Note: Descriptions are shown in the official language in which they were submitted.
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A PASSIVE TEMPERATURE CONTROL SYSTEM FOR TRANSPORT AND STORAGE
CONTAINERS
Field of Invention
[0001] The present invention relates to the field of the transportation and
storage
of goods and to a passive temperature control system for such a transport and
storage containers.
Background to the Invention
[0002] In the field of logistics, that is the field of movement and supply of
produce and materials, there is a substantial requirement for the provision of
a
temperature control system to ensure that certain types of produce and
materials
do not pass through temperature thresholds. It is well known that, for
example,
vegetables when subject to extremes of temperature that they become flaccid,
as
the cell structure is broken down through the formation of icicles or through
dehydration. Similarly, in the transport of drugs and vaccines and certain
other
chemicals, a solution may separate or become solid. It will also be
appreciated
that even relatively small amounts of pharmaceutical product can cost
thousands
of pounds or more; temperature deviations from an allowed temperature can
become very expensive; such goods typically having journey temperature
plotting
indicators, whereby any temperature deviation means that product is discarded
and destroyed, irrespective of the cost of the product.
[0003] In essence, in any transport container with a thermally sensitive load,
the
rate at which heat passes through the packaging material of the transport
container - the amount of heat that flows per unit time through a unit area
with a
temperature gradient per unit distance must not extend beyond a permitted
temperature range for the product. Temperature control of thermally sensitive
goods is particularly challenging when the thermally sensitive goods must be
maintained within a narrow temperature range.
[0004] Multilayer insulation (MLI) is the most common passive thermal control
element used in transport. MLI seeks to prevent both heat losses to the
environment and excessive heating from the environment. Low cost temperature
control in the transport industry relies upon MLI to retain an inside
temperature
subject to the thermal path to a transported product from an outside the
outside
to maintain ideal operating temperature. MLI can simply comprise layers of
plastics foam; more complex MLI can consist of an outer cover layer, an
interior
layer, and an inner cover layer. Some common materials used to the outer layer
are fiberglass woven cloth impregnated with PTFE Teflon, PVF reinforced with
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Nomex bonded with polyester adhesive, and FEP Teflon. The general requirement
for interior layer is that it needs to have a low emittance. The most commonly
used material for this layer is Mylar that is aluminized on both or one side.
The
interiors layers can be thin compared to the outer layer to save weight.
[0005] It has been known to store goods which are sensitive to temperature in
thermally insulated containers in which so-called cooling blocks are housed.
One
simple example of such a container is that used by homemakers to store food.
In
this case, the interior of the thermal container need only be kept cool for a
relatively short period of time. Because of this, and because direct contact
of the
food with the cooling block is not normally harmful, it suffices to freeze the
block
to the necessary temperature prior to using the same. In their simplest form,
the
cooling blocks are filled solely with water, which when frozen has a high heat
of
fusion and consequently is able to maintain the food in a cool environment for
a
considerably period of time. Such an apparatus is effective to keep food
wholesome or to keep beverages cool for a certain period of time at ambient
temperatures which lie above the desired storage temperatures. The use of
cooling blocks filled with water cannot be considered for the storage of
freeze-
sensitive products, such as blood within tolerable temperature ranges,
particularly
in the case when the ambient temperature falls beneath a permitted storage
temperature, since the latent heat of fusion of water on the formation of ice
is not
released until the temperature falls below 0 C, meaning that a product could
be
cooled below an ideal temperature.
[0006] Typical means for shipping temperature sensitive materials involves the
use of an insulated box, with the necessary shipping and warning labels, along
with some cooling agent. These cooling agents have typically been, for
example,
a frozen gel, dry ice, or wet ice, placed within an insulator packing agent,
such as
cotton or, latterly, plastics materials such as expanded polystyrene foam,
wherein
heat is absorbed by such cooling agents.
[0007] There are, however, several problems with the conventional approach.
First, the polystyrene foam used for insulation does not degrade readily,
leading
to disposal problems. Second, the cooling agents also present numerous
practical
problems in field use. Specifically, gel systems are often too expensive for
routine
use and disposal. As for dry ice, the carbon dioxide gas evolved during
shipment
is so dangerous to shipping personnel that hazard warnings must be posted and
additional fees are required to be paid; furthermore, outright bans on dry ice
are
pending in several areas. Finally, wet ice poses handling problems in packing,
as
= well as leakage and product soaking problems.
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[0008] Blood, meaning transfusion blood, must be maintained within a close
temperature range of between +1 C and +6 C during its passage between donor
and receiver. Various biological products, such as platelets, whole blood,
semen,
organs and tissue, must be maintained above a predetermined minimum
temperature and below a predetermined maximum temperature. Pharmaceutical
products are also commonly required to be kept within a specified temperature
range. Food products, flowers and produce frequently have preferred storage
temperature ranges as well. Indeed, certain types of goods have stringent
standards to be adhered to. For example, as part of a World Health
Organisation
(WHO) prequalification scheme, vaccine manufacturers are expected to ensure
their packaging complies with the criteria specified below: Class A packaging:
Vaccines must be packed to ensure that the warmest temperature inside the
insulated package does not rise above +8 C in continuous external ambient
temperatures of +43 C for a period of at least 48 hours. Class B
packaging: Vaccines must be packed to ensure that the warmest temperature
inside the insulated package does not rise above +30 C in continuous external
ambient temperatures of +43 C for a period of at least 48 hours. Class C
packaging: Vaccines must be packed to ensure that the warmest temperature
inside the insulated package does not rise above +30 C in continuous external
ambient temperatures of +43 C for a period of at least 48 hours and the
coolest
storage temperature of the vaccine does not fall below +2 C in continuous
external temperatures of -5 C for a period of at least 48 hours. Many known
methods and systems for shipping such products are not able to keep
temperatures within the desired range.
