Note: Descriptions are shown in the official language in which they were submitted.
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1
A LID FOR A CONTAINER
Technical Field
The present invention relates to a lid for a container and to a process for
making the lid.
Background of the invention
Lids for containers are generally known. For example, lids for disposable
beverage containers, such as foam or paper cups, are known. Such containers
are
generally used for containing heated beverages such as tea, coffee or hot
chocolate, or for containing cold or chilled beverages such as soft drinks,
juice or
water.
It is known to provide lids with small printed or embossed warning signs such
as HOT or COLD on top of the lids to indicate that the contents contained in
the
container are hot or cold, respectively. However, such embossing or printing
does
not provide a true indication of the actual temperature of the contents of the
container.
In order to provide an indication of the actual temperature, it is known to
provide coextruded (two layered) thermochromic beverage lids in which one of
the
layers of the lids contain a thermochromic substance, such as a thermochromic
pigment which changes under the application of heat or cooling to provide an
indication of the temperature of materials contained in a container contained
by the
lid and indicate when the contained material is too hot or too cold for
handling or
safe consumption. One example of such a lid is described in PCT/AU02/00029 by
the present applicants. However, such lids suffer from a number of
disadvantages.
One disadvantage is that, unlike the use of thermochromic materials in
plastic drink bottles, spoons and containers which have relatively thick
substrates
and where the use of thermochromic substances is relatively straightforward,
hot
container lids, such as coffee cup lids, are composed of thin substrates of
the order
of less than 1mm, more particularly of the order of less than 0.5mm and
typically of
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la
100 to 400pm thickness; accordingly the properties of the lid by inclusion of
thermochromic materials by conventional means are compromised.
Another disadvantage is that significant amounts of thermochromic material
must be added to produce a desired colour coverage. Standard pigment dyes can
be added to lids to produce a desired colour by well-known processes, with the
standard dye in a capsulated form added to the masterbatch with minimal add
rates
(2-3%). When a thermochromic dye is used however, in order to achieve the
desired and effective colour, add rates in excess of 12% are typically
required for
thin substrates such as lids (lower ____________________________________
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add rates of 3% to 4% of thermochromic can effectively be used with thick
substrates
but such add rates are not suitable for use with lids). Further, when not
enough
thermochromic material is added, the resulting colour is insufficient in
density and it is
necessary to increase the add rate even further in order to produce a denser
colour. The
use of add rates in excess of 12% compromises the structural integrity of the
lid because
typical thermochromic dyes naturally have an enlarged particle size compared
to standard
dye pigments. Also some lids are formed from high impact polystyrene which
contains a
rubber component to allow the lid to be flexible and suited for hot beverage
container
lids. The particle size of the thermochromic particles causes a loss of lid
flexibility and
io lids
become brittle and have a tendency to tear and thus are unsuitable for the
application
for which they are intended
A further disadvantage is with translucency. Because lids are typically formed
from
thin substrates of the order of less than 1 mm in thickness and because the
lids include in
excess of 10-12% of the thermochromic substance in order to achieve the
desired colour
is
result, whilst the lid may display the appropriate colour in a "cold state",
on heating such
lids to a hot state the lids become translucent with no actual defined colour
present. This
is because the nature of thermochromic substances is that when the
thermochromic
substance changes from its cold ambient colour under heat, the first colour
disappears to
an almost clear translucent state with only a pale light colouring. The
problem with
20
translucency is not improved by adding higher add on rates of up to 20% of the
theanochromic substance which makes no difference to the translucency of the
lids and
which, in view of the high volume of the enlarged particles of the
thermochromic material
in the thin substrate adversely affects and weakens the structural integrity
of the lid
resulting in lids that are brittle and which tear/crack easily and which are
not durable,
25
flexible or bendable. In addition such lids may show pitting or holes from
exploding
thermochromic particles during manufacture. Such pitting or holes compromise
both the
strength and flexibility of the lid and are visually undesirable.
The problem of translucency is exacerbated by the inclusion of regrind from
off-
cuts recycled in the bottom of the lid layers which regrind may be included as
a standard
30 step
in lid manufacture as a cost-cutting measure. When a thermochromic substance
is
applied to a top layer of a lid and regrind is included as a bottom layer, and
the lid is
heated to the hot state, the colour change results in both layers resulting in
loss of colour
and translucency in both layers. This is particularly evident when high impact
polystyrene (HIPS), which is inherently translucent, is used as the layers of
the lid. High
35 impact
polystyrene is the most dominant material used to make lids such as hot
beverage
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lids because it has a rubber content which aids in durability and flexability.
HIPS is
also a cost efficient material and differs from other raw plastic materials,
such as
poly(phenylenesulphide) (PPS), which are too brittle for cup lids.
