CROSS-REFERENCE TO RELATED APPLICATION
FIELD OF THE INVENTION
The present application claims the benefit of U.S. Provisional Application No. 60/557,569, filed Mar. 30, 2004, which is incorporated herein by reference in its entirety and for all purposes.
- BACKGROUND OF THE INVENTION
The present invention relates generally to fibrous structures including structured coextrudable polymeric components, useful for making identifiers or taggants for a variety of products, and to processes for making and using the same.
Materials known generally as taggants have been proposed for incorporation into products to identify and/or verify various characteristics of the same. For example, taggants have been proposed for the identification of products such as explosives, certain bulk chemicals that can be used to make explosives, ammunition, paint, petroleum products, and documents, among others. Materials have also been applied to products to track point of origin, authenticity, and distribution of the products. It also can be useful to include in the identification information such as the date of manufacture and, in case the products are made in different batches or lots, the particular lot with which the product is associated.
One method to identify and verify product information involves the use of inks transparent to visible light. The inks are applied to the product, and the presence (or absence) of the ink is revealed by ultraviolet or infrared fluorescence.
Other identification and verification methods include implanting microscopic additives that can be detected optically. As an example, U.S. Pat. Nos. 4,053,433 and 4,390,452 describe a method of marking a substance with microparticles, which are encoded with an orderly sequence of visually distinguishable colored segments that can be detected with a microscope or other magnifying device.
Many of the methods for identifying and verifying articles using taggant materials can be unsatisfactory. Often the methods used to produce taggant materials are difficult to implement, expensive and time consuming. The materials used to make the taggant products can also be expensive and/or difficult to handle. In addition, taggant materials can adversely affect or degrade the performance of the tagged product. Still further, specialized equipment is often required to manufacture the taggant materials and/or to detect the presence of the same in a product, thereby further increasing the costs associated with the use of such materials.
U.S. Pat. No. 4,640,035 to Kind et al. is directed to particulate coding materials stated to be useful in identifying the origin of a product. The particulate coding material includes thin transverse sections of an assembly of elongate elements, e.g., fibers. The individual fibers of the assembly are separately extruded, combined, and heated to adhere the fibers to one another to form a unitary structure. Alternatively, each fiber is individually extruded and thereafter directed to an assembly where, in a separate processing step, the fibers are bonded together via a low melt matrix material.
- BRIEF SUMMARY OF THE INVENTION
The methods discussed in the '035 patent can be time consuming and costly, as well as require specialized equipment. Further, the methods of the '035 patent are limited to the production of relatively simple shapes of the individual fibers, e.g., round cross sections. The method cannot be readily adapted to produce assemblies with individual components having complex (non-round) cross sectional shapes.
The present invention provides multicomponent fibers suitable for the production of taggant materials. The fibers of the invention allow for the production of taggants having a desired size and are particularly useful in the production of exceptionally small taggants. The resultant taggants can be less noticeable in use and further are less likely to degrade or interfere with the performance of the tagged product. The fibers of the invention can also provide taggants at relatively low costs and with good productivity.
The present invention is based on a common multicomponent fiber construction or structure, which includes a plurality of polymeric components arranged in discrete structured domains. The polymer domains have one or more identifier characteristics that can be varied to form a plurality of different identifying patterns. In one example, the multicomponent fiber structure can have available for inclusion therein a sufficient number of polymer domains to allow selection of various combinations of the domains to be present or absent to form a number of different identifying patterns for individual fibers derived therefrom. As another example, the multicomponent fiber can include one or more polymer domains having a distinctive cross sectional feature, which distinctive feature can be varied to form a number of different identifying patterns for individual fibers derived therefrom. In this aspect of the invention, the distinctive cross section feature of the multicomponent fiber structure can include one or more features that can be present or absent, differently sized, differently shaped, etc. The multicomponent fiber structure thus provides a framework for the production of a group or collection of different individual fibers derived therefrom, wherein the identifier characteristics of fibers with a given pattern are unique as compared to the identifier characteristics of fibers of other patterns. The present invention also includes a collection, series, or group of such fibers, each fiber or subset of fibers within the collection having a unique pattern, which collection includes at least two, and up to five or more, individual fibers or fiber subsets, wherein the collection of fibers can optionally be meltspun simultaneously in a single filament yarn or tow.
