less than 1, preferably between 0.5 and -2, more preferably between 0.25 and -1.5, and most preferably between 0 and -1. b Inorganic bases are strong inorganic bases having a C—H bond.

[0085] Particularly preferred strong bases are selected from the group consisting of alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and mixtures thereof. Preferred alkali metals are selected from the group consisting of Na, K, and Li, and mixtures thereof, most preferably Na and K, and mixtures thereof. Preferred alkaline earth metals are selected from the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures thereof, most preferably Mg and Ca, and mixtures thereof. Most preferably, alkali metals selected from the group consisting of potassium or sodium, and mixtures thereof, are used.

[0086] The use of said bases allows the process of the present invention to be operated at lower temperatures and with higher yields compared to prior art processes, and therefore the use of said bases contributes significantly to reducing operating costs.

[0087] The amount of base in the reaction mixture must be sufficient to catalyze the desired hydrolysis of the polyurethane at a practical rate. Preferably, the weight ratio of base to polyurethane is 0.01 to 25, more preferably 0.1 to 15, even more preferably 0.2 to 10, and most preferably 0.5 to 5. The base is preferably used in the form of a base solution containing the base and water. For efficient conversion, the concentration of the base in the base solution is 5% by weight or more, preferably 5 to 70% by weight, more preferably 5 to 60% by weight, even more preferably 10 to 50% by weight, particularly preferably 15 to 40% by weight, and most preferably 20 to 40% by weight, based on the weight of the base solution.

[0088] In a third particularly preferred embodiment, the hydrolysis in step c. is carried out by contacting the polyurethane dispersion obtained in step b. with water in the presence of a combination of a base and a catalyst (III), wherein the base is a strong inorganic base having a pKb value at 25°C of <1, and the catalyst is a quaternary ammonium salt containing an ammonium cation having 15 to 30, preferably 15 to 28, more preferably 15 to 24, even more preferably 16 to 22, and most preferably 16 to 20 carbon atoms.

[0089] The strong base in the combination of base and catalyst (III) is preferably selected from the group consisting of alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and mixtures thereof. Even more preferably, the alkali metal of the base is selected from the group consisting of Na, K, and Li, and mixtures thereof, most preferably Na and K, and mixtures thereof, and / or the alkaline earth metal is selected from the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures thereof, preferably Mg and Ca, and mixtures thereof. Most preferably, an alkali metal selected from the group consisting of potassium or sodium, and mixtures thereof, is used.

[0090] The quaternary ammonium salts used as catalysts in the preferred embodiment and three particularly preferred embodiments preferably have the general structure R1R2R3R4NX, where R1, R2, R3 and R4 are the same or different and are hydrocarbyl groups selected from alkyl, aryl and arylalkyl, and X is selected from the group consisting of halides, preferably chloride and / or bromide, hydrogen sulfate, alkyl sulfates, preferably methyl sulfate and ethyl sulfate, carbonate, hydrogen carbonate, carboxylate, preferably acetate or hydroxide.

[0091] In a first particular preferred embodiment using a combination of base and catalyst (I), R1, R2, R3 and R4 and X are defined as follows: - R1 and R2 are identical or different and are alkyl groups having 1 to 12, preferably 1 to 10, more preferably 1 to 7, even more preferably 1 to 6, particularly preferably 1 to 5 and most preferably 1 to 4 carbon atoms, wherein the alkyl group may be linear, branched, cyclic, saturated or unsaturated, most preferably a linear saturated alkyl group; R3 is selected from the group consisting of alkyl groups having 1 to 12, preferably 1 to 10, more preferably 1 to 7, even more preferably 1 to 6, particularly preferably 1 to 5, and most preferably 1 to 4 carbon atoms, aryl groups having 6 to 14, preferably 6 to 12, and most preferably 6 to 10 carbon atoms, and aralkyl groups having 7 to 14, preferably 7 to 12, and most preferably 7 to 10 carbon atoms, wherein the alkyl groups may be linear, branched, cyclic, saturated or unsaturated, and are most preferably linear; R4 is selected from the group consisting of alkyl groups having 3 to 12, preferably 3 to 10, more preferably 3 to 7, and most preferably 4 to 6 carbon atoms, aryl groups having 6 to 14, preferably 6 to 12, and most preferably 6 to 10 carbon atoms, and aralkyl groups having 7 to 14, preferably 7 to 12, and most preferably 7 to 10 carbon atoms, wherein the alkyl groups may be linear, branched, cyclic, saturated or unsaturated, and are most preferably linear and saturated; X is selected from the group consisting of halides, preferably chloride and / or bromide, hydrogen sulfate, alkyl sulfate, preferably methyl sulfate and ethyl sulfate, carbonate, hydrogen carbonate, acetate or hydroxide.

