Abstract:
A three or more layered plastic container is provided, wherein the innermost first layer is a plastic layer, the intermediate second layer is a plastic layer adjacent the first layer containing an oxygen scavenging material, and the outermost third layer is a plastic layer. The thickness of the innermost layer is in the range of 0.1 to 3 mils and is controlled based on the desired shelf life of the container in the unfilled condition.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is based on Provisional U.S. patent application Ser. No. 60/392,006, filed Jun. 25, 2002. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to multi-layered containers. More particularly, the present invention relates to blow molded multi-layered plastic containers.  
         BACKGROUND ART  
         [0003]    Multi-layered plastic containers are commonly used for packaging items in a wide range of fields, including food and beverage, medicine, health and beauty, and home products. Plastic containers are known for being easily molded, cost competitive, lightweight, and generally suitable for many applications. Multi-layered containers provide the added benefit of being able to use different materials in each of the layers, wherein each material has a specific property adapted to perform a desired function.  
           [0004]    Because plastic containers may permit low molecular gases, such as oxygen and carbon dioxide, to slowly permeate through their physical configurations, the use of plastic containers sometimes proves to be less desirable when compared to containers formed from other less permeable materials, such as metal or glass. In most applications, the shelf life of the product contents is directly related to the package&#39;s ability to effectively address such molecular permeation. In the case of carbonated beverages, such as beer, oxygen in the atmosphere surrounding the container can gradually permeate inwardly through the plastic walls of the container to reach inside of the container and deteriorate the contents. Likewise, carbon dioxide gas associated with the contents may permeate outwardly through the plastic walls of the container until eventually being released on the outside, causing the carbonated beverage to lose some of its flavor and possibly become “flat”.  
           [0005]    To address some of the foregoing concerns, plastic container manufacturers have utilized various techniques to reduce or eliminate the absorption and/or permeability of such gases. Some of the more common techniques include: increasing the thickness of all or portions of the walls of the container; incorporating one or more barrier layers into the wall structure; including oxygen-scavenging or reacting materials within the walls of the containers; and applying various coatings to the internal and/or external surface of the container. However, a number of conventional barrier and/or scavenger materials will not effectively curtail the permeation of both oxygen and carbon dioxide over extended periods of time. Moreover, there are usually other practical concerns associated with most conventional techniques, most commonly, increased material costs and/or production inefficiencies.  
           [0006]    In recent times, the use of plastics has become a significant social issue. Recycling has become an increasingly important environmental concern and a number of governments and regulatory authorities continue to address the matter. In a number of jurisdictions, legislation pertaining to minimum recycled plastic content and the collection, return, and reuse of plastic containers has either been considered or has already been enacted. For example, in the case of plastic containers used to hold consumable items, such as food items or beverages, regulations often require a certain content and minimum thickness of FDA approved material for the innermost layer that comes in contact with the contents. Conventional processes, such as co- or multiple-injection molding, are often limited as to the amount of recycled plastic that can be effectively incorporated into the structure of the container due to process limitations. Commonly, the amount of recycled content that can be effectively incorporated into conventional co-injection molded containers that are suitable for food contents is less than 40% of the total weight of the container.  
           [0007]    Therefore, a need exists in the industry for, and it is an object of the present invention to provide, an improved multi-layered plastic container including oxygen scavenging materials suitable for holding products such as carbonated beverages or other food products, and having a long shelf life.  
           [0008]    It is a further objective of the present invention to provide a multi-layered plastic container as aforesaid which may include desired levels of recycled material.  
           [0009]    It is a still further object of the present invention to provide a multi-layered plastic container as aforesaid which may be readily and conveniently prepared at a moderate cost.  
           [0010]    Further objects and advantages of the present invention will appear hereinbelow.  
         SUMMARY OF THE INVENTION  
         [0011]    In accordance with the present invention, the foregoing objects and advantages are readily obtained.  
           [0012]    It is desirable for multi-layered plastic containers to effectively utilize an oxygen-scavenging material. However, these materials may not be approved to come into contact with food or beverage if the container is used to hold these items. In a multi-layered container the innermost plastic layer would be a plastic material that is approved for contact with the food or beverage contents of the container.  
           [0013]    Moreover, after a container is manufactured, it often is not filled with food or beverage immediately. Naturally, one desires the oxygen scavenger material to begin working only after the container is filled. Disadvantageously, an oxygen scavenger may start to react prior to filling of the container, limiting the storage life of empty containers in inventory (not filled).  
           [0014]    In accordance with the present invention, a three or more layered plastic container is provided, wherein  
           [0015]    an innermost first layer is a plastic material, preferably approved for contact with food or beverage products,  
           [0016]    an intermediate second layer is a plastic material adjacent the first layer containing an oxygen scavenger material; and  
           [0017]    an outermost third layer is a plastic material, desirably containing recycled plastic,  
           [0018]    wherein the thickness of the innermost layer is in the range of 0.1 to 3 mils and is controlled based on the desired shelf life of the container in the unfilled condition, i.e., the thicker the innermost layer in this range the greater the protection afforded the oxygen scavenger material.  