[0009] Numerous insulated shipping containers have been developed over the
years, with those deploying a phase change material (PCM) generally providing
superior temperature control over extended periods. Insulated shipping
containers employing a PCM can be deployed for a wide range of thermally
sensitive goods over a wide range of target temperatures by using different
PCMs. For example, D20 melts at +4 C, H20 melts at 0 C, a 20% ethylene glycol
solution melts at -8 C, castor oil melts at -10 C, neat ethylene glycol melts
at -
12.9 C, mineral oil melts at -30 C, and a 50% ethylene glycol solution melts
at -
37 C. This permits use of insulated shipping containers for a broad range of
thermally labile goods. However, in order to accommodate the packaging of a
wide variety of thermally labile goods, the shipper needs to purchase and
inventory a sufficient number of PCM panels containing each of the different
PCMs
to meet the highest possible demand for that type of PCM panel. For example,
assume that a shipper typically has between about 800 and 1,200 passive
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thermally regulated shipping containers in transport on any given day, each of
which employ six PCM panels and all of which could require one of two
different
PCM panels containing different PCM. This shipper would need to purchase,
inventory, track and maintain 14,400 PCM panels ((1,200 containers)(6 PCM
panels/container)(2 PCM panel types)). The need to purchase, track and
maintain
such a large number of PCM panels can become cost prohibitive.
[0010] Current design practice in temperature controlled packaging involves
using a single temperature PCM conditioned in an 'ideal' state depending on
the
thermal challenge to be presented to the temperature controlled packaging
during shipment. However this is troUblesome on two counts. Firstly, the PCM
packs must be warmed or cooled to just above or just beloW their Phase Change
Point, this can be difficult to achieve in normal industrial warehousing
scenarios,
as such ideal temperature ranges can be as narrow as (for, hot shipping
Conditions) +15 C to +19 C and (for cold shipping conditions) +20 C to +24 C.
Seco'ndly, it is very hard to predict what conditions will be experienced by
the TCP
during transit.
= [0011] In order to maintain a stable temperature it is advantageous to
use a
Phase Change Material =(PCM) that has a Latent Heat of Fusion both above and
below the standard hold temperature of +20 C (the mid-point of most
pharmaceutical specification warehouses), but this is difficult to achieve
with the
use of just one PCM. Indeed, the use of two PCMs within a shipping container
is
known. In US7908870 to Entropy Solutions and US8424335 to Pelican,
= arrangements that utilise Dual PCM embodiments are taught having a
thermal
insulation and a plurality of different phase change materials within an
interior
volume. Specifically, these documents relate to a container and a plurality of
different phase change Materials within an interior volume, to provide
respectively - and with reference to Figures la and lb, to a container having
exterior thermal insulation lal, a first phase change material PCM1 (for
example =
water), a further layer Of insulation 1a2, a second layer of phase change
material
PCM2, and to a container having exterior thermal insulation lbl, a first phase
change material PCM1 (for example water), a second layer of phase change
material PCM2 (for example paraffin wax), wherein at least one of the PCMs
acts
as a thermal buffer to protect a temperature sensitive payload TSP against
= thermal damage from the other PCM having a temperature outside of a
predetermined temperature range for payload protection. Each container will be
adapted in size / temperature combination to determine a thermally controlled
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container in respect of a particular payload, target temperature, guaranteed
duration of thermal control, size of and weight of container.
[0013] Whilst these systems are stated as working within limited temperature
ranges, fcir periods Of time they can be difficult to set up with different
terhperature profiles to be adhieved. Specifically, where two phase change
materials are employed, these materials have been selected, temperature
conditioned, stored and packed separately, in a correct, predetermined fashion
to
provide the optimal thermal protection. It has been known that the phase
change materials have been confused and Misplaced in a container upon loading
of the container, giving rise to an incorrect temperature-time profile;
equally,
supervisory actions and checking operations become necessary, leading to
increase in loading time i.e. provides an additional delay and incur further
processing costs. Essentially, such known Systems either cannot provide broad
range of temperature thresholds or are complicated to set up and as a result
are
liable to failure.
Object of the Invention
[0014] The present invention seeks to provide a solution to the problems
addressed above. The present invention seeks to provide a phase change
=
material system that can enable goods to reliably be maintained within a=
particular temperature range. The present invention also seeks to provide a
temperature controlled transport/storage assembly for goods palletised or
otherwise, Whereby goods can be maintained within an atmosphere having a
predefined temperature range.
