Patent Publication Number: US-2021172095-A1

Title: Flame Retardant Fiber with Preservative and Products Formed Therefrom

Description:
BACKGROUND 
     Safety concerns and regulatory requirements dictate that many textile-laden products, such as body supports or bedding, should exhibit fire-retardant and/or antimicrobial properties. The textile fibers and yarns used in making such products may supply the desired properties. 
     Although there are existing fibers made from fire-retardant viscose rayon incorporating thiabendazole, an antifungal agent and parasiticide, thiabendazole is not approved for apparel use. Moreover, thiabendazole has been shown to block angiogenesis in human and animal cells and may serve as a vascular disrupting agent to reduce newly established blood vessels. As such, there may be significant regulatory hurdles in obtaining approval for use of thiabendazole in fiber or yarn used for body supports, bedding, or any other textile which comes into frequent contact with the human body. 
     Thus, a need exists for safe, durable and cost-effective fire-retardant and microbial fibers or yarn that would be useful for a wide range of applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  is a cross-sectional view of a sheath-and-core yarn made in accordance with the present disclosure; 
         FIG. 2  is an exploded perspective view of a mattress in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     As used herein, the terms “about,” “approximately,” or “generally,” when used to modify a value, indicates that the value can be raised or lowered by 5% and remain within the disclosed embodiment. 
     Generally speaking, the present invention is directed to a fire-retardant and antimicrobial rayon fiber. The fiber includes zinc pyrithione as an antimicrobial agent. The rayon may be in the form of viscose rayon, Lyocell/Tencel, or any other suitable form. The present invention is further directed to a yarn that includes the fire-retardant and antimicrobial rayon fiber. The yarn may be a sheath-and-core yarn where the fire-retardant and antimicrobial rayon fiber is incorporated into the sheath, and the core is formed from fiberglass or any other suitable material. The present invention is further directed to a fabric formed from the fire-retardant and antimicrobial rayon fiber, such as a nonwoven fabric, a knit fabric, or a woven fabric. Moreover, the present invention is further directed to an article such as one or more layers of a mattress or bedding formed from the fire-retardant and antimicrobial rayon fiber. 
     The present invention is directed to a fire retardant (FR) fiber with an antimicrobial, i.e., antibacterial and/or antifungal, additive. The fiber can be formed from a fire retardant (FR) such as FR cellulose including FR viscose and FR rayon. The cellulose may also be regenerated cellulose. Moreover, the cellulose rayon may be in the form of Lyocell/Tencel fibers. In addition, the fibers may include a fire retardant such as amorphous silicon dioxide. Cellulose fibers incorporating amorphous silicon dioxide are inherently fire-retardant and therefore do not require treatment with extrinsic fire-retardant agents that can release hazardous compounds during use, or that can otherwise be removed or rendered ineffective upon liquid contact from spills, urination, sweating, or routine washing. Optionally, magnesium may be added as a component of the fibers. Most importantly, the fibers include zinc pyrithione (also known as zinc omadine), an antimicrobial agent that has both antibacterial and antifungal properties. By including zinc pyrithione in the fiber production step, the need for post-processing any yarns and/or fabrics made from the fiber for the purpose of adding antimicrobial properties is eliminated. 
     The cellulose may be present in the fiber in an amount ranging from about 80 wt. % to about 98 wt. %. The fire retardant, i.e., amorphous silicon dioxide or silica, may be present in the fiber in an amount ranging from about 2 wt. % to about 23 wt. %. The zinc pyrithione may be present in an amount ranging from about 0.04 wt. % to about 1 wt. %. In addition, magnesium may be present in an amount ranging from 0 wt. % (i.e., no magnesium included) to about 20 wt. %. In one particular embodiment, the zinc pyrithione antimicrobial agent may be present in an amount of about 0.1 wt. % or 1000 parts per million (ppm), which includes about 200 ppm of zinc. 
     The antimicrobial agent zinc pyrithione has both fungistatic and bacteriostatic properties. In other words, zinc pyrithione inhibits the division of fungal cells and inhibits bacterial cell division. In particular, zinc pyrithione has been shown to inhibit the growth of fungi in the form of both yeasts and molds. Additionally, zinc pyrithione inhibits the growth of a broad spectrum of both Gram positive and Gram negative bacteria. Thus, zinc pyrithione can be commonly used as an antifungal and/or antibacterial agent. Zinc pyrithione in particular quantities is safe for topical use on humans and is commonly used as an active ingredient in treatments for dandruff and other fungal or bacterial ailments. Thus, zinc pyrithione may be an optimal antimicrobial agent for use in a variety of applications, e.g., products that humans come into frequent contact with, such as mattresses, bedding, and other textiles in which it is both important and highly desirable to avoid the growth of fungus or bacteria. 
     The fibers of the present invention can be made by, for instance, a coextrusion process known to one skilled in the art. For example, the silica, zinc pyrithione, and magnesium can be added to the cellulose. Then, the mixture can be extruded through a spinnerette into a solution to form the fibers. Optionally, the silica, magnesium, and zinc pyrithione may be added in the production process by immersing the extruded rayon fibers in a bath containing these components and then drying the fibers. 
