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Title:
TIME INDICATOR BASED ON CARBON DIOXIDE PRODUCTION
Document Type and Number:
WIPO Patent Application WO/1998/052035
Kind Code:
A1
Abstract:
An indicator composition includes an ingredient that is sensitive to a component of the air and may change color at pre-selected time after exposure to air. The indicator composition can be used to provide an indication of the freshness of a product.

Inventors:
Ignacio, Ramon T. (21 Campbell Road, Somerville, NJ, 08876, US)
Application Number:
PCT/US1997/007149
Publication Date:
November 19, 1998
Filing Date:
May 12, 1997
Export Citation:
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Assignee:
MINNESOTA MINING AND MANUFACTURING COMPANY (3M Center, P.O. Box 33427 Saint Paul, MN, 55133-3427, US)
Ignacio, Ramon T. (21 Campbell Road, Somerville, NJ, 08876, US)
International Classes:
G01N31/22; (IPC1-7): G01N31/22; C12Q1/04
Domestic Patent References:
WO1997005481A1
Foreign References:
US4003709A
Attorney, Agent or Firm:
Ubel, Andrew F. (Minnesota Mining and Manufacturing Company, Office of Intellectual Property Counsel P.O. Box 3342, Saint Paul MN, 55133-3427, US)
Hilleringmann, Jochen (Bahnhofsvorplatz 1, K´┐Żln, D-50667, DE)
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Claims:
What is claimed is:
1. A method comprising associating with a product an indicator composition that changes color after exposure to carbon dioxide, the indicator composition comprising a carbon dioxide attenuator, the indicator composition being sealed from carbon dioxide, and then exposing said indicator composition to air.
2. The method of claim 1, wherein said indicator composition changes to a targeted color at a preselected approximate time after said exposure to said air.
3. The method of claim 2, further comprising deriving information concerning freshness of the product from the color of the indicator composition.
4. The method of claim 1, wherein said product comprises a cosmetic.
5. The method of claim 1, wherein said indicator composition comprises a pH sensitive colorant.
6. The method of claim 1, wherein said carbon dioxide attenuator comprises a hydroxide salt.
7. The method of claim 1, wherein said indicator composition further comprises a hygroscopic agent.
8. A method comprising associating with a product an indicator composition that changes color after exposure to carbon dioxide, the indicator composition comprising a hygroscopic agent, the indicator composition initially being sealed from carbon dioxide, and then exposing said indicator composition to air.
9. The method of claim 8, wherein said indicator composition changes to a targeted color at a preselected approximate time after said exposure to said air.
10. The method of claim 8, wherein said product comprises a cosmetic.
11. The method of claim 8, wherein said indicator composition comprises a pH sensitive colorant.
12. The method of claim 8, wherein said hygroscopic agent comprises calcium chloride dihydrate.
13. A cosmetic product comprising a cosmetic and an indicator composition that changes color when exposed to carbon dioxide, the indicator composition further comprising a carbon dioxide attenuator.
14. The cosmetic product of claim 13, wherein said indicator composition comprises a pH sensitive colorant.
15. The cosmetic product of claim 13, wherein said carbon dioxide attenuator comprises a hydroxide salt.
16. The cosmetic product of claim 13, wherein said indicator composition further comprises a hygroscopic agent.
17. A cosmetic product comprising a cosmetic and an indicator composition that changes color after exposure to carbon dioxide, the indicator composition further comprising a hygroscopic agent.
18. The cosmetic product of claim 17, wherein said indicator composition comprises a pH sensitive colorant.
19. A time indicator, comprising: an indicator composition that changes color after exposure to carbon dioxide, the indicator composition comprising a carbon dioxide attenuator, and a carbon dioxide impermeable enclosure enclosing said indicator composition, said carbon dioxide impermeable enclosure comprising a movable element that when moved allows carbon dioxide to contact said indicator composition, wherein said indicator composition undergoes a targeted color change at a preselected time after said movable element is removed.
20. The time indicator of claim 19, wherein said movable element comprises a peelable strip, and wherein said time indicator further comprises a layer that is directly exposed to air when said peelable strip is removed, said layer including a hole leading to said indicator composition.
21. A time indicator, comprising an indicator composition comprising an indicator composition that changes color after exposure to carbon dioxide, the indicator composition comprising a hygroscopic agent, and a carbon dioxide impermeable enclosure enclosing said indicator composition, said carbon dioxide impermeable enclosure comprising a movable element that when moved allows carbon dioxide to contact said indicator composition, wherein said indicator composition undergoes a targeted color change at a preselected time after said movable element is removed.
22. The indicator of claim 21, wherein said movable element comprises a peelable strip, and wherein said time indicator further comprises a layer that is directly exposed to air when said peelable strip is removed, said layer including a hole leading to said indicator composition.
Description:
TIME INDICATOR BASED ON CARBON DIOXIDE PRODUCTION Field of the Invention The invention relates to time indicators.

