Thermochromic composition, method of making, and use

Claim 2

A pH indicator composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) a buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient to that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 3

Composition according to claim 1 wherein said buffer solution contains a buffer pair capable of dissociating into organic and inorganic ions.

Claim 4

Composition according to claim 1 wherein said control agent is selected from the group consisting of alcohols, carboxylic acids and precursor substances therefor.

Claim 5

Composition according to claim 1 wherein said precursor of said control agent is capable of yielding an alcohol or a carboxylic acid in said pH indicator composition.

Claim 6

Composition according to claim 1 wherein said buffer solution is more acidic at said second temperature than at said first temperature.

Claim 7

Composition according to claim 1 wherein said buffer solution is more alkaline at said second temperature than at said first temperature.

Claim 8

Composition according to claim 1 wherein said pH indicator composition contains (D) an inorganic salt capable of dissociating in said buffer solution to thereby change the ionic strength of said solution.

Claim 9

A method of using the pH indicator composition of claim 1 comprising lowering the temperature of said pH indicator composition from a first temperature above the freezing point of said pH indicator composition to a second temperature at which said pH indicator composition is in frozen state.

Claim 10

Composition according to claim 1 wherein said change of color occurs at a selected sub-freezing temperature to about -90° C.

Claim 11

Composition according to claim 1 wherein said buffer solution is comprised of a buffer pair in solution in a solvent selected from the group consisting of water, an aliphatic alcohol or mixtures thereof.

Claim 12

Composition according to claim 10 wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol and dodecanol.

Claim 13

A pH indicator composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 14

A pH indicator composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 15

Composition according to claim 12 wherein said buffer solution contains a buffer pair capable of dissociating into organic and inorganic ions.

Claim 16

Composition according to claim 12 wherein said buffer solution is more acidic at said second temperature than at said first temperature.

Claim 17

Composition according to claim 12 wherein said buffer solution is more alkaline at said second temperature than at said first temperature.

Claim 18

A method of using the pH indicator composition of claim 12 comprising lowering the temperature of said pH indicator composition from a first temperature above the freezing point of said pH indicator composition to a second temperature at which said pH indicator composition is in a frozen state.

Claim 19

Composition according to claim 12 wherein said pH indicator composition contains (D) an inorganic salt capable of dissociating in said buffer solution to thereby change the ionic strength of said solution.

Claim 20

Composition according to claim 17 wherein said inorganic salt is a salt of a strong mineral acid.

Claim 21

Composition according to claim 12 wherein said control agent is selected from the group consisting of alcohols, carboxylic acids and precursor substances therefor.

Claim 22

Composition according to claim 19 wherein said alcohol contains at least one hydroxyl group and is selected from the group consisting of methanol, ethanol, glycols, glycerol and carbohydrates.

Claim 23

Composition according to claim 20 wherein said carbohydrate is selected from the group consisting of saccharose, sorbitol and dextrose.

Claim 24

Composition according to claim 19 wherein said carboxylic acid contains at least one carboxyl group and is selected from the group consisting of aliphatic and aromatic carboxylic acids, keto acids, hydroxy acids and amino acids.

Claim 25

Composition according to claim 22 wherein said carboxylic acid is selected from the group consisting of formic acid, acetic acid, succinic acid, citric acid and glutamic acid.

Claim 26

Composition according to claim 19 wherein said precursor substance is a salt of a carboxylic acid or a mixture of an enzyme and a substrate for said enzyme, which mixture is capable of producing the control agent by enzymatic reaction.

Claim 27

Composition according to claim 24 wherein said precursor substance is lipase-esterase/glyceryl tricapronate.

Claim 28

A pH indicator composition having controlled reversible change of color at a selected sub-freezing temperature to about -90° C., said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent selected from the group consisting of alcohols, carboxylic acids and precursor substances thereof, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (a) for a pH indicator composition, which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (b) for a pH indicator composition, which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 29

A pH indicator composition having controlled reversible change of color at a selected sub-freezing temperature to about -90° C., said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent selected from the group consisting of alcohols, carboxylic acids and precursor substances thereof, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (a) for a pH indicator composition, which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (b) for a pH indicator composition, which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 30

A method of using the pH indicator composition of claim 26 comprising lowering the temperature of said pH indicator composition from a first temperature above the freezing point of said pH indicator composition to a second temperature at which said pH indicator composition is in a frozen state.

