U.S. patent application number 11/883301 was filed with the patent office on 2008-08-28 for eutectic plate.
Invention is credited to Sean Flanagan.
Application Number | 20080202128 11/883301 |
Document ID | / |
Family ID | 34307650 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202128 |
Kind Code |
A1 |
Flanagan; Sean |
August 28, 2008 |
Eutectic Plate
Abstract
An eutectic plate comprising: a housing containing a coolant,
and a thermochromic material that undergoes a thermochromic
transition at a predefined temperature.
Inventors: |
Flanagan; Sean; (Surrey,
GB) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
FRANKLIN SQUARE, THIRD FLOOR WEST, 1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Family ID: |
34307650 |
Appl. No.: |
11/883301 |
Filed: |
January 27, 2006 |
PCT Filed: |
January 27, 2006 |
PCT NO: |
PCT/GB06/00286 |
371 Date: |
April 1, 2008 |
Current U.S.
Class: |
62/62 ;
62/371 |
Current CPC
Class: |
C09K 5/10 20130101; F25D
2303/0822 20130101; F25D 3/00 20130101; F28F 2265/00 20130101; Y02E
60/145 20130101; F25D 2400/36 20130101; F28D 20/02 20130101; F25D
2303/085 20130101; Y02E 60/14 20130101; C09K 5/066 20130101 |
Class at
Publication: |
62/62 ;
62/371 |
International
Class: |
F25D 3/00 20060101
F25D003/00; F25D 31/00 20060101 F25D031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2005 |
GB |
0501850.2 |
Claims
1. An eutectic plate comprising: a housing containing a coolant,
and a thermo chromic material that undergoes a thermo chromic
transition at a predefined temperature.
2. A plate as claimed in claim 1, wherein the coolant is an
anti-freeze or an eutectic liquid.
3. A plate as claimed in claim 1, which provides a visual
indication of whether the eutectic plate is: a) within a target
temperature or target temperature range, b) above the a target
temperature or target temperature range, and c) below the a target
temperature or target temperature range.
4. A plate as claimed in claim 3, which comprises a first
thermo-chromic material and a second thermochromic material,
wherein the first thermochromic material undergoes a thermochromic
transition at a first predefined temperature and the second
thermochromic material undergoes a thermochromic transition at a
second predefined temperature.
5. A plate as claimed in claim 3, which comprises a thermo-chromic
material that undergoes a first thermochromic transition at a first
predefined temperature and a second thermochromic transition at a
second predefined temperature.
6. A plate as claimed in claim 1, wherein the housing is provided
with an outer layer comprising the thermochromic material.
7. A plate as claimed in claim 6, wherein the outer layer is
applied by printing, painting or dip-coating.
8. A plate as claimed in claim 6, wherein the outer layer takes the
form of a jacket or sheath.
9. A plate as claimed in claim 1, wherein the housing is moulded
from a material comprising the thermochromic material.
10. A plate as claimed in claim 9, wherein the housing is formed
from a moulding composition comprising the thermochromic material
and a polymer.
11. A plate as claimed in claim 1, wherein the thermochromic
material is incorporated into the coolant.
12. A plate as claimed in claim 11, wherein the housing is provided
with a transparent region through which the coolant may be
viewed.
13. A plate as claimed in claim 1, wherein the thermochromic
material is provided in the form of crystals, a paint or an
ink.
14. A plate as claimed in claim 1, wherein the thermochromic
material is microencapsulated.
15. A plate as claimed in claim 1, wherein a non-thermochromic
background pigment is used in combination with the thermochromic
material.
16. A cold storage apparatus comprising an insulated container and
an eutectic plate as claimed in claim 1.
17. An apparatus as claimed in claim 16, which provides a
controlled temperature environment within -40 to +40.degree. C.
18. An apparatus as claimed in claim 16, which comprises more than
one eutectic plate.
19. An apparatus as claimed in claim 16, wherein the insulated
container contains a temperature-sensitive product selected from a
food product, a beverage, a cosmetic product and a pharmaceutical
product.
20. A method of maintaining a temperature-sensitive product within
a target temperature range, said method comprising: providing an
eutectic plate which includes a housing containing a coolant and a
thermochromic material that undergoes a thermochromic transition at
a predefined temperature, placing the eutectic plate in a
controlled temperature environment, determining whether the
eutectic plate is at a desired temperature or within a desired
temperature range by visual inspection, and placing the cooling
eutectic plate in an insulated container with the
temperature-sensitive product.
