Title: Dyed fluoropolymers
Abstract: Dyed fluoropolymers that are useful, for example, as conformal coatings comprise the reaction product of one or more fluorochemical (meth)acrylate monomers and one or more (meth)acrylate functional dyes. Coating compositions comprise the dyed fluoropolymer and articles are coated with the coating composition.
Patent Number: 6,894,105 Issued on 05/17/2005 to Parent, et al.
| Inventors:
|
Parent; Michael J. (Oakdale, MN);
Savu; Patricia M. (Maplewood, MN);
Johnson; Harry E. (Hudson, WI);
Olson; David B. (Marine on Saint Croix, MN)
|
| Assignee:
|
3M Innovatives Properties Company (St. Paul, MN)
|
| Appl. No.:
|
205764 |
| Filed:
|
July 26, 2002 |
| Current U.S. Class: |
524/520; 428/421; 428/422; 524/544; 526/256; 526/259 |
| Intern'l Class: |
C08L 027/12; B32B027/00 |
| Field of Search: |
428/421,422
524/520,544
526/256,259
|
References Cited [Referenced By]
U.S. Patent Documents
| 2803615 | Aug., 1957 | Ahlbrecht et al.
| |
| 2841573 | Jul., 1958 | Ahlbrecht et al.
| |
| 4036859 | Jul., 1977 | Ribaldone et al.
| |
| 4698240 | Oct., 1987 | Ono et al.
| |
| 4795794 | Jan., 1989 | Winnik et al.
| |
| 5151516 | Sep., 1992 | Beck et al.
| |
| 5415669 | May., 1995 | Bühler et al.
| |
| 5847091 | Dec., 1998 | Shiraki et al.
| |
| 5847156 | Dec., 1998 | Eldin et al.
| |
| 6001936 | Dec., 1999 | Barrera et al.
| |
| 6391807 | May., 2002 | Jariwala et al.
| |
| 6448301 | Sep., 2002 | Gaddam et al.
| |
| 2002/0042470 | Apr., 2002 | Moore et al.
| |
| Foreign Patent Documents |
| 0 004 655 | Oct., 1979 | EP.
| |
| 0 323 060 | Jul., 1989 | EP.
| |
| 0 422 535 | Apr., 1991 | EP.
| |
| 0 554 696 | Aug., 1993 | EP.
| |
| 1 172 418 | Jan., 2002 | EP.
| |
| 1 270 254 | Apr., 1972 | GB.
| |
| WO 9001526 | Feb., 1990 | WO.
| |
| WO 9921937 | May., 1999 | WO.
| |
| WO 0123472 | Apr., 2001 | WO.
| |
| WO 0216306 | Feb., 2002 | WO.
| |
| WO 0216517 | Feb., 2002 | WO.
| |
| WO 0220625 | Mar., 2002 | WO.
| |
| WO 0206/6483 | Aug., 2002 | WO.
| |
Primary Examiner: Sanders; Kriellion A.
Attorney, Agent or Firm: Fulton; Lisa P.
Claims
1. A dyed fluoropolymer comprising the reaction product of (a) one or more fluorochemical
(meth)acrylate monomers and (b) one or more (meth)acrylate functional dyes.
2. The dyed fluoropolymer of claim 1 represented by the following formula:
##STR25##
wherein the sum of a+b is a number such that the compound is polymeric,
R
1 is hydrogen methyl,
R
2 is a straight chain or branched chain alkyl containing 1 to about
4 carbon atoms,
Z is an organic divalent linking group,
D is a dye moiety,
Q is a covalent bond or an organic divalent linking group,
R
f is a fluoroaliphatic group that comprises a fully fluorinated terminal
group having 12 carbon atoms or less, and
X is a hydrogen atom or a group derived from a free radical initiator.
3. The dyed fluoropolymer of claim 2 wherein said Z is a divalent alkylene containing
1 to about 15 carbon atoms, the alkylene optionally containing one or more catenary heteroatoms.
4. The dyed fluoropolymer of claim 3 wherein said Z is represented by —C
nH
2n—,
wherein n is an integer of 1 to about 15.
5. The dyed fluoropolymer or claim 2 wherein said Q is represented by one of
the following general formulas:
##STR26##
wherein n is an integer of 1 to about 4, and
R
3 is hydrogen or a straight chain or branched chain alkyl containing
1 to about 6 carbon atoms.
6. The dyed fluoropolymer of claim 2 wherein said R
f has 3 or 4 carbon atoms.
7. The dyed fluoropolymer of claim 1 wherein said fluorochemical (meth)acrylate
monomers are chosen from the group consisting of N-methyl perfluorobutanesulfonamidoethyl
acrylate and N-methyl perfluorobutanesulfonamidoethyl acrylate.
8. The dyed fluoropolymer of claim 7 wherein at least 75 percent of the fluorochemical
(meth)acrylate monomers are N-methyl perfluorobutanesulfonamidoethyl acrylate.
9. The dyed fluoropolymer of claim 1 further comprising (meth)acrylic acid.
10. The dyed fluoropolymer of claim 9 comprising less than 2 weight percent (meth)acrylic acid.
11. The dyed fluoropolymer of claim 9 comprising fluoroalkyl (meth)acrylate/(meth)acrylic
acid copolymer, wherein said fluoroalkyl group has 12 or fewer carbon atoms.
12. The dyed fluoropolymer of claim 1 further comprising one or more hydrocarbon monomers.
13. The dyed fluoropolymer of claim 12 wherein said hydrocarbon monomers are
chosen from the group consisting of butyl methacrylate and lauryl methacrylate.
14. The dyed fluoropolymer of claim 1 wherein said (meth)acrylate functional
dye is fluorescent.
