An intumescent composition and the foamed product prepared by heating the composition are provided. The composition comprises the reaction product of para-benzoquinone dioxime and a concentrated mineral acid such as sulfuric acid, phosphoric acid, and polyphosphoric acid. The composition is useful as an intumescent agent either by itself or when combined with other materials. A fire-resistant and heat-insulating composition is provided by heating the intumescent composition above its intumescent temperature

Parker, J. A.

Riccitiello, S. R.

English

NASA Technical Reports Server

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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JUL 3 1974
TO: KSI/Scientific & Technical Information Division
.Attn: Miss Winnie M. Morgan
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United States Patent
Riccitiello et al.
[ i i ] 3,819,550
[45] June 25, 1974
[ 54 ] INTUMESCENT COMPOSITION, FOAMED
PRODUCT PREPARED THEREWITH AND
PROCESS FOR MAKING SAME
[ 75 ] Inventors: Salvatore R. Riccitiello, San Jose;
. John A. Parker, Los Altos, both of
Calif.
[73 ] Assignee: The United States of America as
represented by the National
Aeronautics and Space
Administration, Washington, D.C.
[22]
[21]
[62]
[52]
Filed: Dec. 26, 1972
Appl. No.: 318,358
Related U.S. Application Data
Division of Ser. No. 140,946, May 6, 1971, Pat. No.
3,730,891,
U.S. Cl 260/2.5 FP, 106/15 FP, 102/105,
252/8.1, 252/62, 260/2 R, 260/2.5 R,
260/396 N, 260/DIG. 24
[51 ] Int. Cl C08g 53/08
[58] Field of Search 260/2.5 R, 2.5 FP, 2 R
[56] References Cited
UNITED STATES PATENTS
2,446,165 8/1948 Trepognier 260/396
Primary Examiner—Wilbert J. Briggs, Sr.
Attorney, Agent, or Firm—Armand G. Morin, Sr.; Dar-
rell G. Brekke; John R. Manning
[57] ABSTRACT
An intumescent composition and the foamed product
prepared by heating the composition are provided
wherein the composition comprises the reaction prod-
uct of para-benzoquinone dioxime and a concentrated
mineral acid such as sulfuric acid, phosphoric acid,
and polyphosphoric acid. The composition is useful as
an intumescent agent either by itself or when com-
bined with other materials. A fire-resistant and heat-
insulating composition is provided by heating the intu-
mescent composition above its intumescent tempera-
ture.
10 Claims, No Drawings
x^&0>* *;&\A* \^
1
INTUMESCENT COMPOSITION, FOAMED
PRODUCT PREPARED THEREWITH AND
PROCESS FOR MAKING SAME
This is a division of application Ser. No. 140,946 filed
May 6, 1971, now U.S. Pat. No. 3,730,891.
The invention described herein was made by employ-
ees of the United States Government and may be man-
ufactured and used by or for the Government for gov-
ernmental purposes without the payment of any royal-
ties thereon or therefor.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Intumescent agents and compositions. Generally,
these agents and compositions are utilized in conjunc-
tion with or for the improvement of fire-retardent com-
positions and coatings. The present invention also in-
cludes the field of fire-resistant and heat-insulating
compositions resulting from the heating and intumes-
cence of the intumescent agent and to the process for
making such heat-insulating compositions.
2. Description of the Prior Art
Intumescent agents possessing various degrees of
utility and foaming efficiency, and varying greatly in
structure and chemical composition have been known
for many years. The original interest in such materials
probably dates back to the use of pyrotechnics in an-
cient times. More recently, however, H. N. Alyea, J.
Chem. Educ., 33, No. 4, ISA, 1956, discloses the pro-
duction of chemical "serpents" from 4-nitroacetanilide
and sulfuric acid.
In U.S. Pat. No. 3,535,130, J. A. Parker and G. M.
Fohlen disclose a highly efficient char-forming intu-
mescent paint in which the intumescent material com-
prises the bisulfate of para-nitroaniline and of its substi-
tuted derivatives. The paints of the above patent pro-
vide a voluminous fire-resistant and heat-insulating
foam when heated at 260°C. and higher; however, due
to the nature of the intumescent material, the paint is
somewhat sensitive to moisture.
An advantage of the intumescent compositions of the
invention is the provision of a novel class of low tem-
perature intumescent agents. Whereas the well-known
prior art intumescent agents intumesce in the range of
200°C. to 325°C., the agents of the present invention
intumesce at about 110°C. and provide a low density
heat-insulating foam useful, as such, in fire protective
applications.
Another advantage of this type of intumescent agent
is that it can be made by the use of 85 percent phos-
phoric acid. The use of this acid provides an agent or
composition which is less corrosive than prior-art intu-
mescent agents which include or are made with a nitro-
aniline.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an
intumescent composition or agent which comprises the
