Resinous coating composition curable at low temperature

A coating composition comprising as resinous vehicle, a melamine resin, and a crosslink curable type resin having functional groups capable of reacting with the melamine resin, which is characterized in that the melamine resin has a weight-average molecular weight by Gel Permeation Chromatography of 6000 to 12000 and bears as functional groups, imino, methylol and alkoxymethylol groups, the sum of imino and methylol groups being, when expressed in terms of average number per triazine nucleus, 2.0 to 2.5, the number of alkoxymethylol groups being 2.0 or more, and the ratio of methylol groups to imino groups being 1.0 to 2.5. The coating composition is characterized by having, inter alia, a low temperature curing property and excellent intercoat adhesion.

FIELD OF THE INVENTION 
The present invention relates to a coating composition and more 
specifically, a coating composition which is curable at a relatively low 
temperature and is excellent in intercoat adhesion. 
BACKGROUND OF THE INVENTION 
Since melamine resin has active groups as active hydrogen, active methylol, 
active alkoxymethyl or the like, it is customarily combined with a number 
of coating base resins having functional groups which are reactive with 
the abovesaid active groups, like hydroxyl and isocyanate, including alkyd 
resin, polyester resin, acrylic resin, epoxy resin, polyurethane resin, 
polyamide resin and polycarbonate resin, and is widely used as 
thermosetting curable coating compositions. However, in such coating 
compositions based on the combination of melamine resin and the 
abovementioned base resins, it is generally required to use a relatively 
high baking temperature as, for example, 140.degree. C. for the 
combination of commercially available melamine resin and alkyd resin, and 
170.degree. C. and more for the combination of such melamine resin and 
epoxy resin. From the standpoint of energy saving, much preference is 
given to the use of lower baking temperature. It is, however, pointed out 
that with the abovementioned melamine resin, a lower temperature baking 
will inevitably cause insufficient coating hardness and undesired tack 
feeling on the coating and therefore, it has been believed that the curing 
will require a minimum baking condition of 140.degree..about.160.degree. 
C. and 20.about.30 minutes under the circumstances. 
Recently, there has been provided, as the so-called low temperature curing 
type resin, a highly self-condensable melamine resin, which is said to be 
curable at 100.degree..about.120.degree. C. in 20 to 30 minutes. However, 
even with this type of melamine resin, there are such problems that the 
allowable temperature range in obtaining the baked coating with defined 
film performance is rather narrow (i.e. considerable temperature 
dependency for baking temperatures) and if the baking temperature control 
is not so good, Tg and crosslinked density of the coating will fluctuate 
in wider ranges and the intercoat adhesion will get worse due to the 
change in coating shrinkage and accumulation of inner stress of the 
coating. Therefore, in the combination with a variety of base resins, a 
melamine resin has long been desired which will show a small temperature 
dependency for baking temperatures, is curable at a relatively lower 
baking temperature and is excellent in inter-coat adhesion. The invention 
has been made to satisfy this need. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a coating composition 
comprising as resinous vehicle a melamine resin (A) having a 
weight-average molecular weight (MW) by Gel Permeation Chromatography of 
6000.about.12000 and having as functional groups, imino, methylol and 
alkoxymethylol groups, the sum of imino and methylol groups being, when 
expressed in terms of average number of functional groups per triazine 
nucleus, 2.0.about.2.5, the number of alkoxymethylol groups being 2.0 or 
more, and the ratio of methylol groups to imino groups being 
1.0.about.2.5, and crosslink curable type resin (B) having functional 
groups which are reactive with those of said melamine resin. 
PREFERRED EMBODIMENTS OF THE INVENTION 
The most characteristic feature of the present invention resides in the 
employment of particular type of melamine resin controlled in kind and 
amounts of the functional groups and in the molecular weight as 
hereinabove defined, together with a base resin. In a curing step, it is 
believed that co-condensation reaction between melamine resin and base 
resin, self-condensation reaction of melamine resin and the like occur 
simultaneously and macro-molecular weight resin is formed by the so-called 
crosslinking reaction. Therefore, for the improvement in curing property 
of such resinous composition, an attempt has been made to use a melamine 
resin with relatively large molecular weight. However, the intended 
objects had not been attained therewith, because of the poor compatibility 
with alkyd or other base resins and of the decreased reactivity due to the 
loss of motion of the resinous molecule. Thus, the employable melamine 
resins have been limited to the only members having a weight-average 
molecular weight (MW) of 3000.about.3500 and even for the low temperature 
curing purpose, to the members having at most the weight-average molecular 
weight of 3500.about.4500. 
