Note: Descriptions are shown in the official language in which they were submitted.
~L2~'7485
CHIP-RESISTANT FILLED POLYESTER AND AMINOPLAST INTERMEDIATE COATING
The present invention relates to a coating composition, more
specifically to a coating composition capable of forming coatings having excellent
chipping resistance.
It is well-known in the art that paint coating or automobiles,
especially at the bottom surface and side face portions are often damaged by
stones or small rocks thrown up during the passage of the automobiles thereover.
This eventually affects the durability of the automobiles themselves. This so-
called "chipping phenomenon" is particularly conspicuous in the cold northern
regions of the U.S., Canada, and the Scandinavian countries. Where rock salt and
gravel are scattered on roads. The phenomenon is also noticeable in rural areas
where many roads are unpaved.
The problem with conventional automotive paint coats has been that
chipping easily damages the coatings to the substrate metal, resulting ln rusting
and rapid rust growth on the automobile bodies. The chipping resistance is one
of the desired function of coatings for automobiles, i.e., rust-prevention.
Various attempts have been made to eliminate the problems caused
by chipping. For instance, Japanese Examined Patent Publication (kokoku) ~o.
52-43657/77 discloses the inclusion of a special ultrafine silk mica in a coating
composition to produce a coating composition suitable for use as an intermediate
coat for automobiles and capable of forming a chipping-resistant coating.
Further, Japanese Examined
.,,~ -- 1 --
-
~z~
-- 2 --
Patent Publication (Kokoku) No. 53-45813/78 and Japanese
Unexamined Patent Publication (Kokai) No. 55-56165/80 disclose
a method for coating chipping-resistant films and a chipping-
-resistant and corrosion-resistant intermediat~ coating
composition.
However, these proposals are intended to solve chipping
problems caused by the small-sized s'cones i.e., so-called
"soft chipping". They are not intended to solve so-called
"hard chipping", which occurs on such more exposed areas of
automobile bodies as side sills and the front of hoods.
For these "hard chippingl' areas, automobile manufactures
used what are called stone guard compositions~ The stone
guard coating compositions usually contain polyvinyl chloride
sol, rubber latex, or urethane resins as a main ingredien~
and further optionally contain bil:umen and thermoplastic
elastomers as binders, graphite, calcium carbonate, talc,
and other pigments, vermiculite, perlite, woodmeal asbestos,
and sand or fibers as fillers. Thus, a thick coating having
a thickness of 300 to lO00 ~m is obtained
Stone guard coating compositions, however, have their
problems and thereore cannot be economically or efficiently
applied for both soft chipping and hard chipping areas. Stone
guard coating compositions have high viscosity and, therefore,
cannot be applied by conventional air spray coating. They
require an airless spray having a large discharge. More
important, the surface appearance of the resultant stone
guard coat is poor since the coat is applied as a thick film.
Application of an over coat to the stone guard coa~ further
~z~1'7~1~5
reduces the surface finish appearance. As a result, the stone guard coat
compositions can only be used for coating the bottom portions of an automobile
body. Furthermore, stone guard coat compositions cannot be applied to the
so-called "gradient coating" in which the coated film thickness is gradually
decreased. This is because the surface appearances are different depending
upon the f ilm thickness of the stone guard coat, and because extraneous
phenomena such as "craterins" are caused, to the area where stone guard coat
composition is applied as a mist~ by the differences in the surface tension
and in the phenomen~ of the curing and the melt. These phenomena adversely
affect the surface conditions of the upper coat. For these reasons, stone
guard coat compositions are only applied, by means of a masking, to the bottom
portions of automobile bodies.
In any case, no one has yet developed chipping-resistant coating materials
cap~ble of solving both the problems of soft and hard chipping.
Accordingly, the objects of the present invention aro to eliminate the
above-mentioned problems of th0 prior arts and to provide a coating
composition capable of preventing both the soft and hard chipping and of
impnrting a coated film having good surface appearance and physical properties.
Other objects and advantages of the present invention will be apparent
from the following description.
