U.S. patent application number 12/377966 was filed with the patent office on 2009-12-24 for color change cyanoacrylate adhesives.
Invention is credited to Larry A. Lien, Kurt C. Melancon, Scott D. Pearson, George V.D. Tiers.
Application Number | 20090317561 12/377966 |
Document ID | / |
Family ID | 38982666 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090317561 |
Kind Code |
A1 |
Melancon; Kurt C. ; et
al. |
December 24, 2009 |
COLOR CHANGE CYANOACRYLATE ADHESIVES
Abstract
A cyanoacrylate-based adhesive composition is disclosed. The
cyanoacrylate-based adhesive composition includes a cyanoacrylate
monomer, and a bleachable dye including a Michler's hydrol cation
or derivatized Michler's hydrol cation, paired with a
non-nucleophilic anion that provides a stable color to the
cyanoacrylate-based adhesive.
Inventors: |
Melancon; Kurt C.; (White
Bear Lake, MN) ; Tiers; George V.D.; (St. Paul,
MN) ; Lien; Larry A.; (Woodbury, MN) ;
Pearson; Scott D.; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
38982666 |
Appl. No.: |
12/377966 |
Filed: |
September 6, 2007 |
PCT Filed: |
September 6, 2007 |
PCT NO: |
PCT/US07/77679 |
371 Date: |
February 18, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60824970 |
Sep 8, 2006 |
|
|
|
Current U.S.
Class: |
427/516 ;
252/408.1; 427/207.1 |
Current CPC
Class: |
C09B 69/06 20130101;
C09J 4/00 20130101; A61L 24/001 20130101 |
Class at
Publication: |
427/516 ;
252/408.1; 427/207.1 |
International
Class: |
B05D 5/10 20060101
B05D005/10; G01N 31/22 20060101 G01N031/22 |
Claims
1-21. (canceled)
22. A cyanoacrylate-based adhesive composition comprising: a
cyanoacrylate monomer; and a bleachable dye comprising Michler's
hydrol cation, or derivatized Michler's hydrol cation, paired with
a non-nucleophilic anion that provides a stable color to the
cyanoacrylate-based adhesive.
23. A cyanoacrylate-based adhesive composition according to claim
22 wherein the bleachable dye is Michler's hydrol cation.
24. A cyanoacrylate-based adhesive composition according to claim
22 wherein the non-nucleophilic anion is derived from a carbon-acid
having a strength ratio value greater than 0.1 when measured in
sulfolane solvent and using 4-methoxy-2-nitroaniline indicator.
25. A cyanoacrylate-based adhesive composition according to claim
22 wherein the non-nucleophilic anion is derived from a
non-carbon-acid having a strength ratio value greater than 0.2 when
measured in sulfolane solvent and using 4-chloro-2-nitroaniline
indicator.
26. A cyanoacrylate-based adhesive composition according to claim
22 wherein the non-nucleophilic anion is derived from boron
trifluoride methanol, trifluoromethanesulfonic acid, methide acid,
imide acid, ethylimide acid, boron trifluoride acetic acid, or
mixtures thereof.
27. A cyanoacrylate-based adhesive composition according to claim
22 wherein the Michler's hydrol cation or derivatized Michler's
hydrol cation is present in the cyanoacrylate-based adhesive in at
least 1 ppm and the non-nucleophilic anion is present in the
cyanoacrylate-based adhesive at a non-nucleophilic anion/dye mol
ratio of 1 to 5.
28. A cyanoacrylate-based adhesive composition according to claim
22 further comprising a colorant.
29. A method comprising: combining a cyanoacrylate monomer with a
bleachable dye comprising a Michler's hydrol cation, or derivatized
Michler's hydrol cation, paired with a non-nucleophilic anion to
form a dye pair, the dye pair having a stable color, the
cyanoacrylate monomer and dye pair forming a cyanoacrylate-based
adhesive composition.
30. A method according to claim 29 further comprising curing the
cyanoacrylate-based adhesive composition to form a colorless or
light-colored cured cyanoacrylate-based adhesive composition.
31. A method according to claim 29 further comprising combining a
colorant with the cyanoacrylate monomer, and dye pair to provide a
stable altered color to the cyanoacrylate-based adhesive
composition.
32. A method according to claim 31 further comprising curing the
cyanoacrylate-based adhesive composition to form a cured
cyanoacrylate-based adhesive composition having a second color
being different than the stable altered color and stable color.
33. A method according to claim 29 further comprising comparing the
color of the cyanoacrylate-based adhesive composition with a
reference color chart to determine a change in the
cyanoacrylate-based adhesive composition.
34. A method according to claim 29 further comprising disposing the
dye pair on a substrate before the combining step.
35. A method according to claim 29 further comprising disposing the
cyanoacrylate-based adhesive composition on a substrate and curing
the cyanoacrylate-based adhesive composition to a colorless or
light-colored cured cyanoacrylate-based adhesive composition.
36. A method according to claim 29 wherein the non-nucleophilic
anion is derived from a carbon-acid having a strength ratio value
greater than 0.1 when measured in sulfolane solvent and using
4-methoxy-2-nitroaniline indicator.
37. A method according to claim 29 wherein the non-nucleophilic
anion is derived from a non-carbon-acid having a strength ratio
value greater than 0.2 when measured in sulfolane solvent and using
4-chloro-2-nitroaniline indicator.
38. A method according to claim 29 wherein the non-nucleophilic
anion is derived from boron trifluoride methanol,
trifluoromethanesulfonic acid, methide acid, imide acid, ethylimide
acid, boron trifluoride acetic acid, or mixtures thereof.
39. A method according to claim 35 further comprising applying a
surface activator to the substrate prior to the disposing step.
40. A method according to claim 29 wherein the non-nucleophilic
anion is added to the Michler's hydrol cation or derivatized
Michler's hydrol cation in a mol ratio of non-nucleophilic
anion/dye range from 1 to 5 and the Michler's hydrol cation or
derivatized Michler's hydrol cation is present in the
cyanoacrylate-based adhesive composition of at least 1 ppm.
41. A method according to claim 29 further comprising waiting 14
days after the combining step and then visually confirming that the
color persists.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/824,970, filed on Sep. 8, 2006,
which is incorporated by reference herein.
BACKGROUND
[0002] The present disclosure relates generally to color change
cyanoacrylate adhesives and methods of using the same.
[0003] Cyanoacrylate adhesives, also known as "super glues," are a
versatile family of adhesives known to cure in seconds and provide
strong adhesion to a wide variety of surfaces. In spite of these
noteworthy attributes, several issues exist that limit the
popularity of this adhesive class with consumers.
[0004] One issue with cyanoacrylate adhesives is that these
adhesives bond instantly with skin. This issue is compounded by the
fact that cyanoacrylate adhesives are usually colorless and
difficult to observe when applied to a substrate. The inability of
the end-user to observe where the adhesive is (or is not), as well
as whether the adhesive is cured, often leads to unintended bonding
of skin to itself or other substrates.
[0005] Some cyanoacrylate adhesives are lightly tinted to provide
the end-user some ability to discriminate where the adhesive has
and has not been applied. However, these color tints are often so
light that a thinly applied adhesive layer is not perceptible.
Increasing the intensity of color tint so that the thinly applied
adhesive layer is perceptible, results in the cured adhesive
remaining visible on the completed project which may be
objectionable to the consumer.
SUMMARY
[0006] In an exemplary implementation, cyanoacrylate-based adhesive
compositions are disclosed that include a cyanoacrylate monomer and
a bleachable dye such as, for example, a Michler's hydrol cation or
Michler's hydrol cation derivative, that provides a stable color to
the uncured cyanoacrylate-based adhesive when paired with a
non-nucleophilic anion.
[0007] In another exemplary implementation, the method includes
combining an appropriately stabilized cyanoacrylate monomer with a
bleachable dye such as, for example, a Michler's hydrol cation or
derivatized Michler's hydrol cation paired with a non-nucleophilic
anion to form a dye pair. The stabilized cyanoacrylate monomer and
dye pair forms a cyanoacrylate-based adhesive composition. The dye
pair provides a stable color to the cyanoacrylate-based adhesive
composition.
[0008] These and other aspects of the adhesives according to the
subject invention will become readily apparent to those of ordinary
skill in the art from the following detailed description together
with the Examples.
DETAILED DESCRIPTION
[0009] Accordingly, the present disclosure is directed to color
change cyanoacrylate adhesives and methods of using the same. In
particular, the cyanoacrylate adhesive is colored in the uncured
state and becomes colorless or light-colored upon cure. In another
embodiment, the cyanoacrylate adhesive is a first color in the
uncured state and changes to a second color upon cure. These color
change adhesives can allow the end-user to easily observe the lay
of the adhesive as it is dispensed, and additionally, affords a
means of visually assessing uniformity of bond lines, as well as
determining where excess adhesive has been applied. These color
change adhesives can allow the end-user a means of indicating the
state-of-the-cure of the adhesive. In one example, if during the
gluing operation the adhesive is colored, it is not cured, and
accordingly, when said adhesive is fully cured, it is colorless or
lightly colored. Normally if exposed adhesive is colorless or
lightly colored it is sufficiently cured so that it may be touched
without fear of bonding to the skin. While the present invention is
not so limited, an appreciation of various aspects of the invention
will be gained through a discussion of the examples provided
below.
[0010] Unless otherwise indicated, all numbers expressing feature
sizes, amounts, and physical properties used in the specification
and claims are to be understood as being modified in all instances
by the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the following specification
and attached claims are approximations that all variation depending
upon the desirable properties sought to be obtained by those
skilled in the art utilizing the teachings disclosed herein.
[0011] The recitation of numerical ranges by endpoints includes all
numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2,
2.75, 3, 3.80, 4, and 5) and any range within that range.
[0012] As used in this specification and the appended claims, the
singular forms "a", "an", and "the" encompass embodiments having
plural referents, unless the content clearly dictates otherwise. As
used in this specification and the appended claims, the term "or"
is generally employed in its sense including "and/or" unless the
content clearly dictates otherwise.
[0013] The term "polymer" will be understood to include polymers,
copolymers (e.g., polymers formed using two or more different
monomers), oligomers and combinations thereof, as well as polymers,
oligomers, or copolymers that can be formed in a miscible
blend.
[0014] The term "alkyl" refers to a straight or branched chain
monovalent hydrocarbon radical optionally containing one or more
heteroatomic substitutions independently selected from S, O, Si, or
N. Alkyl groups generally include those with one to twenty atoms or
from one to ten atoms. Alkyl groups may be unsubstituted or
substituted with those substituents that do not interfere with the
specified function of the composition. Substituents include alkoxy,
hydroxy, mercapto, amino, alkyl substituted amino, or halo, for
example. Examples of "alkyl" as used herein include, but are not
limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl,
and isopropyl, and the like.
[0015] The phrase "stable color" will be understood to mean that a
color or color intensity that visually persists for at least 14
days as measured by the test method described in the Examples
herein. For example, a flowable cyanoacrylate adhesive is said to
possess a "stable color" if the color or color intensity (e.g.,
blue color) visually persists for at least 14 days in a sealed
container. In some embodiments, the samples remain usefully colored
for a period of at least six months, or at least 1 year, or at
least 2 years.
[0016] Unlike conventional pH indicators which are sequentially
reversible, i.e., reversing color upon sequential exposure
alternately to acid and to base, the bleachable dyes of the present
invention tend to bleach irreversibly when formulated in color
change cyanoacrylate compositions.
[0017] The cyanoacrylate-based adhesive composition described
herein includes a cyanoacrylate monomer and a bleachable dye cation
paired with a non-nucleophilic anion that provides the bleachable
dye with a stable color. As this cyanoacrylate-based adhesive
cures, it becomes colorless or lightly colored. In many
embodiments, the bleachable dye cation paired with a
non-nucleophilic anion is blended with the cyanoacrylate monomer
prior to being applied to a substrate. In some embodiments, the
bleachable dye cation paired with a non-nucleophilic anion is not
blended with the cyanoacrylate monomer before the cyanoacrylate
monomer is disposed on a substrate. In these embodiments, the
bleachable dye cation paired with a non-nucleophilic anion can be
disposed on the substrate and then the cyanoacrylate monomer is
disposed on the bleachable dye cation paired with a
non-nucleophilic anion.
[0018] The bleachable dye cation or cations can be chosen to
produce any color, as desired. In many embodiments, the bleachable
dye cation produces a blue or deep blue color. In many embodiments,
the bleachable dye cation is formed from a Michler's hydrol (i.e.,
4,4'-bis(dimethylamino)benzhydrol) or a derivative thereof.
