Methods for reducing aldehyde emissions in 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, at least one cyclic 1,3-diketone compound, at least one aminoalcohol or alkylhydroxylamine and an alkali metal, phosphonium or ammonium sulfite. Foams so produced emit low levels of formaldehyde, acetaldehyde, acrolein and propionaldehyde.

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 per isocyanate-reactive group, at least one blowing agent, at least one surfactant and at least one catalyst, and curing the reaction mixture in the presence of (i) at least one cyclic 1,3-diketone, (ii) at least one aminoalcohol and/or alkylhydroxylamine selected from the group consisting of one or more of 2-amino-1-butanol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol, 2-amino-1-methyl-1,3-propanediol, 1,1,1-tris (hydroxymethyl) methylamine, N-methylethanolamine, N-butylethanolamine, 2-amino-2(hydroxymethyl)propane-1,3-diol, N-isopropylhydroxylamine, ethylhydroxylamine, methylhydroxylamine, N-butylhydroxylamine and sec-butylhydroxylamine and (iii) an alkali metal, ammonium or phosphonium sulfite, to form the polyurethane foam.

2. A method for reducing aldehyde emissions from a polyurethane foam, comprising: a) combining (i) at least one cyclic 1,3-diketone, (ii) at least one aminoalcohol and/or alkylhydroxylamine selected from the group consisting of one or more of 2-amino-1-butanol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol, 2-amino-1-methyl-1,3-propanediol, 1,1,1-tris (hydroxymethyl) methylamine, N- N-butylethanolamine, monoisopropanolamine, 2-amino-2(hydroxymethyl)propane-1,3-diol, N-isopropylhydroxylamine, ethylhydroxylamine, methylhydroxylamine, N-butylhydroxylamine and sec-butylhydroxylamine and (iii) an alkali metal, ammonium or phosphonium sulfite with 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 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.

3. The process of claim 1 wherein the cyclic 1,3-diketone is represented by structure II ##STR00005## wherein X, Y, Z are independently carbonyl, —C(R.sup.2R.sup.3)—, —NR.sup.4—, —O— or a chemical bond, each R.sup.2 and R.sup.3 are independently H, a substituted or unsubstituted linear or branched alkyl or alkenyl group having 1 to 10 carbon atoms, a substituted or unsubstituted phenyl group, a halogen, —CO.sub.2CH.sub.3, or —CN, with the proviso that any two or more of R.sup.2 and R.sup.3 may be connected intra- or inter-molecularly and each R.sup.4 is independently H, a substituted or unsubstituted linear or branched alkyl or alkenyl group having 1 to 10 carbon atoms or a substituted or unsubstituted phenyl group.

4. The process of claim 1 wherein the cyclic 1,3-diketone is represented by structure (III): ##STR00006## wherein Z is carbonyl, —C(R.sup.2R.sup.3)—, —NR.sup.4—, —O— or a chemical bond, each R.sup.2 and R.sup.3 are independently H, a substituted or unsubstituted linear or branched alkyl or alkenyl group having 1 to 10 carbon atoms, a substituted or unsubstituted phenyl group, a halogen, —CO.sub.2CH.sub.3, or —CN, with the proviso that any two or more of R.sup.2 and R.sup.3 may be connected intra- or inter-molecularly and each R.sup.4 is independently H, a substituted or unsubstituted linear or branched alkyl or alkenyl group having 1 to 10 carbon atoms or a substituted or unsubstituted phenyl group.

