Abstract:
A double bag vacuum insulation panel for use in a temperature assured shipper made in a steam chest molding machine is provided. The double bag VIP comprises a porous core, a heat sealable inner envelope and an outer bag. The inner envelope is made from a substantially gas impermeable first material having a first thickness and defines an interior having a pressure of less than or equal to about 30 millibar. The outer bag is made from a substantially gas impermeable second material having a second thickness. The outer bag encapsulates the inner envelope. The double bag vacuum insulation panel has an R value of at least about 28 hr-ft 2 —° F./BTU-in and the R value drops less than about 10% after being exposed to a temperature of up to 95C for up to 7 seconds.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a double bag vacuum insulation panel (VIP). More particularly, this invention relates to a fully manufactured vacuum insulation panel that is encapsulated inside an outer bag to resist the extreme temperature conditions of steam chest molding. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    Thermally insulated shippers are used to ship perishable materials such as pharmaceuticals, blood and blood products, transplant organs and food products which must be maintained within a certain temperature range. The shipping and transportation of various perishable materials frequently requires that such materials be maintained in a stable temperature range either higher or lower than the ambient temperatures to which the packaging will be exposed. A number of different types of thermally insulated containers have been developed for this purpose. They generally fall into two main categories, active shippers and passive shippers. 
         [0003]    Active shippers are those in which the internal temperature is controlled using a battery operated device or electrical power cord. These systems usually are expensive and quite bulky. Passive shippers are those in which the internal temperature is maintained without any battery or electrical support. Different materials may be used to control the temperature, such as phase change material (material which can absorb or release heat depending on the surrounding temperature), gel bricks (ice bricks), dry ice and vacuum insulation panels (VIPs). 
         [0004]    A vacuum insulation panel is a product composed of a rigid, highly-porous nano size material core enclosed within a metalized or non-metalized plastic bag. The core typically is made of fused silica, glass fiber, aerogel or other porous high insulation materials. To make the VIP, a plastic film bag is wrapped around the core, a vacuum is applied inside the bag, and the bag is sealed. The vacuum reduces the pressure inside the bag to within the range of 30 millibars to 1 millibar. Typically, the plastic film is 25 microns to 75 microns in thickness. Sometimes the pressure is also reduced less than 1 millibar to achieve a high insulation value. 
         [0005]    The vacuum (lack of air molecules) is an excellent insulator where conduction, convection and radiation sources are eliminated. A VIP without any vacuum has an R value of 4-7 hr-ft 2 —° F./BTU-in. A VIP with pressure around 5-10 millibars has R value of 28-35 hr-ft 2 —° F./BTU-in. 
         [0006]    VIPs are very useful as insulators due to their exceptionally high thermally insulating properties. For example, EPS and polyurethane, which are typical insulating materials, have an R value of about 4-4.5 and 5-6 hr-ft 2 —° F./BTU-in respectively, whereas the R value for a VIP of the same thickness is typically 35-40 hr-ft 2 —° F./BTU-in or more. In order for EPS or polyurethane to be as effective as a VIP panel, the same EPS or polyurethane sheets would need to be made about seven or eight times thicker. An open topped box of VIPs can be made from five individual panels taped together using packaging tape or strapped together using band straps. Sonoco Products Company has developed a temperature controlled shipper incorporating VIPs which is the subject of co-pending U.S. patent application Ser. No. 13/908,607. The shipper comprises VIPs sandwiched between an expanded foam outer shell and an expanded foam inner shell. 
         [0007]    The shipper may be made using a steam chest mold according to the following method:
       1. Placing inside a steam chest mold an assembly consisting of VIPs positioned inside an expanded foam outer shell;   2. Positioning a male plug within the assembly to create a space between the VIPs and the male plug; and   3. Molding via steam chest molding, an inner foam shell into the space between the VIPs and the male plug.       