21. A method as claimed in claim 20, wherein the eutectic plate is
refrigerated or frozen prior to use.
22. A method as claimed in claim 20, wherein the eutectic plate is
placed in a controlled temperature environment and chilled to a
lower temperature than desired and then allowed to heat up to the
desired temperature or temperature range by exposing the plate to
the ambient temperature.
Description
[0001] The present invention relates to an eutectic plate.
[0002] Temperature-sensitive products need to be stored within
predetermined temperature ranges. For example, fresh foods, chilled
foods and beverages and frozen foods have to be kept within
particular temperature limits. The same is true for certain
pharmaceutical products, such as medicines and vaccines, as well as
certain cosmetic products, for example, creams and lotions.
[0003] Temperature-sensitive products are generally refrigerated
and transported using cold-chain systems. In a typical unpowered
cold-chain system, the temperature-sensitive product is stored in
an insulated container that is kept at a predetermined temperature
or within a predetermined temperature range using one or more
eutectic plates (also known as cold packs, cold dogs and cold
gels).
[0004] An eutectic plate is a container that typically contains a
phase change material, such as, for example, water or an aqueous
solution. The eutectic plate is typically chilled in a refrigerator
or freezer until the phase change material freezes. The chilled
plate is then placed in an insulated container containing the
temperature-sensitive product. Heat from the container is absorbed
by the chilled plate, causing the phase change material to melt.
This change of state occurs without a change of temperature; thus,
the rate of change of temperature within the insulated container is
reduced.
[0005] Various practices have been adopted to ensure that the
insulated containers are maintained within target temperatures.
Typically, the eutectic plates are chilled for prolonged periods of
time to ensure that the plates are sufficiently cold prior to
use.
[0006] The present inventors have surprisingly found a number of
disadvantages associated with this prior practice. For example, it
has surprisingly been found that, in many instances, the plates are
chilled for far longer than necessary, leading to an increase
refrigeration costs. In other instances, the plates are chilled to
a lower temperature than necessary, causing the
temperature-sensitive product to be chilled to too low a
temperature. This may have a detrimental effect on the
temperature-sensitive product.
[0007] In other cases, it has been found that the eutectic plates
are replaced with freshly chilled plates more frequently than
necessary, leading to an increase in refrigeration costs. It has
also been found that, in some cases, more eutectic plates have been
used in the insulated containers than necessary. Again, this leads
to an increase in the cost of cold-chain distribution and
storage.
[0008] According to the present invention, there is provided an
eutectic plate comprising:
[0009] a housing containing a coolant, and
[0010] a thermochromic material that undergoes a thermochromic
transition at a predefined temperature.
[0011] The thermochromic material undergoes a thermochromic
transition at a predefined temperature. In one embodiment, the
thermochromic material changes from a substantially transparent or
clear state to a coloured state (or vice-versa) at the predefined
temperature. In another embodiment, the thermochromic material
changes from one colour to another at the predefined
temperature.
[0012] The thermochromic transition may be used to provide a visual
indication of whether the eutectic plate is at, above and/or below
a target temperature.
[0013] Mixtures of thermochromic materials may be employed.
[0014] Preferably, the eutectic plate provides a visual indication
of whether the eutectic plate is within or outside a target
temperature range or at or above/below a target temperature. For
example, the eutectic plate may exhibit a different colour or
transparency depending on whether the eutectic plate is within the
target temperature range, above the target temperature range or
below the target range. In one embodiment, this is achieved by
using a thermochromic material having more than one activation
temperature. For example, when a thermochromic material having two
activation temperatures is used, the material undergoes two
thermochromic transitions at two different predefined temperatures.
The first thermochromic change may occur when the temperature of
the eutectic plate falls below the lower limit of the target
temperature range and the second thermochromic change may occur
when the temperature of the eutectic plate exceeds the upper limit
of the target temperature range. As a result of these thermochromic
changes, the eutectic plate will have a different visual appearance
depending on whether the eutectic plate is within the target
temperature range, above the target temperature range or below the
target range. Thermochromic materials with three, four, five or
more activation temperatures may be used.
[0015] Alternatively or additionally, two or more (e.g. three,
four, five or more) thermochromic materials may be employed to
provide the necessary visual indications. For example, a first
thermochromic material may be employed to exhibit a thermochromic
change at the lower temperature limit of the target temperature
range. As this thermochromic change causes the eutectic plate to
adopt a particular appearance, a user would therefore be able to
determine if the temperature of the eutectic plate has fallen below
this lower temperature limit simply by visual inspection.
