Abstract:
The invention relates to a fire resistant flame barrier lightweight fabric substrate consisting of a high temperature resistant continuous filament fiberglass core and a low temperature resistant staple fiber sheath treated with a durable or non-durable fire retardant agent prior to yarn formation. The invention also discloses a process for making a fire resistant corespun yarn by treating fibers with fire retardant agent to make the sheath of the corespun yarn.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application claims priority and the benefit thereof from a U.S. Provisional Application No. 61/362,421, filed on Jul. 8, 2010 and entitled COATED FIRE BARRIERS MADE FROM CORE SPUN YARNS—COATED FIBERS COMPRISING THE SHEATH OF THE CORE SPUN YARNS, the entire contents of which are herein incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a fire resistant flame barrier lightweight fabric substrate consisting of a high temperature resistant continuous filament fiberglass core and a low temperature resistant staple fiber sheath treated with a durable or non-durable fire retardant agent prior to yarn formation. The invention also discloses a process for making a fire resistant corespun yarn by treating fibers with fire retardant agent to make the sheath of the corespun yarn. 
       BACKGROUND OF THE INVENTION 
       [0003]    The United States mattress industry is constantly striving to improve mattress comfort, while complying with 16 Code of Federal Regulations Part 1633, the United States standards for the flammability of mattress sets and improving profitability by reducing manufacturing costs or increasing value added features such as use of more environmentally friendly components, lighter, or more aesthetically pleasing fabrics. 
         [0004]    Fire resistant fabrics used in the manufacture of mattresses today typically require the application of chemical fire retardant agents after fabric formation. Application of fire retardant agents after fabric formation often results in changes to the physical and or aesthetic properties of the fabric, such as changes in strength, elongation, and feel of the fabrics, thereby making the fabrics less desirable in the construction of mattresses, pillow tickings, bedspreads, draperies, upholstery, and other bedding products. (Note: As an alternative, inherently fire-retardant materials can be used; however, these can be more expensive.) 
         [0005]    There is a need to meet United States federal flammability regulations for mattresses and other demands for fire resistant fabrics, by making such fire resistant fabrics more ecologically friendly while maintaining the fabrics&#39; original physical and aesthetic properties. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention, as described below, discloses micro-coating some or all the sheath fiber components of balanced fine corespun yarn, with a durable or non-durable fire retardant agent in the fiber state, which includes a high temperature resistant continuous multifilament fiberglass core and a low temperature resistant staple fiber sheath surrounding the fiberglass core. The invention further includes the process of making the same. 
         [0007]    This invention may include aspects of U.S. Pat. No. 5,540,980 for fire resistant fabric made of balanced, fine corespun yarn incorporated herein by reference in its entirety. The invention may also include aspects of U.S. Pat. No. 4,958,485 for corespun yarn for fire resistant safety apparel incorporated herein by reference in its entirety. U.S. Pat. No. 5,540,980 teaches the formation of fire resistant fabric from corespun yarn comprising of a high temperature resistant continuous filament fiberglass core and a low temperature resistant staple fiber sheath surrounding the core, which may then be woven or knit in a fine, non-plied form. This invention improves upon the previous teaching in that it incorporates into the corespun yarn itself, micro-coated or treated fibers, which are fibers that have been subject to the application of a durable or non-durable fire retardant agent in the fiber state prior to yarn formation, for use as one hundred percent of the sheath fibers in corespun yarn, or blended with other fibers in the sheath. 
         [0008]    According to one aspect of the invention, a fire resistant fabric may include a fine textured fire resistant flame barrier lightweight fabric substrate formed of a nonlively nonplied fine balanced corespun yarn including the yarn being air jet spun without any appreciable twist and including a core of high temperature resistant fibers constituting about 20% to 40% of total weight of the corespun yarn, a sheath of low temperature resistant staple fibers treated with at least one durable or non-durable fire retardant agent prior to the yarn formation process, and the sheath surrounding and covering the core constituting about 80% to 60% of the total weight of the corespun yarn. 
