Abstract:
Polyurethane elastomer yarns (particularly spandex) containing certain silver-based antimicrobial formulations therein are provided. This invention relates to polyurethane elastomer yarns (particularly spandex) containing certain silver-based antimicrobial formulations therein. Such formulations comprise antimicrobial compounds, such as, preferably, triclosan and/or silver-containing ion-exchange resins, such as zirconium phosphate, glass, and/or zeolite compounds. The inventive spandex yarns exhibit excellent antimicrobial qualities as well as surprisingly good anti-tack/frictional characteristics. As a result, antimicrobial spandex yarns are provided which exhibit ease in processing, particularly in further knitting, weaving, etc., to produce fabrics therefrom. Such fabrics are also encompassed within this invention.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to polyurethane elastomer yarns (particularly spandex) containing certain silver-based antimicrobial formulations therein. Such formulations comprise antimicrobial compounds, such as, preferably, triclosan and/or silver-containing ion-exchange resins, such as zirconium phosphate, glass, or zeolite compounds. The inventive spandex yarns exhibit excellent antimicrobial qualities as well as surprisingly good anti-tack/frictional characteristics. As a result, antimicrobial spandex yarns are provided which exhibit ease in processing, particularly in further knitting, weaving, etc., to produce fabrics therefrom. Such fabrics are also encompassed within this invention.  
         DISCUSSION OF THE PRIOR ART  
         [0002]    All U.S. Pat. Nos. listed below are herein entirely incorporated by reference.  
           [0003]    There has been a great deal of attention in recent years given to the hazards of bacterial contamination from potential everyday exposure. Noteworthy examples of such concerns include the fatal consequences of food poisoning due to certain strains of  Eschericia coli  being found within undercooked beef in fast food restaurants; Salmonella contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to  Staphylococcus aureus, Klebsiella pneumoniae , yeast, and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various everyday products and articles. For instance, certain brands of polypropylene cutting boards, liquid soaps, etc., all contain antimicrobial compounds. The most popular antimicrobial for such articles is triclosan. Although the incorporation of such a compound within liquid or certain polymeric media has been relatively simple, other substrates, including the surfaces of textiles and fibers, have proven less accessible. Such compounds are highly desired for fibers and fabrics in order to provide not only antimicrobial benefits, but also mildew and odor control properties.  
           [0004]    There thus remains a long-felt need to provide an effective, durable, reliable antimicrobial spandex yarn which provides such long-term effects. Of additional importance is the need to provide such specific yarns that facilitate, or, at the very least, permit further processing into desired fabrics. Thus, such a desirable yarn must exhibit suitable anti-tack properties thereby permitting continuous utilization without appreciable obstacles to weaving, knitting, and the like, due to cohesion with other spandex yarns or adhesion to process machinery components. In the past, such anti-tack properties have been provided through the incorporation of different compounds, such as metallic soaps (U.S. Pat. No. 4,296,174 to Hanzel et al.), yarn surface finishes, and the like. However, such compounds do not provide antimicrobial characteristics as well.  
           [0005]    Other antimicrobial spandex yarns have been produced of the sheath-core type (Japanese Patent Application 6-146112 to Kawanabe) with the antimicrobial agent utilized within the sheath portion. However, such yarns are of the sheath-core variety that relies primarily on the elasticity of the core component for its ultimate function. There have been no teachings of such antimicrobial spandex yarns wherein the antimicrobial component is dispersed substantially throughout the target yarn itself. As such, there are definite differences and improvements upon utilization of complete antimicrobial yarns rather than such sheath-core types. For instance, it is important to realize that spandex yarns are not always utilized as in complete form from initial production. The yarns themselves are generally either cut for insertion within discrete areas of target fabrics or, upon incorporation within fabrics (e.g., knit, woven, non-woven, and the like), are cut for further insertion as fabric components within other fabrics. In such an instance, sheath-core yarns do not provide any appreciable increase in antimicrobial activity from standard initial production to “cut” configuration. By contrast, single-component yarns exhibiting antimicrobial compounds dispersed throughout provide desirable improvements in antimicrobial characteristics upon being cut since more antimicrobial is exposed.  