Statement of Invention
[0015] In accordance with a general aspect of the invention, there is provided
a
temperature controlled transport/storage container for transporting/storing
temperature sensitive materials comprising: an outer insulating container-
having
a top inner wall, a bottom inner wall and inner sidewalls; insulating means
for
insulating said cavity comprised of a lining disposed adjacent said inner
walls of
said carton to define an insulated cavity; a plurality of temperature contrOl
packs
for placement within said inSulated cavity, adjacent said means fcir lining
said
inner walls to define a payload volume; wherein said temperature control packs
include first and second phase change materials, wherein the phase change
materials are arranged as generally planar packages, each planar package
having
spaced apart first and second major planes, each type of phase change material
providing distinct thermal characteristics, the first major faces of the phase
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change materials being arranged in a co-planar fashion whereby at least two
types of phase change material package face the payload volume.
[0016] In use, the temperature control packs are configured for a particular
period of time, with reference to the type of load, volume of load, and
expected
ambient temperatures likely to be encountered. By configuring the different
types of phase change material in a co-planar fashion, it will be appreciated
that
an effective load volume is increased significantly. This is because the
increase in
effective transport volume is greater than a nominal reduction in thickness
per
insulation layer and phase change materials per given it may well be effective
in
three dimensions, given that previous practice of providing such temperature
control elements in has been to provide such distinct phase control elements
in
= distinct layers. Conveniently, said temperature control packs are
contained within
an envelope comprising a generally rectangular box shape, made from an
insulating sheet material such as cardboard, or a plastics, in the form of a
simple
sheet or corrugated, whereby to define a separation distance.
[0017] Conveniently, said temperature control packs which include first and
second phase change materials, are contained in sealed containers and said
containers are arranged as a unitary element by virtue of being associated
with
= each other. For example, the pack can be defined by one of a cardboard or
plastics sheet box or sleeve the sheet material being a plain sheet or
optionally
corrugated, plastics bag, a blister pack, a sheet cellulose package, a sealed
polymer enclosure. Additional insulation could be provided on an outside
surface
of the pack, although this could have an effect in increasing a conditioning
period
of time in a temperature controlled enclosure, before use, as is known.
Ideally,
=through the common use of a standard sized package, inventory levels can be
simplified.
[0018] The temperature control packs can be configured to provide a thermally
stable atmosphere within the payload volume for a number of days as is typical
for international travel, for example. The present invention can, by the use
of
specially adapted thermal modelling software, be optimised for particular
goods
for specific transport and storage time with respect to a specific payload
space. If
the size and number of product cartons is known that need to be shipped, an
analysis can be simply be performed whereby to provide users with graphical
and
statistical results to ensure cost effective use of the present invention in a
packaging system. By maximising the available useful product volume, it will
be
appreciated that the overall package employed can be smaller than what
otherwise have been used, with a concomitant benefit in a reduction of
transport
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and storage charges. This has the advantage that a particular temperature
sensitive consignment can be tailored for a particular transport scenario.
[0019] The first and second phase change materials could each have a phase
change temperature in the range of +50 C to -80 C; conveniently, the phase
change materials are conditioned at the same temperature ¨ i.e. once placed
within a temperature control pack, whereby overall processes can be
simplified. It
is possible that the temperature control packs include at least one further
phase
change material. The temperature control packs can be arranged such that they
include equal numbers of particular types of phase change materials. More
typically, the first and second phase change materials would have a phase
change
temperature in the range of +250 C to -20 C. Such a range of phase change
materials can cater for most typical temperature controlled storage and
transport
requirements. Typically, however the first and second phase change materials
which define the upper and lower phase change temperatures have a difference
of 6-10 C. This is such that in the case of vegetables, for example,
transport
conditions are typically between 4 C and 12 C; with reference to, say,
lettuce, if
the temperature goes below freezing point, water within the cell structure
present
will become ice and the ice crystals will destroy the leaf structure; equally,
having
the products at extended periods above 12 C will result in the water within
the
cell structure evaporating.
[0020] The phase change materials can be contained in the form of one or more
= of flexible plastics bags; flexible polymer bags; flexible blister packs;
putty; foam
encapsulation. The phase change materials could also be presented in a moulded
plastics container, such as a blow-moulded enclosure such as high density
polyethylene plastics material or similar. Conveniently, the packaging system,
together with such phase change materials, is presented in a container such as
a
cardboard box or sleeve. The phase change materials can be thermally connected
= with each other via a thermally conductive layer of material, which could
be
applied to the container, and could comprise a reflective coating such as an
aluminized coating. Alternatively, the container is manufactured from plastics
sheeting, corrugated cardboard and corrugated plastics. The insulating means
for
insulating said cavity could comprise one of or more of: a plastics foam;
cellulose
fibre (loose); cellulose fibre (compressed); Multilayer insulation (MLI)
including
plastics foam; fibreglass woven cloth; fibreglass woven cloth impregnated with
PTFE Teflon, PVF reinforced with Nomex bonded with polyester adhesive, and FEP
Teflon, Mylar that is aluminized on both or one side. Given that certain
packaging
systems comprise small cartons which such cartons are often transported
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together, it has been found that when grouped, en masse, this has had a
negligible effect. In an alternative system, the present invention provides a
packaging system, wherein the box has a number of sides and for each side of
there is a phase change material temperature control pack. Notwithstanding
this
each phase change material temperature control pack is provided with dual /
multiple phase change materials.