[0092] Even more preferably, R1 to R4 are as defined above, the total number of carbon atoms in the quaternary ammonium cation is 6 to 14, preferably 7 to 14, more preferably 8 to 13; or The total number of carbon atoms in the quaternary ammonium cation is 15 to 30, preferably 15 to 28, more preferably 15 to 24, even more preferably 16 to 22, and most preferably 16 to 20. is selected from the following.

[0093] In a second particularly preferred embodiment using the combination of base and catalyst (II), R1, R2, R3 and R4 and X are defined as follows: R1 to R3 are identical or different and are alkyl groups having 1 to 6, preferably 1 to 5, more preferably 1 to 4, even more preferably 1 to 3, particularly preferably 1 or 2, and most preferably 1 carbon atom, wherein the alkyl group may be linear, branched, cyclic, saturated or unsaturated, and most preferably a linear saturated alkyl group; R4 is selected from the group consisting of alkyl groups having 3 to 11, preferably 3 to 10, more preferably 3 to 8, and most preferably 4 to 6 carbon atoms, aryl groups having 6 to 11, preferably 6 to 10, and most preferably 6 to 8 carbon atoms, and aralkyl groups having 7 to 11, preferably 7 to 10, and most preferably 7 to 9 carbon atoms, wherein the alkyl groups may be linear, branched, cyclic, saturated, or unsaturated, and most preferred are linear saturated alkyl groups; X is selected from the group consisting of halides, preferably chloride and / or bromide, hydrogen sulfate, alkyl sulfate, preferably methyl sulfate and ethyl sulfate, carbonate, hydrogen carbonate, acetate or hydroxide.

[0094] Even more preferably, R1 to R4 are as defined above, When R4 is not a benzyl group, R1 to R4 are selected so that the total number of carbon atoms in the quaternary ammonium cation is 6 to 14, preferably 7 to 14, more preferably 8 to 13, or or When R4 is a benzyl group, R1 to R3 are selected so that the total number of carbon atoms in the quaternary ammonium cation is 6 to 12, preferably 7 to 12, more preferably 8 to 11. is selected from the following.

[0095] In a third particularly preferred embodiment using the combination of base and catalyst (III), R1, R2, R3 and R4 and X are defined as follows: - R1 and R2 are identical or different and are alkyl groups having 1 to 12, preferably 1 to 10, more preferably 1 to 7, even more preferably 1 to 6, particularly preferably 1 to 5 and most preferably 1 to 4 carbon atoms, wherein the alkyl group may be linear, branched, cyclic, saturated or unsaturated, most preferably a linear saturated alkyl group; R3 is selected from the group consisting of alkyl groups having 1 to 12, preferably 1 to 10, more preferably 1 to 7, even more preferably 1 to 6, particularly preferably 1 to 5, and most preferably 1 to 4 carbon atoms, aryl groups having 6 to 14, preferably 6 to 12, and most preferably 6 to 10 carbon atoms, and aralkyl groups having 7 to 14, preferably 7 to 12, and most preferably 7 to 10 carbon atoms, wherein the alkyl groups may be linear, branched, cyclic, saturated or unsaturated, and are most preferably linear; R4 is selected from the group consisting of alkyl groups having 3 to 12, preferably 3 to 10, more preferably 3 to 7, and most preferably 4 to 6 carbon atoms, aryl groups having 6 to 14, preferably 6 to 12, and most preferably 6 to 10 carbon atoms, and aralkyl groups having 7 to 14, preferably 7 to 12, and most preferably 7 to 10 carbon atoms, wherein the alkyl groups may be linear, branched, cyclic, saturated or unsaturated, and are most preferably linear and saturated; X is selected from the group consisting of halides, preferably chloride and / or bromide, hydrogen sulfate, alkyl sulfate, preferably methyl sulfate and ethyl sulfate, carbonate, hydrogen carbonate, acetate or hydroxide.