Generally the common multicomponent fiber structure includes at least about 4 polymer domains or at least about 4 variations of a distinctive polymer domain cross section, and can include up to 100 polymer domains or 100 variations of a distinctive polymer domain cross section, or more, so as to provide at least about 12 different identifying patterns. The number of polymer domains available for arrangement, combination, and/or modification thereof to make different patterns is limited primarily by the cost of the fiber spinning equipment needed to form a sufficient number of different patterns.
In addition, the common multicomponent fiber structure of the invention can include at least one polymer domain that has a unique physical characteristic that is different from that of other of the polymer domains. This can provide an additional variable to choose when selecting various combinations of the polymer domains to be present or absent and/or selecting variations of a distinctive polymer domain cross section to create a particular unique identifier pattern or design.
The present invention also provides a yarn or tow including a plurality of fibers as described above. Advantageously all of the fibers present in the yarn are multicomponent fibers having discrete structured domains forming the same pattern, or the yarn includes multiple subsets of fibers, wherein each fiber subset has the same pattern.
The multicomponent fibers and yarns of the invention are useful in producing a taggant material for identifying a product. The taggant materials can include the fiber, and/or a yarn or tow thereof, incorporated into the tagged product (for example, by weaving or knitting the fiber, yarn and/or tow into a fabric). The taggant materials of the invention can also include only a part or portion of the fiber, and/or of a yarn or tow thereof, incorporated into the tagged product.
The present invention also includes products tagged with one or more of the multicomponent fibers of the invention. Alternatively the product can be tagged with a portion of one or more of the multicomponent fibers of the invention. The fibers, or a portion thereof, can be dispersed in or adhered to the product or material to be tagged. The fibers generally include a pattern formed by one or more of the shape, number, and/or arrangement of the polymer domains in the fiber cross section in a manner that is suitable for use as an unique identifying pattern. In this aspect of the invention, in the tagged product, at least some of the fibers and/or portions thereof have cross section patterns that differ from one another and form a unique identification by the combination of the identifying patterns present in the fibers associated with the product.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
The present invention also provides methods of making an identifier material for tagging products. This aspect of the invention includes defining a multicomponent fiber structure having a plurality of coextruded polymeric components arranged in discrete structured domains. The polymer domains have one or more identifying characteristics that can be varied to form a plurality of different identifying patterns, as discussed above. At least one of the identifying patterns is selected and at least two different polymers are coextruded under conditions to provide a multicomponent fiber having the selected identifying pattern.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
FIGS. 1A, 1B and 1C are transverse cross sectional views of exemplary taggant fibers of the invention having an “islands in the sea” construction; and
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a transverse cross sectional views of another exemplary taggant fiber of the invention also having an “islands in the sea” construction.
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
As used in the specification, and in the appended claims, the singular forms “a”, an “the”, include plural referents unless the context clearly dictates otherwise.
The term “fiber” as used herein means both fibers of finite length, such as conventional staple fiber, as well as substantially continuous structures, such as continuous filaments, unless otherwise indicated. The fibers of the invention can be hollow (including fibers with multiple discrete voids therein) or non-hollow fibers, and further can have a substantially round or circular cross section or non-circular cross sections (for example, oval, rectangular, multi-lobed, and the like).
As used herein, the term “multicomponent fibers” includes staple and continuous filaments prepared from two or more polymers present in discrete structured domains in the fiber, as opposed to blends where the domains tend to be dispersed, random or unstructured. It should be understood that the scope of the present invention is meant to include fibers with two or more structured components. In a preferred embodiment, the two or more polymers that form the multicomponent fiber are co-extruded using a melt-spinning apparatus, meaning each polymer component is extruded together in molten form through a spinneret in a predetermined configuration to form the multicomponent fiber.
FIGS. 1A, 1B and 1C are transverse cross sectional view of multicomponent fibers, designated generally as 10, 10′, and 10″, respectively, representative of fibers of the present invention having polymer domains with identifier characteristics that are varied to form different identifying patterns or designs. The different patterns or designs illustrated in FIGS. 1A, 1B and 1C result from selecting specific combinations of polymer components or domains to be present or absent available from a common fiber structure.
