Patent Publication Number: US-2010108695-A1

Title: Air-pocket insulated disposable plastic cup

Description:
The present invention generally relates to disposable plastic containers, and more particularly to a thermally insulated disposable plastic containers. More specifically, the present invention relates to air pocket thermally insulated double-walled disposable plastic containers. 
     BACKGROUND OF THE INVENTION 
     The production and use of thermally insulated disposable containers, such as cups, are well known and highly desirable. Thermally insulated disposable cups are generally useful for both hot and cold beverages. They are designed to maintain the beverage temperature by preventing undesirable heat transfer between the beverage, the atmosphere, and cup holder&#39;s hand. Currently available thermally insulated disposable cups are generally made from paper, polymeric materials or combinations thereof. 
     Paper-based materials are generally favored for disposable cups, because of low cost and high volume production capability. However, paper-based materials generally do not have good liquid barrier properties. Disposable cups made from such paper-based materials, have a tendency to decompose due to liquid penetration into the paper material, which can cause the cup to lose its structural integrity and become soggy or leak. Furthermore, cups made from paper-based materials generally do not provide adequate thermal insulation. 
     U.S. Pat. No. 5,145,107 to Silver et al. teaches a double-walled thermal insulated disposable paper cup having an inner wall connected to an outer wall at the lip and at the base of the cup. The walls have different tapers which define an air pocket between the two walls. The air pocket is meant to provide thermal insulation. However, as with currently available paper-based disposable cups, structural integrity remains a problem. 
     Polymeric materials, such as polypropylene, polyethylene terephthalate (PET) based polyesters and polystyrenes have been widely used as container materials for disposable containers because of their improved mechanical and barrier properties. Disposable articles such as plastic drinking cups and lids are generally made of polystyrene or polystyrene blends. However, containers made from such polymeric materials do not provide adequate thermal insulation. The lack of good thermal insulation properties often results in rapid heat loss for beverages; or cups that are too hot or cold to hold. Accordingly, it would be desirable to provide a thermally insulated disposable plastic container. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an air pocket insulated double-walled disposable plastic container for containing food or beverages. Air pocket insulated double-walled disposable plastic containers in accordance with the invention provide recyclability, enhanced barrier properties and excellent thermal insulation. In addition a container in accordance with the invention can be transparent or translucent. Accordingly, a method for making the air-pocket insulated disposable double-walled plastic container is also provided herein. The method of manufacture used to make the air pocket insulated double-walled disposable plastic container is cost effective and energy efficient. 
     In an embodiment of the invention, the air-pocket insulated double-walled disposable plastic container includes a container body having an inside sheet having protrusions formed thereon fixedly connected to an outside sheet in a manner which forms air pockets between the first and second sheet. The method of making an air pocket insulated disposable double-walled container includes the steps of joining a first sheet and a second sheet to form a double-walled sheet. The first sheet includes an indented pattern and the second sheet is a smooth sheet having no indentations. The first sheet and the second sheet are joined by contacting the indented face of the first sheet to the second sheet thereby creating air pockets between the two sheets in the double-walled sheet. The double-walled sheet is then used in a molding process to form an air pocket insulated double-walled disposable plastic container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of one embodiment of a container of the invention. 
         FIG. 1A  is a cut-out view of the container of  FIG. 1   
         FIG. 2  is a cross-sectional view of another embodiment of the invention. 
         FIG. 3  shows a process of making the container of the invention. 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The present invention provides am air pocket thermally insulated double-walled disposable plastic container having excellent insulation properties, recyclability, and optionally transparency. As used herein the term “plastic” refers to a wide range of synthetic or semi-synthetic polymerization products, composed of organic condensation or addition polymers and may contain other substances, including bio materials and recycled content, to improve performance or reduce costs. “Disposable” as used herein is meant to describe articles that are most often discarded after one use. “Double-walled” as used herein refers to a structure that includes at least two sheets or layers of polymeric material. The term “insulated or insulating” as used here in refers generally to the prevention of reduction of heat transfer from conducting bodies. The term ‘air pocket insulated double-walled disposable plastic container’ may alternatively be referred to as ‘container’ for convenience. 
     Referring now to  FIGS. 1 and 1A , there is shown an air pocket insulated double-walled disposable plastic container  100 . In one embodiment of the invention, the container  100  is preferably a cup. The container  100  includes an inner sheet  102  and an outer sheet  104 . The inner sheet  102  is formed having inwardly protruding indentations  116  that create a plurality of air pockets  106  when the inner sheet  102  is attached to an inner surface  114  of the outer sheet  104  in a manner whereby the inwardly protruding indentations  116  contact the inner surface  114  of the outer sheet  104 . The air pockets  106  are preferably uniformly distributed over the surface of the inner sheet. The air pockets  106  act as insulating layer. The inner sheet  102  and outer sheet  104  may be formed in any suitable shape that includes an opening at the top  112 , an interior space  110  for containing food or beverages, and a base  108  enclosing the bottom. 
