U.S. patent number RE31,428 [Application Number 06/317,699] was granted by the patent office on 1983-10-25 for fire protective tape.
This patent grant is currently assigned to Thomas & Betts Corporation. Invention is credited to J. Watson Pedlow.
United States Patent |
RE31,428 |
Pedlow |
* October 25, 1983 |
Fire protective tape
Abstract
A fire protective tape using a halogen-free mastic coating on a
fabric support is provided, the essential components of the mastic
being solids including a low fusing ceramic frit, hydrated solids
having chemically bonded water which is released as a fire
protective water vapor when heated, solids which expand or
intumesce during the same heat application to form a porous,
expanded or foamy insulating body, solids which have a fire break
effect, such as antimony oxide and zinc tetraborate, and binder
solids which are thermoplastic resins and serve to bind the solids
into a flexible coating when applied, the binder solids being
dispersed as an emulsion in water and mixed with the other solids
to form a mastic. With further addition of water the mastic is
converted to a selected viscosity for application by troweling,
coatingor spraying. The mastic is applied as a coating upon the
sheet-like carrier, which may be wound as a tape upon single or
grouped electric power and control cables to restrict fire
propagation and to prevent self ignition of cables from fires due
to overloading or other electrical faults, or from oil, waste or
trash fire sources, thereby minimizing the danger of self ignition
of gases or combustible materials such as other cable jacketing,
insulation or other flammable materials.
Inventors: |
Pedlow; J. Watson (Media,
PA) |
Assignee: |
Thomas & Betts Corporation
(Raritan, NJ)
|
[*] Notice: |
The portion of the term of this patent
subsequent to February 19, 1997 has been disclaimed. |
Family
ID: |
26981091 |
Appl.
No.: |
06/317,699 |
Filed: |
November 2, 1981 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
872820 |
Jan 27, 1978 |
4189619 |
Feb 19, 1980 |
|
Reissue of: |
092063 |
Nov 6, 1979 |
04273821 |
Jun 16, 1981 |
|
|
Current U.S.
Class: |
428/215;
106/18.11; 106/18.27; 106/18.36; 174/121A; 428/325; 428/494;
428/500; 428/921; 442/138 |
Current CPC
Class: |
C09D
5/185 (20130101); C09D 5/34 (20130101); H02G
3/0412 (20130101); H02G 3/22 (20130101); Y10T
428/24967 (20150115); Y10T 428/31855 (20150401); Y10T
442/2648 (20150401); Y10T 428/252 (20150115); Y10T
428/31833 (20150401) |
Current International
Class: |
C09D
5/34 (20060101); C09D 5/18 (20060101); H02G
3/04 (20060101); H02G 3/22 (20060101); B32B
007/00 (); B32B 009/04 (); B32B 005/16 (); H02G
003/04 () |
Field of
Search: |
;428/215,265,268,272,273,274,275,921 ;106/18.11,18.27,18.36
;174/121A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dixon, Jr.; William R.
Attorney, Agent or Firm: Rodrick; Robert M. Abbruzzese;
Salvatore J. Woldman; Jesse
Parent Case Text
This application is a continuation in part of my copending
application Ser. No. 872,820 filed Jan. 27, 1978 and now U.S. Pat.
No. 4,189,619 issued Feb. 19, 1980 in which the invention relates
to a fire protective mastic and fire stop for electrical cables and
neighboring wall junctures or partitions through which the cables
pass, the mastic comprising protective water vapor-evolving
substances, other substances which intumesce or expand, and still
others which glaze with sufficient heat and form a stable
protective porous coating having a fused ceramic casing upon the
electric cables and fire stop panels, when exposed to fire. The
mastic is also useful as a precast boot for mounting upon cables or
splices, or as an air and fire seal or caulk disposed upon or
between cables, the mastic filling cracks or crevices between
cables or panels and cables, and serves as a coating upon fire stop
panels and upon neighboring walls, and for wall paneling per se
through which electric cables pass as a fire protective wall and in
which the paneling or boot per se may be formed of the precast dry
mastic.
Claims
I claim:
1. An electrical arc and fire protective tape for disposition about
electrical equipment, cables, cable splices, appurtenant equipment
or the like, comprising a resinous mixture coated as a wet mastic
mixture and dried upon a fabric base or plastic sheet or film
substrate, said mastic comprising an essentially halogen-free
mixture of solids and thermoplastic binder resins dispersed as an
emulsion in water, said solids including heat intumescing and
expanding substances in approximate quantity of 4 to 25% to expand
the mastic to porous heat insulating foam, ceramic frits in
approximate quantity of 5 to 40% to provide a ceramic glaze upon
the surface of the dry expanded mastic when exposed to high
temperatures developed by fire, hydrated substances in approximate
quantity of 10 to 40% and having bonded water evolvable only by
application of sufficient heat to decompose and evolve water
vapors, .Iadd.fire protective solids of the character of antimony
oxide and zinc borate in approximate quantity of about 2 to 15%,
.Iaddend.and a resinous thermoplastic binder in approximate
quantity of 5 to 40% to bind said solids to the form of a flexible
film in coated form of the mastic, said binder being dispersed as
an emulsion in water, there being sufficient water in the emulsion
to convert said solids into a fluidized form for application as a
coating upon said base or substrate, said percentages being by
weight, the said solids quantity being based on the total solids of
the composition.
2. The tape as defined in claim 1, said mastic further containing a
small quantity, less than about 5% of organic fiber said
composition further containing from about 1 to 10% of emulsifying
agents, rust inhibitors, fungicides, viscosity controlling,
thickening, and wet strength enhancing agents.
