Abstract:
Yarns and fabrics are described that have simultaneously dramatic flameproof, heat resistant, and insulating properties. In addition the processes are described for their preparation and their use for the manufacturing of flameproof, heat resistant, and insulating products.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to yarns and fabrics that present simultaneously high flameproof, heat resistant, and insulating characteristics, to their manufacturing process, and to their use for the manufacturing of flameproof, heat resistant, and insulating products.  
         STATE OF THE ART  
         [0002]    As known in various activities, and in particular those relating to safety, it is essential to have products provided with fireproof properties, that allow the user to operate in environments having extremely high temperatures and in the presence fires (as for example in fire-fighting operations).  
           [0003]    Excluding fabrics that contain asbestos, for the well known toxicity of this material, for the manufacturing of fabrics suitable to the above mentioned purposes the meta-aramidic fibres, as for example NOMEX® (that give the fabric the desired fireproof property) and the aramidic and/or para-aramidic ones, like KEVLAR® (that give them resistance to cuts) have been suggested.  
           [0004]    The fabrics manufactured with the above-mentioned fibres, even with their various advantages, nevertheless also present various disadvantages that make their use uncomfortable; in particular, the products manufactured with these fabrics have a significant permeability to heat (and thus, even if they are fireproof, do not allow the operator to be exposed for a long time to the heat source) and, in contact with flames, easily tend to melt or carbonize, and then to disintegrate. Moreover, these materials are difficult to be processed when they have to be manufactured (as, for example, in the manufacturing of fireproof garments).  
           [0005]    It is therefore advisable to develop new materials that allow to overcome the above mentioned disadvantages.  
         ABSTRACT OF THE INVENTION  
         [0006]    The present invention relates to yarns and fabrics comprising pre-anodized acrylic fibres, possibly mixed to aramidic, meta-aramidic, and para-aramidic fibres in the suitable percentages.  
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0007]    The present invention allows to overcome the above-mentioned problems, thanks to yarns and fabrics comprising the fibres as defined above.  
         [0008]    According to the present invention, with pre-anodized acrylic fibres we mean the fibres having this name normally used in the textile field, as for example those manufactured by Ashai Chemicals (LASTAN®), Toho Rajon (PIROMEX®), SGL (PANOX®), and Zoltek (PYRON®), and their blends.  
         [0009]    Also the aramidic, meta-aramidic, and para-aramidic fibres defined according to the invention are those already normally used in the textile field (see for example those manufactured by DuPont) for the manufacturing of fireproof fabrics (see for example the already mentioned NOMEX® and KEVLAR®).  
         [0010]    The fabrics according to the present invention can be wholly composed by pre-anodized fibres, or can present a content in pre-anodized acrylic fibres between 50 and 90% (in weight calculated on the total) and a content in aramidic or meta-aramidic or para-aramidic fibres (or their blend) between 50 and 10% (in weight calculated on the total).  
         [0011]    In case of fabrics comprising one or more type of fibres as above defined, the fabrics comprising 70% of pre-anodized acrylic fibres and 30% of aramidic or meta-aramidic or para-aramidic fibres (or their blend) are particularly preferred. Compared with those comprising only pre-anodized fibres, as above described, these fabrics are easier to be processed, for example when it is necessary to manufacture fireproof garments (and, at the same time, they are able to resist flames, and have insulating properties) and moreover present a special resistance to tear and cut (for example when KEVLAR® is used).  
         [0012]    The yarns and fabrics according to the present invention can be prepared, for example, acording to the process related here following and subject too to this patent application.  
         [0013]    In the process according to the invention the fibres, in flocks, are spun obtaining both single and twisted yarns, having a metric number (that is metres, in thousands, per 1 Kg) between 10 and 60.  
         [0014]    The yarns are dried by heating them on hot rolls (calendering).  
         [0015]    The yarns so obtained can then be used in the manufacturing operations according to the normal weaving techniques of fabrics having any type of weave, for example from plain weave to satin, in which the yarn can be both woven and warped.  
         [0016]    For their weaving both traditional shuttle looms and circular or straight knitting machines can be used, preferably adopting the suitable measures to eliminate dust and fibre remains produced during the weaving.  
         [0017]    The fabrics so obtained then undergo the normal scouring with water and/or solvents.  
         [0018]    Given the smoothness and versatility of the fabric obtained with the fibres processed as mentioned above, the fabrics according to the present invention find a very wide use, for example in the manufacturing of protective clothing for fire-fighting operations, and military, industrial, sports use, etc. Moreover, they can be used in the manufacturing of structures useful for the protection of materials and plants from fire, or the flameproof textile upholstery and accessories for furnishing public areas like cinemas, theatres, discotheques, seats, etc.  