Background of the Invention Cosmetics such as mascara are often sold in sealed containers. Typically, the seal is broken when the product is first used. Once the seal is broken, the cosmetic may be exposed to microorganisms such as bacteria that exist, for example, in the air, on a cosmetic applicator, or on the skin or fingers of a user.

The microorganisms may then begin to grow in the cosmetic. Over time a significant culture of the microorganism may be present in the cosmetic. If the cosmetic has not been exhausted or thrown away before this occurs, further application of the cosmetic to the skin may cause an infection.

Summary of the Invention Generally, the invention relates to an indicator composition that can be used to provide an indication of the freshness of a product such as, for example, a cosmetic. The indicator composition may be activated when the product is first used, and changes color after exposure, for example, to air for a pre-selected period of time. The pre-selected period of time may correspond to the life of the product, and may be, for example, 24 hours, two days, or 30 days. A user of the product, observing the color of the indicator composition, can determine whether the life of the product has expired. If it has, the user can discard or recycle the product thereby avoiding use of the product in its ineffective or unsafe condition.

A preferred indicator composition changes color after exposure to carbon dioxide. The indicator composition may contain a pH sensitive colorant that changes color when carbon dioxide in the air lowers the pH of the composition.

The indicator composition also may contain a carbon dioxide attenuator, which can be used to adjust the timing of the color change. The more carbon dioxide attenuator included in the composition, the longer it will take for carbon dioxide to lower the pH of the composition sufficiently for the color change to occur.

The indicator composition also may contain a hygroscopic agent, which retains water in the composition and thereby provides a source of water. Water facilitates the acid-base reaction that results in the pH-sensitive colorant changing color.

In one embodiment, the invention provides a time indicator including the indicator composition enclosed in a carbon dioxide impermeable enclosure. The enclosure preferably has a movable element (e.g., a peelable cover) that when removed in the presence of air allows carbon dioxide to contact the indicator composition. The enclosure also preferably includes a layer that is exposed to the air when the movable element is removed; the layer includes at least one passage (e.g., a hole) leading directly to the indicator composition.

The indicator composition and time indicator can be used with a variety of products, in addition to cosmetics such as mascara, to indicate, for example, whether the effective, safe, or usable life of the product has expired. Examples of additional products include insecticides, eye solutions, peroxide-containing products, toilet bowl inserts, air fresheners, theme park admission tickets, lawn care products, agricultural products, mechanical products, parking meters, baking soda, car fluids, perishable foods (e.g., milk, brick pack milk, and other dairy products), beverages, smoke detectors, toothbrushes, sponges, prescription drugs, razors, pet care products, water filtration systems, and filters.

Air, as used herein, means the ambient air that people typically breathe.

Ambient air contains only a small quantity (approximately 0.03%) of carbon dioxide.

Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.

Brief Description of the Drawing Fig. 1 is a cross-sectional view of the central portion of an embodiment of a time indicator; Fig. 2 is a cross-sectional view of the central portion of a second embodiment of a time indicator; and Fig. 3 is a cross-sectional view of the central portion of a third embodiment of a time indicator.