5. The process of claim 1 wherein the cyclic 1,3-diketone is one or more of cyclohexane-1,3,5-trione, 1,3-cyclohexanedione, pyrazolidine-3,5-dione, 1,2-dimethylpyrazolidine-3,5-dione, 1-methylpyrazolidine-3,5-dione, 1,1-dimethyl-cyclopentan-2,4-dione, 1-ethyl-cyclohexan-2,4-dione, 1, 1-diethyl-cyclohexan-3,5-dione, 6-methyl-pyran-2,4-dione, 6-ethyl-pyran-2,4-dione, 6-isopropyl-pyran-2,4-dione, 6-(n)-butyl-pyran-2,4-dione, 6-isobutyl-pyran-2,4-dione, 6-pentyl-pyran-2,4-dione, 6-isopentyl-pyran-2,4-dione, 6,7-dihydrocyclopenta [b]pyran-2,4(3H, 5H)-dione, 5,6,7,8-tetrahydro-chroman-2,4-dione, chroman-2,4-dione, 6-trans-propenyl-dihydro-pyran-2,4-dione, 1-oxaspiro-[5,5]-undecan-2,4-dione, 2,2-dipropyl-[1,3]-dioxan-4,6-dione, 2-phenyl-[1,3]-dioxan-4,6-dione, 6,10-dioxa-spiro-[4,5]-decan-7,9-dione, 1,5-dioxa-spiro-[5,5]-undecan-2,4-dione, 1-methyl-2,4,6-trioxo-hexahydro-pyrimidine, 1-ethyl-2,4,6-trioxo-hexahydro-pyrimidine, 1-phenyl-2,4,6-trioxo-hexahydro-pyrimidine, s-indacene-1,3,5,7(2H, 6H)-tetraone, furan-2,4 (3H, 5H)-dione, 3,3′-(hexane-1,1-diyl)bis(1-methylpyrimidine-2,4,6 (1H, 3H, 5H)-trione), 2,2-dimethyl-1,3-dioxane-4,6-dione, furan-2,4(3H, 5H)-dione, pyrimidine-2,4,6(1H, 3H, 5H)-trione and 1,3-dimethylpyrimidine-2,4,6(1H, 3H, 5H)-trione.

6. The process of claim 1 wherein the alkali metal, ammonium or phosphonium sulfite is sodium hydrogen sulfite.

7. The process of claim 1 wherein the cyclic 1,3-diketone is present in an amount of from 0.03 to 0.25 parts by weight per 100 parts by weight of the at least one isocyanate reactive compound having at least two isocyanate-reactive groups per molecule and an equivalent weight of at least 200 per isocyanate-reactive group.

8. The process of claim 1 wherein the aminoalcohol alkylhydroxylamine is present in an amount of from 0.05 to 0.25 parts by weight per 100 parts by weight of the at least one isocyanate reactive compound having at least two isocyanate-reactive groups per molecule and an equivalent weight of at least 200 per isocyanate-reactive group.

9. The process of claim 1 wherein the alkali metal, ammonium or phosphonium sulfite is present in an amount of 0.025 to 0.25 parts by weight per 100 parts by weight of the at least one isocyanate reactive compound having at least two isocyanate-reactive groups per molecule and an equivalent weight of at least 200 per isocyanate-reactive group.

10. The process of claim 1 wherein the reaction mixture is cured in the presence of an antioxidant.

11. The process of claim 10 wherein the antioxidant is a phenolic compound.

12. The process of claim 11 wherein the antioxidant is present in an amount of 0.2 to 1.5 parts by weight per 100 parts by weight of the at least one isocyanate reactive compound having at least two isocyanate-reactive groups per molecule and an equivalent weight of at least 200 per isocyanate-reactive group.

13. The process of claim 1 wherein the cyclic 1,3-diketone is 1,3-cyclohexanedione.

14. 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 per isocyanate-reactive group, at least one blowing agent, at least one surfactant and at least one catalyst, and curing the reaction mixture in the presence of (i) at least one cyclic 1,3-diketone, (ii) 1,1,1 tris(hydroxymethyl) methylamine and (iii) an alkali metal, ammonium or phosphonium sulfite, to form the polyurethane foam, wherein the reaction mixture is cured in the presence of an antioxidant and the antioxidant is a phenolic compound.

15. A polyurethane foam made in accordance with the process of claim 1.

16. 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 per isocyanate-reactive group, at least one blowing agent, at least one surfactant and at least one catalyst, and curing the reaction mixture in the presence of (i) at least one cyclic 1,3-diketone, (ii) 1, 1,1 tris(hydroxymethyl) methylamine and (iii) an alkali metal, ammonium or phosphonium sulfite, to form the polyurethane foam.

