CA1049897A - Suede woven fabric and a process of manufacturing the same - Google Patents

Abstract

ABSTRACT
A suede woven fabric and a process for its manu-facture are described. The fabric has a warp yarn of polyester textured, polyester filament or polyester spun yarn and a unique weft yarn, the surface portions of which are cut to form piles. For making the fabric, the weft yarn used is a single ply made from two kinds of composite filaments, each composite filament consisting of a plurality of island monofilaments randomly distributed in a polymeric sea component having a solubility different from the island monofilaments. After the fabric is woven, the polymeric sea component is removed to leave the monofilaments. Then portions of these monofilaments on a surface of the fabric are cut and raised to form the piles.

Description

The present invention relates to suede fabrics and Tnore particularly to suede woven fabrics which are pre-pared from a woven fabric as the base sheet material.
Hitherto, it has been usual to produce suede fabric from a base sheet material composed of a non-woven fabric and rarely from a base sheet material composed of a woven fabric, as in the present invention, and in particular it should be pointed out that the base sheet material of the present invention is not composed of a knitted fabric.
The following literature reference, however, discloses an example of a suede fabric made from a woven sheet material, namely sritish Patent No. 1,300,268 (this corresponds to Canadian Patent No. 895,611, West German Patent No. 2,035,669, French Patent No. 2,059,828 and Netherlands Patent No. 7,008,329). The British patent claims the material in Claim 1 in the following way: "A pile sheet material comprising a base sheet and a synthetic polymeric superfine fiber pile formed on at least one surface of said base sheet, the pile fibers having a thickness in denier not exceeding 20 0.5 and a length (in mm) to thickness ratio falling within the range 0,4 to 5000 and being associated in bundles of at least five such superfine fibers."
The characteristics of the suede fabric disclosed by the British patent are (a) the pile fibers have a ratio of length (in mm) to thickness (in denier) falling within the range from 0.4 to 5000, and (b) the pile fibers are associated into bundles of at least five super fine fibers. It can be -clearly seen from Fig. 7 and Fig. 9 of the British patent that condition (b), which is believed to be more important --30 than the condition (a) in the British patent, demands that the piles of the suede fabric never exist as individual superfine 1 ~

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fibers but exist only as bundles of at least five such super-fine fibers. This is an essential feature of the cited British patent which enables the invention to use superfine fibers as a material for the pile. Moreover, the "islands-in-a-sea"
type composite fiber which can be used for raising the pile in the British patent is prepared from a molten polymer in a melt spinning apparatus as shown in Fig. 3 of the patent, and examples of embodiments of prepared composite fibers are shown in Figs. 1 and 2, wherein numeral 1 in the figures indicates a sea component and numeral 2 indicates an island component.
The island component 2 is nothlng but the pile fiber and the sea component 1 is removed before the pile is raised. As is apparent from Figs. 1 to 3 of the patent, the thickness of each island is substantially the same and has a value not exceeding 0.5 denier. Moreover, some examples which are very similar to the present invention are disclosed in Examples 7 to 9 of the patent. In these Examples, a woven fabric is prepared by using the composite fiber as a weft yarn rather than by interlocking pile fibers individually into a base sheet material of woven fabric, and then a portion of the composite fiber is raised to form pile fibers ùsing a card wire raising machine. However, in these Examples, the composite fiber is used as a spun yarn obtained from short fibers (staple fibers) prepared by cutting a filamentary composite fiber. The com--posite fiber is never used in the form of a filament.
According to one aspect of the invention there is provided a suede woven fabric compising (a) a warp yarn selected from polyester textured yarn, polyester filament yaro and polyester spun yarn and (b) a weft yarn in the form of a single ply yarn formed from a plurality of composite filaments, each consisting of a plurality of monofilaments, .
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said monofilaments having a mean thickness in tlle range of 0.05 to 0.5 denier and having a degree of variation in thickness in the range of 15 to 60%, a portion of said weft monofilaments on at least one surface of the fabric being raised to form piles of individual monofilaments having mean lengths in the range of 0.5 to 4.0 mm, with the number of floating points on weft yarns whose numbers of floats are within the range of 3 to 11 being in the range of 100 to 500/cm2 of woven fabric and the ratio of shear stress of the fabric at a shear angle of 0.5 and that at a shear angle of 5 being in the range of 1.5 to 15:1.

According to another aspect of the invention there is provided a process for producing a suede woven fabric which comprises (i) formin~ a single ply weft varn from two kinds of romnosite filaments~ each composite filament consistin~ of a plurality island polyester monofilaments randomly distributed in a polymeric sea component having a solubility different from the island monofilaments, said -island monofilaments extending substantially along the length of the composite filament with each monofilament having a mean thickness in the range of 0.05 to 0.5 denier and the degree of variation in thickness among monofilaments being in the range of 15 to 60%, blending said composite .
filaments to form a single ply yarn in which 95 to 40%
by weight of the monofilaments have a low shrinkability in boiling water and 5 to 60~ by weight of said monofilaments have a shrinkability in boiling water at least 3% higher than said low shrinkability monofilaments, (ii) preparing a woven fabric with warp yarn selected from polyester textured yarn, polyester filament yarn and polyester spun yarn and said weft yarn, (iii) removing the. sea components from Raid composite filaments, (iv) heat-setting the woven fabric A
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9~97 under relaxation and (~) raising portions of said weft monofilaments on at least one surface of the fabric to form piles having a mean length of 0.5 to 4.0 mm.

The main differences in the structure of the suede fabric produced according to the present invention from the structure of the suede fabric produced according,~to the said prior patent can be condensed into three main points, as follows.

