A flexible polyurethane foam is provided which is fire retardant and non-dripping upon exposure to flame. The flexible polyurethane foam is prepared by the reaction of a polyol, an isocyanate and a protein.

BACKGROUND OF THE INVENTION 
The field of this invention relates to flexible polyurethane foams and, 
particularly, to flexible polyurethane foams which have a reduced tendency 
to drip when exposed to flame. 
The preparation of flexible polyurethane foams from polyols and isocyanates 
is well known. Polyurethane foams burn easily and, accordingly, the 
incorporation therein of various flame retardant materials is 
conventional. The mere incorporation of flame retardant additives does 
not, however, reduce the unfortunate tendency of polyurethane foams to 
melt in contact with flame and to drip melting fragments. 
Attempts have been made to overcome the melting or dripping tendency of 
polyurethane foams upon exposure to flames, but such attempts have not 
succeeded to an appreciable extent. The problem apparently lies in the 
fact that most attempts to prevent polyurethane foam from dripping upon 
exposure to flame involve the addition of foam precursors or additives to 
the foam which do not provide a homogeneous coherent foam. Accordingly, 
there is a need for providing a polyurethane foam which has a reduced 
tendency to drip upon exposure to flame. 
A distinction must be made between the problems involved in flexible 
polyurethane foams and rigid polyurethane foams upon exposure to flame. 
Rigid polyurethane foams do not drip upon exposure to flame. The very 
structure of a rigid polyurethane foam enables the manufacturer to 
incorporate therein higher amounts of fillers and flame retardants than 
can be incorporated in a flexible polyurethane foam. Were a manufacturer 
of flexible polyurethane foam to incorporate all of the various filler and 
additives which may be added to a rigid foam, the flexible flame would 
lose its flexibility. The manufacturer of rigid foam does not have to 
consider loss in flexibility upon incorporation of high amounts of 
additives. Prior attempts to prevent flexible polyurethane foam from 
dripping resulted in the lowering of the physical properties because of 
addition of high amounts of fillers, and the foam thus produced was of a 
high density which had reduced flexibility and usefulness. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, it has been found that a flexible 
polyurethane foam can be prepared which has a reduced tendency to drip 
upon exposure to flame. The invention contemplates the addition of protein 
to the polyurethane foam during its manufacture. Thus, a protein is added 
to the polyol and isocyanate reactants and the protein thereby reacts with 
and becomes an integral chemical part of the primary polyurethane 
components and acts to partially cross-link the polyurethane foam so as to 
prevent its collapse and dripping when exposed to flame. 
PRIOR ART 
The following prior art is believed relevant to the present invention; 
U.S. Pat. No. 3,658,731 discloses the preparation of a type of rigid 
polyurethane foam which is prepared by the reaction of an isocyanate with 
whey powder and dimethyl sulfoxide. The whey powder contains from 8 to 14 
percent protein. 
U.S. Pat. No. 3,660,321 discloses a polyurethane foam which has been flame 
retarded by the addition of microcapsules filled with flame retardant 
material. The microcapsules may be made from gelatin. 
SPECIFIC EMBODIMENTS OF THE INVENTION 
In accordance with the present invention, it has been found that if protein 
is added during the manfacture of a polyurethane foam and if the protein 
and the foam components, e.g., the polyol and isocyanate, are added in a 
critical sequence, the statistical chances of a high degree of 
crosslinking is reduced and a polyurethane foam having good density and 
flexibility but reduced tendency to drip is afforded. As stated above, the 
problem of reducing the statistical tendency of cross-linking of the 
protein by isocyanate is of no consequence in preparing rigid polyurethane 
foams since, by their very nature, rigid foams are preferably completely 
cross-linked. 
Isocyanates which may be used in acordance with the present invention 
include any of the organic polyisocyanates conventionally employed for 
reaction with polyols, polyetherpolyols or polyesters in the manufacture 
of polyurethanes. Exemplary polyisocyanates include 2,4-tolylene 
diisocyanate, 2,6-tolylene diisocyanate, benzene diisocyanate, m-xylylene 
diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 
4,4'-diphenyl diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 
hexamethylene diisocyanate, tolidine diisocyanate, dianisidine 
diisocyanate, 1,5-naphthalene diisocyanate, 1,4-cyclohexane diisocyanate 
and similar compounds. 
