Patent Publication Number: US-2007101771-A1

Title: Napped face stitch bonded fabric and related process

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of and priority from U.S. Provisional Application 60/708,563 having a filing date of 16 Aug. 2005, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD  
      The present invention generally pertains to plush face fabrics suited for use in home furnishing such as for use in constructing upholstery. More particularly, the present invention is directed to a napped face stitchbonded fabric and to a process for making such fabric.  
     BACKGROUND  
      Felt-like and suede-like fabrics are well known for use in applications such as furnishing and automotive seating upholstery. These fabrics have a pleasing look and tactile feel to their front side. Moreover, these fabrics can stand up to high friction environments while keeping their appearance intact. In the past, processes for creating these fabrics have included shearing, napping, or brushing warp-knitted or woven loop piled fabrics. While such products provide suitable performance characteristics, they face deficiencies due to the costs associated with forming the initial knit and woven fabric substrates.  
      In order to address the deficiencies of using woven or knit base fabrics while still providing a desired plush pile surface, it has been proposed to use stitch bonded base fabrics formed with rows of parallel stitch lines subjected to a sanding or shearing process. Such a product is disclosed in my U.S. Pat. No. 6,423,393 the teachings of which are incorporated herein by reference as if fully set forth herein. Due to the application of the sanding or shearing process, such products exhibit a relatively dense plush pile face with the individual yarns being sharply clipped or cut.  
      Napping is a fabric treatment process wherein a face of the fabric is moved across a treatment apparatus such as one or more rotating cylinders incorporating an arrangement of extensions such as metal points or burrs such that the extensions pluck yarns away from the surface and form a downy layer of broken fibers across the surface. In the past, napping has been used on woven and knitted fabrics to form goods such as flannel, wool broadcloth and the like. However, as indicated in my prior patent 6,423,393, napping has been considered too harsh for stitchbonded fabrics.  
      As will be recognized, stitchbonded fabrics are well known. Such fabrics typically utilize a relatively light-weight substrate layer such as a non-woven web or the like through which parallel rows of stitching yarns are passed by needles to form an arrangement of stitches. The stitching yarns form the body of the fabric and define the fabric surface structure. The stitching yarns themselves provide coherency and strength to the fabric. In formation of a stitch bonded fabric yarns may be passed between adjacent rows over sinker fingers to provide a looped pile surface. The rows of stitches are typically formed in relatively close relation to one another so as to provide desired coverage levels and to impart desired strength characteristics. Due to the close proximity of the stitch rows, napping has generally been considered an unsuitable surface treatment since the crossing yarns between the rows tend to be of inadequate length to efficiently engage the burrs on the napping machine. Moreover, the bristles of the nappers and/or the brushes tend to dig into the stitchbonded fabrics, causing the staple fibers of the nonwoven web to be pulled up through the outer stitching.  
     SUMMARY OF THE INVENTION  
      The present invention provides advantages and alternatives over the prior art by providing a process whereby fabrics of stitchbonded construction may be effectively treated by napping. A resultant fabric construction is also provided.  
      According to one aspect of the invention the stitch bonded fabric includes a planar substrate such as a nonwoven web of staple fibers. A ground yarn is stitchbonded into the substrate in a substantially flat stitch arrangement such as a fully threaded chain stitch, tricot stitch or the like to form rows of stitches defining a ground covering across the substrate. A pile yarn is also stitchbonded into the substrate to form loop pile stitches with upstanding loops. During formation, at least a portion of the pile yarns are shifted over multiple sinker fingers between non-adjacent needles such that loops extend in arching relation over at least one intermediate needle line. Once the yarns have been stitchbonded into the substrate, the upstanding loops are subjected to a napping treatment wherein the loops are pulled away from the substrate until broken. An arrangement of split and frayed yarn ends is thus formed over the ground layer.  
      Other features and aspects of the present invention are discussed in greater detail below.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which:  
       FIG. 1  illustrates schematically a two bar stitch bonding process for selectively forming an arrangement of surface loops in combination with a cooperating ground yarn system through a fibrous substrate;  
       FIG. 2  illustrates schematically the stitching of a ground yarn in an arrangement of substantially flat chain stitches by a multiplicity of reciprocating needles in a fully threaded arrangement;  
       FIG. 3  illustrates schematically the stitching of a surface yarn in a pattern of extended length loops formed by shifting loop-forming yarns between non-adjacent needles;  
       FIG. 4  illustrates a representative napping process for tensioned breakage of surface loops; and  
       FIG. 5  illustrates a stitchbonded fabric having a napped face of frayed surface yarns. 
    
    
      While the invention has been illustrated and will hereinafter be described in connection with certain exemplary embodiments and practices, it is to be understood that in no event is the invention to be limited to such illustrated and described embodiments and practices. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the general principles of this invention within the full and true spirit and scope thereof.  