[0096] Even more preferably, R1 to R4 are selected from the above definitions, wherein the total number of carbon atoms in the quaternary ammonium cation is 15 to 30, preferably 15 to 28, more preferably 15 to 24, even more preferably 16 to 22, and most preferably 16 to 20.

[0097] In a preferred embodiment and three particularly preferred embodiments of step c., a quaternary ammonium salt is used as a phase transfer catalyst. Although the addition of even trace amounts of these phase transfer catalysts accelerates the hydrolysis rate, it is preferred to use at least 0.5 wt. % of the catalyst, based on the weight of the polyurethane, more preferably 0.5 to 15 wt. %, even more preferably 1 to 10 wt. %, particularly preferably 1 to 8 wt. %, especially preferably 1 to 7 wt. %, and most preferably 1 to 6 wt. %.

[0098] In the preferred embodiment and three specific preferred embodiments of step c., water functions as a reactant in the desired polyurethane hydrolysis reaction, and therefore need not be present in stoichiometric excess relative to the urethane functional groups in the polymer to be hydrolyzed. However, it will generally be desirable to utilize a substantial amount of water so that it can conveniently function as a reaction medium and a solvent or carrier for the strong base and activator. For these reasons, water is preferably present in condensed (liquid) form. Typically, the weight ratio of polyurethane to water is 3:1 to 1:15.

[0099] The hydrolysis is preferably carried out at atmospheric pressure, although superatmospheric pressure can be used if desired. Optionally, a water-miscible or water-immiscible solvent such as an alcohol, ketone, ester, ether, amide, sulfoxide, halogenated hydrocarbon, aliphatic hydrocarbon, or aromatic hydrocarbon can be present in the reaction mixture to facilitate the hydrolysis process or to aid in the recovery of the reaction product.

[0100] The hydrolysis reaction can be carried out batchwise, continuously, or semi-continuously in any suitable vessel or other apparatus (e.g., a stirred tank reactor or a screw extruder) whereby the polyurethane can be contacted with water in the presence of a base and an activator. Generally, agitation or stirring of the reaction ingredients will be preferred to ensure intimate contact, a rapid rate of hydrolysis, and adequate temperature control.

[0101] As demonstrated in the following examples, the selection of the hydrolysis process of the aforementioned preferred embodiment and three specific preferred embodiments is advantageous because the recycled polyol has excellent quality and is very similar or even identical to the polyol from which the polyurethane raw material is produced. The recycled polyol can be used in large quantities to produce new polyurethane foams, preferably flexible polyurethane foams, while maintaining the previously known product quality of polyurethane foams. The recycled polyol can be used, in particular, to produce flexible polyurethane foams that have previously been produced without recycled polyol, taking into account the physical and mechanical properties of the resulting polyurethane foams.

[0102] Furthermore, in the preferred embodiment and three particularly preferred embodiments, very short hydrolysis reaction times of 30 minutes are achieved with excellent yields.

[0103] The first particularly preferred embodiment using the combination of base and catalyst (I) has the additional advantage that a wide variety of inexpensive bases and / or low or non-corrosive bases can be used to effectively depolymerize polyurethane. The method of this embodiment is very flexible in terms of the catalyst used. The inventors have found that ammonium cations with fewer carbon atoms can be used as effectively as those with more carbon atoms. This allows for more flexibility in terms of the operating temperature.

