Glycolysis process for converting polyurethane foam into useful dispersions

Abstract

Polyol dispersions are prepared by chemolysis of polyurethane foam. The starting foam is compressed, degassed and combined and wetting with a polyol in a non-backmixing tubular reactor and then digested to produce the polyol dispersion. This rapidly produces a reaction mixture that digests quickly. The process is well-adapted for continuous operation. The polyol dispersion is useful for making polyurethanes.

Description

[0001] GLYCOLYSIS PROCESS FOR CONVERTING POLYURETHANE FOAM INTO USEFUL DISPERSIONS

[0002] This invention relates to glycolysis methods for converting polyurethane foam into useful products.

[0003] Polyurethane foam is produced globally in very large quantities. Polyurethane foam varies widely in properties and end-uses. Flexible foam is used as cushioning in furniture, vehicle seating and bedding, among other things. Mattresses often contain a significant mass of flexible polyurethane foam. Rigid polyurethane foam is widely used in thermal insulation applications such as appliance and building insulation, insulated trucks and railway cars, and similar products.

[0004] These products present a very substantial end-of-life disposal problem. Conventionally, these products have been landfilled, but in many areas of the world landfill space is becoming scarce and less capable of accepting large volumes of waste foam. The waste foam can be burned to recover energy but doing so releases carbon dioxide. Some polyurethane foam is recycled by crushing and grinding it to form small particles that can be incorporated into fresh foam products. However, opportunities for doing this are limited.

[0005] Many attempts have been made to convert polyurethane foam back into useful starting materials via various chemolysis processes. These include hydrolysis processes in which the foam is reacted with water at high temperature and pressure; glycolysis processes in which foam is reacted with a low molecular weight diol; acidolysis processes in which the foam a reacted with a carboxylic acid or anhydride; and aminolysis processes in which the foam is reacted with a primary amine compound. All of the foregoing chemolysis processes produce isocyanate-reactive mixtures containing polyols and / or polyamines. These reactive mixtures by themselves or together with virgin polyols can be reacted with polyisocyanates to produce more polyurethane or polyurea products.

[0006] Hybrid processes that combine two or more of these chemolysis approaches, such as glycolysis-hydrolysis and glycolysis-acidolysis processes, are also known. A hybrid chemolysis process that has become of interest is a glycolysis-acidolyis process as described in US Patent No. 11,124,623. In that process, post-consumer polyurethane foam is reacted with a carboxylic acid or anhydride and a 400-6000 molar mass polyether polyol, followed by further reaction with a short-chain diol or triol, in a combined glycolysis-acidolysis process. Polyurethane foam chemolysis processes are usually operated in batch reactors. Batch processes are less preferred at large industrial scale because cycle times can become quite long. The process of US Patent No. 11,124,623 in particular usually requires batch cycle times of 12 hours or more to heat the starting materials to the required temperature, perform the reactions, and then cool the reaction products. The long cycle times are due in part to the use of somewhat high molecular weight polyether polyols as the glycol component. These polyols are viscous even at the processing temperature compared to low molecular weight polyols previously used in glycolysis methods, so they penetrate into the foam very slowly. In addition, the high molecular weight polyols are generally used in larger proportions by weight due to their relative scarcity of hydroxyl groups. Continuous processes potentially offer significant advantages at large scale, if the chemolysis process can be adapted to continuous operation.

[0007] Some attempts have been made to conduct chemolysis processes continuously in an extruder or similar device. US 4,051,212 describes the hydrolysis of polyurethane foam in a twin- screw extruder to produce toluene diamine and polyether hydrolysis products. DE3232461A describes the glycolysis of polyurethane foam in a twin-screw extruder using propylene glycol and other short chain diols as the glycolytic agent, followed by cooling the product mixture in a refrigerated tank.

[0008] The invention is in one aspect a process for producing a polyol dispersion from polyurethane foam, comprising the steps of: a) continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyether polyol having a weight average molecular weight of 400 to 8,000 g / mol into a non-b ackmixing tubular reactor having a rotating screw comprising forwarding elements, b) at a temperature of 10 to 300°C, compressing and degassing the polyurethane foam and combining and wetting the compressed and degassed polyurethane foam with component ii by action of the rotating screw in the non-backmixing tubular reactor to form a reaction mixture, and then c) digesting the reaction mixture at a reaction temperature of 150 to 300°C to chemically decompose the polyurethane foam produce the polyol dispersion.