         [0009]    Some of or all the sheath of the corespun yarn may be micro-coated with durable or non-durable fire retardant agents. The fire retardant agent may include at least one of ammonium polyphosphate, graphite, boric acid, or others as the fire retardant agent, in gaseous, liquid and/or powder form. The fabric substrate may be knit or woven. The sheath may include blends of natural and or man-made fibers including at least one of animal, vegetable, mineral, wool, cotton, polyester, modacrylic, nylon, rayon, Lyocell, Kenaf, Hemp, Jute, acetate, and blends thereof. 
         [0010]    The fire retardant micro-coated fibers may comprise 100% of the sheath fibers in the corespun yarn. The treated fibers may be blended with other fibers to create a sheath of treated and untreated fibers. The sheath may also include fire retardant micro-coated fibers blended with other inherently fire retardant fibers. 
         [0011]    A process for making a fire retardant corespun yarn by treating the fibers with fire retardant agent to make the sheath of the corespun yarn is also disclosed. The process may include at least one of: mixing the fire retardant chemical or chemicals together, applying the fire retardant chemicals to the fiber, drying and or curing the treated fiber, and forming a yarn from the treated fiber. The treated fibers may partially or fully cover the core high temperature resistant fibers to create a sheath of treated fibers. The treated fibers may also be blended with other non-treated fibers to create a sheath of treated and untreated fibers. 
         [0012]    The application of the fire retardant agent to the fiber may include topically treating the surface of the fiber and or immersing the fiber in at least one fire retardant agent solution, followed by drying and or curing the treated fiber. The process may also include where a fire retardant agent is applied, and reapplied as necessary, to a surface of the fiber by at least one of: mixing, spraying, rolling, and or brushing. 
         [0013]    Potential benefits from applying fire retardant agents to the creation of fine balanced corespun yarn prior to fabric formation may include the production of fire resistant and or flame barrier fabrics that can be deployed in the greige state to preserve the physical and aesthetic properties of the fabrics as well as the upholstered articles made from them. The formation of these yarns may potentially enable businesses to simplify the process routing for these fabrics and maintain lower yarn inventory levels as the same yarn can be used for several end products. 
         [0014]    The invention contemplates the use of environmentally favorable fire retardant chemicals, avoiding those suspect chemicals on Europe&#39;s REACH list or California&#39;s Green Chemistry Initiative, thereby possibly making the fabric more consumer and retailer desirable and potentially lowering the risk of claims of harm from use of other fire retardant chemicals. In addition, this yarn structure may enable the micro-coated fibers to form a char, while the heat stable core creates a lattice to hold the char in place. The coating of the fibers may emit vapor-phase flame retardants that would encourage the extinguishment of flames immediately adjacent to the fire resistant fabric. The possible increase in char strength may enable the use of lighter, more responsive fire barrier fabrics than that using treated cotton alone. 
         [0015]    Additional features, advantages, and embodiments of the invention may be set forth or apparent from consideration of the detailed description and drawings. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the detailed description serve to explain the principles of the invention. No attempt is made to show structural details of the invention in more detail than may be necessary for a fundamental understanding of the invention and the various ways in which it may be practiced. In the drawings: 
           [0017]      FIG. 1  shows a greatly enlarged fragment of the balanced corespun yarn of the invention with a portion of the sheath revealed at one end thereof. 
           [0018]      FIG. 2  shows a process for making a fire retardant corespun yarn by treating the fibers used to make the sheath of the corespun yarn with a fire retardant agent. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The embodiments of the invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and detailed in the following attached description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment may be employed with other embodiments as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the embodiments of the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those of skill in the art to practice the embodiments of the invention. Accordingly, the examples and embodiments herein should not be construed as limiting the scope of the invention, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings. 
         [0020]    The invention sets forth an application of at least one fire retardant agent to some or all of the low temperature resistant sheath fibers, which surround and cover a high temperature resistant continuous multifilament fiberglass core, while in a fiber state. 
         [0021]      FIG. 1  shows a greatly enlarged fragment of the balanced corespun yarn of the invention with a portion of the sheath revealed at one end thereof. 