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. ' '.' ", (a) Although the composite filament of the present invention (a multi~island randomly distributed composite filament) is similar to that of the prior patent, the mean thicknesses of those islands in denier are different from each other within the range from 0.05 to 0.50 and accordingly, they are different from those of the prior patent. Moreover, against the uniform distribution of islands in the sea in the prior patent, the distribution of islands in the present invention is random.
(b) The said multi-island randomly distributed composite fila-ment, which is used in the present inVeDtiOn as a weft yarnfor preparing a woven fabric as a base sheet material for suede fabric, is not used in the form of staple fibers as in the prior patent but in filamentary form. (c) Each pile of the suede fabric in the prior patent exists as a bundle of at least five superfine island fibers whereas each pile of the suede fabric in the present invention exists individually as an island monofilament whose mean thickness is in the range of 0.05 to 0.50 denier, as already mentioned. The characteristic features of the present invention mentioned above, at least in the preferred forms, enable a more superior suede fabric to be produced by the present invention than that of the prior patent.
The suede fabric of the present invention is pre-ferably constructed in the following way.
The woven suede fabric comprises a warp yarn chosen from polyester textured yarn, polyester filament yarn and polyester spun yarn, and a weft yarn of polyester island filaments. The mean thicknesses of the island filaments in denier are within the range from 0.05 to 0.50 and the degree of variation of the thickness of the island filaments is 15 to ~0%. A portion of the island filaments on at least one surface of the fabric is raised to form piles of individual island ' ' '' ' ": ' ' : ' , i . .
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~049897 monofilaments having a mean length of 0.5 to 4.0 mm. The number of floating points on the weft yarn having a number of floats within the range of 3 to 11 is 100 to 500/cm of woven fabric, and the relationship between the shear stress Go 5 at the shear angle of 0.5 and the stress G5 at the shear angle of 5, represented by G5/Go 5~ is 1.5 to 15.
The following is a typical example of the pre-paration of a suede fabric according to one embodiment of the present invention.
A woven fabric is first prepared using a warp yarn chosen from polyester textured yarn, polyester filament yarn and polyester spun yarn and a weft yarn in the form of a single ply yarn composed of two kinds of multi-island randomly distributed composite filaments, wherein each composite filament is prepared from a polyester as the island component and another polymer as the sea component, the polymer of the sea component having a different solubility from that of the island component polyester. The composite filaments are prepared by randomly distributing the islands in the sea component so that the island components extend substantially along the entire length of the composite filament and have such dimensions that the mean thickness in denier is 0.05 to 0.50 and the degree of variation of the thickness is 15 to 60~.
The blending of the composlte filaments is carried out in such a manner that each single ply weft yarn comprises 95 to 40 weight % of islands having a low shinkability in boiling water and the remainder (5 to 60 weight %) of the islands having a degree of shrinkage in boiling water at least 3% higher than ~
that of the other islands. The sea component is then removed ~-from the composite filaments and the woven fabric is heat set in an unstressed state. Finally, a portion of the island ' - - . . : : - . ,, . ., :
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, . ' ~049897 filaments of the weft yarn on at least one surface of the woven fabric is raised to form a woven suede fabric having piles of individual island monofilaments with mean lengths of 0.5 to 4.0 mm.
One of the characteristic features of the present invention is the construction of the filamentary weft yarn.
If the mean thickness in denier of each island in a composite filament is less than 0.05, it is not possible to produce a suede fabric having a proper pile length, the piles tend to break upon raising, and the colour after dyeing is inferior.
On the other hand, if the mean thickness is greater than 0.50 denier, the resulting material does not feel like natural leather and a good writing effect cannot be achieved.
By the term "writing effect" we mean the abillty to make marks, e.g. to write letters or figures, by rubbing a finger over a raised surface of the suede fabric, as a result of bending the piles into the rubbing direction. Generally, a suede fabric having a good writing effect is believed to be superior.
A mean thickness of the islands of the composite 20 filaments between 0.10 and 0.18 denier is considered to be desirable. In the present invention, the thicknesses in denier of almost all of the islands e.g. more than about 95%
of the total number of islands) contained in the sea of the composite filaments are necessarily within the range from 0.05 to 0.50 and, moreover, the thicknesses in denier of the islands contained in the composite filaments are never substantially the same. Here again, it should be pointed out that the degree of variation of the thicknesses of the islands in the composite filaments is necessarily more than 15% and the desired range is 15 to 60%, wherein the degree of variation is the value of the thickness deviations in denier of all of A
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10~9897 the island filaments from the mean value of the thickness in denier of all of the island filaments, which can be obtained by the observation of a photogra,ph of a cross section of the composite filament, represented as a percentage based upon the mean value of the thickness.
When the degree of variation of the thickness is less than 15%, it is not usually possible to obtain a suede fabric which feels like natural leather and has a desirable writing effect. On the other hand, when the degree of variation of the thickness is greater than 60%, a uniform writing effect cannot usually be achieved. The preferred degree of the variation is within the range from 20 to 40%.
The reason why such a limited range in the degree of variation of the thicknesses is necessary for the production of a suede fabric which feels like natural leather and has a desirable writing effect can be easily understood from the fact that natural leather is composed of numerous fine fibers of collagen, and it has a good feel to the touch and a good writing effect because of the existence of variations of the 20 diameters of the collagen fibers ordinarily within the range ~
of 10 to 20%. It can thus be seen that the suede fabric ~ -provided by the prior patent mentioned above cannot have a natural leather-like touch and a nice writing effect, and is, surely, staying within the level of conventional artificial leather, since the degree of variation of the thickness of the islands contained in the sea of the composite fiber manufactured by the prior patent is as low as 6 to 7% at the highest, and is ordinarily 3 to 4%. In other words, the thicknesses of those islands are substantially same. There-fore, even if other desirable conditions for the manufacture of suede fabric are achieved, a desirable suede fabric cannot -. .

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- 10498~7 be obtained by using the composite fibers of the present invention.
It may be useful to point out at this stage that although it is, of course, possible to prepare a weft yarn which apparently satisfies the said conditions of the present invention, i.e. one whose mean thickness of the islands in denier is within the range from 0.05 to 0.50 and whose degree of variation of the thicknesses in denier is also within the range from 15 to 60%, by a combination of several composite filaments having different mean thicknesses of the islands, wherein the mean thicknesses of the various island filaments within a single composite filament are the same or the difference is so small as to be situated outside the said range, it is not possible to achieve the present invention satisfactorily using such a weft yarn for the preparation of woven suede fabric, since it produces non-uniform dyeing and an unevenness in the piles as a result of unsufficient mixing of the island filaments with each other. This is the reason why, in the present invention, apparatus has been provided which is able to produce the desired range of the degree of variation of the thickness in denier from 15 to 60% in every single composite filament, thus avoiding the need to adopt a ~ixing technique of different composite filaments as mentioned above. -~
Composite filaments which are suitable for use in the present invention can be prepared by a melt spinning apparatus to be explained below as one embodiment of the apparatus of the present invention. This apparatus is novel and very different from the spinning apparatus disclosed in the prior patent mentioned above.
In the following description, reference is made to g _ -7~
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the accompanying drawings, in which:
Figure l is a plan view of a first plate used in a melt spinning apparatus;
Figure 2 is a partial cross-sectional view of the plate of Fig. l taken along the line A'-A';
Figure 3 is a plan view of a second plate used in a melt spinning apparatus Figure 4 is a cross-sectional view of the plate of Fig. 3 taken on the line B'-B';
Figure 5 is a plan view of a third plate used in a melt spinning apparatus;
Figure 6 is a partial cross-sectional view of the plate of Fig. 5 taken on the line C'-C';
Figure 7 is an underside plan view of the plate of Fig. 5;
Figure 8 is a plan view of a fourth plate used in a melt spinning apparatus;
Figure 9 is a partial cross-sectional view of the plate of Fig. 8 taken on the line D'-D';
Figure 10 is a cross-sectional view of a composite -~
fiber produced in accordance with one embodiment of the invention;
Figure 11 is a diagram representing a satin weave used in one embodiment of the invention;
Figures 12 and 13 illustrate a weft fiber from a fabric according to one embodiment of this invention and a comparison fiber, respectively;
Figures 14, lS and 16 represent diagrams of shear stress versus shear angle for conventional fabric, natural suede or synthetic leather, and a fabric according to one embodlment of the invention, respectively;