In accordance with the present invention, thare is provided a coating
composition comprlsing:
A. at lesst one polyester resin derived from (1) at least one acid
component selected from the group consisting of dibasic acids and the esters
snd the ester-fo7~in~ derivatives thers~f and (2) at least one alcohol
component selected from the group consisting of polyhydric ~lcohols and the
ester-forming derivatives thereof; and
B. at least one aminoplast hsving a number-average molecular weight
of 800 to 1400,
said polyester resin containin~ at least 20% by weight7 based on
the total amount of the acid component, of an aliphatic dibssic, acid having 4
to 10 carbon atoms and at least 20~7 by weight, bas~d on the total amount of
the alcohol component, of a dihydric alcohol having 2 to 6 carbon atoms, and
,
C. 2% to Z0~ by weight of ultrafine talc, 2~ to 40~ by weight of
ultrafine barium sulfate, or 2% to 40% by weight of a mixture of ultrQfine
talc and ultrafine barium sulfate, said amounts of ultrafine talc and
ultrafine barium sulfate being based on the total solid ~mount of the coating
composition,
3aid polyester resin ha~ing a number-s~erage molecular weight of
20~0 to 4000, a hydroxyl number of 30 to 75, and an Acid number of S to lS,
the weight ratio, in t~r~s of solid content, of the polyester
resin to the aminoplast resin bein~ 60/40 to 95/5, and said components being
incorporated in an organic solvent.
whereby a coated film of said coating composition has an
elongation of 20% to 100% and a static ~lass transition temperature of -10 C
to 20C.
In another aspect, the invention pro~ides a multilayer coated article
having an intermediate coat derived from a coating composition comprising:
A. at least one polyester resin derived from tl) at least one acid
component selected from the group consisting of dibasic acids and the esters
~nd the ester-for~ing derivatives thereof and (2) at least one alcohol
component selected from the group co~sisting of polyhydric alcohols and the
ester-forming derivatives thereof; ~nd
B. at least one aminoplast resin ha~ing a number-av~rage molecular
weight of 800 to 1400,
said polyester resin containing at least 20% by weight, based on
the total amount of the acid component, of an aliphatic dibasic acid ha~ing 4
to lO carbon atoms and at least 20% by weight, based on the total amount of
the alcohol component, of a dihydric alcohol haYing 2 to 6 carbon atoms, and
C. 2% to 20% by weight of ultrafine talc~ 2% to 40% by weight of
ultrafine barium sulfate, or 20~ to 40% by weight of a mi~ture of ultrafine
talc and ultrafine barium sulfate, said amounts of ultrafine talc and
ultrafine barium sulfate being based on the total solid amount of said
composition,
.~, ~,j
- 4a -
s~id polyester resin having a number-a~arage molecular wei~ht of
2000 to 4000, a hydroxyl number o~ 30 to 75, and an acid number of 5 to 15,
the weight ratio, in ter~s of ~ solid content, of the polyester
resin to the aminoplast resin being 60/40 to 95/5,
wherein said coated film of said coating composition has an
elongation of 20% to 100% and a ststic glass transition temperature of -10 C
to 20 C.
The polyester resins usable in the compounding of the present coating
composition are those prepared by polymerizing (i) dibasic acids and/or their
ester forming derivatives and (ii) polyhydric alcohols and/or their ester
forming deriv~tives.
E~amples of the dibasic acids Bre phthalic acid, isophthalic acid,
terephthalic acid, adipic scid, sebacic acid, maleic acid, azelaic acid, and
itaconic acid. ~xamples of the ester-forming derivatives of the dibasic acids
are the ~nhydrides of ths dibssic acids~ the esters of the dibasic
! ~;
~.s_~)
)'79L~;~S
acids, such as dimethylterephthalate dimethyl 1,4-cyclohexane-
dicarboxylate and dimethyltricyclo [5,2,1,02'6]decane-
-3(4),8(9)-dicarboxylate, and diisocyanates. ~hese compounds
can be used alone or in any mixture thereof.
Examples of the polyhydric alcohols are neopentyl ylycol,
ethylene glycol, l,6-hexanediol, diethylene glycol, propylene
glycol, dipropylene glycol, cycl~hexane dimethanol, trimethyl-
pen~ane diol, l,3-butane diol, trimethylol propane, trimethylol
ethane, and glycerine. Examples of the ester forming deriva-
tives of the polyhydric alcohols are the esters of the
above-mentioned dibasic acids, such as ethylene glycol
terephthalate, diethylene glycol terephthalate and neopentyl
glycol adipate. These compounds can be used alone or in any
mixture thereof.
