FIELD OF THE INVENTION

[0001] 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

[0002] 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 sendee 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, personal protective clothing and brushes.

[0003] 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.

[0004] 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 serv ice 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 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. Patent No. 8,980,982 that are detectable with magnetic or X-ray detectors, yet still process as injection moldable thermoplastics and operate in manner similar to their unfilled conventional counterparts .

[0005] By way of example, U.S. Patent 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.

[0006] 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

[0007] 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 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.

[0008] A process for forming a multi-layered laminated scrim-containing material with functional additives is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] The present invention is further detailed with respect to the following figures that depict various aspects of the present invention.

[0010] 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

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] As used herein, the term "yarn" defines multiple fibers wound together into a single continuous strand.

[0017] 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.

[0018] 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.

[0019] 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(l ,4- cyclohexylene dimethvlene 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.

[0020] 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.

[0021] 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

[0022] 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

[0023] 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.

[0024] 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 > 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 25 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 processibilitv or increasing material financial costs with only incremental improvements in detection.

[0025] 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.

[0026] 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.

[0027] 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, microw ^r ave or other RF treatments are readily employed.

[0028] 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. 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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. [0033] 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.

[0034] Modem 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 abov e 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.

[0035] 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.

[0036] 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. 1 A, a scrim 12 is formed from functional polymer. At FIG. IB, 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.

[0037] 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

[0038] 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 by running through a five screen of 40 mesh, 100 mesh, (34 micron), 60 mesh, and 31 mesh, 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 non-woven cloth and subjected to metal detector response on a Loma IQ + balanced coil metal detector alone or with various food products of a box of 8 packages of crackers, 1 pound of chicken on a tray and plastic w ^r rapped, or pizza in a cardboard box. The results are provided in Table 2 for various sizes of cloths and fold configures. The values in millivolts for triplicate repeats with the threshold detections being noted. Table 1.12% by weight stainless steel particles on PP fibers

Property Average MfN MAX

Basis weight ( g/m2 ) 49.8 47.8 51.5

Tensile strength, MD ( N/5cm ) 53.3 47.6 54.6

Tensile strength, CD ( N/5cm ) 26.8 25.4 27.7

Elongation at break, Ml (%) 39.0 32.2 45.4

Elongation at break, CD (%) 52.1 49.5 53.9

Elongation at ION, MD (%) 2.3 2.1 2.4

Add-on (%) 1.1 1.0 1.1

Water absorption (%) 602 580 629

Ash content (%) 12.36 12.0 13.0

Table 2. Data for fibers that contain particles in both core and sheath in millivolts (mV).

[0039] Table 3 is a plot of the ferrous sphere size equivalents of the fibers, where the metal detector was set to a wet conductive product with a phase out point of -90°.

Example 2

[0040] The process of Example 1 is repeated with like conditions except that a 10% by weight sheath of PP devoid of stainless steel particulate The melt pumps for the sheath and core polymers are set to produce a ratio of 90%: 10% of the cross sectional area of each fiber occupied by the polymeric core and particulate loaded core, respectively. The properties are noted to be superior to that to Example 1 with the addition of a surface treatment to enhance water absorption to 600% of the fiber mass for a non-woven fabric. The resulting fibers w ^r here formed into a non-woven cloth 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, 1 pound of chicken on a tray and plastic wrapped, or pizza in a cardboard box. The results are provided in Table 4 for various sizes of cloths and fold configures. The values in millivolts for triplicate repeats with the threshold detections being noted.

Table 4. Data for fibers that contain particulate in only core in millivolts

Table 4- continued. Data for fibers that contain particles in both core and sheath Threshold 2681 5778 3399 6027 2149 2316 11683 2317 12482 3606 3308 9137 3416 9431 22868 =200

2752 4377 3474 5939 2076 2326 1777 2340 12741 3849 3137 9076 3483 9422 22716

[0041] Table 5 is a plot of the ferrous sphere size equivalents of the fibers where the metal detector was set to a wet conductive product with a phase out point of

[0042] 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.