Low Emissions Polyurethane Foam Made with Isocyanate Reactive Amine Catalyst

Abstract

Tertiary amine catalysts having isocyanate reactive groups that are capable of forming thermally stable covalent bonds able to withstand temperatures from 120° C. and higher and up to 250° C. are disclosed. These catalyst can be used to produce polyurethane foam having the following desirable characteristics: a) very low chemical emissions over a wide range of environmental conditions and isocyanate indexes (e.g., indexes as low as 65 but higher than 60) ; b) sufficient hydrolytic stability to maintain the catalyst covalently bound to foam without leaching of tertiary amine catalyst when foam is exposed to water or aqueous solutions even at temperatures higher than ambient (temperature range 25° C. to 90° C.); and c) stable contact interface between the polyurethane polymer and other polymers (for example polycarbonate) with minimal migration of tertiary amine catalyst from polyurethane polymer to other polymers yielding no noticeable polymer deterioration at the point of contact even under conditions of heat and humidity.

Description

[0001]This Application claims the benefit of Application No 62 / 049,568, filed on Sep. 12, 2014. The disclosure of Application No. 62 / 049,568 is hereby incorporated by reference.FIELD OF THE INVENTION[0002]The instant invention relates to tertiary amine catalysts having isocyanate reactive groups that are capable of forming thermally stable covalent bonds and withstanding temperatures from about 120° C. and higher and up to about 250° C. The instant invention also relates to using the inventive catalysts to produce polyurethane foam having the following desirable characteristics: a) very low chemical emissions over a wide range of environmental conditions and isocyanate indexes (e.g., indexes as low as about 65 but higher than about 60); b) sufficient hydrolytic stability to maintain the catalyst covalently bound to foam without leaching of tertiary amine catalyst when foam is exposed to water or aqueous solutions even at temperatures higher than ambient (e.g., temperature range abou...

AI Technical Summary

Benefits of technology

The invention addresses issues with conventional reactive catalysts used in polyurethane foam production. The gelling amine catalyst reduces amine emissions and exposure to end users, while also preventing material deterioration during extreme environmental conditions. The catalyst also helps achieve optimal foam physical properties and foam rate kinetics. The resulting foam has low to no amine emissions, excellent physical properties, and minimal deterioration of other materials. The catalyst is retained in the polyurethane polymer, resulting in minimal or no amine leakage during water contact. This catalyst also reduces use levels of tertiary amine and improves overall emission reduction. Additionally, the foam produced has sufficient hydrolytic stability that allows for the retention of the catalyst in the polyurethane polymer.

Problems solved by technology

This approach can have some limitations because the functionalized tertiary amine can react with isocyanate prematurely causing undesired side effects such as polymer chain termination which would result in poor physical properties, excessive cell opening or foam collapse or excessive cross linking which can result in extensive shrinkage and poor dimensional stability.

Products such as dimethylaminopropyl urea, bis(dimethylaminopropyl) urea, bis(dimethylaminopropyl) amine and N,N-bis(dimethylaminopropyl)-N-(2-hydroxypropyl) amine can provide acceptable physical properties as compared to industry standards whereas most conventional reactive catalysts cannot always achieve today's consumer and manufacturer requirements.

However, the finished articles produced are not typically emissions-free, and VOC and FOG values can reach several hundred ppm according to VDA 278 detection method.

However, in many cases foam produced with some of these reactive catalysts can still have amine emissions because the covalent chemical bonds that holds the amine catalysts into the polyurethane polymer are not sufficiently stable at the temperature of the test.

If the hydrolytic stability of the chemical bond between the polymer and the tertiary amine is not sufficient then tertiary amine catalyst can leach from the polyurethane polymer and may allow amines to directly contact skin leading to skin irritation or skin sensitization.

This is a requirement that is difficult to meet because at low isocyanate index there is not sufficient NCO groups able to react with all OH groups from polyols and water so the new amine additive needs to be able to provide simultaneously sufficient catalytic activity to provide good quality foam and effectively compete with OH groups from polyols and water to become part of the polyurethane polymer and be retained in the polymer once the polymerization process is completed.

In addition, water contacting foam produced using this catalyst can have an increased alkalinity.

One limitation of the composition and method disclosed is lack of thermal stability of the chemical bond as illustrated in the examples shown in U.S. Pat. No. 6,858,654 where 190 ppm decomposition products from bis(3-dimethylaminopropyl)(2-hydroxypropyl)amine is observed when foam is heated to 120° C. during testing according to VDA278 emissions test method.

Limitations of these compounds includes emissions due to the lack of functionality able to react with NCO or inability to form thermally stable covalent bonds as well as hydrolytic instability.

Such a need can become a challenge as the isocyanate index is reduced to low levels (Index as low as 65 but higher than 60) because there is, stoichiometrically, an insufficient amount of NCO to react with all OH from polyol and water.

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