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~049897 Figure 17 is a diagram showing the direction of application of stress to a test fabric; and Figure 18 is a diagram representing an additional fabric used in one embodiment of this invention.
Briefly described, a preferred melt spinning apparatus for producing the composite fibers has a mixing device comprising a plate A (Fig. 1 and Fig. 2) having a plurality of outlet holes arranged in concentric rings, a plate B (Fig. 3 and Fig. 4) located in the apparatus im-mediately below or following the plate A, and having a circularconcave ~roove for receiving molten polymer material from the outlets of plate A. The circular concave groove has a plurality of ou~let holes arranged in a circle at the lowest part of the groove. A plate C (Fig. 5, Fig. 6 and Fig. 7), which is located immediately below plate B9 has a plurality of channels located in its upper surface. One end of each channel is situated at a position immediately below a polymer outlet hole of the plate B. Each channel also has a polymer outlet situated at its other end, and it can be seen from Fig. 7, which is an underside view of plate C, that the outlets are located along radii of the plate. A plate D (Fig. 8 and Fig.
9), which is located immediately below plate C, has slits in ~-the form of concentric rings located at such positions in the plate that the slits communicate with the outlets of the plate C. The slits have a definite depth as shown in Fig. 9, and a plurality of holes located at the bottom of the slits.
An additional plate substantially identical to plate B is located immediately below plate D. The additional plate B, while it may be completely identical to plate B, may alter-natively differ in the actual number of outlet holes. Thus, the number of holes in plate B may be equal to that of the A

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spinning nozzle of the apparatus but additional plate B may have a different number of holes.
All of the plates, i.e. A, B, C~ D and additional plate B, are located in close contact in an extrusion melt spinning apparatus so that the molten polymer material passes from the grooves or slits and holes of one plate into that of the next.
The basic principle of the apparatus for the mixing of two polymer components to form a composite "island-in-a-sea"
type filament will be explained as follows.
The two polymer components are separately fed to different circular grooves of plate A and then the polymer components pass through the succeeding plates which produce a mixing action that can be summarized as follows. (1) Alter-nating multiple layers of the two components are formed by the combination of plate A and the concave groove in succeeding plate B, (2) the layered polymer is divided into a plurality of streams by the holes in plate B, (3) the polymer streams are changed from a circular arrangement into a radial arrange-20 ment on passing through plate C, (4) the streams are again --divided and stretched on passing through plate D~ (5) the streams are then collected by the concave groove of additional plate B, (6) the polymer is again divided into a plurality of streams by the holes in additional plate B. Thus, each polymer stream of the two component system after passed through additional plate B, that is, at the end of the six stages, has the so-called "islands-in-a-sea" structure by virtue of the mixing action of the various plates. That is, the final stream is composed of many island streams a in a sea component b or many islant streams b in a sea component a to form "multi-islands randomly distributed composite filaments"~

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In the following, a practical example of a mixing device is described in much more detail with particular reference to the attached drawings and the flow of the polymer stream, or in other words the mixing mechanism, will also be explained in more detail.
Fig. 1 is a plan view of a plate A showing the outlet side of the plate, and Fig. 2 is a vertical sectional view of the plate A, obtained by cutting it along the line A'-A' shown in Pig. 1. Numerals 1, 2, 3, 4, 5 and 6 indicate polymer outlet slits of concentric ring-like structure, formed on one side of the plate A, and numerals 1', 2', 3', 4', 5' and 6' indicate polymer inlet slits on the other side of the plate, corresponding to 1, 2, 3, 4, 5 and 6 respectively.
Fig. 1 and Fig. 2 show a case where there are six outlets and six inlets of slit-type. Although there should be at least two outlets and two inlets, the more outlets and inlets that are provided, the better from the stand point of the mixing effect. Desirably there are from 4 to 20, and more desirably from 6 to 15. Those outlets and inlets of slit type are connected to each other through a plurality of fine holes 1", 2", 3", ..., which communicate with the corresponding outlets and inlets, such as l-l', 2-2', 3-3', ...
Fig. 3 is a plan view of a plate B and Fig. 4 is a vertical sectional view of the plate B obtained by cutting the plate along the line B'-B' as shown in Fig. 3. Numeral 7 indicates a concave portion of the plate B, but clearly the shape of the concave portion need not be limited to that shown in Fig. 3 and Fig. 4. Numerals 8 and 9 indicate polymer inlet holes which are distributed in a circle. In case of Fig. 4, 24 identical inlet holes are provided. Numerals 8' and 9' indicate polymer outlets corresponding to inlet holes 8 and A :~

