Note: Descriptions are shown in the official language in which they were submitted.
~31~7~
A resinous composition for coating use
Field oE the invention
~he present invention relates to a resinous composition
for coating use, which is excellent in resistance to
abrasion and is specifically useful as resinous vehicle in a
top coat paint, including a solid colored paint and a clear
coat paint, for automobile body, electric appliance and the
iike.
Backgroung of the invention
In a top coat paint for automobile body, electric
appliance and the like, various combination of resins have
- been used as, for example, melamine/alkyd resins,
melamine/polyester resins, melamine/acrylic resins,
melamine/acrylic/epoxy resins, acrylic/urethane resins,
polyester/urethane resins and the like. However, in a deep
color paint containing relatively smaller quantity of
pigment, there are problems that the coating resulted is
liable to be injured and coating scratches show up
conspicuously.
Since an automobile is often subjected to an auto-
washing machine, and recently, a vivid deep color is in much
request in the coating of automobile body and the like,
resistance to abrasion of a coating is getting more and more
important for paint industries and longing for a good
solution for the same. What are wished for are not only the
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improvement in abrasion resistance, but also the improvement
in initial coating qualities and especially prevention of
rapid loss in glamourous appearance.
Employment of resinous mat.erial having a lower glass
transition temperature (Tg) and various other proposals for
hardening a coating have all failed in obtaining the
abovesaid improvements.
It is, therefore, an object of the invention to provide
a resinous composition which can be used as a top coat or a
clear coat for automobile body or the like and capable of
resulting a coating with excellent resistance in abrasion
and chipping resistance, whose glamorous appearance and
gloss would not be disappeared in a short period of time.
Summary of the invention
According to the invention, the aforesaid object can be
attained with a resinous composition for coating use
comprising
(A) a melamine resin having a monomeric content of 50
or more and a degree of etherification of 5 or more, 80
or more of the ether groups contained being methylated
me-thylol groups, and
(B) an aliphatic or alicyclic linear-structured compound
having an average molecular weight of 100 to 1000 and
bearing end hydroxyl groups, which may include ether or
ester bonds, the solid weight ratio of said (A) to(B)
being 3/7 to 7/3.
1 3 ~
Preferred embodiments of the invention
~ lelamine resin is a thermosetting resin prepared by
reacting 2,4,6-triamino-1,3,5-triazine (a common name of
melamine) and formaldehyde to give a methylolated melamine
and subjecting the latter to the reaction with a lower
alcohol. Since the melamine resin can aEford, when baked, a
coating with excellent properties in respects of hardness,
gloss, rub resistance, weather resistance and chemical
resistance, it has widely been used as the coating for
10 automobile body, electric appliance and the like.
Such a resin is usually employed in the form of resinous
varnish.
Generally accepted melamine resins are mainly composed
of polynuclear structure, in which 2 or more melamine
15 molecules are condensed together, and etherification is
mainly of butylation type. Degree of etherification is
commonly 3 or less.
The present inventors, as the results of a series of
studies for improving abrasion resistance of melamine resin
20 while maintaining the desired properties thereof, have
succeeded in finding a resinous composition comprising a
particular melamine resin as a hard component and a
particular linear aliphatic or alicyclic compound as a soft
component in a specific weight ratio, which can result a
25 baked coating having excellent abrasion resistance, gloss
and glamorous appearance, and on the basis these findings,
have succeeded in establishing the present invention.
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The melamine resin as used in the present invention as a
hard component i5 a etherified melamine resin, majority,
i.e. 50% or more, preferably 80~ or more, of which are
composed of monomeric melamine. Degree of etherification
must be 5 or more and 80~ or more of said etherification
must be of methylation type.
Thus, the present melamine resin is mainly composed o
monomeric, methylated methylol melamine. Examples of such
melamine resins are Cymel 303, (trademark, ~litsui Toatsu
lO Chem. Co.), Sumimal ~1100 (trademark, Sumitomo Chem. Co.) and
-the like.
In the present invention, to the abovementioned
melamine resin, is compounded as a soft component a linear-
structured aliphatic or alicyclic compound having end
15 hydroxyl groups and a number average molecular weight of 100
to 1000.
Such compound may include in its main chain ether or ester
bonds. Examples of such compounds are bi-functional
compounds as polyethylene glycol, polypropylene glycol,
20 polybutylene glycol, K-Flex 188 and IC-Flex 148 (trademarks
of polyester polyols
HocH2~CE~200C COOCH2~CH20EI
molecular weights 490 and 478, viscosities 10000 cps and
4000 cps, hydroxyl values 230 and 235, respectively,
25 manufactured by King Co.), reaction products of bi-
functional aliphatic or alicyclic acids and glycol: decane
l,10-diol, dodecane 1,12-diol, polycarbonate diol D-1000
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(trademark, HO-(ROCO ~ RO~I, manufaetured by Toha Gosei
K.K.), bi-functional polycaprolaetones of the formula
EIO ~ (C~l2)5C- ~ R--~--O Cll (CH2)5~0~.1
O O
like Plaecel 205 (polycaprolactone molecular weight 500),
Placcel 208 (molecular weight 800), Placcel 210~(molecular
weight 1000), all trademarks of Daieel K.K.), and X-22-160AS
(end reaetive silicone oil, molecular weight 1000,
manufactured by Shinetsu Kagaku), and tri-funetional
compounds as tri-functional polyeaprolactones of the
formula:
HO~ (CH2)5-1C-O ~ R ~O-ICl(cH2)5-]n OH
O O
~[ O-C-(CH2)5 ]n OEI
like Plaeeel 303 (moleeular weight 310), Placeel 305
(molecular weight 550), Plaecel 308 (molecular weight 860),
all trademarks of Daieel K.K.).
