Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR REPAIRING AND LUSTERING DEFECTS ON HYDROPHILIC
COATSURFACE
Field
The present invention relates to a method for repairing and lustering defects
on a
hydrophilic coat surface and, in particular, to a method for repairing and
lustering defects
on a hydrophilic coat surface that requires a very fine finish, such as an
automobile coat
surface.
Background
Painting is generally performed on an automobile surface fox the purpose of
imparting surface protection, desired colors, and aesthetic appearance.
Painting is an
operation to spread a paint (i.e., is a resin composition) over the surface of
an automobile
body and to harden the paint to form a continuous resin-coated film having an
approximately uniform thickness. The resin-coated film formed on the surface
of an
object by painting is called a coat.
If some functional hindrance of the paint (e.g.,,foaming, adhesion of dust, or
the
like) occurs during the painting step, the uniformity, continuity, or the
surface flatness of
the coat to be formed is inhibited, and defects such as haze marks, recesses,
and wounds
may be generated on the coat surface. Defects are also generated on the coat
surface when
the uniformity, the continuity, or the surface flatness of the coat is altered
by friction or
collision of the automobile body after the coat is formed. If the defects are
present on the
coat surface, the aesthetic appearance of the automobile body is deteriorated,
and the value
of the automobile is decreased. For this reason, defects on the coat surface
must be
repaired and polished.
Japanese Patent Laid-open Publication No. 02-269791 discloses a method for
repairing the defects on the coat surface. According to this method, the
defects of the coat
are removed by first sanding with a very fine grade polishing material. Next,
the trace of
the removed defects is buffed using a buffing composition to remove the
scratches
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produced by the sanding step. Finally, the residual buffing composition is
removed using
a cotton cloth, thereby producing a uniform, glossy finish. One suitable
buffing
composition for use in this method is commercially available under the trade
designation
"FINESSE-IT" from Minnesota Mining and Manufacturing Company.
Various functional paints have been developed in recent years, and a coat is
known
which exhibits an excellent antifouling property against fouling substances
specific to
urban areas (e.g., smoke and exhaust gas). For example, "Painting Technology",
Vol. 31,
No. 7 (1996), pp. 268-273 explains a mechanism of the antifouling function
exhibited by
such a low-fouling type coat against urban fouling substances. Since the low-
fouling type
l0 coat has a high surface energy and shows a hydrophilic and oil-repellent
property,
oleophilic fouling substances (e.g., smoke and exhaust gas) are unlikely to
adhere to the
coat and, if they adhere, are easily washed away by rain or the like.
When defects are generated on the surface of the low-fouling type coat and if
an
attempt is made to repair the defects by a conventional method, problems arise
such as
15 insufficient removal of the defects, poor finish after repairing, and
deterioration of the
antifouling property of the coat against urban fouling substances after
repairing. These
problems are raised because oleophilic ingredients (e.g., aliphatic
hydrocarbon and
petroleum-based solvents) are contained in the buffing composition used in the
step of
buffing the coat surface. These oleophilic ingredients are not compatible with
the
20 hydrophilic coat and have an insufficient polish promoting function. Once
the oleophilic
ingredients penetrate into the hydrophilic coat they cannot be easily removed,
so that the
hydrophilic and oil-repellent function is deteriorated on a portion of the
coat surface where
the oleophilic ingredients have penetrated. On the other hand, if the
oleophilic ingredients
are removed from the buffing composition, removal of the defects by the
buffing step will
25 be insufficient, thereby giving a poor finish after repairing
Summary
The present invention provides a method for repairing and lustering defects on
a
coat surface, by which method the defects on a hydrophilic coat surface is
sufficiently
30 removed with good finish after repairing, and the antifouling function of
the hydrophilic
coat against urban fouling substances is not deteriorated. The method of the
present
invention comprisies the steps of applying a buffing composition on a
hydrophilic coat
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surface; and buffing the hydrophilic coat surface to which the buffing
composition has
been applied, wherein said buffing composition is an aqueous composition which
comprises water and a water-soluble high-boiling-point liquid organic
compound, and
further contains either a combination of abrasive particles and a dispersant,
a lustering
agent, or both.
