Lightweight, fire resistant foams have been developed through the modification of conventional neoprene-isocyanate foams by the addition of an alkyl halide polymer. Extensive tests have shown that the modified/neoprene-isocyanate foams are much superior in heat protection properties than the foams heretofore employed both for ballistic and ablative purposes

Parker, J. A.

Riccitiello, S. R.

English

NASA Technical Reports Server

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J patent Matters
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United States Patent Office 3,772,220-Patented Nov. 13, 1973/
j
- . - - . -•? -:• 3,772,220, •;;-.,-.. ... ,. • .'
FLEXIBLE FIRE RETARDANT POLYISOCYANATE
MODIFIED NEOPRENE FOAM
John A. .Parker, Los Altos, and Salyatpre R. Riccitiello,
San Jose, Calif.', assignors to the United States of
America as represented by the Administrator of the
National Aeronautics and Space Administration
No Drawing. Filed Apr 21, 197i,'Ser. No. 136,253
Int. Cl. G08d 9/0S; .13/08
U.S. Cl. 260—2.5 L 3 aaims 10
ABSTRACT OF THE DISCLOSURE
Lightweight, fire resistant foams' are provided wherein
conventional neoprene-isocyanate, foams are modified by
the addition of an alkyi halide polymer. 15
The invention described. herein..was made by employees
of 'the United States Government
 :and, may be manufac-
tured and used by or for the Government for govern- £0
mental purposes without 'the' payment of any royalties
thereon or therefor.
BACKGROUND OF THE; INVENTION
• ' • • • • •''' Field of-the invention'~- 25
Fire retardant plastic foam.. ". , . , - , .
' • ' • • ' Description of the prior art
Polyisbcyanate reinforced elastphieric foams wherein a
latex of an elastomer is combined with an isocyanate are 30
well known" and' are," described: in detail in U.S. Pats.
2,993,013 .and" 3,450,649." 'Such'foams are highly useful
for, many purposes but they dp not provide char integrity
when subjected'to a sustained abiafion.environment. Thus,
they do hot provide continuing .protection under many ^5
conditions. Suph foams, a'ltHough" they .are normally non-
burning, will ignite,and.sm6lder,.fpr.long periods of time
when impacted with projectiles.".'. _":','t .
• SUMMARY: OF THE: INVENTION 40
The object"of the' pfeserit,"invention is to provide a
plastic foam which will protect structures such as reentry
vehicles or aircraft against damage by heat. The source
of heat might be from a fire generated on the structure, . _
such as by an impact with 'a projectile or the like, or by
the hot gas cap which ^ surrounds-reentry vehicles. In or-
der to. damage'the-underlying-structure-,-heat must be
carried to the structure either by forced or free convec-
tion or by radiation.1 .. : . "
 go
-•" Foams .heretofore; known;prbvided a high resistance to
heat flow between the heat"source and the structure but
such foams'did not "have a high char integrity so that the
cHar would break away, leaving the structure unprotected.
^Another protection, mechanism,js, the, release of gases
 5g
from the thermal protective material when it is subjected
to heat The gases evolved serve to protect the system
by flowing against the. incoming heat,,thus impeding the
flow'of heat from the surf ace,, and
 vaiso if one provides
a gas which .is, rich in, halogens,'they can chemically „„
scavenge the chain'carriers by which-fuel flames are prop-
agated and thus serve as fire .extinguishing agents.
'In .accordance .with, the present invention, neoprene-
isocyanate foams are modified by the addition of from
10 to 30% by weight'of a polymeric talkyl halide. Suita-
 65
ble polymeric, alky 1 halides include all of. the well-known
vinyl and vinylidene hajide hprnppolymers and copoly-'
mers. Included are homppplymers of vinyl chloride, bro-
mide, and" fluoride; homopolymers.of ^vinylidene chloride,
bromide, and fluoride; copolyrners of vinyl and vinylidene ^0
