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, at least one catalyst, and certain aldehyde-suppressing additives. Foams so produced emit low levels of formaldehyde, acetaldehyde 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 hindered amine represented by structure I: ##STR00007## wherein Y is hydrogen, alkyl, or .fwdarw.O, R.sup.1 and R.sup.3 each are independently alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl; R.sup.2 and R.sup.4 each are independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl; m is at least 1, preferably 1 or 2, A is H, —OH, —NH.sub.2, alkyl or a chemical bond when m is 1 and chemical bond or a linking group when m is 2 or more, and Z is —CH.sub.2— or a chemical bond, and ii) at least one compound represented by structure II: ##STR00008## wherein R.sup.6 and R.sup.7 are independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl, and R.sup.8 is: ##STR00009## wherein R.sup.9, R.sup.10 and R.sup.11, are each independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl with the proviso that R.sup.9 and R.sup.10, and/or R.sup.10 and R.sup.11 may form rings.

2. A method for reducing aldehyde emissions from a polyurethane foam, comprising: a) combining (i) at least one hindered amine represented by structure I: ##STR00010## wherein Y is hydrogen, alkyl, or .fwdarw.O, R.sup.1 and R.sup.3 each are independently alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl; R.sup.2 and R.sup.4 each are independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl; m is at least 1, preferably 1 or 2, A is H, —OH, —NH.sub.2, alkyl or a chemical bond when m is 1 and chemical bond or a linking group when m is 2 or more, and Z is —CH.sub.2— or a chemical bond, and ii) at least one compound represented by structure II: ##STR00011## wherein R.sup.6 and R.sup.7 are independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl, and R.sup.8 is: ##STR00012## wherein R.sup.9, R.sup.10 and R.sup.11, are each independently hydrogen, alkyl, aryl-substituted alkyl, aryl or alkyl-substituted aryl with the proviso that R.sup.9 and R.sup.10, and/or R.sup.10 and R.sup.11 may form rings, 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 combination 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 R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each independently C1-C4 alkyl.

4. The process of claim 3 wherein m is 1 and A is hydrogen, hydroxyl, —NH.sub.2 or alkyl.

5. The process of claim 3 wherein m is 2 or more and A is —O—, —NH—, alkylene, arylene, aryl-substituted alkylene, aryl-substituted alkylene, —NH—C(O)—(CH.sub.2).sub.o—C(O)—NH— where 0 is 1 to 20, or —O—C(O)—(CH.sub.2).sub.o—C(O)—O— where o is 1 to 20.

6. The process of claim 1 wherein the structure I compound is selected from one or more compounds represented by any of structures III-XII: ##STR00013## ##STR00014##

7. The process of claim 1 wherein R.sup.6 is C1-C4 alkyl and R.sup.7 is hydrogen or C1-C4 alkyl.

8. The process of claim 1 wherein the structure II compound is a compound represented by any of structures XIII-XVIII: ##STR00015##

9. The method of claim 1 wherein the compound represented by structure I is present in an amount of from 0.02 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 method of claim 1 wherein the compound represented by structure II is present in an amount of from 0.02 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.

11. The method of claim 1 wherein the reaction mixture is cured in the presence of an antioxidant.

12. The method of claim 11 wherein the antioxidant is a phenolic compound.

13. The method of claim 12 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.

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

Description

EXAMPLE 1 AND COMPARATIVE SAMPLES A-C

[0049] 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).

[0050] Formulated Polyol B is made by combining 100.5 parts of Formulated Polyol A with 0.1 part of a compound represented by structure III in a high speed laboratory mixer.

[0051] Formulated Polyol C is made by combining 100.5 parts of Formulated Polyol A with 0.1 part of a compound represented by structure XIII.

[0052] Formulated Polyol 1 is made by combining 100.5 parts of Formulated Polyol A with 0.1 part of a compound represented by structure III and 0.1 part of a compound represented by structure XIII.

[0053] Each of Formulated Polyols A, B, C and 1 are stored at room temperature for 12-24 hours before being processed into a foam.

[0054] 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.

[0055] 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. 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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:

[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.

[0060] The amount of formaldehyde, acetaldehyde and propionaldehyde emitted by each of Comparative Samples A-C 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:

[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.

[0061] The HPLC conditions are as follows:

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 5 min Time: Injection: 10 uL

[0062] The concentrations of formaldehyde, acetaldehyde and propionaldehyde for each of Comparative Samples A-C and Example 1 are as indicated in Table 1.

TABLE-US-00002 TABLE 1 Comp. A* Comp. B* Comp. C* Ex. 1 Additives 0.5% IRGONOX 1135 0.5% IRGONOX 1135 0.5% IRGONOX 1135 0.5% IRGONOX 0.1% Structure III 0.1% Structure XIII 0.1% Structure III compound compound compound, 0.1% Structure XIII compound Formaldehyde, 45-49.sup.1 47 50 34 μg/m.sup.3 Acetaldehyde, 191-202.sup.1 173 194 131 μg/m.sup.3 Propionaldehyde, 58-71.sup.1 52 60 52 μg/m.sup.3 Total Aldehydes, 294-322.sup.1 272 304 216 μg/m.sup.3 *Not an example of this invention. .sup.1Range from duplicate experiments.

[0063] The baseline formulation (Comp. Sample A) emits about 300 μg/m.sup.3 aldehydes. Adding the structure III compound (Comp. Sample B) or the structure XIII compound (Comp. Sample C) by themselves have minimal effect on aldehyde emissions. However, when both the Structure III and Structure XIII compounds are present, emissions of all three aldehydes are reduces significantly. Overall aldehyde emissions are reduced by almost one-third over the baseline case.

[0064] Example 1 and Comparative Sample A are repeated, except this time the foams are produced in a closed mold. Results of the aldehyde measurements are indicated in Table 2.

TABLE-US-00003 TABLE 2 Comp. A* Ex. 1 Additives 0.5% IRGONOX 1135 0.5% IRGONOX 1135 0.1% Structure III compound 0.1% Structure XIII compound Formaldehyde, μg/m.sup.3 43 32 Acetaldehyde, μg/m.sup.3 136 112 Propionaldehyde, μg/m.sup.3 39 35 Total Aldehydes, μg/m.sup.3 218 179 *Not an example of this invention.

[0065] Significant reductions in the emitted quantities of all three aldehydes are again seen with the invention.