Low fire hazard rigid urethane insulation foam, polyol mixtures used in the manufacture thereof, and method for manufacture thereof

A low fire hazard rigid urethane insulation foam having high compressive strength and low friability is disclosed. Rigid foam products of this invention have a Class I flame hazard rating according to the ASTM E-84 Steiner tunnel test. The urethane foam contains a halogenated base polyol and a modifying amount of a 2,5-bis-(hydroxymethyl) furan component.

BACKGROUND OF THE INVENTION 
Rigid polyurethanes are generally prepared by the reaction of a 
polyfunctional hydroxy compound, preferably one with a functionality of 3 
or greater, with a polyfunctional isocyanate, preferably one having a 
functionality of 2.5 or more. In the manufacture of such rigid 
polyurethane foams, the polyfunctional isocyanate is typically admixed 
with a liquid stream comprising a polyhydroxy material, a blowing agent, a 
surfactant for stabilizing cell-size, and a catalyst. The rigid foam can 
be produced by either a "one-shot" method or by employing a 
semi-prepolymer or a prepolymer method. In the so-called "one-shot" 
method, a first stream of reactant containing isocyanate and/or 
polyisocyanate is admixed with a second stream comprising a polyol, a 
surfactant, and a blowing agent. Generally the second stream also contains 
a catalyst. Typically, in the manufacture of urethane board insulating 
stock, the resulting admixture is discharged into a moving conveyor 
provided with physical restraint elements, and the chemical reaction 
immediately commences, generating an exotherm, and the exotherm causes the 
vaporization of the volatile blowing agent if one is used. It is crucial, 
in the manufacture of insulating board stock to balance the reactivity and 
quantity of the respective components so that the exotherm, although great 
enough to cause the vaporization of the blowing agent, is not great enough 
to cause the disintegration of the cellular character of the resulting 
foam. Also, as the molecular weight builds, the viscosity of the reactant 
mixture increases, and this factor plus the presence of a surfactant e.g. 
cell wall stabilizer, assists in maintaining the closed cell structure of 
the resulting foam. 
The fire retardant or, "low fire hazard" properties of furan 
ring-containing materials is well known due to the self-extinguishing 
property of the char which forms when furan-containing materials are 
burned. The disclosure in U.S. Pat. No. 4,029,611 issued to Cenker et al. 
shows a rigid cellular foam having carbodiimide and isocyanurate linkages 
prepared by catalytically condensing an organic polyisocyanate in the 
presence of a carbodiimide-promoting catalyst, a trimerization catalyst, 
and a polyfurfuryl alcohol polymer. The resulting isocyanurate foam has 
improved flame retardancy. The polyfurfuryl alcohol polymer employed 
includes the condensation products of furfuryl alcohol with formaldehyde, 
furfural, urea or mixtures thereof, produced by reaction in the presence 
of an acid catalyst providing a pH of 1 to 4, preferably 1.5 to 3, at a 
temperature of 25.degree. C. to 120.degree. C. 
Likewise, a U.S. Pat. No. 3,865,757 issued to Wade teaches "resinous foam" 
produced by reaction of a furan compound, an isocyanate compound, and a 
phosphorus-containing inorganic acid or complex thereof. The reaction 
mixture disclosed can also contain an alcohol, an amine, a surfactant, 
and/or a supplementary blowing agent. 
In addition, other now conventional low flame hazard polyurethane foams 
achieving a rating of Class I flame hazard rating according to the ASBM 
E-84 Steiner tunnel test are also well known. One of these well known 
non-furan-containing rigid insulating foams are produced by typical 
"standard" methods and is described hereinafter in Test "A" in Example 1. 
An object of this invention is to provide a rigid urethane foam exhibiting 
low flame hazard properties. 
A further object of this invention is to provide a self-extinguishing 
furan-containing urethane foam. 
A still further object of this invention is to provide a furan-containing 
rigid urethane insulating foam having a closed cell content greater than 
80%. 
Another object of this invention is to provide a stable furan-containing 
polyol mixture composition for producing a rigid urethane foam, such 
mixtures having a Freon compatibility greater than 30 parts Freon to 100 
parts of furan-containing polyol mixture. 
Yet another object of this invention is to provide a rigid urethane foam 
having a compressive strength greater than 30 psi and a friability of less 
than 20%, which characteristics substantially exceed the performance that 
is believed to be achieved in the manufacture of present-day industry 
"standard" foams. 
