Acidolysis of polyurethane to polyol products using vapor phase

Abstract

Polyols can be produced from a waste polyurethane product by exposing the waste polyurethane product to a vapor of a reagent and reacting to produce a reaction product comprising one or more polyols, one or more polyesters or both wherein the reagent comprises a carboxylic acid or an acid anhydride or a mixture thereof provided that wherein the reagent is an acid anhydride the reaction occurs in the presence of water.

Description

ACIDOLYSIS OF POLYURETHANE TO POLYOL PRODUCTS USING VAPOR PHASEFIELD OF THE INVENTION

[0001] This invention relates to a method of recycling polyurethanes, particularly polyurethane foams, using acidolysis to produce polyols products.BACKGROUND OF THE INVENTION

[0002] Recycling of polymeric materials can be an important approach to reducing polymer (e.g., plastic) waste and also reducing raw material supply demand.

[0003] As thermosetting material, recycling of polyurethanes typically involves chemolysis (or decomposition to simpler and / or smaller compounds).

[0004] Past approaches to chemolysis of polyurethanes typically involve forming a liquid, dispersion, or paste-like reaction mixture including reagents and fragments of polyurethane products to be recycled. The reagent(s) react with the polyurethane to break down the polyurethane and form polyols. The reaction product can include unreacted reagents, solvents, and by-products. For example, a liquid / solid phase reaction typically results in side reactions such as esterification of the polyols. Thus, hydrolysis of esterified polyols and / or isolation of the polyols from the liquid reaction product is required.

[0005] It would be desirable to have an efficient, simple, and / or rapid means of converting polyurethanes to polyols.SUMMARY OF THE INVENTION

[0006] Disclosed herein is a method of comprising exposing a waste polyurethane product to a vapor of a reagent and reacting to produce a reaction product comprising one or more polyols, one or more polyesters or both wherein the reagent comprises a carboxylic acid or an acid anhydride or a mixture thereof provided that wherein the reagent is an acid anhydride the reaction occurs in the presence of water.DETAILED DESCRIPTION OF THE INVENTION

[0007] It was discovered that polyols can be obtained from a polyurethane product to be recycled by exposing a polyurethane product to a vapor of an organic acid anhydride in the presence of water or to a vapor of an organic acid. The acidolysis can occur at low temperatures. With careful control of the reaction conditions (e.g., temperature, partial pressure or gas phase concentration if the organic acid or acid anhydride) the amount of esterification of the resulting polyols may be reduced.

[0008] The polyurethane product comprises a polyurethane as the major component. For example, the polyurethane product can comprise greater than 50, greater than 60, greaterthan 70, greater than 80, or greater than 90 and up to 100, up to 99, up to 98, up to 97, up to 96, or up to 95 weight percent (wt%) of polyurethane based on total weight of the polyurethane product. The remainder of the polyurethane product may include one or more additives (e.g., fillers); impurities; other polymers that had been mixed or blended with the polyurethane; residual amounts adjacent layers such as metal foils, or polymers, or moisture. The polyurethane can be any polyurethane which is desired to be recycled. For example, the polyurethane can be a polyether polyurethane. The polyurethane product to be recycled can be, for example, a flexible polyurethane foam. For example, a polyurethane product, such as a flexible polyurethane foam, can comprise 0 to 6, 1 to 5.5. or 2-5 wt% residual moisture based on total weight of the polyurethane foam.

[0009] While not required, to increase surface area for reaction, the polyurethane can be provided to in the form of fragments. For example, a polyurethane source (e.g., a polyurethane foam, such as a flexible polyurethane foam) can be cut into pieces and then shredded or chopped to form fragments. The size of the fragments can be, for example, from 0.1, from 0.5, or from 1 up to 100, up to 50, up to 10, or to up 5 millimeters.100101 The vapor comprises an organic acid or an organic acid anhydride. Since it is not required to have a reagent in liquid phase (e.g., above the melting temperature of the acid or anhydride), it is possible to run the reaction at relatively low temperatures. For example, the reaction temperature can be at least 110°C, at least 120°C, or at least 130°C up to 200°C, up to 180°C, up to 170°C, or up to 160°C.

[0011] The organic acid and / or the acid anhydride can have vapor pressures of, for example, from 0.5 or from 0.7 or from 1 up to 300, up to 250, up to 200, up to 150, up to 100, or up to 80 mm Hg at reaction temperatures. Notably, if an organic acid is provided in a vessel and heated, the acid may dehydrate to its anhydride which typically will have a higher vapor pressure.