reaction product of a para-benzoquinone dioxime with
a mineral acid such as sulfuric acid, phosphoric acid,
and polyphosphoric acid. A preferred method for pre-
paring the intumescent agents of the invention includes
the slow addition of the mineral acid to the selected
amount of dioxime. During the addition of the acid, the
temperature of the reaction is kept below 50°C. in
3,819,550
10
1 5
20
25
30
45
50
55
,„
65
order to prevent the development of an active exother-
mic reaction.
It was found that the proportions of the reactants
could vary so long as the mole ratio of the dioxime to
the acid is maintained between .25 and 2.00. In physi-
cal appearance, the reaction products using different
acids and different proportions of such acids ranged
from powders for low acid ratio to a paste as the ratio
of acid was increased.
The intumescent agents prepared in the manner de-
scribed herein may be used per se as intumescent
agents or they may be combined with or incorporated .
into other compositions in the preparation of intumes-
cent composites. For example, the intumescent agent,
per se, either as the dry powder or in the form of dry
pellets, may be blown into or otherwise placed in the
space between building walls, void spaces in ship and
airplane structures, etc., as fire protective agents. Ex-
posure of such structure to intumescent or higher tem-
peratures will cause the intumescent agents to foam
and swell to many times (60-200) their original volume
and fill the void space. Since, as will be shown below,
the products formed by intumescing or foaming the in-
tumescent agents of the invention are both highly fire-
resistant and heat-insulating, filling the void space of a
structure with the intumescing agents of the invention
will tend to suppress and prevent spreading of the fire
across the walls of the structure.
Another object of the invention is to provide a fire-
resistant, thermally-insulating, low-density foam pre-
pared by heating the benzoquinone dioxime-
concentrated acid reaction product prepared as de-
scribed herein. These low-density foams have a distinct
utility apart from the utility of the foams which are
formed in situ by intumescing the intumescent agents
described herein.
In making the .fire resistant, thermally-insulating
foam of the invention, a preferred method consists of
placing the intumescent agent in a reaction vessel,
heating the material above the intumescent tempera-
ture to about 150°C. until completely foamed, then al-
lowing the foamed material to cool. Generally, the den-
sity of the foam will vary from .5 to 10 Ib. ft3. The mate-
rial may be foamed in a mold to a desired shape or the
foam may be crushed into small particles. Thus, using
a mold a heat-insulating slab of the foam could be made
to fit on or around any desired structure to provide
thermal insulation. On the other hand, a confined
space, for example, may be provided with thermal insu-
lation by blowing in or otherwise adding the low-
density foam into the said confined space.
The foamed polymeric material can be crushed into
small particles and added to resinous materials to act
as a density control agent as well as render the compos-
ite thermally and oxidatively stable. The foam can be
compounded with varying substances such as fibers and
inert fillers to make high temperature composite billets
for use as thermal protection materials such as heat
shields for space vehicles.
Another object of the invention is to provide a simple
process for making the intumescent material of the in-
vention with inexpensive and readily available materi-
als.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
The following examples will further illustrate and de-
3,819,550
scribe the invention without, however, limiting its
scope.
EXAMPLE 1
This example illustrates the preparation of the p-
benzoquinone dioxime-sulfuric acid intumescent com-
position using a mole ratio of dioxime to acid of 0.5.
To 1.38 grams of p-benzoquinone dioxime was
added, while stirring, 1.96 grams of concentrated sulfu- 10
ric acid (96 percent; density 1.84) within about five
minutes. The mixture produced an exothermic reac-
tion. It was cooled while stirring and maintained at a
temperature of about 50°C. After cooling, the product
was found to be a greenish-black free-flowing powder.
4
TABLE I
P-BENZOOUINONE DIOXIME-SULFURIC ACID
INTUMESCENT COMPOSITION
Sample
1
2
3
4
5
Weight
Composition
1 38g D-1
l.96gH,SO,
l.38g D-1
0.98g HjSO,
I.SSgD3
0.66g HjSO,
O^lgHjSOj
1 . 3 8g D3
0.39g H2S04
Mol
Rutio
.5
1.0
1.5
2.0
2.5
rc.1
138
111
108
no
in
Yield'
(Foam)tt
72
52
49
50
50
'•* Intumescence temperature and foam yield as determined by TGA ai 3*C. under
Nj atmosphere.
3Para-benzoquinone dioxime
EXAMPLE 2
This process illustrates the preparation of the fire-
resistant heat-insulating foam by heating the product of
Example 1.
One (1) gram of the p-benzoquinone diamine-
sulfuric acid reaction product of Example 1 was placed
in a container and then heated on a hot plate main-
