DEPOLYMERIZATION OF POLYURETHANES UNDER MILD CONDITIONS

Abstract

An improved process can be used for depolymerization of polyurethanes under mild conditions. Polyether polyols and polyamines can be recovered in high yields.

Claims

1: A method of hydrolyzing a polyurethane, the method comprising: contacting said polyurethane with water in the presence of a base, the base comprising an alkali metal cation and/or an ammonium cation and having a pK.sub.b value at 25° C. of from 1 to 10, a catalyst selected from the group consisting of a quaternary ammonium salt containing an ammonium cation containing 6 to 30 carbon atoms and an organic sulfonate containing at least 7 carbon atoms, to yield an active hydrogen containing polyether and an organic polyamine.

2: The method of claim 1, wherein the base is selected from the group consisting of alkali metal phosphate, alkali metal hydrogen phosphate, alkali metal carbonate, alkali metal silicate, alkali metal hydrogen carbonate, alkali metal acetate, alkali metal sulfite, ammonium hydroxide, and a mixture thereof.

3: The method of claim 2, wherein an alkali metal of the base is selected from the group consisting of Na, K, Li, and a mixture thereof.

4: The method of claim 1, wherein the catalyst is a quaternary ammonium salt having the general structure
R.sub.1R.sub.2R.sub.3R.sub.4NX wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are the same or different, and are hydrocarbyl groups selected from alkyl, aryl, and arylalkyl, and X is selected from the group consisting of halide, hydrogen sulfate, alkyl sulfate, carbonate, hydrogen carbonate, carboxylate, and hydroxide.

5: The method of claim 4, wherein R.sub.1 and R.sub.2 are the same or different, and are alkyl groups with 1 to 12 carbon atoms, wherein the alkyl groups may be linear, branched, or cyclic, and saturated or unsaturated, R.sub.3 is selected from the group consisting of a alkyl group with 1 to 12 carbon atoms, an aryl group with 6 to 14 carbon atoms, and an aralkyl group with 7 to 14 carbon atoms, wherein the alkyl group may be linear, branched, or cyclic, and saturated or unsaturated, R.sub.4 is selected from the group consisting of an alkyl group with 3 to 12 carbon atoms, an aryl group with 6 to 14 carbon atoms, and an aralkyl group with 7 to 14 carbon atoms, wherein the alkyl groups may be linear, branched, or cyclic, and saturated or unsaturated, X is selected from the group consisting of halide, hydrogen sulfate, alkyl sulfate, carbonate, hydrogen carbonate, acetate and hydroxide.

6: The method of claim 4, wherein R.sub.1 to R.sub.4 are selected such that a sum of carbon atoms in the quaternary ammonium cation is 6 to 14, or R.sub.1 to R.sub.4 are selected such that the sum of carbon atoms in the quaternary ammonium cation is 15 to 30.

7: The method of claim 4, wherein R.sub.1 to R.sub.4 and X are selected such that a sum of carbon atoms in the quaternary ammonium salt is 6 to 14, or R.sub.1 to R.sub.4 and X are selected such that the sum of carbon atoms in the quaternary ammonium salt is 15 to 30.

8: The method of claim 1, wherein the catalyst is an organic sulfonate selected from the group consisting of an alkyl aryl sulfonate, an alpha-olefin sulfonate, a petroleum sulfonate, and a naphthalene sulfonate.

9: The method of claim 1, further comprising: separating and recovering the organic polyamine and the active hydrogen containing polyether.

10: The method of claim 1, wherein the polyurethane is foamed.

11: The method of claim 1, wherein the polyurethane is reacted with the water, the base, and the catalyst, at a temperature of from 80° C. to 200° C., and/or for 1 minute to 14 hours, and/or at atmospheric pressure.

12: The method of claim 1, wherein an amount of the catalyst is at least 0.5 weight percent, based on a weight of the polyurethane.