SUMMARY OF THE INVENTION 
These and other objects in accordance with this invention, which objects 
will be apparent hereinafter, are achieved in compositions and methods, in 
accordance with this invention, in which a 2,5-bis-(hydroxymethyl) 
furan-containing polyol component is employed in conjunction with a base 
polyol component selected from the group halogenated polyols, in otherwise 
conventional rigid foam manufacturing technology. 
A preferred novel hydroxyl composition for use in manufacture of rigid 
urethane insulating foams, in accordance with the present invention, 
comprise 12-24% 2,5-bis-(hydroxymethyl) furan component, 76-88% 
halogenated polyol base polyhydroxyl component, as well as 25-40 phr. 
(parts per hundred polyol components) blowing agent, 0.8-1.0 phr. 
catalyst, 1.5-2 phr. surfactant, and 2-7 phr. of an acid scavenger, such 
as, for example, an epoxy compound. (Ciba-Geigy CY 179 is eminently 
satisfactory as an acid scavenger. The latter acid scavenger is 3,4 
epoxycyclohexylmethyl-3,4 epoxycyclohexane carboxylate.) This composition 
is stable for shipment, and can be used as the polyhydroxyl stream in a 
so-called "one-shot" method, in conjunction with a second, isocyanate 
stream, to produce rigid insulating foams in accordance with this 
invention. 
By use of the term "bis-hydroxymethyl furan component" we intend to include 
compositions which are substantially pure monomeric 
"2,5-bis-(hydroxymethyl) furan," as well as mixtures of bis-hydroxymethyl 
furan with polymeric components formed by the acid polymerization of 
bis-hydroxymethyl furan. A preferred bis-hydroxymethyl furan component in 
accordance with the present invention is a mixture of 20-40% monomeric 
2,5-bis-(hydroxymethyl) furan and 60-80% polymeric 2,5-bis-(hydroxymethyl) 
furan. Pure bis-hydroxymethyl furan tends to crystallize upon standing, 
whereas the preferred mixtures of monomeric and polymeric 
bis-hydroxymethyl furan are storage stable, with respect to 
crystallization. 
An example of a commercially available mixture of this type is the material 
available under the trademark FA-REZ B-260 (T.M. The Quaker Oats Company). 
This commercially available product is reported to have a viscosity in the 
range of 10,000 cps.+2,000, has a hydroxyl content of 16-18%, a water 
content of 0.5 to 1.0% furfuryl alcohol content of up to 3% and is 
reportedly 85% polyhydroxymethyl functionality. 
Generally speaking, the polyhydroxymethyl furan mixtures useful in 
accordance with the present invention preferably have a viscosity in the 
range of 6,000-12,000 cps. at 25.degree. C., contains 35% to 45%, 
inclusive, monomeric bis-hydroxymethyl furan, less than 3% furfuryl 
alcohol monomer, less than 1.2% water and have an acid number of less than 
or equal to 3.5. 
Such a hydroxymethyl furan diol mixture which is useful as an ingredient in 
accordance with the present invention, can be produced in a number of 
ways. For example, it can be produced by low acidic (i.e. pH above 4) 
polymerization of 2,5-bis-(hydroxymethyl) furan, as well as by the 
hydroxymethylation of furfuryl alcohol with formaldehyde using a weak acid 
such as, for example, acetic acid, propionic acid, or formic acid, under 
conditions which provide a pH above 4. Generally speaking, such products 
can be produced by hydroxymethylation of a furan ring-containing compound 
selected from the group furan and furfuryl alcohol, wherein said furan 
compound is contacted with formaldehyde in the presence of a catalytical 
amount of a weak acid catalyst having a pKa value at 25.degree. C. between 
3.0 and 5.0 inclusive, under conditions which provide a reaction mixture 
having a room temperature acidity pH greater than or equal to 4.0, said 
contacting taking place between 50.degree. C. and 160.degree. C. 
inclusive. 
The "base polyol" which is used in the polyol mixture in accordance with 
the present invention is any of the commercially available conventional 
poly-halogenated polyols. 
These halogenated polyfunctional polyols, generally speaking are reaction 
products between hydroxyl terminated material, and halogenated alkaline 
oxide compounds. For example, the commercially available and eminently 
satisfactory base polyol for use in accordance with the present invention 
which is commercially available under the trademark "Thermolin R.F. 230" 
(T.M. Olin Chemicals) is reportedly the reaction product between 
trichlorobutylene oxide and a suitable hydroxy terminated material such 
as, for example, ethylene glycol, glycerol, pentaerythritol, or sucrose, 
for example, to the desired hydroxyl number. 