To minimise translucency, products using thermochromic materials typically
rely
on a secondary underlying colour to communicate a desired end colour. However,
such
steps are not successful in application to the thin substrates of lids. For
example, most
products employ a thermochromic micro-encapsulated dye in which a secondary
underlying colour is infused within the capsule. However, HIPS used to
manufacture
lids, as provided commercially, is opaque and slightly translucent. In this
regard HIPS is
io naturally a cloudy off white colour (which may be grey when regrind is
included) and the
white pigment is typically added to the mix on making lids in order to prevent
the lids
from becoming transparent. However, the pigment detrimentally affects the
thermochromic colouring ability by adverse colour mixing in the layer and
through light
refraction. For example when a blue to red colour change is desired, the cold
(ambient)
state will present the appropriate cold blue colour but in the hot state,
instead of the
desired red, a translucent pink colouring results because the thermochromic
substances do
not change to a distinct deep colour. Instead a pale semi-clear colour,
lighter than the
cold colour results, and the natural off-white pigment of HIPS mixes with the
pale colour
to make the resulting colour even paler. This result is undesirable and
results in a
confusing colour change such that a user can almost see into the cup when it
is in the hot
state and the colour of the liquid in the cup (for example coffee or tea) can
alter what the
user actually sees as the hot colour.
Another disadvantage is that on the lid becoming translucent, condensation
from the
contents contained in the cup may attach to the underside surface of the lid
making the
semi-translucent lid even more translucent in the parts where the condensation
is attached.
An example of an existing product in the market place that has failed to
overcome
this translucency problem is thermochromic straws. These straws work by
contact of the
straw with a cold beverage which results in a change in the colour of the
straw.
Thermochromic straws are thin by nature and do not have a distinct cold
(ambient)
colour. On cooling with contact of the beverage, the colour seems to disappear
and no
real new colour becomes apparent. The colour is more the colour of the liquid
being
sucked up the straw than any other colour.
The problems referred to above are not solved by using mono-layer lids. A mono-
layer lid is produced as a single layer from one film of plastic and the layer
is thicker than
layers making up multi-layered lids. With a mono-layer lid, thermochromic
material
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needs to be applied to the entire thickness of the layer of the lid and
significant
amounts of thermochromic material needs to be applied so as to achieve a
sufficiently dense colour. Therefore the cost of producing a mono-layer lid is
substantial and not commercially viable. The cost of producing a mono-layer
lid
including a thermochromic material may be 5 to 10 times that of producing a
multi-
layered lid where thermochromic material is included in only one of the
layers.
There is a need for methods for making thermochromic lids in a commercially
viable manner such that a distinct colour results in both the ambient and
heated and
cooled states.
Object of the invention
It is an object of the present invention to overcome or substantially
ameliorate
at least one of the above disadvantages or to provide a suitable alternative.
Summary of the invention
According to the present invention, there is provided a lid for a container,
the
lid comprising a first plastic layer and a second plastic layer disposed on
top of the
first layer;
wherein the first layer comprises at least one first portion comprising at
least
one coloured pigment;
wherein the second layer comprises at least one second portion above the
first portion, the second portion comprising at least one thermochromic
substance,
wherein the thermochromic substance is substantially opaque when the second
portion is at a first temperature, and wherein the thermochromic substance
reversibly or quasi-reversibly becomes substantially translucent when the
second
portion reaches a second temperature in response to heat transfer from or to
contents of the container such that the second portion reveals the first
portion;
wherein the first portion is visually blocked by the second portion and is
thus
substantially invisible from above the lid when the second portion is at the
first
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temperature, and the first portion is visible, through the second portion,
from above
the lid when the second portion is at the second temperature.
Preferably, according to a first aspect of the invention, there is provided a
lid
for a container, the lid comprising a first plastic layer and a second plastic
layer
disposed on top of the first layer, the first layer including at least one
portion
comprising at least one coloured pigment, the second layer including at least
one
portion comprising at least one thermochromic substance which is capable of
becoming substantially translucent upon reaching a predetermined temperature
in
response to heat transfer from or to contents of the container so as to reveal
at least
1 0 one of the portions comprising the coloured pigment of the first layer.
Preferably, according to a second aspect of the invention, there is provided a
lid for a container, the lid comprising a first HIPS layer and a second HIPS
layer
disposed on top of the first layer, the first layer comprising at least one
portion
having at least one coloured pigment, the second layer including at least one
portion having at least one thermochromic substance in an amount up to 12wt %
of
the layer and having a reduced particle size, which thermochromic substance is
capable of becoming substantially translucent upon reaching a predetermined
temperature in response to heat transfer from or to contents of the container
so as
to reveal at least one of the portions comprising the coloured pigment of the
first
20 layer, the second layer having a thickness substantially less than the
thickness of
the first layer.
Preferably, according to another aspect, there is provided a lid for a
container, the lid comprising a layer comprising at least one portion having
at least
one thermochromic substance which is adapted to change colour and/or become
substantially translucent upon reaching a predetermined temperature(s) in
response
to heat transfer from or to contents of the container, the layer being
provided in at
least one portion with at least one coloured pigment, which portion is
observable at
said predetermined temperature(s) and non-observable at a temperature other
than
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the predetermined temperature(s), the colour of said pigment being the same or
substantially the same colour as that of said thermochromic substance at a
temperature other than the predetermined temperature(s) or which portion
becomes
non-observable at said predetermined temperature(s) and observable at a
temperature other than the predetermined temperature(s), the colour of said
pigment being the same or substantially the same colour as that of said
thermochromic substance at the predetermined temperature(s).
Preferably, according to another aspect of the invention, there is provided a
process for preparing a lid for a container comprising:
co-extruding a first plastic layer and a second plastic layer and optionally
one
or more additional plastic layers, the first layer comprising in at least one
portion at
least one coloured pigment, the second layer comprising at least one portion
comprising at least one thermochromic substance which is adapted to become
substantially translucent upon reaching a predetermined temperature in
response to
heat transfer from or to contents of the container to reveal at least one of
the
portions having the coloured pigment of the first layer.
