Time-temperature indicator comprising a side chain crystalline polymer

Patent metadata

Field	Value
Publication number	US-9546911-B2
Application number	US-201414167394-A
Country	US
Kind code	B2
Filing date	Jan 29, 2014
Priority date	Sep 29, 2010
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

A temperature-activatable time-temperature indicator that can be used to monitor the historical exposure of a host product to ambient temperatures includes an optically readable, thermally sensitive indicator element. The indicator element can be inactive below a base temperature and is intrinsically thermally responsive at or above an activation temperature which is equal to or greater than the base temperature. The indicator can record cumulative ambient temperature exposure above the activation temperature irreversibly with respect to time. The indicator element can include a synthetic polymeric material, and optionally, a dye. A side-chain crystallizable polymer such as poly(hexadecylmethacrylate), that is solid below the base temperature and is a viscous liquid above the activation temperature can be employed. Intense indicator element colors can be obtained using an appropriate dye or dyes. Various structural configurations of indicator are described and illustrated.

First claim

The invention claimed is:

1. A temperature-activatable time-temperature indicator comprising an optically readable, thermally sensitive indicator element, the indicator element being inactive below a base temperature and being thermally responsive at or above an activation temperature to record irreversibly with respect to time cumulative ambient temperature exposure above the activation temperature, the activation temperature being equal to or greater than the base temperature, the time-temperature indicator being configured to be associated with a host product to monitor exposure of the host product to ambient temperatures, wherein the indicator element comprises an indicator material comprising a synthetic polymer having a molecular weight of at least about 1,000 Da.

2. The temperature indicator of claim 1 , wherein the indicator material is a solid at or below the base temperature and is a viscous liquid at or above the activation temperature.

3. The temperature indicator of claim 2 , wherein the indicator element comprises a transport member supporting the indicator material and the indicator material displacement is a displacement with respect to the transport member.

4. The temperature indicator of claim 3 , wherein the transport member extends to an optical reading location and the indicator material displacement comprises optically detectable displacement of the indicator material through the transport member.

5. The temperature indicator of claim 4 , wherein the indicator material flows in a first direction toward a viewing surface of the indicator, and the indicator comprises a reservoir of the indicator material and a mask to conceal the reservoir in the optical reading direction, the transport member extending between the reservoir and the viewing surface.

6. The temperature indicator of claim 3 , wherein the transport member is absorbent and the indicator material is absorbable by the transport member.

7. The temperature indicator of claim 6 , wherein the indicator element comprises a ring of indicator material, the transport member comprises a disc-shaped wick, the ring of indicator material extending around the perimeter of the disc-shaped wick, at or near the outer peripheral edge of wick, and the time-temperature indicator comprises a viewing window disposed approximately centrally of the ring of indicator material wherein the indicator material, when liquid, can flow inwardly of the ring towards the viewing window.

8. The temperature indicator of claim 1 , wherein the indicator material comprises a transport material and an optically distinctive material.

9. The temperature indicator of claim 8 , wherein the optically distinctive material comprises a colorant, a dye, a pigment, a fluorescent material, an optical phase modifying material, a liquid crystal, an infrared-reflecting material, an ultraviolet-reflecting material, an infrared-absorbing material, an ultraviolet-absorbing material, an optically refractive material, an optically diffractive material, a holographic material, or a combination thereof.

10. The temperature indicator of claim 9 , wherein the indicator material viscosity is at least about 100 cP and not greater than about 100,000 cP.

11. The temperature indicator of claim 10 , wherein the indicator material has a viscosity activation energy above 10 kcal/mol.

12. The temperature indicator of claim 11 , wherein the synthetic polymeric material has a molecular weight in a range of about 2,000 Da to about 300,000 Da.

13. The temperature indicator of claim 12 , wherein the synthetic polymeric material has a melting temperature range of not more than about 30° C.

14. The temperature indicator of claim 8 , wherein the synthetic polymeric material has side chain crystallinity.

15. The temperature indicator of claim 14 , wherein the synthetic polymeric material comprises a methacrylate polymer, a methacrylate copolymer, an acrylate polymer, or an acrylate copolymer of a monomer unit comprising a crystallizable linear aliphatic side chain having at least 10 carbon atoms.

16. The temperature indicator of claim 14 , wherein the synthetic polymeric material is a poly(alkylmethacrylate), a poly(tetradecylacrylate), a poly(hexadecylmethacrylate), a poly(octadecylmethacrylate), a poly(alkylacrylate), a poly(hexadecylacrylate), poly(dodecylacrylate), a copolymer of hexadecylacrylate and octadecylmethacrylate, a poly(hexyl-co-dodecylacrylate), a copolymer of tetradecylacrylate and octadecylacrylate, a copolymer of hexadecylmethacrylate and octadecylmethacrylate, or a copolymer of tetradecylacrylate and hexadecylacrylate.

17. The temperature indicator of claim 14 , wherein the synthetic polymeric material comprises a polymer including a chain of interconnected monomer units each monomer unit having the formula:

wherein:
R 1 is hydrogen, or a substituted or unsubstituted hydrocarbon group having up to six carbon atoms;
R 2 is a spacer unit and is optional;
R 3 comprises a crystallizable group; and
R 2 and R 3 together constitute a side chain of the monomer unit.

18. The temperature indicator of claim 17 , wherein the spacer unit R 2 , if present, is O, CH 2 , (CO), O(CO), or NR 4 wherein R 4 is hydrogen, a C 1-6 ester group, a C 1-6 amide group, a C 1-6 hydrocarbon group, or a C 1-6 ether group.

19. The temperature indicator of claim 18 , wherein R 3 is a crystallizable group, and is a C 4-30 aliphatic group; a C 6-30 aromatic group; a linear aliphatic group having at least 10 carbon atoms; a combination of at least one aliphatic group and at least one aromatic group, the combination having from 7 carbon atoms to about 30 carbon atoms; a C 14 -C 22 acrylate; a C 14 -C 22 methacrylate; an acrylamide; a methacrylamide; a vinyl ether; a vinyl ester; a fluorinated aliphatic group having at least 6 carbon atoms; or a p-alkyl styrene group wherein the alkyl group has from about 8 carbon atoms to about 24 carbon atoms.

20. The temperature indicator of claim 19 , wherein the backbone carbon atoms are connected directly to each other, or one or more pairs of adjacent backbone carbon atoms are interconnected through an intervening oxygen atom, or through an intervening carbon atom.

21. The temperature indicator of claim 1 , wherein the activation temperature is in a range of from about −10° C. to about 60° C.

22. The temperature indicator of claim 21 , wherein the activation temperature is in a range of from about 10° C. to about 25° C.

23. The temperature indicator of claim 21 , wherein the activation temperature exceeds the base temperature by a temperature in a range of from about 1° C. to about 50° C.

24. The temperature indicator of claim 23 , wherein the base temperature is in a range of from about 0° C. to about 30° C.

25. The time-temperature indicator of claim 1 , wherein the indicator material is hydrophobic.

26. The time-temperature indicator of claim 1 , wherein the viscosity of the indicator material decreases with increasing temperature throughout a temperature range of from 35° C. to 60° C.

Assignees

• Temptime Corp

Inventors

• Huffman Brian S
• Smith Dawn E
• Lentz Carl M

Classifications

• G01K1/02 Primary

  Means for indicating or recording specially adapted for thermometers · CPC title

• G01K11/06

  using melting, freezing, or softening · CPC title

• G01K3/04 Primary

  in respect of time · CPC title