BACKGROUND OF THE INVENTION

The invention is in the field of passive fire protection and specifically relates to improvements in composite fire protection products incorporating intumescent materials, and methods of making the products.

U.S. Patent No. 6,274,647 discloses a compressed composite material for passive fire protection comprising: inorganic fibers and organic fibers with an elastomeric binder forming a fibrous matrix, together with 10-85% of an exfoliating material, such as expandable graphite, vermiculite, or perlite. U.S. Patent No. 6,274,647 is incorporated by reference herein for its teaching of flexible intumescent materials for fire protection.

U.S. Patent Application Publication No. 2015/0151510 discloses a composite heat and flame barrier material in which an active chemical layer, such as mineral hydrate, is mechanically contained, without a polymeric binder, between nonwoven layers of flame resistant fiber. U.S. Patent Application Publication No. 2015/0151510 is incorporated by reference for its teaching of an active chemical layer and nonwoven materials in fire protective materials.

SUMMARY OF THE INVENTION

The inventors herein have developed materials and methods for fire protection which are flexible, lightweight, thin, and easily handled and installed, for construction projects and portable fire resistant applications such as small boxes, tents, or shelters. The composite flame or heat barrier materials according to the invention comprise a sheet of intumescent inorganic fire protection material integrated with at least one nonwoven layer. The fiber layers attached to the sheet of intumescent inorganic material provide additional insulation and protection to keep the composite material stabilized and resistant to wind and high velocity flames and the like.

In a first aspect of the invention there is provided a composite that includes at least one nonwoven fiber layer(s), including flame resistant fibers; and at least one sheet comprising expandable inorganic compound, glass or mineral fibers, and a polymeric binder; wherein the nonwoven fiber layer is mechanically attached to the sheet, so that fibers of the nonwoven layer are positioned in the z direction in the sheet of expandable inorganic materia l. For cla rity, graphite is an inorganic com pound, notwithstanding that it contains carbon.

I n particula r embodiments, the nonwoven fiber layer comprises up to 100% oxidized polyacrylonitrile ("OPAN"), and the sheet of expandable inorganic material comprises exfoliating graphite with glass or mineral fibers in a binder such as polyvinyl acetate ("PVA"). I n particular embodiments, nonwoven fiber layer(s) are mechanica lly attached on opposite sides of the sheet of expandable inorganic materia l by needlepunching.

I n another aspect, the invention is a composite comprising at least one nonwoven fiber layer(s) including flame resistant fibers, at least one sheet comprising expandable graphite, and further comprising a woven layer on a side of the expandable gra phite sheet opposite the nonwoven layer. I n embodiments, the woven and nonwoven fiber layers and the intumescing graphite sheet are integrated by needlepunching, so that fibers of the nonwoven layer are positioned in the z direction in the sheet of expandable inorganic material.

I n another aspect, the invention is directed to a method of im proving the hand-feel of a composite comprising intumescent graphite (or other expandable inorganic) and glass fibers, comprising positioning a layer of nonwoven oxidized polyacrylonitrile adjacent the composite and consolidating the layers by needlepunching.

I n another aspect, the invention is directed to a pre-preg adapted for im proved resin impregation. I n this aspect, one or more nonwoven fire resistant fiber layers is attached by needlepunching to at least one sheet comprising expandable graphite in a matrix (which may include, for example, glass or minera l fibers and a polymeric binder). The needlepunching forms pores in the sheet of expanda ble inorganic which facilitates subsequent thermoplastic resin impregnation to make a composite for fire resista nt applications.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic depiction of com posite material according to one embodiment of the invention. FIG. 2 is a schematic depiction of a composite material according to another embodiment of the invention.

FIG. 3 is a compa rative illustration of burn through performance of a composite material according to the invention and the prior a rt.

FIG. 4 is a schematic depiction of a composite material according to another embodiment of the invention, including an aluminum foil laminate outer layer on opposite sides of the composite.

FIG. 5 is a schematic depiction of another composite material having an aluminum foil outer layer on opposite sides of the com posite.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

As used herein, the term "nonwoven" is intended to include sheet or web structures bonded together by entangling fibers mechanica lly, thermally, or chemically without weaving or knitting. Preferred nonwoven textiles include needlepunched, spunbond, or spunlace sheets or webs.

