Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-04-17
2003-05-13
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...
C521S131000, C521S167000, C521S170000, C521S174000
Reexamination Certificate
active
06562880
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the production of rigid polyurethane or polyisocyanurate foams in which an HFC (hydrogen-containing fluorocarbon) is used in combination with an added amount of carbon dioxide.
BACKGROUND OF THE INVENTION
Processes for the production of rigid polyurethane foams are known. See, for example, U.S. Pat. Nos. 3,085,085; 3,153,002; 3,222,357; and 4,430,490.
At the present time, a major concern of foam producers, particularly rigid foam producers, is the development of rigid foam systems in which the ozone depleting chlorofluorocarbon (“CFC”) or hydrochlorofluorocarbon (“HCFC”) blowing agent is replaced with a more environmentally acceptable blowing agent. HFCs (hydrogen containing fluorocarbons), and hydrocarbons such as n-pentane, cyclopentane, isopentane and blends of these blowing agents are presently considered to be possible alternatives.
U.S. Pat. No. 4,900,365, for example, teaches that a mixture of trichlorofluoromethane, a dichlorofluoroethane selected from a specified group and isopentane is useful as a blowing agent for the preparation of polyurethane foams. Dishart et al's paper entitled “The DuPont Program on Fluorocarbon Alternative Blowing Agents for Polyurethane Foams”,
Polyurethanes World Congress
1987, pages 59-66 discusses the investigation of various HCFCs as possible blowing agents for rigid polyurethane foams. Neither of these disclosures, however, teaches a process for the production of rigid polyurethane foams having good physical properties from polyols with an HFC blowing agent.
U.S. Pat. No. 4,972,002 discloses a process for the production of cellular plastics in which an emulsion is used. A low boiling fluorinated or perfluorinated hydrocarbon or sulfur hexafluoride is emulsified in one of the starting materials (i.e., the isocyanate, polyol, etc.) from which the foam is to be produced
U.S. Pat. No. 5,169,873 discloses a process for the production of foams in which the blowing agent is a mixture of at least one fluoroalkane corresponding to a specified formula and at least one fluorinated ether corresponding to a specified formula.
U.S. Pat. No. 5,164,419 discloses a process for the production of polyurethane foams in which 1,1-difluoroethane in combination with a minimum amount of water is used as the blowing agent. However, the only foam described in this disclosure had a high k-factor of 0.18 BTU-in/hr-ft
2
-° F.
U.S. Pat. No. 5,164,418 discloses a process for producing isocyanate-based foams in which the blowing agent is at least 10 mol % of a fluoroalkane. Mixtures of a fluoroalkane and significant amounts of water (i.e., greater than 20%) are exemplified.
U.S. Pat. No. 4,931,482 discloses the use of 1,1,1,4,4,4-hexafluorobutane as a blowing agent to produce isocyanate-based foams such as polyurethane and polyisocyanurate foams. The disclosed foams are made by reacting an isocyanate with any of the known isocyanate-reactive compounds. Water and other known blowing agents may optionally be used in combination with the required 1,1,1,4,4,4-hexafluorobutane blowing agent. The k-factors for foams produced using the hexafluorobutane blowing agent are not, however, reported.
Even though the use of HFC's may offer the best solution to the appliance industry as an alternative to the use of HCFC's, the costs of such HFC's are expected to be higher than the use of HCFC's. Therefore, means of reducing the levels of HFC's are desired. One way of reducing levels of HFC's is to use water to generate carbon dioxide as a blowing agent in the foam formulation.
U.S. Pat. No. 5,461,084 discloses a process for the production of rigid polyurethane foams produced by reacting an amine, an organic polyisocyanate, an HFC, and also an amount of water.
However, this is undesirable in an industry where the use of increased amounts of water will likely increase the thermal conductivity.
Therefore, a process in which a polyol and water could be used in combination with the more environmentally acceptable HFC blowing agents to produce a rigid polyurethane foam having good physical properties, including low k-factor, would be advantageous.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the production of rigid polyurethane foams in which an HFC in combination with an amount of water and also added carbon dioxide is used as the blowing agent.
It is a further object of the present invention to provide a process for the production of rigid polyurethane foams which are useful in the production of refrigeration units.
These and other objects which will be apparent to those skilled in the art are accomplished by reacting an organic polyisocyanate with an amine-initiated polyether polyol having an average molecular weight of at least about 149, preferably from about 149 to about 1500, in the presence of a hydrogen-containing fluorocarbon, a minor amount of water, carbon dioxide, surfactant and a catalyst. Isocyanate-reactive compounds which are not amine-initiated may optionally be included in the reaction mixture in an amount of up to 70% by weight, based on the total amount of isocyanate-reactive materials.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention is directed to a process for the production of rigid polyurethane foams or polyisocyanurate foams and to the foams produced by this process. In the process of the present invention, (a) an organic isocyanate is reacted with (b) an amine-based polyether polyol having an average molecular weight of at least about 149, preferably from about 149 to about 1500, and an epoxide content of from about 65 to about 98% by weight, preferably from about 75 to about 98% by weight based on the total weight of the amine initiator plus the epoxide, in the presence of (c) a blowing agent made up of (1) at least one hydrogen-containing fluorocarbon and (2) an amount of water and (3) an added amount of carbon dioxide and (d) a catalyst, and (e) at least one surfactant, at an isocyanate index of from about 0.9 to about 3.0, preferably from about 1.00 to about 1.50. The product foams generally have k-factors ranging from about 0.120 BTU-in./hr.ft
2
° F. to 0.160 BTU-in./hr.ft
2
° F. at 75° F.
Any of the known organic isocyanates, modified isocyanates or isocyanate-terminated prepolymers made from any of the known organic isocyanates may be used in the practice of the present invention. Suitable isocyanates include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof. Useful isocyanates include: diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, hexahydro-toluene diisocyanate and its isomers, isophorone diisocyanate, dicyclo-hexylmethane diisocyanates, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate and 3,3′-dimethyl-diphenylpropane-4,4′-diisocyanate; triisocyanates such as 2,4,6-toluene triisocyanate; and polyisocyanates such as 4,4′-dimethyl-diphenylmethane-2,2′,5,5′-tetraisocyanate and the polymethylene polyphenylpolyisocyanates.
Undistilled or a crude polyisocyanate may also be used in making polyurethanes by the process of the present invention. The crude toluene diisocyanate obtained by phosgenating a mixture of toluene diamines and the crude diphenylmethane diisocyanate obtained by phosgenating crude diphenylmethanediamine (polymeric MDI) are examples of suitable crude polyisocyanates. Suitable undistilled or crude polyisocyanates are disclosed in U.S. Pat. No. 3,215,652.
Modified isocyanates are obtained by chemical reaction of diisocyanates and/or polyisocyanates. Modified isocyanates useful in the practice of the present invention include isocyanates containing ester groups,
Doerge Herman P.
Venegas Mauricio H.
Bayer Corporation
Cheung Noland J.
Cooney Jr. John M.
Gil Joseph C.
Mrozinski, Jr. John E.
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