Fire and Sag Resistant Acoustical Panel and Substantially Clear Coating Therefor
A ceiling panel structure which includes a fire retardant mat, a scrim and a substantially clear scrim coating. The fire retardant mat includes a fire retardant fiber component and a binder material which binds the fibers. The fire retardant fiber component includes natural fibers treated with a fire retardant. The scrim being attached to a surface of the mat and the substantially clear coating is applied to the surface of the scrim opposite a surface of the scrim positioned next to the mat. The ceiling panel structure has flame spread index of 25 or less and a smoke generation index of 50 or less, as measured by ASTM E 84 that is uniform throughout the mat.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 61/114,778, filed Nov. 14, 2008, entitled “Fire Retardant Mat And Ceiling Tile Structure Incorporating The Same.”
BACKGROUND OF THE INVENTIONThe present invention is directed to fire and sag resistant panel, and, more particularly, to an enhanced fire rated, sag resistant acoustical ceiling panel having an enhanced fire rated natural fiber mat incorporated therein as well as a substantially clear coating applied thereto.
Natural fibers such as hemp, kenaf, jute, sisal and flax, are gaining interest as a component in a variety of manufactured products, including products for the interior building environment, as natural fibers are a renewable resource and do not emit potentially hazardous materials into the environment. Though renewable and environmentally friendly, natural fibers, and the binder material which holds the fibers together, are highly flammable.
Articles intended for use specifically in a construction which is utilized as a conduit for return air must achieve an exceptional Class A fire resistance rating: namely a flame spread index value of 25 or less and a smoke generation index value of 50 or less, as measured by ASTM E 84. Additionally, when an article is suspended horizontally in a room space, such as in an acoustical ceiling system, not only must the efficacy of any flame retardant applied to natural fibers be substantial but it is also desired that these panels be: highly acoustically permeable; dimensionally stable; self-supporting; and sag resistant with respect to fluctuations in relative humidity. As one of ordinary skill in the art would understand, increasing the amount of binder to improve such features as the self-supporting nature of the fibrous mass, in turn, makes the fibrous article more flammable. As a result of such inverse relationships, an article possessing a combination of the aforementioned properties has not been heretofore achieved.
SUMMARY OF THE INVENTIONThe invention is a ceiling panel structure which includes a fire retardant mat. The fire retardant mat includes a fire retardant fiber component and a binder material which binds the fibers. The fire retardant fiber component includes natural fibers treated with a fire retardant. The fire retardant mat has flame spread index of 25 or less and a smoke generation index of 50 or less, as measured by ASTM E 84 that is uniform throughout the mat. The ceiling panel structure also includes a scrim attached to the bottom surface of the fire retardant mat as well as a substantially clear coating on the exposed surface of the scrim opposite the fire retardant mat. The ceiling panel structure also achieves a flame spread index value of 25 or less and a smoke generation index value of 50 or less, as measured by ASTM E 84 that is uniform throughout the structure.
As previously mentioned, the fiber component includes natural fibers treated with a fire retardant. Bast fibers such as kenaf, hemp, flax, ramie, or jute are examples of natural fibers. The natural fiber ingredient may comprise a single type of fiber or a combination thereof. Additionally, a portion or all of the natural fibers may be recycled fibers. Kenaf, jute, hemp, or combinations thereof are preferred where strength and/or rigidity is sought as these particular fibers are inherently less flexible than other natural fibers.
The fire retardant may be in the form of a powder or liquid and can be, for example, ammonium phosphates, sodium pentaborates, ammonium sulfates, boric acids and mixtures thereof. The fiber component comprises from about 70-99% by dry weight of the mat, and more preferably from about 70 to about 83% by dry weight of the mat. The ratio of the natural fiber to fire retardant in the fiber component is in the range from about 4:1 to about 11.5:1 and more preferably about 5:1.
The amount of binder in the mat in the mat is in the range from about 1 to about 30% by dry weight of the fiber mat. The binder can be either thermoplastic (including bio-based polymers) or thermosetting. For a thermoplastic binder, the material range is more preferably from about 11 to about 30%; most preferably about 13 to about 21%. For a thermosetting binder, the material range is more preferably from about 1 to about 15%; most preferably about 2 to about 8%.
It is well understood in the art that the softening or curing temperature be below the temperature that would cause undesired thermal degradation of the natural fibers. A well known thermoplastic binder fiber is the bi-component sheath-core configuration having a first thermoplastic material coated or encased within a second thermoplastic material having a lower softening temperature. The first thermoplastic material may be, for example, polyethylene terephthalate glycol (PETG), and the second thermoplastic material may be, for example, polyethylene terephthalate (PET).
In the following examples, jute fiber was treated either with a system of ammonium phosphate and borate or with di-ammonium sulfate. The results according to ASTM E 84 for measuring the flame spread and smoke generation index values are shown in Tables 1 and 2. It should be noted that the preferred mat density for use in a ceiling tile structure is in the range from about 4 to about 8 lb/ft3 and, more preferably from about 5 to about 6.5 lb/ft3; most preferably about 5.5 lb/ft3. The preferred thickness of the mat for use in a ceiling tile structure is in the range from about 0.25 to about 2 inches, more preferably about 0.0.375 to about 1.5 inches and most preferably from about 0.4 to about 0.7 inches.