Definitions
The following definitions are intended as general definitions and should in no
way limit the scope of the present invention to those terms alone, but are put
forth
for a better understanding of the following description.
Unless the context requires otherwise or specifically stated to the contrary,
integers, steps, or elements of the invention recited herein as singular
integers,
steps or elements clearly encompass both singular and plural forms of the
recited
integers, steps or elements.
Throughout this specification, unless the context requires otherwise, the word
"comprise", or variations such as "comprises" or "comprising", will be
understood to
imply the inclusion of a stated step or element or integer or group of steps
or
elements or integers, but not the exclusion of any other step or element or
integer or
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6a
group of elements or integers. Thus, in the context of this specification, the
term
"comprising" means "including principally, but not necessarily solely".
Those skilled in the art will appreciate that the invention described herein
is
susceptible to variations and modifications other than those specifically
described. It
is to be understood that the invention includes all such variations and
modifications.
The invention also includes all of the steps, features, compositions and
compounds
referred to or indicated in this specification, individually or collectively,
and any and
all combinations or any two or more of said steps or features.
By "plastic" is meant any synthetic or natural organic material which may be
shaped when soft and then hardened such as resins, resinoids, polymers,
cellulose
derivatives, casein materials and proteins.
By "ambient temperature" is meant the room temperature of the environment
in which the lid is situated.
By "substantially translucent" means that the thermochromic material is
capable of allowing light to pass therethrough but diffusing it so that
objects on the
other side cannot be clearly distinguished. The material however may not
become
totally transparent and may retain some colour.
Brief description of the Drawings
Preferred embodiments of the invention will now be described, by way of
example only, with reference to the accompanying drawings in which:
FIG. 1 is a partial perspective view of a lid in accordance with one
embodiment of the present invention and a container;
FIG. 2 is a perspective view of the lid of FIG. 1 including a cut away section
showing the cross-section of the layers of the lid;
FIG. 3 shows the cross-section of the cut away section of the lid of FIG. 2 in
more detail;
FIG. 4 shows the cross-section of the cut away section of another lid of a
less
desirable embodiment of the invention in which condensation occurs on the
inner
surface of the lid;
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6b
FIG. 5 is a perspective view of another lid in accordance with a less
desirable
embodiment of the invention including a cut away section showing a cross-
section
of the layers of the lid and in which pitting is shown on the surface;
FIG. 6 shows the cross-section of the cut away section of the lid of FIG. 5 in
more detail;
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Fig. 7 shows the cross-section of a cut away section of a lid in accordance
with
another embodiment of the invention; and
Figures 7A and 7B show perspective views of the lid in accordance with Fig. 7
at
ambient temperature (Fig. 7A) and at a predetermined non-ambient temperature
(Fig. 7B).
Detailed Description of Preferred Embodiments of the Invention
There is disclosed herein a lid for a container, the lid comprising a first
plastic layer
and a second plastic layer disposed on top of the first layer, the first layer
comprising at
least one portion having a coloured pigment, the second layer comprising at
least one
portion having at least one thermochromic substance which is capable of
becoming
to substantially translucent upon reaching a predetermined temperature in
response to heat
transfer from or to contents of the container and reveal at least one of the
portions having
the coloured pigment of the first layer.
The lid may optionally include additional plastic layers i.e., the lid may
comprise
two or more layers. For example, the lid may be formed from two, three, four,
or more
layers. When more than two layers are used at least one layer is the first
layer and at least
one layer is the second layer and the additional layers are suitably
positioned below the
first layer. The additional layer(s) may include a coloured pigment and/or
regrind. For
example the additional layer(s) may be a darkened layer, which by virtue of
light
refraction will cause the first layer to appear darker. Using additional
darkened layers
may decrease light refraction between the layers, thereby enabling less
thermochromic
material to be used which may make the lid more economically viable to
manufacture.
The lid of the present invention may be for a hot or cold cup or container and
may
be for a lid for a beverage cup or container, such as a disposable beverage
container for
containing a hot or cold substance such as heated or chilled beverage (coffee,
tea, hot
chocolate, iced chocolate, soft drink, soup, food or foodstuff, although this
list is by no
means comprehensive). The lid may be for use with foam, polystyrene or paper
cups
commonly used in the sale of heated or chilled beverages such as coffee. In
this regard
with heated beverages, it is the heat (or steam) from the beverage which
suitably effects
the change in the thennochromic material and thereby the colour of the lid
such that one
can identify whether the beverage is at a desired temperature or is to hot to
drink. With
chilled beverages, the proximity of the cold liquid to the lid or the actual
contact of the
cold liquid with the lid may effect a change in colour of the thermochromic
material and
thereby the colour of the lid so that one can determine if the drink is cold
enough or is
being served or stored at a desired temperature. Also, the change in colour
may be
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effected by placing the lid in a heated or chilled environment such as in an
oven or
refrigerator.