Description of the Preferred Embodiments A preferred indicator composition includes a pH sensitive dye, a carbon dioxide attenuator, a hygroscopic agent, and a binder.

Suitable pH sensitive dyes change color when carbon dioxide lowers the pH of the indicator composition. The pH at which the color change will occur depends on the dye. For example, phenolphthalein is deep red at about pH 9 and above, and colorless below about pH 8.5. Other pH sensitive dyes include cresol red (sodium salt), neutral red, rosolic acid, brilliant yellow, and o-cresolph- thalein.

The indicator composition should include a sufficient quantity of dye to provide the desired color intensity. The quantity of the dye may also influence the timing of the color change of the indicator composition. In general, the larger the quantity of dye, the longer the composition must be exposed to the air before significantly changing color. The indicator composition may contain, for example, between 0.1% and 10%, or between 0.2% and 5%, of the dye by weight.

The carbon dioxide attenuator also can be used to control the timing of the color change. Preferred attenuators include those, for example, that interact with carbon dioxide from the air and, at least initially, inhibit the carbon dioxide from significantly lowering the pH of the indicator composition. If it is desired to have an indicator composition that will not change color for a longer period of time after exposure to air, a larger quantity of the carbon dioxide attenuator

should be included in the indicator composition. The indicator composition may contain, for example, between 1% and 25%, or between 3% and 15%, of the carbon dioxide attenuator by weight. Examples of other carbon dioxide attenuators include lithium hydroxide, sodium hydroxide, and magnesium hydroxide.

The hygroscopic agent preferably provides a supply of moisture to the indicator composition, to facilitate the acid-base reaction. Examples of hygroscopic agents include calcium chloride dihydrate, calcium chloride hexahydrate, lithium chloride hydrate, magnesium nitrate hexahydrate, and zinc sulfate heptahydrate. A sufficient quantity of the hygroscopic agent should be included in the indicator composition to provide the desired level of moisture.

The indicator composition may contain, for example, between 10% and 85%, or between 25 % and 75 %, of the hygroscopic agent by weight.

The indicator composition preferably includes a binder. Preferably, the binder functions to bind the indicator composition to a substrate. Examples of binders include resins such as methyl cellulose, ethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl pyrollidone, ethyl hydroxyethyl cellulose, and shellacs. Preferably the binder is water soluble. A sufficient quantity of binder preferably should be included in the composition to provide adequate binding of the composition to the substrate. The binder also may influence the rate at which carbon dioxide penetrates into the composition. The indicator composition may contain, for example, between 10% and 35%, or between 15% and 25%, of the binder by weight.

The indicator composition also may contain other ingredients such as additional colorants that do not change color when the indicator composition is exposed to air, resins that perform functions other than binding (e.g., providing water resistance), or opacifying agents.

The indicator compositions may be prepared by a variety of methods.

For example, a preferred binder, methyl cellulose, is purchased in powder form and then combined with water or an alcohol. The components are mixed in a jar until all of the methyl cellulose has dissolved. The other components are then

added, and the composition is then mixed further in a jar until dissolved.

The indicator composition then can be applied to a suitable substrate, such as paper or polyester, by methods such as draw down printing, extrusion printing, and silk screen printing. The quantity of indicator composition loaded into the substrate may influence the timing of the color change. For example, if the indicator composition is applied unevenly as a coating over the substrate, the thinner portion of the indicator composition coating may begin to change color prior to the thicker portion of the indicator composition coating.

Referring to Figure 1, an embodiment 10 of a time indicator includes an indicator composition printed on a bond paper substrate 12 (cut to the appropriate size), an abrasion-resistant transparent film 14, and an outer peelable carbon- dioxide impermeable film 16. Abrasion-resistant film 14 includes an opening 18 through which air can contact the indicator composition when peelable film 16 is removed. Peelable film 16 includes an adhesive on the surface that contacts film 14.

Paper substrate 12 is sandwiched between film 14 and a carbon-dioxide impermeable film 20; all are bound together in an adhesive layer 22. The underside of film 20 includes an adhesive.

