U.S. patent application number 11/159372 was filed with the patent office on 2006-12-28 for uv-c sensitive composition and dosimeter.
This patent application is currently assigned to Cryovac, Inc.. Invention is credited to Marvin Russell Havens, David Ray Kyle, Drew Ve Speer.
Application Number | 20060289796 11/159372 |
Document ID | / |
Family ID | 37056985 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060289796 |
Kind Code |
A1 |
Havens; Marvin Russell ; et
al. |
December 28, 2006 |
UV-C sensitive composition and dosimeter
Abstract
The invention is a UV sensitive composition that undergoes a
color change upon exposure to a predetermined dosage of UV-C
radiation. The UV-C sensitive composition comprises a halogenated
polymer, such as polyvinylidene chloride, that produces an acid
upon exposure to UV radiation, and a pH sensitive dye. Upon
exposure to UV-C radiation, the halogenated polymer undergoes
degradation and produces HCl. The pH sensitive dye changes color as
a result in an increase in HCl in the system. The composition may
also include an acid scavenging composition and/or a diluent to
control the amount of HCl produced in the system. The amount of HCl
liberated from UV-C exposure may be selectively controlled so that
a color change may be produced at a desired UV-C dosage. In some
embodiments, the composition may be used to indicate a UV-C dosage
from about 100 to 1600 mJ/cm.sup.2.
Inventors: |
Havens; Marvin Russell;
(Greer, SC) ; Ve Speer; Drew; (Simpsonville,
SC) ; Kyle; David Ray; (Moore, SC) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
Cryovac, Inc.
|
Family ID: |
37056985 |
Appl. No.: |
11/159372 |
Filed: |
June 22, 2005 |
Current U.S.
Class: |
250/492.2 |
Current CPC
Class: |
C08K 5/0041 20130101;
G01J 1/50 20130101; C08L 57/08 20130101; C08K 5/0041 20130101; G01J
1/429 20130101 |
Class at
Publication: |
250/492.2 |
International
Class: |
G21G 5/00 20060101
G21G005/00 |
Claims
1. A composition for monitoring the amount of UV dosage to which an
object has been exposed, said composition comprising: a) a
halogenated polymer that produces an acid upon exposure to UV-C
radiation; and b) a pH sensitive dye which changes color in
response to a change in acid levels, wherein the amounts of said
halogenated polymer and said pH sensitive dye are selected to
indicate a UV-C dosage up to about 200 mJ/cm.sup.2, and wherein
said halogenated polymer and said pH sensitive dye are soluble in a
lacquer based solution.
2. The composition according to claim 1, wherein said halogenated
polymer includes halogenated polymers selected from the group
consisting of polyvinyl chloride and copolymers thereof,
polyvinylidene chloride and copolymers thereof,
ethylene-chlorotrifluoroethylene copolymer, and combinations
thereof.
3. The composition according to claim 1, wherein said pH sensitive
dye is selected from the group consisting of bromophenol blue,
phenol red, thymol blue, ethyl orange, m-Cresol purple, New
Fuchsin, p-methyl red, lissamine green, aniline blue, methyl
violet, crystal violet, ethyl violet, brilliant green, oralochite
green oxalate, methyl green, cresol red, quinaldine red, para
methyl red, metanil yellow, orange IV, phenylazoaniline, erythrosin
B, benzopurpurin 4B, congo red, methyl orange, bromocresol green,
resazurin, ethyl red, methyl red, alizarin red, bromocresol purple,
chlorophenol red, and combinations thereof.
4. A composition for monitoring the amount of WV dosage to which an
object has been exposed, said composition comprising: a) a
halogenated polymer that produces an acid upon exposure to UV-C
radiation; b) an acid scavenger; and c) a pH sensitive dye which
changes color in response to a change in acid levels, wherein the
amounts of said halogenated polymer, acid scavenger, and said pH
sensitive dye are selected to indicate a UV-C dosage in the range
from about 100 to 1600 mJ/cm.sup.2, and wherein said halogenated
polymer, acid scavenger, and said pH sensitive dye are soluble in a
lacquer based solution.
5. The composition according to claim 4, wherein said halogenated
polymer includes halogenated polymers selected from the group
consisting of polyvinyl chloride and copolymers thereof,
polyvinylidene chloride and copolymers thereof,
ethylene-chlorotrifluoroethylene copolymer, and combinations
thereof.
6. The composition according to claim 4, wherein said pH sensitive
dye is selected from the group consisting of bromophenol blue,
phenol red, thymol blue, ethyl orange, m-Cresol purple, New
Fuchsin, p-methyl red, lissamine green, aniline blue, methyl
violet, crystal violet, ethyl violet, brilliant green, oralochite
green oxalate, methyl green, cresol red, quinaldine red, para
methyl red, metanil yellow, orange IV, phenylazoaniline, erythrosin
B, benzopurpurin 4B, congo red, methyl orange, bromocresol green,
resazurin, methyl red, alizarin red, bromocresol purple,
chlorophenol red, and combinations thereof.
