Patent Publication Number: US-2003221768-A1

Title: Method of making polyolefin spunmelt/film composite material and product made thereby

Description:
FIELD OF INVENTION  
       [0001] The invention is directed to a method for making a spunmelt/film composite material in-line using heated calender rollers to bond the layers of material in the absence of an adhesive, and the composite material resulting from the method. The composite material is suitable for use in civil engineering applications (e.g., roofing, house wraps, etc.), personal care products (e.g., baby diapers, feminine hygiene, adult incontinent products, etc.) and for protective garments in medical and industrial environments.  
       BACKGROUND OF THE INVENTION  
       [0002] The present invention is directed to providing a composite material including a spunmelt filament web and a film material. In conventional processes, individual layer materials which are to be a component of a composite material are individually made and wound onto a storage roll. For example, a nonwoven fabric is separately made (including bonding of the filaments/fibers which make up the fabric) and a film is separately made. Thereafter, the storage rolls are provided on a line where the layer materials are unwound and layered together in a desired order. The ready-made layers are joined or laminated together by use of an adhesive between the layers or alternatively through a separate heated calendering process. Accordingly, prior art processes require multiple separate line processes, use of separate equipment, additional time, additional material and the subjecting of the material to added heat treatments which serve to degrade the material forming the composite. An example of such a laminate is disclosed in U.S. Pat. No. 5,910,225.  
       [0003] Therefore, an on-line process not utilizing an adhesive or added heat processes would be advantageous. Additionally, cost would be decreased based on savings in time, material and equipment.  
       OBJECTS OF THE INVENTION  
       [0004] Accordingly, it is a primary object of the present invention to provide a method of making a spunmelt filament web/film composite material in one in-line process, in particular providing bonding of the layers forming the composite material in the absence of an adhesive.  
       [0005] A further object of the invention is to provide a composite material of dissimilar materials, such as films and spunmelt continuous filament webs, which are joined by simple heat and pressure.  
       [0006] A further object is to provide a process which eliminates bonding agents and reduces the number of heat applications of the material components and composite material to maintain functionality, such as breathability and softness, of the composite as well as achieve minimal degradation of the material.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007] The invention is directed to polyolefin spunmelt continuous filament web/film composite materials and a method of making such composite materials. The composite material is made up of dissimilar materials, i.e., film and spunmelt continuous filament web(s), which are joined together in the absence of adhesives or secondary thermal bonding. The structure and method of the invention involves an in-line formation of a spunmelt continuous filament web(s) and subsequent in-line joinder to a film and, optionally, at least one other nonwoven material.  
       [0008] More particularly, the method of making a polyolefin spunmelt continuous filament web/film composite material includes forming on a moving belt a web of spunmelt polyolefin fibers. A breathable or non-breathable polyolefin film is positioned on top of the formed web as the web is moved to a winder in order to provide a layered structure. Optionally, at least one other layer, such as a nonwoven material, may be positioned on top of the film. Thereafter, the formed layered structure is subjected to calendering utilizing heated rolls in order to join or bond the layers together. The composite material is then wound on a winder. The polyolefin film is positioned atop the web at a speed which is the same as the speed at which the web is moving. Preferred speed of application is in a range of from about  10  to about 100 meters per minute (m/min).  
       [0009] In a preferred embodiment of the composite material, the basis weight of the web of spunmelt fibers is from about 13.5 gsm to about 100 gsm (grams per square meter) and the basis weight of the polyolefin film is from about 10 gsm to about 40 gsm. The total composite basis weight tolerance ranges from about 25 gsm to about 150 gsm.  
       [0010] The polyolefin of the fibers and/or films of the composite material is preferably polypropylene, polyethylene, copolymers of polypropylene and polyethylene, or a composite of polypropylene and polyethylene.  
       [0011] The continuous in-line process of the invention allows for the film to be pre-stretched during the formation process which serves to enhance the “Z” directional properties of the composite. This is due to film/nonwoven composite relaxation after thermal bonding. The elimination of bonding agents or secondary thermal bonding results in cost savings since the overall process involves less stages, as well as results in preservation of more characteristics of the original materials, such as breathability and softness. Minimal degradation of the film and spunmelt web occurs since less heat is utilized in the process.  
       [0012] The composite web material of the invention can be used in various applications. For example, the composite material is useful in civil engineering applications (e.g., roofing, house wraps and the like), in personal hygiene products (e.g., diapers, feminine hygiene products, adult incontinent products and the like), and in protective garments in medical and industrial environments, etc.  
     
