Abstract:
In this method, a fibrous material is embedded between the surfaces of a membrane and a dissimilar coloring material as the mating surfaces of the membrane and the coloring material are cured or cosolidify. This results in an encapsulation bond where fibers embedded in and originating from within the membrane are also embedded in and terminating within the adjacent coloring material. This method also results in delamination-resistant colored laminates comprising dissimilar layers and having a permanent and durable bond between the various layers of the composite.

Description:
[0001]    This application is a continuation of application No. 09/677,713 which is scheduled to issue as U.S. Pat. No. 6,497,833 on Dec. 24, 2002, which in turn is a continuation of Provisional Patent Application No. 60/156,723 filed on Sep. 30, 1999 which is incorporated herein by reference and attachment. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is in the field of colored laminated thermoplastic and thermoset sheet materials. In particular it addresses a method for enhancing the resistance to delamination of such sheet materials 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0003]    [0003]FIG. 1 is a side view of an apparatus for making a two-thermoset-layers delamination resistant colored membrane.  
         [0004]    [0004]FIG. 2 is a side view of an apparatus for making a two-thermoplastic layers delamination resistant colored membrane.  
         [0005]    [0005]FIG. 3 is a side view of an apparatus for making a thermoset bottom layer and a thermoplastic top layer delamination resistant colored membrane.  
         [0006]    [0006]FIG. 4 is a side view of an apparatus for making a thermoplastic bottom layer and a thermoset top layer delamination resistant colored membrane.  
         [0007]    [0007]FIG. 5 is a cross-sectional view of uncured/unsolidified membrane after laying fibrous web on its surface.  
         [0008]    [0008]FIG. 6 is a cross-sectional view of a two-layer delamination-resistant colored membrane.  
         [0009]    [0009]FIG. 7 is a cross-sectional view of a three-layer delamination-resistant colored membrane.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    FIG. ( 1 ) shows an apparatus  52  for making a two-thermoset-layer delamination-resistant colored membrane composite. As shown therein, an uncured thermoset membrane  14  is extruded, in a sheet form, from membrane-forming die  15 . The membrane is formed by mixing of its first reactive component  1 , contained in tank  45 , with its second reactive component  2 , contained in tank  46 . For coloring, reinforcement, cellular structure (foam) development or for other purposes, liquid additives  4 , contained in tank  47 , and/or solid additives  3  may be added to the thermoset membrane-forming mixture, in tank  48 . Typically, mixture  6  is homogenized, for example by mixing stirrer  5  or other means. After mixing all the components of membrane  14 , the mixture is allowed to flow into membrane- forming die  15  by opening valve  7 . In some applications a pump may also be used in order to generate the required pressure and desired volume flow rate. As uncured thermoset membrane  14  is extruded from die  15 , it is laid on a non-stick release liner  8  which is unwound from a roll of non-stick release liner  33 , on conveyor belt  30 , and rewound into a roll  35  which is driven by friction drive roll  34 . Guide rolls  39 ,  42  and  36  are used to direct the release liner  8  and colored laminated composite as the process is performed from one end of apparatus  52  to its other end. Alternatively, release liner  8  may be eliminated if conveyor belt  30  is made of a non-sticking material or is coated with a non-sticking release coating. Conveyor rolls  31  and  32  provide an adjustable or constant rate of travel to belt  30 , which, in combination with the rate of flow of mixture  6 , determine the thickness of membrane  14 . The thickness of membrane  14  is an important parameter in this process since subsequent operations, for example thermoforming or injection molding a layer of molten plastic on it and subsequent or simultaneous stretching of the composite may result in significant surface deformation which may alter the exterior color or the surface characteristics of the delamination-resistant colored membrane. An example of such subsequent operations that may be performed on the colored laminated composite of the present invention is disclosed in U.S. Pat. No. 5,401,457 which is incorporated herein by reference.  
         [0011]    As uncured thermoset membrane  14  is extruded on release liner  8 , its top surface  9  is of a tacky nature. Depending on its rate of curing or solidification, its surface tack and viscosity, a first partial curing zone  16  is provided in order to allow for adequate development of surface of membrane  14  before entering the fibrous media application zone  18 . In doing so, one can have at least a portion of fibers, in fibrous web  37  or sprinkled fibers  38 , partially encapsulated within membrane  14 , as shown in FIG. 5. Such partially encapsulated fibers, when also subsequently partially encapsulated within coloring coating  20 , serve as an interfacial reinforcement that provides a bond between the two layers of colored composite  44 . Such an interfacial reinforcement profoundly enhances the resistance to delamination between the layers of the colored composite.  
         [0012]    Fibrous web  37  is fed into zone  18  from fibrous web roll  10 . In some applications, a guide roll  41  is used to direct fibrous web  37  to the desired location, height and point of contact with uncured or unsolidified surface  9  of membrane  14 .  
         [0013]    Fibrous web  37  may be made of woven, knitted , stitch-bonded or non-woven fibers and/or yarns. In its most preferred embodiment, fibrous web  37  is made of a needle punched non-woven in order to provide the most possible tensile and in-plane shear deformability, without breakage, during subsequent thermoforming or injection molding processes where the colored composite may be formed into three dimensional double curvature surfaces. The fibers of fibrous web  37  may be of a natural origin (for example cotton or other natural staple fibers) or of a man-made type, such as synthetic fibers, regenerated fibers or metallic fibers.  
