FIELD OF THE INVENTION

[0001 ] The present invention generally relates to flame resistant knit fabrics for use as coverings for support articles such as mattresses.

BACKGROUND

[0002] It is well known in the textile industry to produce fire resistant products for use in upholstered furniture, mattresses, foundations, automotive seating, public transportation seating, aircraft seating and the like, using needlepunched, highloft, spunbond or spunlace nonwoven or woven or conventional knit fabrics formed of natural or synthetic fibers, and then treating these fabrics with fire retarding chemicals. Conventional fire retarding (FR) chemicals include borate-based, halogen-based, phosphorus-based, melamine-based and/or antimony-based chemicals. Other fire resistant articles use glass fibers which may have health concerns. Unfortunately, such treated fabrics are heavier than similar types of non-fire retardant fabrics and have reduced wear life. Although flame resistant chemically treated fabrics will self-extinguish and exhibit limited melt behavior when a flame is removed, they typically form brittle chars, shrink and crack open after exposure to a direct flame allowing the underlying materials to ignite. There is a need for low cost, but high performing barrier materials for use in support articles that are also glass fiber free.

BRIEF SUMMARY

[0003] A flame resistant knit fabric containing a first weft yarn set and a second weft yarn set. The first yarn set contains first flame resistant yarns which contain flame resistant rayon fibers. The second weft yarn set contains second weft yarns.

[0004] The knit fabric is knitted such that the first weft yarns are interlinked with one another by a plurality of knit stitches, the second weft yarns are interlinked with one another by a plurality of knit stitches, and the first weft yarns are not interlinked with the second weft yarns. A flame resistant support article containing the flame resistant knit fabric as well as methods for making the knit fabric and support article are also disclosed.

[0005] In another embodiment, the first yarn set contains first flame resistant yarns which contain a blend of partially oxidized polyacrylonitrile fibers and polyoxadiazole fibers.

[0006] Also disclosed are flame resistant support articles which contains the flame resistant knit fabric at least partially surrounding a support article.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 illustrates a schematically exemplary flame resistant knit fabric.

[0008] Figure 2 illustrates schematically the exemplary flame resistant fabric after burning.

[0009] Figure 3 illustrates schematically one embodiment of a flame resistant support article being a mattress.

[0010] Figure 4 is a micrograph of the inner surface of one exemplary flame resistant knit fabric.

DETAILED DESCRIPTION

[0011 ] “Flame resistant”, in this application means a material that provides a thermal barrier and reduces body burn as described in NFPA 1971 and allows the user time to escape the flames and/or fire. Such a fiber, yarn, fabric, or article would preferably resist ignition and be self-extinguishing. In its preferred usage in the present application, the term "flame barrier" means a product incorporated into or on top of a composite article that when tested with a composite type test method, such as: CPSC (Consumer Product Safety Council) CFR 1633, California Test Bulletin 129 (TB 129) or California Test Bulletin 603 (TB603) for mattresses and foundations and California Test Bulletin 133 (TB 133) for upholstered furniture, the flame barrier allows for the continued use of conventional materials such as dress cover fabrics, fiber-fillings and polyurethane foams, while still passing these stringent large open flame tests. It is understood by someone skilled in the art that flame bafflers made of the tubular knit flame barriers described in this invention, even at overall lower basis weights, can be made to pass less stringent open flame tests such California's Revised Test Bulletin 117 (TB 117- draft 02/02 version) and British Standard 5852.

[0012] The flame resistant knit fabric may be formed in any suitable manner and pattern. In one embodiment, the knit fabric is a tubular fabric, and in another embodiment, the knit fabric is a circular knit. These knits are advantageous for use as a barrier material for support articles such as mattresses as the knit would only require two seams to enclose the mattress.

[0013] Referring now to Figure 1 , there is shown a schematic of one exemplary flame resistant knit fabric 10. The knit fabric 10 contains a first weft yarn set and a second weft yarn set. The first weft yarn comprises first weft yarns 100 being flame resistant yarns. The second weft yarn set comprises second weft yarns 200. The knit fabric is knitted such that the first weft yarns are interlinked with one another by a plurality of knit stitches and the second weft yarns are interlinked with one another by a plurality of knit stitches. The first weft yarns and the second weft yarns are not interlinked.

[0014] In the embodiment shown in Figure 1 , the first weft yarn set has a repeating pattern of a knit stitch on a first needle and a welt on a second needle. A welt is also referred to as weft, miss, or float stitch. This stitch is created by not allowing the needle to raise high enough to receive a new yarn, causing the yarn to float behind the face stitches. The second weft yarn set has the same repeating pattern of stitches by offset from the first weft yarn set by one course so that its repeating pattern would be a welt on a first needle and a knit stitch on a second needle. A micrograph of the inner surface of one exemplary flame resistant knit fabric is shown in Figure 4.

[0015] Some examples of other suitable patterns include a knit stitch, a welt, and a welt or a knit stitch, a knit stitch, and a welt. Any combination and repeat pattern of knit stitches, tuck stitches, welts, and any other stitch may be used in the first and/or second weft yarn sets so long as the first weft yarn set is interlinked. Preferably, the second weft yarns are interlinked with one another by a plurality of knit stitches and the first weft yarns and the second weft yarns are not interlinked.

[0016] The first weft yarns 100 of the first weft yarn set are first flame resistant yarns. These may be any suitable flame resistant yarn including inherently flame resistant yarns and chemically treated flame resistant yarns. In one preferred embodiment, the first flame resistant yarns contain flame resistant rayon fibers. In one preferred embodiment, the flame resistant rayon fibers are flame resistant viscose rayon fibers. Preferably, the rayon fibers contain embedded silica particles, such as under the brand name VISIL®.