chloride,
 rbromide,. and fluoride with at least one other
polymerizable mpnpolefin such-as, acrylonitrile, a vinyl
ester of a lower alkanoic acid, such as vinyl acetate, vinyl
butyrate and the like. The molecular weight may vary
from a low to a high value; i.e., from, a low molecular
weight liquid to a high molecular weight solid. The solid
foam can be made by conventional systems and it is only
necessary to add finely dispersed alkyl halide to the neo-
prene latex during the normal processing.
,:~ Extensive tests have shown that the modified neoprene-
isocyanate foams of the present invention are much su-
perior "in" heat protection properties than the neoprene-
isocyanate "foams heretofore employed both for ballistic
and ablative purposes.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
In carrying out the present invention any of the various
sulfur curable latexes can be used. One particularly suita-
ble latex is known as neoprene latex Type 1 which is a
high gel aqueous dispersion of a polycloroprene polymer
having a pH of 10.7, a solids content of 59% and a Brook-
field viscosity of 350 cps. A similar latex is known as Type
2 having a pH of 12, a solids content of 50% and a
Brookfield viscosity of 23 cps. In addition to latexes of the
ueoprene type, one may use styrenebutadiene copoly-
rners. One suitable latex is known as SER which has a
solids content of 73%, a pH of 10.5 and a Brookfield vis-
cosity of 1330. Natural rubber latexes can also be used
and one suitable latex has a rubber solids content of about
60%. Other latexes of rubber-like compounds can be used
such as those made from acrylonitrile or from ethylene-
propylene mixtures copolymerized with dienes.
A large variety of polyisocyanates can be employed
including all of those described in Pat. 3,450,649. One
particularly suitable polyisocyanate is sold under the trade
name PAPI and this contains about 50% by weight of
4,4'-methylene bis-(phenyl isocyanate) and is made by the
phosgenation of polyamides prepared by condensing ani-
line and formaldehyde in a mineral acid. The product
also contains polyisocyanates and phosgenation by-prod-
ucts in such amounts that the average functionality of the
entire mixture is about 3 isocyanato groups per molecule.
Various polymeric alkyl halides may be employed as
previously defined. Suitable commercial alkyl halides are
Saran A, a polyvinylidene chloride homopolymer; VMCH,
which is a commercially available acid modified vinyl
chloride-vinyl acetate copolymer of medium molecular
weight; Tedlar, a poly (vinylidene fluoride) resin; other
resins made by Dow Chemical Company of the Saran type
which are copolyrners of vinylidene chloride and vinyl
chloride or acrylonitrile; Dow polyvinyl chloride homo-
polymers such as Dow 100 (a high molecular weight
resin) and Dow PVC 166 (an extra low molecular weight
resin) as well as intermediate members of the series and
Fluorel, a fluorinated polymer.
Other components can be added to the foam mixture
as are well known to those skilled in the art, such as
gelling agents, vulcanizing agents, antioxidants, and the
like. Typical materials are described in detail in the
working examples.
The mixing procedure is not particularly critical and
that given in the working examples can be employed. It
is important that the isocyanate be added just before the
pour. The temperature of the final cure in the oven may
be at a temperature above room temperature, e.g., from
150° F. to 300° F. If optimum char strength and integrity
are desired, the cure temperature must be maintained be-
tween 275° F. and 300° F. The curing time is about four
hours. If the temperature goes much above 300° F., for
example, to about 325° F., the material burns in the oven.
For ballistic purposes the cure temperature is not im-
portant since it is only necessary to provide sufficient by-
3)772,220,.