[0019] Michler's hydrol or 4,4'-bis(dimethylamino)benzhydrol) is
commercially available (from Sigma-Aldrich, St. Louis, Mo. 63103)
and has the following chemical structure:
##STR00001##
Michler's hydrol is a dye base and is colorless in its free (pure)
form, and because this dye base by virtue of its amine substituents
is nucleophilic, and as such will cause immediate polymerization of
cyanoacrylate monomer, it is acidified prior to introduction into
the cyanoacrylate described herein. When acidified, Michler's
hydrol cation provides a blue (cyan) color: the color intensity
varying with the acidified dye concentration. Selection of the
appropriate acid stabilizer or non-nucleophilic anion to maintain
dye (color) stability upon aging is described below. While not
being bound by any particular theory, it is believed that Michler's
hydrol cation is a dye that is degraded (e.g., bleached)
concomitant with curing of the cyanoacrylate adhesive
composition.
[0020] Derivatized Michler's hydrol can be used for the bleachable
dye cation. Useful derivatized Michler's hydrols include, for
example, the following molecules:
bis[4-(4-morpholinyl)phenyl]methanol (CAS#123344-13-8) having a
chemical structure:
##STR00002##
1,1-bis(4-dimethylaminophenyl)ethanol (CAS#33905-89-4) having a
chemical structure:
##STR00003##
1,1-bis(4-dimethylaminophenyl)ethylene (CAS# 22057-85-8) having a
chemical structure:
##STR00004##
(It is believed that this compound is converted by proton addition
to the methylene group into the same bleachable dye cation as
provided by the preceding structure.)
bis(4-dimethylamino)-2-methylphenyl)methanol) (CAS#4300146-3)
having a chemical structure:
##STR00005##
bis(3-bromo-4-dimethylaminophenyl)methanol having a chemical
structure:
##STR00006##
N-[bis(4-dimethylaminophenyl)methyl]morpholine (CAS#21295-86-3)
having a chemical structure:
##STR00007##
N-[bis[4-(dimethylamino)phenyl]methyl]-N'-n-butyl-urea
(CAS#27086-41-5) having a chemical structure:
##STR00008##
N-[bis[4-(dimethylamino)phenyl]methyl]-N'-(4-ethoxyphenyl)-urea
(CAS#37171-10-1) having a chemical structure:
##STR00009##
N-[bis[4-(dimethylamino)phenyl]methyl]-N'-(4-methylphenyl)-urea
(CAS# 123344-13-8) having a chemical structure:
##STR00010##
N-[bis[4-(dimethylamino)phenyl]methyl]-N'-phenyl-urea
(CAS#34851-49-5) having a chemical structure:
##STR00011##
N-[bis[4-(dimethylamino)phenyl]methyl]-aniline (CAS# 6245-51-8)
having a chemical structure:
##STR00012##
N-[bis[4-(dimethylamino)phenyl]-methyl]-benzenesulfonamide (CAS#
3147-38-4) having a chemical structure:
##STR00013##
[0021] These Michler's hydrol derivatives are either commercially
available or described in U.S. Pat. Nos. or Publication No.:
4,407,960; 3,874,884; 3,856,552; 4,006,018; 3,646,135; and
2005-1488010, all of which are incorporated by reference
herein.
[0022] The bleachable dye cation can be present in the
cyanoacrylate adhesive in any useful amount. In many embodiments,
the bleachable dye cation can be present in the cyanoacrylate
adhesive in an amount from 1 ppm or greater, or 10 ppm or greater,
or 50 ppm or greater, or 100 ppm or greater, or 250 ppm or greater,
or 500 ppm or greater, or 1000 ppm or greater. In some embodiments,
the bleachable dye cation can be present in the cyanoacrylate
adhesive in an amount from 1 ppm to 1000 ppm, or from 10 to 500
ppm, or from 1 to 100 ppm.
[0023] The non-nucleophilic anion is typically derived from acids
of high strength. The strength of such acids is often classified by
means of Acidity Indicators, i.e., members of a series of
increasingly weak nitrated aniline bases that provide a readily
measured color change upon protonation. The accepted measure of the
"strength" of aqueous acidic solutions is pH, the negative
logarithm of the hydrogen ion concentration (or activity), and
pK.sub.A, which similarly is the negative logarithm of the
ionization constant K.sub.A. in aqueous solution, of weak to
moderately strong acids. For extremely strong acids these means of
description fail, as strong acids react with water, acting as a
base, to form hydronium ion, H.sub.3O.sup.+, thus preventing the
expression of higher acidities. For the measurement of the ultimate
proton-donating acidity of pure anhydrous acids, the H.sub.o
(Hammett Acidity Function) scale was created (L. P. Hammett &
A. J. Deyrup, J Amer. Chem. Soc., 54 2721, 4239 (1932), 55 1900
(1933)). Its numerical scale was provided by stepwise dilution of
each acid by water until the composition fell within the measurable
pH range, thus it was termed an extension of the pH scale.
Color-indicating very weak bases were provided, for which the
protonated forms had non-aqueous pH-like behavior that could be
inter-related by stepwise overlap. While useful, the H.sub.o scale
provides no common non-aqueous medium for comparisons, as each
anhydrous acid differs in solvent properties. Nearly all common
"good" solvents are protonated by, or are reactive toward, very
strong acids. Furthermore, to retain both neutral and ionic species
in solution, a relatively high dielectric constant is accepted as
necessary. Nitromethane appeared to be such a solvent (L. C. Smith
& L. P. Hammett, J Amer. Chem. Soc., 67 23 (1945)), but failed
to provide simple buffer equilibria; this behavior was (and
remains) unexplained.
[0024] The Hammett Acidity Function is applied to pure or nearly
pure acids, a situation extremely different from the use in
solution in a cyanoacrylate monomer. It is appropriate therefore to
evaluate acid strengths in a polar organic solvent by a means
analogous to ordinary aqueous buffer systems, which depend on the
strength of the acids employed.
[0025] Anhydrous "Sulfolane" (tetramethylene sulfone;
tetrahydrothiophene-1,1-dioxide, CAS RN 126-33-0), is an acid-inert
non-dissociating good solvent of high dielectric constant, 44, (E.
M. Arnett & C. F. Douty, J Amer. Chem. Soc., 86 409 (1964)),
and has the further advantage that the melting point is a sensitive
measure of its water content (R. L. Burwell Jr & C. H.
Langford, J Amer. Chem. Soc., 81 3799 (1959)). Although requiring
rigorous purification to remove traces of water, and impurities
that are severely discolored by strong acids, it does appear to
yield simple buffer and color-indicator equilibria.
[0026] Therefore we create the non-aqueous analog of the common
buffer system by combining equimolar amounts of a very strong acid
and its salt in anhydrous sulfolane, and evaluate the buffered
acid's strength by means of an Acidity Indicator, 1. (For such an
aqueous 1:1 buffer the aqueous; pH is equal to the pK.sub.A for the
aqueous acid.) The procedure to conduct such measurements is
described in detail in the Test Methods section of this disclosure.
Strength of an acid buffer of any composition may for simplicity be
expressed by means of the ratio of molar extinction coefficients,
.di-elect cons., and .di-elect cons.*, where .di-elect cons. is the
molar extinction coefficient of an Acidity Indicator, 1, in the
acid-free solvent, sulfolane, and .di-elect cons.* is the apparent
molar extinction coefficient of that Acidity Indicator in a
buffered test solution (as described in the Test Methods section)
according to the following equations:
[0027] Extinction Ratio=.di-elect cons./.di-elect cons.=N and
(.di-elect cons.-.di-elect cons.*)/.di-elect cons.=C=(1-N)
[0028] For an Equimolar (1:1) Buffer, for which the Strength Ratio,
E=(.di-elect cons.-.di-elect cons.*)/.di-elect cons. (for a
specified Acidity Indicator, I), E expresses the strength of the
acid itself. To exhibit this relative to the strength of the
conjugate acid, IH.sup.I, of the Acidity Indicator it is convenient
to use the familiar negative logarithmic form:
pA=-log(E/N)=+log(N/E).
[0029] Given a "pK.sub.I" for the (conjugate acid) strength of an
Acidity Indicator, the strength of a buffer's acid on that scale
becomes "pK.sub.A", where "pK.sub.A"="pK.sub.I"+pA. Such a single
self-consistent scale is provided computationally for all of the
Acidity Indicators as described under Indicators in the Test
Methods section.
[0030] For a workable carbon-acid the Strength Ratio, E, defined as
(.di-elect cons.-.di-elect cons.*)/.di-elect cons., for a chosen
1:1 buffer system in the sulfolane solvent described above, is
greater than 0.1 (corresponding to "pK.sub.A"<+2.0), preferably
greater than 0.25 (corresponding to "pK.sub.A"<+1.5) when the
indicator I is 4-methoxy-2-nitroaniline. For a workable
non-carbon-acid, for example an oxyacid, the acid Strength Ratio E,
as measured in the sulfolane solvent described above, is greater
than 0.2, preferably greater than 0.5 (corresponding to
"pK.sub.A"<-1.0), when the indicator is 4-chloro-2-nitroaniline,
or more preferably greater than 0.50 (corresponding to
"pK.sub.A"<-2.3) when the indicator is 2-chloro-6-nitroaniline,
or even more preferably greater than 0.5 (corresponding to
"pK.sub.A"<-5.4) when the indicator is 2,6-dinitroaniline. The
mathematically equivalent Acid Strength measure, "pK.sub.A",
applicable to all buffer ratios, is described in the Test Methods
section. It enables the Strength Ratio, E, to be ascertained by
means of titration.
[0031] Carbon-acids differ qualitatively in being extremely much
weaker than acids bearing the acidic hydrogen on, for example,
oxygen or nitrogen, as is well established in the scientific
literature. It is unusual for a carbon-acid to possess sufficient
acid strength to be measurable using the nitrated aniline Acidity
Indicators utilized herein. For a carbon-acid to be this strong it
is necessary that its anion be non-nucleophilic. As compared to the
strong non-carbon-acids which homopolymerize epoxy compounds, the
observation that these relatively weaker carbon-acids also
homopolymerize epoxy compounds demonstrates the comparably
non-nucleophilic nature of their anions.
[0032] The non-nucleophilic anion can include an
.alpha.,.beta.-highly fluorinated or
perfluorinated(C.sub.1-C.sub.8)alkylsulfonate anion. In further
embodiments, the non-nucleophilic anions include those derived from
bis(.alpha.,.beta.-highly fluorinated or
perfluorinated-sulfonyl)methane, tris(.alpha.,.beta.-highly
fluorinated or perfluorinated-alkylsulfonyl)methane,
bis(.alpha.,.beta.-highly fluorinated or
perfluorinated-alkylsulfonyl)imide, or mixtures thereof. In yet
further embodiments, the non-nucleophilic anion may be formed from
trifluoromethanesulfonic acid, nonafluorobutanesulfonic acid,
fluorosulfonic acid, bis(trifluoromethanesulfonyl)methane
(methylene disulfonic), bis(trifluoromethanesulfonyl)imide (imide
acid), bis(pentafluoroethanesulfonyl)imide (ethylimide acid),
tris(trifluoromethanesulfonyl)methane (methide acid), boron
trifluoride bis-acetic acid, and other boron trifluoride complexes
such as the etherate, methanol, propanol, and tetrahydrofuran
derivatives. Similar reagents that react, decompose, or hydrolyze
to form any of the above recited acids are also useful.
Combinations of the acids from which the aforementioned
non-nucleophilic anions are derived may also be useful in the
practice of this invention. In some embodiments, the
non-nucleophilic anion is formed from trifluoromethanesulfonic
acid, methide acid, boron trifluoride methanol, boron trifluoride
bis-acetic acid, imide acid, and/or ethylimide acid. In certain
preferred embodiments, the non-nucleophilic anion is formed from
imide acid, boron trifluoride bis-acetic acid, and/or methide
acid.
[0033] The non-nucleophilic anion can be present in the
cyanoacrylate adhesive in any useful amount. In many embodiments,
the acid of the non-nucleophilic anion can be present in the
cyanoacrylate adhesive in an acid/dye mol ratio from 1 to 5, or
from 1 to 2.5. In certain embodiments, the acid of the
non-nucleophilic anion can be present in the cyanoacrylate adhesive
in an acid/dye mol ratio from 1 to 5, or from 1 to 3, or from 1.5
to 2.5. With careful formulation, the presence of lesser amounts
(equivalents) of certain nucleophilic anions may sometimes be
tolerated.
