U.S. patent application number 09/824343 was filed with the patent office on 2001-10-11 for time-temperature integrating indicator device with barrier material.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Green, Kevin R., Noyola, Joan M., Qiu, Jean, Yarusso, David J..
Application Number | 20010027741 09/824343 |
Document ID | / |
Family ID | 22089912 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010027741 |
Kind Code |
A1 |
Qiu, Jean ; et al. |
October 11, 2001 |
Time-temperature integrating indicator device with barrier
material
Abstract
A time-temperature indicator device provides a visually
observable indication of the cumulative thermal exposure of an
object. The device includes a substrate having a diffusely
light-reflective porous matrix and a backing. The backing includes
on its surface a viscoelastic indicator material for contacting the
substrate and a barrier material for substantially inhibiting the
lateral and longitudinal flow of viscoelastic indicator material
between the substrate and the backing.
Inventors: |
Qiu, Jean; (Andover, MA)
; Noyola, Joan M.; (Maplewood, MN) ; Yarusso,
David J.; (Shoreview, MN) ; Green, Kevin R.;
(Maplewood, MN) |
Correspondence
Address: |
Attention: Christopher D. Gram
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
22089912 |
Appl. No.: |
09/824343 |
Filed: |
April 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09824343 |
Apr 2, 2001 |
|
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09069576 |
Apr 29, 1998 |
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6244208 |
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Current U.S.
Class: |
116/207 ;
116/219; 374/106; 374/162; 374/E3.004 |
Current CPC
Class: |
G01K 3/04 20130101 |
Class at
Publication: |
116/207 ;
116/219; 374/162; 374/106 |
International
Class: |
G01K 003/00 |
Claims
What is claimed is:
1. A time-temperature integrating indicator device for providing a
visually observable indication of the cumulative thermal exposure
of an object, said device comprising: (a) a substrate having a
diffusely light-reflective porous matrix; and (b) a backing
including on its surface a viscoelastic indicator material for
contacting said porous matrix, and a barrier material for
substantially inhibiting the lateral and longitudinal flow of
viscoelastic material regardless of whether the indicator device is
in an activated state or unactivated state; wherein the device is
in the unactivated state when the viscoelastic indicator material
is out of contact with the porous matrix; and wherein the device is
in the activated state when the viscoelastic indicator material is
in contact with the porous matrix such that the viscoelastic
indicator material migrates into the porous matrix at a rate that
increases with increasing temperature, thereby creating a visually
observable indication of cumulative thermal exposure.
2. The device of claim 1 wherein the barrier material comprises a
pressure sensitive adhesive.
3. The device of claim 2 wherein the backing includes on its
surface alternating strips of the viscoelastic indicator material
and the pressure sensitive adhesive.
4. The device of claim 2 wherein the backing includes on its
surface a central stripe of the viscoelastic indicator material,
one edge stripe of the pressure sensitive adhesive on each side of
the central stripe, and one edge stripe of the pressure sensitive
adhesive on at least one end of the central stripe.
5. The device of claim 1 wherein the barrier material is selected
from the group consisting of glassy polymers, semi-crystalline
polymers, physically crosslinked elastomers, chemically crosslinked
elastomers, segmented polyesters, radiation crosslinked
polybutadiene, and pressure sensitive adhesives.
6. The device of claim 2 wherein the pressure sensitive adhesive is
selected from the group consisting of acrylic pressure sensitive
adhesives, silicone pressure sensitive adhesives, rubber resin
blend pressure sensitive adhesives, triblock copolymer pressure
sensitive adhesives, and vinyl ether polymer pressure sensitive
adhesives.
7. The device of claim 1 wherein the visually observable indication
comprises a color change.
8. The device of claim 1 wherein the visually observable indication
comprises the appearance of latent indicia in the activated state
that are not visible in the unactivated state.
9. The device of claim 1 wherein the visually observable indication
comprises the obscuring of indicia in the activated state that are
visible in the unactivated state.
10. The device of claim 1 wherein the barrier material comprises
polystyrene.
11. The device of claim 1 wherein the barrier material comprises
thermoplastic rubber.
12. A method of providing an indication of the cumulative thermal
exposure of an object, comprising the steps of: (a) providing a
time-temperature integrating indicator device comprising: (i) a
substrate having a reflective porous matrix; and (ii) a backing
including on its surface a viscoelastic indicator material for
contacting said porous matrix, and a barrier material for
substantially inhibiting the lateral and longitudinal flow of
viscoelastic indicator material regardless of whether the indicator
device is in an unactivated state or an activated state, wherein
the device is in the unactivated state when the viscoelastic
indicator material is out of contact with the porous matrix, and
wherein the device is in the activated state when the viscoelastic
indicator material is in contact with the porous matrix such that
the viscoelastic indicator material migrates into the porous matrix
at a rate that increases with increasing temperature, thereby
creating a visually observable indication of cumulative thermal
exposure; (b) activating said device by placing said viscoelastic
indicator material in contact with said porous matrix such that
said viscoelastic indicator material migrates into said porous
matrix at a rate which increases with increasing temperature and
creates a visually observable indication of cumulative thermal
exposure; and (c) mounting the device on an object whose cumulative
thermal history is to be measured.
13. The method of claim 12 wherein the barrier material is a
pressure sensitive adhesive.
14. The method of claim 13 wherein the device is mounted on the
object by placing said pressure sensitive adhesive in contact with
the object.
15. The method of claim 13 wherein the backing includes on its
surface alternating stripes of the viscoelastic indicator material
and the pressure sensitive adhesive.
16. The method of claim 13 wherein the backing includes on its
surface a central stripe of the viscoelastic indicator material,
one edge stripe of the pressure sensitive adhesive on each side of
the central stripe, and one edge stripe of the pressure sensitive
adhesive on at least one end of the central stripe.
17. The method of claim 12 wherein the barrier material is selected
from the group consisting of glassy polymers, semi-crystalline
polymers, physically crosslinked elastomers, chemically crosslinked
elastomers, segmented polyesters, radiation crosslinked
polybutadiene, and pressure sensitive adhesives.
18. The method of claim 13 wherein the pressure sensitive adhesive
is selected from the group consisting of acrylic pressure sensitive
adhesives, silicone pressure sensitive adhesives, rubber resin
blend pressure sensitive adhesives, triblock copolymer pressure
sensitive adhesives, and vinyl ether polymer pressure sensitive
adhesives.
19. The method of claim 12 wherein the visually observable
indication comprises the appearance of latent indicia that are not
visible before activating the device.
20. The method of claim 12 wherein the visually observable
indication comprises a color change.
21. The method of claim 12 wherein the barrier material comprises
polystyrene.
22. The method of claim 12 wherein the barrier material comprises
thermoplastic rubber.