7. The composition according to claim 4, wherein said acid
scavenger is selected from the group consisting
of,4-diazabicyclo[2.2.2]octane; 2,6-di-tert-butylpyridine; dibutyl
2,6-pyridinedicarboxylate; diphenylamine;
2,4-dihydroxybenzophenone; 1,8-diazabichclo[5.4.0]undec-7-ene
(1,5-5); 1,5-diazabicyclo[4.3.0]non-5-ene;
4-(dimethylamino)pyridine; hexamethylenetetramine; and combinations
thereof.
8. The composition according to claim 4, wherein said composition
is disposed on a substrate in the form of a film.
9. The composition according to claim 8, further comprising a
screen layer disposed on a surface of said film.
10. The composition according to claim 4, wherein the amounts of
said halogenated polymer, said acid scavenger, and said pH
sensitive dye are selected to indicate a UV dosage of at least
about 200 mJ/cm.sup.2.
11. The composition according to claim 4, wherein the amounts of
said halogenated polymer, said acid scavenger, and said pH
sensitive dye are selected to indicate a UV dosage of at least
about 400 mJ/cm.sup.2.
12. The composition according to claim 4, wherein the amounts of
said halogenated polymer, said acid scavenger, and said pH
sensitive dye are selected to indicate a UV dosage of at least
about 800 mJ/cm.sup.2.
13. A composition for monitoring the amount of UV-C dosage to which
an object has been exposed, said composition comprising: a) a
halogenated polymer that undergoes dehalogenation to produce an
acid upon exposure to UV radiation; b) an acid scavenger having a
pKa in the range from about 4 to 8, and wherein the amount of said
acid scavenger in said composition is from about 0.5 to 20 percent
based on the total weight of the solids in the composition; c) a
diluent, wherein the amount of said diluent in said composition is
from about 0 to 50 percent based on the total weight of the solids
in the composition; and d) a pH sensitive color indicator having a
pKa in the range from about 2 to 6, wherein the amounts of said
halogenated polymer, acid scavenger, diluent and pH sensitive color
indicator are selected to indicate a UV-C dosage in the range from
about 200 to 800 mJ/cm.sup.2.
14. The composition according to claim 13, wherein said halogenated
polymer comprises polyvinylidene chloride.
15. The composition according to claim 13, wherein the amount of
said halogenated polymer is from about 0.10 to 50 percent, based on
the total weight of the solids in the composition.
16. The composition according to claim 13, wherein said diluent is
selected from the group consisting of cellulose acetate propionate,
starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl
cellulose, gelatin, casein, gum arabic, styrene-maleic anhydride
copolymers, ethylene acrylate copolymers, styrene-butadiene
copolymers, acrylonitrilebutadiene copolymers, poly(ethylenevinyl
acetate), and combinations thereof.
17. The composition according to claim 13, wherein the composition
is present in a non-aqueous solvent, said solvent selected from the
group consisting of toluene, ethyl acetate, tetrahydrofuran, and
combinations thereof.
18. A UV-C dosimeter for measuring the dosage of UV-C radiation to
which an article has been exposed, said UV-C dosimeter comprising:
a substrate having a plurality of UV-C sensitive compositions
coated thereon and wherein said plurality of UV-C sensitive
compositions includes one or more of: a first UV-C sensitive
composition that undergoes a color change in response a UV-C dosage
of 200 mJ/cm.sup.2 or greater; a second UV-C sensitive composition
that undergoes a color change in response a UV-C dosage of 400
mJ/cm.sup.2 or greater; and a third UV-C sensitive composition that
undergoes a color change in response a UV-C dosage of 800
mJ/cm.sup.2 or greater.
19. The UV-C dosimeter according to claim 18, wherein said
plurality of UV-C sensitive compositions comprise a halogenated
polymer that undergoes dehalogenation to produce an acid upon
exposure to UV radiation, an acid scavenger, and a pH sensitive dye
which changes color in response to a change in proton levels,
wherein the amounts of said halogenated polymer, acid scavenger,
and said pH sensitive dye are selected to indicate a UV-C dosage in
the range from about 200 to 800 mJ/cm.sup.2.
20. The UV-C dosimeter according to claim 19, wherein said
halogenated polymer, said acid scavenger, and said pH sensitive dye
are soluble in a lacquer based solution.
21. The UV-C dosimeter according to claim 18, wherein said
halogenated polymer comprises polyvinylidene chloride.
22. The UV-C dosimeter according to claim 18, wherein said
reference card further comprises at least one reference color that
corresponds to a UV-C dosage of about 0 mJ/cm.sup.2.
23. The UV-C dosimeter according to claim 18, wherein said
halogenated polymer comprises polyvinylidene chloride.