Polyols which are used in accordance with the present invention include any 
of the organic polyols, polyetherpolyols and polyesters conventionally 
used in the preparation of polyurethanes. Exemplary compounds include 
ethylene glycol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, 1,3- 
or 1,4-xylylene glycol, 1,4-bisoxymethyl cyclohexane, 
poly(oxyethylene)glycol, poly(oxypropylene)glycol, poly(oxybutylene) 
glycol, poly(oxyalkylene)adducts of glycerin, trimethylolpropane, 
1,2,6-hexanetriol, pentaerythritol, sorbitol and polyesters from glycols 
and aliphatic acids. 
The preparation of a rigid polyurethane foam which has reduced flammability 
is quite different than preparing a flexible polyurethane foam which has a 
reduced tendency to burn and drip. Basically, the alcohols used to prepare 
rigid and flexible foams are different. In rigid polyurethane foams 
polyfunctional alcohols, e.g., polyglycols, are utilized in order to form 
many cross-linking sites with the isocyanate reactant and thus produce the 
rigid foam structure. In flexible polyurethane foams difunctional polyols 
are used so as to reduce the number of sites for cross-linking by the 
isocyanate and thus allow the foam to be flexible. 
Proteins which are added in accordance with this invention include both 
simple and conjugated proteins. Simple proteins are represented by 
albumins such as ovalbumin; globulins; glutelins such as glutenin, 
vegetable casein, flour gluten and casein, prolamins such as gliadin and 
zein; albuminoids such as bone hide and tendon collagens, e.g., bone glue, 
elastin and animal and vegetable gelatin; and protamins. Conjugated 
proteins which are included within the scope of this invention include the 
chemoproteins, mucoproteins, glycoproteins, lipoproteins, phosphoproteins 
and nucleoproteins. Proteins preferably used in the practice of the 
present invention are the glutelins, e.g., casein and the bone hide 
collagens, e.g., bone glue and gelatin. 
In preparing the protein-containing polyurethane foams contemplated by the 
present invention, the proportions of polyol and isocyanate which are 
reacted correspond to our index of from about 80 to about 120, preferably 
from about 90 to about 115. An index is a measure of stoichiometric 
balance of combining substances. As applied to polyurethane foam, it is 
the relationship between the equivalent weights of isocyanate on one side 
and water and polyol on the other side. An index of 100 indicates that the 
equivalent weights are balanced. An index of 80 indicates a 20 percent 
shortage of isocyanate and an index of 120 indicates a 20 percent surplus 
of isocyanate. The concentration of protein, based on the weight of the 
polyol, may be from about 10 to about 100 percent, preferably from about 
20 to about 50 percent. 
It has been found that the order of addition of the polyurethane foam 
reactants is critical in order to form a foam which has a reduced tendency 
to drip but which is still flexible and of good density and having good 
foaming characteristics. Thus, the order of addition of ingredients to 
obtain optimum non-drip characteristics is to (1) form a mixture of the 
polyol, flame retardant, catalyst, surfactant and blowing agent, (2) add 
the protein to such mixture and then (3) add a mixture of isocyanate and 
polymerization catalyst. 
Flexible polyurethane foam is conventionally prepared by mixing polyol, 
amine, silicone and water for 30 seconds, adding the flame retardant and 
stirring for 30 seconds, adding the catalyst and stirring for 6 seconds 
and adding the isocyanate and stirring until foaming begins. 
In the formulations described, finely divided pigments and inorganic 
fillers may be incorporated. Examples of such materials are convention 
pigments such as TiO.sub.2 and fillers such as magnesium carbonate, 
Dawsonite, alumina and hydrated alumina. 
The addition of such materials should be no greater than about 40 PHR 
(parts per hundred parts of resin) to avoid decreasing the flexibility of 
the polyurethane foam. 
Buffering agents may be added to the foam formulations for the purpose of 
maintaining the proper pH to allow the foam reaction to occur at an even 
rate and thereby achieve consistent cell size. Addition of buffers is 
especially important when acidic flame retardants, such as chlorinated 
paraffins or phosphonates, are added. 
Typical buffering agents include lead stearate, sodium acetate, potassium 
hydrogen phthalate, potassium dihydrogen phosphate, disodium hydrogen 
phosphate, borax and similar compounds which are conventionally used to 
prepare solutions having a stable pH. 