 
         [0011]    Any voids between the VIPs and the outer shell and the inner shell may be filled with expanded foam. As a result, the VIPs are enveloped by expanded foam material. 
         [0012]    The plastic film which is used to encapsulate the VIP core is a thin plastic film. Some of the most common plastic films used in VIPs are multi-layer polyethylene/ethylene vinyl alcohol (PE/EVOH) and metalized polyethylene terephthalate (PET). Both PE and PET have low melting points. PE typically melts around 100-120 C and PET starts to soften up around 130 C. Due to their low temperature resistance, these films are susceptible to tear or fracture at high temperatures such as that experienced within a steam chest mold. 
         [0013]    During the steam chest molding process described above, the VIPs may be exposed to temperatures in the range of 80-95C for about three to seven seconds. Experiments show that VIPs subjected to such high temperature conditions have a drop of 20-30% in R value. 
         [0014]    In addition to high temperatures, VIPs used in making these shippers are also subjected to moisture. During steam chest molding, moisture in the form of steam is used at high temperature, and this can cause a reduction in barrier resistance of the VIP plastic film. 
         [0015]    These two factors (high temperature molding and steam exposure) are primary reasons that VIPs can experience a drop in R value of 20-30% when subjected to steam chest molding conditions. 
         [0016]    The present invention is intended to solve these problems by adding an extra protective layer to a VIP, thus protecting it from high temperature and moisture during steam chest molding. 
       BRIEF SUMMARY OF THE INVENTION 
       [0017]    The present invention is a vacuum insulation panel comprising a fully manufactured VIP encapsulated within a second bag to form a double bag VIP. The double bag vacuum insulation panel is intended for use in a temperature assured shipper made in a steam chest molding machine. The double bag VIP comprises a porous core, a heat sealable inner envelope and an outer bag. The inner envelope is made from a substantially gas impermeable first material having a first thickness and defines an interior having a pressure of less than or equal to about 30 millibar. The outer bag is made from a substantially gas impermeable second material having a second thickness. The outer bag encapsulates the inner envelope. The double bag vacuum insulation panel has an R value of at least about 28 hr-ft 2 —° F./BTU-in. The R value drops less than about 10% and preferably only about 1% after being exposed to steam chest molding conditions such as a temperature of up to 95C for up to 7 seconds. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an exploded view of a thermally insulated VIP sandwich shipper for transporting temperature sensitive products. 
           [0019]      FIG. 2  is a cutaway perspective view of a vacuum insulation panel. 
           [0020]      FIG. 3  is a perspective view a double bag vacuum insulation panel according to the disclosure. 
           [0021]      FIG. 3   a  is a perspective view of the VIP of  FIG. 1  being inserted into an outer bag. 
           [0022]      FIG. 4  is a perspective view of the outer bag being sealed around the VIP with a sealing strip. 
           [0023]      FIG. 5  is another perspective view a double bag vacuum insulation panel according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    While this invention may be embodied in many forms, there is shown in the drawings and will herein be described in detail one or more embodiments with the understanding that this disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to the illustrated embodiments. 
       Thermally Insulated VIP Sandwich Shipper 
       [0025]    Turning to the drawings, there is shown in  FIG. 1  an exploded view of a thermally insulated “VIP sandwich” shipper  10  for transporting temperature sensitive products such as that disclosed in co-pending and co-owned U.S. patent application Ser. No. 13/908,607, incorporated herein by reference. The VIUP sandwich shipper  10  comprises an outer shell  12 , an inner shell  14  and one or more vacuum insulation panels  16  (VIPs) located (“sandwiched”) between the outer and inner shells  12 ,  14 . Together the outer shell  12 , inner shell  14  and the VIPs  16  form a box onto which a lid  18  can be fitted to form the shipper  10 . The box and lid  18  together define a payload compartment  20 . 