[0009] This aspect of the invention provides a process in which a polyurethane foam can be converted by reaction with a 400-8,000 molecular weight polyol into a useful polyol dispersion in a vastly reduced cycle time. Cycle times in the process described in U.S. Patent No. 11,124,623 typically range from 10 to 15 hours on an industrial scale. With this invention, those cycle times can be reduced to 5 hours or less, and in some cases to less than one hour. The digestion step can be performed continuously in the batch reactor, in which case the invention offers the advantages of continuous operation. Alternatively, the digestion step is performed in a separate tank reactor, which may be, for example, a batch reactor or continuously stirred tank reactor (CSTR). Even in the latter case, vastly reduced cycle times are obtained, due in large part to the rapid degassing of the foam and efficient wetting of the foam with the polyether polyol.

[0010] The invention in a second aspect is a process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam, (component ii) a polyol, and (component iii) dicarboxylic acid and / or dicarboxylic acid anhydride into a mixing section of a non-backmixing tubular reactor, the mixing section of the non- backmixing tubular reactor having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the mixing section and combining and wetting the compressed and degassed polyurethane foam with components ii and iii in the mixing section to form a reaction mixture, and heating the reaction mixture to a reaction temperature of 150 to 300°C; continuously forwarding the reaction mixture from the mixing section into and through a downstream section of the non-backmixing tubular reactor while maintaining the reaction mixture at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor and continuously withdrawing the polyol dispersion from an outlet end of the non-backmixing tubular reactor.

[0011] In a third aspect, the invention is a process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyol, into a mixing section of a non-backmixing tubular reactor, the mixing section of the non-backmixing tubular reactor having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the mixing section and combining and wetting the compressed and degassed polyurethane foam with component ii in the mixing section to form a reaction mixture, and heating the reaction mixture to a reaction temperature of

[0012] 150 to 300°C; continuously forwarding the reaction mixture from the mixing section into and through a downstream section of the non-backmixing tubular reactor while maintaining the reaction mixture at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor and continuously withdrawing the polyol dispersion from an outlet end of the non-backmixing tubular reactor and cooling the dispersion without applied refrigeration to a temperature of 20 to 30°C.

[0013] In a fourth aspect, the invention is a process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyol, into an extruder, the extruder having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the extruder and combining and wetting the compressed and degassed polyurethane foam with component ii in the extruder to form a reaction mixture, and heating the reaction mixture to a reaction temperature of 150 to 300°C; continuously forwarding the reaction mixture from the extruder into and through a static mixer while maintaining the reaction mixture at the reaction temperature in the static mixer to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the static mixer and continuously withdrawing the polyol dispersion from an outlet end of the static mixer.

[0014] In this invention, polyurethane foam, a polyol and optionally other ingredients as described before are continuously fed into a non-backmixing tubular reactor. The tubular reactor is provided with one or more ports or other openings through which the starting materials are introduced. Suitable apparatus for feeding the foam and other solid starting materials include gravimetric feeders, and “crammers” which mechanically force the foam into a port of the tubular reactor. Liquid starting materials may be introduced in any convenient manner such as by using gravimetric feeders and pumps of various types, typically associated with metering equipment to control rates of introduction. Any two or more of the starting materials can be premixed before being fed into the tubular reactor.

[0015] By “non-backmixed” or “non-backmixing”, it is meant that material flowing through the tubular reactor moves generally in a downstream direction from the point(s) of introduction toward the point(s) of removal without “backwards” movement in an upstream direction (z.e., toward the points of introduction). By “tubular”, it is meant the reactor has an elongated internal cavity, preferably having a length to internal diameter ratio of at least 5, at least 10, at least 20, or any arbitrarily larger value such as up to 500, up to 100 or up to 50. The tubular reactor may have any arbitrary cross-sectional geometry, including circular, ellipsoidal, polygonal, “figure 8”-shaped, etc., and the cross-sectional geometry and area may or may not be constant along the entire length of the tubular reactor. When the internal cavity is not circular in cross-section, the diameter is taken as the diameter of a circle having the same area as the cross-sectional area of the internal cavity. If the internal cavity is not constant in cross-sectional area, the length to diameter ratio is taken as the entire length of the internal cavity of the tubular reactor, divided by its smallest cross- sectional area.

[0016] At least a portion of the non-backmixing tubular reactor has a rotating screw that includes forwarding elements. In particularly preferred embodiments, a single-screw extruder, more preferably a twin-screw extruder, constitutes at least a mixing section of the tubular reactor, i.e., that portion of the tubular reactor in which the polyurethane foam is degassed and combined and wetted with the poly ether polyol. In such embodiments, the operation of the screw(s) provides mixing and motive force to move the reactants through the reactor from the various inlet(s) to the outlet(s).

