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 acetoacetate ester or amide 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) 0.02 to 0.15 parts by weight per 100 parts by weight of the at least one isocyanate-reactive material of at least one acetoacetate ester or amide selected from the group consisting of trimethylolpropane triacetoacetate ester, trimethylolethane triacetoacetate ester, and ##STR00005## an amide compound having the structure (ii) 0.05 to 0.25 parts by weight per 100 parts by weight of the at least one isocyanate-reactive material of at least one aminoalcohol and/or alkylhydroxylamine selected from the group consisting of 1,1,1-tris (hydroxymethyl) methylamine and ethanolamine, and (iii) 0.1 to 1.5 parts by weight per 100 parts by weight of the at least one isocyanat-reactive material of a phenolic antioxidant to form the polyurethane foam.

2. The method of claim 1 wherein the acetoacetate ester or amide is trimethylolpropane triacetoacetate.

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

4. The method of claim 1 wherein the acetoacetate ester or ##STR00006## amide has the structure.

Description

EXAMPLE 1 AND COMPARATIVE SAMPLES A-C

(1) Formulated Polyol A is made by combining 45.34 parts of a glycerin-initiated polypropylene 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 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) and 0.1 part of 1,1,1-tris (hydroxymethyl) methylamine in a high speed laboratory mixer.

(3) Formulated Polyol C is made by combining 100 parts of Formulated Polyol A with 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) and 0.1 parts of AcAcNHPH in a high speed laboratory mixer. Formulated Polyol 1 is made by combining 100 parts of Formulated Polyol A with 0.5 part of IRGANOX? 1135, 0.1 part of AcAcNHPh, and 0.07 part of 1,1,1-tris (hydroxymethyl) methylamine in a high speed laboratory mixer.

(4) Each of Formulated Polyols A, B, C 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 air-tight package for 7 days.

(6) Comparative Sample B is made in the same manner, except 100 parts of Formulated

(7) Polyol B are combined with 28 parts of the same TDI/MDI blend. Comparative Sample C is made in the same manner, except 100 parts of Formulated Polyol C 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 7L 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 ?g/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 amount 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 aldehydeDNPH 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 Time (mn) % A % B Flow (mL/min) Gradient: 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-C and Example 1 are as indicated in Table 1.

(18) TABLE-US-00002 TABLE 1 Comp. A* Comp. B* Comp. C* Ex. 1 Additives None 0.5% IRGANOX 1135. 0.5% IRGANOX 1135. 0.5% IRGANOX 1135. 0.1% 1,1,1- 0.1% AcAcNHPh 0.07% 1,1,1- tris(hydroxymethyl) tris(hydroxymethyl) methylamine methylamine 0.1% AcAcNHPH Formaldehyde, 38 34 21 20 ?g/m.sup.3 Acetaldehyde, 156 128 112 120 ?g/m.sup.3 Propionaldehyde, 178 114 146 129 ?g/m.sup.3 Total 372 276 279 269 Aldehydes, ?g/m.sup.3 *Not an example of this invention.

(19) Adding the antioxidant and 1,1,1-tris(hydroxymethyl) methylamine into the foam formulation (Comp. B) results in little or no reduction in the amount of emitted formaldehyde, and modest reductions in the emitted amounts of each of acetaldehyde and propionaldehyde.

(20) Adding the antioxidant and AcAcNHPh leads to a substantial (about 45%) decrease in formaldehyde emissions but only a modest decrease in acetaldehyde emissions and only a small reduction in propionaldehyde emissions.

(21) Example 1, by contrast, exhibits a reduction in emitted formaldehyde of about 50% and significant reductions in each of acetaldehyde and propionaldehyde emissions. Total emitted aldehyde emissions are lower than any of the Comparative Samples.

EXAMPLE 2-3 AND COMPARATIVE SAMPLES D-G

(22) Formulated Polyol D 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.

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

(24) Formulated Polyol F is made by combining 100 parts of Formulated Polyol D with 0.5 part IRGANOX? 1135 antioxidant and 0.05 part of 1,1,1-tris(hydroxymethyl) methylamine in a high speed laboratory mixer.

(25) Formulated Polyol G is made by combining 100 parts of Formulated Polyol D with 0.5 part IRGANOX? 1135 antioxidant and 0.1 part of trimethylolpropane triacetoacetate (AATMP) in a high speed laboratory mixer.

(26) Formulated Polyol 2 is made by combining 100 parts of Formulated Polyol D with 0.5 part IRGANOX? 1135 antioxidant, 0.1 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.1 parts of AATMP in a high speed laboratory mixer.

