[0001] 1. Field of the Invention
[0002] The present invention relates to flame and heat-resistant insulation, a process for making the insulation flame-resistant, and a method of protecting insulation from the effects of fire. The flame-resistant insulation of the present invention comprises insulation coated with a mixture comprising vermiculite and expandable graphite.
[0003] 2. Discussion of the Background
[0004] Insulating materials are commonly used in the fabrication of components of buildings, such as doors, walls, ceilings and roofs, or in vehicles such as automobiles, trucks, aircraft, and ships. Insulating materials are commonly made of inorganic fibers, such as glass or mineral fibers, in order to provide a degree of fire-resistance. Preferably, the fibers comprise a glass.
[0005] The majority of glass fiber products used in insulating materials are composed of either sodium borosilicate glass having a softening point of approximately 1290° F. or E-type borosilicate glass having a softening point as low as about 1529° F. More refractory glass fibers are also known, such as aluminosilicate S-glass, but these higher melting point glass fibers are relatively expensive, and therefore are unsuitable for low cost applications, such as building insulation, and are used primarily in specialty applications where the higher melting point of these fibers is critical.
[0006] Although glass or mineral fiber insulation materials have superior flame resistance compared to insulation materials based on flammable fibers (e.g., lignocellulose derived fibers), glass insulation materials have only modest flame and heat resistance because of their relatively low melting point. When exposed to flames, glass fiber insulation materials melt, thereby allowing flames and heat to penetrate through the insulation material, and consequently allowing the fire to spread. It is therefore desirable to enhance the flame and heat resistance of glass fiber-based insulation materials.
[0007] Re. 34,020 describes a fibrous composite material that is coated with a lamellar material such as vermiculite to enhance the fire-resistance of the material. While the fire-resistance of the coated fiberglass material is enhanced, the flame-retardancy and thermal insulation properties of the resulting composite are still inadequate.
[0008] U.S. Pat. No. 4,888,233 describes fire-resistant composite materials prepared by coating a polymeric substrate with a mixture of chemically delaminated vermiculite and a copolymer of ethylene and a vinyl monomer. While this coating decreases the flammability of the polymeric substrate, improved flame and heat resistance is still desirable.
[0009] U.S. Pat. No. 5,968,669 describes a fire-retardant coating for lignocellulosic materials which comprises a mixture of expandable graphite particles, an absorbent material such as calcium carbonate to absorb toxic gases, a polymeric binder, a “carbonific” material such as pentaerythritol, which forms a network binding expanded units of expandable graphite together, a blowing agent to generate an intumescent char foam, and a wetting agent to improve wetting of the coating onto the substrate. However, U.S. Pat. No. 5,968,669 only describes coated lignocellulose-based materials, and the resulting coated articles, while flame-resistant compared to uncoated lignocellulose-based materials, are still flammable.
[0010] U.S. Pat. No. 5,972,434 describes fire-resistant glass fiber products coated with a nitrogen-containing compound and a boron-containing compound, which upon exposure to fire or high temperatures react with each other to form a refractory compound on the surface of the fibers.
[0011] However, there is still a need to provide inexpensive insulating materials having improved flame and heat resistance.
[0012] Accordingly, it is an object of the present invention to provide an improved flame and heat resistant insulating material comprising glass fibers coated with a mixture comprising vermiculite and expandable graphite. A second object of the present invention is to provide a method of preparing such flame-resistant insulation. A third object of the present invention is to provide a method of protecting insulation with a coating comprising vermiculite and expandable graphite.
[0013] The insulation of the present invention comprises a glass fiber substrate coated with a mixture comprising vermiculite and expandable carbon. The substrate may include products formed from at least one layer of fibers. The fiber layers may comprise loose fibers, or may be woven, knitted, needle punched, felted, or otherwise combined in various ways to provide a unified structure. The fibers may be continuous, filamentary fibers, or discontinuous, staple fibers or agglomerations of such fibers. The fibers may comprise any conventional glass fiber commonly used in insulation products, including an E-glass, a C-glass, or a high boron content C-glass.