Time indicator 10 is attached to a product by pressing the exposed adhesive against a surface of the product. When the product layer is used for the first time, layer 16 also is peeled off, exposing the indicator composition to air.

Paper (not shown) may be included, for example, between films 14 and 16 at an outer edge of the time indicator to make initiating peeling easier. The indicator composition will change color when the carbon dioxide in the air lowers the pH of the indicator composition to a sufficiently low level.

Layers 14, 16, and 20 may be composed of any suitable material. For example, layers 14 and 20 may comprise a carbon dioxide impermeable material.

The layer may be composed of, for example, polyester film such as 0.5 ml polyester film available from Fasson, a division of Avery-Dennison. Opening 20 can be made in film 14, for example, by poking or slicing the film.

Referring to Figure 2, a second embodiment of a time indicator is described in WO 97/05481, which is hereby incorporated by reference. The time indicator 110 includes a base member 112, an indicator composition 114, an adhesive layer 116, and a two layered covering material 118. The indicator composition 114 is applied to one side of the impermeable base member 112 in a selected pattern and provides a visual indication when it is exposed to a selected component (e.g., carbon dioxide) of an ambient fluid (e.g., air). The adhesive layer 116 is made of an impermeable material and applied in a selected pattern over the indicator composition 114 leaving a selected portion of the indicating material 114 exposed to the ambient fluid. An inner layer 122 of the co-layered cover member 118 is permeable to the ambient fluid. The time indicator 110 remains dormant, i.e., the color of the indicator composition does not significantly change, until some time after outer layer 120 of the co-layered cover member 118 is removed.

Referring to Figure 3, a third embodiment of a time indicator 210 includes a base member 212, an adhesive layer 214, an indicator composition 216, and a two-layer covering material 218, including a transparent inner layer 220 and an outer layer 222. The indicator composition may be printed, for example, by silk screen printing, on either adhesive layer 214 or inner layer 220.

Adhesive layer 214 may be, for example, a cold or hot melt adhesive, and after assembly the adhesive seals indicator composition 216 from the air. Time indicator 210 remains dormant until outer layer 222, which is peelable from inner layer 220, is removed. Inner layer 220 is permeable to air and allows carbon dioxide in the air to contact the indicator composition.

The time indicator also may include a composition that provides a reference color composition, for example, next to or surrounding the indicator composition. The reference color composition may be, for example, the color that the indicator composition will be when its color change is complete.

The following examples of indicator compositions were prepared.

Example 1 An indicator composition that when incorporated into a time indicator would change color approximately 48 hours after exposure to air was prepared.

The indicator composition contained a hygroscopic agent (calcium chloride dihydrate), a carbon dioxide attenuator (calcium hydroxide), a pH sensitive dye (phenolphthalein), and a binder (methocel, a methyl cellulose).

The composition was prepared by first preparing a methocel solution (Solution "A") containing the following components: Ingredient Ouantity Supplier Methocel 50 cps 1.55% Dow Chemical Methocel 4,000 cps 1.55% Dow Chemical Distilled Water 58.14% -- Anhydrous Ethyl Alcohol 38.76% -- The methocel solution was prepared by combining the ingredients and then mixing them in a jar for about two days. The methocel solution then was combined with calcium chloride dihydrate, calcium hydroxide, and phenolphthalein, in the following quantities: Ingredient Quantity Supplier Calcium Chloride Dihydrate 8.91 grams Aldrich Chemical Co.

Calcium Hydroxide 1.11 grams Aldrich Chemical Co.

Phenolphthalein 0.89 grams Aldrich Chemical Co.

Methocel Solution "A" 89.09 grams -- The ingredients then were mixed in a mill jar for four to six hours to provide a solution of the indicator composition.

The solution can be printed onto a suitable substrate. For example, the solution can be printed onto a polyester substrate using an Acculab Junior Draw Down Machine purchased from Industry Tech in Oldsman, Florida (using wire size number zero).