Detailed Description ,
The buffing composition for use with the method of the present invention is an
aqueous composition containing water and a water-soluble high-boiling-point
liquid
organic compound, and further containing either a combination of abrasive
particles and a
dispersant, a lustering agent, or both.
Water-soluble high-boiling-point liquid organic compound:
Preferred water-soluble high-boiling-point liquid organic compounds, are those
that are effective in swelling and softening the hydrophilic coat. Softening
the hydrophilic
coat improves the polishing performance of the buffing composition.
The hydrophilic coat may be generally an acrylic melamine resin, an aminoalkyd
resin, a urethane resin, or the like. The hardness of such a coat is generally
H to 2H (JIS
( 1979, I~5400)) before it is swollen with the water-soluble high-boiling-
point liquid
organic compound. On the other hand, after it is swollen with the water-
soluble high-
boiling-point liquid organic compound, the hardness of the coat is preferably
about B in
view of promoting the polishing.
Since the buffing step is generally carried out for 1 to 5 minutes at an
ambient
temperature of 25 to 60°C, the water-soluble high-boiling-point liquid
organic compound
must be slightly volatile to such a degree that it is not dried during the
buffing step.
Accordingly, the water-soluble high-boiling-point liquid organic compound
preferably has
a boiling point of not less than 100°C, more preferably not less than
130°C.
The water-soluble high-boiling-point liquid organic compound preferably has a
carbon number of 3 to 12, more preferably 3 to 6. If the carbon number is less
than 3, the
boiling point will be too low and it will be dried during the polishing step.
If the carbon
number exceeds 12, the ability of the water-soluable high boiling-point liquid
organic
compound to swell the coat will decrease.
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Also, the water-soluble high-boiling-point liquid organic compound is
preferably
one that can be easily washed away with water with little remaining in the
inside of the
coat, even if it adheres to the coat surface. Further, even if a small amount
remains, it is
preferably one that does not give an adverse effect on the hydrophilic, oil-
repellent
function of the hydrophilic coat.
Preferable examples of water-soluble high-boiling-point liquid organic
compounds
are polyhydric alcohols, hydroxyketones, and ether or ester derivatives of
polyhydric
alcohols. Specific examples include ethylene glycol diglycidyl ether, ethylene
glycol
dimethyl ether, ethylene glycol monoacetate, ethylene glycol monoethyl ether,
ethylene
l0 glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene
glycol
monomethoxymethyl ether, ethylene chlorohydrin, glycerol, diethylene glycol
diacetate,
diethylene glycol dimethyl ether, diethylene glycol monoethyl ether,
diethylene glycol
monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol
monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol
monomethyl
ether, triethylene glycol monoethyl ether, triethylene glycol monomethyl
ether, propylene
glycol monobutyl ether, diacetone alcohol, propylene glycol monomethyl ether,
and
others.
Among these, especially preferable water-soluble high-boiling-point liquid
organic
compounds are diacetone alcohol and propylene glycol monomethyl ether. These
are
excellent especially in the swelling property of the coat, and the polishing
performance of
the buffing composition.
The water-soluble high-boiling-point liquid organic compound is typically
present
in the buffing composition at 1 to 50 parts by weight, more preferably at 1 to
30 parts by
weight, most preferably at 3 to 10 parts by weight with respect to 100 parts
by weight of
water. If the blended amount of the water-soluble high-boiling-point liquid
organic
compound is less than 1 part by weight, the coat will not swell sufficiently,
failing to
provide a polishing promoting effect, whereas if it exceeds 50 parts by
weight, the coat
will be too soft to provide a good finish on the coat surface after repairing.
