Abstract:
A process for manufacturing a laminate is disclosed. The laminate is for forming a package having one or more windows for viewing the contents of said package. The process comprises the step of extrusion laminating, onto a first material perforated by a hole for and defining each of said windows, a heat-sealable second material. A laminate produced by the process is also disclosed. A heat-sealed package produced with the laminate is also disclosed.

Description:
FIELD OF THE INVENTION 
     The invention relates to materials used for packaging, processes for the manufacture thereof and packages produced thereby. 
     BACKGROUND OF THE INVENTION 
     Combinations containing films are commonly used for packages product such as foodstuffs, medical and pharmaceutical products, electronic products and others. These combinations generally comprise at least one layer of non-transparent material such as aluminum foil, metalized polymer film, paper or the like. These combinations often also comprise films of polyethylene, polypropylene, polyester or the like, layered on one or both sides of the non-transparent material. 
     One popular packaging combination consists of a layer of paper having adhesive-laminated thereto a clear heat-sealable plastic layer. The paper portion of the laminate is die-cut prior to lamination, to provide windows to view the contents of packages formed therewith. When forming a bag with this material, it is usually necessary to apply a hot melt or other adhesive on the paper/plastic back seam, and on the paper/plastic interface at the bottom of the bag. 
     Due to the manufacturing complexity associated with the application of adhesive on the bag back seam and bottom, it is conventional to sell pre-made bags to processors, for subsequent filling and closure. The use of pre-made bags is relatively expensive. Also, the use of adhesive lamination can result in gaps between the layers of the finished material, which gaps render the material prone to delamination, loss of barrier and insect infestation. Voids are also prone to occur where the window meets the paper. Yet further, these bags are typically not hermetically sealed. 
     Another popular material comprises a layer of non-transparent, heat-sealable material. Materials of this type can be used in form-fill-seal machines, of the type for producing stand-up pouches and other packages, which is advantageous to processors in terms of cost. Also advantageous, these packages are generally hermetically sealed. However, these packages suffer in terms of consumer acceptance, as consumers cannot view the contents thereof. 
     SUMMARY OF THE INVENTION 
     A process for manufacturing a laminate forms one aspect of the invention. The laminate is for forming a package having one or more windows for viewing the contents of said package. This process comprises the step of extrusion laminating, onto a first material perforated by a hole for and defining each of said windows, a heat-sealable second material. 
     A laminate for forming a package forms another aspect of the invention. The package has one or more windows for viewing the contents of said package. This laminate comprises a layer of a first material, a layer of a second material and a layer of thermoplastic. The layer of first material has formed therein a hole for and defining each of said one or more windows. The layer of second heat-sealable plastic material is spaced from the layer of first material. The layer of thermoplastic has been deposited by extrusion between the layer of first material and the layer of second material in a manner such that the windows are hermetically sealed by plastic through which the contents of a package produced from the laminate can be viewed. 
     A heat-sealed package forms another aspect of the invention. This package comprises an outer layer, an inner layer and an intermediate layer of thermoplastic. The outer layer is of a first material, and has formed therein one or more holes. The inner layer is of heat-sealable second plastic material and is spaced from the outer layer. The intermediate layer of thermoplastic has been deposited by extrusion between the inner and outer layers such that the holes are hermetically sealed by plastic through which the contents of the package can be viewed. 
     Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawing, the latter being briefly described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of a process for manufacturing laminate according to a preferred embodiment of the invention; 
         FIG. 2  is a perspective view of a package formed with the laminate formed by the process of  FIG. 1 ; and 
         FIG. 3  is a schematic cross-sectional view of the laminate formed by the process of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made first to  FIG. 3  which depicts schematically a laminate  46  forming one preferred embodiment of the invention. This laminate  46  includes a first material  22 , namely, 65 gsm (gram per square meter) coated bleached glossy paper, having a print-bearing face  28  and an opposing face  30 . The print, deposited by Flexography, is indicated schematically by thin layer  23 . Material  22  is perforated by a hole indicated with general reference numeral  70 . The print  23  comprises synchronization marks (not shown). This laminate  46  also includes a second material  36 . This second material  36  comprises a 110 gauge (26 micron) transparent barrier  37  film sold by Exxon Mobil as product 110AXT under the trade-mark BICOR, which has been laminated, by a solvent-based adhesive, to a 1 mm transparent sealant film  39  sold by Pliant Corporation as product IO29. The sealant film  39  is orientated to present away from paper  22 , so as to render the second material  36  heat-sealable. This laminate  46  also includes an intermediate layer of LDPE  20 . 
     Attention is now directed to a process for manufacturing this laminate, which process forms another preferred embodiment of the invention and is depicted schematically in  FIG. 1 . 