         [0026]    The outer shell  12  may be made of expanded foam (such as expanded polystyrene (EPS), expanded polypropylene (EPP), expanded polystyrene/polyethylene (EPS/PE) or other suitable insulative material and may be shaped like an open topped box. The outer shell  12  may comprise a bottom  24  having a perimeter and sides  26  extending from the bottom perimeter and terminating in a rim  28 . 
         [0027]    Likewise, the inner shell  14  may be made of expanded foam (such as EPS, EPP, EPS/PE) or other suitable insulative material and may be shaped like an open topped box, albeit smaller than the outer shell  12  so that the inner shell  14  can nest within the outer shell  12 , leaving a gap therebetween for accommodating the VIPs  16 . The inner shell  14  may comprise a bottom  32  and four sides  34  extending upward from the periphery of the bottom  32  and terminating in a rim  36 . The inner shell  14  may be spaced from the outer shell  12  to define a gap, the gap being sealed over to create an enclosed space. 
         [0028]    In the assembled shipper  10 , the VIPs  16  are located between the nested outer and inner shells  12 ,  14  which protect the VIPs  16  from punctures or tearing. Preferably the VIPs  16  are wedged against each other together so that the edge  40  of one VIP panel  16  abuts an adjacent VIP  16 , thereby reducing or eliminating edge leaks. 
         [0029]    The thermally insulated VIP sandwich shipper  10  is used to package and ship temperature sensitive products. Typically these products have a specified or required temperature range that must be maintained during a specific shipping duration and while the thermally insulated VIP sandwich shipper is subject to various ambient temperature conditions. For example, a payload may be expected to be shipped for 120 hours and be exposed to ambient temperatures of between −20 C and 45 C (−4 F and 113 F) but have a temperature tolerance of between 0 C and 15 C (32 F and 59 F). A thermally insulated VIP sandwich shipper can be designed to accommodate these requirements. 
       Making a Thermally Insulated VIP Sandwich Shipper in a Steam Chest Mold 
       [0030]    The thermally insulated VIP sandwich shipper  10  may be made using a steam chest molding machine to mold the expanded foam components according to the following method. First, the outer shell  12  is molded in a steam chest molding machine. next, VIPs  16  may be placed against the bottom  24  and sides  26  of the molded outer shell  12  to create an outer shell/VIP assembly. The outer shell/VIP assembly may be placed inside a steam chest molding machine. A male plug is positioned within the outer shell/VIP assembly, leaving a space therebetween. The inner shell  14  then is molded into the space between the VIPs  16  and the male plug. After molding the inner shell  14 , the VIPs  16  are sandwiched between the outer shell  12  and inner shell  14  and enclosed therebetween so that the VIPs  16  cannot be removed. 
         [0031]    The method has a number of advantages: The molding of the inner shell  14  to the outer shell/VIP assembly in a steam chest mold can create a perfect seal between the outer shell  12  and the inner shell  14 , making it difficult to distinguish where the outer shell  12  ends and the inner shell  14  starts. The method also eliminates the need for adhesive to seal the gap between the outer shell  12  and the inner shell  14 . Also, during high pressure steam chest molding every void/gap between VIPs  16  and the walls of the outer shell  12  and the inner shell  14  are filled with expanded foam, thus creating nearly hermetic seal. Finally, high pressure steam chest molding helps push the VIPs  16  against each other, thus virtually eliminating edge leaks. 
         [0032]    However, since this method involves subjecting the VIPs to steam chest molding conditions, there is a need for a vacuum insulation panel that can withstand the high temperatures and pressures experienced in steam chest molding. A “double bag” VIP has been developed for this purpose. 
       The Double Bag VIP 
       [0033]    The double bag VIP of the present disclosure may be a fully manufactured VIP that is then encapsulated inside an outer bag. 
         [0034]      FIG. 2  shows a fully manufactured VIP  16  like that shown in  FIG. 1 . The VIP  16  may be made by a conventional process, wherein a core  52  having a three dimensional shape lacking cavities and depressions is wrapped in an envelope  54  typically made of plastic film, a vacuum is pulled and the envelope  54  is sealed around the core  52  and conforms to the brick-like shape of the core  52 . The VIP  16  may be rectilinear in shape and comprise opposing first and second sides  42 ,  44  in addition to the four edges  40 . 