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104~897 9, respectiv~ly, and the total number of such outlets is, of course, 24 in this case.
Fig. 5 is a plan view of a plate C, Fig. 6 is a vertical sectional view of the plate obtained by cutting it along the line C'-C' and looking at it from the direction shown by the arrow in the figure, and Fig. 7 is a plan view of the outlet side of the plate. Numerals lO, 11, 12 and 13 indicate polymer inlet portions of channels formed in the plate C. The positions of the inlet portions correspond to the polymer outlets in plate B, and in this case, 24 such polymer inlet portions are provided and are arranged in a circle identical to that of the outlets in plate B. Numerals 14, 15, 16 and 17 indicate polymer outlet portions of the channels which are arranged in a line different from the circumference of the circle of the inlet portions, and in this case, the outlet portions are arranged in radial lines.~ -Thus, as clearly shown in Fig. 7, each set of four polymer outlets are distributed along a radius and there are six such sets so that the plate C has 24 polymer outlets.
Fig. 8 is a plan view of a plate D and Fig. 9 is a vertical sectional view of the plate D obtained by cutting it along the line D'-D'. Numerals 18, 19, 20 and 21 indicate concentric ring-shaped channels formed on the upper surface of the plate D. As shown in Fig. 8 and Fig. 9, in this case there are four such channels which extend into the plate by a short d~stance. A plurality of fine holes 22, 23, 24 and 25 etc., which are provided at the bottoms of the channels, -penetrate through the plate to form polymer outlets. In this example, there are 180 fine holes in total. However, it is, of course, possible to use another type of plate instead of plate D at this stage, such as, for example, a plate which - ~ . . : .: . . : . . :
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has concentric circular channels on both sides of the plate.
By providing an additional plate B just beneath the plate D, a mixing device consisting of a minimum number of units can be obtained. If necessary, a spinning nozzle, having fine orifices at positions corresponding to the polymer outlets of the said additional plate B, can be attached beneath the additional plate B. Incidentally, in the attached drawings, many portions of the structure which are repeated or are symmetrical are omitted for simplification.
The apparatus operates in the following manner.
Individual streams of polymer components a and b are separately introduced into the polymer inlets of the plate A in an alternating fashion. For example, in such a way that com~onent a is introduced into inlets 1', 3' and 5' and component b is introduced into inlets 2', 4' and 6', each in a definite amount measured by a metering pump (gear pump). The polymers pass through plate A and merge in the concave portion 7 of plate B, forming a composite stream of six alternating layers of components a and b. The layers are in the form of concentric circles before they enter the inlet holes 8 and 9 of plate B, and in this case there are six layers of the components corresponding to the number of slit-like polymer outlets (and inlets) in plate A. It is thus easy to prepare a composite conjugate stream of more than six layers, if desired, by changing the number of outlets (inlets) in plate A.
The polymer stream entering the concave portion 7 of the plate B of Fig. 4, passes through the 24 polymer inlet holes 8 and 9, to the 24 polymer outlets 8' and 9'.
The 24 polymer streams extruded from the outlets of plate B, separately enter into the 24 corresponding polymer . : .. - - : . .
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10498~7 inlet portions such as 10, 11, 12, 13, etc., of the channels in plate C as shown in Fig. 5. The polymer streams pass along the channels and then through the outlets 14, 15, 16, and 17, etc. At this stage, the arrangement of the polymer streams is changed from the initial circular arrangement to a radial arrangement by plate C. This rearrangement is important in order to perform a stretching effect in succeeding plate D.
The polymer streams after passing through the plate C enter into the polymer inlets of the concentric ring-shaped channels 10 18, 19, 20 and 21 of plate D which follows plate C.
~pon passing through plate D, the polymer streams are stretched in the concentric channels in the circumferential direction and then partitioned into fine polymer streams by the 130 fine holes such as 22, 23, 24, 25, etc.
The fine polymer streams enter into additional plate B which follows plate D and they are again merged into a single polymer stream in the concave portion of the plate B and then single successively partitioned into 24 polymer streams corresponding to the number of fine holes 8 and 9

2~ provided at the center of the channels of the plate B.
As mentioned above, the polymer consisting of the two components a and b is effectively mixed in a well-controlled -manner during its passage through the mixing device. The actual amount of mixing is usually determined according to the number of fine polymer streams which can be produced without ~
any interruption. Thus, effective mixing makes it possible to -obtain many fine streams of the polymer, and inversely, when it is possible to obtain many such fine streams, the degree of mixing can be high. Each island filament 27 of Eig. 10 30 in the sea component 26 of the composite filament obtained by ~ -the method of the present invention exists as a continuous A ~
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10498g~
phase, i.e. as a practically endless filament extending along the length of the composite filament.
The polymer component which forms the islands in the composite filament is a polyester. Practical examples are those polyesters which can be obtained by the polymerization of aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid or their esters) and/or aliphatic acids (such as adipic acid, sebacic acid or their esters) and diols (such as ethylene glycol, diethylene glycol, 1,4-butane diol, neo-pentyl glycol, cyclohexane-l and 4-dimethanol. Polyesters whose structural units consist of more than 80% of ethylene terephthalate are particularly desirable. Furthermore, hesides the components for polymer synthesis mentioned above, such compounds as polyalkylene glycol, bisphenol A, sulpho-isophthalic acid, etc. can also be used as a component for the co-polymerization, or not more than 5 weight ~ of other additives (such as a delustering agent, a heat stabilizer, a pigment, etc. or an anti-static agent such as polyethylene glycol having an -0 ~ group or an ~ S03H group at the ends of the molecule, dodecyl benzene sulphonic acid, etc.) can be used by adding them to the polymerizatlon reaction system.
The polymer component which constitutes the sea in the composite filament preferably has a solubility parameter differènt from that of the polyester island component mentioned above. Examples of such polymers are polyolefines, such as polyethylene and polypropyleDe, atactic or isotactic poly-styrene, alkylsubstituted or halogen-substituted polystyrene, etc.
The composite filament, prepared by the method explained above, has almost the same cross-sectional configura-tion at any position of the filament along the length thereof.

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10~9897 Fig. 10 shows an example, wherein 26 is the sea and 27 is one of the island filaments. As is apparent from the figure, the various islands in the sea of the composite filament are different from each other in their thickness and are dis-tributed randomly in the sea. It should be pointed out that the number of islands in the composite filament is desirably within the range of from 5 to 100, and preferably 20 to 50.
When the number of islands is greater than 100, it sometimes becomes rather difficult to obtain a suede fabric having a good surface condition since the mean thickness of the island filaments becomes rather small as the number increases if the total thickness of the composite filament remains constant.
As mentioned above, a blending of the component polymers is carried out during a spinning step or a stretching step or during a twisting step, so as to produce a single ply yarn for the weft yarn preférably having 95 to 40 weight ~ of the islands composed of filaments having a low shrinkability -in a boiling water and the remainder, i.e. 5 to 60 weight %, composed of filaments having a high shrinkability, wherein the 20 difference in the degree of shrinkage is more than 37,. There- ~ -fore, the single ply yarn contains a mixture of island filaments having dlfferent shrinkabilities. The single ply yarn can be as defined in the textile industry, that is, a kind of twisted yarn which can be prepared by twisting one or more substantially untwisted multi-filaments. As mentioned already, only a single ply yarn obtained by blending composite filaments, is used, but never a multi-ply yarn e.g. a two ply yarn, a three ply yarn, etc. as known in the textile industry.
Methods which can be used to obtain a difference in ;
30 shrinkability of the island filaments in a single ply yarn ~ -are, for example, as follows.

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I) Two kinds of undrawn composite filaments can first be prepared by the spinning of the same polymer mixture but at two different ratios of draft and then the filaments are stretched at the same time and twisted together.
II) Two kinds of undrawn composite filaments can first be prepared using two different kinds of island components with different shrinkabilities followed by stretching the filaments at the same time and plying them together.
III) One kind of undrawn filament can be stretched under two different thermal conditions and then twisted together.
IV) Roughly half of a group of identical stretched filaments can be heat-treated for shrinkage and then twisted together with the remaining half.
After preparing a woven fabric using such a single ply yarn as mentioned above as weft yarn, the sea component is removed from the fabric and then the fabric is heat-treated to produce setting under relaxation. The island component filaments having a high shrinkability shrink considerably and gather into the center of each yarn in the fabric. On the other hand, the island component filaments having a low shrinkability move to the surface of the fabric forming loops having a length correspondlng to the difference in shrinkage between the filaments. However, since each island monofilament has little freedom to move at each fabricated point crossed by the warp in the fabric, the island filaments having a high shrinkability intermingle with the island filaments having low shrinkability at these points and bind them tightly.
Thus, many loops are formed between any two fabricated points and later these loops become long piles during the raising treatment. Since the piles are strongly bound at every fabricated point, they are firmly held in the fabric.

