Heavily loaded flame retardant urethane and method

The invention disclosed relates to a new polyurethane composition having improved flame retardance and to a method for preparing same. The present composition is prepared by using a suspending agent and a surfactant. The suspending agent may be either a surfactant or an appropriate polymer, but to control the cellular structure, a surfactant that does not perform as a suspending agent is desirable. The resultant composition may be sprayed through a high pressure spray gun while permitting formation of heavily loaded flame retardant urethane foams which are neither dusty nor lose solids upon washing.

This invention relates to a new polyurethane composition having improved 
flame retardancy and to a method for preparing such compositions. 
Numerous attempts have been made in the prior art seeking solutions to 
improving flame retardancy for polyurethane compositions. Typically, these 
attempts have provided compositions which only limitly improve the flame 
retardant capacity while greatly increasing the cost of the final 
composition. 
It has also been recognized that to obtain really good fire retardancy, 
high loadings of hydrated alumina were possible when coupled with certain 
phosphorous compounds. One example of such a formulation is that disclosed 
in U.S. patent application Ser. No. 588,092 filed June 18, 1975, 
(Disclosure No. 4898) by Marans et al. This mixture has two drawbacks. It 
cannot be sprayed through high pressure nozzles, and the resulting foam is 
"dusty" and not resistant to washing. It has been found, however, that by 
practice of the present invention, there results a new improved flame 
retardant polyurethane which is easily prepared both commercially and 
economically, by using a suspending agent, either a surfactant or 
appropriately active polymer, to suspend the alumina hydrate which 
overcomes the spraying problem, and by using a surfactant, preferably one 
with a significantly different chemical structure, to prepare soft, 
resilient foams that are not dusty, can be readily washed and also exhibit 
good physical properties. 
By the present method, flame retardant polyurethanes may be prepared having 
hydrophilic crosslinked polyurethane structures by reacting a particular 
isocyanate capped polyoxyethylene polyol with large amounts of an aqueous 
slurry of an alumina hydrate and a particular combination of surfactants. 
The thus generated polyurethane having alumina hydrate uniformly disposed 
throughout may be sprayed, and the product foam is found to have improved 
flame retardancy without dusting even upon washing. 
Generally, the present polyurethane composition includes a hydrophilic 
polyurethane structure having uniformly dispersed therein an alumina 
hydrate powder additive which is effectively contained without dusting 
even upon washing. 
Because the additives employed herein must be uniformly dispersed in the 
polyurethane structure, it is advantageous to generate a hydrophilic 
polyurethane from relatively large amounts of water or aqueous reactant. 
In this manner, the alumina hydrate additive can be introduced during the 
reaction step or by spraying and thereby insure uniform distribution. The 
product foam effectively contains the alumina hydrate without dusting even 
upon washing. 
One group of polyurethanes useful herein are disclosed in co-pending, 
commonly assigned U.S. patent application Ser. No. 250,012 filed May 3, 
1972, now abandoned, the effective portions of the disclosure of which are 
incorporated herein by reference. Generally, these foams are crosslinked 
polyurethane foams prepared by using a capped polyoxyethylene glycol 
reactant and massive amounts of water. 
The polyoxyethylene polyols used in this invention are water soluble 
reaction products derived from the polymerization of ethylene oxide in the 
presence of a polyfunctional starter compound such as water, ethylene 
diamine ethylene glycol, glycerol, pentaerythritol, sucrose and the like. 
The molecular weights may be varied over a wide range by adjusting the 
relative ratios of ethylene oxide monomer to starter compound. The 
preferred molecular weight ranges are described subsequently. 
It is possible and sometimes desirable to incorporate various amounts of a 
relatively hydrophobic comonomer into the ethylene oxide based 
polymerization products. Thus, comonomers such as propylene oxide or 
butylene oxide may be copolymerized as a random copolymer, block 
copolymer, or both, such that the copolymers remain hydrophilic while 
having other desirable features for certain applications, namely improved 
low temperature flexibility, resistance to compression set, resiliency and 
the like. Up to about 40-60 mole percent but desirably about 25-45 mole 
percent of the relatively hydrophobic comonomer may be copolymerized with 
the ethylene oxide monomer and still yield hydrophilic crosslinked network 
foams when those products are used as polyol intermediates in practicing 
the present invention. Thus, throughout this text, the term 
"polyoxyethylene polyol" is intended to include not only homopolymers of 
ethylene oxide, but also hydrophilic copolymers of ethylene oxide such as 
those described above, wherein all of the polyol derivatives have a 
hydroxyl functionality of about two or greater and an ethylene oxide 
content ranging from about 40 mole percent to about 100 mole percent, and 
preferably greater than about 55 mole percent. 