23. A striped viscoelastic indicator tape for use in a
time-temperature integrating indicator device having a substrate
with a diffusely light-reflective porous matrix, said device for
providing a visually observable indication of the cumulative
thermal exposure of an object, said indicator tape comprising: (a)
a backing material; (b) a viscoelastic indicator material on a
portion of the surface of the backing material, capable of
penetrating the porous matrix at a rate that increases with
increasing temperature; and (c) a barrier material on a portion of
the surface of the backing material for substantially inhibiting
the lateral and longitudinal flow of viscoelastic indicator
material between the backing and another surface when the device is
in an unactivated state, wherein the device is in the unactivated
state when the viscoelastic indicator material is out of contact
with the porous matrix.
24. The striped tape of claim 23 wherein the barrier material
comprises a pressure sensitive adhesive.
25. The striped tape of claim 24 wherein the backing material
includes on its surface alternating stripes of the viscoelastic
indicator material and the pressure sensitive adhesive.
26. The striped tape of claim 24 wherein the backing material
includes on its surface a central stripe of the viscoelastic
indicator material, one edge stripe of the pressure sensitive
adhesive on each side of the central stripe, and one edge stripe of
the pressure sensitive adhesive on at least one end of the central
stripe.
27. The striped tape of claim 23 wherein the barrier material is
selected from the group consisting of glassy polymers,
semi-crystalline polymers, physically crosslinked elastomers,
chemically crosslinked elastomers, segmented polyesters, radiation
crosslinked polybutadiene, and pressure sensitive adhesives.
28. The striped tape of claim 24 wherein the pressure sensitive
adhesive is selected from the group consisting of acrylic pressure
sensitive adhesives, silicone pressure sensitive adhesives, rubber
resin blend pressure sensitive adhesives, triblock copolymer
pressure sensitive adhesives, and vinyl ether polymer pressure
sensitive adhesives.
29. The striped tape of claim 23 wherein the barrier material
comprises polystyrene.
30. The striped tape of claim 23 wherein the barrier material
comprises thermoplastic rubber.
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/069,576, filed Apr. 29,1998.
TECHNICAL FIELD
[0002] This invention relates to time-temperature integrating
indicator devices that give a visual indication of the cumulative
thermal exposure of an object by migrating a viscoelastic indicator
material into a porous substrate at a temperature dependent rate,
and to methods of making and using such devices.
BACKGROUND OF THE INVENTION
[0003] The useful life of a perishable product is a function of its
cumulative thermal exposure, which is a combination of the
temperatures to which the product is exposed and the duration of
the exposure. Degradation reactions occur faster at higher
temperatures than they do at lower temperatures. Therefore, a
perishable product will have a longer useful life if it is exposed
to lower temperatures than if it is exposed to higher temperatures.
Perishable products include, but are not limited to, food, food
additives, chemicals, biological materials, drugs, cosmetics,
photographic supplies and vaccines.
[0004] Many manufacturers mark their products with printed
expiration dates in an attempt to provide an indication of when the
useful life of a perishable product ends. However, these dates are
only estimates and are unreliable because they are based on
assumptions about the thermal history of the product that may not
be true with respect to a particular package on which they appear.
Namely, in computing expiration dates, a manufacturer assumes that
during its useful life a product will be kept at temperatures
within a specific range prescribed for best results. However, if
the actual temperatures of exposure are higher than those used in
calculating the printed expiration date, the perishable item may
the printed expiration date would mislead a consumer into believing
the product was still usable when in fact it was past its useful
life.
[0005] A time-temperature integrating indicator that gives a
visually observable indication of the cumulative thermal exposure
of a specific item, and hence overcomes the problems inherent with
the use of marked expiration dates, is disclosed in U.S. Pat. No.
5,667,303, entitled "Time-Temperature Integrating Device," issued
to Arens et al. (the '303 patent). The device of the '303 patent
includes a first laminate wherein a substrate is coated with an
opaque, porous matrix, and a second laminate having a backing
material coated with a viscoelastic indicator material. The
viscoelastic material and the porous matrix have the same, or
approximately the same, indexes of refraction. The device is
activated by placing the viscoelastic material and the substrate in
contact with each other and mounting the combination on an object
whose cumulative thermal exposure is to be monitored. The
viscoelastic material progressively migrates into the porous matrix
at a rate that increases with increasing temperature. As the
microvoids of the opaque, porous matrix become filled with
viscoelastic material, the porous matrix becomes transparent. The
device thereby provides a visually observable indication that a
predetermined cumulative thermal exposure associated with a change
in the object (such as degradation or spoilage) has been met.
[0006] The visually observable indication in the device of the '303
patent occurs when the cumulative thermal exposure of the device is
equal to the cumulative thermal exposure required to cause the
degradation or other change being monitored in the test object. The
viscoelastic material used in the indicator of the '303 patent is
selected so that the run out time of the indicator, which is the
time needed for the indicator to provide a visually observable
indication, matches the time needed for the monitored change in the
object to occur.
[0007] Matching the temperature dependence of the rates of change
in the indicator device and the monitored object is accomplished by
matching the Q10 or Ea of the viscoelastic material with the Q10 or
Ea of the monitored object, according to the method described in
the '303 patent. Q10 and Ea are both related to the temperature
dependence of the rate of change of an object. Q10 is an indication
of how much faster a reaction occurs in response to a 10.degree. C.
increase in temperature. Ea, or activation energy, is computed with
reference to the Arrhenius Equation, K=Ko exp (-Ea/RT), where K=the
rate constant at temperature T, Ko=the preexponential factor, R=the
ideal gas constant and Ea=activation energy.
[0008] The first laminate and second laminate used in the indicator
devices of the '303 patent are stored in separate rolls until
needed for use. The indicator devices are constructed by cutting a
length from each roll and placing the viscoelastic material of the
second laminate in contact with the porous matrix of the first
laminate.
[0009] One shortcoming of the indicator devices of the '303 patent
is that some viscoelastic materials, in addition to migrating into
the porous matrix, tend to flow laterally between the layers of the
storage rolls and the indicator devices. In the storage rolls, the
viscoelastic material flows laterally between the layers in the
roll and forms a gooey accumulation on the sides of the rolls. This
accumulation interferes with the operation of the laminating
machine used to make the indicators. Furthermore, in the indicators
the viscoelastic material flows out between the substrate and the
backing and creates a sticky mess on both the indicator and the
object to be monitored. As a result of the lateral flow of the
viscoelastic material, the thickness of the viscoelastic material
on the backing is rendered nonuniform.
[0010] Therefore, what is needed is a means to retain the
advantages of the time temperature integrating indicators described
in the '303 patent while preventing the viscoelastic material from
flowing laterally between the backing and the substrate and oozing
out of the indicator.
SUMMARY OF THE INVENTION
[0011] It is an objective of the present invention to overcome the
shortcomings in the art by providing a time-temperature integrating
indicator device wherein the backing material includes on its
surface both a viscoelastic indicator material and a barrier
material. The barrier material is provided to inhibit the lateral
and longitudinal flow of the viscoelastic indicator material
between the layers of the indicator device or between the layers in
a storage roll.