17. A polyurethane foam made in accordance with the process of claim 14.

18. A polyurethane foam made in accordance with the process of claim 16.

19. The process of claim 1 wherein the aminoalcohol and/or alkylhydroxylamine is selected from the group consisting of N-isopropylhydroxylamine, ethylhydroxylamine, methylhydroxylamine, N-butylhydroxylamine and sec-butylhydroxylamine.

20. The method of claim 2 wherein the aminoalcohol and/or alkylhydroxylamine is selected from the group consisting of N-isopropylhydroxylamine, ethylhydroxylamine, methylhydroxylamine, N-butylhydroxylamine and sec-butylhydroxylamine.

Description

EXAMPLE 1 AND COMPARATIVE SAMPLES A AND B

(1) Formulated Polyol A is made by combining 45.34 parts of a glycerin-initiated poly(propylene oxide) capped with 15 percent ethylene oxide and having a hydroxyl number of 27.5 mg KOH/g; 50.11 parts of a copolymer polyol having a hydroxyl number of 22 mg KOH/g and containing 40 percent by weight copolymerized styrene and acrylonitrile solids dispersed in a polyether polyol; 0.48 part of diethanolamine, 0.38 part of glycerine, 0.27 part of a 33 percent triethylene diamine in dipropylene glycol, 0.17 part of a tertiary amine/glycol mixture available as C225 from Momentive Co., Ltd.; 1.15 parts of an organosilicone foam-stabilizing surfactant, 2.1 parts of water and 0.5 part of benzenepropanoic acid, 3,5-bis (1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl esters (available as IRGANOX™ 1135 antioxidant from BASF (China) Co., Ltd).

(2) Formulated Polyol B is made by combining 100.5 parts of Formulated Polyol A with 0.17 part of 1,3-cyclohexanedione and 0.3 part of 1,1,1-tris (hydroxymethyl) methylamine in a high speed laboratory mixer.

(3) Formulated Polyol 1 is made by combining 100.5 parts of Formulated Polyol A with 0.17 part of 1,3-cyclohexanedione, 0.3 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.1 part of sodium hydrogen sulfite (NaHSO.sub.3) in a high speed laboratory mixer.

(4) Each of Formulated Polyols A, B and 1 are stored at room temperature for 12-24 hours before being processed into a foam.

(5) Comparative Sample A is made by combining 100 parts of Formulated Polyol A with 28 parts of a 20/80 by weight blend of toluene diisocyanate (TDI) and methylene diphenyldiisocyanate (MDI), 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 30-gram sample cubes are cut. The foam cubes each are immediately wrapped in aluminum foil to form an airtight package for 7 days.

(6) Comparative Sample B is made in the same manner, except 100 parts of Formulated Polyol B are combined with 28 parts of the same TDI/MDI blend.

(7) Example 1 is made in the same manner, except 100 parts of Formulated Polyol 1 are combined with 28 parts of the same TDI/MDI blend.

(8) 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, acrolein (propenyl aldehyde) and propionaldehyde.

(9) 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.

(10) A standard solution containing 15 μg/mL each of formaldehyde, acetaldehyde, acrolein 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, acrolein 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:

(11) $\mathrm{Response}\mathrm{factor}i=\frac{\mathrm{Peak}\mathrm{Area}i}{0.794}$
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.

(12) The amounts of formaldehyde, acetaldehyde, acrolein and propionaldehyde emitted by each of Comparative Samples A and B and Example 1 are then determined. 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:

(13) $\mathrm{Concentration}\mathrm{of}i=\frac{\mathrm{Peak}\mathrm{Area}i}{\mathrm{Response}\mathrm{factor}i}$
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.

(14) The HPLC conditions are as follows:

(15) TABLE-US-00001 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 Time Flow Gradient: (mn) % A % B (mL/min) 0 45 55 1 7 45 55 1 14 50 50 1 20 85 15 1 25 100 0 1 Equilibration Time: 5 min Injection: 10 uL

(16) The concentrations of formaldehyde, acetaldehyde, acrolein and propionaldehyde for each of Comparative Samples A and B and Example 1 are as indicated in Table 1.

