Note: Descriptions are shown in the official language in which they were submitted.
814,493-D CAN/RRT
1~3~6(~
INTUMESCABLE ~IRE-RETARDANT PRODUCTS
Despite many efforts over the years, there has
never been a fire-retardant asphalt roofing material having
the same widespread acceptance as standard, non-fire-
retardant versions.
The prior efforts have taken several directions:
use of mineral fibers as a filler in the asphalt layers or
as a replacement fiber in the roofing felt for the purposes
of reducing combustible material and limiting flow and ex-
posure of asphalt during a fire (see Fasold et al, U.S. Pat.
2,555,401; Tomlinson et al, U.S. Pat. 3,332,830; and
Schuetz, U.S. Pat. 3,369,956); inc1usion of chemical fire-
retardant agehtS in the roofing (see Tomlinson and Bierly,
U.S. Pat. 2,667,425); and/or use of extra or heavier layers
of roofing granules. Some of these approaches have pro-
duced commercial roofing sufficiently fire-retardant to
be rated Class A by Underwriter's Laboratory (in contrast
to the Class C rating of standard asphalt roofing); but
even those approaches are not the answer the art is seeking,
since they either greatly increase the cost of roofing,
require special manufacturing equipment or processes, or
provide only marginal fire protection. As an example of
the latter deficiency, some commercial roofing materials
with glass fiDer felts pass Underwriter's Laboratory's
"burning brand" test on 3/4-inch-thick (2-centimeters-
thick) roof decks, but they will not pass the test on 3/8-
inch-thick (l-centimeter-thick) roof decks, which are now
approved for use in construction.
A different approach tried by several prior
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3~6~0
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workers is to introduce a layer of intumescable* particles
into the roofing, which, as stated in Donegan, U.S. Pat.
2,782,129, is intended to expand in the presence of a fire
to form "a fire resistant support or rigid sponge which
absorbs the asphalt, preventing flow and providing an ef-
fective fire barrier to the underlying roof." Donegan
suggests use of unexpanded vermiculite as the intumescable
material, disposed as a particulate layer between two layers
of asbestos-filled asphalt. Bick et al, U.S. Pat.
3,216,883, also suggests the use of vermiculite, either
unexpanded or partially expanded,in "built-up" roofing
(formed in place on a roof). Hinds, U.S. Pat. 3,365,322
(1968), cites disadvantages of vermiculite (it is expensive
and, because of its low weight, is difficult to incorporate
into roofing in uniform amounts), and suggests replacing
the vermiculite with mineral granules that carry an intu-
mescable coating of sodium silicate and borax.
None of these efforts with intumescable roofing
have been as effective as some of the other described ap-
proaches. Roofing material as taught in Hinds was com-
mercially sold for awhile, but without apparent success.
Very little intumescence was provided by the coated
granules, and fire-resistance appeared to depend on
presence of asbestos fibers as a filler in the asphalt;
such a filled asphalt is difficult to apply by standard
coating equipment, is costly, and has toxicity and other
disadvantages. In addition, the coated mineral granules
were flood-coated into the roofing material at weights of
100 to 125 kilograms per 10-by-10 meter section of applied
* We use the word "intumescable" herein to describe
material which is capable of intumescing.
"'~';;,,
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roofing, adding to cost and weight of the roofing. Also,
the coating on the granules was soluble in water, and in
the neariy continuous flood-coated layer was especially
susceptible to leaching and consequent 105s of intumesca-
bility.
Vermiculite as suggested by Donegan and Bick alsooffers only low-volume intumescence; and vermiculite will
not intumesce until a fire has progressed sufficiently to
create high temperatures.
In brief, nothing in the known prior work with
intumescable roofing ~uggests that intumescence could be
the basis for an effective and economical fire-retardant
asphalt roofing.