         [0022]    Referring to  FIG. 1 , the fire resistant balanced corespun yarn  100 , which may be knit or woven, may include a core of high temperature resistant continuous filament fiberglass  110  and a sheath of low temperature resistant staple fibers  120  which surround and cover the core  110 . Although the core is described as fiberglass, it should be noted that other heat-stable materials could be used as the core. The fiberglass core  110  extends generally in an axial direction and longitudinally of the corespun yarn  100 , while the majority of the fibers of the sheath  120  extend in a slightly spiraled direction around the core  110 . A few of fibers of the sheath may form a binding wrapper around a majority of the staple fibers  130 . The core  110  may consist of a high temperature resistant continuous multifilament fiberglass, which constitutes about 20% to 40% of the total weight of the corespun yarn  100 . 
         [0023]    The sheath  120  may completely cover the core  110  and the yarn  100  will take on the characteristics of the fiber which forms the sheath  120 , such as the low temperature resistant staple fibers in this case. The sheath  120  may include low temperature resistant staple fibers, which constitutes about 80% to 60% of the total weight of the corespun yarn  100  and may consist of all or some fibers that are micro-coated with durable or non-durable fire retardant agents. The sheath  120  may also consist of fire retardant micro-coated fibers blended with other non-treated fibers or inherently fire retardant fibers to form the sheath  120 . 
         [0024]    The sheath  120  may include blends of natural occurring fibers, such as animal, vegetable, or mineral fibers, and or unnaturally occurring fibers, such as cotton, wool, polyester, modacrylic, nylon, rayon, Lycocell, Kenaf, Hemp, Jute, acetate, and blends thereof. The preferred low temperature resistant staple fibers  120  are cotton and polyester micro-coated with durable or non-durable fire retardant agents. The total practical size of the fine corespun yarn  100  is around 43/1 to 3.5/1 conventional cotton count. 
         [0025]    The invention describes a corespun yarn  100  that may be produced on a Murata air jet spinning apparatus, as disclosed in one or more of U.S. Pat. Nos. 4,718,225; 4,551,887; and 4,497,167. An air jet spinning apparatus may include an entrance trumpet for feeding the fire retardant chemically treated low temperature resistant sheath fibers  120 , one or more drafting rolls, feeding of the high temperature core fibers  110  between two or more drafting rolls, at least one fluid swirling air jet nozzle that may produce air jet spun yarn  100  without any appreciable twist, torque or liveliness, and a delivery roll assembly. 
         [0026]    The fire retardant agents applied to some or all of the fibers in the sheath  120  may include ammonium polyphosphate, graphite, boric acid, and or other mixtures, which may be applied in gaseous, liquid and or powder form. 
         [0027]    This invention may also involve a process for treating the sheath fibers with at least one fire retardant chemical or mixtures.  FIG. 2  shows a process for making fire retardant corespun yarn by treating the fibers used to make the sheath of the corespun yarn with a fire retardant agent. 
         [0028]    Referring to  FIG. 2 , one or more fire retardant chemicals may be mixed together  210  and applied to the low temperature resistant staple fiber sheath  220  which may surround the high temperature resistant fiberglass core. The fire retardant chemicals may be applied  220  to the surface of the sheath fiber by mixing, spraying, rolling, and or brushing, or may be immersed in a fire retardant chemical solution before being dried  230  or allowed to dry. The fire retardant chemical agent or solution may include at least one of ammonium polyphosphate, graphite, boric acid, or other mixtures, and may be applied at least once and reapplied to the fiber as necessary. Drying the chemically treated sheath fibers  230  may involve natural air drying as well as other drying methods as known in the industry. 
         [0029]    The process may further include blending other fibers with the treated fibers to create a sheath of treated and untreated fibers, and then covering the high temperature resistant core with the sheath of treated fibers to form a fire resistant corespun yarn  240 . The process may conclude with the making of a fire resistant fabric  250  which is then used in the manufacture of an end product  260 , such as a mattress, mattress topper, or other upholstery components. 
         [0030]    It should be noted that although the figures show a single core and a single sheath, these aspects are merely exemplary. It is within the scope and spirit of the invention to have multiple cores and/or multiple sheaths. The cores may be the same material or they may include different materials. Similarly, the sheaths may be the same material or they may include different materials. 
         [0031]    While the invention has been described in terms of exemplary embodiments, those skilled in the art will recognize that the invention can be practiced with modifications in the spirit and scope of the appended claims. These examples given above are merely illustrative and are not meant to be an exhaustive list of all possible designs, embodiments, applications or modifications of the invention.