Claim 31

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) a buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 32

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) a buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 33

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 34

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 35

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (1) for a pH indicator composition which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (2) for a pH indicator composition which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 36

A pH indicator composition in a frozen state, said composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (1) for a pH indicator composition which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (2) for a pH indicator composition which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 39

A method as claimed in claim 31 comprising adding as a control agent a carboxylic acid containing at least one carboxyl group and selected from the group consisting of aliphatic and aromatic carboxylic acids, keto acids, hydroxy acids and amino acids.

Claim 40

A method as claimed in claim 32 in which said carboxylic acid is selected from the group consisting of formic acid, acetic acid, succinic acid, citric acid and glutamic acid.

Claim 41

A method as claimed in claim 31 in which said precursor of a control agent is an enzyme-substrate mixture, which produces the control agent by enzymatic reaction.

Claim 42

A method as claimed in claim 34 in which said enzyme-substrate mixture is lipase-esterase-glyceryl tricapronate.

Claim 43

A method as claimed in claim 31 comprising adding as control agent a substance selected from the group consisting of alcohols, carboxylic acids and precursor substances therefor.

Claim 44

A method as claimed in claim 36 in which said alcohol contains at least one hydroxyl group and is selected from the group consisting of methanol, ethanol, glycols, glycerol and carbohydrates.

Claim 45

A method as claimed in claim 37 in which said carbohydrate is selected from the group consisting of saccharose, sorbitol and dextrose.

Claim 48

An article of manufacture comprising a sealed casing at least a portion of which is substantially translucent or transparent, said casing containing a thermochromic composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) a buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 49

An article of manufacture comprising a sealed casing at least a portion of which is substantially translucent or transparent, said casing containing a thermochromic composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) a buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said control agent is in an amount sufficient so that said pH indicator composition is capable of exhibiting a color at a selected temperature below freezing, which color is the same as the color of said pH indicator composition at a temperature above freezing.

Claim 50

A temperature indicating device for use at sub-freezing temperatures comprising a sealed casing at least a portion of which is substantially translucent or transparent, said casing containing a thermochromic composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (a) for a pH indicator composition which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (b) for a pH indicator composition which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 51

A temperature indicating device for use at sub-freezing temperatures comprising a sealed casing at least a portion of which is substantially translucent or transparent, said casing containing a thermochromic composition having controlled reversible change of color at a selected sub-freezing temperature, said composition comprising: (A) at least one pH indicator in an amount sufficient to display a change of color upon change of pH; (b) an aqueous buffer solution containing at least one inorganic ion in solution, wherein said buffer solution has a pH which is capable of changing when temperature of said buffer solution is lowered from a first temperature above the freezing point of said solution to a second temperature at which said solution is in a frozen state; and (C) a control agent or a precursor of a control agent, wherein said control agent is capable of effecting a change in ionic strength and proton composition of said pH indicator composition when frozen to thereby cause, upon freezing, a shift in change in pH of said pH indicator composition from that due to the pH change of said buffer solution; and wherein said pH indicator has a pK value in said pH indicator composition and said control agent is in an effective amount to cause a change in said proton composition so that: (a) for a pH indicator composition which becomes more acidic on freezing, said proton composition is changed to a value less than that at said pK value; and (b) for a pH indicator composition which becomes more alkaline on freezing, said proton composition is changed to a value greater than that at said pK value.

Claim 52

Device according to claim 41 wherein said casing is comprised of a material that is substantially impermeable to moisture at temperatures between about +25° and -90° C.

Claim 53

Device according to claim 41 wherein said casing is a substantially moisture impermeable, flexible, elongated tube comprised of a thermoplastic material mounted on a substantially rigid frame for said tube.

Claim 54

Device according to claim 41 wherein said casing is an elongated tube.

Claim 55

Device according to claim 44 wherein said elongated tube is comprised of glass or plastic.

Claim 56

Device according to claim 41 for indicating temperatures within a preselected range, wherein said casing is comprised of a multiplicity of discrete chambers, each chamber containing said thermochromic composition, such that the change of color exhibited by the contents of each of said chambers occurs at a selected sub-freezing temperature that is different from the sub-freezing temperature at which the contents of any other of said chambers exhibits a color change.

Claim 57

Device according to claim 46 wherein each of said chambers is comprised of a thermoplastic material.

Claim 58

Device according to claim 47 wherein said casing is in the shape of an elongated tube.