Referring first to FIG. 1A, fiber 10 has a configuration known generally in the art as an “islands in the sea” construction. Generally islands in the sea fibers include a “sea” polymer domain or component 12 surrounding a plurality of “island” polymer domains or components 14. FIG. 1A illustrates an array of nine island domains, although more or fewer island domains could be used, so long as a sufficient number of island domains are available to allow selection of various combinations thereof to be present or absent to form the desired number of different identifying patterns for individual fibers. For ease of discussion herein, each of the individual island domains or components 14 has been assigned a different letter designation, from “A” to “I.” The cross sectional configuration of the fiber of FIG. 1A can be prepared using methods and fiber spinning apparatus as known in the art.
Sea component 12 generally forms the entire outer exposed surface of the fiber, although the invention can also include fiber constructions in which at least a portion of one or more of the island domains also forms a part of the exposed surface of the fiber. Sea domain or component 12 can be formed of any of the polymers known in the art for the production of fibrous materials, as discussed in more detail below. Generally such polymers are melt extrudable, although the invention is not limited to the use of melt extruded polymers. Island domains or components 14 can also be formed of any of the types of polymers known in the art for fiber production, but which are different from the sea polymer domain.
FIG. 1B is a transverse cross sectional view of an islands in the sea fiber 10′, and also includes a sea polymer domain or component 12′ surrounding a plurality of island polymer domains or components 14′.
Both fibers 10 and 10′ are derived from a common multicomponent fiber construction (namely, an islands in the sea fiber having up to nine separate island components). The illustrated pattern of island components 14′ of fiber 10′ is different, however, from the pattern of island components 14 of fiber 10. The specific pattern of fiber 10′ is provided by including some, but not all, of islands 14 of fiber 10 of FIG. 1A. In this example, islands A, C, E, G, and I of fiber 10 are also included in fiber 10′. Other of the island domains 14 of fiber 10 are excluded in fiber 10′ (in this example, islands B, D, F, and H are absent). To produce the fiber cross section of FIG. 1B, the spinning apparatus is set up so that the island domain polymer flow paths form a fiber with only five of the nine island domains present in the desired locations. Again, the skilled artisan will appreciate that more or fewer of the island domains can be present in a given fiber.
The skilled artisan will appreciate that the invention is not limited to the selection of the specific islands illustrated in FIGS. 1A and 1B. Islands 14 of fiber 10 can also be present or absent in other combinations to provide further variations of the pattern shown in fiber 10. In this way a series or collection of different fiber constructions can be derived from a common fiber structure. FIG. 1C is provided as yet a further example of the numerous and various patterns that can be achieved by selecting different combinations of components to be present or absent in a particular fiber derived from a common fiber structure. In this example, fiber 10″ includes island components 14″ (I, E, and F remain) within a sea polymer 12″. The other possible islands available for inclusion (A, B, C, D, G, and H) are absent in this particular structure.
Thus, in one embodiment, the present invention provides a plurality of uniquely identifiable islands in the sea multicomponent fibers, each fiber cross section characterized by one of a predetermined number of uniquely identifiable patterns created by the relative position of an array of island domains, wherein each uniquely identifiable pattern is determined by the presence or absence of individual island domains. In the simplest embodiment, each island domain is identical in all visible respects except for relative placement within the matrix or sea polymer (i.e., each island domain has the same cross sectional shape, color, and the like) such that the number of island domains determines the number of uniquely identifiable patterns that can be created by the array of island domains. In essence, each pattern of island domains is created by turning individual island domains “on” or “off” in the array. Such a unitary fiber design is particularly advantageous due to the ease in which individual patterns can be created with relatively minor modifications to the fiber-forming apparatus in order to adjust polymer flow paths such that individual islands will be present or absent as desired. Thus, switching between individual patterns can be accomplished relatively quickly and without expensive equipment modification.
In another embodiment, the number of patterns that can be produced by the plurality of island domains will depend on both the total number of island domains and the presence of additional identifying features, such as particular colors or shapes, which can increase the total number of patterns that are possible.
In yet another embodiment, the present invention provides a plurality of uniquely identifiable multicomponent fibers, each fiber cross section characterized by one of a predetermined number of uniquely identifiable patterns created by the relative position of an array of protrusions or bumps on the periphery of one or more island domains, wherein each uniquely identifiable pattern is determined by the presence or absence of individual protrusions on the periphery of the island domain(s). In essence, each pattern is created by turning individual protrusions “on” or “off” in the array.