[0034] Cyanoacrylate adhesives described herein include, for
example, 2-cyanoacrylates such as, for example,
methyl-2-cyanoacrylate, ethyl-2-cyanoacrylate,
propyl-2-cyanoacrylate, isopropyl-2-cyanoacrylate,
butyl-2-cyanoacrylate, isobutyl-2-cyanoacrylate,
amyl-2-cyanoacrylate, hexyl-2-cyanoacrylate,
cyclohexyl-2-cyanoacrylate, octyl-2-cyanoacrylate,
2-ethylhexyl-2-cyanoacrylate, allyl-2-cyanoacrylate,
propargyl-2-cyanoacrylate, phenyl-2-cyanoacrylate,
benzyl-2-cyanoacrylate, methoxyethyl-2-cyanoacrylate,
ethoxyethyl-2-cyanoacrylate, tetrahydrofulfuryl-2-cyanoacrylate,
2-chloroethyl-2-cyanoacrylate, 3-chloropropyl-2-cyanoacrylate,
2-chlorobutyl-2-cyanoacrylate,
2,2,2-trifluoroethyl-2-cyanoacrylate,
hexafluoroisopropyl-2-cyanoacrylate, and/or the like. In many
embodiments, these reactants are substantially/effectively
anhydrous.
[0035] The cyanoacrylate-based adhesive compositions described
herein are liquid or gels (if a sufficient amount of thickener is
combined) prior to curing. In many embodiments, the liquid or
flowable cyanoacrylate-based adhesive compositions have a viscosity
in a range from 1 to 5000 cP, as desired.
[0036] The color change 2-cyanoacrylate-based adhesive composition
described herein can optionally include an additional colorant, a
radical polymerization stabilizer, a thickener, a curing
accelerator, a crosslinker, a plasticizer and/or a thixotropic
agent, as desired. Desirably all additives should be substantially
anhydrous and free of nucleophilic compounds that may be
deleterious to the bleachable color stability, the viscosity
stability or both. Furthermore, the selection of the acidic
compounds influence curing speed and product life of
2-cyanoacrylate-based compositions. Thus, selection of their
suitable amounts to be added and combination can be determined by
taking into account target curing performance, product life, color
change performance and various other aspects.
[0037] The additional colorant can be provided to achieve change in
colors from a first colored state to a second colored state as the
color change cyanoacrylate-based adhesive progresses from an
uncured state to a cured state. The additional colorant can be any
useful dye or pigment. In some embodiments the additional colorant
is an indicator dye (not a bleachable dye such as Michler's hydrol
or derivative) that can further change color as the
cyanoacrylate-based adhesive progresses from an uncured state to a
cured state. In some embodiments, the additional colorant includes
two or more pigments or dyes, depending on a desired color (in the
cured or uncured state). The change in color of the
cyanoacrylate-based adhesive from a first colored uncured state to
a final colored cured state, or from a first colored uncured state
to a final colorless cured state can be used to indicate the
progress of the curing reaction or change in the
cyanoacrylate-based adhesive. Visual color standards may be
prepared and provided as a reference to the reaction progress. For
example, a simple series of three printed color-matched dots that
diminish in intensity as the concentration of acidified Michler's
hydrol cation in the curing adhesive diminishes might be useful in
determining whether the adhesive was curing properly, and
furthermore aid in identifying whether the initial composition was
sufficiently unpolymerized to be a useful adhesive composition.
[0038] The radical polymerization stabilizer can include
hydroquinone, hydroquinone monomethyl ether, catechol, pyrogallol
and the like. In some embodiments, the radical polymerization
stabilizer can be present in the range of 1 ppm by weight to 1% by
weight.
[0039] In order to decrease bonding time, anion polymerization
accelerators can be added to uncured cyanoacrylate adhesives, which
include polyalkylene oxides and their derivatives, crown ethers and
their derivatives, silacrown ethers and their derivatives,
calixarene derivatives, thiacalixarene derivatives and the like,
and combinations or blends of any of the aforementioned classes of
accelerators. Some useful accelerants are disclosed in U.S. Pat.
No. 6,835,789 and incorporated herein to the extent it does not
conflict. In some embodiments, the accelerant is present in the
range from 200 to 5000 ppm. Nucleophilic polymerization
accelerators, e.g., amines such as N,N-dimethyl-p-toluidine
solutions may also be applied to adherend surfaces prior to
application of an uncured cyanoacrylate adhesive in order to
accelerate cure of the adhesive.
[0040] Thermal performance of cyanoacrylate adhesives is typically
improved by the addition of crosslinkers, i.e., multi-functional
monomers which upon or subsequent to cure crosslink the
polymerizing adhesive. Useful crosslinkers may include
biscyanoacrylates, allyl-2-cyanoacrylate,
propargyl-2-cyanoacrylate, multi-functional acrylates and
(meth)acrylates, and combinations of the aforementioned.
[0041] The thickener can include viscosity modifiers, gel formers,
thixotropic, and/or polymeric additives such as, for example,
polymethylmethacrylate (PMMA), methyl methacrylate/acrylate
copolymers, methyl methacrylate/methacrylate copolymers, cellulose
derivatives, fumed silica, hydrophobic silica, and the like. In
some embodiments, the thickener can be added in the range of 0.1 to
20% by weight. In some embodiments, the thickener can be added to
provide a viscosity in a range from 5 to 5000 cP. In certain
embodiments, the thickener can be added to provide a viscosity in a
range from 2500 to 100,000 cP. In some embodiments, PMMA and fumed
silica are combined in the composition to form a cyanoacrylate
adhesive gel.
[0042] The plasticizer can be added to adjust modulus of the
adhesive from a rigid adhesive to a toughened or flexible adhesive.
Plasticizers can include, for example, phthalate esters, citrate
esters, glycerol triacetate, specific multifunctional
(meth)acrylates and the like. In some embodiments, the plasticizer
can be added in the range of 0.01 to 30% by weight.
[0043] In addition, perfumes, fillers, crosslinking agents,
polymerization initiators, organic solvents or the like can
optionally be added, as desired.
[0044] The present invention should not be considered limited to
the particular examples described herein, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention can be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the instant specification.
Test Methods
Set Time
[0045] Set time was determined by depositing a single drop of
cyanoacrylate adhesive (hereinafter "CA") on a glass microscope
slide, overlapping a second slide atop the first, and applying
modest finger pressure on the top slide in the bonding region to
create a thin glue line. At the time the bond line is closed (2nd
slide put in place) a stop watch is started. While holding the 1st
slide, the 2nd slide non-bonded end is moved slowly from side to
side over a small range of motion, of no more than 30 degrees, to
determine when it can no longer be moved. When slide 2 can no
longer be moved, the time on the stopwatch is recorded as the set
time.
Color Assessment
[0046] A quantitative color assessment was performed to determine
if changes occurred in sample color over time. This quantitative
assessment was conducted by comparing the example to known
colorimetric standards consisting of aqueous methylene blue
solutions (preferably acidified by acetic acid) at concentrations
of 2.0.times.10.sup.-4 M, 1.5.times.10.sup.-4 M,
1.0.times.10.sup.-4 M, and 0.5.times.10.sup.-4 M, packaged in the
same quantity and bottle type as the experimental samples. A
quantitative color scale of 0, 1, 2, 2.5 and 3 was employed where 3
corresponds to the deepest blue and 0 corresponds to colorless.
Methylene blue concentrations of 2-, 1.5-, 1.0-, and
0.5.times.10.sup.-4 M correspond to color ratings of 3, 2.5, 2, and
1 respectively. A colorless sample would be rated 0.
Bleaching
[0047] Bleaching was assessed at the conclusion of the set time
test described above. In this case samples were visually inspected
approximately 1 hour after conducting the set time test and
identified as either "colorless", if they bleached colorless, or
"tinted", if color or hue remained. Results from this test are
labeled "Set Time Bleach".
Acid Strength Determination
[0048] The objective of this test method is to establish the
strength of the acid being tested, as expressed, for example, in a
half-neutralized "buffer" solution in purified sulfolane
(tetramethylene sulfone), from which the strength is revealed by
UV-Vis spectrometry to determine degree of protonation of an
Acidity Indicator, 1, and expressed relative to it as the Strength
Ratio, E. More generally the mathematically equivalent Acid
Strength, "pK.sub.A", available from buffers of all ratios, or by
titration, may be used to calculate the Strength Ratio.
Purification of Sulfolane
[0049] For this test method, sulfolane having a mp of at least
26.0.degree. C., or preferably at least 28.0.degree. C., or more
preferably greater than or equal to 28.4.degree. C. relative to the
mp of 99.999% pure gallium, 29.765.degree. C., (measured using a
thermometer so calibrated) and being substantially transparent,
i.e., giving a stable near-zero absorbance baseline when this
sulfolane is present in the sample cell, with pure water in the
reference cell of a double beam spectrophotometer over the region
350-550 nm, is required. For this and all subsequent absorbance
measurements the reading at 550 nm should be found to be near
zero.
[0050] For this test method, not even the best commercial "Reagent"
or "99+%" sulfolane is suitable. Less pure grades (if wet, they can
be first improved by storing with KOH pellets) can be brought to
"Reagent" level by crystallizing below 20.degree. C., then allowing
to slowly melt at 25.degree. C.-27.degree. C. with frequent or
continuous drainage of the melt liquid, which can be recycled. The
portion remaining solid and/or the commercial "99+%" sulfolane, is
subjected to the following purification regimen. To avoid freezing
of the purified sulfolane during handling, it is advisable to
maintain the work area at or above 30.degree. C.
[0051] To a stoppered 500 ml Erlenmeyer flask, fitted with a Bunsen
valve or other pressure-relief device, is placed 300 to 350 g of
the "99+%" sulfolane and 1.58 g KMnO.sub.4. The liquid, initially
deep magenta, develops a brown cast (from MnO.sub.2). It is warmed
on a hot plate held at 45-55.degree. C. for at least 5 days, with
additional 1 g portions of KMnO.sub.4 being added as needed to
maintain a weak magenta color. The liquid is decanted away from any
settled solids and centrifuged (filtration is difficult) to remove
MnO.sub.2. The supernatant liquid is decanted into a 500 ml
Erlenmeyer flask with pressure-relief stopper, and to it is added
15 g of a previously-prepared drying mixture, which had been made
at least one day earlier by shaking together in a well sealed
bottle equal weights of phosphorus pentoxide and 100-200 mesh
silica gel that had been dried at 170.degree. C. overnight. The
flask of sulfolane and drying mixture is heated for at least 1 week
on a hot plate at 100.degree. C. and soon turns to an amber-brown
color. It is then cooled and the very dark liquid decanted into a
250 ml distilling flask. To control "bumping" during distillation
it is desirable to add 10 to 15 fluoropolymer PFA (or FEP) tubes,
of outside diameter about 3 mm, inside diameter about 1 mm, sealed
off at their tops, and of a length greater than the flask
diameter.
[0052] The flask, heated by a heating mantle, is surmounted by a
simple vacuum fractional distillation unit, comprising first a
short Vigreux column section (to intercept "bumped" liquid) and
above it a section containing a 20 cm length of 1/4'' Pyrex
helices, or preferably a 10 cm long section containing
Podbielniak.TM. Helipak.TM., 1/8'', stainless steel, either
contents being available from Wilmad-LabGlass, Elk Grove Village,
Ill. Above it is a standard vacuum distillation head with reflux
style condenser and thermometer, and stopcocks positioned to allow
controlled take-off, plus exchange and re-evacuation of receptor
flasks, specifically without breaking the vacuum of the
distillation column. Only minimal insulation of the column or head
by means of a few paper towels wrapped around the hot parts is
needed, with provision for observation of a tendency to "flood" in
the packed section, as it may be alleviated by blowing air on the
distilling flask. The entire distilling apparatus should be
assembled with 24/40 standard taper joints fitted with PTFE conical
sleeves and made vacuum tight throughout with perfluorinated vacuum
grease, available as Krytox LVP, from E. I. du Pont de Nemours and
Company, Wilmington, Del., in order to resist hot sulfolane
vapor.