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Reference will now be made to the drawings wherein, to the extent possible, like reference numerals designate like components throughout the various views. In general, the fabric of the present invention comprises a multi-bar stitchbonded fabric made from a multiplicity of yarns stitched through a substrate, particularly a nonwoven substrate. As it is known in the art, a multi-bar fabric refers to a stitchbonded fabric made using at least two independent guide bars.  
      Exemplary fabric construction practices are illustrated and will be described through reference to a stitch bonding machine such as a Liba stitch bonding machine although it is likewise contemplated that other stitch bonding equipment may likewise be used if desired. Referring simultaneously to  FIGS. 1-3 , according to one contemplated practice, a substrate material  30  such as a carded and cross-lapped fleece or a needle punched or spun bonded fleece is conveyed to a stitch-forming position in the direction indicated by the arrow. If desired, the substrate material  30  may include a percentage of low melting point fibers such as low melting point polyester or bicomponent polyester having a core of relatively high melting point material and a sheath of lower melting point polyester to facilitate heat activated point bonding so as to enhance structural integrity.  
      As illustrated, the stitch forming position is defined by a row of reciprocating needles  34  extending in adjacent relation to one another across the width of the substrate material  30  in the cross machine direction substantially transverse to the direction of movement of the substrate material  30 . As will be appreciated, while only four needles have been illustrated, in actual practice a large number of such needles are arranged in close relation to one another between the fingers  47  of a sinker bar. By way of example only, and not limitation, it is contemplated that the so called gauge or needle density in the cross machine direction is preferably about 28 needles per inch, although higher or lower needle densities may likewise be utilized if desired.  
      According to the illustrated and potentially preferred practice, at least two yarns systems are used to form stitches through the substrate material  30 . In the potentially preferred practice, a ground yarn  36  ( FIG. 2 ) is carried through a first set of moveable yarn guides  38  carried by a first guide bar (not shown) for cooperative substantially fully threaded engagement with the needles  34  across the width of the substrate material  30 . For ease of reference, the substrate material  30  is not illustrated in  FIG. 2 .  
      As will be appreciated by those of skill in the art, in operation the ground yarn  36  is moved into engagement with the needles which, in turn, carry the ground yarn  36  in a reciprocating manner through the substrate material  30  without engaging fingers  47  of the sinker bar. This results in formation of an arrangement of substantially flat cooperating ground yarn stitches  40  extending in relatively closely spaced rows along the substrate material  30 . By way of example only, and not limitation, the cooperating ground yarn stitches  40  may be held in a full chain stitch configuration although other stitch arrangements including tricot stitches and the like may likewise be utilized if desired. Preferably, the spacing of the stitch lines formed by the ground yarn  36  will be close enough that the ground yarn stitches  40  define a substantially continuous covering across the technical back  41  of the substrate material  30 . The ground yarn  36  and the substrate material  30  thus define a substantially stable stitch bonded structure.  
      As illustrated in  FIGS. 1 and 3 , in accordance with a potentially preferred practice, an arrangement of loop elements  42  is formed projecting away from, and standing above, the ground yarn stitches  40  in a predefined pattern across the technical back  41  of the fabric. According to the preferred practice of the present invention, the loop elements  42  are formed substantially concurrently with the formation of the ground yarn stitches  40  through the substrate material  30 . As best illustrated in  FIG. 3  (wherein the substrate is not shown for ease of reference) according to one potentially preferred practice, loop elements  42  may be formed by a pile yarn  44  threaded through moveable yarn guides  46  carried by a guide bar (not shown). While only two pile yarns  44  are illustrated for explanatory purposes, it is to be understood that in actual practice, multiple pile yarns  44  are used across the width of the fabric threaded in a pattern relative to the needles to impart a desired loop arrangement.  
      As illustrated, the pile yarn  44  is preferably carried in alternating fashion back and forth between a first pair of non-adjacent needles thereby forming an arrangement of loop elements  42  that extend in arching relation over one or more intermediate needle rows corresponding to skipped needles between the cooperating pair of non-adjacent needles. In this procedure, the pile yarn passes over two or more sinker fingers  47  thus maintaining the desired raised arched relation. Arranging the loop elements to span across one or more intermediate needle rows gives rise to extended length loops that facilitates grasping by napping burrs in a subsequent napping operation as will be described more fully hereinafter. As shown, it is contemplated that the intermediate needles may also be engaged by pile forming yarns from other yarn guides so as to form loops as part of at least a second cooperating needle pair. Of course, the intermediate needles can also be left free of pile forming yarns if desired. Thus, the concentration of loop elements can be readily controlled. In this regard, by controlling yarn guide movement, arched loop elements may extend away from every needle row to predetermined non-adjacent needle rows if desired.  