           [0006]    Another important distinction lies in the potential for moisture to mobilize the antimicrobial compounds within the target yarns. Spandex, being a polyurethane, is somewhat hydrophilic and draws moisture readily from the surrounding atmosphere. Upon such moisture regain by the target yarns, a silver-based antimicrobial (as one example) can exhibit migration of silver particles within and possibly to the surface of the target yarn. With a sheath-core configuration, the potential for relatively quick loss of such particles by moving to the surface (and subsequently removed by friction, etc.) is quite high, considering the short distance required to reach such a destination. However, a single component spandex yarn will not exhibit such high probabilities of rapid antimicrobial loss because of the greater amount of antimicrobial therein and thus the greater distance required for movement to the surface.  
           [0007]    Furthermore, with regard to silver-based inorganic antimicrobial materials, sheath-core yarn configurations are not particularly suitable for full efficacy thereof. For example, it has been found that certain silver-based ion-exchange compounds (such as ALPHASAN® brand antimicrobials available from Milliken &amp; Company) exhibit regenerable characteristics for antimicrobial properties. After a period of time, the silver solids become depleted through bactericidal activity; however, upon frictional contact with the substrate surface, new, unused silver components are brought to the surface, thus providing regenerable antimicrobial source. With a sheath-core configuration, the sheath itself is so thin that the amount of silver particles present therein is very limited. Thus, the antimicrobial lifetime of such a yarn is itself rather limited since very little extra silver particle source is available in such an instance. To the contrary, an entire yarn comprised of such silver particles will theoretically provide long-lasting, renewable antimicrobial properties.  
           [0008]    Additionally, sheath-core configured yarns have proven to be impractical from an industrial production standpoint as well. Sheath-core yarn configurations are limited to production by melt-spun processes. Most spandex yarns, however, are produced via solution-spun processes. Hence, sheath-core types are not widely available. Also, it is very difficult and expensive to uniformly produce sheath-core yarns due to the equipment required and/or available. The trouble inherent with controlling the sheath placement around the core is extremely difficult to handle on a large-scale level and thus limits production speeds.  
           [0009]    Thus, there is a need to provide long-lasting antimicrobial spandex yarns for incorporation within apparel and other fabrics that exhibit proper antimicrobial characteristics and is likewise processable into such fabrics, and the like. Unfortunately, to date, no such particular spandex yarns, or antimicrobial fabrics encompassing such yarns, has been accorded the apparel and fabric industries by the pertinent prior art.  
         DESCRIPTION OF THE INVENTION  
         [0010]    It is thus an object of the invention to provide a spandex yarn comprising silver-based inorganic antimicrobial throughout said yarn. It is further object of the invention to provide a fabric article comprising such spandex yarns, and more particularly an apparel article comprising same. Yet another object of the invention is to provide a spandex yarn (such as above) that exhibits excellent processability within fabric producing machines (e.g., weaving looms, knitting machines, and the like), such that said spandex yarns exhibit extremely low, if not nonexistent, levels a cohesion between different portions of individual spandex yarns or between portions of different spandex yarns. A further object is to provide such excellent processability without the need for high levels of finishing agents contacted with the target yarn substrate, thereby resulting in significant reductions of finishing chemicals used and process steps performed.  
           [0011]    Accordingly, this invention encompasses a spandex yarn comprising an antimicrobial compound in discrete areas of said yarn wherein at least some of said antimicrobial compound is present at the surface of said yarn and at least some of said antimicrobial is present within said yarn at a distance of from the center of such yarn to about least one-half the radius of said yarn from said yarn center. Furthermore, this invention also encompasses a fabric article comprising at least one spandex yarn as described above. Additionally, the invention encompasses a spandex yarn comprising at least one silver-based inorganic antimicrobial compound wherein said spandex yarn exhibits a cohesive property with either itself or a different spandex yarn of the same type of below about 0.8 grams as measured by an over-end take-off tension procedure (thereby exhibiting very low anti-tack properties). Also, this invention encompasses a spandex yarn as defined above, and exhibiting the aforementioned anti-tack characteristics without the presence of an appreciable amount of anti-tack finishing agents thereon.  