[0053] For vacuum distillation an ordinary oil pump capable, with
liquid nitrogen trap, of exhausting the system to 0.05 Torr., is
needed, to enable sulfolane to distill at 68-75.degree. C., as much
higher pressure and temperature may produce discoloration. The
system pressure is continuously monitored by means of an electronic
vacuum gauge reading with reasonable precision from 0.010 Torr. to
1.0 Torr. Water flow through the condenser must be restricted, as
the distillate will freeze and plug it below 30.degree. C., with
hazardous consequences.
[0054] Distillation should become relatively stable around
73.degree. C./0.10 Torr., and a large center cut of 130-150 g
should be taken at 72.degree. C./0.090 Torr. to 68.degree. C./0.050
Torr. This cut, upon crystallization in its ca. 150 mL receiver
flask, should upon warming show melting of its last crystals at
2.degree. C., or preferably 1.5.degree. C., or more preferably
1.degree. C. below the melting point of 99.999% gallium metal,
29.765.degree. C., one of several pure-metal melting points that
officially define the Celsius temperature scale, as explained by H.
Preston-Thomas et al., Metrologia 27 3 (1990). The literature
melting point, 28.86.degree. C., given without reference to one
another by S. F. Birch and D. T. MacAllan, J. Chem. Soc. (London)
2556 (1951) and by E. V. Whitehead, R. A. Dean and F. A. Fidler, J.
Amer. Chem. Soc. 73 3632 (1951), and allegedly obtained by
extrapolation from lower temperature data, is indefensible in view
of direct gallium-based measurement of 29.0.degree. C. minimum.
[0055] Sulfolane has a low heat of fusion, as given by R. L Burwell
Jr. and C. H. Langford, J. Amer. Chem. Soc., 81 3799 (1959), and
therefore has an extremely large freezing point depression, thus
providing an upper limit on water content, increasing by 0.031 m in
water content for each 1.00.degree. C. reduction in melting
point.
[0056] Nevertheless, sulfolane does not have to be treated with
excessive care, as it is virtually nonvolatile at atmospheric
pressure, thus cannot condense moisture by evaporative cooling, nor
lose weight by evaporation, when handled briefly in open vials.
Little or no water is absorbed from the air, as shown by slow
change at the 0.01 mg level of weight of an open vial of sulfolane
on the balance. The measurable, although not large, effect on
spectroscopic acidity measurements produced by addition of 1
microliter of water (ca. 1.00 mg), to a test sample of
approximately 2.5 g, permits ready estimation of the negligible
effect of brief unprotected exposure of samples to air at
30.degree. C. and 20 to 40% relative humidity.
Acidity Indicators
[0057] For the purpose of this work, visibly colored neutral
Acidity Indicator molecules which lose color reversibly upon
accepting a proton from a strong acid are used. To minimize
inconsistency of electronic effects, the selection is restricted to
various substituted 2-nitroanilines, for which a second nitro
group, if present, must be in the 6-position. It is a
characteristic shared by all members of this group thus far
examined that the neutral form has a clean symmetrical absorbance
peak in the range 380-460 nm, which disappears (reversibly) for its
protonated form. Thus, the fractional loss in intensity represents
the reduction in concentration of the neutral Acidity Indicator,
(1), the reduction representing (IH.sup.+). This is readily
measured by a spectrophotometer, or even by a properly filtered
colorimeter.
[0058] In principle all Acidity Indicators might have their
indicator constants in sulfolane related by the stepwise overlap
method as has been done, and variously revised, for measuring
H.sub.o as reported in the cited references. [0059] M. A. Paul
& F. A. Long, Chem. Rev. 57 1 (1957) [0060] M. J. Jorgenson
& D. R. Hartter, J. Amer. Chem. Soc., 85 878 (1963) [0061] E.
M. Arnett & G. W. Mach, J. Amer. Chem. Soc., 86 2671 (1964)
[0062] N. C. Marziano, G. C. Cimino, & R. C. Passerini, J.
Chem. Soc. (London) Perkin 11, 1915 (1973) [0063] D. Farcasiu &
A. Ghenciu, J. Prog. Nucl. Mag. Spect. 29 129 (1996)
[0064] In practice that approach is narrow in scope and suffers
from cumulative procedural and experimental variability. An
alternative system, used here, which is entirely objective,
self-consistent and reproducible, relies experimentally on the
effects of acidity on chosen specified Acidity Indicators. For
convenience, these may be related numerically by means of their
computed "pK.sub.A" values, which may be generated for all known
and predicted 2-nitroaniline derivatives by employing a
computational method provided by Advanced Chemistry Development,
Inc (ACD/Labs), Toronto, ON, Canada, www.acdlabs.com. This software
is ACD/pK.sub.a Batch, version 9-04, ACD/Labs (.COPYRGT.1994-2007.
(Identical "pK.sub.A" values were generated by their Versions 8-14
and 8-19). The "pK.sub.A" values may be accessed through the
Chemical Abstracts Service. These Acidity Indicator "pK.sub.A"
values are here termed "pK.sub.I" for clarity.
[0065] Experimental spectrophotometric data are used to calculate
logarithmic acidity values ("pH", analogous to pH) that are helpful
in determining E by titration. To avoid confusion with aqueous pH
and pK values, and with the many literature H.sub.o values which
they resemble, the logarithmic acidity values in anhydrous
sulfolane are designated "pH", and the derived acid strength
constants "pK.sub.A". One may identify the indicator(s) on which
the "pK.sub.A" are based, by virtue of being close to their
computational "pK.sub.I" values.
[0066] The indicators chosen for the present work, together with
their computational "pK.sub.I" values are shown in Table A.
TABLE-US-00001 TABLE A Chosen Acidity Indicators and Their Computed
"pK.sub.I" Values Chemical Name CAS Ref. No. "pK.sub.I"
4-Methoxy-2-nitroaniline 96-96-8 0.96 4-Methyl-2-nitroaniline
89-62-3 0.46 2-Nitroaniline* 88-74-4 -0.23 4-Chloro-2-nitroaniline*
89-63-4 -1.00 5-Bromo-2-nitroaniline 5228-61-5 -1.53
2-Chloro-6-nitroaniline* 769-11-9 -2.34
2,4-Dichloro-6-nitroaniline* 2683-43-4 -3.08
4-(Methylsulfonyl)-2-nitroaniline 21731-56-6 -3.88
2-Chloro-6-nitro-4-(trifluoromethyl)aniline 57729-79-0 -4.62
2-Bromo-6-nitro-4-(trifluoromethyl)aniline 113170-71-1 -4.74
2,6-Dinitroaniline* 606-22-4 -5.45 4-Chloro-2,6-dinitroaniline*
5388-62-5 -6.03 2,6-Dinitro-4-(trifluoromethyl)aniline 445-66-9
-7.42 2,6-Dinitro-4-(methylsulfonyl)aniline 42760-39-4 -8.88
[0067] To minimize the effects of spectrophotometric uncertainty at
the extremes, it is strongly recommended that the absorbance
measurements fall between 15% and 75% of the value expected if the
indicator were completely non-protonated, i.e., in its neutral
form. For the six indicators identified with an asterisk in Table
X, the computed "pK.sub.I" values differ only by about 0.1 pK.sub.A
unit from the experimentally measured (and revised) pK.sub.A values
reported in the literature references cited above, thus supporting
the validity of the computational method. Additional computed
"pK.sub.I" values for indicators presumed to be useful are listed
in Table B.
TABLE-US-00002 TABLE B Additional Acidity Indicators Presumed
Useful and Their "pK.sub.I" Values Chemical Name CAS Ref. No.
"pK.sub.I" 2,4-Dimethoxy-6-nitroaniline 57715-92-1 0.87
2,4-Dimethyl-6-nitroaniline 1635-84-3 0.27
4-(Methylthio)-2-nitroaniline 23153-09-5 -0.09
2-Methoxy-6-nitroaniline 16554-45-3 -0.35 2-Methyl-6-nitroaniline
570-24-1 -0.44 3-(Methylthio)-2-nitroaniline 351458-30-5 -0.86
4-Bromo-2-nitroaniline 875-51-4 -1.05
4-Chloro-2-methoxy-6-nitroaniline 859877-49-9 -1.09
2-Chloro-4-methoxy-6-nitroaniline 29105-95-1 -1.12
4-Bromo-2-methoxy-6-nitroaniline 77333-45-0 -1.14
2-Bromo-4-methoxy-6-nitroaniline 10172-35-7 -1.24
2-(Methylthio)-6-nitroaniline 494226-39-0 -1.36
2-Nitro-4-(trifluoromethoxy)aniline 2267-23-4 -1.38
5-Chloro-2-nitroaniline 1635-61-6 -1.46
2-Nitro-4(trifluoromethylthio)aniline 404-74-0 -2.34
2-Bromo-6-nitroaniline 59255-95-7 -2.46
2-Nitro-4-(trifluoromethyl)aniline 400-98-6 -2.54
2-Nitro-6-(trifluoromethoxy)aniline 235101-48-1 -2.55
2,4-Dibromo-6-nitroaniline 827-23-6 -3.25
2-Nitro-6-(trifluoromethyl)aniline 24821-17-8 -3.37
2,6-Dinitro-4-methoxyaniline 5350-56-1 -4.66
2,6-Dinitro-4-methylaniline 6393-42-6 -4.93
2-Nitro-4-(trifluoromethylsulfonyl)aniline 400-23-7 -5.30
4-Bromo-2,6-dinitroaniline 62554-90-9 -6.21
4-Cyano-2,6-dinitroaniline 61313-43-7 -8.48 2,4,6-Trinitroaniline
489-98-5 -9.30 2,6-Dinitro-4-(trifluoromethylsulfonyl)aniline
19822-30-1 -10.40
Calculations of "pH" and "pK.sub.A" Values
[0068] The straightforward method of L. C. Smith and L. P. Hammett,
J Amer. Chem. Soc. 67 23 (1945), is used to calculate "pH" and
"pK.sub.A" for the systems of interest. For each Acidity Indicator
chosen the Molar Extinction Coefficient, .di-elect cons., is
calculated from the absorbance of its sulfolane solution,
preferably made up exactly as for the acidity measurement, but
omitting the acid. The equation then takes the form:
.di-elect cons.=AMG/SUD=AYG/U
[0069] where:
[0070] A=Absorbance measured
[0071] M=Molecular weight of the indicator
[0072] G=Weight in grams of sample solution
[0073] S=Weight fraction of solid indicator in its sulfolane
concentrate
[0074] U=Weight in mg of indicator concentrate used
[0075] D=Density of the sample solution, normally 1.2622
[0076] Y=Batch constant for an indicator concentrate (=M/SD)
[0077] The needed density of the reference solution is most easily
established by use of a small Ostwald-Sprengel pycnometer of
approximately 0.5 to 2 ml volume which has been calibrated against
water. To fill the pycnometer by suction its tip may be dipped into
the test solution in the cell after the spectral measurement has
been made.
[0078] For a sample including an acid (or its buffer) its apparent
extinction coefficient, .di-elect cons.*, is related to its
observed absorbance, A*, by the same equation. The fraction of
neutral indicator (I) remaining is N=.di-elect cons.*/.di-elect
cons., and the corresponding fraction of its conjugate acid
(IH.sup.+) is C=(1-N)=(.di-elect cons.-.di-elect cons.*)/.di-elect
cons..
[0079] The acidity "pH" is given by: "pH"="pK.sub.I"+log(N/C) where
"pK.sub.I" is the computed "pK.sub.A" for the indicator, generated
by ACD/Labs software Version 9-04, as cited above.
[0080] For a titration or buffer solution, comprising B millimoles
of base and F millimoles of non-neutralized "free" acid, F=T-B, T
being the total millimoles of acid used (if B is added as the salt
of T, thus not neutralizing T, F=T). From this, the "pK.sub.A" for
the acid is: "pK.sub.A"="pH"+log(F/B)
[0081] This, together with the preceding equations, constitutes the
mathematical interconvertibility of the Acid Strength, "pK.sub.A",
and the Strength Ratio, E. The Strength Ratio, E, is based upon
experimentally known ratios, FIB, resulting from accurate weighings
and the presumption that the molality of T is correct. If the acid
of T is significantly impure, corrections must be made. For an
inert impurity the value of T is simply reduced to T', and F'=T'-B.
If, however, as is often the case, the impurity is the salt of the
acid (typically the hydronium salt, H.sub.3O.sup.+A.sup.-) then
this must also be part of the total base, B'=B+(T-T') and the ratio
becomes:
Ratio=F'/B'=F'/(B+T-T')=(T'-B)/(B+T-T')
[0082] For a given very strong acid sample, originally "pure" (free
from metallic salts, etc) the existing impurity is normally water.