15. The dyed fluoropolymer of claim 14 wherein said (methacrylate functional
dye is represented by the following general formula:
##STR27##
wherein n is an integer from 1 to about 15.
16. The dyed fluoropolymer of claim 15 wherein said n is 4.
17. The dyed fluoropolymer of claim 14 wherein said (meth)acrylate functional
dye is represented by the following general formula:
##STR28##
wherein m is an integer from 1 to about 15.
18. A coating composition comprising a dyed fluoropolymer comprising (a) the
reaction product of (i) N-methyl perfluorobutanesulfonamidoethyl acrylate, (ii)
N-methyl perfluorobutanesulfonamidoethyl methacrylate, (iii) methacrylic acid,
(iv) butyl methacrylate, (v) lauryl methacrylate, and (vi)
##STR29##
wherein n=4, and (b) a solvent comprising one or more hydrofluoroethers.
19. A coating composition comprising the dyed fluoropolymer of claim 1.
20. The coating composition of claim 19 further comprising a solvent.
21. The coating composition of claim 20 wherein said solvent comprises one or
more hydrofluoroethers.
22. An article coated with the coating composition of claim 18.
23. The article of claim 22 wherein said article is a circuit board assembly.
Description
FIELD
This invention relates to dyed fluoropolymers that are useful, for example,
as conformal coatings for electronic components and, in other aspects, to coating
compositions comprising the dyed fluoropolymers, and articles coated with the coating compositions.
BACKGROUND
Conformal coatings are protective coatings that conform to the surface
of a substrate or article (for example, dielectric coatings on electronic components
and circuit board assemblies). Properly applied conformal coatings can increase
the working life of a circuit board assembly by protecting its components and the
board itself. Conformal coatings can, for example, provide a barrier to moisture,
chemicals, dust, fungus, ultraviolet light, and ozone, as well as act as a stress-relieving
shock and vibration absorber.
Various materials such as, for example, polyurethanes, acrylics, epoxies,
and silicones are commonly used for conformal coatings. The selection of a conformal
coating material is generally based upon desired performance and processing requirements
for a specific application. Silicones, for example, are known for high temperature
operating capability and can typically be used at operating temperatures up to
about 200° C., whereas many other conformal coating materials can typically
only be used at operating temperatures up to about 130° C. Silicones, however,
exhibit a high coefficient of thermal expansion and relatively poor adhesion to
many materials. Acrylics, on the other hand, are generally the easiest of the coating
materials to handle and rework, and typically provide better adhesion properties
than silicone. Acrylics, however, often suffer from the temperature limitations
mentioned above.
Another consideration in the selection of a conformal coating material is
the cure mechanism required by the material. Depending upon the type of material,
the conformal coating may be a heat cure, ultraviolet (UV) light cure, moisture
cure, or no cure system. The substrate or article being coated must be capable
of withstanding the cure mechanism required by the material. Therefore, conformal
coating materials that require no cure mechanism are typically most desirable.
Proper coverage and uniformity of the conformal coating over the assembly
is critical for effective protection of the assembly. It can sometimes be difficult,
however, to determine the integrity and uniformity of the conformal coating when
it is coated on an assembly. Therefore, the conformal coating material is sometimes
doped with a dye or "tracer" to aid in the quality assurance inspection of the
assembly for proper coverage. Fluorescent tracers work well in many conformal coating
materials, but the use of fluorescent dyes in fluoropolymers is limited because
of poor compatibility of the dyes with the polymer matrix. This results in poor
color quality and dye bleed and little or no color entrainment into the resulting coating.
SUMMARY
In view of the foregoing, we recognize that there is a need for compositions
that
are suitable for use in conformal coatings used in high temperature applications
and that contain an effective tracer. Furthermore, we recognize that it would be
advantageous for coating compositions that require no curing to form a conformal coating.
Briefly, in one aspect, the present invention provides dyed fluoropolymers
that are useful as conformal coating materials. As used herein, a "dyed fluoropolymer"
refers to a fluoropolymer comprising a dye that is covalently bonded to the polymer
and excludes fluoropolymers in which a dye has merely been dissolved or blended
therein. Dyed fluoropolymers of the invention comprise the reaction product of
one or more fluorochemical (meth)acrylate monomers and one or more olefinic functional
dyes (preferably, one or more (meth)acrylate functional dyes). As used herein,
"(meth)acrylate" refers to both acrylates and methacrylates.
It has been discovered that when used in a conformal coating the above-described
dyed fluoropolymers surprisingly meet the thickness, flexibility, and dielectric
withstand requirements of the IPC specification for conformal coatings, IPC-CC-830
"Qualification and Performance of Electronic Insulating Compound for Printed Board Assemblies."
The dyed fluoropolymers of the invention are also highly resistant to leaching
or blooming of the meth(acrylate) functional dye because the dye is covalently
bonded to the fluorochemical (meth)acrylate monomers. In addition, the dyed fluoropolymers
of the invention are more thermally stable than most conformal coating materials,
being only slightly less stable than silicone. Yet since they are acrylic, the
dyed fluoropolymers of the invention have appreciably better adhesion than silicone
to many materials. Furthermore, the dyed fluoropolymers of the invention do not
require a cure mechanism.
Thus, the dyed fluoropolymers of the invention meet the need in the art for
conformal coating materials that can be used in high temperature applications and
contain an effective fluorescent tracer.