[0104] The process of the present invention preferably comprises an additional step d. of separating and recovering the reaction products of the solvolysis, preferably organic polyamines and / or active hydrogen-containing polyethers, preferably polyether polyols.

[0105] The active hydrogen-containing polyether, preferably polyether polyol, organic polyamine, chain extender, and curing agent produced by solvolysis can be separated and recovered from the crude reaction mixture using any suitable method or combination of methods known in the art, such as, for example, extraction (e.g., using a water-immiscible organic solvent as the extractant), distillation, precipitation, filtration, etc.

[0106] Analysis method Particle size of polyurethane powder A laser diffraction analyzer (model: Horiba LA-950) was used to measure the particle size distribution of the polyurethane after step b1 (dry milling) and step b2 (wet dispersion). To better disperse the particles during the measurement, the samples were treated with ultrasound for up to 120 seconds.

[0107] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following examples are, therefore, to be construed as merely illustrative, and not limitative of the claims or the remainder of the disclosure in any way whatsoever. [Brief explanation of the drawings]

[0108] [Figure 1a] FIG. 1 shows the PU foam after step b1. [Figure 1b] FIG. 10 is a diagram showing details of the PU foam after step b1. [Figure 2a] FIG. 2 shows PU foam particles (Example 1) after the first pass of steps b1 and b2. [Figure 2b] FIG. 1 shows PU foam particles (Example 1) after the 10th pass of steps b1 and b2. [Figure 3] FIG. 1 shows a mixture of 30 g of ground PU in 100 ml of polyol.

[0109] Example Example 1: Preparation of aqueous dispersion The raw material used was a polyurethane foam cube based on 100% polyol, measuring approximately 16 x 24 x 24 cm on the sides. The cube was manually cut into coarse pieces and then metered into a Condux cutting mill (model CS 230 / 220 / N1). The mill was equipped with a sieve bed with 2 mm square perforations. A fluffy, snow-like powder was obtained from the cutting mill, which was dispersed in water. This was done in an IKA colloid mill (model MK 2000 / 5) equipped with a cone insert (model MKO). The polyurethane snow was metered into the colloid mill in a weight ratio of 1:20 with water and dispersed over 10 passes in pass operation mode. The particle size was measured at the end of the process, resulting in an average particle size d 50 = 592 μm. The achieved opening of the foam cell structure is shown in Figures 2a and 2b. The dispersion thus obtained was used for the subsequent hydrolysis reaction.

[0110] Example 2: Preparation of a dispersion in aqueous potassium carbonate solution The raw material was a 100% polyol-based polyurethane foam cube with side lengths of approximately 16 x 24 x 24 cm. The cube was manually cut into coarse pieces and then metered into a Condux cutting mill (model CS 230 / 220 / N1). The mill was equipped with a sieve bed with 4 mm square perforations. A fluffy, snow-like powder was obtained from the cutting mill, which was then dispersed in an IKA colloid mill (model MK 2000 / 5) equipped with a cone insert (model MKO). A 40% by weight aqueous solution of K2CO3 was used as the dispersion medium. This K2CO3 solution was mixed with the additive Tomadol 1-5 in a proportion calculated to achieve 1% additive based on the dry weight of polyurethane. The dispersion was prepared using 50 g of polyurethane snow (dry) and 1.5 kg of K2CO3 solution, which contained 0.5 g of Tomadol 1-5. These ingredients were weighed simultaneously into a colloid mill and then dispersed over 10 passes. At the end of the process, the particle size was measured, resulting in an average particle size of d 50 = 525 microns. This dispersion was used in the subsequent hydrolysis reaction.

[0111] Example 3: Preparation of a dispersion in aqueous potassium carbonate solution In a modification of the experiment described in Example 2, the dispersion was finally filtered through a 300 μm sieve to separate the excess dispersing fluid before using it for hydrolysis, resulting in a reduction of the amount of dispersing fluid by approximately 50%.

