Patent Publication Number: US-2006000024-A1

Title: Mattress having a flammable core and a nonwoven cellulose flame retardant fabric

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This is a continuation-in-part of U.S. patent application No. 10/298,990, filed Nov. 18, 2002, and entitled “FLAME-RETARDANT NONWOVENS.” 
    
    
     BACKGROUND OF THE INVENTION  
      1) Field of the Invention  
      The present invention concerns a mattress having a flammable core and a cellulosic flame-retardant (FR) nonwoven fabric that at least partially encloses the flammable core. While the present invention is described in terms of a mattress, the invention applies equally well to mattress foundations. The nonwoven fabric comprises from about 65 to about 85 weight percent (wt. %) cellulosic flame retardant fibers, and from about 15 to about 35 weight percent of low melt binder (bicomponent fiber or low-melting fiber), the nonwoven fabric prepared from these components, has a basis weight of about 5 to about 20 oz./sq. yd. and is capable of passing stringent flame-resistant tests.  
      2) Prior Art  
      Flame-retardant (FR) or flame-resistant materials are well known to those skilled in the textile art. Such materials can be woven or nonwoven, knitted, or laminates with other materials such that they pass various textile FR or flame-resistant tests, such as California TB 117 &amp; TB 133 for upholstery; NFPA 701 for curtains and drapes; and California TB 129 dated October, 1992, concerning flammability test procedures for mattresses for use in public buildings. Another test for residential mattresses is California TB603. The criterion for compliance for TB 603 is as follows: 
          Less than 25 MJ of total heat release at 10 minutes after burner ignition, and     Less than 200 kW of heat release rate for the duration of 30 minutes after burner ignition. 
 
 Two burners are used to initiate the test. One on the panel, flame duration of 70 seconds, and one on the border with a flame duration of 50 seconds. Both are lit simultaneously. 
       