3. The tape as defined in claim 1, wherein the binder resin solids
are in the range of 20 to 30%, dispersed in water, being
substantially 45 to 65% resin solids and 55 to 35% water, the low
fusible solids are ceramic frits in quantity of 10 to 25%, the
hydrated substances are hydrous oxides in the ranges of 15 to 30%,
the intumescing and expanding substances are cenospheres in the
range of 7-25%, said mastic further containing a small quantity of
about 0.5 to 2.0% of organic fiber, and fire retardants antimony
oxide and zinc tetraborate, each present in quantity of 4 to 10%
and 5 to 10% respectively.
4. The electrical arc and fire protective tape as defined in claim
1, wherein the fabric base is organic fiber in woven, knitted,
netted or non-woven matted form.
5. The electrical arc and fire protective tape as defined in claim
1, wherein the fabric base is polyester fiber in woven, knitted,
netted or non-woven form.
6. The electrical arc and fire protective tape as defined in claim
1, wherein the fabric base is formed of carbonized acrylic fiber in
woven, knitted, netted or matted form.
7. The electrical arc and fire protective tape as defined in claim
1, wherein substrate is a cellulose or polyester film such as
cellophane or mylar in the thickness range of 0.001 to 0.005".
8. The electrical arc and fire protective tape as defined in claim
1, wherein the coating has a thickness in the range of 0.005 to
0.150 inches.
9. The electrical arc and fire protective tape as defined in claim
1, wherein the heat intumescing substances are cenospheres. .[.10.
The electrical arc and fire protective tape is defined in claim 1
further including about 2 to 15% of protective solids of the
character of antimony
oxide and zinc borate..]. 11. The electrical arc and fire
protective tape as defined in claim 1, wherein the fabric base is
formed of inorganic
fiber in woven, knitted netted or matted form. 12. The electrical
arc and fire protective tape as defined in claim 1, wherein the
fabric base is formed of glass fiber in woven, knitted, netted or
matted form.
Description
The invention of the present application relates to an electric arc
and fire protective tape, using the mastic of the parent
application coated upon a sheet or strip-like support typically a
strip of plastic or of woven fiber. The mastic contains large
quantities such as 60 to 85% of a mixture of solids of several
types, each with a distinct function to provide in combination a
superior fire protective effect. The solids are formed into a
mastic by a binder resin dispersed in water in quantity to form a
coherent coating when dry, whereby the solids and the dispersion
may be evenly mixed. Additional quantities of aqueous diluent may
be added in the mixing, for conversion of the dispersion of resins
and dry solids to a trowelable, coatable or even sprayable
composition, as needed to provide the requisite fluidity for
application.
Some of the solids include intumescing or decrepitating substances,
typically cenospheres, which are flyash, inorganic particles
evolved as dust from coal combustion and are very light, volatile
and expandable with heat, like tiny fused balloons. It is that
expansion of such gas evolving substances in combination with other
vapor producing substances mixed therewith which, when the
composition is heated under fire exposure at temperatures above
about 1000.degree. F. such as 1200.degree. F. to 3000.degree. F. to
activate the intumescing components and release vapors which
convert the composition from a thin layer coating disclosed in my
parent application as applied on a cable or panel and herein coated
upon a carrier sheet or strip as a tape, to expand to its heat
insulating form. Such intumescent solids are present in the range
of 5-40%, preferably 7-25%.
Other solids present in the mastic composition are of a chemical
hydrate character, having chemically or physically combined water,
such as hydrous oxides, silicates and other hydrated substances
which firmly bond the water and which decompose with the heat of a
fire and evolve large quantities of cooling, non-corrosive
oxygen-displacing and fire-protective water vapors. Such hydrous
oxides are typically hydrous alumina, magnesia and the other water
evolving hydrous oxides and silicates. These hydrated components
are used in quantity of 10 to 40% and preferably in quantity of 15
to 30%.
Still other solids in the mastic comprise a heat fusible ceramic
frit which, when heated sufficiently upon an outer surface of the
expanded coating, exposed to high fire developed heat, glaze over
and encase the expanded dry mastic as a fire protective film
thereon, protecting the expanded coating and insulating the cables,
or in or upon the fire stop panels or boots. Such frit generally is
a low fusible glass, typically a borosilicate glass frit generally
fusible in the range of about 700.degree. to 1500.degree. F. It is
usefully used in the range of about 5 to 40%, and preferably about
10 to 25%.
The composition includes a thermoplastic resin as a binder
dispersed in water, the aqueous dispersion being mixed evenly with
said solids to form the mastic. The thermosplastic resin is present
in quantities sufficient to form a flexible binder for the mastic
composition when dry, as a coating upon the electrical cables or
panels, or to bind the panels or boots upon drying into a strong
structural form. Sufficient additional water is added in the mixing
as stated, for supplying requisite fluidity for application. The
resinous solids are present in the quantity of about 15 to 40% of
the dry composition, preferably 20 to 30%. Such thermoplastic
substances may be any useful thermoplastic binder resin, which is
halogen-free, but which may melt and flow by heat developed during
fire and allow the composition to expand to a heat insulating
coating. The typical resins for this purpose are halogen-free to
avoid decomposition and release of noxious and corrosive halogen
gases, and may be typically polyvinyl acetate, polyacrylic acid,
polyacrylic lower alkyl esters, such as methyl or ethyl esters
thereof, polymethacrylic acid and its lower alkyl esters, such as
methyl and ethyl esters thereof, as well as mixtures of such
acrylic resins, natural and artificial rubber latices, each as
dispersions in water, said dispersions usually having from 25 to
75% of resin solids therein, usually 45 to 65% resin solids, the
balance being water with minor quantities of dispersing agents.
