FIRE PROTECTIVE TAPE

Abstract: A fire preventive tape using a halogen-free mastic coated on a fabric support, 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, coating or spraying. The mastic (104) is applied as a coating upon the sheet-like carrier (102), which may be wound as a tape (100) upon single or grouped electric power and control cables (108) 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.

Description: FIRE PROTECTIVE TAPE This application 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 com- prising protective water vapor-evolving substances, other sub¬ stances 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 filing 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. 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 pro¬ vide 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 inturαescing or decrepitating substances, typically cenospheres, which are fly-ash, inorgani particles evolved as dust from coal combustion and are very light, volatile and expandable with heat, like tiny fused bal¬ loons. 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°F such as 1200°F to 3000°F to activate the intumescing components and release vapors which convert the composition from a thin layer coat- ing 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 intu- mescent 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 de¬ compose with the heat of a fire • and evolve large quantities of cooling, non-corrosive oxygen-displacing and fire-protec¬ tive water vapors. Such hydrous oxides are typically hydrous alumina, magnesia and the other 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 devel¬ oped 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, typi¬ cally a borosilicate glass frit generally fusible in the rang of about 700° to 1500°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 thermoplasti resin is present in quantities sufficient to for 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 supply ing 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 sub¬ stances may be any useful thermoplastic binder resin, which is halogen-free, but which may melt and flow by heat devel- oped during fire and allow the composition to expand to a heat insulating coating. The typical resins for this purpos are halogen-free to avoid decomposition and release of nox¬ ious and corrosive halogen gases, and may be typically poly¬ vinyl acetate, polyacrylic acid, polyacrylic lower alkyl esters, such as methyl or ethyl esters thereof, polymethacry lic acid and its lower alkyl esters, such as methyl and ethy esters thereof, as well as mixtures of such acrylic resins, natural and artificial rubber latices, each as dispersions i water, said dispersions usually having from 25 to 75% resin solids therein, sually 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 ol- ten 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, gen¬ erally less than 5%, usually 0.5 to 2.0% to supply this tem¬ porary 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 de- velop vapors with heat along with 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 tetra- borate 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 octyi- phenyl-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 fungi- cides, 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 consist¬ ing of water vapor, antimony oxides and minor heat decomposi¬ tion 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 nox¬ ious and corrosive halogen gases. In forming this mastic mixture, the binder emulsion of resi ' in water is further ixed with the dry in umescing 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 thicknessess of 0.025" to -BUREΛ T - u ι - - - ■ ■ --- " ipδ- 0.150" and air dried to form a thick flexible coating on th electrical cables and wall panels forming a heat insulating and fire proofing mastic as well as an effective heat insu¬ lating 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 pane through which electrical cables may pass, or as a thick sus pension in water to be applicable as a protective mastic fil ler 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 Ree ay which is spun-woven polyester, The fabric can also be cotton or a ceramic fiber typically glass fiber or carbon ized acrylic fiber, each with characteristic advantages. Fo 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 fab¬ ric, to a selected thickness and dry the coating thereon at moderately raised temperature below about 200°F. and prefer¬ ably between 125 to 190° 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 servin as the conveyor and becoming permanently embedded as a lami¬ nate, to a dried coated mastic thickness of about .005 to 0.150 Inches preferably .010 to 045 inches. In prior applications of other heat and fire protective insulation substances upon electrical cables including a tape, these according to my prior patents nos. 4,018,962 and '^ .itA ' SUBSTITUTE εHΞΞT . - _% ■ 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. patents Nos. 3,642,531 and 3,928,210 to coat cables as an aqueous emulsion of halogen evolving resins, Including essentially halogen evolving plasticizers, the heat insulating effect of such coating compositions being largely 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 dam¬ age to personnel and equipment. Equally important, such com¬ positions 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 fall to adequately meet the important fire and heat insulating needs to prevent de- struction of cable jacketing and insulatio -protecting criti¬ cal power and multiple conductor control cables and to preven propagation of fire along grouped cables in trays and throug wall floor penetrations at flaming temperatures often exceed¬ ing 1,900°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 arrange in a vertical tier as they will pass through a fire wall pro¬ tected 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 sup¬ port; 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 masonry sep arates spaces A and B as a partition for normal structural purposes and has a rectangular opening 12 cut. therein for pas sage 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 criti cal communication circuitry or conduct electrical power, of times of high voltage. In any case, any building constructio has many cables as a valuable part thereof and, for whatever electrical purpose they serve, great damage can be done to th structure and cables by electrical faults, such as short cir¬ cuitry or extraneously caused fire, such as by exposed to flaming combination of oil, trash or the like, developing"de¬ structive heat in the cables. Again, the cables themselves are valuable in terms of. the numerous communicating conduc¬ tors 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 tha 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 insu¬ lating 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 throug the opening 12 of the wall 10. The layers of cables can be further supported from below by a heat resistant panel moulde or case from the mastic or a knife coated tape or blanket of mastic covered by this invention, the thickness of said blan¬ ket being in the range of .050 to .200 Inches, preferably .100 to .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) t 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 ma 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 inor¬ ganic 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. Op¬ tionally, 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 full 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 paneli 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 bein 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 the top of the cables an for secure closure of any cracks between panels, both around the panel edges as well as " any spacing or cracks between the ad acent panels. As shoT-πi 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 group¬ ing. Additional cables may be passed through the wall of the construction by cutting through the light pre-cast panels, 5 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 'newly formed cut portion. The newly added cables are coated with more fresh 0 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 separate by a partitioning wall 34, in which larger panels of the mas¬ tic 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 or 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-pro¬ tective 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 pre¬ vents heat and flame transfer, as well as the transfer of nox¬ ious vapors or smoke to its opposite wall side where continu¬ ing 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 tern-, peratures that may develop from a cable failure. The paneling may be formed of other useful pre-cast proof materials, but _O PI 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 individ- ual cables disposed as groups or individual cables in sleeve pass through - floor slab 10 with the mastic hereof poured about and within the sleeve to form "' ah 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 con ventional application as a tape and superior in that the mas tic 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; exposure resulting from short circuiting conditions:^ or other fire source, such as * In mines, *' subways, shipboard,-.-buildings and other confined spaces which electri cal equipment is placed or passes through, by virtue of the fact that no halogen Is evolved at decomposition temperature The present composition is highly heat and fire protec¬ tive. It evolves only non-corrosive vapors, such as water vapors, Inert nitrogen and C0 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 intumescent 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, wherebj*- the coating is low heat transferring and does not powder, flake or peel off the sur- face of the cable to which it was applied. Theoretically, it appears that during the heating pro¬ cess when ignition and combustion take place through electri cal 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 C0 ? gases which are occluded in the cenospheres. The antimony oxide at higher temperature can evolve its vapors. The fiber which is ultimately heat decom posable, 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 th resin may be charred to an infusible porous mass, developed .by the expanding intumescing solids. The expanding mass car ries much of the fusible frit to the coating surface, where at high heat exposure temperatures, the frit can fuse pro¬ tectively as a refraction shell over the porous mass to pre¬ vent further heat passing into or from central or inner cabl portions. The glazed frit serving further as a 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 compon¬ ent 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 here- of 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 desire For purposes of easy distribution of the water, various sur¬ factants such as Triton X 100 an alk lphenoxy, polyloweralk eneoxy, loweralkanol in which the alkyl has 102 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 re- mainder being water. Minor additives may be supplied to im¬ prove 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 pr servatives of an anti-fungal nature, such as Troysan, an or¬ ganic 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 pr pylene glycol in quantity usually less than. 2%, such as 0.5 1%. O.V. €_ ** ϊϊ ?CT * " ϊ l" " " ~ THE FOLLOWING IS A GENERAL FORMULA FOR THE MASTIC TOTAL WEIGHT PERCENT RANGE PREFERRED WATER (added to control body) 5 - 15 1 - 30 RESINOUS DISPERSION 20 - 30 15 - 40 Halogen-free resin solids ADDITIVES Common surfactant, e.e. Triton X 100, octyl phenyl polyethyleneoxyethanol, Tamol sodium polycarboxylate; Anti- foaming agent, i.e. colloid, oil based polysiloxane; thickener, QP 4400 hy- droxy ethyl cellulose; Strodex PK 90, potassium polyphosphoric acid methyl ester; at apulgite gel, diatomaceous • clay; fungicidal preservative, Troysan CMP acetate mercurial complex, propy- lene glycol, or wet strength enhancing acrylic resin 0.2 - 5 0.1 - 10 ORGANIC FIBER Typically aramid, rayon, wool or cotton 0.5 - 2.0 0.1 WATER VAPOR EVOLVING Hydrous oxides (inorganic hydrates having chemically combined water evolvable only under fire conditions) 15 - 30 10 - 40 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 borosilicate glasses generally calcium, magnesium, zirconium, boro- silicates (generally lead-free) . 