GB2439797A

GB2439797A - Method of forming patterned textile fabric with textured surface

Info

Publication number: GB2439797A
Application number: GB0710736A
Authority: GB
Inventors: Martin Wildeman
Original assignee: Tietex International Inc
Current assignee: Tietex International Inc
Priority date: 2006-07-03
Filing date: 2007-06-05
Publication date: 2008-01-09
Also published as: DE102007028795A1; GB0710736D0; US20080010793A1

Abstract

A method for forming a texture patterned fabric by selectively printing a corresponding pattern of heat absorbing fluid to the greige fabric to form zones of differential heat absorption capacity across the fabric. The differential heat absorption properties across the fabric are then used to selectively heat shrink yarns surrounding locations of fluid application. The fabric may be subsequently dyed and differential dye acceptance between the zone which has undergone heat shrink and those which have not results in colour shading corresponding to the pattern of heat absorbing fluid. The fabric may comprise yarns having different heat shrinkage capacities, preferably partially oriented polyester yarn and nylon and cellulosic yarn. Preferably the pattern is printed using a rotary screen printer using a chilled aqueous polyacrylate solution. The method is preferably used with pile or flat fabrics used in residential or automotive upholstery.

Description

Textile Fabric with Variable Heat-Shrunk Yarn Constituents

TECHNICAL FIELD

[00011 The present invention relates to textile materials and more particularly to textile materials with textured surface patterning formed by the selective application of heat absorbing fluid to the greige fabric prior to heat setting. Methods of formation are also provided.

BACKGROUND

[0002] Fabrics in general are well known. By way of example only, prior techniques for forming fabrics include weaving, stitch bonding, warp knitting, tricot knitting, raschel knitting and the like. In the past textured patterning across fabrics has been carried out by various techniques including shaving, impinging by hot air so as to selectively melt surface yarns in a desired pattern, chemical degradation in a desired pattern using acid etching or the like, and impingement by high pressure water streams so as to dislodge and/or reorient surface fibers in a desired pattern. While such techniques have been useful, they have nonetheless been relatively complex and difficult to carry out due to the need to use specialized equipment to carry out the patterning procedures. Moreover, these techniques result in abrasion and/or reorientation of surface yarns thereby changing the construction features across the fabric

SUMMARY

10003] The present invention provides advantages and alternatives over the prior art by providing a method for forming a patterned textile fabric by applying a pattern of heat absorbing fluid to a greige fabric surface using, for example, printing equipment to form zones of differential heat absorption across the fabric. The differential heat absorption properties across the fabric are then used to selectively heat shrink at least a portion of the yarns in locations outboard of the fluid application. Because the pattern is formed by printing or other application equipment, the resultant pattern may be of substantial complexity. The resulting fabrics may find uses in any number of applications including residential and/or automotive upholstery wherein substantial fabric integrity is required.

[0004] According to one aspect, yarns with different heat shrinkage character may be used in combination with one another across the fabric structure. It is also contemplated that single surface yarn system may be used if desired.

[0005] According to another aspect, differential pile heights across the fabric may substantially correspond to differential dye acceptance characteristics thereby providing synergistic tactile and visual differentiation across the fabrics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The accompanying drawings which are incorporated in and which constitute a part of this specification illustrate several exemplary constructions and procedures in accordance with the present invention and, together with the general description given above and the detailed description set forth below, serve to explain the principles of the invention wherein: [0007] FIG. I illustrates schematically a stitch bonding process for selectively forming a patterned surface yarn system and a cooperating ground yarn system through a fibrous substrate; [0008] FIG. 2 illustrates schematically the stitching of a ground yarn in an arrangement of substantially flat chain stitches by a multiplicity of reciprocating needles; (0009] FIG. 3 illustrates schematically the stitching of a surface yarns in a pattern of loops by a first pair of cooperating reciprocating needles: [0010] FIG. 4 illustrates schematically a treatment process for selectively heat shrinking surface yarns across a fabric; [0011] FIG. 5 further illustrates schematically an exemplary process whereby a heat sink fluid pattern is applied to the face of the fabric by a rotary screen printer, resulting in a pattern of treated and untreated areas on the fabric surface; [0012] FIG. 6 illustrates schematically a cross-section taken through the fabric with zones treated with heat absorbing fluid; and [0013] FIG. 6A illustrates schematically the fabric of FIG. 6 subsequent to heat treatment.

