Dispersion polyols for hypersoft polyurethane foam

Details Dispersion polyols for hypersoft polyurethane foam Dispersion polyols for hypersoft polyurethane foam

2000-03-06

2001-04-17

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

Reexamination Certificate

active

06218444

ABSTRACT:

TECHNICAL FIELD
The present invention pertains to Polyoxyalkylene Polyol dispersions and their use in preparing Polyurethane foam, particularly hypersoft polyurethane foam. The polyoxyalkylene dispersion polyols comprise a stable liquid-liquid dispersion of two distinct polyoxyalkylene polyols.
BACKGROUND ART
Although polyurethane foam production can be described as a mature technology, processing and performance difficulties associated with polyurethane foam continue to be addressed by the industry. Many of these difficulties arise or are exacerbated when processing and/or performance windows are narrow.
For example, the Montreal Protocol, which mandanted the change from chlorofluorocarbons and other halogenated hydrocarbon physical blowing agents to “environmentally acceptable” blowing agents, particularly to the use of water as a reactive blowing agent, created numerous problems, some of which are being addressed even today. The trend to reduced density in products such as soft cushioning foam has also required significant research to enable efficient production of high quality low density foam having the required softness and durability. Recently, hypersoft foam has been increasingly in demand, and its efficient production has required non-traditional processing improvements.
Hypersoft foam may be produced by reacting a di- or polyisocyanate, preferably toluene diisocyanate (“TDI”) with a polyol component which includes a high polyoxyethylene content polyol. Thus far, hypersoft foams have also required, in addition, a conventional, high polyoxypropylene-content polyol, in order to be successfully produced. While use of these very different polyols has enabled production of hypersoft foam, the foam processing latitude is often marginal. Moreover, these polyols are not physically compatible, and their blends tend to quickly become inhomogeneous after mixing, requiring inventory of two separate polyols and their separate metering to the mixhead.
It would be desirable to provide a polyol blend which is capable of preparing hypersoft and other polyurethane foams without the necessity of inventorying several polyols for this purpose. It would be further desirable to produce polyol blends which avoid rapid separation during storage, and which offer improved processing latitude when used in preparing hypersoft polyurethane foams.
DISCLOSURE OF INVENTION
It has now been surprisingly discovered that compositions containing a first polyol having a substantial, high polyoxypropylene content internal block and a high polyoxyethylene content external block; and at least a second polyol consisting largely of a high oxyethylene-content block, form a fine, liquid-liquid dispersion which resists separation and layering and is highly suitable for preparing polyurethane foams, particularly hypersoft polyurethane foams. It has been further surprisingly discovered that such polyol blends may be elegantly produced in situ by the catalyzed oxyalkylation of a moderate to high molecular weight polyoxypropylene oligomer with a mixture of alkylene oxides containing in excess of 50 weight percent ethylene oxide, in the presence of an oxyalkylatable low molecular weight starter. The catalyst may be a standard basic oxyalkylation catalyst or preferably a double metal cyanide complex. Hypersoft polyurethane foams may be prepared directly from the subject invention dispersions without the need for an additional, high polyoxypropylene content polyol.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polyol blends of the subject invention are termed herein “dispersion polyols”, and consist of a liquid-liquid dispersion of minimally two polyols. These dispersions are stable to sedimentation, separation, or “layering” for minimally about three days of storage, and may range in transparency from clear to milky depending upon the dispersed phase concentration and droplet size. Many of the preferred dispersion polyols of this invention are stable for significantly longer time periods. In addition, if separation should occur, they can be easily returned to a fine uniform dispersion by mechanical mixing. “Microscopically homogenous” blends, i.e. those which are true solutions rather than dispersions, are not part of this invention. The term “dispersion” as used herein includes “emulsions” and “microemulsions”.
The dispersion polyols of the subject invention comprise minimally two distinct polyols, but may consist of three or more polyols as well. At least one polyol, which is believed to constitute the dispersed phase, is a relatively high molecular weight polyol having a substantial high polyoxypropylene content internal block and a high oxyethylene content external block. At least a second polyol has no substantial, high polyoxypropylene content block, but has a substantial, in relation to its molecular weight, high polyoxyethylene content block. The mandatory first and second polyols employed herein are incompatible in the sense that they do not form true solutions at the relative concentrations used in the dispersion polyol blend.
Both polyols may have nominal functionalities of 2 or higher, preferably from 2 to 8, and more preferably from 2 to 6. Diols and triols are preferred. The polyol actual functionalities will depend upon their manner of preparation, specifically upon the content of unsaturation which is indicative of monol byproduct content. Polyols prepared employing double metal cyanide catalysts and other catalysts which allow preparation of polyols with levels of unsaturation less than 0.02 meq/g and preferably less than 0.01 meq/g will generally have actual functionalities which are within 85-90% or more of the nominal functionality. These polyols are preferred, though suitable dispersion polyols may also be produced with standard basic oxyalkylation catalysts which generally yield polyols with somewhat higher unsaturation levels.
A first necessary polyol, as previously disclosed, is a polyol having a substantial, high oxypropylene content internal block, and an external, high oxyethylene content block. The internal block should have a minimum equivalent weight of about 700 Da (Daltons) and preferably 1000 Da or higher. This block should comprise minimally 65 weight percent oxypropylene moieties, preferably 70 weight percent, more preferably weight percent, and most preferably 90 weight percent or more of oxypropylene moieties. While homopolyoxypropylene blocks are acceptable, particularly when produced by catalysts other than double metal cyanide complex catalysts, i.e. by basic catalysts, calcium naphthenate, etc., it is preferred that the internal block contain from about 1.5% to about 30% oxyethylene moieties, more preferably 2% to 20 weight percent, and most preferably about 5 to about 10 weight percent oxyethylene moieties. Oxyacetylene moieties other than oxypropylene and oxyethylene may be present in minor quantities, e.g. C
3
or higher oxyalkylene moieties such as oxybutylene, oxy-n-propylene (derived from oxetane), chloro-substituted oxyalkylene moieties, and the like.
The external block of the first polyol will constitute from about 10 weight percent to about 50 weight percent of the total first polyol weight, more preferably from about 15 weight percent to about 40 weight percent, and most preferably from about 20 weight percent to about 35 weight percent. The external block is minimally about 50 weight percent oxyethylene moieties, more preferably minimally 60 weight percent oxyethylene moieties, and most preferably 70 to about 85 weight percent oxyethylene moieties. External blocks which are greater than 85 percent oxyethylene may also be suitable, particularly when prepared from catalysts other than double metal cyanide catalysts. Most preferably, the remaining moieties of the external block are oxypropylene moieties, but these may also be derived from alkylene oxides other than propylene oxide, e.g. from 1,2-butylene oxide, 2,3-butylene oxide, halogenated alkylene oxides, styrene oxide, etc., and also from oxetane and other monomers copolymerizable with ethylene oxide.
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