Methods for Reducing Aldehyde Emissions in Polyether Polyols and Polyurethane Foams

Abstract

Polyurethane foams are made by curing a reaction mixture that contains an aromatic polyisocyanate, at least one isocyanate-reactive material having an average functionality of at least 2 and an equivalent weight of at least 200 per isocyanate-reactive group, at least one blowing agent, at least one surfactant and at least one catalyst, and a certain 3-oxopropanamide compound. Foams so produced emit low levels of aldehydes.

Claims

1. A process for producing a polyurethane foam comprising forming a reaction mixture that contains an aromatic polyisocyanate, at least one isocyanate-reactive material having an average functionality of at least 2 and an equivalent weight of at least 200 grams per mole of isocyanate-reactive groups, at least one blowing agent, at least one surfactant and at least one catalyst, and curing the reaction mixture in the presence of at least one 3-oxopropanamide compound, to form the polyurethane foam, wherein the 3-oxopropanamide compound is a compound represented by the structure: ##STR00003## wherein R.sup.1 is hydrogen or a hydrocarbon group, R.sup.2 is hydrogen, hydrocarbon, hydroxyalkyl or aminoalkyl, R.sup.3 is hydroxyalkyl or aminoalkyl, and n is at least 1.

2. A process for reducing aldehyde emissions from a polyurethane foam, comprising: a) combining at least one 3-oxopropanamide compound with at least one isocyanate-reactive material having an average functionality of at least 2 and an equivalent weight of at least 200 grams per mole of isocyanate-reactive groups to form a mixture and then b) combining the mixture from step a) with at least one organic polyisocyanate and curing the resulting reaction mixture in the presence of at least one blowing agent, at least one surfactant and at least one catalyst to form a polyurethane foam, wherein the 3-oxopropanamide compound is a compound represented by the structure: ##STR00004## wherein R.sup.1 is hydrogen or an unsubstituted or inertly substituted hydrocarbon group, R.sup.2 is hydrogen, hydrocarbon, hydroxyalkyl or aminoalkyl, R.sup.3 is hydrogen, hydroxyalkyl or aminoalkyl, and n is at least 1.

3. The process of claim 1 wherein R.sup.1 is phenyl or alkyl having up to 6 carbon atoms, R.sup.2 is hydrogen, R.sup.3 is 2-hydroxyethyl or 2-hydroxypropyl and n is 1.

4. The process of claim 3 wherein the 3-oxopropanamide is N-(2-hydroxyethyl)-3-oxobutanamide.

5. A polyurethane foam made in the process of claim 1.

6. A process for reducing aldehyde emissions from a polyether polyol, comprising: a) combining 0.01 to 5 parts by weight of at least one 3-oxopropanamide compound with 100 parts by weight of the polyether polyol that has a hydroxyl equivalent weight of at least 200 grams per mole of hydroxyl groups, wherein the 3-oxopropanamide compound is a compound represented by the structure: ##STR00005## wherein R.sup.1 is hydrogen or a hydrocarbon group, R.sup.2 is hydrogen, hydrocarbon, hydroxyalkyl or aminoalkyl, R.sup.3 is hydrogen, hydroxyalkyl or aminoalkyl, and n is at least 1.

7. The process of claim 6 wherein R.sup.1 is phenyl or alkyl having up to 6 carbon atoms, R.sup.2 is hydrogen, R.sup.3 is 2-hydroxyethyl or 2-hydroxypropyl and n is 1.

8. The process of claim 7 wherein the 3-oxopropanamide is N-(2-hydroxyethyl)-3-oxobutanamide.

9. A polyether polyol containing 0.01 to 5 parts by weight of at least one 3-oxopropanamide compound per 100 parts by weight of the polyether polyol that has a hydroxyl equivalent weight of 200 grams per mole of hydroxyl groups, wherein the 3-oxopropanamide compound is a compound represented by the structure: ##STR00006## wherein R.sup.1 is hydrogen or a hydrocarbon group, R.sup.2 is hydrogen, hydrocarbon, hydroxyalkyl or aminoalkyl, R.sup.3 is hydrogen, hydroxyalkyl or aminoalkyl, and n is at least 1.

10. The polyether polyol of claim 9 wherein R.sup.1 is phenyl or alkyl having up to 6 carbon atoms, R.sup.2 is hydrogen, R.sup.3 is 2-hydroxyethyl or 2-hydroxypropyl and n is 1.

11. The polyether polyol of claim 10 wherein the 3-oxopropanamide is N-(2-hydroxyethyl)-3-oxobutanamide.

12. The process of claim 2 wherein R.sup.1 is phenyl or alkyl having up to 6 carbon atoms, R.sup.2 is hydrogen, R.sup.3 is 2-hydroxyethyl or 2-hydroxypropyl and n is 1.

