MXPA06005075A - Method for producing abrasive non-woven cloth - Google Patents

Abstract

A method for producing abrasive non-woven cloth includes forming a non-woven web of fibers (10) including a first layer (12) adjacent to a first surface of the web (14) containing at least about 5%by weight of thermoplastic fibers. The web (10) is patterned to generate raised regions (16) and lowered regions (18) in the first surface (14), and then heat treated to cause at least part of the thermoplastic fibers to form nodules (20), thereby imparting abrasive properties to at least the raised regions (16) of the first surface (14). The non-woven web preferably includes a second layer (60) adjacent to a second surface (62) of the web (14) made up primarily of fibers which do not form nodules under the heat treatment.

Description

METHOD TO PRODUCE ABRASIVE NON-WOVEN FABRIC FIELD OF THE INVENTION The present invention relates to nonwoven fabric products and, in particular, relates to a method for producing abrasive nonwoven fabric and the fabric resulting from this method.

BACKGROUND OF THE INVENTION The nonwoven cloth is used for an ever increasing range of products and applications. In particular, the steady trend towards the use of disposable products has led to tremendous growth in the market for non-woven materials, and non-woven fabrics have been seen being adapted as an economic basis for many new products. The types of non-woven fabrics can be classified in many forms, for example, in accordance with the type and gauge of fibers used, the placement technique for forming a net, or the bonding technique for joining the fibers into a fabric. Examples of kinds of fabric production techniques to which the present invention is believed to be applicable include, but are not limited to, hot melt, wet-laid and matted in dry-laid water, thermoagglutination, thermoagglutination through air and chemical agglutination. For certain applications, it is desirable to provide various degrees of abrasiveness to non-woven fabrics. This varies from very mild abrasive properties used for facial cleansers or skin treatments to highly abrasive cleansing pads used for cleaning kitchen utensils. The required abrasive properties are generally achieved by the use of thick gauge fibers, which inherently exhibit the required abrasiveness. The American Patent NO. 5,786,065 by T? Nnis et al., Discloses a process for producing an abrasive nonwoven material, from an initially non-abrasive precursor, by heating the fabric which includes between 10% and 50% by weight of thermoplastic fibers at almost the melting point of the thermoplastic fibers, so that they contract to form nodules. These nodules impart abrasive properties to a flat surface of the material. The differential properties between the two surfaces are achieved by ensuring a gradient in the proportion of the thermoplastic fibers through the initial fabric. In accordance with the teachings of innis et al., Abrasivity is a function of the size of the nodules which are, themselves, a function of the gauge of thermoplastic fibers used in the precursor material.

Of the cited examples, Annis et al., Imply that effective high abrasivity can be achieved by using a fiber size in the range of 10-55 denier, which corresponds to approximately 11-60 grams per 10,000 meters of fiber length (referred to as a "decitex" or "d-tex"). This fiber thickness necessarily imparts a remarkable thickness and, after the heat treatment, a degree of rigidity to the resulting fabric. In all cases, the surfaces of the material are clearly declared to be flat. There is therefore a need for a corresponding production method and product, which could provide a controllable degree of abrasiveness of a non-woven fabric, using low gauge fibers and while maintaining a high degree of flexibility in the fabric.

