Patent Publication Number: US-2004052987-A1

Title: Paper based retortable can and method for making same

Description:
TECHNICAL FIELD  
       [0001] The present invention relates generally to retortable cans and is particularly directed to retortable cans of the type which include a layer of paperboard material for mechanical strength. The invention is specifically disclosed as retortable can made of a laminated material with a middle paperboard layer, a barrier layer on each side of the middle layer, and an outer shielding layer covering each of the barrier layers.  
       BACKGROUND OF THE INVENTION  
       [0002] Retortable cans are containers that can withstand a heating event, such as being subjected to steam for a time duration sufficient to kill bacteria. When steam is used in this manner, the container (i.e., the retortable can) essentially undergoes a sterilization process. Retortable cans are typically used to store food items, such as pet food, or canned fruits or vegetables.  
       [0003] In the past, most retortable cans have been made of metal. Such retortable cans were often made to be watertight, or waterproof, which would be especially necessary in the case of canned fruit or vegetables that would contain moisture in most circumstances. There are many watertight containers that are made to store food, although not every one of these conventional containers is also retortable with respect to being able to withstand a sterilization process using steam.  
       [0004] Some waterproof or watertight containers known in the prior art include a layer of paperboard or other paper substrate. For example, U.S. Pat. No. 3,406,891 (by Buchner) discloses a container for holding liquids, including foods. The container can be sterilized, and includes a wall structure having a layer of paper, an outer layer of aluminum foil, and an inner surface layer and outer surface layer of plastic material, such as polypropylene. The end walls of the container include a layer of aluminum foil that forms the outer layer, and the end walls also have an inner layer of polypropylene. The top and bottom covers (i.e., the end walls) are made of deep drawn metal foil with a U-form shaped rim portion that is telescoped over the container wall. A heat seal is established between the covers and the cylindrical walls. A metal foil provides sufficient strength to the weld seam and prevents a deterioration or deformation in the thermoplastic material of the cover, even though a slight softening in the plastic material may occur during a sterilization procedure.  
       [0005] Another waterproof container that includes paper material is disclosed in U.S. Pat. No. 4,679,724 (by Inagaki). The container has a wall made of a paper substrate which is surrounded by a double-wall of heat-shrinkable plastic film. Some of the embodiments of Inagaki use metal for the lids of the container, although some embodiments also show a paper lid that is covered by the plastic film. The plastic film preferably is made of a heat-shrinkable nylon that is laminated with polyethylene.  
       [0006] The Inagaki invention is designed to replace aluminum or steel cans, and the materials used are to be resistant against heat, water content, and pressure due to retort-sterilization procedures. In general, the Inagaki invention is to be used for holding liquids, including juice.  
       [0007] A packaging laminate is disclosed in WO 97/02140 (owned by Tetra), in which a paper or EVOH substrate has an outer coating and an inner coating that are heat resistant and have “good” vapor barrier properties. In general, these coatings are made of PP, PE, or polyester. An additional barrier layer is included between the inner coating and the substrate layer, which is made of Aluminum, silica, EVOH, PP, AlO x , or polyester. The laminate is useful with aseptic food packaging, in which a tube constructed of the laminate is filled at 80-90° C., or in conjunction with a “hotfill” procedure at 75-90° C., or used in an autoclave at 250° F.  
       [0008] A method of sterilizing containers made of a fiber material is disclosed in WO 98/16431 (owned by Tetra), in which the containers are placed in an autoclave at a predetermined temperature and pressure, for a predetermined time period. The advantage of this invention is to reduce the cycle time needed for autoclaving.  
       [0009] A transparent multilayer structure is disclosed in WO 98/32601 (owned by Tetra), in which an exterior film layer is made of HDPE, PP, PEN, PET, or PA, an interior film layer is made of LLDPE, PE, PP, ethylene vinyl acetate, or EVOH, and a middle layer is made of metal oxide, such as SiO x .  
       [0010] It would be an improvement to manufacture a retortable can that had no metal content whatsoever, and also to improve some of the seals made during construction of the can, perhaps without use of metal layers or metal stand-alone members. It would also be an improvement to manufacture a retortable can that uses paper or paperboard as a main structural member, either in a spiral or convolute configuration or in a side seal longitudinal configuration.  
       SUMMARY OF THE INVENTION  
       [0011] Accordingly, it is an advantage of the present invention to provide a retortable can that is based on a paper substrate as its main structural strength layer, but also which includes other protective or shielding layers that are applied to the structural layer using an adhesive to form tie layers therebetween.  
       [0012] It is another advantage of the present invention to provide a retortable can that has a paper or paperboard layer for mechanical strength, an outer shielding layer that is highly heat and moisture resistant, and a protective layer that acts as a barrier to moisture, oxygen, and flavor, which is placed between the paperboard middle layer and the inner shielding layer.  
       [0013] It is a further advantage of the present invention to provide a retortable can made of a paperboard substrate with barrier and shielding layers that can withstand steam sterilization, and which can be manufactured in various shapes and in a variety of configurations, such as a spiral or convolute wrap, a cylindrical wall with side seal, a molded and formed container, and in a wraparound can configuration.  
       [0014] It is yet another advantage of the present invention to provide a retortable can that is constructed of two laminates, perhaps in a spiral or convolute configuration, in which the two laminates each have an outer paper or paperboard layer that, as the can is being constructed, are glued together by an adhesive to form a middle substrate, and in which the can has outer shielding layers and at least one barrier layer.  
       [0015] Additional advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention.  
       [0016] To achieve the foregoing and other advantages, and in accordance with one aspect of the present invention, a retortable container is provided, which comprises: a laminated material forming a substantially hollow cylinder, a first substantially circular end member, and a second substantially circular end member; the first end member being attached to the cylinder in a manner so as to make a liquid-tight seal at first locations of attachment; and the second end member being attached to the cylinder in a manner so as to make a liquid-tight seal at second locations of attachment; wherein the laminated material comprises: (a) a first layer substantially comprising a first shielding material that is resistant to heat and moisture; (b) a second layer substantially comprising a paper material; (c) a third layer substantially comprising a first barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; (d) a fourth layer substantially comprising a second shielding material that is resistant to heat and moisture; and (e) an adhesive material that substantially holds the first, second, third, and fourth layers in place with respect to one another.  
       [0017] In accordance with another aspect of the present invention, a laminate material usable as a structural member of a retortable container is provided, in which the laminate material comprises: (a) a first layer substantially comprising a first shielding material that is sufficiently resistant to heat and moisture to withstand direct contact with steam and retort conditions of 121° C. for 60 minutes at 15 PSI pressure; (b) a second layer substantially comprising a paper material, that is sufficiently resistant to heat to withstand 121° C. for 60 minutes at 15 PSI pressure; (c) a third layer substantially comprising a first barrier material that reduces a rate of transmission of oxygen, moisture, and flavor, and that is sufficiently resistant to heat to withstand 121° C. for 60 minutes at 15 PSI pressure; and (d) a fourth layer substantially comprising a second shielding material that is sufficiently resistant to heat and moisture to withstand retort conditions of 121° C. for 60 minutes at 15 PSI pressure, and is compatible with direct food contact.  
       [0018] In accordance with yet another aspect of the present invention, a method for forming a retortable container is provided, in which the method comprises the steps of: (1) providing a web of laminated material, the laminated material having multiple layers of materials of different properties, in order from a first surface toward a second surface: (a) a first layer substantially comprising a first shielding material that is resistant to heat and moisture; (b) a second layer substantially comprising a first barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; (c) a third layer substantially comprising a paper material; and (d) a fourth layer substantially comprising a second shielding material that is resistant to heat and moisture; (2) moving the web of laminated material through a skiving station to form longitudinal edges in the web that are shaped for being more readily affixed; (3) moving the web of laminated material through a continuous tube forming station which wraps the web into a shape of a substantially hollow cylinder and applies an adhesive to hold the web in its substantially hollow cylindrical shape; (4) cutting the web of laminated material into a plurality of hollow cylinders of a predetermined length, each of the hollow cylinders having a first open end and a second open; (5) attaching a bottom lid to the hollow cylinders at the first open end; (6) filling the hollow cylinders with a product through the second open end; and (7) attaching a top lid to the hollow cylinders at the second open end.  
       [0019] In accordance with another aspect of the present invention, a laminate material usable as a structural member of a retortable container is provided, in which the laminate material comprises: (a) a first layer substantially comprising a first shielding material that is sufficiently resistant to heat and moisture to withstand direct contact with steam and retort conditions of 121° C. for 60 minutes at 15 PSI pressure; (b) a second layer substantially comprising a barrier material that reduces a rate of transmission of oxygen, moisture, and flavor, and that is sufficiently resistant to heat to withstand 121° C. for 60 minutes at 15 PSI pressure; (c) a third layer substantially comprising a paper material, that is sufficiently resistant to heat to withstand 121° C. for 60 minutes at 15 PSI pressure; and (d) a fourth layer substantially comprising a second shielding material that is sufficiently resistant to heat and moisture to withstand retort conditions of 121° C. for 60 minutes at 15 PSI pressure, and is compatible with direct food contact; wherein the second layer of barrier material comprises extrudable nylon that adheres directly to the second layer of paper material without a tie layer therebetween.  