As used herein, "intumescing", "intumescent", etc. are used interchangeably with "expandable" to refer to exfoliating graphite, a nd certain other materials, as described in the aforesaid U.S. Patent No. 6,274,647, which expand by a factor of at least 1.5, when heated, to form a heat or flame barrier.

As used herein, "composite" simply refers to any integral product made of different types of materials. Thus a com bination of expandable inorganic material(s) in a matrix layer of glass fibers and/or mineral fibers may be referred to as a "composite". Likewise, products of the invention may be further resin impregnated to make a different type of product as an end use, also referred to herein as a "composite".

"About", as used herein, means ±15%. "Substantially", when used herein to modify a characteristic, means that a real world deviation from the characteristic is negligible, and a person of skill may ignore the deviation for the purpose of making engineering calculations or decisions. As used herein, a layer of textile is an x-y planar element, and the "z-direction" is perpendicular to the x-y plane, that is, in the thickness direction of the textile.

As shown in an embodiment of the present invention depicted in FIG. 1, a composite flame barrier 10 includes at least one nonwoven textile layer 1 comprising flame resistant fibers, and at least one sheet 2 of expandable inorganic fire resistant material combined with glass and or other inorganic fibers and a polymeric binder. The nonwoven layer 1 is mechanically attached to the sheet material by needlepunching, stitchbonding, sewing, quilting, or the like.

The nonwoven layer(s) may comprise up to 100% by weight of oxidized polyacrylonitrile ("OPAN") fibers. For example, the flame resistant fibers in the nonwoven fiber layer may consist entirely of OPAN. In embodiments, the nonwoven layer consists of substantially 100% OPAN fibers.

In other embodiments, the nonwoven fiber layer 1 may include additional flame resistant fibers, in addition to OPAN, which may be organic fibers or inorganic fibers, selected from the group consisting of meta-aramids, para-aramids (such as diphenylether para-aramid), polybenzimidazole, polyimides, polyamideimides, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylene benzothiazoles), flame retardant viscose rayon, polyetheretherketones, polyketones, polyetherimides, and silica based fibers and polysilicic acid fibers derived from silica and sold under the tradename BelCoTex ^® . Such additional fibers may be present in an amount from about 0.1 % by weight up to about 99.9% by weight of the nonwoven layer(s). In embodiments, the weight ratio of additional flame resistant fibers to OPAN is in a range of 10:90 to 90:10.

The weight of the nonwoven layer(s), whether entirely OPAN or comprising a fiber blend, is in a range of 1 oz/sq. yd. to 30 oz/sq. yd.

Mechanical attachment of the layers by needlepunching ensures that a significant proportion of fibers 5 from the nonwoven layer are forced through the sheet of expandable inorganic fire resistant material in the z direction. The layers of the composite flame barrier are needled together to pass the fibers in the nonwoven layers through the expandable graphite layer in the z direction to mechanically attach the materials together. The loading of binder in the sheet of expandable inorganic material should be low enough so as not to interfere with the needlepunching operation. Passing fibers through the expandable graphite creates an interlocking mechanism between the layers and eliminates the need for adhesives, resins or additional binders, reducing or eliminating combustible materials or heat-sensitive chemicals in the manufacture of the composite.

Additionally, mechanically attaching layers of nonwoven felts or spunlace materials to the expandable graphite layer affords advantages in manufacturing. Incorporating the intumescent materials in a sheet reduces the need to lay up multiple materials during the composite building process, while the holes created during needlepunching provide pathways for resins or chemicals used in a resin infusion stage of a composite construction process, allowing the flowable materials to penetrate through and saturate the layers.

The sheet material 2 according to the invention comprises at least an expandable inorganic (which may be exfoliating graphite, vermiculite, perlite, etc., as disclosed in the aforesaid U.S. Pat. No. 6,274,647), preferably present in an amount of 10-85% by weight of the sheet, glass and/or mineral fibers, present in an amount of 15-90% by weight and a small amount (up to about 10%) of a polymeric binder. In embodiments, PVA may be used as the binder to hold the sheet material together, although an acrylic or other known binder material may be used. The overall weight of the sheet material comprising the expandable inorganic may range from 1 oz./sq.yd. to 50 oz./sq.yd.