FIG. 2 is a transverse cross sectional view of another exemplary multicomponent fiber, designated generally as 20, useful in the present invention. Multicomponent fiber 20 is also an “islands in the sea” fiber including a “sea” polymer domain or component 22 surrounding a plurality of “island” polymer domains or components 24. FIG. 2 illustrates a variation of the fibers constructions of FIGS. 1A, 1B, and 1C, in which the fiber of the invention can include at least one component having a distinctive cross sectional feature, for example shape, that is different from that of other of the polymer domains or components. This difference can impart an additional identifier feature to an individual fiber.
For example, an islands in the sea fiber, such as that illustrated in FIG. 2, can include one or more island domains that differ in some respect from other of the island domains. One or more island domains can differ from other of the island domains, for example, with regard to polymer composition, location, size, shape, color and the like. As a non-limiting example, FIG. 2 illustrates an island domain or core 26, which differs in shape and location from the other of the island domains 24. Core 26 can be substantially centrally located as illustrated, although the invention also contemplates eccentrically located cores. Core 26 can also be formed of any suitable fiber-forming polymer. Although not illustrated, a series or collection of different fiber constructions based upon fiber 20 can be derived in a manner similar to that as described above with respect to FIGS. 1A, 1B and 1C, by selecting different combinations of domains or components 24 and/or 26 to be present or absent in a particular fiber construction, and/or by varying the unique cross sectional shape of core 26 or the cross sectional shape of one or more of island domains 24.
In another embodiment of the invention, one or more of the individual island domains shown in the appended figures can be replaced with voids by utilizing a soluble polymer component to form one or more of the island domains. As would be understood in the art, a solvent extraction technique can be used to remove the soluble polymer component at any point following fiber formation. For example, one or more island domains could be formed from a polymer that is soluble in an aqueous caustic solution such as, without limitation, polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), and copolymers or blends thereof. In another embodiment, the island domains could be formed form a polymer that is soluble in water at a temperature of 70° C. or above such as, without limitation, sulfonated polyesters (e.g., sulfonated polyethylene terephthalate), polyvinyl alcohol, sulfonated polystyrene, and copolymers or polymer blends containing such polymers. A commercially available example of a sulfonated polyester is the Eastman AQ line of copolyesters, such as Eastman AQ 55S.
Other structured fiber configurations as known in the art can also be used, so long as the structured fiber domains or components provide a pattern or design to the fiber when viewed in cross section so as to impart an identifier feature thereto, thereby rendering the fibers useful for the production of taggant materials. The cross section of the fiber is typically circular, since the equipment typically used in the production of synthetic fibers normally produces fibers with a substantially circular cross section. However, the fibers of the invention are not limited to those with a circular cross section.
Another suitable multicomponent fiber construction includes sheath core fibers that include one or more inner core polymer domains and a surrounding sheath polymer domain. In the present invention, the sheath is generally continuous, e.g., completely surrounds the core and forms the entire outer surface of a sheath core fiber, but this is not required. In addition, the core domain can be substantially concentric, or alternatively, the core can be eccentric. The fibers of the invention also include multilobal fibers having three or more arms or lobes extending outwardly from a central portion thereof. Such multilobal fibers can also include a substantially centrally located core component, which can be concentric or eccentric. Side-by-side fibers comprising two polymer domains adjacent to one another, with each polymer domain forming a portion of the outer surface of the fiber, can also be used in the invention. In one embodiment of the invention, the interface between the two polymer components of the side-by-side fiber can provide an identifying characteristic, such as a certain shape, that can be used as a distinguishing feature of the fiber.
Any of these or other multicomponent fiber constructions may be used, so long as the polymer domains are configured so as to impart the desired pattern to the fiber when viewed in cross section and thus to provide an identifier functionality to the fiber, particularly when sectioned to form multicomponent fiber taggants. Island polymer domains can also be incorporated into any of the multicomponent fiber configurations described above, such as sheath/core fibers (wherein the island domains can be in the sheath and/or the core sections) or side-by-side fibers (wherein the domains can be in one or both of the adjacent polymer domains).