24. The UV-C dosimeter according to claim 18, wherein the UV-C
sensitive composition further comprises a diluent selected from the
group consisting of cellulose acetate propionate, starch,
hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
gelatin, casein, gum arabic, styrene-maleic anhydride copolymers,
ethylene-acrylate copolymers, styrene-butadiene copolymers,
acrylonitrilebutadiene copolymers, poly(ethylenevinyl acetate), and
combinations thereof.
25. The UV-C dosimeter according to claim 18, wherein the first
UV-C sensitive composition changes from a yellow to red color upon
exposure of a UV-C dosage of about 200 mJ/cm.sup.2 or greater, and
said second UV-C sensitive composition changes from a yellow to red
color upon exposure of a UV-C dosage of about 400 mJ/cm.sup.2 or
greater.
26. The UV-C dosimeter according to claim 18, wherein the third
UV-C sensitive composition changes from a green to purple color
upon exposure of a UV-C dosage of about 800 mJ/cm.sup.2 or
greater.
27. A kit for measuring the dosage of UV-C radiation to which an
article has been exposed, said kit comprising: a. the UV-C
dosimeter according to claim 18; and b. a UV-C dosage reference
card having one or more reference patterns that are each associated
with a different dosage of UV-C radiation, and wherein said
reference card includes a corresponding reference pattern for each
UV-C sensitive composition on said substrate.
28. The kit according to claim 26, wherein said reference card
further comprises at least one reference pattern that corresponds
to a UV-C dosage of about 0 mJ/cm.sup.2.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates generally to a UV sensitive
composition, and dosimeters for measuring UV radiation, and more
particularly to dosimeters that are adapted to measure UV-C
radiation.
[0002] It is generally known that reducing the exposure to oxygen
of oxygen sensitive articles maintains and enhances the quality and
shelf life of the article. For instance, reducing the oxygen
exposure of oxygen sensitive food products in a packaging system
maintains the quality of the food product and avoids food spoilage.
Reduced oxygen exposure keeps the product in inventory longer,
thereby reducing costs incurred from waste and having to
restock.
[0003] One method of reducing oxygen exposure is to incorporate an
oxygen scavenging composition into the packaging structure, such as
in a film or tray. Oxygen scavenging compositions are compositions
that consume, deplete, or reduce the amount of oxygen in a given
environment. There are a wide variety of different compositions
that can be used in oxygen scavenging applications. Exemplary
compositions are described in U.S. Pat. Nos. 5,211,875; 5,350,622;
5,399,289; and 5,811,027 to Speer et al. and WO 99/48963 to Cai et
al. The oxygen scavenging compositions can be "triggered" by
exposing the composition to a radiation source, such as actinic
radiation, having sufficient power for a sufficient amount of time
to initiate oxygen scavenging.
[0004] Methods of triggering oxygen scavenging compositions
typically use low-pressure mercury germicidal lamps that have an
intensity output from about 5 to 10 mW/cm.sup.2. These lamps are
commonly referred to as germicidal since the principal emission is
at 254 nm. A dosage of UV-C light of about 100 to 1600 mJ/cm.sup.2
is typically needed to trigger oxygen scavenging. For details on
preferred methods for activating such oxygen scavenging
compositions at point of use, see Speer et al., U.S. Pat. No.
5,211,875, Becraft et al., U.S. Pat. Nos. 5,911,910, and 5,904,960,
and co-pending applications U.S. Ser. No. 09/230594 filed Aug. 1,
1997, and Ser. No. 09/230776 filed Jul. 29, 1997, and U.S. Pat. No.
6,233,907 (Cook et al.), all of which are incorporated herein by
reference in their entirety.
[0005] Unfortunately, oxygen scavengers do not always activate on
command. This may result from a number of factors, including
defective scavenger compositions, inadequate triggering conditions,
operator error, or a combination of these or other factors. In many
instances, it may not be readily apparent whether the oxygen
scavenging composition is defective or whether the failure
originated in the triggering equipment. Typically, conventional
oxygen scavengers do not themselves visually indicate whether or
not they are active. In response to this uncertainty, operators of
packaging assembly plants prefer to verify scavenger activity as
soon as possible after triggering. The longer a failed triggering
attempt remains undiscovered, the more waste and expense is
incurred, especially where packaging equipment operates at high
speeds.
[0006] There are several methods for verifying oxygen scavenger
activity. Typically, oxygen concentrations are measured in the
package after it has been assembled. This can typically be
accomplished by using a probe that measures the oxygen
concentration in the package, or with an oxygen indicator that is
disposed in the interior of the package, or in the packaging
material itself. U.S. Pat. No. 6,689,438 to Kennedy et al.
describes a luminescent compound that can be incorporated into a
film or article. The luminescent compound is adapted to detect and
measure oxygen concentration levels in the packaging.