In other aspects, this invention also provides coating compositions comprising
the dyed fluoropolymers of the invention and articles such as, for example, circuit
board assemblies coated with the coating compositions.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a plot of weight percent remaining versus time for a series of coating
compositions described in Comparative Examples C1-C3 and Example 1.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The dyed fluoropolymers of the invention comprise one or more fluorochemical
(meth)acrylate monomers. Suitable fluorochemical (meth)acrylate monomers include,
for example, 1,1-dihydroperfluorobutyl (meth)acrylate, 1,1-dihydropentafluoropropyl
(meth)acrylate, hexafluoroisopropyl (meth)acrylate, 2,2,3,3,4,4,4-heptafluorobutyl
(meth)acrylate, 2,2,3,4,4,4-hexafluorobutyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl
(meth)acrylate, 1,1-dihydroperfluorocyclohexylmethyl (meth)acrylate, 1-pentafluoroethyl-2-(trifluoromethyl)propyl
(meth)acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl (meth)acrylate,
3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl (meth)acrylate, N-methyl perfluorooctanesulfonamidoethyl
(meth)acrylate, N-ethyl perfluorohexylsulfonamidoethyl (meth)acrylate, and N-methyl
perfluorobutanesulfonamidoethyl (meth)acrylate.
Preferably the (meth)acrylate is derived from an alcohol selected from
CF
3CHFCF
2CH
2OH, HCF
2CF
2CH
2OH,
C
2F
5CH(OH)CF(CF
3)
2, C
3F
7CH
2OH,
C
4F
9CH
2OH, C
4F
9SO
2N(CH
3)CH
2CH
2OH,
and alcohols derived from the telomerization of tetrafluoroethylene. Preferred
fluorochemical (meth)acrylate monomers are N-methyl perfluorobutanesulfonamidoethyl
acrylate and N-methyl perfluorobutanesulfonamidoethyl methacrylate. Preferably,
at least 75 percent of the fluoromonomers used in the fluoropolymers of the invention
are N-methyl perfluorobutanesulfonamidoethyl acrylate.
The dyed fluoropolymers of the invention include those that can be represented
by the following general formula:
##STR1##
wherein the sum of a+b is a number such that the compound is polymeric (a
and b can represent non-integral values or averages of the number of each monomer
unit present), R
1 is hydrogen or methyl, R
2 is a straight
chain or branched chain alkyl containing 1 to about 4 carbon atoms, z is an organic
divalent linking group, D is a dye moiety (that is, a moiety comprising a chromophore
that absorbs and/or emits light in the visible region), Q is a covalent bond or
a divalent linking group, R
f is a fluoroaliphatic group that comprises
a fully fluorinated terminal group having 12 carbon atoms or less, and X is a hydrogen
atom or a group derived from a free radical initiator.
The dyed fluoropolymer of the invention contains a plurality of pendant R
f
groups (typically from 2 to about 10) proximal to one another and preferably contains
from about 5 percent to about 80 percent, more preferably from about 20 percent
to about 65 percent, and most preferably about 25 percent to about 55 percent fluorine
by weight, based on the total weight of the compound, the loci of the fluorine
being essentially in the R
f groups. R
f is a stable, inert,
non-polar, preferably saturated, monovalent moiety which is both oleophobic and
hydrophobic. R
f preferably contains at least about 3 carbon atoms, more
preferably about 3 to about 6 carbon atoms, and most preferably about 3 or 4 carbon
atoms. R
f can be a straight chain or branched chain or can be cyclic
if sufficiently large. R
f is preferably free of polymerizable olefinic
unsaturation. It is preferred that R
f contain about 35% to about 78%
fluorine by weight, more preferably about 40% to about 78% fluorine by weight.
The terminal portion of the R
f group contains a fully fluorinated terminal
group such as, for example, —CF
3, or can be partially fluorinated
such as, for example, HCF
2—.
Z and Q are independently chosen linking groups that can be a divalent alkylene
(straight chain or branched chain) containing 1 to about 15 carbon atoms. The alkylene
can optionally contain one or more catenary heteroatom-containing groups. As used
herein, the term "heteroatom-containing group" means a group containing a heteroato
(for example, nitrogen, oxygen, or sulfur) that replaces one or more carbon atoms
of the Z or Q linking group in a manner such that the heteroatom-containing group
is bonded to at least two carbon atoms of the Z or Q linking group.
The Z or Q linking group can be a group that results from the condensation reaction
of a nucleophile such as an alcohol, an amine, or a thiol with and electrophile,
such as an ester, acid, acid halide, isocyanate, sulfonyl halide, sulfonyl ester,
or can result from a displacement reaction between a nucleophile and leaving group.
Illustrative examples of suitable Z and Q linking groups include straight
chain, branched chain, or cyclic aklyenes, arylenes, and aralkylenes that optionally
contain, for example, an oxy, oxo, hydroxy, thio, sulfonyl, sulfoxy, amino, imino,
sulfonamido, carboxamido, carbonyloxy, urethaneylene, urylene, or a combination
thereof (for example, sulfonamidoalkylene).
Representative examples of suitable Z and Q linking groups include
the following:
| |
| —SO2NR1′(CH2)kO(O)C— |
—CONR1′(CH2)kO(O)C— |
| —(CH2)kO(O)C— |
—CH2CH(OR2′)CH2O(O)C— |
| —(CH2)kC(O)O— |
—(CH2)kSC(O)— |
| —(CH2)kO(CH2)kO(O)C— |
—(CH2)kS(CH2)kO(O)C— |
| —(CH2)kSO2(CH2)kO(O)C— |
—(CH2)kS(CH2)kOC(O)— |
| —(CH2)kSO2NR1′(CH2)kO(O)C— |
—(CH2)kSO2— |
| —SO2NR1′(CH2)kO— |
—SO2NR1′(CH2)k— |
| —(CH2)kO(CH2)kC(O)O— |
—CH2)kSO2NR1′(CH2)kC(O)O— |
| —(CH2)kSO2(CH2)kC(O)O— |
—CONR1′(CH2)kC(O)O— |
| —(CH2)kS(CH2)kC(O)O— |
—CH2CH(OR2′)CH2C(O)O— |
| —SO2NR1′(CH2)kC(O)O— |
—(CH2)kO— |
| —(CH2)kNR1′C(O)O— |
—OC(O)NR1′(CH2)k— |
| |
wherein each k is independently an integer of 0 to about 20, R
1′
is hydrogen, phenyl, or alkyl containing 1 to about 4 carbon atoms, and R
2′
is alkyl-containing 1 to about 20 carbon atoms. Each structure is non-directional,
that is, —(CH
2)
kC(O)O— is equivalent to —O(O)C(CH
2)
k —.