The present invention provides a new roofing
material, which is of the intumescable type, but whi~h
offers an economic and effective fire-retardancy that ~ -
promises widespread utility for the roofing material. In
basic construction, the new roofing material can be like
previous intumescable roofing materials, i.e. it generally
comprises a roofing felt; at least one asphalt coating
above the felt; a layer of roofing granules partially
embedded in the top asphalt coating on the roofing felt;
and a layer of intumescable particles disposed within the
roofing material so as to intumesce when the roofing ma-
terial is exposed to fire. Also, the intumescable materialin the new roofing material is hydrated soluble silicate,
which, as indicated above, has previously been used in
fire-retardant roofing as a coating on mineral granules.
Notwithstanding such similarities, roofing ma-
-
~3~6~(~
- 4
terial of the invention is effective where prior-art intu-
mescable roofing has not been. A first difference over
prior-art intumescable roofing is that the intumescable
particles in roofing material of the invention comprise
hydrated soluble silicate at their core, rather than in a
peripheral coating as in the prior-art coated mineral
granules. Despite previous work in the art with hydrated
soluble silicate, there has never, so far as known, been a
commercially available hydrated soluble silicate in par-
ticulate form such as used in roofing material of theinvention, nor has such particulate hydrated soluble sili-
cate been suggested as an intumescable fire-retardant
additive. We have succeeded in providing a commercially
practicable method of manufacture of such particles (as
will be subsequently described), and have found that when
the particles are included as a layer in roofing matexial,
they provide a fire-retardancy far superior to that pro-
vided in any previous intumescable roofing.
Another reason for the superior intumescence of
roofing material of the invention is the protection given
the hydrated soluble silicate glass particles against
attack by moisture. Moisture will leach away alkali metal
oxide from soluble silicate particles and take away their
ability to intumesce. Some protection against such attack
can be provided with extra-heavy layers of asphalt, extra-
- high concentrations of intumescable particles, or construc-
tions in which the particles are sandwiched between imper-
meable films. The effectiveness of these procedures is
assisted by the concentrated nature of ~he intumescable
-``` 113~
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particles used in the present invention; since each indi-
vidual intumescable particle in roofing material of the
invention intumesces in large volume, fewer particles need
be used and the particles can be better surrounded and
isolated by moisture-resistant structure.
However, the present invention achieves even
more effective moisture-protection with a novel hydrated
soluble silicate particle that carries a unique protective
coating. This protective coating includes an ingredient
that is ionized in the presence of water to provide metal
cation capable of reacting with the silicate ion of the
core particle. The reaction between the metal and silicate
ions forms a reaction product that is less water-soluble
than the core particle, whereby a protective layer is
formed around the particle. The protective coating is
regarded as having a self-healing function, in that any
openings which develop in the protective layer tend to be
sealed, thereby limiting action of water on the core par-
ticles and maintaining the intumescent character of the
particles.
The protective coating is also a key to conven-
ient manufacture of the intumescable particles. Prior to
the present invention, the art might have considered two
general kinds of method for manufacturing hydrated soluble
silicate particles: drying of commercially available
solutions of soluble silicates to a solid of the needed
water content; and hydration of commercially available
anhydrous soluble silicate material. Both methods present
difficulties: the drying operation of the first method
il386~
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forms a film that retards evaporation and greatly lengthens
the process; and the hydration step in the second method
tends to form agglomerated glass-like material that is
difficult to comminute to needed sizes. Such difficulties
have now been overcome with the discovery that anhydrous
soluble silicate material, crushed to a desired particle
size, can be coated with the described protective coating
and then hydrated to the desired moisture content under the
heat and pressure of an autoclave, producing ready-to-use
non-agglomerated particles.
In a different manufacturing method, anhydrous
soluble silicate fines can be agglomerated to desired
particle si~es with liquid soluble silicate, coated with
the described protective coating, and heated to form in-
tumescable hydrated soluble silicate particles (the heating
operation is understood as distributing water present in
the liquid soluble silicate throughout the particle to
make the particle intumescable). Particles formed from
agglomerated fines have the advantage that during intu-
mescence they tend to form a multicellular product, which
has greater crush strength.
A less desirable alternative for manufacturing
particles useful in the invention is to hydrate uncoated
anhydrous soluble silicate particles in a bed of inert
particles such as clay. A protective coating of the in-
vention can be applied to particles that have already been
hydrated, as well as to anhydrous particles.