[0014] The fibrous substrate may be flexible or rigid. For example, the fibrous substrate may be a flexible batt, mat, blanket, fabric, or sheet, or a rigid slab or board. The density of the fibrous substrate may range from 1.0 lb/ft
[0015] A binder may be used to capture and hold the fibers of the fibrous substrate together. The binder can be organic or inorganic. The binder can be a thermosetting polymer, a thermoplastic polymer, or a combination of both thermoplastic and thermosetting-polymers. Preferably, the thermosetting polymer is a phenolic resin, such as a phenol-formaldehyde resin, which will cure or set upon heating. When binder is used in the insulation product, the amount of binder can be from 1 to 30 wt %, preferably from 3 to 25 wt %, more preferably from 6 to 18 wt %.
[0016] The fibrous substrate may be composed only of glass fibers, or may have at least one additional layer laminated thereto. The additional layer may include a woven or non-woven fiberglass fabric layer, or may be a FSK (foil-scrim-kraft) sheet glued onto the surface, a gypsum cement layer, or a quick-set cement layer. For example, the quick-set cement layer may be a conventional Portland type cement product. The gypsum cement may be any cementitious material containing gypsum. These coatings can be applied to one or both surfaces of the fiberglass substrate.
[0017] The coating of the present invention, which is applied to the substrate, comprises a dispersion of vermiculite mixed with expandable graphite. The vermiculite may include the minerals known both scientifically and commercially as vermiculite, including the chloride-vermiculites. For example, the vermiculite may be any naturally occurring micaceous hydrated magnesium-aluminum-silicate which has been chemically delaminated, for example by dispersing the vermiculite in an aqueous solution containing cations such as alkylammonium cations, and lithium cations. Particularly effective vermiculite dispersions include MicroLite® dispersions (W.R. Grace & Company). The dispersion of vermiculite may consist of only the chemically delaminated vermiculite and water, but may also include vermiculite dispersions which include a small amount of an organic binder or other additives to stabilize the dispersion and facilitate coating and adhesion to the fibrous substrate (e.g., dispersing agents or organic adhesion promoters). The dispersion of vermiculite may have as low as 1% solids, or levels as high as 50% solids. Solids contents of approximately 5 to 25%, more preferably 10 to 20%, most preferably approximately 16.5% are desirable.
[0018] Any conventional type of expandable graphite may be used. Expandable graphite differs from other forms of graphite in that it is specially treated to expand in volume upon heating. In order to become expandable, the graphite may be treated, for example, with sulphuric acid in order to intercalate sulphuric acid between the layers of the graphite. The treated graphite is then washed and dried, providing a dry pourable material. Upon heating, the intercalated material, e.g., sulphuric acid, volatilizes between the graphite layers, thereby expanding the volume of the graphite flake. The high volume provided by this expansion provides an insulative layer which reduces heat transfer through the material, mass loss, and reduces the generation of smoke.
[0019] The volume expansion of the expandable graphite may be up to 100 times the original thickness of the flake, depending on the specific type and amount of intercalant used. The percent expansion is typically in the range of 50 to 250% by volume, depending upon the amount of intercalant added to the graphite. The onset temperature of the expansion typically occurs at temperatures between 230° C. and 280° C. Suitable particle sizes are in the range of 50 to 220 mesh.
[0020] The relative amounts of vermiculite and expandable graphite in the coatings of the present invention may range from 10:1 to 1:10 (dry weight of vermiculite: dry weight of expandable graphite). The preferred ratio of vermiculite to expandable graphite is 5:1 to 1:5, more preferably 3:1 to 1:3, most preferable approximately 2:1. The total solids content of the coating of the present invention, prior to application, may be approximately 15 to 60 wt. %, preferably from 15 to 50 wt. %, more preferably from 15 to 30 wt. %.
[0021] The coating may be prepared by mixing an aqueous dispersion of vermiculite, optionally containing dispersing agents, binders, and adhesion promoters, with an aqueous dispersion of expandable graphite, or dry expandable graphite. Alternatively, the vermiculite and expandable graphite may be mixed as dry powders, and then dispersed in water using conventional dispersing equipment. The coating of the present invention may be coated onto the substrate by any conventional method such as brushing, spraying, roller coating, gravure coating, curtain coating, and slot-die coating.
