Patent Abstract:
A heat and fire resistant planar unitary shield formed of heat and flame resistant fibers and voluminous bulking fibers. The shield material has a heat and flame resistant zone with a majority of the heat and flame resistant fibers, and a voluminous bulking zone with a majority of the voluminous bulking fibers. The fibers are distributed through the shield material in an manner that the heat and flame resistant fibers collect closest to the outer surface of the shield with the heat and flame resistant zone, and the voluminous bulking fibers collect closest to the outer surface of the shield material with the voluminous bulking zone.

Full Description:
BACKGROUND 
   The present invention generally relates to materials for use in shielding from heat and/or flame, and in particular, heat and/or flame shielding material that can be used in applications such as hood liners for automobiles, engine compartment liners, and the like. 
   Numerous industries require materials which not only deliver heat and flame resistant properties, but can also provide volume, opacity, moldability, and other properties in a cost effective single substrate. Often times these barrier properties are best accomplished by using specialty materials which generate a high level of performance, but also introduce significant cost to the substrate. Especially in a voluminous substrate (high z direction thickness) even the introduction of a small percent of these materials into the shield material can introduce a significant level of cost to the overall substrate. For this reason composites having specialty surface layers are often used to provide these barrier properties. An example of a composite having specialty surface layers would be a skin laminated to a voluminous lower cost material. While this method effectively reduces the cost of the high cost raw material, there are disadvantages to this method such as additional processing steps and the potential delamination of the skin layer. 
   The present invention provides an alternative to the prior art by using a unitary heat shield material with different zones to provide the various desired properties of the material 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
       FIG. 1  shows an enlarged cross-section of one embodiment of the present invention; 
       FIG. 2  shows an enlarged cross-sectional view of another embodiment of the present invention; and, 
       FIG. 3  shows a diagram of a machine for performing a process for forming the planar heat and flame resistant shield material of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now to the figures, and in particular to  FIG. 1 , there is shown an enlarged cross-sectional view of an embodiment of the present invention, illustrated as a planar heat and flame shield material  100 . The shield material  100  may be used in its existing sheet form as a protective blanket or shield in operations such as welding, high temperature manufacturing, or the like. The shield material  100  may also be formed into parts such as automotive hood liners, engine compartment covers, and the like. As illustrated, the planar shield material  100  generally contains heat and flame resistant fibers  101  and bulking fibers  102 . The heat and flame resistant fibers  101  and the bulking fibers  102  are staple fibers that are combined to form the shield material  100 . As used herein, heat and flame resistant fibers shall mean fibers having an Limiting Oxygen Index (LOI) value of 20.95 or greater, as determined by ISO 4589-1. Examples of heat and flame resistant fibers include the following: fibers including oxidized polyacrylonitrile, aramid, or polyimid, flame resistant treated fibers, carbon fibers, or the like. Bulking fibers are fibers that provide volume to the heat shield material. Examples of bulking fibers would include fibers with high denier per filament (one denier per filament or larger), high crimp fibers, hollow-fill fibers, and the like. In one embodiment, the heat and flame resistant fibers  101  and the bulking fibers  102  are air-laid with a binder fiber  105 , and the combination of fibers is heated to activate the binder fiber  105  for bonding together the fibers of the shield material  100 . An additional benefit of using the binder fiber  105  in the shield material  100  is that the shield material  100  can be subsequently molded to part shapes for use in automotive hood liners, engine compartment covers, etc. 
   Still referring to  FIG. 1 , the heat and flame resistant fibers  101  are concentrated in a heat and flame resistant zone  110  of the planar shield material  100 , and the bulking fibers  102  are concentrated in a voluminous bulking zone  120  of the planar shield material  100 . The heat and flame resistant zone  110  provides the shield material  100  with the primary heat and flame resistant attributes. The voluminous bulking zone  120  provides the shield material  100  with the desired z-direction thickness. 
