Hardenable, fluorinated copolymer, process for its manufacture and its application in varnishes and paints

A hardenable fluorinated copolymer of fluorinated monomers and an acrylamide derivative and paints, paints and varnishes comprising such copolymers, and the process of making such hardenable copolymer.

BACKGROUND OF THE INVENTION 
The present invention pertains to a hardenable, fluorinated copolymer of 
vinylidene fluoride (C.sub.2 H2F.sub.2), at least one fluorinated monomer 
selected from tetrafluoroethylene (C.sub.2 F.sub.4), 
chlorotrifluoroethylene (C.sub.2 F.sub.2 Cl) or hexafluoropropylene 
(C.sub.3 F.sub.6), and an acrylamide derivative. This copolymer, which is 
soluble in organic solvents, is particularly recommended for the 
manufacture of paints and varnishes. 
Fluorinated polymers are known for their good mechanical properties and 
their excellent resistance to chemical products and weather. Nevertheless, 
their insolubility in conventional solvents makes them unusable for 
certain application such as, for example, that as a resin for paints and 
varnishes where their properties are sought for the manufacture of 
coatings with good chemical and weather resistance and easy maintenance. 
In order to profit from the desirable properties of the fluorinated 
polymers while avoiding their drawbacks, means were sought to make them 
soluble in conventional organic solvents. In order to achieve this, it is 
known to decrease the crystallinity of fluoride-containing polymers by 
copolymerization of monomers unsaturated in the ethylene position, of 
which monomers at least one is fluorinated. 
In addition, to use such copolymers it is desirable for certain 
applications, particularly for their application in the manufacture of 
paints and varnishes, to preserve for them a sufficient degree of rigidity 
and to make them hardenable by incorporation of functional groups into 
their structure. 
Such hardenable, fluorinated copolymers are described in French Patents 
2,597,873 and 2,569,703. These products are obtained by copolymerization 
of chlorotrifluoroethylene, a fatty acid ester, and hydroxylated or 
ethoxylated allyl glycidyl ether. These copolymers can possibly contain 
less than 20% of another, non-fluoride-containing comonomer. If these 
copolymers contain more than 20% of the preceding comonomer, they lose 
their solubility in solvents and their transparency. In addition, the 
introduction of fluorine by the use of chlorotrifluoroethylene alone also 
brings with it the chlorine-containing element which is not desirable in 
large amounts for the optical properties and resistance to corrosion. 
In JP 59-174,657/84, there is also described a hardenable copolymer based 
on vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, a 
vinyl ester and a hydroxylation agent. This copolymer, which contains less 
than 45% of vinyl ether fluoride and is based on vinyl ester, has the 
drawback of yielding after hydrolysis a rather strongly colored copolymer 
solution, which damages the transparency of the subsequently prepared 
varnishes. 
SUMMARY OF THE INVENTION 
The object of the present invention is a fluorinated copolymer, which is 
easily hardenable in the hot state in the possible presence of a hardening 
agent. When dissolved in an appropriate solvent, this copolymer may be 
used as a paint or varnish to form coatings which are hard, stable and 
transparent in the absence of pigments and which adhere well to metals and 
glass. 
The hardenable copolymer in accordance with the invention, which contains 
the copolymerization radicals of a fluorinated monomer and an acrylamide 
derivative is characterized in that: 
(i) the fluorinated monomer radicals originate from the association of 
vinylidene fluoride and another fluorinated monomer selected from among 
tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, or the 
mixture of at least two of these three monomers, and 
(ii) in that the acrylamide derivative is selected from compounds of 
formula: 
##STR1## 
in which: 
R=H, CH.sub.3, 
##STR2## 
with: 
n representing a number from 0 to 8, 
and 
x representing a number from 0 to 3. 
DETAILED DESCRIPTION 
With respect to the copolymer, the association for 100 moles of the 
totality of fluorinated monomers is usually formed of: 
(i) 50 to 98 moles of vinylidene fluoride, and 
(ii) 2 to 50 moles of the other fluorinated monomer as defined. 
Preferably, the hardenable, fluorinated copolymer in accordance with the 
invention is characterized in that it is comprised of monomer radicals 
originating from: 
(i) 50 to 98 moles, preferably 70 to 85 moles, of vinylidene fluoride, 
(ii) 2 to 50 moles, preferably 15 to 20 moles, of fluorinated monomer 
selected from among tetrafluoroethylene, chlorotrifluoroethylene, 
hexafluoropropylene, or a mixture of at least two of the three monomers, 
and 
(iii) 2 to 30 moles, preferably 5 to 10 moles, of the preceding acrylamide 
derivative per 100 moles of the totality of fluorinated monomers. 