[0014] While a description will hereinafter be provided in connection with certain exemplary embodiments, procedures and practices, it is to be understood and appreciated that in no event is the invention to be limited to the embodiments, procedures and practices as may be illustrated and described herein. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the broad principles of this invention within the true spirit and scope thereof.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0015] Reference will now be made to the drawings, wherein to the extent possible like reference numerals are utilized to designate like elements throughout the various views. A method as utilized to form a fabric of stitch bonded construction is illustrated schematically in FIG. 1. The illustrated method utilizes a stitch bonding machine 10 as will be known to those of skill in the art. Importantly, it is to be understood and appreciated that while various contemplated practices will hereinafter be described in relation to pile fabrics formed on a stitch bonding machine, the invention is not limited to such stitch bonded pile fabrics. To the contrary, it is contemplated and intended that the techniques of the invention are equally applicable to flat fabrics formed by stitch bonding, weaving, knitting and other techniques as well as to pile fabrics formed by techniques other than stitch bonding including tufting, knitting and the like.

[0016] In the illustrated exemplary 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. In a potentially preferred practice, the substrate material 30 is needle-punched fleece formed from about 4 denier polyester staple filaments although other suitable substrate materials may likewise be utilized 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.

[0017] As illustrated through simultaneous reference to FIGS. 1, 2, and 3, the stitch forming position is defined by a row of reciprocating needles 34, 34', and 34" etc. extending in adjacent relation to one another across the width of the substrate material * 30 substantially transverse to the direction of movement of the substrate material 30.

As will be appreciated, while only three needles have been illustrated, in actual practice a large number of such needles are arranged in close relation to one another in the cross machine direction between the fingers 47 of a sinker bar.

[0018] According to the illustrated practice, three yarn systems are used to form stitches through the substrate material 30. In the illustrated practice, a ground yarn 36 (FIG. 2) is carried through a first set of moveable yarn guides 38 carried by a back guide bar (not shown) for cooperative substantially fully threaded engagement with the needles 34, 34', 34" etc. across the width of the substrate material 30. For ease of reference, the substrate material is not illustrated in FIG. 2.

[0019] 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 reciprocating manner through the substrate material 30 without engaging finger elements 47 of the sinker bar so as to form an arrangement of cooperating ground yarn stitches 40 exthnding in relatively closely spaced parallel 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 user contact surface 41 of the substrate material 30. The ground yarn 36 and the substrate material 30 thus define a substantially stable stitch bonded structure. By way of example only and not limitation, one ground yarn 36 that may be particularly suitable is a 70 denier polyester filament yarn, although other yarns may likewise be utilized if desired.

[0020] According to one exemplary practice, a first collection of loop elements 42, is formed projecting away from and standing above the ground yarn stitches across the fabric defining a user contact surface 41. If desired, at least a second collection of loop elements 43, may also be formed projecting away from and standing above the ground yarn stitches across the fabric. In the event that multiple collections of loop elements are utilized, it is contemplated that the loop elements 42 and 43 may be formed from either the same or different yarn materials. Thus, the yarns forming the pile may be characterized by either the same or different heat shrinkage characteristics. In this regard, it is contemplated that using yarns with different heat shrinkage character across the fabric may be desirable in some instances.

[0021] According to a contemplated practice, the loop elements 42, 43 may be formed substantially concurrently with the formation of the ground yarn stitches 40 through the substrate material 30. The loop elements 42, 43 may be selectively formed in a predefined pattern across the surface 41 of the fabric. In this regard it is to be understood that the first collection of loop elements 42 may be formed in either the same pattern or a different pattern than the second collection of loop elements 43.

According to a preferred practice, the loop elements 42, 43 are formed so as to cover substantially the entire face of the fabric. However, it is also contemplated that the loop elements may be present only across selected portions of the fabric if desired to provide a combination of two dimensional and three dimensional surface character.