10 - 25 5 - 40 In forming the composition, the dry components are mixe and evenly blended with the plastic to form a heavy mastic, adding a small quantity øf water in the range stated, suffic¬ ient to bring the mastic up to a viscosity suitable for app- lication upon the cables assembled and panels as shown, filling all of the openings, cracks and crevices. The masti formed as described may be extruded or pressed into sheets of desired thickness, such as 1/4 - 1 1/2 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 tempera¬ ture to 300° - 350°F. in order to complete the polymeriza¬ tion. Without such acrylic additive, the tape or other mas¬ tic product is more sensitive to moisture. The cables themselves are encased in coating, which may be thin and flexible or may be applied as a filler mastic be¬ tween 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 crevices about each cable are then filled with the mastic as shown in Figs 1 and 6. Thus the mastic is applied by spray¬ ing, troweling or brushing upon the cables, between the cables, upon the fire stop wall as a coating and as the pan¬ eling 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 poly¬ ester 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 with¬ in the thickness limits stated. The mastic can also have small fibers 105 as listed above embedded within the mastie: 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 coat¬ ing, the wet coated sheet Is passed through a warmed oven or drying chamber through which a stream of warm air is circu- lated 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 de¬ sirable to dry the coated sheet or fabric in the warm air stream while moving at low speeds of below 10 feet per in- ute, 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 accelerate 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 petrol¬ eum either at a somewhat lower temperature and thereby pro¬ mote 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, how- ever, 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 pretreat- ments 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 manu¬ facturing. 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 ex- pensive. The following examples Illustrate the practice of this inventio :- EXAMPLE 1 Four hundred and sixty-two pounds of v-nyl acrylic pol mer dispersed in water in quantity of about 277 lbs of poly mer, the remainder of said emulsion being water and additiv The additives consist of 13 lbs of propylene glycol, 6 lbs Colloid 677, oil based liquid polysiloxane, 1.5 lbs of hy- droxy methyl cellulose, 6.5 lbs of rayon fiber, 1.5 lbs of Strodex PK 90, potassium polyphosphoric acid ethyl ester an 0.5 lbs of a mercurial complex preservative. The entire mi ture being a viscous dispersion in water. Separately, a di persion of 1.0 lbs of Triton X 100, which is octyl phenyl olye hyleneoxyethanol, and 5.7 lbs of Tamol, sodium salt o polycarboxylic acid, are dispersed in 50 lbs of water. The aqueous solution of dispersing agents and additives is used to dilute the first resinύous emulsion. Thereafter dry pow ders consisting of 190 lbs of hydrous aluminum oxide, 90 lb of cenospheres, 80 lbs of zinc tetraborate, 68 lbs of antim 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 con trol consistency. The dried powders are mixed into the di- luted 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 ap¬ proximately a 1/8 to 1/4 inch thick, on average, coating, firmly and flexibly adherent to the cable surface. The bas of the panel Is commercial ceramic fiber board, such as Kaowool, Duraboard 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 flame having an average firing temperature of 1725F. The flame impinges against the coated side and the temperature the uncoated side was measured to determine the heat transf effect. It was found in a series of three hour burning tes that the maximum temperature measured on the uncoated side was about 330°F for the board with a 1/4" coating the heate 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 temperatur was 350°F. In a comparison with a competitive composition the temperature for a 1/8" coating was 380°F, and for an un¬ coated board the temperature was 400°F. In separate tests I was found that a standard vertical burn test (IEE - 383) ap¬ plied to grouped cables coated with this mastic was self ex- tinguishing. after removal of the flame source; there was no apparent damage to jacketing or insulation during a 20 minut burn in which about 70,000 BTU per hour was applied to the coated cables, and there was no flame propagation after re¬ moval of the burner. The coating of this example is flexibl and after drying, the coated cables can be bent without crac ing of the coating. EXAMPLE 2 A similar mastic as example 1 was formed using a commer cial mixture of polyacrylate resins dispersed in water avail able as UCAR 163, having similarly about 60% of polyacrylate total solids, of which 58% was mixed polyacrylics, the re¬ mainder 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 exampl 1. The mastic coated upon the cables as shox-m is flexible and fire resistant by the same tests, and is highly heat in¬ sulating, a 1" thick panel