By "base polyol" we mean that portion of the polyol mixture which 
constitutes more than half of the polyol mixture, by weight. It should be 
noted that some of the base polyol can be substituted by addition of other 
polyols compatible with the present system, although the basic requirement 
that the "base polyol" constitute more than 50% of the polyol mixture 
would still be required. We prefer that the base polyol which is used in 
accordance with the present invention have a functionality greater than 3, 
but base polyols having functionality of less than 3 can be used. When 
polyols having a functionality of less than 3 are used as the base polyol, 
however, it is desirable to select as the polyisocyanate those compounds 
or components having relatively higher functionality, in accordance with 
practices well known in the rigid foam-producing art. 
Thus the polyol compositions which are used in accordance with the present 
invention comprise 12-35% of bis-hydroxymethyl furan component, and 65-88% 
of the halogenated polyol. We have discovered that in mixtures containing 
more than 24% bis-hydroxymethyl furan component, inadequate compatibility 
with Freon blowing agents is observed with respect to long term storage 
conditions. Nonetheless mixtures including the bis-hydroxymethyl furan in 
an amount in the 24-35% range are useful in "day mix" operations. 
The polyisocyanate used in accordance with the practice of the present 
invention must have a viscosity greater than 250 cps. at 25.degree. C. and 
a functionality of greater than 2, i.e. 2.1 or greater. The polyisocyanate 
can be provided by the addition of "pure" polyisocyanate, or by the 
addition of "prepolymers" as ingredients. Polyisocyanate compositions 
having viscosities substantially less than 250 cps. at 25.degree. C. do 
not provide sufficient compatibility with the bis-hydroxymethyl furan 
component used in accordance with the present invention. 
A preferred polyisocyanate is PAPI 20, (T.M. Upjohn), a compound reportedly 
characterized as polymethylene base polyphenylisocyanate, a well known 
conventional polyisocyanate compound. Another eminently satisfactory 
polyisocyanate, having approximately the same composition, is commercially 
available under the trademark "Mondur" MR-200" (T.M. Mobay). 
With respect to the blowing agent which is used in accordance with the 
present invention, it is preferred that a fluoro-chloro alkane blowing 
agent be used, although other conventional blowing agents such as, for 
example, water, can be used for desired. The fluoro-chloro alkane blowing 
agents provide low "K" factor foams, and are preferable for insulating 
stock to those blowing agents which produce, for example, CO.sub.2 as the 
cell gas for insulation applications. The preferred blowing agent for use 
in accordance with the present invention, is mono-fluoro tri-chloro 
methane, for example, which is commercially available under the trademark 
"Freon 11B" (T.M. DuPont). The blowing agents which are used can be any 
conventional blowing agents, and the selection of a specific blowing agent 
or a combination of agents for use in accordance with this invention is 
entirely within the scope of the skill of a person with ordinary skill in 
the art, and does not constitute for the present invention. 
Likewise, the selection of the specific cell wall stability component, the 
surfactant, is also within the skill of those working in the urethane foam 
art. We regard the preferred surfactant to be Dow Corning's "Q2 5103" 
polyalkyl siloxane-polyoxyalkaline copolymer. 
Nonetheless other commercially available and well known surfactants can be 
used in accordance with the present invention, and the selection of the 
particular surfactant does not constitute part of the novel aspects of the 
present invention. 
By the same token, the catalysts which were used in accordance with the 
practice of the present invention are conventional urethane-specific 
catalysts such as, for example, "Polycat 8" (T.M. Abbott Laboratories), a 
dimethylcyclohexyl-methyl amine. These and other amine catalysts which are 
well known and widely used in the manufacture of rigid polyurethane foams, 
are all eminently satisfactory for use in accordance with the compositions 
and methods of the present invention. 
In the following Examples all percents are in percent by weight based on 
the overall mixture, all temperatures are expressed as degrees centigrade, 
and all parts are in parts by weight, unless otherwise expressed.

EXAMPLE I 
A series of six tests was performed, and the respective ingredients used, 
the reactivities observed, the properties and results of the fire hazard 
testing of the respective products therefrom, are all reported in Table I. 