   Referring still to  FIG. 1 , the heat and flame resistant zone  110  has an outer boundary  111  located at the outer surface of the shield material  100 , and an inner boundary  112  located adjacent to the voluminous bulking zone  120 . The voluminous bulking zone  120  has an outer boundary  121  located at the outer surface of the shield material  100  and an inner boundary  122  located adjacent to the heat and flame resistant zone  110 . The shield material  100  is a unitary material, and the boundaries of the two zones do not represent the delineation of layers, but areas within the unitary material. Because the shield material  100  is a unitary material, and the heat and flame resistant zone  110  and the voluminous bulking zone  120  are not discrete separate layers joined together, various individual fibers will occur in both the heat and flame resistant zone  110  and the voluminous bulking zone  120 . Although  FIG. 1  illustrates the heat and flame resistant zone  110  being a smaller thickness than the voluminous bulking zone  120 , the relative thickness of the two zones can have a substantially different than as shown. 
   Referring still to  FIG. 1 , the heat and flame resistant zone  110  contains both the heat and flame resistant fibers  101  and the bulking fibers  102 . However, the heat and flame resistant zone  110  primarily contains the heat and flame resistant fibers  101 . Additionally, the distribution of the fibers in the heat and flame resistant zone  110  is such that the concentration of the heat and flame resistant fibers  101  is greater at the outer boundary  111  of the heat and flame resistant zone  110  than the inner boundary  112  of that zone. Also, as illustrated, it is preferred that the concentration of the heat and flame resistant fibers  101  decreases in a gradient along the z-axis from the outer boundary  111  of the heat and flame resistant zone  110  to the inner boundary  112  of that zone. 
   Still referring to  FIG. 1 , the voluminous bulking zone  120  contains both the heat and flame resistant fibers  101  and the bulking fibers  102 . However, the voluminous bulking zone  120  primarily contains the bulking fibers  102 . Additionally, the distribution of the fibers in the voluminous bulking zone  120  is such that the concentration of the bulking fibers  102  is greater at the outer boundary  121  of the voluminous bulking zone  120  than the inner boundary  122  of that zone. Also, as illustrated, it is preferred that the concentration of the bulking fibers  102  decreases in a gradient along the z-axis from the outer boundary  121  of the voluminous bulking zone  120  to the inner boundary  122  of that zone. 
   Referring now to  FIG. 2 , there is shown an enlarged cross-sectional view of another embodiment of the present invention, illustrated as a heat and flame shield material  200 . As illustrated, the shield material  200  generally contains heat and flame resistant fibers  201  and bulking fibers  202 . The heat and flame resistant fibers  201  and the bulking fibers  202  are staple fibers that are combined to form the shield material  200 . In one embodiment, the heat and flame resistant fibers  201  and the bulking fibers  202  are air-laid with a binder fiber  205 , and the combination of fibers is heated to activate the binder fiber  205  for bonding together the fibers of the shield material  200 . An additional benefit of using the binder fiber  205  in the shield material  200  is that the shield material  200  can be subsequently molded to part shapes for use in automotive hood liners, engine compartment covers, etc. 
   Still referring to  FIG. 2 , the heat and flame resistant fibers  201  are concentrated in a heat and flame resistant zone  210  of the shield material  200 , and the bulking fibers  202  are concentrated in a voluminous bulking zone  220  of the shield material  200 . The heat and flame resistant zone  210  provides the shield material  200  with the primary heat and flame resistant attributes of the shield material  200 . The voluminous bulking zone  220  provides the shield material  200  with the desired z-direction thickness. 
   Referring still to  FIG. 2 , the heat and flame resistant zone  210  has an outer boundary  211  located at the outer surface of the shield material  200 , and an inner boundary  212  located adjacent to the voluminous bulking zone  220 . The voluminous bulking zone  220  has an outer boundary  221  located at the outer surface of the shield material  200  and an inner boundary  222  located adjacent to the heat and flame resistant zone  210 . The shield material  200  is a unitary material, and the boundaries of the two zones do not represent the delineation of layers, but areas within the unitary material. Because the shield material  200  is a unitary material, and the heat and flame resistant zone  210  and the voluminous bulking zone  220  are not discrete separate layers joined together, various individual fibers will occur in both the heat and flame resistant zone  210  and the voluminous bulking zone  220 . Although  FIG. 2  illustrates the heat and flame resistant zone  210  being a smaller thickness than the voluminous bulking zone  220 , the relative thickness of the two zones can have a substantially different than as shown. 