(27) Formulated Polyol 3 is made by combining 100 parts of Formulated Polyol D with 0.5 part IRGANOX? 1135 antioxidant, 0.05 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.1 parts of AATMP in a high speed laboratory mixer.

(28) Comparative Samples D-G and Examples 2-3 each are formed into polyurethane cup foams and tested, in the manner described in the previous examples. Results are as indicated in Table 2.

(29) TABLE-US-00003 TABLE 2 Comp. D* Comp. E* Comp. F* Comp. G* Ex. 2 Ex. 3 Additives AO.sup.1, pph 0 0.5 0.5 0.5 0.5 0.5 1,1,1-Tris.sup.2, pph 0 0.1 0.05 0 0.1 0.05 AATMP.sup.3, pph 0 0 0 0.1 0.1 0.1 Test Results Formaldehyde, 87 86 72 10 4 4 ?g/m.sup.3 Acetaldehyde, 298 193 223 192 180 182 ?g/m.sup.3 Propionaldehyde, 87 61 59 96 54 65 ?g/m.sup.3 Total Aldehydes, 472 330 354 298 238 251 ?g/m.sup.3 *Not an example of this invention. .sup.1Antioxidant. .sup.21,1,1-tris(hydroxylmethyl)methylamine. .sup.3Trimethylolpropane triacetoacetate.

(30) As the data in Table 3 shows, the combination of antioxidant, aminoalcohol and AATMP results in the greatest reduction of aldehyde emissions.

(31) Example 3 and Comparative Samples D-F are repeated, except this time the foams are produced in a closed mold. Results of the aldehyde measurements are indicated in Table 3, indicated in this case as total measured emissions from the test sample in micrograms.

(32) TABLE-US-00004 TABLE 3 Comp. D* Comp. E* Comp. F* Ex. 3 Additives AO.sup.1, pph 0 0.5 0.5 0.5 1,1,1-Tris.sup.2, pph 0 0.1 0.05 0.05 AATMP.sup.3, pph 0 0 0 0.1 Test Results Formaldehyde, 0.39 0.36 0.43 0.08 ?g/test piece Acetaldehyde, 1.81 0.80 1.04 1.04 ?g/test piece Propionaldehyde, 0.47 0.27 0.31 0.34 ?g/test piece Total Aldehydes, 2.67 1.43 1.79 1.46 ?g/test piece *Not an example of this invention. .sup.1Antioxidant. .sup.21,1,1-tris(hydroxylmethyl)methylamine. .sup.3Trimethylolpropane triacetoacetate.

(33) Large reductions in the emitted quantities of all three aldehydes are again seen with the invention, compared with the control. Formaldehyde in particular is reduced to a very low level without sacrificing reductions in the other aldehyde emissions.

EXAMPLE 4 AND COMPARATIVE SAMPLES H-J

(34) Formulated Polyol H 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.

(35) Formulated Polyol I is made by combining 100 parts of Formulated Polyol H with 0.5 part IRGANOX? 1135 antioxidant and 0.05 part of 1,1,1-tris(hydroxymethyl) methylamine in a high speed laboratory mixer.

(36) Formulated Polyol J is made by combining 100 parts of Formulated Polyol H with 0.5 part IRGANOX? 1135 antioxidant and 0.05 part of AATMP in a high speed laboratory mixer.

(37) Formulated Polyol 4 is made by combining 100 parts of Formulated Polyol J with 0.5 part IRGANOX? 1135 antioxidant, 0.05 part of 1,1,1-tris (hydroxymethyl) methylamine and 0.05 part of AATMP in a high speed laboratory mixer.

(38) Comparative Samples H, I and J and Example 4 each are formed into polyurethane cup foams and tested, in the manner described in the previous example. Results are as indicated in Table 4.

(39) TABLE-US-00005 TABLE 4 Comp. H* Comp. I* Comp. J* Ex. 4 Additives AO.sup.1, pph 0 0.5 0.5 0.5 1,1,1-Tris.sup.2, pph 0 0.05 0 0.05 AATMP.sup.3, pph 0 0 0.05 0.05 Test Results Formaldehyde, 78 75 51 43 ?g/test piece Acetaldehyde, 233 189 234 178 ?g/m.sup.3 Propionaldehyde, 104 79 107 74 ?g/m.sup.3 Total Aldehydes, 415 343 392 296 ?g/m.sup.3 *Not an example of this invention. .sup.1Antioxidant. .sup.21,1,1-tris(hydroxylmethyl)methylamine. .sup.3Trimethylolpropane triacetoacetate.

(40) As the data in Table 4 shows, the combination of aminoalcohol and AATMP leads to the greatest reduction in the amount of all three emitted aldehydes and the lowest level of total aldehyde emissions.