The effective purity, T'/T, may be estimated by (gravimetric)
titration in anhydrous sulfolane with an anhydrous weighable base.
Note that unknown but limited amounts of water present in the
sulfolane will partially "neutralize" a very strong acid and modify
the titration and "pK.sub.A" calculation accordingly, but will not
change the validity of the resulting "pK.sub.A".
[0083] In order to find the half-neutralized "1:1 Buffer"
mid-point, at which E is defined, one needs to ascertain the
end-point with reasonable confidence. This requires an indicator
having a "pK.sub.A" two or three units less acidic than "pH"
measured for a (supposedly) equimolal buffer, such that the
titrated "pH" is within (passes through) the "best" indicator
range, namely N=.di-elect cons.*/.di-elect cons. between 0.15 and
0.75. Such an end-point is reliable.
[0084] Imidazole, readily soluble in sulfolane, is normally an
excellent choice as the titration or buffer-making base. Results
agree with those from ethyldiisopropylamine, despite the latter's
volatility and its very limited solubility in sulfolane. They also
agree with those from the additive bases,
CF.sub.3SO.sub.3.sup.-Na.sup.- and CF.sub.3SO.sub.3.sup.-
(Bu.sub.4N).sup.+, these of course being limited to
CF.sub.3SO.sub.3H. In view of its low molecular weight, a 1.000
molal concentrate of imidazole in sulfolane is recommended.
[0085] Acidity measurements are best made with F and B about 0.1 nm
or lower, for solubility reasons and to keep the sulfolane, as the
solvent medium, in great excess. At greater dilution of very strong
acids, extremely dry sulfolane is needed to minimize
interference.
[0086] A list of "pK.sub.A" values thus measured for acids of
interest in stabilization of bleachably-colored cyanoacrylate
adhesives is in Table C.
TABLE-US-00003 TABLE C Acid Strength, "pK.sub.A" Chemical Structure
"pK.sub.A" 95% Confidence Limits (CF.sub.3SO.sub.2).sub.2NH -6.6
.+-.0.2 (C.sub.2F.sub.5SO.sub.2).sub.2NH -6.6 .+-.0.5
CF.sub.3SO.sub.3H -6.1 .+-.0.5 BF.sub.3.cndot.2 CH.sub.3CO.sub.2H
-3.0 .+-.0.1 BF.sub.3.cndot.2 CH.sub.3OH -0.5 .+-.0.02
BF.sub.3.cndot.2 H.sub.2O -0.2 .+-.0.1 CH.sub.3SO.sub.3H 1.26
.+-.0.06 CF.sub.3CO.sub.2H 3.15 .+-.0.06
(CF.sub.3SO.sub.2).sub.3C.sup.-(H.sub.2O).sub.16H.sup.1 0.93
.+-.0.30 (CF.sub.3SO.sub.2).sub.2C(H)C.sub.6H.sub.5 0.97 .+-.0.04
(CF.sub.3SO.sub.2).sub.2CH.sub.2 1.32 .+-.0.06
[0087] Use of Titration to Determine Acid Strength, "pK.sub.A", of
a Strong Acid, and Consequent Strength Ratios. The Strength Ratio,
E, defined as (.di-elect cons.-.di-elect cons.*)/.di-elect cons.
for a chosen 1:1 buffer system, HA:A.sup.-, plus indicator
IH.sup.-:I, in sulfolane solvent, is not correct unless the true
concentrations of HA and A.sup.- are known to be equal. This is
best ascertained and verified by gravimetric-spectrophotometric
titration, to determine the true concentration of the strong acid
component in the measurement sample, as described below.
[0088] A stock solution is made from 0.28133 g of pure, colorless
sublimed crystals of methylene disulfone, MDS, and sulfolane to
total 9.99476 g. In a stoppered 1 cm fused silica
spectrophotometric cell is placed 2.41146 g. of the stock solution.
It contains 67.877 mg (T=0.24228 mmol) of MDS, plus 23.29 mg
indicator concentrate, U, to total G grams. The indicator
concentrate is made by dissolving 6.07 mg of
4-Methoxy-2-nitroaniline (molecular wt. M=168.15, "pK.sub.I"=+0.96)
in sulfolane to total 2193.78 mg, giving S=0.002767 and thus
Y=48147. (The .di-elect cons. value of this indicator was
determined to be 5497 by spectrophotometry on a diluted solution in
sulfolane.) The absorbance at the indicator's spectral maximum, 446
nm, is only 0.022, relative to the reference cell containing only
the stock solution.
[0089] Titration is begun by adding a small drop, 14.46 mg, of
1.0000 m sulfolane solution of purified imidazole, which thus adds
0.01446 mmol of base, B, producing absorbance 0.158. Additional
increments of the imidazole solution are added, with the results
shown in Table D.
TABLE-US-00004 TABLE D Results of Titration to Determine E for MDS
Increment # & imidazole Total g Total mmol C = "pK.sub.A" (mg)
in cell, G (= g) of B Ratio B/T Absorbance A (.epsilon. -
.epsilon.*)/.epsilon. "pH" (MDS) 1 (14.46) 2.44914 0.01446 0.0597
0.158 0.8545 0.19? 1.39? 2 (18.26) 2.46740 0.03272 0.1351 0.284
0.7365 0.51 1.32 3 (20.72) 2.48812 0.05344 0.2206 0.396 0.6295 0.73
1.28 4 (21.28) 2.50940 0.07472 0.3084 0.495 0.5329 0.90 1.25 5
(30.21) 2.53961 0.10493 0.4331 0.610 0.4174 1.10 1.22 6 (44.44)
2.58405 0.14937 0.6165 0.757 0.2644 1.40 1.20 7 (50.31) 2.63436
0.19968 0.8242 0.891 0.1173 1.84 1.17 8 (21.04) 2.65540 0.22072
0.9110 0.948 0.0533 2.21? 1.20? 9 (25.62) 2.68102 0.24634 1.0168
0.983 0.0089 3.01?? (--) ? -- indicates substantial uncertainty
resulting from the extreme absorbances
[0090] The average of the six most reliable "pK.sub.A" values is
1.24.+-.0.05 (95% confidence limits). The sudden increase in "pH"
signals the end-point of the titration, which is seen to occur at
B/T=1.0 as expected for a pure acid. The mid-point (buffer ratio
1:1) most reliable value for the Strength Ratio, E=0.34, is
calculated from "pK.sub.A"=1.24, and "pK.sub.I"=0.96 by the
equation: E=1/[1+antilog("pK.sub.A"-"pK.sub.I")]. (By interpolation
of C values, E may be approximated as 0.36.)
Materials
[0091] Unless otherwise noted, all materials were or can be
obtained from Sigma-Aldrich Corp., St. Louis Mo.
[0092] "PR01" refers to 2-ethylcyanoacrylate, 100 cP, super fast
cure, 10-30 second set time, available from Chemence, Inc.,
Alpharetta, Ga. 30005.
[0093] "SB20" refers to 2-ethylcyanoacrylate, 5 cP, ethyl hybrid,
0-20 sec set time, high strength bonds on acidic surfaces,
available from Chemence, Inc., Alpharetta, Ga. 30005.
[0094] "SB14" refers to 2-ethylcyanoacrylate, 100 cP, 10-60 second
set time, high strength bonds on plastic and rubber, available from
Chemence, Inc., Alpharetta, Ga. 30005.
[0095] "RX-100" refers to 2-ethylcyanoacrylate, 100 cP, non-surface
sensitive, 10-30 sec set time, available from Pacer Technology,
Rancho Cucamonga, Calif. 91730.
[0096] "TX-100" refers to 2-ethylcyanoacrylate, 100 cP, 10-30 sec
set time, available from Pacer Technology, Rancho Cucamonga, Calif.
91730.
[0097] "NO100" refers to 2-methoxy-ethoxy-.alpha.-cyanoacrylate,
100 cP, no odor, no frost, 30-50 sec set time, available from Pacer
Technology, Rancho Cucamonga, Calif. 91730.
[0098] "HC150" refers to 2-isopropylcyanoacrylate, 150 cP, low
chlorosis, high clarity, better moisture resistant than
ethylcyanoacrylates, 10-30 sec set time, available from Pacer
Technology, Rancho Cucamonga, Calif. 91730.
[0099] Scotchweld cyanoacrylate adhesives, available from 3M,
Maplewood, Minn. 55144 are listed in Table E below:
TABLE-US-00005 TABLE E Scotchweld Cyanoacrylate Adhesives Viscosity
Set Time Product Chemistry (cP) (sec) Scotchweld .TM. CA-40
2-ethylcyanoacrylate 2-10 1-30 Scotchweld .TM. CA-4
2-ethylcyanoacrylate 60-120 5-40 Scotchweld .TM. CA-40H
2-ethylcyanoacrylate 400-600 5-40 Scotchweld .TM. CA-5
2-ethylcyanoacrylate 2000-3000 20-70 Scotchweld .TM. CA-7
2-methylcyanoacrylate 15-40 1-30 Scotchweld .TM. CA-8
2-ethylcyanoacrylate 70-120 5-40 Scotchweld .TM. CA-9
2-ethylcyanoacrylate 1000-1700 20-70 Scotchweld .TM. CA-100
2-ethylcyanoacrylate 2500-4500 20-70 Scotchweld .TM. CA-50
2-ethylcyanoacrylate gel 60-120
[0100] Scotch.TM. Super Glue Liquid, catalog number AD110,
2-ethylcyanoacrylate, available from 3M, St Paul, Minn., 55144.
[0101] "Nexcare.TM. props Liquid Bandage", n-butyl cyanoacrylate, 5
cP, 30-60 sec set time, available from 3M, St. Paul, Minn.
55144
[0102] Michler's hydrol, recrystallized from toluene, mp
102-102.5.degree. C., available from Sigma-Aldrich, St. Louis, Mo.
63103.
[0103] Bis(trifluoromethanesulfonyl)methane "methylene disulfone"
"MDS", synthesized using the procedures disclosed in U.S. Pat. No.
3,776,950.
[0104] Bis(trifluoromethanesulfonyl)imide "imide acid", synthesized
using the procedures disclosed in U.S. Pat. No. 5,874,616.
[0105] Bis(pentafluoroethanesulfonyl)imide "ethylimide acid",
synthesized using the procedures disclosed in U.S. Pat. No.
5,874,616.
[0106] Trifluoromethanesulfonylamide "sulfonyl amide", synthesized
using the procedures disclosed in U.S. Pat. No. 5,874,616.
[0107] Tris(trifluoromethanesulfonyl)methane, "methide acid", 58.4%
solids aqueous, synthesized using the procedures disclosed in U.S.
Pat. No. 5,554,664.
[0108] Boron trifluoride-methanol complex in excess methanol, about
50 wt % BF.sub.3, (corresponding to BF.sub.3:2CH.sub.3OH) available
from Sigma-Aldrich Corp., St. Louis Mo.
[0109] Boron trifluoride-acetic acid complex, 98%, available from
Sigma-Aldrich Corp., St. Louis Mo.
[0110] Bis-(3-bromo-4-dimethylaminophenyl)methanol--The ketone,
4,4'-bis-(dimethylamino)-3,3'-dibromobenzophenone (E. Grimaux,
Comptes Rendus de l'Academie des Sciences, 126 1117-1118, [1898];
Chemisches Centralblatt [SF., 2J.] 1898, I, p. 1105), is reduced
using 3% sodium mercury amalgam in aq. ethanol by the method of C.
C. Barker et al., J. Chem. Soc. (London), 3962-63 [1959], to give
bis-(3-bromo-4-dimethylaminophenyl)methanol. This product gives an
intense blue color upon dissolution in acetic acid, as shown by
Barker et al., on p. 3963, thus verifying reduction of ketone to
hydroxyl. The structure is further confirmed by NMR.
[0111] Dye base concentrate A--9 pt methyl acetate and 1 pt
Michler's hydrol.
[0112] "MSA Concentrate"--solution consisting of 1.8 pt PR01 and
0.2 pt methanesulfonic acid.
[0113] "TFMSA Concentrate"--solution consisting of 1.8 pt PR01 and
0.2 pt triflic acid (i.e., trifluoromethanesulfonic acid).
[0114] Microscope slide, VWR Cat #48300-025, selected precleaned,
25.times.75.times.1 mm thick.