The composition may further include small quantities of combustible
fiber, such as cotton, rayon, aramide or the like, to provide a
temporary coating stability for the wet or molten mastic. For this
purpose the fiber need not be fire proof and may burn as the
composition becomes heated when exposed to fire and will only be
used in minor quantity, generally less than 5%, usually 0.5 to 2.0%
to supply this temporary binding function. In present use as a
coating upon a fibrous sheet, the additional fiber may optionally
be omitted, with the sheet-like base usually of fiber performing
much of this function.
The composition will further contain among the solids, such fire
retardant substances as antimony oxides, which develop vapors with
heat along with the protective water vapors evolved. Antimony oxide
also is a low fusible component and contributes to the formation of
the fused frit casing during fire exposure. Another fire retardant
solid is zinc tetraborate which, through synergistic action,
further improves the fire-retardant character of antimony oxide in
the mixture. These fire retardant antimony oxides and zinc
tetraborates are each used in quantity of 2 to 15%, preferably 4 to
10% and 5 to 10% respectively.
Other solids present in the composition are each added for a
specific minor function and will be present generally in quantity
from about 0.1 to 10%, some, generally less than 2%, adequate only
to perform the function. Thus, other solids may consist of
emulsifying agents, typically octyphenyl-polyethoxy ethanol
available commercially as Triton X 100, in quantity of about 0.5 to
5%. Rust inhibitors, generally in quantity of about 0.2 to 5%, such
as potassium polyphosphoric acid esters. Preservatives, such as
fungicides, which are mercury complexes, in quantity of about 0.01
up to about 0.05. Viscosity controlling agents, such as alkali
metal salts of polycarboxylic acid or oil based liquid
polysiloxanes in quantity of 0.2 to 5%. Thickeners, such as hydroxy
ethyl cellulose and a clay type inorganic gelling agent, such as
attapulgite clay in quantity of 0.1 to 2%. These several minor
additive components for these functions are used in quantity
sufficient for the stated function, and each generally will be
present in quantity of less than 10%, and usually from 0.2 to
2%.
Thus the vapors evolved are non-corrosive gases consisting of water
vapor, antimony oxides and minor heat decomposition vapors of the
resin and fiber. Such halogenated resins as release halogen,
typically chlorine, such as polyvinyl chloride or numerous
halogenated plasticizers as also are commonly used in the fire
proofing art and whose destruction and release by heat during cable
failure, as by arcing, short circuitry or destruction by fire from
other sources in the neighborhood of the cables and protectively
coated with such fire proofing substances, as release halogen, are
avoided, whereby both the mastic composition and carrier sheet upon
which the mastic is coated as a tape hereof releases no noxious and
corrosive halogen gases.
In forming this mastic mixture, the binder emulsion of resin in
water is further mixed with the dry intumescing and fire proofing
solids, and reduced with a small additional quantity of water as
needed to homogeneously mix the filler solids and emulsion for
application.
The mastic can be sprayed in thicknesses of 0.025" to 0.150" and
air dried to form a thick flexible coating on the electrical cables
and wall panels forming a heat insulating and fire proofing mastic
as well as an effective heat insulating air seal and fire stop.
The mastic of my parent application is intended both as moldable
mixture for forming into fire proofing boots to be installed upon
cable joints and splices or on dry wall panels through which
electrical cables may pass, or as a thick suspension in water to be
applicable as a protective mastic filler and coating body upon and
about group cables, entering leaving and passing through a floor
slab or fire wall. Wall penetrations may be framed by a
laminate-rigid panel board such as pressed ceramic fiber, gypsum,
Marinite, having said mastic coating applied and dried upon one or
both surfaces thereof, said mastic being poured, troweled or
sprayed up to depths of two inches as required.
According to the present invention the mastic is coated upon a
sheet or strip substrate preferably a woven or matted fiber fabric
such as a polyester fabric typically DuPont Reemay which is
spun-woven polyester. The fabric can also be cotton or a ceramic
fiber typically glass fiber or carbonized acrylic fiber, each with
characteristic advantages. For instance, cotton is almost
smokeless, but inorganic fibers are stronger and heat resistant. It
is preferred to knife coat the mastic composition upon the
substrate usually fabric, to a selected thickness and dry the
coating thereon at a moderately raised temperature below about
200.degree. F. and preferably between 125.degree. to 190.degree.
the temperature being regulated to prevent formation of bubbles by
vapors evolving too rapidly. A convenient handling is to knife the
coating on the fabric as it advances on rolls through the dryer,
the fabric serving as the conveyor and becoming permanently
embedded as a laminate to a dried coated mastic thickness of about
0.005 to 0.150 inches preferably 0.010 to 0.045 inches.
In prior applications of other heat and fire protective insulation
substances upon electrical cables including a tape, these according
to my prior U.S. Pat. Nos. 4,018,962 and 4,018,983 included halogen
evolving resins and have been loosely wound as tape or mounted as a
boot about a cable joint as fire protective means while or after
the cables were assembled, both the tape and boot being relatively
non-coherent to the cable. It was also proposed in U.S. Pat. Nos.