Similarly, a second thermochromic material may also be provided to
exhibit a thermochromic change at the upper temperature limit of
the target temperature range. As this thermochromic change causes
the eutectic plate to adopt a different appearance, a user would be
able to determine if the temperature of the eutectic plate had
exceeded the upper limit of the target temperature range by visual
inspection.
[0016] In one embodiment, the eutectic plate exhibits a red colour
when it is above the target temperature range, a green colour when
it is within the target temperature range and a blue colour when it
is below the target temperature range. In another embodiment, the
eutectic plate exhibits a red colour when it is above the target
temperature range, a blue colour when it is below the target
temperature range and is clear or transparent when it is within the
target temperature range.
[0017] The target temperature range may be broad or narrow.
Generally speaking, products that are highly sensitive to
temperature changes are stored within narrow temperature ranges. On
the other hand, the target temperature range may be broader for
products that are less sensitive to temperature changes. The
magnitude of the target temperature range may be 0.1 to 20.degree.
C., preferably, from 0.2 to 10.degree. C., more preferably, 0.3 to
5.degree. C., for example, 0.5 to 3.degree. C. For highly
temperature-sensitive products, the magnitude of the target
temperature range may be 2.degree. C. or less, preferably 1.degree.
C. or less, more preferably 0.5.degree. C. or less.
[0018] The eutectic plate may also provide a visual record of
whether the temperature of the eutectic plate has changed over a
predetermined period of time. For example, the eutectic plate may
provide the user with a visual indication of whether the
temperature of the eutectic plate exceeded the upper limit of the
target temperature range and/or dropped below the lower limit of
the target temperature range over a predetermined period of use.
This information is preferably apparent to the user even if the
current temperature of the eutectic plate is within the target
temperature range. Thus, the eutectic plate may be used to provide
the user with an indication of the temperature history of the
eutectic plate.
[0019] In one embodiment, the eutectic plate is provided with a
plurality of separate thermochromic materials which undergo
thermochromic changes at different predefined temperatures. These
thermochromic materials may be located at different locations on
the eutectic plate, for example, in different thermochromic cells
or areas. Each material may undergo a thermochromic change at a
characteristic predefined temperature. Thus, as the temperature of
the eutectic plate increases, a series of thermochromic changes may
occur. Each of these thermochromic changes may cause each
thermochromic cell or area to adopt a particular colour. Thus, a
user would be able to determine by visual inspection how the
temperature of the eutectic plate changed over a predetermined
period of use. A chart (e.g. colour chart) may be provided, for
example, on the surface of the eutectic plate, to assist the user
in the "reading" of the relevant temperature changes.
[0020] In one embodiment, the eutectic plate may be provided with
an outer layer comprising the thermochromic material. The outer
layer may surround a substantial portion of the housing of the
eutectic plate. For example, the outer layer may take the form of a
sheath or jacket. Alternatively, the thermochromic material may be
applied to at least a portion of the housing, for example, by
painting, dip-coating, spraying or printing.
[0021] Preferably, the thermochromic material forms at least part
of the housing. For example, in a preferred embodiment, the housing
is moulded from a composition comprising the thermochromic
material. As the thermochromic material forms part of the housing
itself, it advantageously provides an accurate indication of the
temperature of the housing.
[0022] Alternatively or additionally, the thermochromic material
may also be incorporated into the coolant. In this embodiment, the
thermochromic material will form part of the eutectic plate itself.
Thus, it can advantageously be used to provide an accurate
indication of the temperature of the plate. For example, the
thermochromic material may be dissolved or suspended in the
coolant. Preferably, the coolant is visible through the housing.
For example, the housing may be formed of a substantially
transparent or clear material and/or include a substantially
transparent or clear window through which the coolant may be
viewed.
[0023] Any suitable material that exhibits a thermochromic
transition at a predefined temperature may be used as the
thermochromic material. As mentioned above, the thermochromic
material may change colour or change from a substantially
transparent or clear state to a coloured state (or vice-versa) at a
predefined temperature. Preferably, the thermochromic transition is
reversible. Thus, the thermochromic transition observed when the
temperature of the material exceeds a particular threshold is
reversed when the temperature of the material falls below that
threshold.