13: The method of claim 1, wherein a weight ratio of the base to the polyurethane is in a range of from 0.01 to 50.

14: The method of claim 1, wherein the base is in a form of a base solution comprising the base and water.

15: A method, comprising: producing a polyurethane foam with the active hydrogen containing polyether and/or the organic polyamine obtained from the method according to claim 1.

16: The method according to claim 1, wherein the polyurethane is produced by reacting an active hydrogen containing polyether and an organic polyisocyanate.

17: The method according to claim 1, wherein the active hydrogen containing polyether is a polyether polyol.

18: The method according to claim 1, wherein the base has a pK.sub.b value at 25° C. of from 1.5 to 6.

19: The method according to claim 4, wherein X is chloride, bromide, methylsulfate, ethylsulfate, or acetate.

20: The method according to claim 14, wherein the base solution is a saturated base solution, and wherein a weight ratio of the saturated base solution to the polyurethane is in a range of from 0.5 to 25.

Description

EXAMPLE 1-10 AND COMPARATIVE EXAMPLES 1 TO 7

[0062] A reactor from Parr instrumental company equipped with a PTFE liner and a mechanical stirrer, was charged with 25 g of compressed polyurethane foam pieces (ca. 1 cm×1 cm) and 75 g of an aqueous base solution was added. Thereafter catalyst was added, the reactor closed and heated to the operating temperature. After the desired reaction time was over the mixture was allowed to cool down, the reactor was opened and the reaction mixture was transferred into a round-bottom flask.

[0063] Water was removed and the remaining solid was extracted with cyclohexane. The cyclohexane solution was washed with 1 N aqueous HCl solution, dried over magnesium sulfate and the solvent was removed. The solid was extracted with warm toluene to obtain the amine after drying and removal of solvent.

[0064] The used base solution and catalyst, their amounts, reaction time and temperature as well as yields of the recovered polyether polyol and amine are given in Table 1.

TABLE-US-00001 TABLE 1 Concentration of base Amount of Reaction Reaction Yield Yield in base solution at catalyst Temper- Time Polyether Polyamine Example Base pKb ambient temperature catalyst [wt. %] ature [C.] [hours] polyol [%] [%] 1 K.sub.2CO.sub.3 3.67 Saturated in H.sub.2O TBMAC 5 130 14 80.4 N.D. 4 Na.sub.2SiO.sub.3 2.23 Saturated in H.sub.2O TBAHS 5 150 14 83 N.D. 5 NH.sub.4OH 4.75 25% in H.sub.2O TBAHS 5 150 14 80 N.D. 6 K.sub.2CO.sub.3 3.67 Saturated in H.sub.2O TBAHS 5 150 14 81 95 7 K.sub.3PO.sub.4 1.77 Saturated in H.sub.2O TBAHS 5 150 14 78 N.D. 8 KOAc 9.25 Saturated in H.sub.2O TBAHS 5 150 14 56 N.D. 5 NH.sub.4OH 4.75 25% in H.sub.2O TBMAC 5 150 14 78.2 N.D. 9 K.sub.2CO.sub.3 3.67 Saturated in H.sub.2O TBMAC 5 150 14 81.4 N.D. 10 K.sub.2CO.sub.3 3.67 Saturated in H.sub.2O TBMAC 2.5 150 14 66.7 N.D. CE1 K.sub.2SO.sub.4 12.04 Saturated in H.sub.2O TBAHS 5 150 14 3.2 N.D. CE2 CaCO.sub.3 30% w/w dispersion TBMAC 5 150 14 12.56 N.D. CE3 Ca.sub.3(PO.sub.4).sub.2 30% w/w dispersion TBMAC 5 150 14 11.31 N.D. CE4 Ca(OAc).sub.2 30% w/w aq. Solution TBMAC 5 150 14 5.15 N.D. CE5 MgHPO.sub.4 30% w/w dispersion TBMAC 5 150 14 3.39 N.D. CE6 MgCO.sub.3 30% w/w dispersion TBMAC 5 150 14 5.15 N.D. CE7 Mg(HCO.sub.3).sub.2 30% w/w dispersion TBMAC 5 150 14 1.76 N.D. TBMAC = Tributylmethylammonium chloride (C = 13) TBAHS = Tetrabutylammouniumhydrogensulfate (C = 16) N.D. = Not Determined