[0012] The organic acid can be a monocarboxylic acid or can be polycarboxylic, such as a dicarboxylic acid. Reaction rates may be faster using a polycarboxylic acid. The polycarboxylic acid can be a dicarboxylic acid. Examples of monocarboxylic acids include propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, benzoic acid, substituted benzoic acids such as -nitrobenzoic acid, 2-fluorobenzoic acid, 3-fluorobenzoic acid, 4- methylbenzoic acid, and 4-methoxybenzoic acid. Examples of polycarboxylic acids include maleic acid, phthalic acid, homophthalic acid, succinic acid, glutaric acid, 2-methyl glutaric acid, 3 -methyl glutaric acid, adipic acid, and pimelic acid.

[0013] The acid anhydride can be, for example, an anhydride of any of the above mentioned organic acids, such as, for example, phthalic anhydride, succinic anhydride.

[0014] A mixture of two or more carboxylic acids, two or more acid anhydrides, or one or more carboxylic acids with one or more acid anhydrides may be used.

[0015] The acid anhydride can have a higher vapor pressure and thus, be more efficiently provided in vapor phase to the polyurethane product than its corresponding carboxylic acid. In addition, when the carboxylic acid is initially provided in solid form and then vaporized, at least a portion of the carboxylic acid may be converted in the process of heating for vaporization to the anhydride.

[0016] The vapor can be provided by, for example, providing a solid or liquid organic acid or a solid or liquid acid anhydride in a physically separated location from the solid polyurethane product but in an environment where the vapor or the organic acid or acid anhydride can contact the polyurethane product. The vapor of the organic acid or acid anhydride can be generated for example by heating the solid or liquid organic acid or the solid or liquid acid anhydride to cause vaporization. The temperature for vaporization can be, for example, from 120 to 210°C, or 130 to 200°C, or 140 to less than 180°C. Notably, if an organic acid is provided in a vessel and heated, the acid may dehydrate to its anhydride which typically will have a higher vapor pressure. Alternatively, the vapor can be provided in a separate location and injected into the reactor where the polyurethane is to cause the acidolysis.

[0017] When vapor comprises the acid anhydride the reaction occurs in the presence of water to convert the anhydride to the corresponding diacid to facilitate the acidolysis reaction. The water can be provided in the form of a liquid in contact with, in (e.g., in pores in a polyurethane foam), or mixed with the polyurethane product (e.g., mixed with shredded pieces of the polyurethane product. The water can be in the form of ambient humidity. The amount of water can be from 0.03 wt% (weight percent), from 0.05 wt%, from 0.1 wt%, from 0.2 wt%, from 0.3 wt%, from 0.4 wt%, from 0.5 wt%, from 0.7 wt%, or from 1 wt% up to 6 wt%, up to 5 wt%, up to 4 wt%, or up to 3 wt% based on total weight of the polyurethane in the polyurethane product. Since the polyurethane product (e.g., polyurethane foam) may include residual moisture, it may not be necessary to add additional water to the reaction mixture. When the reagent is an acid, the presence of water is optional, but water can be present in amounts of 0 to 6 wt%, 0.03 wt% to 5 wt%, 0.1 wt% to 4 wt%, 0.2 wt% to 3 wt%, 0.3 wt% to 2 wt% based on total weight of the polyurethane product.

[0018] The polyurethane product to be converted can initially be in solid form. The solid form can be free of or substantially free of added polyols. For example, there can be zero added polyols or there can be added polyols in amounts of less than 0.1, less than 0.05, less than 0.02, less than 0.01, or can have 0 parts by weight polyol per part by weight of polyurethane. No catalyst is required for the reaction. However, there can be a catalyst in amounts less than 0.001 or, less than 0.0005, less than 0.0002, less than 0.0001, or can have 0 parts by weight per part by weight of polyurethane.

[0019] The reactants can be heated by any suitable means, including convection, conduction, radiation or a combination thereof. No radiation (e.g., microwave radiation) is needed for a rapid acidolysis of the polyurethane. The reaction temperature can impact the vapor pressure of the organic acid and / or acid anhydride, the diffusivity of the reagents, and the reaction rates. Where reaction temperature is low the reaction will take more time to proceed which can lead to increased side reactions such as esterification of the polyols. On the other hand, where reaction temperature is high reaction kinetics and / or a higher amount of acid and / or anhydride vapor at the foam may also lead to increased side reactions.|0020| Thus, control of reaction temperature can facilitate reduction of undesirable side reactions. Thus, for example, the reaction temperature can be between 170 and 180°C which leads to a reasonably fast reaction without undue esterification. The reaction temperature range may vary depending on the reagent selected.