The abovesaia melamine resin and the abovementioned
soft component eompound are blended in a weight ratio (on
solid basis) of 3/7 to 7/3.
When the present resinous eomposition is applied on a
substrate and bakea at a higher temperature as, for example
160DC or more, the melamine resin (hard eomponent) and the
- soft eomponent eompound are reaeted together in sueeessive
order, to give a network struetural, erosslinked resin,
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~ 3 ~
which is speciEically excellent in abrasion resistance and
still maintains desired properties of melamine resin.
To attain the object of the invention, the following are
essential.
(l) ~1elamine resin must be mainly composecl of mono-
meric structure. If it is of conventional type, i.e.
mainly composed of trimeric structure, there only
results an excessively hard coating.
(2) ~lonomeric melamine and soft component compound
must be reacted in successive order so as to give a
network s-tructure product, otherwise the desired abrasion
resistance cannot be obtained.
(3) In order to attain a defined level of hardness of the
coating, etherification of said melamine must be mainly of
lS methylation type.
(4) Degree of etherification of melamine must be 5 or
more to prevent possible reaction of mutual melamine
resins themselves.
(5) ~lolecular weight of the soft component compound must
be in a range of lO0 to lO00, preferably 300 to 600. If
the molecular weight is outside the abovementioned range,
the desired sprlng-like action of the soft component
compound cannot be expected.
(6) The maximum quantity of either soft component or hard
component must be limited to 70~ by weight. If the former
exceeds over the upper limit of 70~ by weight, there
results a deEicient crosslinking, and if the latter, an
7~
excessively progressed hardening. In either case, the
desired abrasion resistance can hardly be obtaine-l.
The inventors have also Eound that though it is not
essential in the present invention, a strong acidic catalyst
as p-toluene sulfonic acid, dinonyl naphthalene disulfonic
acid, dodecyl benzene sulfonic acid and the like may
advantageously be added to the present resinous composition
in an amount corresponding to 0.2 to 3~ by weight of the
total solid, thereby reducing the baking temperature to
10 160C or less. Therfore, in a particularly preferred
embodiment, a strong acidic catalyst is present in the
present resinous composition. If desired, pigment and other
paint additives may be successfully added to the present
resinous composition. Thus, the present resinous
composition is useful as a resinous vehicle in a top coat
composition including both solid color paint and clear
coating composition, to be applied on automobile body,
electric appliance and the like. The clear coating
composition may be applied on both solid color paint and
metallic coating. In either case, the abrasion resistance
of such coating is excellent.
The invention shall be now more fully explained in the
following Examples. Unless otherwise being stated, all
parts and percentages are by weight.
7.~
Example l
K-Flex 188 (trademark, polyester polyol, molecular
weight 490, manuEactured by King Co.) as a soft component
and Cymel 303 (trademark, melamine resin: monomeric
5 structure content 60% by weight, ~egree of etheriEication
about 5.5, degree of methoxylation about 5.5, manufactured
by Mitsui Tohatsu K.K.) as a hard component were blended in
a solid weight ratio of 5:5, and the mixture was treated in
a disper for 30 minutes to obtain a uniform solution. To
10 this solution, N~CURE 155 (trademark, King Co.) was added as
a catalyst in an amount of l~ of the total weight of the
composition and stirred well to obtain a resinous
composition for coating use.
Examples 2 to 4
Resinous compositions were prepared by repeating the
procedures of Example l, excepting revising the weight ratio
of soft component/hard component as follows. That is, in
Example 2, said ratio was changed to 4/6, in Example 3, to
3/7 and in Example 4, to 7/3.
Example 5
2.0 parts of carbon black and 50 parts on K-Flex 188
were mixed together. To this, were added equal quantities
of glass beads (2mm diameter) and the combined mixture was
treated in a disper for 60 minutes. Thereafter, 50 parts
25 Cymel 303 were added and mixed well in the disper for
additional 30 minutes. Nacure 155 (catalyst) was then added
in an amount of l~ of the total weight of the composition
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~3~7.5
and mixed well to obtain a coating composition.