[0012] In accordance with these objectives, the present invention
provides a time-temperature integrating indicator device for
providing a visually observable indication of cumulative thermal
exposure, having a barrier material to prevent the lateral and
longitudinal flow of viscoelastic indicator material. The device
comprises a substrate and a backing. The substrate includes a
diffusely light reflective porous matrix. The backing includes on
its surface a viscoelastic indicator material for contacting the
porous matrix and a barrier material for inhibiting the lateral
flow of the viscoelastic indicator material between the substrate
and the backing. The device has an unactivated state, in which the
viscoelastic indicator material is substantially out of contact
with the porous matrix, and an activated state in which the
viscoelastic indicator material is in substantial contact with the
porous matrix. In the activated state, the viscoelastic indicator
material migrates into the porous matrix at a rate that increases
with increasing temperature and thereby creates a visually
observable indication of cumulative thermal exposure.
[0013] The invention also provides an embodiment in which the
barrier material substantially inhibits both the lateral and the
longitudinal flow of viscoelastic material regardless of whether
the indicator device is in an activated state or an unactivated
state.
[0014] The invention also provides an embodiment in which the
barrier material used on the indicator device is a pressure
sensitive adhesive. In another embodiment the barrier material is
polystyrene. And, in yet another embodiment of the invention the
barrier material is thermoplastic rubber.
[0015] The invention also provides a method of indicating the
cumulative thermal exposure of an object, comprising the steps of
providing a time-temperature integrating indicator device according
to the invention, activating the device by placing the viscoelastic
indicator material in substantial contact with the porous matrix,
and mounting the device on an object, the thermal history of which
is to be measured.
[0016] The invention also includes a striped viscoelastic indicator
tape for use in a time-temperature integrating indicator device.
The indicator tape includes a backing material having on its
surface a viscoelastic indicator material and a barrier material.
The viscoelastic indicator material is capable of penetrating a
porous medium at a rate that increases with increasing temperature.
The barrier material inhibits the lateral and longitudinal flow of
viscoelastic indicator material between the backing and a surface
with which it is in contact.
[0017] The invention also provides an embodiment of the striped
viscoelastic indicator tape in which the barrier material
substantially inhibits both the lateral and the longitudinal flow
of viscoelastic material regardless of whether the indicator device
is in an activated state or an unactivated state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention will be further explained with
reference to the appended Figures, wherein like structure is
referred to by like numerals throughout the several views, and
wherein:
[0019] FIG. 1 is a cross-sectional view of the time-temperature
integrating indicator device of the invention in an unactivated
state.
[0020] FIG. 2 is a cross-sectional view of the time-temperature
integrating indicator device of the invention in an activated
state.
[0021] FIG. 3 is a top view of the backing used in the
time-temperature integrating indicator device of the invention.
[0022] FIG. 4 is a top view of the substrate used in the
time-temperature integrating indicator device of the invention.
[0023] FIG. 5 is a top view of the time-temperature integrating
indicator device of the invention, before migration of viscoelastic
material is complete.
[0024] FIG. 6 is a top view of a time-temperature integrating
indicator device of the invention, after the viscoelastic indicator
material has migrated into the porous matrix.
[0025] FIG. 7 is a perspective view of the time-temperature
integrating indicator device of the invention mounted on an object
whose cumulative thermal exposure is being monitored.
[0026] FIG. 8 is a top view of a time-temperature integrating
indicator device of the invention.
[0027] FIG. 9 is a top view of another time-temperature integrating
indicator device of the invention.
[0028] FIG. 10 is a top view of another time-temperature
integrating indicator device of the invention, before migration of
viscoelastic material is complete.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The time-temperature integrating indicator device 10 of the
present invention is shown in its unactivated state in FIG. 1. The
indicator device 10 includes first laminate 20 and second laminate
30, which are not in contact with one another in the unactivated
state.
[0030] The first laminate 20 includes a substrate 28 with a
diffusely light-reflective porous matrix 22 provided on one of its
surfaces. In one embodiment, an adhesive 27 is provided on the
other surface of the substrate for mounting the indicator device 10
on an object whose cumulative thermal exposure is to be monitored.
A release liner 29 may be placed in contact with adhesive 27 so
that first laminate 20 can be rolled upon itself into storage
rolls. The first laminate 20 is made using the materials and
methods for constructing the first laminate of the time-temperature
integrating indicator device described in U.S. Pat. No. 5,667,303,
entitled "Time-Temperature Integrating Indicator," issued to Arens
et al.
[0031] Second laminate 30 includes a light transmissive backing 32
having a viscoelastic indicator material on a central portion 34
and barrier material on two edge portions 36, 38 of the backing 32.
By light-transmissive, it is meant that the backing material is
sufficiently light-transmissive or translucent to allow a user of
the indicator device 10 of the invention to visually observe the
indication of cumulative thermal exposure through the backing. In
one embodiment, the central portion 34 of the backing 32 is at
least as wide as a cross section of the first laminate 20. In an
alternative embodiment of the invention, backing 32 may include any
number of alternating stripes of viscoelastic indicator material
and barrier material.
[0032] As shown in FIG. 2, the indicator device 10 is activated by
placing the viscoelastic indicator material 34 and the porous
matrix 22 in substantial contact with one another. In one
embodiment of the invention, the edge portions 36, 38 of the
backing 32 overlap the porous matrix, and the barrier material
inhibits the lateral flow of viscoelastic indicator material
between the backing 32 and the porous matrix 22 and thereby
prevents the viscoelastic indicator material from oozing out of the
indicator device 10. In addition, when the second laminate 30 is
rolled upon itself in a storage roll, the stripes of pressure
sensitive adhesive provide a barrier that prevents viscoelastic
indicator material from oozing out of the roll and accumulating on
its sides.
[0033] The barrier material may be any material that is capable of
inhibiting the lateral flow of viscoelastic indicator material
between the backing 32 and the porous matrix 22. The barrier
material is a viscoelastic solid at all temperatures to which the
indicator device 10 will be exposed. The barrier material may
include a pressure sensitive adhesive. However, the barrier
material cannot be the same material as the viscoelastic indicator
material on the central portion 34 of the backing 32.
[0034] Where the barrier material on the edge portions 36, 38 is a
pressure sensitive adhesive, the edge portions 36, 38 are placed in
contact with the object to be monitored 40 so that the pressure
sensitive adhesive mounts the indicator 10 on the object 40. The
porous matrix 22 is thereby sandwiched between the backing 32 and
the object 40, and the porous matrix 22 and the viscoelastic
indicator material 34 are held securely in contact with one
another. In this manner, the pressure sensitive adhesive on edge
portions 36, 38 prevents the backing 32 from peeling away from the
porous matrix 26 and rendering the indicator 10 inoperative. In
addition, as best shown in FIGS. 2 and 5, when the indicator device
10 is activated and mounted on the object, the pressure sensitive
adhesive on edge portions 36, 38 forms a barrier that inhibits
viscoelastic indicator material from oozing out of the indicator
device 10 between the first laminate 20 and second laminate 30.