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As mentioned above, in order to ensure that the loops are formed in good condition, it is desirable that 95 to 40 weight % of the island filaments has a low shrinkability and the remainder, that is 5 to 60 weight %, of the filaments has a high shrinkability. If the content of high shrinkage filaments is less than 5%, an unsatisfactory formation of loops and an insufficient binding of low shrinkage filaments at the fabricated points sometimes occurs since the compressive force produced during the shrinkage is small. On the other hand, if the content is larger than 60%, the number of loops decreases and a woven suede fabric having rather a small number of piles is produced. A desirable range for the content of the high shrinkage filaments is 20 to SO weight %, and the difference in the degree of shrinkage of the two kinds of composite filaments in boiling water should be more than 3%.
When the difference is less than 3%, the loops are small and a woven suede fabric having rather short piles is obtained, which is not desirable. A difference of more than 5% is preferred.
The degree of shrinkage in boiling water is the degree of shrinkage of the multi-islands randomly distributed composite filament yarn treated in boiling water at 100C
for 10 min. without any load being applied and is determined by the following formula.
The degree of shrinkage in boiling water (WSr) = 11 1 x 100(%), wherein lo is the initial length of the yarn before the treatment observed under a load of 2 mg/d, and 1 is the length of the yarn after the treatment also observed under the load of 2 mg/d. Furthermore, it is desir-30 able to use a single ply yarn composed of two kinds of -composite filaments whose degrees of shrinkage are different ... .... .

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by more than 3~ (as mentioned already) after the yarn has been twisted within the range from 50 to 500 turns/m. By twisting the yarn by more than 50 turns/m, it becomes possible to obtain a woven suede fabric having piles which rarely drop out even if they are rather long. However, when the number of twists is more than 500 turns/m, although dropping out can be almost prevented, the raising treatment becomes rather difficult.
As the warp yarn, conventional polyester textured yarn, polyester filament yarn and polyester spun yarn can be used.
Preferably the structure of the woven fabric is of a kind which has many weft yarns on the surface of fabric. An example is satin weave.
As already mentioned, a single ply yarn composed of two kinds of composite filaments is used as the weft yarn. The thickness of the single ply yarn after the sea component has been removed is preferably 75 to 500 denier or, more desirably, 150 to 350 denier. As previously noted, two ply yarn or three ply yarn etc. is never used as the weft yarn, since it is almost impossible to obtain a woven suede fabric having indivi-dual piles when other than single ply yarn is used.
Since it is desirable that about 5 to 40%, and more desirably about 5 to 15%, of the total number of island mono-filaments which constitute the weft yarn of the fabric are cut at floating points,~when the pile is raised, a desirable number of island mono-filaments which constitutes the weft yarn is 500 to 10,000, or more desirably 1000 to 6000, and the weft yarn preferably has a twist of 50 to 500 turns/m, or more 30 preferably 75 to 200 turns/m.
Here, the meaning of the term floating point on the -, .' ' . ~ -we~t yarn denotes any point on the weft yarn between two fabricated points which appears on the surface of the woven fabric, and by the number of floats we mean the number of warp yarns which exist under the floating weft yarn. The number of floating points on the weft yarn having a number of floats of from 3 to 11 is determined from the construction of the woven fabric and its density. That is, the number of floating points on weft yarns per cm2 (A) is given by the following equation. m A = N.M I ai wherein N is the warp yarn density (yarns/cm), M is the weft yarn density (yarns/cm), n is the number of warp yarns per repeat, m is the number of weft yarns per repeat and ai is the number of floating points per repeat of the number i weft yarn. For example, in the case of a satin weave shown in Fig. 11 (which denotes one repeat of a

3-counter, 5-end weft satin weave), wherein the weft yarns appear on the surface of the fabric much more often than the warp yarns, A is given by the following relation.

' 1 a2 a3 a4 a5 1 A = N.M/5 (cm Even if a considerable number of floating points exist on weft yarns whose number of floats is less than 3, the piles obtained from those floating filaments are not usually useful for manufacturing a woven suede fabric having a satisfactory writing effect since the piles are too short.
On the other hand, the lie of the piles obtained from the floating points on the weft yarns whose number of floats is more than 11 becomes rather irregular and does not usually produce a natural leather-like woven suede fabric. Therefore, the number of floating points on weft yarns whose number of floats is outside the range from 3 to 11, is preferably excluded A

.,., .. .. . . ...... ........ . . . ., .. . .. ............. ~ . ~ . .. ~ . . .

from the value of A in the above equations.
When the value of A is less than 100/cm , the woven suede fabric obtained has a lot of long piles and the appearance of the fabric is inferior. On the other hand, when A is greater than 500/cm2, the piles are too short to cover up the inner structure of the fabric.
The mean length of the piles of the woven suede fabric is in the range from 0.5 to 4.0 mm. If the pile length is shorter or longer, the woven suede fabric does not have a good appearance. Moreover, it is desirable that the distribu-tion of pile length is as narrow as possible. The length of the pile can be easily observed experimentally from a micro-scopic picture of a weft yarn taken from the fabric. Fig. 12 and Fig. 13 are such examples, wherein Fig. 12 is a picture of a weft yarn taken from a suede fabric produced in accordance with the present invention, and Fig. 13 is a comparative example of a weft yarn taken from a fabric prepared by using a spun yarn composed of staple fibers whose length is 51 mm.
The meaning of a narrow distribution of pile length mentioned above can be clearly understood from these microscopic pictures.
That is, the piles 28 shown in Fig. 12 all have almost the same length, whereas the lengths of the piles 28 shown in Fig. 13 are very much different from each other. Although the length of the piles of the fabric of Fig. 13 could be cut by suitable shearing to an almost constant length, the suede fabric thus obtained would have a poor appearance different from that of the fabric of the present invention and natural suede.
Another important factor for the suede woven fabric of the present invention relates to the shear stress of the fabric. Three examples of shear stress-strein (angle) - . , . . . . -, : ................... , , - : . . :: : -: - . - . ., . .. : ~ . :
,: . . , , ~