It should be noted that the polyesker resins used in the
present invention contain at least 20% by weightt based on
the total amount of the acid component, of an aliphatic
dibasic acid having 4 to 10 ca~bon atoms and at least 20% by
weight, based on the total amount of the alcohol component,
of a dihydric alcohol having 2 to 6 carbon atoms.
Examples of the aliphatic dibasic acids having 4 to 10
carbon atoms are adipic acid, sebacic acid~ maleic acid,
azelaic acid, an~ itaconic acid. These linear aliphatic
dibasic acids are desirable because they impart soft and
flexible properties to the polyester resins. Examples of the
dihydric alcohols having 2 to 6 carbon atoms are ethylene
glycol, 1,6-hexanediol, diethylene glycol, trimethylpentane
diol~ 1,3-butemediol, propylene glycol, and triethylene
~20';~
-- 6 --
glycol. These dihydric alcohols are desirable because they
also impart soft and flexihle properties to polyester resins.
The polyester resins containing 20% by weight or more of
these dibasic acids and 20% by weight or more of these
dihydric alcohols result in the desired elongation percent
and static glass transition temperature.
The polyester resin used in the present invention should
have a number~average molecular weight (Mn) of 2000 to 4000,
a hydroxyl number of 30 to 75, desirably 35 to 60, and an
acid number of 5 to 15. A polyester resin having an Mn of
more than 4000 would increase the viscosity of the resin,
making it difficult to produce a high concentration coating
composition and to apply a thick coat. Contrary to this, a
polyester resin having an Mn o~ less than 2000 would results
lS in an undesirably brittle coating.
A polyester resin having a hydroxyl number of less
than 30 has decreased compatibility with aminoplast resin.
The decreased compatibility results in undesired gloss and
also in undesired wetting of the resin with pigments during a
pigment dispersing opPration. Thus, so-called 'Iflocculation''
is likely to occur due to the insufficient wetting of the
resin with the pigments and the so-called "hazing" readily
occurs~
A polyester resin having a hydroxyl number of more
than 75 results in the undesirable change of the reactivity
thereof with the aminoplast resin depending on baking con-
ditions.
A polyester resin having an acid number of less than 5
. . . ~
~u~ s
-- 7 --
does not react well with aminoplast resin, whereas a polyester
resin having an acid number of more than 15 results in the
undesirable affect on the reactivity thereof with the amino-
plastic resin depending on baking conditions.
The terms "number-average molecular weight", "hydroxyl
number", and "acid number" used herein means the following:
1. Number-average molecular weight (Mn). The value
determined by using a GPC model lA-R (manufactured by Shimadzu
Seisakusho, Japan3.
2. Hydroxyl number: The number of milligrams of KOH
- necessary to neutralize the carboxyl group corresponding to
the hydroxyl group contained in 1 g of a sample.
3. Acid number: The number of milligrams of KOH
necessary to neutralize the free carboxyl ~roup contained in
1 g o a sample~
The polyester resins usable in the present invention can
be produced hy reacting an acid component and an alcohol
component desirably selected from the above-mentioned dibasic
acidsr polyhydric alcohols, and the ester-forming derivatives
thereof in the presence o~ necessary, a conventional
esterification catalyst such as dibutyltin oxide under the
conditions of, for example, a reaction temperature of 180C
to 200C and a reaction time of 1 to 2 hours. Then, ~he
reaction mixture is heated to 200C to 24QC or more to form
a polyester resin having the desired number-average molecular
weight, hydroxyl number, and acid number. The resultant
polyester resins can be diluted in a conventional aromatic,
ester, or ketone solvent.
~2~ 4~5
As mentioned above, the weight ratio of the polyester
resin to the aminoplast resin (i.e.~ polyester resin/amino~
plast resin) in the coating composition of the present
invention is 60/40 to 95/5, desirably 65/35 to 85/15, in
terms of solid content. A coating composition having a ratio
of less than 60/40 is subject to self-co~densation of the
excess methylol groups due to the relative decredse in the
hydroxyl number of the polyester resin, whereby the resultant
coating film becomes rigid and the adhesion property of the
10 coating is decreased. Further the compatibility of the
polyester resin with -the aminoplast resin may be decreased~
A coating composition having a ratio of more than 95/5 has a
decreased cross linking density of the polyester resin and
the aminoplast resin, which, in turn, causes decreased
humidity resistance of the resultant coating.