drogen halide (from' the decomposition of the alkyl ha-
lide") 'to 'quench 'the fire-which-would -otherwise'result. "For
ablative purposes, char strength and integrity are im-
portant and one should employ the higher temperature
range for optimum results.
In carrying out all-of the examples, the following" ma-
terials were used.
Formulation: Dry-wt. parts
Latex compound 100-0
Petrolatum ,— 3.0
Masterbatch -9-5
Thiate B 2-0
'Tepidone . .-- 1-Q
Isocyanate LD-699 20.0
Gelling agent 2.0
Polymeric alkyl halide 0-30
Ingredients of masterbatch: Parts by weight
Zinc oxide (Kadox 15) 79
Neozone D (Du Pont-Co.) 21
Maraperse N (10%) 57
Gelling agent:
Patossium silico fluoride 100
Bentonite clay 20
Water 380
Latex compound is Du Font's LD-700 -neoprene con-
version latex described above as Type 1.
Neozone D is Du Font's trademark for a rubber anti- .
oxidant phenyl beta naphthyl amine.
Thiate B is R. T. Vanderbilt's trademark for a'trialkyl 30
thiourea -neoprene accelerator.
Tepidone is Du Font's trademark for a dithiocarbamate
rubber accelerator.
LD-699 is Du Font's trademark for its-polyisocyanate
known as PAPI. 35
Marasperse is American Can Company's trademark for
a phenyl propane lignosulfonate dispersant.
A :mixer was employed for mixing the components'to-
gether, and for curing purposes an electric or gas fired
oven capable of maintaining 300° F. was used. The -latex
compound is first placed in the mixer and the mixer
started. Thereafter at short intervals one adds the petro-
latum, the masterbach, Thiate B, Tepidone and then-the
alkyl-halide polymer. Mixing is then continued and finally
the -isocyanate and the galling agent are added. After &
EXAMPLE 2
10
15
20
25
A foam was prepared containing 20% by weight of
VMCH.
EXAMPLE 3
A foam was prepared'-containing 20% of Saran A.
• ' ' • • ; . ' ."^EXAMPLE-4-,_••:."
A foam was •prepared containing 30%-of -VMGH.
" ' '• • ...-EXAMPLE 5 . '.- • . • •-',
A foam was-prepared containing 30% of'Saran A. "
" . . . -IEXAMPLE 6 "..,-
A "foam was prepared containing 10% of Saran A and
it was cured at-250°. p. • . .
.EXAMPLE 7 .
A foam -was .preparedjcontaining -10%-of Saran A and
it was cured at 300° f.
-EXAMPLE 8
A foam was prepared containing 10% of VMCH .and
it was cured at 250° F.
.EXAMPLE 9 .
A foam was prepared containing 10% of VMCH and
it was cured at 300°-F.
A series of test were -run .comparing the materials of
the present invention with the neoprene-isocyanate foams
of the prior art. In the first -of these tests, -a test fixture
was employed ,known as the -Ames 3-.Terminal Test
Facility. This is essentially an oil burner which burns.JP—4
jet-fuel in a fire'brick lined combustion chamber at-a rate
of about '1V4 .gallons -per:hour. The combustion chamber
had various-openings so that samples could'be tested at a
desired -heating-rate: The heating rate selected was 10
B.t;U./ft:2 per second and the -test consisted of .placing a
sample-of the-cured foam over an opening in the combus-
tion'chamber-with "an-aluminum backing plate over the
sample. A temperature'sensing-device-was placed over the
backing >plate so-that one could check to see'how-long, it
required for the plate to reach a' set temperature. In "the
case of some samples,-the foam iburned'through before
the temperature was.attained and this is marked BT. The
following results were obtained:
Example
1
2
3
3
4
5
6
7
g
9.
Materials
.Time to
- ' • • "- reach
. .Thickness Density 200° F. Temp.,
Alkyl halide polymer . (Inches) -Ob./ft.<) (seconds) . • F.
Neoprene isocyanftt-fiEE - - - Nona _ _ _ _ .
do - - - VMCH foolvvlnv chloride-acetate cocolvmert. 20%_-
do
do.
do
do
do
do
do
...do
.. . Saran A, 20%
do
...VMCH, 30% •
Saran A, 30%
SaranA.10% ..
.do -
VMCH,10% • •-•
do
,.2
2
2.25
. 2.25 ,
:2
. -2 .
2.25 .
2.00
-- 2.00
2.00
. 6.0
6.1
5.:4
5.5
•6.-5
'6.4
.4.4 .
•'5.5
;3.2
6.1
'90
135
225
260
169
- 495 '1
 190
150
''120
. 130