           [0012]    The antimicrobial compound of this invention may be any type which imparts the desired log kill rates discussed below to  Staphylococcus aureus  and  Klebsiella pneumoniae . Furthermore, such compounds must be able to be incorporated within the target spandex yarns. Thus, silver-based antimicrobials, triclosan, and the like, and non-limiting potential compounds for this purpose. The preferred compounds are silver-based inorganic antimicrobials which include silver particles or silver ions that exhibit such antimicrobial effects. More preferred compounds are those selected from the group consisting of silver-based ion-exchange resins, such as silver-based zirconium phosphates, silver-based zeolites, silver-based glasses, and any mixtures thereof. Most preferably, such a compound is a silver-based ion-exchange compound and particularly does not include any added organic bactericide compounds (thereby not permitting a release of volatile organic compounds into the atmosphere during processing at high temperatures, etc.). The preferred silver-based ion exchange material is an antimicrobial silver zirconium phosphate available from Milliken &amp; Company, under the tradename ALPHASAN®. Other potentially preferred silver-containing solid inorganic antimicrobials in this invention are silver-substituted zeolites available from Sinanen under the tradename ZEOMIC®, or a silver-substituted glasses available from Ishizuka Glass under the tradename IONPURE®, may be utilized either in addition to or as a substitute for the preferred species. Other possible compounds, again without limitation, are silver-based materials such as MICROFREE®, available from DuPont, as well as JMAC®, available from Johnson Mathey. Generally, such a metal compound is added in an amount of from about 0.01 to 10% by total weight of the particular spandex fibers; preferably from about 0.1 to about 5%; more preferably from about 0.1 to about 2%; and most preferably from about 0.2 to about 2.0%.  
           [0013]    The term spandex, as noted above, is intended to cover any standard polyurethane-type yarns which exhibit excellent elongation and recovery characteristics. Spandex has been utilized within fabrics for many years and are generally produced from fiber-forming, long-chain, synthetic polymers comprised of at least 85% of a segmented polyurethane, such as those based on polyethers or polyesters. Manufacture of such fibers is well known and taught within U.S. Pat. Nos. 4,296,174, 3,555,115, 3,553,290, 3,428,711, 3,097,192, and 2,929,804, all herein entirely incorporated by reference.  
           [0014]    Such yarns should be well appreciated by the ordinarily skilled artisan as possessing a single-layer configuration (not a sheath-core configuration which exhibits undesirable and limited properties, as discussed above). As such, as alluded to above, the target yarns will contain antimicrobial compounds throughout their structures. In such an instance, at least a portion of the surface of any inventive yarn will exhibit some antimicrobial compounds as well as the interior of such a yarn. Thus, at least some antimicrobial compound must be present within the target inventive yarn as well, particularly in the area from the center of the yarn to a distance measured to be at least one-half of the radius (and thus such a distance from the center). In such a manner, it is clear that the prior art sheath-core type yarns are not encompassed within such a definition since the entire antimicrobial compound taught in that instance resides either at the yarn surface or as relatively close to the surface. It is to be understood that such a definition does not require every center portion of the target inventive yarn to exhibit such antimicrobial activity, only that such antimicrobial compounds are not limited in location to the surface or an area strictly adjacent thereto (i.e., in a sheath portion). Preferably, the distance from the center at which such antimicrobials will reside will be at least one-third of the radius; more preferably about one-fourth of the radius; and most preferably about one-fifth of the radius from the center.  
           [0015]    Furthermore, such inventive spandex yarns may exhibit deniers from anywhere between 0.01 to 1,000,000. Such yarns may also be monofilament or multifilament in structure. Preferably, the inventive yarns are monofilament and possess deniers from 1 to 100,000; more preferably from 10 to 10,000; and most preferably from about 50 to about 1,000.  