Particularly useful foams may be prepared by first capping a 
polyoxyethylene polyol with a polyisocyanate such that the capped product 
has a reaction functionality greater than 2. Thereafter, the resin is 
reacted by combining with water such that a crosslinked foam result. It is 
also possible to use a capped polyoxyethylene polyol having a 
functionality approximating 2 in which case a polyfunctional reactive 
member such as one having three, or up to about 8 reactive amine, hydroxy, 
thiol, or carboxylate sites per average molecule is included to form a 
three dimensional crosslinked product. Useful polyfunctional reactive 
members include materials such as diethylenetriamine, 
triethylene-tetramine, tetraethylene-pentamine, polyethyleneimine, 
glycerol, trimethylolpropane, pentaerythritol, tolylene-2,4,6-triamine, 
ethylenediamine, trimethylenediamine, tetramethylenediamine, 
pentamethylenediamine, hexamethylenediamine, aminoethanol, diethanolamine, 
hydrazine, triethanolamine, benzene-1,2,4- tricarboxylic acid, 
nitrilotriacetic acid, citric acid,4,4',-methylenebis (p-chloraniline), 
and the like. 
Polyoxyethylene polyol used as a reactant in preparing the capped product 
to be formed may have a weight average molecular weight of about 200 to 
about 20,000, and preferably between about 600 to about 6,000, with 
hydroxyl functionality of about 2 or greater, preferably from about 2 to 
about 8. 
Polyoxyethylene polyol is capped by reaction with a polyisocyanate or 
polyisothiocyanates. The capping materials include PAPI (a polyaryl 
polyisocyanate as defined in U.S. Pat. No. 2,683,730), tolylene 
diisocyanate, triphenylmethane-4,4',4",-triisocyanate, benzene-1, 
3,5-triisocyanate, toluene-2,4,6-triisocyanate, diphenyl-2, 
3,3'-triisocyanate, hexamethylene diisocyanate, xylene diisocyanate, 
naphthalene-1, 5-diisocyanate, xylene-alpha, alpha' diisothiocyanate, 
3,3'-dimethyl-4,4'-biphenylene diisocyanate, 
3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 2,2' 
5,5'-tetramethyl-4,4'-biphenylene diisocyanate, 4,4'-methylenebis 
(phenylisocyanate), 4,4'-sulfonylbis (phenylisocyanate), 4,4'-methylene 
diortho-tolylisocyanate, ethylene diisocyanate, ethylene diisothiocyanate, 
trimethylenediisocyanate and the like. 
Capping of the polyoxyethylene polyol may be effected using either about 
stoichometric amounts of reactants or an excess of isocyanate to insure 
complete capping of the polyol. 
To effect foaming and preparation of the crosslinked network polymer, the 
component including the isocyanate capped polyoxyethylene polyol having a 
functionality about 2 or greater is simply combined with water by most any 
suitable means such that a crosslinked hydrophilic foam results. 
Because foaming of the present resin reaction is effected simply, it is 
possible to add the surfactants to either the resin reactant, or to the 
water reactant or to both. Also, supplemental materials such as those well 
known to the artificial sponge foaming art maybe added as desired, 
provided they do not detrimentally affect the product foam. 
The significance of adding materials such as alumina hydrate may be 
realized by means of the Oxygen Index Method, a flammability test for 
plastics, ASTM D-2863-70. This method describes a procedure for 
determining the relative flammability of polyurethane by measuring the 
minimum concentration of oxygen in a slowly rising mixture of oxygen and 
nitrogen that will just support combustion. 
The oxygen index value as used herein is the minimum concentration of 
oxygen, expressed as volume percent, in a mixture of oxygen and nitrogen 
that will just support combustion of a material under the conditions of 
this method. 
