TECHNICAL FIELD

This invention relates to f1ame-retardant occludant coatings having improved properties of providing flame retardancy to various 5 overlaid substrata by having the characteristic of withstanding sustained elevated temperatures. In particular, this invention relates to a novel and heretofore unknown composition and method for imparting flame-retardancy to various otherwise flammable substrata by means of a dome producing occludant coating; wherein said flame-retardant Q occludant coating includes a heat releasable expandable fluid applied polymeric or resinous coating material and high temperature fibrous material dispersed therein. When subjected to heat or a constant source of flame the material of this invention will produce a protectant dome over the substrata. 5 BACKGROUND OF THE INVENTION

The use and application of such terms as fireproof, flameproof, self-extinguishing, non-burning, non-combustible, and others are used ambiguously about the relative flam ability of different substrata. Most of the materials used in our immediate surroundings are

20 combustible and much of the materials of construction are likewise combustible. Under the right conditions almost any type of material can be made to burn; many materials ignite readily and burn vigorously. The search is continuous to find means to render various substrata non-combustible or at least to reduce the flammability

25 thereof.

Various inorganic salts have been proposed and used to accomplish noncombustibilit ^» f various flammable substrata. Ammonium salts of sulfuric, phosphoric, and hydrochloric acids nave been found effective, as well as certain mixtures of these salts with borax. The

30 effect of mixing antimony oxide with organic halogen compounds also was found effective. These efforts represent the m-jor discoveries on which modern flame-retardant chemicals are based.

Certain prior art has used fluid intumescent based materials in conjunction with refractory or high melting fibers to produce a

35 protective coating for various substrata. U.S. Patent 4,879,320 relates to an intumescent fire retardan :oating material which includes a fluid intumescent material ana refractory fibers of various

sizes dispersed or suspended therein. The fluid intumescent material of 4,879,320 includes a foaming agent, a blowing agent - gas source, a charring agent, a film forming binder, a solvent and in some cases a pigment of filler. The principle function by which the coating composition of U.S. 4,879,320 provides fire protection is by intumescence. Intumescence is the process which describes the bubbling, swelling, expansion or foam formation when heat is applied to the coating. The source of gas for the foam formation is from the coating, whether inherent in the material itself or from an additive to the coating formulation. As in U.S. 4,879,320, small air cells are formed in the coating. Further, U.S. 4,879,320 adds the fibrous material to interfere with the gas bubble size and thereby operates to limit or control the size of the gaseous bubbles or air cells. Other prior art which form gas bubbles or air cells have no restraints on the increasing size of the air cells being formed. As a result the air cells eventually become so large that they burst or erupt thereby exposing the substrata surface beneath the coating to the flame source. Also, in the nature of intumescent coatings the coating material will char, become brittle and often become consumed by the flame during the exposure. Therefore, such eruptions and consumption of the coating itself interferes with the flame-retardant effectiveness of the intumescent material.

It is accordingly an object of the present invention to provide an improved fire and heat retardant coating that is easily applied by its fluid consistency and includes a novel combination of fire and heat retardant polymeric coating material and ceramic fibers or other high-temperature fibrous material dispersed therein.

It is also an object of this invention to provide a method by which an otherwise flammable substrata may be protected from sustained flame impingement by the formation of a protectant fire and heat resistant dome thereover.

It is a further object of this invention to provide a non-intumescent dome forming protective occludant coating as a fire and heat protectant for an underlying flammable substrata.

It is a further object of this invention to provide a new and novel thermal protectant as a protective fire and heat dome occludant coating over a substrata to protect said substrata against combustion by forming a stabilized protectant bubble or dome thereover. It is yet a further object of this invention to stabilize the protectant occludant bubble or dome formed from heating a flame-retardant polymeric or resinous material by the inclusion therein of high-temperature fibrous material, such as asbestos or ceramic fibers. Of special utility is the application of the fire and heat retardant dome forming occludant coating of the present invention to modified bituminous/polymer emulsion overlaid on a wood surface. As described in U.S. Patent 4,722,953, bituminous emulsion/polymer emulsion combinations are preferred substrata coatings over wood or other surfaces. The modified bituminous/polymer emulsion coatings are flexible under a wide variety of temperatures and resist shrinkage and cracking. They can be applied as a coating directly over wood, concrete or other construction material. The coating also can be used on existing built-up roof systems. SUMMARY OF THE INVENTION

In the present invention, there is provided a fire and heat retardant occludant coating material which includes a fluid-applied dome forming occludant material and high-temperature fibrous materials dispersed therein. The fluid-applied occludant material includes various additives, in addition to the fire retardant polymer and the fibrous materials, such ingredients as pigment, solvents, fillers, if necessary a gas source, as a blowing agent and further, if necessary a wax or other release agent. The high-temperature fibrous material must sustain its integrity at high temperatures of at least 800 - 1200° F (426 - 643° C) . This includes, for example, ceramic fiber, asbestos, graphite or other high-temperature fibers.

More particularly, this invention relates to unique coating compositions, which are fire and heat retardant, dome forming occludants. This invention also relates to the method of producing fire and heat retardant domes over otherwise flammable surfaces at the

point or points of flame or heat impingement with coating compositions capable of forming fire and heat retardant domes, whereby the domes protect the surface from the fire and heat; and this invention relates to the use of said dome forming coating compositions to retard the advance of a persistent flame impinging upon an otherwise flammable surface and to thermally protect the flammable substrata thereunder by the formation of such domes. This is true as well when a wind or air movement is passing over the flame or heat source. DESCRIPTION OF THE INVENTION The composition of the present invention contains at least one type of ceramic or high-temperature fibrous material dispersed in a flame-retardant polymeric or resinous coating material. The polymeric or resinous binder within said coating composition is flexible at the temperature to which the coating is raised when subjected to a persistent heat source, so as to permit the protectant dome formation. The composition of this invention is fluid-applied to the surface of an otherwise flammable substrata. The surface contains a release agent to release the coating when affected by the heat; alternatively, the coating itself may contain agents which permit release of said coating from the surface. Said release agents may be in the form of a wax or other material which interferes with the adhesion of the coating to the surface, or in the form of a low melting resin or other material, such as asphalt, which melts or softens to allow the coating subjected to a heat source impinging thereon to release itself from the surface to which it is applied.

Either this composition or the surface to which it is applied may contain some form of heat sensitive material which emits a gas that causes a dome to form over the area subjected to a fire or heat source. The covering of the dome is composed of the flame-retardant polymeric or resinous material and the included high-temperature fibrous material, such as asbestos or ceramic fibers.

By the term fire retardant is meant the property which increases the threshold of ignition of the treated material. This refers to a compound that retards or stops an undesired combustion reaction. Therefore, the term fire-retardant implies that the flammability of the material is decreased, not eliminated. Therefore, by the term fire-

retardant coating is meant a coating which retards or stops the spread of fire on or by the coating itself.

By the term heat-retardant is meant the property of maintaining a surface temperature substantially lower than the temperature to which the coating is subjected.

By the term high-temperature fiber it is meant any fiber that substantially maintains its integrity at a high-temperature. The term high-temperature may seem ambiguous, but is meant to refer to any temperature substantially above the temperature which substrata surface is designed to tolerate. Various fibers can be included in such a listing, for example, such fibers as nylon, aramid, ceramic, chopped glass fibers, graphite and carbon can be considered high-temperature fibers. Even though some of said fibers may burn, to the extent said fibers maintain their integrity at temperatures that the surface to which they are applied cannot tolerate, they are to be considered high-temperature fibers.

The preferred high-temperature fibers are not only heat-resistant, but also fire-resistant. Such fibers include, among others, asbestos, glass and ceramic fibers. Typical ceramic fiber material consists of a uniformly dispersed mixture of silica (sand, about 75 percent), soda ash (about 20 percent) and lime (about 5 percent) often combined with such metallic oxides as those of calcium, lead, lithium, cerium and the like. The blend or melt is heated to fusion temperature, approximately about 700 - 800° C, and then annealed to a rigid, friable state, often referred to as vitreous. Glass is considered an amorphous, undercooled liquid of extremely high viscosity which has all the appearances of a solid. In fibrous form glass is a good thermal insulator. Depending on the composition, continuous upper use temperatures may be very high, such as in the glass-ceramic fibers. Glass-ceramic is a devitrified or crystallized form of glass whose properties can be made to vary over a wide range. Usually a standard glass formula to which a nucleating agent, such as titania, has been added is melted, rolled into sheets and cooled. Glass-ceramics lie between borosilicate glasses (heat-resistant glass) and fused silica (quartz) in high-temperature capability.

742 PCT/US91/04683

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The fibers in the coating preparation must be present in at least 2 percent by weight of the non-volatile ingredients. The fiber can be of varying length from about 25 microns to longer lengths. Th diameter of the fibers can vary about 0.5 microns. To be functional, it has been found that the length must be substantially greater than the diameter. Preferred ratios of diameter to length are from about to about 10 or greater. Tests have been performed with fibers varyin in length from 70 microns to about 400 microns with diameter to lengt ratios of about 1 to about 25, and about 1 to about 160. The greater the diameter to length ratio the better the integrity of the dome or bubble.