In the self-condensation reaction of melamine resin, co-condensation 
reaction between melamine resin and other base resin or the like, it is 
expected that the functional groups carried on the respective resins 
naturally take part in the reactions, and a number of such groups may 
participate in the curing of the resins. The inventors, therefore, have 
examined the structural characteristics based on the number of functional 
groups (average number of these groups per triazine nucleus), molecular 
weight and the like of heretofore commercialized melamine resins, 
including low temperature curing type resins, and obtained the following 
results. 
TABLE 1 
______________________________________ 
melamine resin 
article a 
article b 
article c 
article d 
______________________________________ 
characteristics 
3100 3400 4500 3500 
wt-ave. mol. weight 
--NH + --NCH.sub.2 OH 
2.40 2.35 2.61 2.85 
--NCH.sub.2 OH/--NH 
1.79 2.79 0.67 2.90 
--NCH.sub.2 OR 
2.43 2.31 1.99 1.80 
NV (%) 60 60 50 60 
R n-butyl iso-butyl 
n-butyl 
iso-butyl 
______________________________________ 
In the abovesaid analysis, the molecular weight was measured by using Toyo 
Soda's GPC (Column SHODEX KF-803, with tetrahydrofuran solvent) and 
calculating in terms of polystyrene; nitrogen by conventional Kjeldahl 
method; total bound formaldehyde by phosphoric acid decomposition method 
(J. J. Levenson, Ind. Eng. Chem. Anal. Ed. 12, 332 (1940)); free 
hydroxymethyl group by Iodo method (Miyauchi, Kobunshi Kagaku, 20, 46 
(1963) and alkoxy (butoxy) group by Colorimetry with a part of said 
phosphoric acid decomposition fraction using p-dimethylaminobenzaldehyde 
colorant (Miyauchi, Kobunshi Kagaku, 20, 42 (1963)). 
Next, the inventors have prepared various melamine resins each having 
different molecular weight and functional group number, by changing the 
condensation reaction conditions, and examined the curing conditions and 
film performance for these resins. As the result, it was found that in 
regard to the molecular weight of the melamine resin, even with a resin 
having a considerably larger molecular weight, good compatibility with 
other base resins and hence an improved curing property can be obtained by 
controlling the number of alkoxymethylol groups of the melamine resin and 
controlling the average number of functional groups per triazine nucleus 
in defined ranges and the self-condensation could be further exaggerated 
as compared with the co-condensation, thereby attaining a low temperature 
curing, lowering the temperature dependency for baking temperatures and 
improving the intercoat adhesion of the composition. 
Thus, in the present invention, such melamine resin as having a weight 
average molecular weight of 6000.about.12000, preferably 8000.about.10000 
(considerably higher molecular weight than those of heretofore used 
melamine resins) is selectively used. Furthermore, the average number of 
alkoxymethylol groups per triazine nucleus is selectively determined to be 
2.0 or more. If the average number of said groups is less than 2.0, such 
resin cannot be used because of the inferior compatibility with base 
resins. Even if the alkoxymethylol group number is increased to 2.0 or 
more, the maximum molecular weight must be limited at most to about 12000 
from the standpoint of compatibility with the base resin. Whereas, with 
the melamine resin having a weight average molecular weight of less than 
6000, temperature dependency for the baking temperatures would be 
increased and hence the intercoat adhesion would be undesirably lowered. 
Next, in the present invention, besides the abovesaid requirement on 
alkoxymethylol groups per triazine nucleus, the sum of imino groups and 
methylol groups should be in a range of 2.0.about.2.5 and the ratio of 
methylol group number to imino group number in a range of 1.0.about.2.5. 
According to the finding by the present inventors, to attain an object of 
low temperature curing, it is essential to exaggerate the 
self-condensation of melamine resin compared to the co-condensation 
property thereof. To this end, it is desired, expressed in terms of 
average number of functional groups per triazine nucleus, to have the 
greatest possible sum of the imino groups and methylol groups and to make 
the ratio of methylol group number to imino group number as close to 1 by 
all means. Since there are limits in the functional group numbers per 
triazine nucleus, the increase in alkoxymethylol group number will 
naturally cause a decrease in the number of other groups. Under the 
circumstances, it was found that to have similar baking conditions as 
proposed for heretofore known low temperature curing type melamine resins, 
i.e. 100.degree..about.120.degree. C. and 20.about.30 minutes, the sum of 
imino groups and methylol groups, when expressed in terms of average 
number per triazine nucleus, must be 2.0.about.2.5, the number of 
alkoxymethylol groups must be 2.0 or more and the ratio of methylol group 
number to imino group number must be in a range of 1.0.about.2.5. 
