FIELD OF THE INVENTION

The invention relates to a thermal buffer assembly for separating a temperature- sensitive product from a refrigerant pack in a shipping package for improved temperature control.

BACKGROUND TO THE INVENTION

Many pharmaceutical products such as vaccines and insulin require strict temperature control during transportation and storage in order to maintain the quality and viability of the product. Commonly, such products must be kept within a temperature range of between 2°C to 8°C. If a product is subjected to temperatures outside this range for an appreciable time, there is a risk of a loss of potency which may cause the product to be ineffective.

In order to transport temperature-sensitive products to an end user, it is necessary to provide a suitable temperature-controlled distribution system (commonly referred to as a cold chain distribution system).

Cold chain distribution systems may incorporate active systems, passive systems, or a combination of both for maintaining a product at a target temperature. Active systems typically use a continuous external power source to regulate the temperature in an insulated enclosure. Examples of active systems include refrigerated containers, trailers, vans and so on.

Passive systems require no external power source, and instead typically use a pre cooled phase change material, together with suitable insulation, to maintain a target temperature range in an enclosure for sufficient time to complete the transportation of the product to its destination. This approach enables suppliers of temperature- sensitive products to transport small quantities of product in an economic manner. In particular, passive systems can be incorporated into parcels or shipping packages so that an enclosure inside the package is maintained at the appropriate temperature. Conveniently, such packages can be transported and stored in vehicles and environments that are not themselves temperature-controlled.

Shipping packages with passive cooling are commonly insulated using expanded polystyrene (EPS), rigid polyurethane foam (PUR), rigid polyisocyanurate foam (PIR) or vacuum insulated panels (VIP). Natural materials such as wool, cork, or starch-based foams can also be used. Typically, the insulating material is arranged within an outer carton to define a cavity within the package that is surrounded on all sides by the insulating material.

The product can be placed within the cavity together with the phase change material, which is usually contained in a rigid or flexible pack, commonly referred to as a refrigerant pack, cooler pack or ice pack.

The phase change material controls the temperature inside the cavity by absorption of heat energy in the environment as latent heat during the phase transition from solid to liquid. To maintain safe temperatures between the 2°C to 8°C range, phase change materials with melting temperatures that lie within the range required may be selected. One example is methyl laurate, which has a melting point of around 5°C. However, methyl laurate and similar materials are relatively expensive, and may also have irritant or toxic characteristics.

Water (ice) may also be used as a phase change material, as it has a high specific latent heat of fusion and is inexpensive. However, a disadvantage of using water for this purpose is that its melting point is around 0°C, which is lower than the ideal lowest temperature of 2°C for many temperature-sensitive products. Furthermore, ice packs are typically frozen and stored at temperatures considerably below 0°C, increasing the risk of temperature excursions when the shipping package is first packed.

To prevent temperature excursions outside the target range when using water as the phase change material, specific packing arrangements and preconditioning measures may be applied. For example, the World Health Organisation (WHO) suggests using ‘conditioned’ ice packs for the transport of refrigerated products. To condition an ice pack, the ice pack is removed from a freezer (at a temperature below freezing) and then rested at ambient temperature until liquid water starts to appear inside the ice pack. The presence of liquid water can be verified by shaking the ice pack to ensure there is movement inside the pack. This approach requires constant monitoring and judgement by a user to decide when it is safe to pack the product, and can substantially increase the time required for packing. Furthermore, if a conditioned ice pack is not used as soon as liquid water is present, the duration of thermal protection is reduced.

In addition to the use of conditioned ice packs, additional materials may be used within the cavity to separate the product from the ice pack, preventing direct contact. Examples of such materials include corrugated board and bubble wrap. However, this approach merely delays the time it takes for the temperature on each side of the separating material to reach an equilibrium, and therefore may not reduce the risk of thermal excursion over a sufficiently long time period in some cases.

Against that background, it would be desirable to provide components for shipping packages that can be used to reduce the risk of thermal excursions, particularly when using water as a phase change material.

SUMMARY OF THE INVENTION

From a first aspect, the present invention provides a thermal buffer assembly for separating a temperature-sensitive product from a refrigerant pack in a shipping package. The thermal buffer assembly comprises a first phase change layer containing a first phase change medium, a second phase change layer containing a second phase change medium, and an insulating panel disposed between the first and second phase change layers. The insulating panel comprises a core sheet of trapped-air material.

With this arrangement, the thermal buffer assembly regulates the temperature of the product and in particular can prevent the product from reaching temperatures outside a target range, even when the refrigerant pack is at a temperature outside the target range.

