Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-07-22
2004-12-21
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, C521S159000, C521S170000, C521S172000, C521S173000, C521S174000
Reexamination Certificate
active
06833390
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for preparing closed-cell water-blown rigid polyurethane foams which have reduced friability and acceptable adhesion to substrates and which also have acceptable compressive strength. The present invention is also directed to closed-cell water-blown rigid polyurethane foams produced by the process of the present invention. The invention is further directed to a polyurethane-foam forming mixture which is used to produce closed-cell water-blown rigid polyurethane foams which have reduced friability and acceptable adhesion to substrates and which also have acceptable compressive strength.
BACKGROUND OF THE INVENTION
Rigid polyurethane foams are widely known and are used in numerous industries. Rigid polyurethane foams are produced by reacting a polyisocyanate with a polyol in the presence of a blowing agent. Chlorofluorocarbons (CFC's) were typically used as blowing agents to produce rigid polyurethane foams which have excellent insulating properties. CFC's are now believed to contribute to the depletion of ozone in the stratosphere. As a result, mandates have been issued which prohibit the use of CFC's.
Hydrogen-containing chlorofluorocarbons (HCFC's), hydrofluorocarbon compounds (HFC's) and mixtures of HCFC's and HFC's are blowing agents considered to be acceptable alternatives to CFC's. HCFC
141
b
is currently used as an alternative to CFC's. However, due to the fact that the use of HCFC
141
b
will be phased-out beginning in 2003, effort has been directed to using water as a blowing agent in the production of some rigid polyurethane foams.
There are, however, drawbacks to using water as a blowing agent for producing rigid polyurethane foams. One such drawback is the fact that foams produced using relatively high levels of water as a blowing agent are friable and have relatively poor adhesion to substrates. See U.S. Pat. No. 5,013,766, column 1, lines 11-13.
A process for producing rigid polyurethane foams which are less brittle and which have acceptable adhesion to substrates has been investigated. For example, U.S. Pat. No. 5,013,766 describes a process for producing closed-cell rigid polyurethane foams which are less friable and adhere well to substrates. The process disclosed in this patent focuses on reacting an isocyanate with a polyol mixture in the presence of a catalyst, water, trichlorofluoromethane (Freon 11) and a foam stabilizer. However, from the examples contained in U.S. Pat. No. 5,013,766, one skilled in the art would recognize that foams produced by the process described in this patent would have low compressive strength.
Open-cell rigid polyurethane foams having acceptable compressive strength which are produced using polymer polyols are known. For example, U.S. Pat. No. 6,127,443 discloses a process for producing open-cell rigid energy absorbing polyurethane foams by reacting certain polymer polyols with an isocyanate in the presence of a blowing agent (water) to generate rigid polyurethane foams in which the total polymer solids content of the foam is in excess of about 15 weight percent. Foams produced by the process described in this patent are designed for energy management. Due to their open-cell structure, one skilled in the art would expect that the foams produced by the process described in U.S. Pat. No. 6,127,443 would have poor insulating properties. See W. A. Kaplan et al.,
Low-Density All Water-Blown Rigid Foam for Pour-in-Place Applications
, Polyurethanes Expo '96 Conference Proceedings, pp. 179-89 (1996) wherein it states that, unlike closed-cell water blown polyurethane foams, open-cell polyurethane foams are poor insulators.
There therefore remains a need for closed-cell water-blown rigid polyurethane foams which have reduced friability and acceptable adhesion to substrates but which also have acceptable compressive strength.
SUMMARY OF THE INVENTION
The present invention relates to a process for preparing closed-cell water-blown rigid polyurethane foams which have reduced friability and acceptable adhesion to substrates and which also have acceptable compressive strength. The present invention also relates to closed-cell water-blown rigid polyurethane foams produced by the process of the present invention. The invention further relates to a polyurethane-foam forming mixture which is used to produce closed-cell water-blown rigid polyurethane foams which have reduced friability and acceptable adhesion to substrates and which also have acceptable compressive strength.
DESCRIPTION OF THE INVENTION
The present invention is directed to a process for preparing water-blown rigid polyurethane foams having at least an 80% closed-cell content which involves reacting a) at least one polyol mixture which is composed of i) at least one polymer polyol; ii) at least one polyol which has a hydroxyl value within the range of from about 200 to about 800; and iii) optionally, at least one polyol having a hydroxyl value within the range of from about 25 to about 115; with b) at least one polymeric isocyanate and/or a prepolymer thereof; in the presence of c) optionally, at least one catalyst; d) water; and e) optionally, at least one additive or auxiliary agent.
The present invention is also directed to the closed-cell water blown rigid polyurethane foams produced by the process of the present invention. The invention is further directed to a polyurethane-foam forming mixture which is used to produce water-blown rigid polyurethane foams having at least an 80% closed-cell content which is composed of a) at least one polyol mixture which is composed of i) at least one polymer polyol; ii) at least one polyol which has a hydroxyl value within the range of from about 200 to about 800; and iii) optionally, at least one polyol having a hydroxyl value within the range of from about 25 to about 115; b) at least one polymeric isocyanate and/or a prepolymer thereof; c) optionally, at least one catalyst; d) water; and e) optionally, at least one additive or auxiliary agent.
Any polymer polyol known in the art can be used as component i) in the polyol mixture of the present invention. Polymer polyols are dispersions of polymer solids in a polyol. Polymer polyols which are useful in the present invention include the “PHD” polymer polyols as well as the “SAN” polymer polyols.
SAN polymer polyols are typically prepared by the in situ polymerization of one or more vinyl monomers, preferably acrylonitrile and styrene, in a polyol, preferably, a polyether polyol, having a minor amount of natural or induced unsaturation. Methods for preparing SAN polymer polyols are described in, for example, U.S. Pat. Nos. 3,304,273; 3,383,351; 3,523,093; 3,652,639, 3,823,201; 4,104,236; 4,111,865; 4,119,586; 4,125,505; 4,148,840 and 4,172,825; 4,524,157; 4,690,956; Re-28715; and Re-29118.
SAN polymer polyols useful in the present invention typically have a polymer solids content within the range of from about 10 to about 60 wt. %, preferably, from about 30 to about 45 wt. %, based on the total weight of the SAN polymer polyol. As mentioned above, SAN polymer polyols are typically prepared by the in situ polymerization of a mixture of acrylonitrile and styrene in a polyol. When used, the ratio of styrene to acrylonitrile polymerized in situ in the polyol is typically in the range of from about 80:20 to about 0:100 parts by weight, based on the total weight of the styrene/acrylonitrile mixture. SAN polymer polyols useful in the present invention typically have hydroxyl values within the range of from about 15 to about 50, preferably, from about 20 to about 30.
Polyols used to prepare the SAN polymer polyols of the present invention are typically triols based on propylene oxide, or mixtures of propylene oxide and ethylene oxide. Alkoxylation of the starter can be accomplished by using either propylene oxide, a mixture of propylene oxide and ethylene oxide to form mixed block co-polymers, or by adding propylene oxide followed by ethylene oxide to form an ethylene oxide-
Forsythe John P.
Haider Karl W.
Nodelman Neil H.
Suddaby Brian R.
Bayer Polymers LLC
Cooney Jr. John M.
Gil Joseph C.
Mrozinski, Jr. John E.
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