Furthermore, these conditions should be coupled with the condition that 
weight-average molecular weight is in a range of 6000.about.12000, as 
already stated. 
When departing from the abovementioned conditions, one is unable to attain 
the objects of the invention of having a low temperature 
(100.degree..about.120.degree. C.) curing and an improved intercoat 
adhesion, as shown stated hereinunder. The inventors have further found 
that the base resin can be any conventional crosslink type resins having 
functional groups reactive with those of melamine resin, providing they 
can be coupled with the above-mentioned melamine resin, as for example, 
alkyd, polyester, acrylic, epoxy, polyurethane, polyamide, polycarbonates 
resins and mixtures thereof. Also, when selecting an inner catalytic type 
resin and especially the resin stated in Japanese Patent Application No. 
232900/82 whose resinous acid value based on a polycarboxylic acid having 
a titration midpoint potential in non-aqueous potentiometric titration, 
under the state capable of developing resinous acid value, of less than 
-300 mV, is 2 to 50 and which has functional groups reactive with those of 
melamine resin, a very low temperature (e.g. 80.degree..about.120.degree. 
C.) bake curing can be realized and far better intercoat adhesion can be 
obtained therewith. Preferably, the solid weight ratio of the melamine 
resin to the cross link curable resin is 5/95-40/60. 
The invention shall now be more fully explained in the following Examples. 
Unless otherwise stated, all parts are by weight.

EXAMPLE 1 
(Preparation of melamine resin) 
Into a four necked flask fitted with stirrer, reflux condenser and 
thermometer, were placed 335 parts of Formit NB (40% formaline n-butanol 
solution, manufactured by Koei Chem. K.K.), 140.4 parts of n-butanol and 
126 parts of melamine resin, and the mixture was reacted at a reflux 
temperature for 10 minutes, adjusted to pH 3.2 with hydrochloric acid and 
further reacted under refluxing condition for 20 minutes. Thereafter, a 
mixed solution of 168 parts of n-butanol, 126 parts of xylene and 28 parts 
of deionized water was added and the mixture was refluxed while removing 
the formed water, for 3 hours and then concentrated under reduced pressure 
to obtain a melamine resin solution A (non-volatile content of 60%). This 
was analyzed and the test results were as shown in Table 2. 
EXAMPLE 2 
In a similar reaction vessel as used in Example 1, were weighted 335 parts 
of formit NB, 158 parts of n-butanol and 126 parts of melamine and the 
mixture was reacted at a refluxing temperature for 10 minutes. After 
adjusting the pH to 3.6 with formic acid, the reaction was continued under 
refluxing condition for additional 10 minutes, and the mixture was added 
with a mixed solvent of 127 parts of n-butanol, 102 parts of xylene and 
9.8 parts of deionized water, refluxed for 3 hours while removing the 
formed water and finally subjected to a vacuum concentration to obtain a 
melamine resin solution B having a solid content of 60%. Analytical data 
are shown in Table 2. 
EXAMPLE 3 
In a similar reaction vessel as used in Example 1, were weighed 337 parts 
of formit NB, 141 parts of n-butanol and 126 parts of melamine, and the 
mixture was reacted at a refluxing temperature for 10 minutes. After 
adjusting the pH at 3.2 with hydrochloric acid, the reaction was continued 
under refluxing condition for additional 20 minutes, and the mixture was 
added with a mixed solvent of 121 parts of n-butanol, 56 parts of xylene 
and 9.3 parts of deionized water, reacted under refluxing condition while 
removing the formed water for 3 hours and finally concentrated under 
reduced pressure to obtain a melamine resin solution C having a solid 
content of 60%. This was analyzed and the test results were as shown in 
Table 2. 