[0022] The coating of the present invention may be applied as a single coating to the substrate, or applied in two or more coating steps. In addition, a coating of vermiculite or expandable graphite may be applied to the substrate, prior to coating with the mixture of vermiculite and expandable graphite. The coating may be air-dried, or oven-dried. The dry weight of the coating may be 5 to 30 g/100 in
[0023] The flame and heat-resistance of insulation boards, both coated and uncoated with the coating composition of the present invention, were tested for flame resistance in the following manner. The coated board was mounted horizontally above a Bunsen burner flame so that the coated surface of the board was exposed directly to a flame having an approximate flame temperature of 1750° F. The temperature of the board was measured over a one hour period at the middle of the thickness of the board, directly above the flame, and the opposing surface of the board directly above the flame (i.e., the surface opposite the side directly exposed to the flame). The maximum temperature measured at the center of the thickness of the board (i.e., the maximum center of thickness temperature) and the maximum temperature at the top surface (i.e., the maximum top surface temperature) were measured for one hour after exposing the board to the flame. Lower temperatures are indicative of better flame and heat-resistance.
[0024] A 4.8 lb/ft
[0025] A 4.6 lb/ft
[0026] A 4.3 lb/ft
[0027] A 4.5 lb/ft
[0028] A 4.7 lb/ft
[0029] A 4.5 lb/ft
[0030] A 4.4 lb/ft
[0031] A 4.8 lb/ft
[0032] A 4.5 lb/ft
[0033] A 4.6 lb/ft
[0034] A 4.6 lb/ft
[0035] A 4.6 lb/ft
[0036] An uncoated 4.6 lb/ft
[0037] A 4.96 lb/ft
[0038] A 4.5 lb/ft
[0039] As shown in the above Examples (Summarized in Table 1, below), a glass fiber insulation board coated with a mixture of vermiculite and expandable carbon provides significantly better flame and heat resistance compared to uncoated insulation, or insulation coated with vermiculite alone
TABLE 1 Horizontal Insulation board exposed to a Bunsen burner flame - approximately 1750° F. Maximum Maximum Center of Top Dry weight Thickness Surface of Treat- Tempera- Tempera- ment for ture ture 100 square within within Description inch board 1 hour 1 hour Examples 1 2:1 by Weight HTS Vermicu- 18.7 666 424 lite: Expandable Graphite 2 2:1 by Weight HTS Vermicu- 21.3 476 488 lite: Expandable Graphite 3 1) HTS Vermiculite 6 698 348 2) 2:1 by Weight HTS Ver- 15.1 miculite: Expandable Graphite 4 1) HTS Vermiculite 5.2 382 426 2) 2:1 by Weight HTS Ver- 14.4 miculite: Expandable Graphite 5 1) 2:1 by Weight HTS Ver- 18.7 584 449 miculite: Expandable Graphite 2) 6.4 g FSK facing applied 7.3 with Henkel glue 6 1) 2:1 by Weight HTS Ver- 16.9 756 366 miculite: Expandable Graphite 2) 6.1 g FSK facing applied 8.5 with Henkel glue 7 1) 2:1 by Weight HTS Ver- 19.2 645 368 miculite: Expandable Graphite 2) Gypsum (43 g cement 21 g 71 H2O) 8 1) 2:1 by Weight HTS Ver- 23.2 636 454 miculite: Expandable Graphite 2) Quick Set Cement (90 g 56.4 cement 17.5 g H2O) 9 1:1 by Weight HTS Vermicu- 16.6 900 434 lite: Expandable Graphite 10 3:1 by Weight HTS Vermicu- 14.1 1144 442 lite: Expandable Graphite 12 5:1 by Weight HTS Vermicu- 10.5 682 367 lite: Expandable Graphite 13 10:1 by Weight HTS Ver- 8.2 796 385 miculite: Expandable Graphite Comparative Examples: 1 Untreated Board 972 794 2 HTS Vermiculite 5.6 800 673 3 HTS Vermiculite 5.9 982 631
[0040] Obviously, numerous modifications and variations on the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practice otherwise and as specifically described herein.