Preferably Z is a divalent alkylene (straight or branched chain) containing
1 to about 15 carbon atoms, the alkylene optionally containing one or more catenary
heteroatoms. More preferably Z is —C
nH
2n—,
wherein n is 1 to about 15.
Preferably Q is a covalent bond or divalent linking group represented
by one of the following formulas:
##STR2##
wherein n is an integer of 1 to about 15 (preferably 1 to about 4) and R
3
is hydrogen or a straight chain or branched chain alkyl containing 1 to about 6
carbon atoms.
Preparation of the fluorochemical (meth)acrylates and fluorocopolymers
useful in the invention are known in the art and are described, for example, in
U.S. Pat. No. 2,803,615 (Ahlbrecht et al.) and U.S. Pat. No. 2,841,573 (Ahlbrecht
et al.), which are incorporated herein by reference in their entirety.
Preferably, the dyed fluoropolymers of the invention further comprise
(meth)acrylic acid. Incorporating a small amount (preferably less than 2 weight
percent) of (meth)acrylic into the fluoropolymer improves the adhesion of the coating
to polar substrates such as, for example, the metallic surfaces of printed circuit
boards. Preferred dyed fluoropolymers of the invention comprise (meth)acrylate/(meth)acrylic
acid copolymers wherein the fluoroalkyl group has 12 or fewer carbon atoms (preferably
6 or fewer).
Preferably, the dyed fluoropolymers of the invention also comprise one
or more hydrocarbon monomers. Suitable hydrocarbon monomers include, for example,
(meth)acrylates containing 2 to about 20 carbon atoms and vinyls. Preferred hydrocarbon
monomers include butyl methacrylate and lauryl methacrylate.
The dyed fluoropolymers of the invention comprise one or more olefinic functional
dyes. Preferably, the dyed fluoropolymers of the invention comprise one or more
(meth)acrylate functional dyes. The (meth)acrylate functional group is capable
of reacting with a nucleophile to form a covalent bond either through addition
or displacement. In the dyed fluoropolymers of the invention, the (meth)acrylate
functional group of the dye copolymerizes with the fluoromonomer to form the dyed
fluoropolymer. The dyed fluoropolymers are therefore highly resistant to leaching
and blooming, which is an advantage over dyed polymers in which the dyes are fixed
through adsorption or mechanical entrapment.
(Meth)acrylate functional dyes consist basically of three components:
a dye moiety, a bridging or linking group, and the (meth)acrylate functional group.
The dye can be fluorescent or non-fluorescent.
Fluorescent dye useful in the present invention include, for example,
dyes from the coumarin, naphthalic acid derivatives, perylene, benzanthrone, benzothioxanthone,
diketopyrrolopyrrole, rhodamine, cationic methine, and azomethine dye classes.
A description of fluorescent dyes and their synthesis can be found, for example,
in R. M. Christie, Rev. Prog. Coloration 23, 1-18 (1993).
Non-fluorescent dyes useful in the present invention include, for
example, those from the azo, anthraquinone, benzodifurnanone, indigoid, quinophthalone,
and sulfur classes of dyes.
Representative examples of (meth)acrylate functional dyes that are
useful in the dyed fluoropolymers of the invention include:
##STR3##
Preferably, the (meth)acrylate functional dyes are fluorescent. Preferred
fluorescent (meth)acrylate functional dyes are those that are relatively more soluble
in solvents such as, for example, acetone and hydrofluoroethers and the monomer
mixture. Preferred fluorescent (meth)acrylate functional dyes include:
##STR4##
The (meth) acrylate functional dyes can generally be prepared using methods known
in the art. For example, first a chromogen is prepared. Typically, the chromogen
is a cyclic, fused aromatic derivative containing the appropriate chromophores
to achieve the desired absorbance/emission spectra characteristics. Alternatively,
a commercially available dye chromogen such as, for example, 1-amino-2-bromo-4-hydroxyanthroquinone
can be purchased. The chromogen can be reacted with reagents to prepare a hydroxy-functionalized
dye derivative. The hydroxy-functionalized dye derivative can then be transformed
to the corresponding (meth)acrylate functional dye by methods known in the art
such as, for example, by esterification using acrylic acid or acrylol chloride,
or by transesterification using methyl acrylate.
Dye loading in the dyed fluoropolymers of the invention generally varies depending
upon the final application of the coating. Typically, however, the dyed fluoropolymers
of the invention contain between about 0.001 and 3.0 weight percent of (meth)acrylate
functional dye based upon the total polymeric content of the composition (preferably
between about 0.01 and 2.0 weight percent).
The dyed fluoropolymers of the invention can be prepared by free radical solution
polymerization of the fluorochemical (meth)acrylate monomers with the (meth)acrylate
functional dye(s) (and optionally with (meth)acrylic acid and/or other hydrocarbon
monomers) in any conventional solvent, including both fluorinated and non-fluorinated
solvents. Typically, the dye is dissolved into the melted fluorochemical monomers
or, if used, the hydrocarbon monomers before the solvent is added.