         [0035]    The inner envelope  54  may define an interior occupied solely by the core  52 . The envelope  54  may be made of common plastic films such as multi-layer polyethylene/ethylene vinyl alcohol (PE/EVOH) or metalized polyethylene terephthalate (PET). The envelope thickness typically is about 1 mil. 
         [0036]      FIG. 3   a  shows the VIP  16  being inserted into an outer bag  56 . The outer bag  56  may be pre-formed, that is, pre-shaped so that the VIP  16  fits snugly inside. More specifically, the outer bag  56  may be rectilinear in shape and comprise opposing first and second sides  58 ,  60  having dimensions similar to the first and second sides  42 ,  44  of the VIP  16 . A bottom edge  62  and side edges  64  extend between the first and second sides  58 ,  60 . Once the VIP  16  is inserted into the outer bag  56 , the top flap of the outer bag  56  may be sealed as shown in  FIG. 3 . 
         [0037]      FIG. 4  shows the outer bag  56  being sealed around the VIP  16  with a sealing strip  66 . A top (closure) flap  68  extends from the second side  60  and is configured to be folded over the exposed top edge  40  of the VIP  16  and lie flat against the first side  58 . The sealing strip  66  may then be used to secure the flap against the first side  58 . Alternatively, and without limitation, the flap  68  may include adhesive for adhering to the first side  58 . 
         [0038]      FIG. 5  is a perspective view of a “double bag” VIP  70  according to the disclosure. The fully manufactured VIP  16  is securely encapsulated within the outer bag  56 . The outer bag  56  should be temperature and moisture resistant, and may be made of Nylon. The outer bag  56  may also be made of other materials such as PET, polyethylene terephthalate glycol modified (PETG), PE, PP, ethyl vinyl acetate (EVA), EVOH, polyvinylidene fluoride (PVDF), polycarbonate (PC), polyvinyl chloride (PVC), aluminum foil or other plastic materials used in film making, or a combination of these materials. 
         [0039]    The film used to make the outer bag  56  may be either monolayer or made of multiple layers to give added protection. Multiple layers can offer multiple forms of protection. For example, PE has excellent resistance to moisture; Nylon has excellent resistance to oxygen. By selecting each layer carefully, a double bag VIP can be created having a strong structure with excellent barrier properties. 
         [0040]    The outer bag  56  may have a thickness of between about 1 mil and about 15 mil (about 25 microns and 375 microns), and preferably between about 6 mils and 10 mils (about 152 microns and 254 microns). 
       Example 
       [0041]    Experiments show that VIPs subjected to steam chest molding conditions, such as temperatures in the range of 80-95 C for about three to seven seconds, have a drop of 20-30% in R value. Thus a drop of only 10% in the R value of a VIP after steam chest molding would represent a significant advance over a conventional VIP. 
         [0042]    In one example, a double bag VIP  70  according to the disclosure having an outer bag  56  made of multi-layer Nylon/EVOH film and having a thickness of 8 mil (about 203 microns) had an R value drop after steam chest molding of only about 1%. 
         [0043]    This there has been described a vacuum insulation panel  70  having an R value of at least about 28 hr-ft 2 —° F./BTU-in and wherein the R value drops about 10% or less, and preferably about 1% or less, after being exposed to a temperature of up to 95 C for up to 7 seconds such as might occur in a steam chest molding machine. 
         [0044]    It is understood that the embodiments of the invention described above are only particular examples which serve to illustrate the principles of the invention. Modifications and alternative embodiments of the invention are contemplated which do not depart from the scope of the invention as defined by the foregoing teachings and appended claims. It is intended that the claims cover all such modifications and alternative embodiments that fall within their scope.