       [0020] In accordance with yet another aspect of the present invention, a method for forming a hollow tube of laminated material used in a retortable container is provided, in which the method comprises the steps of: (1) providing a first web of laminated material, the first web of laminated material having multiple layers of materials of different properties, in order from a first surface toward a second surface: (a) a layer substantially comprising a paper material; and (b) at least one layer comprising: at least one of (i) a first shielding material that is resistant to heat and moisture, and (ii) a first barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; (2) providing a second web of laminated material, the second web of laminated material having multiple layers of materials of different properties, in order from a third surface toward a fourth surface: (a) a layer substantially comprising a paper material; and (b) at least one layer comprising: at least one of (i) a second shielding material that is resistant to heat and moisture, and (ii) a second barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; (3) moving the first and second webs to a forming station, and directing the first and second webs into an orientation such that the first surface of the first web is proximal to the third surface of the second web; and (4) applying an adhesive to at least one of the first surface of the first web and the third surface of the second web, and pressing the first and third surfaces together while wrapping the first web and the second web so as to form a substantially hollow tube of laminated material.  
       [0021] In accordance with still another aspect of the present invention, a laminate material usable as a structural member of a retortable container is provided, in which the laminate material comprises: (a) a first half-structure which comprises: (i) a first layer substantially comprising a paper material; and (ii) a second layer comprising at least one of (A) a first shielding material that is resistant to heat and moisture, and (B) a first barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; (b) a second half-structure which comprises: (i) a third layer substantially comprising a paper material; and (ii) a fourth layer comprising at least one of (A) a second shielding material that is resistant to heat and moisture, and (B) a second barrier material that reduces a rate of transmission of oxygen, moisture, and flavor; and (c) a layer of adhesive material located between the first layer and the third layer, which affixes the first half-structure to the second half-structure.  
       [0022] In accordance with a further aspect of the present invention, a packaging laminate for a retortable packaging container is provided, in which the laminate comprises: a core layer; outer, liquid-tight coatings; and a gas barrier disposed between the core layer and one of the outer coatings; wherein the gas barrier is bonded to the core layer by a layer of a lamination or sealing agent which has a higher melting point than the maximum temperature to which the retortable packaging container is to be subjected during a heat treatment in a retort.  
       [0023] Still other advantages of the present invention will become apparent to those skilled in this art from the following description and drawings wherein there is described and shown a preferred embodiment of this invention in one of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0024] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description and claims serve to explain the principles of the invention. In the drawings:  
     [0025]FIG. 1 is a perspective view from above and from the front of the major components of a paper-based retortable can, as constructed according to the principles of the present invention.  
     [0026]FIG. 2 is a diagrammatic view of a cross-section of the paper-based material used to create the retortable can of FIG. 1.  
     [0027]FIG. 3 is a perspective view of a continuous tube forming manufacturing process that constructs the cylindrical shape of the paper-based retortable can of FIG. 1.  
     [0028]FIG. 4 is a cross-sectional view looking down the centerline of the tube-forming mandrel of FIG. 3, while showing some of the details of the side-seam of the retortable can as it is being constructed in FIG. 3.  
     [0029]FIG. 5 is an end view showing the paper-based and layered material used in the present invention to form a retortable can, before being formed into a longitudinal seam (also known as a side seam or a body seam).  
     [0030]FIG. 6 shows the next step in the process for forming the longitudinal seam, illustrating the skived shape of the seam-forming members from the paperboard-layered material from FIG. 5.  
     [0031]FIG. 7 shows the next step in the process of forming a longitudinal seam, in which the protruding members illustrated in FIG. 6 have been folded back upon themselves.  
     [0032]FIG. 8 is the next step in the process for forming a longitudinal seam, in which the folded-back protruding members are joined together with a sealant compound, thereby forming the longitudinal seam.  
     [0033]FIG. 9 is a cut-away view showing the details of a reinforced seam that joins a lid to a cylindrical body, using the paperboard-layered material of the present invention.  
     [0034]FIG. 10 is a side view in cross-section of the bottom portion of a retortable can constructed according to the principles of the present invention, and using the corner or end seam/seal of FIG. 9.  
     [0035]FIG. 11 is a cross-sectional view of a corner or end seam/seal having a ring shape, used for joining a lid to the cylindrical body, as constructed using the paperboard-layered material of the present invention.  
     [0036]FIG. 12 is a side view in cross-section of the bottom portion of a retortable can constructed according to the principles of the present invention, and using the corner or end seam/seal of FIG. 11.  
     [0037]FIG. 13 is a cross-sectional view of an alternative embodiment of the paperboard-layered material of the present invention, while also showing the construction of this material in a manner that is closer to the ratio of actual physical dimensions.  
     [0038]FIG. 14 is a cross-sectional view looking down the longitudinal axis of the cylindrical side member of the retortable can of FIG. 1 without the mandrel, and showing some of the details of the longitudinal seal in which the folded members are of an increased dimension with respect to the diameter of the cylindrical member.  
     [0039]FIG. 15 is a cross-section view looking down the longitudinal axis of the cylindrical side wall member of the retortable can similar to that of FIG. 1, however, in FIG. 15 the configuration of the laminated paperboard material is in the form of a spiral or in a convolute shape.  
     [0040]FIG. 16 is a cross-sectional view showing details of another configuration for constructing a longitudinal seam for use in the retortable can of FIG. 1.  
     [0041]FIG. 17 is a cross-sectional view showing details of yet another configuration for constructing a longitudinal seam for use in the retortable can of FIG. 1.  
     [0042]FIG. 18 is a cross-sectional view showing details of still another configuration for constructing a longitudinal seam for use in the retortable can of FIG. 1, using a reinforcing member along the inner surface.  
     [0043]FIG. 19 is a perspective view from the side and somewhat from one end of a retortable can constructed of the laminated material of the present invention, in which the can is constructed using a spiral or convolute configuration, as shown in FIG. 15.  
     [0044]FIG. 20 is a perspective view from the side and somewhat from above of a retortable can made of the laminated material of the present invention, which also includes a ring for opening the container, as constructed according to the principles of the present invention.  
     [0045]FIG. 21 is a side view in cross-section of two portions of the laminated material as constructed according to the present invention, after a skiving operation has been performed, thereby producing two protruding members in a first step of a procedure for forming a longitudinal seam.  
     [0046]FIG. 22 is a side view in cross-section of the next step in the procedure for forming a longitudinal seam, in which the two protruding members are brought closer to one another and are beginning to be bent.  
     [0047]FIG. 23 is a side view in cross-section of the next step in forming a longitudinal seam, in which the two protruding members are brought yet closer together and are further bent, and it is now apparent that they will become interlocked with one another.  
     [0048]FIG. 24 is a side view in cross-section showing a further step in the operation for producing an interlocked side seam, in which the two protruding members are further bent and more clearly interlocked.  
     [0049]FIG. 25 is a side view in cross-section illustrating the final result, which is an interlocked side seam after the interlocking protruding members are brought together and sealed in place with adhesive.  
     [0050]FIG. 26 is a flow chart illustrating some of the important operations for manufacturing a retortable can, as constructed according to the principles of the present invention.  
     [0051]FIG. 27 is a diagrammatic view of a cross-section of an alternative embodiment for the paper-based material used to create the retortable can of FIG. 1.  
     [0052]FIG. 28 is a diagrammatic view of a cross-section of yet another alternative embodiment for the paper-based material used to create the retortable can of FIG. 1.  
     [0053]FIG. 29 is a side view in partial cross-section, and a partially exploded view, of a spiral retortable container tube constructed according to the principles of the present invention, in which two different “half-structures” are joined together to form the side walls of the container.  
     [0054]FIG. 30 is an end view in cross-section of the spiral retortable container tube of FIG. 29, depicting the two “half-structures” after they are assembled.  
     [0055]FIG. 31 is a side view in cross-section of a body seam according to the principles of the present invention, in which the two portions of laminated paperboard material are skived, and have protruding fingers that interlock while the entire seam is protected by the shielding layers.  
     [0056]FIG. 32 is a side view in cross-section of a corner joint or corner seal, constructed according to the principles of the present invention, in which the shielding layers are used to protect the inner structure throughout the joint/seal. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0057] Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings, wherein like numerals indicate the same elements throughout the views.  
     [0058] Referring now to the drawings, FIG. 1 illustrates in an exploded view the main structural members of a retortable container (typically referred to herein as a “can”), generally designated by the reference numeral  10 . The cylindrical side wall  12  is to be joined by a top or first end  14 , and a bottom or second end  16 . The structure of this cylindrical side wall  12  is depicted in relatively simplistic form, and does not show any of the details of a longitudinal seam that would be required to make the can watertight.  
     [0059]FIG. 2 shows some of the details in a diagrammatic form of the various layers that make up the material used to create the retortable can illustrated in FIG. 1. The overall structure is generally designated by the reference numeral  20 , which comprises a middle paperboard substrate  22 , two outer shielding layers  24  and  26 , and two intermediate barrier layers  28  and  30 . Each of the adjoining layers is to be affixed to the next adjoining layer by a tie layer, which is a type of adhesive compound. In FIG. 2, the tie layers are designed at the reference numerals  32 ,  34 ,  36 , and  38 . It will be understood that the chemical compound that makes up the tie layers  32 - 38  could be the same for each of the individual tie layers, or alternatively, some of the tie layers could be of one compound while other tie layers are of a second compound, depending upon the adhesive-contacting properties of the actual shielding, barrier, or paperboard layers.  