In each of these tests, all the components except for the respective 
polyisocyanate ingredient (the "Papi" ingredients) were first mixed 
together in a first stream in the proportions set forth in Table I, and 
were then admixed with the second stream consisting of the Papi component 
in the amount and type as set forth in Table I as well for each respective 
test. A conventional metering, mixing machine, was used, specifically, a 
100 pound per minute Martin-Sweets machine. The resulting mixture was cast 
into wood molds, 4 inches deep, lined with "butcher" paper. To each mold, 
five and one half pounds of the reaction mixture was dispersed as a thin 
film on the respective molds. The reaction mixture, and the wooden molds 
were at ambient room temperature, i.e. between 65.degree. and 75.degree. 
F. After the mixture was poured into the molds, the molds were closed, and 
after 15 minutes the samples were pulled out of the molds. A rigid foam 
having a two pound per cubic foot density was produced in each instance. 
The components listed refer to: FA Rez B-260 (T.M. The Quaker Oats 
Company) is 2,5-bis-(hydroxymethyl) furan mixture comprising 35% monomeric 
bis-hydroxymethyl furan, and 61% polymeric bis-hydroxymethyl furan, and 4% 
of contaminants including furfuryl alcohol (about 1.5%), water and 
formaldehyde. 
Thermolin RF-230 (T.M. Olin Chemicals) is a commercially available 
chlorinated polyol flame retardant polyhydroxyl composition which is well 
known and widely used in the art. "Poly-G 30-56" is a trademark of Olin 
Chemical and is characterized as trimethylolpropane propoxylate. The Dow 
Corning Q2-5103 surfactant was described above, as was Freon 11B, and 
Polycat 8. The Papi polyisocyanates are also well known commercially 
available polyisocyanates, the most significant difference between them 
being the viscosity. The viscosities of Papi 20, 135 and 580 are 
reportedly 2,150, 250, and 700, respectively cps. at 25.degree. C. 
Under reactivities, "Cream," "Firm," "Rise," "Tackfree Time," and "Exotherm 
(max.)," are terms which are standard in the art, and need no further 
description here. Likewise the items listed under "Properties" are also 
standard terms in the art requiring no further description. The Monsanto 2 
ft. tunnel test is the well known test previously published by Monsanto 
Chemical, the NBS, D.sub.s, refers to the National Bureau of Standards 
smoke development test, the U.S.B.M. refers to the well known U.S. Bureau 
of Mines flame penetration test. E-84 refers to the Underwriters 
Laboratories "Steiner" tunnel test which is also the well known test which 
needs no further description here. 
TABLE I 
______________________________________ 
A B C D E F 
______________________________________ 
Components 
(Indicated by Trademark) 
FA Rez B-260, g 
-- 100.0 93.5 15.7 24.0 31.7 
Furfuryl Alcohol, g 
-- -- 6.5 -- -- -- 
Thermolin RF-230, g 
84.3 -- -- 84.3 76.0 68.3 
Poly-G 30-56, g 
15.7 -- -- -- -- -- 
Dow Corning 1.6 1.5 1.7 1.57 2.0 1.27 
Q2-5103 surfactant, g 
Freon 11B, g 24.7 25.0 32.0 28.0 34.2 25.0 
Polycat 8, g 0.94 0.80 0.8 0.94 1.0 1.08 
Papi 20, g -- 161.5 137.1 
-- 122.6 
127.7 
Papi 135, g 81.96 -- -- 107.7 
-- -- 
Papi 580, g -- -- -- -- -- -- 
Reactivity 
Cream, sec. 18 46 27 15 22 25 
Firm, sec. 105 70 65 70 100 45 
Rise, sec. 115 80 65 90 120 70 
Tackfree Time, sec. 
125 80 85 75 100 55 
Exotherm (max.), .degree.C. 
98 153 160 88 108 120 
Properties 
Compressive Strength- 
22 37.5 26 26.4 34.5 34.5 
Parallel, psi 
Friability (10 min.), pct. 
44 1 4.5 17.6 4.7 6.3 
Closed Cell Content, pct. 
83 20 15 81 88 86 
Fire Hazard Testing* 
Monsanto 2 ft. Tunnel, in. 
16.3 14 13.2 15.3 14.3 -- 
NBS, D.sub.s 73 24 22 -- -- -- 
USBM, sec./pcf. 
254 776 -- 653 982 810 
E-84 Flame 20 -- 36 15.4 15.0 -- 
Smoke 87 -- 323 67 41 -- 
______________________________________ 
Note: 
D, E, F, are in accordance with this invention. 