For example, when the thermal buffer assembly is in use with the first phase change layer adjacent to a pre-frozen refrigerant pack and the second phase change layer adjacent to the product, the first phase change layer will transfer its heat to the refrigerant pack, raising the temperature of the refrigerant pack to its melting point. The first phase change layer will fall in temperature and hold at its melting point. The first phase change layer draws latent heat energy from the second phase change layer, which in turn reduces in temperature as a result. The rate of temperature loss of the second phase change layer is limited by the insulating panel, so that the product remains at an acceptable temperature. Furthermore, no pre-conditioning of the refrigerant pack is required, reducing the time required for the packing process.

Preferably, the first and second phase change layers each comprise a plurality of cells for containing the respective phase change medium. By containing the phase change medium in cells in this way, the phase change medium is more uniformly distributed across the phase change layers than would otherwise be the case, and also freezes in a more uniform manner.

Each of the phase change layers may comprise first and second polymeric sheets for containing the phase change medium therebetween, and the cells may be defined by border regions in which the first and second polymeric sheets are connected together. The first and second polymeric sheets may be connected together in the border regions by heat sealing.

The first and second phase change layers may be connected along a common edge. In this way, the first and second phase change layers can be manufactured together as a single component, which can then be folded around the insulating panel during assembly. A border region between at least one pair of adjacent cells may be disposed along the common edge. The insulating panel may include a lining comprising a heat-reflective material. The lining of the insulating panel may be provided on first and second sides of the core sheet. The lining may comprise a metallised polymeric material.

In one example, the core sheet of the insulating panel comprises an air bubble film material. In another example, the core sheet of the insulating panel comprises a corrugated cardboard material. In both cases, the core sheet provides a lightweight but effective insulating component for controlling the rate of heat transfer through the insulating panel.

The thermal buffer assembly may comprise a carton for containing the first and second phase change layers and the insulating panel.

Preferably, the first phase change material and the second phase change material comprise water.

In a second aspect, a shipping package for a temperature-sensitive product is provided, comprising a thermally-insulated container, a receiving region within the container for receiving the temperature-sensitive product, at least one refrigerant pack, and at least one thermal buffer assembly according to the first aspect of the invention. The thermal buffer assembly is disposed between the refrigerant pack and the receiving region.

Preferably, the thermal buffer assembly defines a wall of the receiving region. For example, when the thermal buffer assembly includes a carton, a top or bottom side of the carton may define a top or bottom wall of the receiving region. In one arrangement, the package includes two thermal buffer assemblies that are spaced apart to define opposing walls of the receiving region.

In a third aspect, the invention resides in a method of manufacturing a thermal buffer assembly for separating a temperature-sensitive product from a refrigerant pack in a shipping package. The method comprises folding a mat containing a phase change material around an insulating panel, thereby to provide a first phase change layer on a first side of the insulating panel and a second phase change layer on a second side of the insulating panel.

The method may comprise forming the mat by selectively connecting a first polymeric sheet and a second polymeric sheet together to define a chamber therebetween for containing the phase change material, and at least partly filling the chamber with the phase change material.

Selectively connecting the first and second polymeric sheets together may comprise forming a plurality of cells separated by border regions in which the first and second sheets are connected together. The method may further comprise forming a central border region that extends across a width of the mat and is disposed midway along a length of the mat. In this case, the method may comprise aligning an edge of the insulating panel with the central border region of the mat before folding the mat around the insulating panel.

The method may comprise enclosing the first and second phase change layers and the insulating panel in a carton.

Preferred and/or optional features of each aspect and embodiment of the invention may also be used, alone or in appropriate combination, in the other aspects and embodiments also.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference signs are used for like features, and in which:

Figure 1 is a perspective view of a thermal buffer assembly according to the present invention; Figure 2 is a perspective view of the thermal buffer assembly of Figure 1 from another angle;

Figure 3 is a cross-sectional view of the thermal buffer assembly of Figure 1 with an exaggerated vertical scale;

Figure 4 is a cross-sectional view of a shipping package including a thermal buffer assembly according to the invention;

Figure 5 shows a set of parts for assembling a thermal buffer assembly according to the invention;

Figures 6a and 6b show steps in assembling a thermal buffer assembly using the parts of Figure 5;

Figures 7a to 7f show further steps in assembling a thermal buffer assembly using the parts of Figure 5;

Figure 8 shows cross-sectional views of three further shipping packages, each including two thermal buffer assemblies according to the invention;

Figures 9a to 9f show schematic plan views of mat components for use in thermal buffer assemblies according to the invention; and

Figure 10 is a graph showing the temperature in a receiving cavity of a shipping package when fitted with thermal buffer assemblies according to the invention compared to when fitted with cardboard pads.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figures 1 to 3 show a thermal buffer assembly 20 according to an embodiment of the present invention. The thermal buffer assembly 20 comprises a first phase change layer 22, which is uppermost in this example, a second phase change layer 24, which is lowermost in this example, and an insulating panel 26 disposed between the first and second phase change layers 22, 24.