     [0060] The properties of the various layers depicted in FIG. 2 will now be discussed in a certain detail. For example, at least one of the shielding layers  24  and  26  should be constructed to withstand steam sterilization, and should exhibit a relatively high heat resistance of at least 250° F. (about 121° C.). In addition, at least one of the shielding layers  24  and  26  would preferably be water and grease resistant, and approved for food contact. Moreover, if the shielding layer  26  is to be the inner layer (as illustrated in FIG. 2) of the can, then it would preferably exhibit food compatibility such that it would not interact with the food product after the product is placed into the can, for potentially long-term storage. The outer shielding layer (e.g., layer  24 ) may not necessarily need complete food compatibility, but would still need to be steam and heat resistant if it were to be sterilized in any process that would not isolate the outer shielding layer from the steam or heat itself. Of course, during a retort procedure, with the food product already in the can, the outer layer  24  must endure the retort conditions, including direct contact with steam.  
     [0061] The tie layers should provide good bonding between the paperboard substrate and the barrier layer for the tie layers  34  and  36 , and should provide good bonding between the barrier layer and the shielding layer for the tie layers  32  and  38 . The tie layers will also need to have a relatively high heat resistance (of at least 250° F.), and potentially will need to have the ability to withstand steam sterilization and otherwise be approved for food packaging compatibility. Of course, the tie layers will normally not come into direct contact with the food products, because the shielding layer would normally be the outermost layer that would be in contact with the food products. However, at the point of cutting the laminate material  20 , one or more of the tie layers could become exposed and thus potentially come into contact at a very small area with a food product.  
     [0062] The barrier layers  28  and  30  are mainly required to greatly inhibit transmission of moisture, oxygen, and flavor through the laminate material  20 . In addition, it would be preferred that the barrier layers can withstand steam sterilization and exhibit a relatively high heat resistance (at least 250° F.). For the same reasons as discussed with regard to the tie layers above, the barrier layers would preferably be approved for food contact and otherwise for food compatibility purposes.  
     [0063] The paperboard substrate  22  provides the main mechanical strength, and also is referred to herein as a “structural layer.” Paperboard layer  22  will preferably exhibit certain important properties, such as: high ring crush value, high puncture resistance, high tear resistance, high stiffness, high tensile strength, high bursting strength, high crimping properties, relatively low thickness, relatively low weight, relatively low extractability, and food compatibility.  
     [0064] The overall laminated structure of FIG. 2 can be constructed of relatively low cost materials while obtaining the properties described above. For each of the structural layers, processing compatibility and structural integrity are important for ease of manufacturing. Also of consequence is product protection capability, and the ability for a desirable appearance after the can has been manufactured and filled with the food product. For most applications, the retortable can of the present invention should be able to withstand 250° F. (about 121° C.) temperature for a minimum time period of sixty minutes and a minimum pressure of fifteen PSI. It would be preferred if the can&#39;s moisture resistance specification is less than 0.1 grams per one hundred square inches per day, and if the OTR (oxygen transmission rate) specification would be less than 0.1 cubic centimeters per one hundred square inches per day. Other desirable characteristics would be a physical strength of greater than one hundred fifty pounds TBC, and a product protection time interval of greater than six (6) months.  
     [0065] It should be noted that the above-described structure of FIG. 2 is substantially symmetrical with respect to the types of layers involved. There is a barrier layer (i.e., layers  28  and  30 ) on each side of the paper substrate  22 , and of course some type of shielding layer (i.e., layers  24  and  26 ) is also provided on each side of the paper substrate. Both barrier layers may not be necessary in many designs for retortable cans; however, it may be desirable to use a symmetrical laminate structure (such as laminate material  20 ) to construct cans in a high-speed automatic process manufacturing line, so that either side of the laminate  20  can be skived or folded when creating corners or side seams. It really depends upon the precise manufacturing system and the shapes of the corners and seams.  
     [0066] Once the various layers are laminated together into the laminate material  20  (as illustrated in FIG. 2), cylindrical retortable cans can easily be made in a continuous operation, including a continuous tube-forming operation that is partially illustrated in FIG. 3. In FIG. 3, a tube-forming station, generally designated by the reference numeral  40 , is illustrated, which takes a web of the laminate material and forms it around a mandrel to create a cylindrical tube, after which a longitudinal seam (also known as a “body seam” or a “side seam”) is formed.  
     [0067] The web of laminate material  20  is first directed over a stationary tension roller  42 , and then re-directed toward an adjustable tension roller  56 . By the time the web of laminate material  20  has reached this stage, it has already been slit to the proper width (to form the correct diameter can), and in some processes has already been skived along its outer edges, which is useful for quickly forming a durable longitudinal seam.  
     [0068] The laminate web is now directed over a forming roller  58 , and then the web is directed over a V-shaped collar that is not visible on FIG. 3, but is formed of members that are at locations using dashed lead-lines designated by the reference numerals  70  and  72 . The web of laminate material covers the collar  70 ,  72  at this point, at the areas designated by the reference numerals  46  and  48 . The web of laminate material is also formed about a mandrel  44 , which creates the cylindrical shape that will become the retortable can&#39;s final shape.  
     [0069] The web of laminate material is now directed downward (when viewed in FIG. 3), and has now become a hollow cylinder as seen at the reference numeral  52 . The laminate material overlaps itself along a longitudinal edge, as seen at reference numeral  54 . The cylindrical material continues downward at the reference numeral  50 , and will become sealed along this longitudinal overlay, to create the (body seam, side seam) longitudinal seam. This is depicted in greater detail in FIG. 4.  
     [0070]FIG. 4 shows the cross-sectional view of the cylindrical laminated material  20  as it is being directed down the tube-forming mandrel  44 . The side edges of the laminated web have been formed into protruding and folded fingers that overlap one another, as illustrated at the reference numerals  60  and  62  in FIG. 4. These overlapping and folded protrusions are glued or otherwise affixed in place, preferably by an adhesive compound or sealant illustrated at  64 . Further details of the manufacturing and forming of these protrusions  60  and  62  are provided in FIGS.  5 - 8 .  
     [0071] It will be understood that the folded fingers design illustrated in FIG. 4 can be used with both a longitudinal or side seam, and with a spiral-wrapped (or convolute-wrapped) retortable can design. This statement is also true for many of the other seam designs that are discussed below and illustrated in the drawings.  
     [0072] It will be further understood that references herein to a spiral container design or a convolute container design are often interchangeable. A spiral or tube shape is usually in reference to a “round” design, such as a hollow cylinder for the overall shape of the container. A convolute container may refer to a non-round shape, such as an oval, or a rectangular shape (typically with rounded corners) for the container when viewed from above the can.  
     [0073] Referring now to FIG. 5, the laminated material  20  is illustrated from an end view such that it has a left side edge  70  and a right side edge  72 . This would be the appearance of the laminated material as it is being formed into a web that will later become a cylinder. These side edges  70  and  72  are skived in an edge skiving operation (see step  510  on FIG. 26), after which two protrusions  74  and  76  remain along the edges of the laminate web  20 , as illustrated in FIG. 6. After these protrusions  74  and  76  are formed, they are folded back upon themselves as illustrated in FIG. 7 (see step  518  on FIG. 26). The protrusion  74  now becomes the folded member  82 , which has a 180° turn at  60 , and a sealant or adhesive  86  is used to hold the two portions of the protrusion  82  in place. In a similar manner, the protrusion  76  is folded back upon itself, and becomes the member  80 , which undergoes a 180° turn at  62 , and is adhered to itself by a sealant or adhesive  84 .  
     [0074] Once the fold-over members have been created, the web of laminate material  20  is formed around the mandrel  44  to form a hollow cylinder, and the members  80  and  82  come into relatively close contact with one another, as illustrated in FIG. 8. A sealant or adhesive material is applied between these members  80  and  82 , as depicted at  64  on FIG. 8. The edge sealant is applied at a step  520  on FIG. 26, and the cylindrical tube is formed at a step  522 .  
     [0075] The result is a longitudinal seal, generally depicted by the reference numeral  150 . If the upper portion of FIG. 8 is the outer surface of the retortable can, then a member  170  forms this outer surface along the longitudinal seal, and a member  172  forms the inner surface of the longitudinal seal. Other configurations for making longitudinal seals are discussed below, and other configurations for creating a cylindrical laminated material surface are described below.  
     [0076] Referring now to FIG. 9, a relatively square corner seal is illustrated and is used to hold the top of the can  14  to the cylindrical surface of the can  12 . This corner seal would typically not be made until after the can has been filled with a food product or other type of liquid to be stored therewithin. In FIG. 9, the end of the cylindrical tube  12  is bent at right angles, as illustrated at  106 , to create a reinforcing member for additional mechanical strength. The lidding material  14  is also bent at 90°, as depicted at  108 , so as to surround the reinforcing member portion  106  of the side wall material  12 . A sealant material is applied at  110  to provide a permanent bond between the structural members  106  and  108 .  