[0017] In some embodiments, a single- or twin-screw extruder constitutes the entire non- backmixing tubular reactor. In other alternative embodiments, the non-backmixing tubular reactor comprises two or more single- or twin-screw extruders operated in tandem, with an upstream extruder (including at least the mixing section) feeding one or more downstream extruders in series (where digestion may take place). In still other alternative embodiments, a progressive cavity pump constitutes all or a part of the non-backmixing tubular reactor, including at least the mixing section. For example, a progressive cavity pump may feed one or more downstream static mixers, where digestion takes place in certain embodiments. The polyurethane foam is compressed and degassed, and combined and wetted with component ii (i.e., the polyether polyol) and other optional ingredients as discussed below, by action of the rotating screw or screws in the mixing section. The steps of compression, degassing and combining and wetting in the mixing section are performed at a temperature of 10 to 300°C. When elevated temperatures are used in this step, the starting materials preferably are heated to such temperature in the mixing section of the non-backmixing tubular reactor.

[0018] In some embodiments, the steps of compression, degassing and combining and wetting are performed at a temperature of 180 to 300°C, preferably 180 to 250°C or 180 to 225°C. Higher temperatures such as these are particularly suitable in embodiments in which the step of digesting the reaction mixture and chemically decomposing the polyurethane foam to produce the polyol dispersion is performed entirely or primarily in the non-backmixing tubular reactor. Some chemolysis typically takes place in the mixing section of the non-backmixing tubular reactor.

[0019] In alternative embodiments, the steps of compression, degassing and combining and wetting are performed at temperature of 10 to 200°C, 10 to 150°C, 20 to 150°C, 20 to 100°C or 20 to 60°C. Lower temperatures such as these are particularly suitable in embodiments in which the subsequent step of digesting the reaction mixture and chemically decomposing the polyurethane foam to produce the polyol dispersion is performed outside of non-backmixing tubular reactor. Surprisingly, a small amount of chemolysis takes place even when very low temperatures such as 150°C or lower or even 60°C or lower are used.

[0020] Gas removed from the starting polyurethane foam may be vented from the non-backmixing tubular reactor separately from the reaction mixture, if desired. A vent or other gas removal port may be provided for this purpose.

[0021] The reaction mixture obtained after the steps of compressing, degassing, and combining and wetting is generally a viscous fluid or paste-like semi-solid material that requires further digestion, even if some digestion has taken place during the compressing, degassing and combining and wetting steps.

[0022] Thereafter, the reaction mixture is digested at a reaction temperature of 180 to 300°C, preferably 180 to 250°C or 180 to 225°C. This can be done in the non-backing mixing tubular reactor, or in other apparatus such as a tank reactor (for example, a continuous stirred tank reactor (CSTR). Digestion times can be, for example 2 minutes to 10 hours. A preferred digestion time, when the digestion is performed in the non-backmixing tubular reactor, is 10 to 120 minutes, preferably 20 to 60 minutes. Digestion in a tank reactor may be performed, for example, for a period 20 minutes to 5 hours.

[0023] The digestion step preferably is performed under mixing conditions.

[0024] When the digestion is performed in the non-backmixing tubular reactor, the reaction mixture is continuously forwarded from an upstream mixing section, where the compression, degassing and combining and wetting steps are performed, into and through a downstream section of the non-backmixing tubular reactor. The reaction mixture is maintained at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor. Mixing can be provided by operation of a rotating screw when the downstream section of the tubular reaction is a single- or twin-screw extruder or portion thereof. Static mixing elements can also provide the mixing conditions within the downstream section of a non-backmixing tubular reactor.

[0025] In embodiments in which the digestion step is performed outside of a non-backmixed tubular reactor, such as in a tank reactor, the reactor preferably is agitated, such a through operation of agitator, or an agitator in combination with static mixing elements.

[0026] The non-backmixing tubular reactor may comprises apparatus for controlling pressure within the reactor. An example of such an apparatus is back pressure regulator or valve that is mounted onto an outlet port, i.e., a port for removal of the products obtained in the process. The pressure in the non-backmixing tubular reactor can be maintained at a predetermined value by operation of such apparatus. In some embodiments, a superatmospheric pressure sufficient to maintain the various ingredients and reaction products in liquid or solid form is maintained in the non-backing tubular reactor during the process.

[0027] During the digestion step, the polyurethane foam is converted to a polyol dispersion by reaction with the polyol(s) and, when present, other materials that can be added into the mixing region of the non-backmixing tubular reactor as one of the starting ingredients and / or added later during or prior to the digestion step. The dispersion comprises a liquid phase that includes one or more polyols, and a solids phase that is dispersed in the liquid phase. The polyols in the liquid phase typically include a portion of the polyol(s) used as starting materials as well as polyols generated by the decomposition of the polyurethane foam. The solids typically comprise solid decomposition products produced in the digestion step. The polyol dispersion may have a hydroxyl number of, for example, 20 to 300 mg KOH / g, as measured according to ASTM D6342-22.