When present, a core domain or component can be either concentric or eccentric. Generally centrally located domains are substantially or completely surrounded by an encapsulating polymer domain having a generally uniform thickness. This is in contrast to an eccentric configuration, in which the thickness of any surrounding polymer domain surrounding and encapsulating the core varies so that the core domain or component does not lie in the center of the fiber. Concentric multicomponent fibers can be defined as fibers in which the center of the core component is biased by no more than about 0 to about 20 percent, preferably no more than about 0 to about 10 percent, based on the diameter of the multicomponent fiber, from the center of the surrounding or encapsulating domain.
The polymer domains of the multicomponent fibers of the invention can be selected from any of the types of polymers known in the art that are capable of being formed into fibers, including polyolefins, polyesters, polyamides and the like. Examples of suitable polymers useful in the practice of the present invention include, without limitation, polyolefins including polypropylene, polyethylene, polybutene, and polymethyl pentene (PMP), polyamides including nylon, such as nylon 6 and nylon 6,6, polyacrylates, polystyrenes, polyurethanes, acetal resins, polyvinyl alcohol, polyesters including aromatic polyesters, such as polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate) (PCT), and aliphatic polyesters such as polylactic acid (PLA), polyphenylene sulfide, thermoplastic elastomers, polyacrylonitrile, cellulose derivatives, acetals, fluoropolymers, copolymers and terpolymers thereof and mixtures or blends thereof.
The weight ratio of the respective polymeric components of the fibers of the invention can vary. For example, in bicomponent fibers, the weight ratio of the polymeric components can range from about 10:90 to 90:10. In other examples the weight ratio of the polymeric components can range from about 30:70 to about 70:30 and from about 25:75 to about 70:25.
The polymeric components of the multicomponent fibers of the invention can optionally include other components or materials not adversely affecting the desired properties thereof. Exemplary materials that can be present include, without limitation, antioxidants, stabilizers, surfactants, waxes, flow promoters, solid solvents, particulates, and other materials added to enhance processability or end-use properties of the polymeric components. Such additives can be used in conventional amounts.
One or more of the polymer domains of the multicomponent fibers of the invention can optionally include one or more colorants as known in the art as an additional identifier feature. For example, useful colorants include luminescent colorants, such as fluorescent colorants, phosphorescent colorants, and mixtures thereof. Numerous types of phosphorescence and fluorescence colorants are known, and include without limitation photoluminescence colorants, electroluminescence colorants, chemiluminescence (i.e., luminescence resulting form a chemical reaction); bioluminescence (i.e., luminescence resulting from a living organism typically mediated by enzymatic or other biological system); and triboluminescence (i.e., luminescence resulting from friction such as by crushing, rubbing or scratching a crystal). Any of the types of colorants known in the art can be used in conventional amounts.
Methods for making multicomponent fibers are well known and need not be described here in detail. Generally the multicomponent fibers of the invention are prepared using conventional multicomponent textile fiber spinning processes and apparatus and optionally utilizing mechanical drawing techniques as known in the art. Processing conditions for the melt extrusion and fiber-formation of fiber forming polymers are well known in the art and may be employed in this invention.
To form the multicomponent fiber of the invention, at least two polymers are melt extruded separately and fed into a polymer distribution system wherein the polymers are introduced into a spinneret plate. The polymers follow separate paths to the fiber spinneret and are combined in a spinneret hole. The spinneret is configured so that the fiber has the desired shape.
An exemplary fiber spinning apparatus useful for producing the multicomponent fibers of the invention with polymer domains designed to have specified patterns as identifiers is described in U.S. Pat. No. 6,361,736, issued Mar. 26, 2002, the entire disclosure of which is hereby incorporated by reference. This spinning apparatus generally includes a distribution plate for distributing flowable material in a direction perpendicular to the spinning direction and a metering plate positioned downstream of the distribution plate and likewise oriented perpendicular to the spinning direction. The distribution plate contains at least one flow path which is in fluid flow connection with at least one exit hole. The metering plate contains one or more orifices which are desirably positioned immediately downstream of an exit hole of the distribution plate.
The orifices in the metering plate are adapted to moderate the pressure of a material flowing from an exit hole of the distribution plate through the metering plate. For example, the metering plate can be positioned downstream of the distribution plate so that plural orifices of the metering plate are immediately downstream of each of the distribution plate exit holes. In addition, the diameter of at least a portion of the metering plate orifice can also be smaller than the diameter of the distribution plate exit hole so that it moderates the pressure of a material flowing from the distribution plate through the metering plate, thereby providing a flow of material to a downstream spinneret at a relatively more consistent pressure.
The distribution plate holes can be “shaped” (i.e., non-circular) to produce multicomponent fibers of the invention having selectively shaped regions of specific components as described above. Similarly, the flow paths can assume any configuration chosen by the plate designer to achieve the desired fiber shape, composition and cross-section, and can be of greater complexity than practicable using prior art spin pack assemblies, as will be readily recognized by those having ordinary skill in the art.
Because the spinning apparatus can serve to equilibrate the pressure of the flow of a plurality of flowable materials, the apparatus can allow production of intricate and/or precisely shaped components, such as the crescent shaped core of FIG. 2 above. To this end, advantageously the polymer stream exiting the distribution flowpath through multiple metering orifices affords a high degree of precision in feeding the polymer stream to the spinneret backhole. This can allow production of a plurality of flowable material streams that collectively substantially maintain the shape of the stream exiting the distribution plate.
The present invention allows the ready manufacture of multicomponent fibers having different cross sectional patterns by proper selection of polymer flow distribution plates in the spin pack. In this regard, a particular multicomponent fiber cross sectional pattern or design can be selected, and the spinning apparatus can be readily set up to make fibers with the selected pattern by addition or removal of appropriate polymer distribution plates. In this way a large number of multicomponent fibers, each with a different cross sectional pattern or design, can be readily and economically manufactured.
Following extrusion through the die, the resulting thin fluid strands, or filaments, remain in the molten state before they are solidified by cooling in a surrounding fluid medium, which may be chilled air blown through the strands, or ambient air, or immersion on a bath of liquid such as water. Once solidified, the filaments are taken up on a godet or another take-up surface. In a continuous filament process, the strands are taken up on a godet which draws down the thin fluid streams in proportion to the speed of the take-up godet.
Generally the thin fluid streams are drawn down in a molten state, i.e., before solidification occurs to orient the polymer molecules for good tenacity. Typical melt draw down ratios known in the art may be utilized. Where a continuous filament or staple process is employed, it may be desirable to draw the strands in the solid state with conventional drawing equipment, such as, for example, sequential godets operating at differential speeds.
Following drawing in the solid state, the continuous filaments may be crimped or texturized and cut into a desirable fiber length, thereby producing staple fiber. The length of the staple fibers generally ranges from about 25 to about 75 millimeters, although the fibers can be longer or shorter as desired.
The fibers of the invention can be staple fibers or continuous filaments. In general, staple fibers and continuous filaments formed in accordance with the present invention can have a fineness of about 0.5 to about 100 denier.
Advantageously the fibers or filaments are directed to a suitable apparatus as known in the art to form a yarn or tow of the fibers or filaments, which can be optionally crimped. The resultant yarn and/or tow can include a plurality of multicomponent fibers in accordance with the present invention in which each of the fibers has the same identifier pattern when viewed in cross section. Other types of fibers or filaments, however, can also be present in the yarn.
The filament yarn or tow prepared according to the present invention can comprise a plurality of multicomponent fibers according to the invention wherein each fiber has the same identifying characteristic, such as the same cross sectional pattern. Alternatively, the filament yarn or tow may comprise a plurality of multicomponent fibers wherein each fiber exhibits a uniquely identifiable pattern as compared to each of the remaining fibers in the yarn or tow. In this manner, a large number of uniquely identifiable fibers can be formed quickly and efficiently by simultaneously coextruding the plurality of fibers through the same spinneret. For example, the filament yarn or tow may comprise a plurality of fibers, wherein the cross section of each fiber is visually distinguishable from the remaining fibers within the yarn or tow, each fiber comprising a uniquely identifiable cross sectional pattern of island domains, each pattern being formed from an array of a predetermined number of island domains in predetermined locations within the array, wherein each pattern is determined by classifying individual island domains within the array as present or absent from the pattern. In another example, each individual filament of the yarn or tow has a fiber cross section characterized by one of a predetermined number of uniquely identifiable patterns created by the relative position of an array of protrusions or bumps on the periphery of one or more island domains, wherein each uniquely identifiable pattern is determined by the presence or absence of individual protrusions on the periphery of the island domain(s). Thus, where the desired taggant will comprise more than one fiber cross section having a uniquely identifiable feature, the present invention provides a convenient and efficient method of producing the multiple fibers that will be used together as the taggant.
