Abstract:
An article is provided with a web of polymer fibers forming a scrim with openings between the polymer fiber elements. A particulate is distributed in, or on the polymer fiber in a quantity to make the scrim detectable by X-ray detection or magnetic detection. One or more layers are laminated to the scrim. A process for detecting a multi-layered laminated scrim-containing article with magnetic or X-ray detection equipment in a production setting is also provided. With process implementation article loss in a product can be detected thereby reducing precautionary product discard.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 15/257,230 filed 6 Sep. 2016 that in turn claims priority benefit of U.S. Provisional Application Ser. No. 62/218,570 filed 15 Sep. 2015; the contents of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the technical field of polymeric composite fibers, and in particular to a scrim material formed with polymeric fibers with high loadings of metal or other particulate that render articles formed from such fibers X-ray or magnetic detectable. 
       BACKGROUND OF THE INVENTION 
       [0003]    Servicing of a food or pharmaceutical production line currently has strict guidelines that require exclusion zones from which various material packaging components and accessories are excluded. In spite of these exclusion policies, plastic debris does enter production lines and with even a single piece of plastic entering a production stream, large quantities of otherwise usable product must be discarded. Rules regarding processing of ground meat are exemplary of those that require discard of the product if possibly contaminated. Common plastic packaging or service articles that are inadvertently brought into production exclusion zones include aerosol cans, grease cartridge tubes, grease tube caps, plastic fiber toweling, packing straps, pail lids, jar caps, and personal protective clothing. 
         [0004]    Metal detectors are commonly found on food processing lines to assure that metal shards that represent a laceration hazard do not end up in food products. Similarly, pharmaceutical and biomedical device production are also vulnerable to not only the hazards associated with metal debris ending up in product streams, but also the prospect that such metal can degrade active pharmaceutical ingredients or serve as a potential source of infection. Numerous technologies are known to the art to detect spurious metal within a production line. These technologies include a transmitter coil-receiver coils for metal detection systems, systems that use radio frequencies, and magnetic field based systems. In recognition of the fact that some metallic materials are not ferromagnetic and simultaneously not particularly good electrical conductors, x-ray scanners and other electromagnetic field (emf) spectral region spectral detection techniques have been added to food and pharmaceutical product lines to facilitate the detection of a wider range of contaminants. 
         [0005]    Many industries have a need for metal detectable polymers and articles made therefrom. By way of example, a food, medical, or pharmaceutical production line maintains tight audit control of service items that enter the manufacturing facility to assure such items do not accidently enter the production stream as a contaminant that can be fragmented into dangerous shards. Historically, plastics have been precluded from some environments due to the inability to locate such articles with product screening X-ray or magnetic detectors. Recently, plastic articles have been developed that are filled with metal particulate or barium sulfate, as detailed in U.S. Pat. No. 8,980,982 that are detectable with magnetic or X-ray detectors, yet still process as injection moldable thermoplastics and operate in a manner similar to their unfilled conventional counterparts. 
         [0006]    By way of example, U.S. Pat. No. 5,897,673 teaches fibers containing fine metallic particles that are cross-linked to the polymeric fiber. While various pure metals are contemplated in the literature, little attention has been paid to the unique problems associated with stainless steel particulate. As many foods and manufactured substances can only be exposed to stainless steel, the lack of stainless steel particle filled fibers precludes the usage of many useful articles from these controlled manufacturing sites. By way of example various wipes, scrub pads, hair covers, suits, aprons and shoe covers and other manufacturing aids or personal protective equipment if made from stainless steel containing fibers could allow better quality control of manufacturing with less stringent audit processes as any such articles lost in a production stream could be detected by X-ray or magnetic anomaly. 
         [0007]    Thus, there exists a need for a thermoplastic fiber filled scrim structure with detectable particulate or functional additives. There also exists a need for such fibers that process and retain properties of conventional thermoplastic fibers to promote production of various articles from fibers that have the added benefit of being X-ray or magnetically detectable while operating in a manner similar to conventional articles. 