           [0019]    Thus, for example, it has been found that a three layered plastic container with an innermost layer of polyethylene terephthalate (PET) that is 0.5 mils thick, and with an intermediate plastic layer containing an oxygen scavenging material, can be stored in a warehouse in the unfilled condition for at least six (6) weeks without the oxygen scavenging material beginning to react with oxygen. When the container is thereafter filled with product, as for example, a beverage, the oxygen scavenging material will be fully effective to protect the product. Naturally, the innermost layer may be thicker if longer protection times are desired in the unfilled condition, and thinner if shorter protection times are desired.  
           [0020]    The process of the present invention comprises:  
           [0021]    forming a plastic container with three or more layers of plastic, with  
           [0022]    the innermost first layer being a plastic layer preferably approved for contact with food or beverage products,  
           [0023]    the intermediate second layer is a plastic layer adjacent the first layer containing at least one oxygen scavenger material, and  
           [0024]    the outermost third layer is a plastic layer, preferably containing recycled plastic,  
           [0025]    including the step of controlling the thickness of the innermost layer in the range of 0.1 to 3 mils based on the desired shelf life of the container in the unfilled condition.  
           [0026]    Further features of the present invention will appear hereinbelow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    The present invention will be more readily understandable from the following illustrative drawings, wherein:  
         [0028]    [0028]FIG. 1 is an elevational view of a preform for forming a container in accordance with the present invention;  
         [0029]    [0029]FIGS. 1A, 1B and  1 C are enlarged cross-sectional views of various areas of the preform of FIG. 1;  
         [0030]    [0030]FIG. 2 is an elevational view of a container of the present invention; and  
         [0031]    [0031]FIGS. 2A, 2B and  2 C are enlarged cross-sectional views of various areas of the container of FIG. 2.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]    The molded innermost plastic layer is comprised of a thermoplastic material. The following resins are representative of resins that may be used as plastic materials for the innermost layer: polyethylene, polypropylene, polystyrene, cycloolefin copolymer, polyethylene terephthalate, polyethylene naphthalate, ethylene-(vinyl alcohol) copolymer, poly-4-methylpentene-1, poly (methyl methacrylate), acrylonitrile, polyvinyl chloride, polyvinylidene chloride, styrene-acrylo nitrile, acrylonitrile-butadiene-styrene, polyamide, polyacetal, polycarbonate, polybutylene terephthalate, ionomer, polysulfone, polytetra-fluoroethylene, and the like. When food product contents are involved, the innermost layer should be formed from resins approved for contact with food products, as virgin polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and/or blends of polyethylene terephthalate or polyethylene naphthalate. However, other thermoplastic resins approved for contact with food products may also be used.  
         [0033]    The molded outermost layer may be any desired plastic material, such as those set out hereinabove.  
         [0034]    Desirably, the molded outermost layer includes recycled plastic material, including the plastics set forth above, but is preferably formed from recycled polyethylene terephthalate.  
         [0035]    However, the invention is not limited to a particular type of recycled plastic and other recycled plastic materials may be used. Moreover, any desired amount of recycled plastic material may be used in the outermost layer, for example, at least five (5) percent, at least forty (40) percent, or at least ninety (90) percent. Further, the outermost layer desirably comprises at least 40% by weight of the total weight of the container, but can comprise at least 85% by weight of the total weight of the container. The outermost layer generally has a wall thickness, taken along its vertical length, that is in the range of 3 to 23 mils (0.1524 mm to 0.5842 mm). Moreover, the thicknesses of each layer can be separately and independently varied along their vertical length, as desired.  
         [0036]    The intermediate layer is a plastic layer that contains an oxygen scavenging material. Oxygen scavenging materials are well known and include materials marketed for such a purpose by several large oil companies and resin manufacturers. A specific example of such a material is marketed under the trade name AMOSORB and is commercially available from the Amoco Corporation. Polyolefin oligomer segments are prepared for copolycondensation by first functionalizing the polyolefin oligomer segments with end groups capable of entering into polycondensation reactions The polyolefin oligomers are, in effect, addition polymers. Functionalization of the polyolefin oligomers with end groups affords a convenient method for incorporation of addition polymer segments into a copolycondensate. A preferred polyolefin oligomer as an oxygen scavenger in the present invention is polybutadiene because it has good oxygen scavenging capacity and reacts quickly with oxygen especially in the presence of a transition metal catalyst, such as cobalt, and in the presence of benzophenone, or both cobalt and benzophenone. Desirably, the intermediate layer can be made of or include a barrier material. The barrier material or layer is desirably an oxygen barrier and is preferably formed from PEN, saran and ethylene vinyl alcohol copolymers (EVOH) or acrylonitrile copolymers, such as Barex. The term saran is used in its normal commercial sense to contemplate polymers made for example by polymerizing vinylidene chloride and vinyl chloride or methyl acrylate. Additional monomers may be included as is well known. Vinylidene chloride polymers are the most commonly used, but other oxygen barrier materials are will known.  
         [0037]    Naturally, other layers may be provided as desired.  
