Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-03-09
2002-10-29
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...
C252S182250, C252S182260, C252S182270, C252S182290, C521S167000, C521S173000, C521S174000
Reexamination Certificate
active
06472446
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to dimensionally stable polyurethane/polyiscyanurate foams and to polyol blends used to make such foams. Particularly, the present invention relates to polyol blends comprising a co-initiated propylene oxide polyether polyol, a polyester polyol, a hydrocarbon blowing agent and a compatibilizing agent.
BACKGROUND OF THE INVENTION
Due to environmental legislation restricting the use of chloroflorocarbons and hydrochloroflorocarbons as blowing agents, hydrocarbons are being employed in greater numbers as viable alternative blowing agents in the manufacture of rigid polyurethane or polyisocyanurate foams. Hydrocarbons are readily available and provide a cost-effective alternative to chloroflorocarbons and hydrochloroflorocarbons.
Due to the non-polar hydrophobic characteristics of hydrocarbons, they are only partially soluble in many polyols used to manufacture rigid polyurethane or polyisocyanurate foams. As a result of the poor solubility of hydrocarbon blowing agents, the blowing agent must usually be added to the polyol just prior to dispensing it through a mix head. The limited shelf life of hydrocarbon-polyol mixtures has limited the ability of storing batches for later use.
Another problem with these mixtures is their potential limited process phase stability or limited resistance to separation into layers of different composition. If there is a phase separation during the process, the hydrocarbon blowing agent has the tendency to rise to the top of the mixture and vaporize; thereby posing a potential safety hazard should the concentration of the hydrocarbon reach the explosion limit.
A phase separation during the process often causes non-uniform and uneven cell structures in the resultant polyurethane or polyisocyanurate foam. Such non-uniform cell structure can lead to variations in the properties of a foam product, such as the thermal conductivity or insulation value (R-factor). It would be undesirable to have such variations, particularly for foams utilized for insulation applications. The density of the foam may also be affected by the phase separation, leading to undesirable physical characteristics, such as increased hardness or brittleness.
SUMMARY OF THE INVENTION
There is provided a phase stable polyol blend composition comprising a polyether polyol, a polyester polyol, a compatibilizing agent and a hydrocarbon blowing agent. The polyol blend components including the hydrocarbon blowing agent forms a micro-emulsion and is therefore soluble and phase stable in the polyol blend. Upon forming a substantially homogeneous blend of the composition's components, the composition remains phase stable for at least 24 hours.
In one embodiment, the polyether polyol component comprises a sucrose and dipropylene glycol co-initiated propylene oxide polyether polyol.
In another embodiment, the polyester polyol utilized in the invention is a phthalic anhydride-initiated polyol.
The hydrocarbon blowing agents in the composition are C
4
-C
6
hydrocarbons or mixtures thereof. The pentanes are particularly preferred and are present in the polyol blend in amounts of from 20 to 30 parts by weight based on the total weight of the polyol composition.
The compatibilizing agents useful in the present invention are butanol-initiated propylene oxide polyether surfactants.
In another embodiment, an additional polyether polyol may be used as a substitute for the polyester polyol or may be combined with the composition. The additional polyether polyol is preferably a TDA-initiated propylene oxide polyether polyol.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The phase stable polyol blend of the present invention includes a propylene oxide polyether polyol, a polyester polyol, a compatibilizing agent and a hydrocarbon blowing agent.
The phase stable polyol blend is deemed to be phase stable when the blend composition has the capacity of retaining the hydrocarbon blowing agent in solution for a specified period of time; generally at least 24 hours, after blending the polyol composition components. Generally, a determination as to the phase stability of the composition is measured by mixing the hydrocarbon blowing agent with the propylene oxide polyether polyol, polyester polyol, and compatibilizing agent in a clear container having a lid. The container is then agitated vigorously to fully mix the composition, and the container is allowed to stand undisturbed for at least a 24-hour period. If there is no visible phase separation into distinct layers, or a cloudy appearance, then the composition is deemed to be phase stable.
Methods of forming polyoxyalkylene polyether polyols are well known, for example, by the base catalyzed addition of alkylene oxides to an initiator molecule containing reactive hydrogens such as a polyhydric alcohol. In one embodiment of the present invention, the initiator molecules are a combination, mixture or blend of a diol and a sugar. Other examples of such initiators include: glycerol; 1,1,1-trimethylolpropane; 1,1,1-trimethylolethane; 1,2,6-hexanetriol; pentaerythritol; and sorbitol. Other suitable initiators include both aliphatics and aromatics, such as ethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. Also included within the term “polyhydric alcohol” are compounds derived from phenol such as 2,2-bis(4-hydroxyphenyl)propane, commonly known as Bisphenol A. The polyether polyols may be prepared by any known process such as, for example, the process disclosed by Wurtz in 1859,
Encyclopedia of Chemical Technology,
Vol. 7, pp. 257-262, Published by Interscience Publishers, Inc. (1951) or in U.S. Pat. No. 1,922,459, incorporated herein by reference.
Examples of useful alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, amylene oxide, mixtures thereof, tetrahydrofuran, alkylene oxide-tetrahydrofuran mixtures, epihalohydrins, and aralkylene styrene. The alkylene oxides are added onto the initiator molecule and chain propagation is carried out in the presence of catalysts by either anionic polymerization or by cationic polymerization.
The preferred catalysts are potassium hydroxide, sodium hydroxide, alcoholates of potassium hydroxide, alcoholates of sodium hydroxide, cesium catalysts, amines, Lewis acid catalysts, or double metal complex catalysts, all of which are known in the art.
The phase stable polyol blend of the present invention contains a propylene oxide polyether polyol, a polyester polyol, a compatibilizing agent, and a hydrocarbon blowing agent. Other ingredients that may be included in the phase stable polyol blend are additional polyols, catalysts, surfactants, other blowing agents, flame retardants, fillers, stabilizers and other additives.
The propylene oxide polyether polyol useful in accordance with the present invention comprises a sucrose and dipropylene glycol co-initiated polyoxyalkylene polyether polyol having only propylene oxide as the alkylene oxide. It has been found that the addition of other alkylene oxides, for example, ethylene oxide to the initiator molecules may adversely affect the solubility of the hydrocarbon blowing agent in the polyol composition.
The sucrose and dipropylene glycol co-initiated polyol preferably has a nominal functionality between 4 and 5, even more preferably of 4.4. The co-initiated polyol has a hydroxyl number from 250 to 400 meq polyol/g KOH. Even more preferably, the polyol has a hydroxyl number of from 300 meq polyol/g KOH to 400 meq polyol/g KOH. The sucrose and dipropylene glycol co-initiated polyol is preferably present in an amount of from 30 to 80 parts by weight based on the overall weight of all components of the phase stable polyol blend.
In one embodiment of the present invention an additional polyether polyol, a toluene diamine (TDA)-initiated polyoxyalkylene polyether polyol having only propylene oxide as the alkylene oxide may be included. The TDA-initiated poly
Patterson Jim
Riley Robert E.
White, III Walter R.
BASF Corporation
Borrego Fernando A.
Cooney Jr. John M.
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