The composition of polymeric or resinous material and high-temperature fibrous material is blended to the consistency of a substantially uniformly dispersed mixture. This mixture may be a soli or liquid at room temperature. However, at application temperature, this mixture has a viscosity ranging from a thin liquid to a semi-soli paste capable of application to the surface of a solid or semi-solid substrata.

The coating composition also may consist of a drying oil, a latex emulsion, a synthetic resin, or other film-forming component, otherwise termed a binder; a solvent or thinner; and an organic or inorganic pigment. The binder and the solvent are collectively calle the vehicle. Further, components in the coating composition, in addition to the high-temperature fibrous material, such as ceramic fibers, may include pigments, colorants, fillers, and extenders. Surfactants and protective colloids are necessary to stabilize the product. Emulsions are characterized by the fact that the binder is i a water-dispersed form, in contrast to those where a solvent is used and the ingredients are in a soluble form. Latex formulations include among other polymer types; styrene-butadienes, ethylene vinyl acetates, polyvinyl acetates, vinyl chlorides, epoxys, urethanes, acrylic emulsions, styrenated acrylics, and copolymers thereof or blends thereof. Typical percentage compositions of a latex coating material may be 12-40 percent by volum solid binder, 8-18 percent by volume pigment and 49-70 percent by

volume water, plus varying amounts of stabilizers, such as surfactants and protective colloids, as necessary. Such a formulation in a water-based system can be used on both interior and exterior surface applications. Typical uses of this occludant coating, in addition to its use as a dome forming fire and heat protectant coating over roofing substrata, include the protection of other combustible substrata such as wood buildings, furniture, toys, decks, and the like. In addition this dome-forming occludant coating can be used as a heat-retardant coating over those surfaces commonly referred to as non-combustible surfaces, which contain materials that can combust, ignite, melt or otherwise degrade when subjected to heat. The occludant coating of this invention also can be used on other combustible and non-combustible surfaces which will deform, degrade or otherwise lose their integrity when subjected to heat; for example, gas tanks, and other tanks storing combustible liquids or gasses, munition containers, heat-sensitive equipment and the like.

Heat flux (heat rate at the surface exposed to flame) is a factor which causes most otherwise fire-retardant coatings and polymers to burn. Heat itself can be defined as a form of energy associated with, and proportional to, molecular motion. Heat can be transferred from one body to another by radiation, conduction or convection. Usually the heat of combustion is the heat evolved when a definite quantity of a substance is completely oxidized, as in burning. Without being limited to any theory, it is believed that the formation of the dome or large bubble at the point of heat source impingement associated with the occludant coating composition of this invention over an otherwise flammable substrate, causes the heat transfer from a sustained flame or heat source to be minimized. The protectant dome formed is equal to or larger then the area affected by the flame or heat source. That is, transmission of thermal energy is minimized by means of a lowered temperature gradient of thermal energy from the heat source to the flammable surface over which the occludant coating composition is applied. This lowered temperature gradient occurs by means of the protective dome or bubble that forms over the

substrate in the area of heat or flame impingement. Of necessity, the protective dome or bubble must be resistant to further degradation and decomposition in order to offer sustained flame protection to the flammable or heat deformable substrate beneath the coating. The desired quality of a stable flame heat resistant dome or bubble from the occludant coating herein described is ascribed to the high-temperature fibers contained therein.

Occludation is the process to retard the advance of flames by dome or large bubble formation, wherein the dome or bubble is formed from a substantially fire or heat retardant coating material applied to an otherwise flammable substrate, and wherein the polymeric or resinous material contains flame or heat resistant fibers, such as ceramic fibers. Acting together the polymer or resin and the incorporated heat-resistant fibers form a tight network-like skin on the formed.thin wall dome thus containing the gases formed during the heating process inside the dome and further stabilizing the dome.