       SUMMARY OF THE INVENTION 
       [0008]    An article is provided with a web of polymer fibers that each have a cross-section and a length arranged as bi-directional elements each with an element width and defining openings between intersecting elements. The openings having an opening width greater than the element width of contiguous elements to the opening to form a scrim having a first surface and a second surface in opposition to the first surface. A particulate distributed is in, or on the polymer fiber in a quantity to make the scrim detectable by X-ray detection or magnetic detection. One or more layers are laminated to at least the first surface of the scrim. A scrim or web material made from polymer containing functional additives, and other additives is provided, where the scrim may be used as a substrate for nonwoven fabric or other laminated engineered materials. The particulate additives are incorporated into the polymer prior to web formation, and may be manufactured by any of several means commercially known such as injection molding, extrusion, weaving extruded filaments, or thermally bonding laid scrim, or by methods currently unknown. Properties imparted to the scrim materials may include electromagnetic spectral detectability, thereby making articles incorporating the scrim suitable for usage in a variety of fields including food production, medical, and pharmaceutical production environments. 
         [0009]    A process for detecting a multi-layered laminated scrim-containing magnetically or X-ray detection equipment in a production environment is also provided. With process implementation article loss in a product can be detected thereby reducing precautionary product discard. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention is further detailed with respect to the following figures that depict various aspects of the present invention. 
           [0011]      FIGS. 1A-C  illustrate the sequential formation of a multi-layered laminated scrim-containing fabric with functional additives in accordance with embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    The present invention has utility as a scrim or web material made from polymer containing functional additives, and other additives, where the scrim may be used as a substrate for nonwoven fabric or other laminated engineered materials. Embodiments of the base web material forming the scrim may have properties imparted by the various functional additives that are incorporated into the polymer prior to web formation, and may be manufactured by any of several means commercially known such as injection molding, extrusion, weaving extruded filaments, or thermally bonding laid scrim, or by methods currently unknown. Properties imparted to the scrim materials may include electromagnetic spectral detectability, thereby making the scrim suitable for usage in a variety of fields including food production, medical, and pharmaceutical production environments. 
         [0013]    Embodiments of the inventive detectable scrim may be used independently or fashioned into a laminated material by the addition of one or more layers of secondary materials. A non-limiting illustrative example of an embodiment of a laminated composite material is a metal detectable scrim layered between a face and back layer of absorbent fibers. A specific inventive example is a hydroentangled hybrid wipe composed of extruded metal detectable scrim bound to wet laid absorbent fiber layers resulting in a wiping cloth which is both absorbent and metal detectable. The nonwoven engineered wipe is both absorbent and metal detectable making it employable for various wiping applications such as personal hygiene, equipment and parts cleaning in food processing critical environments. 
         [0014]    It is noted that the innovative detectable scrim by itself would not have the characteristics of a wipe. By layering the scrim with other components a useful wipe may be fashioned. The laminated material allows multiple functionalities in a single product. 
         [0015]    As used herein, the term “fiber” defines both fibers of finite length, such as conventional preselected length fiber, as well as substantially continuous structures, such as continuous filaments, unless otherwise indicated. The fibers of the present invention are appreciated to be hollow or solid fibers, and further can have a substantially round or circular cross-section or cross-sections of different symmetry space groups with other cross-sections illustratively including oval; lobular; polygonal such as triangular, square, rectangular, trapezoidal, pentagonal, and hexagonal. A fiber of the present invention in some embodiments has a sheath that varies in polymer or particulate, with the variation being as to composition or concentration, or both such properties. 
         [0016]    As used herein, the term “multi-component fibers” is defined to include preselected length fiber and continuous filaments with two or more discrete structured domains of deliberately different composition or component concentration and is intended to specifically include sheath/core and island configurations. 