[0065] The examples show that the process of the invention leads to good yields even at reaction temperatures below 140° C. and under non-corrosive conditions. If the pKb value of the base is too high, as shown in comparative example CE 1, or if alkaline earth metal bases are used, as shown in comparative examples CE 2 to 7, the yields dramatically decrease.

[0066] Performance Tests of Recycled Polyols

[0067] Production of Hot-Cure Flexible PU Foams (Flexible Slabstock Foam)

[0068] For the performance testing of the recycled polyols, the hot-cure flexible PU foam formulations specified in Table 2 were used.

TABLE-US-00002 TABLE 2 Formulations for hot-cure flexible PU foam production. Parts by mass (pphp) Formulation 1 Polyol.sup.1) 100 parts Water 4.00 parts KOSMOS ® T9.sup.2) 0.20 parts DABCO ® DMEA.sup.3) 0.15 parts TEGOSTAB ® BF2370.sup.4) 1.0 part Desmodur ® T 80.sup.5) Variable, Constant Index of 105 Formulation 2 Polyol.sup.1) 100 parts Water 3.00 parts KOSMOS ® EF.sup.6) 0.60 parts DABCO ® NE1050.sup.7) 0.15 parts TEGOSTAB ® BF 2370LC.sup.8) 1.0 part Desmodur ® T 80.sup.5) Variable, Constant Index of 110 .sup.1)Polyol 1: Standard virgin polyol Arcol ® 1104 available from Covestro, this is a glycerol-based polyether polyol having an OH number of 56 mg KOH/g and an average molar mass of 3000 g/mol or inventive recycled polyols or non-inventive recycled polyol. The recycled polyols are obtained by chemical recycling from flexible polyurethane foams. A recycled polyol of the prior art is obtained by the procedure described in the following paragraphs. As inventive recycled polyol the polyol of Example 6 was used .sup.2)KOSMOS ® T9, available from Evonik Industries: tin(II) salt of 2-ethylhexanoic acid. .sup.3)DABCO ® DMEA: dimethylethanolamine, available from Evonik Industries. Amine catalyst for production of polyurethane foams. .sup.4)Polyether-modified polysiloxane, available from Evonik Industries. .sup.5)Tolylene diisocyanate T 80 (80% 2,4 isomer, 20% 2,6 isomer) from Covestro, 3 mPa .Math. s, 48% NCO, functionality 2. .sup.6)KOSMOS ® EF, emission free metal catalyst, available from Evonik Industries: tin(II) salt of ricinoleic acid .sup.7)DABCO ® NE1050: low emission amine catalyst, available from Evonik Industries. .sup.8)Low emission polyether-modified polysiloxane with <0.03 wt % of total cyclic siloxanes, available from Evonik Industries.

[0069] Production of Recycled Polyols for Performance Tests

[0070] Recycled Polyol 1 (Non-Inventive) The non-inventive recycled polyol 1 was produced following a procedure published by H&S Anlagentechnik in 2012: https://www.dbu.de/OPAC/ab/DBU-Abschlussbericht-AZ-29395.pdf

[0071] A Reactor from Parr instrumental company equipped with a glass in liner and a mechanical stirrer, was charged with 300.2 g of compressed polyurethane foam pieces (ca. 1 cm×1 cm). The used polyurethane foam was produced according to Formulation 1, Table 2 by using the conventional polyol Arcol® 1104.

