Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1998-07-24
2002-04-16
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...
C521S168000, C521S172000, C521S173000, C521S174000
Reexamination Certificate
active
06372811
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to foams having improved flame resistance. In particular, the foams of the invention are closed celled rigid polyurethane or urethane-modified polyisocyanurate.
BACKGROUND OF THE INVENTION
A critical factor in the large scale commercial acceptance of rigid polyurethane foams in the building insulation industry has been their ability to provide a good balance of properties. Rigid polyurethane foams are known to provide outstanding thermal insulation, excellent fire performance and superior structural properties, all at reasonably low density. Such rigid foams are (in general) prepared by reacting the appropriate polyisocyanate and isocyanate-reactive compound in the presence of a blowing agent. Chlorofluorocarbon blowing agents (CFCs) such as CFC-11 (CCl
3
F) and CFC-12 (CCl
2
F
2
) have been the most commercially important blowing agents primarily because of their good thermal insulating properties and low or non-flammability. Use of such blowing agents has been a key reason for the good balance of properties of rigid polyurethane foams. Recently, CFCs have been associated with the declining ozone concentration in the earth's atmosphere and their use has been severely restricted. Hydrochlorofluorocarbons, especially HCFC-141b (CCl
2
FCH
3
) and HCFC-22 (CHClF
2
) have become the interim solution in many applications, once again due to their good thermal insulating properties and low or non-flammability. HCFCs still have an ozone depletion potential and their use is under constant scrutiny. The production and use of HCFC-141b is presently scheduled to end by the year 2003 in the USA.
Such environmental concerns have led to a need to develop reaction systems which utilize blowing agent(s) having a zero ozone depletion potential while retaining the good balance of properties for which rigid polyurethane foams are known. A class of materials which have been investigated as such blowing agents are hydrofluorocarbons (HFCs), for example: 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3,3-pentafluorobutane (HFC-365mfc); 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1-difluoroethane (HFC-152a). There are numerous patents and literature references on the use of HFC's as blowing agents for rigid polyurethane foam. The use of such materials is disclosed, e.g., in U.S. Pat. No. 5,496,866 (Bayer); U.S. Pat. No. 5,461,084 (Bayer); U.S. Pat. No. 4,997,706 (Dow); U.S. Pat. No. 5,430,071 (BASF); U.S. Pat. No. 5,444,101 (ICI). Although HFCs are environmentally more acceptable than CFCs and HCFCs, they are inferior in fire properties. The polyurethane foams prepared using the HFC blowing agent must have good fire properties while retaining the good thermal and structural properties, all at densities comparable to those possible with CFC and HCFC blowing agents. Fire properties are especially important for rigid polyurethane foams used in the building industry as they must meet strict fire resistance codes.
At present, hydrofluorocarbons and hydrocarbons are the two leading classes of materials that are being evaluated by the rigid foam industry as zero ozone depletion potential (ODP) blowing agents. Neither of these two materials has all the attributes of an “ideal” blowing agent. For example, the global warming potentials of HFCs are high (lower than CFCs but still high by some accounts) but the VOC content is low. Hydrocarbons have extremely low direct global warming potential but they are considered VOCs.
Thus, there still remains an unfulfilled need to develop reaction systems in which blowing agents have a zero ozone depletion potential, and which produce foams with good balance of properties for which rigid polyurethane foams are known.
SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention to provide closed celled rigid polyurethane or urethane-modified polyisocyanurate foams which have, even when blown with hydrofluorocarbons, equivalent or improved fire resistance properties than CFC or HCFC blown foams.
It is another object of the present invention to provide closed celled rigid polyurethane or urethane-modified polyisocyanurate foams blown with hydrofluorocarbons which have good thermal insulation and structural properties along with the improved fire properties.
It has now been unexpectedly discovered that the use of over 40 weight % of aromatic polyester polyols of average functionality lower than 3.0 as the polyfunctional isocyanate-reactive composition, along with the use of organo-phosphorous compounds in the foam formulation improves the fire properties of polyurethane foam prepared in the presence of HFC blowing agents. Such HFC blown foams also have surprisingly good thermal insulation and structural properties along with the improved fire properties. The compositions of the present invention advantageously make it possible to obtain the balance of properties best suited to meet both the commercial and environmental demands of the present times.
It has now surprisingly been found that rigid polyurethane foam having a density between 1.2 to 4.2 lb/cu.ft. with excellent fire properties and good thermal and structural properties can be obtained by using the formulation
(1) organic polyisocyanates,
(2) a blowing agent comprising
(a) C
1
-C
4
hydrofluorocarbons which are vaporizable under the foaming conditions as the physical blowing agent, and
(b) water
(3) polyfunctional isocyanate-reactive compositions containing over 40 weight % of aromatic polyester polyols of average functionality lower than 3.0,
(4) organo-phosphorous compounds, and
(5) one or more other auxiliaries or additives conventional to formulations for the production of rigid polyurethane and urethane-modified polyisocyanurate foams. Such optional additives include, but are not limited to: crosslinking agents, foam-stablilising agents or surfactants, catalyst, infra-red opacifiers, cell-size reducing compounds, viscosity reducers, compatibility agents, mold release agent, fillers, pigments, and antioxidants, wherein the amount of said organo-phosphorous compound used is such that the amount of phosphorous is between about 0.01 to about 2.5% by weight, based on the total weight of the foam forming reaction mixture.
In summary, the surprising technical advantages of this invention are the discovery of rigid polyurethane foam formulations blown using hydrofluorocarbons (zero ODP) blowing agents which give foams whose fire performance in laboratory tests are equal or superior to those foams blown with CFCs or HCFCs; structural performance, such as compressive strength and long term dimensional stability, is comparable or better than foam blown with CFCs or HCFCs; and initial and long term insulation performance comparable to those foams blown with CFCs or HCFCs.
The foams of the present invention are suitable for use in continuous lamination boardstock foams for commercial roof and residential wall insulation, as well as metal-faced panels, spray foams, and fire-rated doors.
DETAILED DESCRIPTION OF THE INVENTION
Each of the above disclosed materials utilized in the foams of the present invention are described hereinafter.
(1) Isocyanate: Any organic polyisocyanates may be used in the practice of the invention. A preferred isocyanate is polyphenylene polymethylene polyisocyanate (PMDI). A most preferred isocyanate is those PMDI with diphenyl methane diisocyanate content of about 15 to about 42% by weight based on 100% by weight of the isocyanate.
The amount of isocyanate is typically about 30-75%, more preferably about 40-70% and most preferably about 45-65% by weight based on 100% of the total foam formulation.
(2a) HFC blowing agent: Any of the C
1
-C
4
hydrofluorocarbons which are vaporizable under the foaming conditions can be used alone or as mixtures. Suitable HFCs include difluoromethane (HFC-32); trifluoromethane (HFC-23); 1,1-difluoroethane (HFC-152a); 1,1,1-trifluroethane (HFC-143a); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoroethane (HFC-125); all isomers of pentafluoropropane (HFC-245 fa, ca, eb, ea etc.); all isomer
Burns Steve B.
Jones Patricia A.
Singh Sachchida N.
Boland Kevin J.
Cooney Jr. John M.
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