The minimum concentration of oxygen in a slowly rising mixture of oxygen 
and nitrogen that will just support combustion is measured under 
equilibrium conditions of candle-like burning. The balance between the 
heat from the combustion of the specimen and the heat lost to the 
surroundings establishes the equilibrium. This point is approached from 
both sides of the critical oxygen concentration in order to establish the 
oxygen index. 
Another significant and unexpected value of the present polyurethane 
composition resides in the low smoke density determination. Accordingly, 
not only does the present composition have a superior flame retardant 
value, but also this advantage is supplemented by the fact that should 
some portion of the composition be consumed by flame, the consumption 
produces very low smoke density relative to other polyurethane structures 
which do not include the present additives. 
Typically, polyurethane compositions which do not include addition of the 
additives now found to be essential, have an oxygen index value of about 
0.15 to about 0.30 at best. In contrast, the present polyurethane 
compositions have corresponding oxygen index values up to about 0.40 and 
greater without resultant dusting or loss of solid additives even upon 
washing as is often experienced in prior developed formulations. 
The present polyurethane compositions include about 50 to about 400 parts 
of alumina hydrate additive per 100 parts of prepolymer resin to be 
reacted. Preferably, amounts of about 100 to about 275 of alumina hydrate, 
same weight basis, are employed. 
Alumina hydrates, also commonly called hydrated aluminas, for use herein, 
are known and are highly refined, inorganic white granular crystalline 
powders with the chemical formula of Al.sub.2 O.sub.3. XH.sub.2 O, such as 
especially, Al.sub.2 O.sub.3. 3H.sub.2 O. These materials generally are 
produced by the Bayer process from bauxite ore and contain small amounts 
of soda, iron oxide and silica. They are chemically inert and have been 
used as a filler in organic systems where a filler is normally employed. 
The particle size of useful alumina hydrate ranges from an average particle 
size of about 0.5 to about 120 microns. Fine particles having a size of 
about 6.5 to about 9.5 microns are particularly useful. Also, where color 
of the resultant polyurethane is important, the aluminum hydrate should 
have a snow-white color grade. 
Phosphorus containing compounds may optionally be included herein if 
desired, such as phosphites, polyphosphites, ammonium phosphates, 
polyphosphates, phosphate salts, organic phosphates, phosphonates and 
polyphosphonates, and mixtures thereof. 
The phosphorus containing additive, when included, are in an amount from 
about 1 to about 200 parts by weight per 100 parts by weight polymer to be 
reacted and preferably about 2 to about 100 parts, similar weight basis. 
A number of phosphorus containing additives are available and may be used 
herein. One useful material is sold under the mark Phosgard C-22-R by 
Monsanto. This material has the structural formula: 
##STR1## 
Because the above formulated material is insoluble in water, it may be 
added to the reaction by means of an emulsion, suspension or dispersion as 
desired, but is usually added as a liquid misable in the prepolymer phase. 
An additional phosphorus containing additive for possible use in 
combination with aluminum hydrate to prepare the present polyurethane 
compositions is ammonium polyphosphate, available under the mark Phoschek 
P/30 by Monsanto. 
Specific phosphorus containing materials which may be useful include, but 
are not limited to, derivatives of P.sub.2 O.sub.5, phosphorus acid, 
phosphorus acid and phosphorus halides; ureaphosphoric acid, monophenyl 
phosphate and the like; sodium hexametaphosphate, ammonium salts of 
phosphonomethylated ethers, and the like; monoammonium phosphate, 
diammonium phosphate and the like; melamine phosphate and salts of 
phosphorus or phosphoric acid with organic amines; salts of 
urea-phosphoric acid, monophenyl phosphate, phosphorus pentoxide or 
chlorides of partially esterified phosphoric acids. Phosphonomethylated 
ethers, diethyl chlorophosphate, triallyl phosphate, phosphoroxytriamide 
and the like may also prove useful; also tris (.beta.-chloroethyl) 
phosphate, tris (2,3-dibromopropyl) phosphate, etc. 
