Reversible detector for gaseous carbon dioxide

• US 6,677,159 B1
• Filed: 12/02/1998
• Issued: 01/13/2004
• Est. Priority Date: 06/06/1990
• Status: Expired due to Fees

• Current Assignee: Southwest Research Institute
• Original Assignee: Southwest Research Institute
• Inventors: Mallow, William A.
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US09/735,292
• Time in Patent Office: 1,868 Days
• Field of Search: 436/169, 436/133, 436/167, 128/207.14, 422/57, 422/61
• US Class Current: 436/133
• CPC Class Codes: G01N 31/22 using chemical indicators G01N31/02 takes precedence
• CPC Class Codes: G01N 31/223 for investigating presence of specific gases or aerosols G01N31/221, G01N31/222 take precedence; actuation of fire alarm by presence of smoke or gases G08B17/10
• CPC Class Codes: G01N 33/004 CO or CO2
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y10T 436/204998 Inorganic carbon compounds

Abstract

An apparatus and method for visually and continuously monitoring gaseous concentrations of electrophiles such as carbon dioxide. A coating composition comprising an organic binder, filler/pigment, an activator, and carbon dioxide sensitive color indicator interacts with a primed substrate to which it is applied for support. The coated primed substrate may then be used for estimation of carbon dioxide concentration by the detection of a substantially instantaneous and reversible color change of the coated primed substrate.

Claims

1. A reversible carbon dioxide detector comprising:

a primed substrate comprising a primer comprising a first amount of a first plurality of dyes comprising pH sensitive color indicators and an amount of moisture effective to permit said pH sensitive color indicators to interact with carbon dioxide without substantial migration or flow of said first plurality of dyes on said substrate;

a coating over at least a portion of said substrate, said coating comprising a second amount of an effective activator, a third amount of a water insoluble organic binder, and a fourth amount of a second plurality of dyes comprising carbon dioxide sensitive color indicators;

wherein said water insoluble binder facilitates permeation of carbon dioxide from a surrounding medium through said coating into reversible contact with a combination of said first plurality of dyes and said second plurality of dyes;

wherein said first, second, third, and fourth amounts are effective to permit said combination of said first plurality of dyes and said second plurality of dyes to interact with said carbon dioxide to substantially instantaneously produce incremental reversible changes in color comprising a reproducible array of separate colors in which said separate colors correlate to separate given concentrations of carbon dioxide in a surrounding medium.

2. The detector of claim 1 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

3. The detector of claim 1 wherein said water insoluble organic binder is ethylcellulose.

4. The detector of claim 3 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

5. The detector of claim 1 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

6. The detector of claim 5 further comprising a persistent humectant effective to maintain components in said coating in a form selected from the group consisting of ionized form and ionizable form.

7. The detector of claim 6 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

8. The detector of claim 1 wherein said first plurality of dyes comprise N-methyl-4-(phenylazo)benzamine.

9. The detector of claim 8 further comprising a persistent humectant effective to maintain components in said coating in a form selected from the group consisting of ionized form and ionizable form.

10. The detector of claim 8 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

11. The detector of claim 10 further comprising a persistent humectant effective to maintain components in said coating in a form selected from the group consisting of ionized form and ionizable form.

12. The detector of claim 10 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

13. The detector of claim 8 wherein said water insoluble organic binder is ethylcellulose.

14. The detector of claim 13 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

15. The detector of claim 14 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

16. The detector of claim 13 further comprising a persistent humectant effective to maintain components in said coating in a form selected from the group consisting of ionized form and ionizable form.

17. The detector of claim 16 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

18. A reversible carbon dioxide detector comprising:

a primed substrate comprising a primer comprising a first amount of a first plurality of dyes comprising about 50% by weight N-methyl-4-(phenylazo)benzenamine and

approximately equal parts by weight of dyes selected from the group consisting of o-cresolsulfonaphthalein;

thymolsulfonaphthalein;

p-benzenesulfonic-azo-dimethylaniline;

o-carboxybenzene-azo-dimethylaniline;

amino-dimethyl amino-toluphenazonium chloride;

benzene-azo-dimethyl-amine;

2,4,6-trinitrophenyl-methyl-nitro amine;

p-nitro benzene-azo-salicylic acid; and

thymolphthalein, said primer further comprising an amount of moisture effective to permit said first plurality of dyes to interact with carbon dioxide without substantial migration or flow of said first plurality of dyes on said substrate;

a coating over at least a portion of said substrate, said coating comprising a second amount of an effective activator, a third amount of a water insoluble organic binder, and a fourth amount of a second plurality of dyes comprising carbon dioxide sensitive color indicators;

wherein said water insoluble binder facilitates permeation of carbon dioxide from a surrounding medium through said coating into reversible contact with a combination of said first plurality of dyes and said second plurality of dyes;

wherein said first, second, third, and fourth amounts are effective to permit said combination of said first plurality of dyes and said second plurality of dyes to interact with said carbon dioxide to substantially instantaneously produce incremental reversible changes in color comprising a reproducible array of separate colors in which said separate colors correlate to separate given concentrations of carbon dioxide in a surrounding medium.

19. The detector of claim 18 wherein said second dye is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

20. The detector of claim 19 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

21. The detector of claim 18 wherein said water insoluble organic binder is ethylcellulose.

22. The detector of claim 21 wherein said second dye is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

23. The detector of claim 21 wherein said effective activator is an ether amine selected from the group consisting of dodecyl ether amine and tetradecyl ether amine.

24. A reversible carbon dioxide detector comprising:

a primed substrate comprising a primer comprising a first amount of a first plurality of dyes comprising pH sensitive color indicators and an amount of moisture effective to permit said pH sensitive color indicators to interact with carbon dioxide without substantial migration or flow of said first plurality of dyes on said substrate;

a coating over at least a portion of said substrate, said coating comprising;

a second amount of an effective activator;

a third amount of a water insoluble organic binder,

a fourth amount of a second plurality of dyes comprising carbon dioxide sensitive color indicators; and

,

a fifth amount of a persistant humectant effective to maintain components in said coating in a form selected from the group consisting of ionized form and ionizable form;

wherein said water insoluble binder facilitates permeation of carbon dioxide from a surrounding medium through said coating into reversible contact with a combination of said first plurality of dyes and said second plurality of dyes;

wherein said first, second, third, fourth, and fifth amounts are effective to permit said combination of said first plurality of dyes and said second plurality of dyes to interact with said carbon dioxide to substantially instantaneously produce incremental reversible changes in color comprising a reproducible array of separate colors in which said separate colors correlate to separate given concentrations of carbon dioxide in a surrounding medium.

25. The detector of claim 24 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

26. The detector of claim 24 wherein said water insoluble organic binder is ethylcellulose.

27. The detector of claim 26 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

28. The detector of claim 24 wherein said first plurality of dyes comprise about 50% by weight of said N-methyl-4-(phenylazo)benzenamine;

and approximately equal parts by weight of dyes selected from the group consisting of o-cresolsulfonephthalein;

thymolsulfonaphthalein;

p-benzenesulfonic-azo-dimethylaniline;

o-carboxybenzene-azo-dimethylaniline;

amino-dimethyl amino-toluphenazonium chloride;

benzene-azo-dimethyl-amine;

2,4,6-trinitrophenyl-methyl-nitro amine;

p-nitro benzene-azo-salicylic acid; and

thymolphthalein.

29. The detector of claim 28 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.

30. The detector of claim 28 wherein said water insoluble organic binder is ethylcellulose.

31. The detector of claim 30 wherein said second plurality of dyes is a combination of bromothymol blue and bromothymol purple at a ratio of about 2:

1.