Because of the moisture-resistant nature of
coated particles of the invention, together with their
` ~ ~386~0
small size and high degree of intumescence, they can be
conveniently and economically included in asphalt roofing
materials without significant change of standard manufac-
turing procedures. A rather low amount of the particles
can be applied per unit area of the roofing material, and
the particles can be cascaded directly onto and partially
embedded in asphalt coatings already incorporated into
standard asphalt roofing materials.
The amount of intumescence exhibited by roofing
material of the invention can be controlled through se-
lection of the amount of intumescable particles. A rather
low amount of particles gives the roofing material a large
volume of intumescence and a high degree of fire-retardancy.
Roofing material of the invention passes Underwriter's
Laboratory's "burning brand" test on either 2-centimeter
or l-centimeter-thick decks, and in fact, will pass a more
stringent laboratory test in which a Bunsen burner is
trained continuously for 30 minutes on a 15-by-15-centimeter
sample of applied roofing material (i.e. overlapped in the
manner that roofing shingles are applied to a roof deck),
but laid over a piece of unsaturated organic felt paper
rather than a roof deck. In neither test does fire pene-
trate through the test sample.
Further, extended tests of roofing material of
the invention at restricted test sites as well as acceler-
ated aging tests indicate that the described fire-
retardancy is retained over a useful lifetime for roofing.
The total combination of properties is a significant
advance in the roofing material art, and appears to offer
38~,f~
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for the first time the potential for asphalt-saturated,
felt-based roofing material to be offered in a form that
is both highly fire-retardant and economical.
Besides use in roofing material, coated particles
of the invention can be included in a wide range of ma-
terials -- ranging from solid foams to liquid coating
compositions. The moisture-resistance and highly intu-
mescent character of the particles make their use conven-
ient and effective, all at moderate cost.
Some additional prior art background for the
present invention can be summarized as follows:
According to Vail, J. G., Soluble Silicates
(1952, Reinhold Publishing Company), Volume 2, page 481,
the United States patent literature on intumescence of
soluble silicates begins in 1883 with Kelly, U.S. Pat.
283,789, which teaches a cellular mass of expanded silicate
as a thermal insulation for fireproof safes. Ar~hur, U.S.
Pat. 1,041,565, issued in 1912, teaches a particulate
soluble silicate such as sodium or potassium silicate which
may be intumesced to form expanded or cellular particulate
material useful as thermal insulation.
The patent literature very early discusses ways
to insolubilize the soluble silicate glasses. Gesner, U.S.
Pat. 419,657, issued in 1890, teaches the treatment of
cellular silicate glasses with chemical agents such as
calcium chloride; acids such as sulfuric or hydrochloric
acid; and soluble oxides and salts of metals other than
alkaline metals, including such oxides as barium or
strontium hydroxide and such salts as calcium or barium
. -
11386(~0
g
nitrite. Gesner also teaches that the cellular materialmay be made impervious to water by coating it with paraffin,
drying oils, asphalt, rubber and fused or dissolved insol-
uble metallic soaps or oleates or stearates, and solutions
of resins or gums.
The Hinds patent mentioned abov~ suggests that
the intumescable coated granules may be coated with asphalt
emulsions, oils, silicones, or latex emulsions to prevent
water-absorption by the gxanules.
Another example of prior teachings as to use of
intumescable silicate materials for fire retardancy is
Vail's report (page 483) that wooden beams have been coated
with heavy silicate solutions to reduce the hazard of fire.
In a different kind of teaching, Cohen, U.S. Pat.
917,543 suggests the use of sodium silicate in roofing
material as an adhesive to bond a sheet of asbestos to a
sheet of organic fibers and form a fire and waterproof
material. However, there is no suggestion that the sodium
silicate be particulate or intumescable as in the case in
our new roofing material.
Insofar as known, nothing in the prior art
teaches asphalt-saturated, felt-based roofing material
containing a layer of hydrated soluble silicate particles
for fire-retardancy. Nor does the known prior art teach
particulate silicate glasses, not yet expanded but still
intumescable, and coated with a coating that protec~s and
increases the expansibility of the particles during intu-
mescence and makes possible their convenient manufacture.