Preferably fluorinated solvents are used. More preferably, non-ozone depleting,
non-flammable, and fast drying partially fluorinated (rather than perfluorinated)
solvents such as, for example, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons
(HFCs) and hydrofluoroethers (HFEs) are used. As used herein, the term "hydrofluorocarbon"
means compounds consisting only of the elements carbon, hydrogen and fluorine,
the term "hydrochlorofluorocarbon" means compounds consisting only of the elements
carbon, hydrogen, fluorine and chlorine, and the term "hydrofluoroether" means
compounds that contain carbon, hydrogen, fluorine, and at least one ether oxygen,
and are free of chlorine, bromine and iodine.
Most preferably, one or more hydrofluoroethers or mixtures of one or more hydrofluoroethers
with one or more other hydrofluorocarbons such as, for example, CF
3CH
2CF
2CH
3
are used. Hydrofluoroethers useful in this invention are typically liquid at ambient
temperature and pressure, are non-ozone depleting and can be non-flammable. Non-flammable
hydrofluoroethers (that is, hydrofluoroethers which do not exhibit a flash point
when tested in a closed cup flash point test performed according to ASTM D 56-87)
are preferred. Particularly preferred hydrofluoroethers are perfluoroalkyl alkyl
ethers and more preferably, the hydrofluoroethers correspond to the following general formula:
wherein x is 1 or 2, R is an alkyl group having from 1 to about 4 carbon
atoms, and R′
f is a fluoroaliphatic group.
R′
f preferably comprises between about 2
to about 9 carbon atoms. When x is 1, R′
f is preferably selected
from the group consisting of a linear or branched perfluoroalkyl group, perfluorocycloalkyl
group-containing perfluoroalkyl groups, perfluorocycloalkyl groups, linear or branched
perfluoroalkyl groups having one or more catenary atoms, perfluorocycloalkyl-group-containing
perfluoroalkyl groups having one or more catenary heteroatoms, and perfluorocycloalkyl
groups having one or more catenary heteroatoms. When x is 2, R′
f is
preferably selected from the group consisting of linear or branched perfluoroalkylene
groups, perfluorocycloalkyl group-containing-perfluoroalkylene groups, perfluorocycloalkylene
groups, linear or branched perfluoroalkylene groups having one or more catenary
atoms, perfluorocycloalkyl-group-containing perfluoroalkylene groups having one
or more catenary heteroatoms, and perfluorocycloalkylene groups having one or more
catenary heteroatoms.
Representative examples of hydrofluoroethers suitable for use in the
invention include n-C
4F
9OCH
3, n-C
4F
9OCH
2CH
3,
CF
3CF(CF
3) CF
2OCH
3, CF
3CF(CF
3)
CF
2OC
2H
5, C
8F
17OCH
3,
CH
3O—(CF
2)
4—OCH
3, C
5F
11OC
2H
5,
C
3F
7OCF
3, CF
3OC
2F
4OC
2H
5,
C
3F
7OCF(CF
3)CF
2OCH
3, (CF
3)
2CFOCH
3,
C
4F
9OC
2F
4OC
2F
4OC
2H
5,
and C
4F
9O(CF
2)
3OCH
3.
Typically an initiator is used to initiate polymerization. A wide range
of molecules (for example, monoperoxycarbonates and peroxydicarbonates, perisononanoate,
tert-amyl and tert-butylperesters, tert-amyl and tert-butyl perketal, bisperoxides,
diazo compounds, and others) can be used as free radical sources for the initiation
of polymerization.
The dyed fluoropolymers of the invention can be used in coating compositions.
Coating compositions comprising the dyed fluoropolymers of the invention can further
comprise a solvent. Any solvent in which the dyed fluoropolymer dissolves to a
suitable degree, which does not deleteriously affect the substrate, and which does
not leave a harmful residue can be used. It is preferable, however, to use the
same solvent that was used in the polymerization reaction. Therefore, preferences
for coating solvents are the same as the preferences stated for polymerization solvents.
Typically, the coating composition comprises up to about 50 weight percent
dyed fluoropolymer (preferably up to about 35 weight percent; most preferably up
to about 28 weight percent). The resulting coatings are generally less than about
3 mils (0.08 mm) thick, but the desired thickness depends upon the specific application.
Thicker or thinner coatings can be prepared if desired, typically by selection
of the solvent(s) (for example, C
4F
9OCH
3) and/or
concentration of the fluoropolymer in the coating composition. The coating composition
can be applied to a substrate or article using any suitable means known in the
art such as, for example, brushing, dipping, spraying, and flow coating. An advantage
of the invention is that the composition-coated substrate or article can be allowed
to air dry, no curing mechanism is required.
It has been discovered that the coating compositions of the invention meet the
thickness and dielectric withstand requirements of IPC-CC-830 and can be used as
conformal coatings for electronic components and circuit board assemblies. Conformal
coatings comprising the dyed fluoropolymers of the invention are chemically stable
and more thermally stable than many common conformal coating materials. They are
therefore well suited for high temperature applications where silicone conformal
coatings have traditionally been used, and at least some coating compositions of
the invention appear to have better adhesion properties than silicone.
Circuit board components and assemblies can be coated with the present coating
composition to insulate them from contaminants and preserve their electronic functions.
Circuit board assemblies can be coated before or after the components have been
mounted, but they are typically conformally coated after they have been completely
assembled and soldered.
Proper coverage and uniformity of the conformal coating over the assembly
is critical for effective protection of the assembly. The (meth)acrylate functional
dye of the coating compositions of the invention aids in the quality assurance
inspection of the circuit board assembly for proper coverage of the coating.
The fluorescent dyed fluoropolymers of the invention can be readily observed
by the human eye using, for example, "black light" or on-line with an electro-optical
device. When a fluorescent (meth)acrylate functional dye is used, coating thickness
(or coating weight) can be measured on-line using techniques in which the dye is
excited by optical radiation and the thickness of the coating is determined by
the magnitude of the emitted fluorescent radiation.