[0112] Example 4: Preparation of a dispersion in aqueous potassium carbonate solution by recycling Example 2 was repeated with the following changes: The polyurethane snow obtained from the cutting mill was dispersed in a colloid mill in recirculation mode rather than pass mode. A pump was installed at the liquid outlet of the colloid mill, which pumped the dispersion medium back to the supply tank at the top of the mill. The supply tank was filled with dispersion medium, this time containing Tomadol 1-5, and the mill was started. While the dispersion medium was being pumped through the mill and back to the supply tank, the required amount of polyurethane snow was continuously metered into the liquid circulation section. After the target polyurethane concentration was reached, the dispersion was circulated in the liquid circulation section for a short period and then removed for further use. At the end of the process, the particle size was measured, yielding an average particle size of d 50 =694 μm.

[0113] Example 5: Hydrolysis of polyurethane snow dispersions From 50 g of the polyurethane snow dispersion of Example 1, the excess aqueous phase was separated by filtration, and 490 g of a 40 wt. % K2CO3 solution in water was added to the dispersion. The resulting dispersion was further mixed with 2.5 g of tetrabutylammonium hydrogen sulfate (C=16), a quaternary ammonium salt. The suspension was then added to a pressure-resistant reactor, where thorough mixing was ensured.

[0114] The stirred mixture was heated to the desired reaction temperature by a thermostat connected to the reactor jacket and cooled after completion of the reaction. The reaction was carried out at an internal temperature of 150°C and elevated pressure (equal to or greater than the boiling pressure of the reaction mixture). The reaction was terminated after 30 minutes by draining the reaction solution from the reactor.

[0115] The conversion was determined by weighing the dry residue of the organic fraction of the reaction mixture and is shown in Table 1. For this purpose, the organic phase and DMSO-soluble solids were dissolved in DMSO. The undissolved solids, i.e., the remaining PU and K2CO3, were filtered and washed with HCl. The HCl wash dissolved the potassium carbonate, leaving only the unreacted PU on the filter.

[0116] Comparative Example 1: The procedure described in Example 5 was repeated in Comparative Example 1. Instead of the polyurethane snow dispersion of the present invention, polyurethane foam cubes were used for hydrolysis. This was obtained by hot-compressing the same raw polyurethane foam at 160°C with a holding time of 10 minutes and cutting the hot-compressed polyurethane into cubes with an average size of approximately 1 x 1 x 2 cm. The conversion rate was determined at each time point and is shown in Table 1.

[0117] [Table 1]

[0118] As can be seen from Table 1, the inventive dispersion of Example 5 obtained using steps b1. (cutting mill) and b2. (dispersion step) can be fully converted within 30 minutes. In contrast, the same polyurethane foam processed by hot pressing and cutting as proposed in the prior art could only convert to 97% even after a reaction time of 90 minutes.

[0119] Comparative Example 2: In Example 1 of US Patent Application Publication No. 2016 / 00347927, 500 g of rigid PU was ground. A total of 500 g of recycled polyol was added during grinding, resulting in a mixture containing 50 wt. % ground PU powder in polyol. US Patent Application Publication No. 2016 / 0347927 does not provide details about the grinder used. Therefore, it is impossible to directly reproduce this example.

[0120] However, to compare the grind of U.S. Patent Application Publication No. 2016 / 0347927 with the present invention, pre-ground polyol was added to 100 ml (97 g) of polyol with stirring until the resulting mixture formed a wet powder rather than a dispersion, i.e., the reaction mixture could not be pumped through a conduit. It was found that the addition of 30 g of ground PU resulted in a wet powder, as shown in Figure 3. Even under pressure, no liquid could be forced out of the wet powder.

[0121] This indicates that mixtures of ground PU and polyol with a PU content of 30 wt. % or more, such as the ground powder obtained in Example 1 of US Patent Application Publication No. 2016 / 0347927, cannot be considered dispersions, especially pumpable dispersions as in the present invention. Mixtures of ground PU in polyol with such high solids contents must be handled and conveyed by solid conveying means such as screw conveyors or conveyor belts, and cannot be pumped through small diameter conduits.