     The present invention may be further directed to a yarn formed from the fire-retardant fiber having an antimicrobial, e.g., antibacterial and/or antifungal, additive as described above. For instance, the yarn can be a yarn having a fiber sheath and filament core structure as illustrated in  FIG. 1 . In a sheath-and-core arrangement, the core component  101  is fully surrounded by the sheath fiber component  102 , such as by spinning a sheath of fiber material  103  around a core filament material. The sheath material  103  may be formed from the fiber of the present disclosure. Spinning of sheath fibers around the core may utilize air jet, air vortex, ring, open end, or friction spinning methods. 
     The core of the yarn contemplated by the present disclosure can include any suitable material. For instance, the core can include fiberglass, carbon, ceramic, quartz, or a combination thereof. The core can be in the form of one or more continuous filaments of the inorganic material, such as from about 1 to about 2000 filaments, such as from about 25 to about 1850 filaments, such as from about 50 to about 1700 filaments. The one or more filaments can each have a diameter ranging from about 1 micron to about 50 microns, such as from about 2 microns to about 40 microns, such as from about 3 microns to about 50 microns. Regardless of the specific number and type of continuous filaments utilized, the core of continuous filaments can be present in an amount ranging from about 25 wt. % to about 75 wt. %, such as from about 30 wt. % to about 60 wt. %, such as from about 35 wt. % to about 50 wt. % based on the total weight of the yarn. 
     The sheath of the yarn contemplated by the present disclosure can be formed from the flame-retardant fiber having zinc pyrithione as an antimicrobial additive as described above. In addition, the sheath may contain the fire-retardant, antimicrobial fiber as described above in addition to one or more other fibers to form a sheath blend. The sheath can be present in an amount ranging from about 25 wt. % to about 75 wt. %, such as from about 30 wt. % to about 60 wt. %, such as from about 35 wt. % to about 50 wt. % based on the total weight of the yarn. 
     The fiber of the present disclosure may be formed into a fabric. For instance, a yarn as described above may be used to make a woven fabric or a knit fabric. Additionally or alternatively, the fiber of the present disclosure may be used to form a nonwoven material, e.g., a nonwoven fabric. Because the fiber of the present disclosure has fire-retardant and antimicrobial, e.g., antibacterial and antifungal, properties, the fiber of the present disclosure thus eliminates the need to post-finish a yarn or fabric with antimicrobial additives after the formation of the yarn or fabric. As a result, the number of steps to produce the fabric or yarn, and the cost of such production, is significantly reduced. 
     The fiber of the present invention, having the characteristics described above, may be used in a wide variety of applications. For instance, when formed into a fabric, such fabric may be used as a layer of fire-retardant and antimicrobial, e.g., antibacterial and antifungal, fabric in a variety of end products. The fabric can be a nonwoven fabric formed from the fibers, a knit fabric incorporating yarns formed from the fibers, or a woven fabric incorporating yarns formed from the fibers. A woven fabric of the present invention may use of any suitable weaving pattern known in the art such as a “crowfoot” or broken twill, plain, basket, oxford, satin, twill, or any other weaving pattern as is suitable for the intended use of the fabric. 
     In some aspects, the fabric can be used as one or more layers within a mattress  200 , as shown in  FIG. 2 . For instance, the fabric can form an antimicrobial fire barrier between the mattress support layer(s), e.g., foam layers  202  and  204 , and the mattress ticking  210  to act as a thin fabric layer to protect the support layer(s), e.g., foam layers  202  and  204 , from catching on fire. Additionally or alternatively, the fiber of the present invention can be incorporated directly into the mattress ticking  210 , including as part of a cushioned or pillow-top mattress upper surface  212 . Ultimately, the fiber of the present disclosure, incorporated into a woven fabric, a knit fabric, or a nonwoven fabric, could be incorporated into any layer within a mattress. Such fabric may also be used to form one or more layers in another bedding product, such as a comforter, duvet insert, or pillow. 
     However, in addition to the mattress  200  illustrated in  FIG. 2 , it should be understood that a woven, knit or nonwoven fabric incorporating the fiber of the present disclosure may be used to form any textile product in which it is desirable to have fire-retardant and antimicrobial properties. For instance, the fiber of the present disclosure could be incorporated into carpets; furnishings, e.g., upholstered furnishings; textiles, e.g., hospital textiles, sports textiles, and socks; footwear; wipes and towels; and bandages, dressings, and other hospital applications. 
     EXAMPLES 
     A knit fabric was produced containing fire-retardant rayon with zinc pyrithione added during the FR rayon fiber production, as described above (the “ZnPt sample”). As shown in Table 1, the FR rayon contained 0.1 wt. % zinc pyrithione (1000 ppm). The FR rayon including the zinc pyrithione made up 43.49 wt. % of the fabric. In addition, a conventional fabric formed of FR rayon with thiabendazole (TBZ) antifungal agent added during the fiber production was provided for comparison (the “comparative sample”). The comparative knit fabric sample included between 0.04 wt. % and 0.1 wt. % (between 400 and 1000 ppm) of TBZ in the fibers. Additionally, the FR rayon containing TBZ was present in an identical amount as the test sample, i.e., 43.49 wt. % of the total fabric was made up of the FR rayon containing TBZ. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 TBZ 
                 ZnPt 
               