~049897 hysterisis diagrams are shown in Fig. 14 to Fig. 16, wherein - Fig. 14 is a diagram of a conventional fabric, Fig. 15 is a diagram of a natural suede or an artificial leather, and Fig.
16 is a diagram af a woven suede fabric of the present invention.
These diagrams were obtained in the following manner.
Apparatus: Shear Stress Tester KES-Fl (manufactured by Kato Iron-Works Corp.) Conditions: Shear velocity = 0.417 mm/sec, max. shear angle = 8, uni-axial tension = 10 g/cm (constant), sample size = 20 cm x 4 cm.
Remarks: as shown in Fig. 17, the shear stress was applied in a direction parallel to the direction of the warp yarn.
The shear stress at the shear angle of 0.5 is denoted as Go 5 and the shear angle of 5 is denoted as G5, and attention is paid to the value of the ratio~G5/Go 5 As shown in Fig. 14, in the case of a conventional fabric, the stress-strain curve rises gradually in a straight line except for an initial stage where the curve rises rapidly (this larg-e resistance to initial deformation surely shows the existance of a rather geometrically rigid three dimensional structure of the fabric due to the intimate contact or entanglement between yarns which, however, can be easily destroyed). The value of G5/Go 5 is thus almost equal to 1. On the other hand, in the case of the natural suede or artificial leather, since the fibers are entangled with each other quite tightly and never flow with respect to each other, a rapid increase of shear stress continues up to 3 - 5 of shear angle as shown in Fig.
15 and then the stress increases more gradually, showing the so-called buckling phenomenon. The value of G5/G~ 5 is ~ -, - . : ,. , . . .. . : .: - . ... .

10~9897 therefore less than 1 in this case. The fabric of the present invention shows a characteristic behaviour demonstrated in Fig. 16 and the value of G5/Go 5 is within the range of from 1.5 to 15. The stress-strain curve of the fabric up to about 2 - 4 of shear angle is almost similar to that of the conven-tional fabric shown in Fig. 14 and also the value of Go 5 is nearly equal to that of the conventional fabric. However, the stress-strain curve again begins to rise rapidly when the shear angle exceeds the said range and the value of G5/Go 5 exceeds 1.5 and no buckling phenomenon is observed. That is, the woven suede fabric has a good draping property and a soft-ness as a textile fabric, but at the same time has a proper initial Young's modulus very similar to natural suede. This indicates that the new material is well suited for clothes.
The woven suede fabric having the characteristics mentioned above can be manufactured in the following way.
First of all, a woven fabric is prepared from a warp yarn chosen from polyester textured filament yarn, poly-ester filament yarn and polyester spun yarn, and a weft yarn composed of composite filament yarn as described above. The construction and the density of the fabric are designed so as to have a number of floating points on weft yarns whose number of floats is within the range from 3 to 11, such that the value of A (defined before) is 100 to 500/cm . The sea component in the composite filaments is then removed by dissolving it with a solvent for the sea component or by decomposing it with a decomposing agent, such as acids, alkalis, oxidizing agents or water-containing surface active agents, or by mechanical treatment such as rubbing. After the removal of the sea component, the fabric is heat-set. Next, a raising process including buffing is carried out. For this purpose, it is A
, , , .: , ~

desirable to use a raising machine such as a double type card-wire raising machine comprising a pile roller and a counter pile roller. It is especially desirable to carry out the raising in such a way that, firstly, the raising treatment is carried out repeatedly 3 to 10 times increasing the strength from weak to medium and finally to strong and then, secondly, the direction of the fabric is inversed and another raising treatment is carried out 2 to 8 times increasing the strength from medium to strong. Further, it is desirable to add a temporary anti-static agent or a raising agent or to carry out a tentering treatment to remove wrinkles before the raising treatment is carried out. After the raising treatment, the fabric is dyed and then finished.
The woven suede fabric thus obtained can be treated further to produce special finishes. For example, the fabric may be treated with resins, such as acrylate resin, vinyl acetate resin, urethane resin or melamine resin, to reduce the liklihood of the piles dropping out. Furthermore, 0.5 to 10% of a cationic compound, an anionic compound, a non-ionic compound, a polyamine compound, a silicone compound, etc. can be added as a softening agent or an anti-static agent or a feeling control agent. The surface of the woven suede fabric after raising may also be treated with card wires or a brush in order to impart a direction to the piles, or the piles may be treated with a hot roller, a hot press, a calender roll or a decatizer, in order to set the piles in the same direction and at the same time to give the piles an elegant lustre.
These specially treated woven suede fabrics are, of course, within the scope of the present invention as defined in the appendant claims.
In the following, the invention will be explained - . ~ .

in more detail by reference to specific Examples.
- Example 1 Two kinds of composite multi-filament yarns were prepared, each comprising 24 filaments, by the melt spinning of a polymer mixture cOnsisting of 60 weight% of polyethylene terephthalate as the island component whose [~] (the intrindic viscosity of the polyethylene terephthalate dissolved in a solvent mixture consisting of equal amounts of phenol and tetrachloroethane, observed at 30C controlled by a thermostat using a Ubellohde's viscometer) was 0.60 dl/g, and 40 weight %
of polyethylene produced by a high pressure method, as the sea component, using a melt spinning apparatus as shown in Figs.
1 - 9 and by drawing.
The two kinds of composite filaments thus obtained were, of course, substantially untwisted and had a structure consisting of a plurality of islands randomly distributed in a sea component, similar to that shown in Fig. 10, and had the following different properties. The number of island filaments - of one of the composite filaments (X) was 48, the mean thick-ness in denier of those island filaments was 0.13, the degreeof variation of thickness in denier of the island filaments was 32%, and the degree of shrinkage of the composite filaments in boiling water (WSr) was 18%. The number of island filaments of the other composite filament (Yj was 42, the mean thickness in denier of those filaments was 0.15, the degree of variation of thickness in denier of the filaments was 36% and the degree of shrinkage of this composite filament in boiling water was as low as 8%.
A multi-filament single ply yarn to be used as a weft yarn was prepared from the two kinds of composite fila-ments (X) and (Y) mentioned above, by plying them together and - 27 _ .. :. . . . ... . .

twisting at 300 turns/m. Using the said single ply yarn as a weft yarn and a conventional polyester false twist yarn as a warp yarn of 150d/48f, a satin fabric similar to that shown in Fig. 11 was prepared. In Fig. 11, P denotes a floating warp yarn and Q denotes a floating weft yarn. After treating the satin fabric in boiling water to produce thermal relaxation, the polyethylene contained in the fabric as the sea component was extracted with toluene at 80C and the fabric was set at -180C. After adding an anti-static agent to the satin fabric, a raising treatment was carried out on one surface of the fabric 10 times using a raising machine of the card wire system. The island filaments were uniformly raised as individual island mono-filaments on the surface of the satin fabric and it was impossible to determine the internal structure of the fabric through the piles from the outside. After a dyeing treat-ment, and after adding a certain amount of an acrylic resin and an anti-static agent, the suede fabric was again subjected to the raising treatment three times.
The satin fabric had warp yarn and weft yarn 20 densities of 120 and 75 yarns/inch and the number of floats was 4 (as can be seen in Fig. 11) so that the value of A was estimated to be 297/cm2. Moreover, the observed values of Go 5 and G5 of the suede fabric were respectively 1.2g/cm and