[0028] The digested product is cooled from the reaction temperature to 20 to 30°C. In the third aspect of the invention, this cooling is performed after withdrawing the polyol dispersion from the non-backmixing tubular reactor, and is performed without applied refrigeration. By “without applied refrigeration”, it is meant that the polyol dispersion is not contacted directly or indirectly with a fluid coolant having a temperature below 20°C or with a cooled surface having a temperature below 20°C, as the polyol dispersion cools from the reaction temperature to a temperature of 20 to 30°C. Cooling in the other aspects may similarly be performed without applied refrigeration.

[0029] The starting polyurethane foam may be a flexible, semi-flexible or rigid foam. The foam is characterized by having urethane groups and may also contain other groups produced in various reactions of isocyanate groups, such as urea, isocyanurate, biuret, allophanate, carbodiimide and similar groups. The foam may have open cells, closed cells, or both open and closed cells in any combination. The foam may be thermoplastic but is typically crosslinked. Preferred foams are reaction products of ingredients comprising at least one polyisocyanate and at least one polyether polyol, especially at least polyether polyol having a weight average molecular weight of 400 to 8,000 g / mol (as measured by size exclusion chromatography against polyether standards) and 2 to 4 hydroxyl groups per molecule.

[0030] The starting polyurethane foam most preferably is waste foam, i.e., post-consumer waste and / or scrap or other waste from a foam manufacturing or fabrication process. A particular postconsumer waste foam comprises foam recovered from bedding products such as mattresses and pillows, and / or seating cushions such as furniture cushions and automotive seating. Another preferred starting polyurethane foam is post-consumer waste rigid foam recovered from appliance products, insulated panels and the like.

[0031] The polyurethane foam may be shredded, ground or otherwise comminuted into small pieces to facilitate feeding into the non-backmixing tubular reactor.

[0032] The polyol continuously fed into the mixing region of the non-backmixing tubular reactor in the first aspect of the invention includes at least one polyether polyol having a weight average molecular weight of 400 to 8,000 g / mol, especially at least 1000 g / mol or at least 1500 g / mol and preferably up to 6,000 g / mol. The polyether polyol may be, for example, a polymer of one or more of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide or tetrahydrofuran. A preferred poly ether polyol is a random and / or block copolymer of 60 to 95% by weight 1,2- propylene oxide and 5 to 40% ethylene oxide.

[0033] Such a polyether polyol preferably is all or part of the polyol ingredient fed into the mixing region of the non-backmixing tubular in the other aspects of the invention. At least 50, at least 100 or at least 150 parts by weight and up to 500, up to 300 or up to 200 parts by weight of poly ether polyol may be fed into the mixing region per 100 parts by weight of the polyurethane foam.

[0034] In such other aspects of the invention, the polyol may instead or in addition comprise a low equivalent weight polyol having a hydroxyl equivalent weight of up to 75, preferably up to 70 g / equivalent (as measured by obtaining a hydroxyl number according to ASTM D6342-22, and converting the hydroxyl number to equivalent weight using the relation equivalent weight = 56,100 / hydroxyl number), and 2 to 4 hydroxyl groups per molecule. Examples of such low molecular weight polyols include 1,2-ethane diol, diethylene glycol, 1,3-propane diol, dipropylene glycol, tripropylene glycol, 1,4-butane diol, glycerin, dimethylolpropane, dimethylol ethane, trimethylolpropane and trimethylolethane. Such a low equivalent weight polyol may also be an ingredient in the first aspect of the invention. In embodiments of the invention in which the polyols include a polyether polyol having a molecular weight of 400 to 8,000 g / mol, a suitable amount of low equivalent weight polyol (if used at all) is at least 0.1, at least 0.25 or at least 0.5 parts by weight and, for example up to 5, up to 10 or up to 5 parts by weight per 100 parts by weight polyurethane foam. In embodiments of the invention in which no polyether polyol having a molecular weight of 400 to 8,000 g / mol is used, a suitable amount of low equivalent weight polyol is at least 1 part or at least two parts by weight and up to 25, up to 15 or up to 10 parts by weight per 100 parts by weight polyurethane foam.

