Patent Publication Number: US-2019177885-A1

Title: Process and an apparatus for producing coarse count and tridimensional crimped multifilament bcf yarns, yarns thus obtained and applications thereof

Description:
TECHNICAL FIELD 
     The present invention relates to the field of yarns for non-textile applications and, specifically, to the production and use of multifilament BCF (Bulk Continuous Filament) yarns. 
     More specifically, the present invention relates to the production and use of coarse count and tridimensional crimped multifilament BCF yarns having controlled chemical-physical and mechanical properties. 
     More specifically, the present invention relates to a manufacturing process, and the relevant equipment for the production of coarse count and tridimensional crimped multifilament BCF yarns, starting from synthetic materials, in particular polyamide 6.6. 
     Further, the present invention relates to yarns obtained by the aforesaid process or the aforesaid apparatus both in a wound form and in a cut form. 
     The present invention finds preferred and beneficial application in non-textile applications, and particularly for the manufacture of carpets for large surfaces. 
     State of the Art 
     BCF (Bulk Continuous Filament) multifilament yarns, such as are known in the technical field of reference and described, for example, within the U.S. Pat. No. 3,401,516, are continuous yarns composed of many filaments that have been imparted with curling and rippling effects that are typical of natural fibers. 
     BCF yarns are usually produced by production processes which include spinning by means of molten polymer extrusion, the formation of multiple filaments, drawing and mechanical crimping by air treatment of the multifilament yarns in order to impart to them the aforesaid curling and rippling effects; in general, such traditional production processes allow curling and rippling effects to be obtained only on two axes, namely to achieve two-dimensional crimping of the yarns, which prevents optimal bonding between the baves of the yarns and therefore requires an additional operation known as “interlacing” by interspaced node points in order to hold together the baves of the yarns. 
     An example of a traditional process for the production of BCF yarns is described in the U.S. Pat. No. 6,776,943 B2, which envisages starting with polyamide 6 and performing the step of mechanical crimping by a jet of low speed and high temperature air; the BCF yarns produced with this process have an alpha-crystalline content of about 45% and a yarn hank shrinkage of less than about 12.7 mm (0.50 inches); the disadvantages of this solution consist mainly in the fact that the chemical and physical properties cannot be modified insofar as the conditions that determine them cannot be modified and in the fact that the mechanical crimping forces the yard to take a predefined path whereby the shapes obtained in the process (angles and arcs) cannot be varied. 
     In addition, the multifilament BCF yarns available generally have uncontrolled chemical-physical (specifically amorphicity/crystallinity degree, basicity and dyeing affinity) and mechanical (specifically elasticity and tenacity) properties. 
     The bidimensional crimping along with the uncontrolled chemical-physical and mechanical properties of the yarns is the root cause of poor agglomeration problems that occur during the carding of the same, resulting in unevenness of the carded fabric obtained. 
     Finally, the multifilament BCF yarns currently available have a single filament count of under 40 denier, i.e. 44.44 decitex, and a total count (sum of the counts of the individual filaments) of less than 2,000 decitex. 
     To achieve workable multifilament BCF yarns in the manufacture of non-textile fabrics it is necessary to reach total counts equal to or greater than 4,000 dtex and this, up until now, has been achieved by means of twisting and cabling operations using multiple yarns; however, these fitting operations, in addition to making the tooling cycle longer and more complicated, also lead to stressing of the yarns and a consequent reduction in the quality thereof. 
     The need to produce multifilament BCF yarns with tridimensional crimping therefore remains unsatisfied. 
     Further, the need to control the chemical-physical and mechanical properties of the BCF yarns produced remains unsatisfied. 
     Finally, the need to produce multifilament BCF yarns with total counts equal to or greater than 4,000 dtex, preferably up to 8,000 dtex, and a count for single-filament up to more than ten times greater than those currently available remains unsatisfied. 
     In summary, until now, to the knowledge of the Applicant, there are no known solutions that make it possible to avoid the yarn interlacing operations, which overcome the problems of agglomeration that occur during the carding of the same yarns and make it possible to arrange the coarse count multifilament BCF yarns, namely at total counts equal to or greater than 4,000 dtex, preferably up to 8,000 dtex, in order to manufacture technical fabrics without resorting to non-textile twisting and cabling operations using multiple yarns. 
