Abstract:
A fabric is formed from yarn comprised of inorganic filaments coated with rayon. Specifically, the inorganic filaments are spun from a melt of volcanic black rock and are comprised of calcium oxide, magnesium oxide, potassium oxide, aluminum oxide, iron oxide, silicon dioxide, titanium dioxide, sodium oxide, and boron. As a result of its composition, the fabric is temperature resistant and lightweight, yet strong. Preferably, the fabric exhibits a melting point between 1500° C. and 1650° C., a working range of −130° C. to 700° C., a density of 1.6 g/cc, a surface density between 160 g/m 2  and 350 g/m 2 , and a tensile strength between 500 lbf/in 2  and 1800 lbf/in 2 .

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to fabrics formed from yarn. More particularly, the present invention pertains to high performance fabrics formed from yarns comprised of inorganic filaments. The present invention is particularly, but not exclusively, useful for creating a fabric from yarn derived from inorganic raw materials including black rock. 
     BACKGROUND OF THE INVENTION 
     Conventional fabrics are typically produced from organic or synthetic polymeric fibers. Due to their composition, these fabrics have very limited use at high temperatures and under conditions where force resistance is required. Specifically, such fabrics rapidly deteriorate when subjected to high temperatures, and they typically have limited strength under most conditions. 
     Increasingly, fabrics are being formed from high performance yarns rather than conventional yarns. High performance yarns have both increased strength and an increased elastic modulus compared to conventional yarns. Typically, the high performance yarns are formed from inorganic filaments. The use of these filaments has resulted in a new family of yarns and fabrics that have high tensile strengths and moduli, and they have the ability to maintain these properties at elevated temperatures. Nevertheless, the strength and heat resistance of fabrics formed from known inorganic filaments can be improved upon. 
     To improve upon the strength and heat resistance of known fabrics, the present invention utilizes unrefined raw materials, such as volcanic rock, to manufacture inorganic filaments that can be woven into fabric. Inorganic filaments manufactured from volcanic rock have been found to exhibit excellent strength and heat resistance qualities. Likewise, fabrics woven or otherwise formed from these inorganic filaments also exhibit these same excellent strength and heat resistance qualities. 
     In light of the above, it is an object of the present invention to provide a fabric formed from inorganic yarn. Another object of the present invention is to provide a fabric formed from an organic yarn derived from volcanic rock. It is yet another object of the present invention to provide a fabric formed from a yarn comprising inorganic filaments coated with rayon. Still another object of the present invention is to provide high strength, heat resistant fabrics that are relatively easy to manufacture, simple to use and comparatively cost effective. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a fabric formed from yarn comprised of inorganic filaments formed from a volcanic rock and coated with rayon. Specifically, the inorganic filaments are spun from a melt of the volcanic rock. Preferably, the volcanic rock is black rock that contains aluminum oxide, iron oxide, silicon dioxide, titanium dioxide, magnesium oxide, calcium oxide, sodium oxide, and potassium oxide. In addition to the black rock, the melt includes an additive that preferably comprises iron oxide, whitestone and boron. 
     After the filaments are spun from the melt, they are sized or coated with a rayon sizing agent. The sized filaments are then twisted together to form the yarn in a manner that is well understood in the art. Preferably, the resulting yarn has a diameter in a range of ten to fifteen millimeters and is approximately 98 wt. % inorganic filaments and 2 wt. % rayon. 
     While volcanic black rock is formed by a range of components, it is preferred that the manufacturing process is controlled so that the yarn is comprised of approximately 35–45 wt. % calcium oxide, 30–40 wt. % magnesium oxide, 5–10 wt. % potassium oxide, less than 2 wt. % aluminum oxide, 5–10 wt. % iron oxide, less than 2 wt. % silicon dioxide, less than 2 wt. % titanium dioxide, less than 2 wt. % sodium oxide, less than 2 wt. % boron, and 1–5 wt. % rayon. More preferably, the yarn is comprised of approximately 40 wt. % calcium oxide, 36.6 wt. % magnesium oxide, 8.4 wt. % potassium oxide, 0.8 wt. % aluminum oxide, 8.85 wt. % iron oxide, 0.85 wt. % silicon dioxide, 0.8 wt. % titanium dioxide, 0.8 wt. % sodium oxide, 0.6 wt. % boron, and 2 wt. % rayon. 
     As a result of its composition, the fabric of the present invention has a melting point between approximately fifteen hundred degrees Centigrade (1500° C.) and approximately sixteen hundred and fifty degrees Centigrade (1650° C.). Further, the fabric has a working range of approximately negative one hundred thirty degrees Centigrade (−130° C.) to approximately seven hundred degrees Centigrade (700° C.). 