[0072] 152.64 g of the polyol Arcol® 1104, 75.63 g phthalic acid and 11.97 g hydrogen peroxide (30 wt % in water) were added to the foam pieces. The reaction mixture was heated to 250° C. inner-temperature. The reaction was kept under this condition for 5 hours at an inner-temperature between 237° C. and 256° C. After the heating was stopped the second portion of 140.63 g Arcol® 1104 was added at 160° C. under nitrogen atmosphere. At 80° C. the reaction mixture was decanted and then cooled down to room temperature. The cooled and decanted reaction mixture was used as non-inventive recycled polyol 1. The process was repeated to generate a sufficient quantity recycled polyol for the foaming experiments.

[0073] Recycled Polyol 2 (Inventive)

[0074] The inventive recycled polyol of Example 6 was used.

[0075] General Procedure for Production of the Foam Samples For each foaming test 300 g or 400 g of polyol was used; the other formulation constituents were recalculated accordingly. 1.00 part of a component denoted 1.00 g of this substance per 100 g of polyol for example.

[0076] The foaming was carried out in the so-called manual mixing process. Formulation 1 or Formulation 2 as specified in Table 2 were used. To this end, a paper cup was charged with the different polyols, the respective amine catalyst, the tin catalyst tin(II) 2-ethylhexanoate, water and a foam stabilizer, and the contents were mixed at 1000 rpm for 60 seconds with a disc stirrer. After the first stirring the isocyanate (TDI) was added to the reaction mixture and stirred at 2500 rpm for 7 s and then the reaction mixture was immediately transferred into a paper-lined box (30 cm×30 cm base area and 30 cm height). After being poured in, the foam rose in the foaming box. In the ideal case, the foam blew off on attainment of the maximum rise height and then fell back slightly. This opened the cell membranes of the foam bubbles and an open-pore cell structure of the foam was obtained.

[0077] Defined foam bodies were cut out of the resulting hot-cure flexible PU foam blocks and were analyzed further.

[0078] Characterization of the Flexible PU Foams:

[0079] The flexible polyurethane foams produced were assessed according to the following foam properties a) to l): [0080] a) Fallback of the foam after the end of the rise phase (=settling): The settling, or the further rise, is found from the difference of the foam height after direct blow-off and after 3 minutes after foam blow-off. The foam height is measured at the maximum in the middle of the foam crest by means of a needle secured to a centimeter scale. A positive value here describes the settling of the foam after blow-off; a negative value correspondingly describes further rise of the foam after the blow off. [0081] b) Foam height: The height of the freely risen foam formed after 3 minutes. Foam height is reported in centimeters (cm). [0082] c) Rise time: The period of time between the end of mixing of the reaction components and the blow-off of the polyurethane foam. The rise time is reported in seconds (s). [0083] d) Porosity by dynamic pressure measurement: The gas permeability of the foam was determined in accordance with DIN EN ISO 4638:1993-07 by a dynamic pressure measurement on the foam. The dynamic pressure measured was reported in mm water column, and lower dynamic pressure values characterize a more open foam. The values were measured in the range from 0-300 mm water column. The dynamic pressure was measured by means of an apparatus comprising a nitrogen source, reducing valve with pressure gauge, flow regulating screw, wash bottle, flow meter, T-piece, applicator nozzle and a graduated glass tube filled with water. The applicator nozzle has an edge length of 100×100 mm, a weight of 800 g, an internal diameter of the outlet opening of 5 mm, an internal diameter of the lower applicator ring of 20 mm and an external diameter of the lower applicator ring of 30 mm. The measurement is carried out by setting the nitrogen admission pressure to 1 bar by means of the reducing valve and setting the flow rate to 480 l/h. The amount of water in the graduated glass tube is set so that no pressure difference is built up and none can be read off. For measurement on the test specimen having dimensions of 250×250×50 mm, the applicator nozzle is laid onto the corners of the test specimen, flush with the edges, and also once onto the (estimated) middle of the test specimen (in each case on the side having the greatest surface area). The result is read off when a constant dynamic pressure has been established. The final result is calculated by forming the average of the five measurements obtained. [0084] e) Number of cells per cm (cell number): This is determined visually on a cut surface (measured to DIN EN 15702). [0085] f) Compression hardness CLD, 40% to DIN EN ISO 33861:1997+A1:2010. The measured values are reported in kilopascals (kPa). [0086] g) Constant Deflection Compression Set (also commonly called compression set) [0087] Five test specimens each of size 5 cm×5 cm×2.5 cm were cut out of the finished foams. The starting thickness was measured. Compression set was measured no earlier than 72 h after production in accordance with DIN EN ISO1856 2018. The test specimens were placed between the plates of the deforming device and were compressed by 90% of their thickness (i.e. to 2.5 mm). Within 15 minutes, the test specimens were placed into an oven at 70° C. and left therein for 22 h. After this time, the apparatus was removed from the oven, the test specimens were removed from the apparatus within 1 min, and they were placed on a wood surface. After relaxation for 30 min, the thickness was measured again and the compression set was calculated and results are reported as a percentage of the original thickness:

