Intumescent composite

An intumescent firestop device having a layer of non-curing moldable two-stage intumescent composite and a restraining layer. When the firestop device is installed around a pipe near the wall opening through which the pipe runs, the intumescent composite exudes into the annular space between the pipe and the wall opening thereby forming a cold-gas seal. The composite is a two-stage intumescent composite that contains two different intumescent components that begin to intumesce at two different temperatures to form a hard char.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to intumescent composites and, in particular, 
to an intumescent firestop device, a method for manufacturing the device, 
and an intumescent composite for the device. 
2. Statement of Related Art 
An intumescent firestop device is used to prevent fire from spreading from 
one room to another through an opening or aperture in a wall, floor, or 
ceiling through which a pipe runs. A conventional firestop device is 
wrapped around a pipe (e.g., a PVC plastic pipe) adjacent to the wall (or 
floor or ceiling) opening. If a fire breaks out in the room, the 
intumescent material within the firestop device will begin to intumesce 
(i.e., expand) when the temperature reaches a certain level. The expansion 
of the intumescent material is directed inward by the outer restraining 
layer of the firestop device. As a result, the intumescing material 
crushes the pipe, which is softened by the heat of the fire, and closes 
off the opening in the wall with a hard char. The resulting hard char must 
be fire resistant, a thermal insulator, a smoke depressant, and able to 
withstand the forces exerted by a stream of water from a fire hose. 
Many conventional firestop devices require field installation, whereby 
foil-lined strips of intumescent material are wrapped around a pipe and 
then a restraining collar is wrapped around the intumescent material and 
secured by screws or straps. In order to create a cold-gas seal, caulk 
must be used to fill the annular space between the outside of the firestop 
device and the opening in the wall. 
U.S. Patent No. 4,951,442 (Harbeke, Jr.) discloses a pre-formed firestop 
collar assembly made of two rigid semi-circular bands that are connected 
at a hinge line. Each half comprises a rigid restraining layer and two 
layers of solid intumescent composite. The two layers of solid intumescent 
composite and the restraining layer must be glued together. Because the 
intumescent composite is a solid, caulking must still be used to form a 
cold-gas seal. 
In addition, the firestop devices of Harbeke, Jr. require some mechanism, 
such as foil lining, screws, or metal tabs, to provide heat transfer to 
ensure that the firestop device starts to intumesce at an appropriate 
ambient temperature and continues to intumesce at an adequate rate. 
SUMMARY OF THE INVENTION 
In a preferred embodiment, the present invention is an intumescent 
composite having a first intumescent component, a second intumescent 
component, a blowing agent, and a char promoter. The first intumescent 
component intumesces at a first temperature and the second intumescent 
component intumesces at a second temperature, where the second temperature 
is different from the first temperature. 
In another preferred embodiment, the present invention is an intumescent 
composite having a first intumescent component and a binder. The first 
intumescent component is suspended in the binder. The intumescent 
composite is a moldable putty. 
In yet another preferred embodiment, the present invention is a firestop 
device having a restraining layer and a layer of moldable intumescent 
composite adjacent to the restraining layer. 
In still another preferred embodiment, the present invention is a firestop 
device having a restraining layer and a layer of intumescent composite 
adjacent to the restraining layer. The intumescent composite comprise a 
first intumescent component that intumesces at a first temperature and a 
second intumescent component that intumesces at a second temperature, 
where the second temperature is different from the first temperature. 
The present invention is also a method for manufacturing a firestop device 
having a restraining layer and a layer of moldable intumescent composite 
adjacent to the restraining layer. According to a preferred embodiment of 
the method of the present invention, a first sheet of a material is placed 
onto a die, where the material is of a composition that does not easily 
adhere to the moldable intumescent composite. The moldable intumescent 
composite is placed onto the first sheet. A second sheet is placed onto 
the moldable intumescent composite. Pressure is applied to the second 
sheet to force the moldable intumescent composite into the die. One of the 
first or second sheets is removed to expose a surface of the moldable 
intumescent composite. The restraining layer is placed onto the exposed 
surface of the moldable intumescent composite. 
It is an object of the present invention to provide an intumescent 
composite that is moldable. 
It is another object of the present invention to provide an intumescent 
composite that is a non-curing putty. 