[0021] In a further aspect of the invention, the phase change materials can be
disposed in separate interlocking moulded elements, with for example, a first,
peripheral resilient moulded container operably filed with a first phase
change
material in the general shape of an oval, with a central aperture defining a
cavity,
with a second, central resilient moulded container operably filed with a
second
phase change material, whereby to provide a unitary temperature control
element, optionally provided with an insulation layer, whereby to be placed
adjacent product, without a further, separate layer of insulation, to thereby
still
further maximise an internal volume but also enabling a simplifying the
associated packing process.
[0022] In accordance with another aspect of the invention, there is provided a
method of packing a container for shipment comprising the steps of
a. obtaining a container;
.. b. lining the entire interior surface of the container with insulator
material;
c. selecting a plurality of temperature control packs for placement within
said
insulated cavity, wherein said temperature control packs include at least
first and
second phase change materials arranged as generally planar packages, each
planar package having spaced apart first and second major planes with edge
faces connecting the first and second major planes; wherein the phase change
materials provides distinct thermal characteristics, wherein the at least two
types
of phase change material packages are arranged in a coplanar orientation with
respect to each other;
d. determining a temperature at which to condition a temperature control pack
means with regard to the size of the container, the duration of
transport/storage
of the container; expected ambient conditions;
e. placing the temperature control pack at the determined temperature in a
temperature conditioning apparatus, whereby to ensure the temperature control
pack is brought to said set temperature;
f. placing the temperature control packs having been brought to said set
temperature in the container whereby to define a payload volume;
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g. placing a payload within the payload volume;
h. placing a temperature control pack upon the payload and other temperature
control means; and,
i. closing and sealing the container.
It will be appreciated that separate layers of insulation may need to be
provided.
[0023] The present invention can thus provide a simple to use solution,
conveniently using only one type of phase change material wallet for a
particular
container system, thereby reducing the chance of failure through the incorrect
orientation / placement of one of two types of phase change material. Whilst
possible, one could temperature condition the two types of phase change
material separately; this would not ordinarily be beneficial - by correct
selection
of the two phase change materials, placement of the phase change material
containers within the wallet provides a convenient and method simplifying a
loading process. Additionally, the use of two phase change materials arranged
in
co-planar fashion as opposed to being arranged in a thicker, spaced apart in a
parallel fashion can reduce wastage within a container, meaning that more
goods
for a given unit volume can be employed or a smaller box can be selected.
Additionally, a substantial benefit is that all the temperature conditioning
of the
phase change materials occurs with respect to one fridge/cool room prior to
placement within a container for transport / storage of temperature sensitive
goods, where the sleeves are either highly insulating in themselves or benefit
from further internal and or external thermally insulating media comprising
panels, sleeves or other insulating materials. Additionally, in one
embodiment,
the invention also benefits from its ability to use the same size temperature
control packs to be utilised in different containers; commonality of parts
between
ranges of product can provide more cost-effective construction and/or
different
functionality.
Brief Description of the Figures
[0024] For a better understanding of the present invention, reference will now
be
made, by way of example only, to the Figures as shown in the accompanying
drawing sheets, wherein:-
Figures la, lb illustrate sections through two known temperature control
configurations from an inside wall of a container through to a payload;
Figure 2a, 2b illustrate first and second perspective views of a "phase
change cassette";
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Figure 2c, 2d show two different orientations of phase change packets
with a "phase change cassette";
Figure 3a shows a view of a container in accordance with the invention
prior to placement of the insulating material cover and cassettes of phase
change
material with respect to a load;
Figure 3b shows an arrangement of phase change plastics bags within a
phase change cassette;
Figure 3c shows a sections through a temperature control configuration
in accordance with another embodiment of the invention from an inside wall of
a
container through to a payload;
Figure 3d shows a plan view of a phase change cassette in accordance
with the embodiment shown in Figure 3c;
Figure 4 shows a typical non-integrated pallet with a load;
Figures 5a and 5b show a first component in accordance with one aspect
of the invention in perspective view and the temperature - phase
characteristic of
the two types of phase change material;
Figure 6 shows an exploded view of a container in accordance with the
invention indicating the placement of cassettes of phase change material with
respect to a load;
Figures 6a and 6b comprise graphs comparing temperature change over
time in packaging in accordance with the inventions at with respect to typical
external ambient temperatures, as encountered during travel;
Figures 6c and 6d comprise graphs detailing the temperature change
over time in packaging in accordance with the inventions at constant specific
external ambient temperatures;
Figures 7a - 7c show how modular PCM strips can be configured;
Figures 8a - 8d show the manufacturing steps in manufacturing PCM
modules;
Figures 9a - 9c detail a still further embodiment of a PCM module; and,
Figure 9d shows a still further embodiment of a PCM arrangement.