     The inner sheet  102  and outer sheet  104  may be joined or connected by any suitable techniques. A person skilled in the art would appreciate that various chemical or mechanical techniques may be used to join the inner sheet  102  and outer sheet  104  such as, without limitation, welding, ultrasonic welding, adhesive sealants, rim rolling or snap fitting sealing engagement. In a preferred, overhang rims of the inner sheet  102  and outer sheet  104  are rolled together by a conventional rim rolling process to form a curled overturned rim  120 . Such double curling enhances the rigidity of the container  100 . 
     The inner sheet  102 , the outer sheet  104  may be formed of any suitable plastic. Preferred plastics include polypropylene (PP), polyethylene terephthalate (PET), polylactic acid (PLA), polystyrene (PS) or combinations thereof. It is also preferred that the plastic be food grade plastic. 
     In accordance with an embodiment of the invention, the outer sheet  104  is preferably of from about 0.005 to 0.030 inches in thickness and more preferably of from about 0.010 to 0.020 inches in thickness; and the inner sheet  102  is preferably of from about of 0.001 to 0.012 inches in thickness, and more preferably from about 0.005 to 0.010. The thickness between an inner surface  106 ′ surface of the air pockets  106  and the inner section  114  of the outer sheet  104  is preferably of from about 0.002 to about 0.006 inches, more preferably, from about 0.100 to 0.200 inches and even more preferably, from about 0.130 to 0.150 inches. 
     In one embodiment of the invention, the container  100  is transparent. Preferably, at least the inner sheet  102  and the outer sheet  104  are transparent. The inner sheet  102  and the outer sheet  104  may be formed from any suitable food grade plastics having transparent properties and a transparency value of 80 to 100%. 
     In another embodiment of the invention, the container  100  is translucent. Preferably at least the inner sheet  102  and outer sheet  104  are translucent. The inner sheet  102  and the outer sheet  104  may be formed from any suitable food grade plastics having translucent properties. 
     The container  100  may be of any suitable size or shape. The container  100  may be the size or shape of commonly used take-out containers to store food or beverage. Without limitation, the container may be a box-type container or have a length larger than the height. The container is preferably also suitable for use in a microwave or freezer. 
     In an embodiment, wherein the container  100  is a cup, the cup may be of any suitable size. For example, the cup can be made in sizes generally used in restaurants and coffee shops, including but not limited to 12, 16, 20, 21, 22, 32 and 44 oz cups. 
     In another embodiment of the invention shown in  FIG. 2  a cover sheet  222  may be formed over the inner sheet  202  to contact the outwardly protruding air pockets  206 , thereby creating additional air pockets  226 . The cover sheet  222  preferably has a smooth surface. The cover sheet  222  may be formed of any suitable material. In a preferred embodiment the cover sheet  222  is formed from a polymer based material, and even more preferably is a laminate surface. The cover sheet  222  may also be transparent or translucent, and in a preferred embodiment is transparent. The cover sheet creates a smooth interior lining for the container. The cover sheet  222  also facilitates container to container nesting and de-nesting during storage and on store shelves. 
     An air pocket insulated double-walled disposable plastic container in accordance with the invention may be formed by any suitable means. The outer sheet may be injection molded or thermoformed to the preferred thickness range. In an exemplary process of making the container of the invention shown in  FIG. 3 . The process of making the container includes, without any limitation, the steps of forming a first sheet  302  and a second sheet  304  from a polymeric material. Indentations or inwardly extending protrusions  316  are formed in the first sheet  302  by any suitable means to form an indented pattern. The indented pattern may be a series of notches or dents on one side of sheet which leads to a raised appearance on the other side. The second sheet  304  is preferably a smooth sheet having no indentations. The first sheet  302  and the second sheet  304  are then joined by contacting the inwardly protruding indentations  316  of the first sheet  302  to a surface of the second sheet  304 , using any suitable joining mechanism. In a preferred embodiment, rollers  340  are used to attach the first sheet  201  and the second sheet  304 . In another embodiment, the two sheets may be joined together using a fusing process. In yet another embodiment of the invention, the two sheets are bound together using a chemical mechanism, such as an adhesive or epoxy to create a double-walled sheet  318 . Air pockets  306  are created between the inwardly extending protrusions. The air pockets  306  form insulation and act as a barrier useful for reducing heat transfer and keeping the contents of the container hot or cold. 
     The double-walled sheet  318  may then be used in a molding process to form a container  300 . Any suitable molding processes may be used to form the container  300 , including without limitation, thermoforming, vacuum forming, compression forming, transfer forming or combinations thereof. In an embodiment of the invention, the double-walled sheet  318  is molded using a cup-mold  350  and cup mandrel  360  by passing and pressing the double-walled sheet  318  between the cup-mold  350  and cup mandrel  360 . Preferably the double-walled sheet has an overall thickness of from about 0.030 to about 0.300, and even more preferable from about 0.0115 to 0.230. The molding results in the formation of the container  300 . 
     It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general sprit and scope of the invention as defined by the following claims and equivalents thereof.