In a further embodiment, a collection of fibers is provided by the invention, wherein the collection of fibers comprises two or more subsets of fibers, each subset of fibers characterized by a fiber cross section that is uniquely identifiable as compared to each of the other subsets of fibers. Each subset of fibers within the collection can be meltspun separately and then collected. Alternatively, the entire collection of fibers can be derived from the same filament yarn or tow. In this manner, a relatively small number of fiber cross sections can be selected and manufactured quickly and efficiently in a single processing run with a single filament yarn or tow. For example, if a particular fiber cross section design has 12 possible uniquely identifiable patterns, but only 2 of the patterns are desired, a single filament yarn or tow can be formed that includes a first subset of fibers characterized by the first desired cross section pattern and a second subset of fibers characterized by the second desired cross section pattern, the two subsets forming the entire filament yarn or tow. As would be appreciated, the number of subsets can be varied as desired depending on the desired number of patterns. Each subset may comprise one or more individual filaments, preferably a plurality of individual filaments.
The present invention also provides a set of a plurality of distribution plates for use in a melt-spinning apparatus, wherein the set of distribution plates are configured to form a common multicomponent fiber cross section design exhibiting at least one identifying characteristic that can be varied to form a plurality of different identifying patterns. The plurality of distribution plates can be manipulated in order to change the identifying characteristic and thereby form a variety of identifying patterns. For example, one or more distribution plates could be exchanged in the melt-spinning apparatus, or the relative placement of one or more distribution plates could be modified, such that a new identifiable pattern is formed in the multicomponent fiber cross section. The set of distribution plates are useful for providing a means for quickly and efficiently changing the fiber cross section in a manner that alters the identifiable characteristics of a fiber or a subset of fibers within a filament yarn or tow.
The multicomponent fibers and/or yarns including the same are suitable for the production of taggant materials for identification and/or security applications and can be incorporated in any suitable manner into a product to be tagged. For example, the fibers and/or yarns and/or tows including the same can be included as is in the product to be tagged, for example, by knitting or weaving the fiber, yarn, and/or tow into a fabric. Alternatively a portion of the fiber, yarn and/or tow can be removed from the fiber using suitable techniques and incorporated into the product to be tagged. For instance, the fiber may be cut into very short lengths and dispersed in or adhered to the product or material to be tagged.
The multicomponent fibers and/or yarns and/or tows of the invention can be useful in providing taggant materials for identifying many types of materials or objects, including without limitation bulk materials (e.g., fertilizer, chemicals, paints, oils, plastics, pigments, clays, fertilizers, explosives, etc.), prepackaged materials (e.g., shampoo, conditioner, lotion, motor oils, pharmaceuticals, etc.) and individual product units (e.g. stereos, cameras, computers, VCRs, furniture, motorized vehicles, livestock, etc.). This can allow a user to trace products diverted from their intended distribution routes, to identify the manufacturer and/or distributor of a product, to identify a given batch of a product, and the like. The multicomponent fibers and/or yarns and/or tows of the invention can also provide taggants useful for authentication, for example, to authenticate the genuine nature of a given product to combat counterfeiting, for warranty purposes, and the like. The multicomponent fibers and/or yarns and/or tows of the invention can also be useful as taggants in law enforcement and other arenas, for example, as identifiers for evidence materials, high security documents, tracing of hazardous materials and explosives, and the like. The present invention also includes products or materials including the fibers and/or portions thereof dispersed in, adhered to, or otherwise incorporated therein. It is preferable for the uniquely identifying characteristic of each fiber cross section prepared according to the invention to be readable by a machine vision system, meaning a machine vision system can discern one pattern from another.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
- EXAMPLE 1
The following examples are provided to illustrate certain embodiments of the invention and are not intended to limit the scope of the invention as defined by the appended claims.