EXAMPLE 4 
In a similar reaction vessel as used in Example 1, were weighed 395 parts 
of formit NB, 121 parts of n-butanol and 126 parts of melamine and after 
adjusting the pH to 7.8 with triethylamine, the mixture was reacted at a 
refluxing temperature for 10 minutes. Thereafter, a mixed solvent of 57 
parts of n-butanol, 16 parts of xylene and 8 parts of deionized water was 
added and the mxiture was adjusted to pH 3.4 with formic acid and reacted 
at 95.degree. C. for 60 minutes. Then, 57 parts of xylene were added and 
the mixture was refluxed for 3 hours and 30 minutes while removing the 
formed water therefrom, and finally subjected to vacuum concentration to 
obtain a melamine resin solution D having a solid content of 60%. The 
analytical datas are shown in Table 2. 
EXAMPLE 5 
Using the similar reaction vessel as used in Example 1 and the materials as 
used in Example 4, a methylolization was carried out. Thereafter, a mixed 
solvent of 84 parts of n-butanol, 24 parts of xylene and 12 parts of 
deionized water was added and after adjusting the pH to 3.2 with formic 
acid, reacted at 95.degree. C. for 60 minutes. 50 Parts of xylene were 
then added and the mixture was refluxed, while removing the formed water 
therefrom, for 4 hours and finally condensed under reduced pressure to 
obtain a melamine resin solution E having a solid content of 60%. The 
analytical data are shown in Table 2. 
EXAMPLE 6 
In a similar reaction vessel as used in Example 1, were weighed 447 parts 
of formit NB (40% formaline isobutanol solution, manufactured by Koei 
Chem. K.K.), 144 parts of isobutanol, 50 parts of deionized water and 126 
parts of melamine and the mixture was reacted at a refluxing temperature 
for 20 minutes. Thereafter, a mixed solvent of 45 parts of xylene, 36 
parts of isobutanol and 4.3 parts of deionized water was added and 
subjected to dehydration under refluxing condition for 5 hours. The 
mixture was concentrated under reduced pressure to obtain a melamine resin 
solution F having a solid content of 60%, whose analytical data are shown 
in Table 2. 
EXAMPLE 7 
(Preparation of acrylic resin) 
Into a four necked flask fitted with stirrer, reflux condenser, thermometer 
and dropping funnel, were placed 10 parts of xylene, 60 parts of 
n-butanol, 2.6 parts of acrylic acid (AA), 40 parts of styrene (St), 21.1 
parts of n-butyl methacrylate (n-BMA), 20.7 parts of n-butanol acrylate 
(n-BA) and 15.5 parts of 2-hydroxyethyl methacrylate (2-HEMA) and the 
mixture was heated to 120.degree. C. To this, a mixture of 30 parts of 
xylene and 2.0 parts of azobisisobutyronitrile (AIBN) was added dropwise 
at a constant speed over 3 hours and after completion of said addition, 
the mixture was kept standing for 2 hours to complete the reaction. Thus 
obtained acrylic resin varnish (I) had the characteristics of molecular 
weight about 20,000 (GPC analysis), non-volatile content 50%, resinous 
acid value 20, hydroxyl number 70 and viscosity U. 
EXAMPLE 8 
(Preparation of polyester resin) 
Into a four necked flask fitted with stirrer, reflux condenser, 
thermometer, water separation tube and fractionating tower, were placed 
133 parts of isophthalic acid, 29.2 parts of adipic acid, 25.1 parts of 
trimethylolpropane, 52.8 parts of neopentylglycol and 56 parts of 
1,6-hexanediol and the mixture was heated. At the stage when the materials 
were melted and reached a stirrable condition, stirring was commenced and 
the vessel temperature was raised to 220.degree. C. At this time, from 
160.degree. to 220.degree. C., the temperature was raised at a constant 
speed in 3 hours. The formed water was continuously removed out of the 
system. When the temperature reached to 220.degree. C., the mixture was 
maintained at the same temperature for 1 hour and then 5 parts of xylene 
were gradually added as refluxing solvent and the reaction was switched to 
condensation in the presence of solvent and continued for additional time 
until the resinous acid value was 8.0. After cooling the reaction mixture, 
18.2 parts of xylene and 13.7 parts of cellosolve acetate were added to 
obtain a polyester resin varnish II, which had the characteristics of 
molecular weight (by GPC) about 8000, solid content 65.2%, resinous acid 
value 8.0 and viscosity V. 