           [0016]    The particular antimicrobial compound (or compounds as more than one type may be present) should exhibit an acceptable log kill rate after 24 hours in accordance with the AATCC Test Method 100-1983. Such an acceptable level log kill rate is tested for  Staphylococcus aureus  or  Klebsiella pneumoniae  of at least 0.1 increase over baseline. Alternatively, an acceptable level will exist if the log kill rate is greater than the log kill rate for non-treated (i.e., no solid inorganic antimicrobial added) yarns (such as about 0.5 log kill rate increase over control, antimicrobial-free yarns). Preferably these log kill rate baseline increases are at least 0.3 and 0.3, respectively for  S. aureus  and  K pneumoniae ; more preferably these log kill rates are 0.5 and 0.5, respectively; and most preferably these are 1.0 and 1.0, respectively. Of course, the high end of such log kill rates are much higher than the baseline, on the magnitude of 5.0 (99.999% kill rate). Any rate in between is thus, of course, acceptable as well. However, log kill rates which are negative in number are also acceptable for this invention as long as such measurements are better than that recorded for correlated non-treated spandex fibers. In such an instance, the antimicrobial material present within the latex at least exhibits a hindrance to microbe growth.  
           [0017]    As defined herein, the term “take-off tension” is the tension required for the delivery of 50 meters per minute of spandex yarn over the end of the yarn package. This tension is measured in accordance with the following procedure and by means of the apparatus depicted in FIG. 1, described more fully below. Such a procedure thus measures the average tension required to remove the yarn from a yarn package at a set rate of removal. Any spikes in the recorded tension graph above 0.8 grams is highly undesirable (and represents an area on the yarn which exhibits an excessive level of tack). Such spikes are known as tension transients; the inventive yarns will not exhibit more than 20 of such tension transients in any measurement of 250 consecutive meters of yarn; preferably the number of tension transients is below about 15; more preferably less than 10; and most preferably as low as zero.  
           [0018]    Without intending to be limited to any specific scientific theory, it is believed that such anti-tack benefits are the result of antimicrobial particles present on the surface of the target spandex yarns. Such particles appear to extend outward from the yarn surface a distance sufficient to prevent repeated and continuous contact between polyurethane components of two separate yarns (or different portions of the same yarn). Such a benefit is best noted through the ability to drastically reduce, if not essentially eliminate, the need for the utilization of finish additives from the spandex yarn production method. As noted above, and more succinctly in U.S. Pat. No. 4,296,174, discussed and incorporated herein above, spandex exhibits high tack levels inherently on its surface. Finish additives (such as fiber lubricants), incorporating such active ingredients as metal salts (magnesium stearate, for example) and metallic soaps, as well as other formulations, have been utilized traditionally to prevent such tack problems (for example Kehnar® 660, from Kelmar, Inc., a silicone lubricant comprising magnesium stearate). Surprisingly, it has been found that the utilization of certain antimicrobial particles (compounds) within spandex yarns provides not only desirable antimicrobial characteristics, but also excellent anti-tack properties. Thus, the utilization of such antimicrobial as taught within this invention permits a drastic reduction in the amount of finish additives required to provide such anti-tack properties. Furthermore, since the finish additives are generally removed after further processing (e.g., knitting, weaving, and the like) of the spandex yarns, the utilization of such antimicrobial spandex yarns as now taught permits a reduction in the number of process steps required as well as potential effluent discharge after removal of such finish formulations. The level of finish additives needed for anti-tack improvements can thus be lowered to at most 2.5% owf, preferably as low as 2.0% owf, more preferably at most 1.5% owf, and, most preferably at most 1.0% owf.  