4.2g/cm, and accordingly G5/Go 5 was estimated to be 3.5. As shown in Fig. 12, the length of the pile was almost uniform and the pile length distribution was believed to be very narrow. The mean length of the piles was observed as 1.5 mm.
The woven suede fabric had a soft surface completely covered with fine piles and showed a very superior writing effect.
The surface condition of the woven suede fabric j . . .

was very similar to that of sheep suede. A blazer coat pre-pared from the fabric was, of course, soft and flexible but was also rather expandable, and the comfort during wearing and the draping properties were similar to clothes made of ordinary woven fabric. It was considered that the fabric would be suitable for makin8 intO such a coat on a large scale since it had a proper resistance to bending and had a nice suede touch of high quality. Of course, the material did not feel like ordinary woven fabric and also felt somewhat different from natural leather.
Although the blazer coat was washed in a cleaning test three times during a wearing test of one month, there was no recognizable change in the shape and size of the garment and the piles recovered their original state after brushing and without pilling.
Comparative Example 1 A woven suede fabric was obtained by a process similar to that of Example 1 except that the extraction of ;
the sea component and the raising treatment were carried out in the reverse order. The island filaments were thus raised as bundles on the fabric and it was easy to determine the internal structure of the fabric through the pile bundles.
The values A and G5/Go 5 of the fabric were 235/cm and 1.30`
respectively. Since the piles were formed in bundles, con-siderable pilling took place and the suede surface became ugly ln appearance.
Comparative Example 2 A staple fiber identified in the following descrip-tion was prepared from a multi-island uniformly distributed composite filament having 26 islands obtained by the spinning of the following polymer mixture using a spinning apparatus - . :' ~ . , ' . :
. , . . .

shown in British Patent No. 1,300,268.
Sea component : polyethylene Island component : polyethylene terephthalate Mean thickness in denier of the island filaments : 0.15 Degree of variation of thickness in denier of the islands : 7%
Mean length of the staple fiber : 51 mm Mean number of crimps in staple fibers : 8/inch A woven fabric was manufactured and subjected to a raising treatment as in Ex. 1, except that a 20'S two ply spun yarn prepared from the staple fiber obtained above was used as the weft yarn and the raising treatment was carried out 5 times in only one direction. The fabric thus obtained had the following properties: the value of A was 311/cm , G5/Go 5 was ~ -1.13 and the mean length of the piles was 4.5mm. The distribu-tion of the pile length was rather broad and very similar to that shown in Fig. 13. Though the piles had a tendency to ~ ~
orientate themselves, and accordingly had a writing effect, ~ -the center of each pile curled as if forming a pill. Therefore, the appearance of the piled surface of the fabric was not good, and by turning the fabric in the reverse direction of the piles, it was possible to see the internal structure of the fabric.
Furthermore, as can be recognized from the value of G5/Go 5' the feeling of the fabric in bending deformation was almost the same as that of a conventional woven fabric, and accordingly the suede fabric was not worth tailoring into a blazer coat since its resistance to bending was too small. Furthermore, considerable pilling took place for example, after 2 days of a wearing test, the appearance of the suede surface become ugly.
As already mentioned, the raising -treatment was - ~ '',. , ,', ,' ' , ': ' carried out only 5 times in only one direction. This was because an attempt to carry out the raising treatment in the reverse direction was not successful since the piles dropped out rapidly.
An attempt to make the pile length less than 3 mm by shearing after brushing was also not successful, since the shearing machine very often cut off the selvage portion of the fabric or a portion oE the base sheet of the fabric entered the machine. An additional attempt to increase the value of G5/Go 5 of the suede fabric by the use of a certain amount of urethane resin instead of acrylic resin was carried out, but it was also unsuccessful since the value G5/Go 5 became less than 1 by the increase of Go 5, which was contrary to the object of the attempt.
Examples 2 7 _3, 4_and 5 and Comparative Examples 3 and 4 Satin fabrics the same as the fab-ric of Ex. 1 were prepared from weft yarns comprising a single ply yarn composed of two kinds of multi-islands randomly distributed composite multi-filaments yarns X and Y shown in Table 1, and warp yarns comprising a conventional polyester false twist yarn of 150d/48f. The island filaments of the weft yarns were substan-tially continuous in each sea component. The island component consisted of polyethylene terephthalate whose [~] was 0.62 dl /g and the sea component consisted of polystyrene. The woven fabric was treated in tetrachloroethylene at 40C to remove the poly-styrene contained in the fabric as the sea component and then, after a pre-setting at 160C, the fabric was subjected to a raising treatment. The fabric was dyed and a further raising treatment was carried out twice followed by brushing. The yarn ;
density, the number of floats and the value of A of the fabric were ~ust same as those of the fabric obtained in Ex. 1.

A
.

10498~' Various important characteristics of the materials and treatment are summarized in Table 1, and various properties of the thus obtained fabrics are summarized in Table 2.

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- . ' ' -. ~ ' ' . ' ' ' ' ' , 1049~397 Example 6 In Ex. 1, two kinds of composite filaments X and Y
were used to form the single ply yarn used as the weft. In this Example, however a multi-filament single ply yarn of 48f composed of only the composite filament X in Ex. 1 was prepared. Using this single ply yarn as the weft yarn and a polyester false twist yarn of 150d/48f as the warp yarn, a woven fabric having the same construction as that of the fabric of Ex. 1 except for the yarn density, was ~repared and subjected to a raising treatment in the same way as in Ex. 1. The results obtained are shown in Table 3.
Exam~le 7 and Comparative Examples 5 and 6 - In these Examples, woven suede fabrics having the - same structures as the fabric of Ex. 6, but having yarn densities somewhat different from the latter, were prepared ` as in Ex. 6, using various composite filaments X as the weft yarn, wherein those composite filaments X were different from the composite filament X used in Ex. 6 in their mean thickness in denier as shown in Table 3. The results obtained in these Examples together with those of Ex. 6 are shown in Table 3.

