Compositions – Compositions containing a single chemical reactant or plural... – Organic reactant
Reexamination Certificate
1999-05-04
2001-11-27
Foelak, Morton (Department: 1711)
Compositions
Compositions containing a single chemical reactant or plural...
Organic reactant
C521S174000
Reexamination Certificate
active
06322722
ABSTRACT:
BACKGROUND OF THE INVENTION
Polyether polyols can be used in the preparation of polyurethane and polyisocyanurate foams (foams), and are typically prepared from propylene oxide and/or ethylene oxide, using initiators such as sucrose, sorbitol, or glycerol, for example. Polyurethane foams prepared from polyether polyols are used in a variety of applications, including construction, appliance, automotive, and carpet applications. Rigid foams, in particular, are used in appliance and construction applications, for example. A polyol mixture used to prepare polyurethane foam formulations can include a blowing agent, in addition to other components. Blowing agents can be used to create cellular structures within a foam. Some conventional blowing agents, such as halogenated hydrocarbons, for example, can be perceived as harmful to the environment.
Non-halogenated hydrocarbon blowing agents, that is, hydrocarbon blowing agents (HCBAs) are important alternatives to traditional halogenated hydrocarbon blowing agents. Hydrocarbons such as pentane and cyclopentane have been used successfully as blowing agents in polyurethane systems, and are not believed to harm the ozone layer of the atmosphere. The use of hydrocarbons as blowing agents is demonstrated in, for example, U.S. Pat. No. 3,072,582. The use of hydrocarbon blowing agents can present problems, however.
Insolubility of hydrocarbon blowing agents in polymer formulations can lead to processing problems, particularly in producing polyurethane and polyisocyanurate foam products, for example. The possibility of phase separation of HCBAs from a foam formulation makes it necessary to take measures to maintain a homogeneous mixture or dispersion when HCBAs are used. One way of using HCBAs in conventional polyol mixtures can be to limit the amount of HCBA included in a polyol mixture to a low concentration, in order to avoid separation of the HCBA from the mixture. While separation of the HCBA can be avoided, the amount of blowing agent actually included in a polyurethane foam formulation can be an important factor in determining the quality of a polyurethane foam product. Having too low a concentration of blowing agent in a foam formulation can detrimentally affect the quality of a foam. For example, using too little blowing agent can cause the density of the foam to be too high. To prepare a low density foam, that is, a foam having a density of less than 2.5 lbs per cubic foot (pcf), it can be necessary to include more water than would otherwise be desirable when using conventional blowing agents. Increasing the amount of water in a foam formulation can detrimentally affect the
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dimensional stability and long-term thermal conductivity of a foam due to the relatively fast rate of diffusion of carbon dioxide from a foam, compared with a hydrocarbon or halogenated hydrocarbon blowing agent.
HCBAs such as pentane and cyclopentane can be particularly incompatible with polyols substantially prepared using ethylene oxide and/or propylene oxide. Aromatic polyester polyols can incorporate only a limited amount of HCBAs. Surfactants can aid in making the components of a polyol mixture compatible, but are not completely helpful in making HCBAs compatible in a polyol mixture.
It would be desirable in the art of preparing polyurethane foams to utilize hydrocarbon blowing agents in a polyurethane foam formulation. It would also be desirable in the art of preparing polyurethane foams to make a low density foam from a polyurethane foam formulation that includes hydrocarbon blowing agents but does not require additional water in the formulation. Finally, it would be desirable in the art of preparing polyurethane foams to include hydrocarbon blowing agents in a foam formulation at a concentration that will yield a low density foam, wherein the hydrocarbon blowing agent does not phase separate from the formulation.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a polyol mixture comprising: a polyol substantially derived from butylene oxide, and at least one HCBA, wherein solubility of the HCBA in the polyol is increased by at least about 30% over HCBA solubility in a polyol not substantially derived from butylene oxide.
In another aspect, the present invention is a foam prepared from a polyol mixture wherein the polyol mixture comprises: a polyol substantially derived from butylene oxide, and at least one HCBA, wherein solubility of the HCBA in the polyol is increased by at least about 30% over HCBA solubility in a polyol not substantially derived from butylene oxide.
In still another aspect, the present invention is a process for preparing a foam comprising the steps: (1) forming a reactive mixture by admixing a polyisocyanate with a polyol mixture, wherein the polyol mixture comprises: a polyol derived substantially from butylene oxide; a catalyst; a surfactant, and at least one HCBA, wherein solubility of the HCBA in the polyol is increased by at least about 30% over HCBA solubility in a polyol not substantially derived from butylene oxide; (2) pouring the reactive mixture into a mold; (3) allowing the reactive mixture to cure to a tack-free foam; and (4) optionally removing the foam from the mold.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In one embodiment, the present invention is a polyol mixture useful for preparing polyurethane and polyisocyanurate foams. Hereinafter, it is to be understood that for the purposes of the present invention, “polyurethane” can refer to both polyurethane polymers as well as to polyisocyanurate polymers. A polyol mixture of the present invention includes a polyol and at least one HCBA, together with optional components. Polyols useful in the practice of the present invention are polyether polyols substantially derived from 1,2-butylene oxide(butylene oxide), including aliphatic and aromatic polyether polyols. For example, Bisphenol-A can be modified to obtain a polyol that is useful in the practice of the present invention. Polyols of the present invention can be prepared exclusively from butylene oxide monomer, or from mixtures of butylene oxide with other oxide monomers. For example, polyether polyols of the present invention can be prepared from a combination of butylene oxide and alkylene oxides having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, and 2,3-butylene oxide. A polyol of the present invention is substantially derived from butylene oxide if it includes at least about 25 percent by weight butylene oxide. Preferably, a polyol of the present invention is substantially derived from butylene oxide if it includes at least about 50 percent, more preferably at least about 70 percent, and most preferably at least about 80 percent by weight of the polyol is derived from butylene oxide. Polyols substantially derived from butylene oxide (BO polyols) can be reacted with isocyanate groups under conditions suitable for preparing a polyurethane.
Polyols of the present invention can be prepared by methods known and practiced in the art of preparing polyether polyols. Such methods are described, for example, in U.S. Pat. No. 3,153,002. Generally, a polyol of the present invention can be prepared by reacting butylene oxide and an initiator in the presence of a catalyst. The ratio of initiator to alkylene oxide can be any ratio that is effective for making polyols suitable for use in the present invention, and will depend on the targeted molecular weight and functionality of the base polyol. The catalyst can be alkaline or acidic. Polyols of the present invention can be prepared, for example, by combining butylene oxide, with an initiator such as ethylene glycol or propylene glycol, in the presence of a catalyst.
Catalysts suitable for use in the practice of the present invention include, for example, amine compounds such as dimethylcyclohexylamine, dimethylethanolamine, and diethylethanolamine, like compounds, and mixtures thereof; Group I and Group II metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, lithium hydroxide, like compounds a
Bhattacharjee Debkumar
Latham Dwight D.
Nelson Gilbert L.
Foelak Morton
The Dow Chemical Company
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