The layers of the lid may be in the form of thin substrates of the order of
micron to
millimeter thickness. Typically each layer of the lid may range from about 100
m up to
about 400 m thickness, with the total thickness of the lid for a two layer lid
being of the
order of about 200pm to about 800 m . The thickness of the lid is largely
determined by
the process of manufacture and equipment used and whether a thicker, sturdier
high-
quality lid or a cheaper, thinner lid is desired for the end application. For
example the
total thickness of a lid in accordance with one embodiment of the invention
may be of the
io order of about 0.3 to about 0.4nun (about 300 to about 400[1m).
The second layer is suitably an upper layer of the lid. The first layer is
suitably a
lower layer of the lid which, in the absence of additional plastic layers, is
in direct contact
with any heat from a substance contained in the container. The upper layer of
the lid
containing the thermochromic material may be suitably substantially thinner
than the
lower layer. For example, the upper layer of the lid may be about 15% to about
50%,
about 20% to about 40% or about 25% to about 30% of the total lid thickness.
In one
embodiment the upper layer of the lid may range in thickness from about
120[Lin to about
1601..un and the lower or bottom layer of the lid may range from about 18Own
to about
240 m.
The portion of thennochromic substance and coloured pigment in each layer may
be
substantially all of the lid or one or more smaller portion(s) of the lid. The
portion of the
upper layer need not necessarily be the same size as the portion of the lower
layer,
however at least one of the portions of the upper layer must sufficiently
cover a portion of
the lower layer so as to reveal that portion at the predetermined temperature.
The lid is founed from a plastics material. In one embodiment the lid is
suitably
made from high impact polystyrene (HIPS). The lid may be in the form of a co-
extruded
outer and inner layer. The portion(s) having the translucent properties may be
only in the
outer layer. The inner layer may comprise regrind of a lid of the present
invention or a
regrind of a different lid.
In various embodiments additional plastic layers may also be present.
With respect to regrind, manufacturing of lids typically generate excess
material
refened to as "webbing". Webbing is recycled in a process called regrind.
Regrind is
used because thermochromic materials are expensive and adding a portion of the
regrind
may lower the cost of manufacturing the lid. Typically regrind is added to the
first or
lower layer (which may be the bottom or base layer adjacent the contents of
the container)
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of the lid. Regrind is typically not added to the upper layer as the regrind
may discolour
the thermochromic pigment. For example with HIPS which typically includes a
white
pigment, the regrind may cause the HIPS to become grey with loss of sheen. The
discolouration of the regrind pigment may also create a denser colour affect
on the colour
of the lid at a temperature other than the predetermined temperature and allow
a reduction
in the add rate of the thennochromic material in the upper or second layer.
However, in
certain embodiments a small percentage of regrind may be added to the upper
layer so as
to provide an opportunity to use excess regrind stockpiles (which may occur)
and/or to
add depth to the colour of the lid at a temperature not being the
predetermined
1 o temperature.
By inclusion of regrind in the first layer, the first layer may thereby
contain
thermochromic substance together with a coloured pigment from the regrind.
Where a
different lid is used as regrind, it may be desirable to use one having a
thermochromic
material having a reduced particle size such as BW Grade or PS Conc. available
from
Matsui International, although the invention is not limited to such regrinds
and regrinds
having no thermochromic material or containing standard thermochromic
materials of
conventional particle size may be used.
Typically the coloured pigment of the first layer is chosen so that the first
layer is
opaque at both the predetermined temperature and a temperature other than the
zo predeteilnined temperature so as to provide a dense colour. The coloured
pigment may be
any standard pigment dye other than a white pigment, although the first layer
may
additionally contain a white pigment. Suitably the coloured pigment is added
in an add-
on rate of about 2 to about 3wt%. The pigment may be chosen to be the colour
of the
desired colour at the predetermined temperature. For example, the first layer
may contain
a red pigment so that the colour of the lid at the predetermined temperature
is red.
Standard colour may also be added to the first layer via regrind, and
consequently the
total add on rate of the standard pigment may be in the range of about 1 to
about 4wt%.
The amount of pigment that is added may differ depending on the desired
colour. For
example less pigment may be added when the pigment is black than when the
pigment is
blue.
A standard pigment dye is suitably chosen for the first layer as when the
thennochromic material becomes substantially translucent at the predetermined
temperature, the standard pigment dye in this layer is observable as a
distinct colour.
When HIPS is used in the second layer, due to the nature of the HIPS also
being mostly
translucent, at the predetermined temperature the standard pigment dye of the
bottom
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layer is observable and if this pigment is red, the lid will be a distinct red
colour at
the predetermined temperature. The red in the bottom layer may thereby prevent
the
bottom layer from becoming translucent at the predetermined temperature.
Further by
inclusion of the standard pigment, a denser colour may be provided to the lid
at a
5 temperature other than the predetermined temperature.
The thermochromic material in the upper layer may be used in the absence of
any
other coloured pigments aside from any underlying colour contained within= the
thermochromic material itself. Materials having thermochromic properties,
including but
not limited to thermochromic pigments, are known. The thermochromic material
is
io chosen such that it is only visible when the temperature is other than
the predetermined
temperature. For example, in one embodiment, the thennochromic material in the
second
layer is visible when the lid is at a temperature other than the predetermined
temperature
but becomes substantially translucent at the predetermined temperature. The
translucent
colour change may be gradual from near the predetermined temperature and
complete by
the predetermined temperature. In this regard the effect of heating or cooling
may not
result in total translucency. Rather the colour may change in the upper layer
from a dark
solid colour to a different much paler colour which by light refraction mixes
with the
standard, non-colour changing pigment in the bottom layer, the colour of the
standard
pigment completely dominating the thermochromic material at the predetermined
temperature. Whilst it would appear that the upper layer has become totally
translucent it
may in fact be a pale see-through colour (for example for a lid changing from
a dark
brown to red, the layer including the thennochromic material may be a very
pale
pinky/red colour).