tained at a temperature of about 150°C. The reaction
product melted to a dark liquid and produced a thick
foam as soon as the material temperature reached
150°C. (about one minute). 0.72 grams of foam was
produced for a yield of 72 percent. The foamed prod-
uct was cooled, dried, and broken up to a fine particle
size. The foamed product had a density of 0.6 Ibs./ft3,
was insoluble in such powerful solvents as dimethyl
formamide, dimethyl sulfoxide, and hot sulfuric acid,
and withstood temperatures of over 600°C. without
combustion or destruction when exposed to a JP-4 avi-
ation fuel fire. A fire of this type exposes the product
to a total flux of 10 B.T.U./ft2-sec. The product foam
density varies from 0.6 lb./ft3 to about 15 Ibs./ft3
depending on the acid used and the weight fraction of
acid used. This is particularly true in the case when
polyphosphoric acid is used. At a weight ratio of 1.380
grams dioxime to 1.96 grams of acid, the resulting foam
is approximately 16 Ibs./ft3. The foams for all the reac-
tions are chemically inert to most common solvents
such as acetone, petroleum ether and benzene as well
as the more exotic solvents like dimethyl sulfoxide, di-
methyl formamide, and hot sulfuric acid. The foams
produced in the manner described herein are black, co-
herent and mainly closed cell. The foams have com-
pressive strengths varying from 1/2 psi to about 10 psi
depending on the density and condition of preparation.
Other intumescent compositions were prepared by
the procedure of Example 1 with p-benzoquinone diox-
ime and different proportions of sulfuric acid, phos-
phoric acid, and polyphosphoric acid. Tables I, II, and
HI below set forth typical examples of such composi-
tions and the corresponding intumescing temperature
and char (foam) yield obtained by heating the respec-
tive samples in a thermogravimetric analysis (TGA) ap-
paratus at 3°C./min. under nitrogen.
20 TABLE II
P-BENZOQUINONE DIOXIME-PHOSPHORIC ACID
INTUMESCENT COMPOSITION
25 Sample
1
2
30
3
Mol
Weight Composition Ratio T°C.'
l.38g D" 0.25 110
4.62g 85r/( phos-
phoric acid
l.38g D" 0.50 105
2.3 Ig 85% phos-
phoric acid
l.38g D' 1.0 115
1.1 5g 859, phos-
phoric acid
Yield2
( Foam ) <J<
80
76
67
• '• 'Same as Table I
35
TABLE III
40
45
P-BENZOOUINONE DIOXIME-POLYPHOSPHORIC ACID
INTUMESCENT COMPOSITION
50
Sample
1
2
3
Weight Composition
1.38g D3
0.98g Polyphos-
phoric acid
l.38g D"
1.96g Polyphos-
phoric acid
1.38g D3
0.5 Ig Polyphos-
phoric acid
T°C.'
112
115
115
Yield2
(Foam) 9
78
75
75
:
-
 3Same as Table I
Polyphosphoric acid is commercially available and has the following general
formula: HB » i PB Oa* . t where n ranges from 2 to 4.
,„ It is believed that the fire-resistant, heat-insulating
foamed compositions obtained by heating the intumes-
cent compositions of the invention are stable heteropo-
lymers of the class commonly known as semi-ladder
and ladder polymers. Such polymers are formed by
,„ condensation and hydrolysis reactions of ring or ring-
forming reactants. The end product may be a heat-
resistant polyquinoxaline-type polymer or a poly-
phenoxazine-type polymer. Although the exact struc-
ture of the foamed polymer is not known, elemental
65 analysis and other data support the proposition that the
• actual structure is probably a combination of open and
closed ring structures related to polyquinoxaline poly-
mers (Equation 1).
3,819,550
N-OH
N—OH
acid
—HiO
This structure is derivable from the starting material
by condensation and ring closure to varying degrees. If
hydrolysis occurs to any of the oxime groups, then the
structure can be proposed as follows:
What is claimed is:
1. The process for making a fire-resistant, thermally-
insulating, low density foam comprising heating an in-
tumescent composition at a temperature above the in- 25
tumescent temperature of the composition, said intu-
mescent composition comprising the reaction product
of para-benzoquinone dioxime and a concentrated
mineral acid at a temperature of 50°C or below, the
5 mole ratio of the said dioxime to the said acid ranging
from 0.25 to 2.0.
2. The product made by the process of claim 1.
3. The process of claim 1 which further comprises
cooling the foam and reducing the cooled foam to a
10 uniform small particle size.
4. The process of claim 3 wherein the composition is
heated at 150°C.
5. The process of claim 1 wherein the mineral acid is
sulfuric acid and the composition is intumesced at
15 150°C.
6. Product made by the process of claim 5.
7. The process of claim 1 wherein the mineral acid is
phosphoric acid and the composition is intumesced at
150°C.
' 20 8. Product made by the process of claim 7.
9. The process of claim 1 wherein the mineral acid is
polyphosphoric acid and the composition is intumesced
at 150°C.
10. Product made by process of claim 9.
30
35
40
45
50
55
60
65


Intumescent composition, foamed product prepared therewith and process for making same

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