      Various FR fibers are well known to those skilled in the textile art. FR fibers based on polyester, rayon, melamine, nylon, acrylic, and polyolefin fibers such as polyethylene or polypropylene fibers, are known and commercially available.  
      U.S. Pat. No. 6,214,058 issued to Kent et al. on Apr. 10, 2001, describes fabrics made from melamine fibers that may or may not be flame-resistant fabrics. This reference describes a process for dyeing melamine fabrics including blends of melamine and natural fibers (such as wool or cotton) or other synthetic fibers such as rayon or polyester. As a passing comment, it mentions that the melamine fiber may be FR.  
      U.S. Pat. No. 6,297,178 issued to Berbner et al. on Oct. 2, 2001, discloses flameproof fabrics based on FR melamine fibers and FR rayon fibers. The melamine and rayon fibers are made FR by coating the fibers with aluminum.  
      U.S. Pat. No. 4,863,797 (Sep. 5, 1989); U.S. Pat. No. 5,208,105 (May 4, 1993); U.S. Pat. No. 5,348,796 (Sep. 20, 1994); U.S. Pat. No. 5,503,915 (Apr. 2, 1996); U.S. Pat. No. 5,513,916 (Apr. 2, 1996); and U.S. Pat. No. 5,506,042 (Apr. 9, 1996) issued to Ichibori et al. disclose an FR composite fiber comprising: (A) 85 to 15 parts by weight of a fiber comprising a polymer containing 17 to 86% by weight of a halogen, and 6 to 50% by weight of an Sb compound based on the polymer, and (B) 15 to 85 parts by weight of at least one fiber selected from the group consisting of natural fibers and chemical fibers, the total amount of the fibers (A) and (B) being 100 parts by weight.  
      PCT application WO 03/023108 filed Sep. 11, 2002 in the name of Mater and Handermann discloses a highloft FR material composed of FR rayon or FR melamine that are inherently FR. Additionally the application also discloses and requires the use of modacrylic fibers. These materials have no coating thereon.  
      In spite of the above-mentioned patents and numerous other nonwoven FR fabrics, there is still a need in the mattress industry to create economical mattresses that pass the stringent guidelines for the California TB 603 and/or 129.  
      Generally, the California TB 129 test for mattresses states that the mattress may char, but not burn through, for a minimum of three minutes based on certain conditions such as the position of the flame, the temperature of the flame, the source of fuel being used, etc. Furthermore, after one hour (57 minutes after the flame source has been extinguished) of burning the test is terminated and certain conditions must be met, as more fully set forth herein.  
      For the California TB 603, the test for mattresses states that two burners are used to initiate the test. One on the panel, flame duration of 70 seconds, and one on the border with a flame duration of 50 seconds. Both are lit simultaneously. Then 10 minutes after burner ignition the mattress must emit less than 25 MJ of total heat release. Also for the duration of 30 minutes after burner ignition the mattress must emit less than 200 kW of heat release rate.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a mattress having a flammable core and a cellulosic flame-retardant (FR) nonwoven fabric that at least partially encloses the flammable core wherein the mattress is capable of passing the California TB 603 and/or 129 tests.  
      The nonwoven fabric/article, as a component of the mattress of the present invention, has from about 65 to about 85 weight percent (wt. %) cellulosic flame retardant fibers, and from about 15 to about 35 weight percent of low melt binder (bicomponent fiber or low-melting fiber), the nonwoven fabric prepared from these components, has a basis weight of about 5 to about 20 oz./sq. yd. Optionally, up to 20 wt. % of other fibers may be employed. The other fibers may be synthetic (this includes manufactured/man-made fibers) and/or from natural fibers. The cellulosic fibers may be inherent FR fibers or post treated, coated FR fibers.  
      In the broadest sense, the present invention relates to a mattress having a flammable core with a cellulosic FR nonwoven fabric at least partially enclosing the flammable core, wherein the nonwoven fabric comprises from about 65 to about 85 wt. % FR cellulosic fibers and from about 15 to about 35 weight percent of low melt binder, and optionally up to 20 wt. % of other synthetic and/or natural fibers.  
      In the broadest sense, the present invention relates to a mattress having a flammable core with a nonwoven fabric at least partially enclosing the flammable core, wherein the nonwoven fabric comprises from about 65 to about 85 wt. % FR cellulosic fibers and from about 15 to about 35 weight percent of low melt binder, wherein said fabric has a basis weight of about 5 to about 20 ounces per square yard. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
      The FIGURE is a graph of heat transmittance temperature in degrees Fahrenheit versus weight percent low melt binder for simple rayon/low melt binder nonwoven constructions. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The mattress of the present invention has a flammable core containing foam, wood, or fabrics, for example. The flammable core combusts in a fire and can contribute to the injury of a user. To prevent this or at least greatly impede the combustion of the flammable materials, a nonwoven cellulosic FR fabric is employed to at least partially enclose the flammable core. The nonwoven fabric, among other things, forms a char upon being exposed to excess heat. If the core is totally enclosed in the fabric, then the char minimizes the flame from burning the flammable core.  
      The nonwoven FR fabric comprises from about 65 to about 85 wt. % cellulosic FR fiber and from about 15 to about 35 wt. % low melt binder. The cellulosic FR fibers are either inherently flame resistant, or are post treated (coated) with an FR coating. Inherent FR fibers are those that have FR material incorporated into the structure prior to formation of the fiber. Post treated FR fibers are those that apply a FR coating after the formation of the fiber. Suitable FR fibers are those that when made into a fabric, as a component for a mattress, can pass California TB 603 and/or 129. FR fabrics having too little flame resistance are not suitable for the present invention.  
      Suitable cellulosic FR fibers are fibers of rayon, cotton, hemp, jute, flax, kenaf, cellulose acetate or a mixture of 2 or more of these. Inherent FR fibers employed in the fabric component of the present invention are FR rayon, sold under the registered trademark “Visil” by Säteri Oy, or Lenzing Fibers and marketed as Lenzing FR Visil is permanently fire resistant (“inherent”) as described in patent U.S. Pat. No. 5,417,752 to Paren et al. The silica forms an insulating barrier to the source of heat. Lenzing FR has a fire retardant chemical incorporated into the rayon itself. On the other hand, post treated FR coated fibers may be any of the above suitable cellulosic fibers coated with a suitable amount of FR composition.  
      The post treated FR coating employed is nontoxic, such as non-halogenated (halogenated coatings release harmful gasses upon exposure to heat) and has phosphorus, a phosphorus compound, red phosphorus, esters of phosphorus, or phosphorus complexes. Typically, the FR coating resin is clear or translucent latex (where color is important, or any color and not translucent where color is unimportant) and can be applied by spraying, saturation, meniscus coating, foaming or padding the fiber. A suitable commercially available FR coating resin is known by the trade name “GLOTARD” made by GLO-TEX Chemicals in Spartanburg, South Carolina. There are different GLOTARD variants and those skilled in the textile art can pick and choose among them to find that which is most compatible, taking into account such things as cost, appearance, smell, and the effect it may have on the other fibers in the nonwoven batt (does it make the other fibers rough, or have a soft hand, or discolor the other fibers). The FR coating resin may be applied to the nonwoven batt in a range from about 6 to about 25 weight percent of the nonwoven batt. It is also within the scope of the invention to apply the FR coating to just a portion of the fibers before such fibers are employed in the nonwoven batt. For example, the FR coating could be applied to the fibers, before they are dry laid/air laid onto a conveyor belt. Nevertheless, when considering the nonwoven batt as a whole, the amount of the FR coating remains within the range of 15 to 35 weight percent of the nonwoven batt. More typically the FR coating is applied in a range from about 15 to about 25 wt. % of the fibers to which it is applied.  
