Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1998-10-26
2001-06-19
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C008S568000, C252S070000, C252S079000, C252S301500, C252S964000
Reexamination Certificate
active
06248890
ABSTRACT:
BACKGROUND OF THE INVENTION
Fluorescent tracers have been employed to detect leaks in fluid systems such as refrigeration systems, which utilize hydrocarbon refrigerants and lubricants. The site of a leak the refrigerants and refrigerant lubricants which contain the fluorescent tracer escape; they are visible when illuminated with light having wavelengths in the range of 300 to 450 nanometers.
The refrigerant are typically hydrofluorocarbons, hydrochlorofluorocarbons, and mixtures thereof. Common refrigeration lubricants are polyalkylene glycols, polyolesters, mineral oil, polyalphaolefins, and synthetic hydrocarbons.
Traditionally, the typical fluorescent dyes that have been used in fluroescent tracers for refrigeration systems are rhodamine B, Fluorescent Yellow 133SC, auramine B and certain conventional naphthalimide dyes. Some of these dyes are unstable at high temperatures and may be converted to tars, which plug the system. Other dyes have low solubility in the refrigerants and refrigerant lubricants which results in aggregates of precipitated dye circulating through the system. Some of these dyes, while showing good initial solubility in the refrigerants and refrigerant lubricants, tend to be unstable over storage and operation time thus resulting in aggregates of precipitated dye circulating through the system. These aggregates may clog the refrigeration system.
Conventional naphthalimide dyes are fluorescent in polyalkylene glycols, and other polar lubricants. However, naphthalimide dyes have limited solubility in the polar lubricants, and very low solubility in non-polar lubricants such as mineral oil, synthetic oil, and motor oil. The fluorescence of the naphthalimide dyes is often severely limited by the poor solubility. Furthermore, the naphthalimide dyes require long mixing times and/or elevated temperatures to dissolve the dye into the lubricant. Dissolution at elevated temperatures results in solutions that are supersaturated at room temperature. These supersaturated solutions tend to precipitate dye either in the lubricant during shelf storage, or in the refrigerant system during long term operation. The presence of precipitated dye tends to decrease the fluorescence of the solution, thus reducing its effectiveness, and also tends to clog the refrigerant system.
A fluorescent dye that is soluble in refrigerants and refrigerant lubricants, chemically stable at high temperatures and provides improved shelf stability is desirable.
SUMMARY OF THE INVENTION
The present invention provides a highly fluorescent naphthalimide diester dye that is miscible or soluble in a variety of polar and non-polar organic liquids such as, for example, mineral oil, polyalkylene glycols, polyolesters, motor oil, gear oil, synthetic oils, and polyalphaolefins. The fluorescent naphthalimide diester is useful as a tracer to detect leaks within a fluid systems such as, for example, refrigerant systems, transmission systems, and hydraulic systems. The fluorescent naphthalimide diester dye is stable during storage and operation time, thus eliminating the dye precipitation problem associated with conventional naphthalimide dye tracers. The fluorescent naphthalimide diester dye is stable at high temperatures. Preferably, the fluorescent naphthalimide diester dye is a liquid at room temperature.
The fluorescent naphthalimide diester dye is comprised of a chromophore having the following structure:
wherein:
Z and Z′ are esters having a saturated or unsaturated, linear or branched, hydrocarbon chain attached thereto, having from 8 to 24 carbon atoms in length, preferably from 12 to 22 carbon atoms in length, most preferably from 16 to 20 carbon atoms in length, and from 1 to 4 double bonds, most preferably 2 to 3 double bonds;
R and R′ are saturated, linear hydrocarbon chains, having from 2 to 10 carbon atoms in length, preferably from 2 to 8 carbon atoms in length, most preferably from 3 carbon atoms in length. R is attached to Z by the ester linkage, and R′ is attached to Z′ by the ester linkage.
