Abstract:
There is described a process for preparing a “double layer” non-woven fabric having a non-woven fabric surface covered with microfiber including needle-punching of a mat formed by at least one carded web of macrofibers and at least one carded web of microfibers and subsequent treatment of the mat with high pressure water jets to split the microfibers into filaments

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a process for preparing a non-woven fabric having a surface covered with microfiber that can advantageously be used to produce cleaning cloths and mops. In particular, the present invention relates to a process for preparing “double layer” composite textile materials formed by a microfiber surface layer and a non-woven fabric supporting layer. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are known procedures for the production of non-woven fabrics produced with mechanical needle-punching and spunlace or hydroentangled technologies and/or optionally subsequently bonded by means of thermal bonding of thermoplastic fibers and/or by adding resins or latexes in general. 
         [0003]    These non-woven fabrics are used to produce cleaning cloths or to produce mops. According to prior art techniques to produce needle-punched non-woven felts with mechanical needle-punching systems, these felts are optimally used to produce cleaning cloths, and have the advantage of having a low density and consequently a relatively high volume with respect to the weight per square meter. Moreover, regardless of the type of fibers used, their mass creates a mechanical volume that increases their absorption capacity. Their volumetric mass with low weight density per cm 3  also allows the production of articles such as mops or swabs that must have a volume in addition to a cleaning surface. Cloths obtained with this process are formed by fibers with a fineness greater than 1 dtex (macrofibers) and are produced by subjecting both surfaces of the fiber layer to mechanical needle-punching, optionally followed by a thermal bonding process to increase the mechanical consistency of the cloth, or using chemical binders such as acrylic resins, EVA, rubber latexes and the like by means of spray application, impregnation using padding machines or by coating or the like according to prior art. The disadvantage of this type of technology if used to produce microfiber non-woven fabrics is that the majority of the fibers remain inside the thickness of the non-woven fabric and accordingly their cleaning capacity is not used: therefore costs are also higher due to the use of microfibers for the whole thickness of the non-woven fabric structure. 
         [0004]    With another prior art technique, known as spunlace or hydroentangled, non-woven fabrics are produced with a higher weight density, generally greater than 0.16 g/cm 3 , with respect to those produced through the mechanical needle-punching process: these fabrics have the characteristic of greater compactness and low thickness with respect to non-woven fabrics produced with mechanical needle-punching systems having the same basis weight per square meter and the same fiber composition. Said process is generally used to produce microfiber non-woven fabrics as it also splits the splittable microfiber into filaments: it is performed on both surfaces of a mat of extruded continuous filaments deriving from microfibers coming from production systems using spunbonded and/or meltblow technologies or from staple fiber mats coming from carding systems. 
         [0005]    The drawback of this production process is that to obtain a thickness that is sufficiently high to allow easy handling for use as cleaning cloths, or to produce strip mops, the weight per square meter of the product must be greatly increased, thus increasing costs due to the quantity of fibers used. Moreover, increasing the weight of the product in this way leads to high production costs, as high pressure water jets are required during the hydroentanglement process to achieve bonding of the fibers inside the layer of non-woven fabric. 
         [0006]    Another type of non-woven fabric is represented by microfiber and macrofiber bonded materials produced by thermal bonding of a microfiber layer with a macrofiber layer, optionally subsequently calendering the double layer thus obtained, where each layer has been prepared previously according to the techniques described above. However, this thermal process is costly from the viewpoint of energy and due to the use of hot melt glues which are required to allow adhesion of the two different layers. 
       SUMMARY OF THE INVENTION 
       [0007]    The object of the present invention is to produce a non-woven fabric for cleaning cloths using a process capable of solving and overcoming all the aforesaid drawbacks of prior art. 
         [0008]    A further object is that of providing a process of this type that can also be used to obtain a double-layer textile material in which the layers have very different unit weights or densities from each other, guaranteeing sufficient mechanical consistency of the material without macrofiber impurities on the microfiber surface. 
         [0009]    Yet another object of the present invention is to provide a process to obtain a double-layer textile material in which the microfiber layer is thin without decreasing the cleaning power of the non-woven fabric. 
         [0010]    These objects are achieved by a process in accordance with the invention having the characteristics listed in the appended independent claim  1 . 