Without being limited to any particular theory as to the means by which the ingredients function, it is believed that the added fibrous material acts in conjunction with the substantially fire and heat retardant polymeric material during the protectant dome or bubble formation to stabilize the dome or bubble and to maintain the integrity of the formed dome or bubble thereby diverting the flame or heat source away from the surface. As the heat or flame spreads over the surface of the coated substrate the dome forms, then the dome acts to deflect the heat or flame away from the surface of the coated substrate. A flame and heat retardant occludant is a coating material which will first release from the substrate surface and then flex and expand to cause the formation of a dome or bubble of substantially larger area than the heat or flame impingement area, when the coated surface is heated with a continuous flame or other high-temperature heat source. Said temperature will normally ignite the substrate or material over which the occludant coating is applied. The occludant coating material must itself be somewhat fire and heat retardant, and flexible and expandable, at the elevated temperature to which it is initially subjected by exposure to the heat or flame in order to be able to form

a satisfactory dome over the substrata . If the desired coating polymer or resin is not itself fire or heat retardant, the use of the fire or heat retardant agents in conjunction with a fire or heat retardant material, or a non-fire or heat retardant material, is incorporated therewith to achieve the same result.

The following experimental work illustrates the present invention. They are set forth as further description but are not to be construed as limiting. All parts are by weight. EXPERIMENTAL To assess the effectiveness of the compositions and methods herein in providing fire and heat retardancy, various compositions were prepared and applied to substrate surfaces and subjected to fire and heat conditions simulating real situations.

The following examples and results as described, and further exemplified in the drawings and photographs submitted herewith, will serve to exemplify the above described improved characteristics of the novel flame-retardant dome producing occludant coating compositions, method and method of use of the present invention. Satisfactory results have been achieved in the various preferred forms of coatings, prepared, applied and subjected to various flame and heat tests, wherein the aforementioned critical flame temperat e, duration and exposure conditions were maintained.

The following coating compositions are offered as representative of those coating compositions prepared and employed in the tests to follow. Each coating composition contains by [weight/volume] the ingredients listed in the initial pigment dispersion prepared in a slurry until homogeneous, then processed under hiyn shear until dispersed followed by addition of the selected high-temperature f ->er or frit, with the coating composition completed with the addition of the "let down" materials.

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Added to the pigment dispersion and disperse:

Ceramic Fiber 88 176

Added to the dispersion is a thickener in water as a carrier: Thickener 10 6

Then, mix-in until smooth "let down" materials:

Ethylene vinyl chloride emulsion 808 968

Anionic surfactant 8 — Acrylic emulsion 161 — Defoamer 2 2

Rheology modifier 3 3

Ethylene glycol 3 3

After mixing well the resulting mixture is coated out onto the selected substrata, such as a layer of modified bitumen.

In a similar procedure the following occludant coatings were prepared using Acrylic Modified Ethylene Vinyl Acetate.

ACRYLIC MODIFIED ETHYLENE VINYL ACETATE

Exam le 3 x

After mixing well the resulting mixture is coated out onto the selected substrata, such as a layer of modified bitumen.

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In a similar procedure the following occludant coatings were prepared using Ethylene Vinyl Acetate.

After mixing well the resulting mixture is coated out onto the selected substrata, such as a layer of modified bitumen.

In a similar procedure the following occludant coatings were prepared using Acrylic polymers - hard polymer and soft polymer.

ACRYLICS (Cont. )

Example 6 Example 7

Thickener 3 3

Acrylic polymer emulsion 331 301

Rheology modifier 2 2

Ethylene glycol 2 2

After mixing well the resulting mixture is coated out onto the selected substrata, such as a layer of modified bitumen. These coatings were prepared in accordance with the above procedure: first, forming a mixture comprising the pigment dispersion, mixing the slurry composition until homogeneous, followed by processing under high shear until dispersed. To this dispersion was added high-temperature frit and/or fiber, such as ceramic frit and ceramic fiber. Fir , the "let down" materials were added to complete the coating f. nulation. The thus-prepared coating compositions were applied to a flammable substrata, for example, modified bitumen, which were subjected to a series of investigations and evaluations to determine their flame and heat retardant levels required to produce acceptable coating compositions, exhibiting no substantial flame or heat damage to the substrata of modified bitumen.

As a guideline for testing roof coverings of the compositions of the instant invention, the ASTM Standard Methods of Fire Tests of Roof Coverings were followed as close as possible. By reference the Standard Methods of Fire Tests of Roof Coverings, ASTM E 108-80a is herein incorporated by reference. These methods cover the measurement of the relative fire characteristics of roof coverings under simulated fire originating outside the building. These tests are applicable to roof coverings intended for installation on either combustible or noncombustible decks, when applied as intended for use.

These methods measure the surface spread o* Harne and the ability of the roof covering material or system to resist fire penetration from the exterior to the underside of a roof deck under the conditions of exposure. These test methods do not necessarily illustrate the expected performance of roof coverings under all actual

fire conditions, but they do provide a basis for comparing roof covering materials when subjected to fire sources which are intended to simulate exposure conditions which could develop in actual fires.