3,642,531 and 3,928,210 to coat cables as an aqueous emulsion of
halogen evolving resins, including essentially halogen evolving
plastizers, the heat insulating effect of such coating compositions
being largely provided by inorganic fiber which functions
comparatively poorly for this purpose, and the halogen gas evolved
with heat decomposition is highly corrosive and toxic, a source of
substantial danger and damage to personnel and equipment. Equally
important, such compositions coat poorly and crack upon drying,
and, under the destructive effect of high temperature, tend rapidly
to peel, flake or powder away from the protective position upon the
electrical cables which they were intended to protect. Such
coatings, in contrast to the present fail to adequately meet the
important fire and heat insulating needs to prevent destruction of
cable jacketing and insulation-protecting critical power and
multiple conductor control cables and to prevent propagation of
fire along grouped cables in trays and through wall and floor
penetration at flaming temperatures often exceeding 1,900.degree.
F.
The invention is further explained with reference to the drawings
wherein:
FIG. 1 shows a perspective of groups of mastic covered cables
passing through a wall which may be protected by the fire stop
paneling and mastic hereof;
FIG. 2 is an elevation of several trays of cables arranged in a
vertical tier as they will pass through a fire wall protected by
the paneling hereof;
FIG. 3 is a detail showing the mastic as an outer lamina layer upon
a conventional heat resistant wall board base;
FIG. 4 is a detail showing the mastic poured about cables passing
through a floor opening;
FIG. 5 shows a section of mastic coated cable;
FIG. 6 illustrates a detail of conduit or pipe sleeve carrying
cables which is filled with mastic;
FIG. 7 shows the mastic coating hereof on a fabric support; and
FIG. 8 shows the tape hereof wound about an electrical cable;
FIG. 9 shows a composite of several insulated conductors wrapped
with the tape of FIG. 8 prior to the application of an extruded
weatherproofing jacket.
Referring to FIG. 1, a wall 10 of concrete or masonary separates
spaces A and B as a partition for normal structural purposes and
has a rectangular opening 12 cut therein for passage of a tier of
trays 14 and 16 which support and partially enclose electrical
cables 18. These cables are conventional groups of power or
multiple conductor control cables mounted, insulated and jacketed
for purposes of electrical insulation and moisture imperviousness.
Thus the cables may carry critical communication circuitry or
conduct electrical power, oft-times of high voltage. In any case,
any building construction has many cables as a valuable part
thereof and, for whatever electrical purpose they serve, great
damage can be done to the structure and cables by electrical
faults, such as short circuitry or extraneously caused fire, such
as by exposed to flaming combination of oil, trash or the like,
developing destructive heat in the cables. Again, the cables
themselves are valuable in terms of the numerous communicating
conductors and the redundant circuits which must be provided, as
well as importance of wires which may be a part of the cables per
se, all being desirably protected. The coating hereof effectively
protects cables longitudinally or vertically against propagation of
any fire, regardless of source, so that fire cannot damage
redundant control and power circuits and penetrate into critical
control areas.
Finally, it is desirable not only to encase the cables by fire
preventive mastic, but also to protect one side of a partitioning
wall 10 as a fire stop with insulation and insulating panels formed
by the combination of a fire stop panel and mastic hereof, thus to
prevent transfer of heat, flame or evolved gases to the opposite
wall side of the fire stop.
Electrical cables 18 therefore, and for this purpose, are mounted
in supporting trays 14 and 16, which may comprise channel irons 20,
connected by a metallic ladder, expanded mesh or solid framework 22
which can terminate or pass through the opening 12 of the wall 10.
The layers of cables can be further supported from below by a heat
resistant panel moulded or cast from the mastic or a knife coated
tape or blanket of mastic covered by this invention, the thickness
of said blanket being in the range of 0.050 to 0.200 inches,
preferably 0.100 to 0.125 inches.
At the wall opening 12 a further set of wall panels 26, 28 and are
mounted each with cut-away portions (not shown) to fit over the
cables and close the wall opening 12, as well as to closely close
any spaces between cables passing through the wall. The cables pass
directly through or themselves may each be enclosed in a supporting
heat resistant metal sleeve or conduit (not shown). It is sometimes
desirable to cover the interstices between the cables with loosely
matted inorganic fiber which forms a filler for large spaces
directing and supporting the mastic to close engagement with the
cables and for allowing an overall coating as a bed of cables.
Optionally, however, the mastic itself may be supplied alone to
fill the space between the cables through the entire depth above
the lower panel 24 up to a point above the surfaces of the cables
as shown in FIG. 1, whereby, the cables become fully embedded
within the dried mastic. The mastic can be sprayed over the grouped
cables as 1/8" minimum thickness coating.
Moreover, the mastic 30 is extended to cover the paneling 26, 28
and to fill all of the cracks and crevices therein, whereby the
cables pass through the paneling and through the opening 12 of the
wall 10, each crack, opening or space being filled with mastic. It
may also be applied within conduit carrying cables to fill or plug
the same as shown in FIG. 6. Moreover, the mastic is applied over
the top of the cables and for secure closure of any cracks between
panels, both around the panel edges as well as any spacing or
cracks between the adjacent panels.
As shown in FIG. 1 two trays of cables pass through the wall 10
with the construction described. The cables may be present in any
number and arranged in the trays in any grouping. Additional cables
may be passed through the wall of the construction by cutting
through the light pre-cast panels, cutting away some of the mastic
and penetrating through the panel in a circular cut in a manner to
accommodate one or more additional cables to be added from time to
time, and the new cable being readily thrust through a newly formed
cut portion. The newly added cables are coated with more fresh
mastic and any cracks or crevices remaining about the newly added
cables in the panels are further coated and sealed with more
mastic, whereby additional cables are easily added from time to
time.
