Foam laminates which include ASTM E-84 class 1 rated foams

A foam laminate comprising a polyurethane foam core sandwiched between two facing material, wherein said foam core has: a flamespread as determined by ASTM E-84 of 25 or less, a smoke density as determined by ASTM E-84 of less than 450, a dimensional stability measured as a % volume change as determined by ASTM D-2126, after 28 days (1) at -30.degree. C. of no more than 1, (2) at 100.degree. C. of no more than 8, and (3) at 70.degree. C. and 100% relative humidity of no more than 12, and a firmness of no more than 0.6 centimeters after 5 minutes. The foam core is produced by reacting: a polymethylene poly(phenyl isocyanate) based isocyanate, one or more aromatic polyester polyols having hydroxyl functionalities of 2.4 or more and hydroxyl numbers of 350 or more, one or more polyether polyols having hydroxyl functionalities of 4 or more and hydroxyl numbers of 340 or more, one or more flame retardants, and, one or more blowing agents, one or more catalysts, and one or more surfactants.

BACKGROUND OF THE INVENTION 
Field of the Invention 
Rigid polyurethane foams are well known and are commonly prepared from 
organic polyisocyanates and organic polyols together with known blowing 
agents, surfactants and catalysts for the reaction of --OH and --NCO 
groups. Such foams are used in construction, refrigeration and insulation 
applications because they may be prepared in a wide variety of densities 
and because they are closed cell foams. 
Perhaps the most critical requirements for rigid foams for use in building 
panels are the combustibility standards imposed by the various building 
codes in the United States. The basic combustibility test for the foam is 
ASTM E-84. Rigid foam used in metal faced building panels is required to 
pass ASTM E-84 with a Class 1 rating, flamespread of 25 or less, and smoke 
of less than 450. In general, panels produced on continuous laminators 
utilize Class 1 rated polyisocyanurate foam systems. While such systems 
provide high line speed and short dwell times, such systems typically have 
narrow processing windows. One example of this is the sensitivity of such 
systems to small changes in processing temperatures. In comparison, 
polyurethane foams are not sensitive to small changes in processing 
temperatures and have better adhesion to metal. 
In order to improve the ASTM E-84 performance of foams, aromatic polyester 
polyols have been used in the production of polyurethane foams and 
urethane modified polyisocyanurate foams. The use of such polyester 
polyols is described, for example, in U.S. Pats. Nos. 4,544,679 and 
4,797,428, and the various references cited therein. See also the Hercules 
technical data bulletin numbers S166A (dated December 1977) and OR-255 
(dated April 1980), and the Mobil Chemical product bulletin dated 
11-20-78. 
Finally, in a paper entitled "Polyester Polyols in Rigid Polyurethane and 
Polyisocyanurate Foams in Structural Building Panels", presented at the 
Polyurethanes World Congress in late 1987, the authors therein concluded 
that aromatic content, functionality, free glycol content and hydroxyl 
number are the four key variables of polyester polyols affecting the ASTM 
E-84 classification of polyisocyanurate and polyurethane foams for 
building panels. 
It was a primary object of the present invention to provide rigid 
polyurethane (PU) foams having an ASTM E-84 Class 1 rating as well as 
desirable physical and insulation properties which foams may be produced 
under a variety of processing conditions. 
DESCRIPTION OF THE INVENTION 
The present invention is directed to a foam laminate comprising a 
polyurethane foam core sandwiched between two facing materials, preferably 
metal skins, sheets or foils, wherein said foam core has the following 
properties: 
(i) a flamespread as determined by ASTM E-84 of 25 or less, 
(ii) a smoke density as determined by ASTM E-84 of less than 450, 
(iii) a dimensional stability measured as a % volume change as determined 
by ASTM D-2126,after 28 days (1) at -30.degree. C. of no more than 1, (2) 
at 100.degree. C. of no more than 8, and (3) at 70.degree. C. and 100% 
relative humidity of no more than 12, and 
(iv) a firmness of no more than 0.6 centimeters after 5 minutes, and 
wherein said foam core is produced by reacting: 
(a) a polymethylene poly(phenyl isocyanate), a isocyanate group containing 
prepolymer based on a polymethylene poly(phenyl isocyanate), or mixtures 
thereof, 
(b) from 37 to 43% by weight of one or more aromatic polyester polyols 
having hydroxyl functionalities of 2.4 or more and hydroxyl numbers of 350 
or more, or a mixture of aromatic polyester polyols, with said mixture 
having an average hydroxyl functionality of 2.4 or more and an average 
hydroxyl number of 350 or more, 39% by weight of one or more, 
(c) from 31 to 39% by weight of one or more polyether polyols having 
hydroxyl functionalities of 4 or more and hydroxyl numbers of 340 or more, 
(d) from 22 to 30% by weight of one or more flame retardants, and, 
(e) one or more blowing agents, one or more catalysts, and one or more 
surfactants, said % by weight totalling 100%, wherein the amount of 
component (b) is greater than component (c), and wherein the isocyanate 
index is from about 100 to about 115. 