     [0077] Referring now to FIG. 10, some details of the bottom portions of the can construction are illustrated. The lidding material at  116  is formed into a relatively right-angle shape, as illustrated at  114 . The side wall of the can (at  12 ) is then placed against this corner construction  114 , with a sealant material at  112  interposed therebetween to create a permanent bond. In FIG. 10, the remaining portion of the lidding material at  116  is substantially planar in shape.  
     [0078] An alternative construction for the corner seal is illustrated in FIG. 11, in which the end of the cylindrical body of the can is formed in a circular or arcuate shape, as depicted at  102 . The lidding material is now formed in a ring (or arcuate) shape, as illustrated at  104 , to encompass the circular or ring-like shape at  102 . Again, a sealant material at  110  is used to provide a permanent bond between the members  102  and  104 .  
     [0079]FIG. 12 illustrates an alternative construction for the bottom portions of the retortable can of the present invention. The side wall material  12  is not straight throughout its run to the bottom of the can, but instead forms a half-circle near its bottom terminus, as illustrated at  124 . The lidding material of the can is also formed into a half-circle, as depicted at  128 , and the most protruding portion of these two half circles of material at  124  and  128  are positioned such that they come quite close to one another, and are then bonded by a sealant material  122 . The remaining portion of the lidding material has an indentation in this embodiment, as seen at  126 .  
     [0080]FIG. 13 is a cross-sectional view of an alternative embodiment of laminate material  21  used to make the retortable can  10 , and in this figure the various layers are portrayed in a more correct appearance with regard to the ratio of actual dimensions. As can be seen in FIG. 13, the paperboard substrate  22  makes up the largest component by far, and the shielding layers and barrier layers are quite thin by comparison. Moreover, the thickness of the tie layers is minimized to the extent possible while ensuring proper bonding and structural integrity of the other laminate layers, but at the same time to minimize costs by using a minimum amount of tie layer material.  
     [0081] It should be noted that, in FIG. 13, there is only a single barrier layer at  30 . This illustrates the possibility of deleting the “second” barrier layer as it was illustrated at  28  in FIG. 2; of course, the associated tie layer  38  could then also be deleted from the structure  20  in FIG. 2, as is illustrated in FIG. 13. If the “interior” barrier layer  30  has sufficiently great reduction of transmission properties for oxygen and moisture, etc., then perhaps only a single barrier layer is needed within the entire laminate structure  21 .  
     [0082] It will be understood that for most (or all) purposes of the present invention, either laminate material structure (i.e., laminate  20  in FIG. 2 or laminate  21  in FIG. 13) can be used, and in effect, laminates  20  and  21  are substantially interchangeable with one another. In many of the illustrations herewith, the laminated material of the present invention will be referred to as both reference numerals  20  and  21 . With regard to the written description, both laminates  20  and  21  in general will sufficiently serve the purposes and provide the important advantages of the present invention, and a reference to only the laminate  20  will, by inference, typically apply to the alternative structure laminate  21 .  
     [0083] It will be understood that there are certain circumstances where the barrier layers and shielding layers could be combined into a single layer of material that would exhibit the necessary properties to perform the functions of both the shielding and barrier layers. This would also eliminate one of the tie layers. Furthermore, it may be possible to coat the paperboard substrate with a material that would not only provide the necessary shielding and/or barrier properties, but may also be self-adhering and therefore, eliminate the need for a tie layer at all. This aspect of the present invention will be discussed in greater detail below.  
     [0084] It will be further understood that the materials used for the two shielding layers  24  and  26  will often be identical, however, that need not be the case for all structures that are encompassed by the present invention. Many different materials can be used for these shielding layers, and a listing of examples of such is provided below. The same is true for the barrier layers  28  and  30  when the laminate structure  20  is used-i.e., if there are two separate barrier layers, then their materials may be identical, but that need not be the case for all structures that are encompassed by the present invention. A listing of example materials for the barrier layer(s) is also provided below.  
     [0085]FIG. 14 portrays one of the overlapping longitudinal seams, generally designated by the reference numeral  150 . In FIG. 14, the protruding fingers or members are designated at the reference numerals  170  and  172 , forming the outermost and innermost layers at the seam, respectively. Of course, these two sets of protruding fingers are bonded together by a layer of sealant or adhesive  180 . In FIG. 14, the seam is larger in dimension with respect to the overall circumference of the can, as compared to the earlier examples illustrated in FIG. 4.  
     [0086] An alternative construction of the retortable can&#39;s cylindrical walls is illustrated in FIG. 15. Instead of a single laminate layer that is constructed using a longitudinal seam, FIG. 15 illustrates a convolute or spiral-shaped construction. A body joint at  180  is formed at the outermost surface where the laminated material is skived at an angle to form the outer member  190 . A sealant or adhesive is applied along the contact surface (i.e., at  194 ) between the outermost layer of material  190  and the center layer of material  184  at this portion of the circumference of the can. A corresponding inner body joint is formed at  182 , which is the innermost terminus of a skived member  192  that also is skived at an angle. A sealant or adhesive material is applied between the innermost member  192  and the center laminated layer at  184 . This adhesive or sealant material is applied along the contact surface at  196 .  
     [0087] By use of this convolute or spiral configuration, the retortable can of the present invention can be made with a non-longitudinal side seal, and will result in a can having a structure that is illustrated in FIG. 19, described below.  
     [0088] FIGS.  16 - 18  illustrate different configurations for a longitudinal seam along the side of the hollow cylindrical shape that forms the retortable can of the present invention. Referring now to FIG. 16, two different portions of the laminate material  20  are illustrated at  206  and  208 . Both of these end portions have already been skived, and therefore, exhibit protrusions at  202  and  204 . A sealant or adhesive material is placed along the inner surfaces of these two protrusions, essentially along the Z-shaped line at  210  on FIG. 16. This creates a longitudinal seal, generally designated overall by the reference numeral  200 .  
     [0089] Referring now to FIG. 17, the laminate material  20  is illustrated as two portions  226  and  228 , in which their end edges are brought together to form a longitudinal seal. The left-hand edge in FIG. 17 is designated at the reference numeral  222 , while the right-hand edge is designated at the reference numeral  224 . A small portion of the protrusions  222  and  224  is removed by a skiving operation, to form a small indentation along their outer surfaces. A sealant material is then placed into these indentations, which are illustrated on FIG. 17 at  230 . A sealant material is also used to join the two edges together, as illustrated at  232 . This forms a longitudinal seal, which is generally designated as an overall structure by the reference numeral  220 .  
     [0090] If desired, in an alternative construction the sealant at the areas  230  can be replaced by two solid reinforcing members having the necessary chemical and physical properties. Of course, such reinforcing members  230  would need to have resistance to relatively high heat (e.g., for a steam sterilization step) and chemical resistance to food products. Moreover, such reinforcing members would have to have the necessary adhesive characteristics so that they would be adherable to the sealant used at  232 .  
     [0091] Referring now to FIG. 18, the laminated material  20  is illustrated as having two portions at  246  and  248 . These represent the edges of the laminate after it has been formed into a cylinder. These two edges are brought together and affixed to one another using a sealant or an adhesive at  250 . In addition, a reinforcing member  242  is placed along the inner surface  244  of the members  246  and  248 . This reinforcing member can be made of any desirable material, but obviously would need to have proper qualities so that it would adhere to the adhesive or sealant  250 . Moreover, if it is to be used in a retortable can, the reinforcing member  242  must also have the necessary physical and chemical properties to withstand high temperature and to be compatible with food products. By use of this configuration, the longitudinal seam is formed at  250  along with the reinforcing member  242 , and the overall structure is generally designated by the reference numeral  240 .  
     [0092] It will be understood that the sealant materials or adhesive materials that are described in the various embodiments herein must also exhibit the necessary physical and chemical properties. In other words, the sealant (and adhesive) material itself must be able to withstand the high temperatures and steam or moisture-resistant properties so that it can be used in a sterilization process. Moreover, it must have chemical properties such that it would not react with or leach out into any type of food product that it may come into contact with in the interior surfaces of the retortable can.  
     [0093] The sealant material could comprise a thermoset adhesive, but would be required to withstand retort conditions of sterilization, for example. The top and bottom end members  14  and  16 , respectively, could be made of the same laminate material  20  that is primarily paperboard, if desired. Of course, the top member  14  could also be a standard aluminum flip-top lid that is used in conventional pet food cans, or could be a standard aluminum flip-top lid used to contain carbonated beverages, or other types of juices. Such a design is illustrated in FIG. 20, described below.  
     [0094] As noted above, the laminated paperboard material  20  can be converted to a cylinder either by a spiral winding or by a longitudinal edge sealing procedure. While the edge sealed embodiment is illustrated in FIG. 1, the spiral-wound cylinder embodiment is illustrated in FIG. 19. Referring now to FIG. 19, the retortable can is generally designated by the reference numeral  300 . Its cylindrical sidewall structure is designated at the reference numeral  312 , and is sealed in a spiral pattern along the lines  320  and  322 . One of these spiral curves  320 ,  322  represents the outer seal (i.e., which would be equivalent to the body joint  180  on FIG. 15) while the other spiral such as  322  would represent the inner body joint (e.g., equivalent to the body joint  182  on FIG. 15). These two spiral seals may be constructed of two “half-structures” that each consist of a different laminated material; this type of construction is described below in greater detail, in reference to FIGS. 29 and 30.  