     Therefore, the Applicant, with the process and the apparatus according to the present invention intends to remedy this deficiency. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the present invention is to overcome the drawbacks of the known art relating to the production of multifilament BCF yarns. 
     More precisely, the object of the present invention is to overcome the drawbacks of the known art relating to the production of multifilament BCF yarns in terms of optimal bonding between the baves of the yarns, poor agglomeration and an insufficient count for the manufacture of non-textile technical fabrics. 
     In particular, the present invention intends to solve the problem of avoiding the yarn interlacing operations, to overcome the single bidimensional crimping and to control the physical-chemical and mechanical properties of the yarns themselves, in order to improve the homogeneity of the BCF yarns obtained and of the subsequent products. 
     Still in particular, the present invention intends to solve the problem of imparting both high counts for single filament and high total counts of the multifilament BCF yarns for use in the manufacture of non-textile technical fabrics. 
     These objects are achieved with the process and with the apparatus according to the present invention, advantageously and especially by virtue of cooling in water and of a subsequent non-mechanical treatment with a mixture of air and steam, that make it possible to produce coarse count and tridimensional crimped multifilament BCF yarns having controlled chemical-physical and mechanical properties, in order to improve the agglomeration and homogeneity thereof, to increase the volume thereof and to achieve optimal cohesion between the baves of BCF yarns. 
     Specifically, the aforesaid objects and other objects and advantages of the invention, as will appear from the following description, are achieved with a process for the production of coarse count and tridimensional crimped multifilament BCF yarns according to claim  1 . 
     Further, the aforesaid objects and other objects and advantages of the invention are achieved with an apparatus for the production of coarse count and tridimensional crimped multifilament BCF yarns according to claim  6 . 
     Further, the aforesaid objects and other objects and advantages of the invention are achieved with coarse count and tridimensional crimped multifilament BCF yarns according to claim  9 . 
     Further, the aforesaid and other objects and advantages of the invention are achieved with a carpet manufactured with coarse count and tridimensional crimped multifilament BCF yarns according to claim  12 . 
     Preferred embodiments and variants of the apparatus for the production of coarse count and tridimensional crimped multifilament BCF yarns, as well as yarns thus obtained and the applications thereof according to the present invention are the subject of the dependent claims; in particular, in preferred and advantageous embodiments, the multifilament BCF yarns according to the present invention may be in a wound form or in a cut form. 
     Another aspect of the present invention relates to the use of multifilament BCF yarns in non-textile applications, and particularly for the manufacture of carpets for large surfaces. 
     It is understood that all of the attached claims form an integral part of the present description, and that each of the technical features claimed therein is possibly independent and autonomously usable with respect to other aspects of the invention. 
     It will be immediately evident that innumerable modifications may be made to that disclosed (relating for example to shape, sizes, arrangements and parts with equivalent functionality) without departing from the scope of the invention as claimed within the attached claims. 
     Advantageously, the technical solution according to the present invention makes it possible to:
         increase the count for single filament and the total count of the multifilament BCF yarns, also improving the quality thereof;   achieve controlled chemical-physical (specifically amorphicity/crystallinity degree, basicity and dyeing affinity) and mechanical (specifically elasticity and toughness) properties of the BCF yarns produced;   achieve optimum bonding between the baves of the yarns, thus avoiding interlacing operations;   improve the agglomeration of the yarns, resulting in better product homogeneity;   simplify the production process, consequently reducing the related costs and consumption of materials; and   use the BCF yarns produced in the field of non-textile technical fabrics, in particular, for the manufacture of carpets for large surfaces.       