As shown in FIG. 2 many trays can be assembled in a tier of trays
passing to or through the wall, depending upon the wall size
according to the size and height needed above the floor 32, whereby
two stacks or more trays as may be needed to accommodate all of the
cables can be used. In that case the separate stacks of cables C
and D may be further separated by a partitioning wall 34, in which
larger panels of the mastic hereof are assembled as a separating
partition 34 and the partition may be supported as shown by angle
iron brackets 36. It may be useful to separate the panels by a
central laminated layer 38 which may be of metal wire of glass
fiber or other reinforcing material.
The fire stop wall may be formed of fire proof paneling material,
resistant to heat, whereby to operate as a fire-protective shield
or partition between the opposite wall sides of spaces, as an
easily assembled fire stop partition through which a group of
cables pass, whereby the protective wall prevents heat and flame
transfer, as well as the transfer of noxious vapors or smoke to its
opposite wall side where continuing or redundant circuits may be
installed. Particularly, the fire stop wall is intended to prevent
transfer of heat, to the wall side opposite to that facing fire
exposure and remains relatively cool on the opposite wall side from
the high temperatures that may develop from a cable failure. The
paneling may be formed of other useful pre-cast fire proof
materials, but often is of the same dried mastic material as the
mastic, also being applied as a coating upon the cables hereof, the
mastic being cast into panels for assembly as dried panels into the
fire stop wall hereof.
FIG. 3 illustrates a panel board which can be of any commercial
ceramic fiber rigid insulating board (41) and which has coated
thereon a thin 1/8 to 1/4" coating 42 of the mastic hereof.
As shown in FIG. 4 cables disposed as groups or individual cables
disposed as groups or individual cables in sleeves pass through a
floor slab 10 within the mastic hereof poured about and with the
sleeve to form an air seal as well as a fire stop. FIG. 5 shows a
section of a single coated cable with mastic applied by spraying,
hand-wiping or extrusion.
Particularly for the present invention, the tape hereof is superior
for wrapping of cables and electrical splices in that the mastic is
more easily wrapped thereabout in the conventional application as a
tape and superior in that the mastic does not evolve halogen vapors
at or above decomposition temperatures. It is outstanding for
protection of personnel and corrodable equipment exposed in
confined spaces under high temperatures resulting from short
circuiting conditions or other fire source, such as in mines,
subways, shipboard, buildings and other confined spaces in which
electrical equipment is placed or passes through, by virtue of the
fact that no halogen is evolved at decomposition temperatures.
The present composition is highly heat and fire protective. It
evolves only non-corrosive vapors, such as water vapors, inert
nitrogen and CO.sub.2 gases, antimony oxides and zinc tetraborate.
It produces a porous heat expanded heat insulating body protective
of the cable when destructive heat is applied, the coating being
developed by expansion of the intumenscent substances and evolving
gases which convert the coating to an expanded, porous, heat
insulating body. The coating further contains a heat fusible frit
which forms a glaze, strengthening and protecting the coating
despite very high temperatures, whereby the coating is low heat
transferring and does not powder, flake or peel off the surface of
the cable to which it was applied.
Theoretically, it appears that during the heating process when
ignition and combustion take place through electrical faults such
as arcing or short circuitry or other source of high heat
evolution, the coating first in the presence of heat softens the
thermoplastic component. The intumescing substances such as
cenospheres and the hydrous oxides with enough heat begin to expand
as well as to evolve water vapor as well as nitrogen and CO.sub.2
gases which are occluded in the cenospheres. The antimony oxide at
higher temperatures can evolve its vapors. The fiber which is
ultimately heat decomposable, operates in the cold to help bond the
composition into a firm, strong and crack-free coating while it
dries. As the initial heating is applied, the thermoplastic binder
melts, but the fiber tends to prevent the resin from flowing away,
maintaining the integrity of the composition while it steadily
expands with the heat. Ultimately the fiber and the resin may be
charred to an infusible porous mass, developed by the expanding
intumescing solids. The expanding mass carries much of the fusible
frit to the coating surface, where at high heat exposute
temperatures, the frit can fuse protectivey as a refraction shell
over the porous mass to prevent further heat passing into or from
central or inner cable portions. The glazed frit serving further as
reinforcing shell to prevent further ingress of great heat and
prevents the mass from peeling or flaking away from its protective
position about the cable.
The composition functions similarly either as a component of the
total panel body or as an even outer layer on the paneling, whereby
the mastic substance thereof will expand with heat protectively as
a fire barrier or stop. One side of the panel of great heat
exposure absorbs and prevents passage of heat, acting as a heat and
fire stop partition or protective wall, allowing little heat to
pass to the opposite side which remains comparatively cool. A
similar effect is achieved both by using ordinary non-heat
conductive paneling substances such as commercially available
insulating board of ceramic fiber which, however, is coated with
the mastic hereof to improve the wall paneling as a fire stop
through which the cables pass.
The water component hereof is free water. The resinous emulsion may
be quite thick and more water to that contained in the resinous
emulsion is usually added merely supplied as free water in quantity
sufficient to adjust the mixture to a trowelable, pourable, on down
to sprayable mastic, as desired. For purposes of easy distribution
of the water, various surfactants such as Triton X 100 an
alkylphenoxy, polyloweralkyleneoxy, loweralkanol in which the alkyl
has 1-2 carbon atoms, and the product may contain from about 10-40
alkyleneoxy groups.