Detailed description of the Preferred Embodiments
[0025] There will now be described, by way of example only, the best mode
contemplated by the inventor for carrying out the present invention. In the
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following description, numerous specific details are set out in order to
provide a
complete understanding to the present invention. It will be apparent to those
skilled in the art, that the present invention may be put into practice with
variations of the specific.
[0026] With reference to Figure 2, an aspect of one embodiment in accordance
with the present invention shall be described in a simple to use assembly
comprising a cardboard wallet (aka "cassette" / "envelope" / "sleeve") 20 in
which a number of first 21 and second 22 plastics bags are placed containing,
respectively, first and second phase change materials are placed. The wallet
may
also be represented as a sleeve. Conveniently, there are four elements placed
therein or - alternatively - eight elements placed therein in two layers.
Other
configurations are possible; simplicity is, nonetheless, of benefit. This
embodiment of the invention utilises plastic bags 21, 22 filled with different
phase change materials (PCM), to maintain the internal product temperature
between +15 to +25 , which temperature is also known as the Control Room
Temperature (CRT). Figure 2c shows the separate phase change materials placed
in parallel spaced apart relationship; in Figure 2d, the phase change
materials are
spaced diagonally with respect to each other. Especially with the use of a
conductive film interface in contact with the plastics bags, such difference
in
packaging has not realised a significant difference in internal temperatures
measured.
[0027] Such wallets are conveniently dimensioned to be placed with a suitably
tight fit within a container 30 as shown in Figure 3a but a typical cassette
will
have dimensions of 300 x 250 x 25 mm. Figure 3b shows an arrangement of first
and second phase change materials as contained within plastics bags, as can
conveniently be simply manufactured using standard bag filling techniques.
Figure 3c shows a similar cassette, save that the phase change materials are
contained within plastics trays (as shall be discussed below), with the
cassette
being shown in cross-section vis-à-vis a load and wallet/cassette 20. This
figure
can be compared to the cross-sectional views shown in relation to the prior
art in
Figures la and lb. Whilst, the present invention may well have a first and
second insulation layers, it can be readily understood, the a layer of phase
change material has been removed, whereby to make the packing of shipping (or
storage) containers simpler and, importantly, less liable to incorrect
packing, by
for example, a reversal of the order of the first and second coolant wallets
20. A
significant effect is that the effective payload area for a given volume is
increased, given that the prior art perception of a requirement of separation
of
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distinct phase control materials is not, in actual fact, required.
[0028] Figure 3d shows a plan view of a coolant wallet with the two different
phase change materials, PCM1 & PCM2, having phase change temperatures as
indicated (+17 C and +22 C). A main advantage of the concept behind the
present invention is that a single temperature control wallet is placed within
a
container having been temperature conditioned at a single temperature, the
types of phase change materials, the respective amounts of the different phase
change materials and the conditioning temperature being selected dependent
upon the anticipated temperatures, the desired internal temperature and the
nature of the filling, taking into account the nature of the packing container
and
associated insulation surrounding the temperature control wallets.
[0029] In a first variation, there can be further provided a layer of material
having a high thermal conductivity in contact with the plastic bags containing
the
phase change material, to enable the creation of a surface having a
substantially
homogenous temperature within the wallet, which material is preferably
associated with the face adjacent the payload space. In particular, the
thermally
conductive layer can conveniently be positioned between the plastics bags of
phase change material and the face of the cassette that would face the payload
area. Materials such as metallized film adhered to a carrier paper or a
metallized
.. film applied to a rigid plastics sheet and associated with corrugated board
can be
conveniently provided. Such a material could also form part of the wallet
body.
[0030] The present invention enables phase change materials about a payload to
absorb heat / release energy to resist cold by enabling a phase change
material
to react with respect to changes in external temperatures, where the phase
change materials are selected to define a selected permissible range of
temperatures within a payload area of the container. As will be appreciated,
as
the container enters a reduced temperature zone, the phase change materials
will
release energy due, at least in part, to a change in phase of a lower
temperature
rated phase change material. Equally, as the container enters an elevated
.. temperature zone, the phase change materials will absorb energy due, at
least in
part, to a change in phase of a higher temperature rated phase change
material.
That is to say, each phase change material will change state from liquid to
solid
to release energy or will change state from solid to liquid, to absorb energy.
As
will be appreciated, in a change of phase state, a material will remain at
substantially the same temperature; i.e. the temperature of the material
remains
stable, as can be seen in the graph shown in Figure 4. It is important to
realise
that in a freezing phase, energy is released in an exothermic process; whilst
in a
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melting phase, energy is absorbed by the phase change material in an
endothermic reaction.
[0031] With reference to Figures 5a and 5b, there is shown an example of a
temperature control wallet comprising two types of phase change material. This
dual PCM system, for example, allows for the two phase change materials to be
stored at +20 C and achieve a composite of solid / liquid segments within the
temperature control wallet. The overall thermal effectiveness of the pack
permits
protection of the temperature sensitive goods to be achieved with a single
conditioning temperature of, for example +20 C. Specifically, and as has been
tested in respect of the present invention, a combination of a +17 C PCM and a
+22 C PCM, when placed in a wallet can be simply considered at 20 C as
comprising a first liquid phase change material (i.e. the +17 C PCM), offering
Maximum thermal protection against cold thermal stress on the system and a
second solid phase change material (i.e. the +22 C PCM), offering maximum
thermal protection against thermal stress on the system. Applicants have
determined that by the placement of these distinct phase change materials
within
the same container (wallet, cassette, etc.) then the overall temperature
balancing
effect can be retained, without the previously determined requirement to have
separate containers in respect of the separate phase change materials. It has
been found that the provision of a layer of material having a high thermal
conductivity in contact with the phase change materials plastics bags to allow
a
homogenous temperature to be created on the contact face (lowermost face) of
the assembly - where it would contact the payload space in the temperature
controlled package.