It is another object of the present invention to provide a two-stage 
intumescent composite that has two intumescent components, each of which 
begins to intumesce at a different temperature. 
It is another object of the present invention to provide an intumescent 
composite that intumesces to yield a hard char that is fire resistant, a 
thermal insulator, a smoke depressant, and able to withstand the forces 
exerted by a stream of water from a fire hose. 
It is another object of the present invention to provide a firestop device 
having an intumescent composite with the aforementioned objects. 
It is another object of the present invention to provide a firestop device 
having an intumescent composite that exudes into the annular space between 
a pipe and an aperture to form a cold-gas seal when the firestop device is 
installed around the pipe adjacent to the aperture. 
It is another object of the present invention to provide a flexible 
firestop device that is easily installed around a pipe. 
It is another object of the present invention to provide a firestop device 
in which no glue or other sealant is required to join the restraining 
layer and the intumescent composite. 
It is another object of the present invention to provide an efficient 
method of manufacturing a firestop device with the aforementioned objects.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is an intumescent composite, a firestop device that 
uses that intumescent composite, and a method for manufacturing that 
firestop device. According to a preferred embodiment of the present 
invention, the intumescent composite is a non-curing, moldable, two-stage 
intumescent putty that contains two different intumescent components that 
begin to intumesce at two different temperatures. 
A preferred embodiment of the firestop device of the present invention is a 
two-layer assembly--one layer being made of the intumescent composite 
according to the present invention and the other layer being a flexible 
restraining layer made of durable galvanized steel. The firestop device is 
installed by wrapping the two-layer assembly around a pipe and anchoring 
the device to the adjacent wall. 
No caulking is required during installation of the firestop device of the 
present invention, because the moldable intumescent composite exudes 
during assembly to fill the annular space between the restraining layer 
and the wall opening. Moreover, no extraneous mechanisms for heat transfer 
are required, because the first intumescent component of the two-stage 
intumescent composite starts to intumesce at a sufficiently low 
temperature and the second intumescent component continues the intumescing 
process at sufficient rates as ambient temperature increases. 
Referring now to FIG. 1, there is shown a plan view of restraining layer 
100 of an intumescent firestop device according to a preferred embodiment 
of the present invention. Restraining layer 100 is formed from a sheet of 
24-gauge galvanized steel. Those skilled in the art will understand that 
thicker or thinner sheets of galvanized steel may be used in alternative 
preferred embodiments. Restraining layer 100 has a metallic band 102, 
first and second end portions 104 and 106, four attachment tabs 108, and a 
plurality of support tabs 110. In the assembled firestop device, a layer 
of intumescent composite (not shown) abuts metallic band 102. The layer of 
intumescent composite is of approximately the same area as metallic band 
102 and is approximately as thick as the support tabs 110 are long. 
No glue or other sealant is required to join the intumescent composite to 
restraining layer 100, because the intumescent composite adheres to the 
galvanized steel of restraining layer 100. 
The firestop device is installed by wrapping it around a pipe near the 
opening or aperture in a wall (or floor or ceiling) with the layer of 
intumescent composite facing toward the pipe. The pipe may be a plastic 
(e.g., polyvinylchloride) pipe, a fiberglass pipe, or a pipe of any other 
suitable material. The firestop device is secured to the pipe by bolting 
end portions 104 and 106 together through holes 112. In a preferred 
embodiment, first and second end portions 104 and 106 are pre-bent away 
from the layer of intumescent composite (about 90 degrees). The firestop 
device is secured to the wall by screwing attachment tabs 108 to the wall 
through holes 114. In a preferred embodiment, attachment tabs 108 are 
pre-bent away from the layer of intumescent composite (about 90 degrees). 
The intumescent composite is held in place between restraining layer 100 
and the pipe by support tabs 110 which are preferably pre-bent toward the 
layer of intumescent composite (about 90 degrees). 
Referring now to FIG. 2, there is shown an intumescent firestop device 200 
according to a preferred embodiment the present invention after it is 
installed. Firestop device 200 is wrapped around pipe 202 adjacent to 
aperture 204 in wall 206. End portions 104 and 106 of restraining layer 
100 are bolted together to secure firestop device 200. Attachment tabs 108 
are bolted to wall 206 to secure firestop device 200 to wall 206. Support 
tabs 110 hold composite material 208 in place. During the installation 
process, some of moldable composite material 208 is exuded into the 
annular space between restraining layer 100 and aperture 204 in wall 206 
thereby forming a cold-gas seal. Pipe 202 and wall 206 form no part of the 
present invention. 