The resinous binder hereof is dispersed as an emulsion in water in
concentration of 45 to 65% resin solids the remainder being water.
Minor additives may be supplied to improve the body and
flexibility, typically an anti-foam agent such as Colloid 677, an
oil based polysiloxane, thickeners such as hydroxylethyl cellulose,
rust inhibitors such as Strodex PK-90, a potassium polyphosphoric
acid ester, and preservatives of an anti-fungal nature, such as
Troysan, an organic mercurial complex. Such additives will be used
in the minor quantity 0.1 to 5% and sometimes as high as 10%, but
generally less than 1%, and usefully less than 0.2% such as 0.1 to
1%, and are generally mixed in a carrier such as a propylene glycol
in quantity usually less than 2%, such as 0.5-1%.
__________________________________________________________________________
THE FOLLOWING IS A GENERAL FORMULA FOR THE MASTIC WEIGHT PERCENT
TOTAL PREFERRED RANGE
__________________________________________________________________________
WATER (added to control body) 5-15 1-30 RESINOUS DISPERSION
Halogen-free resin solids 20-30 15-40 ADDITIVES Common surfactant,
e.e. Triton X 100, octyl 0.2-5 0.1-10 phenyl
polyethyleneoxyethanol, Tamol sodium polycarboxylate; Anti-foaming
agent, i.e. colloid, oil based polysiloxane; thickener, QP 4400
hydroxy ethyl cellulose; Strodex PK 90, potassium polyphosphoric
acid methyl ester; attapulgite gel, diatomaceous clay; fungicidal
preservative, Troysan CMP acetate mercurial complex, propylene
glycol, or wet strength enhancing acrylic resin ORGANIC FIBER
Typically aramid, rayon, wool or cotton. 0.5-2.0 0.1-5 WATER VAPOR
EVOLVING Hydrous oxides (inorganic hydrates having 15-30 10-40
chemically combined water evolvable only under fire conditions).
INTUMESCENTS Cenospheres 7-25 5-40 FIRE-PREVENTATIVES Zinc
Tetraborate 5-10 2-15 Antimony Oxide 4-10 2-15 FRIT Ceramic Glazing
Solids (typically low-fusing 10-25 5-40 borosilicate glasses
generally calcium, magnesium, zirconium, borosilicates (generally
lead-free).
__________________________________________________________________________
In forming the composition, the dry components are mixed and evenly
blended with the plastic to form a heavy mastic, adding a small
quantity of water in the range stated, sufficient to bring the
mastic up to a viscosity suitable for application upon the cables
assembled and panels as show, filling all of the openings, cracks
and crevices. The mastic formed as described may be extruded or
pressed into sheets of desired thickness, such as 1/4-11/2 inches
thick. In order to improve both the dry and wet structural
properties of the panel pressed or extruded from the mastic mass,
an addition of a heat polymerizable acrylic resin, such as Rohm and
Haas X-980 is added. The wet panel may be set by drying and
removing the moisture at ambient temperatures. When the acrylic
additive in the range of 2-10%, preferably in the range of 4-6%, it
is necessary to raise the panel temperature to
300.degree.-350.degree. F. in order to complete the polymerization.
Without such acrylic additive, the tape or other mastic product is
less sensitive to moisture.
The cables themselves are encased in coating, which may be thin and
flexible or may be applied as a filler mastic between a group of
cables as shown in FIG. 1 and which may pass through the paneling,
cut with holes to allow cables or trays having a number of
separately spaced cables to pass through from side to side of the
fire stop wall, and the cracks and cervices about each cable are
then filled with the mastic as shown in FIGS. 1 and 6. Thus the
mastic is applied by spraying, troweling or brushing upon the
cables, between the cables, upon the fire stop wall as a coating
and as the paneling substance from which the wall per se is
formed.
As shown in FIG. 7 an electrical arc and fire protective tape is
provided having cellulose sheeting or non-woven polyester film or
fabric base 102 or preferably cellulose fibers such as cotton or
rayon which have been previously treated with fire retardant salts
and, on this substrate a coating 104 of the mastic described above
is applied preferably within the thickness limits stated. The
mastic can also have small fibers 106 as listed above embedded
within the mastic. In forming the tape, the fabric 102 becomes a
conveyor and the wet mastic is applied in the thickness within the
range stated by a knife and doctor blade as in conventional
coating, the wet coated sheet is passed through a warmed oven or
drying chamber through which a stream of warm air is circulated to
provide a drying temperature lower than about the boiling point of
water, whereby the water will evaporate to leave the dried mastic
coating upon the fabric. It is desirable to dry the coated sheet or
fabric in the warm air stream while moving at low speeds of below
10 feet per minute, a rate slow enough within the drying chamber to
allow removal of the moisture from the tape at a slow enough rate
to avoid any significant formation of vapor bubbles in the wet
mastic while drying. That drying rate can be accelerated somewhat
by inclusion of a small quantity of mineral spirits such as
petroleum about 1 to 2% added to the mastic mixture, to supply an
azeotropic vaporization of the water and petroleum ether at a
somewhat lower temperature and thereby promote a faster drying
rate. The azeotropic component can be omitted and the drying can be
effected at a slower rate. The tape having dry mastic thereon bears
the benefits of the superior fire and arcing prevention character
of the mastic.
As shown in FIG. 8 the tape 100 may be wound about a cable sheath
108 in the manner typical for the insulation of a cable by a tape.