Additional ingredients such as fire resistant organic fibers, active fire retardant chemicals and particulates may also be included in the sheet material 2. Materials in sheet form capable of being positioned against a nonwoven fiber layer and needlepunched, while still retaining their integrity are particularly preferred. Suitable expandable graphite sheet materials for use with the invention include Technofire ^® brand expandable graphite sheet materials, made by Technical Fibre Products, United Kingdom.

As shown in FIG. 1, an additional nonwoven fire protecting layer 3 may be attached to the sheet of expandable inorganic flame barrier material opposite the first layer 1 of nonwoven. The composition of nonwoven layer 3 may be different or the same as the composition of first layer 1. However, the same fiber types in the same ranges may be used. Nonwoven layer 3 is preferably a needle punched felt and is preferably attached to the other layer(s) of the composite by needle punching.

In another embodiment, depicted in FIG.3, a woven layer 4, such as, without limitation, a plain or twill weave, may be attached on the opposite side of the sheet comprising the expandable inorganic material. The fibers of the woven layer 4 may be the same or different from the fibers of the nonwoven layer 1, and the same relative amounts of different fibers may be employed to make the woven layer 4 as are used to make nonwoven layer 1. In some embodiments, the woven layer may consist entirely of non-OPAN fibers, such as aramid. The nonwoven layer 3 or woven layers 4 may be mechanically attached to the sheet materials in the same manner as the nonwoven layer 1, by sewing, quilting or needlepunching. Preferably, the additional woven layer 3 or additional nonwoven layer 4 is attached to nonwoven layer 1 and the sheet material 2 containing the expandable inorganic in the same needlepunching step. The needlepunching step provides a plurality of pores in the material which is advantageous for a later resin impregnation step by an end user.

The additional woven and nonwoven layer(s) may be used to provide a desired finish on the surface of the product, and may comprise fire resistant fibers selected from the group consisting of OPAN fibers, meta-aramids, para-aramids (such as diphenylether para-aramid), polybenzimidazole, polyimides, polyamideimides, novoloids, poly(p-phenylene benzobisoxazoles), poly (p-phenylene benzothiazoles), flame retardant viscose rayon, polyetheretherketones, polyketones, and polyetherimides. In other embodiments, one or more of the woven or nonwoven textile layers may include inorganic flame resistant fibers, including, without limitation, basalt fibers, ceramic fibers, glass fibers, carbon fibers, and silica based fibers and polysilicic acid fibers derived from silica and sold under the tradename BelCoTex ^® . A woven layer of aramid contributes to structural strength of the finished composite which the nonwoven cannot provide on its own. Greater than 50 by weight BelCoTex ^® fibers in the additional nonwoven layer will contribute to the insulation properties of the product. I n embodiments, the nonwoven and/or woven layer(s) may include additional high temperature reinforcing fibers, selected from the group consisting of glass, minera l fibers, ceramic fibers, carbon fibers, stainless steel fibers and combinations thereof.

An advantage of a needlepunched construction according to the invention is the im proved feel of the consolidated textile. Whereas intumescent material provided in sheet form with glass fibers may be difficult or uncomfortable to handle, com bining the filled sheet with one or more layers of OPAN or OPAN blend textile on one or both sides makes the composite easier a nd more comfortable for the end user to install or use without irritation to the eyes or skin caused by the glass or mineral fibers. I n other embodiments, a nonwoven layer may be positioned on one side a nd a woven layer may be positioned on the opposite side. I n embodiments, the nonwoven a nd woven layers are positioned on opposite sides of the intumescent composite layer and consolidated by needlepunching. I n some of the non-limiting examples below, the combined weight of the OPAN or OPAN blend layer(s) is at least about equal to the weight of the expandable inorganic sheet material, which ensures that the properties of the nonwoven material are prominent in the finished material.