     Further advantageous features will become more apparent from the following description of preferred but non-exclusive embodiments, provided purely by way of non-limiting examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described below by means of certain preferred embodiments, given by way of non-limiting examples, with reference to the accompanying drawings. These drawings illustrate different aspects and examples of the present invention and, where appropriate, structures, components, materials and/or similar elements in different figures are indicated by similar reference numbers. 
         FIG. 1  is a flowchart showing the steps of the process for the production of coarse count and tridimensional crimped multifilament BCF yarns according to the present invention; 
         FIG. 2  is a schematic representation for the production of coarse count and tridimensional crimped multifilament BCF yarns according to the present invention; 
         FIG. 3A  is a side view schematic representation illustrating the tridimensional crimping of the multifilament BCF yarns according to the present invention; 
         FIG. 3B  is a top view schematic representation illustrating the tridimensional crimping of the multifilament BCF yarns according to the present invention; 
         FIG. 3C  is a tridimensional schematic representation illustrating the tridimensional crimping of the multifilament BCF yarns according to the present invention; 
         FIG. 4A  is a side view schematic representation illustrating the bidimensional crimping of traditional multifilament BCF yarns; 
         FIG. 4B  is a top view schematic representation illustrating the bidimensional crimping of traditional multifilament BCF yarns; 
         FIG. 4C  is a tridimensional schematic representation illustrating the bidimensional crimping of traditional multifilament BCF yarns; 
         FIG. 5A  shows a cross-section of a carpet produced using multifilament BCF yarns according to the present invention; 
         FIG. 5B  shows a plan view of a carpet produced using multifilament BCF yarns according to the present invention; 
         FIG. 6A  shows a cross-section of a carpet produced using traditional BCF yarns; and 
         FIG. 6B  shows a plan view of a carpet produced using tradition BCF yarns. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the invention is susceptible to various modifications and alternative constructions, certain preferred embodiments are shown in the drawings and will be described in detail below. 
     It should be understood, however, that there is no intention to limit the invention to the specific illustrated embodiments, but, on the contrary, the invention is intended to cover all modifications, alternative constructions, and equivalents that fall within the scope of the invention as defined within the claims. 
     In the following description, therefore, the use of “for example”, “etc.”, “or/or else” means non-exclusive alternatives without limitation, unless otherwise indicated; the use of “also” means “including, but not limited to” unless otherwise indicated; the use of “includes/comprises” means “includes/comprises, but not limited to” unless otherwise indicated. 
     The process and the apparatus for the production of coarse count and tridimensional crimped multifilament BCF yarns of the present invention, as well as the yarns obtained by this process and/or such apparatus and the applications thereof, are based on the innovative concept of subjecting the extruded polyamide 6.6 filaments to cooling in water and the multifilament BCF yarns obtained to subsequent non-mechanical treatment with a mixture of air and steam, in such a way that the multifilament BCF yarns have controlled chemical-physical and mechanical properties and have a coarse count (both total and for each single filament) as well as tridimensional crimping. 
     The Inventors have in fact surprisingly and unexpectedly discovered the possibility to achieve a coarse count (both total and for each single filament) by virtue of the cooling in water of extruded polyamide 6.6 filaments and also the tridimensional crimping of the multifilament BCF yarns obtained by virtue of the subsequent non-mechanical treatment with a mixture of air and steam of the latter. 
     An important feature of said process and apparatus resides in the fact that it is possible to control the chemical-physical (specifically amorphicity/crystallinity degree, basicity and dyeing affinity) and mechanical (specifically elasticity and toughness) properties of the multifilament BCF yarns. 
     In the present description, the term “filament” or “bave” is meant to indicate the single filament or single bave which, together with a variable number, between 8 and 600, of other filaments or other baves, forms the multifilament BCF yarn; it should be noted that in the present description, the terms “filament” and “bave” are used interchangeably, as synonyms; it should be noted, moreover, that the count of the single filament or single bave, expressed in decitex (d/tex), multiplied by the number of filaments or baves provides the total count, again expressed in decitex (d/tex) of the multifilament BCF thread; each single filament or each single bave can also be expressed, in the literature of the field, in dpf (denier per filament), the conversion between decitex and dpf being known. 
     In the present description, the term “BCF (Bulk Continuous Filament) yarns” is meant to indicate threads continuously obtained during the spinning step and, thus, differently from yarn threads obtained by means of the process of the spinning of natural or artificial fibers of variable length. 
     In the present description, the term “multifilament” is meant to indicate a yarn comprising a defined plurality, preferably variable from 8 to 600, of filaments and having a defined dimension expressed in decitex, preferably variable from 13 to 420 decitex. 
     In the present description, the term “polyamide 6.6” is meant to indicate the material commonly known by the generic name nylon 6.6 having the following chemical formula: 
     