         [0017]    As used herein, the term “yarn” defines multiple fibers wound together into a single continuous strand. 
         [0018]    It is to be understood that in instances where a range of values are provided that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4. 
         [0019]    It is appreciated that both the cross-sectional shape of the fiber and the configuration of the particulate and other components therein depends upon the equipment that is used in the preparation of the fiber, the process conditions, and the melt viscosities of the various components. A wide variety of fiber configurations are readily produced according to the present invention to achieve loadings sufficient for magnetic or X-ray detection. 
         [0020]    The polymeric component of the fiber is readily selected from any of the types of polymers known in the art that are capable of being formed into fibers, including polyolefins, polyvinyl, polyvinyl alcohol, polyesters, polyamides, co-polymers containing any of the aforementioned polymers as blocks of a copolymer, and combinations thereof. Specific polyolefins operative herein illustratively include polypropylene; polyethylene; polybutene; and polyisobutylene; polyamides such as NYLON 6 and NYLON 6,6; polyacrylates; polystyrenes; polyurethanes; acetal resins; polyethylene vinyl alcohol; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate) (PCT), polycarbonates; and aliphatic polyesters such as polylactic acid (PLA); polyphenylene sulfide; thermoplastic elastomers; polyacrylonitrile; cellulose and cellulose derivatives; polyaramids; acetals; fluoropolymers; copolymers and terpolymers thereof and mixtures or blends thereof, and without regard as whether a given polyolefin is syndiotacic, eutectic, isotactic, or atactic. 
         [0021]    Specific examples of aliphatic polyesters operative in the present invention include fiber forming polymers formed from a combination of an aliphatic glycol such as ethylene glycol, propylene glycol, butylene glycol, hexanediol, octanediol or decanediol) or an oligomer of ethylene glycol (e.g., diethylene glycol or triethylene glycol) with an aliphatic dicarboxylic acid such as succinic acid, adipic acid, hexanedicarboxylic acid or decaneolicarboxylic acid); or the self-condensation of hydroxy carboxylic acids other than poly(lactic acid), such as polyhydroxy butyrate, polyethylene adipate, polybutylene adipate, polyhexane adipate, and copolymers containing the same. Aromatic polyesters operative in the present invention include fiber forming polymers formed from polyesters of alkylene glycols having 2-10 carbon atoms and aromatic diacids; polyalkylene naphthalates, which are polyesters of 2,6-naphthalenedicarboxylic acid and alkylene glycols, as for example polyethylene naphthalate; or polyesters derived from 1,4-cyclohexanedimethanol and terephthalic acid, as for example polycyclohexane terephthalate. Exemplary polyalkylene terephthalates include polyethylene terephthalate (also PET) and polybutylene terephthalate. 
         [0022]    In some inventive embodiments that are compliant with food, medical and pharmaceutical processing standards, the particulate is stainless steel. Other compositions of particulate to render an inventive fiber magnetic or X-ray signal detectable include iron, bronze, brass, steel, barium salts, cobalt, titanium, tin, copper, tungsten, platinum, silver, bismuth, zinc, lead, molybdenum, neodymium, samarium, alloys of any of the aforementioned, oxides of any of the aforementioned metals, nitrides of any of the aforementioned. It is appreciated that cobalt alloys such as cobalt-samarium, and neodymium alloys have exceptionally high magnetic moments that allow for magnetic detection at lower weight loading compared for ferrite. In some inventive embodiments, the stainless steel is ferromagnetic and detectable by magnetic induction coil detectors. Specific grades of stainless particulate operative herein include 300 series, 400 series and in particular 306 (L), 316 and 430 compositions 
         [0023]    The present invention attempts to retain the processing and performance properties of the native polymer while imparting the ability to render the fiber and articles formed therefrom X-ray or magnetic anomaly detectable. This is achieved by inclusion of particulate having a shortest linear dimension, as measured from among the three orthogonal Cartesian coordinate axes X-Y-Z that is less than or equal to one half the fiber cross-sectional average dimension along the three orthogonal Cartesian coordinate axes X-Y-Z. For the purposes of calculation of the particulate dimension, the average particle dimension is used for polydisperse particulate. By way of example, a circular cross-section fiber with a diameter of 35 microns is loaded with spherical particulate having a diameter of less or equal to 17 microns. In some inventive embodiments containing cylindrical rod particulate, the ratio of rod length to diameter is between 1.3-20: 1 and in still other embodiments between 1.5-8:1 