     [0095] The top of the spiral-wound can  300  is illustrated at  314 , while the bottom cannot be seen in this view, but is designated in dashed lines at  316 . The actual corner seals to adhere the top and bottom end surfaces to the cylindrical hollow laminated surface can be made up of the types of corners illustrated in FIGS.  9 - 12 , as discussed above.  
     [0096] Referring now to FIG. 20, a retortable can generally designated by the reference numeral  350  is illustrated as having a cylindrical sidewall at  352 , a top  354 , and a bottom that is not visible in this view, but is generally designated by the reference numeral  356  in dashed lines. This retortable can could use the materials of the present invention for the cylindrical wall  352  and the bottom lid or end  356 . However, a metallic material might be best for the top lid  354 , and a metallic ring at  360  could then be provided to open the package. This could be the standard aluminum flip-top lid that is commonly used for pet food cans and for other types of foods and beverages.  
     [0097] FIGS.  21 - 25  illustrate a process by which a longitudinal seam is constructed in a similar manner to the process and structure illustrated in FIGS.  5 - 8 , however, in this instance the protruding fingers become interlocked. In FIG. 21, two portions of laminated paperboard material  20  are illustrated at  406  and  408 . Both of these “end” portions have already been skived, and a protrusion  400  has been made in the end portion  406 , while a protrusion  402  has been made in the end portion  408 .  
     [0098] In FIG. 22, the next process step is being performed, in which the tip portion of the protrusion  400  has started to be bent, as illustrated at  410 . Similarly, the tip portion of protrusion  402  has begun to be bent at  412 . Additionally, the two end portions  406  and  408  have been brought closer to one another. In FIG. 23, the next step of the process is illustrated by which the tip  420  of the protrusion  400  has been bent further, and now has exhibited a 90° angle. Similarly, the tip portion  422  of protrusion  402  has been bent to the same degree. In FIG. 24, the following process step is illustrated, by which the two protrusions  400  and  402  have been made into a U-shape, at their tip portions  430  and  440 , respectively.  
     [0099]FIG. 25 illustrates the final form of the longitudinal seal, which is generally designated as an overall structure by the reference numeral  446 . The two protrusions  400  and  402  have both been completely bent into a U-shape, as illustrated at their tip portions  440  and  442 . A sealant or adhesive material has been applied at  444  to maintain the positioning of the interlocking protrusions, and to make sure that they are affixed well to one another. Similar to the seals described above, the adhesive or sealant material  444  will need to have certain physical and chemical properties, and for use in a retortable can the sealant would need to have a relatively high temperature capability, and would need to be compatible with foods and/or beverages.  
     [0100]FIG. 26 is a flow chart that illustrates some of the important steps in a manufacturing process to create retortable cans that are based on a laminated paperboard material. Beginning with a paperboard master roll at a step  500 , the paperboard material is first directed through an unwinding operation at a step  502 . At this time, the paperboard material or web is slit to its proper width (i.e., to create a can of the proper diameter) at a slitting step  504 . After that has occurred, the web of material is sent through a rewinding step  506 , where it once again becomes a roll. At this point, the “siit roll” could be stored for a long time duration, if desired. This “storing” procedure can decouple the winding step  506  from the next step in the manufacturing process, so that the slit rolls can be stored until needed, perhaps much later.  
     [0101] The next step in the manufacturing operation is an unwinding step  508 , after which the web of material is directed through an edge skiving step  510 . It is at this step that, for example, the protrusions  74  and  76  as illustrated in FIG. 6, are formed. After being skived, the web of material is directed to a skived roll winding step  512 . At this point, the skived roll can be stored (at a step  514 ), if desired. Otherwise, the skived roll storing step  514  can be eliminated, and the skived roll can be immediately directed to a rewinding step  516 . This forms a web of material that is next directed to a skive folding step  518  which, for example, forms the U-shaped fingers or protrusions  80  and  82  as illustrated in FIG. 7. After this skive folding step  518 , the web of material has a sealing compound applied to its edges at a step  520 .  
     [0102] Once the sealing compound has been applied to the web, it is important that the paperboard web be more or less immediately formed into a tube, by use of a structure and method as illustrated in FIG. 3, for example. This occurs at a continuous tube-forming step  522  on the flow chart of FIG. 26.  
     [0103] Once the tube has been formed with either a side seal or a spiral-configuration seal, the next step in the process is to cut the tube into individual can sizes at a tube cutting step  524 . The next step in the process at  526  is to apply sealing compound to the ends. After that occurs, a bottom lid closing step  528  is used to attach the bottom end, such as the bottom end portion  16  on FIG. 1. The types of corner seals that could be used for forming these seals include those illustrated on FIGS.  9 - 12 , as described above.  
     [0104] The next step in the processing of the retortable can is to fill the can with a product at a step  530 . Once that has occurred, a top lid closing step  532  would likely need to be performed immediately, both to prevent germs or other undesirable compounds from reaching into the contents, and also to prevent any spillage. The top lid could be a laminated paperboard member such as the top  14  illustrated in FIG. 1. For certain products, it may be desirable to use a metal top with a ring opening mechanism. The top corners could be such as those illustrated on FIGS.  9 - 12 , as described above. Once the top lid closing step  532  has been performed, the final step is to distribute the retortable cans with their intact contents, at a final step  534 .  
     [0105] The materials used to create the laminated paperboard can be critical with regard to its retortable characteristics. The material of the paperboard layer itself may not be entirely critical, because it will generally be protected from physical contact with the food products. Of course, it still must be able to withstand the high temperatures of sterilization or other germ-killing procedures. In general, the paperboard could be unbleached Kraft paper, or SBS (solid bleached sulfate). The paperboard could be single or multi-ply, and it could be clay-coated, if desired.  
     [0106] The paperboard substrate would typically be coated on both sides with various layers, typically some type of plastic material or polymer to obtain suitable performance characteristics. As noted above, the structural layers and barrier layers would typically be affixed to one another with adhesive tie-layers, all of which would need to withstand retort temperatures, such that the complete structure is able to withstand the retort pressure and filling line pressure without leakage or mechanical damage.  
     [0107] The coated paperboard laminate could be symmetrical in its construction, if desired, or its inner surface could be somewhat different from its outer surface. Of course, its inner surface would be the one that normally comes into contact with the food products. Naturally, both the inner and outer surfaces would have to be able to withstand the retort temperatures and be able to withstand direct contact with steam when used in such a sterilization procedure. The inner layers must certainly be capable of withstanding moisture while also providing an oxygen barrier.  
     [0108] Many different types of structural layers could be used as a moisture and oxygen barrier. For example, amorphous nylon, moisture-resistant nylon blends, thermoplastic polyester (PET), crystallized polyester (CPET), polyethylene naphthalate (PEN), a PET-PEN blend, moisture resistant polyester, polypropylene (PP), or high crystallinity polypropylene (HCPP) could be used that have the ability to withstand moisture and retort temperatures.  
     [0109] The innermost layers could also be mainly composed of polymer layers that would meet the moisture, oxygen, and flavor barrier properties as well as the temperature and pressure requirements. Examples of such materials are PET-LCP alloys, or LCP (thermotropic liquid crystal polymer), or EVOH (ethylene vinyl alcohol copolymer) co-extruded coating, or EVOH-amorphous nylon blend as co-extruded coatings with suitable intervening adhesive tie-layers. An example of an LCP is VECTRA™ A-950 made by Allied-Signal.  
     [0110] As an alternative, the oxygen, flavor, and moisture barrier properties could be provided with materials such as silicon oxide (SiO x ), alumina (Al x O y ), or aluminum (Al) coated on one of the intervening polymers, or even a layer of aluminum foil.  
     [0111] For some applications, the layered material used in the present invention does not necessarily need both a shielding layer and a barrier layer on both sides of the paperboard middle (or core) layer. For example, if the barrier layer on the inner half of the layered material is sufficiently “strong” to prevent significant transmission of oxygen, moisture, and flavor, then a second barrier layer would not really be required on the outer half of the layered material.  
     [0112] Some further example structures encompassed by the present invention are listed below, in which the first (left-most) material listed represents the outermost layer, which typically would be covered with a label. The final (right-most) material listed above represents the innermost layer that would be in contact with the food product. The term “TL” represents a tie layer of adhesive or sealant material.  
                                          HCPP/TL   paperboard   TL/HCPP/TL/EVOH/TL/PET       HCPP/TL   paperboard   TL/EVOH-amorphous               nylon blend/nylon-6       nylon-6/TL/HCPP   paperboard   TL/HCPP/TL/EVOH/TL/PET       nylon-PP moisture   paperboard   amorphous nylon/       resistant blend       EVOH/TL/PET       moisture-resistant   paperboard   TL/LCP/TL/HCPP       polyester/TL       HCPP/TL   paperboard   TL/PET-LCP alloy/TL/CPET       CPET/TL   paperboard   TL/LCP/TL/CPET       PET-PEN blend/TL   paperboard   LCP/TL/amorphous nylon       PET/TL/SiO x /PET   paperboard   TL/nylon-6,6/TL/PP       moisture resistant PET/TL   paperboard   TL/Aluminum foil       PET/TL/Al x O y /PET   paperboard   TL/nylon-6,6/TL/PP       CPET/TL   paperboard   TL/SiO x /TL/CPET       PET/TL   paperboard   TL/PET metalized               with Al/TL/PET       PEN/TL/HCPP/TL   paperboard   EVOH/TL/HCPP       nylon-6,6/TL/HCPP   paperboard   TL/EVOH/TL/PP                  
 
     [0113] The layers of materials could be coated onto the paperboard substrate by commonly-known processing techniques, such as co-extrusion coating, extrusion lamination, or co-extrusion lamination, etc. The SiO x  or Al x O y  or aluminum could be deposited on a polymer layer or film, or on a PET-coated paperboard with a vapor deposition technique, also commonly known in the industry.  