[0035] After the indicator device 10 is activated the viscoelastic
indicator material 34 progressively migrates into the porous matrix
22 at a temperature dependent rate and gradually fills the
microvoids in the porous matrix 22. As the microvoids of the porous
matrix become filled with viscoelastic indicator material, the
porous matrix 22 is transformed from opaque to transparent and
provides a visually observable indication of the cumulative thermal
exposure of the indicator device 10. The visually observable
indication of cumulative thermal exposure may include the
appearance of latent indicia that were not visible before the
viscoelastic indicator material 34 filled the microvoids of the
porous matrix 22. The latent indicia are visible through the
transparent backing 32, the viscoelastic indicator material 34, the
porous matrix 22 and the substrate 28. In an alternative
embodiment, the visually observable indication may also include the
disappearance or obscuring of indicia that were visible before the
microvoids were filled. In another embodiment, the visually
observable indication may include a combination of the appearance
of latent indicia and the obscuring of obscurable indicia. In yet
another alternative embodiment, a color change may occur as the
porous matrix 22 becomes transparent. Any of the methods described
for providing a visually observable indication of cumulative
thermal exposure in U.S. Pat. No. 5,667,303 may be used.
[0036] In a certain embodiment, a black substrate 28 or black
adhesive 27 is used in the first laminate 20, which becomes visible
as the porous matrix 22 becomes transparent. FIGS. 4-6 show a
preferred embodiment of the invention in which a dye or ink is
imprinted on the surface of the porous matrix 22 in a pattern that
leaves only certain geometrically defined indication areas 50
uncoated and available to react with viscoelastic indicator
material. FIG. 4 shows the first laminate of this embodiment prior
to activation. FIG. 5 shows an activated indicator device 10 of
this embodiment that has not yet accumulated sufficient thermal
exposure to trigger a visually observable response in the
indication areas 50. In FIG. 6, the same indicator device 10 is
shown after the porous matrix 22 has become transparent and
revealed a colored pattern 50 in the underlying adhesive 27 or
substrate 28.
[0037] The porous matrix 22 may be any suitable microporous,
diffusely light-reflective layer that can be made increasingly
translucent or transparent by filling its voids with a material
having an index of refraction close to that of the matrix. The
porous matrix may be made using any of the materials and methods
described for making the porous matrix disclosed in U.S. Pat. No.
5,667,303. In one embodiment, shown in FIG. 1, the porous matrix 22
includes a plurality of particles 24 in a binder 26. The binder 26
may have an index of refraction in the same range as the index of
refraction of the particles 24. In certain embodiments, the binder
26 has an index of refraction that is substantially the same as the
index of refraction of the particles 24.
[0038] Initially, the porous matrix 22 is opaque because its voids
are filled with a material having an index of refraction that does
not match the index of refraction of the rest of the matrix.
Typically, the material is air, but it may be any other material
that has an index of refraction that is different than that of the
matrix 22. The viscoelastic indicator material 34 and the porous
matrix 22 are selected to have indexes of refraction that are the
same or close to the same. After activation of the indicator device
10, as the viscoelastic indicator material 34 gradually migrates
into matrix 22, it displaces the air in the microvoids of the
matrix 22 and the matrix 22 becomes increasingly light
transmissive. When the microvoids become filled with viscoelastic
indicator material 34, the matrix 22 becomes transparent or nearly
transparent.
[0039] The indicator device 10 of the invention may be used to
monitor a change in object 40 that is dependent on cumulative
thermal exposure. The object 40 may be any object, such as a
perishable item subject to degradation and spoilage in response to
cumulative thermal exposure beyond certain definable limits. Such
perishable items include, but are not limited to, foods, drugs,
cosmetics, photographic supplies, and vaccines. In one embodiment,
the indicator device 10 of the invention is used to give a visually
observable indication when the cumulative thermal exposure of the
indicator device 10 corresponds with the measured change, such as
degradation, spoilage or loss of activity, in the object 40.
[0040] In certain embodiment of the invention, shown in FIGS. 1-3,
the second laminate 30 is a striped viscoelastic indicator tape
having a backing material 32 with a central stripe of viscoelastic
indicator material 34 and two edge stripes 36, 38 of pressure
sensitive adhesive. The backing 32 of the second laminate 30 may be
sufficiently light transmissive or translucent to allow a user of
the indicator 10 to visually observe the indication of cumulative
thermal exposure through the backing 32. In certain embodiments,
backing 32 is transparent. Backing 32 can comprise any suitable
substrate such as glass, cellophane or film. For example, backing
32 may include a polymeric film such as a transparent film of poly
(ethylene terphthlate) or polypropylene. Backing 32 may include a
film such as low-density polyethylene when flexibility or
conformance to contour is desired.
[0041] Viscoelastic indicator material 34 may comprise any suitable
viscoelastic material that provides the desired properties for
migration into the porous matrix 22 in response to cumulative
thermal exposure, and which has an index of refraction in the same
range as the particles 24 and the binder 26. In certain
embodiments, the viscoelastic indicator material 34 is in a
viscoelastic liquid state at all anticipated temperatures to which
it will be exposed in the indicator device 10. This allows the
viscoelastic indicator material to migrate into the porous matrix
throughout the anticipated temperature range. Viscoelastic
materials are in a viscoelastic liquid state at temperatures above
their glass transition temperature Tg. A viscoelastic liquid is a
viscoelastic material that continues to deform indefinitely when
subjected to a shearing stress. It is possible for some
viscoelastic solid materials to function as viscoelastic indicator
material 34 provided that the material is able to deform and
penetrate entirely through the porous matrix.
[0042] Viscoelastic indicator material 34 is selected in such a
manner that the indicator run out time matches the time needed for
the measured change in object 40 to occur. The viscoelastic
indicator material is selected in accordance with the methods
described above and in U.S. Pat. No. 5,667,303, by matching the Q10
of the viscoelastic indicator material with the Q10 of the object
to be monitored 40, or, alternatively, by matching the Ea of the
viscoelastic indicator material with the Ea of the object to be
monitored 40.
[0043] An illustrative, but by no means exclusive, list of
viscoelastic materials that may be suitable for use as the
viscoelastic indicator material of the present invention includes
natural rubber, polybutadiene and its copolymers with acrylonitrile
and styrene, poly alpha olefins such as polyhexene, polyoctene, and
copolymers of these and others, polyacrylates, polychloroprene,
silicone elastomer, and block copolymers such as styrene-isoprene
block copolymers, and mixtures of any of the above. The
viscoelastic indicator material can comprise, for example, a
polyisoprene, atactic polypropylene, polybutadiene,
polyisobutylene, silicone, ethylene vinyl acetate, or a
polyacrylate, and can typically include a tackifying agent and/or a
plasticizing agent. The viscoelastic indicator material can
comprise adhesive including isooctyl acrylate (IOAK) or isooctyl
acrylate/acrylic acid (IOA/AA) based pressure sensitive adhesive.