[0024] When a reversible thermochromic material is employed, it may
have a narrow or broad hysteresis. If a thermochromic material with
a narrow hysteresis is heated above its predefined temperature and
then cooled, it will return to its original state more quickly than
a material with a broad hysterisis. Narrow hysteresis materials,
therefore, are useful for providing an indication of the current
temperature of the eutectic plate. Broad hysterisis materials, on
the other hand, are generally useful for providing an indication of
the temperature history of the eutectic plate. Unlike narrow
hysteresis materials, broad hysteresis materials can "memorise"
previous thermochromic changes, as the shape of a curve formed by
plotting the colour density of a broad hysteresis material against
increasing temperature differs significantly from a curve formed by
plotting colour density against decreasing temperature.
[0025] In one embodiment, one or more irreversible thermochromic
material is employed in combination with one or more reversible
thermochromic material. The irreversible thermochromic material may
be used to provide a permanent visual indication of whether a
predefined threshold temperature has been exceeded over a
particular period of use or whether the temperature of the plate
has dropped below a predefined threshold over a particular period
of use.
[0026] The thermochromic material may be provided in the form of an
ink, paint, crystals or in any other suitable form.
[0027] Suitable thermochromic materials include thermochromic
polyacetylenes, such as those described in U.S. Pat. No. 4,339,951,
and thermochromic polythiophenes, such as those described in U.S.
Pat. No. 6,706,218.
[0028] In one embodiment, the thermochromic material comprises a
thermochromic composition comprising a) an electron donating
colour-developing organic compound, b) an electron-accepting
compound and c) a reaction medium. The reaction medium typically
plays an important role in determining the temperature at which the
colour-developing reaction between components a) and b) arises.
Examples of thermochromic compositions of this type are described
in U.S. Pat. No. 4,957,949, U.S. Pat. No. 6,468,088, U.S. Pat. No.
4,028,118 and U.S. Pat. No. 4,732,810.
[0029] The electron-donating colour-developing organic compound (a)
may be a colourless compound that forms a coloured product upon
reaction with the electron-accepting compound (b). Suitable
electron-donating colour-developing organic compounds (a) include
phenylmethanes, phthalides, phthalans, lactones, carbinols,
auramines, lactams, indolines, spiropyrans and fluorans. For
example, diaryl phthalides, indolylphthalides, polyarylcarbinols,
leuco-auramines, acylauramines, arylauramines, fluoran leuco
compounds, triphenylmethane phthalide leuco compounds and lactam
leuco compounds may be used.
[0030] Examples of compounds (a) include 3,3'-dimethoxyfluoran,
3-chloro-6-phenylaminofluoran,
3-diethylamino-6-methyl-7-chlorofluoran,
3-diethyl-7,8-benzofluoran,
3,3',3''-tris(p-dimethylaminophenyl)phthalide,
3,3'-bis(p-dimethylaminophenyl)-7-phenylaminofluoran and
3-diethylamino-6-methyl-7-phenylaminofluoran.
[0031] Other examples of compounds (a) include Crystal Violet
lactone, Malachite Green lactone, Michler's hydrol, Crystal Violet
carbinol, Malachite Green carbinol, N-(2,3-dichlorophenyl)-leuco
auramine, N-benzoyl auramine, N-acetyl auramine, N-phenyl auramine,
Rhodamine B lactam,
2-(phenylimonoethylidene)-3,3-dimethyl-indoline,
N,3,3-trimethyl-indolinobenzo-spiropyran,
8'-methoxy-N,3,3-trimethylindolino-spiropyran,
3-diethylamino-6-methyl-7-chloro-fluoran,
3-diethylamino-7-methoxy-fluoran,
3-dimethlamino-6-benzyloxy-fluoran,
1,2-benzo-6-diethylaminofluoran,
3,6-di-p-toluidino-4,5-dimethylfluoran-phenylhydrazide-gamma-lactam,
3-amino-5-phenyl-8methyl-fluoran,
2-methyl-3-amino-6-methyl-7-methyl-fluoran,
2,3-butylene-6-di-n-butylamino-fluoran,
3-diethylamino-7-anilino-fluoran,
3-diethylamino-7-(p-toluidino)-fluoran,
7-acetamino-3-diethylamino-fluoran,
2-bromo-6-cyclohexylamino-fluoran and
2,7-dichloro-3-methyl-6-n-butylamino-fluoran.
[0032] Suitable electron-accepting compounds (b) include phenolic
compounds, such as phenolic hydroxyl compounds. Monophenolic and
polyphenolic compounds may be employed. These may be substituted,
for example, with alkyl, aryl, acyl, alkoxycarbonyl and/or halogen
atoms. Azoles, organic acids, organic acids and organic salts may
also be used.