It is also possible to use materials such as tricresyl phosphate, cresyl 
diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, trialkyl phosphate 
and triaryl phosphate as a source of phosphorous for the present 
polyurethane composition. Another useful source of phosphorous for 
possible use herein is that marketed as Fyrol 6, a composition by Stauffer 
having the formula: 
EQU (C.sub.2 H.sub.5 O).sub.2 P(O)CH.sub.2 N(CH.sub.2 CH.sub.2 OH).sub.2 
a wide variety of known phosphorous sources are available for use herein. 
It is important, however, to realize that the phosphorous source must be 
included along with the aluminum hydrate additive. 
To effect foaming and preparation of the crosslinked network polymer, the 
component including the isocyanate capped polyoxyethylene polyol having a 
functionality about 2 or greater is simply combined with a particular 
aqueous component. For simplicity, this isocyanate capped reaction 
component will be referred to herein as the resin reactant. 
The aqueous component may appear as water, a water slurry or suspension, a 
water emulsion, or a water solution having water soluble materials 
disposed therein. For convenience, the aqueous component is referred to 
herein as the aqueous reactant. 
In contrast to typical polyurethane reactions such as those using catalyst 
or like promoters where one mole of --NCO is reacted with one-half mole 
water, the present reaction proceeds simply with a large but controlled 
excess of water. 
In typical polyurethane reactions known to the art, it is known to employ 
an excess of water in prepolymer foaming formulations to obtain improved 
properties. This has been observed at page 43 in the publication by 
Saunders and Frisch entitled "Polyurethanes," published by Interscience 
Publishers, where it is further observed that if less than stoichiometric 
amounts of water are used, the foam is more crosslinked, firmer, has lower 
elongation and higher density. A large excess of water, they observe, will 
use up the free isocyanate groups, leaving insufficient isocyanate 
available for effective crosslinking and resulting in the formation of 
many free amino end groups. As water content increases, the foam density 
decreases and above 30-50% excess water over stoichiometry results in a 
marked decrease in physical properties. 
The dramatic way in which the addition of water influences practice of the 
present invention is seen by consideration of the Water Index: 
##EQU1## 
Here, keeping in mind that in polyurethane foaming reactions one mole of 
water ultimately consumes two NCO groups, i.e. 1.0 mole H.sub.2 O - 2 
equivalents --OH which react with 2 equivalents of NCO, Water Index Value 
of 100 indicates the equivalents of water and equivalents of isocyanate 
are balanced. An Index of 95 indicates that there is a 5% shortage of 
water equivalents while an Index of 105 indicates a 5% surplus of water 
equivalents. A slight shortage of water equivalents (i.e. a slight excess 
of isocyanate), usually 3-5%, is common practice in the prior art, 
particularly with flexible foams. 
Using the present resin reactant and water in amounts from about 0.5 mole 
H.sub.2 O/mole NCO groups (H.sub.2 O Index Value of 100) up to about 2 
moles H.sub.2 O/mole NCO groups (H.sub.2 O Index Value of 400) results in 
poor foaming unless materials such as surfactants and catalysts or the 
like are included. Amounts up to about 2 moles H.sub.2 O/mole NCO (H.sub.2 
O Index Value of 400) require a catalyst. When using about 6.5 moles 
H.sub.2 O mole/NCO groups (H.sub.2 O Index Value of 1300) up to about 390 
moles H.sub.2 O/mole NCO groups, (H.sub.2 O Index Value 78,000) 
surprisingly good foams result which improve in characteristics with added 
amounts of molar water. Thus, the available water content in the aqueous 
reactant is from about 6.5 to about 390 moles H.sub.2 O/NCO groups in the 
resin reactant, i.e. an H.sub.2 O Index Value of about 1300 to about 
78,000 and desirably from about 4,000 to about 40,000, i.e. about 20 to 
about 200 moles H.sub.2 O/NCO groups. 
"Available water" in the aqueous reactant is that water accessible for 
reaction with the resin reactant, and which is exclusive of water which 
may layer during reaction, or supplemental water which may be necessary 
because of further water-absorbtive or water-binding components or 
additives present in and forming the aqueous reactant. 