The tests reported are identified as tests A through F. Tests A, B, and C 
are not in accordance with the present invention, whereas Tests D, E, and 
F are in accordance with the present invention. Test A sets forth the 
practice which may be regarded as a "standard" in the art. It is noted 
that the polyol consists of 84.3% Thermolin (the base polyol), and 15.7% 
of a supplemental plasticizing polyol. It is apparent from a consideration 
of the properties and fire testing data that the resulting product 
exhibits useful compressive strengths, a high degree of friability, and a 
satisfactory closed cell content. The fire hazard testing data indicates 
that the resulting foam is a Class I fire hazard rated material. 
Tests identified as Test B and C constitutes "controls," which are provided 
for the purpose of comparison only, and also are not in accordance with 
the present invention, utilize either substantially all polyhydroxymethyl 
furan or a mixture of polyhydroxymethyl furan with furfuryl alcohol as the 
sole polyol ingredient. From the data it is seen that the compressive 
strengths are very high in the case of Test B, and are improved in Test C 
over the test results obtained in Test A, but that in both instances the 
friability is vastly improved. Nonetheless, neither the product of Test B 
or C is useful as an insulation material because of the closed cell 
content is relatively low, e.g. 20% of B and 15% in C. Thus complete fire 
test data was not obtained in either of these since neither were regarded 
as useful as insulating rigid foams. Nevertheless it is apparent that the 
U.S. Bureau of Mines test results for Test B was outstanding compared to 
that in the "standard" of the industry represented by Test A. 
Tests D, E, and F are in accordance with the present invention. It is noted 
that Test D, E and F each uses a successively greater portion of the 
bis-hydroxymethyl furan component, in accordance with the present 
invention. Consequently these tests used successively less of the standard 
polyhalogenated polyol, as base polyol. It is apparent from the data that, 
compared to the results obtained in Test A, for example, that the 
compressive strengths is improved in accordance with the present 
invention, the friability is vastly improved and that the closed cell 
content is entirely satisfactory. In addition the fire hazard testing data 
indicates that the samples obtained by the method of Test D and E are 
Class I flame hazard rated foams. It should be noted that the viscosity of 
the polyol mixtures utilized in Test F was extremely high (estimated to be 
about 3,000). Inasmuch as the same identical equipment was used in each of 
these tests, the equipment being set to accommodate a polyol having a 
viscosity in the neighborhood of less than 2,000 cps. at 25.degree. C., 
the settings employed were not optimum for Test F. Consequently, it is 
believed that inadequate mixing was encountered and that in order to be 
meaningful, tests, including fire hazard testing, should be done only on a 
thoroughly, homogeneously mixed material free of the color striations 
which were observed in the product of Test F, which color striations are 
believed to indicate poor, i.e. inadequate mixing prior to foam formation. 
EXAMPLE II 
The purpose of this test is to compare the dimensional stability under 
flame heating stress between a product produced in accordance with the 
present invention and a commercially available glass reinforced 
isocyanurate foam and a "standard" urethane foam. The results are set 
forth in Table II. The commercially available isocyanurate foam is one 
commercially available for roof decking, and this sample was glass fiber 
reinforced. In this test a 6".times.6".times.1" foam sample is supported 
on a ring stand and heated from below by a Meeker burner 
(1900.degree.-2000.degree. F. flame) in which the flame tip is 
approximately 1.33" below the sample, and the percentage shrinkage of the 
various dimensions are measured after 15 minutes of the test. The foams to 
which the commercially available rigid foam sample is compared were 
unreinforced urethane foams produced in accordance with Test A and Test D 
as reported in Table I. Thus "Test A" is the "standard" urethane foam not 
in accordance with the present invention, and Test D column data sets 
forth data from material which is made in accordance with the present 
invention in the procedure of Test D in Example 1, herein. 
TABLE II 
______________________________________ 
HEAT STABILITY SCREENING TEST 
J.W. 
Glass Reinforced 
Urethane 
Isocyanurate Test A Test D* 
______________________________________ 
Shrinkage 
Width 1.9 20.9 2.8 
Length 1.9 19.9 1.5 
Thickness 12.9 27.7 24.7 
______________________________________ 
*In accordance with this invention 
Thus it is manifest from a consideration of the data of Table II that the 
product produced in accordance with the present invention exhibited heat 
stability characteristics vastly superior to the characteristics observed 
in connection with products produced in accordance with "standard" 
methods, and in fact, the unreinforced product of the present invention 
compared quite favorably to the characteristics observed in connection 
with a commercially available glass reinforced isocyanurate roof decking 
material.