- EXAMPLE 2
In a multicomponent fiber spinning apparatus as described in U.S. Pat. No. 6,361,736, which is incorporated by reference in its entirety, distribution plates and metering plates were formed so as to produce a round cross section fiber with twelve round “island” polymer domains in a “sea” polymer domain, said twelve island domains positioned around the perimeter of the fiber and surrounding a central core comprising an additional domain of the “island” polymer, said core being predominantly circular but having a substantial indentation as well as a fully-enclosed domain comprising the “sea” polymer, such that the shaped core resembled a “Pac-Man” shape similar to that of the computer game character. Plasticized polyvinyl alcohol was extruded through the distribution plate channels to form the “sea” polymer domains, and polylactic acid was extruded through the distribution plates to form the “island” polymer domains. The fiber was melt extruded through 175 round-hole spinneret capillaries, solidified (quenched) in a transverse stream of air, taken up on godets and wound onto a bobbin. The resulting fibers were then cut into very short lengths and adhered to a number of different products, where they were analyzed by a microscopic machine vision system capable of identifying the number and position of the twelve islands in the cross section.
- EXAMPLE 3
In the same spinning apparatus as used in Example 1, a single distribution plate was replaced by a new distribution plate that prevented the “island” polymer from flowing into position for three of the twelve circumferential islands formed in the fiber of Example 1. In all other respects, the production of the fiber was identical to that of the fiber of Example 1. The resulting fiber's cross section had the same shaped core domain, and had “island” polymer domains in the same positions as in Example 1, in the case of only nine of the twelve “islands,” whereas only “sea” polymer was present where the missing three “islands” appeared in the fiber of Example 1. This fiber was also subsequently cut into short lengths and adhered to products, where they were analyzed by the same machine vision system, which was able to distinguish the cross section of these fibers from those of Example 1 by virtue of the number and position of the missing islands.
- EXAMPLE 4
The fibers of Examples 1 and 2 were alternately processed with a step that exposed the fibers to water, which dissolved and removed the polyvinyl alcohol “sea” component. As a result, the twelve and nine (respectively) “islands” were dissociated from the shaped core, and the “eye” of the shaped core was made hollow. Without the association of the twelve or nine (respectively) islands with the core, the fibers lost their ability to be distinguished by the machine vision system.
- EXAMPLE 5
In a multicomponent fiber spinning apparatus as described in U.S. Pat. No. 6,361,736, distribution plates and metering plates were formed so as to produce a round cross section fiber with a central first polymer domain enclosing a single “island” domain of a second polymer. A sheath of the second polymer also encloses the first polymer domain. The distribution and metering plates were formed to further modify the first polymer domain so as to contain twelve peripheral indentions, the indentions being filled with the second polymer. One of the twelve indentions was substantially deeper than the other eleven. The distribution plates were formed so that by replacing a single plate with a plate of minor design difference, flow of the second polymer to the position of any one or any combination of the peripheral indentions would be impeded, thereby resulting in a fiber cross section with the corresponding indention(s) missing. Polylactic acid was extruded through the distribution plate channels to form the first polymer domain, and plasticized polyvinyl alcohol was extruded through the distribution plates to form the second polymer domains, namely the single island within the first polymer domain, the twelve peripheral indentions, and the outer sheath of the fiber. The fiber was melt extruded through 175 round-hole spinneret capillaries, solidified (quenched) in a transverse stream of air, taken up on godets, and wound onto a bobbin. The resulting fibers were then cut into very short lengths and adhered to a number of different products, where they were analyzed by a microscopic machine vision system capable of identifying the number and position of the twelve indentions in the fiber cross section.
The fibers of Example 4 were alternately processed with a step that exposed the fibers to water, which dissolved and removed the polyvinyl alcohol polymer. The resulting fiber cross section includes the central core of polylactic acid, with a hollow island formed therein, wherein the core of polylactic acid has a serrated circumference comprising twelve indentations (i.e., a series of protrusions are present around the periphery thereof). Particles of this fiber cut to very short length were adhered to a number of different products and analyzed by a machine vision system capable of identifying the presence and position of each of the twelve indentations, thereby rendering this fiber more suitable than that of Example 3 for applications involving exposure to water.