The phase change layers 22, 24 are connected along a common edge 28 (see Figure 2). In this way, the phase change layers 22, 24 each define half of a mat 30 that is folded around the insulating panel 26, as will be explained in more detail below.

The mat 30 is formed from a polymeric material, such as low-density polyethylene (LDPE). As can be seen in Figure 3, the mat 30 comprises overlapping first and second sheets 30a, 30b of the polymeric material, which are heat-sealed together in a grid pattern to seal the periphery 32 of the mat 30. The heat-sealing also forms border regions 34, 36 in each of the phase change layers 22, 24. Some of the border regions 34 extend across the phase change layers 22, 24 to divide each layer 22, 24 into a plurality of cells 38. An edge border region 36 (see Figure 2) separates the first phase change layer 22 from the second phase change layer 24.

Each of the cells 38 defines a chamber that is filled with a phase change medium, which is preferably water. In the example of Figures 1 to 3, each phase change layer 22, 24 comprises three cells, each one of which extends along a length of the assembly 20 towards the common edge 28.

Returning to Figure 3, the insulating panel 26 comprises a core sheet 40 of a trapped-air material, which in this case comprises a double-thickness layer of LDPE bubble film (bubble wrap) material in which air is trapped in a plurality of bubbles 41 . The top and bottom surfaces of the core sheet 40 are lined with a lining material 42, which in this case is a metalized polyethylene terephthalate (PET) film. The overall thickness of the insulating panel 26 in this example is approximately 6 mm.

The phase change layers 22, 24 and insulating panel 26 are contained within a carton 46 (see Figure 3, not shown in Figures 1 and 2). The carton 46 is of a cardboard material, and is sized to accommodate the phase change layers 22, 24 and insulating panel 26 with minimal clearance.

Figure 4 shows the thermal buffer assembly 20 in use in a shipping package 50. The shipping package 50 comprises an insulated box 52 and removable insulated lid 53, which together enclose a cavity 54. The box 52 and lid 53 are of a suitable insulating material, such as an expanded polystyrene foam, and may be housed in an outer carton (not shown).

In this example, a plurality of vials 56, containing a temperature-sensitive product, are placed in a receiving region 58 at the bottom of the cavity 54. Although not illustrated, the vials 56 may be held in place by recesses in the bottom wall of the cavity 54, by a shaped insert, or by other suitable means. The thermal buffer assembly 20 is placed on top of the vials 56, so that the bottom side of the carton 46 contacts the top of the vials 56.

A refrigerant pack 60 including a phase change coolant material is placed on top of the thermal buffer assembly 20. In this example, the refrigerant pack is an ice pack, and the coolant material is water (ice). The thermal buffer assembly 20 separates the ice pack 60 from the temperature-sensitive product in the vials 56. The carton 46 of the assembly is a close fit within the cavity 54, so minimise convective heat transfer within the cavity. The bottom side of the carton 46 of the assembly 20 defines an upper wall of the receiving region 58.

In the arrangement of Figure 4, the thermal buffer assembly 20 serves to regulate the temperature of the receiving region 58 by exchanging thermal energy with the ice pack 60 and the receiving region 58.

For instance, when the shipping container 50 is first packed, the ice pack 60 may have a temperature of approximately -18°C following its removal from a freezer. The thermal buffer assembly 20 may be pre-conditioned to a temperature of approximately 5°C, by storage in a refrigerator. The first phase change layer 22, which is next to the ice pack 60, will transfer its heat to the ice pack 60, bringing the adjacent surface of the ice pack 60 to its melting point (0°C). The first phase change layer 22 will rapidly fall in temperature and hold at the melting point of 0°C.

The first phase change layer 22 draws latent heat energy from the second phase change layer 24, which reduces in temperature as a result. However, the rate of temperature loss of the second phase change layer 24 is limited by the relatively low thermal conductivity of the insulating panel 26. In this way, the receiving region 58 remains at an acceptable temperature for substantially longer than could be achieved without the use of the thermal buffer assembly 20. Furthermore, because both the ice pack 60 and the thermal buffer assembly 20 can be used immediately upon removal from a freezer and refrigerator respectively, the time required for the packing process is considerably lower than the time required for pre-conditioning an ice pack.