The coating compositions of the invention can also be used in many other anti-corrosion,
anti-migration, anti-stiction, and particulate shedding protection applications
such as, for example, flat panel displays, pellicles, semiconductor chips, wafers,
and components, microelectromechanical systems (MEMS), fiber optic components,
cellular phone components, medical respiratory masks, and in any application in
which sensitive materials require protection from their environment.
EXAMPLES
The invention will be further explained by the following illustrative examples
which are intended to be non-limiting.
| |
Description, Formula |
|
| Descriptor |
and/or Structure |
Availability |
| Acryloyl chloride |
CH2═CHCOCl |
Sigma- |
| |
|
Aldrich, |
| |
|
Milwaukee, WI |
| AD-1 |
##STR5##
|
See preparation below |
| AD-2 |
##STR6##
|
See preparation below |
| AD-3 |
##STR7##
|
See preparation below |
| AD-4 |
##STR8##
|
See preparation below |
| AD-5 |
##STR9##
|
See preparation below |
| AD-6 |
##STR10##
|
See preparation below |
| AD-7 |
##STR11##
|
See preparation below |
| 1-amino-2-bromo-4- hydroxyanthroquinone |
##STR12##
|
Aceto Chemical Co., Lake Success, NY |
| 1,4-diamino-2,3- dicyano anthraquinone |
##STR13##
|
Aceto Chemical Co., Lake Success, NY |
| 5-amino-1-pentanol |
NH2(CH2)5OH |
Sigma-Aldrich |
| 2-amino-1-ethanol |
NH2(CH2)2OH |
Sigma-Aldrich |
| 6-amino-1-hexanol |
NH2(CH2)6OH |
Sigma-Aldrich |
| 2-aminothiophenol |
##STR14##
|
Sigma-Aldrich |
| BMA |
Butyl methacrylate |
Sigma-Aldrich |
| 4-chloronaphthalic anhydride |
##STR15##
|
Acros Organics, Pittsburgh, PA |
| 8-chloro-1-octanol |
Cl(CH2)8OH |
Sigma-Aldrich |
| CYTA |
Conap ™ CE-1170 acrylic |
Cytec, |
| |
conformal coating |
Olean, NY |
| DMF |
dimethylformamide; |
Sigma-Aldrich |
| |
(CH3)2NC(O)H |
| DOWS |
Dow ™ 3-1765 silicone |
Dow Corning, |
| |
conformal coating |
Midland, MI |
| ethylene carbonate |
##STR16##
|
Sigma-Aldrich |
| HAS |
HumiSeal ™ 1B-31 acrylic |
Humiseal, |
| |
conformal coating |
Woodside, NY |
| HFE-7100 |
3M ™ NOVEC ™ HFE-7100; |
3M Company, |
| |
C4F9OCH3 perfluorobutyl |
St. Paul, MN |
| |
methyl ether |
| HFE-7200 |
3M ™ NOVEC ™ FLUID HFE-7200; |
3M Company |
| |
C4F9OC2H5 perfluorobutyl |
| |
ethyl ether |
| HFE-72DE |
3M ™ NOVEC ™ HFE-72DE (HFE- |
3M Company |
| |
7100 (10%), HFE-7200 |
| |
(20%), and trans- |
| |
dichloroethylene (70%)) |
| 2-hydroxy benzanthrone |
##STR17##
|
Can be prepared according to U.S. Pat. No. 4,036,859 (Example 1 and 2) |
| LMA |
Lauryl methacrylate |
Sigma-Aldrich |
| LUPEROX |
Luperox ™ 26M50, t-butyl |
Atofina |
| |
peroctoate (50%) |
Chem., |
| |
|
Philadelphia, |
| |
|
PA |
| MAA |
Methacrylic acid |
Sigma-Aldrich |
| NBS |
N-bromosuccinimide |
Sigma-Aldrich |
| sodium nitrite |
NaNO2 |
Sigma-Aldrich |
| tetraethyl ammonium |
(C2H5)4NI |
Sigma-Aldrich |
| iodide |
| triethyl amine |
N(C2H5)3 |
Sigma-Aldrich |
Preparation 1: Synthesis of MeFBSEA
Ethoxylation of MeFBSA with Ethylene Carbonate
Reaction:
Charges:
- A. 100 g MeFBSA (C4F9SO2NHCH3,
MW=313, 0.32 moles)
- B. 2.8 g Na2CO3 (0.026 moles)
- D1. 8 g ethylene carbonate (MW=88) (available from Sigma-Aldrich, Milwaukee,
Wis.) melted in oven at 50° C.
- D2.8 g ethylene carbonate
- D3.8 g ethylene carbonate
- D4.10 g ethylene carbonate (total weight=34 g, 0.38 moles)
- E. 300 ml water
- F. 300 ml water
- G. 300 ml 3 wt % sulfuric acid
- H. 300 ml water
- I. 300 ml water
- J. 300 ml water
Procedure:
1. Charges A and B were placed in a one liter 3-necked flask with an overhead
stirrer, thermocouple, addition funnel, and reflux condenser.
2. The batch was heated to 60° C. (140° F.) at which point the
batch was molten and stirring was begun. The set point was increased to 120°
C. (248° F.).
3. When the batch reached 120° C., Charge D1 was removed from the oven
and transferred to the addition funnel. Charge D1 was then added slowly over a
period of 10 minutes. Outgasing (carbon dioxide) was observed. Thirty minutes elapsed
until the rate of outgasing was noticed to have diminished.
4. Charge D2 was then transferred to the addition funnel and added over
a period of 5 minutes. After 25 minutes, the rate of outgasing had slowed and Charge
D3 was added over a 5 minute period. After 30 minutes, Charge D4 was
removed from the oven, added to the addition funnel, and added to the batch over
a 5 minute period.
