Scorch inhibiting compositions for polyurethane foams

Details Scorch inhibiting compositions for polyurethane foams Scorch inhibiting compositions for polyurethane foams

2000-06-02

2003-04-01

Cooney, Jr., John M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C252S182240, C252S182270, C521S131000, C521S134000, C521S137000, C521S155000, C521S170000, C560S330000, C560S336000, C560S359000

Reexamination Certificate

active

06541532

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to surprisingly effective antiscorch compositions for utilization within polyurethane foam production methods which utilize very popular tertiary amine catalysts. Such compositions require the presence of nominal yet effective amounts of organic cyclic ester materials. The ring systems of such materials appear to open during exposure to heat (during the curing process) and release carboxylic acids into the curing formulation. The tertiary amines become quenched by the carboxylic acids and thus do not exhibit heat destabilization. The resultant foams exhibit extremely low, if no, areas of excessive heating (i.e., scorch) and thus are substantially uniformly colored throughout. The processes and resultant foams are also contemplated within this invention.
BACKGROUND OF THE PRIOR ART
Polyurethane products, such as foams, resins, and the like, have traditionally been colored by pigments, polymeric colorants, and dyes. Generally, these colorations are performed in situ during foam, resin, etc., formation. For instance, polymeric colorants (i.e., polyoxyalkylenated colorants), such as those described in U.S. Pat. No. 4,284,279 to Cross et al., have been introduced within polyol compositions during slabstock foam production. The “colored” polyol then reacts with an isocyanate composition, in the presence of a catalyst possibly, to form the desired colored foam. Pigments have also been added in the past, most notably in solid, paste, or powder form, to a polyol stream to form the same type of colored foam products. Such foamed products require the presence of at least one catalyst to effectuate the desired reaction between the polyol and isocyanate components. The most prevalent catalysts, due to cost in producing, using, and disposing, are tertiary amine-based compounds. These catalysts include hydroxyl terminated types, such as the most popular types used throughout the industry, DMEA (dimethyl ethanol amine), DABCO TL catalysts (blends of triethylene diamine and 2-[[2-(dimethylamino)ethyl]methylamino]ethanol), and Texacat ZF10 (N,N,N′-trimethyl-N′-hydroxyethyl-bis(aminoethyl)ether). These catalysts unfortunately present the ability to exaggerate certain problems within the resultant foams, most notably scorch discolorations and/or degradations. Scorching is a common occurrence within exothermic foam-producing reactions, particularly when air flow is minimized within the foam-making procedure. Apparently, such catalysts react readily with free isocyanate due to their reactive hydroxyls within the polyurethane and/or colorants and/or other additives present. In particular, such reactivity is pronounced due to the avoidance of CFC-type blowing agents (which dissipate heat during high temperature exothermic reactions upon use). As it is, the foam blowing agents now utilized throughout the industry are ineffective at dissipating the very high temperatures generated during the curing process. These high temperatures appear to oxidize the aromatic amines formed by reaction with free radicals and hydroperoxides generated during the curing process. Such compounds react readily with hard polyurethane segments within the foam product to for quinonoids which consequently cause color bodies to form. These resultant color bodies thus create discolorations within the final foam product since they are always of a different color than the desired foam product. Apparently, such high temperature discolorations and degradations more readily occur between about 30 and 60 minutes after foam generation (during gelation and blowing of the foam-producing composition) has taken place. During such exothermic oxidation reactions, the foam is then “burned” by the high temperatures thereby producing the highly undesirable discolored areas within the resultant foam article. Such scorching may also cause degradation of “burned” portions of foam to the extent that the affected areas exhibit much different physical properties than the unaffected foam. In such an instance, generally the scorched portions will become more brittle (and more prone to breaking or crushing) than the properly formed foam.
Attempts at alleviating these particular problems have included the addition of relatively expensive, potentially environmentally unfriendly, and potentially toxic antioxidants, such as 2,6-di-t-butyl-4-methylphenol (BHT), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoate (Irganox® 1076, from Ciba Geigy), and octyl-3(3,5-di-t-butyl-4-hydroxyphenyl)propanoate (Irganox® 1135), within the curing process. This has proven only marginally effective; however, again due to the expense and the large amount of such antioxidant compounds required, as well as the large amount remaining within the foam (which may be troublesome due to environmental and safety concerns), such a procedure is necessarily avoided if at all possible. Since there is a 15 to 30 minute window of opportunity to control high temperature exposures, some foam producers have practiced forced air cooling of the foam-producing composition in the past to reduce scorch problems. Unfortunately, however, the cost involved with providing the necessary degree of heavy air flow (particularly in a specific limited direction) is prohibitive. With both procedures, the costs involved have resulted in transferred costs to the foam purchaser and end user. Alternative methods, either simpler and less inexpensive in nature, have not been forthcoming within the industry. As a result, any marked improvements in such a manner are of utmost importance within the polyurethane foam production industry. To date, again, there have been no significant or helpful improvements nor advancements disclosed within the pertinent prior art.
OBJECTS OF THE INVENTION
It is therefore an object of this invention to provide a relatively inexpensive and simple method of providing antiscorch within polyurethane foam producing methods which utilize amine-based catalysts. A further object is to provide an easy-to-add liquid composition for introduction within polyurethane foam production procedures which effectively reduces and/or eliminates scorch problems associated with amine-based catalysts. A further objective of this invention is to provide a colored polyurethane foam product which exhibits substantially no scorch discolorations without the need for the addition of an appreciable amount of antioxidants or significantly increased airflow during foam production.
SUMMARY OF THE INVENTION
Accordingly, this invention is directed to a method of producing a polyurethane foam article comprising the steps of: a) providing a polyol composition; b) providing an isocyanate composition; c) adding a composition comprising at most 3.0 php of an organic cyclic ester to either or both of the compositions in steps “a” and “b”, above; d) reacting all of the compositions from steps “a”, “b”, and “c” together in the presence of an tertiary amine-based catalyst. Also encompassed within this invention is the same method wherein at least one coloring agent (such as a pigment, polymeric colorant, dye, dyestuff, and the like) is added to any of the compositions within steps “a” and “b”. The particular compositions from these steps including the organic cyclic ester and, optionally, at least one coloring agent, are also contemplated within this invention. Although a coloring agent is preferred in some embodiments, white foams also exhibit such problematic discolorations due to scorch. Surprisingly, the inventive utilization of organic cyclic esters in specific proportions provides the same improvements in discoloration for such non-colored foam products as well. Furthermore, an polyurethane foam article produced by these methods is also contemplated within this invention.
In general, polyurethane foam is produced through the catalyzed polymerization of the reaction products of polyols and isocyanates. Such a reaction is well known throughout the polyurethane industry and has practiced for many years. The potential number and types of polyols u

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