The buffering agents are used in an amount of from about 0.1 to about 10 
percent by weight based on the polymer. A preferred concentration of 
buffer is from about 0.5 to about 5 percent by weight. The amount of 
buffer used will vary, of course, depending on the acidity of the system 
and the pH desired. Generally, an amount of buffer is used which will 
result in a pH of from about 5.5 to about 8.5, preferably from about 6.5 
to about 7.5. 
Flame retardant agents which are utilized in the present invention are 
those conventionally used for such purposes. They include phosphorus 
compounds and halogenated phosphorus compounds such as trialkyl 
phosphates, e.g. tributyl phosphate, tris-2,3-dichloropropyl phosphate, 
tris-2,3-dibromopropyl phosphate, trioctyl phosphate, triundecyl 
phosphate; dialkylaryl phosphates, e.g., dibutyl phenyl phosphate, 
alkyldiaryl phosphates, e.g., isodecyl diphenyl phosphates and octyl 
diphenyl phosphate; triaryl phosphates, e.g., tricresyl phosphate, 
triphenyl phosphate, cumylphenyl diphenyl phosphate. Other phosphorus 
compounds used include diethylene glycol bis(di-2-chloroethyl)phosphate, 
2,2-bis(chloromethyl)trimethylene bis[bis(2-chloroethyl)phosphate] and 
polyphosphonates of the formula 
##STR1## 
wherein n has an average value of 1 to 2. 
In the following Examples, certain flammability tests are conducted and 
conclusions are drawn therefrom. The flammability tests used are the 
conventional horizontal and vertical burning tests, the former being 
identified as ASTM 1692-74 and the latter being identified as UL94. 
The flammability tests are described as follows: ASTM 1692 is the most 
widely used burning test for cellular plastics. In such test, a specimen 
(152.4 mm..times.50.8 mm..times.25.4 mm) is supported on a horizontal 
hard-cloth support with the 25.4 mm. dimension vertical. 
One end is contacted for 60 seconds with a 38.1 mm. high blue flame from a 
9.5 mm. diameter barrel Bunsen burner fitted with 47.6 mm. wide wingtop. 
If the specimen instantly goes out, it is self-extinguishing. If the 
specimen burns and subsequently goes out, it is characterized as 
self-extinguishing/burn rate given as mm. and seconds burned. If the 
specimen completely burns, its burn rate in mm./minute is given. 
The "UL-94" test is utilized to determine the resistance of a plastic 
material to continued combustion and to ignition. In this test, a standard 
specimen is supported, from the upper 6.4 mm. of the specimen with the 
longitudinal axis vertical, by a clamp on a ring stand so that the lower 
end of the specimen is 9.5 mm. above the top of the burner tube and 305 
mm. above a horizontal layer of dry absorbent surgical cotton. The burner 
is placed remote from the specimen, ignited and adjusted to produce a blue 
flame 19 mm. high. The test flame is placed centrally under the lower end 
of the test specimen and allowed to remain for 10 seconds. The test flame 
is then withdrawn and the duration of the flaming of the specimen noted. 
When the flaming of the specimen ceases, the test flame is immediately 
placed again under the specimen. After 10 seconds, the test flame is again 
withdrawn and the duration of flaming and glowing noted. 
In this procedure, V-0 is the highest rating obtainable. It indicates an 
average burn time of less than 50 seconds (2 ignitions for each of 5 
specimens), no one burn of greater than 10 seconds, no dripping flame, no 
afterglow beyond 30 seconds after the second removal of the flame and no 
ignition of the layer of cotton. A rating of V-1 allows up to 250 seconds 
average burn time and a V-2 rating indicates the sample drips and flames.

EXAMPLE I 
This example illustrates the preparation and vertical burn testing of a 
flexible polyurethane foam containing a flame retardant but no protein. 
A flexible polyurethane foam was prepared from the following formulation: 
______________________________________ 
Ingredients Parts by Weight. 