The use of large molar excesses of water in the aqueous reactant leads to 
several important advantages and improvements over the conventional flame 
retardant polyurethane foam compositions. For example, in conventional 
polyurethane foam compositions, the water concentration must be carefully 
controlled to near the theoretical amount, usually an amount much less 
than about an H.sub.2 O Index Value of 400 (2.0 moles H.sub.2 O/NCO groups 
in the polyurethane reaction components) and the flame retardants must be 
separately included. This low concentration dictates the use of a catalyst 
to promote the rate of the polymerization foaming reaction, and requires 
an intensive mixing step to achieve good mixing of reactants and catalyst 
so as to insure a controllable and uniform cellular product, other 
additives are avoided. In contrast, the present invention requires a very 
large but controlled excess of water, e.g., typically about an H.sub.2 O 
Index Value of about 1300 to about 78,000. Using this technique, the 
product quality and uniformity is not highly sensitive to accuracy of 
metering or mixing of the aqueous reactant and the use of a polymerization 
catalyst is optional. Thus, the present additives are included in the 
polyurethane structure at the time of foaming. 
There are two broad classes of suspending agents that can be used to form 
and maintain stable hydrated alumina slurries, (1) water soluble or 
hydrophilic polymers and (2) surfactants. Appropriate candidates from the 
latter would be further defined as amphoteric, cationic or non-ionic. 
Examples of the polymeric suspending agents, often described as solution 
thickness, include but are not limited to hydroxyethyl cellulose polymers, 
sold as Natrosol.TM. by Hercules or as Cellosize .TM. by Union Carbide, 
hydroxy propyl cellulose sold as Klucel.TM. by Hercules, ethyl 
hydroxyethyl cellulose sold as EHEC.TM. by Hercules, ethyl cellulose, 
sodium carboxymethylcellulose, water soluble polyoxyethylene polymers sold 
by Polyox.TM. by Union Carbide Corp., gelatin, guar gums and agar. 
Examples of amphoteric surfactants that can be used include but are not 
limited to Sulfobetain TA 75 (tallow amido ammonium sulfonic acid betain) 
sold by Textilana Corp. and Antaron FC34 (complex fatty amido compound) 
sold by General Aniline and Film. Examples of cationic surfactants include 
but are not limited to Aliquat.TM. 21 (n-fatty trimethyl quaternary 
ammonium chloride) and Aliquat.TM. 221 (n-difatty dimethyl quaternary 
ammonium chloride) sold by General Mills and Atlas.TM. G265 sold by ICI 
America. Examples of effective nonionic surfactants include but are not 
limited to Arlacel.TM. 20 (sarbitum monolaurate) and Arlacel.TM. 85 
(sorbitan trioleate) made by ICI America, Pluronic.TM. L-72 
(ethylene/propylene oxide condensation product with propylene glycol) or 
Pluronic.TM. P-75 (ethylene/propylene oxide condensation product with 
propylene glycol) made by BASF-Wyandotte and Tween.TM. 20 (POE(20) 
sorbitan monolaurate(polysorbate 20)) or Tween.TM. 85 (POE(20) sorbitan 
trioleate(polysorbate 85)) made by ICI America. 
When hydrophylic polymers are used as the suspending agents, it is 
appropriate to use nonionic surfactants to control the cell size 
characteristics of the cellular plastic. Non-ionic surfactants with HLB 
numbers (hydrophobic to lyophobic balance) from 2 to 16 can be used. 
If the suspending agent is a nonionic surfactant then it is appropriate to 
use either amphoteric or cationic surfactants to control the cellular 
structure. 
The suspending agents may be added in an amount from 0.0001 to 0.04 parts 
by weight per part by weight of the resin reactant. Preferably the amount 
ranges from 0.001 to 0.01 parts by weight. 
The cellular control surfactant may be added in an amount from about 0.0005 
to .10 parts by weight per part of the resin reactant. Preferably, the 
amount ranges from 0.001 to 0.04 parts by weight. 
The hydrophilic foams of the present invention may be formulated so as to 
be flexible, semi-rigid or rigid in nature and to be of primarily open 
cell or primarily closed cell structure as desied. 
Because the present polyurethane composition is characterized with high 
flame retardancy and low smoke value it may be used for cushioning for 
furniture and transportation vehicles, mattresses, foamed coating for 
mattress covers and pads, upholstery fabrics, mattress ticking, sound 
absorbing wall coverings, carpet and rug underpadding, and the ike. 