[0022] An exemplary technique for forming the loop elements 42, 43 is illustrated in FIG. 3 wherein the substrate material 30 and ground yarn 36 have been eliminated for ease of reference. According to this practice, the first collection of loop elements 42 may be formed by a surface yarn 44 fully threaded through moveable yarn guides 46 carried by a middle guide bar (not shown). While only a single surface yarn 44 is illustrated for explanatory purposes, it is to be understood that in actual practice, multiple surface yarns 44 are used across the width of the fabric. During the pile formation process, the surface yarn 44 is carried in alternating fashion back and forth between a first pair of needles 34, 34' thereby forming a row of loop elements 42 as the pile yarn 44 is carried over the sinker finger 47 between the needles 34, 34' during stitch formation.

[0023] According to the illustrated practice, the second collection of loop elements 43 may be formed by a surface yarn 48 fully threaded through moveable yarn guides 49 carried by a front guide bar (not shown). While only a single surface yarn 48 is illustrated for explanatory purposes, it is to be understood that in actual practice, multiple surface yarns 48 are used across the width of the fabric. During the pile formation process, the surface yarn 48 is carried in alternating fashion back and forth between a first pair of needles 34, 34' thereby forming a row of loop elements 43.

[0024] As will be appreciated, the formation practice illustrated results in the formation of double loops formed from two different surface yarns 44, 48. As long as the surface yarns pass between the needles 34, 34' in a regular stitch forming procedure, a substantially continuous arrangement of loop elements 42, 43 will be formed along the length of the technical face 41 of the fabric. Of course, a single yarn system may also be utilized wherein one of the surface yarns 44, 48 is eliminated.

According to a potentially preferred practice, the loop elements 42, 43 are formed so as to form a loop length in the range of about 1 mm to about 5 mm and more preferably a

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loop length of about 3 mm. Of course, it is likewise contemplated that the fabric formed may have a substantially flat construction. Such a construction may be achieved by simply disengaging the sinker fingers 47. It is also contemplated that the fabric may be formed to have flat zones and pile-forming zones. The stitch density for the surface yarns in the machine direction of both the loop elements and the ground yarns is preferably about 18 to about 60 stitches per inch and more preferably about 40 stitches per inch.

[0025] According to one contemplated practice wherein yarns with different heat shrinkage characteristics are utilized across the fabric surface, the surface yarn 44 may have a high heat shrinkage capacity with shrinkage activated at temperatures such as the fabric would encounter during normal heat setting operations, while the surface yarn 48 is preferably characterized by a substantially lower heat shrinkage capacity at the same temperature. Accordingly, loop elements 42 shrink to a greater extent than loop elements 43 when exposed to temperatures such as the fabric would encounter during normal heat setting. In this regard it is to be understood that the term "heat shrinkage capaciW' is intended to refer to percentage of shrinkage on a length basis that a yarn undergoes when it is raised to a given temperature.

[0026] In the event that different yarn systems having differential heat shrinkage capacity are used, one potentially preferred high shrink yarn is a partially-oriented yarn (POY) of polyester. The polyester POY is preferably a cold drawn yarn with a draw ratio of about 1.35 to about 1.75 (most preferably about 1.57). In this regard, it is to be understood that the term "cold drawn" refers to yarn formed from filaments that are drawn at temperatures below the softening point of the fiber polymer. Most preferably, such drawing is carried out at substantially ambient temperatures. In the absence of elevated temperatures, substantially no thermal setting takes place during the drawing process. The term "partially-oriented yarn" refers to filament yarn that is drawn to a degree such that only partial longitudinal molecular orientation is achieved. One exemplary high shrink capacity surface yarn 44 is 72-filament bright trilobal polyester that has been cold drawn down to 150 denier. An exemplary low shrink capacity surface yarn 48 is a nylon yarn such as a textured yarn formed from Nylon 6 or Nylon

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6,6. By way of example only, one such nylon yarn is a 70 denier false twist textured yarn formed from Nylon 6,6. Such yarns undergo a substantially reduced shrinkage at temperatures such as the fabric would encounter during normal heatsetting. As will be described further hereinafter, such yarn combinations facilitate the development of a highly textured face as the greige fabric is passed through a tenter or other heating unit following formation. It is also contemplated that other low shrink capacity yarns such as cellulosic filament yarns of viscose rayon and the like may also be used if desired [0027] In the event that a single yarn system is to be utilized, the selection of the yarn material utilized will be dependent upon the degree of differential height desired across the fabric. Thus, if substantial differential height is desired, a material with high heat shrinkage capacity such as the polyester POY previously described may be desirable. Likewise, if a subtle differential pile height is desired across the fabric, a yarn material such as the false twist nylon or the like may be desirable.