______________________________________ 
PLURACOL GP 3030.sup.1 
50.00 
Water 2.00 
DABCO 33 LV.sup.2 Accelerator 
0.33 
Surfactant L520.sup.3 
0.50 
PHOSGARD 2XC20.sup.4 
10.00 
Stannous octoate catalyst 
3 drops 
Tolylene diisocyanate 
27.00 
______________________________________ 
.sup.1 Polyether polyol (Wyandotte Chemical Company) 
.sup.2 Triethylamine diamine/dipropylene glycol (Houdry Process Company) 
.sup.3 Block siloxane/polyoxyalkylene copolymer (Union Carbide) 
.sup.4 [2,2bis(chloromethyl)]trimethylene bis[bis(2chloroethyl)phosphate 
(Monsanto) which has the structural formula 
##STR2## 
Vertical burn tests classified the sample as V-2. 
EXAMPLE II 
This Example illustrates the preparation and vertical burn testing of a 
polyurethane foam having the formulation of Example I but with the 
addition of protein. 
A polyurethane foam was prepared as in Example I, but 25 phr of the 
polyether polyol was replaced by 25 phr of Knox gelatin. 
Vertical burn tests classified the sample as V-0 (i.e., combustion lasted 
less than 2 seconds after application of test flame with no dripping of 
flaming particles that ignite cotton pad located 305 mm. below test 
specimen). 
EXAMPLE III 
This Example illustrates the preparation and horizontal and vertical burn 
testing of a polyurethane foam containing protein and a filler. 
A flexible polyurethane foam was prepared from the following formulation: 
______________________________________ 
Ingredients Parts by Weight 
______________________________________ 
PLURACOL GP 3030 70.00 
Water 4.00 
DABCO 33LV 0.65 
Surfactant Y6634* 
1.00 
PHOSGARD 2XC20 20.00 
Knox Gelatin 40.00 
Al.sub.2 O.sub.3 30.00 
Stannous Octoate 6 drops 
Tolylene diisocyanate 
54.00 
______________________________________ 
*Siloxane/polyoxyalkylene block copolymer (Union Carbide) 
The foam had a density of 0.37 kg/cm.sup.2, was self-extinguishing in the 
horizontal burn test and was classified V-0 in the vertical burn test. 
There was no dripping of the foam on exposure to flame. 
EXAMPLE IV 
This Example illustrates the preparation and vertical burn testing of 
polyurethane foams, one of which contains a sodium acetate buffering 
agent. 
______________________________________ 
Ingredients Sample #1 Sample #2 
______________________________________ 
PLURACOL GP 3030 
50 50 
Water 2 2 
DABCO 33LV 0.40 0.40 
L520 0.5 0.5 
Uniclor 70.sup.1 
4 4 
PHOSGARD C22R.sup.2 
4 4 
Sodium acetate -- 2 
Gelatin 15 15 
Stannous octoate 
0.10 0.10 
Tolylene diisocyanate 
27 27 
______________________________________ 
.sup.1 Chlorinated paraffin (Neville Chemical 
.sup.2 Polyphosphonate of the formula set forth at page 8, line 7 
(Monsanto) 
In the absence of a buffering agent, Sample #1 collapsed and no foam was 
obtained due to the acidity of the formulation caused by use of 
chlorinated paraffin and PHOSGARD C22R. Sample #2, containing a buffering 
agent, produced a good foam and was classified V-0 in the vertical burn 
test. 
EXAMPLE V 
This example illustrates the criticality of addition of polyurethane foam 
reactants. Two samples were prepared from the following formulation: 
______________________________________ 
Parts by Weight 
Ingredients Sample #1 Sample #2 
______________________________________ 
PLURACOL GP 3030 
25 25 
Water 2 2 
DABCO 33LV 0.4 0.4 
L520 0.5 0.5 
PHOSGARD 2XC20 10 10 
Gelatin 25 25 
Stannous Octoate 
.08 .08 
Tolylene diisocyanate 
27 27 
______________________________________ 
Sample #1 was mixed in the conventional manner described immediately 
preceding Example I. There was obtained a boardy foam of low quality that 
was Classified V-1 in the vertical burn test. 
Sample #2 was mixed, as were the formulations in Examples I through IV, as 
follows: 
1. The stannous octoate catalyst and tolylene diisocyanate are premixed and 
set aside; 
2. All ingredients are mixed, except the premix of Step 1 and the gelatin; 
3. The gelatin is added to the mixture of Step 2; 
4. The premix is added. 
Sample #2 gave a good foam having a classification of V-0 in the vertical 
burn test.