Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-01-18
2004-02-10
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S555000, C524S110000, C524S358000
Reexamination Certificate
active
06689826
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to cyanoacrylate compositions and methods of detecting cure of the cyanoacrylate compositions using luminescent dyes.
Brief Description of Related Technology
Cyanoacrylate adhesives are known for their fast adhesion and ability to bond a wide variety of substrates. They are marketed as “super glue” type adhesives. They are useful as an all-purpose adhesive since they are a single component adhesive, very economical as only a small amount will do, and generally do not require any equipment to effectuate curing. However, in some instances there is a tendency for adhesion failure to occur, particularly when the end user does not know when the adhesive has fully cured.
Fluorescing agents have previously been incorporated into curable compositions to provide a non-destructive method of inspection such as identifying cured films, and ensuring proper coating of the composition on an article. These fluorescing agents are typically used in UV/VIS (ultraviolet/visible) curable compositions. Most cyanoacrylate compositions do not require actinic radiation to effect cure.
Other dyes have been incorporated into polymeric compositions generally to color the composition rather than as a cure indicator as there is no color change associated therewith.
U.S. Pat. No. 6,017,983 (Gilleo) appears to refer to the use of a diazo dye that is believed to form a salt or complex with acid anhydrides, which acts as a color indicator for particular anhydride/epoxy resin thermoset adhesives. The resulting salt or complex is reported to produce a chromophoric shift in the dye which is indicative of the amount of acid anhydride present, and hence, the degree of cure. As the epoxy resin cures, the amount of acid anhydride diminishes thus producing a color change. This system appears to be limited to acid anhydride hardeners used to cure epoxy resins.
U.S. Pat. No. 5,302,627 (Field) reports the addition of a dye to UV radiation curable silicone-containing polymeric compositions that contain photoinitiators. Upon exposure to UV radiation, the silicone-containing polymeric composition undergoes a color change indicating that the composition has cured. The dyes used include an anthraquinone dye having a Color Index Solvent Blue 104, 1-hydroxy-4-[(methylphenyl)amino]-9,10-anthracenedione, and an azo dye mixture of azo benzene azo naphthyl benzene amine alkyl/alkoxy derivatives having a Color Index Solvent Blue 99, and azo benzene azo naphthyl benzene amine alkyl derivatives having a Color Index Solvent Red 166. Large amounts of the dye, greater than 30 ppm based on the weight of the composition, are reported to inhibit cure.
Notwithstanding the state of the technology, it would be desirable to provide a cyanoacrylate composition that has a built in method of detection or is “self-indicating” when cure has been achieved.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is directed to a cyanoacrylate composition having a cure indicator. The composition includes a cyanoacrylate component; and a dye dissolved in the cyanoacrylate component to provide a solution having a first color, where upon curing of the cyanoacrylate component, the resultant cured composition has a second color.
In a second aspect, the present invention is directed to a cyanoacrylate composition. The composition includes a cyanoacrylate component; a member selected from the group consisting of accelerators, fillers, opacifiers, thickeners, viscosity modifiers, inhibitors, thixotropy conferring agents, and combinations thereof; and a fluorescent dye in an amount of about 100 to 400 ppm based on an amount of the cyanoacrylate component which imparts a first non-fluorescent color to the cyanoacrylate component. The fluorescent dye is selected from fluorescein, dibromofluorescein, diiodofluorescein, tetrabromofluorescein, tetrabromotetrachlorofluorescein, and combinations thereof. Upon curing, the cured composition exhibits a fluorescent color.
In a third aspect, the present invention is directed to a method of making a cyanoacrylate composition having a cure indicator. The method includes the steps of providing a cyanoacrylate component; providing a dye; substantially dissolving the dye in the cyanoacrylate component to form a cyanoacrylate component having a first color; and curing the cyanoacrylate component to form a cured composition having a second color.
In a fourth aspect, the present invention is directed to a method of curing a polymeric composition. This method includes the steps of providing a cyanoacrylate component; providing a cure indicator; dissolving the cure indicator in the cyanoacrylate component to form a visually color-less solution; exposing the visually color-less solution to conditions appropriate to effect cure; and detecting fluorescence of the cure indicator as an indication of substantial cure.
In a fifth aspect, the present invention is directed to a method of detecting cure of an adhesive. The detection method includes the steps of providing a first article and a second article; providing, on a surface of the first article, an adhesive; contacting a surface of the second article to the surface of the first article having the adhesive thereon; exposing the first and second articles to conditions appropriate to effect cure; and detecting fluorescence of the cured adhesive. The adhesive, in its uncured state, includes a visually colorless solution of a cyanoacrylate component and a dye.
Preferably, in the present invention, the fluorescent dye is selected from fluorescein, dibromofluorescein, diiodofluorescein, tetrabromofluorescein, and tetrabromotetrachlorofluorescein. Preferably, the dyes are present in an amount sufficient to impart observable color when the composition is cured, preferably about 50 to about 1000 ppm, and more preferably, about 100 to about 400 ppm based on an amount of the cyanoacrylate monomer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a cyanoacrylate composition, having a cure indicator. That is, the cyanoacrylate composition is “self-indicating” with respect to its ability to allow the end user to visually inspect the composition to determine whether, and the extent to which, cure has occurred. The composition includes a cyanoacrylate component, and a dye dissolved in the cyanoacrylate component. The cyanoacrylate composition has an initial color, oftentimes colorless or substantially so to the naked eye, and when cured, the cured cyanoacrylate composition has a different or second color including fluorescence. Observation of the different or second color is indicative that cure has occurred and the extent of the color change can be used to determine the degree of cure that has occurred. The cured cyanoacrylate composition undergoes a color change and glows, i.e., luminesces, under black light, thereby confirming cure of the cyanoacrylate composition.
The cyanoacrylate component useful in the present invention includes cyanoacrylate monomers, such as those represented by the structure:
wherein R
1
is selected from C
1-16
alkyl, alkoxyalkyl, cycloalkyl, alkenyl, aralkyl, aryl, allyl and haloalkyl groups. Preferably, the cyanoacrylate monomer is selected from methyl cyanoacrylate, ethyl-2-cyanoacrylate, propyl cyanoacrylates, butyl cyanoacrylates (such as n-butyl-2-cyanoacrylate), octyl cyanoacrylates, allyl cyanoacrylate, &bgr;-methoxyethyl cyanoacrylate and combinations thereof. A particularly desirable cyanoacrylate monomer is ethyl-2-cyanoacrylate. The cyanoacrylate component should be included in the compositions in an amount within the range of about 50 wt to about 99.8 wt. %, preferably about 90 wt. % to about 98 wt. %.
The compositions of the present invention may also contain additives such as stabilizers, accelerators, fillers, opacifiers, thickeners, viscosity modifiers, inhibitors, thixotrophy conferring agents, and combinations thereof. These additives are known to those of skill in the art. The cyanoacrylate monomers are preferably stabilized using ac
Bauman Steven C.
Henkel Loctite Corporation
Sanders Kriellion
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