[0028] As previously noted, it is to be understood that the stitch bonded fabric constructions as outlined above are exemplary only. In this regard it is likewise contemplated that other greige state fabric constructions as will be known to those of skill in the art may likewise be utilized. By way of example only, and not limitation, such alternative fabric constructions may include woven fabrics, warp knitted fabrics, raschel knitted fabrics, chenille fabrics and the like.

[0029] Regardless of whether a single yarn system or a multiple yarn system is utilized, the present system permits the controlled development of surface texturing such that different zones across the finished fabric have different pile heights and dye acceptance characteristics thereby providing substantial tactile and visual differentiation across the fabrics. One exemplary practice for carrying out this method is depicted schematically in FIGS. 4 and 5. As shown, after formation the greige fabric is advanced towards a printing station 20. According to an exemplary embodiment, the printing station 20 may include a rotary screen printer incorporating a roller 51 adapted to selectively transfer a volume of heat absorbing fluid to the pile surface 41 of the greige fabric as the fabric is advanced through printing station 20. The screen printing roller may include a screen pattern 60 disposed about its circumferential face 52. The screen pattern 60 is selected according to the pattern desired to be imparted on the fabric, and may be easily altered or substituted as desired. Due to the versatility inherent in screen printing, any number of patterns may be imparted to the fabric, ranging from simple geometric forms to such complex patterns as curvilinear forms and text. It is also contemplated that other printing systems may be used to apply the pattern of fluid to the fabric. By way of example only, and not limitation, various alternative fluid printing techniques as may be utilized include flat bed screen printing, fluid jet printing and the like that are suitable for the application of complex patterns. Regardless of the printing technique utilized, the heat absorbing fluid is transferred to the fabric such that a desired pattern of wet or treated zones 62 and dry or untreated zones 64 is produced (FIG. 6).

E0030] In the event that the surface 41 incorporates POY polyester yarns as described above (either alone or in combination with a higher heat shrinkage yarn), the heat absorbing fluid applied to the greige fabric may have a relatively low heat capacity such as a solution of water with an appropriate thickener such as polyacrylate or the like sufficient to increase the solution's viscosity as may be desired to promote the printing process. A viscosity of about 12,000 centipoise may be desirable to promote controlled application and retention of the heat absorbing fluid in patterned relation across the greige fabric. However, higher and lower viscosity levels may be used as desired. Of course, it is contemplated that other aqueous or non-aqueous solutions may likewise be utilized if desired.

[0031] According to one contemplated practice, the heat absorbing fluid may be chilled prior to application to the fabric. By way of example, it has been found that chilling an aqueous polyacrylate solution to about 40 degrees Fahrenheit prior to application to the fabric may be desirable. As will be described more fully hereinafter, the applied fluid is characterized by a heat capacity so as to substantially protect the wetted portions of the fabric from experiencing temperatures that would cause yarn shrinkage. If desired, the applied solution may further include a fugitive tint. The fugitive tint is a temporary coloring that allows an operator to verify that the fabric has been properly wetted according to the desired pattern, thus providing a quality control means to detect and correct any printing errors prior to further processing. Additional or alternative additives may be added to the solution as desired.

[0032] As depicted in FIG. 4, after the heat absorbing fluid is applied to the surface 41 of the fabric, the fabric is advanced through a heating unit 52 such as a tenter frame for application of heat. Of course, other heating units may likewise be used including laser heaters and the like as may be known to those of skill in the art. As the fabric is advanced through the heating unit 52, the fabric is exposed to heat, which tends to preferentially shrink the high shrink capacity face yarns forming loop elements 42 such as the POY polyester in the dry portions of the fabric as depicted schematically in FIG. 6A. In the dry portions of the fabric the low shrink capacity yarns forming the loop elements 43 shrink much less than the high shrink capacity yarns in those regions.