The material having thennochromic properties may be a thermochromic pigment,
resin or the like. The thermochromic material may be chosen such that it has a
reduced
particle size in comparison with conventional thermochromic materials. The
present
inventors have found that thermochromic materials having a reduced particle
size are
desirable for use in the thin plastic layers of the lid.
Thennochromic pigments are available from several sources, for example, those
denoted F4, G7 or J8 sold under the trademark CHROMICOLOR by Matsui
International
Co., Inc. of Gardena, CA, United States of America. The thermochromic material
may be
included in the second plastic layer in add rates of less than about 12wt%,
for example
less than about 1 Owt% or less than 5wt%.
The thennochromic material may be included in the second plastic layer in an
amount of about 6wt% to about 1Owt%. Lower add on rates may be beneficial in
terms of
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costs of manufacture and the high cost of the raw materials. Use of above
about
12wt% of the thermochromic material results in a lid which is less
economically viable
and the structural integrity of the lid may be compromised such that it tears
easily as a
result of its brittleness and is more susceptible to pitting during
production.
Whilst standard thermochromic materials can be used, in one embodiment the
thermochromic material is a concentrate such as Matsui Chromocolor BW Grade
available from Matsui International Inc., Gardena, CA, USA. This product has a
reduced
particle size relative to conventional thennochromic materials and has been
the subject of
migration and food safety testing and approved by FDA and other Food Safety
Bodies in
August 2004 for use in a food contact situation. Other thermochromic materials
may be
standard thermochromic materials altered to reduce their particle size by the
thermochromic material manufacturer, for example Matsui PS Conc and other
microencapsulated masterbatches. In one embodiment the thermochromic material
used
in the second (upper) layer is suitably fresh or virgin material and not
material from
regrind.
In one embodiment the thermochromic substance and the coloured pigment are
chosen so that, in combination, the layers present one observable colour at a
temperature
other than the predetermined temperature. Colour mixing may occur in the first
layer as a
result of any regrind present containing thennochromic material which mixes
with the
coloured pigment and also as a result of the slight effect of the opaqueness
of the HIPS
when used. It is the combination of this colour mixing in the first layer and
light
refraction through the layers which results in the overall observable colour
of the lid. The
colour of the first layer contributes to the colour of the lid at a
temperature other than the
predetermined temperature because of the translucent nature of the layer
containing the
thermochromic material.
In one embodiment the extent of the colour change may be affected by the
coverage
of any dark colour (which may be the pigment colour contained in the
thermochromic
material) which differs from a second distinguishable colour (which is the
colour of the
coloured pigment in the first layer) at the predetermined temperature and
different from
the observable colour at the temperature other than the predetermined
temperature. This
affect may occur when the first (lower) layer also includes a thermochromic
material in
combination with the standard pigment, as the presence of the thermochromic
material
may lead to a discolouration/alteration of the final colour of the first layer
which
discolouration is observable through the second (upper layer) due to the
thinness of the
second layer i.e., the colour of the lower layer can be seen through the top
layer. This
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discolouration may be further compounded by the fact that standard dyes are
much
stronger than thermochromic dyes. For example when a blue thermochromic is
placed in
an upper layer of the lid with a standard red pigment in the lower layer, the
result is a lid
which has the desired colour at the predetermined temperature (red) but the
discolouration
of the observable colour at for example, ambient temperature results in the
ambient colour
being only slightly darker than the hot colour- eg., a reddy-purple colour and
there is
practically no colour contrast between the hot and ambient states.
Accordingly, the
colour of the thermochromic additives and coloured pigment in each layer may
suitably
be selected so that a colour or combination of colours which results is an
observable
io colour at the temperature other than the predetermined temperature and
which colour is
distinguishable from the colour of the lid at the predetermined temperature.
As an example, the observable colour of the lid at a temperature other than
the
predetermined temperature such as at ambient temperature may be dark
brown/black and
the colour at the predetermined temperature may be bright red. This may be
achieved
using a mixture of green thermochromic and turquoise thermochromic in the
second
(upper) layer which, by means of light refraction, can show an observable dark
brown/black colour at the temperature other than the predetermined temperature
when a
standard red dye is used (together with any thermochromic from regrind but in
the
absence of any white pigment) in the first or lower layer. On heating or
cooling, the lid
will present the bright red colour at the predetermined temperature.
As another example the observable colour of the lid at a temperature other
than the
predetermined temperature may be black and the colour at the predetermined
temperature
may be green. This may be achieved by using a mixture of black thermochromic
and
gold/orange thermochromic in the second or upper layer which, by means of
light
refraction, can show an observable dark black cold colour at the temperature
other than
the predetermined temperature such as at ambient temperature when a mixture of
standard
green and white dyes are used (together with any thermochromic from regrind)
in the first
or lower layer. On heating or cooling, the lid will present a green colour at
the
predetermined temperature.