Compounds of the following formulas can be cited among the preferred 
acrylamide derivatives: 
##STR3## 
It is, of course, not excluded to associate several of these acrylamide 
derivatives, particularly an alkoxylated derivative and a hydroxylated 
derivative. 
In order to be able to use these copolymers in a liquid coating composition 
such as paint or varnish, it is recommended that the inherent viscosity of 
the copolymer dissolved in dimethyl formamide at 25.degree. C. at a 
concentration of 1 g/dL be within the range of 0.02 to 0.2 dL/g. 
The copolymer in accordance with the invention is principally obtained 
according to the known solution polymerization procedures. A procedure 
consists of copolymerizing the monomers in a medium which is a solvent for 
all of the monomers, in the presence of an organosoluble initiator, at a 
temperature between 30 and 120.degree. C., preferably between 40.degree. 
and 80.degree. C., under a pressure of approximately 10 to 80 bars, 
preferably between 15 and 40 bars. 
In accordance with the invention, the hardenable copolymer is obtained by 
copolymerization of vinylidene fluoride, at least one fluorinated monomer 
selected from tetrafluoroethylene, chlorotrifluoroethylene, or 
hexafluoropropylene and the previously defined acrylamide derivative. The 
following are employed for 100 moles of polymerized, fluorinated monomers: 
(i) 50 to 98 moles of vinylidene fluoride, and 
(ii) 2 to 50 moles of tetrafluoroethylene or chlorotrifluoroethylene or 
hexafluoropropylene or a mixture of at least two of the three monomers, 
with which is associated the previously defined acrylamide derivative. 
In order to obtain a hardenable copolymer with the best properties, one 
usually associates 2 to 20 moles of the previously defined acrylamide 
derivative per 100 moles of the totality of the fluorinated monomers. 
In accordance with the preferred copolymerization mode, the solvent is 
heated to the selected reaction temperature in an agitated reactor which 
has first been degassed. A mixture of fluorinated monomers as well as an 
initial fraction of the acrylamide derivative are introduced into the 
reactor. 
The amount of monomer mixture to be introduced to reach the selected 
reaction pressure depends on the solubility conditions of the fluorinated 
monomers in the selected solvent. The monomer solvent weight ratio is 
generally between 0.1 and 1. 
When the reaction pressure and the reaction temperature are reached, the 
polymerization initiator is introduced into the reaction. The formation of 
polymer is manifested by a drop in pressure which is compensated for by 
adding fluorinated monomer mixture. 
One can add a fluorinated monomer mixture of molar composition identical to 
that which was introduced initially. It is also possible to take into 
account the individual reactivities of each comonomer and adjust the 
composition of the mixture added during polymerization in order to create 
a copolymer of homogeneous composition. 
The acrylamide derivative can also be added during polymerization. The 
level of this derivative added continuously is generally higher than the 
levels of acrylamide derivative added initially, to take into account the 
greater reactivity of these derivatives. 
The acrylamide derivative is added in such a manner that the composition of 
the mixture of fluorinated monomers and acrylamide derivative introduced 
remains constant during the duration of the polymerization. 
The addition of monomer mixture for maintaining the pressure is continued 
for a sufficiently long period of time to reach a dry extract on the order 
of 10 to 60%, preferably 15 to 40%. 
The volatile residual monomers can be eliminated by degassing. 
The final solution is extracted from the reactor and can be stored in that 
form. It can also be concentrated immediately or subsequently in order to 
obtain the amount of dry extract selected for the use of the copolymer. 
The solvents selected for the copolymerization reaction must allow 
solubilization of the monomer mixture while remaining inert in relation to 
the other reaction components. They are selected preferably from among the 
acetates and alcohols or their mixtures, ketones, and ether alcohols. 
Ethyl acetate, butyl acetate, methanol or tertiobutanol are particularly 
recommended. When the copolymer is prepared for the purpose of application 
in formulations for paint or varnish, a mixture of butyl acetate and 
methanol employed as solvent during the copolymerization can make it 
possible to obtain directly, without subsequent treatment, a composition 
which is usable as it is with, possibly, elimination of the methanol and 
addition of the complementary additives which are standard for these types 
of formulations. 