As shown in FIG. 9 the tape 100, which in this case is a thin
laminate of mylar (0.001") 103 and mastic (0.010") 100 wrapped
around the insulated multiple conductors and the mastic/mylar
laminate wrap covered with an extruded water resistant jacket 108
of polyethylene, polypropylene, ethylene propylene rubber or
equivalent of some 30 mils thickness.
As noted the tape support or substrate 102 may be of various types
of woven or matted fiber, of which Reemay, a polyester spun-woven
fabric is often preferred because of its substantial strength. It
bears the disadvantage, however, that it evolves smoke with heat
decomposition and from that aspect ordinary very light rayon or
cotton fabric, such as gauze or even cheesecloth made fire
retardant by pretreatments can be used because these evolve little
smoke and will serve to adequately support the mastic layer while
it is being applied as a knife coated surface layer. As a tape
cotton fabric is physically of weaker construction but has the
stated advantage of giving off little smoke upon heat
decomposition. Polyester film such as Mylar as thin as stated can
be used as a substrate in tapes for cable manufacturing. Also,
ceramic fiber fabric or sheet can be used advantageously in that
they give off no smoke and are more heat resistant, but from the
aspect of economy are more expensive.
The following examples illustrate the practice of this
invention:
EXAMPLE 1
Four hundred and sixty-two pounds of vinyl acrylic polymer
dispersed in water in quantity of about 277 lbs of polymer, the
remainder of said emulsion being water and additives. The additives
consist of 13 lbs of propylene glycol, 6 lbs of Colloid 677, oil
based liquid polysiloxane, 1.5 lbs of hydroxy methyl cellulose, 6.5
lbs of rayon fiber, 1.5 lbs of Strodex PK 90, potassium
polyphosphoric acid ethyl ester and 0.5 lbs of a mercurial complex
preservative. The entire mixture being a viscous dispersion in
water. Separately, a dispersion of 1.0 lbs of Triton X 100, which
is octyl phenyl polyethyleneoxyethanol, and 5.7 lbs of Tamol,
sodium salt of polycarboxylic acid, are dispersed in 50 lbs of
water. The aqueous solution of dispersing agents and additives is
used to dilute the first resinous emulsion. Thereafter dry powders
consisting of 190 lbs of hydrous aluminum oxide, 90 lbs of
cenospheres, 80 lbs of zinc tetraborate, 68 lbs of antimony oxide
and 163 lbs of frit, a low temperature borosilicate glass
essentially lead-free calcium silicate ceramic glass, available
from the Ferro Corporation as FB282. Thickeners such as Attagel 40
are added to the extent of 10 lbs to control consistency. The dried
powders are mixed into the diluted liquid emulsion to form a
sprayable mastic which is sprayed upon electrical cables and upon
fire stop panels. The mastic dries at ambient temperatures in air
to form approximately a 1/8 to 1/4 inch thick, on average, coating,
firmly and flexibly adherent to the cable surface. The base of the
panel is commercial ceramic fiber board, such as Kaowool, Duraborad
board of 1 inch thickness.
The coated panel of example I, about 1" thick was tested according
to ASTME 119 by supporting the panel above a flame having an
average firing temperature of 1725.degree. F. The flame impinges
against the coated side and the temperature of the uncoated side
was measured to determine the heat transfer effect. It was found in
a series of three hour burning tests that the maximum temperature
measured on the uncoated side was about 330.degree. F. for the
board with a 1/4" coating the heated mastic generated only a small
amount of smoke, the coating remained well adherent to the
insulating board. For a 1/8" thick coating with mastic the average
transferred temperature was 350.degree. F. In a comparison with a
competitive composition the temperature for a 1/8" coating was
380.degree. F., and for an uncoated board the temperature was
400.degree. F. In separate tests it was found that a standard
vertical burn test (IEE - 383) applied to grouped cables coated
with this mastic was self extinguishing after removal of the flame
source; there was no apparent damage to jacketing or insulation
during a 20 minute burn in which about 70,000 BTU per hour was
applied to the coated cables, and there was no flame propagation
after removal of the burner. The coating of this example is
flexible, and after drying, the coated cables can be bent without
cracking of the coating.
EXAMPLE 2
A similar mastic as example 1 was formed using a commercial mixture
of polyacrylate resins dispersed in water available as UCAR 163,
having similarly about 60% of polyacrylate total solids, of which
58% was mixed polyacrylics, the remainder being additives as in
example 1. This thick resin was similarly diluted with water and
additives, thinning the thick emulsion and into which is added the
powders as example 1. The mastic coated upon the cables as shown is
flexible and fire resistant by the same tests, and is highly heat
insulating, a 1" thick panel coated with the mastic to a thickness
of 1/8" average, and similarly exposed to a 1725.degree. F. exposed
flame for a three hour time period, transferred the average
temperature to the opposite side of about 345.degree. F. over the
test period. Seven conductor control cables coated with a thickness
of 1/8" min. were still flexible, and, in a special Factory Mutual
test, were immersed and cycled in and out of 60.degree. C. 1% salt
water solution for thirty days, and the coating was unaffected and
remained firmly adherent. In each of the tests examples 1 and 2 the
heated surface had a ceramic glaze and the coating had expanded to
a porous film of about twice the original applied and dried film
thickness.