[0115] Lexan.TM. polycarbonate sheeting 2.9 mm thick, cut into 26.5
mm.times.103 mm coupons, available from GE Plastics, Pittsfield,
Mass. 01201.
[0116] Pronto.TM. Surface Activator, acetone solution of
N,N-dimethyl-p-toluidine, available from 3M, St. Paul, Minn.
55144.
EXAMPLES
[0117] Unless otherwise noted, all example formulations are
provided in parts by weight.
Example 1 and Comparative Example 1
[0118] A variety of commercially available cyanoacrylate
compositions were converted to colored-cure indicating compositions
by adding a dye masterbatch to each. The dye masterbatch was
prepared by first formulating a 10 wt % dye base solution of
Michler's hydrol in ethyl acetate and a 10 wt % acid solution of
triflic acid in PR01. The 10 wt % dye base solution contained 1.35
part ("pt") ethyl acetate and 0.15 pt Michler's hydrol. The acid
solution contained 1.8 pt PR01 and 0.2 pt triflic acid. The dye
masterbatch was prepared by combining 9.4 pt PR01, 0.366 pt 10%
triflic acid solution, and mixing well, before adding 0.3 pt 10%
dye base solution and mixing to complete the preparation and obtain
a dye masterbatch having an acid/dye mol ratio of approximately
2.2/1 which contained approximately 3000 ppm dye. The final samples
were made by combining, in a HDPE bottle, 0.25 pt of the dye
masterbatch with 10 pt of the commercial cyanoacrylates shown in
Table 1 to provide samples having a final dye content of
approximately 75 ppm.
[0119] The resulting samples were all deep blue in color. Set time
was assessed as described in the Test Methods section, and shows
that set time is essentially unaltered in these compositions by the
addition of the dye masterbatch. In the set time test all of the
samples bleached from deep blue to colorless upon cure. These
results show that acid/dye combinations of the present invention
are suitable to convert a wide variety of commercially available
cyanoacrylate adhesive into color change compositions.
TABLE-US-00006 TABLE 1 Set time of Color Change Cyanoacrylate
Adhesives Sample Set Time Set Time Example Commercial CA No Dye
Dyed Bleach 1A Scotchweld CA40 1 1-2 colorless 1B Scotchweld CA4 7
4 colorless 1C Scotchweld CA40H 4 3-4 colorless 1D Scotchweld CA5
18-20 17-20 colorless 1E Scotchweld CA7 1 1 colorless 1F Scotchweld
CA8 2-3 3 colorless 1G Scotchweld CA9 5-7 5 colorless 1H Scotchweld
CA100 35 35-40 colorless 1I PR01 7 7 colorless 1J RX-100 3-4 3-4
colorless 1K TX-100 3-4 5 colorless 1L NO-100 20 11-15 colorless 1M
HC-150 25-35 30-60 colorless
[0120] Comparative Example 1 demonstrates that upon cure,
pentamethoxy red (PMR), one of the dyes of US 2004/0254272 A1, does
not bleach to a colorless form when employed as shown in Example 1.
A 2% solution of PMR in ethyl acetate was prepared and 0.25 pt of
this PMR solution was added to 9.75 Pt PR01 to provide solution
PMR-CA containing approximately 500 ppm PMR dye in PR01. Upon
standing for 15 minutes sample PMR-CA thickened considerably, in 30
minutes was completely gelled, and in 2 hr was solid. This result
shows that such a solution can not be made without adding a
complementary charge of acid to the system for stability
purposes.
[0121] To circumvent gelation of the dye masterbatch, a PMR dye
concentrate masterbatch was made by stabilizing PR01 with triflic
acid prior to introducing the PMR dye. In this preparation a 10%
PMR solution, PMR-0, was prepared by combining 1.35 pt methyl
acetate and 0.15 pt PMR. PR01, TFMSA Concentrate, and PMR-10 were
combined in a ratio 9.58 pt to 0.165 pt to 0.3 pt respectively to
create a dye concentrate, PMR-3000, having an acid/dye molar ratio
of approximately 1.5/1 and containing approximately 3000 ppm dye.
This solution was made by first combining PR01 and TFMSA
Concentrate in a HDPE container and mixing well to obtain a
homogenous solution followed by addition of the PMR-10 solution and
additional mixing to homogeneity. Dye masterbatch PMR-3000 was
further diluted with PR01 to provide sample PMR-500, containing
approximately 500 ppm PMR, by combining 8.34 pt PR01 and 1.66 pt
PMR-3000 and mixing to homogeneity.
[0122] Final samples were prepared as in Example 1 by adding 0.5 pt
PMR-500 solution to 4.5 g of the various Scotchweld cyanoacrylates
and PR01, shown in Table C1, to provide comparative examples having
a dye content of approximately 50 ppm. All of the resulting
comparative samples were purple in color, and were tested for
initial set time and bleaching as described in the Test Methods
section. The results are presented in Table C1, which show that
although set times of all the samples are generally reasonable,
perhaps some of the samples exhibit a slowing of cure, none of
these PMR-containing comparative samples bleached colorless upon
cure, i.e., all the examples retained a purple tint after cure.
This is in contrast to the samples prepared in Example 1, based on
Michler's hydrol, where upon cure all samples bleached completely
in the set time test.
TABLE-US-00007 TABLE C1 Set time of Pentamethoxy Red Containing
Cyanoacrylate Adhesives Initial Set Set Time Example Commercial CA
Time (sec) Bleach C1A Scotchweld CA40 2 tinted C1B Scotchweld CA4 4
tinted C1C Scotchweld CA40H 4 tinted C1D Scotchweld CA5 9 tinted
C1E Scotchweld CA7 2 tinted C1F Scotchweld CA8 4 tinted C1G
Scotchweld CA9 20-30 tinted C1H Scotchweld CA100 >60 tinted C1I
PR01 7 tinted
Example 2 and Comparative Example 2
[0123] This example examines the solution and color stability of
color change cyanoacrylate compositions based on a variety of
different organic and fluorochemical acids. Dye masterbatches
employing each acid were-prepared by first formulating a 10%
solution of each acid in PR01. The acid solutions contained the
components and quantities shown in Table 2 (in parts by
weight).
TABLE-US-00008 TABLE 2 Acid Concentrates Acid PR01 Acid
borontrifluoride etherate 1.35 0.15 trifluoromethanesulfonic acid
1.35 0.15 methylene disulfone 1.35 0.15 methide acid 1.24 0.26
imide acid 1.35 0.15 ethylimide acid 1.35 0.15
trifluoromethanesulfonic anhydride 1.35 0.15 trifluoroacetic acid
1.35 0.15 trichloroacetic acid 1.35 0.15 sulfuric acid (96%) 1.35
0.15 hydrochloric acid (36%) 1.08 0.42 phosphoric acid (85%) 1.32
0.18 nitric acid (69%) 1.35 0.15 sulfonyl amide 1.35 0.15
methanesulfonic acid (98%) 1.35 0.15 dodecylbenzenesulfonic acid
1.35 0.15
[0124] The acid concentrates prepared in Table 2 were mixed with
PR01 and dye base concentrate A in the proportions (in parts by
weight) shown in Table 3 to prepare dye masterbatches. This was
accomplished by adding the acid concentrate to PR01 in a HDPE
bottle and mixing well for 15 minutes on a rotary agitator prior to
introducing the dye concentrate. Following the addition of dye base
concentrate the samples were placed back on the rotary agitator and
allowed to mix at ambient temperature. All of the samples were
charged to provide a dye concentration of approximately 3000 ppm
and an acid/dye mol ratio of approximately .about.2/1, with the
exception of trifluoromethanesulfonic anhydride which had a 1/1
anhydride/dye mol ratio. Inspecting the samples after 30 minutes of
mixing revealed that Comparative Examples C2A-Master through
C2G-Master had all either solidified or gelled, and thus were
discarded. With respect to C2A-Master and C2B-Master the anions of
the acids alone are too nucleophilic, and therefore cause gelling.
In the cases of Comparative Examples C2C-Master through C2F-Master,
containing water, when compared to 2D-Master containing about 40%
water, which did not cause gelling, it is apparent that the anions
of the acids employed in MastersC2C-Master through C2F-Master were
the causes of gelling, not the water content. Regarding C2G-Master,
although slightly acidic, it fails to stabilize the dye, in
contrast to its imide acid, 2E-Master. With respect to C21-Master,
it is considered to closely resemble C2H-Master with respect to
nucleophilicity of its anion. It is expected that other
fluorine-free organic sulfonic acids will be equivalent to these in
anion nucleophilicity.
TABLE-US-00009 TABLE 3 Dye Masterbatches Acid Dye Base Example Acid
PR01 Concentrate Concentrate A 2A-Master borontrifluoride 4.723
0.157 0.15 etherate 2B-Master trifluoromethane- 4.715 0.167 0.15
sulfonic acid 2C-Master methylene disulfone 4.585 0.311 0.15
2D-Master methide acid 4.453 0.457 0.15 2E-Master imide acid 4.584
0.312 0.15 2F-Master ethylimide acid 4.484 0.423 0.15 2G-Master
trifluoromethane- 4.724 0.157 0.15 sulfonic anhydride C2A-Master
Trifluoroacetic acid 4.751 0.127 0.15 C2B-Master Trichloroacetic
acid 4.702 0.181 0.15 C2C-Master sulfuric acid (96%) 4.767 0.109
0.15 C2D-Master hydrochloric acid 4.829 0.040 0.15 (36%) C2E-Master
phosphoric acid 4.767 0.109 0.15 (85%) C2F-Master nitric acid (69%)
4.802 0.070 0.15 C2G-Master sulfonyl amide 4.716 0.165 0.15
C2H-Master methanesulfonic 4.769 0.107 0.15 acid (98%) C2I-Master
dodecylbenzene- 4.539 0.362 0.15 sulfonic acid
[0125] The remaining dye masterbatches were all deep blue colored
fluids and were further employed to formulate colored cure
indicating cyanoacrylate compositions by mixing 0.25 pt dye
masterbatch with 9.75 pt PR01, as described in Example I to provide
samples having a final dye content of approximately 75 ppm. The
resulting samples were divided into equal portions in separate HDPE
bottles and one aged at ambient conditions and the other at
49.degree. C. As the samples aged, qualitative viscosity
observations were made to determine if viscosity was stable or
increasing, by inverting the bottle and observing the adhesive
flow. Color of the samples was also monitored during aging, as
described in the Test Methods section of this document. The
viscosity and color assessment results are shown in Tables 4
through 7. Set time data was monitored periodically and results
obtained reported in Table 8.
TABLE-US-00010 TABLE 4 Viscosity of Color Change CAs Aged at
49.degree. C. Example Parent Acid 3 day 7 day 14 day 28 day 56 day
2A boron trifluoride etherate liquid Liquid liquid no flow gel 2B
trifluoromethanesulfonic liquid Liquid liquid liquid liquid acid 2C
methylene disulfone liquid Liquid liquid liquid liquid 2D methide
acid liquid liquid liquid liquid liquid 2E imide acid liquid liquid
liquid liquid liquid 2F ethylimide acid liquid liquid liquid liquid
liquid 2G trifluoromethanesulfonic liquid liquid liquid liquid
viscous anhydride C2H methanesulfonic acid solid solid -- -- -- C2I
dodecylbenzenesulfonic acid hi visc solid -- -- --
TABLE-US-00011 TABLE 5 Viscosity of Color change CAs Aged at Room
Temperature Example Parent Acid 3 day 7 day 14 day 28 day 56 day 2A
boron trifluoride etherate liquid liquid liquid no flow solid 2B
trifluoromethanesulfonic acid liquid liquid liquid liquid liquid 2C
methylene disulfone liquid liquid liquid liquid liquid 2D methide
acid liquid liquid liquid liquid liquid 2E imide acid liquid liquid
liquid liquid liquid 2F ethylimide acid liquid liquid liquid liquid
liquid 2G trifluoromethanesulfonic liquid liquid liquid liquid gel
anhydride C2H methanesulfonic acid liquid hi visc no flow -- -- C2I
dodecylbenzenesulfonic acid liquid slight visc slow flow -- --
increase
TABLE-US-00012 TABLE 6 Color Stability of Color Change CAs Aged at
Room Temperature 14 28 56 Example Parent Acid Initial 7 day day day
day 2A boron trifluoride etherate 3.00 3.00 3.00 0 0 2B
trifluoromethanesulfonic 3.00 3.00 3.00 3.00 1.50 acid 2C methylene
disulfone 3.00 3.00 3.00 3.00 2.50 2D methide acid 2.75 3.00 2.50
2.25 1.50 2E imide acid 3.00 3.00 3.00 3.00 2.50 2F ethylimide acid
3.00 3.00 3.00 3.00 2.50 2G trifluoromethanesulfonic 3.00 3.00 3.00
3.00 0.00 anhydride C2H methanesulfonic acid 3.00 0.00 0.00 -- --
C2I dodecylbenzenesulfonic 3.00 0.50 0.00 -- -- acid
TABLE-US-00013 TABLE 7 Color Stability of Color change CAs Aged at
49.degree. C. 14 28 56 Example Parent Acid Initial 7 day day day
day 2A boron trifluoride 3.00 3.00 3.00 1 0 etherate 2B
trifluoromethanesulfonic 3.00 3.00 3.00 3.00 2.00 acid 2C methylene
disulfone 3.00 3.00 3.00 3.00 2.50 2D methide acid 2.75 3.00 2.50
2.25 2.00 2E imide acid 3.00 3.00 3.00 3.00 2.50 2F ethylimide acid
3.00 3.00 3.00 3.00 2.50 2G trifluoromethanesulfonic 3.00 3.00 3.00
3.00 0 anhydride C2H methanesulfonic acid 3.00 0.00 -- -- -- C2I
dodecylbenzenesulfonic 3.00 0.00 -- -- -- acid
[0126] The results in Tables 4 through 7 show that Comparative
Examples C2H and C2I provide only limited stability as both of
these Examples cured in the bottle during heat aging, in less than
7 days, and likewise lost their color in both room temperature and
49.degree. C. aging.
