Patent Application
20060059634
Several occupations require an individual to be exposed to hazards such as flash fires or electrical arcs. To avoid being injured while working in such conditions, these individuals typically wear protective garments constructed of materials designed to protect them from heat and flame.
To cite an example, many utility and industrial workers wear denim garments. As referred to herein, “denim” is a twill fabric that is yarn dyed such that one yarn component (e.g., warp yarns) is dyed prior to constructing the fabric and the other yarn component (e.g., filling yarns) is not. It is the weaving of the dyed yarns with the undyed yarns that gives denim its distinctive appearance. Such denim is typically constructed of 100% cotton. Although not ideal from the standpoint of offering protection against flash fire and electrical arc hazards, many workers like the appearance and feel of cotton denim garments and believe that the protection they offer is adequate.
Unfortunately, a number of issues arise when cotton denim garments are used to protect against flash fires, electrical arcs, and other similar hazards. Although some protection is offered by such garments, better protection could be afforded by garments composed of flame resistant fabrics. Although it is possible to treat cotton denim fabric in order to increase its flame resistance, this flame resistance may degrade over the life of the fabric through physical wear and laundering. Aside from issues concerning flame resistance, yarn dyeing processes used to create known denim fabrics are relatively expensive as compared to piece-dyeing processes, and therefore increase the overall cost of producing a garment.
Disclosed are flame resistant fabrics and garments having the appearance of denim. In one embodiment, a piece-dyed, flame resistant fabric includes first flame resistant yarns that extend along the fabric in a first direction and second flame resistant yarns that extend along the fabric in a second that is different from the first direction so as to interweave the second flame resistant yarns with the first flame resistant yarns, wherein the first flame resistant yarns are dyed due to the piece dyeing but the second flame resistant yarns are substantially undyed to create the denim appearance.
The disclosed fabrics and methods can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale.
In some embodiments, the warp yarns 202 comprise a blend of inherently flame resistant fibers and another type of fiber, such as a flame resistant (FR) cellulosic fiber (i.e., a fiber that is not naturally flame resistant, but which can be made so through appropriate treatment). For example, a para-aramid/FR rayon blend or a meta-aramid/FR rayon blend may be used. In other embodiments, the warp yarns 202 comprise a blend of modacrylic and FR rayon. In cases in which an aramid blend is used, a para-aramid (e.g., Kevlar® or Twaron®)/FR rayon blend and/or a non-crystalline meta-aramid (e.g., Nomex® type 462)/FR rayon blend may be used. As is known in the art, Kevlar® and Twaron® fibers are composed of 100% para-aramid while Nomex® type 462 fibers are composed of 93% non-crystalline meta-aramid. Although para-aramid can be difficult to dye, suitable dyeing of a blended yarn may be achievable, for instance by only or primarily dyeing the non-para-aramid component(s). Other FR cellulosics that could be used include FR cotton, FR acetate, FR triacetate, and FR lyocell.
In some embodiments, the filling yarns 204 are composed of inherently flame resistant material that resists the employed dyeing process and therefore remains substantially undyed (i.e., substantially uncolored) after the piece-dyeing process used to dye the warp yarns 202 is completed. In one embodiment, the filling yarns 204 comprise an aramid material that resists dyeing such as crystalline meta-aramid (e.g., Nomex® type 450). In another embodiment, the filling yarns 204 comprise 100% para-aramid fibers (e.g., Kevlar® or Twaron®). As is known in the art, Nomex® type 450 fibers are composed of 100% crystalline meta-aramid, which is relatively difficult to dye. Typically, the resultant fabric has a weight ranging from approximately 4 ounces per square yard (osy) to approximately 15 osy.
The dyeing techniques and dyes used to achieve a flame resistant fabric having the appearance of denim depend upon the materials selected for the warp yarns 202 and the filling yarns 204 and the desired result in terms of which component (warp or filling) is dyed and which is not. In some embodiments, the dyeing techniques used comprise low temperature (i.e., less than the boiling temperature) dyeing with or without a dye-assistant (or “carrier”). Example dyeing methods are described in U.S. Pat. No. 6,547,835, which is hereby incorporated by reference. In that particular dyes cannot be used to dye some materials and some materials can only be dyed by certain dyes if a dye-assistant is used, it can be appreciated that the desired result, whether it be dyed warp yarns and undyed filling yarns or undyed warp yarns and dyed filling yarns, can be achieved by varying one or more of the materials used, dyes used, and dye-assistant used (if any). Example dyes include direct/disperse, fiber reactive/disperse, direct/basic, fiber reactive/basic, direct, fiber reactive, vat, and sulfur dyes, and may be, for instance, blue or black (i.e., popular colors for denim garments).
Example fabrics and dyeing techniques are identified in Table I that result in dyed warp yarns and substantially undyed filling yarns, which yields a flame resistant fabric having the appearance of denim. However, as noted above, the same effect can be achieved if the filling yarns 204 are dyed and the warp yarns 204 remain substantially undyed.
At this point, the fabric (once rinsed and dried) will have the appearance of conventional denim, but will further have a relatively durable flame resistance. Accordingly, the fabric is suitable for replacement of cotton denim in garments used by those who encounter heat and flame hazards.