         [0019]    In particular, the fabrics comprising only pre-anodized fibres have an exceptional heat resistance, that make them particularly suited to the manufacture of insulating elements (for example panels for fire doors, carters for protecting engines or machine parts, insulating elements for boots and similar equipment, etc.). Among these fabrics the felt ones are specially preferred.  
         [0020]    Among these fabrics the felt ones are specially preferred. Usually this type of fabric has a low resistance, and therefore its use is limited; this is specially true in the fire protection applications, because any tear in the fabric would compromise its function.  
         [0021]    The felt according to the present invention is prepared, for example, according to the process hereinafter described which is also a subject of the present application.  
         [0022]    The pre-anodized fibres, in flocks, are turned into veils through the carding process; these veils are then needle felted so as to obtain the desired uniformity and solidity in the finished product.  
         [0023]    The product&#39;s solidity is a function of the number of veils, the number of needles per square metres used, and the number of beatings carried out in the needle felting process (the higher the number of veils, needles, and beatings, the more solid ans resistant the product will be).  
         [0024]    The felts having an areal mass higher than 100 g/m 2  are specially preferred.  
         [0025]    Preferred are felts obtained with a carding process in which at least 6 to 11 veils are created (preferably from 7 to 9 veils) per finished product; and a needle felting process in which at least 5.000 to 10.000 needles per m 2  are used. (preferably from 7.000 to 9.000 needles per m 2 ) and at least from 400 to 800 beatings per minute (preferably from 600 to 800 beatings per minute).  
         [0026]    Once this process is finished, finished felts having various thickness can be needle felted together, with the same number of needles and beatings previously specified; this so as to obtain new finished felts having a total number of veils, needles used, and beatings that are the sum of the veils, needles, and beatings of the original felts. This further improves the toughness and resistance of the finished product.  
         [0027]    If preferred, to further improve the product&#39;s mechanical properties the felt, after being needle felted, can be quilted with a yarn, in more or less large stitches, containing 100% of pre-anodized acrylic fibres, or these pre-anodized acrylic fibres in a blend with aramidic, or metal-aramidic, or para-aramidic fibres; or with a yarn comprising 100% aramidic, or metal-aramidic, or para-aramidic fibres; or again, during the needle felting process a net made in a mechanically resistant material (for example a Kevlar® net) that will make up a weave for the same felt can be added inside the felt.  
         [0028]    According to a further aspect of the invention, the net can be applied on one of the felt surfaces through the usual lamination or sizing techniques.  
         [0029]    The above-mentioned processes, that are an integral part of the invention, are targeted, and allow to obtain a resistance and a toughness currently not available in the state of the art.  
         [0030]    The felts manufactured according to the invention, comprising 100% in pre-anodized acrylic fibres like PANOX® and LASTAN®, underwent some resistance tests that gave the following results: Tension resistance, according to the UNI EN ISO 29073/93 part 3a regulation, of a felt having an areal mass equal to 108 g/mq  
                                                           Lengthwise   Average breaking force   27.4 N               Average breaking force   2.79 Kg               Breaking stretch     37%           Transversal   Average breaking force   20.5 N               Average breaking force   2.09 Kg               Breaking stretch   46.5%                      
 
         [0031]    Tension resistance, according to the UNI EN ISO 29073/93 part 3a regulation, of a felt having an areal mass equal to 206 g/mq  
                                                           Lengthwise   Average breaking force   44.6 N               Average breaking force   4.55 Kg               Breaking stretch     50%           Transversal   Average breaking force   56.6 N               Average breaking force   5.77 Kg               Breaking stretch   31.5%                      
 
         [0032]    Moreover, oxy-hydrogen flame resistance tests have been carried out, to verify the drilling times of that same flame on a felt having an areal mass of 108 g/m 2  (100% pre-anodized acrylic fibres of the PANOX® tipe), with an average thickness of 1.62 mm, at a distance of 15 cm from the nozzle of the oxyacetylene burner and a 800° C. temperature.  
         [0033]    The drilling time has been higher than 3 minutes, and the temperature at the opposite side, at 3 cm from the felt, before the drilling, never exceeded 50° C.  
         [0034]    This behaviour makes the use of felts manufactured with this technique available as stuffing both for furniture and clothing use; up to now this was not possible with the said materials, due to their low resistance.  
         [0035]    If necessary, the fabric according to the present invention can be laminated, sized, spread, and quilted with any other type of fabric to give the garment the desired characteristics.