A method of manufacturing a thermal buffer assembly according to the invention will now be described with reference to Figures 5 to 7.

Figure 5 shows a set of component parts for use in the method. The parts include a mat 30 divided into cells 38; an insulating panel 26; and a cardboard blank 70 for forming the carton 46 of the assembly.

Referring to Figure 6a, in a first step of the method, the insulating panel 26 is placed over one half of the mat 30, with an edge of the insulating panel 26 aligned with the edge border region 36 of the mat 30. Then the uncovered half of the mat 30 is folded over the insulating panel 26, to sandwich the insulating panel 26 between the two halves of the mat 30 as shown in Figure 6b.

Referring to Figure 7a, the folded mat 30 (now concealing the insulating panel 26) is placed on a base panel 72 of the cardboard blank 70. An inner top panel 74 is then folded on top of the mat 30 (Figure 7b). Two side panels 76 are then folded on top of the inner top panel 74 (Figure 7c), and a backing strip 78 is removed from an outer top panel 80 to reveal an adhesive strip 82 (Figure 7d). The outer top panel 80 is then folded over and adhered to the inner top panel 74 using the adhesive strip 82, enclosing the assembly 20 in its carton 46 as shown in Figures 7e and 7f. Both the outer top panel 80 and the inner top panel 74 include a pair of holes which align to provide finger holes 84 in the top of the carton 46, which allow the assembly 20 to be easily inserted into and removed from the cavity of the shipping package.

Optionally, after folding the mat 30 around the insulating panel, the mat 30 may be cut along the edge border region 36 to separate the two phase change layers. In another variant, the two phase change layers may be provided separately (for example by cutting a mat prior to assembly, or otherwise) and stacked together with the insulating panel in between during assembly.

A shipping package may be provided with one or more refrigerant packs 60 and one or more thermal buffer assemblies 20, and the number and arrangement of the refrigerant packs 60 and thermal buffer assemblies 20 in relation to each other and to the receiving region 58 can be selected for optimum performance in a given application. Factors that may influence the configuration of a shipping package include the size and thermal mass of the product to be packaged, the volume and dimensions of the container, the amount of insulation provided, the size of refrigerant pack, the ambient temperature, and so on.

By way of illustration, Figure 8 shows three variants of shipping packages with different configurations. In each case, two refrigerant packs 60 and two thermal buffer assemblies 20 are provided. In the first variant 50a, the receiving region 58 is disposed centrally within the cavity 54, with a thermal buffer assembly 20 on each side of the receiving region 58. The refrigerant packs 60 are disposed at the top and bottom of the cavity 54. This configuration may be suitable for use in relatively high ambient temperatures.

In the second variant 50b, the receiving region 58 is at the base of the cavity 54. Two thermal buffer assemblies 20 are stacked on top of the receiving region 58, and two refrigerant packs 60 are stacked on top of the thermal buffer assemblies 20. This configuration may be suitable for use in relatively low ambient temperatures.

In the third variant 50c, a thermal buffer assembly 20 is placed at the base of the cavity 54 and provides a bottom wall of the receiving region 58. A second thermal buffer assembly 20 is disposed above the receiving region 58, and two refrigerant packs 60 are stacked on top of the second thermal buffer assembly 20. This configuration may be suitable for use in intermediate ambient temperatures.

By dividing the phase change layers into a plurality of cells, an even distribution of phase change material across each of the phase change layers can be achieved, and a relatively uniform thickness is obtained across the mat when the phase change material freezes. The dimensions of the thermal buffer assembly may be selected to suit a shipping package of a particular size, and the number of cells in each phase change layer can be similarly selected to achieve an appropriate distribution of phase change material.

Figure 9 illustrates six variants of mats suitable for providing the phase change layers of thermal buffer assemblies of various sizes when folded around a suitable insulating panel. In the first variant, the mat 30a has three cells 38a on each half in a 1x3 arrangement, similar to the embodiment of Figures 1 to 3. In the second and third variants, the mats 30b, 30c have four cells 38b, 38c on each half, in a 2x2 arrangement.

The mat 30d of the fourth variant provides ten cells 38d on each half, in a 2x5 arrangement. The mats 30e, 30f of the fifth and sixth variants each provide twelve cells 38e, 38f on each half, in a 2x6 arrangement and a 3x4 arrangement respectively.