[0033] Examples of suitable phenolic compounds include phenyl
phenol, bisphenol A, cresol, resorcinol, chlorolucinol,
.beta.-naphthol, 1,5-dihydroxynaphthalene, pyrocatechol,
pyrogallol, trimer of p-chlorophenol-formaldehyde condensate and
the like.
[0034] Examples of azoles include benzotriazoles, such as
5-chlorobenzotriazole, 4-laurlaminosulfobenzotriazole,
5-butylbenzotriazole, dibenzotriazole, 2-oxybenzotriazole,
5-ethoxycarbonyl-benzotriazole; imidazoles, such as
oxybenzimidazole; tetrazoles and the like.
[0035] Examples of organic acids include aromatic carboxylic acids,
aliphatic carboxylic acids and substituted derivatives thereof.
Examples of aromatic carboxylic acids are salicylic acid,
methylenebissalicyclic acid, resorcyclic acid, gallic acid, benzoic
acid, p-oxybenzoic acid, pyromellitic acid, .beta.-naphthoic acid,
tannic acid, toluic acid, trimellitic acid, phthalic acid,
terephthalic acid and anthramilic acid. Examples of aliphatic
carboxylic acids include those containing about 1-20 carbon atoms,
preferably about 3-15 carbon atoms, such as stearic acid,
1,2-hydroxystearic acid, tartaric acid, citric acid, oxalic acid
and lanric acid. Examples of esters include alkyl esters of
aromatic carboxylic acids in which the alkyl moiety has 1 to 6
carbon atoms, such as butyl gallate, ethyl p-hydroxybenzoate and
methyl salicylate. Examples of salts include ammonium salt and
metal salts of the above organic acids. The metal salts include,
for example, lithium, sodium, calcium, magnesium, aluminium, zinc,
tin, titanium, nickel or the like metal salts.
[0036] Other examples of electron-accepting compounds (b) include
tert-butyl phenol, nonyl phenol, dodecyl phenol, styrenated phenol,
2,2'-methylene-bis(4-methyl-6-tert-butyl-phenol), alpha-naphthol,
beta-naphthol, hydroquinone monomethyl ether, guaiacol, eugenol,
p-chlorophenol, bromophenol, o-chlorophenol, o-bromophenol,
o-phenylphenol, p-phenylphenol, p-(p-chlorophenyl)-phenol,
0-(o-chlorophenyl)-phenol, methyl p-hydroxybenzoate, ethyl
p-hydroxybenzoate, propyl p-hydroxybenzoate, octyl
p-hydroxybenzoate, dodecyl phenol p-hydroxybenzoate,
3-isopropyl-catechol, p-tert-butyl-catechol,
4,4'-methylene-diphenol
4,4'-thio-bis(6-tert-butyl-3-methyl-phenol), bisphenol A,
1,2-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, chlorocatechol,
bromocatechol, 2,4-dihydroxybenzophenone, phenol, phthalein,
o-cresol phthalein, methyl protocatechuate, ethyl protocarechuate,
propyl protocatechuate, octyl protocatechuate, dodecyl
protocatechuate, 2,4,6-trihydroxymethyl-benzene, methyl gallate,
ethyl gallate, ethyl gallate, propyl gallate, butyl gallate, hexyl
gallate, octyl gallate, dodecyl gallate, cetyl gallate,
2,3,5-trihydronaphthalene, tannic acid and phenol-formaldehyde
prepolymers.
[0037] The reaction medium may be an alcohol, such as an aliphatic
monovalent alcohol. Preferably, the alcohol has more than 8 carbon
atoms. More preferably, the alcohol has 10 to 30 carbon atoms, for
example, 12 to 20 carbon atoms. Specific examples include fatty
alcohols, such as lauryl alcohol, myristyl alcohol, cetyl alcohol,
stearyl alcohol, docosyl alcohol and oleyl alcohol. Other examples
include octyl alcohol and dodecyl alcohol.
[0038] The ratio of components a), b) and c) may be varied to suit
requirements. Typically, the composition contains 1 to 50 weight %,
preferably 5 to 20 weight % of component (a), 2 to 40 weight %,
preferably, 5 to 30 weight % of component (b) and 10 to 90 weight
%, preferably 20 to 60 weight % of component (c).
[0039] Components (a), (b) and (c) may be each a mixture of two or
more compounds.