[0035] All or part of the digestion step can be performed in the presence of additional materials that perform useful functions. Among these are a dicarboxylic acid or anhydride thereof, including for example, one or more of phthalic acid, phthalic anhydride, terephthalic acid, terephthalic anhydride, maleic acid, maleic anhydride, adipic acid, adipic anhydride, glutaric acid, glutaric acid anhydride, succinic acid, succinic acid anhydride, hydrogenated phthalic acid, hydrogenated phthalic anhydride, hydrogenated terephthalic acid and hydrogenated terephthalic anhydride. The dicarboxylic acid or anhydride in some embodiments is fed continuously into the mixing region of the non-backmixing tubular reactor and is therefore present during the compression, degassing and combining and wetting steps. In some embodiments, solid dicarboxylic acids or anhydrides may be melted in such mixing region. In other embodiments, the dicarboxylic acid or anhydride is added after the compression, degassing and combining and wetting steps have been completed, in a downstream section of the non-backmixing tubular reactor and / or a tank reactor in which the digestion step is performed.

[0036] A suitable amount of dicarboxylic acid or anhydride, when used, is at least 1, at least 5 or at least 10 parts by weight and up to 50, up to 30 or up to 25 parts by weight per 100 parts by weight of the polyurethane foam.

[0037] Another useful additional material is a free-radical initiator. Examples of these include hydrogen peroxide, t-butyl hydroperoxide, t-amyl hydroperoxide, 1,1, 3, 3 -tetramethylbutyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, acetyl peroxide, benzoyl peroxide, t- butyl perbenzoate, l,l-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, an acyl alkylsulfonyl peroxide, a dialkyl peroxydicarbonate, a diperoxy ketals, a ketone peroxide, 1 ,1 -bis(ter / - butylperoxy)-3,3,5-trimethylcyclohexane, 2,2’-azobisisobutyronitrile (AIBN), 2,2’-azobis(2,4- dimethylpentanenitrile), 4,4’ -azobi s(4-cyanoval eric acid), l,l’-azobis (cyclohexanecarbonitrile), various tetrazines and various persulfate compounds such as potassium persulfate. Hydrogen peroxide is especially useful. As with the dicarboxylic acid or anhydride, the free radical initiator may be fed continuously into the mixing region of the non-backmixing tubular reactor and in such cases is therefore present during the compression, degassing and combining and wetting steps. Alternatively the free radical initiator is added after the compression, degassing and combining and wetting steps have been completed, in a downstream section of the non-backmixing tubular reactor and / or a tank reactor in which the digestion step is performed. A suitable amount of free radical initiator, when used, is at least 0.1 or at least 1 part by weight and up to 20, up to 10 or up to 5 parts by weight per 100 parts by weight of the polyurethane foam.

[0038] In a particular embodiment of the invention, the starting polyurethane foam and a polyether polyol having a weight average molecular weight of 400 to 8,000 are continuously fed into the mixing zone of the non-backmixing tubular reactor where the foam is compressed and degassed and combined and wetted with the polyether polyol to form the reaction mixture at a temperature of 180 to 300°C, preferably 180 to 250°C or 180 to 225°C, and the reaction mixture is continuously forwarded from the mixing section into and through a downstream section of the non-backmixing tubular reactor where further materials comprising one or more of a dicarboxylic acid or anhydride, low equivalent weight polyol and free radical initiator are combined with the reaction mixture and the reaction mixture is digested to chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor.

[0039] In another particular embodiment of the invention, the starting polyurethane foam, a poly ether polyol having a weight average molecular weight of 400 to 8,000 and one or more further materials comprising one or more of a dicarboxylic acid or anhydride, low equivalent weight polyol and free radical initiator are combined are continuously fed into the mixing zone of the non- backmixing tubular reactor where the foam is compressed and degassed and combined and wetted with the polyether polyol to form the reaction mixture at a temperature of 180 to 300°C, preferably 180 to 250°C or 180 to 225°C, and the reaction mixture is continuously forwarded from the mixing section into and through a downstream section of the non-backmixing tubular reactor where the reaction mixture is digested to chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor.

[0040] In another particular embodiment of the invention, the starting polyurethane foam and a polyether polyol having a weight average molecular weight of 400 to 8,000 are continuously fed into the mixing zone of the non-backmixing tubular reactor where the foam is compressed and degassed and combined and wetted with the polyether polyol to form the reaction mixture at a temperature of 10 to 200°C, preferably 10 to 150°C, 20 to 150°C, 20 to 100°C or 20 to 60°C, and the reaction mixture is continuously forwarded from the mixing section into a tank reactor where further materials comprising one or more of a dicarboxylic acid or anhydride, low equivalent weight polyol and free radical initiator are combined with the reaction mixture and the reaction mixture is digested at a temperature of 180 to 300°C to chemically decompose the polyurethane foam to produce the polyol dispersion in the tank reactor.