The static glass transition temperature ~a static Tg) of
the coating obtained from the coating composition of the
present invention should be -10C to 20C, desirably -5C
to 5C. The '~static Tg" used herein is defined as the
temperature at which a correlation curve of specific volumes
of resin and temperatures is turned. It i5 distinguished
from the so-called l'dynamic glass transition temperature",
which is determined while the resin is vibrated by a vibrating
machinel for example, Vibron ~. A coating film having a
static Tg of more than 20C shows an undesirably low chipping
resistance, whereas a coating having a static Tg of less than
-10C tends to crack when, applied in layers. Thus, the
coating composition capable o~ forming a coating film having
~L2~)7~
g
an extremely high durability for environment resistance, even
a~ainst hard chipping, as compared with conventional chipping-
-resistant coating compositions, is provided by adjusting the
static Tg of the coating film t.o a temp~rature of -lO~C
to 20C. This results, in the desired chipping resistance
being exhibited under the temperature conditions most severe
for chipping.
The use of the coating composition of the present
invention can effectively prevent both soft chipping and hard
chipping. Of course, there is no clear boundary between
"soft chipping" and "hard chipping". The term l'hard chipping"
merely derives from the term "hard chipping stone guard coat"
referring to material able to withstand use on portions such
as the side sills and the f~ont o:E the hood of automobile
bodies.
When the chipping resistant coating composition of the
present invention containing the ~pecified soft polyester
resin is used, a coating film having no substantial difference
in the surface visual appearance of the coating film having a
thickness of 0 to 150 ~m and applied by conventional "gradient
coating" of stone guard coat composition and having sufficient
hard chipping resistance and no substantial surface roughening
in a dusting portion even in a thin film ~e.g., 2 to 150 ~m)O
Accordingly, the masking step required for conventional stone
~uard coat before coating can be omitted.
The coating composition of the present invention can
further contain inorganic pigments such as metallic oxides
(e.g., titanium oxide, iron oxides, and maynesium oxide) and
. .. ...... . . ..
~Z~)'7~
-- 10 --
nonferrous ~etal compounds (e.g., aluminum silicate, strontium
chromate, and zinc chromate), and organic pigments such as
carbon black, phthalocyanine blue, phthalocyanine green,
quinacridone, flavanthrone, and benzimidazolone. These
pigments can be used alone or in any mixture thereof.
Although there is no limitation in the compounding amount of
these pigments, the pigment can be compounded into the compo-
sition generally in an amount of 10 to 70% by weight, desira
bly 30 to 60% by weight, based on the total solid amoun~ of
the coating composition. The coating composition containing
a too large amount of the pigment results in the brittle
coating film, whereas the coating composition containing a
too small amount of the pigment results in the ready gener-
ation of the substrate scratches (or damage~, "popping" and
"sagging~.
It has also been found that the inclusion of ultrafine
barium sulfate, together with titanium oxide or other in-
organic pigments, or carbon black or other organic pigments,
in the coating composition of the present invention can result
in the good stabilization of the dispersed pigment or pigments
to prevent the undesirable flocculation and in the further
increas~ in the uniformity of the resulting coating film.
The "ultrafine barium sulfate" used herein means barium
sulfate powder having an average particle diameter of 0.1 ~m
or less and a particle diameter of at least 90% by weight,
desirably 100~ by weight, of the primary particles of 0.2 ~m
or less. The ultrafine barium sulfate is usually compounded
into the coating composition in an amount oE 2% to 40% by
~z1(3~
weight based on the total solid amount of the coating compo-
sition. The desirable pigment volume concentration (PVC) is
about 15% to about 40%. A compounding ratio of the ultrafine
barium sulfate of less than 2~ by weight does not result in
the desired flocculation preventing effect, whereas a com-
pounding ratio of more than 40% by weight results in the
undesirably brittle coating film.
It has further been found that the inclusion of ultrafine
talc in the coating composition of the present invention can
result in a ~urther improvement in the chipping resistance of
the resultant coating film. The "ultrafine talc" used herein
means talc having an average particle diameter of 2 ~m or
less and a particle diameter of at least 90% by weight,
desirably 100% by weight, of the primary particles of less
than 5 ~m, desirably 2 ~m or less.
These ultrafine powder particles have more spherical
shapes as compared with the conventional talc powder and
barium sulfate powder and also have a remarkably large
specific surface ar~a. It appears to be for these reasons
2U that the above-mentioned desirable e~fects are obtained.