[0032] Current design practice in temperature controlled package involves:
i) in the case of the use of a single phase change material, then this phase
change materials is conditioned in an `ideal' state depending on the likely
thermal
challenge to be presented to the temperature controlled package during
shipment. However this is troublesome on two counts, namely that the phase
change packs must be warmed or cooled to just above or just below their
determined phase change temperature, which can be difficult to achieve in
normal industrial warehousing scenarios, as such ideal temperature ranges can
be as narrow as (for hot shipping conditions) +15 C to +19 C and (for cold
shipping conditions) +20 C to +24 C and; it is very hard to predict what
conditions will be experienced by the temperature controlled package during
transit.
ii) When two phase change materials are employed, the distinct phase change
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materials are contained/packaged/installed as two distinct components. It will
be
noted that these distinct components need to be selected, labelled,
conditioned
and placed in distinct these components have to be stored at the correct
temperature and must be packed in the correct manner to provide the optimal
thermal protection.
[0033] The present invention thus allows for a simple, single temperature
preparation of the dual phase change containers/cassettes at standard Control
Room Temperature (CRT) conditions. The design requires little training to
facilitate use which will safeguard quality of shipment. Importantly the
margin
for error is significantly reduced. In use, the temperature of the phase
change
materials is calculated to enable the temperature to be centred about an ideal
temperature depending on the thermal challenge to be presented to the
temperature controlled package during shipment. However this is troublesome on
two counts:
[0034] The phase change materials plastics bags that are filled with two
different
PCMs that have different Freeze/Thaw temperatures. With reference to the
embodiments in Figures 5a ¨ 7c:
[0035] PCM1 has a Freeze/Thaw temperature at around +17 C, that at +20 C
would be in a liquid state and would temperature stabilise at +17 C as it
freezes
if the TCP was exposed to temperatures less than +17 C. There is a capability
to
tailor the amount of phase change material in the cassettes whereby the
overall
thermal response characteristics can be adjusted depending on the thermal
challenge anticipated.
[0036] PCM2 has a Freeze/Thaw temperature at around +22 C, that at +20 C
would be in a solid state and would temperature stabilise at +22 C as it thaws
if
the TCP was exposed to temperatures greater than +22 C.
Embodiment #1 - Adjacent ¨ in line
[0037] This embodiment has the two phase change materials in separate plastics
bags in-line with each other, packed into the same cardboard container or
cassette. It has been found that the provision of a layer of material having a
high
thermal conductivity in contact with the phase change materials plastics bags
to
allow a homogenous temperature to be created on the contact face (lowermost=
face) of the assembly ¨ where it would contact the payload space in the =
temperature controlled package.
Embodiment #2 - Adjacent ¨ alternating
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[0038] This embodiment has the two phase change materials in separate plastics
bags alternating with each other, packed into the cardboard container or
cassette. This design is believed, in principle, to provide greater thermal
stability
than the first embodiment due to the better spread of the differing latent
heat
materials, but this might not be noticeable in practice. It has been found
that the
provision of a layer of material having a high thermal conductivity in contact
with
the phase change materials plastics bags to allow a homogenous temperature to
be created on the contact face (lowermost face) of the assembly - where it
would
contact the payload space in the temperature controlled package.
[0039] To enable a simple appraisal of the thermal capability of the present
invention, extensive thermal testing has been performed, with reference the
results of which show a distinct advantage of the Dual Adjacent PCM system of
a
system with only one or the other PCM contained within. Specifically, with
reference to Figure 6, which shows a container with external insulating panels
outside of the PCM panels, in first and second series of tests under,
respectively,
summer and winter conditions, the three systems being tested, as follows:
Si) The use of a single type of PCM material only - +17PCM - which provided
poor
HOT protection as no phase change occurs since such a phase change material is
liquid at +20 C.
Sii) The use of a single type of PCM material only - +22 PCM - which provided
good HOT protection as phase change occurs at +22 C.
Siii) The use of two types of phase change materials - +17 and +22 PCM
materials - which provided good HOT protection as phase change occurs at +22 C
- for the +22PCM material.
Wi) The use of a single type of PCM material only - +17PCM - which provided
good cold protection as phase change occurs since such a phase change material
= has a phase transition temperature of +17 C.
Wii) The use of a single type of phase change material only - +22 PCM - which
provided poor cold protection as phase change occurs at +22 C.
Wiii) The use of two types of phase change materials - +17 and +22 PCM
materials - which provided good cold protection as phase change occurs at +17
C
- for the +17PCM material.