[0041] In yet another particular embodiment of the invention, the starting polyurethane foam, a poly ether polyol having a weight average molecular weight of 400 to 8,000 and one or more further materials comprising one or more of a dicarboxylic acid or anhydride, low equivalent weight polyol and free radical initiator are combined are continuously fed into the mixing zone of the non- backmixing tubular reactor where the foam is compressed and degassed and combined and wetted with the poly ether polyol to form the reaction mixture at a temperature of 10 to 200°C, preferably 10 to 150°C, 20 to 150°C, 20 to 100°C or 20 to 60°C, and the reaction mixture is continuously forwarded from the mixing section into a tank reactor where the reaction mixture is digested at a temperature of 180 to 300°C to chemically decompose the polyurethane foam to produce the polyol dispersion in the tank reactor.

[0042] The polyol dispersion made by any of the processes of the invention is useful for making polyurethanes of various types, in particular rigid, semi-rigid, and / or flexible polyurethane foams, by reaction with a polyisocyanate. In general, the polyol dispersion and polyisocyanate are combined to form a reaction mixture that is then cured to form the polyurethane. Curing is typically spontaneous, even when the polyol dispersion and polyisocyanate are combined at about room temperature. However, catalysts and / or elevated curing temperatures may be used to adjust the curing rate if desired. Curing may be performed in a mold; polyurethane foam can be made if desired in a free-rise process in which the foam formulation is dispensed into an open trough or box and allowed to rise without vertical constraint. Various other ingredients may be present in the reaction mixture, including, for example:

[0043] A) additional polyols, such as polyether and / or polyester polyols, having hydroxyl numbers of 375 mg KOH / g or less and 1 to 8 hydroxyl groups per molecule;

[0044] B) short-chain polyols having 2 to 4 hydroxyl groups per molecule and hydroxyl numbers of 376 to 1870;

[0045] C) aminoalcohols such as diethanolamine, monoethanolamine and triethanolamine;

[0046] D) amine-terminated polyethers;

[0047] E) blowing agents, including chemical blowing agents such as water and physical blowing agents of various kinds;

[0048] F) catalysts, including catalysts for the reaction of an isocyanate group with an alcohol, catalysts for the reaction of an isocyanate group with water, and isocyanate trimerization catalysts;

[0049] G) surfactants, including foam-stabilizing surfactants as are useful for making polyurethane foam;

[0050] H) colorants, fillers, and other particulates;

[0051] I) reinforcing fibers;

[0052] J) preservatives such as biocides, fungicides, antioxidants;

[0053] K) “cool touch” additives such as an encapsulated phase change material; as well as other additives as may be useful for making polyurethanes of various types.

[0054] Suitable methods for making polyurethanes of various types are described, for example, in U.S. Patent Nos. 3,632,707, 4,350,778, 7,704,410, 4,970,243, 5,157,056, 5,582,840 and_6,005,016, and U.S. Published Patent Application No. 2020 / 0040153, among many others. In general, the stabilized polyol dispersion of the invention may be used to produce polyurethanes in the same general manner as conventional polyols of similar hydroxyl functionality and equivalent weight.

[0055] The following examples are provided to illustrate the invention and are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

[0056] Examples 1-3

[0057] For Example 1, scrap rigid polyurethane foam powder is subjected to a hybrid glycolysis / acidolysis process using a Thermo Fisher Scientific Process 11 parallel co-rotating intermesh 11 mm diameter twin screw extruder with clamshell barrel. The L / D ratio of the extruder is 44 L / D, which includes a 40 L / D barrel and a 4 L / D barrel extension. A MiniTwin MT0 gravimetric feeder supplies the starting materials into the feed port of the extruder.

[0058] For Example 2, a heated, 0.375-inch outside diameter, 11 inch long, 21 element Kenics Koflo tube static mixer is coupled to the extruder so the contents of the extruder are fed into and through the static mixer by the forwarding operation of the extruder screws.

[0059] For Example 3, a Swagelok SS-18RF8 high temperature back pressure valve is positioned at the outlet of the static mixer.

[0060] In each of Examples 1-3, 46.8 parts of the scrap foam powder are premixed with 41.6 parts of a 3000 weight average molecular weight trifunctional polyether polyol, 10.4 parts of phthalic anhydride and 1.2 parts of maleic anhydride. This premix is fed continuously into the feed port of the extruder at the rate of 150 g / hr. The extruder temperature is set to 200°C. In Examples 2 and 3, the static mixer and back pressure valve (Ex. 3) are maintained at the same temperature. The screw is operated at 300 rpm. Materials are continuously withdrawn through an exit port of the apparatus.