   Still referring to  FIG. 2 , the heat and flame resistant zone  210  contains both the heat and flame resistant fibers  201  and the bulking fibers  202 . However, the heat and flame resistant zone  210  primarily contains the heat and flame resistant fibers  201 . Additionally, the distribution of the fibers in the heat and flame resistant zone  210  is such that the concentration of the heat and flame resistant fibers  201  is greater at the outer boundary  211  of the heat and flame resistant zone  210  than the inner boundary  212  of that zone. Also, as illustrated, it is preferred that the concentration of the heat and flame resistant fibers  201  decreases in a gradient along the z-axis from the outer boundary  211  of the heat and flame resistant zone  210  to the inner boundary  212  of that zone. 
   Referring still to  FIG. 2 , the bulking fibers  202  of the shield material  200  comprise first bulking fibers  203  and second bulking fibers  204 . In one embodiment, the first bulking fibers have a higher denier per filament, and/or mass per fiber, than the heat and flame resistant fibers  201 , and the second bulking fibers  204  have a higher denier per filament, and/or mass per fiber, than the first bulking fiber  203  and the heat and flame resistant fibers  201 . Also, the voluminous bulking zone  220  is divided into a first bulking zone  230  and a second bulking zone  240 . The first bulking zone  230  has an outer boundary  231  located adjacent to the heat and flame resistant zone  210  and inner boundary  232  located adjacent to the second bulking zone  240 . The second bulking zone  240  has an outer boundary  241  located adjacent to the outer surface of the shield material  200  and an inner boundary  242  located adjacent to the first bulking zone  230 . As previously stated, the shield material  200  is a unitary material, and as such, the boundaries of the two bulking zones do not represent the delineation of layers, but areas with in the unitary material. Because the shield material  200  is a unitary material, and the first bulking zone  230  and the second bulking zone  240  are not discrete separate layers joined together, various individual fibers will occur in both the first bulking zone and the second bulking zone  240 . Although  FIG. 2  illustrates the heat and flame resistant zone  210  being a smaller thickness than the voluminous bulking zone  220 , the relative thickness of the two zones can have a substantially different than as shown. 
   Still referring to  FIG. 2 , the first bulking zone  230  contains both the first bulking fibers  203  and the second bulking fibers  204 . However, the first bulking zone  230  will contain more of the first bulking fibers  203  than the second bulking fibers  204 . The distribution of the fibers in the first bulking zone  230  is such that the concentration of the first bulking fibers  203  increases in a gradient along the z direction from the outer boundary  231  of the first bulking zone  230  to a first bulking fiber concentration plane  235  located between the inner boundary  232  and the outer boundary of the first bulking zone. Also, as illustrated, it is preferred that the concentration of the first bulking fibers  203  decreases in a gradient along the z-axis from the first bulking fiber concentration plane  235  to the inner boundary  232  of that zone. 
   Referring still to  FIG. 2 , the second bulking zone  240  contains both the first bulking fibers  203  and the second bulking fibers  204 . However, the second bulking zone  240  will contain more of the second bulking fibers  204  than the first bulking fibers  203 . The distribution of the fibers in the second bulking zone  240  is such that the concentration of the second bulking fibers  204  is greater at the outer boundary  241  of the second bulking zone  240  than the inner boundary  242  of that zone. Also, as illustrated, it is preferred that the concentration of the second bulking fibers  204  decreases in a gradient along the z-axis from the outer boundary  241  of the second bulking zone  240  to the inner boundary  242  of that zone. 
   Still referring to  FIG. 2 , the first bulking zone  230  will also contain heat and flame resistant fibers  201 . However, the first bulking zone  230  will contain more of the first bulking fibers  203  than the heat and flame resistant fibers  201 . The heat and flame resistant zone  210  can have some amount of the second bulking fiber  204 ; however, the amount of second bulking fiber  204  in the heat and flame resistant zone  210  is significantly lower than the first bulking fibers  203 . The second bulking zone  240  can also have some amount of the heat and flame resistant fibers  201 ; however, the amount of the heat and flame resistant fibers  201  in the second bulking zone is significantly lower than the first bulking fibers  203 . An advantage of using the two distinct bulking fibers  203 / 204  ( FIG. 2 ) over using a single bulking fiber  102  ( FIG. 1 ), is that for the same respective weights of heat and flame resistant fibers  101 / 201  and voluminous bulking fibers  102 / 202 , a shield material  200  having two types of bulking fibers  203  and  204  will have fewer heat and flame resistant fibers  201  located in the voluminous bulking zone  120 / 220  than a shield material  100  having only one type of bulking fiber  102 . 