As shown in Table 1, only sample 1 having a binder level of 15% by wt. of the mat achieved the exceptional Class A fire rating sought when using the system of ammonium phosphate and borate, i.e. a flame spread index reached the 25 value threshold. In contrast when 18.5% bonder or greater was utilized, the flame spread index value was too high. The use of di-ammonium sulfate achieved the exceptional Class A rating both at lower and higher binder levels. Moreover, flame spread index value reached 10 and the smoke generation index value reached 5 when the di-ammonium sulfate was used.
It should be noted that this exceptional Class A fire rating for each of the examples is uniform throughout the entire fire retardant mat 1. What is meant by “uniform throughout the entire fire retardant mat” is that any cross-sectional surface of the fire retardant mat 1 has the same fire rating as any outside surface of the fire retardant mat 1.
A facing scrim 3 and a scrim coating 6 composite was then adhered to sample mats 4-8 of Table 2. The scrim applied to sample mats 4-8 was a fiberglass scrim available from Owens Corning, item number A80PKR-YK111, however, the scrim 3 may be any suitable scrim that is resistant to flame spread and preferably has a Class A fire rating of 25/50, examples of which are fiberglass or flame retardant blends of fiberglass, cellulose and polyester. The fiberglass scrim is bound with a flame retarded polymeric binder. The scrim 3 can be attached to a surface of the fire retardant mat 1 using any suitable attachment method. Here, the fiberglass scrim is affixed to the mat with flame-retarded vinyl-acetate glue 5. The air flow resistance of the A80PKR-YK111 scrim is 40 MKS Rayls.
In the example embodiments set forth above, the scrim was then painted with DURABRITE paint available from Armstrong World Industries. The paint was applied at an application level of 29 g/ft2. What is key for achieving the desired acoustic performance in the fully constructed ceiling panel is that the combination of the scrim, the glue application and the paint application must have an air-flow permeability that allows sound to enter and be absorbed in the structure. A composite air flow resistance of about 400 to about 600 MKS Rayls has been found to achieve an noise reduction coefficient (NRC) greater than 0.80. In order to achieve the desired air flow resistance, and thus, the desired NRC, the scrim weight must be in the range from about 4.5 to about 10.5 g/ft2 and the glue application rate must be in the range from about 3 to about 10 g/ft2 (dry weight). The paint application rate must be in the range from about 10 to about 50 g/ft2 (dry weight).
Table 3 illustrates examples of fully constructed two feet by two feet panels comprising the fire retardant mat samples shown in Table 2.
The completed structural panels utilizing sample mates 4-8 were indeed found to obtain the desired fire resistance, sag and acoustical properties. Specifically, a completed structural panel achieved a noise reduction coefficient (NRC) of at least 0.85. The noise reduction coefficient (NRC) is a useful indicator of the acoustical properties of a given material. The Noise Reduction Coefficient (NRC) is a scalar representation of the amount of sound energy absorbed upon striking a particular surface. It is well known in the art that NRC is the average of four sound absorption coefficients of the particular surface at frequencies of 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz.
In addition, the desired sag performance was also achieved; namely a statistical value more positive than negative 0.150 inches. To measure the sag performance, several 2×2 inch panels were suspended horizontally from a perimeter support frame and deflection was measured over the course of four 24-hour cycles in which relative humidity was varied: namely 8 hours at 90% relative humidity and then 6 hours at 35% relative humidity. The negative most deflection from horizontal was recorded for each panel formulation. Statistically, an average negative value minus 2 standard deviations that is more negative than negative 0.150 inches represents a threshold performance value for a 2×2 panel at which the sag in the middle of the panel becomes apparent and begins to show an unsightly pillowed appearance in a horizontal installation.
The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. For example, although the fire retardant mat 1 is shown and described herein as being incorporated in the ceiling tile structure 2, it will be appreciated by those skilled in the art, however, that the fire retardant mat 1 may have other applications, for example, in the building, furniture, or automotive industry. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.
For example, the coating 6 may be colored, opaque, or substantially clear depending on the desired appearance of the ceiling tile structure 2. For example, suitable substantially clear coatings include Safe-T-Guard, WT-103, No. 133A, Flamex PF, JB-1D, Fabric Seal concentrate, Flamort 6-3, Disflammoll DPO, and DPK. A substantially clear coating may comprise, for example, a fire retardant, a binder, a clay, a dispersant, and a defoamer. The fire retardant may be halogen free and may comprise at least one material selected from the group consisting, for example, of ammonium polyphosphate (Exolit AP 420, 412, 422, and 423) and melamine polyphosphate (Flamestab Nor 116, Melapur MC 15, MP, and 200). The binder may be selected to prevent yellowing, offer moisture resistance, and provide durability. The binder may be, for example, an acrylic binder. Suitable binders include, for example, vinyl acrylic Rovace 9100, Flexbond 325, acrylic Rhoplex AC 260, ethylene vinyl chloride Airflex 4530, and polyvinyl acetate Vinac 828 m. The fire retardant dosage is in the range from about 5%- to about 95% by weight and the binder level is in the range from about 3% to about 95% by weight. The solids of the substantially clear coating are in the range from about 30% to about 60% by weight; the application rate is in the range from about 8 to about 42 g/ft2 and the filler/binder ratio is about 0.05:1 to about 33:1.