[0061] In Example 1, the residence time is 3 minutes. A well-wetted, partially digested pasty dispersion is produced. In Example 2, the residence time is about 8 minutes. Better mixing and additional reaction are seen, producing a softer, more uniform pasty material. In Example 3, the residence time is about 12 minutes, and the product is significantly softer, indicating further digestion of the starting PU foam. Examples 4-8

[0062] Premixes are prepared by combining the ingredients listed in Table 1.

[0063] Table 1

[0064] The premixes are processed through an extruder (Examples 4-6) or a tandem extruder / static mixer apparatus (Examples 7 and 8), each as described with regard to Examples 1 -3. The extruder temperature (and static mixer temperature, when used) is as indicated in Table 2. In each case, the extruder screw is operated at 400 rpm. Feed rates are 300 g / hr except for Example 8, in which case the feed rate is only 150 g / hr. Approximate residence times are as indicated in Table 2. The obtained paste-like product dispersion is dissolved in a suitable solvent and the resulting solution analyzed by proton NMR to estimate the amount of polyols, insoluble materials and conversion of the starting polyurethane to soluble depolymerization products, with results as indicated in Table 2.

[0065] Table 2 As the data in Table 2 shows, a large proportion of the starting polyurethane foam is converted to soluble materials in the extruder or extruder / static mixer apparatus at low (180- 200°C) temperatures in short residence times. The results from Example 4 are particularly notable in that a simplified reaction mixture that does not include hydrogen peroxide or dipropylene glycol is used. Hydrogen peroxide and dipropylene oxide are known to have an accelerating effect on the chemolysis reaction; the ability to achieve good conversions under mild conditions and short residence times in the absence of these materials is especially notable.

[0066] Examples 9 and 10

[0067] Premixes are prepared by combining the ingredients listed in Table 3.

[0068] Table 3

[0069] The premixes are processed through an extruder as described with regard to Examples 1- 3, without attached static mixer. The extruder temperature is 135°C for Example 9 and room temperature for Example 10. In each case, the extruder screw is operated at 400 rpm and feed rates are 300 g / hr. Approximate residence time is approximately 1.5 minutes. A thick paste-like product dispersion is obtained in each case. Proton NMR indicates about 10-11% conversion of the starting polyurethane foam for each of Examples 9 and 10, despite the low temperature of operation.

[0070] Each of the pasty extrudates is then further digested in a glass batch reactor to produce Examples 9A-D and 10A.

[0071] Example 9A is made by heating 100 parts of Example 9 extrudate to 200°C and combining it with 9 parts of phthalic anhydride. The resulting mixture is maintained at 200°C for 2 hours with stirring to produce a thick yellow-brown fluid dispersion. Polyurethane foam conversion is measured as 37% using the proton NMR method. Example 9B is made by heating 100 parts of Example 9 extrudate to 215°C and combining it with 9 parts of phthalic anhydride and 2 parts hydrogen peroxide. The resulting mixture is maintained at 215°C for 1.5 hours with stirring, at which time 1 part of maleic anhydride is added followed by heating at the same temperature for another 30 minutes with continued stirring. A dark brown fluid dispersion is obtained. Polyurethane foam conversion is 66%.

[0072] Example 9C is made by heating 100 parts of Example 9 extrudate to 200°C and combining it with 9 parts of phthalic anhydride and 2 parts hydrogen peroxide. The resulting mixture is maintained at 200°C for 2.5 hours with stirring, at which time 1 part of maleic anhydride is added followed by heating at the same temperature for another 90 minutes with continued stirring. A dark brown fluid dispersion is obtained. Polyurethane foam conversion is 55%.

[0073] Example 9C is made by combining 100 parts of Example 9 extrudate with 9 parts of phthalic anhydride and 2 parts hydrogen peroxide at room temperature. The resulting mixture is heated to 200°C for 2.5 hours with stirring, at which time 1 part of maleic anhydride is added followed by heating at the same temperature for another 90 minutes with continued stirring. A dark brown fluid dispersion is obtained. Polyurethane foam conversion is 66%.

[0074] Example 10A is made by combining 100 parts of Example 10 extrudate with 2 parts of hydrogen peroxide at room temperature and heating the resulting mixture to 200°C for 2.5 hours with stirring, followed by adding 1 part of maleic anhydride and heating at the same temperature for another 90 minutes with continued stirring. A dark brown fluid dispersion. Polyurethane foam conversion is 72%.

Claims

CLAIMS:

1. A process for producing a polyol dispersion from polyurethane foam, comprising the steps of: a) continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyether polyol having a weight average molecular weight of 400 to 8,000 g / mol into a non-backmixing tubular reactor having a rotating screw comprising forwarding elements, b) at a temperature of 10 to 300°C, compressing and degassing the polyurethane foam and combining and wetting the compressed and degassed polyurethane foam with component ii by action of the rotating screw in the non-backmixing tubular reactor to form a reaction mixture, and then c) digesting the reaction mixture at a reaction temperature of 150 to 300°C to chemically decompose the polyurethane foam produce the polyol dispersion.