         [0011]    Advantageous embodiments of the invention are apparent from the dependent claims. The present invention relates to a process for preparing a non-woven fabric material, where a supporting layer is bonded with a microfiber cleaning layer, comprising: 
         [0000]    (a) needle-punching of a mat formed by at least one layer of carded web of macrofibers and at least one layer of carded web of microfibers, and
 
(b) treatment of the needle-punched mat by means of spunlace/hydroentangled technology with high pressure water jets to split the microfibers into filaments.
 
         [0012]    The needle-punching (a) and the subsequent treatment (b) are performed and applied from the same side and, i.e. only on the free side (i.e. the side not in contact with the microfibers) of the microfiber layer of the bonded non-woven fabric material. 
         [0013]    The macrofiber layer to be used in step (a) can be pre-needled, needle-punched or even only constituted by a plurality of folded or carded webs. The effect of the use of the macrofiber layer is achieved provided that a microfiber web layer is deposited over said macrofiber layer and that subsequent needle-punching (a) is performed only from this microfiber side. 
         [0014]    In practice, the first mechanical needle-punching step produces a non-woven fabric, which is used as base for application to one of the two surfaces of a splittable fiber web, in this case splittable microfibers and, again with the prior art mechanical needle-punching technique, this surface web of fibers is entangled to take, through mechanical action, the fibrils of the microfiber inside the lower layer of non-woven fabric so as to cover one of the two surfaces and to bond the two layers of non-woven fabric though entanglement of the fibrils of the surface layer with those of the layer below. In this manner, the fibril is given its direction by the needle that conveys it inside the lower supporting layer, without contaminating the microfiber layer with less prestigious macrofibers, which instead would occur in the case of bonding only using mechanical needle-punching, as in the art needle-punching is also performed on the other side (lower) of the material. Following this operation, surface bonding is applied using the prior art technique of hydroentanglement, again only from one side on which the microfibers have been deposited so as to entangle the fibres of the surface and in the case of microfibers, also to split the fibrils so as to produce microfibers as a result of hydroentanglement. 
         [0015]    The non-woven fabric thus produced can be used as is, or can be subsequently dyed and/or coated on one or both sides and/or printed, to produce dry and/or moistened cloths for cleaning, to produce mops or for uses in the medical sector, where fabrics with different densities and compositions are required, and in all those applications that require the efficacy of microfiber which, due to the physical structure of the fibers of which it is composed, removes dirt very effectively. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Reference shall now be made to the accompanying  FIGS. 1 and 2 , which represent schematically in cross section, respectively the textile material before step (a) and after the process in order to better illustrate the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The term “bonded material”  100 , illustrated in  FIG. 2 , is intended herein to identify a material composed of two superimposed layers  1  and  2  formed by different fibers that have been subjected to processing through which they have been mutually bonded. The mechanical needle-punching step (a) is carried out according to prior art. 
         [0018]    The treatment with high pressure water jets used in step (b) of the present process is a technology known in the art also called spunlacing or hydroentangling. See for example U.S. Pat. No. 3,485,706, or the description of patent application EP 1359241 incorporated herein by reference. 
         [0019]    The non-woven fabric  100  is prepared according to the following procedure: the fibres constituting the supporting layer  2 , having deniers greater than 1 dtex (illustrated with a light line), are fed on a conveyor belt from a first carding system. The fibers of said supporting layer  2  are then bonded, for example with water jets or mechanical needle-punching, as in the carded web the fibers are maintained joined through mutual bonding but break up and separate if subjected to traction. 
         [0020]    The splittable microfiber fibers (illustrated with a heavy line) are fed from a second carding system in the form of one or more air-formed webs, on top of the free surface of the previously formed macrofiber supporting layer  2 . By means of the needle-punching operation (a) of the mat formed by two layers  1  and  2  which is positioned on the conveyor belt, part of the microfibers of the upper layer  1  are driven and bonded with part of the macrofibers of the lower layer  2 , as illustrated in  FIG. 2 . In this way part of the microfiber fibers of the layer  1  are bonded with part of the fibers of the lower supporting layer  2  below as the needle drives the fibrils  3  from the upper layer  1  to the lower layer  2  for the entire depth (thickness) of the material (mat) creating a coupling point between the two layers as shown in  FIG. 2 . 
