Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-11-13
2003-09-09
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...
C521S137000, C521S174000, C521S176000
Reexamination Certificate
active
06617368
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the preparation of an isotropic rigid foam comprising the step of reacting: (A) an organic polyisocyanate component selected from the group consisting of: (1) a polymethylene poly(phenylisocyanate) and (2) an NCO-terminated prepolymer, and comprising the reaction product of: (a) a polyester comprising the reaction product of (i) pure ortho-phthalic acid or phthalic anhydride and (ii) a glycol and (b) a polymethylene poly(phenylisocyanate); with (B) an isocyanate-reactive component comprising: (1) a liquid OH-terminated prepolymer having a viscosity of at least about 100,000 mPa·s at 25° C., and which comprises the reaction product of: (a) an organic aromatic polyisocyanate component; and (b) an amine initiated polyether polyol component; (2) at least one polyether polyol and optionally (3) at least one aromatic polyester polyol; in the presence of: (C) at least one catalyst; and (D) at least one blowing agent; wherein the relative amounts of components present is such that the Isocyanate Index is from 90 to 170. This invention also relates to the isotropic rigid foams prepared thereby.
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing rigid foams with desirable insulation characteristics (as measured by k-factor) and with isotropic closed cells (as measured by the aspect ratio), and to the foams produced thereby. Closed celled rigid polyisocyanate foams are in general prepared by reacting the appropriate polyisocyanate and polyol in the presence of a blowing agent. One use of such foams is as a thermal insulation medium as for example in the construction of refrigerated storage devices. The thermal insulating properties of closed celled rigid foams are dependent upon a number of factors including the cell size and the thermal conductivity of the contents of the cells.
Rigid foams of commercial densities of about 2 lb/ft
3
typically suffer from a cell elongation in the flow direction. The cell elongation causes the foam to have very different properties in the different dimensions. As is well known, the thermal conductivity of a foam generally increases with a poor cell structure. The object of the present invention is to eliminate anisotropy in foam physical properties due to flow direction. By making the cell rounder, or more isotropic, a uniform and high quality foam results. As the cell becomes more isotropic, the aspect ratio of the properties in the parallel (flow direction) to the perpendicular (flow direction) becomes closer to unity.
In order to improve the thermal insulation of closed celled rigid polyurethane and polyisocyanate foams blown with blowing agents a variety of techniques have been proposed, most of them concentrated on decreasing the thermal radiation component of the thermal conductivity of the rigid foam. One of these techniques consists of adding carbon black to the foam formulation. The use of carbon black to improve the thermal insulation of closed celled rigid polyurethane foam is described in U.S. Pat. Nos. 4,795,763, 5,149,722 and 5,192,607 and Japanese patent publication Kokai No. 57/147510.
Another way of decreasing the thermal radiation component consists of decreasing the foam cell sizes. Thus European patent publication No. 0 508 649, and U.S. Pat. Nos. 4,981,879, 5,034,424 and 4,972,002 describe the use of a substantially fluorinated or perfluorinated hydrocarbon additive as (co)-blowing agent or nucleating agent in closed celled rigid polyurethane foam in order to reduce the foam cell size.
Chlorofluorocarbons were the blowing agents most commonly used until recently. However, when it became known that these chlorofluorocarbons posed environmental problems, the search for alternative blowing agents began. Among the blowing agents considered to be promising alternatives to the chlorofluorocarbons (CFCs) are hydrocarbons such as hydrogen-containing chlorofluorocarbons (HCFCs), highly fluorinated compounds (HFCs) and mixtures of HCFCs and HFCs. HCFC-141b is one of the more promising alternative blowing agents and has been the subject of a number of publications. U.S. Pat. No. 5,397,808, for example, discloses low thermal conductivity foams made with a combination of HCFC-141b, perfluorinated compounds and carbon black.
U.S. Pat. No. 6,245,826 discloses an isocyanate-based rigid foam comprising the reaction product of an organic polyisocyanate, a resin blend and, optionally, a relatively low molecular weight chain extender or crosslinker in the presence of a catalyst, and, optionally, further auxiliaries and/or additives. The resin blend comprises a phthalic anhydride-initiated polyester polyol, a blowing agent comprising a C
4
-C
6
hydrocarbon, and a fatty acid or fatty alcohol ethoxylate compatibilizing agent. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction.
U.S. Pat. No. 5,840,781 discloses a polyether polyol made by reacting propylene oxide with o-toluene diamine. The polyether polyol is reacted with organic polyisocyanates, optionally further compounds with at least 2 hydrogen atoms reactive to isocyanates, in the presence of traditional blowing agents to form a rigid foam. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction.
U.S. Pat. No. 5,840,212 discloses rigid foams having improved insulation properties made by reacting a polyisocyanate with an isocyanate-reactive material in the presence of a blowing agent mixture composed of from a C
2
-C
5
polyfluoroalkane and an HCFC. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction.
U.S. Pat. No. 5,318,996 discloses rigid insulating polyurethane oams prepared from ternary blowing agent mixtures which blowing agent ixtures were composed of water, HCFC-22 or HCFC-141b and a perfluorinated hydrocarbon having from 3 to 8 carbon atoms. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction
U.S. Pat. No. 5,276,067 discloses rigid polyurethane foams having low thermal conductivities made by reacting an organic polyisocyanate with an organic material having at least 2 isocyanate reactive hydrogen atoms in the presence of a blowing agent. The blowing agent is an HCFC and water. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction.
U.S. Pat. No. 5,391,317 sought to manufacture a foam having both good dimensional stability and thermal insulation using hydrocarbons as blowing agents. This reference taught the use of a particular mixture of C
5
-C
6
alicyclic alkanes, isopentane and n-pentane blowing agents in particular molar percents, in combination with a polyol mixture made up of an aromatic initiated polyether polyol, an aromatic polyester polyol, and a different amine initiated polyether polyol. An OH-terminated prepolymer is not disclosed as a component on the isocyanate-reactive side of the reaction.
Others have also tried to modify the polyol components in a polyol composition in an attempt to solubilize a hydrocarbon blowing agent in the polyol composition. In U.S. Pat. No. 5,547,998, the level of aliphatic amine initiated polyether polyols in a polyol composition is limited to solubilize cyclopentane in the polyol composition. When reacted with an organic isocyanate, the polyol composition, comprising an aromatic amine initiated polyoxyalkylene polyether polyol and an aliphatic amine initiated polyoxyalkylene polyether polyol in an amount of 10 weight percent or less by weight of the polyol composition produces a dimensionally stable rigid closed cell polyurethane foam having good thermal insulation properties.
The problem of obtaining a closed cell rigid polyurethane foam having both good dimensional stability and thermal insulation at low densities was also discussed in “An Insight Into The Characteristics of a Nucleation Catalyst in HCFC-Free Rigid Foam System” by Yoshimura et al. This publication reported the result
Ball Edward E.
Bushmire Alan D.
Steppan David D.
Bayer Corporation
Brown N. Denise
Cooney Jr. John M.
Gill Joseph C.
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