As another example the observable colour of the lid at a temperature other
than the
predetermined temperature such as at ambient temperature may be red and colour
of the
lid at the predetermined temperature may be yellow. This may be achieved by
using pink
thennochromic in the second or upper layer which, by means of light
refraction, can show
an observable dark red cold colour at the temperature other than the
predetermined
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13
temperature when a mixture of standard yellow and white dyes are used
(together
with any thermochromic from regrind) in the first or lower layer.
In use, with the addition of heat or cooling to the predetermined temperature,
the
colour of the second (upper) layer containing the thermochromic material may
disappear
and the colour of the pigment added to at least one portion of the first
(bottom) layer may
become visible. The portion which becomes visible may form words, symbols or
patterns
against the remainder of the lid when the contents are at the predetermined
temperature.
The thermochromic material may be capable of returning to its original colour
in
response to the temperature of the regions falling below the predetermined
temperature.
In one embodiment different portions of the lid may contain different
thermochromic materials. For example the lid may include at least two regions
having
different thermochromic properties which are each capable of changing upon
reaching
differing predetermined temperatures in response to heat transfer from or to
the contents
of the container. In another embodiment three, four or more regions may be
provided.
The thermochromic material(s) used may also be quasi-reversible and allow two
or more
colour changes. For example a thermochromic pigment may be blue at one
temperature
(such as ambient temperature), red at a different temperature (such as a
temperature of
about 45 C) and yellow at another temperature (such as a temperature of about
60 C).
It is therefore clear from the above that it is possible to use two or more
colours and
zo
more than two layers, and where more than two layers are used, with the
addition of
different or the same thermochromic materials in each layer having varying or
similar
colour changing temperatures. It is possible to select a particular
combination of
colour(s) to indicate most desired temperatures. One possible use of the lid
is one with a
safe cold colour (such as blue), a colour which indicates that the beverage is
at the right
temperature to drink (such as orange), and a third colour (such as red) which
indicates
that the beverage is too hot.
The predetermined temperature may be a predetermined non-ambient temperature
such as a predetermined heated non-ambient temperature or a predetermined
cooled non-
ambient temperature. The temperature other than the predetermined temperature
may be
ambient temperature. In one embodiment the ambient temperature is about 20 C
to about
30 C. The predetermined heated non-ambient temperature may be above about 25
C, for
example about 30 C, about 35 C, about 40 C, about 45 C, about 50 C, about 55
C, about
60 C, or about 65 C. In alternative embodiments the temperature may be about
45 C,
about 50 C, about 55 C, or about 60 C. The predetermined cooled non-ambient
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14
temperature may be below about 25 C, for example about 20 C, about 15 C, about
C, about 5 C, about 0 C, about -5 C, about -10 C, or about -15 C.
There is also disclosed herein a lid for a container, the lid comprising a
layer
comprising at least one portion having at least one thermochromic substance
which is
5 adapted to change colour and/or become substantially translucent upon
reaching a
predetermined temperature(s) in response to heat transfer from or to contents
of the
container, the layer being provided in at least one portion with a coloured
pigment, which
portion is observable at said predetermined temperature(s) and non-observable
at a
temperature other than the predetermined temperature(s), the colour of said
pigment being
io the same or substantially the same colour as that of said thermochromic
substance at a
temperature other than the predetermined temperature(s) or which portion
becomes non-
observable at said predetermined temperature(s) and observable at a
temperature other
than the predetermined temperature(s), the colour of said pigment being the
same or
substantially the same colour as that of said thermochromic substance at the
predetermined temperature(s).
In this embodiment, the lid may be one in accordance with the first aspect of
the
invention and the layer may be coated on the second plastic layer or may be
located
between the first and second plastic layers.
In this embodiment, a logo, symbol or writing (such as branding or
advertising)
may be made to appear on the top of a lid which at ambient temperature appears
to have
no logo, symbol or writing visible on it. The logo, symbol or writing may be
coated by
stamping or impregnating the pigment onto the top of the lid using a standard
regular non-
changing ink after the lid is made using a colour substantially identical or
similar to that
of the lid at ambient temperature i.e., the colour may be chosen to be
substantially
identical to or similar to the thermochromic material. In this embodiment, the
logo,
symbol or writing may be stamped onto the lid as a standard dye (i.e., one
that does not
change colour on top of the lid in a colour that matches the colour of the
thermochromic
at a temperature below the predetermined temperature (such as at ambient
temperature)
and thus is not visible below the predetermined temperature but when the lid
changes
colour the logo, symbol or writing stays the same colour and is thereby
revealed.
Alternatively or additionally the logo, symbol or writing rnay be formed from
a
thermochromic material such as a quasi-reversible or non-reversible
thermochromic.
More than one logo, symbol or writing may be present and the logo, symbol or
writing
may be revealed at different temperatures. In one embodiment, when the lid is
at a
temperature other than the predetermined temperature, a user cannot see
anything on the
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top of the lid, however once the lid is put on the cup and heated or cooled to
the
predetermined temperature, the thermochromic material changes colour and
becomes
clear, revealing the logo, symbol or writing to the user.