Z and Z′ are preferably fatty acid esters. Preferred linear fatty acid esters are, for example the esters of: decanoic acid, nonanoic acid, octanoic acid, citronellic acid, undecanoic acid, lauric acid, tridecanoic acid, myristoleic acid, myristic acid, pentadecanoic acid, palmitoleic acid, palmitic acid, heptadecanoic acid, linolenic acid, linoleic acid, oleic acid, nonadecanoic acid, cis-11-eicosanoic acid, eicosanoic acid, 11, 14-eicosadienoic acid, erucic acid, docosanoic acid, and behenic acid. Preferred branched acids are, for example: isononanoic acid, neoheptanoic acid, neononanoic acid, neodecanoic acid, iso-octanoic acid, neo octanoic acid, and isostearic acid.
The invention also relates to methods of making and using the fluorescent naphthalimide diester dye, as well as to fluorescent naphthalimide diester tracers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a fluorescent naphthalimide diester dye that is miscible in organic compounds used in fluid systems. As used herein “fluid” means liquid and gas. Fluid systems are closed systems which contain a fluid; examples are refrigerant systems, hydraulic systems, transmission systems, heating systems, ventilating systems, and systems which utilize petrochemical oils, and which utilize hydrocarbon lubricant.
The fluorescent naphthalimide diester dye is soluble or miscible in a variety of polar and non-polar organic liquids such as refrigerant lubricants and refrigerants, mineral oil, polyalkylene glycols, coolants, polyolesters, motor oil, gear oil, transmission fluid, synthetic oils, and polyalphaolefins. The fluorescent naphthalimide diester dye is useful to detect leaks within a fluid system. The fluorescent naphthalimide diester dye is highly fluorescent, possesses excellent solution stability during storage and operation, and is stable at high temperatures.
The Fluorescent Naphthalimide Diester Chromophore
The fluorescent naphthalimide diester chromophore has the following structure:
wherein:
Z and Z′ are esters having a saturated or unsaturated, linear or branched, hydrocarbon chain attached thereto, having from 8 to 24 carbon atoms in length, preferably from 12-22 carbon atoms in length, most preferably from 16 to 20 carbon atoms in length, and from 1 to 4 double bonds, most preferably 2 to 3 double bonds;
R and R′ are saturated, linear hydrocarbon chains, having from 2 to 10 carbon atoms in length, preferably from 2 to 8 carbon atoms in length, most preferably from 3 carbon atoms in length. R is attached to Z by the ester linkage, and R′ is attached to Z′ by the ester linkage.
Z and Z′ are preferably esters of fatty acids. Preferred linear fatty acid esters are, for example esters of: decanoic acid, nonanoic acid, octanoic acid, citronellic acid, undecanoic acid, lauric acid, tridecanoic acid, myristoleic acid, myristic acid, pentadecanoic acid, palmitoleic acid, palmitic acid, heptadecanoic acid, linolenic acid, linoleic acid, oleic acid, nonadecanoic acid, cis-11-eicosanoic acid, eicosanoic acid, 11, 14-eicosadienoic acid, erucic acid, docosanoic acid, and behenic acid. Preferred branched acids are, for example: isononanoic acid, neoheptanoic acid, neononanoic acid, neodecanoic acid, iso-octanoic acid, neo octanoic acid, and isostearic acid.
The fluorescent naphthalimide diester chromophore has a number average molecular weight of from about 570 to about 2000, preferably from about 600 to about 1500, more preferably from about 700 to about 1100. At molecular weights above about 2000, the fluorescent naphthalimide diester chromophore looses solubility, particularly in non-polar materials such as mineral oil. At molecular weights below about 570, the fluorescent naphthalimide diester chromophore tends to crystallize and loose solubility.
The Fluorescent Naphthalimide Diester Dye
The fluorescent naphthalimide diester dye is comprised of at least one fluorescent naphthalimide diester chromophore. Where a single chromophore is used it is preferred that Z
Dipietro Thomas C.
Likavec Wayne R.
Calfee Halter & Griswold LLP
Day-Glo Color Corp.
Higel Floyd D.
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