           [0019]    The preferred embodiments of these alternative yarn treatments are discussed in greater detail below. Fabrics comprising such inventive yarns may be of knit, woven, in-laid, scrim, non-woven, and the like construction and may include the inventive spandex yarns woven, knitted, etc., with any other fiber types to produce a fabric blend. Furthermore, the individual yarns may also be covered with different types of fibers including, without limitation, such natural fibers as cotton, wool, ramie, hemp, abaca, and the like, or such synthetic fibers as nylon, polyester, acrylic, and the like. Again, as noted above, such covered yarns permit stretch characteristics with excellent hand and feel for the wearer (if apparel is produced from such yarns). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0020]    [0020]FIG. 1 depicts the process of measuring take-off tension as discussed above.  
       DETAILED DESCRIPTION OF THE DRAWING  
       [0021]    As presented in FIG. 1, a spandex yarn  2  is strung-up in succession over the end of a yarn package  1 , through a ceramic eyelet  3 , across a tension head  4 , and taken-up on a drive wheel  5 . The tension head  4  is connected via electrical lines (not illustrated) to a computer (not illustrated) where five measurements per second are made throughout the run time. Take-up drive wheel  5  is driven to remove yarn  2  from the package  1  at 50 meters per minute. The test is run for 5 minutes, so that for each measurement 250 meters of yarn are examined and 1500 readings are performed.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Examples of particularly preferred compounds and yarns within the scope of the present invention are set forth below.  
         [0023]    Spandex Yam Production  
         [0024]    Thermoplastic polyurethane (TPU) pellets (Pellethane2103-70A) were obtained from Dow Plastics and mixed with 0.5%, 1.0%, and 2.0% of each antimicrobial additive. The coated pellets were then dried in a vacuum oven at 105° F for 24 hours to remove any residual moisture. The pellets were then melt extruded into 70 denier monofilament yarns, coated with a standard spandex fiber lubricant (Kelmar®660, available from Kelmar, Inc.) to a finish level of 2.5% FOY, and wound on a package at Alex James and Associates, Inc. in Greenville, S.C.  
         [0025]    The test procedure of FIG. 1 was used to measure the reduction in take-off tension for inventive and comparison spandex yarns containing commercially available antimicrobial additives.  
       EXAMPLE 1  
       [0026]    Pellethane 2130-70A pellets were were placed in a KitchenAid Proline Model KSM5 mixer and 0.5% AlphanSan® RC5000 was added. The mixer was run for 30 minutes to ensure uniform coating of the pellets and then dried in a vacuum oven at 105 F. for 24 hours to remove any residual moisture. The coated pellets were then melt extruded, coated with spin finish (Kelmar® 660) to a finish on yarn (FOY) level of 2.5% and the yarn was wound on a package. The average take-off tension and tension transients were then measured according to the above-mentioned test method. After yarn production, it was noted that the antimicrobial was dispersed throughout the yarn structure.  
       EXAMPLE 2  
       [0027]    Pellethane 2130-70A pellets were were placed in a KitchenAid Proline Model KSM5 mixer and 0.5% IonPure® Type H was added. The mixer was run for 30 minutes to ensure uniform coating of the pellets and then dried in a vacuum oven at 105° F. for 24 hours to remove any residual moisture. The coated pellets were then melt extruded, coated with spin finish (Kelmar® 660) to a finish on yarn (FOY) level of 2.5% and the yarn was wound on a package. The average take-off tension and tension transients were then measured according to the above-mentioned test method. After yarn production, it was noted that the antimicrobial was dispersed throughout the yarn structure.  
       EXAMPLE 3  
       [0028]    Pellethane 2130-70A pellets were were placed in a KitchenAid Proline Model KSM5 mixer and 0.5% Zeomic® AJ80H was added. The mixer was run for 30 minutes to ensure uniform coating of the pellets and then dried in a vacuum oven at 105° F. for 24 hours to remove any residual moisture. The coated pellets were then melt extruded, coated with spin finish (Kelmar® 660) to a finish on yarn (FOY) level of 2.5% and the yarn was wound on a package. The average take-off tension and tension transients were then measured according to the above-mentioned test method. After yarn production, it was noted that the antimicrobial was dispersed throughout the yarn structure.  