I n another aspect, textiles according to the invention a re used for resin impregnation to make composites as an end use. I n this aspect, the textiles of the invention, prior to resin impregnation, are referred to as "pre-pregs". Pre-pregs integrated by needlepunching afford two principal advantages in connection with the impregnation process. First, because the nonwoven and woven layers are mechanically attached to the layer filled with expanda ble inorganic, the need for laying up multiple layers is avoided, thus sim plifying the resin infusion process. Second, the needlepunching process pushes fibers (OPAN or OPAN blended with other fibers) through the sheet materia l, which creates a plurality of pores and pathways, allowing for improved wetting of the layered material and better integration of the layer properties. Thus, a pre-preg comprising a layer of nonwoven fire resistant fibers, and a sheet com prising expandable inorganic, consolidated by needlepunching is easier to use in the resin impregnation process than the conventiona l products.

I n other embodiments, a composite flame barrier may include one or more laminate layer(s) comprised of metal foil, coated paper, or polymeric film on an outer surface of the product. I n the composite 40, depicted in Fig. 4, internal textile layers are assembled similar to Figure 1 and attached by needlepunching. Thereafter, layers 6 of 1 mil aluminum foil are laminated to the opposite outer surfaces with heat and pressure. An adhesive, such as a thermoset adhesive which cures over time may also be used to adhere the foil to the outer layers. In the composite 50, depicted in Fig. 5, the internal layers include woven and nonwoven layers on opposite sides of the expandable graphite mat 2, respectively. Metal layers 6 of 1 mil aluminum are laminated on opposite outer surfaces. Foil is found block air movement through the material, reducing the movement of hot gasses in a fire and boosting the insulating effect of the felt/graphite composite.

A composite barrier according to the invention affords fire resistance and slows down the transmission of heat by providing greater depth of insulation when the expandable graphite expands. The properties of the invention may be partially captured in testing, including burn through tests. Preferably, a 12 oz/yd ² sheet of a composite will burn through when exposed to a 1900 degree blow torch for at least 30 seconds, more preferably 40 seconds, and still more preferably 50 seconds.

EXAMPLE 1

A rolled textile according to Figure 1 was prepared having a first nonwoven layer consisting of a 4 oz./sq.yd. blend of aramid and OPAN fibers in the form of a needle punch felt, a sheet material comprising a 4 oz./sq.yd. expandable graphite mat comprising glass fibers and a binder, commercially available under the Technofire ^® brand name, and a further nonwoven layer consisting of 4 oz/sq.yd. blend of aramid and OPAN fibers in the form of a needle punch felt. The layers were assembled by placing the expandable graphite sheet material between two layers of the blended felt and processing through a finishing loom where the fibers of the felt were moved through the 3 layers of material in the "Z" direction mechanically locking the 3 layers together. This method eliminates the need to use additional adhesives or other binders, which would otherwise increase the finished weight, while at the same time maintaining increased fire resistance. COMPARATIVE EXAMPLE 1

As a comparative example, a 12 oz./sq.yd. expandable graphite mat was obtained from Technical Fibre Products. The material was an expandable graphite provided in a fibrous matrix with a high temperature resistant mineral fiber and an organic binder (sold under the tradename Technofire ^® ) and having a weight of 12 oz/yd ² . Thus, Example 1 and Comparative Example 1 have the same areal weight and the composition of the graphite mat in Example 1 and Comparative Example 1 is substantially the same.

BURN THROUGH TEST

A burn through test was conducted with a composite according to the invention (Example 1), compared to the prior art product having the same areal weight (Comparative Example 1). The results are shown in FIG. 3. Both materials were subjected to a 1900°F blow torch direct flame and the time to burn through was measured. The prior art material exhibited burnthrough in 24 seconds. The material according to the invention exhibited burnthrough at 52 seconds, a marked improvement.

EXAMPLE 2

A rolled textile according to Figure 1 is prepared having 4 oz./sq.yd. blend of BelCoTex ^® silica fibers and OPAN fibers in the form of a needle punch felt, a sheet material comprising a 4 oz./sq.yd. expandable graphite mat, and a nonwoven layer consisting of 4 oz./sq.yd. blend of silica fibers and OPAN fibers in the form of a needle punch felt. The layers are assembled according to Example 1: expandable graphite material is placed between two layers of the blended felt and processed through a finishing loom where the fibers of the felt are moved through the 3 layers of material in the "Z" direction mechanically locking the 3 layers together. The resulting consolidated material does not have significant glass fibers on the surface.