       
         
         
             
             
         
       
     
     Nylon 6.6 differs from nylon 6 having the following chemical formula: 
     
       
         
         
             
             
         
       
     
     In the present description, the term “total count” is meant to indicate the sum of the counts of the single filaments that make up the yarn expressed in decitex or denier. 
     In the present description, the term “total coarse count” is meant to indicate a total count of not less than 4,000 decitex. 
     In the present description, the term “count for single filament” is meant to indicate the unitary count, expressed in decitex or denier of the single bave or single filament. 
     In the present description, the term “coarse count for single filament” is meant to indicate a count for single filament of not less than 40 decitex and up to 600 decitex. 
     In the present description, the term “amorphicity/crystallinity degree” is meant to indicate the ratio within the filament, and specifically of all of the filament, between the amorphous and crystalline areas; it should be noted that the determination of the amorphicity/crystallinity degree is performed using x-ray diffraction. 
     In the present description, the term “basicity” is intended to indicate the prevalence of basic areas in relation to the acidic areas within the filament; it should be noted that the identification of the basic areas takes place by means of birefringence analysis or else density measurements or else IR spectroscopy; in particular, in this description, the “basicity” is linked to the presence of terminal NH 2  amine groups and, specifically, the basicity increases as the terminal NH 2  amine groups increase (normally the concentration of NH 2  in standard viscosity polyamide 6.6 is around 46 meq/kg, milliequivalents per kg). 
     In the present description, the term “dyeing affinity” is meant to indicate the ability of the filament to retain the coloring substances within the central core thereof. 
     In the present description, the term “elasticity” is meant to indicate the ability of the filament to deform under the action of external forces applied thereto and to regain the initial shape thereof when the applied external forces cease. 
     In the present description, the term “tenacity” is meant to indicate the ability of the filament to absorb an amount of energy per unit of volume without breaking; in order to measure the “tenacity” the splitting strength (cN) can be used in relation to the initial filament count (tex or decitex). 
     In the present description, the term “agglomeration” is meant to indicate the ability to bond between individual filaments or cut portions of BCF yarns in order to achieve a non-woven fabric, commonly called “web”; it should be noted that the ability to bond between the filaments takes place when the filaments themselves remain naturally linked together, without the need for further tooling or the use of additives. 
     In the present description, the term “cohesion” is meant to indicate the predisposition of the BCF yarn filaments or cut portions to interlace between them evenly and without the aid of further tooling or the use of additives. 
     In the present description, the term “homogeneity” is meant to indicate the regularity of weight and thickness due to the bonding. 
     In the present description, the term “crimping” is meant to indicate the process in order to impart to the filaments or cut portions of BCF yarns the nonlinear wrinkling curves that are exemplary of natural fibers. 
     In the present description, the term “wrinkling” is meant to indicate the particular curling and rippling imparted to the filaments or cut portions of BCF yarns with the aforementioned crimping process. 
     In the present description, the term “non-textile technical fabrics” is meant to indicate products other than those that are textile; non-textile technical fabrics are differentiated by the requirement of having to tolerate much higher mechanical stresses, starting from 100% higher. 
     With reference to  FIG. 1 , the process for producing coarse count and tridimensional crimped multifilament BCF yarns, comprises the following steps:
         arranging polyamide 6.6 as starting material (step  100 );   drying said polyamide 6.6 with nitrogen (step  101 );   extruding said polyamide 6.6, thus obtaining filaments ( 6   a ) (step  102 );   immediately downstream of the extrusion, cooling in water the filaments  6   a  obtained in the previous step  102  at a predetermined temperature and for a predetermined time, thus obtaining coarse count multifilament BCF yarns  6   b  (step  103 );   subjecting to a non-mechanical treatment with a mixture of air and steam the coarse count multifilament BCF yarns  6   b  obtained in the previous step  103 , wherein the amounts of air and steam are in a predetermined ratio between them, thus obtaining coarse count and tridimensional crimped multifilament BCF yarns  6   c  (step  104 ).       