The adhesives suitable for use as the viscoelastic indicator
material of the invention may be prepared from pressure sensitive
adhesive compositions comprising from abut 50 to 100 parts by
weight of at least one alkyl acrylate monomer, and correspondingly,
from about 50 to 0 parts by weight of an optional reinforcing
comonomer. Throughout this application, compositions are described
in percentages or ratios by weight, unless indicated otherwise.
[0044] Monomers useful in preparing the viscoelastic indicator
material of the invention are those that have a homopolymer glass
transition temperature less than about 0.degree. C. Useful alkyl
acrylates are unsaturated monofunctional (meth)acrylic acid esters
of non-tertiary alkyl alcohols having from 2 to 20 carbon atoms in
the alkyl moiety, preferably from 4 to 18 carbon atoms, and more
preferably, from 4 to 12 carbon atoms. Examples of useful alkyl
acrylate monomers includes, but are not limited to, n-butyl
acrylate, hexyl acrylate, octyl acrylate, isooctyl acrylate,
2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, dodecyl
acrylate, lauryl acrylate, octadecyl acrylate, and mixtures
thereof.
[0045] The optional reinforcing co-monomer in the viscoelastic
indicating material is a monoethylenically unsaturated monomer
having a homopolymer glass transition temperature greater than
about 25.degree. C., and may be co-polymerized with the acrylate
monomers. Examples of useful co-polymerizable monomers include, but
are not limited to, meth(acrylic) acid, N-vinyl pyrrolidone,
N-vinyl caprolactam, substituted (meth)acrylamides, such as
N,N,-dimethyl acrylamides, acrylonitrile, isobornyl acrylate, and
mixtures thereof. When a co-polymerizable monomer is used, the
alkyl acrylate is present in the composition in amounts from about
50 to 99 parts by weight and the co-polymerizable monomer is
present in corresponding amounts from 50 to 1 parts by weight
wherein the total amount by weight is 100.
[0046] A suitable polar IOA/AA adhesive for use as the viscoelastic
indicator material of the present invention contains a weight ratio
of IOA/AA of from about 80/20 to 98/2. Useful IOA/AA based pressure
sensitive adhesives includes those having ratios of 90/10 and 94/6.
Other useful pressure sensitive adhesives include non polar
copolymers of isooctyl acrylate/methacrylate (IOA/MA), isooctyl
acrylate/isobornyl acrylate (IOA/IBA), or ethyl acrylate/methyl
acrylate (EA/MA). The pressure sensitive adhesive used as the
viscoelastic indicator material can include an added tackifier
and/or plasticizer in a tackifier to adhesive base weight ratio or
a plasticizer to adhesive base weight ratio of up to about 2:1.
Suitable tackifiers include hydrogenated rosin esters commercially
available as Foral 85.TM., Foral 105.TM., or Abitol.TM. E, and
hydrocarbon tackifiers such as Regalrez.TM., all available from
Hercules Incorporated of Wilmington, Del. Suitable plasticizers
include hydrocarbon oils such as Shellflex.TM. (available from
Shell Chemical Co.), USP grade mineral oil, phthalate and
diisononyl phthalate, and allyl phthalates.
[0047] The barrier material on the edge stripes 36, 38 of the
backing 32 may suitably be any material capable of preventing the
viscoelastic indicator material 34 from flowing laterally between
the backing 32 and the porous matrix 22, or alternatively between
the successive layers of backing 32 in a storage roll, and oozing
out of the indicator device 10 or the storage roll. In certain
embodiments, the barrier material is a viscoelastic solid in the
temperature range in which the indicator device 10 will be used. A
viscoelastic solid is a material that resists flow when subjected
to a constant shearing stress. Suitable barrier materials for use
in the indicator device 10 include glassy polymers,
semi-crystalline polymers, physically and chemically crosslinked
elastomers, segmented polyesters, radiation crosslinked
polybutadiene, and pressure sensitive adhesives. Examples of
suitable glassy polymers include polystyrene and polymethyl
methacrylate. Examples of suitable semi-crystalline polymers
include polyethylene, polypropylene and polyesters. Examples of
suitable physically crosslinked elastomers include triblock
copolymers, such as styrene-isoprene-styrene block copolymers, and
segmented polyurethane elastomers. An example of a suitable
chemically cross-linked elastomer is sulfur crosslinked natural
rubber.
[0048] In one embodiment of the invention, the barrier material is
a pressure sensitive adhesive that is a viscoelastic solid in the
temperature range in which the indicator device 10 will be used.
The pressure sensitive adhesive should be one that will not readily
flow or ooze out of a storage roll or an indicator in the range of
temperatures to which it will likely be exposed. Suitable pressure
sensitive adhesives that may be used as barrier materials in the
indicator device 10 include acrylic pressure sensitive adhesives,
silicone pressure sensitive adhesives, rubber resin blend pressure
sensitive adhesives, triblock copolymer pressure sensitive
adhesives, and vinyl ether polymer pressure sensitive adhesives.
Suitable rubber resin blend pressure sensitive adhesives include
natural rubber, polybutadene, polyisobutalene, styrene butadiene
random copolymers, synthetic polyisoprene, and butyl rubber.
Suitable triblock copolymer pressure sensitive adhesives include
styrene-isoprene-styrene copolymers, styrene-butadiene-styrene
copolymers, styrene-ethylenebutylene-styrene copolymers, and
styrene-ethylene propylene-styrene copolymers. The pressure
sensitive adhesive used as a barrier material 36, 38 must be a
different material than the viscoelastic indicator material 34 used
in indicator device 10.
[0049] The striped indicator tape of the invention is made by
simultaneously coating barrier material and viscoelastic indicator
material onto a backing using a dual manifold die. The die includes
a faceplate and a back manifold section, which is divided into an
upper manifold and a lower manifold. One of the manifolds is used
for storage and delivery of barrier material and the other is used
for storage and delivery of viscoelastic indicator material.
Precision gear pumps are used to supply the barrier material, such
as a pressure sensitive adhesive, and the viscoelastic indicator
materials to the manifold. The face plate has a series of orifices
that deliver barrier material to the backing 32 to form edge
stripes 36, 38 and a separate set of orifices to deliver the
viscoelastic indicator material to the backing 32 to form the
indicator stripe 34. The indicator stripe orifices are in
horizontal alignment with the barrier orifices on the faceplate. A
total of three indicator stripes bordered by a PSA stripe on each
side can be coated simultaneously. The striped coating is dried
with a forced air oven. The coated film backing is laminated on the
coated side to a silicone-treated paper release liner (BL 55 CC2
Silox B2J/0 Paper, Akrosil, Manasha, Wis.) and the resulting sheet
converted by slitting down the middle of each PSA stripe to provide
strips of the second laminate.