Alternatively, the solution can be printed by silk screen printing onto inner layer 220 of time indicator 210. The time indicator then can be associated with a product for which it is desired to provide an indication that at least 48 hours have passed since the product was first used. For example, base member 212 may include an adhesive and a peelable layer on its base surface; the peelable layer can be removed and the time indicator attached to a product.

When the product initially is used, the user at that time removes outer layer 222, allowing air to contact and pass through inner layer 220 to contact indicator composition 216. The phenolphthalein in the indicator composition, and as a result the indicator composition, initially are red, and over the initial two to six hours, they become a slightly darker red. After about 24 hours, the red color gradually begins to fade as the carbon dioxide attenuator begins to be used up, and the pH of the indicator composition lowers, causing the color of the phenolphthalein to fade. After 48 hours, indicator composition 216 is colorless, or essentially colorless, providing the user with an indication that it has been 48 hours since the product was first used.

Example 2 An indicator composition that when incorporated into an appropriate time indicator would change color approximately 30 days after exposure to air was prepared. The indicator composition contained the same components as the indicator composition described in Example 1, but with a larger quantity of the carbon dioxide attenuator (calcium hydroxide), plus some additional water. The quantities of components used to prepare the indicator composition in solution are listed below:

Ingredient Ouantity Calcium Chloride Dihydrate 8 grams Calcium Hydroxide 13 grams Phenolphthalein 0.8 grams Methocel Solution "A" 80 grams Distilled Water 20 grams The indicator composition can be incorporated into time indicator 210 as described previously. The time indicator then can be associated with a product for which it is desired to provide an indication that at least 30 days have passed since the product was first used. When the product initially is used, the user at that time removes outer layer 222. The indicator composition initially is red, and remains red for a much longer period of time than the period of time the indicator composition described in Example 1 remains red because it contains the much larger quantity of the carbon dioxide attenuator. Because of the larger quantity of carbon dioxide attenuator, it takes much longer for the pH of the indicator composition to lower sufficiently to cause the indicator composition to become colorless or essentially colorless.

Example 3 An indicator composition that when incorporated into an appropriate time indicator would change color approximately 14 days after exposure to air was prepared. The indicator composition contained the same hygroscopic agent and carbon dioxide attenuator as the indicator compositions described in Examples 1 and 2, but included a different pH sensitive dye (cresol red, sodium salt). The indicator composition also included a different binder (polyvinyl pyrollidone, purchased from GAF Chemical Co.) and an opacifying agent (Ropaque-OP-62- LO, purchased from Rohm & Haas). A solution of the indicator composition was prepared containing the following components:

Distilled Water 500 Grams Ethyl Alcohol 185 Grams Polyvinyl Pyrollidone K-30 35 Grams Polyvinyl Pyrollidone K-90 5 Grams Calcium Hydroxide 70 Grams Calcium Chloride Dihydrate 200 Grams Cresol Red Sodium Salt 3 Grams Ropaque-OP-62-LO 10 Grams The solution was prepared by adding the polyvinyl pyrollidone to the water and alcohol. The mixture is stirred until the polyvinyl pyrollidone was fully dissolved. The remaining ingredients were added, and the mixture ground in a #0 mill jar for four hours.

The indicator composition (in solution) can be printed onto a paper substrate, for example, by extrusion printing, and incorporated into time indicator 10 as described previously. The time indicator then can be associated with a product for which it is desired to provide an indication that at least 14 days have passed since the product was first used. When the product is first used, the user removes peelable film 16. The cresol red in the indicator composition, and as a result the indicator composition, initially are purple. But air contacts the indicator composition on paper substrate 12 through opening 18, and over time the carbon dioxide attenuator begins to be used up, causing the pH of the indicator composition to lower and the color of the creosol red to change from purple to yellow. After approximately 14 days, the pH of the indicator composition is sufficiently low, causing the color of the creosol red to change from purple to yellow, thus providing an indication to a user that at least 14 days have elapsed since the product initially was used.

Other embodiments are within the claims.