5. The set point was reduced to 110° C. (230° F.) and allowed
to stir overnight.
6. In the morning, the batch was cooled to 90° C. (194° F.) and
the batch was sampled. Gas chromatographic (GC) analysis showed the material to
be 96.1% desired product and to contain no amide. Charge E was added. The batch
was stirred for 30 minutes, allowed to phase split and the upper water phase was
vacuum decanted off. The operation was repeated for Charge F at 63° C. (145° F.).
7. The batch was then agitated with Charge G for 30 minutes at 63°
C. (145° F.), then was phase split, and vacuum decanted. The pH of the water
layer was tested and found to be less than 2.
8. The batch was then washed with water charges H, I, and J successively
at 63° C. (145° F.).
9. The batch was melted and poured out of the flask into a bottle and allowed
to solidify. A small amount of water on top of the resulting solid was poured off,
and the remaining solid material in the jar was found to weigh 124 g.
10. The solid material was melted into a two-necked 500 ml flask. The melting
point was found to be 57° C. (135° F.).
11. The resulting liquid material (113 g) was distilled at 667-933 Pa (5-7
torr Hg). 104 g (92% of undistilled material) distilled at a head temperature of
130-137° C. (266-279° F.) and a pot temperature of 136-152° C. (277-306°
F.). Further increase of the pot temperature to 170° C. (338° F.) resulted
in no further material distilling over.
Preparation of MeFBSEA (N-methyl-(perfluorobutanesulfonamido)ethyl acrylate)
Reaction:
Charges:
A. 112 g MeFBSE alcohol (C4F9SO2N(CH3)CH2CH2OH,
0.313 moles)
B. 0.07 g phenothiazine (available from Sigma-Aldrich, Milwaukee, Wis.)
C. 0.11 g methoxyhydroquinone (MEHQ) (available from Sigma-Aldrich, Milwaukee, Wis.)
D. 100 g heptane
E. 27.5 g acrylic acid (0.38 moles)
F. 1 g anhydrous triflic (trifluoromethanesulfonic) acid (available as FC-24
from 3M, St. Paul, Minn.)
G. 300 g water
H. 300 g water
Procedure:
1. Charges A, B, C, D, E and F were added to a 3-necked flask equipped with
decanter assembly, overhead stirrer, and a thermocouple under positive nitrogen pressure.
2. The flask was warmed to 60° C. and the stirring was begun. The batch
was stirred at reflux which was initially at 96° C. and rose to 102°
C. by the end of the reaction. The theoretical water that should be collected in
the decanter was 6.3 ml. After 15 minutes of refluxing, 2 ml had collected. After
1 hour and 15 minutes, the reflux temperature was 99° C. and 5 ml had collected.
After 5 hours and 15 minutes the reflux temperature was 102° C. and 5.4 ml
had collected. A sample was withdrawn from the batch and GC analysis showed no
unreacted alcohol, 92.6% desired product and 7.4% high boiler.
3. The batch was stripped atmospherically to the decanter until at 103°
C. no more heptane collected in it.
4. The batch was cooled to 64° C. and vacuum was pulled slowly. More
heptane was stripped off until at 5 torr no more liquid was observed to be distilling off.
5. Vacuum was broken and Charge G was added. The batch was stirred at 64°
C. for 15 minutes, allowed to phase spilt and the upper layer was vacuumed off.
6. This operation was repeated with Charge H and then the batch was allowed
to cool to room temperature at which point the product was a solid. The remaining
water was poured off and the product material was melted out of the container into
a jar. The weight of the product was 125 g (theoretical 129 g). GC analysis showed
the material to be 92.64% desired acrylate and 7.36% acrylic acid Michael adduct.
Preparation 2: Synthesis of MeFBSEMA
MeFBSEMA (N-methyl-(perfluorobutanesulfonamido)ethyl methacrylate) was prepared
as described in Preparation 1 above, except using methacrylic acid in place of
acrylic acid
##STR18##
Step A: Preparation of (2)
A 1000 mL round bottom flask equipped with a heating mantle, stirrer and dropping
funnel was charged with 4-chloronaphthalic anhydride ((1), 125 g, 0.54 moles),
potassium carbonate (36.9 g, 0.27 moles), 215 g isopropyl alcohol, and 322 g sulfolane
and heated to about 50° C. 2-aminothiophenol (73.9 g moles) was added dropwise
so that the temperature was maintained below 80° C. The mixture was then heated
to 90° C. and held for 3 hours. The mixture was cooled to 15° C. and
the resulting orange precipitate was recovered via filtration with a Buchner funnel.
The solid was resuspended in DI water (470 g) and then filtered using a Buchner
funnel. The solid was dried and analysis via
13C NMR confirmed the structure (2).
Step B: Preparation of (3)
A 5000 mL round bottom flask fitted with a dropping funnel and immersed in an
ice-water
cooling bath was charged with (2) (241.0 g, 0.75 moles) and 3600 g DMF. HCl (600
g, concentrated) was slowly added dropwise, keeping the temperature below 15°
C. An aqueous solution of sodium nitrite (52.5 g, 21%) was added and the reaction
mixture was stirred for two hours, maintaining the temperature below 5° C.
CuSO
45H
2O (3.0 g, 0.012 moles) was added and a mild exotherm
occurred. The cooling bath was then replaced with a heating mantle, and nitrogen
gas evolved as the temperature was slowly elevated to 100° C. and held for
3 hours. The mixture was cooled to ambient temperature (˜25° C.) and
filtered using a Buchner funnel. The resulting solid was resuspended in DI water
(1000 g) and filtered again using a Buchner funnel. The solid (3) was dried to
yield 171 g (75% of the theoretical material).