         [0014]    Alternatively or in addition to fibrous web  37 , loose fibers  12 , contained in hopper  11 , may be sprinkled on the top surface  9  of uncured/unsolidified membrane  14  by using fiber sprinkler  13 . As shown in FIG. ( 1 ), sprinkled fibers  38  are deposited on membrane  14  in fibrous media application zone  18 . Similar to fibrous web  37 , sprinkled fibers  38  may be of a natural origin or of a man-made type, such as synthetic fibers, regenerated fibers or metallic fibers.  
         [0015]    In a similar manner, an uncured thermoset coloring coating  20  is formed and extruded through coloring coating application die  50  onto the surface of membrane  14  covered by fibrous web  37  and/or sprinkled fibers  38 .  
         [0016]    Coloring coating  50  is also prepared in a manner similar to that of preparing membrane  14 . A first reactive component  22  and a second reactive component  23 , of coloring coating  20 , are directed from tanks  28  and  29  into mixing tank  51 . Liquid additives  24 , which may also include coloring agents or pigments, are also directed from tank  49  into mixing tank  51 . Similarly, solid additives  25  may be added to the coloring coating mixture  26  in tank  51 . The mixture is then homogenized by rotating stirrer  27  or some other means and is allowed to flow into coloring coating application die  50  by opening valve  17  and controlling flow rate to yield the desired thickness of coloring coating  20 . As discussed above and for the same reasons stated in connection with membrane  14 , the thickness of coloring coating  20  is an important parameter and a variety of means, known in the art, including metering pumps may be used for its control.  
         [0017]    As uncured coloring coating  20  is extruded onto the surface of membrane  14 , which is covered by fibrous web  37  and/or sprinkled fibers  38 , its bottom surface  21  is of a tacky or liquid nature and thus encapsulates the remaining portions of those fibers which had been partially encapsulated within membrane  14 . The two-layer thermoset composite then proceeds through curing or cooling zone  19  where the components are fully cured/solidified and directed to a take up unit along the direction of arrow  43  as a delamination-resistant colored composite  44 .  
         [0018]    Using same or similar components and zones (as  8 ,  10 ,  11 ,  12 ,  13 ,  16 ,  18 ,  19 ,  30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38 ,  39 ,  41 ,  42 , and  43 ) shown in FIG. ( 1 ) and described above and following similar steps and thickness controls, an apparatus  63  for making a thermoplastic delamination-resistant colored composite  68  is shown in FIG. ( 2 ). As shown therein, a first molten thermoplastic membrane  53  is extruded, through molten membrane extrusion die  57 , in a similar manner and is treated in the same way as uncured thermoset membrane  14 . Hopper  61  feeds the thermoplastic material into plasticating extruder  59  which, in turn, melts it and feeds it into die  57 . Also, similarly, the top surface  55  of molten thermoplastic membrane  53  is treated and coated with fibrous web  37  and/or sprinkled fibers  38  in a manner similar to that of treating top surface  9  of membrane  14 . Also, as shown in FIG. ( 2 ), a similar thermoplastic coloring coating  54  is produced by using feeding hopper  62 , plasticating extruder  60  and molten coloring coating extrusion die  58 . The thermoplastic material contained in feeding hopper  62  may be of a pre-compounded colored nature or a blend of colored and uncolored thermoplastic materials selected to produce the desired exterior color of composite.  
         [0019]    Also, similarly, the bottom surface  56  of molten thermoplastic coloring coating  54  is treated and coated with fibrous web  37  and/or sprinkled fibers  38  in a manner similar to that of treating top surface  9  of membrane  14 .  
         [0020]    Again, using combinations of same or similar components and zones, as shown in FIGS. ( 1 ) and ( 2 ) and as described above, FIG. ( 3 ) shows a side view of an apparatus  64  for making a thermoset bottom layer and a thermoplastic top layer delamination resistant colored composite  66  and FIG. ( 4 ) shows a side view of an apparatus  65  for making a thermoplastic bottom layer and a thermoset top layer delamination resistant colored composite  67 .  
         [0021]    [0021]FIG. 5 shows an uncured or molten membrane  69  in fibrous application zone  18  with fibers  73  completely encapsulated within it, fibers  71  partially encapsulated in it and other loose fibers  72  lying completely outside of it. As shown therein, first layer  70  has a bottom surface  95  and a top uncured or molten surface  85 .  
         [0022]    [0022]FIG. 6 shows a cross-sectional view of a two-layer delamination-resistant colored composite  74  comprising bottom layer  70 , top layer  84 , joined at their interface  86 , and having fibers  71  partially encapsulated in bottom layer  70  and partially encapsulated in top layer  84 , thus providing enhanced resistance to delamination.  
         [0023]    [0023]FIG. 7 shows a cross-sectional view of a three-layer delamination resistant colored composite  75  comprising bottom layer  76 , middle layer  77 , top layer  78 , joined at their respective interfaces  87  and  88  and, as described earlier, having an enhanced resistance to delamination which is attributable to interlaminar reinforcement fibers  80  and  82 . Such a colored composite may be produced by combining a plurality of successive membrane-making steps, fibrous web/sprinkled fibers application zones and coloring coating membrane application zones of thermoplastic and thermoset materials as described in this invention.  
         [0024]    It should be noted that other variants of the above described methods or combinations of their steps may be utilized, for coloring the surface of a thermoset or thermoplastic membrane, without departing from the spirit and scope of the disclosed invention.