         [0024]    In certain embodiments, each of the polymeric components of an inventive fiber includes other substances known conventionally to modify a processing property or performance property. Such additive substances illustratively include antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, dyes, pigments, plasticizers and combinations thereof It is appreciated that a pigment can encompass a composition of a particulate material detailed above to impart detectability to the inventive fiber and in such instances the pigment is compositionally distinct from the particulate and present in a lower weight percentage than the particulate. 
         [0025]    It is appreciated that the loading of particulate to achieve X-ray or magnetic detection of articles formed from inventive fibers is dictated by factors including the X-ray cross-section or the magnetic susceptibility of a given particulate. Generally, ferromagnetic materials are detectable at loadings of from &gt;2 total weight percent by magnetic induction detection. In those embodiments when the ferromagnetic material is a rare earth magnet, typical loadings are from 2 to 4 total weight percent for magnetic induction detection. In specific embodiments where the particulate is magnetic stainless steel or any other electromagnetic spectrally detectable particulate, typical loadings are from 5 to 50 total weight percent for magnetic induction detection. It is appreciated that the above typical loading can be exceeded, yet often at the expense of detrimentally influencing processibility or increasing material financial costs with only incremental improvements in detection. 
         [0026]    The continuous filaments in certain inventive embodiments are mechanically crimped and cut into a desirable fiber length, thereby producing staple fiber. The length of the staple fibers typically ranges from 25 to 50 millimeters, although the fibers can be cut to any desired length outside this range. 
         [0027]    The multi-component fibers of the invention can be staple fibers, continuous filaments, or meltblown fibers. In general, staple fibers, multifilament, and spunbond fibers formed in accordance with the present invention can have a fineness of 0.1 to 500 microns per filament. Meltblown filaments can have a fineness of 0.1 to 500 microns. Monofilament fibers can have a fineness of 0.1 to 500 microns. 
         [0028]    The multi-component fibers of the invention are useful in the production of a wide variety of products, including without limitation nonwoven structures, such as but not limited to scrims used in forming carded webs, wet laid webs, dry laid webs, spunbond webs, meltblown webs, and the like. The nonwoven webs can be bonded to transform the webs into a coherent nonwoven fabric using bonding techniques known in the industry. Exemplary bonding techniques for nonwoven webs include mechanical bonding, such as hydro-entanglement and needle punching, adhesive bonding, thermal bonding, and the like. An example of thermal bonding is through air bonding, although other thermal bonding techniques, such as calendaring, microwave or other RF treatments are readily employed. 
         [0029]    A characteristic of a scrim according to the present invention is the presence of openings between the fibers that bound the opening. The fibers bounding an opening are referred to synonymously as elements. The openings have a width greater that the width of the bounding elements. It is appreciated that the fibers can be woven or non-woven or even random as still form a bi-directional web inclusive of such openings. 
         [0030]    In some inventive embodiments, the inventive fibers are subjected to a coating, laminate, or otherwise cover the outer and/or inner surfaces of threads or layers of material contained within any final product without falling outside the scope of the invention. In the context of a scrim, these correspond to a first surface and a second surface in opposition to the first surface. This is a practice well known to those experienced in the art, and is commonly used to impart non-stick, low-friction, or additional chemical and heat resistance properties to the final product. It is appreciated that additional non-polymeric particles identical, similar, or fundamentally different to the particles already contained within the composite fibers of the invention are readily added to the fibers. Such additions can come, at the expense of lowering the overall metal content loading of the resultant article. 
         [0031]    In certain embodiments of the present invention a fiber or core portion of a sheathed fiber has particulate protruding from the wall of the fiber and a concomitant relative depletion of particulate from the central region of a fiber. The inclusion of a particulate protrusions and centrally depleted fiber region has been found to afford considerable benefits in increasing the loading amount of particulate to detectable levels and the energy needed to slide fibers past one another. 
         [0032]    In some embodiments of the present invention, following extrusion but prior to coating or lamination, the fibers or other non-woven creations of the invention are coated, dusted, or otherwise induced to carry on the exterior of individual filaments or layers additional particulate identical, similar, or fundamentally different to the particulate already contained within the composite fibers of the invention. 