According to a preferred embodiment, the composite material of the present 
invention is made by suspending two intumescent components, a blowing 
agent, and a char promoter in a viscous liquid binder to yield a 
non-curing, moldable, two-stage intumescent composite. 
The first intumescent component preferably includes an acid-treated 
intercalated graphite flake such as TG-317, distributed by UCAR Carbon 
Company Inc., P.O. Box 6116, Cleveland, Ohio 44101. The acid-treated 
intercalated graphite flake provides intumescence and carbonific 
insulation after intumescing. 
The second intumescent component preferably includes a mixture of a 
polyhydric alcohol and a melamine/uninhibited formaldehyde syrup. The 
polyhydric alcohol is preferably dipentaerythritol, distributed as 
Di-Penta by Perstorp Polyols, Perstorp AB, S-284 80 Perstorp, Sweden. The 
melamine/uninhibited formaldehyde syrup is preferably triamino-s-triazine, 
distributed as Melamine Crystal GP by Melamine Chemical, Inc., River Road, 
Highway 18, P.O. Box 748, Donaldsonville, La. 70346. The polyhydric 
alcohol releases gas, intumesces, and provides carbonific insulation after 
intumescing. The melamine/uninhibited formaldehyde syrup acts as a blowing 
agent for the polyhydric alcohol to improve continuity in the intumescing 
foam. 
The blowing agent preferably includes a preparation with carbonate 
compounds and polycarbonic acids such as Hydrocerol.RTM. BIH, manufactured 
by Boehringer Ingelheim and distributed by Henley Chemical, Inc., 50 
Chestnut Ridge Road, Montvale, N.J. 07645. The carbonate 
compound/polycarbonic acid mixture acts as a blowing agent and a catalytic 
acid. 
The char promoter preferably includes a chlorinated paraffin such as 
Chlorez 700 and a chlorinated paraffin/resin mixture such as Chlorovis 
150-A. Both Chlorez 700 and Chlorovis 150-A are distributed by Dover 
Chemical Corp., West Fifteenth and Davis Streets, P.O. Box 40, Dover, Ohio 
44622. The chlorinated paraffin and chlorinated paraffin/resin mixture act 
as blowing agents and contribute carbon to the hard char that remains 
after the intumescent composite has intumesced. 
The binder preferably includes a plasticized rubber and more particularly a 
polyisobutylene such as Polybutene 128, distributed by Synthetic Oils & 
Lubricants of Texas, Inc. (SOLTEX), 15603 Kuykendahl, Suite 210, Houston, 
Tex. 77090. The binder is a non-curing liquid that makes the intumescent 
composite a non-curing, moldable putty. 
Table I presents a preferred formula for the intumescent composite of the 
present invention. Each ingredient is pre-weighed prior to mixing in a 
mixtruder (a kneading machine that mixes when driven in one direction and 
extrudes when driven in the other direction). Ingredient Nos. 1 through 5 
are added into the mixtruder. The mixtruder blade and screw are driven in 
the mix direction to mix the ingredients for two to three minutes. The 
mixtruder is stopped and Ingredients Nos. 6 and 7 are added. The 
ingredients are mixed for about 10 minutes or until the composite is 
uniform. The mixtruder is then changed from the mix direction to the 
extrude direction. The composite is extruded into one-inch by four-inch 
rectangular bars and broken off at desired lengths. The composite may then 
be checked for density, needle penetration, and heated volumetric 
expansion. 
TABLE I 
______________________________________ 
FORMULA FOR INTUMESCENT COMPOSITE 
PRIMARY 
No. INGREDIENT FUNCTION BY WEIGHT 
______________________________________ 
1 Hydrocerol BIH Blowing agent 
4.4 +/- 0.1% 
2 UCAR TG-317 Graphite 
Intumescent 40.0 +/- 2.0% 
3 Di-Pentaerythritol 
Intumescent 8.0 +/- 0.4% 
4 Melamine Crystal 
Blowing agent 
8.0 +/- 0.4% 
5 Chlorez 700 Paraffin 
Char promoter 
3.2 +/- 0.2% 
6 Chlorovis 150-A Paraff. 
Char promoter 
5.4 +/- 0.3% 
7 Soltex 128 Polybutene 
Binder 31.0 +/- 1.6% 
______________________________________ 
The intumescent composite of Table I contains two different intumescent 
components that begin to intumesce at two different temperatures. The 
dipentaerythritol begins to intumesce at about 220 degrees centigrade, 
while the intercalated graphite flake begins to intumesce at about 260 
degrees centigrade. In a typical burn test for intumescent firestop 
devices, the temperature rises from ambient (about 25 degrees centigrade) 
to around 538 degrees centigrade in five minutes. 