[0040] Optionally, the thermochromic composition may further
comprise an alcohol ester (d). Suitable alcohol ester components
include octyl caprylate, decyl caprylate, octyl caprate, decyl
caprate, cetyl caprate, stearyl caprate, butyl laurate, octyl
laurate, lauryl laurate, stearyl laurate, butyl myristate, decyl
myristate, myristyl myristate, cetyl myristate, octyl palmitate,
butyl stearate, decyl stearate, lauryl stearate, stearyl stearate,
12-hydroxy stearic acid triglyceride and the like. The alcohol
ester component may affect the sharpness and temperature of the
colouration reaction. Component d) may optionally be present in an
amount of 1 to 10 weight % of the composition.
[0041] The thermochromic composition may be microencapsulated prior
to use. Any coating material may be used to microencapsulate the
composition. Examples include polyurea, polyamide, polyurethane,
polyester, epoxy resin, melamine resin, urea resin,
methylcellulose, carboxymethylcellulose, cationized starch,
carboxymethylated starch, ethylcellulose, polystyrene, polyvinyl
acetate, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid,
polyacrylamides and polymers and copolymers of maleic acid. Other
examples of coating materials include alginic acid and salts
thereof, carrageenan, pectin and gelatin.
[0042] The microcapsules may be prepared by any suitable method.
Examples include interfacial polymerization, in-situ
polymerization, submerged hardening, coating, phase separation from
an aqueous solution, phase separation from an organic solvent,
meltdispersion cooling, air suspension coating and spray
drying.
[0043] The microcapsules may have a particle diameter of from 0.01
to 100 .mu.m, preferably from 0.01 to 50 .mu.m, more preferably
from 0.01 to 30 .mu.m and yet more preferably 0.01 to 6 .mu.m.
[0044] The microencapsulated or non-microencapsulated thermochromic
material may be formulated as an ink, paint or dye before being
used in the eutectic plate of the present invention. Alternatively,
the thermochromic material may be employed in crystal form.
[0045] Suitable thermochromic materials are sold under the
trademark ColorTell.TM. of Clark R&D Limited and
Chromicolor.TM.. These materials contain thermochromic pigments
supplied by the Matsui Shikiso Chemical Company (see, e.g. U.S.
Pat. No. 4,957,949).
[0046] The thermochromic material(s) may undergo a thermochromic
transition(s) at a temperature from -60 to +60.degree. C.,
preferably from -40 to +40.degree. C. Within this range, the
transition(s) may occur at a temperature from 10 to 35.degree. C.,
preferably 15 to 30.degree. C., for example, 20 to 25.degree. C.
Alternatively, the transition(s) may occur at a temperature of from
0 to 10.degree. C., preferably 1 to 8.degree. C., for example 2 to
4.degree. C. In yet another alternative, the transition(s) may
occur at a temperature of from -1 to -30.degree. C., preferably, -5
to -10.degree. C., for example -5 to -15.degree. C. The
transition(s) may alternatively occur at a temperature of from -10
to -60.degree. C., for example -25 to -40.degree. C.
[0047] The thermochromic material may be used in combination with a
non-thermochromic pigment. Such pigments are background pigments
that may take on a different appearance depending on the state of
the thermochromic material. For example, if a thermochromic
material that is transparent below a threshold temperature and
yellow above a threshold temperature is used in combination with a
blue background pigment, the combination will appear blue below the
threshold temperature and green above the threshold temperature. By
selecting suitable background pigments, therefore, the colour
changes may be tailored accordingly.
[0048] The housing may be made from any suitable material.
Preferably, the housing is formed from a polymer, more preferably a
thermosetting resin. Examples of suitable polymers include
polyolefins (e.g. polypropylene and polyethylene), polyesters,
polyurethanes, polyacrylates, poly(ethylene terephthalate)s,
polystyrenes, polycarbonates, polyacrylics, polyacrylamides,
polymethacrylics, polyvinylethers, polyvinylhalides (e.g. PVC),
polyesters, polystyrene and polyamides.
[0049] The housing may be formed by any suitable technique.
Preferably, the housing is injection moulded, rotor moulded or blow
moulded into shape. As described above, the housing may be moulded
from a moulding composition comprising the thermochromic material.
The concentration of thermochromic material in the moulding
composition may be from 0.1 to 30%, preferably 0.5 to 15%, for
example 1 to 10%, of the total weight of the composition. In one
embodiment, a thermochromic material is grounded or otherwise mixed
with a polymer and the resulting composition is used to mould the
housing.