Step C. Preparation of (4)
A 1000 mL round bottom flask fitted with a condenser was charged with (3) (40.0
g, 0.13 moles), 5-amino-1-pentanol (13.5 G, 0.13 moles) and DMF (240 g) and the
ensuing mixture was heated to reflux (-155° C.) for 3 hours. After it was
determined that no starting material remained (via thin layer chromatography (TLC)
in ethyl acetate) the mixture was cooled to 80° C. and 400 g DI water was
added, keeping the temperature between 70-80° C. until all the water was added.
The resulting suspension was then filtered using a Buchner funnel and the solid
material was resuspended in 500 g DI water and filtered again using a Buchner funnel.
The yield of resulting material (4) was 41 g.
Step D: Preparation of AD-1
A one liter three neck round bottom flask fitted with an overhead stirrer and
dropping
funnel was charged with (4) (25.0 g; 0.062 moles), dimethyl formamide (310.0 g)
and triethyl amine (8.15 g; 0.08 moles). The resulting mixture was stirred and
heated to 40° C. at which time acryloyl chloride (6.44 g, 0.07 moles) was
added drop wise to the mixture over 30 minutes while keeping the temperature at
approximately 40° C. After two hours, additional triethyl amine (3.0 g) and
acryloyl chloride (2.2 g) were added. The resulting mixture was stirred for another
hour and then cooled to 20° C. Deionized (DI) water (500.0 g) was added to
the cooled mixture and solid AD-1 was isolated via filtration with a Buchner funnel.
AD-1 was re-suspended in DI water (700.0 g), filtered using a Buchner funnel and
air dried (yielding 24.7 g; 96% purity of AD-1. The structure and purity were confirmed
via
13C nuclear magnetic resonance (NMR) analysis.
##STR19##
Step A: Preparation of (6)
A 1 liter three neck round bottom flask was charged with 630 g sulfuric acid.
The
solution was stirred and heated to 80° C. 1,4-diamino-2,3-dicyano anthraquinone
((5)123.4 g 0.43 moles) was added to the flask, using a water bath and heating
mantle to control the reaction temperature at 140-150° C. Once all of the
anthraquinone was added, the reaction temperature was held at 150° C. for
one hour. The reaction mixture was then cooled to 40° C. and 255 g water was
added, using cooling to control the exotherm to below 50° C. and then cooled
to room temperature.
The reaction mixture was filtered through a glass frit funnel. The resulting
solid filtrate was washed with water. About 500 g additional water was added and
the solid was filtered again. The resulting solid (6) was air dried and used in
the following steps.
Step B: Preparation of (7)
A one liter three neck round bottom flask was charged with 60 g (0.22 moles)
of
the (6), 320 g 1,2-dichlorobenzene and 26.6 g (0.44 moles) 2-amino-1-ethanol (both
available from Aldrich). A dean-stark trap and condenser, and a mechanical stirrer
were used. The batch was heated to about 120° C., distilling out a small amount
of solvent and water. Gradually the batch temperature was raised to 150° C.
and held for three hours. TLC (in ethyl acetate) showed no residual (6).
The batch was cooled to room temperature and about 400 g methanol was added.
The resulting mixture was filtered through a buchner funnel. About 500 g. water
and 25 g. concentrated HCl was added to the resulting solid. The mixture was stirred
and filtered, and then repeated. The resulting blue solid (7) was air dried and
used in the following step.
Step C: Preparation of AD-2
For the preparation of AD-2 the procedure described in Preparation 3 (step D:
preparation of AD-1) was essentially followed, substituting 7 (0.062 moles) for
4.
##STR20##
Step A: Preparation of (9)
A three neck 250 ml round bottom flask was charged with 25 g (0.079 moles) of
1-amino-2-bromo-4
hydroxy anthraquinone (8), 54.5 g (0.55 moles) of 1-methyl-2-pyrollidinone, 92
g (0.78 moles) 1,6-hexane-diol, 8.8 g (0.94 moles) phenol, and 12 g (0.086 moles)
potassium carbonate (all available from Aldrich). The batch was heated to 125°
C. and held for 12 hours. TLC (in ethyl acetate) found no residual starting material.
The reaction was cooled to 50° C. and 150 g methanol was added. The reaction
was then cooled to room temperature and filtered with a buchner funnel. 300 g methanol
was added to the resulting solid and then stirred and filtered. The resulting solid
product was dried in an oven at 100° C. The yield was 19.8 g.
13C
NMR analysis shows the material was 94% pure of (9).
Step B: Preparation of AD-3
For the preparation of AD-3, the procedure described in Preparation 3 (Step D:
preparation of AD-1) above was essentially followed, substituting (9) (0.062 moles)
for (4).
##STR21##
Step 1: Preparation of (11)
A 1 L three neck round bottom flask equipped with a mechanical stirrer and thermometer
was charged with 2-hydroxy benzanthrone ((10), 75.0 g; 0.3 mole), ethylene carbonate
(35.0 g; 0.4 mole), tetraethylammonium iodide (18.0 g; 0.07 mole) and dimethylformamide
(300.0 g). The ensuing mixture was heated at reflux for 15 hours, and additional
ethylene carbonate (25.0 g; 0.3 mole) and tetraethylammonium iodide (8.0 g; 0.03
mole). The resulting mixture was cooled to ambient temperature and DI water was
added (200.0 g). The precipitate was filtered, allowed to air dry and recrystallized
in isopropyl alcohol (yielding 70 g. of (11)).
Step 2: Preparation of (12)
A 1 L three neck round bottom flask equipped with a mechanical stirrer and condenser
was charged with 11 (70.0 g; 0.24 mole), NBS (53.0 g; 0.3 mole) and dimethylformamide
(500.0 g). The ensuing stirred mixture was heated to a