In one embodiment when using a quasi-reversible thermochromic material in the
lid -
s capable of two colour changes (for example blue to yellow to red),
stamping a logo,
symbol or writing on the top of the lid (or a layer of the lid) with normal
ink that matches
the colour at a temperature below the predetermined temperature i.e. the
ambient cold
colour (such as blue), the logo, symbol or writing will be visible at both the
red stage and
the yellow stage but not the blue stage. Alternatively by stamping the logo,
symbol or
io writing in a standard dye that is yellow, then the logo, symbol or
writing will be visible at
the blue stage and the red stage, but not the yellow stage. Similarly using a
standard red
dye will result in visibility during the blue and yellow stage but no
visibility of the logo,
symbol or writing during the red stage. In another embodiment, by stamping a
logo,
symbol or writing that is made from a thermochromic material that is capable
of
15 becoming substantially translucent on the application of heat, then when
using a
quasireversible material in the lid as above, it is possible that when the
logo, symbol or
writing is stamped in a blue thermochromic with only one translucent colour
change the
change occurring during the red stage, then the logo, symbol or writing will
not be visible
during the blue stage, will be visible during the yellow stage but will not be
visible during
zo the red stage. This offers branding and marketing options as well as
enabling logos,
symbols or writing to indicate to consumers that the beverage is at the right
temperature
to drink or is too hot. Another scenario is stamping the lid or a layer of the
lid with two
(or more) different types of coloured pigments one or both being a
thermochromic
material(s) capable of becoming substantially translucent at various
predetermined
zs temperatures. This allows different logos to appear/disappear at various
temperatures.
Where more than two layers are used for example in a multi-layer lid, logos,
symbols or writing can be provided in any or between any layers in any desired
variation
of logo, symbol or writing or combination of colours. In this embodiment it is
possible
for the logo, symbol or writing to be in the form of a picture.
30 There is also disclosed herein a process for preparing a lid for a
container, the
process comprising co-extruding a first plastic layer, a second plastic layer
and optionally
one or more additional plastic layers, the first layer including in at least
one portion a
coloured pigment, the second layer including at least one portion including at
least one
thermochromic substance which is adapted to become substantially translucent
upon
35 reaching a predetermined temperature in response to heat transfer from
or to contents of
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the container to reveal the at least one of the portions having the coloured
pigment of
the first layer.
In one embodiment the lid is thermoformed, with thermochromic pigments added
to
molten plastic material such as HIPS before forming. In one embodiment, a
process for
producing the thermochromic regions of the lids involves co-extruding two or
more layers
of HMS from separate drums. The inner layer (ie., that adjacent to or closest
to the
contents of the cup in use) of HIPS may be produced conventionally to which is
added a
coloured pigment (other than the normal base pigment of white or grey tone)
which does
not change colour under heat or cooling and which provides a depth of colour
to the lid.
io The inner layer may be formed from scrap and may include a thermochromic
material.
The outer layer (i.e., that remote from the contents of the cup in use) may be
produced
from HIPS to which is added a thermochromic pigment in the absence of any
white
pigment.
In one embodiment the lid is formed from a plastics material in which portions
are
impregnated or blended where appropriate with the material having
thermochromic
properties or with a standard dye and where appropriate thermochromic from
regrind. In
various embodiments no water may be present in the thermochromic material
prior or
during addition.
Referring to the drawings, Figure 1 shows a beverage container lid 2 of the
present
invention which includes a sidewall 2A, corresponding top wall 2B, a rim or
lip 3 for
engaging beverage cup 67. Edge 4 flares outwardly and independent from contact
with
cup 67. Beverage container lid 2 also includes a steam release hole 1.
Figure 2 shows the lid of Figure 1 including a cut out cross section 5 showing
an
inner layer 7 and an outer layer 6.
Figure 3 shows the cross-section 5 of Figure 2 in more detail. It can be seen
that
Figure 3 represents a magnified representation of cut out cross section 5 of a
beverage
container lid 2A. Figure 3 includes a top surface 11, a layer 14 which
corresponds to outer
layer 6 of Figure 2, a bottom layer 15 which corresponds to inner layer 7 of
Figure 2, and
bottom surface 13. Region 12 denotes a bonding area between top layer 14 and
bottom
layer 15(a combination of heat and applied pressure allows the layers to bond
and meld
together on contact on exit from a drum). At ambient temperature the outer
surface 11
displays an observable colour combination of layers 14 and 15 in an unmolested
state.
For this purpose the top layer 14 includes virgin High Impact Polystyrene
(HIPs) and at
least one thennochromic material and the bottom layer 5 includes virgin HIPs,
at least one
standard dye pigment and regrind in the form of recycled material of a like
lid. In one
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17
embodiment the standard dye pigment is added in an amount sufficient to
provide
an opaque covering of bottom layer 15. In one embodiment top layer 14
represents a
layer between 15-35% of the entire thickness of the lid 2. In one embodiment
the
thermochromic material is a standard thermochromic material suitable for use
with HIPs.
In another embodiment the thermochromic material is a concentrate of a
standard
thermochromic material having its particle size reduced as mentioned
hereinbefore.
Suitably layer 14 contains at least about lOwt% thermochromic material with
the
remaining material being the virgin HIP.
In use, the lid 2 of the invention is placed on container 67 containing a hot
or cold
io beverage and subjected to thermal communication from the contents of the
container 67
thereby activating the thermochromic material. The thermochromic material
present in
top layer 14 is activated and becomes substantially translucent at a pre-
determined non-
ambient temperature to thereby reveal the underlying colour present in the
bottom layer
15.
