Patent Publication Number: US-2015083659-A1

Title: Bicomponent fiber with systems and processes for making

Description:
BACKGROUND OF THE INVENTION 
     The present disclosure relates to a bicomponent fiber, in addition to systems and processes for making the bicomponent fiber. More particularly, the present disclosure relates to increasing the versatility of fibers and fiber products while reducing costs. 
     Fabrics and fiber components serve important technical purposes in a variety of fields, including industrial and air filtration. Depending on need, fibers may be processed into a variety of materials. Fibers of different composition can be used to form selectively or “semi-permeable” substances. The physical properties of a fabric or fiber-based product depend from the substances used in each individual fiber. For example, changing the structure of a fiber can influence resilience to external factors or affect the costs of production. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A first aspect of the disclosure provides a bicomponent fiber comprising a glass core; and a polytetrafluoroethylene (PTFE) sheath circumferentially enclosing the glass core; wherein the bicomponent fiber has a diameter between approximately five micrometers and approximately twenty micrometers. 
     A second aspect of the disclosure provides a system for making a bicomponent fiber, the system comprising: a container having an inlet and an outlet; an aqueous dispersion within the container, wherein the aqueous dispersion includes polytetrafluoroethylene (PTFE); and a heated surface configured to receive a core fiber coated with the aqueous dispersion from the outlet of the container, wherein the heated surface sinters the coated aqueous dispersion into a sheath. 
     A third aspect of the invention provides a process of making a bicomponent fiber, the process comprising: passing a glass fiber through an aqueous dispersion including polytetrafluoroethylene (PTFE) to coat the glass fiber with the aqueous dispersion, thereby yielding a PTFE coat of the glass fiber; and contacting the PTFE coat of the glass fiber with a heated surface to form a PTFE sheath, wherein the PTFE sheath circumferentially encloses the glass fiber, thereby yielding the bicomponent fiber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and other features of the disclosed system will be more readily understood from the following detailed description of the various aspects of the system taken in conjunction with the accompanying drawings that depict various embodiments, in which: 
         FIG. 1  is a cross-sectional diagram of a bicomponent fiber according to an embodiment of the disclosure. 
         FIG. 2  is a perspective view of a laminate made from a bicomponent fiber according to an embodiment of the invention. 
         FIG. 3  is a perspective view of a woven fabric made from a bicomponent fiber according to an embodiment of the invention. 
         FIG. 4  is a cross-sectional diagram of a needle felt fabric made from a bicomponent fiber according to an embodiment of the invention. 
         FIG. 5  is a perspective view of a filter bag with materials made from a bicomponent fiber according to an embodiment of the invention. 
         FIG. 6  is a perspective view of a pleated filter element with materials made from a bicomponent fiber according to an embodiment of the invention. 
         FIG. 7  is a schematic diagram of a system for making a bicomponent fiber according to an embodiment of the disclosure. 
         FIG. 8  is a schematic flow diagram of a process of making a bicomponent fiber according to an embodiment of the disclosure. 
     
    
    
     It is noted that the drawings are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting its scope. In the drawings, like numbering represents like elements between the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the present teachings may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings, and it is to be understood that other embodiments may be used and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely illustrative. 
     Embodiments of the present disclosure include a bicomponent fiber. The bicomponent fiber can include a glass core enclosed by a polytetrafluoroethylene (PTFE) sheath. In some circumstances, the bicomponent fiber can have a diameter between approximately five micrometers and approximately twenty micrometers. 
     Referring to the drawings,  FIG. 1  depicts a bicomponent fiber  2  according to an embodiment of the disclosure. Bicomponent fiber  2  can include a core  10  of a material that can substantially maintain its structural integrity by not failing or melting at temperatures exceeding approximately 250° C. Specifically, core  10  can include glass materials or derivatives. As one example, core  10  can be made from a texturized glass filament. Some materials used in core  10 , such as glass, may not have a corresponding ability to withstand acidic environments. For the purposes of comparison, the properties of other acid-resistant materials such as polymers are discussed elsewhere herein. In some embodiments, core  10  can include a glass core with a coefficient of thermal expansion approximately equal to 4.0×10 −6  meters over meters per kelvin (sometimes abbreviated as “m/m/K” or “/K”). 