The essential elements of the fire test apparatus include a test roof deck, a frame on which the test roof deck is mounted, preferably the frame is angularly adjustable, a gas burner as a source of sustained flame, and a wind tunnel or variable speed wind supply, as a blower. An air velocity meter, a gas pressure gage and a control valve are also desirable. Control of the shape and size of the flame depends upon minimizing air turbulence in the immediate vicinity of the apparatus.

The test deck for the intermittent flame exposure test is generally made of white pine lumber, or if the roof covering is applied to a solid test deck, such as plywood, exterior type C-C plugged or higher grade conforming to U.S. Product Standard PSI-74 for softwood plywood.

Representative samples of roof covering materials for various tests, such as the intermittent flame exposure, the spread of flame test, and the burning brand test, were applied and investigated. The roof covering materials as formulated hereinafter were applied to modified bituminous/polymer emulsion coatings over the appropriate wooden deck. The polymer coatings were applied to the edges of the deck, with an over coat application of the flame and heat resistant dome-forming compositions of the instant invention. In all of the fire tests, mortar (asbestos-fibered gypsum and water) was troweled into the joint formed by the leading edge of the roof covering material and the framework of the carriage. This is to prevent air or the test flame from traveling under the material being tested. In the fire tests, all decks were subjected to an air current that flows uniformly over the top surface of the roof covering. Midway up the sloped test deck the velocity of the air current was at least 12 ^* miles per hour (19 kilometers per hour). Each test deck was placed at a slope.

In the intermittent flame exposure test, the test deck was subjected to a luminous gas flame approximately the width of the deck at its bottom edge. The temperature of the flame is adjusted to about 1400° F (760° C). The flame is applied intermittently for specified periods, depending upon the Class sought. For Class A, fifteen, two-minute cycles each of flame on and flame off is used. For Class B, the number of cycles is reduced to eight, and for Class C, the number of cycles is three. In each Class, the air current is maintained throughout the test and after the last application of flame, until all evidence of flame, glow and smoke has disappeared from both the exposed surface of the material being tested and the underside of the test deck, or until failure occurs.

For the spread of flame test, a 13-foot (3.9 meters) long deck is subjected to a luminous gas flame for ten minutes. This is for a Class A or Class B test. Class C is for a four minute period. During and after the application of the test flame, the test sample is observed for the distance to which flaming of the material has spread, production of flaming or glowing brands and displacement of portions of the test sample. In the burning brand test, various size brands are used for the various classifications. The Class A brand is a grid 12 inches (30.48 cm) square and about 2 1/4 inches (5.7 cm) thick made of dry Douglas fir lumber free of knots and pitch pockets. Before application to the test deck, the brand is ignited so as to burn freely in still air. The burning brand is then placed on the surface of the test deck at a location considered to be most vulnerable, such as the point of minimum coverage over a deck joint. The individual test is continued until the brand is totally consumed and until all evidence of flame, glow, and smoke has disappeared from both the exposed surface of the material being tested and the underside of the test deck, or until failure occurs. BRIEF DESCRIPTION OF DRAWINGS

Reference now is made to the drawings FIGURES 1 and 2 and the Photographs - PHOTOS 1 and 2. FIGURES 1 and 2 are artistic renditions of the tests being performed in photographs PHOTOS 1 and 2. PHOTO 1 and FIGURE 1 represent the spread of flame test. This test was

conducted according to the description given hereinabove. The flame can be seen rising above the dome of occludant material in the center of PHOTO 1. The flame is diverted in an upward direction, rather than allowed to crawl along the surface of the simulated roof. PHOTO 2 and FIGURE 2 represent the resulting dome of occludant material after being subjected to the spread of flame test for 10 minutes. Except for blackening of the dome, the modified bitumen substrata was protected from the flame and heat. The substrata was intact with no burning or other heat caused damage. The other occludant coatings whose preparation is described above performed similarly. With slight variation in dome size formation and degree of performance all other coatings according to this invention were more than satisfactory. No other coating material is known to perform similarly over flammable substrata as disclosed and described herein.

While described in terms of the presently preferred embodiment, it is to be understood that such disclosure is not to be interpreted as limiting. Various modifications and alterations will no doubt occur to one skilled in the art to which this invention pertains, after having read the above description of the disclosure. Accordingly, it is intended that the appended claims will be interpreted as covering various such modifications and alterations as fall within the true spirit and scope of the invention and can be considered as equivalent.