[0122] Attempts to produce a mixture of ground PU in a polyol with a solvent content of 30% by weight in a mill again resulted in wet powder. The wet powder adhered to the walls of the mill, which required a lot of effort to clean the mill after the experiment. Continuous operation of the mill is not possible with such material.

[0123] When a hydrolysis experiment was carried out using the wet powder obtained in Comparative Example 2 under the conditions described in Comparative Example 1, the conversion was incomplete even when the reaction time was extended by 50% compared to when the dispersion according to the present invention was used.

Claims

1. 1. A method for solvolysis of polyurethanes, comprising: a. providing a polyurethane; b. preparing a polyurethane dispersion from the polyurethane; c. Solvolyzing the polyurethane dispersion; A method comprising: the polyurethane to be dispersed has an average particle size of 0.1 to 12 mm as measured by a laser diffraction analyzer; 3. A method according to claim 1, wherein the polyurethane content in the dispersion after step b. and / or in the dispersion used in step c. is in the range of 4 to 20% by weight.

2. Step b. b1. chopping, pulverizing, grinding, milling, cutting or otherwise pulverizing the polyurethane provided in step a. to obtain a polyurethane powder; b2. Producing a dispersion from the polyurethane powder obtained in step b1. using a device selected from the group consisting of a colloid mill, a single-stage or multi-stage rotor-stator system with various geometries, or a high-speed operating dissolver disk or a sawtooth impeller in an agitated vessel; The method of claim 1 , comprising:

3. The polyurethane powder to be dispersed has an average particle size of 0.2 to 4 mm as measured by a laser diffraction analyzer, and / or a viscosity of 30 kg / m ３ 3. The method of claim 2, characterized in that it has a higher bulk density.

4. Step b1. is carried out at a temperature ranging from ambient temperature to 120°C; and / or Step b2. is carried out at a temperature of 10 to 90°C.

3. The method according to claim 2, characterized in that

5. The liquid or mixture of the liquid and other components used as a reactant and / or solvent in step c, or the solvolysis reaction product of step c, is used as a dispersion medium in step b or b2, and / or Mixing polyurethane powder with the dispersion medium in a weight ratio of 1:5 to 1:40; and / or the polyurethane content in the dispersion after step b. and / or in the dispersion used in step c. is in the range of 5 to 18 wt.%, and / or The particle size of the polyurethane particles measured by a laser diffraction analyzer in the dispersion after step b. and / or the dispersion used in step c. is in the range of 10 to 2000 μm.

2. The method according to claim 1, characterized in that

6. 2. The method of claim 1, wherein step b or step b2 is carried out in a solvolysis reactor, and the entire amount of polyurethane is dispersed before the solvolysis reaction is initiated.

7. 2. The method of claim 1, wherein step c. is carried out as hydrolysis to obtain an active hydrogen-containing polyether and an organic polyamine.

8. The hydrolysis in step c. is carried out by contacting the polyurethane dispersion obtained in step b. with water in the presence of a base-catalyst combination (I), (II) or (III), wherein: The combination of base and catalyst (I) comprises a base containing an alkali metal cation and / or an ammonium cation and having a pKb value of 1 to 10 at 25°C, and a catalyst selected from the group consisting of quaternary ammonium salts containing ammonium cations having 6 to 30 carbon atoms and organic sulfonates having at least 7 carbon atoms; or The base and catalyst combination (II) comprises a strong inorganic base having a pKb value of <1 at 25°C and a quaternary ammonium salt containing an ammonium cation having 6 to 14 carbon atoms as a catalyst; or The base and catalyst combination (III) comprises a strong inorganic base having a pKb value of <1 at 25°C and a quaternary ammonium salt containing an ammonium cation having 15 to 30 carbon atoms as a catalyst.

8. The method according to claim 7, characterized in that

9. 9. The method of claim 8, wherein the alkali metal cation constituting the base in the combination of base and catalyst (I) is selected from the group consisting of alkali metal phosphates, alkali metal hydrogen phosphates, alkali metal carbonates, alkali metal silicates, alkali metal bicarbonates, alkali metal acetates, alkali metal sulfites, ammonium hydroxide, and mixtures thereof.