               
                 Active ingredient 
                 (Thiabendazole) 
                 (Zinc Pyrithione) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Percent FR Rayon 
                 43.49% 
                 43.49% 
               
               
                 (containing antifungal) 
               
               
                 in fabric 
               
               
                 Percent of active antifungal 
                 400-1000 PPM 
                 1000 PPM ZnPt 
               
               
                 in FR Rayon portion 
                   
                 (200 PPM Zn) 
               
               
                 Antibacterial Activity 
               
               
                 (determined by JIS L 
               
               
                 1902: 2015) 
               
               
                 
                   Staph aureus 
                 
                 1.2 
                 3.9 
               
               
                 Kleb pneumoniae 
                 −0.6 
                 3.4 
               
               
                 AATCC 30 Part III 7 day 
               
               
                 Mineral salts agar w/3% 
               
               
                 Glucose 
               
               
                 Aspergillus niger 
                 Macroscopic and 
                 No macroscopic or 
               
               
                 (sample 1) 
                 microscopic 
                 microscopic growth; 
               
               
                   
                 growth on sample; 
                 ZOI: 20 × 40 mm 
               
               
                   
                 No ZOI 
               
               
                 Aspergillus niger 
                 Macroscopic and 
                 No macroscopic or 
               
               
                 (sample 2) 
                 microscopic 
                 microscopic growth; 
               
               
                   
                 growth on sample; 
                 ZOI: 26 × 50 mm 
               
               
                   
                 No ZOI 
               
               
                   Penicillum  sp. 
                 No macroscopic or 
                 No macroscopic or 
               
               
                 (sample 1) 
                 microscopic 
                 microscopic growth; 
               
               
                   
                 growth; 
                 Insufficient growth of 
               
               
                   
                 No ZOI 
                 organism for ZOI 
               
               
                   Penicillum  sp. 
                 No macroscopic or 
                 No macroscopic or 
               