[0021] The reaction product will include polyols, amides, imides, and potentially some polyesters. Carbon dioxide and water may also be produced in the reaction but at the reaction temperatures will be in gas form and not part of the liquid reaction product. Any polyesters can be hydrolyzed to form polyols.

[0022] The method can include separation steps to isolate the polyols.

[0023] For example, an aqueous base can be added directly to liquid reaction product. This can be after the reaction is thermally quenched. The addition of the aqueous base can itself quench the reaction by neutralizing the reagent. The aqueous base can hydrolyze any polyesters in the liquid reaction product to polyols.

[0024] For example, at the end of the acidolysis reaction an aqueous base (e.g., NaOH (aq)) solution can be added (e.g., at a 1 :1 molar ratio, or 1: 1.5 ratio of OH’: -COOH from the reagent used in the acidolysis reaction). The temperature can be lowered from the reaction temperature but maintained at a temperature to reflux (e.g., about 100°C, 120°C, or 150°C) to cause the hydrolysis of the polyesters. After hydrolysis, the mixture can be cooled, washed, and separated by liquid-liquid extraction methods (e.g., in a separatory vessel or flask withaddition of water and an organic solvent such as toluene. The polyol product is isolated in the organic solvent (e.g., toluene) layer while the other impurities and by-products are separated, remaining in the aqueous phase.

[0025] Any solids not previously removed after hydrolysis can be removed by mechanical separation (e.g., filtering, centrifugation, settling, etc.). The polyols can then be separated by liquid / liquid extraction. Prior to the liquid-liquid extraction, the pH of hydrolysis solution can stay as is, or can be tuned to a favorable pH range (i.e., pH 5, 6, 7, or 8) to minimize the emulsion between organic and aqueous layers. A centrifugation method can be combined with this liquid-liquid extraction strategy to accelerate and enhance the organic layer separation from the aqueous phase. G-force of centrifuge used, can be from less than 100, or less than 200, or less than 500, or less than 1000, or up to 3000 rotations per minute (rpm). The neat polyol product is collected after separating the toluene phase and evaporating the toluene solvent.

[0026] As another example, one may first undertake one or more separation steps. If a thermal quench is used any remainder of acid reagent can solidify. Such solidified reagent and any solid components from the polyurethane product can be removed. The liquid portion can be separated by liquid / liquid extraction. Hydrolysis can then be performed.

[0027] For example, the liquid reaction product can be dissolved in organic solvent (e.g., ethyl acetate) and mixed well with sodium hydroxide aqueous solution. The phases can be separated - e.g., using centrifugation or separatory flask. A top phase includes ethyl acetate solvent containing polyol, polyesters, and amides products, the middle phase includes polyol products with some water / ethyl acetate mixture, the bottom phase contains leftover excess organic acid, sodium salts, and other by-products. The phases including polyols can be combined and dried to remove ethyl acetate and water.

[0028] The hydrolysis can be for example a three-step process including (1) separating the polyol middle phase from centrifugation, (2) subjecting the collected polyol to liquid-liquid extraction (for example in ethyl acetate) followed by solvent removal and drying; and (3) refluxing the dried polyol product in basic solution (e.g., NaOH (aq)). The amount of OH’ can be in 1 : 1 or 1 : 1.5 molar ratio with respect to the total -COOH from the reagent used in the acidolysis reaction. Alternatively, the hydrolysis can involve two steps and be performed on the crude rection mixture (liquid reaction product) bypassing centrifugation.EXAMPLESMaterial

[0029] Foam 1 was a model foam received in cubic meter size block and comprised a polyurethane from the following ingredients.Methods

[0030] 13C Nuclear Magnetic Resonance (13C NMR) Spectroscopy was done with a Bruker Avance NEO 500 MHz spectrometer which was equipped with a 5 mm X-nuclei optimized double resonance cryoprobe. For each measurement, 100-150 mg samples were dissolved in 600 gL DMSO-de and packed in a 5 mm glass tube. For quantitative13C NMR, 100 / .iL 25 mM Cr(acac)3 was added to 150 mg sample with 600 / zL DMSO-de in the 5 mm NMR glass tube.13C NMR of virgin polyol, purified re -polyol from model foam, and re-poly ol from end-of life foam were obtained. The13C NMR spectra confirm that our invention successfully produced re-polyol with the same chemical shifts as virgin polyol.Example 1

[0031] Chunks of Foam 1 were placed in a beaker and a vial of carboxylic acid was placed inside the beaker separating the solid carboxylic acid from the solid Foam 1 and the beaker was covered. In a separate beaker a chunk of Foam 1 was placed for reference. Both beakers were placed in an oven at 160°C for 10 hours. After 10 hours Foam 1 was decomposed to a liquid in the first beaker while in the reference remained solid but slightly discolored.