         [0033]    Particulate is most easily adhered to the outside of the fibers using a process which passes the extruded filament or non-woven creation through an enclosed chamber, in which a fan system lifts and circulates the particulate throughout the air contained within the chamber such that a fraction of the particles that contact the filament will adhere to the surface. 
         [0034]    In another embodiment of the invention, the fibers of the invention are used to weave or knit a scrim. In addition, an inventive scrim is laminated to a woven, knit, or non-woven fabric layer. 
         [0035]    In yet another embodiment of the invention, custom composite fibers of the invention are woven or otherwise used in the construction of fabric or fabric-like structures. The fabric performs comparably to standard polymer containing fabrics with respect to most attributes, such as strength, durability, and hand, yet like the fibers exhibits properties which deviate significantly from those normally associated with the polymeric material by those experienced in the art, these unique properties beside detectability illustratively include high density, conductivity, electromagnetic shielding, cut-resistance, heat-resistance, and radiation shielding relative to the base polymer absent particulate loading. 
         [0036]    Modern metal detection is based on creating a magnetic field with a transmitter coil and two receiving coils wired in reverse. The resulting field is interrupted when a conductive or magnetic contaminant passes through the field. The contaminant is detected by measuring the change in voltage above the change in voltage of non-contaminated product. If a contaminant is detected, that product is rejected. Contaminants are generally categorized as sphere equivalents in millimeters. The sensitivity and throughput are machine dependent. 
         [0037]    X-ray inspection is based on density. The higher the density of the object being examined; the more energy is absorbed. X-ray detection measures how much energy is absorbed by a product or contaminant. X-ray detection can detect contaminants such as glass or bone that a metal detector will not detect. X-ray detection can perform other quality functions outside the scope of product contamination. The present invention focuses on contaminant detection. The contaminants are generally categorized as sphere equivalents. The sensitivity and throughput are machine dependent. In a production setting, the X-ray detector or the magnetic detector is associated with a production line that can be stopped when an inventive scrim is detected by way of detector signal in the production stream. As a result, the effects of the contamination event are mitigated. Alternatively, a rejected product is shunted from the production line in response to the positive detector signal of contaminant being present. 
         [0038]      FIGS. 1A-C  illustrate a process  10  for the formation of a multi-layered laminated scrim-containing structure  18  with functional additives in accordance with embodiments of the invention. At  FIG. 1A , a scrim  12  is formed from a web of functional polymer formed as fiber elements  11 . The scrim  12  has a first surface  13  and a second opposing surface  15 . Openings  17  are defined by bounding fiber elements  11 . An opening  17  has a width greater than that of any of the bounding fiber elements  11 . At  FIG. 1B , an upper layer  14  and a lower layer  16  are introduced and laminated to the scrim  12  ( FIG. 1C ) to form a multi-layered laminated scrim-containing structure  18 . The upper layer  14  and lower layer  16  may be made of the same or of different materials, and illustratively may include functional or nonfunctional fibers. 
         [0039]    The following example specific non-limiting examples of present invention. These examples should not be considered to be a limit on the scope of the appended claims. 
       EXAMPLE 1 
       [0040]    Spherical stainless steel particulate (430 series) having a Poisson size distribution and an average particle size of 12 microns is mixed into polypropylene (PP) to form pellets with a particulate loading of 12 percent. The particles are melt-spun and the melt is then drawn to a fiber. Some of the particulate is noted to be flattened or misshaped. The resulting fibers where formed into a scrim and subjected to metal detector response on a Loma IQ 3 + balanced coil metal detector alone or with various food products of a box of 8 packages of crackers, or frozen pizza in a cardboard box. The results are provided in Table 1 for various sizes and fold configurations of scrim. The values in millivolts for triplicate repeats with the threshold detections being noted. All sample pieces were cut with longest dimension oriented in machine direction 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Data for 12% by weight stainless steel particles in PP scrim, data in millivolts (mV), 
               