Figure 1 is a sectional view through an illus-
~.~386i(~)
-- 10 --
trative roofing material 10 of the invention. The roofingmaterial 10 can be made as follows: A roofing felt paper
11 is saturated, and co~ted on its top surface to form a
layer 12, with an asphaltic composition. Intumescable
soluble silicate particles 13 are cascaded onto the coated
felt where they become partially embedded in the layer 12
A layer 14 of asphaltic composition is then applied over
the particles ~f the invention; and roofing granules 15 are
cascaded onto the layer 14, where they become partially
embedded. A back coating 16 of asphaltic composition is
applied to the bottom of the felt paper 11, and a dust
coating 17 of mica or the like is applied to make the back
side of the material tack-free.
Figure 2 is a sectional view through a repre-
sentative intumescent particle 19 of th~ invention, whichcomprises a core particle 20 and a protective coating 21
surrounding the particle.
Figure 3 is a graph showing the amount of intu-
mescence versus water content for coated particles of the
invention and particles that are the same except for being
uncoated.
Sodium silicates are pxeferred as the soluble
silicate glass in intumescable particles of the invention
because of their lower costs, but silicates formed from
other alkali metals may also be used, including, for
example, those formed from potassium and lithium. The
silicates used may also have different ratios of silica
to alkali-metal oxide, but silicates having a ratio above
about 2 to 1 are preferred because they are less water-
1~3~36(10
soluble than those of lesser ratios.
The intumescable particles can range widely insize, though as shown in Table I, volume of intumescence
varies with the size of the particles. As the particle size
Table I
Volume Intumescence of Sodium Silicate Particles
(~iO2; Na2O ratio of 3.22, and hydrated with 13
percent water)
Particle Size Volume to which
~ two-milliliter
10 Range of sizeAveraqe diameter sample expands
(micrometers)(micrometers) ~ (mi~~ers)
2000 - 2380 2200 200
840 - 2000 1400 200
590 - 840 710 175
15420 - 590 500 175
297 - 420 350 160
176 - 297 230 125
125 - 176 150 110
88 - 127 105 90
2070 - 88 80 80
62 - 74 67 70
~4 - G2 53 50
2~ 25
~ 20 14 3
25~ 10 6 3
reported in the table rises above minimal values, the volume
of intumescence increases significantly; the reported par-
ticles that average approximately 25 micrometers in size
intumesce over ten-fold, and the reported particles that
average approximately 100 micrometers, intumesce over forty-
113~36(~0
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fold. Particles of the invention should intumesce at least
four-fold and preferably at least forty-fold for most uses
as a fire-retardant additive. For the highest volume-
percent of intumescence, particles above about 300 micro-
meters in diameter are preferably used (in giving value~for maximum and minimum diameter, the values stated apply
for only 90 volume-percent of the particles, since after a
screening operation some of the remaining particles are
outside the screen sizes). For the most satisfactory use
in roofing material the particles should average less than
2 millimeters, and preferably less than 1 millimeter in
diameter. However, particles up to several centimeters in
diameter can also be used for special purposes.
The particles will intumesce in different amounts
depending on the amount of water present. Curve 1 in
Figure 3 is a graph of the intumescence at a typical
actuating temperature range (i.e., about 200 to 300C) for
coated sodium silicate particles generally of the type
described in Example 1 below, but with varying water con-
tent, and Curve 2 is a similar curve for uncoated particles.(The curves show the volume in milliliters to which a 2-
milliliter sample expands.)
To obtain a useful amount of intumescence the
soluble silicate should generally include at least 3 per-
cent, and preferably at least 10 percent, water. Peakintumescence for the illustrated sodium silicate occurs
at around 15 percent water. With greater amounts of water
beyond 15 percent, intumescence declines, though it will
occur for contents of water up to, and in fact beyond, the
~386(;~0
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point (about 30 percent) at which ~he soluble silicate
dissolves in water. Typically, no significant benefits are
obtained by including more than 20 percent water.