EXAMPLE 9 
(Preparation of resin having inner catalytic function) 
In a similar reaction vessel as used in Example 8, were placed 127 parts of 
isophthalic acid, 29.2 parts of adipic acid, 25.1 parts of 
trimethylolpropane, 52.8 parts of neopentylglycol and 56.0 parts of 
1,6-hexanediol, and the mixture was reacted as in Example 8 until the 
resinous acid value was 2.0. Thereafter, the mixture was cooled to 
100.degree. C., added with 3.7 parts of pyromellitic anhydride, heated to 
160.degree. C. and reacted until the resinous acid value was 8.0. After 
cooling, 118.2 parts of xylene and 13.7 parts of cellosolve acetate were 
added to obtain a polyester resin solution III, the molecular weight (by 
GPC) of the resin being about 8000, and the resinous varnish showing solid 
content of 64.6%, resinous acid value of 8.6 and viscosity of X. 
TABLE 2 
______________________________________ 
Example 1 2 3 4 5 6 
______________________________________ 
varnish A B C D E F 
MW* 6100 6900 8000 8500 11800 7500 
--NH + --NCH.sub.2 OH 
2.45 2.17 2.24 2.10 2.03 2.36 
--NCH.sub.2 OH/--NH 
2.10 1.15 1.30 2.33 2.32 1.56 
--NCH.sub.2 OR 
2.20 2.22 2.18 2.32 2.22 2.07 
non-volatile % 
60.6 60.0 60.2 59.7 60.4 60.3 
viscosity W UV X W-X Z W 
______________________________________ 
*weight average molecular weight 
EXAMPLE 10 
35.0 parts (solid weight parts) of acrylic resin I obtained in Example 7 
and 15.0 parts (solid weight parts) of melamine resin A obtained in 
Example 1 were mixed well. The composition was applied on a tinplate with 
a 16 mil doctor blade. After standing for a defined period of time, these 
plates were cured under different baking conditions, and the coatings were 
peeled off by a mercury amalgamation process and then subjected to a clear 
film test. 
In the next series of film tests, a white colored dispersion paste was 
first prepared by adding to a composition of 35.0 parts (solid weight 
parts) of the acrylic resin I and 15.0 parts (solid weight parts) of the 
melamine resin A, 8.0 parts of xylene, 4.0 parts of Solvesso 100, 7.0 
parts of n-butanol, 0.010 part of Silicon KF-69 (silicon oil, manufactured 
by Shinetsu Kagaku K.K.) and 45 parts of Titanium white CR-95 (Ishihara 
Sangyo K.K.) and mixing well. To this, were added a diluting solvent 
mixture comprising 20.0 parts of Solvesso 100, 50.0 parts of toluene, 10.0 
parts of xylene and 20.0 parts of n-butanol to adjust the viscosity to 20 
sec./25.degree. C. Ford cup #4 viscosity. Thus obtained white coating 
composition was then applied onto a zinc phosphate treated dull steel 
plate by spraying and baked under different conditions, and film 
performances were evaluated. The clear film properties and film 
performances obtained are shown in Table 3. 
EXAMPLES 11- 18 
The same procedures as stated in Example 10 were repeated, excepting using 
melamine resins C.about.F obtained in Examples 2.about.6 and acrylic resin 
I or polyester resin II obtained in Example 8 and following the 
prescriptions given in Table 3. Thus obtained clear film properties and 
film performances are also shown in Table 3. 
COMATIVE EXAMPLES 1-4 
Using the same procedures as stated in Example 10, commercialized melamine 
resin a or c and acrylic resin II or polyester resin II were mixed well in 
the solid weight ratio as shown in Table 3. The clear film properties and 
film performances were evaluated as in Example 10 and the results are 
given in Table 3. 
As is clear from the results shown in Table 3, low temperature baking and 
improved intercoat adhesion had been achieved with the melamine resins 
specified in the present invention. 
EXAMPLE 19 
In the solid weight ratio shown in Table 4, melamine resin D and polyester 
resin III obtained in Example 9 were compounded and the coating 
composition was prepared as in Example 10. After applying onto a similar 
steel plate, the coating was baked under the condition as given in Table 
4. The clear film properties and film performances were evaluated and are 
shown in Table 4. 