[0050] Suitable moulding compositions comprising the thermochromic
material are described in U.S. Pat. No. 4,957,949. For example, the
moulding composition may be formed from a thermochromic masterbatch
comprising a wax having substantially dispersed therein a
thermochromic granular material which is microencapsulated as
described above. The wax may be paraffin wax, microcrystalline wax,
montan wax, carnuba wax, polystyrene wax, polyethylene wax,
propylene wax or a mixture thereof. The granular material may be a
mixture of a polymer resin and a thermochromic composition
comprising a) an electron donating colour-developing organic
compound, b) an electron-accepting compound and c) a reaction
medium as described above. The polymer resin present in the
thermochromic masterbatch is preferably compatible with or is the
same as the polymer resin from which the housing is moulded. For
example, when the housing is moulded from a polyolefin, the resin
in the thermochromic masterbatch is preferably a polyolefin.
[0051] The thermochromic masterbatch may be ground or otherwise
mixed with a polymer and the resulting mixture may be used to mould
the housing.
[0052] In an alternative embodiment, the thermochromic material may
be applied to the housing, for example, by painting or printing.
The thermochromic material may comprise microcapsules of
thermochromic composition.
[0053] The housing may be provided with an aperture through which
coolant may be introduced. Preferably, the aperture may be sealed
by a closure, such as a screw cap.
[0054] The housing may be shaped such that it can absorb heat from
the surroundings in an efficient manner. For example, in one
embodiment, the housing is a substantially flat container with a
large surface area to volume ratio. The outer surface of the
housing may be provided with dimples or contours. Passages or
apertures may also extend through the housing. These may assist the
user in lifting and carrying the plates.
[0055] The housing is preferably substantially cuboid. However,
housings that are, for example, substantially cylindrical in shape
may be employed. When a substantially cuboid housing is used, the
housing may have a width of 5 to 120 cm, preferably 10 to 100 cm,
for example, 20 to 80 cm. The length of the housing may be 5 to 120
cm, preferably 10 to 100 cm, for example, 20 to 80 cm, whilst the
depth of the housing may be 1 to 30 cm, preferably 2 to 20 cm, more
preferably 3 to 15 cm, for example, 5 to 10 cm.
[0056] Any suitable coolant may be introduced into the housing. The
coolant may be an antifreeze material. Antifreeze materials may be
formed by dissolving inorganic salts, such as, for example, sodium
chloride, magnesium chloride, calcium chloride, potassium acetate,
sodium acetate, ammonium phosphate and ammonium nitrate in a liquid
such as water. Alternatively or additionally, organic compounds
such as alcohols, glycols, lactates and urea may be dissolved in
water. In one embodiment, the antifreeze material comprises an
aqueous solution of sugar alcohols, ethylene glycol and/or
propylene glycol.
[0057] The coolant may also be a phase change material or eutectic
liquid. When a phase change material melts, it absorbs latent heat
from its surroundings. The latent heat absorbed causes the phase
change material to change state. However, it does not cause the
temperature of the phase change material to rise.
[0058] Suitable phase change materials include water and/or organic
liquids. Preferred phase change materials are obtainable under the
trademark TEAP Energy.TM..
[0059] The coolant may have a melting/freezing point in the range
of from -60 to +60.degree. C., preferably from -40 to +40.degree.
C. Within this range, the melting/freezing point of the coolant may
be from 10 to 35.degree. C., preferably, 15 to 30.degree. C., for
example, 20 to 25.degree. C. Alternatively, the coolant may have a
melting/freezing point of may be 0 to 10.degree. C., preferably, 1
to 8.degree. C., for example, 2 to 40.degree. C. In yet another
alternative, the melting/freezing point of the coolant may be -1 to
-30.degree. C., preferably, -5 to -20.degree. C., for example, -5
to -15.degree. C. Coolants with melting/freezing points of from -10
to -60.degree. C., preferably, -25 to -40.degree. C., may also be
employed.
[0060] The eutectic plate of the present invention may be used to
provide a controlled temperature environment for a
temperature-sensitive product. Therefore, the eutectic plate of the
present invention is preferably used in combination with an
insulated container. According to a further aspect of the
invention, there is provided a cold storage apparatus comprising an
insulated container and the eutectic plate of the present
invention.
[0061] In use, the eutectic plate of the present invention may be
chilled in a refrigerator or freezer until the phase change
material freezes. If desired, the plate may be chilled to a
temperatures lower than the target temperature range and then left,
for example, at room temperature to heat up to the desired
temperature/temperature range prior to use. When the plate reaches
its target temperature, the thermochromic material of the eutectic
plate has a characteristic appearance. Thus, a user is able to
determine whether the plate has reached its target temperature
simply by visual inspection. The chilled plate may then be placed
in an insulated container containing the temperature-sensitive
product. Heat from the container is absorbed by the chilled plate.