SUMMARY OF THE INVENTION The present invention is a method for producing an abrasive nonwoven fabric, and the resultant fabric from this method. In accordance with the teachings of the present invention, there is provided a method for producing an abrasive nonwoven fabric comprising: (a) forming a nonwoven web of fibers including at least a first layer adjacent to a first surface of the network that contains at least about 5% by weight of the thermoplastic fibers, (b) design the network to generate a design of raised regions and regions recessed in the first surface; and (c) perform heat treatment in the network, enough to cause at least part of the thermoplastic fibers to undergo changes in physical morphology, thereby, imparting abrasive properties in at least the raised regions of the first surface. According to a further feature of the present invention, the non-woven fabric is implemented to include at least a second layer adjacent to a second surface of the network, the second layer containing mainly fibers which do not undergo changes in morphology physical under heat treatment. In accordance with a further feature of the present invention, the design is implemented to cause migration of at least a proportion of fibers within the first layer from the recessed regions to the raised regions. In accordance with a further feature of the present invention, the design is implemented to cause migration of a majority of fibers that make the first layer in the recessed regions to the raised regions. In accordance with a further feature of the present invention, the design is implemented by use of water jets to displace the fibers. In accordance with a further feature of the present invention, the water jets are directed towards a portion of the network that passes over a cylinder with a perforated surface. In accordance with a further feature of the present invention, the water jets are directed towards a portion of the network that passes over a cylinder with a mesh surface. In accordance with a further feature of the present invention, the water jets are directed towards a portion of the network that passes along a designed conveyor belt. In accordance with a further feature of the present invention, there is also provided a step to employ jets of water to cause entanglement of the fibers in the network. In accordance with a feature of the present invention, the design is implemented in such a way that the raised regions include a plurality of isolated projection features surrounded by the recessed regions. In accordance with a further feature of the present invention, the design is implemented in such a way that the raised regions include a plurality of elongated ridges. In accordance with a further feature of the present invention, the thermoplastic fibers have a weight of no more than about 4.5 grams per 10,000 meters, and preferably no more than about 2.2 grams per 10,000 meters. In accordance with a further feature of the present invention, the first layer contains at least about 10% by weight of the thermoplastic fibers. In accordance with certain implementations of the present invention, the first layer contains less than about 50% by weight of the thermoplastic fibers. In alternative implementations, it is preferable that the first layer contains more than about 50% by weight of the thermoplastic fibers. Also provided in accordance with the teachings of the present invention is an abrasive nonwoven fabric comprising at least a first layer of fibers adjacent to a first surface of the fabric, the first layer containing at least about 5% by weight of the heat-treated thermoplastic fibers, to include a plurality of nodes, the first layer is designed such that the first surface exhibits a pattern of raised regions and lowered regions..

In accordance with a further feature of the present invention, at least one second layer of fibers adjacent to a second surface of the fabric is also provided, wherein the plurality of nodes is substantially only in the first layer. In accordance with a further feature of the present invention, a majority of material from the first layer is placed within the raised regions. In accordance with a further feature of the present invention, the fabric is formed from a process of entanglement in water. In accordance with a further feature of the present invention, the raised regions include a plurality of isolated projection features, surrounded by the recessed regions. In accordance with a further feature of the present invention, the raised regions include a plurality of elongated ridges.

BRIEF DESCRIPTION OF THE FIGURES The invention is described herein, by way of example only, with reference to the accompanying drawings, wherein: Figures 1A-1C are schematic cross-sectional views, illustrating stages in the production of a first implementation of an abrasive fabric, in accordance with the teachings of the present invention; Figures 2A-2C are schematic cross-sectional views, illustrating steps in the production of a second implementation of an abrasive cloth, in accordance with the teachings of the present invention; Figure 3 is a schematic side view of a production line for implementation of the method of the present invention; Figure 4A is an isometric view of a cylinder for use in the production line of Figure 3; Figure 4B is an enlarged view of a portion of the cylinder of Figure 4A, as indicated; Figure 4C is a schematic, partially sectional, isometric view of a non-woven abrasive fabric produced by use of the cylinder of Figure 4A; Figure 5A is an isometric view of a cylinder for use in the production line of Figure 3; Figure 5B is an enlarged view of a portion of the cylinder of Figure 5A as indicated; Figure 5C is a schematic, partially sectioned, isometric view of a non-woven abrasive fabric produced by use of the cylinder of Figure 5A; Figure 6A is an isometric view of a conveyor belt for use in the production line of the Figure 3; Figure 6B is an enlarged view of a portion of the conveyor belt of Figure 6A as indicated; and Figure 6C is a schematic, partially sectional, isometric view of a non-woven abrasive fabric produced by the use of the conveyor belt of Figure 6A.