     Optionally, the process according to the present invention may also include the following step:
         between step  101  and step  102 , adding coloring substances.       

     According to the present invention, the optional dyeing operation is performed en masse, specifically in adding bulk coloring substances to the starting material, for example as granules or powder; preferably the coloring substances are natural and artificial pigments; more preferably, the coloring substances are a balanced mixture of natural and artificial pigments, because natural pigments are brighter and lively but tend to suffer migration in water, while the artificial pigments are less lively but do not migrate and therefore are technically superior. 
     According to step  100  of this invention, polyamide 6.6 is used as the starting material; in particular, the polyamide 6.6 used is in the form of granules or “chips,” with an average particle size in the order of 2 mm×2 mm×3 mm. 
     As mentioned above, the polyamide 6.6 used in the present invention has the chemical formula reported above and preferably has a fusion point equal to 260° C. and a specific weight equal to 1.15 g/cm 3 . 
     According to the subsequent step  101  of the present invention, the polyamide 6.6 is dried with nitrogen. 
     This operation is performed within drying towers, for an average duration of 10 hours at an average temperature of 82° C. 
     The nitrogen used is preferably 90% pure; the flow of nitrogen is made to flow with an average flow rate of 20 kg/h. 
     The dried polyamide 6.6 has a residual moisture content of less than 700 p.p.m. (parts per million), or less than 0.07% by weight of polyamide 6.6. 
     According to the subsequent step  102  of the present invention, the dried polyamide 6.6 is extruded, thus obtaining the filaments  6   a.    
     The extrusion is performed in a conventional spinneret and will therefore not be described in detail. 
     The filaments  6   a  of polyamide 6.6 obtained by means of extrusion in the previous step  102  are then, immediately downstream of the extrusion, cooled in water at a temperature and for a predetermined period of time, according to step  103  of the present invention. 
     Preferably, the cooling in water takes place in a tank placed at a distance equal to or less than 5 mm from the exit from an extruder, wherein the temperature of the cooling water ranges between 17° C. and 50° C., preferably it is equal to 35° C., and wherein the cooling time ranges between 0.5 seconds and 0.8 seconds, preferably it is equal to 0.6 seconds. 
     Further, the cooling in water takes place at a speed ranging from 5,800 mm/second and 8,300 mm/second, preferably equal to 6,000 mm/second. 
     As anticipated, the Inventors have surprisingly and unexpectedly discovered that the cooling in water of extruded polyamide 6.6 filaments  6   a  under the conditions indicated above, and specifically at a high speed, makes it possible to achieve coarse count filaments for each single filament and corresponding total coarse count multifilament BCF yarns  6   b.    
     In particular, the filaments obtained by the process according to the invention include a count for each single filament of up to 420 decitex, and the corresponding coarse count multifilament BCF yarns  6   b  have a total count equal to or greater than 4,000 decitex, preferably up to 8,000 dtex. 
     By way of comparison it is reported that the filaments obtained by traditional processes have a count for each single filament up to 44 decitex, and the corresponding multifilament BCF yarns have a total count up to 2,000 decitex. 
     Further, the cooling in water according to step  103  of the present invention makes it possible to control the chemical-physical and mechanical properties of the multifilament BCF yarns. 
     Specifically, the process according to the present invention makes it possible to control the amorphicity/crystallinity degree, the basicity and dyeing affinity as chemical-physical properties, and the elasticity and tenacity as mechanical properties. 
     The Inventors believe that controlling the speed of the cooling in water of the individual extruded filaments makes it possible to control their percentage content of amorphous zones, upon which depend the amorphicity/crystallinity degree, the basicity and the dyeing affinity; in particular, the higher the cooling speed, the more, within individual filaments, the amorphous zones prevail with respect to the crystalline zones; a filament with a higher degree of amorphicity means that few amide groups are engaged in the formation of hydrogen bridges and this, consequently, results in increased basicity and in the improved dyeing affinity of the individual filaments and of the corresponding multifilament BCF yarns. 
     The Inventors believe that also the uniformity of the cooling in water, by virtue of the increased heat transfer efficiency between the single filaments and the water itself, contributes to the improvement of the chemical-physical and mechanical properties thereof. 
     In more detail the amorphicity/crystallinity degree, as a function of the cooling/glass transition speed, is controllable through the cooling water temperature; in traditional spinning processes the crystalline composition prevails insofar as the glass translation is slower (approximately five times slower) and the molecules have time to orient themselves in the same direction, increasing the degree of crystallinity. 
     According to the Inventors, the control of the amorphicity/crystallinity levels is due to the polyamide 6.6 solidification speed. 