Abrasive particles:
Abrasive particles are a particulate material which provide a polishing
effect. They
are preferably a hard material which has a good cutting property and which
does not give
deep wounds easily on the polished surface when they are used as free abrasive
particles.
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The average particle size of the abrasive particles is preferably from 10 nm
to 100 ~,m,
more preferably from 1 to 10 ~,m. The particle size distribution should be
fairly narrow so
that the buffing composition does not produce any undesired scratches.
The material of the abrasive particles is preferably aluminum oxide, silica,
aluminum silicate, talc, kaolin, clay, or a mixture thereof. Especially
preferable abrasive
particles are alumina particles.
The abrasive particles are included in the buffing composition if a buffing
function
is desired. The content of the abrasive particles is not more than 60 parts by
weight,
preferably 10 to 60 parts by weight, more preferably 20 to 40 parts by weight
with respect
to 100 parts by weight of water. If the abrasive particles are included in an
amount of 60
parts by weight, the polishing performance is not improved; and on the
contrary, the finish
of the coat surface after repairing is deteriorated.
Dispersant:
A dispersant is included in the buffing composition so that the abrasive
particles do
not agglomerate. Since the buffing composition of the present invention is an
aqueous
composition containing water, a water-soluble high-boiling-point liquid
organic
compound, abrasive particles, and other ingredients, the dispersant must
perform the
function of dispersing the abrasive particles, even in a water-alcohol medium.
The dispersant may be generally a Water-soluble surfactant. Specific examples
2o include polycarboxylic acids and salts thereof, polyaminoamides, and acid
esters thereof.
The dispersant is included in the buffing composition preferably at an amount
of
0.5 to 5 parts by weight with respect to 100 parts by weight of water. If the
amount of the
dispersant is less than 0.5 part by weight, the abrasive particles tend to
agglomerate in the
buffing composition, whereas if the dispersant is included in an amount
exceeding 5 parts
by weight, the dispersibility of the abrasive particles is not improved and
they are likely to
remain on the coat surface after repairing.
Lustering agent:
A lustering agent is included in the buffing composition so as to make a finer
finish -
or to impart luster to the coat surface after repairing. This makes the
repairing and
lustering method of the present invention also suitable as a countermeasure
against so-
called hazing of the coat surface. Since the lustering agent is a component
that performs a
function of filling fine wounds by remaining on the coat surface after
repairing, the
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lustering agent is preferably one that does not give an adverse effect on the
hydrophilic
oil-repellent function of the hydrophilic coat.
The lustering agent to be used may be a hydrophilic silicone or a hydrophilic
wax.
Specific examples include polyether denatured silicone, hydrophilic
aminosilicone,
hydrophilic epoxy silicone, glycerol, hydrogenated castor oil and derivatives
thereof,
amido compounds, and others.
In particular, a hydrophilic aminosilicone composed of a block copolymer of
polyether and amino denatured silicone is preferred because it remains on the
coat surface
or inside the coat and produces an effect of maintaining the luster and the
hydrophilicity of
the coat.
The amount of the lustering agent may be suitably adjusted in accordance with
the
required finish of the coat surface after repairing. Generally, the lustering
agent is allowed
to be contained in the buffing composition in an amount of not more than 10
parts by
weight, preferably 0.5 to 10 parts by weight, with respect to 100 parts by
weight of water.
Even if the lustering agent is allowed to be contained at an amount exceeding
10 parts by
weight, the finish of the coat surface after repairing is not significantly
improved.
Other additives:
Thickeners can be added to increase and adjust the viscosity of the buffing
compositions of the present invention. If the viscosity of the buffing
composition is too
low, it tends to run down the vertical surfaces of the automobile, and
consequently, the
operators cannot properly buff with it. Therefore, thickeners are utilized to
adjust the
viscosity of the buffing composition.