EXAMPLE 3

A rolled textile according to Figure 4 was prepared with an aluminum foil outer layer. The inner layers were prepared as in Example 1, having 4 oz./sq.yd. OPAN fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 4 oz./sq.yd. OPAN fibers in the form of a needle punch felt. As in Example 1, the expandable graphite material was placed between two layers of the felt and processed through a finishing loom where the fibers of the felt were moved through the 3 layers of materia l in the "Z" direction mechanically locking the 3 layers together. This method eliminates the need to use additional adhesives or other binders which reduces the finished weight and maintains increased fire resistance. The combined materials then have a 1 mil a luminum foil layer laminated to the exterior between a pair of rollers with the application of heat and pressure, thus encapsulating the OPAN/graphite/OPAN com posite.

EXAMPLE 4

A rolled textile according to Figure 2 is prepared having 4 oz./sq.yd. 100% OPAN fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 8 oz./sq.yd. aramid 2 x 2 twill weave. To assemble, the expandable graphite sheet material is placed between the layer of the blended OPAN felt and the woven a ramid and processed through a finishing loom where the fibers of the felt a re moved through the 3 layers of material in the "2" direction mechanically locking the 3 layers together.

EXAMPLE 5

A rolled textile according to Figure 2 is prepa red having 4 oz./sq.yd. % OPAN and aramid fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 8 oz./sq.yd. aramid 2 x 2 twill weave assembled. The expandable graphite material is placed between the layers of the blended OPAN felt and mechanica lly attached as in the preceding example.

EXAMPLE 6

A rolled textile according to Figure 2 is prepa red having a nonwoven layer com prising 4 oz./sq.yd. OPAN and Belcotex ^® silica fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat sheet material, and 8 oz./sq.yd. aramid weave assembled by placing the graphite material between the layer of the blended OPAN felt and the woven aramid and processing through a finishing loom.

EXAMPLE 7

A rolled textile according to Figure 2 is prepa red having 4 oz./sq.yd. OPAN fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 10 oz./sq.yd. OPAN/aramid plain weave assembled as follows. The expanda ble gra phite material is placed between the layer of the blended OPAN felt and the woven a ramid and processed through a finishing loom where the fibers of the felt a re moved through the 3 layers of material in the "Z" direction mechanically locking the 3 layers together.

EXAMPLE 8

A rolled textile according to Figure 5 is prepa red having 4 oz./sq.yd. OPAN fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 10 oz./sq.yd. opan and aramid plain weave. The expandable graphite materia l is placed between the layer of the blended OPAN felt and the woven fiber layer and processed through a finishing loom where the fibers of the felt are moved through the 3 layers of materia l in the "2" direction mecha nica lly locking the 3 layers together.

EXAMPLE 9

A rolled textile according to Figure 2 is prepared having 4 oz./sq.yd. OPAN and silica fibers in the form of a needle punch felt, a 4 oz./sq.yd. graphite mat, and 8 oz./sq.yd. aramid twill or plain weave assembled with the expandable graphite materia l placed between the layer of the blended OPAN felt and the woven aramid a nd processed through a finishing loom to mechanically attach the 3 layers. The com bined woven, nonwoven and graphite mat sheet materials then have a 1 mil aluminum foil layer laminated to the exterior on both sides thus encapsulating the OPAN/graphite/woven composite.

The com posites according to the invention may be flexible enough that they ca n be provided in a roll format, with a texture and ha nd-feel much superior to glass fibers, yet with all the functionality of the conventional graphite mat materials. I n many cases, the composites are suitable for use as intermediates or "pre-pregs" which can be im pregnated with a thermoplastic resin to make rigid panels and the like. Further, the use of OPAN aramid, and/or silica fibers on one surface of the composite, including wovens, creates a significant array of product formats which ca n be ada pted for a variety of passive fire protection environments.

The description of the foregoing preferred em bodiments is not to be considered as limiting the invention, which is defined according to the appended claims. The person of ordina ry skill in the art, relying on the foregoing disclosure, may practice variants of the embodiments described without departing from the scope of the invention claimed. A feature or dependent claim limitation described in connection with one embodiment or independent claim may be adapted for use with another embodiment or independent claim, without departing from the scope of the invention.