300
188
260
280
230
205
205
,190
"B.T.
very short mixing of the complete batch, e.g., 30 seconds,
the mixer is stopped and the .material is poured into pre-
viously prepared molds. The molds are allowed to stand
for about three hours at room .temperature and at this
point they have sufficient strength to be demolded. The
foam is then .allowed to dry in the air for about .four
hours and finally it is cured in an oven at the tempera-
ture specified in the examples for four hours.
Utilizing the .procedure set forth above, the following
materials were prepared:
EXAMPLE 1
A neoprene-isocyanate foam was prepared containing
no alkyl halide to serve as a control. -In Examples 1
through 5 the foam was cured at 300° F. for four hours.
65
70
75
.' It can :be seen "from the above table that in the case of
Example 1, -which typifies -the prior art, a 2-inch sample
burned through in 90 seconds. Examples '2 through 5, 7
and'9 did not bum-through and required from 130 to 260
seconds to reach'200-° F.: Examples ; 6-and 8 -burned
through, showing the effect of-curing at a low tempera-
ture but sthese -materials -were -satisfactory for -ballistic
purposes as the next table shows. -
In another series of tests, 'a test'fixture-was used where-
in 50 caliber API bullets were fired at an aluminum
striker plate set at-an Bangle of about 45-degrees to bore-
line. The layer of-foam "under-test covered the aluminum
striker .plate. The:shots were;fired at a distance from about
250 feet at a velocity of about 3,000-3,100 feet per sec^
ond. The-foam was observed- after-the -test as to the-barn-
3,772,220
5 6 (
ing and degree of damage. The results of this test are set ture prepared from the phosgenation of polyamines pre-
forthon the following table: pared by condensing aniline and formaldehyde in a min-
BALLISTICS TESTS—50 CALIBER ROUND
Material
Polymeric
alkyl halide
Neoprene isocyanate None— -
Do irws.VMr.ir
Do
Do
Do
10% Saran A
20% Saran A.
30% Saran
Cure
temp.,0
 F. Density Remarks
250
250
150
250
300
2. 8 Burned and smoldered after Impact.
3. 7 Large tears.
3. 6 Small hole— small tears.
3. 2 Small tears.
3. 3 Small tears— no burning.
It will be seen from the above that material containing
the alkyl halide is satisfactory for ballistic purposes even
when cured at temperatures as low as 150° F.
We claim:
1. In the process for the preparation of a foam by
frothing an aqueous latex of sulfur curable elastomeric
polymer wherein said latex contains from about 10 to 100
parts by weight of an organic polyisocyanate per hundred
parts of elastomeric solid in the latex, the improvement
comprising incorporating in said frothing mixture from
10 to 30% by weight of a polymeric vinyl or vinylidene
halide and curing the resulting foam at a temperature of
from 275° to 300° F. for about four hours.
2. The process of claim 1 wherein the vinyl or vinyl-
idene halide is selected from vinyl and vinylidene halide
homopolymers and copolymers.
3. The process of claim 1 wherein the aqueous latex
is a latex of neoprene prepared from polycloroprene poly-
mer having a solids content of about 59%, and the or-
ganic polyisocyanate is an undistilled polyisocyanate mix-
15
eral acid containing about 50% by weight of 4,4'-meth-
ylene bis-(phenyl isocyanate) and the remainder of the
product consists of polyisocyanates and phosgenation
byproducts wherein the average functionality of the entire
mixture is about 3 isocyanato groups per molecule.
20 3,627,710
3,393,166
3,033,804
25 966,260
References Cited
UNITED STATES PATENTS
12/1971 Crary 260—2.5 L
7/1968 Rupar 260—2.5 L
5/1962 fiethe et al. 260—2.5 FP
FOREIGN PATENTS
8/1964 Great Britain 260—2.5 L
30
WILBERT J. BRIGGS, SR., Primary Examiner
U.S. Cl. X.R.
260—2.5 H, 2.5 BE, 2.5 FP, 29.7 UA, 890, Dig. 24


Flexible fire retardant polyisocyanate modified neoprene foam

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