The isocyanate materials useful in the practice of the present invention 
include any of the polyphenyl polymethylene polyisocyanates which may be 
obtained by aniline-formaldehyde condensation followed by phosgenation 
(crude MDI). Also preferred are the isocyanate prepolymers prepared by 
reacting the polyphenyl polymethylene polyisocyanates with hydroxyl 
functional materials. Typically, such prepolymers will have isocyanate 
group contents of from 15 to 31% by weight. 
Substantially any of the aromatic polyester polyols known in the art are 
useful herein so long as they have the required hydroxyl functionality and 
hydroxyl number. In the case of mixtures, the mixture must have the 
requisite hydroxyl functionality and hydroxyl number. Specific 
commercially available polyesters include RES D 304 (having a 
functionality of 2.5, an hydroxyl number of 440, and available from Cape 
Industries), RES D 304 A (having a functionality of 2.5, an hydroxyl 
number of 420, and available from Cape Industries), Rymsapol 186 (having a 
hydroxyl functionality of 2.5, an hydroxyl number of 460, and available 
from Resinas y Materiales), Rymsapol RC-101 (having a hydroxyl 
functionality of 2.5, an hydroxyl number of 552, and available from 
Resinas y Materiales), Rymsapol RC-126 (having a hydroxyl functionality of 
2.5, an hydroxyl number of 443, and available from Resinas y Materiales), 
Bayer P-277 (having a hydroxyl functionality of 2.9, an hydroxyl number of 
450, and available from Bayer AG), and Bayer P-276 (having a hydroxyl 
functionality of 2.4, an hydroxyl number of 435, and available from Bayer 
AG). 
In addition to the polyester polyol which is required in the present 
invention, the polyether component may be any of the conventional 
polyether polyols known to those skilled in the art, so long as they have 
the required hydroxyl functionality and hydroxyl number. Specific 
commercially available polyethers useful herein include the following 
sucrose based polyethers available from Mobay: 
______________________________________ 
Name OH # OH F 
______________________________________ 
Multranol M-4034 470 5.2 
Multranol M-4030 380 5.8 
Multranol M-9171 340 5.7 
Multranol M-9173 460 5.6 
Multranol M-9153 367 6.4 
______________________________________ 
Although not preferred, the reaction mixture can also contain up to 10% by 
weight based on the total weight of components b), c), and d) of other 
isocyanate-reactive compounds, so long as the blend of polyols has an 
overall average hydroxyl functionality of 4.0 or more and an overall 
average hydroxyl number of 340 or more. Such compounds are those compounds 
with less than five hydrogen atoms that are reactive toward isocyanates 
having a molecular weight generally of 400 to 10,000. Compounds that 
contain amino groups, thio groups or carboxyl groups as well as compounds 
that contain hydroxyl groups may be used. Compounds which contain hydroxyl 
groups, particularly compounds that contain 2 to 4 hydroxyl groups, 
specifically those having a molecular weight of 400 to 6000, preferably 
600 to 4000 are preferred. Polyesters, polyethers, polythioethers, 
polyacetals, polycarbonates and polyesteramides having 2 to 4 hydroxyl 
groups known to be useful in the production of homogeneous and cellular 
polyurethanes (described e.g., in U.S. Pat. No. 4,544,679) are among the 
more preferred isocyanate-reactive materials. Particularly preferred are 
polyethers which are obtained through the addition of one or more 
alkleneoxyides (ethylene oxide and particularly propylene oxide) or bi- or 
multivalent "starters" such as propylene glycol, glycerin, triethanolamine 
or trimethylol propane. Polyethers which contain polyaddition products of 
diisocyanates and hydrazine and/or diamines and/or glycols or polymers 
and/or graft polymers (preferably of styrene or acrylonitrile) in 
dispersed or dissolved form are also preferred. These polyethers generally 
have an average functionality of more than 2.0. 