[0007] If the oxygen scavenging activity is too low it will be
necessary to determine whether the problem is associated with the
compound or the triggering equipment. Typically, this requires the
operator to stop production and review the current status and
operation of the triggering equipment. In many cases, an operator
may waste time in verifying that the triggering unit is functioning
when the problem is with the compound itself. To quickly eliminate
the triggering equipment as a source of the problem, it has been
proposed to incorporate fiber optic monitors into the trigger
equipment. The fiber optic monitors would measure the output of the
lamps. The monitors could then be checked to verify that the
triggering equipment is working properly. Unfortunately, fiber
optic monitors are typically cost prohibitive and may require
retrofitting the existing UV triggering equipment. In some
instances, it may not be feasible to use the fiber optic monitors
with the existing equipment.
[0008] Thus, there remains a need in the art for a significantly
faster method and article for verifying that oxygen scavenging
compositions have been exposed to a sufficient dosage of UV-C
radiation.
BRIEF SUMMARY OF THE INVENTION
[0009] In one embodiment, the invention comprises a UV sensitive
composition that undergoes a color change upon exposure to a
predetermined dosage of UV-C radiation. The UV-C sensitive
composition comprises a halogenated polymer, such as polyvinylidene
chloride, that produces an acid upon exposure to UV radiation, and
a pH sensitive dye. Upon exposure to UV-C radiation, the
halogenated polymer undergoes degradation and produces HCl. The pH
sensitive dye changes color as a result of increased levels of HCl
in the system. The composition may also include an acid scavenging
composition and/or a diluent to control the amount of free HCl
produced in the system. The amount of HCl liberated from UV-C
exposure may be selectively controlled so that a color change may
be produced at a desired UV-C dosage. In some embodiments, the
composition may be used to indicate a UV-C dosage from about 100 to
1600 mJ/cm.sup.2.
[0010] The UV-C sensitive composition may comprise a non-aqueous
lacquer based system in which the components of the composition are
miscible in a suitable lacquer solvent. The lacquer based system
allows the composition to be applied to the surface of a substrate
without the need for further polymerization or cross-linking.
[0011] In a second embodiment, the invention comprises a dosimeter
having one or more UV-C compositions deposited thereon and wherein
each composition is selectively formulated to be sensitive to a
predetermined dosage of UV-C radiation. In some embodiments, the
UV-C dosimeter comprises a first composition that undergoes a color
change in response to a UV-C dosage of about 200 mJ/cm.sup.2 or
greater; a second composition that undergoes a color change in
response to a UV-C dosage of about 400 mJ/cm.sup.2 or greater; and
a third composition that undergoes a color change in response to a
UV-C dosage of about 800 mJ/cm.sup.2 or greater. In one alternative
embodiment, the dosimeter may be in the form of a kit having a test
card and an associated reference card. In this embodiment, the test
card comprise a substrate having one or more UV-C sensitive
compositions that are formulated to undergo a color change in
response to a predetermined dosage of UV-C radiation, e.g., 200,
400, 800 mJ/cm.sup.2 or greater, that are deposited on the
substrate. The reference card may include one or more reference
colors that are each associated with a different dosage of UV-C
radiation, and wherein the reference card includes a corresponding
reference color for each UV-C sensitive composition on said
substrate. A user compares the test card to the reference card to
determine the dosage of UV-C radiation to which the test card may
have been exposed.
[0012] Thus, the invention provides a composition and article for
efficiently determining the UV-C dosage to which an item may have
been exposed.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0013] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0014] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0015] FIG. 1A is a graphical illustration of a test card having a
plurality of UV-C sensitive films coated thereon;
[0016] FIG. 1B is a color illustration of the test card of FIG.
1A;
[0017] FIG. 2A is a graphical illustration of a reference card that
may be used to determine the UV-C dosage to which the test cards of
FIGS. 1A and 1B may have been exposed;
[0018] FIG. 2B is a color illustration of the reference card of
FIG. 2A;
[0019] FIG. 3A is a graphical illustration of an operator using the
test card of FIGS. 1A or 1B in conjunction with the reference card
of FIGS. 2A or 2B to determine the UV-C dosage to which the test
card may have been exposed; and
[0020] FIG. 3B is a color illustration of the illustration of FIG.
3A.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The invention now will be described more fully hereinafter
with reference to the accompanying drawings, in which some, but not
all embodiments of the invention are shown. Indeed, the invention
may be embodied in many different forms and should not be construed
as limited to the embodiments set forth herein; rather, these
embodiments are provided so that this disclosure will satisfy
applicable legal requirements. Like numbers refer to like elements
throughout.
[0022] The UV sensitive composition of the present invention in one
embodiment comprises a non-aqueous lacquer based mixture of a
halogenated polymer that produces an acid upon exposure to UV
radiation, such as polyvinylidene chloride, and at least one dye
that is sensitive to changes in pH. The halogenated polymer is
capable of producing an acidic product upon exposure to ultraviolet
radiation. The pH sensitive dye is capable of producing a change in
color in response to a change in the concentration of the acidic
product. As a result, the UV sensitive composition may undergo a
color change within a predetermined color range in response to
exposure to ultraviolet radiation. In some embodiments, the UV
sensitive composition may also include one or more acid scavengers
and one or more diluents.