(17) TABLE-US-00002 TABLE 1 Comp. A* Comp. B* Ex. 1 Additives 0.5% IRGANOX 1135 0.5% IRGANOX 1135 0.5% IRGANOX 1135 0.3% 1,1,1- 0.3% 1,1,1- tris(hydroxymethyl) tris(hydroxymethyl) methylamine methylamine 0.17% 1,3-cyclohexanedione 0.17% 1,3-cyclohexanedione 0.1% NaHSO.sub.3 Formaldehyde, 6 0 0 μg/m.sup.3 Acetaldehyde, 267 188 21 μg/m.sup.3 Acrolein, μg/m.sup.3 23 13 0 Propionaldehyde, 302 111 45 μg/m.sup.3 Total Aldehydes, 598 312 66 μg/m.sup.3 *Not an example of this invention.

(18) When the antioxidant is present by itself (Comp. A), acetaldehyde and propionaldehyde values in particular are quite high, as are total aldehydes. Further incorporating the 1,3-cyclohexandione and 1,1,1-tris(hydroxymethyl) methylamine into the foam formulation (Comp. B) reduces formaldehyde emissions to zero on this test, reduces acetaldehyde emissions by about 30%, reduces acrolein emissions by 45% and reduces propionaldehyde emissions by about two-thirds. Total aldehydes are reduced by nearly half. As this data shows, the combination of antioxidant, cyclic 1,3-diketone and aminoalcohol is already very effective at removing each of the measured aldehydes.

(19) With the further addition of sodium hydrogen sulfite into Example 1, however, a much greater reduction in aldehyde emissions is seen, even compared with the good results of Comp. B. Formaldehyde and acrolein are reduced to zero. Acetaldehyde emissions are reduced by over 90%. Propionaldehyde emissions are reduced by 85%. Total aldehyde emissions are reduced by almost 90%.

EXAMPLES 2-3

(20) Formulated Polyol 2 is made by combining 100.5 parts of Formulated Polyol A with 0.17 part of 1,3-cyclohexanedione, 0.3 parts of 1,1,1-tris (hydroxymethyl) methylamine and 0.05 part sodium hydrogen sulfite in a high speed laboratory mixer. 100 parts of Formulated Polyol 2 are reacted with 28 parts of the TDI/MDI mixture described before to make a cup foam.

(21) Formulated Polyol 3 is made by combining 100 parts of Formulated Polyol A with 0.06 parts of 1,3-cyclohexanedione, 0.1 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.1 part sodium hydrogen sulfite in a high speed laboratory mixer. 100.76 parts of Formulated Polyol 2 are reacted with 28 parts of the TDI/MDI mixture described before to make a cup foam.

(22) The cup foams are made and tested in the manner described in the previous example. In addition, Comp. A and Example 1 are repeated and again tested. Results are as indicated in Table 2.

(23) TABLE-US-00003 TABLE 2 Comp. A* Ex. 1 Ex. 2 Ex. 3 Additives 0.5% IRGANOX 1135 0.5% IRGANOX 1135 0.5% IRGANOX 1135 0.5% IRGANOX 1135 0.3% 1,1,1- 0.3% 1,1,1- 0.1% 1,1,1- tris(hydroxymethyl) tris(hydroxymethyl) tris(hydroxymethyl) methylamine methylamine methylamine 0.17% 1,3- 0.17% 1,3- 0.06% 1,3- cyclohexanedione cyclohexanedione cyclohexanedione 0.1% NaHSO.sub.3 0.05% NaHSO.sub.3 0.1% NaHSO.sub.3 Formaldehyde, 12 0 0 0 μg/m.sup.3 Acetaldehyde, 125 5 34 13 μg/m.sup.3 Acrolein, μg/m.sup.3 22 0 0 0 Propionaldehyde, 251 19 76 33 μg/m.sup.3 Total Aldehydes, 410 24 110 46 μg/m.sup.3 *Not an example of this invention.

(24) As the data in Table 2 shows, the combination of cyclic 1,3-ketone, aminoalcohol and sodium hydrogen bisulfite leads to drastic reductions in the emitted amounts of all four aldehydes.