[0040] The results of the first and second tests are shown with reference to
Figures 6a and 6b and it is clear to see that the system using the two phase
change material embodiment out performs the systems that only utilise one
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phase change material type, which is common in the TCP market place today.
[0041] In a further set of tests, a prototype system using the same +17 and
+22PCM materials ¨ changing phases, respectively at +17 C and +22 C. The
system was prepared with all the phase change materials conditioned at +20 C
.. and then tested at two ambient stresses, namely a constant +30 C
(equivalent to
many ambient summer conditions) and a constant +5 C (equivalent to many
ambient winter conditions). The results of these tests are graphically shown
in
Figures 6c and 6d, respectively, where it is shown that: under summer
conditions
a payload temperature was maintained payload between +15 C to +25 C for
38hr5; and under winter conditions a payload temperature was maintained
between +15 C to +25 C for 68hr5. It will be appreciated that the ratio of +17
to
+22 phase change materials can be altered to help 'balance' the performance
levels achieved against the hot and cold stress test profiles. Equally
different
types of phase change material could be employed.
[0042] Applicants have also developed a process of manufacturing phase change
materials wherein phase change materials, in liquid form, can be placed in
trays
defined in multi-layer thermo-formed plastics films. Plastics such as
Acrylonitrile-
butadiene-styrene (ABS) and acrylic can also be used to prove relatively rigid
assemblies, which can be of benefit. Pre-set phase change material ratios can
be
adapted for particular circumstances and are placed in respective trays, the
material conveniently being placed whilst in a liquid state under low
atmospheric
pressure and sealed with a plastics film which is used to seal under the
application of heat and/or an adhesive. This plastics film could also be
conductive,
as discussed above.
[0043] Further types of phase change materials are being continuously
developed
and presently phase change materials are being developed which have putty-like
formable handling characteristics at certain temperatures, whereby to enable
particular shapes to be created. Such shapes can be encased in plastics films
to
provide phase change materials in something analogous to blister pack pockets.
Manufacturing methods for producing blister packs are well-developed. The
primary component of a blister pack is a cavity or pocket made from a formable
web, usually a thermoformed plastic. This usually has a backing of paperboard
or
a lidding seal of aluminium foil or plastic. Blister packs are useful for
protecting
products against external factors, such as humidity and contamination for
extended periods of time. Opaque blisters also protect light-sensitive
products
against UV rays. In a further alternative of the present invention blister
packs
can be produced with a shape arranged such that only a percentage of cavities
of
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a blister pack in a pattern being employed, with apertures present where
unfilled
blisters are present; by combining with another blister pack arrangement in
respect of a second phase change material, a two dimensional array of two
phase
change materials could be prepared. Equally, not all the "blister centres in a
.. pattern need be occupied. A third or further phase change material could be
provided in the gaps that have remained unfilled. Given that a range of phase
change materials exist, by the use of colour coding, visible, for example
through
a small aperture in a cassette or wallet enclosure, a make-up of a cassette
can be
determined and temperature conditioned prior to use in a simple fashion.
[0044] It should also be noted that the presentation of PCM materials is being
continually developed. For example, Microencapsulated phase change material
sometimes referred to as microPCM - products are now becoming commonplace.
Microencapsulated phase change material products comprise very small dual-
component entities consisting of a core material comprised of a phase change
material PCM - and an outer shell or capsule wall. The PCM substance can
conveniently be provided as a wax - such as a paraffin-wax or a fatty acid
ester
operable to absorb and release energy in the form of heat in order to maintain
a
particular temperature. In use, in a warm environment with an increasing
temperature, the PCM would initially absorb the heat (the PCM melts inside the
capsule wall) and store it until the temperature drops from the outside
environment; at which time, the heat is released (the PCM re-solidifying
within
the capsule wall) releasing energy in the form of heat, which can assist in
temperature control. At all times, the capsule wall contains the PCM, so
regardless of whether the actual PCM is in the liquid or solid state, the
capsule
itself remains as a solid particle containing the PCM. The capsule wall can
conveniently be provided as an inert, very stable polymer. Such PCMs can be
provide in a manner of slurry, where, for example a capsule size of 1 - 41Jm
is
employed with 35-45% as solid in an aqueous slurry, a paste, where capsules of
a size between 10 and 30pm are present as 70% solids with water or as a dry
powder, the micro capsules of 10 - 30pm being processed such that they can be
provided with polyurethane foams and the like. Larger beads or capsules, of
the
order of 2 - 5mm - sometimes referred to as macroPCM capsules can also be
employed.
[0045] Thus, by the use of such micro/macroPCM particles, used with PU foam,
and other binders stable products of two or more PCM materials can be reliably
be produced. PU foam may be considered as having too much insulator gas by
volume; accordingly, a binder may be employed such that the particles are
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compressed and retained without too much dead space, which can also affect the
rate of change. It is also to be. noted that the micro/macroPCM particles may
be
filled with one or more types of PCM. Equally, there may be provided two
distinct
types of micro/macroPCM particle. By the use of organic-based phase change
.. material, the phase change properties are not been observed to lose their
efficacy
over thousands of cycles.
[0046] With reference to Figures 8a - 8d, an outline process shall now be
described: In figure 8a, a base multi-layer film is thermo-formed into
'trays'.