     [0114] It will be understood that the exact materials used in constructing the laminated materials using the present invention are not inclusive, and other materials could be used without departing from the principles of the present invention. This is particularly true with respect to some of the various shapes of corner construction and seal construction of seals that are described above. Moreover, the manufacturing process steps are certainly not dependent upon any particular materials used in the web or laminated paperboard material that is described in more detail above. Furthermore, the exact shapes of the various seals illustrated herein can be changed with respect to dimensional proportions, again without departing from the principles of the present invention.  
     [0115] Further examples of laminate structures are illustrated in FIGS. 27 and 28. In FIG. 27, a laminated material generally designated by the reference numeral  450  includes most of the individual layers that were found in the laminate  20  depicted in FIG. 2. This includes two shielding layers  24  and  26  and two “outer” tie layers  32  and  38 , as well as a paper or paperboard substrate  22 . There is also a first barrier layer  30  that has an “inner” tie layer  34  that affixes first barrier layer  30  to the substrate  22 . However, the second barrier layer  452  has no tie layer interposed between the substrate  22  and second barrier layer  452 .  
     [0116] This laminate structure  450  can be accomplished, for example, by use of an extrudable nylon material for this second barrier layer  452 . By coating the paper/paperboard substrate  22  with extrudable nylon, a tie layer may be eliminated as compared to laminate  20  (of FIG. 2). Examples of appropriate extrudable nylon barrier layers include a nylon layer that is 0.5 mils (0.005 inches) in thickness, or eight to ten pounds per ream (i.e., per 3000 square feet of laminate material). A “high barrier” nylon may be used for this purpose.  
     [0117] In FIG. 28, another laminated material generally designated by the reference numeral  460  also includes most of the individual layers that were found in the laminate  20  depicted in FIG. 2. This again includes two shielding layers  24  and  26 , but only one “outer” tie layer  38 , as well as a paper or paperboard substrate  22 . There is only a single barrier layer  452  that, similar to the structure  450  in FIG. 27, has no tie layer interposed between the substrate  22  and second barrier layer  452 . Moreover, the only other tie layer at  462  is interposed directly between the substrate  22  and one of the shielding layers at  26 . In this laminate structure  460 , the “second” barrier layer is missing completely, and thus the tie layer  462  is used to affix the shielding layer  26  directly to the paper/paperboard substrate  22 . The material for tie layer  462  may be different than that of tie layer  38 , but that depends upon the exact materials used for the various individual shielding layers  24 ,  26 , barrier layer  452 , and substrate  22 .  
     [0118] It would be best if the shielding layer  26  for laminate structure  460  has some barrier characteristics, at least against moisture, and perhaps oxygen. A nylon film could be used for shielding layer  26  (see Example #12, below), or perhaps a layer of OUB-R film could be used (which is described below in greater detail).  
     [0119] As compared to the laminate structure  20  of FIG. 2, this alternative laminate  460  eliminates both a barrier layer and two tie layers. Of course the single barrier layer  452  must provide sufficient characteristics to reduce oxygen transmission, etc., and this barrier layer  452  should also have proper extrusion properties so as to be able to coat the paper or paperboard substrate  22  in a relatively fast manufacturing process to make this configuration a commercially viable one.  
     [0120] Another example of a spiral-wrapped construction is illustrated in FIG. 29, generally designated by the reference numeral  310 , which is based upon the structure illustrated in FIG. 19. In FIG. 29, two different laminate materials are used as the “half-structures” that make up a “total” laminate that is used for the entire sidewall of the cylindrical container  310 . The first laminate material is designated by the reference numeral  332  on one side of its spiral seam  320 , and by the reference numeral  334  on the other side of its spiral seam  320 . The second laminate material designated by the reference numeral  336  on one side of its spiral seam  322 , and by the reference numeral  338  on the other side of its spiral seam  322 . The first laminate is not precisely the same as the second laminate.  
     [0121]FIG. 29 depicts the various layers of the two “half-structures” that each consist of a laminate. For the laminate  332 , the outer layer  308  is a shielding layer, the adjacent layer  306  is a tie layer, the next adjacent layer  304  is a barrier layer, and the main substrate layer  302  is a paper or paperboard layer. The layer  330  represents an adhesive, which will be discussed further, below.  
     [0122] For the laminate  336 , the outer layer  348  is a shielding layer, the adjacent layer  346  is a tie layer, the next adjacent layer  344  is a barrier layer, the next further adjacent layer  342  is another tie layer, and the main substrate layer  340  is a paper or paperboard layer. When both of these half-structures  332  and  336  are spiral wrapped together, the two paper/paperboard layers  304  and  340  become adjacent to one another, separated only by the adhesive material at layer  330 . This adhesive  330  is, of course, compatible with affixing the two paper/paperboard layers to one another, regardless as to whether or not the paper layer  304  is made of the precise same material as the other paper layer  340 .  
     [0123] As can be seen from FIG. 29, the two half-structures  332  and  336  are not identical in structural form: the laminate  332  does not include a tie layer between its paper layer  302  and its barrier layer  304 , while the laminate  336  does include a tie layer  342  between its paper layer  340  and its barrier layer  344 . This is a situation in which the material used for the barrier layer  304  has been applied directly to the paper layer  302  without the need for an adhesive or sealant therebetween, such as the use of a nylon coating (e.g., at 8 pounds per ream) that has been extruded onto the paper layer  302 . In this example of FIG. 29, the tie layer  342  is used along with a material for barrier layer  344  that, for example, could be a sheet of aluminum foil. Many other examples of half-structures are discussed below which could be used in such a spiral container, or in a convolute container.  
     [0124] Referring now to FIG. 30, the spiral tubular structure  310  is viewed from its end, clearly showing the adhesive layer  330  being located between the two paper layers  302  and  340 . As can be seen on FIG. 30, the two paper layers  302 ,  340  end up comprising the middle layers of the “total” laminate  310 , and the non-paper layers consist of  342 ,  344 ,  346 , and  348  on the inner surface, while the non-paper layers on the outer surface consist of  304 ,  306 , and  308 .  
     [0125] As described above, the laminated structural material generally uses paper or paperboard material to provide strength and stiffness. Paper is structurally strong and stiff material when it is dry, and the general function of the shielding layer or material is to protect the paper structural layer from moisture during the retort process. To keep the structural integrity intact for the laminated material, the paper layer needs to be protected from moisture at all times. Therefore, the protection for the paper at the joints or seams is particularly important.  
     [0126] In one aspect of the present invention, the joints/seams are protected by a skiving and folding technique, and in this embodiment a uniform wall or laminated material thickness is maintained while the paper barrier layer remains shielded. At all times, the paper barrier remains as one of the inner layers, even at the joints, by using this inventive technique. At the same time, the shielding layers are always made to be the outside layers, and thus remain the only layers that come into contact with steam during the sterilization or retort process.  
     [0127] Referring now to FIG. 31, a side seam or body seam (e.g., for a longitudinal seal or a spiral seal) is illustrated, generally designated by the reference numeral  400 . A left (in this view) laminated structure  410  arrives from the left side in this drawing, while a right (in this view) similar laminated material  450  arrives from the right side in this drawing. The “left” structure  410  includes an innermost structural layer  412 , which generally is made of a paper or paperboard material.  
     [0128] In this particular embodiment, it is probably better if the laminated structure  410  is symmetrical, and from that standpoint this is in reference to the material and location of shielding layers  418  and  428 , and barrier layers  414  and  424 . In some of the embodiments described above, the “inner” and “outer” shielding layers were not always comprised of the same materials, and the same was true with respect to the barrier layers for the “inner” and “outer” portions of the laminated material. In fact, in some of the above-described embodiments, the barrier layer did not even exist on one of the “inner” or “outer” portions of the laminated structure. In the structure  400  of FIG. 31, the material will be skived, and thus the laminated material would probably be more useful if it was symmetrical from the standpoint of the types of barrier and shielding layers, and as such, either outer surface could be used as a protruding finger that will become part of the seam or joint. Alternatively, the layered-orientation and types of compounds used for the laminated material  400  could of course be made specific, and the shielding layers and barrier layers would not necessarily need to be symmetrical for both the inner and outer surfaces of the overall laminated material.  
     [0129] In the upper-left portion of FIG. 31, the shielding layer  418  and barrier layer  414  have a common surface at  416 , which in general would comprise a tie layer that would normally consist of an adhesive material. This tie layer will run down the length of the protruding finger, which will be described below. A similar common surface or tie layer at  426  is formed between the shielding layer  428  and barrier layer  424  that are illustrated in the lower-left corner of FIG. 31.  