[0127] Set time of the liquid samples aged at room temperature and
49.degree. C. are presented in Table 8. A control sample of PR01
had an initial set time of 5-6 seconds and as room temperature
aging proceeded, at all test times between 14 and 56 days, a set
time of approximately 3 seconds was observed. The data in Table 8
show that commercial cyanoacrylate containing dye masterbatches
based on a variety of acids, cured the same as the control from
which they were formulated, thus the presence of the dye
masterbatch in PR01 did not alter cure speed. All of these
inventive samples bleached from deep blue to colorless as they
cured in the set time test.
TABLE-US-00014 TABLE 8 Set Time of Color-Change Cyanoacrylate
Samples Aged at Room Temperature and 49.degree. C. Set Time (sec)
Set Time (sec) after after RT Aging 120.degree. F. Aging Sample 14
28 56 14 28 ID Stabilizing Acid Initial day day day day day 56 day
2A boron trifluoride etherate 5-6 3 -- -- 4 -- -- 2B
trifluoromethanesulfonic 5-6 3 4 3 2 2 2 acid 2C methylene
disulfone 5-6 4 4 3 3 1 3 2D methide acid 4-5 3 2 2 2 2 3 2E imide
acid 5-6 3 4 4 3 2 2 2F ethylimide acid 5-6 3 3 4 2 2 2 2G
trifluoromethanesulfonic 5-6 3 3 -- 2 3 10 anhydride
Example 3
[0128] This example examines stability of a series of color change
cyanoacrylates containing various ratios of triflic acid and
methanesulfonic acid. Two dye masterbatches were prepared employing
the components and quantities (in parts by weight) shown in Table 9
to provide samples having acid/dye mol ratio of approximately 2/1
and containing approximately 3000 ppm dye. These dye masterbatches
were then blended with each other to provide the mol ratios of
triflic acid content shown in Table 10 (in parts by weight).
TABLE-US-00015 TABLE 9 Dye Masterbatches MSA TFMSA Dye Base Example
Acid PR01 Concentrate Concentrate Concentrate A 3A-Master
methanesulfonic acid 9.54 0.213 -- 0.3 (98%) 3E-Master
trifluoromethanesulfonic 9.43 -- 0.333 0.3 acid
TABLE-US-00016 TABLE 10 Dye Master Batches Triflic Acid Content -
Mol % Example 3A-Master 3E-Master of Total Acid 3B-Master 3.75 1.25
0.25 3C-Master 2.50 2.50 0.50 3D-Master 1.25 3.75 0.75
[0129] Five color change cyanoacrylate compositions were prepared
from these 5 dye masterbatches by blending 0.25 pt of each with
9.75 pt PR01 as described in Example 1 to obtain samples containing
approximately 75 ppm dye. The samples thus prepared were all deep
blue in color and were checked for set time then aged at room
temperature and assessed after 16 days for any change in color or
viscosity. These results are presented in Table 11, which show that
stability increases, with respect to color and viscosity, as the
ratio of triflic acid/methane sulfonic acid in the samples
increases, i.e., as methanesulfonic acid, and so the nucleophilic
anion content, decreases.
TABLE-US-00017 TABLE 11 Room Temperature Aged Color change
Cyanoacrylate Triflic Acid Content - Initial Set 16 Day 16 Day
Example Mol % of Total Acid Time (sec) Viscosity Color 3A 0.00 3
gel 0 3B 0.25 3 gel 0 3C 0.50 3 high visc 1 3D 0.75 3 liquid 3 3E
1.00 2 liquid 3
Example 4
[0130] This example examines the effect of accelerant on the set
time and bleaching speed of a color change cyanoacrylate. In this
example 0.13 g dye masterbatch 3E-Master, having acid/dye mol ratio
of approximately 2/1 and containing approximately 3000 ppm dye
Michler's hydrol cation, was added to a 5 g bottle of Scotch.TM.
Super Glue Liquid and mixed well to obtain a deep blue colored
sample containing approximately 75 ppm dye. The set time of this
color change cyanoacrylate and an AD110 control were measured as
described in the Test Method section with the exception that the
test was conducted on Lexan.TM. polycarbonate. The set time on
polycarbonate (hereinafter "PC") was found to be quite long and
protracted, i.e., rather than the quick rigid set observed on
glass; the set time on PC was more a continuum where the coupons
could be moved easily initially, then with more difficulty as
viscosity increased, and finally to a stiff stage where the coupons
could still be moved but required significant force to move. In the
time frame of 1-3 minutes after bond closure increasing viscosity
of the adhesive could be detected, by 10-15 minutes the bond
strength was building significantly, but the coupons could still be
moved with moderate hand force. Probing of the bond strength was
discontinued at 15 minutes. The dye-containing sample progressed
toward cure slightly faster than did the control adhesive
throughout all phases of cure. With respect to color change during
the 15 minutes of observation, the bonded area of both samples
became cloudy, due to the PC imbibing the monomer, and slightly
grey in color, with the exception that the dye-containing sample
was a light blue-grey color. After standing for 16 hr in a constant
temperature and humidity room (CTH), at 22.degree. C. and 50% RH,
the samples appeared fully cured and the faint blue hue had
vanished from the dye-containing sample.
[0131] The next experiment undertaken examined the effect of a cure
accelerant on the cure speed of the dye-containing sample. One of
the PC coupons was misted with Pronto.TM. Surface Activator, by
depressing the spray bottle pump mechanism one time, and allowing
the accelerator to dry for a few minutes. Cyanoacrylate was applied
to the uncoated coupon and the bond was closed immediately. A set
time of 3-4 seconds was recorded with the sample bleaching
colorless immediately upon cure. In this case the bonded area was
clear and did not exhibit the cloudy appearance observed above when
no accelerator was employed. The above findings show that by
employing an appropriate accelerant, the set time and bleach speed
on PC of colored cure indicating of the present disclosure can be
reduced from many minutes to a matter of seconds.
Example 5
[0132] This example examines the effect of dye concentration on set
time and color stability of cyanoacrylate gel. The components
employed to prepare the samples of this composition were dye
masterbatch 3E-Master, having acid/dye mol ratio of approximately
2/1 and containing approximately 3000 ppm Michler's hydrol cation,
and CA-50 gel, used in the proportions (in parts by weight) shown
in Table 12. Sample 5D consisted of 1 pt sample 5A and 8 pt CA-50
gel and provided a dye content of approximately 5 ppm. The samples
were formulated by hand mixing, with a spatula, the appropriate
ratio of gel and dye masterbatch, and transferring the homogenous
blue colored cure-indicating gel to a polypropylene container.
Sample color and set time were assessed using the tests described
in the Test Methods section and are presented in Table 12. The data
show that the color intensity of the gels decreased with decreasing
dye concentration. All of the samples bleached colorless during the
set time test. A sample of the neat colorless gel was tested for
set time and found to have set time of 16 seconds, thus the
presence of dye in Examples 5A to 5D did not slow the set time.
TABLE-US-00018 TABLE 12 Color Change Cyanoacrylate Gel Sample CA-50
3E- Dye Conc in Set Time ID Gel Master Gel (ppm) Color (Sec) 5A
9.85 0.1500 45 2.0 13 5B 9.90 0.1000 30 1.5 13 5C 9.95 0.0500 15
1.0 12 5D -- -- 5 0.5 12
Example 6
[0133] This example examines the effect of acid/dye ratio on
stability of color change cyanoacrylate compositions. In this
series, dye concentrates consisting of PR01, triflic acid, and
Michler's hydrol were prepared by the procedure described in
Example 1 using the components in the proportions (in parts by
weight) shown in Table 13 to obtain dye masterbatches containing
approximately 3000 ppm dye.
TABLE-US-00019 TABLE 13 Dye Masterbatches Acid/Dye Dye mol TFMSA
Concentrate Sample ID Ratio PR01 Concentrate A 6A-Master 2.5 9.36
0.416 0.3 6B-Master 2.0 9.43 0.333 0.3 6C-Master 1.5 9.51 0.250 0.3
6D-Master 1.0 9.58 0.167 0.3
[0134] The masterbatches of Table 13 were further formulated with
PR01 to provide the color change cyanoacrylates of Table 14 by
combining 0.25 pt masterbatch with 9.75 pt PR01, as described in
Example 1, to obtain samples containing approximately 75 ppm dye.
Color and set time of the samples were assessed as described in the
Test Methods section and are reported in Table 14.
TABLE-US-00020 TABLE 14 Acid/Dye Ratios Masterbatch Acid/Dye Set
Time Sample ID mol Ratio Color Set Time Bleach 6A 2.5 2.75 4
colorless 6B 2.0 2.75 5 colorless 6C 1.5 3 5 colorless 6D 1.0 3 7
colorless
Example 7
[0135] This Example examines the effect of dye concentration on set
time, color, and bleaching of color change cyanoacrylate
compositions. In this Example a dye masterbatch consisting of PR01,
triflic acid, and Michler's hydrol was prepared by the procedure
described in Example 1, employing 9.43 pt PR01, 0.333 pt TFMSA
Concentrate, and 0.3 pt dye base concentrate A, to obtain dye
masterbatches having an acid/dye mol ratio of approximately 2/1 and
containing approximately 3000 ppm dye. The dye masterbatches were
further formulated with PR01 to provide the color change
cyanoacrylates of Table 15 using the proportions (in parts by
weight) disclosed therein. Color, set time, and bleaching of the
samples were assessed as described in the Test Methods section and
are reported in Table 15. Samples 7D through 7F were considerably
darker than the reference solutions, thus were labeled 3+. Set time
results show that no cure inhibition is observed and that all the
samples have essentially the same set time. All of the samples
bleached colorless in the Set Time Test.
TABLE-US-00021 TABLE 15 Dye Content Dye Set Set Time Sample (ppm)
PRO-1 Masterbatch Color Time Bleach 7A 10 9.97 0.0333 2 5 colorless
7B 50 9.83 0.1667 2.75 5 colorless 7C 100 9.67 0.3333 3 5 colorless
7D 250 9.17 0.8333 3+ 5 colorless 7E 500 8.33 1.6667 3+ 5-6
colorless 7F 1000 6.67 3.3333 3+ 4-6 colorless
Examples 8 and 9
[0136] In these Examples two color change cyanoacrylate
compositions were prepared that changed from a first colored state
to a second colored state, and did not exhibit the colored to
colorless transition state, exhibited as the cyanoacrylate-based
adhesive progresses from an uncured state to a cured state, of many
of the previous examples. Example 8 contained the bleachable dye of
Michler's hydrol and the non-indicator dye
1,8-dihydroxyanthraquinone. Example 9 contained two color-change
dyes, that of Michler's hydrol, and methyl yellow
(4-(dimethylamino)azobenzene).
