Fire retardant foam

Fire retardant polyurethane foam materials and methods of producing the same are disclosed. Such foams are produced by encapsulating or depositing fire retardant materials within the cell structure of previously formed foam materials. In one embodiment, the foam is passed through a liquid medium containing fire retardant materials, with the foam being subjected to periodic compression during contact with the liquid medium. In an alternative embodiment, the foam is subjected to a dust or particulate atmosphere in which fire retardant material is the particulate material.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to fire retardant foam materials. More 
particularly, the present invention relates to fire retardant polyurethane 
flexible foam materials and methods of producing the same, whereby fire 
retardant materials are deposited in the cell structure of the foam to 
inhibit propagation of flame throughout the foam mass. 
Previous methods for producing fire retardant polyurethane flexible and 
semi-flexible foams have included incorporating into the formulation, 
prior to the foam reaction taking place, a variety of ingredients such as 
halogenated phosphorus compounds and, more recently, alumina trihydrate to 
obtain flame spread values as required by various tests. Thus, for 
example, automotive tests require only small amounts of additives and the 
foams exhibit a low degree of fire retardancy. While such treated foam may 
self-extinguish itself when exposed to a flame while in the horizontal 
position, the specimen may nevertheless burn readily if placed in a 
vertical position. 
Some agencies have more stringent test parameters which require that the 
specimen be tested in the vertical position. To meet such parameters, 
higher loadings of fire retardants are necessary in the formulation, 
reducing some physical properties of the foam and significantly increasing 
foam density. 
In some instances, foams utilized in the manufacture of furnishings for 
public places must pass a "Radiant Panel Test", also known as 
ASTME-162-79. This test requires the foam to be tested at a 45 degree 
angle while placed in a chamber at elevated temperature. In order to pass 
such a test, it has been necessary in one case to use a mixture of 
additives which increases the density of the foam from 1.3 lbs. per cubic 
foot to 4 lbs. per cubic foot. 
An important consideration related to fire retardancy in urethanes is the 
migrating phenomenon of the additives. Also, there is evidence to indicate 
that some foams may lose their fire retardancy upon aging. 
In U.S. Pat. Nos. 3,717,597 and 3,730,917 there are described various 
methods of obtaining a degree of fire retardancy. Both of these prior art 
patents are concerned with the use of regenerated scrap foam, i.e. scrap 
foam which is chopped into pieces and then glued together to form a usable 
piece. In U.S. Pat. No. 3,717,597, the method described therein employs 
urea to obtain a degree of fire retardancy. 
The present invention deals with the use of virgin foam rather than foam of 
the rebonded type. The prior art patents are concerned with a composite 
(regenerated foam). Also, the prior art patents are concerned with mixing 
the urea with the foam particulate in a vat and adding adhesive. In the 
present invention, on the other hand, solid particulate material is 
deposited inside the cells of the foam, and such solid particulate 
material acts as a fire retardant. 
By the present invention, there are provided fire retardant foam materials 
and methods of producing fire retardant polyurethane foams derived from 
polyethers and polyesters, with such foams having highly fire retardant 
properties which are imparted to the foam after it is produced. The 
present method includes depositing and encapsulating within the previously 
manufactured polyurethane foam cell structure, which may be either 
flexible or semi-flexible, certain materials or compounds which function 
as flameproofing or fire retardant agents, inhibiting propagation of the 
flame throughout the foam mass. The terms "flameproofing" and "fire 
retardant" are used interchangeably throughout the present specification 
and claims. 
In one embodiment, the invention includes passing previously formed foam 
material in a compressed condition through a solution or dispersion of a 
fire retardant compound in a liquid medium, followed by allowing the foam 
material to dry, with the fire retardant material being retained within 
the cellular structure of the foam. Fire retardant compounds or materials 
which have been found to be useful in this embodiment of the invention 
include, ammonium sulfate, sodium bicarbonate and urea, with each of such 
materials being employed in the form of a solution or dispersion in water. 
In variation of this embodiment, a small amount, less than 10% by weight, 
or a casein based glue or adhesive composition is added to stimulate 
adhesion of the solid particles within the foam cell structure. 
An alternative embodiment of the invention is a dry process in which the 
foam material is subjected to one or more compressions in the presence of 
a dust atmosphere wherein the dust particles are of the desired fire 
retardant material. The foam material absorbs and retains the dust 
particles within the cell structure of the foam. Fire retardant compounds 
or materials which have been found to be useful in this embodiment include 
urea, ammonium, sulfate and sodium bicarbonate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the embodiment of the invention as shown in FIG. 1, there is provided a 
fire retardant foam material obtained by passing the previously formed 
foam material through a liquid medium containing a fire retardant agent. 
To obtain the desired product, a foam material 10 in sheet form is passed 
from right to left through a roller construction 12 containing two rows 
14, 16 of horizontally aligned rollers 18 which are provided with suitable 
means (not shown) of conventional construction for compressing the foam 10 
between the rows 14, 16 at intervals along the length thereof. 