      As previously indicated, the substrate used as the base of the stitchbonded fabric is preferably a nonwoven web structure, although a film, a woven, or a knitted product may also be used if desired. A nonwoven fiber fleece formed from staple fibers of a synthetic material such as polyester may be particularly preferred. However, other synthetic fibers such as polypropylene or nylon as well as natural fibers such as wool may be used if desired. A blend of different fibers may also be used. According to one contemplated practice the staple fibers can have a denier of from about 2 to about 6 with a staple length of about 2 to 4 inches. In one potentially preferred embodiment, the staple fibers have a denier of about 4 and a staple length of about 4 inches.  
      If desired, binder fibers can be incorporated into the nonwoven substrate in combination with the staple fibers. As used herein, binder fibers refers to fibers that when subjected to heat will bond with one another and with other materials contained within the web. Binder fibers are typically made from synthetic materials having a relatively low softening temperature such as low melting point polyesters. Although the binder fibers can be made entirely form a low melting point polymer, in one particular embodiment of the present invention, the binder fibers incorporated into the nonwoven substrate are multicomponent fibers, such as bicomponent fibers in which the low melting point polymer comprises the sheath polymer and a higher melting point fiber comprises the core polymer.  
      The fiber fleece is preferably formed by carding and cross-lapping a nonwoven web followed by needle punching to impart fiber cohesion. However, other construction techniques such as air laying, spun bonding and the like may also be used if desired. The basis weight of the nonwoven substrate can vary depending upon the particular application for which the fabric is being used. However, for most applications such as upholstery and the like, the nonwoven substrate can have a basis weight of from about 80 to about 150 grams per square meter or higher.  
      The pile yarn  44  is preferably a multifilament yarn of polyester, nylon or other suitable synthetic fiber. By way of example only, and not limitation, one contemplated construction for the pile yarn is 150 denier, 200 filament polyester. One potentially preferred stitch notation for insertion of the pile yarn is 1,0/2, 3. The pile stitch density is preferably in the range of about 20 to about 30 stitches per inch and more preferably about 23 to about 26 stitches per inch. Although the pile yarn is preferably a texturized filament yarn, it is also contemplated that flat yarns and even some spun yarns may be used if desired.  
      According to a potentially preferred practice, the ground yarns  36  are preferably flat, dull yarns meaning the yarns are not texturized and refract little light. Although flat, dull yarns are desirable, it should be understood that any suitable yarn may be used without limitation. For instance, texturized and spun yarns may be used if desired. As previously indicated, the ground yarns  36  are preferably stitched in covering relation to the substrate material  30 . Preferably, a chain stitch, such as 0.1/0.1, is used which gives stability in the warp direction (machine direction). Once incorporated into the substrate material, the ground yarn provides the web with integrity and strength. According to one contemplated practice, the ground yarn  36  is a multifilament polyester yarn having a denier of from about 70 to about 150. One exemplary ground yarn is a 70 denier  34  filament polyester. Although ground yarns polyester may be preferred, it is likewise contemplated that other synthetic and natural fibers may be utilized if desired.  
      According to the potentially preferred practice, once the substrate has been stitchbonded, the resultant fabric structure  43  is heat set by traditional techniques to impart stability. By way of example, the fabric structure  43  may be conveyed through a tenter frame such as will be well known to those of skill in the art at about 350° F. for about 30 seconds. During the heat treatment the fabric is firmed up and the fibers are stabilized. Also, the texturized yarns may bulk thereby making the yarns look fuller. Further, during heat treatment, any binder fibers that may be present in the substrate melt and bond. After heat setting, the fabric can be dyed as desired as is known within the textile art. Of course, it is also contemplated that the fabric can be dyed after napping if desired.  
      In accordance with the contemplated practice, after heat treatment and any desired dyeing, the stitch bonded fabric is preferably delivered to a napping operation where the surface loops  42  formed by the pile yarns  36  are preferably broken by applied tension as they are pulled away from the substrate material  30 . According to one potentially preferred practice, the fabric  43  is delivered to a napping machine  60  such as a double action napper as will be well known to those of skill in the art. As will be appreciated, in the napping machine  60  the technical back  41  of the fabric with the formed surface loops  42  contacts an arrangement of burr wheels  64 . In the potentially preferred practice, the burr wheels are mounted on a cylinder that rotates in the same direction as the fabric but at a different speed so as to cause the burr wheels to pluck and brush the surface loops  42 .  
      A representative embodiment of a napped fabric  70  formed by the practice of the present invention is illustrated in  FIG. 5 . As shown, the napped fabric  70  includes a pile layer  72  disposed above a backing formed by the substrate material  30  and ground yarn stitches  40 . Due to the tensioned breakage caused by the napping treatment, at least a substantial portion of the pile yarns are frayed such that free ends of individual broken filaments and/or fibrils of the pile yarns define a surface covering across a user contact surface of the napped fabric  70 .  
      The present invention has been described with reference to exemplary and potentially preferred embodiments and practices. However, it will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. Thus, in no event is the scope of the present invention to be limited to the structures and practices described in this application. Rather, it is intended that the invention shall extend to all alternatives and equivalents embracing the broad principles of this invention within the full spirit and scope thereof.