     In an embodiment, bicomponent fiber  2  can further include a sheath  12  circumferentially enclosing core  10 . Sheath  12  can generally include any currently known or later developed material with acid-resistant properties, such as a polymer. The acid resistance of sheath  12  is discussed in further detail elsewhere herein. In some embodiments, sheath  12  can be a layer circumferentially enclosing core  10 . Sheath  12  can be deposited according to systems and processes discussed elsewhere herein. 
     Sheath  12  can include a polymer such as polytetrafluoroethylene (PTFE), with material properties that prevent sheath  12  from reacting, disintegrating, or otherwise failing when exposed to acidic environments. In some embodiments, sheath  12  can maintain structural integrity when exposed to an acid having a pH of approximately 2.0 or less. The acid-resistant properties of sheath  12  can also accompany resistance to high temperatures, such as temperatures above 250° C. However, sheath  12  need not maintain structural integrity over the same range of temperatures as the material used in core  10 . Sheath  12  can also have a coefficient of thermal expansion that is significantly different from materials used in core  10 . Where sheath  12  includes PTFE, the coefficient of thermal expansion of sheath  12  can be approximately equal to 135.0×10 −6  m/m/K. 
     Bicomponent fiber  2  can be customized to have desired size or shape. In specific applications such as air filtration and industrial filtration, bicomponent fiber  2  can have a diameter between approximately five micrometers and approximately twenty micrometers. In more specific applications, bicomponent fiber  2  can have a diameter between approximately five micrometers and ten micrometers. The size of bicomponent fiber  2  can allow bicomponent fiber  2  to be deployed or used as a weavable fabric. Specifically, bicomponent fiber  2  can be used in filtration devices, such as filter paper materials or filter bags. 
     Bicomponent fiber  2 , by having a core  10  and sheath  12  with the properties described herein, can be deployed in a broader context of situations than each of the components used in core  10  and/or sheath  12  alone. In particular, the acid-resistant properties of sheath  12  can allow bicomponent fiber  2  to be applied in acidic environments with a pH value of at most approximately 2.0. Sheath  12  can remain structurally stable and may not react, disintegrate, or otherwise fail when exposed to acids. Thus, the properties of sheath  12  can also protect the structural integrity of core  10 . 
     Similarly, sheath  12  and/or core  10  can remain structurally stable when exposed to high-temperature environments. In some embodiments, sheath  12  can conduct heat. Due to its design, bicomponent fiber  2  can retain the temperature-resistant properties of both glass and PTFE. Both core  10  and sheath  12  can absorb heat or thermal energy from the environment. As a result, both core  10  and sheath  12  of bicomponent fiber  2  can be applied in environments having temperatures exceeding 250° C. This property reduces the risk of damage, structural breakdown, melting, or other temperature-related failure. 
     As shown in  FIG. 2 , embodiments of bicomponent fiber  2  can be converted into a laminate  20 . Bicomponent fibers  2  capable of conversion to laminate  20  can have a diameter between approximately five micrometers and approximately twenty micrometers. In other embodiments, bicomponent fiber  2  can have a diameter between approximately five micrometers and approximately ten micrometers. 
     Bicomponent fiber  2  can be converted into laminate  20  according to currently known or later developed methods for weaving fibers or other weavable substances into a continuous fabric. The resulting fabric can be laminated to a membrane  21 . Some examples of processes for creating laminate  20  are discussed elsewhere herein. 
     Turning to  FIG. 3 , a woven fabric  22  is shown. Woven fabric  22  can be composed of bicomponent fiber  2  ( FIG. 1 ). Similar to conventional threads, bicomponent fiber  2  can be subjected to weaving via currently known or later developed processes for forming a fabric. The resulting woven fabric  22  may have some (or all) of the properties of bicomponent fiber  2 . Woven fabric  22  can therefore be used in various applications and to form filtration equipment, as discussed elsewhere herein. 
     In  FIG. 4 , a needle felt fabric  24  is shown. As known in the art, a needle felt fabric may refer to a material in which individual fibers are entangled with each other to form a fibrous structure. Similar to laminate  20  ( FIG. 2 ), needle felt fabric  24  may include several bicomponent fibers  2  ( FIG. 1 ) laminated to membrane  21 . Needle felt fabric  24  may have some (or all) of the properties of bicomponent fiber  2 . Needle felt fabric  24  may also be applied in this form or used to create filtration equipment, as discussed elsewhere herein. 