[0050] FIG. 8 shows an alternative embodiment of the indicator
device 100 of the invention in which the backing 132 has two
indicator stripes 134 and 135, which are bordered by barrier
stripes 136, 138 and 139. The indicator stripes 134 and 135 may
have different viscoelastic indicator materials or the same
viscoelastic indicator material. In addition, the barrier stripes
136, 138 and 139 may have different barrier materials than each
other, or may have the same barrier material. Although FIG. 8
illustrates an indicator with alternating indicator and barrier
stripes in which there are two indicator stripes, the invention is
not limited to any particular number of alternating stripes, since
the principles set forth herein can readily be applied to make
indicators having any number of indicator stripes.
[0051] FIG. 9 shows another alternative embodiment of the indicator
device 200 of the invention in which the backing 232 has two
indicator areas 234 and 235, which are bordered by two horizontal
barrier stripes 242 and 243 and by three vertical barrier stripes
246, 247, and 248. The indicator areas 234 and 235 may have
different viscoelastic indicator materials or the same viscoelastic
indicator material. In addition, the barrier stripes 242, 243, 246,
247, and 248 may have different barrier materials than each other,
or may have the same barrier material. Although FIG. 9 illustrates
an indicator device with a backing having a single
indicator/barrier stripe bordered by two barrier stripes, the
invention is not limited to any particular number of alternating
stripes, since the principles set forth herein can readily be
applied to make indicator devices having any number of alternating
indicator/barrier and barrier stripes.
[0052] FIG. 10 shows the top view of an activated indicator device
300 of the invention similar to the devices shown in FIG. 2 and
FIG. 5, except that the backing 310 has a single viscoelastic
indicator area 320 bordered by horizontal barrier stripes 330 and
vertical barrier stripes 340. The backing 310, as one alternative,
could be constructed by die cutting the backing 232 (FIG. 9). The
device 300 is activated by placing the viscoelastic indicator
material of backing 310 and the porous matrix 22 (of the first
laminate 20) in substantial contact with one another. In one
embodiment of the invention, the edges of the backing 310 overlap
the porous matrix 22 and the barrier stripes 330 and 340 inhibit
both the lateral and longitudinal flow of viscoelastic indicator
material between the backing 310 and the first laminate 20 and
thereby prevents the viscoelastic indicator material from oozing
out of the indicator device 300. FIG. 10 shows an activated
indicator device 300 of this embodiment that has not yet
accumulated sufficient thermal exposure to trigger a visually
observable response in the indicator view area 350. After
sufficient thermal exposure, the indicator view area 350 would, for
example, begin to darken (not shown).
[0053] The operation of the present invention will be further
described with regard to the following detailed examples. These
examples are offered to further illustrate the various specific and
preferred embodiments and techniques. It should be understood,
however, that many variations and modifications maybe made while
remaining within the scope of the present invention.
EXAMPLES
[0054] The following examples are offered to aid in understanding
of the present invention and are not to be construed as limiting
the scope thereof. Unless otherwise indicated, all parts and
percentages are by weight.
Indicator Compositions A and B
[0055] Viscoelastic indicator compositions A and B were prepared by
mixing together the ingredients as listed in Tables 1 and 2,
respectively.
Barrier PSA Composition
[0056] A PSA composition was prepared by mixing together the
ingredients listed in Table 3.
1TABLE 1 Indicator Composition A Parts Ingredient (by Wt.)
Polyisoprene LIR-50 (Kuraray Co., Tokyo, Japan) 11 Hydrocarbon
resin ARKON .TM. P-115 (Arakawa Chemical 15 Industries Ltd., Osaka,
Japan) Resin tackifier REGALREZ .TM. 1018 (Hercules, Inc., 13
Wilmington, DE) IRGANOX .TM. 1010 antioxidant (Ciba-Geigy,
Tarrytown, NY) 0.4 Toluene 60
[0057]
2TABLE 2 Indicator Composition B Parts Ingredient (by Wt.) KRATON
.TM. G1750 ethylene propylene copolymer (Shell 11 Chemical Co.,
Houston, TX) Resin tackifier REGALREZ .TM. 1085 (Hercules, Inc.) 10
Resin tackifier REGALREZ .TM. 1018 (Hercules, Inc.) 19 IRGANOX .TM.
1010 antioxidant 0.4 Toluene 60
[0058]
3TABLE 3 Barrier PSA Composition Parts Ingredient (by Wt.) KRATON
.TM. G11107 styrene-isoprene-styrene block 20 copolymer (Shell
Chemical) WINGTACK .TM. PLUS hydrocarbon tackifying resin 20
(Goodyear Tire and Rubber Co., Akron, OH) Toluene 60
First Laminate
[0059] A calcium carbonate dispersion was prepared by mixing
together the ingredients listed in Table 4. The dispersion was
coated onto a corona-treated, low-haze, 1.4-mil
poly(ethyleneterephthalate) (PET) transparent film with
conventional Gravure coating equipment and subsequently dried in a
forced air oven for about 3 minutes at 100.degree. C. to produce a
dry microporous coating approximately 13 microns thick. A black
adhesive (A842 Acrylate Adhesive with Carbon Black, 3M Company, St.
Paul, Minn.) was then coated on the uncoated side of the PET film
with conventional knife coating equipment and subsequently dried in
a forced air oven for about 1 minute at 100.degree. C. to produce a
dry coating of about 25 microns thick. A silicone-treated 1.4-mil
PET film release liner was then laminated (room temperature,
pressure about 138 KPa) to the black adhesive side of the PET film
to prevent unintended adhesion to other surfaces.
4TABLE 4 Calcium Carbonate Dispersion Parts Ingredient (by Wt.)
Calcium Carbonate, particle size distribution: 0.0005 to 0.015
37.44 mm (Dryca Flo 125, Sylacauga Calcium Products, Sylacauga, AL)
Acrylic Binder (Carboset 526, B. F. Goodrich, Akron, OH) 3.16
Dowicide A Antimicrobial Agent (Dow Chemical, Midland, 0.14 MI)
Ethanol 12.96 Ammonium Hydroxide (2%) 0.44 Water 45.85
Example 1
[0060] Alternating stripes of Indicator Composition B ("indicator
stripe") and Barrier PSA Composition ("PSA stripe") were coated
simultaneously onto an untreated, low-haze, 1.4-mil polyester PET
transparent film backing by utilizing a dual manifold die. Briefly,
the die included a face plate and back manifold section having two
separate manifolds, one in the upper part of the back section and
the other in the lower part of the back section. A precision gear
pump was used to supply the PSA composition to the top manifold and
another precision gear pump was used to supply the indicator
composition to the bottom manifold. Each pump could be adjusted
independently to control flow rate of the compositions to the die.