DVR=(d0−dr)/d0×100% [0088] h) Tensile strength and elongation at break to DIN EN ISO1798:2008. The measurements of tensile strength are reported in kilopascals (kPa), and those of elongation at break in percent (%). [0089] i) Rebound resilience to DIN EN ISO 8307: 2007. The measurements are reported in percent (%). [0090] j) Emission profile at room temperature according to DIN EN ISO 16000-9:2008-04. The materials are characterized here with regard to the type and the amount of the organic substances emitting therefrom. The analysis method serves to ascertain emissions from materials that are used in furniture and mattresses. This is done by using test chambers to measure the emissions at room temperature. [0091] Analysis [0092] Test specimen: sample preparation, sampling and specimen dimensions [0093] The reaction mixture is transferred into a box (30 cm×30 cm base area and 30 cm height) which is covered by a PE plastic bag which is open at the top. After being poured in, the foam rose in the foaming box. In the ideal case, the foam blew off on attainment of the maximum rise height and then fell back slightly. This opened the cell membranes of the foam bubbles and an open-pore cell structure of the foam was obtained. After the foam has risen and blown off, the PE bag is closed 3 min after the blow-off. The foam is stored in this way at room temperature for 12 hours in order to enable complete reaction, but simultaneously in order to prevent premature escape of VOCs. Subsequently, the PE bag is opened, and a 7 cm×7 cm×7 cm cube is taken from the centre of the foam block and immediately wrapped in aluminium foil and sealed airtight in a PE bag. It was then transported to the analytical laboratory, and the foam cube was introduced into a cleaned 30 l glass test chamber. The conditions in the test chamber were controlled climatic conditions (temperature 21° C., air humidity 50%). Half the volume of the test chamber is exchanged per hour. After 24 hours, samples are taken from the test chamber air. Tenax adsorption tubes serve to absorb the VOCs. The Tenax tube is then heated, and the volatile substances released are cryofocused in a cold trap of a temperature-programmable evaporator with the aid of an inert gas stream. After the heating phase and cryofocusing has ended, the cold trap is rapidly heated to 280° C. and the focused substances are evaporated. They are subsequently separated in the gas chromatography separation column and detected by mass spectrometry. Calibration with reference substances permits a semi-quantitative estimate of the emission, expressed in “μg/m.sup.3”. The quantitative reference substance used for the VOC analysis (VOC value) is toluene. Signal peaks can be assigned to substances using their mass spectra and retention indices. The following equipment is used for the analysis: Gerstel, D-45473 Mühlheim an der Ruhr, Eberhard-Gerstel-Platz 1, Germany, TDS-3/KAS-4, Tenax® desorption tubes, Agilent Technologies 7890A (GC)/5975C (MS), column: HP Ultra2 (50 m, 0.32 mm, 0.52 μm), carrier gas: helium. More specific procedural instructions can be taken from DIN EN ISO 16000-9:2008-04. [0094] k) Odor testing of the resulting foams. The finished foams were packed in odor-neutral plastic bags and stored under airtight conditions. For the odor assessment of the foam, cubes measuring 10 cm×10 cm×10 cm were cut out and transferred to jars with a volume of 1 L, from which the samples were smelled. The jars were closed with a screw lid. The odor test took place after storing the jars for 24 hours at 22° C. The odor test was assessed by a panel of 13 trained odor testers. They were questioned here about the intensity of the odor, a low odor level was rated +, moderate odor ++, and high odor +++. [0095] l) Emission of aldehydes according to VDA 275 [0096] In the method, test specimens having a certain mass and size are secured above distilled water in a closed 1 L glass bottle and stored for a defined period at constant temperature. The bottles are subsequently cooled down and the absorbed aldehydes are determined in the distilled water. The amount of aldehydes determined is based on the dry weight of the foam sample (mg/kg). [0097] After the foams have been taken out of the foaming box, they are stored at 21° C. and about 50% relative humidity for 24 hours. Samples of the foam blocks are then taken at suitable and representative sites distributed uniformly across the width of the (cooled) foam block. The foam samples are then wrapped in aluminum foil and sealed in a polyethylene bag. The samples each have a size of 100×40×40 mm thickness (about 9 g). For each foam block, 3 test specimens are taken for the determination of aldehydes. [0098] The sealed samples are sent for direct determination immediately after receipt. The samples are weighed on an analytical balance to an accuracy of 0.001 g before analysis. A 50 ml quantity of distilled water is pipetted into each of the glass bottles used. The samples are introduced into the glass bottle, and the vessel is sealed and kept at a constant temperature of 60° C. in a thermal cabinet for 3 hours. The vessels are removed from the thermal cabinet after the test period. After standing at room temperature for 60 minutes, the samples are removed from the test bottle. This is followed by derivatization by the DNPH method (dinitrophenylhydrazine). For this, 900 μl of the aqueous phase is admixed with 100 μl of a DNPH solution. The DNPH solution is prepared as follows: 50 mg of DNPH in 40 ml of MeCN (acetonitrile) is acidulated with 250 μl of dilute HCl (1:10) and made up to 50 ml with MeCN. [0099] On completion of derivatization, a sample is analyzed by means of HPLC. Separation into the individual aldehyde homologues is effected. [0100] HPLC Instrument Parameters [0101] The following instrument is used for the analysis: [0102] Agilent Technologies 1260 [0103] Chromatography column: Phenomenex Luna250*4.6 mm C18, 5p particle size [0104] Eluent: water acetonitrile gradient [0105] Detection: UV 365 nm