       EXAMPLE 4  
       [0029]    Pellethane 2130-70A pellets were were placed in a KitchenAid Proline Model KSM5 mixer and 0.5% Triclosan was added. The mixer was run for 30 minutes to ensure uniform coating of the pellets and then dried in a vacuum oven at 105° F. for 24 hours to remove any residual moisture. The coated pellets were then melt extruded, coated with spin finish (Kelmar® 660) to a finish on yarn (FOY) level of 2.5% and the yarn was wound on a package. The average take-off tension and tension transients were then measured according to the above-mentioned test method. After yarn production, it was noted that the antimicrobial was dispersed throughout the yarn structure.  
         [0030]    The results of the take-off tension tests are as follows with a control comparison comprising no antimicrobial:  
                                                                             Take-Off Tension Measurements                Number of Tension           Transients            Example   Tension (in grams) by average   &gt;0.8 g   &gt;1.2 g                    Control   1.113 g   1,440   44       1   0.459 g   14   0       2   0.453 g   1   0       3   0.604 g   148   0       4   0.587 g   81   0                  
 
         [0031]    The Example spandex yarns were also tested for discoloration (photoreduction) after exposure to typical indoor (fluorescent) light after 1 month of such storage. Of the silver-based antimicrobials, AlphaSan® clearly exhibited the best performance in this instance. Thus, for this purpose AlphaSan®-type antimicrobials are most preferred. The triclosan exhibited excellent colorations as well; however, such an antimicrobial is highly water soluble and thus washes easily from the surface of the target spandex yarn. Thus, for anti-tack, discoloration, and resiliency within and on the target spandex yarns, the AlphaSan® antimicrobials are, again, most preferred. The discoloration results are as follows, again with a non-antimicrobial control for comparison:  
                                         Discoloration Determinations            Example   Resultant Color               Control   Off-White       1   Off-White       2   Brown       3   Bronze       4   Off-White                  
 
         [0032]    These Examples were also tested for antimicrobial activity in accordance with proposed ASTM Draft Test Method for Determining the Antimicrobial Activity of Immobilized Antimicrobial Agents Under Dynamic Contact Conditions, No. Z8459Z, herein entirely incorporated by reference, for measuring log kill rates for  Staphylococcus aureus  after 22 hours exposure at room temperature. The results are as follows, again with a non-antimicrobial control yarn:  
                                                           Antimicrobial Results                Example   Log Kill Rate                            Control   0.015           1   1.70           2   1.45           3   0.55           4   1.65                      
 
         [0033]    Thus, the Control exhibited very little antimicrobial activity without any of such additives present. Also, the inventive spandex yarns exhibit excellent anti-tack characteristics as well as acceptable antimicrobial properties. Furthermore, the preferred ion-exchange antimicrobial compound exhibited excellent colorations (and thus low degrees of discoloration) within the target yarns as well.  
         [0034]    A fabric sheet was then woven from such Example 1 yarns which exhibited excellent stretch characteristics as well as the other properties measured above.  
         [0035]    There are, of course, many alternative embodiments and modifications of the present inventions which are included within the spirit and scope of the following claims.  
                                                                        Example   Log Kill Rate                            Control   0.015           1   1.70           2   1.45           3   0.55           4   1.65                      
 
         [0036]    Thus, the Control exhibited very little antimicrobial activity without any of such additives present. Also, the inventive spandex yarns exhibit excellent anti-tack characteristics as well as acceptable antimicrobial properties. Furthermore, the preferred ion-exchange antimicrobial compound exhibited excellent colorations (and thus low degrees of discoloration) within the target yarns as well.  
         [0037]    A fabric sheet was then woven from such Example 1 yarns which exhibited excellent stretch characteristics as well as the other properties measured above.  
         [0038]    There are, of course, many alternative embodiments and modifications of the present invention which are intended to be included within the spirit and scope of the following claims.