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing an abrasive nonwoven fabric, and the fabric resulting from this method. The principles and operation of the production methods and corresponding products in accordance with the present invention can be better understood with reference to the figures and the accompanying description. With reference now to the drawings, the Figures 1A-1C and Figures 2A-2C illustrate various steps during two implementations of a method for producing abrasive nonwoven fabric in accordance with the teachings of the present invention, in single layer and multiple layer implementations, respectively. Referring generically to both implementations in general terms, the method requires forming a non-woven network of fibers 10 (Figures 1A and 2A), which include at least a first layer 12 adjacent a first surface 14 of the network, wherein the layer 12 contains between about 5% and 100% by weight (preferably at least 10%) of thermoplastic fibers. The network 10 is then designed to generate a pattern of raised regions 16 and recessed regions 18 in a first surface 14 (Figures IB and 2B). A heat treatment is then carried out in the network 10, to cause at least part of the thermoplastic fibers to undergo changes in physical morphology, for example, by forming nodes 20 (Figures 1C and 2C), thereby imparting abrasive properties in at least the raised regions 16 of the first surface 14. It should be appreciated that the method of the present invention and the resulting product provide distinct advantages over the method and product proposed by Annies et al., Reference mentioned above. Using a design to ensure a desired surface topography of the fabric, the level of abrasiveness can be controlled independently of the particle size of the nodes. Specifically, in Annis et al., The abrasiveness results from nodules which are adjacent to the flat surface of the fabric and vary as a function of the size of the nodes which, in turn, are a function largely of the initial fiber size. On the contrary, the texture of the product of the present invention provides an extra degree of freedom to adjust the abrasiveness of the product, similar to the edges of a metal file, which produces an effective abrasiveness much greater than that of a smooth surface of similar material. As a result, d-tex fine thermoplastic fibers of no more than 4.5, and more preferably no more than 2.2, can be used, thereby, avoiding thickness and stiffness, which results from the use of larger gauge fibers. . These and other advantages of the present invention will be better understood by reference to the following detailed description. Before addressing the features of the preferred implementations of the present invention in more detail, it will be useful to define certain terminology as used herein in the description and claims. First, the term "thermoplastic" is used herein in the description and claims to refer to any polymer, which flows in the application of heat. Preferably, the present invention is implemented with thermoplastics having a crystalline fraction when they are at temperatures below their characteristic melting point, i.e., wherein the sections of the polymer chains are folded in an orderly pattern. Examples of crystalline polymers useful for implementing the present invention include, but are not limited to, polypropylene, polyethylene, polyester terephthalate, and polyamides. A more preferred example is polypropylene. In certain cases, amorphous polymers (that is, they do not have a crystalline fraction) can also be used. The reference can also be made to a "Polymer transition temperature" 'of the thermoplastic material as a reference point in the definition of the heat treatment carried out in accordance with the teachings of the present invention. In the case of a polymer with a crystalline fraction, the melting point is typically used as the reference point. For amorphous polymers, the vitreous transition point can be used as the reference point. In both cases, the reference point will be referred to generically as the "transition temperature" of the polymer. The term "nodule" is used to refer to agglomerations of the thermoplastic material caused by the heat treatment of the present invention, such as the minimum dimension of the "nodule" is significantly greater than the diameter of the original fibers. It should be noted that the "nodes" do not need to be of any particular shape, and can in fact be complex interconnected masses formed of partial or total conglomeration of a plurality of fibers. When referring to the fiber gauge in the production of cloth, reference is made to "d-tex" or "decitex" and "denier" scales. Decitex or d-tex, are defined as the weight in grams of 10,000 meters of a fiber. Denier is defined as the weight in grams of 10,000 yards (approximately 9,000 meters) of a fiber and is therefore related by a ratio of approximately 9:10 to the d-tex value. When referring to the composition of the various fiber layers according to the present invention, reference is made to "percentage by weight" of the various fibers. It should be noted that the weight percentage of the thermoplastic fibers in layer 12 is calculated in accordance with the initial fiber mixture used for such an individual layer. Although, after the treatment, a proportion of the fibers have been converted into nodules or otherwise conglomerated so that they are not longer "fibers", the weight of the nodules is still taken into account when referring to the composition of the fibers. the corresponding layer in the final product. Turning now to the features of the present invention in more detail, it should be noted that the present invention is applicable to a wide range of types of non-woven cloth production techniques. By means of a particularly preferred, non-limiting example, the invention will be illustrated in the context of a dry-entangling technique of water matting. Thus, Figure 3 shows schematically, a production line for production of entanglement in water placed in dry of nonwoven fabric modified by implementation of the method of the present invention. Specifically, Figure 3 schematically shows a feeding system 30 for supplying one or more layers of fibers to a water-binding agglutination system 32 with arrangements of water jet nozzles 34 facing cylindrical rotating screens 36 under which one or more suction boxes are placed (details not shown). These systems together, produce a network of bonded cloth corresponding to the network 10 of Figures 1A or 2B. Both the feed system 30 and the water-binding agglutination system 32, include many details not shown in this document, including devices for fiber opening, mixing, feeding and carding. All the details are well known in the art and will not be further discussed in this document.

