Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1997-06-10
2003-07-01
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S155000, C521S902000, C252S067000, C252S069000, C252S364000, C062S114000, C570S134000, C510S415000, C510S408000, C510S177000, C585S001000, C585S002000
Reexamination Certificate
active
06586488
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to azeotrope-like compositions that include 1,1,1,3,3-pentafluoropropane and at least one hydrocarbon selected from the group n-pentane, isopentane, cyclopentane, n-hexane and isohexane. The compositions of the invention are useful as blowing agents in the manufacture of rigid and flexible polyurethane foams and polyisocyanurate foams as well as aerosol propellants.
BACKGROUND OF THE INVENTION
Rigid polyurethane and polyisocyanurate foams are manufactured by-reacting and foaming a mixture of ingredients, in general an organic polyisocyanate with a polyol or mixture of polyols, in the presence of a volatile liquid blowing agent. The blowing agent is vaporized by the heat liberated during the reaction of isocyanate and polyol causing the polymerizing mixture of foam. This reaction and foaming process may be enhanced through the use of various additives such as amine or tin catalysts and surfactant materials that serve to control and adjust cell size and to stabilize the foam structure during formation. Foams made with blowing agents such as CCl
3
F (“CFC-11”) and CCl
2
FCH
3
(“HCFC-141b”) offer excellent thermal insulation, due in part to the very low thermal conductivity of CFC- 11 and HCFC- 141b vapor, and are used widely in insulation applications.
Flexible polyurethane foams are generally open-cell foams manufactured using an excess of diisocyanate that reacts with water, also included as a raw material, producing gaseous carbon dioxide and causing foam expansion. The flexible foams are widely used as cushioning materials in items such as furniture, bedding, and automobile seats. Auxiliary physical blowing agents such as methylene chloride and/or CFC-11 are required in addition to the water/diisocyanate blowing mechanism in order to produce low density, soft grades of foam.
Many foam producers have converted from chlorofluorocarbon (“CFC”) blowing agents, such as CFC- 11, to environmentally safer hydrochlorofluorocarbon (“HCFC”) agents and hydrocarbons. However, HCFCs, such as HCFC-141b, also have some propensity to deplete stratospheric ozone albeit significantly less than that of the CFCs.
Hydrocarbon agents, such as n-pentane, isopentane, and cyclopentane, do not deplete stratospheric ozone, but are not optimal agents because foams produced from these blowing agents lack the same degree of thermal insulation efficiency as foams made with the CFC or HCFC blowing agents. Further, the hydrocarbon blowing agents are extremely flammable. Because rigid polyurethane foams must comply with building code or other regulations, foams expanded with a blowing agent composed only of hydrocarbons often require addition of expensive flame retardant materials to meet the regulations. Finally, hydrocarbon blowing agents are classified as Volatile Organic Compounds and present environmental issues associated with photochemical smog production in the lower atmosphere.
In contrast to the foregoing blowing agents, hydrofluorocarbons (“HFCs”) such as 1,1,1,3,3-pentafluoropropane (“HFC-245fa”) do not deplete stratospheric ozone. This invention provides azeotrope-like compositions based on HFC-245fa and hydrocarbons for use as blowing agents for polyurethane-type foams.
Azeotropic blowing agents possess certain advantages such as more efficient blowing than the individual components, lower thermal conductivity or K-factor, and better compatibility with other foam raw materials. Additionally, azeotropic or azeotrope-like compositions are desirable because they do not fractionate upon boiling or evaporation. This behavior is especially important where one component of the blowing agent is very flammable and the other component is nonflammable because minimizing fractionation during a leak or accidental spill minimizes the risk of producing extremely flammable mixtures.
This invention provides azeotrope-like compositions that are environmentally safe substitutes for CFC and HCFC blowing agents, that have a reduced propensity for photochemical smog production, and that produce rigid and flexible polyurethane foams and polyisocyanurate foams with good properties. The invention also provides blowing agent compositions with reduced flammability hazards compared to hydrocarbon blowing agents.
Foams made with the blowing agent compositions of this invention exhibit improved properties, such as thermal insulation efficiency, improved solubility in foam raw materials, and foam dimensional stability, when compared to foams made with hydrocarbon blowing agents alone. Although the compositions of the invention contain a hydrocarbon, it is present as a minor component and, overall, the compositions are nonflammable.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides azeotrope-like compositions comprising 245fa and at least one hydrocarbon selected from the group consisting of n-pentane, isopentane, cyclopentane, n-hexane, isohexane, and mixtures thereof that are useful as blowing agents for polyurethane and polyisocyanurate foams.
For azeotrope-like mixtures containing n-pentane, the azeotrope-like compositions comprise from about 5 to about 70 percent by weight n-pentane and from about 95 to about 30 percent by weight HFC-245fa and have a boiling point 9±1° C. at 745 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 35 percent by weight n-pentane and from about 95 to about 65 percent by weight HFC-245fa and have a boiling point of 9±0.5° C. at 745 mm Hg.
For azeotrope-like mixtures containing isopentane, the azeotrope-like compositions comprise from about 5 to about 70 percent by weight isopentane and from about 95 to about 30 percent by weight HFC-245fa and have a boiling point 7±1° C. at 748 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 45 percent by weight isopentane and from about 95 to about 55 percent by weight HFC-245fa and have a boiling point of 7±0.5° C. at 748 mm Hg
For azeotrope-like mixtures containing cyclopentane, the azeotrope-like compositions comprise from about 5 to about 60 percent by weight cyclopentane and from about 95 to about 40 percent by weight HFC-245fa and have a boiling point 11.7±1° C. at 745 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 40 percent by weight cyclopentane and from about 95 to about 60 percent by weight HFC-245fa and have a boiling point of 11.7±0.5° C. at 745 mm Hg.
For azeotrope-like mixtures containing n-hexane, the azeotrope-like compositions comprise from about 2 to about 45 percent by weight n-hexane and from about 98 to about 55 percent by weight HFC-245fa and have a boiling point 14±1° C. at 749 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 2 to about 30 percent by weight n-hexane and from about 98 to about 70 percent by weight HFC-245fa and have a boiling point of 14±0.5° C. at 749 mm Hg.
For azeotrope-like mixtures containing isohexane, the azeotrope-like compositions comprise from about 2 to about 45 percent by weight isohexane and from about 98 to about 55 percent by weight HFC-245fa and have a boiling point 13.5±1° C. at 744 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 2 to about 25 percent by weight isohexane and from about 98 to about 75 percent by weight HFC-245fa and have a boiling point of 13.5±0.5° C. at 744 mm Hg.
The azeotrope-like compositions of the invention exhibit zero ozone depletion and low global warming potential. Further, the HFC-245fa component reduces the flammability hazard associated with handling and using the blowing agent, especially when compared to the use of the hydrocarbon component alone.
Polyurethane foams expanded with the blowing agents of the invention exhibit superior performance to foams expanded with the hydrocarbon blowing agent alone. The thermal conductivity of foams prepared using the azeotrope-like compositions of the invention is lower, hence superior,
Allied-Signal Inc.
Sergent Rabon
Szuch Colleen D.
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