     As shown in  FIG. 5 , laminate  20  of bicomponent fiber  2  ( FIGS. 1 ,  2 ) and/or woven and needle felt fabrics  22 ,  24  ( FIGS. 3 ,  4 ) can be used to form a filtration device. According to the example shown in  FIG. 5 , laminate  20  of one or more bicomponent fibers  2  ( FIGS. 1 ,  2 ) can be used to form a filter bag  26  from laminate  20 . Although filter bag  26  is shown to be made from laminate  20 , filter bag  26  can also be made from woven and needle felt fabrics  22 ,  24  ( FIGS. 3 ,  4 ). Filter bag  26  can be implemented in a variety of situations, including industrial or air filtration. For example, some substances can pass through laminate  20  of filter bag  26 , while other substances will be stopped and retained within filter bag  26 . In addition, filter bag  26  can include a retaining member  27 , to which laminate  20  may be affixed. In the example of  FIG. 5 , retaining member  27  is substantially annular. In this manner, filter bag  26  can have a desired structure. 
       FIG. 6  depicts a pleated filter element  28  which may also be made from laminate  20  of bicomponent fiber  2  ( FIGS. 1 ,  2 ) and/or woven and needle felt fabrics  22 ,  24  ( FIGS. 3 ,  4 ). Pleated filter element  28  is another piece of filtration equipment which may offer the acid resistance and temperature resistance of bicomponent fiber  2 . Similar to filter bag  26 , retaining member  27  can be affixed to at least one laminate  20 . Several laminates  20  can be affixed to retaining member  27  to form a “pleated” filter structure of pleated filter element  28 . Although  FIG. 6  depicts a pleated filter element  28  with laminate  20  by way of example, pleated filter element  28  can also be made with woven and needle felt fabrics  22 ,  24  ( FIGS. 3 ,  4 ). Through the use of bicomponent fiber  2  ( FIG. 1 ), pleated filter element  28  can exhibit the acid and temperature resistant properties discussed elsewhere herein. 
     Laminate  20 , woven fabric  22 , needle felt fabric  24 , filter bag  26 , and/or pleated filter element  28  can be used in various filtration applications. For example, laminate  20 , woven fabric  22 , and/or needle felt fabric  24  can be used to make a physical filter such as a semi-permeable felt structure, filter paper, and/or woven fabric. In addition, each material made from bicomponent fiber  2  ( FIG. 1 ) can have some or substantially all of physical properties of core  10  ( FIG. 1 ) and sheath  12  ( FIG. 1 ), including resistance to acidic environments with a pH of approximately 2.0 or less and/or temperatures greater than approximately 250° C. 
     In addition to bicomponent fiber  2  and materials made therefrom (e.g., laminate  20  ( FIG. 2 ), fabrics  22 ,  24  ( FIGS. 3 ,  4 ), filter bags  26  ( FIG. 5 ), and pleated filter element  28  (FIG.  6 )), the present disclosure also contemplates a system and process of making bicomponent fiber  2 . 
     Turning to  FIG. 7 , an embodiment of a system  30  for making a bicomponent fiber  2  is shown. System  30  can operate on a core fiber  32 . Core fiber  32  can include materials discussed elsewhere herein with respect to core  10  ( FIG. 1 ), such as a texturized glass filament. Core fiber  32  can be processed along the direction of phantom line A to enter a container  34 , optionally with the aid of a first roller  36 . 
     Container  34  can be a tank, bath, box, or another equivalent structure for housing liquid and/or solid materials. Container  34  can include a reserve of sheathing materials  38  capable of contacting core fiber  32  and remaining thereon. In an embodiment, sheathing materials  38  can be in the form of an aqueous dispersion. In this case, sheathing materials  38  can be a powder of substances similar to or the same as those discussed elsewhere herein with respect to sheath  12  ( FIG. 1 ), including PTFE. The powder of sheathing materials  38  can be added to a liquid to form an aqueous dispersion. In some embodiments, sheathing materials  38  is an aqueous dispersion that includes approximately 60% PTFE. System  30  can include one container  34  or multiple containers  34  arranged in succession. Increasing the number of containers may improve the deposition of sheathing materials  38  on core fiber  32 . 