After the agglutination of the fabric, or as a component step thereof, the network is designed in accordance with the teachings of the present invention, to form raised and lowered regions. Figure 3 illustrates two subsystems for performing this design, i.e., a transport subsystem 40 and a cylinder subsystem 42, only one of which is typically driven at any time. Each subsystem includes arrangements of water jet nozzles and corresponding suction boxes, details of which are not shown in this document, as will be clear to one ordinarily skilled in the art. Various implementations of each of these subsystems will be described separately below with reference to Figures 4-6. After design, the network typically passes to a drying system 44, to remove an excess proportion of water from the network, followed by a drying system 46, which preferably performs both drying and heat treatment functions, in accordance with the teachings of the present invention. Finally, the network typically passes to a winding station 48 to wind and cut it to form rolls of a required size. Referring now to particular preferred implementations of the design system, Figures 4A and 4B show a first implementation of a cylinder 50 for use in a cylinder subsystem 42, wherein the cylinder 50 is drilled with sufficient holes to allow the entry of portions of the cylinder 50. of fiber, thereby forming a design of isolated projection features 16 surrounded by recessed regions 18 as shown in Figure 4C. The size of the perforations and thus of the resulting raised projections, is typically in the range of 1-3 mm in diameter, and the pitch (ie, closest neighbor spacing from center to center), is typically at least 1 mm. greater than the diameter, and typically not more than about 6 mm. As a result, for a hexagonally closed packaged presentation (ie, where all the nearest neighbor spacings are equal), the open area of the perforations, and the corresponding resulting projections, are generally counted from a few hundred to about 60. percent of the total surface area, with a particularly preferred range of about 20 to about 50 percent. In general, the relatively large open area is advantageous for increased proportions of production, but the diameter of each individual perforation must be limited to avoid damage to the quality of the resulting fabric. The "depth" or "height" of the resulting projections is determined by a combination of the size of perforations and the parameters of the water-entangling process, as is known in the art. Turning now to Figures 5A and 5B, these show an alternative implementation of a cylinder 52 for use in a cylinder subsystem 42, wherein the cylinder 50 is formed with an open network surface, thereby forming a design of characteristics of rectangular or rectangular projections 16, surrounded by recessed regions 18 as shown in Figure 5C. The network surface can be implemented either by a network layer overlapping a perforated cylinder, or by a cylinder formed directly from the network type material. "Network" in this context refers to any repetitive design with substantially polygonal openings, typically triangular or rectangular. The structure may be formed of a woven arrangement of strands or strips, such as metal strands, or as a smooth surface with appropriately formed perforations, for example, of polymeric materials. Typically, a stainless steel mesh is used. The size and spacing of the apertures typically varies in a manner similar to that of cylinder 50 discussed above. In accordance with a particularly preferred example of a square network design, the strands and spaces have equal amplitudes, such that the total open area of the network (and corresponding raised areas of the product) correspond to approximately 25% of the area of total surface. Figures 6A and 6B show a preferred implementation of a conveyor belt 54 for use in the conveyor belt subsystem 40 of Figure 3. In this case, the ex-textured conveyor belt to impart a design corresponding to the surface of the non-woven network by physical processes equivalent to those described with reference to cylinder subsystem 42. In the example shown in this document, the web has a woven fabric texture which imparts an undulating woven texture to the surface of the non-woven web as shown in Figure 6C. The resulting texture is less aggressive in its abrasivity than the isolated projections of various implementations, providing the right product for a range of applications of lower abrasiveness, such as products for personal hygiene and skin care. It will be noted, however, that conveyor belts with other types can be used to form designs with a range of different textures, resulting in final products with different degrees of abrasiveness. In each case of the conveyor belt or cylinder subsystem, one or more arrays of water jets are directed towards the surface of the conveyor belt or cylinder, to force the fibers into closed engagement with the corresponding characteristics of the fundamental surface. Switching now briefly again to Figures 2A-2C, it should be noted that the particularly preferred implementations of the present invention employ a multilayer network made of two or more layers, wherein at least a second layer 60, and typically all the different layers of layer 12 contain mainly fibers which do not form nodules or otherwise undergo physical structural changes under the heat treatment conditions used. More