10. The method of claim 9, wherein the alkali metal is selected from the group consisting of Na, K and Li and mixtures thereof.

11. 9. The method of claim 8, wherein the strong inorganic base in the base and catalyst combination (II) or (III) is selected from the group consisting of alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and mixtures thereof.

12. The method of claim 11, wherein the alkali metal is selected from the group consisting of Na, K, and Li and mixtures thereof, and / or the alkaline earth metal is selected from the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures thereof.

13. The catalyst has the general structure R １ R ２ R ３ R ４ NX, where R １ , R ２ , R ３ and R ４ 9. The method of claim 8, wherein X is the same or different and is a hydrocarbyl group selected from alkyl, aryl, and arylalkyl, and X is selected from the group consisting of halide, hydrogen sulfate, alkyl sulfate, carbonate, bicarbonate, carboxylate, or hydroxide.

14. Regarding the base and catalyst combinations (I) and (III), the catalyst has the general structure R １ R ２ R ３ R ４ NX, where: -R １ and R ２ are the same or different and are alkyl groups having 1 to 12 carbon atoms, wherein said alkyl groups may be linear, branched, cyclic, saturated or unsaturated; -R ３ is selected from the group consisting of alkyl groups having 1 to 12 carbon atoms, aryl groups having 6 to 14 carbon atoms, and aralkyl groups having 7 to 14 carbon atoms, wherein said alkyl groups may be linear, branched, cyclic, saturated, or unsaturated; -R ４ is selected from the group consisting of alkyl groups having 3 to 12 carbon atoms, aryl groups having 6 to 14 carbon atoms, and aralkyl groups having 7 to 14 carbon atoms, wherein said alkyl groups may be linear, branched, cyclic, saturated, or unsaturated; X is selected from the group consisting of halides, hydrogen sulfates, alkyl sulfates, carbonates, hydrogen carbonates, acetates or hydroxides; and / or Regarding the combination of base and catalyst (II), the catalyst has the general structure R １ R ２ R ３ R ４ NX, where: -R １ ~R ３ are the same or different and are alkyl groups having 1 to 6 carbon atoms, wherein said alkyl groups may be linear, branched, cyclic, saturated or unsaturated; -R ４ is selected from the group consisting of alkyl groups having 3 to 11 carbon atoms, aryl groups having 6 to 11 carbon atoms, and aralkyl groups having 7 to 11 carbon atoms, wherein said alkyl groups may be linear, branched, cyclic, saturated, or unsaturated; 14. The method of claim 13, wherein X is selected from the group consisting of halides, hydrogen sulfates, alkyl sulfates, carbonates, bicarbonates, acetates or hydroxides.

15. Regarding the combination of base and catalyst (I), R １ ~R ４ is selected so that the total number of carbon atoms in the quaternary ammonium cation is 6 to 14, or or R １ ~R ４ is selected so that the total number of carbon atoms in the quaternary ammonium cation is 15 to 30.

16. Regarding the combination of base and catalyst (II), R ４ is not a benzyl group, and R １ ~R ４ is selected so that the total number of carbon atoms in the quaternary ammonium cation is 6 to 14, or or R ４ is a benzyl group, and R １ ~R ３ is selected so that the total number of carbon atoms in the quaternary ammonium cation is 6 to 12.

17. 9. The method of claim 8, wherein the quaternary ammonium salt is used as a phase transfer catalyst in an amount of at least 0.5% by weight based on the weight of the polyurethane.

18. 10. The method of claim 1, including the additional step of separating and recovering the reaction products of the solvolysis.

19. The solvolysis in step c. At temperatures between 80°C and 200°C, and / or 10. The method of claim 1, wherein the method is carried out for 1 minute to 14 hours.

20. 10. The method of claim 1, wherein the solvolysis in step c. is carried out at atmospheric pressure or at elevated pressure.

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