However, ultrafine calcium carbonate is not good because it
has poor water resistance.
The ultrafine talc is usually compounded into the coating
composition in an amount of 2% to 20% by weight, desirably S
to 20% by weight, base~ on the total solid amount of the
coating composition. The compounding ratio of the ultrafine
talc of less than 2% by weight does not result in the desired
1Occulation preventing ef~ect, whereas the compoundiny ratio
~2~t~s
- 12 -
of more than 20% by weight results in the high viscosity of
the coating composition due to the high oil absorption in the
undesirable low gloss of the coating film, and in an undesira-
bly brittle coating film.
The ultrafine talc and the ultrafine barium sulfate can
be compounded into the coating composition in any mixture
thereof in an amount of 2% to 40% by weight.
The chipping resistance of the coating composition is
also affected by the compounding of pigments. For instance,
the use of a large amount of a pigment such as talc having a
relatively large particle size results in the large peeling
off area due to cohesive failure and, therefore, results in
the undesirable surface appearance. However~ for example,
when ultrafine barium sulfate powder having a particle size
15 of Ool ~m or less is compounded, the scattered stone energy
can be absorbed without extending the peeling-off area and,
therefore, the generation of scratches in substrate can be
extremely decreased. ~hen the soft polyester resin containing
coating composition of the present invention is used under an
intermediate coa~in~ or under a conventional chipping re-
sistant coating composition, the compounding of titanium
pigments in~3 the present coating composition is not recom-
mended in the case of a relatively large guantity of titanium
dioxide is compounded in an upper coating composition or a
chipping resistant intermediate coating composition. This is
because the compounding of titanium pigments results in a
hard coating film havlng a low Young's modulus and also
results in unsatisfactory surface appearance. ~ccordingly,
- 13 -
it is desirable to compound as little kitanium pigments into
the present coating composition as possible.
Conventional coating of automobiles in automotive manu-
facturer is generally carried out, for example, in the
following eight steps.
1. Pretreatment: conversion coating with, for example
zinc phosphate or iron phosphate.
2. Under coating: Application of an electrondeposition
primer for the purpose of rust prevention.
3~ Baking: Baking of under coating.
4. Primary intermediate coating: Application of a
chipping resistant intermediate coating composition~
5. Secondary intermediate coating: Application of an
intermediate coating for the purpose of enabling a beautiful
finish of an upper coating composition (wet-on~wet coating).
6. Baking: Baking of primary and secondary intermedi-
ate coating compositions.
7. Upper coating: Application of a metallic coating
compcsition and clear coating composition, or a non metallic
colored coating composition. In the case of the metallic
coating, the metallic coating composition and the clear
coating composition are applied in a wet~on-wet method.
8. Baking: Baking of upper coating composition.
In this coating process, the coating composition of the
present invention can be applied between step 3 and 4 or can
be used as an intermediate coating composition at step 4.
Japanese Examined Patent Publication (Kokoku)
No. 54-73836/79 discloses the use of soft type p~lyurethane
74~5~
materials as a chipping resistant material (i.e. stone guard
coat). However, the elongation percent of this coated film
is 10 to 300~. When the elongation is more than 100%, the
static Tg of the film is less than -10C. Accordingly, when
these -materials are used in combination with conventional
intermediate and upper coating compositions, especially a
conventional upper coating composition of which film generally
has a static Tg of 15 to 40C in view of the required quality
of the upper coat, the difference in the static Tg between
the adjacent filmlayers becomes undesirably large and also
the strength of the film is small.
For instance, static Tg, linear expansion coefficients a
and elongations o conventional chipping resistant coating
compositions and the present coating composition can be
summarized as follows.
s
- 15 -
Under ooating
electrodeposition 70 1.36 0.73 3
composition *l
Cbnvei~tional
intermediate ooat- 26 1.6 0.73 5
ing oompo&ition *l
Upper coating 37 1 7 1.14 3
o~mQosition *3
Soft type ure~hane less bhan ool~ld not 15
sb~n~ guard c~at *4 -10C 1.55 determined
Pre æ nt ooating *5 10 1.6 0.75 80
comEosition
*1 F~wertsp U-30*(cationic electrodeEosition c~ating oomFositi~n
ma~ufacturzd by Nippon Paint Cbo~ Ltd.)