13. The process of claim 12 wherein the 3-oxopropanamide is N-(2-hydroxyethyl)-3-oxobutanamide.

14. A polyurethane foam made in the process of claim 2.

Description

EXAMPLE 1 AND COMPARATIVE SAMPLE A

[0062] Ex. 1: 3 grams of an 1800 equivalent weight random copolymer of propylene oxide and ethylene oxide and 200 mg of N-(2-hydroxyethyl)-3-oxobutanamide (HEOBA) are mixed. 0.2 grams of the mixture are weighed into a headspace vial and conditioned at 100° C. for 10 minutes. The headspace is then analyzed for acetaldehyde and propionaldehyde by gas chromatography/mass spectrometry.

[0063] Comp. Sample A: For comparison, a sample of the random copolymer by itself is treated and analyzed in the same way. Results are as indicated in Table 1. Aldehyde concentrations are expressed in parts by weight per million parts of the random copolymer.

TABLE-US-00001 TABLE 1 Parts Per Million Comp. % Aldehyde Sample A Ex. 1 Reduction (no HEOBA) (w/HEOBA) with HEOBA Acetaldehyde 158 7 96% Propionaldehyde 1.0 0.1 90%

[0064] The HEOBA is found to vastly reduce aldehyde generation in the polyether polyol.

EXAMPLES 2-4 AND COMPARATIVE SAMPLE. B-F

[0065] General foaming method: A formulated polyol is made by combining 40 parts of a nominally trifunctional polyether polyol having a hydroxyl number of 29.5, 52.7 parts of a 1700 equivalent weight polyether polyol initiated from a mixture of sucrose and glycerine, 0.8 part of glycerine, 1.6 parts of a urethane catalyst mixture, 0.5 parts of an organosilicone foam-stabilizing surfactant and 4.2 parts of water. Polyurethane foams are made from the formulated polyol by combining the formulated polyol with an isocyanate-terminated prepolymer at a 1.8:1 weight ratio, pouring the resulting reaction mixture into a cup and allowing the reaction mixture to rise and cure to form a polyurethane foam. After the foam has cured enough to be dimensionally stable, it is removed from the cup and, except for Comparative Samples B and C, 10 cm×10 cm×14 cm samples, weighing about 38 to 41 grams are cut. For Comparative Samples B and C, 30 gram samples are cut. The foam cubes each are immediately wrapped in aluminum foil to form an air-tight package for 7 days.

[0066] Comparative Samples B and C are made using the general foaming method. Comparative Sample B is made without any additive. In Comparative Sample C, 0.1% of trimethylolpropane triacetylacetate ester (AATMP) (based on formulated polyol weight) is added to the formulated polyol before making the foam.

[0067] Comparative Sample D and Example 2 are made in the same manner. Comparative Sample D contains no additive. In Example 2, 0.3% of HEOBA is added to the formulated polyol before making the foam.

[0068] Comparative Sample E and Example 3 also are made in the same manner. Comparative Sample E contains no additive. In Example 3, 0.17% of HEOBA is added to the formulated polyol before making the foam.

[0069] Comparative Sample F and Example 4 also are made in the same manner. Comparative Sample F contains no additive. In Example 4, 0.1% of HEOBA is added to the formulated polyol before making the foam.

[0070] Aldehydes emitted from the foam samples are analyzed using the Toyota gas bag method. The cubed foam samples are in each case removed from the foil and put into a 10 L Tedlar gas bag that has been washed with pure nitrogen three times and emptied. An empty gas bag is used as a blank. After the foam sample is put into the gas bag, the bag is filled with about 7 L of nitrogen gas and heated in the oven for 2 hours at 65° C. The nitrogen gas in the gas bag is then pumped out by an air pump and analyzed for formaldehyde, acetaldehyde and propionaldehyde.

[0071] The gas from each bag is passed through a dinitrophenylhydrazine (DNPH) cartridge (CNWBOND DNPH-Silica cartridge, 350 mg, Cat. No. SEEQ-144102, Anple Co., Ltd.) at a sampling speed is 330 mL/min. The aldehydes emitted from the foam into the gas are absorbed by the cartridge to form DNPH derivatives. The DNPH cartridge is eluted with 3 g of acetonitrile, and the resulting acetonitrile solution is analyzed by HPLC to quantify the carbonyls in the sample, as follows.