Whereas the core particle in coated particles of
S the invention can be quite soluble in water, the protective
coating comprises ingredients that have a low solubility,
preferably a room-temperature solubility in water of less
than 0.2 gram/cubic centimeter. However, even with this
low solubility, there is sufficient dissociation to provide
metal cations for self-healing reaction with silicate ion
of the core particle.
The preferred protective coating, providing the
longest-lasting and most thorough ~oisture protection, com-
prises a metal salt of a long-chain fatty acid. Stearic
acid is the preferred long-chain fatty acid but others,
such as oleic or palmitic acid, can also be used. Also,
although calcium is a preferred metal, other metals, such
as the alkaline-earth metals barium and magnesium, and
aluminum and zinc, can be used.
In preferred coatings as just described, the best
water-stability has been obtained when the coating includes
metal, in an ionizable compound, in excess of that needed
for stoichiometric association with the anion of the long-
chain fatty acid. The excess metal of such metal~cation-
rich coatings can be provided, for example, as the hydrox-
ide, carbonate, chloride, or fluoride of the metal. Typi-
cally the excess-metal-providing ionizable compound, which
is desirably present in an amount accounting for at least
one-half volume-percent of th~ protective coating, is more
1138~Q~)
soluble than the metal salt of the long-chain fatty acid.
Other water-insoluble components can be included
in protective coatings of the invention, either as a sup-
plement or as a substitute for the metal salt of ~ long-
chain fatty acid. For example~ organic polymeric films suchas polyethylene, polypropylene, wax, epoxy resins, or
urethane resins may be used. An ionizable ingredient pro-
viding metal cation for reaction with silicate ion of the
core particle should be included in such coatings to obtain
the best water-stability.
A further ingredient preferably included in pro-
tective coatings on particles of the invention is silicone
water-repellent agents. A large list of such agents are
known to repel moisture from a surface on which they are
applied. Use of such a repellent coating has been found
to add significantly to the moisture-resistance provided by
the protective coating.
The long-term stability of coated particles of
the invention h~s been demonstrated both in extended aging
tests on test decks, and by accelerated laboratory tests in
which the particles are totally immersed in water and their
intumescability measured at various intervals. In the
latter kind of testing, for example, sodium silicate par-
ticles as described in Example 1 below, after having been
immersed in water for 40 days, still exhibit useful intu-
mescence upon heating. ~hen sodium silicate particles the
same as those of Example 1, but without any protective
coating, are subjected to the same test, they will not
intumesce a~ all after 1 - 3 days of exposure. Also, when
1~386~0
sodium silicate particles the same as those Qf Example 1
except coated with calcium stearate in which the calcium
and stearate are in stoichiometric proportions are subjected
to the same testing, intum~scence of the particles declines
after 6 to 9 days to the level exhibited by particles of
Example 1 after 40 days of exposure.
The protective coating on coated particles can
be applied by known coating procedures. For example, the
core particles can be mixed with the coating material while
the latter is in a liquid form, e.g. by melting or dis-
solving. The coating is then allowed to harden to a sub-
stantially continuous film, as by cooling, drying or re-
acting. In one useful coating operation, the core par-
ticles are first coated with a liquefiable portion of the
coating -- e.g. melted stearic acid; oleic acid, which is
liquid at room temperature; molten polymer such as poly-
ethylene; or a li~uid uncured epoxy resin-hardener compo-
sition. Then, before the coating has cooled ox hardened,
other ingredients such as the metal-cation-supplying ingre-
dient are added, as by mixing a powdered form of that in-
gredient and the coated core particles. For example,
powdered calcium hydroxide is conveniently mixed with par-
ticles that have been first coated with molten stearic
acid. After such mixing, the calcium hydroxide becomes
partially embedded in the stearic acid coating; the calcium
reacts with the stearic acid to form nearly insoluble cal-
cium stearate; and any unreacted calcium hydroxide remains
present in the layer to provide excess calcium cation for
a self-healing function.
113~6~
- 16 -
Alternatively to the above procedure, metal-
cation-supplying ingredient such as calcium hydroxide can
be incorporated into other ingredients of the protective
coating, such as stearic acid, prior to coating of the core
particles. In the case of calcium hydroxide and tearic
acid, calcium stearate is produced during such a premixing
operation and must be melted before the core particles can
be coated.