     In an embodiment, container  34  can include an inlet  40  and an outlet  42  between the inside of container  34  and the environment. Inlet  40  can allow core fiber  32  to enter container  34  and contact sheathing materials  38 . Outlet  42  can allow core fiber  32  to exit container  34 . Thus, inlet  40  and outlet  42  can allow passage of core fiber  32  through container  34 . 
     Core fiber  32 , following passage through sheathing materials  38  of container  34 , can become a coated core fiber  44 . Coated core fiber  44  contains a layer of sheathing materials  38  provided thereon. In some embodiments, core fiber  44  can include approximately 20% of sheathing materials by weight of core fiber  32 . To form sheath  12  ( FIG. 1 ) of bicomponent fiber  2 , coated core fiber  44  can contact one or more heated surfaces as described herein. 
     In an embodiment, coated core fiber  44  can pass over three heated rollers  46 A,  46 B,  46 C. Heated rollers  46 A,  46 B,  46 C can include, for example, an industrial roller currently known or later developed. Each heated roller  46 A,  46 B,  46 C can be supplied with heat energy from a thermal source  48 . In specific embodiments, heated rollers  46 A,  46 B,  46 C can be sintering rolls. Although thermal source  48  is shown to be one unit distinct from each of heated rollers  46 A,  46 B,  46 C, system  30  can include several thermal sources  48 , each of which can optionally be directly coupled to heated rollers  46 A,  46 B,  46 C. Other embodiments of the present disclosure can, for example, include only one heated roller, or as many heated rollers as desired. Alternatively, other currently known or later developed heated surfaces can be used in system  30  to transfer heat to coated core fiber  44 . 
     System  30 , through heated surfaces such as heated rollers  46 A,  46 B,  4 C, can cause sheathing materials  38  to become a coated sheath on core fiber  32 . For example, PTFE can sinter when subjected to heat. In an embodiment, heated surfaces of rollers  46 A,  46 B,  46 C can be at a temperature of approximately 350° C. Therefore, heat applied from heated rollers  46 A,  46 B,  46 C can sinter sheathing materials  38  into a solid sheath circumferentially enclosing core fiber  32 . Bicomponent fiber  2  is yielded from heated rollers  46 A,  46 B,  46 C along line B as a result. As discussed elsewhere herein, bicomponent fiber  2  can be processed, optionally along with other bicomponent fibers  2 , to create derivative substances such as laminate  20  ( FIGS. 2 ,  3 ) and filter bag  26  ( FIG. 5 ). 
     Turning to  FIG. 8 , a flow diagram representing an embodiment of a process  50  for making a bicomponent fiber is shown. Process  50  can use any of the equipment discussed herein with respect to system  30 , and/or their equivalents. Process  50  can operate on a core fiber  32  ( FIG. 7 ) in step S 52 , with core fiber  32  ( FIG. 7 ) being provided from a user or machine. 
     Core fiber  32  ( FIG. 7 ) can be coated with sheathing materials  38  in step S 54 , for example, by entering a container  34  ( FIG. 7 ) in step S 54 . Sheathing materials  38  ( FIG. 7 ) of coated core fiber  44  ( FIG. 7 ) can sinter in response to being passed over heated surfaces in step S 56 . Bicomponent fiber  2  ( FIG. 1 ) can be obtained in step S 58  of process  50  as a result of contacting heated surfaces (e.g., heated rollers  46 A,  46 B,  46 C ( FIG. 7 )). In some embodiments, bicomponent fiber  2  ( FIG. 1 ) yielded from process  50  can have a diameter between approximately five micrometers and approximately twenty micrometers. In other embodiments, bicomponent fiber  2  can have a diameter between approximately five micrometers and approximately ten micrometers. 
     Bicomponent fiber  2  ( FIG. 1 ) can be further modified in additional, optional steps of process  50 . As an example, bicomponent fiber  2  ( FIG. 1 ) can be weaved in step S 60  into a woven fabric. Woven fabrics yielded from process  50  can include some or substantially all of the acid and temperature resistant properties discussed elsewhere herein with respect to bicomponent fiber  2  ( FIG. 1 ). 
