Reactive catalyst compositions for improving water blown...

Details Reactive catalyst compositions for improving water blown... Reactive catalyst compositions for improving water blown...

1997-06-20

2001-05-15

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...

C521S155000, C521S170000

Reexamination Certificate

active

06232356

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to tertiary amine catalysts for producing polyurethane foam.
Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. One such additive is a chlorofluorocarbon (CFC) blowing agent which vaporizes as a result of the reaction exotherm, causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Production of water-blown foams, in which blowing is performed with CO2 generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with isocyanate to generate CO2) and gelling (reaction of polyol with isocyanate).
The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of a particular polyurethane foam. If a catalyst promotes the blowing reaction to a too high degree, much of the CO2 will be evolved before sufficient reaction of isocyanate with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in collapse of the foam. A foam of poor quality will be produced. In contrast, if a catalyst too strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam, this time characterized by high density, broken or poorly defined cells, or other undesirable features, will be produced.
Tertiary amine catalysts generally are malodorous and offensive and many have high volatility due to their low molecular weight. Release of tertiary amines during foam processing may present significant safety and toxicity problems, and release of residual amines from consumer products is generally undesirable.
Amine catalysts which contain urea functionality have an increase in molecular weight and hydrogen bonding and reduced volatility and odor when compared to related structures which lack this functionality. Furthermore, catalysts which contain urea functionality chemically bond into the urethane during the reaction and are not released from the finished product. Catalyst structures which embody this concept are typically of low to moderate activity and promote both the blowing (water-isocyanate) and the gelling (polyol-isocyanate) reactions to varying extents.
U.S. Pat. No. 4,644,017 discloses the use of certain diffusion stable amino alkyl ureas having tertiary amino groups in the production of a polyisocyanate addition product which do not discolor or change the constitution of surrounding materials. Specifically taught are Catalyst A and Catalyst D which are reaction products of dimethylaminopropylamine and urea.
U.S. Pat. No. 4,007,140 discloses the use of N,N′-bis(3dimethylaminopropyl)urea as a low odor catalyst for the manufacture of polyurethanes.
U.S. Pat. No. 4,194,069 discloses the use of N-(3-dimethylaminopropyl)-N′-(3-morpholino-propyl)urea; N,N′-bis(3-dimethylaminopropyl)urea and N,N′-bis(3-morpholinopropyl)urea as catalysts for producing polyurethane foams.
U.S. Pat. No. 4,094,827 discloses the use of certain alkyl substituted ureas including N,N-bis(3-dimethylaminopropyl)urea which provide lower odor and a delay in the foaming reaction that aids in the production of polyurethane foam.
U.S. Pat. No. 4,330,656 discloses the use of N-alkyl ureas as catalysts for the reaction of 1,5-napthylene diisocyanate with polyols or for the chain extension of prepolymers based upon 1,5-napthylene diisocyanate without accelerating atmospheric oxidation.
DE 30 27 796 A discloses the use of higher molecular weight dialkyl aminoalkyl ureas as reduced odor catalysts for the production of polyurethane foam.
EP 499 873 discloses the preparation and use of pyrrolidines as catalysts for the polyisocyanate polyaddition process.
SUMMARY OF THE INVENTION
The present invention provides a reactive catalyst composition for making a water blown flexible polyurethane foam. The catalyst composition comprises a tertiary amino alkyl urea and/or bis(tertiary amino alkyl) urea in combination with either a gelling catalyst or blowing catalyst. The use of such catalyst composition improves the physical properties of the polyurethane foam.
The reactive catalysts contain ureido functionality which enables the catalyst to react into the polyurethane matrix. These reactive catalysts can be used as gelling catalysts or blowing catalysts with complementary blowing or gelling co-catalysts, respectively, which may or may not contain reactive functional groups to produce polyurethane foam materials. The reactive catalysts produce polyurethane foams which have no amine emissions.
The use of these catalysts in conjunction with complementary gelling or blowing co-catalysts improves physical properties and enhances processibility of the foam. As gelling catalysts, these urea catalysts in conjunction with blowing co-catalysts improve the airflow of the foam. Improved airflow means improved porosity and openness of the foam which is an indication of improved dimensional stability of the foam. As gelling catalysts, these urea catalysts in conjunction with blowing co-catalysts also improve, i.e., reduce, the force-to-crush of the foam. Reduced force-to-crush means the foam is more easily compressed which is an important advantage for minimizing foam shrinkage during processing. As blowing catalysts, these urea catalysts in conjunction with gelling co-catalysts improve the load bearing properties of the foam.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst compositions according to the invention catalyze the reaction between an isocyanate functionality and an active hydrogen-containing compound, i.e. an alcohol, a polyol, an amine or water, especially the urethane (gelling) reaction of polyol hydroxyls with isocyanate to make polyurethanes and the blowing reaction of water with isocyanate to release carbon dioxide for making foamed polyurethanes.
The flexible polyurethane foam products, slab and molded, are prepared using any suitable organic polyisocyanates well known in the art including, for example, hexamethylene diisocyanate, phenylene diisocyanate, toluene diisocyanate (“TDI”) and 4,4′-diphenylmethane diisocyanate (“MDI”). Especially suitable are the 2,4- and 2,6-TDI's individually or together as their commercially available mixtures. Other suitable isocyanates are mixtures of diisocyanates known commercially as “crude MDI”, marketed as PAPI by Dow Chemical, which contain about 60% of 4,4′-diphenylmethane diisocyanate along with other isomeric and analogous higher polyisocyanates. Also suitable are “prepolymers” of these polyisocyanates comprising a partially prereacted mixture of a polyisocyanate and a polyether or polyester polyol.
Illustrative of suitable polyols as a component of the polyurethane composition are the polyalkylene ether and polyester polyols. The polyalkylene ether polyols include the poly(alkylene oxide) polymers such as poly(ethyiene oxide) and poly(propylene oxide) polymers and copolymers with terminal hydroxyl groups derived from polyhydric compounds, including diols and triols; for example, among others, ethylene glycol, propylene glycol, 1,3-butane diol, 1,4-butane diol, 1,6-hexane diol, neopentyl glycol, diethylene glycol, dipropylene glycol, pentaerythritol, glycerol, diglycerol, trimethylol propane and like low molecular weight polyols.
In the practice of this invention, a single high molecular weight polyether polyol may be used. Also, mixtures of high molecular weight polyether polyols such as mixtures of di- and trifunctional materials and/or different molecular weight or different chemical composition materials may be used.
Useful polyester polyols include those produced by reacting a dicarboxylic acid with an excess o

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