*2 Orga S-52-E*9aaler (p~lyesber ~yEe intennediaba
ooating oompo&ition m3nu~actlLn31 by Nippon Paint C~., Ltd.)
*3 Orga C~25~whibe (melamine-alkyd type coating cGmposition
manuactured by Nippon Paint Cb., Ltd.3
*4 RP*prim2r (F~lyurethane type SGC manufac~ured by NippDn
Faint Cb., Lbd.)
*5 See Example 1
*6 Elongation Percent: $est p~e oe s were ~Lepared as follows.
That is, ooating oomposition samples were spray coated
onto tinplates anl, then, bahed bD fiDnn films having
a dry thickless of about 100 ~m. qhe coat0d tinplabes
were cut int~ pieces each having a si æ of 10 mm x 70 mm
anl the films were peeled off firom the tinplates ~y using
the so-called merc~ry amalgam meth~d.
* Trade Mark
, ~
~2~3'7~
- 16 -
The elongations of the test pieces of the films were
determined by drawing the test pieces under the conditions of
a temperature of 20C, a humidity of 75~ and a draw rate of
10 mm/min (the initial length of the test pieces between the
grips was 30 mm) in a tension determining apparatus (Tensilon *
Model UTM-III manufactured by Tokyo Baldwin Co., Ltd).
Coating films obtained by coating the a~Gve-mentioned
soft type polyurethane compounding coatlng composition and
polyvinyl chloride sol (see Comparati~e Examples 5 and 6) in
a conventional manner were subjected to a chipping test by
using a GRAVALO Meter ~ ~Q PANEL CO.) and, then, subjected
to a thermocycle test (i.e., 8 hr's blister test -~ 1 hour at
a room temperature -~ 6 hour at -20C -~ 1 hour at a room
temperature -~ 6 hour at 80C -~ 2 hour at a room temperature).
As a result, cracking phenomenon was observed from the
chipping marks after one or two cycles. This cracking phe-
nomenon was also confirmed by a ~alt-spray test after the
chippin~ test or an exposure test for one year at Okinawa,
Southern part of Japan. These materials cannot be applied to
conspicuous portions such as the hoods of automobiles and the
sides of automobiles. The cracking is believed to occur in
the course of the temperature changes in the cycle test for
the following reasons. The film layers are repeatedly
subjected to a temperature region less than the static Tg
thereof and a temperature region more than the static Tg
thereof, whereby the ~ilm layers are expanded and shrinked
according to the linear expansion coefficients thereof at
ambient temperature. The values of the linear expansion
; Trade tlark
,
~ .
'74~3~
- 17
coefficients ~ are considerably different depending upon the
temperature differences between the ambient temFeratures and
the static Tg. Thus, the laminated films are warped. In
this case, when one layer is strongly adhered to, for example,
a steel surface, shear occurs between said layer and the
adjacent coating film layer, or a stress is concentrated to
the weak portions where the chipping marks are generated.
Thus, cracking occurs by action of a certain force. Further-
more, it is commonly carried out, especially in automobile
coating to reapply over coating composition to the coated
articles for covering the undesired portions, where "popping"
or ~Isagging~ is generated, or dusts are adhered. However, a
coating composition having a too low static Tg is used,
cracking occurs in the upper coat at one thermocycle even by
adjusting the pigment concentration in the composition (The
increase in the pigment concentration results in the decrease
in t`ne linear expansion coefficient).
The aminoplast resins usable in the present invention
can be any conventional aminoplast resins used in conventional
coating comp~sitions, so long as they have a number-average
molecular weight of 800 to 1400. Examples of such resins are
alcohol-modified melamine resins (e.g., methylol, ethylol,
isopropylol, n-butylol and iso-butylol melamine resins)~ urea
resins and benzoguanamine resins. ~he aminoplast resins
having a molecular weight of less than 800 do not result in
the desirable good chipping property, because the aminoplast
resins having a lower molecular weight have poor reactivit~
Contrary to this, the aminoplast resins having a molecular
748S
- 18 -
weight of more than 1400 result in no good appearance, because
this aminoplast resins have poor affinity with polyester
resins.
The weight ratio of the resin to the pigment contained
in the coating film component of the present invention is
generally 65/35 to 20/80, desirably 60/40 to 30/70. The
increase in the static Tg of the composition is at most about
5C to about 10C due to the compounding of the pigment into
the coating composition.