      The FR fibers come in different deniers from approximately 1.5 to about 10 dpf (denier per filament).  
      The low melt binder may be either a bicomponent fiber, for example, or a low melt polymer fiber. The low melt binder is generally employed in a range of from about 15 to about 35 weight percent of the nonwoven batt. The bicomponent fiber generally contains a low melt portion and a high melt portion. Consequently, the bicomponent fiber may be either the side-by-side type wherein the low melt component is adjacent to high melt component, or the sheath-core type wherein the high melt component is the core and the low melt component forms the sheath. Such bicomponent fibers are well known to those skilled in the textile art and may be based upon polyolefin/polyester, copolyester/polyester, polyester/polyester, polyolefin/polyolefin, wherein the naming convention is the low melt component followed by the high melt component. In those types wherein it is polyester/polyester, or polyolefin/polyolefin, the high melt component has at least 5 and preferably 8 degrees Fahrenheit higher melt temperature than the low melt temperature. More specifically, for example, a polyolefin/polyolefin could be polyethylene/polypropylene. Suitable bicomponent fibers are preferable a 50:50 low melt portion to high melt portion. But the present invention also contemplates a broader range of 20:80 to 80:20 for the bicomponent fiber.  
      Where the low melt binder is a low melt polymer fiber, those fibers mentioned above with respect to the low melt component of the bicomponent fiber are also suitable low melt polymer fibers. In other words, the low melt polymer fiber may be copolyester, or polyolefin, such as polyethylene. Lastly, the low melt binder may also be latex sprayed onto the nonwoven batt. In this situation, the latex employed has a low melt temperature so that once the latex is sprayed on to the nonwoven fiber batt, it can be cured by means of heat (subjecting the nonwoven batt to an oven for a short period of time sufficient to cure the latex). Such low melt binders are well known to those skilled in the textile art. Preferably, the low melt binder is in the form of bicomponent fibers.  
      Other fibers may optionally be employed up to about 20 wt. % of the nonwoven batt or fabric. The other fiber may be other FR fibers, either inherent or post treated FR coated fibers, or non-FR fibers; and they may be either synthetic or natural fibers. The other fibers are non-toxic, such as non-halogenated. Suitable non-FR synthetic fibers can be polyester such as polyethylene terephthalate (PET) or a copolyester, rayon, nylon, polyolefin such as polyethylene fibers, acrylic, melamine, and combinations of these. When non-FR synthetic fibers are employed, they give the batt certain characteristics like loft, resilience (springiness), tensile strength, and thermal retention, useful for household goods. Preferred other fibers are PET and rayon fibers. Suitable FR synthetic fibers are modacrylic fibers, inherent FR polyester such as that sold by Trevira as type CS, and the like.  
      Other fibers in the form of natural fibers may also be employed in the nonwoven batt of the present invention. Natural fibers such as flax, kenaf, hemp, cotton, and wool may be employed, depending on the properties desired. Preferred is cotton. These may be post treated to be FR or not.  
      One flame-resistant test for mattresses is the state of California, Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulation, Technical Bulletin 129. The purpose of this test is to set a standard for the behavior of mattresses used in public occupancy such as hotels, motels, dormitories, prisons, etc. Specifically, this test measures the mattress when it is subjected to a specific flaming ignition source under well-ventilated conditions. Under such conditions, it should char but not support flame for at least 3 minutes. The California TB 129 test specifies a fabric wrapped around foam with a horizontal flame at 1800 degrees Fahrenheit for 3 minutes. There can be no drips, and the fabric must contain the foam although the foam may be melted or partially melted. The fabric cannot let the flame reach and ignite the foam. California TB 603 is for residential mattresses. Two burners are used to initiate the test. One on the panel (the flat bottom of a mattress), flame duration of 70 seconds, and one on the border (side edge) with a flame duration of 50 seconds. Both are lit simultaneously. Then 10 minutes after burner ignition the mattress must emit less than 25 MJ of total heat release. Also for the duration of 30 minutes after burner ignition the mattress must emit less than 200 kW of heat release rate.  
      The nonwoven batt of the present invention may be constructed as follows. The various combinations of fibers that can be employed in the present invention may be weighed and then dry laid/air laid onto a moving conveyor belt, for example. The size or thickness of a nonwoven batt is generally measured in terms of ounces per square yard. The speed of the conveyor belt, for example, can determine or provide the desired batt weight. If a thick batt is required, then the conveyor belt moves slower than for a thin batt. The weight percent of the total fibers in the batt is 100 percent. This does not include the weight of the FR resin since it is not in fiber form. It does, however, include the bicomponent fibers.  
      Suitable nonwoven fabrics of the present invention have a batt weight greater than about 5 oz./sq. yd. Preferably the batt weight ranges from 5 oz./sq. yd. to 20 oz./sq. yd., with the most preferred range being 6 oz./sq. yd. to 11 oz./sq. yd. Using a batt weight greater than about 20 oz./sq. yd. offers no significant improvement in performance and is more costly. If desired, any rearrangement of the fibers such as by carding occurs next. After any desired rearrangement of the fibers, if there is any FR coating to be sprayed onto the nonwoven batt, then the conveyor belt transports the batt to an area where the spray-on material is applied. So the FR coated fibers can be coated prior to being laid during batt production, or the FR coating can be applied after the fibers are laid to form a batt. If the conveyor belt is foraminous, the excessive liquid FR resin drips through the belt and may be collected for reuse later. Once all the sprayed-on materials have been applied, if any, the conveyer belt can then move the nonwoven dry laid batt to an oven for melting and curing the low melt component of the bicomponent fiber or the low melt polymer fiber. The temperature and residence time in the oven depends on the fibers employed and is easily determinable by one skilled in the textile art. Thereafter, the nonwoven batt is cooled and cut to any size desired to serve as a component for a mattress. Alternatively after carding the nonwoven batt can be subjected to a spray to apply the FR coating.  
     GENERAL PROCEDURES  
      Various fiber components, some FR fibers (having a range of dpf between 1.5 and 10) and some synthetic fibers having a denier between 1.5 and 20 (primarily employed for optimizing physical properties of the nonwoven batt), are set forth in the various examples. Also, the weight of the fiber batt as well as the burn test results according to California TB 129, measured in seconds, are set forth in the examples.  
      More specifically, for Example 3, the specimen consisted of a twin-size, innerspring mattress and foundation set. The specimen was covered with a white/off-white-colored ticking material. The construction of the mattress is well described in California TB 129.  
      The test specimen, after conditioning to 73 degrees and 50 percent relative humidity was placed on a steel frame on a load cell platform along the far side of the test room. The specified propane burner was placed centrally and parallel to the bottom horizontal surface of the mattress 1 inch from the vertical side panel of the mattress. The computer data acquisition system was started, then the burner was ignited and allowed to burn for 180 seconds. The test was continued until either all combustion ceased, or one hour passed.  
      The specimen does not meet the test requirements if any of the following criteria are exceeded:  
      1. Weight loss of 3 lbs or greater in the first 10 minutes;  
      2. Maximum rate of heat release of 100 KW; or  
      3. Total heat release of 25 MJ in the first 10 minutes.  
      For Example 3, a pair of twin mattresses was tested under California TB 603 for residential use. The criterion for compliance with TB 603 is as follows: 
          Less than 25 MJ of total heat release at 10 minutes after burner ignition, and     Less than 200 kW of heat release rate for the duration of 30 minutes after burner ignition. 
 