The copolymerization initiators are known per se, the most popular being 
selected from among the radical polymerization initiators such as the 
perdicarbonates, perpivalates and azo compounds, such as diisopropyl or 
dicyclohexyl percarbonate, tertiobutyl or tertioamyl perpivalate, 
azobisisobutyronitrile and azo-bis-2,2-dimethylvaleronitrile. 
When the cross-linkable copolymer in accordance with the invention is to be 
used as the basis for a paint or varnish formulation, it can, as was 
already mentioned, be used as it is in its initial reaction solvent 
medium. It can also be more or less concentrated and put again into 
solution in a solvent which is better adapted to the type of paint or 
varnish desired. As is, the copolymer in solvent medium yields a colorless 
and transparent solution. To this solution can be added the desired 
additives such as pigment, fillers, diluents, ultraviolet absorption 
agent, stabilizing agent or even hardening agent to improve the hardening 
reaction via hot cross linking. Among the most well-known hardening agents 
can be cited melamine formaldehyde, urea formaldehyde, the epoxides, 
isocyanates, organic acids or their anhydrides. The cross-linking 
temperature of these copolymers is generally between 0 and 260.degree. C. 
and essentially depends on the chemical nature of the hardener and the 
conditions of implementation.

The invention will be further described in connection with the following 
examples which are set forth for purposes of illustration only. 
EXAMPLE 1 
Two liters of methanol are introduced into a 3.3-L autoclave equipped with 
effective agitation, which has been degassed under vacuum. The autoclave 
is brought to a temperature of 50.degree. C. At this temperature, one adds 
440 g of fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene to reach 20 bars of 
pressure in the respective molar proportions of 79/15/6. 
One then adds 4 g of N-methylolacrylamide and then 5 g of cyclohexyl 
perdicarbonate. 
To maintain the pressure at 20 bars, one adds over five hours 540 g of 
fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene in the respective molar 
proportions of 79/15/6. 
One adds simultaneously and continuously over the same duration of 
polymerization 16 g of N-methylolacrylamide (NMA). 
After five hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
25%. The copolymer contains fluorinated structural units originating from 
the vinylidene fluoride, tetrafluoroethylene and chlorotrifluoroethylene 
in the respective molar proportions of 81/13/7, determined by NMR (nuclear 
magnetic resonance) of the fluorine 19. The molar level of 
N-methylolacrylamide in the copolymer is 2.6 mol.% in relation to the 
totality of fluorinated structural units. The inherent viscosity of the 
copolymer is 0.0437 dL/g. 
EXAMPLE 2 
Two liters of methanol are introduced into a 3.3-L autoclave equipped with 
effective agitation, which has been degassed under vacuum. The autoclave 
is brought to a temperature of 50.degree. C. At this temperature, one adds 
436 g of fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene to reach 20 bars of 
pressure in the respective molar proportions of 79/15/6. 
One then adds 13.6 g of methylacrylamidoglycolate methyl ether (MAGME) then 
5 g of cyclohexyl perdicarbonate. 
To maintain the pressure at 20 bars, one adds over six hours 440 g of 
fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene in the respective molar 
proportions of 79/15/6. 
One adds simultaneously and continuously over the same duration of 
polymerization 41 g of methylacrylamidoglycolate methyl ether. 
After six hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
22%. The copolymer contains fluorinated structural units originating from 
the vinylidene fluoride, tetrafluoroethylene and chlorotrifluoroethylene 
in the respective molar proportions of 81/13/7, determined by NMR Of the 
fluorine 19. The molar level of methylacrylamidoglycolate methyl ether in 
the copolymer is 5 mol. % in relation to the totality of fluorinated 
structural units. The inherent viscosity of the copolymer is 0.0483 dL/g. 
EXAMPLE 3 
Two liters of methanol are introduced into a 3.3-L autoclave equipped with 
effective agitation, which has been degassed under vacuum. The autoclave 
is brought to a temperature of 50.degree. C. At this temperature, one adds 
440 g of fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene to reach 20 bars of 
pressure in the respective molar proportions of 79/15/6. 
One then adds 11.5 g of acrylamidoglycolic acid and then 5 g of cyclohexyl 
peroxydicarbonate. 
To maintain the pressure at 20 bars, one adds over three hours 350 g of 
fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene in the respective molar 
proportions of 79/15/6. 
One adds simultaneously and continuously over the same duration of 
polymerization 23 g of acrylamidoglycolic acid. 