Surfactants are typically employed in the preparation of rigid foams of the 
urethane and isocyanurate type. Silicone fluids which improve the cell 
size and uniformity of the foam are among the most commonly used 
surfactants. One particular surfactant which has been successfully 
employed in the practice of the present invention is a silicone fluid 
manufactured by Goldschmidt available under the designation Tegostab 
B-8404. 
Any known catalyst for the reaction of isocyanate groups with hydroxyl 
groups may be used in the practice of the present invention. Such catalyst 
may be used alone or together with a catalyst for the isocyanurate ring 
formation reaction to produce foams in accordance with the present 
invention. Any catalyst which is capable of catalyzing the simultaneous 
urethane and isocyanurate reactions may also be used. Trimer catalysts 
such as DMP-30 (a dimethylaminomethyl substituted phenol available from 
Rohm & Haas) and Potassium Hex-Cem 977 (a potassium octoate available from 
Mooney Chemicals) admixed with dimethylaminoethanol, a tertiary amine 
urethane catalyst manufactured by Rhein-Chemie (9/1 ratio by weight) are 
preferred catalysts. 
Conventional polyurethane foam blowing agents are used in the preferred 
embodiment of the present invention. Vaporizable liquid halogenated 
hydrocarbons such as trichlorofluoromethane are preferred. 
The flame retardant materials useful herein are also known in the art, and 
are commercially available. Preferred flame retardants include PHT-4 DIOL, 
available from Great Lakes Chemical (or the equivalent Ethyl Corporation 
product RB-79), tris(chloropropyl) phosphate (Fyrol PCF, available from 
Akzo Chemical, Antiblaze 80, available from Mobil, and Pelron 9338, 
available from Pelron), KPM 9214, available from PPG, Antiblaze 500, 
available from Mobil, Ixol B-251 and Ixol 350, both available from Kali 
Chemie, Fyrol CEF, available from Akzo Chemical, dimethylmethyl 
phosphonate-, triethyl phosphate and Kronitex FR-1028, available from FMC. 
In accordance with the present invention, the isocyanate and 
isocyanate-reactive components may be reacted together by the known 
one-shot process, prepolymer process or semi-prepolymer process, in many 
cases using mechanical devices, such as those described in U.S. Pat. No. 
2,764,565. Details about processing apparatus which may also be used 
according to the present invention may be found in Kunststoff-Handbuch, 
Volume VII, published by Vieweg and Hoechtlen, Carl-Hanser Verlag, Munich 
1966, for example on pages 121 to 205. 
Useful facing materials include metal foils such as aluminum foil, paper, 
wood panels, metal sheets, gypsum board, and other materials generally 
known in the art. The laminates are produced on conventional laminating 
equipment of the type known in the art. 
As noted above, the foam core must have a firmness of no more than 0.6 
centimeters after 5 minutes. The laboratory method used to make the 
firmness determination measures the penetration of a constant load at 
different times in the foaming process. The centimeter reading is obtained 
by applying a 1.7 Kg/cm.sup.2 load to a polyethylene plunger having a 
circular cross section, the surface which comes into contact with the 
foaming sample having an area of 5.07 cm.sup.2. The foam chemicals are 
poured into an 11 inch by 11 inch by 4 inch cardboard box in an amount 
sufficient to produce a foam having a height of 4 inches. Little 
penetration means high initial rigidity which correlates with increased 
productivity on a laminator. 
The present invention is not to be limited to the foregoing specific 
examples of suitable isocyanates, surfactants, catalysts, blowing agents, 
fire retardants or polyols. Any of the large number of materials available 
from a variety of suppliers for use in polyurethane foam manufacture may 
be substituted for the specifically identified materials by one skilled in 
the art and are deemed to fall within the teachings of the present 
invention.