Using foam technology, for example, a shape-stable foam is placed into the
tray
.. cavities - per Figure 8b. First and second phase control materials are then
introduced into the stabilising foam - per Figure 8c, followed by sealing of
the
cavities by the placement of a thermally conductive web used to seal the
cavities
closed.
[0047] Figure 9a and 9b show an alternative arrangement in respectively spaced-
apart perspective and spaced apart edge view. The phase change materials are
enclosed within two separate container elements 91 and 92. Container 91,
conveniently manufactured from a plastics material such as high density
polyethylene and manufactured using well-known blow moulding techniques,
comprises a generally plano-rectangular container with inside walls 93
defining an
.. aperture 94 defined in the middle, into which aperture the separate
container 92
can be placed therein. Conveniently, by the use of resilient materials of
close
corresponding dimensions, the container 92 can be resiliently retained within
the
aperture 94. Container 91 and container 92 will be filed with different phase
change materials. The generally plano-rectangular shape of the container 91
can
be shaped to provide indentations 95 to assist in manual handling of the
container. It will be appreciated that the aperture need not be centrally
arranged
within the outer container 91. Equally, a further insert container (not shown)
could be provided adjacent the first insert container, with the overall
peripheral
dimensions of the second 92 and further container corresponding with the
.. internal dimensions of aperture 94. Equally, there could be provided first
and
second apertures 93.
[0048] Figure 9b shows a variant wherein there is also provided a layer of
insulating material 96 - in two parts, whereby an additional cardboard/sheet
plastics envelope element is not require to address any requirement for
.. insulation/spacing of temperature control elements from product. Materials
such
as metallized film, adhered to a carrier paper and, for example, converted
into
corrugate board is a good option and could even be used as the material used
to
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form the cassette body. Figure 9c shows a perspective view of phase change
material container assembly 91, 92 with a single insulation layer 96. Figure
9d
shows a still further cassette, with the cardboard cover in outline and with
three
blow-moulded containers therein, with the containers each filled with one of
two
types of PCM.
[0049] This method of manufacture can provide several benefits to users,
including the opportunity to Fine tune packaging performance by adjusting a
volume fill of each container unit of phase change material. A specific
cassette
could be provided for a particular user /category of use. This benefit could
be
realised, for example by having instantly available solutions for a particular
user,
who may wish to have, for example winter and summer configurations, selected
on time of year/weather outlook. This would help ensure 'fit for purpose'
package
design and cost saving for the customer.
[0050] If the packaging were to be only used in extremely cold conditions,
then
the volume of PCM1 (+17 C) could be increased, and the volume of PCM2
reduced. This could be achieved by following methods:
1) Increase the Z dimension of the Shape Stable Foam.
2) Increase either the X or Y dimension of the Shape Stable Foam.
3) Altering the Volume of phase change material into each body, typical
percentage liquid saturation to shape stable foam volume are in the order of
65%
to 90%, therefore the foam volume could be dosed according to the performance
requirement without altering the geometry.
[0051] This embodiment allows for simple, single temperature preparation of
the
Dual phase change material packs at standard Control Room Temperature (CRT)
conditions. The design requires little training to facilitate use which will
safeguard
quality of shipment.
[0052] By changing the fill ratio between first and second phase change
materials, the thermal capabilities can be 'tuned' to cope with a specific
transport/storage requirement. For example, a customer with a travel
requirement under very hot conditions could opt to pack the shipper with more
'Heat Protective' phase change material than the 'Cold Protective' phase
change
material, thus enabling fine tuning of a shipper's capabilities. This coupled
with
the use of thermal simulation software could be a very useful and powerful
combination enabling the very best fit of a customer's needs to the
capabilities of
the shipping system.
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[0053] Indeed, by the use of a configurable system as provided by the present
invention, a logistics company could fine tune the exact performance level
required for a logistics company to overcome differing thermal challenges,
coupled with the use of thermal simulation software whereby to allow logistics
companies to make informed, safe and reliable decisions about how best to
configure their modular phase change material shippers. For example, by the
use
of the micro/macro PCM particles, a 'tuned' performance of a particular
package
can be achieved by the simple expedient of controlling the ratio of PCM1 to
PCM2.
[0054] Pharmaceuticals, proteins, biological samples and other temperature
sensitive products, including food items, are regularly shipped in containers
year
round and are subjected to a wide range of temperatures. Though they are
shipped in insulated containers and/or climate controlled environments, the
temperature stability of the shipping containers can be significantly improved
by
applying the techniques of the present invention, whereby to provide a simple
solution to the maintenance of temperature profiles for the transport and
storage
of ternperature sensitive products.
[0055] The advantages of using phase change materials for temperature
controlled packaging are numerous. Phase change materials can easily replace
dry ice or gel packs to reduce the size of shipping containers; they can
increase
the duration of a temperature control period during shipping. A reduction in
transportation costs can simply be realised since less space is devoted to
cooling
systems, when phase change materials are employed. Phase change materials
are reusable. Phase change materials assure predictable and stable temperature
control. Phase change materials are available to cover a wide range of
temperature ranges.