[0137] Example 8 employed two different dye solutions. The
bleachable dye solution was 3E-Master, containing triflic acid and
Michler's hydrol in PR01 having an acid/dye mol ratio of 2/1 and a
dye content of 3000 ppm. The non-bleachable dye solution contained
38.92 pt SB20 and 1.2 pt of a 10% solution of
1,8-dihydroxyanthraquinone in methyl acetate, to provide a
non-indicating dye content of approximately 3000 ppm. To 9.67 pt of
the non-bleachable dye solution was added 0.333 pt of 3E-Master, to
provide a bright green color change cyanoacrylate composition
having a 1,9-dihydroxyanthraquinone dye content of approximately
2900 ppm and a Michler's hydrol cation content of approximately 100
ppm. This sample was tested for set time as described in the Test
Methods section and provided a set time of 1-2 seconds, which was
the same as the parent SB20 adhesive. As this cyanoacrylate-based
adhesive progressed from an uncured state to a cured state, the
color changed almost instantaneously from green to bright
yellow.
[0138] Example 9 employed two different dye solutions, both of
which contained indicating dyes. The first dye solution consisted
of the Michler's hydrol cation masterbatch of Example 1 based on
PR01, triflic acid, and Michler's hydrol, and had an acid/dye mol
ratio of approximately 2.2/1 and a dye content of approximately
3000 ppm.
[0139] The second dye solution was prepared as in Example I by
combining 9.25 pt PR01, 0.2 pt TFMSA Concentrate, and 0.6 pt of a
5% solution of methyl yellow in methyl acetate to provide a methyl
yellow dye concentrate having an acid to dye mol ratio of 1/1 and a
dye content of 3000 ppm.
[0140] The adhesive composition was prepared by combining 8.08 pt
PR01, 0.25 pt Michler's hydrol cation masterbatch, and 1.67 pt
methyl yellow dye concentrate, to provide a color change
cyanoacrylate composition containing approximately 75 ppm Michler's
hydrol and 500 ppm methyl yellow. This sample was tested for set
time as described in the Test Methods section and provided a set
time of approximately 5 seconds, which was the same as the parent
PR01 adhesive. As this cyanoacrylate-based adhesive progressed from
an uncured state to a cured state, the color changed from an
initial deep red color to an intermediate green and finally to a
light orange color.
Example 10
[0141] This example demonstrates that a medical grade butyl
cyanoacrylate adhesive can be converted to a color change adhesive
composition by addition of a Michler's hydrol dye masterbatch. The
dye masterbatch and color change cyanoacrylate adhesive were
prepared as described in Example I by first formulating a 10 wt %
dye base solution of Michler's hydrol in methyl acetate and a 10 wt
% acid solution of triflic acid in Nexcare.TM. props Liquid Bandage
(NDLB). The 10 wt % dye solution contained 1.35 pt methyl acetate
and 0.15 pt Michler's hydrol. The acid solution contained 1.8 pt
NDLB and 0.2 pt triflic acid. The dye masterbatch contained 9.46 pt
NDLB, 0.30 pt 10% triflic acid solution, and 0.30 pt 10% dye
solution which resulted in a dye masterbatch having an acid/dye mol
ratio of approximately 1.8/1 and a dye content of approximately
3000 ppm dye.
[0142] The adhesive composition was prepared by combining 9.75 pt
NDLB and 0.25 pt dye masterbatch to provide a color change medical
grade cyanoacrylate adhesive composition containing approximately
75 ppm dye. This deep blue sample was tested for set time as
described in the Test Methods section and provided a set time of
approximately 3-4 seconds, which was the same as the parent NDLB
adhesive. As this cyanoacrylate-based adhesive progressed from an
uncured state to a cured state in the set time test, the color
changed from an initial deep blue color to colorless. A drop of
this adhesive composition was applied to the skin of a human hand,
spread with a cotton-tipped applicator to provide a thin uniform
layer, and observed for color change and set time. In approximately
1 minute the adhesive bleached colorless and was dry to the
touch.
Example 11
[0143] This example displays the Strength Ratio of a variety of
acids with various nitrated aniline Acidity Indicators using the
procedures described in the Test Methods section of this
disclosure. The results are given in Table 16 and show the
differentiation between workable and nonworkable acids in the
instant invention.
TABLE-US-00022 TABLE 16 Strength Ratio of Various Acids (from
Titration) Strength Workable Acid Indicator X Ratio E (Y/N)
(CF.sub.3SO.sub.2).sub.2NH 2,6-dinitroaniline 0.93 Y
(C.sub.2F.sub.5SO.sub.2).sub.2NH 2,6-dinitroaniline 0.93 Y
CF.sub.3SO.sub.3H 2,6-dinitroaniline 0.82 Y BF.sub.3:2 acetic acid
2-chloro-6-nitroaniline 0.82 Y
(CF.sub.3SO.sub.2).sub.3C.sup.-(H.sub.2O).sub.16H.sup.+
4-methoxy-2-nitroaniline 0.52 Y
(CF.sub.3SO.sub.2).sub.2C(H)C.sub.6H.sub.5 4-methoxy-2-nitroaniline
0.49 Y (CF.sub.3SO.sub.2).sub.2CH.sub.2 4-methoxy-2-nitroaniline
0.34 Y BF.sub.3:etherate 2-chloro-6-nitroaniline 0.30 Y (not
buffered) BF.sub.3:2 CH.sub.3OH 4-chloro-2-nitroaniline 0.24 Y
Methanesulfonic acid 4-chloro-2-nitroaniline <0.01 N
Methanesulfonic acid 2,6-dinitroaniline <0.001 N Methanesulfonic
acid 2-chloro-6-nitroaniline <0.001 N BF.sub.3:2 H.sub.2O
4-chloro-2-nitroaniline 0.14 N CF.sub.3CO.sub.2H
4-methoxy-2-nitroaniline <0.01 N
Example 12
[0144] This example examines color change properties of various
Michler's hydrol dye derivatives. Masterbatches of each dye are
made by combining 0.44 pt 10% solution of TFMSA in PR01 with 0.40
pt 10% solution of dye base in THF and mixing well, followed by the
addition of 9.16 pt PR01. The resulting dye masterbatches are
agitated slowly for 30 minutes to assure homogeneity. Combining
4.91 pt PR01 with 0.094 pt dye masterbatch and agitating slowly for
30 minutes completes the preparation of color change cyanoacrylate
samples. The resulting samples are tested by placing 1 drop of
color change cyanoacrylate on a first glass microscope slide,
placing a second glass slide atop the first and observing after 1
minute to detect cure and note any color change that occurred.
Inspecting the samples for cure reveals that all samples cure.
Table 17 provides the color change behavior.
TABLE-US-00023 TABLE 17 Bleach Behavior of Color Change
Cyanoacrylate Compositions Initial Color Sample Dye Name Color
After Cure 12-1 N-[bis[4-(dimethylamino)phenyl]- blue colorless
methyl]-aniline 12-2 N-[bis[4-(dimethylamino)phenyl]- blue
colorless methyl]-N'-(4-ethoxyphenyl)-urea 12-3
N-[bis[4-(dimethylamino)phenyl]- blue colorless
methyl]-N'-n-bulyl-urea 12-4 N-[bis[4-(dimethylamino)phenyl]- blue
colorless methyl]-N'-phenyl-urea 12-5
N-[bis[4-(dimethylamino)phenyl]- blue colorless methyl]-morpholine
12-6 N-[bis[4-(dimethylamino)phenyl]- light blue colorless
methyl]-benzenesulfonamide 12-7
Bis[4-(4-morpholinyl)phenyl]methanol blue colorless 12-8
1,1-bis(4-dimethylaminophenyl)ethanol blue colorless 12-9
1,1-bis(4-dimethylaminophenyl)- blue colorless ethylene 12-10
bis(4-(dimethylamino-2-methylphenyl)- blue colorless methanol 12-11
bis(3-bromo-4-dimethylaminophenyl)- blue colorless methanol
Example 13
[0145] This Example examines the effect of acid/dye mol ratio on
the behavior of color change cyanoacrylate adhesives. The acids
examined were BF.sub.3:2CH.sub.3OH, BF.sub.3(AcOH).sub.2, and imide
acid at acid/dye mol ratios ranging from 1:1 to 5:1. For the two
BF.sub.3-complexes, the acid/dye mol ratio was based on mols
BF.sub.3, not mols of the BF.sub.3-complexes. Acid/dye
masterbatches were formulated by preparing 10 wt % solutions of
each acid in SB14 and combining these acid concentrates with Dye
Base Concentrate A and SB14 in the ratios shown in Table 18.
Specifically, Dye Base Concentrate A was added to acid concentrate
and mixed well before SB14 was added and mixed to complete
preparation of the acid/dye concentrates. Mixing 0.25 parts of
acid/dye concentrate with 9.75 pt SB14 in HDPE bottles completed
preparation of the color change cyanoacrylate adhesives.
TABLE-US-00024 TABLE 18 Acid/Dye Concentrates Acid/Dye Dye Base
Sample Acid mol Ratio SB14 Conc A Acid Conc 13-1-AD
BF.sub.3(AcOH).sub.2 1.00 9.210 0.3 0.578 13-2-AD
BF.sub.3(AcOH).sub.2 2.00 8.690 0.3 1.155 13-3-AD
BF.sub.3(AcOH).sub.2 3.00 8.170 0.3 1.733 13-4-AD
BF.sub.3(AcOH).sub.2 4.00 7.650 0.3 2.311 13-5-AD
BF.sub.3(AcOH).sub.2 5.00 7.130 0.3 2.889 13-6-AD
BF.sub.3.cndot.2CH.sub.3OH 1.00 9.595 0.3 0.150 13-7-AD
BF.sub.3.cndot.2CH.sub.3OH 2.00 9.459 0.3 0.301 13-8-AD
BF.sub.3.cndot.2CH.sub.3OH 3.00 9.324 0.3 0.451 13-9-AD
BF.sub.3.cndot.2CH.sub.3OH 4.00 9.188 0.3 0.602 13-10-AD
BF.sub.3.cndot.2CH.sub.3OH 5.00 9.053 0.3 0.752 13-11-AD Imide Acid
1.00 9.449 0.3 0.312 13-12-AD Imide Acid 2.00 9.168 0.3 0.624
13-13-AD Imide Acid 3.00 8.888 0.3 0.936 13-14-AD Imide Acid 4.00
8.607 0.3 1.248 13-15-AD Imide Acid 5.00 8.326 0.3 1.560
[0146] Sample 13-6, based on BF.sub.3:2CH.sub.3OH and having
acid/dye mol ratio of 1:1, gelled shortly after preparation, and
Sample 13-11, based on imide acid and having an acid/dye mol ratio
of 1:1 gelled sometime between 1 and 2 weeks while aging at room
temperature. The color stability of the adhesives was assessed
after aging them for various lengths of time at room temperature as
shown in Table 19. For each acid, increased acid/dye ratios
resulted in increased bleach times.
TABLE-US-00025 TABLE 19 Color of Color Change CA Adhesives Aged at
Room Temperature Acid/Dye 1 Week 2 Week 3 Week Sample Acid mol
Ratio Color Color Color 13-1 BF.sub.3(AcOH).sub.2 1.00 2.75 2.75
2.75 13-2 BF.sub.3(AcOH).sub.2 2.00 2.75 2.5 2.5 13-3
BF.sub.3(AcOH).sub.2 3.00 2.75 2.5 2.5 13-4 BF.sub.3(AcOH).sub.2
4.00 2.5 2.25 2.25 13-5 BF.sub.3(AcOH).sub.2 5.00 2.5 2.25 2.25
13-6 BF.sub.3:2CH.sub.3OH 1.00 -- -- -- 13-7 BF.sub.3:2CH.sub.3OH
2.00 2.75 2.5 2.25 13-8 BF.sub.3:2CH.sub.3OH 3.00 2.75 2.5 2.25
13-9 BF.sub.3:2CH.sub.3OH 4.00 2.75 2.5 2.25 13-10
BF.sub.3:2CH.sub.3OH 5.00 2.75 2.75 2.5 13-11 Imide Acid 1.00 -- --
-- 13-12 Imide Acid 2.00 2.75 3 2.75 13-13 Imide Acid 3.00 2.25 2.5
2.25 13-14 Imide Acid 4.00 2 2 2 13-15 Imide Acid 5.00 1.5 1.5
1.5
[0147] The present invention should not be considered limited to
the particular examples described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention may be applicable will be readily apparent to those of
skill in the art to which the present invention is directed upon
review of the instant specification.
* * * * *
References