Typical examples of thickeners include hydrous aluminum silicate, a
dimethyldioctadecyl salt of montmorillonite clay, an alkali-soluble acrylic
polymer
emulsion, colloidal silica, heavy metal soaps such as lead oleate, zinc
oleate, zinc stearate,
and aluminum stearate. The preferred thickener for use with the present
invention is an
aqueous alkali-soluble acrylic polymer emulsion.
Stabilizers and preservatives can be employed to inhibit bacterial growth in
the
buffing composition. Typical examples include methyl paxaben, ethyl paraben,
propyl
3o paraben, butyl paraben, potassium sorbate, sorbic acid, and o-phenylphenol.
Pigments, dyes, and perfumes can also be added to the buffing composition of
the
invention as desired.
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Preparation of buffing composition:
A buffing composition for use with the method of the present invention is
obtained
by mixing the above-mentioned components with water. The water for use may be
tap
water, distilled water, ox deionized water. Deionized water is preferred
because the
likelihood of bacterial growth is reduced due to the removal of ions and other
minerals
which may promote microbial growth in the buffing composition.
The order of addition in preparing the buffing composition is, for example;
water,
additives, a water-soluble high-boiling-point liquid organic compound, a
lustering agent, a
dispersant, and abrasive particles. The mixture is continuously mixed as the
various
ingredients are added. Thereafter, the buffing composition is mixed to form a
homogeneous dispersion with a high shear mixer.
Method for repairing and lustering defects on a hydrophilic coat surface:
According to the method of the present invention, surface defects are first
discovered on the coat surface. The surface defects are, for example, haze
marks caused
by poor hardening, pinholes caused by foaming in painting, abrasions caused by
friction of
an automobile body, adhesion of dusts, and scratches, hazing, and others
remaining after
these defects are removed in the sanding step. Then, the buffing composition
is applied to
the area on the hydrophilic coat surface where the surface defects are formed.
Next, the hydrophilic coat surface, to which the buffing composition has been
applied, is buffed. The buffing is generally performed in the following
manner. First, a
buffing pad is secured to a buffing tool. The pad and the buffing tool for use
can be, for
example, those manufactured by Minnesota Mining and Manufacturing Company.
Next,
the buffing pad is placed on the coat surface to which the buffing composition
has bean
applied. The tool is turned on, and the coat surface is buffed as pressure is
applied to the
tool. The buffing period is typically 3 to 30 seconds. The buffing may be
performed
several times as the pressure is increased or decreased.
Thereafter, the buffing composition remaining on the polished surface is
removed
by means of washing with water, wiping with woven cloth (e.g., cotton cloth),
nonwoven
cloth, very fine fiber cloth of 0.1 to 0.5 denier, or the like. An additional
step of polishing
the surface may result in an even finer finish.
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Examples
The present invention will be described further specifically by the following
Examples. However, the present invention is in no way limited to the examples.
In the
Examples, "parts" are based upon weight unless otherwise indicated.
Example 1:
The buffing composition of this Example was made by mixing 100 parts of ion-
exchange water, 2 parts of polycarboxylate (commercially available under the
trades
designation "Carbopol" from BF Goodrich Co., Ltd.), 1 part of triethanolamine,
5 parts of
diacetone alcohol, and 30 parts of aluminum oxide particles having an average
particle
size of 5 ~.m, and stirring the mixture to form a uniform dispersion with a
high shear
mixer.
Example 2:
The buffing composition of this Example was made according to the procedure
used in Example 1, except that diacetone alcohol was replaced with propylene
glycol
monomethyl ether.
Example 3:
The buffing composition of this Example was made according to the procedure
used in Example 3, except that 1 part of hydrophilic aminosilicone (a block
copolymer of
polyether and amino-denatured silicone commercially available under the trade
2o designation "NUC-SILICONE" from Nippon Unicar Co., Ltd.), was also added.