     [0130] A protruding finger is formed by skiving the left-hand member  410  of the body seam  400 , and its initial rectangular segment (as seen on FIG. 31) is designated at the reference numeral  440 , which exhibits the “outer” shielding and barrier layers at  430 . This protruding finger continues after making a right angle change in direction, and becomes a rectangular member  442 , still with its “outer” barrier and shielding layers at  432 . After another change in direction at a right angle, the protrusion continues as a rectangular member  444 , again with its “outer” barrier and shielding layers at  434 . Continuing with another right angle change in direction, the protruding finger reaches a rectangular segment  446 , having its “outer” barrier and shielding layers at  436 . The final portion of the protruding finger is a rectangular member  448 , which still has its “outer” shielding and barrier layers at  438 .  
     [0131] The portion of the body seam  400  that arrives from the right (i.e., the member  450 ), includes a main structural layer  452 , that generally will be made of a paper or paperboard material. This laminated material  450  includes an outermost shielding layer  468  and a barrier layer  464 , separated by a common surface or a tie layer  466 , as viewed in the upper-right portion of FIG. 31. A similar shielding layer  458  and barrier layer  454  are joined by a surface or tie layer at  456 , in the bottom-right corner of FIG. 31.  
     [0132] This right-member  450  is skived in a similar manner to the left-member  410 , and will thus exhibit a protruding finger that will be described next. The protruding finger after the skiving operation begins as a rectangular member  480 , which exhibits an outer shielding and barrier layer at  470 . The protruding finger continues after making a right angle change in direction as a rectangular member  482 , also exhibiting an “outer” shielding and barrier layer at  472 . After another right angle change in direction, the protruding finger continues as a rectangular member  484 , which exhibits its “outer” barrier and shielding layers at  474 , and this is followed by another right angle change in direction to a rectangular member  486  that exhibits its “outer” barrier and shielding layers at  476 . A final rectangular member at  488  extends from the member  486  after making another right angle change in direction, and it also exhibits its “outer” shielding and barrier layers at  478 .  
     [0133] It will be understood that the continuous barrier and shielding layers that follow the protruding fingers all the way to the innermost portions of this body seam  400  need not necessarily literally extend all the way to this innermost portion. If desired, the barrier and/or shielding layers could themselves be removed (e.g., by a skiving operation) along any portion of these protruding fingers once they make their first or initial right angle change of direction, thereby “aiming” toward the middle portions of the structural paper layers  412  or  452 .  
     [0134] At the innermost portions of the body seam structure  400 , the skived paper layers meet along a set of line segments  494 , along their rectangular members  448 ,  446 ,  488 , and  486 . An adhesive material can be placed here if desired, although other adhesive contact can be made for this body seam that will likely keep these right-angle members joined together without an extra adhesive. The adhesive in the tie layers at the shielding and barrier layers may possibly be used for some of the structural integrity of the body seam  400 , although the entire structure would have to be heated above the melting point of the adhesive in the tie layers, if this was to be a desired methodology for permanently joining the two half-members  410  and  450  together.  
     [0135] On the other hand, the shielding layers must be used to protect the inner paper substrate layers, and this means that the outer joints at  490  and  492  need to be sealed in a manner that the shielding layers are essentially continuous through these joints  490  and  492 . One way to insure good structural integrity at these joints is to form the overall body seam structure at a seam-forming station, and while the members are held together mechanically, to also then raise the temperature of the entire structure above the melting point of either the shielding layer itself, or the tie layers that are in contact with the shielding layer at the barrier layers (i.e., the tie layers  466  and  426 ). In any event, it is important that the shielding layer in effect cover the entire joints at  490  and  492 , thereby keeping the inner paper substrate layers protected from moisture during retort or sterilization procedures. Of course, the actual shape of body seam  400  can be much different than illustrated in FIG. 31 without departing from the principles of the present invention.  
     [0136] Referring now to FIG. 32, a corner or end seal (or joint)  500  is illustrated, and generally comprises a first laminated material structure  510  and a second similar laminated material structure  530 . The laminated material structure  510  could comprise a lid of a retortable can, and in FIG. 32 includes an inner paper or structural layer  516 , as well as outer shielding and/or barrier layers at  512  and  514 . This laminated material continues into the joint along rectangular segments  520 ,  522 ,  524 , and  526 . As can be seen in FIG. 32, this laminated material that makes up the member  510  is not necessarily skived to make this end seal.  
     [0137] The other structural member  530  also is made of a laminated material, which includes an inner structural layer  536  (made of paper or paperboard in a preferred embodiment), and also includes outer shielding and/or barrier layers at  532  and  534 . This laminated material of member  530  continues along rectangular segments  540 ,  542 ,  544 ,  546 , and  548 .  
     [0138] As in all of the laminated materials used in the present invention to make retortable cans, generally it is important to keep the inner structural layers dry, particularly if they are made of a paper or paperboard material. Therefore, the “joints” where the two members  510  and  530  meet need to be maintained as liquid-tight joints (i.e., as seals), and also protective against steam used in many sterilization or retort chambers. These joints/seals  560  and  562  can comprise a separate adhesive, if desired, or in another form of this embodiment, these joints/seals could comprise the shielding layers themselves, if such shielding layers are also capable of acting as an adhesive when they are raised above their melting temperature and allowed to flow from one of the members  510  to the other member  530 , for example. When cooled, the shielding layers could then form a continuous liquid-tight and steam-protective joint/seal at these locations  560  and  562 .  
     [0139] Additional detailed examples of materials that may be used in the laminate structures of the present invention are presented below. As in the above examples, the first (left-most) material listed represents the outermost layer, while the last (right-most) material listed represents the innermost layer. In the listings below, the abbreviations used have the following meanings:  
     [0140] S=shielding layer  
     [0141] B=barrier layer  
     [0142] P=paper or paperboard layer  
     [0143] T=tie layer  
     EXAMPLE #1  
     S/T1/P/T2/B/T3/S, where:  
     [0144] Both S are a moisture protective layer, e.g., high crystalline PP (HCPP);  
     [0145] T1 and T2 are tie layers made of maleic anhydride modified polyolefin;  
     [0146] T3 is a tie layer made of: ethylene, acrylic ester, or maleic anhydride terpolymers;  
     [0147] P is made of: 10 point cupstock or 10 point Kraftboard (i.e., 10 points=10 mils=0.010 inches);  
     [0148] B is an oxygen barrier layer made of: EVOH, Am Nylon, PET-LCP, Al foil, metalized PET, SiO x , or PET; or  
     [0149] B may also have a “rigidity” enhancement property, made of: Nylon 6-6, CPET, PET-PEN, or PET-LCP.  
     EXAMPLE #2  
     S/T/B1P/T/B2/T/S, where:  
     [0150] Both S are 1 mil HCPP;  
     [0151] T are any appropriate tie layer material;  
     [0152] The outer B is nylon;  
     [0153] P is any appropriate paper;  
     [0154] The inner B is Al foil, 0.00028 inches thick.  
     EXAMPLE #3  
     S/T/B1/P/T/B2/T/S, where:  
     [0155] Both S are 12-16 pounds/ream HCPP;  
     [0156] T are any appropriate tie layer material;  
     [0157] B1 is nylon;  
     [0158] P is any appropriate paper;  
     [0159] B2 is Al foil, 0.00028 inches thick.  
     EXAMPLE #4  
     S/T/B1/P/T/B2/T/S, where:  
     [0160] Both S are 1 mil HCPP;  
     [0161] T are any appropriate tie layer material;  
     [0162] B1 is 0.5 mil nylon;  
     [0163] P is 12 point paper;  
     [0164] B2 is Al foil, 0.00028 inches thick.  
     EXAMPLE #5  
     S/T/B1/P/T/B2/T/S, where:  
     [0165] Both S are 1 mil, or 12-16 pounds/ream HCPP;  
     [0166] T are 0.5 mil or 3-5 pounds/ream of any appropriate tie layer material;  
     [0167] B1 is 0.5 mil or 8-10 pounds/ream nylon;  
     [0168] P is 16 point paper;  
     [0169] B2 is Al foil, 0.00028 inches thick.  
     EXAMPLE #6  
     S/T/B1/P/T/B2/T/S, where:  
     [0170] Both S are 1 mil, or 12-16 pounds/ream HCPP;  
     [0171] T are 0.5 mil or 3-5 pounds/ream of any appropriate tie layer material;  
     [0172] B1 is 0.5 mil or 8-10 pounds/ream high barrier nylon;  
     [0173] P is 16 point paper;  
     [0174] B2 is Al foil, 0.00028 inches thick.  
     EXAMPLE #7  
     S/T/B1/P/B2/T/B3/T/S, where:  
     [0175] Both S are 12-16 pounds/ream HCPP;  
     [0176] T are 3-5 pounds/ream of any appropriate tie layer material;  
     [0177] B1 and B2 are 8-10 pounds/ream high barrier nylon;  
     [0178] P is 16 point Everest Cup stock;  
     [0179] B3 is 70 gauge metalized PP.  
     EXAMPLE #8  
     S/Ti/B1/P/T2/B2/T3/S, where:  
     [0180] Both S are 12-16 pounds/ream PP (Montell PF 611);  
     [0181] T1 and T3 are 3-5 pounds/ream Morton Tymor 2205;  
     [0182] B1 is 8-10 pounds/ream nylon (Allied Capron 2120 FN);  
     [0183] P is 20 point Everest Cup stock paper CS 1357;  
     [0184] T2 is 5-8 pounds/ream Dow Primacor 3460;  
     [0185] B2 is Al foil, 0.00028 inches thick.  