The intercalated graphite flake contains trace amounts of nitric acid on 
the surface of the graphite flake and sulfuric acid, air, and water 
entrapped within the layers of the graphite flake. During a typical burn 
test, the trace nitric acid is liberated and acts as a blowing agent. In 
addition, the entrapped sulfuric acid, air, and water vaporize and cause 
the graphite flake to expand. 
The liberated acids catalyze the dipentaerythritol and graphite flake 
(i.e., the carbonifics), which decompose into carbon and regenerated acid. 
At the same time, the blowing agents release gases which cause the 
carbonifics to foam or intumesce. The melamine melts to form a film over 
the carbon to improve the continuity of the carbon foam. The char 
promoters improve the hardness of the carbon char that remains after the 
intumescent composite intumesces. 
The use of dipentaerythritol and intercalated graphite flake as intumescent 
components ensures that the intumescent composite will begin to intumesce 
when the plastic pipe around which the firestop device is installed begins 
to soften. The intumescent composite continues to intumesce at 
sufficiently high rates to completely close off the wall opening. The 
intumescent composite forms a hard insulating char capable of withstanding 
the forces exerted by a stream of water from a fire hose. The resulting 
hard char also provides thermal insulation, smoke depression, and fire 
resistance. 
The firestop device of FIGS. 1 and 2 is preferably manufactured by placing 
onto a rectangular box-shaped die a first sheet of plastic (or other 
material that does not easily adhere to the intumescent composite). A 
pre-weighed amount of the intumescent composite is then placed onto the 
first sheet of plastic. A second sheet of plastic is then laid over the 
intumescent composite. Pressure is then applied onto the second sheet of 
plastic with a flat plate to force the intumescent composite into the 
shape of the die. This step is preferably performed with the intumescent 
composite heated to at least 30 degrees centigrade to soften the 
composite. The pressure plate is then removed. 
At this point, the second sheet of plastic may be removed, the pre-formed 
restraining layer of FIG. 1 may then be placed over the exposed, shaped 
intumescent composite, and the assembled firestop device may be removed 
from the die. Alternatively, the shaped intumescent composite may be 
removed from the die with both plastic sheets in place, one of the plastic 
sheets may then be removed, and the restraining layer may be placed over 
the exposed intumescent composite. In either case, the assembled firestop 
device will have the layer of sticky intumescent composite sandwiched 
between the restraining layer and a sheet of plastic. The firestop device 
may be installed with the remaining plastic sheet in place. 
Those skilled in the art will understand that intumescent composites other 
than the specific preferred embodiment described herein fall within the 
scope of the present invention. For example, intumescent composites within 
the scope of the present invention may have percentages of components 
different from those listed in Table I. In addition, intumescent 
composites within the scope of the present invention may have intumescent 
components, blowing agents, char promoters, and/or binders other than 
those explicitly described herein. 
While a preferred embodiment of the present invention comprises first and 
second intumescent components, a blowing agent, a char promoter, and a 
non-curing liquid binder, nevertheless those skilled in the art will 
understand that alternative embodiments need not comprise all five types 
of components to produce a composite that will intumesce. Intumescent 
composites of the present invention may be made with or without a blowing 
agent, a char promoter, and/or a non-curing liquid binder. Those skilled 
in the art will also understand that intumescent composites of the present 
invention may be made with a binder other than a non-curing liquid binder. 
Those skilled in the art will also understand that the first intumescent 
component may comprise materials other than an acid-treated graphite 
flake, such as other forms of graphite. 
It will be further understood that various changes in the details, 
materials, percentages, and arrangements of the components and parts which 
have been described and illustrated in order to explain the nature of this 
invention may be made by those skilled in the art without departing from 
the principle and scope of the invention as expressed in the following 
claims.