   Referring now to  FIG. 3 , there is shown a diagram of a particular piece of equipment  300  for the process to form the planar unitary heat and flame shield from  FIGS. 1 and 2 . A commercially available piece of equipment that has been found satisfactory in this process to form the claimed invention is the “K-12 HIGH-LOFT RANDOM CARD” by Fehrer A G, in Linz, Austria. The heat and flame resistant fibers  101 / 201  and the voluminous bulking fibers  102 / 202  are opened and blended in the appropriate proportions and enter an air chamber  310 . In an embodiment using the binder fibers  105 / 205 , the binder fibers  105 / 205  are also opened and blended with the heat and flame resistant fibers  101 / 201  and the bulking fibers  102 / 202  prior to introduction into the air chamber  310 . In an embodiment where the voluminous bulking fibers  202  contain multiple types of bulking fibers  203 / 204 , those multiple types of bulking fibers  203 / 204  are also opened and blended in the appropriate portions with the other fibers before introduction into the air chamber  310 . The air chamber  310  suspends the blended fibers in air, and delivers the suspended and blended fibers to a roller  320 . The roller  320  rotates and slings the blended fibers towards a collection belt  330 . The spinning rotation of the roller  320  slings the heavier fibers a further distance along the collection belt  330  than it slings the lighter fibers. As a result, the mat of fibers collected on the collection belt  330  will have a greater concentration of the lighter fibers adjacent to the collection belt  330 , and a greater concentration of the heavier fibers further away from the collection belt  330 . 
   In the embodiment of the shield  100  illustrated in  FIG. 1 , the heat and flame resistant fibers  101  are lighter than the voluminous bulking fibers  102 . Therefore, in the process illustrated in  FIG. 3 , the heat and flame resistant fibers  101  collect in greater concentration near the collection belt  330 , and the voluminous bulking fibers  102  collect in greater concentration away from the collection belt  330 . It is this distribution by the equipment  300  that creates the heat and flame resistant zone  110  and the voluminous bulking zone  120  of the planar unitary shield material  100 . 
   In the embodiment of the shield  200  illustrated in  FIG. 2 , the heat and flame resistant fibers  201  are lighter than the voluminous bulking fibers  202 . Therefore, in the process illustrated in  FIG. 3 , the heat and flame resistant fibers  201  collect in greater concentration near the collection belt  330 , and the voluminous bulking fibers  202  collect in greater concentration away from the collection belt  330 . It is this distribution by the equipment  300  that creates the heat and flame resistant zone  210  and the voluminous bulking zone  220  of the planar unitary shield material  200 . Additionally, the first bulking fibers  203  of the voluminous bulking fibers  220  are lighter than the second bulking fibers  204 . Therefore, in the process illustrated in  FIG. 3 , the first bulking fibers  203  are collected in greater concentration nearer the collection belt  330  than the second bulking fibers  204 . It is this distribution that creates the first bulking zone  230  and the second bulking zone  240  of the voluminous bulking zone  220  of the planar unitary shield material  200 . 
   In one example of the present invention, planar unitary heat and flame resistant shield material was formed from a blend of four fibers including:
         1) 4% by weight of a heat and flame resistant fiber being 2 dpf partially oxidized polyacrylonitrile   2) 25% by weight of a first bulking fiber being 6 dpf polyester   3) 41% by weight of a second bulking fiber being 15 dpf polyester, and   4) 30% by weight of a low melt binder fiber being 4 dpf core sheath polyester with a lower melting temperature sheath.
 
The fibers were opened, blended and formed into a shield material using a K-12 HIGH-LOFT RANDOM CARD” by Fehrer AG. The shield had a weight per square yard of about 16–32 ounces and a thickness in the range of about 12–37 mm. In the resulting shield material, the heat and flame resistant fibers in the heat and flame resistant zone comprised at least 70% of the total fibers in that zone, and the heat and flame resistant fibers in the voluminous bulking zone were less than about 2% of the total fibers in that zone.
       

   Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. For example, an additional layer of material such as a nonwoven can be added to the outside surface or the inside surface of the present invention for additional purposes. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

Technology Classification (CPC): 3