In one embodiment layer 14 may also contains regrind material.
Figure 4 shows another cross section 10 of a lid 2 however in this embodiment
the
standard dye pigment is insufficient to provide an opaque coverage of the
bottom layer
15. In this regard typically less than lwt% is insufficient and 1 to 3wt% may
be
insufficient however sufficiency is dependent on the strength and brand of
pigment used.
Where HIPS is used and a white pigment is not contained therein, a standard
dye
contained within the thermochromic capsule and acting as a secondary colour
was
insufficient to provide coverage. In use hot liquid 22 from beverage cup 67
generates
steam 23 causing the activation of the thermochromic material however because
of the
insufficient coverage, the bottom layer 15 itself becomes translucent and
condensation 20
is able to be seen through the lid 2 on the surface 13 of the bottom layer 15.
Figure 5 shows a lid 2 however in this embodiment pitting 31 occurs on the lid
surface. Layer 14 includes a standard thermochromic additive suitable for HIP
environments. The enlarged particle size of the thermochromic additive
inherent in the
standard material and overcrowding of the thermochromic particles causes an
explosion
of the crowded particles because the particles are unable to retain their
natural
configuration resulting in pitting 30 visible on the outer surface 11 of the
lid 2. Figure 6
shows a cross-section of the lid 10 showing this pitting in detail. The
pitting also leads to
a loss of rubber content causing brittleness.
Figures 7, 7A and 7B show a lid 2 having a patterns or logos 62 or 64 on their
surface. The patterns or logos 63 are selected to be a colour combination of
upper layer 14
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18
and lower layer 15 in the cold ambient state and is not
observable. When
thermochromic additive is subjected to heat or cooling and becomes
translucent, the
visible outer substrate 60 colour becomes the colour of the standard pigment
contained in
lower layer 15 but the logo 62 remains the colour combination of both layers
in the cold
ambient state and becomes observable as the remaining colour changes to the
secondary
underlying colour. The logo may be in the form of a standard non-changing
pigment
stamped on the lid or it may be a quasi-reversible or non-reversible
thermochromic
material.
The invention will now be described by reference to the following examples:
In the following examples all add rates assume that the top layer of the
beverage lid has a
thickness being approximately 40% of the thickness of the lid, and the bottom
layer being
approximately 60% of thickness of lid. These thicknesses can vary and when
they do so
add rates may vary.
EXAMPLE 1:
To achieve a dark brown to bright red lid.
25. Top Layer:
Chromicolor PS Conc BW Grade Green Type #45 about 10%
Chromicolor PS Conc BW Grade Turqoise Blue Type #45 about 5%
Virgin HIPS about 85%
Bottom Layer:
Pigment Red 247 about 1.0%
Pigment Red 242 about 0.1%
Balance (regrind from top layer and virgin hips) about 98.9%
2)
Top Layer:
Chromicolor PS Cone BW Grade Green Type #45 about 15%
Virgin HIPS about 85%
Bottom Layer:
Pigment Red 247 about 1.0%
Pigment Red 242 about 0.1%
Balance (regrind from top layer and virgin hips) about 98.9%
EXAMPLE 2:
To achieve a Red to bright Yellow lid:
1)
Top Layer:
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19
Chromicolor PS Cone BW Grade Pink Type #45 about 15%
Virgin HIPS about 85%
Bottom Layer:
Pigment White 6 about 0.06%
Pigment Yellow 138 about 0.055%
Balance (regrind from top layer and virgin hips) about 99.885%
2)
Top Layer:
Chromicolor PS Cone BW Grade Pink Type #45 about 15%
Virgin HIPS about 85%
Bottom Layer:
Pigment White 6 about 0.03%
Pigment Yellow 138 about 0.0275%
Balance (regrind from top layer and virgin hips) about 99.9425%
EXAMPLE 3:
To achieve a Charcoal to Green:
1)
Top Layer:
Chromicolor PS Cone BW Grade Fast Black Type #45 about 11%
zo Chromic lor PS Cone BW
Grade Gold Orange Type 445 about 4%
Virgin HIPS about 85%
Bottom Layer:
Pigment White 6 about 0.105%
Pigment Green 7 about 0.0275%
Balance (regrind from top layer and virgin hips) about 99.8675%
2)
Top Layer:
Chromic lor PS Conc BW Grade Fast Black Type #45 about 11%
Clu-omicolor PS Cone BW Grade Gold Orange Type 445 about 4%
Virgin HIPS about 85%
Bottom Layer:
Pigment White 6 about 0.05%
Pigment Green 7 about 0.0015%
Pigment Yellow 138 about 0.0125%
Balance (regrind from top layer and virgin hips) about 99.936%
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=
Lids according to the embodiments described above may have one or more
advantages. For example, the lids may be used in the case of hot beverages to
include a
warning that there are hot and potentially hazardous contents contained
therein. The lids
may also provide an improved indication of temperature to persons with minimal
5 eyesight, numbness of the hands and/or fingers and to persons in darkened
locations.
Although the invention has been described with reference to specific examples,
it
will be appreciated to those skilled in the art that the invention may be
embodied in many
other fonlis.