After three hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
17.3%. The copolymer contains fluorinated structural units originating 
from the vinylidene fluoride, tetrafluoroethylene and 
chlorotrifluoroethylene in the respective molar proportions of 81/13/7, 
determined by NMR of the fluorine 19. The molar level of 
acrylamidoglycolic acid in the copolymer is 4.1 mol. % in relation to the 
totality of fluorinated structural units. The inherent viscosity of the 
copolymer is 0.046 dL/g. 
EXAMPLE 4 
Two liters of methanol are introduced into a 3.3-L autoclave equipped with 
effective agitation, which has been degassed under vacuum. The autoclave 
is brought to a temperature of 50.degree. C. At this temperature, one adds 
450 g of fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and hexafluoropropylene to reach 20 bars of pressure 
in the respective molar proportions of 75/15/10. 
One then adds 13.6 g of methylacrylamidoglycolate methyl ether (MAGME), 
then 5 g of cyclohexyl perdicarbonate. 
To maintain the pressure at 20 bars, one adds over six hours 400 g of 
fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and hexafluoropropylene in the respective molar 
proportions of 75/15/10. 
One adds simultaneously and continuously over the same duration of 
polymerization 41 g of methylacrylamidoglycolate methyl ether. 
After six hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
20.5%. The copolymer contains fluorinated structural units originating 
from the vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene 
in the respective molar proportions of 79/15/6, determined by NMR of the 
fluorine 19. The molar level of methylacrylamidoglycolate methyl ether in 
the copolymer is 5.1 mol. % in relation to the totality of fluorinated 
structural units. The inherent viscosity of the copolymer is 0.0506 dL/g. 
EXAMPLE 5 
Two liters of methanol are introduced into a 3.3-L autoclave equipped with 
effective agitation, which has been degassed under vacuum. The autoclave 
is brought to a temperature of 50.degree. C. At this temperature, one adds 
440 g of fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene to reach 20 bars of 
pressure in the respective molar proportions of 79/15/6. 
One then adds 13.6 g of methylacrylamidoglycolate methyl ether (MAGME), 
then 4 g of N-methylolacrylamide (NMA), then 75 g of cyclohexyl 
perdicarbonate. 
To maintain the pressure at 20 bars, one adds over five hours 440 g of 
fluorinated monomer mixture containing vinylidene fluoride, 
tetrafluoroethylene and chlorotrifluoroethylene in the respective molar 
proportions of 79/15/6. 
One adds simultaneously and continuously over the same duration of 
polymerization 41 g of methylacrylamidoglycolate methyl ether and 12 g of 
N-methylolacrylamide. 
After five hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
22%. The copolymer contains fluorinated structural units originating from 
the vinylidene fluoride, tetrafluoroethylene and chlorotrifluoroethylene 
in the respective molar proportions of 82/12/6, determined by NMR of the 
fluorine 19. The molar levels of MAGME and NMA in the copolymer are 5 to 
2.5 mol. % in relation to the totality of fluorinated structural units. 
The inherent viscosity of the copolymer is 0.046 dL/g. 
EXAMPLE 6 
Into a 3.3-L autoclave equipped with effective agitation, which has been 
degassed under vacuum, one introduces 2 liters of a 1/1 mixture by weight 
of methanol and tertiobutanol. The autoclave is brought to a temperature 
of 50.degree. C. At this temperature, one adds 550 g of fluorinated 
monomer mixture containing vinylidene fluoride and chlorotrifluoroethylene 
to reach 20 bars of pressure in the respective molar proportions of 85/15. 
One then adds 13.6 g of methylacrylamidoglycolate methyl ether (MAGME) and 
then 5 g of cyclohexyl perdicarbonate. 
To maintain the pressure at 20 bars, one adds over six hours 440 g of 
fluorinated monomer mixture containing vinylidene fluoride and 
chlorotrifluoroethylene in the respective molar proportions of 75/25. 
One adds simultaneously and continuously over the same duration of 
polymerization 49.5 g of methylacrylamidoglycolate methyl ether. 
After six hours of polymerization, the autoclave is degassed and one 
discharges a transparent copolymer solution which has a dry extract of 
22.5%. The copolymer contains fluorinated structural units originating 
from the vinylidene fluoride and chlorotrifluoroethylene in the respective 
molar proportions of 75/25, determined by NMR of the fluorine 19. The 
molar level of methylacrylamidoglycolate methyl ether in the copolymer is 
5 mol. % in relation to the totality of fluorinated structural units. The 
inherent viscosity of the copolymer is 0.069 dL/g. 