Numerous additional uses will become obvious to those skilled in the art.

Practice of the present invention will become more apparant from the 
following examples wherein all parts are given by weight unless otherwise 
indicated. 
EXAMPLE 1 
A prepolymer is prepared from 2 moles of polyethylene glycol, 1000 M.W., 
one mole of Trimethylol propane and 7.7 moles of the commercial 80/20 
mixture of 2, 4 and 2, 6-tolyldiisocyanate. 100 parts by weight of 
prepolymer, 10 parts of tris -2, 3-dibromopropyl phosphate and 0.63 parts 
of Aliquat 221 cationic surfact were mixed. 150 parts of H.sub.2 O, 125 
parts of Al(OH).sub.3 and 0.63 parts of Arlacel 85 nonionic surfactant 
were mixed for 45 seconds with a motor driven propeller blade and then 
added to the above prepolymer mixture. After creaming, the sample was 
poured into a mold. After curing, it was placed in a microwave oven for 6 
minutes and then allowed to dry overnight in a 70.degree. C. vacuum oven. 
The sample was cut for testing and conditioned for 24 hours at 50% 
relative humidity, 25.degree. C. The oxygen index was 0.314. The sample 
was subjected to a standardized procedure of beatings by a motor driven 
paddle and lost 1.0% of its weight in dusting. Also, by a standard 
technique of motor driven washings in distilled water, 3.0% of the sample 
weight leached out. This foam was also made by spraying the aqueous 
solution from the Grac Hydra-Cat as in Example 2. Even after sitting in 
the sprayer overnight, the solution did not pack out. 
EXAMPLE 2 
One hundred parts by weight of the prepolymer of Example 1 were mixed with 
1.0 part of Pluronic L-62 surfactant. Then, 100 parts of Al(OH).sub.3 and 
100 parts of H.sub.2 O were mixed. The foaming was attempted by using a 
Graco Hydra-Cat to spray the aqueous solution and mix with the polymer. 
However, the aqueous solution packed out in the sprayer. 
This foam was also made according to the technique of Example 1. It was 
tested for dusting and washing as in Example 1; the percent weight loss 
for dusting was 7.0 and 8.5% for washing. 
EXAMPLE 3 
The procedure of Example 1 was repeated except using 100 parts by weight of 
prepolymer, 16 parts of tris-2, 3 dibromopropyl phosphate and 0.2 parts of 
Aliquat 221. 100 parts of H.sub.2 O 100 parts of Al(OH).sub.3 and 0.2 part 
of Arlacel 85 were mixed for 45 seconds and added to the prepolymer 
mixture. Identical conditioning procedures followed. The oxygen index was 
0.334. It was also tested for dusting and washing as in Example 1; the 
percent weight loss for dusting was 0.3 and 1.5% for washing. 
EXAMPLE 4 
The procedure of Example 1 was repeated except using 100 parts by weight of 
prepolymer, 20 parts of tris-2,3 dibromopropyl phosphate and 0.1 parts of 
Aliquat 221. 120 parts H.sub.2 O, 200 parts of Al(OH).sub.3 and 0.25 parts 
of hydroxyethyl cellulose were mixed for 45 seconds and added to the 
prepolymer mixture. After identical conditioning procedures, the oxygen 
index was 0.450. It was also tested for dusting and washing as in Example 
1; the percent weight loss for dusting was 0.5 and 2.0% for washing. 
EXAMPLE 5 
One hundred parts by weight of prepolymer and 16 parts of tris-2,3 
dibromopropyl phosphate were mixed. 0.5 parts of hydroxyethyl cellulose 
were added slowly to a mixture of 100 parts H.sub.2 O and 0.2 parts 
Arlacel 85. This was allowed to stand 20 minutes, the 100 parts of 
Al(OH).sub.3 were added and this was added to the prepolymer mixture. 
After creaming, the sample was poured into a mole. The foam was dried for 
24 hours in a 70.degree. C. forced air oven. It was tested for dusting and 
washing as in Example 1; the percent weight loss for dusting was 0.7 and 
1.6% for washing. 
It is understood that the foregoing detailed description is given merely by 
way of illustration and that many variations may be made therein without 
departing from this invention.