[0106] Results of the Foaming Experiments

[0107] The results of the influence of the recycled polyols according to the invention on foaming process and foam physical properties of the resulting hot-cure flexible PU foams are compiled in the tables below. Hot-cure flexible PU foams were produced following Formulation 1, Table 2 with a standard virgin polyol, recycled polyol not inventive and with the inventive recycled polyol.

TABLE-US-00003 TABLE 3 Foaming results and foam physical properties of the foams with use of different types of polyols according to Formulation 1, Table 2. For each foaming test 400 g polyol were used; the other formulation constituents were recalculated accordingly. Foam Sample #1 #2 #3 #4 #5 Arcol ®1104, OHN 56, 100 70 70 Reference Recycled Polyol 1 100 30 (non-inventive), OHN 82 Recycled Polyol 2 100 30 (inventive), OHN 55 Index 105 105 105 105 105 Rise time (s) 122 — 123 122 129 Rise height (cm) 33.2 — 30.4 32.8 29.4 Settling (cm) 0.3 — 0.1 0.2 0.1 Cells (per cm) 12 — 12 12 12 Porosity (mm water column) 14 — 14 15 89 Hardness CLD 40% 3.5 — 3.0 3.4 2.5 compression (kPa) Elongation (%) 143 — 180 140 124 Tensile Strength (kPa) 118 — 136 125 110 Ball Rebound (%) 38 — 38 38 34 Compression Set 90% 6 — 8 6 32 22 h at 70° C. (%) Remarks Standard collapse Standard Standard Standard foam foam Foam Foam