         [0021]    Then, by means of a device with high pressure water jets, pressure is applied to the free surface of the upper layer  1  of the mat  100  along the lines of the nozzles to perform step (b); said lines represent longitudinal bonding lines along which the microfibers are bonded to a greater degree with the macrofibers below. In this bonding operation final entanglement of the microfibers occurs, with formation of the cleaning layer fixed to the supporting layer, at said longitudinal bonding lines, preferably spaced apart from one another so that they are alternated. Along said lines the fibres are more compressed due to the water jet and therefore, when the lines are spaced apart, the microfiber surface has embossments or micro-embossments (illustrated in  FIG. 2  without reference numeral) alternated with said lines that represent grooves. In this step (b) very fine water jets are used with pressures up to 80/400 bar produced by hydraulic injectors (or spray nozzles) distributed in various ways, mutually adjacent and in contact with one another, or suitable spaced apart so as to create different paths. In practice the high energy of the water jets is transferred to the fibers, bonding them. Subsequently, the bonded material obtained is air-dried and wound on a reel or can be coated with resins, preferably acrylic resins, on the macrofiber side to obtain fabrics with one side similar to chamois leather, which are very effective for cleaning glass. 
         [0022]    Macrofibers can be used as fibers for the lower layer  2 , with the same or different density, made of viscose, polypropylene, nylon, rayon, cellulose, mixed viscose and polyester, cotton and the like, or alternatively, of regenerated or recycled materials, for example 100% recycled PET, or of a mixture of 70% regenerated cellulose fibres and 30% recycled PET fibres. A preferred composition of macrofibers contains 70% of viscose and 30% of polyester, or a 50/50 mixture of viscose/polyester. 
         [0023]    The unit weight of the macrofiber layer  2  can range from 50 g/m 2  to 300 g/m 2 , preferably greater than 100 g/m 2 , for example comprised between 180 and 280 g/m 2 , more preferably comprised between 200 and 250 g/m 2 . It is understood that macrofibers with greater unit weight, such as 400 g/m 2 , could also be used without departing from the spirit of the present invention. 
         [0024]    The fibers of the microfiber layer  1  are, as stated, preferably splittable fibers formed, for example, by polyester/polyamide, having deniers of around 1-2 Dtex before being split and capable of generating microfilaments (multi filaments) having deniers below 1 Dtex. This microfiber can have a unit weight similar to that of the macrofiber layer  2  or lower, preferably lower, for example comprised between 40-70 g/m 2 . 
         [0025]    A preferred embodiment of the textile material obtained by the present process provides a microfiber layer  1  with unit weight comprised between 60-70 g/m 2  and a non-woven fabric macrofiber layer  2  with unit weight comprised between 200 and 250 g/m 2 . 
         [0026]    The total thickness of the textile material and/or of its single layers is not binding for the purposes of the present invention. For example, to produce mops, a non-woven fabric with total thickness from 1 mm to 3 mm and with a thickness of the microfiber layer from 0.3 mm to 1 mm can be used. 
         [0027]    Numerous advantages can be achieved due to the present process. In fact, it is possible to use a microfiber with low unit weight as the mechanical resistance of the material is given by the less prestigious macrofiber layer  2 , thus using a smaller quantity of microfiber with consequent reduction of costs. Moreover, an economic saving is obtained with respect both to the thermal bonding process and to a conventional spunlace process, as due to the initial bonding performed with mechanical needle-punching, lower water pressures can be used. 
         [0028]    Moreover, the presence of embossments on the microfiber surface provides an improved cleaning power with respect to conventional microfiber cloths as it is even rougher and more abrasive with a “spatula” effect that allows more effective removal of dirt and grease with respect to conventional microfiber cloths. 
         [0029]    The materials obtainable from the present process can be used as non-woven fabric to produce cleaning devices and/or medical textiles, for example to produce mops, conventional floor cloths, cloths for glass and for any other type of surface, sponges, dry and/or moistened cloths for cleaning, or cloths for use in the medical sector where fabrics with different densities and compositions are required, and in all those applications in which the efficacy of microfiber is required. 
         [0030]    In practice the non-woven fabric material  100  formed by a microfiber cleaning layer  1  and a macrofiber supporting layer  2 , wherein said layers are bonded by needle-punching and subsequent treatment of the microfiber surface with high pressure water jets, and provided with the technical characteristics described above, such as thickness, total unit weight or weight of the single layer, materials, the presence of embossments, etc., is particularly suitable for producing cleaning devices and/or medical textiles, said material being preferably obtainable from the process as described above. 
         [0031]    Numerous modifications and variations of detail within the range of those skilled in the art could be made to the present embodiment of the invention, all however falling within the scope of the invention expressed by the appended claims.