     In addition to its excellent thermal characteristics, the fabric of the present invention exhibits superior strength and has good ballistic properties. Specifically, it has a tensile strength between approximately five hundred pound-force per square inch (500 lbf/in 2 ) and approximately eighteen hundred pound-force per square inch (1800 lbf/in 2 ). Further, the fabric has a surface density between approximately one hundred and sixty grams per square meter (160 g/m 2 ) and approximately three hundred and fifty grams per square meter (350 g/m 2 ). Also, the fabric is relatively very lightweight, with a density of about one and six tenths grams per cubic centimeter (1.6 g/cc). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is an enlarged, diagrammatic side view of a fabric in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic diagram exemplifying a method for manufacturing inorganic yarn in accordance with the present invention; and 
         FIG. 3  is a diagrammatic depiction of several exemplary weave styles which may be employed in the fabric in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a high strength, heat resistant fabric in accordance with the present invention is shown and generally designated  10 . As shown, the fabric  10  is comprised of a plurality of fill yarns  12  arranged substantially parallel to one another. Further, a plurality of warp yarns  14  are woven with the fill yarns  12  in a serpentine fashion (i.e., over and under adjacent fill yarns  12 ). For the present invention, both the fill yarns  12  and warp yarns  14  are comprised of a yarn  16  formed from inorganic volcanic rock, additives and rayon. As a result, the fabric  10  consists solely of the inorganic yarn  16  and exhibits certain desired characteristics discussed below. 
     Referring now to  FIG. 2 , a system  18  for manufacturing the inorganic yarn  16  is depicted. As shown, the system  18  includes a furnace  20 . The furnace  20  is preferably a cupola furnace and includes a chamber  22  formed by a sidewall  24 . The chamber  22  is dimensioned to receive the raw materials  26  needed to manufacture the inorganic yarn. Specifically, the raw materials  26  include black rock  28  and an additive  30 . As indicated, the black rock  28  and additive  30  are provided to the chamber  22  in the form of crushed solids. Once they are received in the chamber  22 , they are liquefied therein to form a melt  32 . 
     Downstream of the furnace  20 , the system  18  includes a spinning device  34 . The spinning device  34  may be integral with the furnace  20  or it may be connected directly to the furnace  20  for receiving the melt  32 . Alternatively, the melt  32  may be delivered to the spinning device  34  via a carrier such as a ladle or the like. In either case, the spinning device  34  includes a pump or other means to force the melt  32  though an aperture, or several apertures, to form a plurality of filaments  36 . Preferably, the apertures of the spinning device  34  are formed by a stationary platinum nozzle that can withstand the high temperatures of the melt  32 . 
     As shown in  FIG. 2 , the system  18  further includes a cooling device  38  that is positioned downstream of the spinning device  34 . Similar to the spinning device  34 , the cooling device  38  may be integral with the furnace  20  or it may be connected thereto. As shown, the cooling device  38  is positioned to receive the plurality of filaments  36  from the spinning device  34 . Further, a sizing station  40  is positioned downstream of the cooling device  38  to receive the plurality of filaments  36  therefrom. The sizing station  40  includes a sizing agent  42  that can be applied to the plurality of filaments  36  to form a plurality of fibers  44 . As is further shown in  FIG. 2 , a twisting device  46  is positioned immediately downstream of the sizing station  40 . The twisting device  46  receives the plurality of fibers  44  and forms the inorganic yarn  16  therefrom. 
     In more detail, the black rock  28  of the present invention is preferably of the type of volcanic rock that is commonly found in Oregon, Washington and other locations. Such black rock  28  typically contains about 44 wt. % calcium oxide, 41 wt. % magnesium oxide, 10 wt. % potassium oxide, 1 wt. % aluminum oxide, 1 wt. % iron oxide, 1 wt. % silicon dioxide, 1 wt. % titanium dioxide, and 1 wt. % sodium oxide. Unless treated or mixed with other materials, the black rock  28  typically has a melting point of over twelve hundred degrees Centigrade (1200° C.). Before it is introduced to the chamber  22  of the furnace  20 , the black rock  28  is graded to individual pieces having diameters “d” of about 4–8 inches. Preferably, the individual pieces of black rock  28  all have substantially the same diameter “d”. 