         [0038]    The container of the present invention may be formed by any of several known processing techniques which permit the manufacture of a multi-layered blow molded plastic container having a plastic molded inner layer and a relatively thick molded plastic outer layer which may include recycled plastic, and an intermediate plastic layer, all as aforesaid. In a preferred embodiment, the multi-layered container is formed via a blow molding operation involving a multi-layered preform. Although not a required feature, the preform may include a neck flange, which is convenient for handling purposes, and outer threads to secure a closure. In a preferred embodiment, the preform may be produced by extrusion molding an inner and intermediate layer and injection molding an outer layer. Extrusion of the preform allows the manufacturer to produce thinner inner and/or intermediate layers of controlled thicknesses. Further, an extrusion or co-extrusion process permits the manufacturer to readily vary the thickness of material being extruded along the length of the extrudate. The multi-layered container can then be blow molded using conventional blow molding operations.  
         [0039]    Referring now to the drawings in detail, there is shown in FIG. 1 an elevational view of a preform, in accordance with the present invention, designated generally as  10 . Preform  10  preferably includes a threaded and flanged upper portion  12 , an angled intermediate portion  14 , a vertical intermediate portion  16  and a base portion  18 . In the configuration shown in FIG. 1, preform  10  is adapted to be blow molded into a container in accordance with the present invention.  
         [0040]    Referring now to FIGS. 1A, 1B &amp;  1 C, which show enlarged cross-sectional views of areas  1 A,  1 B and  1 C, respectively of FIG. 1, preform  10  is preferably formed from three layers of material. These clearly show encircling innermost first layer  20 , encircling second intermediate layer  22 , and the third outermost layer of the preform, encircling outer layer  24 . As can be seen from FIGS.  1 A- 1 C, the thicknesses of the layers may if desired vary in accordance with specific portions of preform  10 . Outer layer  24  desirably has increased thickness at threaded and flanged upper portion  12 . Innermost layer  20  also desirably may vary in thickness depending upon the portion of the bottle, i.e., threaded and flanged upper portion  12 , angled and vertical intermediate portions  14  and  16 , and base portion  18 .  
         [0041]    Innermost layer  20  and intermediate layer  22  are preferably coextruded via an extrusion process, and outer layer  24  is preferably formed onto the extruded layers via an injection molding process, which allows the formation of the threaded upper portion  12 . As a result of the extrusion process, innermost layer  20  can be readily controllably adjusted in thickness based upon the functions to be performed by the various portions and especially to provide a desired degree of protection to the oxygen scavenger material in the intermediate layer.  
         [0042]    The intermediate layer  22  is preferably maintained at a constant thickness, but this also can be varied in thickness if desired.  
         [0043]    Variations in thickness of the inner layer are also desirable for reasons which include aesthetics, efficient material use and reduced costs, and variable strength requirements. Efficient material use is evident in innermost layer  20  at upper portion  12 , where innermost layer  20  is thinnest. Strength considerations are evident in base portion  18 , where additional support is required and as a result, innermost layer  20  may be thickest.  
         [0044]    With reference now to FIG. 2, a container  58  is shown which is formed from preform  10  of FIG. 1 via a blow molding operation. Similar to the preform, container  58  desirably includes a threaded upper portion  60 , an angled intermediate portion  62 , a substantially vertical intermediate portion  64  and a base portion  66 , which is shown in the embodiment of FIG. 2 as a self-supporting base. Naturally, other base configurations may be used, as a footed base for example. As shown in FIGS.  2 A- 2 C, container  58  also has three layers of material, each of which may have differing properties and relative thickness relationships.  
         [0045]    Referring to FIGS.  2 A- 2 C , which represent enlarged cross-sectional views of areas  2 A,  2 B and  2 C, respectively, of FIG. 2, container  58  includes innermost layer  68 , central layer  70  and outer layer  72 . Because innermost layer  68  is not subject to blowing at the neck region in forming the container shape, the thickness ratios between the various portions of the container may differ from those of preform  10 . However, the thicknesses of the layers of the container may if desired vary in accordance with specific portions of the container in a manner after the thickness variations of the preform.  
         [0046]    Self-supporting base portion  66  is preferably comprised of a circumferential encircling member  74 , particularly a ring defining an annulus and an indented center positioned wall  75 , whose function is to sturdily support container  58  on a flat surface. Encircling member  74  forms the lower circumference of the container at the lower end  76  thereof. Indented wall  75  joins the inside portions of encircling member  74  and is located in the center of encircling member  74 . Encircling member  74  starts at the bottom  77  of container  58  and extends upwardly forming lower end  76  and is continuous with the inner and outer diameters of the container wall defined by layers  68 ,  70  and  72  of container  58 . Due to the increased thickness of innermost layer  68  at the self-supporting base  66 , base  66  including encircling member  74  is substantially harder and less flexible than intermediate portions  62  and  64  providing increased support.  
         [0047]    The shape and parts of container  58 , shown in FIG. 2 are by way of example only and accordingly, a plurality of shapes with varying parts are contemplated, all of which have a layered structure similar to as discussed above. For example, the container may contain greater than three layers if desired and the shape shown in FIG. 2 is exemplificative only.  
         [0048]    It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope.