Abstract:
A multilayered sheet ( 10 ) is made by extruding a sheet ( 20 ) and bringing it into immediate contact with a non-woven sheet ( 40 ) before bringing the abutting sheets into a first nip ( 201 ) formed by a pair of pressure rollers ( 121,122 ). The multilayered sheet ( 10 ) then passes through a second nip ( 202 ) formed between two pressure rollers ( 122,123 ) and is cooled down through a series of additional chill rollers ( 123,124,125,126 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This Application claims priority on pending U.S. Provisional Application No. 60/771,289 filed on Feb. 8, 2006, which is herein incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to a multilayered sheet and more particularly, to a sheet constructed of at least two materials melded during construction thereof to form a resilient and flexible plastic sheet with a relatively soft side for use in packaging to protect and/or separate goods during transportation or storage. Other uses are also disclosed. The invention also is to the method of making the multi-layered sheet.  
       BACKGROUND OF THE INVENTION  
       [0003]     Fragile, precision items and/or specialized items are specially packaged to ensure they are not damaged during packing, unpacking, transporting and storing. Often times, customized dunnage is used to both hold and prevent the product, e.g., items or pieces, from moving or being injured. In addition, packing sheets can be used, such as between products or wrapped around products, to ensure separation between the products and to prevent movement of and injury to the products. Such sheets often require the characteristics of being rigid, flexible and yet soft. The rigid, flexible structure is frequently important to withstand the forces caused by the product and movement of the package. Softness is important to prevent marring of the product if it rubs against the sheet. These sheets should further be robust with a long lifespan, wherein the sheet can be used over and over without degradation. Finally, it is often important to have a low weight sheet to keep the overall weight of the package as low as possible.  
         [0004]     This packing or separation sheets are also used in trunks as linings to protect or separate items, such as a spare tire or in luggage to separate compartments.  
         [0005]     Packing/separation sheets can be made from plastic, such as polypropylene. It has been found that non-woven, spun-bound polypropylene works well as a surface for packing sheets. This material is well suited for packaging as spacers, dunnage and separators primarily because it can act as a cushion and does not scratch or mar surfaces. However, the non-woven, spunbond sheets do not generally have the strength or integrity alone to act in some packing environments and as separator sheets. As such, such sheets must be bound to a carrier substrate, such as a sheet of polypropylene, to give it strength.  
         [0006]     Multi-layered sheets such as those discussed above generally incorporate adhesives to bond the layers to one another. This affects recyclability since the use of the adhesive makes the lamination undesirable as a recyclable. In addition, using an adhesive increases the costs of making the product, due to the extra equipment to incorporate the adhesive and due to the cost of the adhesive.  
       SUMMARY OF THE INVENTION  
       [0007]     The present development solves the problems discussed above and other problems, and provides advantages and aspects not provided by prior multilayered sheets used in packaging and as dividers. A multilayer sheet is formed by the lamination process wherein an extruded sheet is pressed against a non-woven sheet downstream from the die of the extruder and just prior to the first nip formed by confronting chill rollers. The combined sheet is passed through a second nip and a series a chill rollers before it is wound. The extruded sheet can be substantially solid or extruded corrugated plastic.  
         [0008]     According to a first aspect of the present invention, a multilayered sheet is disclosed having both strength and softness. The sheet includes a preformed first sheet and a second sheet laminated to the first sheet, the second sheet being extruded onto the first sheet before both sheets are passed through a nip formed by confronting rollers. The preformed sheet is a non-woven, spunbond polypropylene having a thickness of about 0.010″ and the second sheet is a polypropylene having a thickness of about 0.020″ to 0.050″.  
         [0009]     According to a second aspect of the present invention, the method of making the multilayered sheet comprises the steps of feeding a preformed sheet to a nip so that the sheet passes therethrough, and extruding a second sheet onto the preformed sheet before the preformed sheet passes through the nip to form a multilayered sheet. The preformed sheet is a non-woven spunbond polypropylene sheet and the second, extruded sheet is a polypropylene. The multilayered sheet is cooled immediately upon entering the first nip. It is thereafter passed over a series of cooling rollers.  
         [0010]     The multilayer sheet is also passed through a second nip downstream of the first nip. Both nips are formed by confronting rollers and are positioned to compress the multilayered sheet passing therethrough. In the preferred embodiment, the non-woven, spunbond polypropylene has a thickness of about 0.010″ and the second, extruded sheet of polypropylene has a thickness of about 0.020″ to 0.050″.  
         [0011]     The second sheet is extruded onto the preformed sheet approximately 5″ from the first nip. The nip has a gap of approximately 0.025″ to 0.50″ and is formed between two chill rollers of between 150° F. and 180° F. and between 200° F. and 230° F., respectively. The second nip has a gap substantially similar to the gap at the first nip.  
         [0012]     Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and the detailed description of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Following are the brief descriptions and legends of the figures.  
         [0014]      FIG. 1  is a schematic diagram of the process for making the multilayered sheets according to the teachings of the present invention;  
         [0015]      FIG. 2  is a detail of a portion of the diagram shown in  FIG. 1 ; and,  
         [0016]      FIG. 3  is a schematic representation of the resultant, multi-layered product. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0017]     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, preferred embodiments of the invention with the understanding the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. The present invention will have the following main components and techniques for operation of the device.  