Example 4:
The buffing composition of this Example was made according to the procedure
used in Example 3, except that hydrophilic aminosilicone was replaced with a
hydrogenated castor oil (commercially available under the trade designation
"EMULSION
A OIL" from CASCHEM Co., Ltd.).
Example 5:
The buffing composition of this Example was made according to the procedure
used in Example 3, except that hydrophilic aminosilicone was replaced with
glycerol.
Example 6:
3o The buffing composition of this Example was made according to the procedure
used in Example 1, except that diacetone alcohol was replaced with propylene
glycol
monoethyl ether acetate.
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Example 7:
The buffing composition of this Example was made according to the procedure
used in Example 1, except that diacetone alcohol was replaced with
acetylacetone.
Example 8:
The buffing composition of this Example was made according to the procedure
used in Example 1, except that diacetone alcohol was replaced with ethylene
glycol
monomethyl ether acetate.
Example 9:
The buffing composition of this Example was made according to the procedure
to used in Example 1, except that diacetone alcohol was replaced with ethylene
glycol
monomethyl ether.
Example 10:
The buffing composition of this Example was made according to the procedure
used in Example 1, except that diacetone alcohol was replaced with dipropylene
glycol
monomethyl ether.
Example 11:
The lustering composition of this Example was made by mixing 100 parts of ion-
exchange water, 5 parts of propylene glycol monomethyl ether, and 1 part of
hydrophilic
aminosilicone, and stirring the mixture to form a uniform dispersion with a
high shear
mixer.
Comparative Example 1:
The buffing composition of this Example was made by mixing 100 parts of ion-
exchange water, 2 parts of polycarboxylate (commercially available under the
trade
designation "CARBOPOL" from BF Goodrich Co., Ltd.), 1 part of triethanolamine,
and
30 parts of aluminum oxide particles having an average particle size of 5 pm,
and stirring
the mixture to form a uniform dispersion with a high shear mixer.
Comparative Example 2:
A buffing composition commercially available under the trade designation
"ULTRA FINISH" from Minnesota Mining and Manufacturing Company was used. This
buffing composition contains an oleophilic component.
Performance Evaluation:
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The buffing compositions of Examples and Comparative Examples were left to
stand at 50°C for 7 days for observation by eye of presence or absence
of separation and
evaluation of stability of the compositions with the passage of time. The
results are shown
in Table 1 and Table 2.
The coat surface of a metal test panel painted with a black-colored
hydrophilic coat
was sanded using a grade 1500 sanding disc (commercially available under the
trade
designation "FINESSE-IT MICRO FINE" from Minnesota Mining and Manufacturing
Company) attached to a hand sanding pad (commercially available under the
trade
designation "FINESSE-IT" from Minnesota Mining and Manufacturing Company). The
to sanding was done with a circular motion and approximately four drops of
water were
added to the sanding interface as a lubricant. The sanding step formed round
scratches
having a diameter of about 4 cm on the coat surface. The average roughness
(Ra) of the
scratches was about 0.15 ~,m over the entire surface of the area where the
scratches were
formed. Then, the painted panel was wiped dry with a cotton cloth.
15 Next, the prepared buffing composition was applied as a liquid drop having
a
diameter of about 1.5 cm to the sanded area. A buffing pad and a finishing
pad,
(commercially available under the trade designations "FINESSE-IT" and "FINESSE-
IT
ROLOC", available from Minnesota Mining and Manufacturing Company) were
secured
to a rotary sander buffing tool.
2o The buffing pad was placed on top of the coat surface to which the buffing
composition had been applied, and the finishing material was spread over this
area before
the buffing tool was started. The buffing tool was turned on and the sanded
area was
buffed for eight seconds as very firm pressure was applied to the tool. After
the eight
second period, the pressure was reduced, and it was buffed for additional
three seconds.
25 Thereafter, the buffing composition remaining on the polished surface was
washed
with water and the polished surface was dried.