               
                 (sample 2) 
                 microscopic 
                 microscopic growth; 
               
               
                   
                 growth; 
                 ZOI: 30 × 40 mm 
               
               
                   
                 No ZOI 
               
               
                   
               
            
           
         
       
     
     Both the test sample and the comparative sample were tested for antibacterial activity in accordance with the Japanese Industrial Standards (JIS) method L 1902:2015, titled “Testing Antibacterial Activity and Efficacy on Textile Products,” which is designed to test the ability of fabrics that have been treated with antimicrobial agents to prevent microbial growth and to kill microorganisms over an 18 hour period. Both  Staph aureus  and  Kleb pneumoniae  bacteria were used in this test. Each test microorganism was prepared by growth in a liquid culture medium, then a suspension of test microorganism was standardized by dilution in a nutritive broth. Each of the ZnPt sample fabric and the comparative sample fabric were then inoculated with the microorganisms. Initial microbial concentrations were determined for each fabric at “time zero,” and then the final microbial concentrations were determined after 18 hours of undisturbed incubation. The antibacterial activity was calculated by subtracting the logarithm of the average numbers of bacteria after incubation from the logarithm of the average initial number of bacteria at time zero. A higher value for antibacterial activity corresponds to increased prevention of microbial growth and/or kill of microorganisms present. 
     As shown in Table 1, in the testing performed in accordance with the JIS L 1902:2015 standard, the ZnPt fabric sample showed significantly improved antibacterial activity as compared to the comparative sample with both the  Staph aureus  and  Kleb pneumoniae  bacteria tests. The ZnPt fabric test resulted in an antibacterial activity value of 3.9 for  Staph aureus  whereas the comparative fabric had an antibacterial activity value of only 1.2 for the same bacteria. Similarly, ZnPt fabric test resulted in an antibacterial activity value of 3.4 for  Kleb pneumoniae . In contrast, the comparative fabric had an antibacterial activity value of −0.6 for the same bacteria, indicating that the bacteria concentration actually increased instead of decreasing in the presence of the TBZ-containing fabric. 
     Both the ZnPt fabric and the test fabric were additionally tested in accordance with the American Association of Textile Chemists and Colorists (AATCC) test method 30, part 3, titled “Antifungal Activity, Assessment on Textile Materials: Mildew and Rot Resistance of Textiles.” This method is an antimicrobial test commonly used for textiles where growth would harm a product&#39;s visual appeal but not necessarily its material strength. The 7-day version of this test was performed using 3% glucose. This test was performed using samples of both  Aspergillus niger  fungus and  Penicillum  sp. fungus. In this test, samples of each fungus were grown on a solid medium and a spore suspension was created. Then, an agar medium was prepared in a petri dish and inoculated with the spore suspension of the respective fungus before placement of the fabric sample. The fabric sample was placed on top of the inoculated agar medium, and the top of the fabric sample was also inoculated with the spore suspension after placement. The petri dishes were sealed to maintain humidity during a 7-day incubation period. Finally, each inoculated test sample was evaluated after the 7-day period and rated whether it had macroscopic (i.e., visible with the naked eye), microscopic, or no visible growth of the fungus. Additionally, the zone of inhibition (“ZOI”), if any, was measured. The zone of inhibition is the area surrounding the fabric sample that is clear of the fungus as a result of the antimicrobial agent leaching from the fabric sample into the agar and exerting a growth-inhibiting effect. 
     In the AATCC 30 test, the ZnPt fabric sample again exhibited significantly better antimicrobial results as compared to the TBZ comparative sample. No macroscopic or microscopic growth was found in any sample performed on the ZnPt fabric. In comparison, the TBZ comparative sample resulted in both microscopic and macroscopic growth of  Aspergillus niger  in both samples. Moreover, the ZnPt fabric resulted in a significant zone of inhibition (ZOI) resulting from the antimicrobial agent zinc pyrithione inhibiting the growth of the fungus surrounding the fabric in nearly every sample. In contrast, even when the comparative TBZ fabric showed no growth on the fabric of  Penicillum  sp., it did not exhibit any zone of inhibition surrounding the fabric. 
     These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.