             
          
           
               
                   
                 Sample Size (in.) 
               
             
          
           
               
                   
                 1 × 2 
                 2 × 2 
                 3 × 2 
                 3 × 4 
                 6 × 2 
                 6 × 4 
               
             
          
           
               
                   
                 Sample Orientation 
               
             
          
           
               
                   
                   
                   
                   
                 Machine 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                   
                   
                 Machine 
                 direction 
                   
                   
                   
                   
                   
                   
                 Folded 
               
               
                   
                 Perpen- 
                   
                 direction 
                 perpen- 
                 Perpen- 
                 Perpen- 
                 Perpen- 
                   
                 Perpen- 
                   
                 Perpen- 
                 Folded 
                 Perpen- 
               
               
                   
                 dicular 
                 Parallel 
                 parallel 
                 dicular 
                 dicular 
                 dicular 
                 dicular 
                 Parallel 
                 dicular 
                 Parallel 
                 dicular 
                 Parallel 
                 dicular 
                 Parallel 
               
               
                   
                   
               
             
          
           
               
                 Mode 
                 78 
                 96 
                 122 
                 124 
                 123 
                 129 
                 262 
                 396 
                 459 
                 160 
                 154 
                 254 
                 110 
                 412 
               
               
                 QC (dry) 
                 63 
                 710 
                 139 
                 118 
                 120 
                 146 
                 278 
                 346 
                 505 
                 187 
                 137 
                 217 
                 110 
                 398 
               
               
                 Thresh- 
                 114 
                 97 
                 112 
                 132 
                 104 
                 141 
                 276 
                 309 
                 467 
                 184 
                 179 
                 245 
                 102 
                 384 
               
               
                 old = 100 
               
               
                 Mode 
                 52 
                 87 
                 91 
                 85 
                 82 
                 175 
                 227 
                 219 
                 496 
                 145 
                 111 
                 181 
                 136 
                 389 
               
               
                 Crackers 
                 75 
                 50 
                 80 
                 140 
                 64 
                 225 
                 267 
                 223 
                 492 
                 168 
                 92 
                 182 
                 135 
                 384 
               
               
                 (wet) 
               
               
                 Thresh- 
                 46 
                 63 
                 90 
                 70 
                 102 
                 161 
                 248 
                 263 
                 477 
                 177 
                 84 
                 211 
                 141 
                 397 
               
               
                 old = 100 
               
               
                 Mode 
                 1264 
                 1855 
                 2447 
                 2365 
                 2219 
                 2575 
                 5288 
                 5395 
                 8076 
                 3656 
                 2478 
                 3904 
                 304 
                 5433 
               
               
                 Pizza 
                 1267 
                 1845 
                 2500 
                 2381 
                 2257 
                 2619 
                 4980 
                 5352 
                 7640 
                 3585 
                 2677 
                 3925 
                 1279 
                 5179 
               
               
                 (wet) 
               
               
                 Thresh- 
                 1284 
                 1849 
                 2467 
                 2385 
                 2204 
                 2786 
                 5136 
                 5409 
                 7454 
                 3497 
                 2729 
                 3775 
                 1296 
                 5115 
               
               
                 old = 275 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Continued data for scrim, data in millivolts (mV). 
               
             
          
           
               
                   
                 Sample Size (in.) 
               
             
          
           
               
                   
                 6 × 4 
                 6 × 6 
                 3 × 8 
                 6 × 8 
               
             
          
           
               
                   
                 Sample Orientation 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Twice 
                 Twice 
               
               
                   
                 Fold- 
                 Fold- 
                   
                 Fold- 
                 Fold- 
                 Twice 
                   
                   
                 Fold- 
                 Fold- 
                   
                   
                 Fold- 
                 Fold- 
                 Fold- 
                 Fold- 
               
               
                   
                 ed 
                 ed 
                   
                 ed 
                 ed 
                 Fold- 
                   
                   
                 ed 
                 ed 
                   
                   
                 ed 
                 ed 
                 ed 
                 ed 
               
               
                   
                 Perpen- 
                 Par- 
                   
                 Perpen- 
                 par- 
                 ed 
                 Perpen- 
                 Par- 
                 Perpen- 
                 Par- 
                 Perpen- 
                 Par- 
                 Perpen- 
                 Par- 
                 Perpen- 
                 Par- 
               
               
                   
                 dicular 
                 allel 
                 Square 
                 dicular 
                 allel 
                 Square 
                 dicular 
                 allel 
                 dicular 
                 allel 
                 dicular 
                 allel 
                 dicular 
                 allel 
                 dicular 
                 allel 
               
               
                   
                   
               
             
          
           
               
                 Mode 
                 200 
                 344 
                 253 
                 208 
                 5972 
                 6904 
                 100 
                 483 
                 297 
                 516 
                 259 
                 415 
                 429 
                 3426 
                 4048 
                 14642 
               
