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 and at least one aminoalcohol or alkylhydroxylamine. Foams so produced emit low levels of formaldehyde, acetaldehyde and propionaldehyde.

Claims

1. A method 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) 1,3-cyclohexanedione, (ii) 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, of 1,1,1 tris(hydroxymethyl) methylamine and (iii) a phenolic antioxidant, to form the polyurethane foam.

2. A method for reducing aldehyde emissions from a polyurethane foam, comprising: a) combining (i) 1,3-cyclohexanedione, (ii) 1,1,1-tris (hydroxymethyl) methylamine, and (iii) a phenolic antioxidant, 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 provide 0.05 to 0.25 parts by weight of the 1,1,1-tris (hydroxymethyl) methylamine 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, 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 method of claim 1 wherein the cyclic 1,3-cyclohexanedione 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.

4. The method of claim 1 wherein the phenolic 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.

Description

EXAMPLE 1 AND COMPARATIVE SAMPLES A AND B

(1) Formulated Polyol A is made by combining 45.34 parts of a 2, 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 and 2.1 parts of water.

(2) Formulated Polyol B is made by combining 100 parts of Formulated Polyol A with 0.5 parts 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) and 0.1 parts of 1,1,1-tris (hydroxymethyl) methylamine in a high speed laboratory mixer.

(3) Formulated Polyol 1 is made by combining 100 parts of Formulated Polyol A with 0.5 parts of IRGANOX™ 1135, 0.1 parts of 1,1,1-tris (hydroxymethyl) methylamine and 0.06 parts of 1,3-cyclohexanedione 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) The polyols are stored at room temperature for 0 to 2 weeks before foaming experiment.

(6) 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 air-tight package for 7 days.

(7) 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.

(8) 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.

(9) 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.

(10) 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.

(11) A standard solution containing 15 μg/mL each of formaldehyde, acetaldehyde 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 and propionaldehyde derivatives. The response factor is calculated from the area of the elution peak for each derivative, according the formula:

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

(13) The concentration of formaldehyde, acetaldehyde 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:

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

(15) The HPLC conditions are as follows:

(16) 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 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 Time: 5 min Injection: 10 uL

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

(18) TABLE-US-00002 TABLE 1 Comp. A* Comp. B* Ex. 1 Additives None 0.5% IRGANOX ™ 1135 0.5% IRGANOX ™ 1135 0.1% 1,1,1- 0.1% 1,1,1- tris(hydroxymethyl) tris(hydroxymethyl) methylamine methylamine 0.06% 1,3-cyclohexanedione Formaldehyde,  46-52.sup.1 46 25 μg/m.sup.3 Acetaldehyde, 200-205.sup.1 160 118 μg/m.sup.3 Propionaldehyde,  65-77.sup.1 56 43 μg/m.sup.3 Total Aldehydes, 317-328.sup.1 262 186 μg/m.sup.3 *Not an example of this invention. .sup.1Range from duplicate experiments.

(19) Adding the antioxidant and 1,1,1-tris(hydroxymethyl) methylamine into the foam formulation (Comp. B) results in little or no reduction of formaldehyde, and a modest reduction (about 20%) in each of acetaldehyde and propionaldehyde. Example 1, by contrast, exhibits a reduction in emitted formaldehyde of about 50% and a reduction of about 40% in each of acetaldehyde and propionaldehyde emissions. Total aldehydes are decreased by about 40%. The further addition of the cyclic 1,3-diketone to the antioxidant and aminoalcohol results in a dramatic reduction in the amounts of all three aldehydes as well as total aldehydes.

(20) Example 1 and Comparative Samples A are repeated, except this time the foams are produced in a closed mold. Results of the aldehyde measurements are indicated in Table 2.

(21) TABLE-US-00003 TABLE 2 Comp. A* Ex. 1 Additives None 0.5% IRGANOX ™ 1135 0.1% 1,1,1-tris(hydroxymethyl) methylamine 0.06% 1,3-cyclohexanedione Formaldehyde,  40-46.sup.1  25-26.sup.1 μg/m.sup.3   Acetaldehyde, 130-142.sup.1  99-108.sup.1 μg/m.sup.3   Propionaldehyde, 39.sup.1  28-30.sup.1 μg/m.sup.3 Total Aldehydes, 209-227.sup.1 154-162.sup.1 μg/m.sup.3 *Not an example of this invention. .sup.1Range from duplicate experiments.

(22) Large reductions in the emitted quantities of all three aldehydes are again seen with the invention.

EXAMPLE 2 AND COMPARATIVE SAMPLES C AND D

(23) Formulated Polyol C is a commercially available formulated polyol that contains a mixture of polyols having a functionality of at least 2 and an equivalent weight of at least 200; urethane catalysts, water and surfactant.

(24) Formulated Polyol D is made by combining 100 parts of Formulated Polyol C with 0.5 part IRGANOXT™ 1135 antioxidant and 0.1 part of 1,1,1-tris(hydroxymethyl) methylamine in a high speed laboratory mixer.

(25) Formulated Polyol 2 is made by combining 100 parts of Formulated Polyol A with 0.5 part IRGANOX™ 1135 antioxidant, 0.1 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.06 part of 1,3-cyclohexanedione in a high speed laboratory mixer.

(26) Comparative Samples C and D and Example 2 are formed into polyurethane cup foams and tested, in the manner described in the previous example, from each of Formulated Polyols C, D and 2, respectively. Results are as indicated in Table 3.

(27) TABLE-US-00004 TABLE 3 Comp. C* Comp. D* Ex. 2 Additives None 0.5% IRGANOX ™ 1135 0.5% IRGANOX ™ 1135 0.1% 1,1,1- 0.1% 1,1,1- tris(hydroxymethyl) tris(hydroxymethyl) methylamine methylamine 0.06% 1,3-cyclohexanedione Formaldehyde,  77-79.sup.1 76 34 μg/m.sup.3 Acetaldehyde, 220-245.sup.1 214 174 μg/m.sup.3 Propionaldehyde,  97-111.sup.1 98 64 μg/m.sup.3 Total Aldehydes, 394-435.sup.1 388 272 μg/m.sup.3 *Not an example of this invention. .sup.1Range from duplicate experiments.

(28) As the data in Table 3 shows, the combination of antioxidant and aminoalcohol alone results negligible reduction in formaldehyde emissions and at most small reductions in the other aldehydes. By further adding the cyclic 1,3-diketone, the emitted amount of all three aldehydes is reduced dramatically.