[0032] 13C NMR spectra of polyol obtained from vapor-phase (from the physically segregated reaction) acidolysis of Foam 1 with varying carboxylic acids - maleic acid, succinic acid (SA), phthalic acid (PA), and adipic (AA) indicate recovery of a polyolsubstantially identical to the virgin polyol (VORANOL-8316). Unlike a polyol obtained from liquid phase acidolysis with physical mixing between Foam 1 and solid / liquid carboxylic acid the signal of the OH end group was observed suggesting the esterification side reaction between the carboxylic acid and polyol was limited.Example 2

[0033] To test the mobility and reactivity of anhydrides, phthalic anhydride (PAnh) and its corresponding acid phthalic acid (PA) were tested for vapor-phase PU acidolysis at 180°C. Foam 1 was sealed in a graduated bottle with a calcination boat containing acid or anhydride and placed in an oven for four hours; the experiment was then repeated with 325 microliters (pL) of water. Both PA and PAnh were able to decompose the Foam 1; however, the rate of acidolysis with PA was slower than with PAnh, suggesting that PAnh vapor more effectively transports to the PUF foam than PA. Furthermore, the addition of water accelerated acidolysis with both PA and PAnh. This indicates that hydrolysis of PAnh to PA is required to initiate the acidolysis reaction. The increased rate of acidolysis observed for PA with the addition of water suggests that transport of PA to the foam surface is facilitated by the acid- anhydride equilibrium, with PA dehydrating to PAnh, transporting in the vapor phase, then subsequently hydrolyzing back to PA and inducing acidolysis. Similar results were obtained for vapor-phase acidolysis with succinic acid (SA) and succinic anhydride (SAnh), although SA appears to be more mobile than PA under otherwise identical conditions, which is expected given their relative volatilities.Example 3

[0034] About 0.6-0.65 grams of polyurethane Foam 1 in the form of a chunk or shredded was provided in a vessel. (Chunks were used except as noted in Table 1). Adjacent to the foam in a separate open container in the vessel about 2 grams of either succinic acid (SA) or phthalic acid (PA) was provided in solid form. There was no direct contact of the acids with the foam. The vessel was sealed and heated to varying temperatures. After reaction, the acid remaining in the container was weighed to determine rate of vaporization. The reaction products in the vessel were either predominantly liquid or predominantly solid. Liquid products were dissolved in ethyl acetate and placed in pre-weighed vial. The ethyl acetate was removed under vacuum and the vial was weighed to determine mass of liquid products.

[0035] Solid products were weighed as-is, then washed with ethyl acetate to extract soluble components. Ethyl acetate was removed from soluble components under vacuum.

[0036] Quantitative GPC and quantitative13C NMR analysis were performed on soluble components of reaction products. The quantitative GPC analysis indicated percent completion of the reaction while the NMR analysis indicated percent esterification.

[0037] Here the samples for the13C NMR analysis made with 150 mg of product, 500 pL DMSO-de, 125 jrL 25 mM Cr(acach (in DMSO-de), 130 ,uL MeOH (internal standard). Polyol peaks were integrated in 5 regions (PO 1 = 76 - 74 ppm, PO 2 = 74 - 72 ppm, PO 3 = 72 - 70 ppm, PO 4 = 69 - 68 ppm, PO 5 [OH ends] = 66 - 65 ppm). Integrals were normalized with respect to PO 1 and degree of esterification was determined by the formula % esterification = (1 - (PO 5)SamPie / (PO 5)VORANOL SB6) * 100 where (PO 5)VORANOL SB6 is the normalized integral of the -OH ends for the13C NMR of the virgin polyol.

[0038] For the GPC analysis, approximately 30 mg samples were dissolved in 3 mL tetrohydrofuran (THF) at constant concentration of 10 mg sample I 1 mL THF overnight. GPC of samples were run and referenced to polyethylene oxide (PEO) standards. The polyol peak was integrated for each sample and its area was normalized to 1. The extent of reaction was determined by the formula % complete = 100 * hsampie / 11VORANOL8136 where hsamPie and hvoRANOL8i36 are the peak heights of the sample and the virgin polyol, respectively.