In the wet zones both the high shrink capacity surface yarns and the low shrink capacity yarns experience relatively little if any shrinkage. By way of example only, according to one potentially preferred practice, the fabric is advanced through about 30 feet of a tenter frame at a rate of about 50-60 yards per minute with a temperature setting of about 200 F. At these settings, it has been discovered that in a stitch bonded fabric made up of a 4 denier needled fleece (substrate 30) including 3 mm loops of 70 denier nylon in combination with 3 mm loops of trilobal POY polyester cold drawn to 150 denier, the dry loops of POY polyester will shrink to about 50% of their original length while the wetted loops exhibit substantially no shrinkage.

[0033] Referring again to FIG. 4, after the fabric is passed through the heating unit 52, it is preferably wound onto a beam 54 with substantial tension. In this regard it has been found that winding the fabric at high tension levels tends to stabilize the fabric and lock in the heat induced texturing. The fabric may thereafter be subjected to hot water heat setting followed by a dyeing process such as jet dyeing or beam dyeing as may be desired. After dyeing, the fabric is dried, in a drying unit such as a tenter frame or the like. It has been found that the differential shrinkage imparted in the initial heating step is substantially retained. The fabric may thereafter be subjected to a brushing or sanding operation to shear the high and/or low loops across the surface.

10034] The result of the process as described above is a fabric having a three dimensional pattern defined by areas with differential pile height. Without being limited to a specific theory, it is believed that the selective wetting of the fabric protects the wetted zones while the character of the pile yarns concurrently facilitates shrinkage of the dry zones at relatively low levels of heat input during initial heating. Thus, selective shrinkage can be achieved without overwhelming the protective heat absorbing fluid.

[0035] As previously noted, it has been found that the differential pile heights may substantially correspond to differential dye acceptance characteristics across the fabric.

That is, when the fabric is subjected to substantially uniform dyeing, the zones subjected to proteátive wetting take on a substantially different shade relative to the zones where substantial shrinkage has taken place. Thus, there is a complementary tactile and visual differentiation between the treated and untreated zones across the fabric.

[0036] Aside from the ability to provide simultaneous differentiation of both pile height and dye acceptance character, the process of the instant invention is believed to provide the benefit of substantially retaining the integrity of the fabric construction.

Specifically, by using heat induced shrinkage rather than yarn removal or displacement, it is believed that the structural character of the fabric system may be substantially retained. This, in turn, may promote strength in the final product.

[0037] It is to be understood that while the present invention has been illustrated and described in relation to potentially preferred embodiments, constructions, and procedures, that such embodiments, constructions, and procedures are illustrative only and that the invention is in no event to be limited thereto. Rather, it is contemplated that modifications and variations embodying the principles of the invention will no doubt occur to those of ordinary skill in the art. It is therefore contemplated and intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the invention within the true spirit and scope thereof.

Claims

CLAIMS: 12 1. A method of forming a fabric characterized by localized

variable surface texturing and substantially aligned dye shading, the method comprising: providing a fabric comprising a plurality of pile-forming yarn elements formed from a partially oriented polyester yarn characterized by a predefined heat shrinkage capacity; printing a volume of heat absorbing fluid onto the fabric according to a predetermined pattern to define treated zones where the fluid is applied and untreated zones where the fluid is not applied; heating the fabric such that pile-forming yarn elements of partially oriented polyester yam which are located in untreated zones undergo preferential shrinkage relative to pile-forming yarn elements of partially oriented polyester yarn located in treated zones; and subjecting the fabric to a substantially uniform dye treatment, wherein pile-forming yarn elements of partially oriented polyester yam which are located in untreated zones are characterized by differential dye acceptance relative to pile-forming yam elements of partially oriented polyester yarn located in treated zones such that the fabric exhibits differential color shading across the surface corresponding substantially to the pattern of fluid applied during the printing step.