 This test does not require a weight loss characteristic like the TB 129. 
       

     EXAMPLE 1  
      The various fibers (rayon and bicomponent fibers) were dry laid onto a moving conveyor belt as is known in the textile art. An FR resin (Glotex&#39;s Glotard FFR-2) was sprayed on to the nonwoven fiber batt at a 24 wt. % add-on. The bicomponent fiber was a low melt sheath component of copolyester and a high melt core component of PET. The denier per filament (dpf) of the FR rayon was 3.5. The nonwoven fiber batt was transported via the conveyor belt to an oven and thereafter cooled and cut to an 88 inches wide batt. The nonwoven batt was then subjected to a burn time test similar to the California TB 129 test. In the test, the nonwoven fabric was wrapped once around the foam. A flame was applied directly to the nonwoven fabric for at least 300 seconds and the structural integrity was noted. The test sample maintained its structural integrity for at least the time indicated, and the flame did not reach the foam. The burn time is listed in seconds. The batt weight is listed in ounces per square yard. The nonwoven batt construction and results are set forth below in Table 1.  
                                       TABLE 1                                   FR       Batt weight   Burntime       Sample   Rayon   PET   Resin*   Bico   (oz/yd 2 )   (seconds)                  1   80       (24)   20   9.5   600                 *Weight % based on weight of all other components.             
 