     In this process, the first material  22  is released from a secondary unwind roller  24  and passed through a die cutting unit  26 . 
     In the die cutting unit  26 , the synchronization marks are detected by an optical sensor (not shown). Detection of a synchronization mark initiates a punching operation in the die cutting unit  26 , such that holes  70  are formed in the first layer material  22  in predetermined locations relative to the synchronization marks, to produce a perforated material  32 . The manner in which such detection and die cutting is carried out is well known to persons of ordinary skill in the art, and as such, is not described in detail herein. 
     The perforated material  32  advances next to a laminating section  34 , along with the second material  36  that has been released from a primary unwind roller  38 . 
     In the laminating section  34 , an extruder  40  applies a 11.5 gsm layer of an extrudant  20  onto the barrier film  37  portion of the second material  36  before the barrier film portion  37  of the second material  36  is overlaid upon the opposing face  30  of the first material  22  and laminated thereto by passage through a nip-roller  42 , to produce laminate  46 . The laminant extrudate  20  in this process is LDPE applied at a curtain temperature of 300° C., and forms intermediate layer  20  shown in  FIG. 3 . 
     In this process, the laminator  34  includes a chill roll  44  bearing a mirror pocket finish (not shown), so as to facilitate smooth release of the laminate  46  therefrom. 
     This laminate  46  is then advanced to rewind roller  48 , and spooled for subsequent use. 
       FIG. 2  shows such a subsequent use, namely, a hermetically-sealed bag or pouch  90  made from laminate  46  by a conventional vertical form-fill-seal machine. As illustrated, the pouch or package  90  has a window  100  for viewing its contents. This window  100  is not fully transparent, but rather is slightly translucent, owing to the chill roll  44  texture. The degree of opacity/translucence of window  100  is such that the contents of the package can be viewed through the window  100 , so as to permit potential consumers to readily inspect the contents, while at the same time facilitating smooth release of the laminate  46  from the chill roll  44 . It is noted that, in this bag, the paper first material  22  forms the bag outer layer, whereas the second material  36  forms the inner layer. 
     The specific package  90  described hereinbefore is known to be useful for the packaging of tortilla chips, but could be used for other purposes. 
     Whereas a specific process, laminate and package produced thereby are herein described, it should be understood that various changes to the process, laminate and package produced thereby can be made. 
     Firstly, whereas a 65 gsm paper is herein described to be utilized, paper stocks of other weights can be utilized. For example, weights of the type normally utilized in packaging, to wit, between 20 gsm and 120 gsm, are known to be useful. As well, whereas a bleached, glossy finish paper is described, natural and other papers can be used, as can matte and other finishes. Additionally, materials other than paper, such as plastics, metal foils or laminates thereof can be utilized. 
     Further, whereas a print deposited by Flexography is herein described, other printing processes, such as rotogravure, lithography and others can readily be employed. 
     Moreover, the print could be deposited on the first layer material either prior to forming the holes or subsequent thereto. A print could also be omitted. 
     As well, whereas the laminate extrudate in the described process is LDPE, other thermoplastics, including but not limited to PE, LLDPE, MDPE, EVA, EMA, EAA and HDPE could be utilized. As is readily understood by persons of ordinary skill in the packaging arts, modification of the extrudate composition may compel alteration of the curtain temperature, so as to ensure that the extrudate both flows and bonds properly to the first and second layer materials. Whereas a 11.5 gsm layer of extrudate is hereinbefore described, this may be modified, to, inter alia, meet the specific performance requirements of the product to be packaged. Weights between 3 and 40 gsm are known to be useful. 
     Additionally, whereas a specific laminated transparent film is described as forming the second material, other heat-sealable films may be employed. For example, barrier properties may, in some cases, not be required. Other weights and compositions could also be employed. Of course, barrier films other than AXT, and sealant films other than IO29, could readily be utilized. As well, lamination techniques other than solvent-based could be utilized, and monolithic films (i.e. non-laminated films) could be employed as the second material. 
     Further, whereas the print is indicated to include synchronization marks for the purposes of window positioning, these synchronization marks, or other syncronization marks, can be used at a later processing stage for cutting the packaging materials in appropriate places to form unit packages. 
     Further still, whereas die cutting is taught, other cutting apparatus, such as laser cutting or water jet cutting, could be employed. 
     Additionally, whereas the bag illustrated was formed by a vertical form-fill-seal machine, laminates constructed according to the invention can be utilized in horizontal form-fill-seal machines as well. 
     Finally, whereas a textured chill roll is described, which facilitates removal of the laminate from the nip roller, untextured i.e. smooth-finished rollers can also be utilized, to produce laminate with substantially transparent windows, although this may have deleterious impacts on lamination throughput. 
     Accordingly, it should be understood that the invention is to be limited only by the claims appended hereto, purposively construed.