2. The invention of claim 1, wherein the fabric is a stitch bonded fabric.

3. The invention of claim 1 or claim 2, wherein the printing is carried out by a rotary screen printer.

4. The invention as recited in any of claims 1 to 3, wherein the heat absorbing fluid comprises an aqueous polyacrylate solution.

5. The invention as recited in claim 4, wherein the polyacrylate solution is chilled below room temperature for application during the printing step. a

6. The invention as recited in any preceding claim, comprising the further step of tip shearing substantially.

all pile-forming yarn elements in the treated and untreated zones.

7. A fabric formed by a method according to any preceding claim.

8. A method of forming a fabric characterized by localized variable surface texturing, the method comprising: providing a fabric comprising a first plurality of pile-forming yarn elements formed from a first yarn characterized by a first heat shrinkage capacity and a second plurality of pile-forming yarn elements formed from second yam characterized by a second heat shrinkage capacity, wherein the first heat shrinkage capacity is greater than the second heat shrinkage capacity; printing a volume of heat absorbing fluid onto the fabric according to a predetermined pattern to define treated zones where the fluid is applied and untreated zones where the fluid is not applied, wherein at least a portion of the treated zones and at least a portion of the untreated zones include pile-forming yarn elements formed from the first yarn in combination with pile-forming yarn elements formed from the second yarn; and heating the fabric such that pile-forming yarn elements formed from the first yarn and which are located in untreated zones undergo preferential shrinkage relative to pile-forming yarn elements formed from the first yarn which are located in treated zones and relative to pile-forming yarn elements formed from the second yarn in both treated and untreated zones.

9. The invention of claim 8, wherein the fabric is a stitch bonded fabric.

10. The invention of claim 8 or claim 9, wherein the printing is carried out by a rotary screen printer.

11. The invention of any of claims 8 to 10, wherein the first yarn is a multi-filament partially oriented polyester yarn.

12. The invention as recited in any of claims 8 to 11, wherein the second yarn is nylon.

13. The invention as recited in any of claims 8 to 11, wherein the second yarn is a cellulosic yarn.

14. The invention as recited in any of claims 8 to 13, wherein the heat absorbing fluid comprises an aqueous polyacrylate solution.

15. The invention as recited in claim 14, wherein the polyacrylate solution is chilled below room temperature for application during the printing step.

16. The invention as recited in any of claims 8 to 15, comprising the further step of tip shearing substantially all pile- forming yarn elements in the treated and untreated zones.

17. A fabric formed by a process of any of claims 8 to 16.

18. A method of forming a fabric characterized by localized variable surface texturing and substantially aligned dye shading, the method comprising: providing a fabric comprising a first plurality of pile-forming yarn elements formed from partially oriented polyester yarn characterized by a predefined first heat shrinkage capacity and a second plurality of pile-forming yarn elements formed from at least one of the group consisting of nylon and cetlulosic yarn characterized by a second heat shrinkage capacity, wherein the first heat shrinkage capacity is greater than the second heat shrinkage capacity; printing a volume of heat absorbing fluid onto the fabric to define treated zones where the fluid is applied and untreated zones where the fluid is not applied, wherein at least a portion of the treated zones and at least a portion of the untreated zones include pile-forming yarn elements formed from the first plurality of pile-forming yarn elements in combination with pile-forming yarn elements formed from the second plurality of pile- forming yarn elements; -heating the fabric such that pile-forming yarn elements formed from the polyester yarn and which are located in untreated zones undergo preferential shrinkage relative to pile-forming yarn elements formed from the polyester yarns which are located in treated zones and relative to the second plurality of pile-forming yarn elements in both treated and untreated zones; and subjecting the fabric to a substantially uniform dye treatment, wherein pile-forming yarn elements of partially oriented polyester yarn which are located in untreated zones are characterized by differential dye acceptance relative to pile-forming yarn elements of partially oriented polyester yarn located in treated zones such that the fabric exhibits differential color shading across the surface corresponding substantially to the pattern of fluid applied during the printing step.

19. A fabric formed by the process of claim 18.

20. A method substantially as hereinbefore described with reference to the accompanying drawings.

21. A fabric substantially as hereinbefore described with reference to the accompanying drawings.