[0023] In some embodiments, the UV sensitive composition may
undergo several changes in response to increasing dosage or
alternatively, may undergo a single color change after exposure to
a predetermined dosage. For example, a first color change may
represent a relatively low concentration of the acidic product
while a second color change represents a relatively high
concentration of the acidic product. The first color and the second
color may represent the endpoints of the color range or one or both
of the first color and the second color may represent intermediate
colors within the range. The color range may include different
colors, different hues of one or more colors or a combination of
different colors and different hues. The first color and the second
color may be selected so as to represent a desired or predetermined
amount of UV-C dosage.
[0024] In some embodiments, the UV-sensitive composition may
comprise a solvent based lacquer. In general, lacquers may comprise
a non-aqueous solution that may be used to form a film. In some
embodiments, the lacquer may comprise a hydrophobic system. The
components of the UV sensitive composition may be soluble in
non-aqueous solutions and are therefore capable of forming a
solution comprising a substantially continuous non-aqueous phase.
The lacquer-based solution typically includes the halogenated
polymer, pH sensitive dye, and a non-aqueous solvent that may act
as a carrier for the above and any additional ingredients. In some
embodiments, the lacquer-based UV-sensitive composition is applied
to a substrate in the form of a solution. In some embodiments, the
lacquer may have a viscosity that allows the lacquer to be applied
to a substrate so that running or smearing may be reduced.
Evaporation of the solvent results in the UV-sensitive composition
forming a film on the surface of the substrate, without requiring
any additional cross-linking or polymerization.
[0025] In some embodiments, the UV sensitive composition may
include a resin that may be dissolved or dispersed in a non-aqueous
solution. The UV sensitive composition is typically produced by
dissolving or dispersing the halogenated polymer, pH sensitive dye,
and any additional components such as an acid scavenger and diluent
in a non-aqueous solvent. In some embodiments, the solvent system
may comprise a hydrophobic solvent. Suitable solvents for use in
the invention should be able to dissolve each of the components
into solution. Suitable solvents may include toluene, ethyl
acetate, tetrahydrofuran, and combinations thereof. In one
embodiment, the UV sensitive solution comprises from about 15 to 30
percent solid content, such as a solid content of about 20 percent.
The dissolved UV sensitive composition may then be applied to a
substrate, after which the solvent is evaporated to produce a film
comprising the UV sensitive composition. Typically, a solution
having about 20 percent solids laid down 5 mils thick may result in
a dry coating that is about 1 mil thick.
[0026] Halogenated polymers that may be useful in the invention
include polymers comprising halogenated monomers and copolymers
that undergo degradation in response to UV exposure. Typically, the
halogenated polymers of the invention undergo radiation induced
degradation when exposed to radiation at wavelengths below about
400 nm. In some embodiments, the halogenated polymers are
particularly sensitive to UV-C radiation having wavelengths from
about 200 to 280 nm. UV degradation of the polymer typically
results in the release of at least one halogen component and an
associated hydronium ion. As a result, UV induced degradation
produces HCl and thereby lowers the pH of the composition.
Continued UV exposure results in further degradation of the
polymer, and hence, a further decrease in the pH of the
composition. Suitable halogenated polymers include, without
limitation, polyvinyl chloride (PVC), polyvinylidene chloride
(PVDC), ethylene-chlorotrifluoroethylene copolymer, chlorinated
rubber, and copolymers thereof. In some embodiments, the
halogenated copolymers may also be combined with one or more
monomers that have little or no halogen content. As a result, the
UV sensitivity of the composition may be controlled or attenuated
by selecting polymers having a desired halogen content. In one
alternative embodiment, the composition may include from 0.1 to 50
wt. percent halogenated polymer, based on the weight of the solid
content.
[0027] At first glance, it would not seem practical to use a
halogenated polymer as a component in measuring UV-C dosage because
these polymers typically undergo non-linear degradation that can be
difficult to predict. This is especially true in situations where
it is desirable to measure UV-C dosages that exceed 100
mJ/cm.sup.2. UV degradation of halogenated polymers such as PVC and
PVDC produce a degradation process that becomes auto-excited and
self-propagating. As a result, the extinction coefficient of the
reaction increases and shifts to longer wavelengths resulting in
even further degradation. This effect is heightened as the UV dose
is increased. The production of the halogenated acid product, such
as HCl, also further increases degradation of the polymer. However,
it has been discovered, that such halogenated polymers can be used
in determining UV-C dosages that exceed 100 mJ/cm.sup.2 by
balancing the amount of halogenated polymer with the buffering
capacity of the system including the pH sensitive dye.