As shown in Figure 1, the intumescable particles
in roofing material of the invention need not be closely
packed, since upon expansion they occupy a much larger
volume. Coated particles of the invention can generally be
included in an amount of no more than about 50, and more
commonly are included in an amount of no more than about
25, kilograms per 10-by-10-meter section of applied roofing
material At least 5, and preferably at least 10, kilograms
of particles are generally used per 10-by-10-meter section~
Though generally embedded in an asphalt coating on the roof-
ing felt, the layer of particles may be disposed elsewhere
in the roofing material, e.g~, in the felt itself.
Besides utility in roofing matexial, coated par-
ticles of the invention are also useful as fire-retardant
additives in a variety of polymeric articles, including
rigid or flexible foams, molded or sheet articles, extruded
or cast films, elastomeric articles, etc~ Such articles
may be made ~rom polyurethanes, epoxy resins, polyesters,
etc. Also, the particles can be introduced into various
coating materials to fo,rm fire-retardant coatings; such
coating materials general`ly comprise a liquid vehicle that
--"` 113~6~!~
hardens to a solid coating upon exposure as a thin coating
in predetermined environments. Also, the particles can be
added in a loose mixture with other powdered materials for
fire-retardant purpo~es. ` In addition to protecting a sub-
s strate against fire, particles of the invention can performa heat insulating function; for example, a coating con-
taining a layer of particles oE the in~ention can be used
to protect steel beams from reaching temperatures during a
fire that would damage the beams and cause them to sag.
Also, particles of the invention can be intumesced and
used for a variety of purposesi for example, particles can
be intumesced at a building site and introduced into the
walls or other structure of the building as thermal insu-
lation.
The invention will be further illustrated by the
following examples.
Example 1
One-hundred parts of anhydrous sodium silicate
glass particles having a SiO2:Na2O ratio of 3.22 and a
range in size from about 300 to 840 micrometers were heated
in an oven to 250F tl20CC). After reaching that tempera-
ture, the particles were dumped into a cement mixer and 2
parts of powdered stearic acid added, whereupon the stearic
acid melted and became coated on the particles. Ater the
mixing had continued for about 10 minutes, 2 parts of
calcium hydroxide was added and the mixing continued for
an additional 10 minutes. Next, 1 part of a silicone water
repellent (DC-772*sodium siliconate from Dow Corning) was
ddded and mixed in ~or 10 minutes.
*Trade Mark
~386~
The coated particles were discharged into trays
to a bed depth of about 5 centimeters. The trays were
loosely fitted with aluminum foil lids and placed in an
autoclave where they were hydrated at a steam temperature
of 285F (140C~ for 2 hours. After removal from the auto-
clave the particles were free-flowing, had a water content
of 10 weight-percent, and expanded upon heating about 65
fold. Intumescence was measured by gradually pouring 2-
milliliter-size samples into an aluminum pan heated by a
hot plate to a temperature above 400F (205C), whereupon
the particles immediately intumesced. The intumescent
particles were then gathered and their volume measured in
a graduated cylinder.
Particles of the example were incorporated into
a standard roofing material in the manner shown in Figure
1. The weight amount of the various layers was as follows:
layer 12, 100 kilograms; layer 13, 15 kilograms; and layer
14, 300 kilograms per 10-by-10-meter section of applied
r~ofiny. Whcn th~ rcsulting roofing material was tested by
the "burning brand" and more stringent laboratory tests
noted above, the fire did not burn through the test
samples.
Samples of the described roofing material were
placed on roof decks in restricted test ~ites for five
years, and when removed from the deck showed no visible
change and again passed the noted "burning brand" and more
stringent laboratory te~ts.
Example 2
Example 1 was repeated in a laxger batch size
~i386(~1~
-- 19 --
with a rotary autoclave. Instead of 2 parts of calcium
hydroxifle, 20 parts were used. The larger amount ~ormed
a thicker coating on the particles and made them more free-
flowing without reducing intumescence.
Example 3
Example 1 was repeated except the silicone
water-repellent agent was omitted. When the resulting
particles were tested in the described accelerated aging
test, they exhibited useful intumescence after a 20-day
exposure .