     As mentioned above, the basicity is a function of the amorphicity/crystallinity degree and therefore by X-ray spectrometry (birefringence), density, FTIR (infrared spectroscopy) and DSC (Differential Scanning Calorimetry) measurements, it can be stated that the multifilament BCF yarns according to the present invention are more basic than traditional BCF yarns. 
     As mentioned above, the dyeing affinity depends also upon the percentage of amorphous zones in the filaments, and therefore the multifilament BCF yarns according to the present invention have better dyeing affinity than traditional BCF yarns; it should be noted that it is the amorphous areas that receive the coloring and, therefore, the colors of the multifilament BCF yarns according to the present invention remain more vivid, natural and shiny. 
     According to the Inventors, the control of the dyeing affinity is due to the control over the creation of the amorphous zones. 
     The elasticity also depends upon the amorphous/crystalline properties of the yarn and, consequently, better elasticity corresponds to a greater presence of amorphous zones; it should be noted that the elasticity is expressed as a percentage of the original length of the sample. 
     According to the Inventors, the control over the elasticity is due to the glass transition temperature and therefore of the orientation and mobility of the molecules within the filament that enable the filament itself to be drawn in order to achieve the tenacity, but at the same time to not lose the elasticity. 
     The relationship between elasticity and tenacity is narrow and proportional; an elastic thread will not be tenacious because it has undergone little stretching, namely an extension of less than 100% of the original length, while a tenacious thread is not elastic because it has undergone significant stretching, namely an extension greater than 150% of the original length. 
     The tenacity depends upon the amount of strength that must be exercised in order to elongate the filament; according to the Inventors, the control over the tenacity is mainly due to the cooling in water conditions according to the step  103 , as mentioned above, and to the drawing conditions. 
     The coarse count of the yarns makes it possible to avoid interlacing operations and those of twisting and cabling of multiple yarns, in such a way as to achieve higher-quality products and also to simplify and speed up the production process. 
     The coarse count multifilament BCF yarns obtained in the previous step  103  are, subsequently, subjected to non-mechanical treatment with a mixture of air and steam, wherein the amounts of air and steam are in a predetermined ratio between them, according to step  104  of the present invention. 
     It is to be pointed out here that “non-mechanical treatment” is meant to indicate a treatment that, unlike traditional mechanical treatments, is not accomplished by contact with the crimping device; the non-mechanical treatment according to the present invention instead envisages the passage of the multifilament BCF yarns within a device containing a mixture of air and steam, without the exercising of any mechanical action, and therefore contact, of the device upon the multifilament BCF yarns; in summary, the term “non-mechanical treatment” is used, in this description, as a synonym for “treatment without contact with the crimping device”. 
     As anticipated, the Inventors have surprisingly and unexpectedly discovered that the non-mechanical treatment with a mixture of air and steam of coarse count polyamide 6.6 multifilament BCF yarns under the conditions indicated above makes it possible to obtain tridimensional crimped multifilament BCF yarns. 
     Preferably, the amounts of air and steam are in a ratio ranging between 50:50 by volume and 70:30 by volume, preferably are in the ratio 60:40 by volume. 
     With reference to  FIGS. 3A-3C and 4A-4C , respectively visible are the tridimensional crimping of the multifilament BCF yarns according to the present invention in comparison to the bidimensional crimping of traditional BCF yarns; in particular,  FIGS. 3A and 4A  are side views,  FIGS. 3B and 4B  are views from above and  FIGS. 3C and 4C  are tridimensional views. 
     As can be seen, the multifilament BCF yarns according to the present invention, by virtue of the tridimensional crimping, have profiles that are curvilinear and variously oriented in space; conversely, the traditional multifilament BCF yarns, due to the bidimensional crimping, have cracked profiles that are oriented along only two directions in space. 
     The tridimensional crimping of the yarns makes it possible to obtain optimal bonding between the baves of the yarns and to improve the agglomeration thereof, in order to obtain products of better quality. 
     With reference to  FIG. 2 , the apparatus  1  for the production of coarse count and tridimensional crimped multifilament BCF yarns, that makes up an independent and autonomously usable aspect in relation to the other aspects of the invention, comprises:
         a feed hopper  2  for polyamide 6.6;   a drying room  3  for drying said polyamide 6.6 with nitrogen;   an extruder  4  for extruding said polyamide 6.6, thus obtaining filaments  6   a;      immediately downstream of the extruder  4 , a tank  5  for cooling in water said filaments  6   a , thus obtaining coarse count multifilament BCF yarns  6   b;      a device  7  comprising a compartment  8  and a tube  9  placed inside said compartment  8 , said compartment  8  being suitable to house a mixture of air and steam and said tube  9  being suitable to host said coarse count multifilament BCF yarns  6   b  previously obtained, thus obtaining coarse count and tridimensional crimped multifilament BCF yarns  6   c.          