preferably, the layer 60 is made substantially exclusively of fibers, which do not significantly change their physical structure under the heat treatment conditions used. In this case, the layer 12 is arranged facing the roller or conveyor belt of the subsystems 40 and 42, while the additional layer or layers, face the arrangements of water jet nozzles 34. The layer 60 can be made of any fiber or mixture of fibers which are known for the production of non-woven fabric, which includes various natural, synthetic and artificial fibers. Furthermore, it should be noted that the layer 60 may include thermoplastic fibers with a higher transition temperature than that of the heat treatment conditions used to generate nodes in the layer 12. More preferably, the layer 60 is formed mainly of fibers which imparts softness and / or absorbent properties to the adjacent surface 62 of the network. For optimum fine and high quality opacity, d-tex fine gauge fibers of no more than 4.5 (denier of 4), and more preferably no more than 2.2 (denier 2) are used. It should be noted that there is a profound synergy between the implementation of multiple layers of the present invention and the design techniques such as those described herein, which generate fiber migration within the network, to form the required design. In other words, the water from the water jets used in the design techniques described above drains through the network and the fundamental cylinder or conveyor belt, carrying them with fibers which become accommodated in the openings to form projections. This results in a pure migration of fibers from the network adjacent to the "raised regions". This remains contrary to the stamping techniques used in certain other production techniques, which merely crush part of the structure that generates fibers of varying density without migration of fibers. Thus, in accordance with a preferred multilayer implementation of the present invention, the design process is performed to cause the migration of at least one proportion and preferably, a majority of the thermoplastic fibers within the layer 12 of recessed regions. 18 to raised regions 16. This preferably results in a majority of the total material of layer 12 which is located within raised regions 16 in the final product. This migration produces a structure such as in Figure 2B, wherein the fibers forming nodes are concentrated in said raised regions for maximum contribution to the abrasive properties of the fabric while the main structural component of the fabric is provided by the fibers of the fabric. layer 60, which remains soft, flexible and absorbent after heat treatment. The result is a dual-function product in which one side provides abrasive properties, while the opposite side has a soft absorbent high-quality non-woven fabric finish, and wherein the entire product maintains a highly flexible feel. Originally, it should be noted that both the primary water entangling process and the design process described in this document, cause a lower degree of fiber mixing between the layers. In practice, this mixing has been found corresponding to no more than some percentage of the total composition of each layer, and therefore, does not significantly impact, the volume properties of the various layers. Turning now to Figure 3, as mentioned above, the drying system 46 preferably performs both heat and dry treatment functions, in accordance with the techniques of the present invention. The operating temperature of the dryer is chosen to be near or above the transition temperature of the active polymer component of the layer 12 and to maintain such a temperature slightly higher than that which is required to achieve the drying of the network. The maximum temperature reached by the fabric after drying and the period of time by which it is maintained at such temperature affects both the proportion of thermoplastic fibers which undergo changes in physical morphology and / or the extent of the changes which take place. By adjusting these parameters, as well as the engraving depth and the proportion of the thermoplastic fibers in the layer, it is possible to achieve fine adjustment of both the abrasiveness level and the "feel" of texture of the final product. By means of a non-limiting example, the heat treatment and drying steps can be performed by a "through air" dryer, in which hot air is conducted through the fabric as it passes over a cylinder or conveyor system. In this case, the dryer configuration is preferably arranged so that the etched surface of the layer 12 faces separated from the cylinder or conveyor belt during this process to avoid mechanical contact with the etched design during heat treatment processing. It should be noted that the present invention can be used to provide products over a wide range of different applications, ranging from very mildly abrasive products for personal or cosmetic care applications, to cleaning pads for cleaning domestic surfaces. In applications where an absorbent, soft texture is required, the proportion of thermoplastic fibers used in layer 12 is preferably below about 50%. For other applications where greater abrasion is required, proportions in excess of 50% may be preferred. In both cases, additional absorbency and a "soft" back surface may be provided by additional layer (s) 60 if desired. In the case of a cleaning pad, this can provide a reversible cleaning and rubbing product.