[0028] In one alternative embodiment, the pH sensitive dye may have
some initial buffering capacity. The buffering capacity of the pH
sensitive dye may be used to initially control the pH of the
composition. A formulation comprising the halogenated polymer and
the pH sensitive dye may be used to prepare a UV sensitive
composition that undergoes a color change at relatively low doses
of UV-C radiation. Such low doses are typically up to about 200
mJ/cm.sup.2, with a dosage up to about 100 mJ/cm.sup.2 being
somewhat more typical. By "pH sensitive dye" is meant one or more
compounds which change color dependent upon pH, preferably with
sharp color changes over a narrow pH range, and which are soluble
in a non-aqueous solution. Examples include bromophenol blue,
phenol red, thymol blue, ethyl orange, m-Cresol purple, New
Fuchsin, p-methyl red, lissamine green, aniline blue, methyl
violet, crystal violet, ethyl violet, brilliant green, oralochite
green oxalate, methyl green, cresol red, quinaldine red, para
methyl red, bromothymol blue, metanil yellow, orange IV,
phenylazoaniline, erythrosin B, benzopurpurin 4B, congo red, methyl
orange, resazurin, methyl red, alizarin red, bromocresol purple,
chlorophenol red, or combinations of dyes for multiple color
changes. Such dyes may be provided in an amount between 0.5 to 25
percent by weight, based on the total weight of the solids in the
composition. The pH sensitive dyes that may be useful in the
invention may generally be soluble in the lacquer based solvent
systems.
[0029] It has been discovered that the ability of the UV sensitive
composition of the invention to measure higher doses of UV-C
radiation can be increased by including one or more acid scavengers
and/or one or more diluents. The acid scavenger helps reduce or
lessen the amount of free acid that is present in the UV sensitive
composition. As a result, the amount of UV dosage that is required
to produce a color change in the composition can be controlled by
increasing or decreasing the amount of the acid scavenger that is
present in the composition. As used herein, the term "acid
scavenger" refers generally to any composition that has the ability
to neutralize acidic species in the UV sensitive composition that
are present as a result of UV induced degradation of the
halogenated polymer. In some embodiments, the acid scavenger is
soluble in non-aqueous solutions with the halogenated polymer and
the pH sensitive dye. Suitable acid scavenging components include,
but are not limited to, 1,4-diazabicyclo[2.2.2.]octane;
2,6-di-tert-butylpyridine; dibutyl 2,6-pyridinedicarboxylate;
diphenylamine; 2,4-dihydroxybenzophenone; [5.4.0.]undec-7-ene
(1,5-5); 1,5-diazabicyclo[4.3.0.]non-5-ene;
4-(dimethylamino)pyridine; hexamethylenetetramine; and combinations
thereof. When present, the amount of acid scavenger in the UV
sensitive composition may be from about 0.5 to 20 percent by
weight, based on the total weight of the solids of the coating
composition. In some embodiments, the acid scavenger may have a pKa
from about 8 to 4.
[0030] The UV sensitive composition may also include, in another
embodiment, a diluent that helps attenuate the UV sensitivity of
the composition. In this embodiment, the addition of a diluent
decreases the amount of halogenated polymeric resin that is present
in the UV sensitive composition, while maintaining the desired
solid content of the composition. As a result, the amount of acid
that is produced during UV exposure can be controlled by increasing
or decreasing the content of the halogenated polymer. The diluent
typically comprises a non-halogenated resin that allows the amount
of the halogenated polymer to be increased or decreased while
maintaining the desired solid content of the resin component.
Suitable diluents should also be soluble in non-aqueous solutions
with the halogenated polymer and the pH sensitive dye. Useful
diluents may include cellulose acetate propionate (CAP), starch,
hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
gelatin, casein, gum arabic, styrene-maleic anhydride copolymers,
ethylene-acrylate copolymers, styrene-butadiene copolymers,
acrylonitrilebutadiene copolymers, poly(ethylene vinyl acetate),
and combinations thereof. When present, the amount of diluent
generally used is about 1 percent to about 50 percent by weight,
and preferably about 5 percent to about 25 percent by weight, based
on the total weight of the solids of the coating composition.
[0031] The proportions of each component in the UV sensitive
composition are selected to provide a desired color change upon
exposure to a predetermined dosage of UV-C radiation. It should be
recognized that the UV dosage that produces a color change is
dependent upon the particular formulation and may be varied
depending upon its desired application.
[0032] In some embodiments, the UV sensitive composition may also
include a screen layer that prevents the UV sensitive composition
from being exposed to radiation longer than about 300 nm, such as
longer than 280 nm. The screen layer may comprise a screening agent
that is coated over the UV sensitive composition layer. Substances
may be used as a screening agent provided they do not interfere
with transmission of UV-C radiation to the UV sensitive
composition. This can include screening agents known to selectively
screen UV-A radiation and visible radiation such as Parsol.TM.