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The mean length of the piles of Comp. Ex. 5 was too small and it was possible to see the internal structure of the fabric through the piles. Accordingly, the dyeing effect of the fabric was unsatisfactory and the lustre of the piled surface was not good. As can be understood from the value of G5/Go S' the suede fabric of Comp. Ex. 5 was too soft, so that it was inferior to the touch and also in resistance to deformation.
The suede woven fabric of Comparative Ex. 6 had no writing effect and its touch was very similar to that of wool fabric of the cashmere type.
The suede woven fabrics of Ex. 6 and Ex. 7 were very similar to natural suede in their appearance and surface condition. On the other hand, they were also very similar to - ordinary woven fabric in flexibility and draping properties.
Comparative Example 7 ` A woven suede fabric was prepared in the same way as in Ex. 6, except that the construction of the woven fabric was 2/1-twill and the warp and weft densities were g8 and 65 ; yarns/inch, respectively. Since the number of floats of the woven fabric was 2, the value of A was estimated to be zero.
The observed value of G5/Go 5 was 1.15 and the mean length of - the piles was 0.30mm.
''! The internal woven structure of the woven suede fabric thus obtained could be seen through the piles, since they were too short, and the value of G5/Go 5 was as small as - 1.15, that is, very similar to that of ordinary woven fabric, -since the piles of the suede fabric thus obtained had no ` ~b-llity to play the important role desired of them.
Comparative Example 8 A woven fabric of 13-ends weft weave was prepared ; u~ing a weft yarn consisting of a composite multi-filaments yarn ' A
- . . .. . . .. .
,~ . , . . . . . . . .... .~.. . ... . ..

of 150d having a twist of 100 turns/m, a mean thickness in denier of the island filaments of 0.18, and a degree of variation of thickness of the islands of 21%. A polyester false twist filament yarn of 75d/36f was used as the warp yarn and the fabric was subjected to a raising treatment after removing the sea component. The fabric thus obtained had an A value of 94, a mean pile length of 3.1 mm, and a G51Go 5 value of 1-51. The evenness of the piles was very poor and it was possible to see the internal structure of the suede fabric through the piles. In addition, the appearance of the piled surface was very inferior since there were many pills at the ends of piles entangling each other.
Example 8 .~
A woven fabric having a velveteen structure as shown in Fig. 18 was prepared using a polyester filament yarn as the warp yarn and a weft yarn consisting of a single ply yarn of composite filaments having polystyrene as the sea component and polyethylene terephthalate as the island , component. ~he mean thickness in denier of island filaments was 0.10 and the degree of variation of the thickness of island filaments was 33%.
After the woven fabric was treated for thermal relaxation and for extraction of the sea component, an anionic anti-static agent was added and the fabric was subjected to a tentering treatment at 160C under an extension of 3% in both .
directions. A raising treatment was then carried o~t 4 times by means of a raising machine and then the raising treatment - was!~epeated twice in the reverse direction. The fabric was dyed a dark color in a rapid dyeing machine and 3% of vinyl acetate resin, 0.5% of a softening agent and 1% of an anti-static agent were added. Finally, after rai-sing the fabric one more time and brushing it, the fabric was passed through a - 38 ~

.

~-` 10491!397 paper calender, brushed once in the direction reverse to that of the direction of the piles, and again brushed twice the direction of the piles, and then finally the suede fabric was set at 160C.
The woven suede fabric had the following properties:
250/cm for ~ (n=10, m=6 al=a4~o, a2 a3 a5 6 1.5mm for the mean length of piles, and 4.1 for G5/Go 5 The fabric had a nice appearance and a touch similar to deer-skin suede, and it also had a superior writing effect. ~foreover, it had good draping properties since its thickness was much less than that of natural leather (the thickness of the present example was 0.6mm).

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A

. . . . .
.
.

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A suede woven fabric comprising (a) a warp yarn selected from polyester textured yarn, polyester filament yarn and polyester spun yarn and (b) a weft yarn in the form of a single ply yarn formed from a plurality of composite filaments, each consisting of a plurality of monofilaments, said monofilaments having a mean thickness in the range of 0.05 to 0.5 denier and having a degree of variation in thickness in the range of 15 to 60%, a portion of said weft monofilaments on at least one surface of the fabric being raised to form piles of individual monofilaments having mean lengths in the range of 0.5 to 4.0 mm, with the number of floating points on weft yarns whose numbers of floats are within the range of 3 to 11 being in the range of 100 to 500/cm of woven fabric and the ratio of shear stress of the fabric at a shear angle of 0.5° and that at a shear angle of 5° being in the range of 1.5 to 15:1.

2. The suede woven fabric according to claim 1 wherein the weft yarn contains 500 to 10,000 monofilaments.

3. The suede woven fabric according to claim 2 wherein about 5 to 40% of said weft monofilaments are cut at every floating point to raise them as piles on the fabric.

4. The suede woven fabric according to claim 3 wherein about 5 to 15% of said weft monofilaments are cut at every floating point to raise them as piles on the fabric.

5. The suede woven fabric according to claim 1, 2 or 3 wherein the monofilaments have a degree of variation of thickness in the range of 20 to 40%.

6. The suede woven fabric according to claim 1, 2 or 3 wherein the monofilaments have a mean thickness in the range of 0.10 to 0.18 denier.

7. The suede woven fabric according to claim 1, 2 or 3 warp yarn is a polyester textured yarn.

8. A suede woven fabric according to claim 1, 2 or 3 wherein the weft yarn has a thickness in the range of 75 to 500 denier.

9. A process for producing a suede woven fabric which comprises (i) forming a single ply weft yarn from two kinds of composite filaments, each composite filament consisting of a plurality island polyester monofilaments randomly distributed in a polymeric sea component having a solubility different from the island monofilaments, said island monofilaments extending substantially along the length of the composite filament with each monofilament having a mean thickness in the range of 0.05 to 0.5 denier and the degree of variation in thickness among monofilaments being in the range of 15 to 60%, blending said composite filaments to form a single ply yarn in which 95 to 40%

by weight of the monofilaments have a low shrinkability in boiling water and 5 to 60% by weight of said monofilaments have a shrinkability in boiling water at least 3% higher than said low shrinkability monofilaments, (ii) preparing a woven fabric with warp yarn selected from polyester textured yarn, polyester filament yarn and polyester spun yarn and said weft yarn, (iii) removing the sea components from said composite filaments, (iv) heat-setting the woven fabric under relaxation and (v) raising portions of said weft monofilaments on at least one surface of the fabric to form piles having a mean length of 0.5 to 4.0 mm.

10. A process according to claim 9, wherein the piles of individual island monofilaments are formed by cutting about 5 to 40% of the total number of island monofilaments in the weft yarn.

11. A process according to claim 10, wherein the piles of individual island monofilaments are formed by cutting about 5 to 15% of the total number of island monofilaments in the weft yarn.

12. A process according to claim 9, wherein 20 to 50 weight % of the composite filaments having high shrinkability are blended with 80 to 50% of the composite filaments having low shrinkability to form the weft yarn.

13. A process according to claim 9, wherein the island monofilaments have mean thicknesses in the range from 0.10 to 0.18 denier.

14. A process according to claim 13, wherein the variation of thickness of the island monofilaments is 20 to 40%.

15. A process according to claim 14, wherein the warp yarn is polyester textured yarn.