     Embodiments of process  50  can optionally include a further step S 62  (shown in phantom) of making materials such as laminate  20  ( FIG. 2 ) from the woven fabric yielded from step S 60 . As one example, a user or system can in step S 62  laminate the woven fabric to an expanded PTFE membrane  21  ( FIG. 2 ) of PTFE to form a laminate  20  ( FIG. 2 ). A user can also form laminate  20  ( FIG. 2 ) according to equivalent processes currently known and later developed. Laminate  20  ( FIG. 2 ) can have some or substantially all of the same temperature and acid resistant properties described elsewhere herein with respect to bicomponent fiber  2  ( FIG. 1 ). 
     A further option for processing bicomponent fiber  2  ( FIG. 1 ) in process  50  can include chopping bicomponent fiber  2  into staple fibers in Step S 64 . Staple fibers in step S 64  can be used to form a felted fabric by any currently known or later developed process, such as needle punching or hydroentangling, in step S 66 . The resulting felted fabric can include some or substantially all of the acid and temperature resistant properties of individual bicomponent fibers  2  discussed elsewhere herein. In addition, felted fabrics yielded from step S 66  can optionally be converted into a laminate  20  ( FIG. 2 ) by laminating the felted fabric to an expanded PTFE membrane  21  ( FIG. 2 ) as discussed elsewhere herein with respect to step S 62 . 
     Fabrics or laminate  20  ( FIGS. 2-4 ) yielded from any of steps S 60 , S 62 , and S 68  can be processed into filtration equipment. As an example, a user of process  50  in step S 68  can form filter bag  26  ( FIG. 5 ) by affixing a fabric or laminate  20  ( FIG. 2 ) to a structural component. For instance, filter bag  26  ( FIG. 5 ) can be formed by affixing fabrics and/or laminate  20  ( FIGS. 2-4 ) to retaining member  27  ( FIG. 5 ) according to any currently known or later developed process for forming a bag, such as adhesive bonding. 
     In addition to the processes described herein, including the example flow diagram of  FIG. 8 , other methods of making a bicomponent fiber  2  ( FIG. 2 ) are contemplated. As one example, a film of sheathing materials ( FIG. 7 ) such as PTFE can be rolled circumferentially around core fiber  32  ( FIG. 7 ). Core fiber  32  can be a glass filament core or a glass-based yarn. The rolled film of sheathing materials  38  ( FIG. 7 ) and core fiber  32  ( FIG. 7 ) can then be heated to a temperature of approximately 350° C. The heating can allow the film of sheathing materials  38  ( FIG. 7 ) to form a continuous sheath about core fiber  32  ( FIG. 7 ). In an embodiment, the film of sheathing materials can include PTFE. The resulting bicomponent fiber  2  ( FIG. 1 ) can have a diameter between approximately five micrometers and twenty micrometers, or between approximately five micrometers and ten micrometers. 
     Making bicomponent fiber  2  ( FIG. 1 ) according to the film coating and heating process described herein produces a component that can also be further processed into other materials or devices. For example, bicomponent fiber  2  can be chopped and pressed into a felt structure. In other embodiments, bicomponent fiber  2  ( FIG. 1 ) can be processed into a woven fabric. In additional embodiments, bicomponent fiber  2  ( FIG. 1 ) can be woven into a laminate structure  20  ( FIG. 2 ), a fabric ( FIGS. 3 ,  4 ), a filter bag  26  ( FIG. 5 ), and/or a pleated filter element  28  ( FIG. 6 ). These resulting structures can have some or substantially all of the acid or temperature resistant properties discussed elsewhere herein. 
     The various embodiments discussed in the present disclosure can offer several technical and commercial advantages. An advantage that may be realized in the practice of some embodiments of the described apparatuses is a fiber applicable to industrial filtration applications, such as air filtration, that includes both heat and acid resistant properties. Some potential applications for bicomponent fiber include use in hazardous waste generators, kilns, industrial waste incinerators, and radioactive waste incinerators. A further advantage is that bicomponent fiber  2  ( FIGS. 1 ,  2 ,  4 ) can be deployed without an additional surface coating upon sheath  12  ( FIG. 1 ). 
     The ability to combine a core fiber of glass with a sheath of PTFE through the processes described herein is a departure from the art in that each of the combined materials may have significantly different coefficients of thermal expansion. Thus, system  30  ( FIG. 7 ) and process  50  ( FIG. 8 ) described herein allow the advantageous properties of each material to be present in a single fiber. Further, significant cost savings can be achieved with bicomponent fibers of glass and PTFE as compared to single-component fibers of PTFE alone. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.