               
                 QC 
                 222 
                 373 
                 242 
                 218 
                 6069 
                 7068 
                 79 
                 455 
                 254 
                 530 
                 203 
                 382 
                 444 
                 3354 
                 3719 
                 14679 
               
               
                 (dry) 
               
               
                 Thresh- 
                 201 
                 378 
                 235 
                 246 
                 5915 
                 7105 
                 102 
                 427 
                 301 
                 520 
                 224 
                 348 
                 464 
                 3387 
                 4331 
                 14735 
               
               
                 old = 
               
               
                 100 
               
               
                 Mode 
                 177 
                 389 
                 287 
                 265 
                 4830 
                 3177 
                 202 
                 644 
                 247 
                 547 
                 446 
                 463 
                 30 
                 1677 
                 1940 
                 11832 
               
               
                 Crack- 
                 185 
                 386 
                 261 
                 264 
                 4714 
                 3217 
                 193 
                 599 
                 238 
                 544 
                 433 
                 466 
                 417 
                 1724 
                 1444 
                 11900 
               
               
                 ers 
               
               
                 (wet) 
               
               
                 Thresh- 
                 191 
                 369 
                 267 
                 285 
                 4821 
                 3357 
                 196 
                 606 
                 226 
                 574 
                 567 
                 461 
                 415 
                 1538 
                 1546 
                 12053 
               
               
                 old = 
               
               
                 100 
               
               
                 Mode 
                 3668 
                 6007 
                 4003 
                 4330 
                 15343 
                 15517 
                 1877 
                 6956 
                 5363 
                 9142 
                 304 
                 524 
                 719 
                 8376 
                 8652 
                 20537 
               
               
                 Pizza 
                 3724 
                 6041 
                 4118 
                 4428 
                 14663 
                 15469 
                 1861 
                 6727 
                 5483 
                 9025 
                 305 
                 534 
                 696 
                 8354 
                 8483 
                 20509 
               
               
                 (wet) 
               
               
                 Thresh- 
                 3758 
                 6047 
                 4079 
                 4522 
                 14097 
                 15057 
                 1835 
                 7256 
                 5406 
                 8907 
                 306 
                 463 
                 718 
                 8304 
                 8602 
                 20534 
               
               
                 old = 
               
               
                 275 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Ferrous sphere size equivalent for scrim where the metal detector was 
               
               
                 set to wet conductive product with phase out point of ~90°. 
               
             
          
           
               
                   
                 ~Fe Sphere Equivalent (wet mode frozen) 
               
             
          
           
               
                   
                   
                   
                 Folded 
                   
                 Folded Twice 
                 Folded 
               
               
                 Size 
                 Perpen- 
                   
                 Perpen- 
                 Folded 
                 Perpen- 
                 Twice 
               
               
                 (in.) 
                 dicular 
                 Parallel 
                 dicular 
                 Parallel 
                 dicular 
                 Parallel 
               
               
                   
               
               
                 1 × 2 
                 1.0 mm 
                 1.0 mm 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 2 × 2 
                 1.0 mm 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 3 × 2 
                 1.0 mm 
                 1.0 mm 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 3 × 4 
                 1.5 mm 
                 1.5 mm 
                 N/A 
                 N/A 
                 N/A 
                 N/A 
               
               
                 6 × 2 
                 1.5 mm 
                 1.5 mm 
                 1.5 mm 
                 1.5 mm 
                 N/A 
                 N/A 
               
               
                 6 × 4 
                 1.0 mm 
                 1.5 mm 
                 1.0 mm 
                 1.5 mm 
                 N/A 
                 N/A 
               
               
                 6 × 6 
                 1.5 mm 
                 N/A 
                 2.0 mm 
                 1.5 mm 
                 2.0 mm 
                 N/A 
               
               
                 3 × 8 
                 1.0 mm 
                 1.5 mm 
                 1.5 mm 
                 1.5 mm 
                 N/A 
                 N/A 
               
               
                 6 × 8 
                 0.8 mm 
                 0.8 mm 
                 0.8 mm 
                 1.5 mm 
                 1.5 mm 
                 2.5 mm 
               
               
                   
               
             
          
         
       
     
         [0041]    The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.