2. The process of claim 1 wherein step c) is performed by heating the reaction mixture to a reaction temperature of 150 to 300°C in a mixing section of the non-backmixing tubular reactor and continuously forwarding the reaction mixture into and through a downstream section of the non-backmixing tubular reactor while maintaining the reaction mixture at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non- backmixing tubular reactor.

3. The process of claim 1 wherein a back pressure regulator or valve is mounted onto an outlet end of the non-backmixing tubular reactor and a superatmospheric pressure sufficient to maintain the ingredients and the polyol dispersion in liquid or solid form.

4. The process of claim 2 further comprising a step d) of continuously withdrawing the polyol dispersion from an outlet end of the non-backmixing tubular reactor.

5. The process of claim 1 wherein step c) is performed by withdrawing the reaction mixture from the non-backmixing tubular reactor and digesting the reaction mixture in a batch reactor.

6. The process of any of claims 1-5 wherein the temperature in step b) is 10 to 200°C.

7. The process of claim 6 wherein the temperature in step b) is 10 to 150°C.

8. The process of any of claims 1-5 wherein the temperature in step b) is 180 to 300°C.

9. The process of any of claims 1 -7 wherein the ingredients further comprise a dicarboxylic acid or anhydride.

10. The process of claim 9 wherein the dicarboxylic acid or anhydride is one or more of phthalic acid, phthalic anhydride, maleic acid, maleic anhydride, adipic acid, adipic anhydride, glutaric acid, glutaric acid anhydride, succinic acid, succinic acid anhydride, hydrogenated phthalic acid, hydrogenated phthalic anhydride, hydrogenated terephthalic acid and hydrogenated therephthalic anhydride.

11. The process of any of claims 1-10 wherein the ingredients further comprise a peroxide.

12. The process of any of claims 1-11 wherein the ingredients further comprise a polyol having a hydroxyl equivalent weight of up to 75 and 2-4 hydroxyl groups.

13. The process of any of claims 1-12 wherein the polyol polyether polyol having 2 to 4 hydroxyl groups and a weight average molecular weight of 400 to 8,000 constitutes 40 to 70% by weight of the ingredients and the polyurethane foam and constitutes 25 to 60% of the weight of the ingredients.

14. A process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam,(component ii) a polyol, and (component iii) dicarboxylic acid and / or dicarboxylic acid anhydrideinto a mixing section of a non-backmixing tubular reactor, the mixing section of the non- backmixing tubular reactor having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the mixing section and combining and wetting the compressed and degassed polyurethane foam with components ii and iii in the mixing section to form a reaction mixture, and heating the reaction mixture to a reaction temperature of 150 to 300°C; continuously forwarding the reaction mixture from the mixing section into and through a downstream section of the non-backmixing tubular reactor while maintaining the reaction mixture at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor and continuously withdrawing the polyol dispersion from an outlet end of the non-backmixing tubular reactor.

15. A process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyol, into a mixing section of a non-backmixing tubular reactor, the mixing section of the non-backmixing tubular reactor having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the mixing section and combining and wetting the compressed and degassed polyurethane foam with component ii in the mixing section to form a reaction mixture, and heating the reaction mixture to a reaction temperature of 150 to 300°C; continuously forwarding the reaction mixture from the mixing section into and through a downstream section of the non-backmixing tubular reactor while maintaining the reaction mixture at the reaction temperature in the downstream section of the non-backmixing tubular reactor to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the non-backmixing tubular reactor and continuously withdrawing the polyol dispersion from an outlet end of the non-backmixing tubular reactor and cooling the dispersion without applied refrigeration to a temperature of 20 to 30°C.

16. A process for producing a polyol dispersion from polyurethane foam, comprising continuously feeding ingredients comprising (component i) a polyurethane foam and (component ii) a polyol, into an extruder, the extruder having a rotating screw comprising forwarding elements, compressing and degassing the polyurethane foam in the extruder and combining and wetting the compressed and degassed polyurethane foam with component ii in the extruder to form a reaction mixture, and heating the reaction mixture to a reaction temperature of 150 to 300°C; continuously forwarding the reaction mixture from the extruder into and through a static mixer while maintaining the reaction mixture at the reaction temperature in the static mixer to digest the reaction mixture and chemically decompose the polyurethane foam to produce the polyol dispersion in the static mixer and continuously withdrawing the polyol dispersion from an outlet end of the static mixer.

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