EXAMPLE 3
The mastic of Example 3 was formed by similarly thinning the
commercial resinous dispersion of polyacrylic resins, reducing the
extra quantity of water used in the thinning to a maximum of 15
lbs., whereby, the mastic was thicker and trowelable. In order to
enhance the physical properties, particularly the wet modulus of
the panels heat polymerized acrylic resin is added in the range of
2-10%, preferable 4-6%. In this form it was cast into panels and
used as a fire stop panel in a test by exposure to a
1700.degree.-1750.degree. F. flame. The maximum temperature on the
cool side a 1" panel was 285.degree. F., on average over a three
hour test period, the panel expanding and charring in the area of
the applied heat, but conducted no flame when the burner was
withdrawn.
As shown in FIG. 4 one or more cables can be passed vertically
through a masonry floor, for which purpose they may be mounted
within a pre-formed sleeve and the mastic poured around the sleeve.
The mastic may also, as shown in FIG. 6 be filled into the body of
the sleeve or applied only in separated portions thereof for
support, thus acting as a firestop and sealing the cables for
prevention of gas flow between spaces separated by the floor. The
mastic will be filled or applied around the outside of the sleeve
as shown to a selected depth, and other fire stop paneling as shown
in FIG. 1 may also be used to close the floor opening.
FIG. 5 shows a single cable having a dried precoated film of mastic
thereon, a form in which the cable itself may be handled.
EXAMPLE 4
The mastic composition as set forth in Example 1 is wet coated by
doctor blade upon a strip of spun-woven Reemay fiber, a commercial
product available commercially from the duPont Company, in a
thickness of 0.035 inches and passed through an air drying oven
slowly at about 1.5-5 linear feet per minute while being warmed by
a counter current flow of air at 180.degree. F. being substantially
dried, cooled in air, slit into appropriate widths and wound into a
roll of tape. That roll of tape was wound upon a cable, the cable
was wound in 1/2 overlap per turn about 11/2 inch lead sheathed
cable, as shown in FIG. 8, and heated to a temperature between
1700.degree. and 1750.degree. F. by a Fischer burner.
__________________________________________________________________________
The tape formed has the following characteristics: SUPERIOR FIRE
PROTECTION CHARACTERISTICS DERIVED FROM:
__________________________________________________________________________
Length of roll - 25' to give a. Chemically bound water great
economy in shipping, in mastic composition driven handling. off
during fire exposure to Weight per 3" .times. 25' roll - 28 ozs.
provide cooling and reduce oxygen. Thickness - 0.045" b. Inert
gases (CO.sub.2, N.sub.2) Tensile strength - 350 psi (ASTM D-100)
physically entrapped in millions Elongation - 125% at break of
hollow spheres (cenospheres) released during fire to displace
oxygen needed to support combustion. Color - grey c. Formation of a
refractory, heat reflective surface over the burned area. Resistant
to fresh and salt water, d. Mild intumescence providing sewage,
acids, radiation. additional heat insulation. Flexible and
conformable. Fumes from combustion - noncorrosive with minimal
health hazard. Cellulose based substrate gives low smoke level.
Burn - through resistance - prevents 1700.degree. F. flame from
burning through and melting lead (625.degree. F.) for periods in
excess of 30 minutes.
__________________________________________________________________________
The following table compares the results with several other
commercial fire protective tapes offered in the trade for
electrical similar purposes:
__________________________________________________________________________
E - U.S. Pat. F - Example 4 TAPE A B C D No. 4018962 Example above
__________________________________________________________________________
CURVE SUBSTRATE Carbonized Glass Skrim Polyester Nylon Spunwoven
Cotton Gauze Organic Fabric Embedded Spunwoven Woven Polyester
Fabric Fabric between PVC Fabric Skrim Fabric Film Fabric ELASTOMER
PVC PVC Calendered PVC Calen- Neoprene PVC Plastisol Mastic
water-based Coating Film dered Film Calendered Example above. Film
Lam- inate COLOR Black White White Brown Gray Gray THICKNESS 0.065"
0.053" 0.050" 0.047" 0.055" 0.045" TIME (mins) TEMP .degree.F. TEMP
.degree.F. TEMP .degree.F. TEMP .degree.F. TEMP .degree.F. TEMP
.degree.F. 1/2 165.degree. 140.degree. 100.degree. 200.degree.
100.degree. 1 340.degree. 290.degree. 330.degree. 260.degree.
200.degree. 2 380.degree. 308.degree. 500.degree. 500.degree.
375.degree. 290.degree. 3 550.degree. 412.degree. 640.degree.
610.degree. 410.degree. 385.degree. 4 625.degree. 500.degree.
650.degree. 435.degree. 437.degree. 5 624.degree. 470.degree.
472.degree. 6 515.degree. 500.degree. 8 565.degree. 537.degree. 9
600.degree. 12 582.degree. 14 595.degree. 16 609.degree. 18
615.degree.
__________________________________________________________________________
It will be noted from the data on this table that various
commercial tapes listed as A, B, C and D have poor insulating
effects to destroy it at high temperature and temperatures of
625.degree. F..+-.25.degree. which is the melting point of a lead
sheath were reached in times of four minutes or less, whereas the
tape E of U.S. Pat. No. 4,018,962 had a much superior fire
resistance but chlorine fumes resulted from the PVC combustion. The
tape F of this invention, besides having even superior fire
resistance, is halogen free.
The tape hereof can be applied protectively about other electrical
equipment, cables, cable splices and appurtenant equipment for fire
and electrical arcing protection.
Various modifications will occur to those skilled in the art,
particularly other hydrous oxides and other known ceramic frits may
be substituted.
Accordingly, it is intended that the disclosure be regarded as
exemplary and not limiting, except as defined in the claims.
* * * * *