The faceplate was constructed with precision orifices having a 1.0
mm diameter and 1.1 mm center-to-center spacing. To obtain one PSA
stripe about 2.5-cm wide, a series of orifices were placed at an
angle such that the inlet of the orifices in the back of the face
plate was aligned with the top manifold and the outlet of the
orifices on the front side of the face plate were approximately 1.3
mm below a sharp notch. Positioned next to these orifices were a
series of orifices, extending through to the lower manifold, for
coating an indicator stripe about 1.2-cm wide. These indicator
stripe orifices were in horizontal alignment with the PSA stripe
orifices on the front of the faceplate. This pattern was repeated
across the face of the die so that a total of three indicator
stripes bordered by a PSA stripe on each side could be coated
simultaneously. Different spacing of orifices and/or number of
stripes could be achieved by machining a new faceplate and
utilizing the existing back manifold section. The die was run in
the fluid-bearing mode, with the die positioned in contact with a
free span of web located between two idler rolls attached to the
die stand. The die was mounted in an assembly on a precision die
mount that allowed for adjustment of the engagement of the die with
the web and also allowed for rotational adjustment of the die
relative to the web.
[0061] The striped coating was dried by utilizing a forced air oven
located directly after the die station to provide a dry coating
thickness of about 25 microns. Movement through the oven was at a
rate of about 6 m/minute and the oven had three zones, which were
heated to 79.degree. C., 121.degree. C., and 135.degree. C.,
respectively. The coated film backing was then laminated on the
coated side to a silicone-treated paper release liner (BL 55 CC2
Silox B2J/0 Paper, Akrosil, Manasha, Wis.) and the resulting sheet
was converted by slitting down the middle of each PSA stripe to
provide strips of the second laminate. Each strip included a center
indicator stripe about 1.2 cm wide bordered on each side by a PSA
stripe about 1.25-cm wide.
[0062] A time-temperature integrating device was prepared and
activated by placing an about 5-cm long strip of the second
laminate (with paper release liner removed and striped coating side
down) onto an about 5-cm long strip of the first laminate (with
microporous coating side up) and laminating the two strips together
by immediately rolling down with a 5-cm wide hand roller. A strong,
permanent adhesive bond was observed to form between the two
laminates. The device was then measured for optical image.
[0063] The optical density (OD) of the time-temperature integrating
device was measured over time at room temperature (about 23.degree.
C.) using a densitometer (X-RITE.TM. Model 404, X-Rite Inc.,
Grandville, Mich.). The OD values provide a darkness measurement of
the center indicator stripe of the device with a value of about 0.4
appearing light gray and a value of about 0.7 appearing nearly
black. The width of the darkening center indicator stripe was
measured at the same time that OD was measured. The results are
provided in Table 5 and show that OD exceeded 0.7 at 140 hr.
Additionally, the width (1.2 cm) of the center indicator stripe did
not increase with time, which indicates that the indicator material
was confined by the two PSA edge stripes.
5TABLE 5 Time (Hours) Optical Density Indicator Stripe Width (Cm) 0
0.42 1.2 23 0.55 1.2 47 0.61 1.2 101 0.68 1.2 144 0.73 1.2
Example 2
[0064] A time-temperature integrating device was prepared and
activated as described in Example 1, except that Indicator
Composition A was substituted for Indicator Composition B in the
construction of the second laminate. It was observed over time at
room temperature that the center indicator stripe of the device
darkened, while the width of the stripe remained unchanged.
Example 3
[0065] A time-temperature integrating device was prepared and
activated as described in Example 2, except that the
silicone-treated PET film release liner was substituted for the
silicone-treated paper release liner in the construction of the
second laminate. It was observed over time at room temperature that
the center indicator stripe of the device darkened, while the width
of the stripe remained unchanged.
Example 4
[0066] Alternating stripes of Indicator Composition A and Barrier
PSA Composition were coated simultaneously onto silicone-treated
paper release liner by utilizing a dual manifold die as described
in Example 1. The striped coated paper release liner was dried as
described in Example 1 and then laminated (to the silicone-treated
side) to an untreated, low-haze, 1.4-mil PET transparent film
backing. The resulting sheet was converted by slitting down the
middle of each PSA stripe to provide strips of the second laminate.
Each strip was coated with an about 1.2-cm wide center indicator
stripe bordered on each side with an about 1.25-cm wide PSA
stripe.
[0067] A time-temperature integrating device was prepared and
activated by placing an about 5-cm long strip of the second
laminate (with paper release liner removed and striped coating side
down) onto an about 5-cm long strip of the first laminate (with
microporous coating side up) and laminating the two strips together
by immediately rolling down with a 5-cm wide hand roller. It was
observed over time at room temperature that the center indicator
stripe of the device darkened, while the width of the stripe
remained unchanged.
Example 5
[0068] A time-temperature integrating device was prepared and
activated as described in Example 4, except that Indicator
Composition B was substituted for Indicator Composition A in the
construction of the second laminate. It was observed over time at
room temperature that the center indicator stripe of the device
darkened, while the width of the stripe remained unchanged.
Example 6
[0069] A time-temperature integrating device was prepared and
activated as described in Example 5, except that the
silicone-treated PET film release liner was substituted for the
silicone-coated paper release liner in the construction of the
second laminate. It was observed over time at room temperature that
the center indicator stripe of the device darkened, while the width
of the stripe remained unchanged.
Example 7
[0070] A time-temperature integrating device was prepared and
activated as described in Example 5, except that biaxially oriented
polypropylene (BOPP) transparent film backing was substituted for
the PET transparent film backing in the construction of the second
laminate. It was observed over time at room temperature that the
center indicator stripe of the device darkened, while the width of
the stripe remained unchanged.
Example 8
[0071] Time-temperature integrating devices were prepared and
activated as described in Example 4 except that gear pumping speeds
were adjusted so that different amounts of coatings were applied to
the silicone-treated paper release liner to provide separate
samples having dry coating thicknesses of 17, 31, 44, and 50
microns. It was observed over time at room temperature that the
center indicator stripe of each device darkened, while the width of
the stripe remained unchanged.
Example 9
[0072] Time-temperature integrating devices were prepared as
described in Example 2, except that a color reference was printed
on the microporous coating of the first laminate. The color
reference was printed with a gray ink made from a mixture of gray
(SSK-15125) and black (SSK-6862) inks available from Werneke Ink,
Plymouth, Minn. Utilizing conventional flexographic techniques, the
microporous layer was printed so that circular areas were left
unprinted within the printed regions. The unprinted circular areas
were 4-mm in diameter and were 15 mm apart (center to center).
Strips of the first and second laminates were laminated together as
described in previous examples and then cut to provide
5.5-mm.times.16-mm devices having a center indicator stripe about
12-mm wide bordered on each side with an about 2-mm wide PSA
stripe, and an unprinted 4-mm diameter circular area positioned in
the center of each device. Immediately after lamination
("activation") of the device, the area within the unprinted circle
appeared light gray and much lighter in color than the surrounding
gray printed reference region. The device was then left in an
incubator at 50.degree. C. for about one hour during which time the
area within the circle became much darker in color (nearly black)
than the surrounding printed reference region.