         [0018]      FIG. 1  shows a schematic representation of the process for making the multilayered sheet  10 . An extruder  110  generally extrudes a sheet  20  of polypropylene through a die  111 . The preferable die is about 72″ (width) by 9.5″ (height) by 11″ depth. The die lip opening is approximately 66″ wide, but it can be reduced or deckled so as to more closely match or align width-wise with the sheet it is being applied to or laid upon (discussed below). The extruded sheet&#39;s thickness can be varied depending upon the application and desired results. Thicknesses can range from 0.020″ and upwards. Specific thicknesses that have proved sufficient and adequate are 0.25″, 0.30″, 0.35″ and 0.40″. Widths range from about 40″ to about 58″. The lengths range from about 40″ and upwards. The extruded sheet  20  is passed through a series of nips  201 , 202  formed between a series of chill rollers  121 , 122 , 123  and passed over and partially around additional chill rollers  124 , 125 , 126  and idlers  131 , 132 . In the preferred embodiment, the nip  201  is produced by confronting rollers  121 , 122 . Roller  121  has a diameter of about 32″ and is maintained at a temperature of about 150° F. to about 180° F. while roller  122  has a diameter of about 32″ and is maintained at a temperature of about 200° F. to about 230° F. A second nip  202  is produced by confronting rollers  122 , 123 . Roller  123  also has a diameter of about 32″ and is maintained at a temperature of about 200° F. to about 230° F. The chill rollers  124 , 125 , 126   123  are preferably sized and maintained to bring the temperature down towards room/ambient temperature.  
         [0019]     A supply of non-woven, spunbond polypropylene  40  (in sheet form) is carried by a supply roller  140 . The spunbond polypropylene is available from many suppliers. The spunbond polypropylene can be any width meeting a customer&#39;s demand or need, generally between about 40″ and 58″, and a thickness of various gauges. For example, a gauge spunbond of about 0.010 works well.  
         [0020]     The making of spunbond fabrics is well-known in the industry. Such fabrics are used in many products today.  
         [0021]     The non-woven sheet  40  is passed around one or more idlers  133 , 134  and fed into the first nip  201  downstream of the die  111  wherein it is forced into abutment with the extruded sheet  20 . This specific area of the process is shown in further detail of  FIG. 2 .  
         [0022]     The feeding of the non-woven-sheet  40  with the extruded sheet  20  occurs within inches of the extruder&#39;s die  111  and just before contacting the rollers  121 , 122  forming the nip. In this manner, it is believed, the extruded polypropylene  20  is bonded to the non-woven sheet  40  by a melding of fibers from the non-woven sheet  40  into the extruded sheet  20 .  
         [0023]     The first nip  201  has a clearance or opening sized to compress the multilayered sheet passing therethrough. The gauge or thickness depends on the end product desired. For example, for 0.025″ thick (gauge) multilayered sheets, the nip gap is set at about 0.030″; for 0.030″ thick sheets, the nip gap is set at about 0.035″, for sheets of 0.035″ and 0.040″ thick, the nip gap is set at about 0.040″ and 0.045″, respectively. The second nip gap  202  can be set similar to the first gap  201 .  
         [0024]     The above process and resulting product are very different from those in which the extrusion is extruded directly onto a substrate. Here, there is an intentional space (X in  FIG. 2 ) between the die nozzle or lip  111  and the mating of the non-woven sheet  40  to the extruded sheet  20 . That distance X has been found to be about 5 inches. The non-woven substrate  40  is carried by the bottom roller  121  to contact with the extruded sheet  20  and first nip  201 .  
         [0025]     The plastic exits the die&#39;s nozzle/lip  111  at about 450° F. and immediately cools down to about 340° F. The melting point of polypropylene is roughly 340° F. The two sheets  20 , 40  come together at the first nip  201  to form the combined (multilayered) sheet  10 . The combined product goes through a controlled cool-down by passing around and over a series of chill rollers. Specifically, the chiller rollers  121 ,  122 , 123 , 124 , 125 , 126 , generally 32″ diameter, are positioned to bring the temperature of the multilayered sheet  10  down in temperature. As noted, in practice, it has been found that chill rollers with the following temperatures work well: Roller  121  at approximately 150° F.-180° F.; Roller  122  at approximately 200° F.-230° F.; Roller  123  at approximately 200° F.-230° F. ; and, Rollers  124 - 126  at a moderate rate of cooling down towards room temperature (approximately 100° F.-150° F.).  
         [0026]     The resultant product can be gauged so as to have a thickness of any desired or preferred amount. For example, successful gauges have been produced having a gauge of 0.025″, 0.030″, 0.035″ and 0.040″.  
         [0027]     A test sample combining a non-woven polypropylene sheet ( 40 ) (2.0-3.0 oz/yd spunbond) of 0.013″ with an extruded polypropylene sheet ( 20 ) gauged at 0.025″. The resultant multi-layered sheet was measured at 0.030″. It is believed multilayered products of 0.025″-0.080″ would be typical. It is also believed that some melting occurs the in non-woven substrate  40  in the plane of intersection with the extruded sheet  20  ( FIG. 3 ).  
         [0028]     The results of the above process were extremely surprising to those investigating setting-up, running, and analyzing the above process and sheets. The resulting product was an extremely well-bonded multilayered sheet having strength and integrity with a “softer” side. The sheet is easily recyclable because no adhesive is used with the two layers of polypropylene. And, significantly, as compared to prior products, the above described product is less expensive to produce and arguably easier to make since adhesive is neither purchased nor incorporated in the manufacturing process. In addition, there is an inseparable bond between the non-woven sheet  40  and the extruded sheet  20 . This resolves a common de-lamination problem associated with similar sheets bonded adhesively together.  
         [0029]     It should be noted that while the extruded sheet  20  is shown and depicted as being substantially solid, it can also be an extruded corrugated plastic. The extruding of corrugated plastic sheets is known in the industry and can include internal hollows or channels between the outer surfaces of the sheets.  
         [0030]     While the above process and resulting product were discussed broadly, it is recognized other variants can be made without deviating from the spirit of the invention. For example, other plastics, apart from polypropylene, can be used. The size, temperatures and number of the pressure rollers can be varied. In addition, other uses of the resultant product can be made.