During stage A, as shown, the foam 10 is compressed by the rows 14, 16 of 
rollers 18. When the foam 10 reaches stage B, the rollers 18 release 
compression on the foam, allowing the cells of the foam structure to 
absorb the liquid medium 20 containing fire retardant material. As the 
foam enters stage C, the rollers 18 compress the foam 10 again, releasing 
most of the liquid that had been absorbed. The foam 10 then enters stage D 
which is the drying portion of the process, provided by a heat convection 
oven 22 maintained at a suitable temperature such as about 250.degree. F. 
As the foam 10 exits in a dry condition, the density increases due to the 
fire retardant material which has been absorbed within the cell structure 
of the foam 10. 
The method as shown in FIG. 1 yields a foam of very high fire retardant 
properties. Depending upon the properties desired, various parameters may 
be varied, including the concentration of fire retardant material in the 
liquid, the compression effect of the rollers 18 and the density of the 
foam 10. 
In a specific example of the invention as carried out by the method of FIG. 
1, a sample of urethane flexible foam having a density of 1.3 pounds per 
cubic foot was passed through an aqueous solution containing 30% by weight 
of dissolved ammonium sulfate crystals. As the foam exited from the drying 
stage D, the foam density had increased to approximately 2.7 pounds per 
cubic foot. The ammonium sulfate crystals formed within the cell structure 
of the foam 10 were found to be larger than the individual cells, so that 
the cell walls prevented the crystals from exiting the foam mass. 
The amount of fire retardant particles in the solution or dispersion, and 
also the amounts deposited in the foam, will depend on the final 
properties desired. For example, a 20% by weight solution of ammonium 
sulfate in water, depositing 250 grams per cubic foot of foam, on a 
non-fire retardant grade foam is sufficient to obtain a degree of fire 
retardancy that will meet the requirements of the New York Port Authority 
Code. A binding agent, of conventional type, may be added to the solution 
or dispersion if desired. 
In FIGS. 2 and 3 there is shown an embodiment of the invention in which a 
fire retardant foam material is obtained by subjecting the foam to a dust 
or particulate atmosphere containing fire retardant materials as the 
particulate matter. To obtain the desired product, a foam material 30 in 
sheet form is passed from right to left into a press assembly 32 which 
includes a vertical air piston and cylinder 34 connected to a board member 
36 having a hollow interior portion 38 with a plurality of tubular needles 
40 extending downwardly in parallel relation from the board 36. The 
needles 40 are located in a horizontal lower surface of board member 36. 
The interior of each of the needles 40 is in fluid communication with 
interior portion 38. A source of fire retardant material in dust form is 
connected to interior portion 38 through conduit 42 having valve control 
44. 
Located directly below board member 36 and spaced therefrom is a chamber 46 
having a plurality of upwardly extending tubular needles 48, the interior 
of each of which is in fluid communication with chamber 46. The needles 48 
are located in a horizontal upper surface of chamber 46. A source of air 
under pressure is connected to the interior of the chamber 46 through 
conduit 50 having valve control 52. The position of chamber 46 relative to 
board member 36 should be such as to allow smooth passage of a sheet of 
foam between members 36 and 46. 
During operation, piston 45 is activated in a conventional manner to lower 
the board member 36, compressing the foam 30 and allowing needles 40 and 
48 to enter the foam 30. Pressure is then released and air is passed 
through needles 48 into the foam 30, thus expanding the foam. Next a fire 
retardant material is passed under pressure through needles 40 into the 
foam 30. The foam 30 is then released from the needles 40, 48 by suitable 
mechanical means and the operation is completed with the fire retardant 
agent having been introduced into the foam 30. 
In a specific example of the invention as carried out by the method of 
FIGS. 2 and 3, a sample of polyurethane foam 30 was treated with 
pulverized ammonium sulfate. Upon completion of the procedure as described 
above, the foam 30 may be coated with a flexible coating of a rubberized 
material or other similar material to prevent dust from exiting the foam 
mass. 
In the practice of this invention according to any of the above described 
embodiments, the quantities and types of materials to be employed will 
vary depending on the properties desired. Furthermore, it is to be 
expected that some degree of synergism will be encountered when 
combinations of fire retardant materials are utilized or when one of the 
materials is utilized in combination with a standard fire retardant agent 
previously incorporated into the foam. Furthermore, it has been found that 
some compounds do not work well in the present invention. For example, 
alumina trihydrate, a fire retardant that is incorporated into the foam 
during the formulation stage, as described in the prior art, does not 
produce desirable results when encapsulated within the foam cells in 
accordance with the present invention. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential characteristics thereof. The present 
embodiments are therefore to be considered in all respects as illustrative 
and not restrictive, the scope of the invention being indicated by the 
appended claims rather than by the foregoing description, and all changes 
which come within the meaning and range of equivalency of the claims are 
therefore intended to be embraced therein.