     EXAMPLE #9  
     S/T/B1/P/T2B2/T3/S, where:  
     [0186] Both S are 14 pounds/ream PP;  
     [0187] T1 and T3 are 3 pounds/ream of any appropriate tie layer material;  
     [0188] B1 is 8 pounds/ream nylon;  
     [0189] P is 210 pounds/ream paperboard;  
     [0190] T2 is 5 pounds/ream of any appropriate tie layer material;  
     [0191] B2 is 12 pounds/ream Al foil.  
     EXAMPLE #10  
     S/T1/B1/T2/P/B2/T3/S, where:  
     [0192] Both S are 16 pounds/ream PP;  
     [0193] T1 is 5 pounds/ream of any appropriate tie layer material;  
     [0194] B1 is Al foil, 0.00028 inches thick;  
     [0195] T2 is 8 pounds/ream of any appropriate tie layer material;  
     [0196] P is 20 point paperboard;  
     [0197] B2 is 10 pounds/ream nylon;  
     [0198] T3 is 3 pounds/ream of any appropriate tie layer material.  
     EXAMPLE #11  
     S1/T/B1/P/B2/S2, where:  
     [0199] S1 is 16 pounds/ream PP;  
     [0200] T is 5 pounds/ream of any appropriate tie layer material;  
     [0201] B1 is 10 pounds/ream nylon;  
     [0202] P is 20 point paperboard;  
     [0203] B2 is 12 is Al foil, 0.00028 inches thick;  
     [0204] S2 is OUB-R nylon film (Allied Signal).  
     EXAMPLE #12  
     S1/T/B/P/T/S2, where:  
     [0205] S1 is HCPP;  
     [0206] T are any appropriate tie layer material;  
     [0207] B is nylon;  
     [0208] P is any appropriate paper;  
     [0209] S2 is nylon film.  
     [0210] As noted above, some of the laminate materials can be formed from two “half-structures” that each consist of a laminate that has a paper or paperboard layer at one of its outer surfaces, and which are spiral wound and affixed into position during the spiral tube-forming operation. The paper/paperboard layer of the first component (half-structure) is placed adjacent to the paper/paperboard layer of the second component (half-structure), and an adhesive material is applied between these two paper/paperboard layers. Examples of such half-structures are as follows:  
     EXAMPLE #13  
     S/T/B/P, where:  
     [0211] S is PP;  
     [0212] T is any appropriate tie layer material;  
     [0213] B is nylon;  
     [0214] P is any appropriate paper.  
     EXAMPLE #14  
     P/T/B/T/S, where:  
     [0215] P is any appropriate paper;  
     [0216] T are any appropriate tie layer material;  
     [0217] B is Al foil;  
     [0218] S is PP.  
     EXAMPLE #15  
     P/T/B, where:  
     [0219] P is any appropriate paper;  
     [0220] T is any appropriate tie layer material;  
     [0221] B is nylon.  
     EXAMPLE #16  
     P/T/B/T/S, where:  
     [0222] P is any appropriate paper;  
     [0223] T are any appropriate tie layer material;  
     [0224] B is a blend of PET and LCP;  
     [0225] S is PP.  
     EXAMPLE #17  
     P/B/T/S, where:  
     [0226] P is 12 point paperboard;  
     [0227] B is 10 pounds/ream nylon;  
     [0228] T is 3 pounds/ream of any appropriate tie layer material;  
     [0229] S is 16 pounds/ream PP.  
     EXAMPLE #18  
     S/T1/B/T2/P, where:  
     [0230] S is 16 pounds/ream PP;  
     [0231] T1 is 3 pounds/ream of any appropriate tie layer material;  
     [0232] B is Al foil, 0.00028 inches thick;  
     [0233] T2 is 8 pounds/ream of any appropriate tie layer material;  
     [0234] P is 12 point paperboard.  
     EXAMPLE #19  
     P/B/S, where:  
     [0235] P is 12 point paperboard;  
     [0236] B is 12 pounds/ream nylon;  
     [0237] S is OUB-R film.  
     EXAMPLE #20  
     P/T/B/T/S, where:  
     [0238] P is 12 point paperboard;  
     [0239] T are 3 pounds/ream of any appropriate tie layer material;  
     [0240] S is 16 pounds/ream PP.  
     EXAMPLE #21  
     P/T/B/T/S, where:  
     [0241] P is 12 point paperboard;  
     [0242] T are 3 pounds/ream of any appropriate tie layer material;  
     [0243] B is 10 pounds/ream PET-PEN;  
     [0244] S is 16 pounds/ream PP.  
     EXAMPLE #22  
     [0245] Note that if one uses the laminate of Example # 13 as the first half-structure along with the laminate of Example #16 as the second half-structure, the total combination after being spiral-wrapped would have the following structure:  
     S1/T/B1/P1/A/P2/T/B2/T/S2, where:  
     [0246] A is an adhesive layer between the two paper substrate layers P1 and P2.  
     EXAMPLE #23  
     S/T1/B1/P/T2/B2/T3/S, where:  
     [0247] S are each 16 pounds/ream PP—Montell PF 611;  
     [0248] T1 is 3 pounds/ream—Morton Tymore 2205;  
     [0249] B1 is 10 pounds/ream nylon—Allied Capron 2120 FN;  
     [0250] P is 20 point Everest Cupstock paperboard—International Paper CS 1394;  
     [0251] T2 is 8 pounds/ream—Morton Tymore 2205;  
     [0252] B2 is Al foil, 0.00028 inches thick;  
     [0253] T3 is 5 pounds/ream—Morton Tymore 2205.  
     [0254] The above notation about OUB-R film refers to a three-layer film produced by Allied Signal Inc., which is described in detail in U.S. Pat. No. 5,547,765. The three layers essentially consist of a first outer nylon layer, a blend of nylon and EVOH, and a second outer nylon layer. If this OUB-R film is used on the side of the laminate that contacts the (food) product, then the film can act as a shielding layer. In fact, the three layers of the OUB-R film can essentially be viewed as three individual shielding layers; or the three layers of OUB-R can alternatively be viewed as a shielding layer (which would be placed at the surface of the overall laminate structure), and two “inner” barrier layers. Certainly the middle layer of OUB-R will act as an oxygen barrier, mainly due to the EVOH in the blend of nylon and EVOH of this middle layer.  
     [0255] As noted above, nylon can be applied to paperboard without use of a tie layer. Moreover, OUB-R film can be laminated to a nylon layer without use of a tie layer. Notations above for PET-PEN, or PET-LCP refer to a blend of the two resins that are applied as a single layer, where indicated.  
     [0256] Another material that can be used in the shielding layers is high density polypropylene (HDPP). This could be used in many of the above-described embodiments that include other forms of polypropylene, such as in lieu of polypropylene in the above Examples #9, #10, or #11. In Example #8, perhaps HDPP could be used in lieu of the Montell PF  611 . HDPP could also be used in shielding layers for the “half-structures” that are described in Examples #13, #14, #16, #17, #18, #20, #21, and #23.  
     [0257] The various material layers used in the present invention will often require different tie layer materials depending, for example, upon the precise materials used for the barrier or shielding layers. In general, a tie material or resin is used as an adhesive to chemically bond two adjacent layers, each of which have different end-group chemical functionality. Some common examples are provided below, and represent fairly common practice to those skilled in the art. These below examples first list the type of tie layer material, and then the types of adjacent layers materials:  
     EXAMPLE A:  
     [0258] Tie material: maleic anhydride modified polyolefin (MAPP);  
     [0259] used between: non-polar PP and polar paperboard.  
     EXAMPLE B  
     [0260] Tie material: ethylene acrylic ester;  
     [0261] or ethylene methacrylic acid with metal neutralization;  
     [0262] or ethylene methacrylic acid without metal neutralization;  
     [0263] used between: paper and Al foil.  
     EXAMPLE C  
     [0264] Tie material: maleic anhydride polypropylene;  
     [0265] used between: nylon and PP.  
     EXAMPLE D  
     [0266] Tie material: ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer;  
     [0267] used between: paper and PET.  
     [0268] It will be understood that in all cases, the product contact layer must have a shielding functionality, and that the use of certain materials will allow the product contact layer to also serve a dual purpose of providing a barrier functionality. An example of this configuration is given above in Example #12, in which a nylon film acts as both the inner shielding layer and a barrier layer between the paper substrate and the product.  
     [0269] The above Examples #1 through #23 have all been constructed as prototypes by the inventors and tested for retort conditions, and each of these Examples ##1-23 are able to withstand retort conditions. It will be understood that two primary factors will need to be considered before determining which precise construction will be used for manufacturing the final retortable can or container: (1) the cost of the materials making up the laminate structure, and (2) the ease of manufacturing such materials into the laminate structure. Of course, the “ease” of manufacturing involves its own set of factors, and capital equipment cost is always a consideration, but also the speed of the process will be balanced against the equipment cost.  
     [0270] If a very thick paperboard material is desired (or necessary) to contain a particular product, then certain shapes and sizes may not be an option. For example, the bending stresses to form the longitudinal (or side) seal as depicted in FIG. 3 may be greater than the bending stresses to form a spiral or convolute tube of a particular diameter.  
     [0271] The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.