Examples 4 and 5
.
Example 3 was repeated except that the stearic
acid was replaced with either oleic acid (Example 3) or
palmitic acid (Example 4). In the accelerated aging test
the calcium-oleate-treated particles had a useful life of
6 days in water, and the calcium-palminate-treated particles
of 7 days.
Examples 6 - 8
Example 3 was repeated with sodium silicate par-
ticles except that the calcium hydroxide was replaced witheither aluminum hydroxide (Example 6), magnesium hydroxide
(Example 7), or barium hydroxide (Example 8). In the ac-
celerated aging test, the aluminum-stearate-treated par-
ticles had a life of 6 days, and the barium-stearate-
treated particles of 9 days.
Examples 9 and 10
Example 3 was repeated except that the sodiumsilicate particles were replaced in Example 9 with lithium
silicate (SiO2:K2O ratio of 2O50) and in Example 10 with
- 2~ -
potassium silicate (SiO2:K2O ra~io of 2.50). Upon heating
to about 200C, the particles intumesced many-fold~
Example 11
Example 3 was repeated except that 2 parts of
polyethylene low-density polyethylene powder replaced the
stearic acid, and 2 parts o~ calcium hydroxide were used.
In the accelerated aging test the coated particles had a
life of 6 days.
Example 12
Sixty parts of particles of Example 3 were mixed
into 100 parts of a mixture of Part~ A and B of precursors
(available from Freeman Chemical Corporation, Port
Washington, Wisconsin) that form a pour-in-place, rigid
urethane foam having a density of about 0.032 gram p~r
cubic centimeter. The mixture was poured into trays and
allowed to cure. After removal from the trays, the cured
samples were conditioned according to the specifications
outlined in Underwriter's Laboratory's tests for flam-
mability of plastic materials, and then subjected to the
~o horizontal burning test for classifying materials (Test No.
9~ HBF) and the vertical burning test for classifying
materials (Test No. 94 VE-O). In each test the samples
passed the test.
Example 13
Ten parts of particles of Example 3 were mixed
into a mixture of 100 parts polyol (TP74~ commercially
available from Wyandotte Chemical Corporation) and 55 parts
of polyisocyanate (Mondur*MRS commercially available from
Mobay). The mixture was then catalyzed by adding 0.3 part
*Trade Mark
--` 11386~0
- 21 -
lead octoate. Samples were cured and conditioned according
to the specifications outlined in Underwriter's Laboratory's
tests for flammability of plastic materials, and then sub-
jected to the horizontal burning test for classifying ma-
terials (Test No, 94 HBF) and the vertical test for clas-
sifying materials ~Test No. 94 VE-O). In each test the
samples passed the test.
Example 14
Uncoated sodium silicate particles (SiO2:Na2O
ratio of 3.22) ranging between 300 and 840 micrometers in
diameter and hydrated with a water content of about 14
percent were incorporated into roofing material as shown
in Figure 1. Weights were as listed for the roofing mater-
ial described in Example 1, except that the layer of intu-
mescent particles 13 weighed 100 kilograms per 10-by-10-
meter section of applied roofing. After exposure on a test
deck for 3 years, the roofing material still exhibited
useful intumescence when exposed to a fire.
Example 15
One-hundred-sixty parts of anhydrous sodium
silicate fines having a 5iO2:Na2O ratio of 3.22 and a
particle size smaller than about 300 micrometers were
mixed in a Hobart mixer with 40 parts of liquid sodium
silicate having a silica-to-soda ratio of 3.22 and a water
content of about 62 percent. Agglomerated particles were
formed and screened to leave particles in a size range of
300 to 840 micrometers. The particles were coated in the
manner described in Example 1 with 2 parts stearic acid
and 5 parts calcium hydroxide, and then heated in an oven
1~386~C)
- 22 -
for about 4 hours. The resulting particles intumesced
about 50~fold when heated to 300C.
Alternatively, the paxticles can be prepared by
coating the core particlesonly with calcium hydroxide and
no stearic acid, although the particles are not as free-
flowing during the hydrating operation.
