Emissions from polyurethane foam are a concern in many applications, especially when workers or end users are exposed to the foam within an enclosed space. Aldehyde emissions, such as formaldehyde, are a particular cause of concern. To reduce such aldehyde emissions, several methods have been developed to reduce the aldehyde content of the raw materials used in producing polyurethane foam. For example: U.S. Pat. No. 7,879,928 discloses a method for preventing the formation of aldehyde compounds in polyether or polyester polyols by incorporating a phenolic antioxidant and an aminic antioxidant into the polyol; U.S. Pat. Publ. No. 2009/0227758 discloses a method of reducing aldehydes in polyols and polyisocyanates by reacting the polyol with an oxazolidine-forming amino alcohol and the polyisocyanate with a nitroalkane; U.S. Pat. App. No. 2006/0141236 discloses the addition of a hydrazine to a polyol to act as an aldehyde-scavenger; U.S. Pat. App. No. 2008/0281013 discloses a method for reducing aldehyde emissions from a polyurethane foam by the addition of hydrogen sulfites and disulfites to the polyol component; U.S. Pat. App. No. 2009/0326089 discloses the use of a compound having a carbon amide group and a nitrile group to produce foams having a lowered emission of formaldehyde; WO2009/114329 teaches the addition of an oxazolidine-forming amino alcohol to a polyol and a nitroalkane to a polyisocyanate to reduce aldehyde emissions prior to their reaction in the production of a polyurethane; U.S. Pat. App. No. 2013/0203880 which teaches the addition of a polyhydrazodi-carbonamide polyol to the polyol component or a trimerized hexamethylene diisocyanate to the polyisocyanate component results in foams exhibiting decreased aldehyde emissions; and U.S. Pat. No. 5,506,329 discloses the use of certain aldimine oxazolidine compounds for scavenging formaldehyde from polyisocyanate-containing preparations.
In addition to polyols and polyisocyanates, amine catalysts are often utilized as a raw material in the production of polyurethane foam. The aldehydes found in amine catalysts may be derived from a variety of sources, for example, they may be present as a contaminant from the manufacture of the amine, or they may result from the oxidation or free radical attack of various carbon segments of the amine during storage. Methods to reduce the aldehyde content in amine catalysts include the use of inert gas (see U.S. Pat. Publ. No. 2013/0085193), primary amines (see U.S. Pat. Publ. No. 2011/0009513) free radical scavengers (see U.S. Pat. Publ. No. 2012/0271026) and combining an amine which has urea, amide, secondary-amine, primary amine or secondary-hydroxyl functionality with a carboxylic diacid or triacid (see U.S. Pat. Publ. No. 2013/0137787). Additionally, DE102008025005 teaches the use of urea nanoparticles in the treatment of amine catalysts to remove formaldehyde; however, when the amine catalyst is subsequently used in the production of foam, the urea is found as an emission in the foam and therefore the foam will generally fail environmental specifications for total emissions.
Despite the state of the art, there is a continuing need for developing other inexpensive and effective methods to reduce the aldehyde content in amine catalysts and in polyurethane foams. Preferably, such methods do not result in significant changes to the properties or performance of the amine catalyst or the resulting polyurethane foam. Moreover, preferably such methods do not produce other fugitive species which may provide additional environmental, health and safety issues to the amine catalyst and resulting polyurethane foam.
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