     As further shown in  FIG. 2 , the additive  30  is provided in the form of crushed solids. The additive  30  preferably has a melting point of about 900° C. and includes about 26–33 wt. % potassium permanganate, 39–45 wt. % iron oxide, 22–31 wt. % whitestone and 3 wt. % boron. For the invention, the potassium permanganate is provided as a fuel source for melting the raw materials  26  and the iron oxide is provided to modify the black rock  28 . Further, the boron and whitestone, which contains about 58 wt. % calcium oxide, 41 wt. % magnesium oxide, less than 1 wt. % silicon oxide, and less than 1 wt. % iron oxide, are provided to reduce the melting point and facilitate processing of the mixture of raw materials  26 . 
     As a batch process, a desired amount of black rock  28  and additive  30  are delivered to the furnace  20 . Preferably, the raw material  26  provided to the chamber  22  consists essentially of 60–90 wt. % black rock  28  and 40–10 wt. % additive  30 . In certain preferred embodiments, the raw material  26  consists essentially of 87–88% black rock  28  and 13–12% additive  30 . In such an embodiment, the mixture of raw material  26  includes about 5–6 wt. % potassium permanganate, 4–6 wt. % whitestone, 8 wt. % iron oxide, and 0.6 wt. % boron. Volumetrically, the raw material  26  is preferably about one hundred parts of black rock  28  and about fourteen parts of additive  30 . 
     When positioned in the chamber  22  of the furnace  20 , the mixture of raw materials  26  is heated to a temperature in the range of approximately 955° C.–1270° C., and preferably to between 1200° C. and 1270° C. Regardless of the specific temperature attained, the mixture of raw materials  26  is heated sufficiently to reduce the raw materials  26  to liquefy to a melt  32  having a viscosity proper for processing. During heating, the potassium permanganate is burned as a fuel and facilitates liquefying the other raw materials  26 . 
     After the melt  32  is properly formed, it is delivered to the spinning device  34 . The spinning device  34  extrudes the melt  32  into a plurality of filaments  36  by forcing the melt  32  through its nozzle. The resulting filaments  36  have diameters substantially in a range between one and ten microns. In order to prevent deformation of the filaments  36 , they are delivered to the cooling device  38  to be cooled and hardened to a soft solid state. During the cooling process, the cooling device  30  first cools the plurality of filaments  36  to 800° C. and maintains that temperature for 30 minutes. Then it cools the plurality of filaments  36  to 355° C. and maintains that temperature for 30 minutes. As a result, the plurality of filaments  36  reaches a substantially soft solid state that facilitates further processing. 
     After being cooled to 355° C., the filaments  36  are passed to the sizing station  40 . At the sizing station  40 , a rayon sizing agent  42  is applied to the plurality of filaments  36 . Specifically, the plurality of filaments  36  is coated with the rayon agent  42  to form a plurality of fibers  44 . The rayon agent  42  is preferably in yarn form and is provided in an amount such that rayon forms 2 wt. % of the resulting fibers  44 . As a result of the rayon coating, the fibers  44  are protected from mechanical damage and formation of yarn from the fibers  44  is facilitated. Once they have been sized, the fibers  44  are collected and processed by the twisting device  46 . Specifically, the twisting device  46  drafts and twists the plurality of fibers  44  to form the inorganic yarn  16 . Preferably, the resulting inorganic yarn  16  has a diameter in a range of ten to fifteen millimeters. 
     For the present invention, a yarn  16  manufactured according to the above method is preferably comprised of about 40 wt. % calcium oxide, 36.6 wt. % magnesium oxide, 8.4 wt. % potassium oxide, 0.8 wt. % aluminum oxide, 0.85 wt. % iron oxide, 0.85 wt. % silicon dioxide, 0.8 wt. % titanium dioxide, 0.8 wt. % sodium oxide, 0.6 wt. % boron, 8 wt. % iron oxide, and 2 wt. % rayon. Such a yarn  16  has a melting point in the range between approximately 1500° C. and approximately 1650° C. and has a working range of about −130° C. to 700° C. Further, the yarn is relatively very light, with a density of about one and six tenths grams per cubic centimeter (1.6 g/cc). 
     While  FIG. 1  depicts a representative weave comprising the inorganic yarn  16 , it will be understood that any number of weaves may be utilized in forming the inventive fabric  10 . Several exemplary weaves, all well known in the pertinent art, are shown in  FIG. 3 . Specifically,  FIG. 3  includes depictions of a plain weave, crowfoot satin weave, 2×2 basket weave, 2/2 twill weave, 2/1 twill weave, and leno weave. For the present invention, such weaves may be selected, designed or utilized to control the weight, thickness, density, and strength of the fabric  10 . Further, specific weaves may be desired for specific applications of the fabric  10 . 
     While the particular fabric as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.