Then, the polished surface was lustered by using the lustering composition
prepared in Example 11. The lustering composition of Example 11 was applied to
a
surface of coating which had been repaired by the buffing composition of
Example 2, and
30 the surface was buffed in the manner described above.
to
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The polishing performance of each buffing composition, the finish of the coat
surface, hydrophilicity, and stain resistance were evaluated. The results are
reported in
Table 1 and Table 2.
Buffing performance:
If the scratches formed on the coat surface completely disappeared on the coat
surface after repairing and lustering, it was rated as "o"; if they remained
only faintly, it
was rated as "~1"; and if they remained conspicuously, it was rated as "x".
Finish
The 20° gloss of the polished surface was measured.
l0 Hydrophilicity
Water was applied to the coat surface with a hand spray after repairing and
lustering for observation of the state of adhering water. If the entire
surface was wetted, it
was judged that the hydrophilicity was "present". If water drops were formed,
it was
judged that the hydrophilicity was "absent".
Stain resistance:
A test piece having a surface of coating which had been repaired and lustered
was
positioned horizontally. Onto the surface was sprinkled uniformly the 15 kinds
of test dust
defined in JIS Z 8901 (72% Kantoh loam, 23% carbon black, 5% cotton linter)
thereafter,
using a sieve. The test piece was placed in a high temperature oven at
50°C for 2 hours. It
2o was removed from the oven and was left at room temperature for 1 hour.
The test piece was raised horizontally, arid dropped slightly to pull down the
test
dust. The test piece was silently dipped in a water bath for 1 minute, and
took out.
Excessive water was wiped by using filter paper, and the test piece was left
at room
temper ature for 1 hour.
Stain level of the surface of coating was evaluated visually. If the stain was
came
off, it was evaluated as "o". If the stain was stayed in, it was evaluated as
"x".
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Table 1
Example
1 2 3 4 5 6 7
Ion-exchange 100 100 100 100 100 100 100
water
polycarboxylate 2 2 2 2 2 2 2
triethanolamine 1 1 1 1 1 1 1
aluminum oxide 30 30 30 30 30 30 30
propylene glycol 5
monoethyl ether
acetate
acetylacetone 5
diacetone alcohol5
ethylene glycol
.o monomethyl ether
~o acetate
o
propylene glycol 5 5 5 5
monomethyl ether
ethylene glycol
monomethyl ether
dipropylene glycol
monomethyl ether .
hydrophilic 1
aminosilicone
hydrogenated ' 1
castor oil
glycerol 1
Presence or absenceAbsentAbsent AbsentAbsentAbsentPresentPresent
of
separation
Buffing performanceo 0 0 0 o x o
Finish 78.5 78.1 82.5 81.0 78,4 68.2 69.7
W Hydrophilicity PresentPresentPresentPresentPresentPresentPresent
Stain resistanceo 0 0 0 0 0 0
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Table 2
Example Comparative
Example
8 9 10 11 1 2
ion-exchange water100 100 100 100 100
polycarboxylate 2 2 2 2
triethanolamine 1 1 1 1 0
aluminum oxide 30 30 30 30
propylene glycol
monoethyl ether
acetate
acetylacetone
U
diacetone alcohol
ethylene glycol 5
o monomethyl ether
_
acetate
o propylene glycol 5
~
monomethyl ether
ethylene glycol 5
.
.,
r
monomethyl ether w
dipropylene glycol 5
monomethyl ether
0
hydrophilic 1
aminosilicone o
hydrogenated castor
oil
glycerol U o
Presence or absencePresentAbsent Absent - Absent Absent
of
separation
. Buffing performanceQ x x - x 0
'~ Finish 58.2 51.4 58.7 82.8 57.7 82.3
W
Hydrophilicity PresentPresentPresentPresentPresentAbsent
Stain resistance o 0 0 o x x
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The surface of coating which had been repaired and lustered by using the
composition of Example was hydrophilic, and was superior in stain resistance
by
comparison with that of Comparative Example.
14