EXAMPLE 7 
The fluorinated copolymer of Example 1 is heated under vacuum until 
evaporation of the methanol and then diluted with methyl isobutyl ketone. 
A varnish is prepared by simple mixing of the constituents (in parts by 
weight): 
______________________________________ 
(i) fluorinated copolymer (2.6% of 
100 
NMA and 49% of dry extract in 
methyl isobutyl ketone) 
(ii) partially methylated melamine 
23.3 
formaldehyde resin (viscosity 
7,000 mPa .multidot. s at 90% dry extract 
in isobutanol) 
(iii) p-toluene sulfonic acid 
0.2 
______________________________________ 
The varnish is applied in 100 .mu.m strokes on a 0.7 mm thick chromated 
aluminum support, then baked for 30 minutes at 180.degree. C. to yield a 
25 .mu.m thick film. The cross-linkage is evaluated by the methyl ethyl 
ketone (MEK) resistance test in which a cotton cloth impregnated with 
methyl ethyl ketone is rubbed with a back and forth movement over the film 
until the film is abraded. A number of back and forth strokes between 50 
and 100 is an indication of good cross-linkage. A number equal to 100 or 
more is the indication of excellent cross-linkage. The compatibility of 
the varnish is evaluated on the basis of the transparency of the films 
obtained with: 
______________________________________ 
E = excellent total transparency 
G = good slight clouding 
P = poor translucent film 
______________________________________ 
The film produced above resisted more than 100 back and forth strokes with 
MEK and displayed an excellent transparency. 
EXAMPLE 8 
A paint is prepared under the following conditions: 
One mixes 200 g of a solution in methyl isobutyl ketone of the copolymer of 
Example 7 with 98 g of titanium dioxide and 22 g of ethoxyethylpropionate 
in a ball mill so as to obtain a grinding paste with a grinding fineness 
smaller than 10 .mu.m. 
One takes 160 g of this paste and deconcentrates it with 23.3 g of 
partially methylated melamine formaldehyde resin, 0.2 g of p-toulene 
sulfonic acid and 30 g of ethoxyethylpropionate to yield a white paste 
which has a Ford cup number 4 viscosity of 85 seconds. 
This white paint is applied on chromated aluminum with 100 m spiral strokes 
and then baked for 30 minutes at 180.degree. C. in order to obtain a 25 
.mu.m thick film. The paint obtained resists more than 100 back and forth 
strokes with methyl ethyl ketone (MEK), has a Gardner luster measured at 
60" of 42.2%, a class 0 adherence determined according to NFT standard 30 
038 and is not affected by a 1,000 hour exposure to the Q.U.V. The Q.U.V. 
is an accelerated aging device in which the effects of sunlight are 
reproduced by means of four tubes emitting ultraviolet rays. The 
temperature during the ultraviolet exposure is 63.degree. C. A 
water-condensation device makes it possible to maintain the humidity level 
at 100% relative humidity during the condensation phase. The temperature 
of the sample during the condensation phase is 50.degree. C. The 
condensation and irradiation phases, each lasting four hours, are 
alternated. 
EXAMPLE 9 
The fluorinated copolymer of Example 2 is heated under vacuum until 
evaporation of the methanol and then diluted with methyl isobutyl ketone 
(MIBK). 
A varnish is prepared by simple mixing of the constituents (in parts by 
weight): 
______________________________________ 
(i) fluorinated copolymer (5 mol. % of 
100 
MAGME at 50% of dry extract in 
methyl isobutyl ketone) 
(ii) partially methylated melamine for- 
23.8 
maldehyde resin (viscosity 7,000 
mPa .multidot. s at 90% dry extract in isobutanol) 
(iii) p-toluene sulfonic acid 0.2 
______________________________________ 
This varnish is applied in 10 .mu.m strokes on a 0.7 mm thick chromated 
aluminum support, then baked so as to reach a minimum plate temperature 
(MPT) of 250.degree. C. for 45 seconds so as to yield a 24 .mu.m thick, 
dry film. 
EXAMPLE 10 
A paint is prepared under the following conditions: 
One mixes 200 g of a solution in MIBK of the copolymer of Example 9 with 
64.2 g of blue cobalt pigment and 31.5 g of ethoxyethylpropionate in a 
ball mill so as to obtain a grinding paste with a grinding fineness 
smaller than 10 .mu.m. 