It will be appreciated that many other arrangements of the cells of the mat are possible. It is also conceivable that only one cell could be provided in one or both of the phase change layers (so that the mat includes a total of two cells). To illustrate the effectiveness of the invention, the temperature was measured in the receiving cavity of a shipping package of the first configuration 50a shown in Figure 8, fitted with two thermal buffer assemblies of the type described above with reference to Figures 1 to 3. The ice pack was chilled to an initial temperature of 18°C in a freezer, and then removed and allowed to rest at ambient temperature for 5 minutes before packing, such that the ice pack reached a temperature of approximately -10°C at the start of the test. The initial temperature of the thermal buffer assembly was 5°C and the ambient temperature was 20°C. The dimensions of each thermal buffer assembly were 152 mm in length and width and 19 mm in thickness, and each ice pack had a mass of 480 g. The results are shown as line 101 in Figure 10. As can be seen, the temperature remains always within the target range R of between 2°C and 8°C for at least 40 hours.

For comparison, the test was repeated with each of the thermal buffer assemblies being removed and replaced by a single walled, C-flute corrugated cardboard pad having a thickness of 3 mm, as would typically be used in the prior art. The results are shown as line 102 in Figure 10. Initially, the temperature drops below 0°C, and then recovers to between 0°C and 2°C. The temperature remains outside the target range R for the whole duration of the test, and the initial drop in temperature would introduce a risk of freezing of the product.

The size and dimensions of the thermal buffer assembly can be selected as appropriate for a particular application. It is desirable that the thermal buffer assembly is a tight fit in the cavity of the shipping container to minimise convective heat flow around the assembly, thereby encouraging heat exchange with the thermal buffer assembly. For use in many applications, the length of the mat may be between approximately 200 mm and approximately 1000 mm, with the corresponding length of the thermal buffer assembly being half of the length of the mat. The width of the mat, and the thermal buffer assembly, may be between approximately 100 mm and approximately 750 mm. Dimensions outside these ranges are also possible. The amount of phase change material in the mat may depend on the amount of phase change material provided in the associated refrigerant pack. For example, for shipping packages comprising an expanded polystyrene box and lid, the weight of the phase change material in a thermal buffer assembly may be between approximately 30% and approximately 40% of the weight of the adjacent refrigerant pack, with the phase change material being evenly distributed between the sides of the mat (i.e. between the first and second phase change layers) and between the cells in each layer. In one example, the refrigerant pack is an ice pack having a mass of approximately 480 g, and the phase change material is water with a total mass of approximately 150 g. In another example, the refrigerant pack is an ice pack having a mass of approximately 1050 g, and the phase change material is water with a total mass of approximately 400 g.

Preferably, to ensure uniform distribution and freezing of the phase change material, each cell has a capacity of not more than approximately 100 ml, and more preferably not more than approximately 75 ml.

In the above examples, water is used as the phase change material in the thermal buffer assembly and also as the coolant material in the refrigerant pack. This provides a particularly cost-effective and convenient solution for the transportation of products with a target temperature range of approximately 2°C to approximately 8°C. However, the invention is not limited to the use of water, and any suitable material could be used for these purposes. For example, the phase change material and/or the coolant material could comprise a gel material (for instance by the addition of hydroxy ethyl cellulose, sodium polyacrylate, silica gel or another suitable material). The phase change material and/or the coolant material could comprise methyl laurate or other similar materials. It is also possible for different phase change materials to be used in the first and second phase change layers.

It will be understood that, by the selection of suitable phase change material and coolant material, the invention can be used in applications in which the required temperature range differs from the 2°C to 8°C range discussed above. The insulating panel may differ from that described above. The purpose of the insulating panel is to allow heat transfer between the first and second phase change layers at an appropriate rate to optimise the temperature-time profile of the phase change layer closest to the product in use. The preferred rate of heat transfer may depend upon several factors, including the expected ambient temperature, the size and mass of the shipping package, the material, thickness and effectiveness of the insulation in the box and lid of the shipping package, and so on. In variants, therefore, the insulating panel may comprise a core, such as bubble film, with a reflective lining on only one side or on neither side (i.e. the insulating panel consists only of the core). As an alternative to bubble film, the core may comprise a different trapped-air material, such as corrugated cardboard or foam. The use of corrugated cardboard may be desirable to provide increased thermal transfer through the thermal buffer assembly compared to a bubble film core, for example for use with shipping packages insulated with natural materials. Arrangements in which the core comprises two or layers of different materials are also possible.

Further modifications and variations not explicitly described above may also be contemplated without departing from the scope of the invention as defined in the appended claims.