[0072] A standard solution containing 15 μg/mL each of formaldehyde, acetaldehyde, acrolein, acetone, and propionaldehyde (in each case in the form of DNPH derivatives) (TO11A carbonyl-DNPH mix, Cat. No. 48149-U, Supelco Co., Ltd) is diluted with acetonitrile. A vial containing 2 mL of the diluted solution (containing 0.794 ppm of each of formaldehyde, acetaldehyde and propionaldehyde) is refrigerated to −4° C. The refrigerated solution is injected into the HPLC system and analyzed for formaldehyde, acetaldehyde, acrolein and propionaldehyde derivatives. The response factor is calculated from the area of the elution peak for each derivative, according the formula:

[00001]$\mathrm{Response}\mathrm{factor}i=\frac{\mathrm{Peak}\mathrm{Area}i}{0.794}$

where Response factor i=Response factor of derivative i; Peak Area i=Peak Area of derivative i in standard solution and 0.794=the concentration of each derivative in the standard solution.

[0073] The amounts of formaldehyde, acetaldehyde, acrolein, and propionaldehyde emitted by each foam sample are then determined. Acetone and volatile organic compounds (TVOC) are also measured. In each case, the acetonitrile solution obtained by eluting the DNPH column is injected into the HPLC system and the area of the elution peak is determined from each derivative. The concentration of the aldehyde-DNPH derivative in the sample solution is calculated as follows:

[00002]$\mathrm{Concentration}\mathrm{of}i=\frac{\mathrm{Peak}\mathrm{Area}i}{\mathrm{Response}\mathrm{factor}i}$

where: Concentration of i=Concentration of aldehyde-DNPH derivative in the sample solution, Peak Area i=Peak Area of Derivative i in sample solution and Response factor i=Response factor of derivative i, determined from the standard solutions as described above.

[0074] The HPLC conditions are as follows:

TABLE-US-00002 Instrument: Agilent 1200 HPLC Column: Supelco Ascentis Express C18, 15 cm*4.6 mm, 2.7 um Mobile Phase: Solvent A: 0.1% H.sub.3PO.sub.4 in Acetonitrile Solvent B: 0.1% H.sub.3PO.sub.4 in DI water Column Oven: 15° C. Detection: DAD detector at 360 nm Gradient: Time (mn) % A % B Flow (mL/min) 0 45 55 1 7 45 55 1 14 50 50 1 20 85 15 1 25 100 0 1 Equilibration 5 min Time: Injection: 10 uL

[0075] The concentrations of formaldehyde, acetaldehyde acrolein, acetone and propionaldehyde for each of Comparative Samples B-F and Examples 2-4 are as indicated in Tables 2-5.

TABLE-US-00003 TABLE 2 Comp. B* Comp. C* % Reduction No 0.1% with Additive AATMP AATMP Formaldehyde, μg/m.sup.3 64.2 62.9  2% Acetaldehyde, μg/m.sup.3 77.6 63.2 19% Acrolein, μg/m.sup.3 0 20.8 — Propionaldehyde, μg/m.sup.3 61.8 Not Detected 100%  *Not an example of this invention.

[0076] As the data in Table 2 shows, AATMP leads to only small reductions in the amounts of emitted formaldehyde and acetaldehyde.

TABLE-US-00004 TABLE 3 Comp. D* Ex. 2 % Reduction No 0.3% with 0.3% Additive HEOBA HEOBA TVOC, μg/m.sup.3 1814 1225 32.5%   Formaldehyde, μg/m.sup.3 469 69 85% Acetaldehyde, μg/m.sup.3 145 78 46% Acrolein, μg/m.sup.3 411 84 80% Acetone, μg/m.sup.3 50 16 68% Propionaldehyde, μg/m.sup.3 100 49 51% *Not an example of this invention.

TABLE-US-00005 TABLE 4 Comp. E* Ex. 3 % Reduction No 0.17% with 0.17% Additive HEOBA HEOBA TVOC, μg/m.sup.3 1148 ND ND Formaldehyde, μg/m.sup.3 444 108 76% Acetaldehyde, μg/m.sup.3 67 57 15% Acrolein, μg/m.sup.3 284 67 76% Acetone, μg/m.sup.3 157 84 46% Propionaldehyde, μg/m.sup.3 156 87 44% *Not an example of this invention. ND—not determined.

TABLE-US-00006 TABLE 5 Comp. F* Ex. 3 % Reduction No 0.1% with 0.1% Additive HEOBA HEOBA TVOC, μg/m.sup.3 2251 1808 20% Formaldehyde, μg/m.sup.3 349 151 57% Acetaldehyde, μg/m.sup.3 77 44 43% Acrolein, μg/m.sup.3 433 78 82% Acetone, μg/m.sup.3 93 41 44% Propionaldehyde, μg/m.sup.3 91 74 19% *Not an example of this invention.

[0077] As the data in Tables 3 and 5 shows, the addition of 0.1 to 0.3% HEOBA results in significant decreases in formaldehyde, acetaldehyde, proprionaldehyde, acrolein and acetone emissions.