(4-(1,1-Dimethylethyl)-4'-methoxydibenzoylmethane) or related
agents such as phorone, menthyl anthranilate,
2-hydroxy-4-methoxybenzophenone,
2,2-dihydroxy-4-methoxybenzophenone, or 2-amino-benzophenone.
[0033] With reference to FIGS. 1A and 1B, an exemplary UV-C
dosimeter is illustrated and broadly designated as reference number
100. In the embodiment illustrated in FIG. 1, the UV-C dosimeter
comprises a test card 100 having a plurality of UV sensitive
compositions in the form of a film deposited thereon. Each
composition is selectively formulated to change color at a
predetermined dosage of UV-C radiation. In some embodiments, each
UV sensitive composition comprises a discrete region or portion of
the test card. In some embodiments, the color change may be
dramatic so that it will be easily recognizable by an operator.
Here, for example, each successive film from left to right may
change color in response to increasing dosage of UV-C
radiation.
[0034] In this illustration, the first film 112, from left to
right, may represent the most sensitive composition. Exposure to a
UV-C dosage greater than about 200 mJ/cm.sup.2 may cause the first
film 112 to change color. In some embodiments, each UV sensitive
film, such as films 114, 116, may be capable of going through
several color changes as the UV-C dosage to which the film has been
exposed increases. The second film 114 may be formulated to change
color at an exposure greater than about 200 mJ/cm.sup.2. The third
film 116 may comprise a UV-sensitive composition that may be
formulated to undergo a color change after exposure to a UV dosage
of about 400 mJ/cm.sup.2 or greater. The fourth film 118 may
comprise a composition that may be formulated to undergo a color
change at dosages exceeding about 800 mJ/cm.sup.2 or greater.
[0035] As can best be seen in FIG. 1B, films 112, 114, 116 may
initially be formulated to have a yellow color before any exposure
to UV-C radiation occurs. Subsequent exposure to increased dosages
of UV-C radiation may cause each film to change from a yellow color
to a final red color (see briefly FIG. 2B). The final red color may
represent an exhaustion of the halogenated polymer or the pH
sensitive dye. In some embodiments, film 118 may be formulated to
have a composition that only undergoes a change at higher dosages
of UV-C radiation, e.g., 800 to 1600 mJ/cm.sup.2.
[0036] It should be recognized that the arrangement and desired
color change can be varied depending upon preference. It should be
also recognized that the number of UV-C sensitive compositions
deposited on the UV-C dosimeter and their respective UV-C color
change thresholds can be varied to accommodate varying uses and
possible UV-C dosage exposures.
[0037] FIGS. 2A and 2B illustrate an exemplary UV dosage reference
card 200 that may be adapted to be used in conjunction with UV
dosimeter 100. The exemplary UV dosimeter reference card 200 may
comprise four sides, each of which may have four different
reference patterns printed thereon 202, 204, 206, 208. Each
reference pattern may refer to a different UV-C dosage. Here, the
reference card 200 includes a first reference pattern 202 of four
discrete colors that may match the appearance of the UV dosimeter
100 before any UV-C exposure has occurred. For example, the first
reference pattern 202 may be used to indicate a UV-C dosage of
about 0 mJ/cm.sup.2. As shown, the first reference pattern 202 may
include a total of four color marks, wherein three of the color
marks 212, 214, 216 may have the same color, such as yellow, and
the fourth color mark 218 may be same color or have a different
color, such as green. This first reference pattern 202 may be used
to indicate that the test card 100 has not been exposed to UV-C
radiation or has been exposed to a dosage of UV-C radiation that is
insufficient to produce a color change.
[0038] The second reference pattern 204 may also include four
discrete color marks that show the change in color that may occur
as the test card 100 is exposed to increasing doses of UV-C
radiation. For example, in this illustration, color mark 212 has
changed from a yellow color (see reference pattern 202) to a red
color. Color marks 214, 216, and 218 have not noticeably changed
color to an observer. The change in color of color mark 212 may be
used to indicate that the test card has been exposed to a threshold
dosage of UV-C radiation, such as 200 mJ/cm.sup.2.
[0039] Moving to reference pattern 206, it can be now be seen that
both 212 and 214 are now a red color and color mark 216 has changed
from a previous yellow color in reference patterns 202, 204 to an
orange color. Color mark 218 has not noticeably changed color to an
observer. Likewise, color mark 212 may not have changed color
because the corresponding film on the test card (see FIG. 1,
reference number 112) may comprise a more sensitive formulation
that has previously been exhausted. The change in color of color
marks 214 and 216 may be used to indicate that the test card has
been exposed to a threshold dosage of UV-C radiation, such as 400
mJ/cm.sup.2.
[0040] In reference pattern 208, color mark 218 may have changed to
another color. In FIG. 2B this may be represented as change from a
green color to a purple color. This change in color of color mark
218 may be used to indicate that the test card has been exposed to
a threshold dosage of UV-C radiation, such as 800 mJ/cm.sup.2.