Example 10
[0073] Alternating stripes of Indicator Composition B ("indicator
stripe") and a Non-Tacky Composition containing 40% (by wt.)
polystyrene (PS666, Dow Chemical) dissolved in toluene ("non-tacky
stripe") were coated simultaneously onto a PET transparent film
backing by utilizing a dual manifold die as described in Example 1.
The striped, coated film backing was dried as described in Example
1 to provide a dry coating thickness of about 25 microns. The dried
non-tacky stripes did not feel sticky (tacky) when touched by a
finger. The dried film backing was then laminated on the coated
side to a silicone-treated paper release liner and the resulting
sheet was converted by slitting down the middle of each non-tacky
stripe to provide strips of the second laminate. Each strip was
coated with an about 1.4-cm wide center indicator stripe bordered
on each side with an about 1.25-cm wide non-tacky stripe.
[0074] A time-temperature integrating device was prepared and
activated by placing an about 5-cm long strip of the second
laminate (with paper release liner removed and striped coating side
down) onto an about 7-cm long strip of the first laminate (with
microporous coating side up) and laminating the two strips together
by immediately rolling down with a 5-cm wide hand roller. It was
observed that the indicator stripe, but not the two non-tacky
stripes, had adherence to the microporous layer of the first
laminate, and that, due to the overall weak adhesion, the whole
second laminate could be separated from the first laminate by
gentle hand pulling. Another strip of the second laminate (with
paper release liner removed and striped coating side down) was more
permanently secured to a strip of the first laminate by
hand-rolling on top a 5-cm wide strip of box sealing tape (Product
No. 351, 3M Company, St. Paul, Minn.). With the adhesion provided
by the box sealing tape, the second laminate could not be separated
from the first laminate by hand. It was observed over time at room
temperature that the center indicator stripe of the device
darkened, while the width of the stripe remained unchanged.
Example 11
[0075] A time-temperature integrating device was prepared and
activated as described in Example 10, except that 40% (by wt.)
KRATON.TM. G1750 dissolved in toluene was used as the Non-Tacky
Composition in construction of the second laminate. As in Example
10, the dried non-tacky stripes did not feel sticky (tacky) when
touched by a finger, and the box sealing tape was used to more
permanently adhere the first and second laminates together. It was
observed over time at room temperature that the center indicator
stripe of the device darkened, while the width of the stripe
remained unchanged.
Example 12
[0076] A time-temperature integrating device was prepared as
described in Example 1, except that the second laminate, striped
coating process was carried out using a face plate constructed to
produce alternating indicator stripes about 4-mm wide and PSA
stripes about 4-mm wide. Strips of the first and second laminates
were laminated together ("activated") as described in previous
examples and then cut to provide an approximately
50-mm.times.100-mm device having 25 alternating indicator and PSA
stripes. It was observed over time (about two weeks) at room
temperature that the indicator stripes of the device darkened,
while the width of the indicator stripes remained unchanged.
[0077] For comparative purposes, a second time-temperature
integrating device was prepared as described in the previous
paragraph, except that no PSA was coated between the indicator
stripes. Therefore, the final device had 25 alternating indicator
stripes and uncoated stripes. It was observed over time (about two
weeks) at room temperature that the indicator stripes of the device
darkened, while the width of the indicator stripes increased from
about 4 mm to about 5-6 mm.
Example 13
[0078] Comparative time-temperature integrating devices were
prepared as described in Example 12, except that Indicator
Composition A was substituted for Indicator Composition B. Results
were similar to those described in Example 12, except that the
width of the indicator stripes of the device having no PSA coated
between the indicator stripes increased from about 4 mm to greater
than 6 mm over the two week observation period.
[0079] The results of Examples 12 and 13 support the conclusion
that the PSA border stripes within the time temperature integrating
devices prevent lateral migration of the viscoelastic indicator
striped coatings over time.
Example 14
[0080] Viscoelastic indicator composition C was prepared by mixing
together the ingredients as listed in Table 6.
6TABLE 6 Indicator Composition C Parts Ingredient (by Wt.) KRATON
.TM. G1750 ethylene propylene copolymer (Shell 11 Chemical) Resin
tackifier REGALREZ .TM. 1085 (Hercules, Inc.) 23 Mineral Oil 6
IRGANOX .TM. 1010 antioxidant (Ciba-Geigy) 0.4 Toluene 60
[0081] Patches of Indicator Composition C ("indicator") surrounded
by Barrier PSA Composition ("PSA") were coated simultaneously onto
an untreated, low-haze, 1.4-mil (36 microns) polyester PET
transparent film backing by utilizing a multi-material pressure
feed coating die similar to the die disclosed in U.S. Pat. No.
4,756,271 entitled "Coating Die", issued to Maier. Briefly, the die
is comprised of a body with multiple fluid chambers, which are
connected to inlet ports and a die opening or slot. A movable cam
is positioned in the fluid chambers. By rotating the cam, different
inlet ports are connected to the die slots. This permits the
application of different materials in the same down web stripe. The
die was set-up to coat three 19-mm wide stripes with 1.5 mm between
stripes. The cam was constructed with 1.5-mm wide baffles between
cam partitions. The top and bottom outside stripe fluid chambers
were connected to a pump, which supplied the PSA. With this
arrangement continuous stripes of PSA coating exited the outside
die slots. The indicator was supplied to the top of the middle
stripe fluid chamber and the PSA was supplied to the bottom of the
middle slot fluid chamber. By rotating the cam PSA or indicator
exited the die from the middle slot. An actuator with a controller
was connected to the die. The cam rotation was controlled to
produce 12.7-mm long indicator patches and 7.6-mm long PSA patches
(pitch of 20.3 mm). The die was mounted in an assembly on a
precision die mount that allowed for adjustment of the engagement
of the die with the web and also allowed for rotational adjustment
of the die relative to the web.
[0082] The coated film backing was dried by utilizing a forced air
oven located directly after the die station to provide a dry
coating thickness of about 25 microns. Movement through the oven
was at a rate of about 6 m/minute and the oven had two zones, which
were heated to 95.degree. C. and 115.degree. C., respectively. The
coated film backing was then laminated on the coated side to a
silicone-treated paper release liner.
[0083] A time-temperature integrating device was prepared and
activated. A 20.3-mm long section of the second laminate (backing)
was cut from the web. The cut lines passed through the middle of
the PSA patches in the center stripe. This gave a second laminate
with a 12.7-mm.times.19-mm patch of indicator surrounded by PSA.
This second laminate (with the liner removed) was laminated to a
20.3-mm.times.60-mm strip of the first laminate (substrate with
microporous coating side up). A strong, permanent adhesive bond was
observed to form between the two laminates. It was observed that
over time at room temperature the patch of indicator material
darkened, while the surrounding PSA areas remained unchanged.
[0084] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this invention will become
apparent to those skilled in the art without departing from the
scope and spirit of this invention. It should be understood that
this invention is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the invention intended to be limited only by the
language of the claims set forth herein as follows.
* * * * *