When a phase change material is used as the coolant, this
absorption of heat causes the phase change material to melt. This
change of state occurs without a change of temperature; thus, the
rate of change of temperature within the insulated container is
reduced.
[0062] After a period of time, however, the heat absorbed from the
container may be sufficient to cause the temperature of the plate
to rise. When the-temperature of the plate rises above a predefined
temperature, the thermochromic material undergoes a thermochromic
change. Thus, by visual inspection, the user will know that the
predefined temperature has been exceeded. This may provide the user
with an estimate of the remaining "life" of the plate or indicate
that the plate should be replaced with a freshly refrigerated
plate.
[0063] The eutectic plate of the present invention may be used for
cold chain distribution (transport) and storage applications. In
particular, the eutectic plate of the present invention may be used
to provide a controlled temperature environment for a
temperature-sensitive product, such as a food product, a beverage,
a cosmetic product or a chemical or pharmaceutical product.
Suitable food products include meat, fish, fruit, vegetables and
dairy products. Suitable beverages include chilled drinks, fresh
juices and milk. Suitable chemicals include inks and solvents.
Suitable cosmetic products include creams, lotions and waxes.
Suitable pharmaceutical products include medicines and
vaccines.
[0064] The eutectic plate may be chilled and used to provide a
target temperature range that typically falls between -60 and
+60.degree. C., preferably between -40 and +40.degree. C. Within
this range, so-called "room temperature" products may be stored at
a target temperature range of, for example, from 10 to 35.degree.
C., preferably, 15 to 30.degree. C., for example, 20 to 25.degree.
C. For chilled products, the target temperature range may be 1 to
10.degree. C., preferably, 2 to 8.degree. C., for example, 2 to
4.degree. C. For frozen products, the target temperature range may
be -1 to -30.degree. C., preferably, -5 to -20.degree. C., for
example, -5 to -15.degree. C. Other frozen products may require
target temperature ranges of -10 to -60.degree. C., preferably, -25
to -40.degree. C.
[0065] The eutectic plate may be used to provide broad and narrow
target temperature ranges. As described above, the magnitude of the
target temperature range may be 0.1 to 20.degree. C., preferably,
from 0.2 to 10.degree. C., more preferably, 0.3 to 5.degree. C.,
for example, 0.5 to 3.degree. C. For highly temperature-sensitive
products, the magnitude of the target temperature range may be
2.degree. C. or less, preferably 1.degree. C. or less, more
preferably, 0.5.degree. C. or less.
[0066] The eutectic plate may be used in, for example, vending
machines for fresh, chilled and frozen foods, snacks and beverages;
storage and/or transport containers for chilled and frozen foods,
cosmetics, medicines and vaccines; and vehicle
refrigeration/freezing, for example, truck refrigeration/freezing
and refrigeration/freezing onboard other vehicles such as ships and
aeroplanes.
[0067] An embodiment of the present invention will now be described
with reference to the accompanying drawing which is a schematic
diagram of a eutectic plate according to one embodiment of the
present invention.
[0068] The eutectic plate 10 comprises a housing 12 moulded from a
moulding composition comprising a thermochromic material and a
plastics material. The housing 12 is a substantially flat container
comprising an aperture 14 for the introduction of an eutectic
liquid (not shown). When the housing is filled, the aperture may be
closed using a screw cap (not shown). The outer surface of the
housing 12 is provided with a plurality of apertures 16 that extend
through the depth of the housing 12. The apertures make it easier
for the eutectic plate to be lifted and held by a user. They also
increase the surface area over which heat may be absorbed.
EXAMPLE
[0069] Pellets of a thermochromic concentrate comprising 18% of a
microencapsulated thermochromic composition and 82% of a
polyethylene resin (Chromicolour.TM.) were mixed with polyethylene
pellets in a tumbling mixer in a weight ratio of 1:9. The mixture
was then injection moulded to form the housing shown in the drawing
at a moulding temperature of 210.degree. C., a mould temperature of
50.degree. C. and an injection pressure of 800 kg/cm.sup.3.
[0070] The housing was colourless and clear at room temperature.
However, when the housing was chilled to -4.degree. C. and below,
the housing appeared coloured. The colour change was reversed when
the temperature of the housing raised above -4.degree. C. The
reversible colour change could be repeated over and over again.
* * * * *