     EXAMPLE 2  
      In this example, the nonwoven batt includes 30 weight percent low melt binder (bicomponent fiber) and 70 weight percent FR coated rayon. The FR rayon was coated with 15 weight percent add-on FR coating resin from Glotex-Glotard FFR. The batt weight was 9 oz./sq. yd. The 30/70 batt had a heat transmittance value of about 520° Fahrenheit.  
      Generally for simple nonwoven batts constructed from low melt binder and FR coated rayon, there appears to be a “sweet spot” in terms of performance between 15% and 25% low melt binder, as illustrated in the Figure. Although there is a performance deterioration after about 30% low melt binder, such simple construction nonwovens are capable of passing the above identified tests. Therefore it offers a low cost solution for manufacturing FR mattresses, for example.  
     EXAMPLE 3  
      Two twin size mattresses were constructed and tested under TB 603 testing conditions. The construction of the barrier and the results from the test are set forth below.  
      Mattress Barrier Blend #1: D  
     
         
         
           
              Panel—70% treated rayon and 30% low melt.  
              Border—70% treated rayon and 30% low melt  
              Construction—Mattress was a two-sided, baseline-3, tight top produced by Restonic Mattress Corporation.  
           
         
       
    
      The TB603 data was as follows; 
          10-minute total heat release-1.07 MJ     30-minute heat release rate-0 kW.        

      Mattress #1 was TB 603 compliant.  
      Mattress Barrier Blend #2:  
     
         
         
           
              Panel—70% post treated cotton and 30% low melt  
              Border—70% post treated rayon and 30% low melt  
              Construction-Mattresses were two-sided, baseline-3, tight top produced by Restonic Mattress Corporation.  
           
         
       
    
      The TB603 data was as follows; 
          10-minute total heat release-2.15 MJ for Mattress 2-A and 1.61 MJ for Mattress 2-B     30-minute heat release rate-35 kW for Mattress 2A and 25 kW for Mattress 2B.        

      Both mattresses blends #2 (Mattress A and B) were TB 603 compliant.  
      Mattress Barrier Blend # 3:  
     
         
         
           
              Border—0.85 ounces per square foot-70% Treated Rayon and 30% low melt  
              Panel—0.85 ounces per square foot-70% Treated Rayon and 30% low melt  
              Construction—Two sided pillow top/polyurethane foam encased  
           
         
       
    
      The TB603 data was as follows; 
          10-minute total heat release-MJ=1.78     30-minute heat release rate-kW=28.21        

      Mattress #3 was TB 603 compliant.  
      Mattress Barrier Blend # 4:  
     
         
         
           
              Border—1.00 ounces per square foot-70% Treated Rayon and 30% low melt  
              Panel—1.00 ounces per square foot-70% Treated Rayon and 30% low melt  
           
         
       
    
      Mattress—One sided pillow top/336 coil count/polyurethane foam  
      The TB603 data was as follows; 
          10-minute total heat release-MJ =2.5     30-minute heat release rate-kW =7.0        

      Mattress #4 was TB 603 compliant.  
      Mattress Barrier Blend # 5: 
          Border—1.00 ounces per square foot-70% Treated Rayon and 30% low melt     Panel—1.00 ounces per square foot-70% Treated Rayon and 30% low melt     Mattress—One sided pillow top/528 coil count /visco &amp; latex foam        

      The TB603 data was as follows; 
          10-minute total heat release-MJ =4.8     30-minute heat release rate-kW=6.0        

      Mattress #5 was TB 603 compliant.  
      Thus, it is apparent that there has been provided, in accordance with the present invention, a nonwoven fabric that fully satisfies the objects, aims, and advantages set forth above. While the present invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the textile art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the present invention.