Finally, it should be noted that the functionality of the resulting product can optionally be improved by impregnation with various additives, finishing agent or cleaning agents, in accordance with the proposed use. In this way, a makeup removal pad can be impregnated with a makeup solvent and / or skin conditioning agent, while a cleaning pad can be impregnated with detergent or the like. It will be appreciated that the above descriptions are only intended to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.

Claims (27)

NOVELTY OF THE INVENTION Having described the present is considered as a novelty, and therefore, it is claimed as property contained in the following: CLAIMS

1. A method for producing abrasive nonwoven fabric, characterized in that it comprises: (a) forming a non-woven fabric of fibers including at least a first layer adjacent a first surface of the network containing at least about 5% by weight of thermoplastic fibers; (b) designing the network so as to generate a design of raised regions and lowered regions on said first surface; and (c) performing heat treatment in said network, sufficient to cause at least part of said thermoplastic fibers to undergo changes in physical morphology, thereby imparting abrasive properties in at least said raised regions of said first surface.

2. The method according to claim 1, characterized in that the formation of said non-woven network is implemented to include at least a second layer adjacent to a second surface of the network, said second layer contains mainly, fibers which do not undergo to changes in physical morphology under said heat treatment.

3. The method of compliance with the claim 2, characterized in that said design is implemented to cause migration of at least a proportion of fibers within said first layer from said recessed regions in said raised regions.

4. The method of compliance with the claim 2, characterized in that said design is implemented to cause migration of a majority of fibers by making said first layer in said recessed regions in said raised regions.

5. The method of compliance with the claim 1, characterized in that said design is implemented by the use of water jets to displace fibers.

The method according to claim 5, characterized in that said water jets are directed towards a portion of said network that passes over a cylinder with a perforated surface.

The method according to claim 5, characterized in that the jets of water are directed towards a portion of said network that passes over a cylinder with a network surface.

8. The method according to claim 5, characterized in that the jets of water are directed towards a portion of said network that passes along a designed conveyor belt.

9. The method of compliance with the claim 5, characterized comprises a step of using jets of water to cause entanglement of fibers in the network.

The method according to claim 1, characterized in that said design is implemented in such a way that said raised regions include a plurality of isolated projection features surrounded by said recessed regions.

The method according to claim 1, characterized in that said design is implemented in such a way that said raised regions include a plurality of elongated ridges.

The method according to claim 1, characterized in that said thermoplastic fibers have a weight of no more than about 4.5 grams per 10,000 meters.

The method according to claim 1, characterized in that said first fiber layer has a weight of no more than about 2.2 grams per 10,000 meters.

The method according to claim 1, characterized in that said first layer contains at least about 10% by weight of said thermoplastic fibers.

15. The method according to claim 1, characterized in that said first layer contains less than about 50% by weight of said thermoplastic fibers.

The method according to claim 1, characterized in that said first layer contains more than about 50% by weight of said thermoplastic fibers.

17. A non-abrasive woven fabric, characterized in that it comprises at least a first layer of fibers adjacent to a first surface of the fabric, said first layer contains at least about 5% by weight heat-treated ther oplastic fibers, to include a plurality of nodes, said first layer is designed such that said first surface exhibits a pattern of raised regions and lowered regions.

18. The fabric in accordance with the claim 17, characterized in that it also comprises a second layer of fibers adjacent to a second surface of the fabric, wherein said plurality of nodes are substantially only in said first layer.

19. The fabric according to claim 18, characterized in that a majority of the material of said first layer is located within said raised regions.

20. The fabric according to claim 17, characterized in that said fabric is formed from a process of entangling in water.

The fabric according to claim 17, characterized in that said raised regions include a plurality of isolated projection features surrounded by said recessed regions.

22. The fabric in accordance with the claim 17, characterized in that said raised regions include a plurality of elongated ridges.

23. The fabric according to claim 17, characterized in that said fabric is formed mainly of fibers having a weight of no more than about 4.5 grams per 10,000 meters.

24. The fabric according to claim 17, characterized in that said fabric is formed mainly of fibers having a weight of no more than about 2.2 grams per 10,000 meters.

25. The fabric according to claim 17, characterized in that said first layer contains at least about 10% by weight of said thermoplastic fibers.

26. The fabric according to claim 17, characterized in that said first layer contains less than about 50% by weight of said thermoplastic fibers.

27. The fabric according to claim 17, characterized in that said first layer contains more than about 50% by weight of said thermoplastic fibers.