Example 6
The same procedures as stated in Example 1 were
repeated, excepting substituting polye-thylene glycol 400
(trademark, polyethylene glyco:l manufactured by Aldrich Co.)
for K-Flex 188 and Sumimal ~llO0 (trademark, melamine resin,
monomeric structure content 80~ by weight, degree of
etherification about 5.5, degree of methoxylation about 5.5,
manufactured by Sumitomo Chem. Co.) for Cymel 303, to obtain
10 a coating composition.
Example 7
The same procedures as stated in Example 1 were
repeated, excepting substituting polyethylene glycol 600
(trademark, polyethylene glycol manufactured by Aldrich Co.)
for K-Flex 188 to obtain a coating compositon.
Example 8
The same procedures as stated in Example 1 were
repeated, excepting substituting polypropylene glycol 425
(trademarX, polypropylene glycol manufactured by Aldrich
Co.) for K-Flex 188 to obtain a coating composition.
Example 9
The same procedures as stated in Example 1 were
repeated, excepting substituting Sumimal ~llO0 for Cymel 303
to obtain a coating composition.
Example 10
The same procedures as stated in Example 3 were
repeated, excepting substituting K-Flex 1~8 (trademark,
~3~7~3'
polyester polyol, molecular weight 47~, manufactured by King
Co.) for l<-Flex 1~8 and Sumimal 11100 for Cymel 303 to obtain
a coating composition.
Example 11
K-Flex 14~ as a soft component and Cymel 303 as a hard
component were blended in a solid weight ~atio of 5:5 and
stirred and mixed well in a disper for 30 minutes.
~hereafter, p-toluene sulfonic acid, diethanolamine and
xylene were added each in the amounts corresponding to 1%,
0.92% and 40~ of the total weight of the resulted coating
composition, and the combined mixture was stirred well until
a uniform solution was obtained, heated under stirring to
100C and reacted at the same temperature for 2 hours to
obtain a resinous composition comprising a polymer having a
number average molecular weight of 5000.
Preparaion of coated test panels (A)
To a series of test steel panels (each 300x500xO.Bmm
size) previously treated with Granodine SD5000 (zinc
phosphate pre-treating agent, trademark of Nippon Paint Co.,
Ltd.), was applied Power top U-30 (Epoxy urethane cationic
electrodepositing coating composition, trademark of Nippon
Paint Co., Ltd.) in a dry film thickness of 30~, baked at
170C for 20 minutes, was applied an intercoat of Orga P-2
(trademark, gray intercoat composition based on polyester
resin, Nippon Paint Co., Ltd.) in a dry film thickness oE
35~ and baked at 140C for 20 minutes. Onto thus coated
panels, coating compositions obtained in Examples 1 to 6 and
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1 3 ~ 7 ~
Orga S-20 clear coating composition tEor comparison salce)
(trademark, polyester resin base clear coating composition,
Nippon Paint Co., Ltd.) each was applied in a dry film
thickness oE 30~ and then baked at 140C for 20 minutes.
Thus obtained test panels were subjected to the following
tests and their abrasion resistance, pencil hardness, gloss,
accelerated weather resistance and water resistance
properties were examined. The test results are shown in
Table 1.
Preparation of coated test panels (B)
To a series of test steel panels (each 300x500xO.8mm
size) previously treated with Granodine SD5000 (zinc
phosphate pre-treating agent, trademark of Nippon Paing Co.,
L,td.), was applied Power top U-30 (trademark, epoxy urethane
cationic electrodeposition coa-ting composition, Nippon Paint
Co., Ltd.) in a dry film thickness on 30J~, baked at 170C
for 20 minutes, was applied an intercoat of Orga P-2 in a
dry film thickness of 35~ and baked at 1~0C for 20
minutes. Onto thus prepared plates, was applied Superlack
~I-90 Silver (trademark, acryl-melamine resin base silver
colored coating composition, Nippon Paint Co., Ltd.) to a
dry film thickness of 15~ and then, on wet-on-wet basis,
each clear coating composition obtained in F.xample 1,
Examples 7 -to 11 and Superlack 0-128 (trademark, acryl-
melamine base clear coating composition, Nippon Paing Co.,Ltd.) in a dry film thickness of 15~ . Finally, they were
baked at 140C for 20 minutes.
7 ~
Thus obtained test panels were subjected to the following
tests and their abrasion resistance, pencil hardness, gloss,
accelerated weather resistance and water resistance
properties were examined. The test results are shown in
Table 2.
The test methods and evaluation standards used are as
follows.
l. Abrasion resistance
Test plate is fixed on the roof of an automobile and
10subjected to an auto-washer 20 times. Thereafter, the
coating conditions are visually examined.
O ....... no scratch
O ....... faint scratch
~ ....... slight scratch
X ....... scratches
X X ........ quite many scratches
2. Pencil hardness
JIS K 500 6.14 method
3. Gloss
20JIS K 5400 6.7 method
4. impact resis-tance
JIS K 5400 6.13 method
5. ~ccelerated weather resistance
JIS K 5400 6.17 me-thod
256. Water resistance
JIS IC 5400 7.2 method
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13.~7~
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