Moisture sensor

• US 6,342,295 B1
• Filed: 12/22/1999
• Issued: 01/29/2002
• Est. Priority Date: 12/28/1998
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Kobayashi, Nobuo
• Primary Examiner(s): Copenheaver, Blaine
• Assistant Examiner(s): Paulraj, Christopher
• Application Number:
  US09/468,913
• Time in Patent Office: 769 Days
• Field of Search: 338/34, 338/35, 428/323, 428/328, 428/423.1, 428/425.9, 428/479.4, 428/480, 428/913, 73/290.1, 733/350.2, 733/350.3, 733/350.4, 733/350.5
• US Class Current: 428/323
• CPC Class Codes: G01N 27/121 for determining moisture content, e.g. humidity, of the fluid moisture content of the tested material G01N27/048
• CPC Class Codes: G01N 27/126 comprising organic polymers
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/31609 Particulate metal or metal compound-containing

Abstract

A moisture sensor includes a moisture-sensitive film between a pair of electrodes having conductive particles dispersed in a hygroscopic polymer. The hygroscopic polymer is a polymer comprising a polyether amine, an epoxy compound, and optionally a water-soluble nylon. Alternatively, the hygroscopic polymer is a polyether ester amide and optionally a water-soluble nylon. The sensor enables DC measurement, can detect a humidity in the range of RH 60% to 100%, and ensures high performance stability against repetitive operations.

Claims

1. A moisture sensor comprising a pair of electrodes and a moisture-sensitive film disposed therebetween having conductive particles dispersed in a hygroscopic polymer composition comprising a polyether amine having at least two amino groups, and an epoxy compound having at least two epoxy groups and an ether bond.

2. The moisture sensor of claim 1 wherein said polyether amine has a polyether skeleton consisting of propylene oxide, ethylene oxide or a mixture thereof.

3. The moisture sensor of claim 1 wherein said polyether amine is terminated with two or three primary amino groups.

4. The moisture sensor of claim 1 wherein said polyether amine has a molecular weight of 100 to 5,000.

5. The moisture sensor of claim 1 wherein said epoxy compound is of the following formula (1):

wherein A is a di- to tetra-valent aliphatic saturated hydrocarbon group, aliphatic ether group or heterocyclic group, and k is an integer of 2 to 4.

6. The moisture sensor of claim 1 wherein said hygroscopic polymer has an amine equivalent and an epoxy equivalent which are in a ratio of from 1:

1 to 1;

4.

7. The moisture sensor of claim 1 wherein said hygroscopic polymer composition additionally comprises a water-soluble nylon.

8. The moisture sensor of claim 7 wherein said water-soluble nylon has an ether structure.

9. The moisture sensor of claim 7 wherein said water-soluble nylon comprises units of the following formula (7) or units of the following formula (8) or both:

wherein R₁ is an alkyl group of 2 to 4 carbon atoms.

10. The moisture sensor of claim 7 wherein the content of the water-soluble nylon is 0.1 to 50% by weight based on the weight of said polyether amine and said epoxy compound combined.

11. The moisture sensor of claim 1 wherein said conductive particles comprise carbon black having a specific surface area of 30 to 300 m²/g.

12. The moisture sensor of claim 1 which can detect a humidity in the range of RH 60% to RH 100%.

13. A moisture sensor comprising a pair of electrodes and a moisture-sensitive film disposed therebetween having conductive particles dispersed in a hygroscopic polymer composition comprising a polyether ester amide.

14. The moisture sensor of claim 13 wherein said polyether ester amide is of the following formula (2):

wherein R is an alkyl group of 2 to 12 carbon atoms, m is an integer of 6 to 12, n is an integer of 1 to 4, p is an integer of 1 to 70, q is an integer of 5 to 200, and r is an integer of at least 3.

15. The moisture sensor of claim 14 wherein in formula (2), m is equal to 11 and n is equal to 2.

16. The moisture sensor of claim 13 wherein said hygroscopic polymer composition additionally comprises a water-soluble nylon, and an epoxy compound having at least two epoxy groups.

17. The moisture sensor of claim 13 wherein said hygroscopic polymer composition is a mixture of the polyether ester amide and a water-soluble nylon.

18. The moisture sensor of claim 16 or 17 wherein said water-soluble nylon has an ether structure.

19. The moisture sensor of claim 16 or 17 wherein said water-soluble nylon comprises units of the following formula (7) or units of the following formula (8) or both:

wherein R₁ is an alkyl group of 2 to 4 carbon atoms.

20. The moisture sensor of claim 16 or 17 wherein the content of the water-soluble nylon is 0.1 to 50% by weight based on the weight of said polyether ester amide.