FREEZE INDICATORS SUITABLE FOR MASS PRODUCTION
First Claim
1. A freeze indicator comprising:
- (a) an indicator volume;
(b) an indicator dispersion of solid particles dispersed in a liquid medium, the indicator dispersion being contained in the indicator volume and being capable of coagulating to provide an irreversible appearance change when subject to freezing; and
(c) at least one vapor block member extending around the indicator volume to prevent loss of liquid vapor from the indicator dispersion.
6 Assignments
0 Petitions
Accused Products
Abstract
A freeze indicator employs, as active indicator element, dispersion of solid particles in a liquid medium which can be water or aqueous and which coagulates to provide an irreversible appearance change when subject to freezing. The liquid dispersion can be contained in an indicator volume around which extends a vapor block layer. The vapor block layer can prevent loss of liquid vapor from the dispersion and consequent drying out and dysfunctionality of the freeze indicator. For containing an aqueous medium, bilayer and trilayer laminate materials can be used which have a low water vapor transmission rate. The active indicator element can be a dilute colloidal dispersion of a metal such as gold or silver or other inorganic pigment material in water or an aqueous medium. Some embodiments avoid use of dispersants and the like and employ an active indicator element consisting of inorganic pigment particles, water and optionally an ice nucleating agent. Heavy water, or deuterated water can be components of the water, if desired.
37 Citations
30 Claims
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1. A freeze indicator comprising:
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(a) an indicator volume;
(b) an indicator dispersion of solid particles dispersed in a liquid medium, the indicator dispersion being contained in the indicator volume and being capable of coagulating to provide an irreversible appearance change when subject to freezing; and
(c) at least one vapor block member extending around the indicator volume to prevent loss of liquid vapor from the indicator dispersion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 25, 26, 27)
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20. A freeze indicator comprising a dispersion of solid inorganic pigment particles in an aqueous dispersion medium, the dispersion exhibiting an irreversible appearance change in response to freezing of the dispersion, an indicator volume containing the inorganic pigment dispersion and a viewing window for viewing the dispersion, the freeze indicator optionally comprising an attachment device for securing the indicator to a host product to be monitored.
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21. A freeze indicator according to claim 21 wherein the pigment particles comprise a material selected from the group consisting of pigments, ink pigments, minerals, unreactive metals, noble metals, precious metals, gold, silver, aluminum, iridium, platinum, zinc, selenium or carbon black, sulfur, ferric oxide, kaolinite, montmorillonite, talc, halloysite, calcite, dolomite, rutile titanium dioxide, gibbsite, zincite, barite, crystalline silica, amorphous silica, hydrated silica, fluorite, hydroxyapatite, and a combination of any two or more of the foregoing materials the combination comprising a coating of one material upon the other material.
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22. A freeze indicator according to claim 22 wherein the indicator volume is in the range of from about 5 μ
- L to about 50 μ
L, the concentration of pigment particles is not more than about 0.05 percent by weight, the indicator dispersion is opaque before freezing and visibly light-transmissive after freezing of the dispersion or the indicator dispersion is colored before freezing and is substantially colorless after freezing of the dispersion.
- L to about 50 μ
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23. A freeze indicator comprising:
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(a) an indicator volume;
(b) an indicator dispersion of solid particles dispersed in a freezable liquid dispersion medium, the indicator dispersion being contained in the indicator volume and being capable of coagulating to provide an irreversible appearance change when subject to freezing; and
(c) a concentration-responsive coagulating agent dissolved in the dispersion medium;
wherein freezing of the dispersion medium increases the concentration of the coagulating agent and effects an appearance-changing coagulation of the dispersion medium. - View Dependent Claims (24)
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- 28. A freeze indicator according to claim 28 wherein the indicator dispersion consists of, consists essentially of, or comprises pigment particles dispersed in a non-aqueous liquid.
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29. A freeze indicator according to claim 29 wherein the liquid medium is a single phase before, during and after freeze exposure
Specification