COMATIVE EXAMPLE 5 
Commercialized melamine resin c and polyester resin III were mixed well in 
the solid weight ratio shown in Table 4 and thereafter the same procedures 
as given in Example 10 were repeated excepting using the baking condition 
given in Table 4. The clear film properties and film performances were 
evaluated and the results are shown in Table 4. These results clearly show 
that the combination of the present melamine resin and the crosslinking 
type resin whose resinous acid value based on a polycarboxylic acid having 
a titration midpoint potential in non-aqueous potentiometric titration, 
under a state capable of developing resinous acid value, of less than -300 
mV, is 2-50 can afford far better results in regard to low temperature 
baking and intercoat adhesion as compared with those of the control. In 
these Examples, the following tests were conducted. 
Clear film properties 
(1) Measurement of gel fraction percentage 
A coating was subjected to a solvent extraction using Soxhlet apparatus and 
mixed solvent of acetone/methanol=1/1 (Wt ratio) at 70.degree. C. for 5 
hours, and then dried in a dryer at 120.degree. C. for 30 minutes and 
allowed to cool in a desiccator. After cooling, the coating was weighed 
and gel fraction percentage was calculated. 
(2) 
.DELTA.Tg=Tg at 160.degree. C..times.30'13 Tg at 100.degree. C..times.30' 
.DELTA.Tg'=Tg at 140.degree. C..times.30'--Tg at 80.degree. C..times.30' 
Determination of glass transition point Non-resonant forced oscillation 
dynamic viscoelastometer (REO VIBRON, 
DDV-II-EA, manufactured by Toyo Baldwin Co. Ltd.) was used. 
Measuring conditions were set to 
frequency=11 Hz, temperature raising speed=2.degree. C./min. 
Film performance 
(3) Pencil hardness 
Judgement was made by the maximum hardness which does not cause any 
scratches by Mitubishi Uni pencil. 
(4) Solvent resistance 
Test plate was subjected to 100 times xylene rubbings and the surface 
condition was visually observed. 
.circle. : no abnormality X: damaged 
(5) Intercoat adhesion 
The first coat was baked under the condition stated in the Table, the 
second coat was applied after the lapse of 60 minutes, baked under the 
condition stated in the parenthesis and kept standing for 30 minutes at 
room temperature. Lattice cut adhesion test was carried out. 
.circleincircle. : no peeling 
.circle. : slight peeling 
.DELTA.: whole peeling in the square 
X: whole peeling from the squares other than the cut portion 
TABLE 3 
__________________________________________________________________________ 
E (example) C (Comp. Ex.) 
E 10 
E 11 
E 12 
E 13 
E 14 
E 15 
E 16 
E 17 C 1 
C 2 
E 18 
C 3 
C 4 
__________________________________________________________________________ 
Compounding* 
melamine resin 
A 15 
B 15 
C 15 
D 15 
E 15 
F 15 
C 5 
C 20 c 15 
a 15 
D 15 
c 15 
a 15 
acrylic resin I 
35 35 35 35 35 35 45 30 35 35 
polyester resin II 35 35 35 
Clear film properties 
gel frac. percentage % 
87 90 92 95 93 92 83 94 93 53 92 93 48 
(100.degree. C. .times. 30') 
.DELTA.Tg (.degree.C.) 
24 21 17 16 20 24 15 16 38 40 14 35 40 
Film performances 
pencil hardness 
H.about.2H 
2H 2H 2H 2H 2H H 2H.about.3H 
2H 2B F F 4B 
(100.degree. C. .times. 30') 
solvent resistance 
.circle. 
.circle. 
.circle. 
.circle. 
.circle. 
.circle. 
.circle. 
.circle. 
.circle. 
X .circle. 
.circle. 
X 
(100.degree. C. .times. 30') 
intercoat adhesion 
.circle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
X .circle. 
.circleincircle. 
X .circle. 
(140.degree. C. .times. 40') 
(2nd coat 100.degree. C. .times. 30') 
__________________________________________________________________________ 
*solid weight parts 
TABLE 4 
______________________________________ 
E (example) C (Comp. Ex.) 
E 19 C 5 
______________________________________ 
Compounding 
melamine resin D 15 c 15 
polyester resin III 
35 35 
Clear film properties 
gel frac. percentage % 
89 92 
(80.degree. C. .times. 30') 
.DELTA. Tg' (.degree.C.) 
15 40 
Film performances 
pencil hardness F.about.H F.about.H 
(80.degree. C. .times. 30') 
solvent resistance 
.circle. .circle. 
(80.degree. C. .times. 30') 
intercoat adhesion 
.circleincircle. 
X 
(120.degree. C. .times. 40') 
(2nd coat 80.degree. C. .times. 30') 
______________________________________