One takes 148 g of this paste and deconcentrates it with 23.8 g of 
partially methylated melamine formaldehyde resin, 0.2 g of para-toluene 
sulfonic acid, and 20 g of ethoxyethylpropionate to obtain a Ford cup 
number 4 viscosity of 80 seconds. 
This blue paint is applied on a 0.7 mm thick chromated aluminate plate with 
100 .mu.m strokes and then baked so as to achieve a MPT of 250.degree. C. 
for 45 seconds, yielding a 23 .mu.m thick, dry film. 
The paint obtained resists more than 100 back and forth strokes with MEK, 
has a Gardner luster measured at 60% of 44%, a class 0 adherence 
determined according to NFT standard 30 038 and is not affected by a 1,000 
hour exposure to the Q.U.V. 
EXAMPLE 11 
The fluorinated copolymer of Example 3 is heated under vacuum until 
evaporation of the methanol and then diluted with diacetone alcohol. 
A varnish prepared by simple mixing of constituents (in parts by weight): 
______________________________________ 
(i) fluorinated copolymer (4.1 mol. % of 
100 
acrylamidoglycolic acid at 50% in 
diacetone alcohol) 
(ii) blocked cycloaliphatic polyisocyanate 
50.9 
(in solution at 60% in n-butylacetate/ 
xylene blocked NCO content 8%) 
(iii) dibutyltin dilaurate 0.1 
______________________________________ 
This varnish is applied in 10 .mu.m strokes on a 0.7 mm thick chromated 
aluminum plate, then baked at 150.degree. C. for 30 minutes so as to yield 
a 20 .mu.m thick film. 
This film endures without damage 100 back and forth strokes with MEK and 
exhibits excellent transparency. 
EXAMPLE 12 
The fluorinated copolymer of Example 4 is heated under vacuum until 
evaporation of the methanol and then diluted with methyl isobutyl ketone. 
A varnish prepared by simple mixing of the constituents (in parts by 
weight): 
______________________________________ 
(i) fluorinated copolymer 100 
(5.1 mol. % of MAGME at 52% of dry 
extract in methyl isobutyl ketone (MIBK)) 
(ii) partially methylated melamine formalde- 
24.8 
hyde resin (viscosity 7,500 mPa .multidot. s at 
90% in isobutanol) 
(iii) p-toluene sulfonic acid 0.2 
______________________________________ 
This varnish is applied in 100 .mu.m strokes on a 0.7 mm thick chromated 
aluminum support, then baked at 80.degree. C. for 30 minutes so as to 
yield a 24 .mu.m thick, dry film. 
This film endures without damage 100 back and forth strokes with MEK and 
exhibits excellent transparency. 
EXAMPLE 13 
The fluorinated copolymer of Example 5 is heated under vacuum until 
evaporation of the methanol and then diluted with methyl isobutyl ketone. 
A varnish is prepared by simple mixing of the constituents (in parts by 
weight): 
______________________________________ 
(i) fluorinated copolymer (2.5% NMA + 
100 
MAGME at 50% of dry extract in MIBK) 
(ii) p-toluene sulfonic acid 0.2 
______________________________________ 
This varnish is applied in 150 .mu.m strokes on a 0.7 mm thick chromated 
aluminum support, then baked at 200.degree. C. for 30 minutes so as to 
yield a 19 .mu.m thick, dry film. 
This film endures without damage 100 back and forth strokes with MEK and 
exhibits excellent transparency. 
EXAMPLE 14 
The fluorinated copolymer of Example 6 is heated under vacuum until 
evaporation of the methanol and then diluted with diacetone alcohol. 
A varnish is prepared by simple mixing of the constituents (in parts by 
weight): 
______________________________________ 
(i) fluorinated copolymer 100 
(5.1 mol. % of MAGME at 55% of dry 
extract in diacetone alcohol) 
(ii) hexamethoxymethylmelamine resin 
9.7 
(iii) p-toluene sulfonic acid 
0.2 
______________________________________ 
This varnish is applied in 100 .mu.m strokes on a 0.7 mm thick chromated 
aluminum support, then baked so as to reach a minimum plate temperature 
(MPT) of 250.degree. C. for 40 seconds, yielding a 23 .mu.m thick, dry 
film. 
This film endures without damage 100 back and forth strokes with MEK and 
exhibits excellent transparency. 
While the invention has been described in connection with a preferred 
embodiment, it is not intended to limit the scope of the invention to the 
particular form set forth, but on the contrary, it is intended to cover 
such alternatives, modifications, and equivalents as may be included 
within the spirit and scope of the invention as defined by the appended 
claims.