    
    
     BRIEF DESCRIPTION OF DRAWING  
     [0013] The sole FIGURE is a schematic illustrating a production line for making a spunmelt/film composite material in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS  
     [0014] The invention concerns a composite material made of dissimilar materials, i.e., film and continuous filament spunmelt web(s), which are made in a continuous in-line process. The process of the invention is more cost and time effective as compared to conventional multi-stage lamination processes. Further, the process of the invention provides for improved material properties based on the ability to bond in the absence of adhesive and secondary thermal calendering which allows the formed product to have minimal degradation as to material and thus properties.  
     [0015] The composite material has two essential layers, a film layer and a spunmelt layer. Optionally, one or more other layers may be included. The spunmelt layer and film layer are preferably formed of a polyolefin, more preferably polypropylene, polyethylene, copolymers of polypropylene and polyethylene, or composite of polypropylene and polyethylene. The film is preferably a breathable polyolefin. The film, however, can be any film which can be bonded by heat and pressure, including nonbreathable films. The basis weight of the spunmelt layer is from about 13.5 gsm to about 100 gsm. The basis weight of the film is from about 10 gsm to about 40 gsm. The total composite basis weight tolerance ranges from about 25 gsm to about 150 gsm.  
     [0016] With reference to the sole figure, in the method of the invention, the spunmelt fibers are formed at station  1  in a conventional manner as known to one skilled in the art, such as for example by extrusion. Spunmelt fibers formed are allowed to fall to a moving belt  3  to form a spunmelt web  5  on belt  3 . Spunmelt web  5  then moves along continuing moving belt  7  where a film  9  and optionally at least one nonwoven material  11  are positioned or laid on top of spunmelt web  5 . Film  9  is received from unwinder  13  and the optional nonwoven material  11  is received from the unwinder  15 . Tension rollers  17  are utilized to control the tension, placement and speed of the film and nonwoven material in relation to web  5 . Film  9  is positioned upon web  5  at the same speed at which web  5  is moving along belt  7 . A preferred speed is in a range of from about 10 to about 100 m/min. This is beneficial to insure aligned placement without pulling of one material upon another such as could occur if one moved at a lower speed.  
     [0017] The layered structure of web  5 , film  9  and optional nonwoven material  11  is then moved downstream for heated calendering, e.g., by a heated engraving roller  19  and heated smooth roller  21 . The heat and pressure serve to join or bond the multi-layer structure. Following calendering, the joined structure is taken up by winder  23 . Once wound to a desired capacity, the wound material will be removed from the winder and taken to storage or a point of use depending upon the application to which the material will be used.  
     [0018] The composite fabric(s) of the invention can be applied to various uses. For example, the composite fabric(s) may be used in civil engineering applications such as roofing, house wraps and the like; in personal hygiene applications, such as a backsheet material in a diaper; for protective garments in medical and industrial environments; and the like.  
     [0019] The in-line method of the invention is advantageous in providing a composite material of dissimilar materials which are joined by means other than conventional adhesives or a secondary thermal bonding stage. In terms of the process, savings are present with respect to cost and time. Fewer stages and thus less equipment is necessary, added cost of adhesive is unnecessary. In terms of the material produced, the elimination of adhesive or secondary thermal bonding preserves more properties of the original materials which are joined together. Due to lack of adhesive and less exposure to heat, the material&#39;s functionality (such as breathability and softness) are less compromised, and the reduced exposure to heat results in minimal degradation of the original material. Additionally, the method allows the film to be “pre-stretched” during the formation process to enhance the “Z” directional properties of the finished composite material. Such does not interfere with on-going method. Thus, the in-line continuous method of the present invention has numerous advantages over conventional processes where several various layers are separately formed at individual lines and then are combined off-line.  
     [0020] The invention is not to be restricted to the above described embodiments. Modifications may be introduced, in particular as regards the constitution of the various components or by substituting equivalent techniques, without thereby transcending the protected scope of the invention.