The coating composition of the present invention ma~
contain any organic solvents such as aromatic, ester, ketone
and alcohol solvents, which are conventionally used for
coating compositions. The coating composition of the present
invention can fur~her contain, as an optional component, any
conventional additives or ingredients suitable for use in the
compounding of coating compositions, such as a segregation
(or color separation) preverting agent, a leveling agent, and
an anti-settling agent.
The present coating composition can be prepared or
compounded ~y any known method. For instance, ~he above-
-mentioned polyester resin, inorganic and/or organic pigments,
and ultrafine talc and/or ultrafine barium sulfate are ground
to a desired particle size and dispersed by using a dispersing
machine such as a sand grinding mill, a ball mill, and a roll
mill and, then, the aminoplast resin, the solvent and the
other optional additives are further added and uniformly
stirred to produce a liquid coatiny oomposition.
The coating composition of the present inveniton can be
-- 19 --
applied, as an intermediate coat, to a Rrimer coating surface
(derived from, for example, electrodeposition coating or
powder coating) on a substrate by a conventional coating
method such as an air spray, or an electrostatic spray
coating. The dry film thickness of the intermidiate coat
derived from the present coating composition is generally 2Q
to 150 ~m, desirably 30 to 100 ~m. Furthermore, the present
coating composition is partially applied, in a desired thick-
ness, to the portion where chipping resistance is required,
and, then, a conventional intermediate coating may be applied
thereon in the so-called "wet-on-wet" coating method. The
applied coating composition is baked, for example, at a
temperature of 120 to 160C for 20 to 30 minutes and, then~
a conventional over coatin~ composition such as an acryl,
polyester or alkyd coatihg compo5ition may be applied thereon.
Thus, the desired finish can be obtained.
The present invention now will be further illustrated
by, but is by no means limited to, the followin~ ~xamples, in
which all percentages are expressed on a weight basis unless
otherwise specified.
Examples 1 to 9 and Comparative Examples 1 to 6
Polyester resins were prepared from the dibasic acids
and the dihydric alcohols listed in Table 1 below in the
amounts listed in Table 1 in a conventional manner in the
presence of dibutyltin oxide catalyst. The result polyesters
were dissolved with xylene and cellosolve acetate so as to
adjust to a solid concentration of 60% in the solution.
Then, coating composition samples were prepared according to
,"~....
12~'74
- 20 --
coating composition recip2s listed in Table 1 (10% of titanium
dioxide and 0.05% of carbon black were further compounded in
all coating compositions and butyl Cellosolve*was used as a
solvent for a coating composition ? -
The present coating compositions and compartive and
reference coating compositions were applied to test panels
comprising SPC-l dull steel panels each having a size of
100 x 150 x 0.8 mm and treated with zinc phosphate. First,
powder or electrodeposition primer was applied to ~he test
p2nels and, then, the coating composition samples were applied
thereon by spray coating. Thereafter, conventional intermedi-
ate coating composition, Orga S-52 E S~aler (polyester type
intermediate coating compos1tion manufactured by Nippon Paint
Co., Ltd.) was applied in the so~called "wet-on-wet- method
so as to form a dry film thickness of 30 ~m and, finally, the
coated coating compositions were baked under the conditions
of 140C x 30 min. To the intermediate coating films thus
obtained, an alkyd resin type upper coating composition, Orga
G 25 White (manufactured by Nippon eaint Co., Ltd.) was
applied so as to obtain the dry film thickness of 35 to 45 ~m
and was baked under the conditions of 140C x 30 min.
The results are shown in Table 2.
* Trade Mark
~i' "''~;
- 21 ~ ~2~
~ -- . _
I
~ o .
~, o ~ o e~ o * ~ ~ o u~ o
U~ o ~ o
U~ C~ o o o ~, ~ ~ ~ ~ ~ o o U~
Qt ~ U~ O O ~ O
r~ ~ O O Q~
_ o
n ~ ~ o
c ~ In
I o ,, ~ o ~ . o U~ o
~1 o o
c:~ o o o o o r~ X
o~
~ o
. o o ~ o o ~.o ~ ~ .~ ~ ~
.. ~ ~ o , ~ ~
I o o o c ~ ~ ~ 3
O '~ '
C~ ~ O
u~ ~ o ~ ~ 8 ~
~ I ~ o o o O O ~ O U~ ~ ei I o
~ I ~ ~ ~ ~ W "~
o ~ ~ ou~o
o~ o o o U~O ~ o
o ~ o u~ a~ u~ O u~
I
,1 o o o o o o r~ o *- ~ ~ o _. o u~ u~
O ~ O
G
~ u~ 3 ~ 5 ~ ~ _
~ ~ ~ 9 ~
R~ o ~
4~
- 22 -
Remarks:
*l Isobutyletherified melamine resin manufactured by
Dai-Nippon Ink and Chamicals Inc.