[0039] The results are shown in Table 1. At 185°C and 175°C and for Samples SA165b and SA165c the foam was fully liquified. Samples labeled n / a did not proceed far enough to have soluble polyol products.Table 1

[0040] This disclosure further encompasses the following aspects.

[0041] Aspect 1: A method of comprising exposing a waste polyurethane product to a vapor of a reagent and reacting to produce a reaction product comprising one or more polyols, one or more polyesters or both wherein the reagent comprises a carboxylic acid or an acid anhydride or a mixture thereof provided that wherein the reagent is an acid anhydride the reaction occurs in the presence of water.

[0042] Aspect 2: The method of Aspect 1 wherein the polyurethane product is initially in solid form and is physically separated from any solid or liquid source of the vapor of the carboxylic acid or of the acid anhydride.

[0043] Aspect 3: The method of Aspect 1 or 2 wherein the temperature is in the range of 130 to less than 180°C.

[0044] Aspect 4: The method of Aspect 1 or 2 wherein the temperature is in the range of 170 to 180°C.

[0045] Aspect 5: The method of any one of the previous Aspects wherein the polyurethane product comprises a polyether polyurethane.

[0046] Aspect 6: The method of any one of the previous Aspects wherein the polyurethane product is a flexible polyurethane foam.

[0047] Aspect 7: The method of any one of the previous Aspects wherein the reagent comprises maleic acid, phthalic acid, homophthalic acid, succinic acid, glutaric acid, 2- methyl glutaric acid, 3-methyl glutaric acid, phthalic anhydride, succinic anhydride, or a combination of two or more thereof.

[0048] Aspect 8: The method of any of the previous Aspects wherein the reagent comprises succinic acid, succinic anhydride, or both.

[0049] Aspect 9: The method of any one of the previous Aspects further comprising converting the one or more polyesters to polyols.

[0050] Aspect 10: The method of any one of the previous Aspects further comprising separating the one or more polyols from the reaction product.

[0051] Aspect 11 : The method of Aspect 10 further comprising reacting the one or more polyols with isocyanate to form a polyurethane.

[0052] Aspect 12: A polyurethane made by the method of Aspect 11.|0053| All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt.% to 25 wt.%,” etc.). Moreover, stated upper and lower limits can be combined to form ranges (e.g., “at least 1 or at least 2 weight percent” and “up to 10 or 5 weight percent” can be combined as the ranges “1 to 10 weight percent”, or “1 to 5 weight percent” or “2 to 10 weight percent” or “2 to 5 weight percent”).

[0054] The disclosure may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The disclosure may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objectives of the present disclosure.

[0055] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

[0056] Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

Claims

What is claimed is:

1. A method of comprising exposing a waste polyurethane product to a vapor of a reagent and reacting to produce a reaction product comprising one or more polyols, one or more polyesters or both wherein the reagent comprises a carboxylic acid or an acid anhydride or a mixture thereof provided that wherein the reagent is an acid anhydride the reaction occurs in the presence of water.

2. The method of claim 1 wherein the polyurethane product is initially in solid form and is physically separated from any solid or liquid source of the vapor of the carboxylic acid or of the acid anhydride.

3. The method of claim 1 or 2 wherein the temperature is in the range of 130 to less than 200°C.

4. The method of claim 1 or 2 wherein the temperature is in the range of 170 to 180°C.

5. The method of any one of the previous claims wherein the polyurethane product comprises a polyether polyurethane.

6. The method of any one of the previous claims wherein the polyurethane product is a flexible polyurethane foam.

7. The method of any one of the previous claims wherein the reagent comprises maleic acid, phthalic acid, homophthalic acid, succinic acid, glutaric acid, 2- methyl glutaric acid, 3-methyl glutaric acid, phthalic anhydride, succinic anhydride, or a combination of two or more thereof.

8. The method of any of the previous claims wherein the reagent comprises succinic acid, succinic anhydride or both.

9. The method of any one of the previous claims further comprising converting the one or more polyesters to polyols.

10. The method of any one of the previous claims further comprising separating the one or more polyols from the reaction product.

11. The method of claim 10 further comprising reacting the one or more polyols with isocyanate to form a polyurethane.

12. A polyurethane made by the method of claim 11.

Images