[0017] In another embodiment, the first flame resistant yarns comprise partially oxidized polyacrylonitrile fibers (also known as panox fibers) and/or polyoxadiazole fibers (also known as podlon fibers). Preferably, the first flame resistant yarns comprise a blend of partially oxidized polyacrylonitrile fibers and polyoxadiazole fibers. In one embodiment, the first flame resistant yarns comprise between about 25 and 75% by weight partially oxidized polyacrylonitrile fibers.

[0018] In another embodiment, the flame resistant yarns can be flame resistant core spun yarns which has a core of a typically flame resistant material surrounded by at least one sheath of other fibers/yarns. More information on the core spun yarns and the method of making the yarns may be found in US Patent 6,410,140 (Land et al.), which is incorporated herein in its entirety. In another embodiment, the first weft yarns contain additional flame resistant fibers, such as polyphenylene sulfide fibers, aramid fibers, carbon fibers, or additional other non-flame resistant fibers.

[0019] The size of the first flame resistant yarns will vary depending on the final application of the yarn and the particular fabric characteristics desired but is preferably within the range of from about 30/1 to 1/1 conventional cotton count, preferably from about 21/1 to 5/1 conventional cotton count for one embodiment. In one preferred embodiment, the cotton count of the first flame resistant yarns are 25/1 or lower, more preferably 15/1 or lower, more preferably 12/1 or lower.

[0020] The second weft yarns 200 of the second weft yarn set may be any suitable yarn, which may have flame resistant characteristics or not. In one embodiment, the second weft yarns 200 are flame resistant spun yarns. In another embodiment, the second weft yarns do not contain continuous fibers such as monofilament or multifilament fibers. In another embodiment, the second weft yarns do not contain fiberglass.

[0021 ] In another embodiment, the second weft yarns comprise monofilament or multifilament fibers. In one preferred embodiment, the second weft yarns 200 are formed from a blend of at least two of the following: fire resistant rayon, modacrylic, cotton, and polyester staple fibers. When exposed to flame, the second weft yarns may melt and/or degrade. In one preferred embodiment, the second weft yarns contain a mixture of flame resistant rayon fibers and polyester fibers. In one embodiment, the second weft yarns comprise between about 25 and 95% by weight flame resistant rayon fibers, more preferably between about 50 and 85% by weight flame resistant rayon fibers.

[0022] In one embodiment, the second weft yarns have a smaller denier than the first flame resistant yarns. Preferably, the first flame resistant yarns have at least two times the denier of the second weft yarns. This difference in size gives the knit a different look as can be seen in Figure 4. The two different yarns could also have different looks, feels, colors, or other properties so that the knit can be more easily seen in garments for interesting knit looks.

[0023] Preferably, there is little to no glass fibers in the flame resistant knit fabric. There is a move in the bedding industry to remove glass fibers from products for safety concerns. In one embodiment, the flame resistant knit fabric comprises less than about 0.1 % glass fibers. In another embodiment, the flame resistant knit fabric is essentially glass fiber free, defined as containing less than about 0.01 % by weight glass fibers. [0024] In one embodiment, the second weft yarn set could contain an alternating arrangement of an A yarn and a B yarn. These yarns are alternated in the set preferably in a 1 :1 alternating pattern (but the pattern could also be 2:2, 1 :2, 2:1 , or other suitable ratio and pattern).

[0025] The flame resistant knit fabric has an upper surface and a lower surface (thought the upper and lower surfaces can be reversed and do not indicate the orientation that the fabric is used in a finished article), wherein the majority of the upper surface comprises the first weft yarns and the majority of the lower surface comprises the second weft yarns. Majority means greater than 50% by weight.

[0026] After the flame resistant knit fabric is exposed to heat and/or flame, in one embodiment, the second weft yarns 200 may be compromised. These yarns may completely melt, disintegrate, or have a significant reduction in their physical properties. The first weft yarns 100 will remain and provide the integrity of the knit fabric. Because the first weft yarns are interlinked with one another through the plurality of knit stitches, the first weft yarns will still form an interconnected grid and the knit will still have integrity after burning. An illustration of the knit fabric 15 having the second weft yarns 200 removed through burning is shown in Figure 2.

[0027] The flame resistant knit fabric 10 may be used as a flame barrier to any suitable article. Figure 3 illustrates a flame resistant support article 20 (in this Figure a mattress 12) surrounded by the flame resistant knit fabric 10 (part of the knit fabric 10 was removed in order to show lower layers in the Figure). The flame resistant knit fabric 10 preferably completely encapsulates the support article. Preferably, the support article passes the Consumer Product Safety Council CFR 1633 test (and other industry standard flame tests).

[0028] The support article may be any article providing support and flame resistance. Some examples of support articles include, but are not limited to, upholstered furniture, mattresses, foundations, automotive seating, public transportation seating, aircraft seating, and the like. In one preferred embodiment, the support article is a mattress. Preferably, the mattress is a foam containing mattress. Example

[0029] A flame resistant fabric was made with the first weft yarns containing 100% by weight rayon fibers containing embedded silica particles and the second weft yarns contained a blend of 75% by weight rayon fibers containing embedded silica particles and 25% by weight polyester fibers. The first weft yarns were a 11/1 and the second weft yarns were 24.5/1. The first weft yarns were at least 2 times the denier of the second weft yarns. The fabric was circular knitted such that the first weft yarns were interlinked with one another by a plurality of knit stitches, the second weft yarns were interlinked with one another by a plurality of knit stitches, and the first weft yarns were not interlinked with the second weft yarns such as illustrated in Figure 1 and shown in a photograph in Figure 4.

[0030] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0031] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e. , meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0032] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above- described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.