coated with the mastic to a thick ness of 1/8" average, and similarly exposed to a 1725°F ex- Q .viPi posed flame for a three hour time period, transferred the average temperature to the opposite side of about 345°F over the test period. Seven conductor control cables coated with a thickness of 1/8" min. were still flexible, and, in a spe- cial Factory Mutual test, were immersed and cycled in and out of 60°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 has a cera¬ mic 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 was forme by similarly thinning the commercial resinous dispersion of polyacrylic resins, re¬ ducing 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 1700-1750°F. flame The maximum temperature on the cool side a 1" panel was 285°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 ver¬ tically through a masonry floor, for which purpose they may be mounted within a pre-for ed 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 sep- arated portions thereof for support, thus acting as a fire- stop and sealing the cables for prevention of gas flow be¬ tween 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 sa 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°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 1-1/2 inch lead sheathed cable, as shown in Fig. 8, and heated to a temperature between 1700 and 1750°F. by a Fischer burner. SUBSTITUTE SHEET O.V.PI * The tape formed has the following characteristics :- SUPERIOR FIRE PROTECTION CHARACTERISTICS DERIVED FROM: Length of roll -- 25' to give a. Chemically bound wat great economy in shipping, in mastic composition dr handling. off during fire exposure provide cooling and redu Weight per 3" x 25' roll - 28 ozs. oxygen. Thickness - 0.045" . ■■ , b. Inert gases (C0 ? , N physically entrapped in" Tensile strength - 350 psi (ASTM D-100) millions of hollow spher (cenospheres) released d I Elongation - 125% at break fire to displace oxygen CoM needed to support combus I Color - grey c. Formation of a refra Resistant to fresh and salt water, hefat reflective surface sewage, acids, radiation. the burned area. Flexible and conformable. d. Mild intumescence pr viding additional heat i Fumes from combustion - noncorrosive lation. with minimal health hazard. Cellulose based substrate gives low smoke level. Burn - through resistance - prevents 1700°F flame from burning through and melting lead (625°F) for periods in ON excess of 30 minutes. * * *. r. O O The following table compares the results with several other commercial fire protective tapes offered in the trade for electrical similar purposes:- SUB Ώ .- oy.pi 1> C7-.Ln .p-U> p> Ml o s« TJ σ * > * o lw NϊOPO -P » w • *χ - p. < O PJ H -f 0 ro oo O 2 o H- PΏ rt cr fa o o o o o TJ Ln ft 3 LO ro Ω o - fa P 1 ro 3 ro M ro CL we Vi en CPFlir i r E cm b e dd e d ss m Sk r i - a-. CPi Ln Ln * Ln IJI >- .p- O ro to H o i— ! θvooo uo jωoovoo o P trl rr" S T) Ω I I*r1 ϊri t-{ cr * fa fu P o 1 LπvO Ln ro ~-0 O ro -*j ι_π o o o o o o o o o o o 2 o o to to en o o cr rt P t=_ TJ • " - * - * *< • < 3 ro rt H rr Ln cr X ro TJ p. p. H- O o o P z • P" ro o 3 ^_ < 3 ro ro Ti. 51 Ω p> fa ro rt 3 ro N -P- ro It will be noted from the data on this table that various commercial tapes listed as A, B, C and D have poor insulat¬ ing effects to destroy it at high temperature and tempera¬ tures of 625° F. + 25° which is the melting point of a lead sheath were reached in times of four minutes or less, where¬ as the tape E of U. S. Patent 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 appur¬ tenant 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 re¬ garded as exemplary and not limiting, except as defined in the claims. ' '

Claims: WHAT IS CLAIMED: 1. An electrical arc and fire protective tape for dis¬ position about electrical equipment, cables, cable splices, appurtenant equipment or the like, comprising a resinous mix¬ ture 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 approx¬ imate 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 ex¬ panded 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 suf¬ ficient heat to decompose and evolve water-vapors, and a re¬ sinous 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 con¬ vert said solids into a fluidized form for application as a coating upon said base or substrate, said percentages being by xveight, the said solids quantity being based on the total solid 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 re¬ sin 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 quantify of 10 to 25%, the hydrated substances are hydrous oxides in the ranges of 15 to 30%,, the intumescing and expanding substances are cen ospheres in the range of 7-25%, said mastic further containing a small quantity of about 0.5 to 2.0% of organic fiber, and fi retardants antimony oxide and zinc tetraborate, each present i quantity of 4 to 10% and 5 to 10% respectively. 4. The electrical arc and fire protective tape as define 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 define in claim 1, wherein the fabric base is polyester fiber in wove knitted, netted or non-woven form. 6. The electrical arc and fire protective tape as define 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 define 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 define in claim 1, wherein the coating has a thickness in the range o 0.005 to 0.150 inches. 9. The electrical arc and fire protective tape as define in claim 1, wherein the heat intumescing substances are ceno¬ spheres. 10. The electrical arc and fire protective tape as define in claim 1 further including about 2 to 15% of protective soli 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 fibe 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. - 1 REA

Inventors: PEDLOW WATSON J, STAHL JAMES P
Applicants: THOMAS & BETTS CORP
Application year: 1981
Main classification: B32B7
IPC codes: C04B26, H01B7, H02G3