     The feed hopper  2 , the drying chamber  3  and the extruder  4  are of a conventional type and, therefore, will not be described in detail. 
     The extruder  4 , however, may be appropriately modified in such a way that the filaments assume different sections such as, for example, in the shape of a “delta”, trilobal, mixed polygonal and/or curvilinear, and so on, according to the specific requirement. 
     The tank  5  for cooling the filaments  6   a  in water, placed immediately downstream of the extruder  4  envisages that the path of the filaments  6   a  be modifiable both as to the length thereof and the depth and is preferably manufactured from stainless steel; preferably, said tank  5  contains osmotic water, preferably in an amount of 500 liters; it is evident that the amount of water can be modified according to specific requirements. 
     In more detail and according to a preferred embodiment of the invention (not shown), in order to modify the path of the filaments  6   a  in length and depth, within said tank  5  plasma coated stainless steel rollers are positioned, in order to promote the slipping of the filaments  6   a ; said rollers, preferably in a number equal to four, are mounted on a single plunging arm which, depending upon the assigned inclination which is adjustable by suitable means, increases or decreases the depth thereof in water, from surface free up to being in contact with the bottom of the tank, and lengthens or shortens the path of the filaments  6   a  up to +30% and, consequently, the period of time that the same remain in water; as mentioned above, the pitch of the plunging arm is assigned according to the specific requirements and is appropriately adjusted between five preset positions by as many mechanical end-of-travel stops of the same arm; the pitch can vary between 30° and 60° with respect to the direction of entry into the tank of the filaments  6   a.    
     The tank  5  for cooling the filaments  6   a  in water is preferably placed at a distance equal to or shorter than 5 mm from the exit from the extruder  4 , in order to obtain coarse count multifilament BCF yarns  6   b.    
     The device  7 , which comprises a compartment  8  and a tube  9  placed inside said compartment  8 , is of a variable size from 0.6 to 5 mm depending upon the bundle of threads to be housed, it is perforated in order to ensure controlled roughness and is preferably manufactured from stainless steel; this configuration of the device  7  makes it possible to obtain coarse count and tridimensional crimped multifilament BCF yarns  6   c.    
     The apparatus  1  may further comprise means  10  (not shown) for wrapping said coarse count and tridimensional crimped multifilament BCF yarns  6   c ; these means  10  for wrapping the yarns are known and are therefore not discussed in detail. 
     As an alternative to the aforementioned configuration, the apparatus  1  may further comprise means  20  (not shown) for cutting said coarse count and tridimensional crimped multifilament BCF yarns  6   c ; these means  20  for cutting the yarns are known and are therefore not discussed in detail. 
     The multifilament BCF yarns obtained by the process and/or through the device according to the present invention, make it possible, therefore, to attain advantageous features and properties. 
     In particular, the coarse count and tridimensional crimped multifilament BCF yarns obtained through the process disclosed above and/or with the apparatus described above, which constitute an aspect that is independent and autonomously usable with respect to other aspects of the invention, having a total count equal to or higher than 4,000 decitex, preferably up to 8,000 dtex, with each filament having a count up to 420 decitex, and having controlled chemical-physical and mechanical properties, in particular the amorphicity/crystallinity degree ranges between 70/30% and 50/50%, preferably it is equal to 60/40%, the basicity ranges between 4 French degrees and 10 French degrees, preferably it is equal to 7 French degrees, the dyeing affinity ranges between 80% and 95%, preferably it is higher than 90%, the elasticity ranges between 30% and 100%, preferably it ranges between 40% and 70%, more preferably it is equal to 60% and the tenacity ranges between 15 cNW/tex and 50 cNW/tex, preferably it is equal to 30 cNW/tex. It should be noted that the use of French degrees to measure basicity is known in the reference field of the invention. 