*2 Methyletherified melamine resin manufactured by
Sanwa Chemicals Co., Ltd.
*3 Isobutyletherified melamine resin manufactured by
Hitachi Chemical Co., Ltd.
*4 Buthylekherified melamine resin manufactured by
Mitsui Toatsu Chemical Inc.
*5 Methyletherified melamine resin manufactured by
Mitsui Toatsu Chemical Inc.
*6 Urea resin manufactured by Dai-Nippon Ink and
Chemicals Inc.
*7 Urea resin manufacturecl by Dai-Nippon Ink and
Chemicals Inc.
*8 Ultrafine barium sulfat:e powder having an average
diameter of primary pa~ticles of about 0.05 ~m
manufactured by Sakai Chemicals Industry Co., ~td.
*9 Ultrafine talc powder having an average diameter o
primary particles of about 1 ~m manufactured by
Fuji Talc Co., Ltd.
*10 Ultrafine talc powder having an zverage diameter of
primary particles of a~out 1 ~m manufactured by
Sakai Chemicals Industry Co., Ltd.
*11 Calcium carbonate powder manufactured by Shiraishi
Kogyo Co., Ltd.
*12 Prapared by crosslinking the following product with
ethylene glycol in the presence of a alkali metal
~LZ~'ô'4~3S
- 23 -
oxide catalyst. That is, OH groups were introduced
into the ends of butadiene polymer and urethanized
by an excess amount of tolylene diisocyanate (TDI).
The remainder of TDI was blocked by ethylalcohol.
*13 Thermoplastic film derived from a mixture of a
dispersion type vinyl chloride resin Zeon #121
(manu actured by Nippon Zeon Co., Ltd.), an adhesive
resin (including nitrile rubber and maleated vinyl
chloride resin), a plasticizer, a stabilizer and a
pigment .
- 2 4 ~ 7~
,
~V ^
~ + + $ + ~ ' $
o~ -
8. ~ - I
o ~ Z
. ~_ ~ .. + ~ + ~ ~ + +
~ a
~ 0 0 ~ 3 C:~ _9 0 ~ O O 5~J N
;~
5 ~ I Q o O ~ O C~ U
~ ....
~ ~ _ _
~1 ~ L C) a ,~, , . 8 1~
~ f) L C~ C O ~: O
;~ ~
~-- --
'7~5
- 25 -
Remarks:
*1 Power Top U-30, electrodeposition coating
composition manufactured by Ni~pon Paint Co.,
Ltd.
*2 Powdex P (Trade Mark), Po~der coating composition
manufactured by Nippon-Paint Co., Ltd.
*3 A salt-spray test was carxied out in a Q PANEL
GRAVALO METER ~ by using a test piece having a
size of 10 x 15 cm under the conditions.of #6
.10 crushed stone, an air pressure of 5 kg/cm2 and
500 g weight x 5 times. The amount of rusts
(i.e. the number of the substrate scratches)
were counted after 120 hours.
*4 Visual determination (orange peel determination~
: 15 *5 Visual appearance was observed after applying the
dust of the materials of Examples and Comparative
Examples on ED (electrodeposition) or PD ~powder)
primer by a gradient coating, followed by inter-
mediate coating and, then, upper coating.
*6 One cycle comprises 16 hours in a blister box
5 hours at 20C > 3 hours at -30C ~ o.5 hours
at 20C ` 3 hours at 80C > 1 hour at 20C
(24 hours in total)
*7 According to a JIS (Japanese Industriai Standards~-
-Z-0'236 method (120 hours)
*8 After markiny an H-type cross-cut on the test
pieces, a mandrel type bending test was carried
out,
.~
~!~U~85
-- 26 --
Evaluation score standards of each test
.
~+ : Excellent
+ : Good
- : Fair
~~ : Poor
. . ~