The substantially clear coating according to one embodiment of the invention comprises about 85 to about 87% by weight ammonium polyphosphate (e.g. Exolit AP 423), about 4 to about 7% by weight clay (e.g. EG 44), about 6 to about 8% by weight acrylic binder (e.g. Rhoplex AC 261), about 0.1 to about 0.4% by weight dispersant (e.g. Nopcote 63900), and about 0.01 to about 0.05% by weight defoamer (e.g. Tego Foamex 1488). The solids of the substantially clear coating are about 35-42% weight with Brookfield viscosity approximately 300-500 cps at 10 rpm with a #1 spindle. The filler/binder ratio is about 10:1 and about 14:1 and the application rate is about 6-32 grams per feet squared.
Moreover, such substantially clear coating shown and described herein is fire retardant and is substantially durable and moisture resistant such that the coating 6 adequately protects the scrim 3 and provides RH 70 & RH 90 sag resistance for the fire retardant mat 1 when the scrim 3 is attached thereto. Additionally, because the coating 6 is substantially clear, the natural fiber elements of the scrim 3 are visible, which causes the ceiling tile structure 2 to have an aesthetically pleasing and natural look. Further, the coating 6 is environmentally friendly in that it does not contain formaldehyde, acetaldehyde, or halogen.
Yet another modification is that a second coating 4 may be applied to the surface of the fire retardant mat 1 opposite the scrim 3 to help provide rigidity and stability against sag induced by fluctuations in relative humidity. This coating must have a low surface flame-spread smoke generation and allows the product to meet the Class A 25/50 requirement. In one example embodiment, the back coating 4 may be a filled styrene acrylate latex resin which is a non-cross linking thermoplastic resin of substantially high T(g). The T(g) of the latex is important with respect to sag and should be in the range of about 0° C. to about 100° C. For a filled styrene acrylate latex resin the T(g) is 33° C. The application weight of the back coat is in the range from about 20 to about 70 g/ft2 dry wt. and preferably about 45 g/ft2 dry wt. A filler/binder ratio range for the back-coat would be in the range from about 30:1 to about 5:1, and preferably 20:1.
The back-coat can optionally be formulated with a reactive thermosetting or hydrogen bonding binder. Examples of thermosetting binders are: acrylic, (i.e. our Armstrong ESP back-coat), phenol-formaldehyde, melamine or urea formaldehyde, epoxy, polyurethane, or poly-urea. Examples of hydrogen bonding binders are polyvinyl alcohol and starch, or other polysaccharide or polyol binders. Effective filler/binder ratio and back-coat application weight ranges would be from about 10/1 t about 1/1 and from about 5 to about 30 g/ft2, respectively.
Alternatively, instead of a coating, the back-side could have a fiberglass or other stable scrim adhered thereto. The scrim may or may not need to be painted on its opposite face depending on the ability of such a scrim to resist flame-spread and smoke generation to the point that the product meets Class A 25/50 performance. If necessary, an inert paint could be applied to the scrim at a low level to reduce surface flame-spread without impacting the products acoustical performance.
Claims
1. A ceiling tile structure comprising:
- a fire retardant mat and a scrim attached to a surface thereof, wherein the fire retardant mat comprises a binder and a fiber component, the fiber component including natural fibers treated with a fire retardant material; and
- a substantially clear coating on a surface of the scrim opposite a surface of the scrim positioned next to the fire retardant mat, the coating comprising a fire retardant, a binder, a clay, a dispersant, and a defoamer;
- wherein the fire retardant mat having a fire rating that is uniform throughout all planes of the fire retardant mat, and wherein the fire rating includes a flame spread index value of 25 or less and a smoke generation index value of 50 or less, as measured by ASTM E 84.
2. The ceiling tile structure of claim 1, comprising a coating on a surface of the fire retardant mat opposite the scrim.
3. The ceiling tile structure of claim 1, wherein the flame spread index value is 10 or less and the smoke generation index value is 10 or less, as measured by ASTM E 84.
4. The ceiling tile structure of claim 1, wherein the fire retardant material is di-ammonium sulfate.
5. The ceiling tile structure of claim 4, wherein the flame spread index value is 10 or less and the smoke generation index value is 10 or less, as measured by ASTM E 84.
6. The ceiling tile structure of claim 1, wherein the density of the fire retardant mat in the range from about 4 to about 8 lb/ft3.
7. The ceiling tile structure of claim 1, wherein the thickness of the fire retardant mat in the range from about 0.25 to about 2 inches.
Type: Application
Filed: Nov 16, 2009
Publication Date: Jun 17, 2010
Inventors: Anthony L. Wiker (Lancaster, PA), Michelle X. Wang (Lititz, PA)
Application Number: 12/619,284
International Classification: E04B 1/94 (20060101); E04C 2/26 (20060101);