     The coarse count and tridimensional crimped multifilament BCF yarns according to the present invention may be in a wound form or in a cut form. 
     As mentioned above, the coarse count and tridimensional crimped multifilament BCF yarns according to the present invention are particularly suitable for non-textile applications; preferably and advantageously, the coarse count and tridimensional crimped multifilament BCF yarns according to the present invention are employed in the manufacture of carpets for large surfaces. 
     It therefore, finally, constitutes an aspect that is independent and autonomously usable with respect to the other aspects of the invention  50 , manufactured with coarse count and tridimensional crimped multifilament BCF yarns  6   c.    
     With reference to  FIGS. 5A and 5B , it is observed that the carpet  50  according to the present invention is produced with multifilament BCF yarns according to the present invention, which does not need to be further treated with twisting or other assembly processes; by way of comparison, in  FIGS. 6A and 6B , a carpet  50 ′ produced with traditional BCF yarns is visible; in particular,  FIGS. 5A and 6A  are cross-sections and  FIGS. 5B and 6B  are plan views. 
     As can be seen, the carpet  50  according to the present invention, by virtue of the use of coarse count and tridimensional crimped multifilament BCF yarns  6   c , has a flat structure; conversely, the carpet  50 ′ produced using traditional coarse count and bidimensional crimped multifilament BCF yarns, has a twisted structure. 
     The carpet  50  according to the present invention is manufactured using wrapped multifilament BCF yarns. 
     The carpet  50  according to the present invention has advantages such as the absence of unsightly “pills”, due to the fact that the thread used is not twisted, of durable color, has stain-resistant properties and is resistant to wear and abrasion; these properties are demonstrated by the following tests. 
     As can be deduced from the above, the innovative technical solution described here has the following advantageous features:
         the increase in the count for single filament and of the total count of the multifilament BCF yarns, also improving the quality thereof;   the achieving of controlled chemical-physical (specifically amorphicity/crystallinity degree, basicity and dyeing affinity) and mechanical (specifically elasticity and toughness) properties of the BCF yarns produced;   the achieving of optimum bonding between the baves of the yarns, thus avoiding interlacing operations;   the improving of the agglomeration of the yarns, resulting in better product homogeneity;   the simplification of the production process and consequent reduction of the associated costs and consumption of materials; and   the possibility of using the BCF yarns produced in the field of non-textile technical fabrics, in particular, for the manufacture of carpets for large surfaces.       

     From the description above it is evident, therefore, how the technical solution according to the present invention, in the different aspects thereof, would achieve the objects proposed. 
     It is equally clear, to a technician in the field, that it is possible to make changes and further variants to the solution described with reference to the attached figures, without going beyond the teaching of the invention and the scope of protection as defined by the attached claims.