[0108] The foaming results in Table 3 show that replacing the standard virgin polyol Arcol®1104 by the inventive recycled polyol 2 allows to produce flexible PU foam with comparable foaming processing characteristics to the reference foam #1. Furthermore, the foam physical properties porosity, cell count, ball rebound and compression set of the inventive foam #3 are comparable to the reference foam #1. The physical properties with respect to elongation and tensile strength are even improved by using the inventive recycled polyol #2 compared to the reference foam #1. On the contrary it was not possible to produce any reasonable foam by using 100 pphp of the non-inventive recycled polyol 1, this foam was collapsing (foam #2). Only at reduced use levels of 30 pphp for the non-inventive recycled polyol 1 in combination with the standard virgin Polyol Arcol®1104, a reasonable foam could be obtained (foam #5). But even at this lower use level, the foam physical properties were worse compared to the foam based on 100 pphp of the inventive recycled polyol 2 (foam #3). Foam #5 was significantly more closed than foam #1 or foam #3. Furthermore, the results for compression set (90% at 7000), elongation, tensile strength and ball rebound were worse for foam #5 compared to foam #3.

[0109] The results of the influence of the recycled polyols according to the invention on foam emissions at room temperature are compiled in Table 4. Hot-cure flexible PU foams were produced following Formulation 2, Table 2 by using a standard virgin polyol, a recycled polyol 1 (not inventive) or the inventive recycled polyol 2.

TABLE-US-00004 TABLE 4 Emission and odor testing results of the foams with use of different polyol types according to Formulation 2, Table 2. For each foaming test 300 g of polyol were used; the other formulation constituents were recalculated accordingly. Foam Sample #9 #10 #11 Arcol ®1104, OHN 56, 100 Reference Recycled Polyol 1 100 (non-inventive), OHN 82 Recycled Polyol 2 100 (inventive), OHN 55 Index 110 110 110 Emissions according 50 140 to DIN EN ISO 16000-9:2008-04 [μg/m.sup.3] Odor ++ − ++ Emission of aldehydes 0.2 − 0.2 according to VDA 275, Formaldehyde [ppm] Emission of aldehydes 0.3 − 0.3 according to VDA 275, Acetaldehyde [ppm] Emission of aldehydes 0.3 − 0.2 according to VDA 275, Propionaldehyde [ppm] Remarks Standard No foam Standard Foam Foam

[0110] The hot-cure flexible PU foams according to the invention are found to have low emissions if emissions-optimized additives are used. This can be seen in the VOC tests according to DIN EN ISO 16000-9:2008-04. Even though the total emissions are slightly increased when using 100 pphp of the inventive recycled polyol 2 (from 50 μg/in.sup.3 for foam #9 to 140 μg/in.sup.3 for foam #11), the emissions are still well below the typical limits for TVOC of 500 μg/in.sup.3. The recycled polyol 2 is thus suitable for low-emissions formulations. On the contrary it was not possible to produce any reasonable foam by using 100 pphp of the non-inventive recycled polyol 1.

[0111] The results in Table 4 show that replacing the standard virgin polyol Arcol® 1104 by the inventive recycled polyol 2 allows to produce flexible PU foam with comparable odor characteristics as well as aldehyde emissions. The emissions of formaldehyde, acetaldehyde and propionaldehyde, measured according to VDA275, are in a comparable range for foam #9 and foam #11.