Also, reference patterns 202, 204, 206 in some embodiments may now
have about the same color as each other, which may be an indication
that the corresponding films on the test card may have exhausted
the halogenated polymer.
[0041] It should be recognized, that the color patterns discussed
above and the change in colors with respect to various dosages of
UV-C radiation may be varied depending upon their intended
application. It should also be recognized that the number of
reference patterns, color marks, and formulations on the test card,
respectively, may be varied to accommodate a broader or narrower
range of UV-C dosages.
[0042] With respect to FIGS. 3A and 3B, an exemplary method of
using reference card 200 in conjunction with test card 100 is
illustrated. Here, the test card 100 has been exposed to UV-C
radiation. To determine the dosage of the UV-C exposure, an
operator may take the test card 100 and align the films thereon
with a color pattern on the reference card 200 that most closely
matches the color change in the films. As shown, an operator is
shown aligning test card 100 with reference card 200. When properly
aligned, films 112,114, 116, and 118 should be aligned with color
marks 212, 214, 216, 218 on the reference card. If the color change
of each film matches the reference pattern 206, the UV-C dosage to
which the test card has been exposed may be approximated. Here, the
color change of the films most closely resembles the third
reference pattern 206, which in this illustration refers to a UV-C
dosage of at least 400 mJ/cm.sup.2. In some embodiments, the test
card and the reference card may be available in a kit or as a
package. In this embodiment, the "kit" may include one or more
reference cards with a plurality of test cards.
[0043] In some embodiments, the UV sensitive composition can be
quantified according to conventional color classification systems
including the Hunter L,a,b color classification system. In one
alternative embodiment, the UV dosimeter and color formulations may
be used in conjunction with a color meter that may be used to
detect a change in the color of the composition.
[0044] The foregoing, as well as other, aspects and advantages of
the invention may be further understood by reference to the
following examples, which are provided for illustrative purposes
only and are not intended in any way to be limiting.
EXAMPLES
[0045] In the examples below the following materials were used:
[0046] "F310" is a lacquer based copolymer of vinylidene chloride
and vinyl chloride available from Dow Chemical. [0047] "CAP" is
cellulose acetate propionate available from Eastman Chemical,
product number CAP-504-0.2. [0048] "SY56" is Color Index Solvent
yellow 56: N,N-diethyl-4-(phenylazo)aniline, available from
Colorweigh Chemical Co. [0049] "SB59" is Color Index Solvent Blue
59: 1,4-bis(ethylamino)-9,10-anthraquinone, available from
Aldrich.
[0050] "HMTA" is hexamethylenetetramine, available from Aldrich.
TABLE-US-00001 TABLE 1 UV-C Dosimeter Compositions Net Color Change
in response to different dosages of UV-C radiation Test F 310 CAP
SY 56 HMTA SB 59 0 100 200 400 800 Sample (gm) (gm) (mg) (mg) (mg)
mJ/cm.sup.2 mJ/cm.sup.2 mJ/cm.sup.2 mJ/cm.sup.2 mJ/cm.sup.2 Sample
1 1 -- 40 -- -- Yellow Red/orange red red red Sample 2 2 1 40 20 20
Yellow Yellow/orange Red/orange red red Sample 3 1 1 40 20 20
Yellow Yellow Yellow/org. Red/orange red Sample 4 0.5 1.5 40 20 20
Yellow Yellow Yellow Yellow/orange orange Sample 5 1 1 10 10 20
Green Green Green Green Purple
[0051] TABLE-US-00002 TABLE 2 Rel P/S Net Rel (P + B)/S Test Sample
(mmoles) Rel B/S (mmoles) Sample 1 0.16 0.00 0.16 Sample 2 0.08
0.29 0.36 Sample 3 0.16 0.57 0.73 Sample 4 0.32 1.14 1.46 Sample 5
0.08 0.57 0.65 P = acid sensitive dye; S = halogenated polymer; and
B = acid scavenger.
[0052] From Table 1 above, it can be seen that the UV-C sensitive
composition of the invention can be used to determine the UV-C
dosage to which a composition, such as an oxygen scavenging (OS)
composition, has been exposed. In one embodiment, the UV-C
sensitive composition of the invention may be used to help
determine if an OS composition has been exposed to sufficient UV-C
radiation to produce the desired oxygen scavenging in the film. As
a result, the UV-C sensitive composition may help improve
efficiencies in the packaging of oxygen sensitive goods.
[0053] From Table 2 it can be seen that for samples 1 through 4,
for each doubling of the UV dosage at which a color change occurs,
the ratio of the amount of halogenated polymer to the amount acid
sensitive dye and acid scavenger in the composition is roughly
doubled. It has been discovered by the Applicants, that this
doubling provides a dramatic color change that may be easily
observable by a user.
[0054] Many modifications and other embodiments of the invention
set forth herein will come to mind to one skilled in the art to
which the invention pertains having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the invention is
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *