Note: Descriptions are shown in the official language in which they were submitted.
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1 BACKGROUND CF THE INVENTION
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1. Field of the Invention
This invention relates to a method for filling the
spaces between joining parts of or depressions in a surface, ~ -
e.g., an automobile body and the like, using a plastic solder,
and to plastic solder compositions which can be used especially
advantageously in the above method. More specifically, this
invention relates to an improved method for filling the spaces
between joining parts of a surface, e.g., of an automobile body
and the like which occur at the time of fabricating steel body
panels to form the surface, or the depressions in the surface,
e.g., in the automobile body, resulting from spot welding,
which comprises depressing the above joining parts or depressions
to a certain extent, and filling the resulting depressed areas
with a plastic solder so ~hat the finished surface, e.g., of the ~ -
automobile body, is smooth. ~-
2 Descri tion of the Prior Art - -
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Previously, metallic lead solders have been widely
used as a filling material for automobile bodies or the like,
but because of plumbism or the unsatisfactory operability of
the solder, such lead solders have the following defects.
(a) Toxic lead gas that is generated when filling ~ -
is performed using a spatula while exposing the metallic lead
solder and the areas being filled to an acetylene burner, and
lead dust that occurs at the time of sanding after filling are
detrimental to the health of the working personnel, and also
tend to cause pollution in areas where these solders are used. -
~ b) Electrodeposition coating, intermediate coating
and top coating are applied to automobile bodies, and higher bak-
ing temperatures ~or the coatings give better quality coatings
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1 with increased strength and luster. Since lead solder has amelting point of 183C, the baking temperatures for automobile
bodies subjected to filling using lead solder is about 170C at
the highest.
(c) Since lead solder softens during the baking
operation, air entrapped at the time of filling expands during
the baking, and tends to form projections or holes on the surface
of the filled area.
(d) The amount of the solder now used is about 1 to
0.5 Kg for an average size automobile. Since the density of the
solder is higher than that of steel, the solder adds to the
weight of the car.
With a view to removing these defects, attempts have
been made to use synthetic resins for filling.
One of these attempts is a method which involves the
use of a thermosetting resin paste. Since, however, filling is
performed using a spatula in this method, it is very difficult
to avoid entrapping air bubbles in the filled areas. Moreover,
because the filled areas are dried in the open, a sagging
phenomenon occurs.
Another attempt involves bonding a solid thermosetting
resin pre-fabricated to fit into the area to be filled and which
does not to contain air bubbles, to area to be filled using an
adhesive. This method has the defect that a complicated
procedure is involved because the method includes the step of
coating the adhesive.
SUMMARY OF THE INVENTION
An object of this invention is to provide a method for
filling the spaces between joining parts of or depressions in
a surface, e.g., of automobile bodies and the like, which is free
from the above-described defects.
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1 This invention provides a method for filling depressions
in a surface which comprises placing partially cured (B-state)
article of a thermosetting resin composition, which has been
fabricated so as to fit into the depression and which is as
free of air bubbles as is possible, in the depression to be
filled, and heating it to a temperature above the temperature
at which the shaped articles softens or melts.
Another embodiment of this invention provides a
method for filling the depressions in a surface, e.g., depressions
in an automobile body or spaces between joining parts and the
like, which comprises filling a depression with a partially
cured article of a thermosetting resin composition or of a
thermosetting resin composition paste, so as to fit into the
depression to be filled, heating the article or paste under
pressure from the surface, e.g., using an applicator capable
of being heated and having a fluorine resin sheet adhered to
the applicator surface, thereby to complete the filling without
forming air bubbles on the surface of the depression to be
filled. -
Still another embodiment of this invention provides
a method for filling a depression in a surface, e.g., spaced
between joining parts or depressions in automobile bodies and
the like, where air bubbles are eliminated, which comprises
placing a shaped article of a thermosetting resin composition
in the depression to be filled in a specific relation as described
hereinafter, and curing the shaped article under heating, e.g.
using a heated applicator.
A further embodiment of this invention provides an
epoxy resin solder composition that can be used especially
advantageously in the above filling methods.
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1 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional view showing the placing of
the resin shaped article in a depression to be filled using a
test panel.
Figure 2 is a sectional view showing the filling of
the resin shaped artic]e in the depression to be filled after
use of a heatable applicator.
Figure 3 (a) shows a test panel obtained by spot
welding a cold-rolled steel plate used in an example.
Figure 3 (b) shows the placement of a partially cured
article of a thermosetting resin on the test panel of Figure 3(a),
and
Figure 3 (c) shows the test panel of Figure 3(a)
filled with the partially cured article of the thermosetting
resin after subjection to heat and pressure.
Figure 4 and Figure 5 show additional embodiments of
test panels used in the examples.
Figure 6 shows exothermic curing data obtained in an
example for a thermosetting resin in an A-state degree of cure. ~-
Figure 7 shows exothermic curing data obtained in an
example for a thermosetting resin in a B-state degree of cure.
Figure 8 shows the particle size distribution of iron
powders used in an example.
Figure 9 shows the particle size distribution of
aluminum powders used in an example.
DETAILED DESCRIPTION OF THE INVENT ION
As is set forth above, the embodiments of the method
of this invention are~ particularly useful in filling the spaces
between body panels of an automobile body or depressions in the
- 30 surface therein but the embodime~ts of the method of
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1 this invention are not limited thereto, however~ For
simplicity in the description to follow, the application
of the embodiments of the method of this invention will be with
reference to their utility in filling spaces and depressions in
an automobile body surface but it will be recognized that the
principles of this invention are appropriate to other applications
as well.
According to a first embodiment of this invention, a
method is provided for filling the spaces between joining parts
of or depressions in a surface, e.g., of automobile bodies and
the like, which comprises placing a partially cured shaped article ~ -
of a thermosetting resin composition in the area to be filled
and heating it to a temperature above the softening or melting
temperature of the resin composition to fix the shaped article
provisionally to the area, the resin composition being pre-
fabricated so as to fit in the area to be filled and being as
free from air bubbles as is possible, heating the shaped article
under pressure using a heated applicator, and then surface-
finishing the filled area.
According to this embodiment, a suitable curing agent,
inorganic filler, and metal powder are added to a thermosetting
resin, and mixed thoroughly to form a composition. Then, the
thermosetting resin composition is converted to a partially
cured (i.e., B-state) article by shaping the resin composition
under heat and pressure e.g., using a temperature of about 50
to ~50C and a pressure above about 0 to about 50 Kg/cm2 so
that the article fits into the area to be filled, or by mixing
the thermosetting resin with additives under a reduced pressure,
e.g., less than about 50 mmHg and injecting the resulting mixture
into a receiving plate or mold. Then, the filling part is heated
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1 to a temperature above the temperature at which the resin compo-
sition softens or melts, e.g., at about 50C to about 250C
(in the case of an epoxy or polyester resin composition, the
area to be filled is heated to about 100 to 200C). The above
resin shaped article is placed in the heated area to be filled
to soften or melt the surface of the resin shaped article in
contact with the heated area to be filled, and then the back
surface of the resin shaped article ~the surface not in contact
with the area to be filled) is heated under pressure, for
example, at about 200C and about 10 to 20 Kg of total pressure
for less than about 3 minutes, using a heatable applicator to
embed the softened resin shaped article in the area to be filled.
Then, the embedded resin shaped article is cured, e.g., by
heating to about 100 to 250C at a pressure of about 0.3 to
10 Kg/cm2, to complete the filling, and the surface of the
filled area is finished, for example, by sanding.
As used herein the term partial curing means that the
thermosetting resin is cured to the extent that it has a vis-
cosity at 140C of about 0.1 to 105 poise using a KOKA flowtester
(a viscometer for plastics, manufactured by Shimazu Seisakusho
Ltd. (Japan)~ and this term includes the B state degree of cure -
as is generally employed in the art (see nsulation/Circuit
Directory/Encyclopedia., June and ~uly, 19~3, page 3~.
When the resin shaped article used in this method is ~ ;
of the same shape as the area to be filled, no flow of resin
between the steel panel on the body side and the heated applicator
occurs until the shaped article is set, and air bubbles tend to
be contained in the interface between the steel panel surface
-and the resin layer. Therefore, the resin shaped article
preerably has a certain shape and relationship with respect to
the space or area to be filled as will be described in detail
hereinafter.
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1 This method can be utilized primarily for the filling
of welded parts of automobile bodies, but can also be used
effectively in similar uses, for example, for building up
depressed areas and raised parts of various steel materials to
a desired shape, such as the filling of the joining parts of
steel panels formed at the time of fabricating steel panels of
vehicles or the depressions in steel panels resulting from spot
welding of the panels or bad pressing of the panels.
Since a synthetic thermosetting resin composition is
applied to a heated area to be filled, the softened resin adheres
to the filled area, and upon setting, is firmly fixed thereto.
Thus, the use of an adhesive is not necessary in this method.
Furthermore, since a synthetic thermosetting resin is used
instead of a metal solder, there is no danger of the generation
of toxic gases or dust, and moreover, the filling of the spaces
between joining areas or depressions of automobile bodies or the
like can be performed using a simple procedure.
Examples of suitable thermosetting resins which can
be used in this method are phenol resins, epoxy resins, silicone
resins, urea resins, acrylic resins, urethane resins, melamine
resins, and polyester resins, with epoxy resins being most
preferred. Examples of suitable curing agents for these resins
are those well known in the art for these thermosetting resins
- and include aliphatic amines, aromatic amines, acid anhydrides,
polyamides, and modified amines. A suitable particle size for
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these during agents is less than about 149 microns. The thermo-
setting resin composition can of course contain inorganic fillers
such as silica, talc, clay, mica, glass powder, carbon powder,
calcium carbonate, or alumina, or metal powders such as aluminum
powder, iron powder, copper powder, antimony powder or nickel
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1 powder, e.g., in a volume % of about 5 to 50 of the total
volume of the composition. A suitable particle size for the
inorganic fillers and metallic powders is less than about 149
microns.
According to a second aspect of this invention, a
method is provided for filling the spaces between joining parts
or of depressions in automobile bodies and the like, which
comprises placing a partially cured (B-state cure) shaped article
of a thermosetting resin composition in an area to be filled -
with the resin composition being pre-fabricated so as to fit into
the area to be filled, or prefabricating a thermosetting resin
composition paste in the area to be filled, and heating the
thermosetting resin composition under pressure on the surface
of the thermosetting resin composition using a heatable
applicator having a surface capable of fitting into the area
to be filled and including a fluorine resin sheet adhered to the
surface of the applicator contacting the thermosetting resin
composition, to fill the area.
According to the first embodiment described above, the
surface of the resin layer after curing is not smooth. However,
by using a special heatable applicator in the second embodiment,
the adhesion of the applicator to the resin and the generation
of air bubbles in the closed portion and the surface layer of
the filled area can be prevented, and a smooth surface finish
can be obtained.
The fluorine resin sheet used in this embodiment can
be, for example, a sheet of polytetrafluoroethylene, polyvinylidene
fluoride, or a tetrafluoroethylene/hexafluoropropylene copolymer.
The sheet may be a sheet of the fluorine resin alone produced
by conventional means (for example, cutting or rolling), or a
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1 sheet of a mixture of the fluorine resin and a filler such as
molybdenum, glass fiber powders or copper powder, which may or
may not be embossed in a raised and depressed pattern or per-
forated. The sheet can also be an impregnated cloth obtained
by impregnating a thermally stable fibrous cloth made, for
example, of glass fibers, asbestos fibers, carbon fibers or
metallic fibers, with a dispersion of the fluorine resin, and
heating the cloth, or a laminate of a plurality o~ such
impregnated cloths. Especially preferred sheets are the above-
mentioned impregnated cloths or the laminates of these cloths,and those sheets having a depressed and raised pattern on
their surfaces and containing gas passages adapted to permit the
discharge of gases, such as air bubbles, air, reaction gases,
or decomposition gases, generated between the applicator and
the resin layer. In a more preferred embodiment, air-permeable
holes or grooves are also provided on the surface of the
applicator (heater) itself and the above-described preferred
fluorine resin sheet is adhered to such a surface so that air
bubbles generated at the time of filling can be discharged
through the surface of the applicator.
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In this embodiment of the method of the invention,
preferably, the area to be filled also is heated to a temperature
above the softening or melting temperature of the resin because
this permits the resin to be easily placed in the area to be
filled and to adhere and fix the resin provisionally to the
filling part.
; According to a third embodiment of the method of this
invention which is especially advantageous and preferred, a
method is provided for filling the spaces between ~oining parts
of Qr depressions in, e.g., automobile bodies and the like,
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1 which comprises placing a pre-~ormed partially cured (B-state
cure) article of a thermosetting resin composition in an area to
be filled so that the maximum length (~) of the normal that
extends from the undersurface of said partially cured resin
article to the surface at the area to be filled, e.g. r the
steel panel surface of an automobile body, is not less than
one-sixth of the maximum length (~') of the normal that extends
from the top surface (outside surface) of the cured filled
resin article to the surface at the area to be filled, e.g., -
the steel panel surface of an automobile body (~>- V 6), and then
heating the filled resin article under pressure using a heatable
applicator to camplete the filling of the area.
This embodiment of the method of this invention will -
be specifically described below by reference to the accompanying
- drawings.
Figure l is a sectional view showing the setting of
a resin shaped article in an area to be filled using a test
panel, and Figure 2 is a sectional view showing the placing of
the resin shaped article in the depression to be filled after use
of a heatable applicator.
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Referring to Figure l, a pre-formed partially cured
article 2 of a thermosetting resin composition is placed on the
surface of a depressed area to be fllled l of a steel panel 3.
In this case, the maximum distance between the undersurface of
the pre-formed partially cured article 2 and the point A which
lntersects the normal that extends from the undersurface of
the resin article towards the steel panel surface 3' of the
area to be filled is designated as e. On the other hand,
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Figure 2 shows the shaped article 2 which has been heated under
3~0 pressure using a heatable applicator (not shown) from the
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1 condition shown in Figure 1. B in Figure 2 shows a point of
intersection of the normal extending from the top surface
(outside surface) of the filled resin layer at the area filled
towards the steel panel surface 3' at the area filled with the
steel panel surface 3' at the area filled, and ~' shows the
maximum distance between this point B and the steel
panel surface 3'. According to this embodiment,
the shape of the resin article is determined so as
to satisfy the relation ~- 1/6 ~', and the pre-formed resin
article is placed at the area to be filled. Then, the shaped
article is cured using a heated applicator, thereby to complete
the filling.
Various thermosetting resins can be used in this
method, but epPxy resins are especially preferred because of
their superior bond strength and mechanical strength. Since -~
rapid curing is required, dicyandiamide is especially preferred
as a curing agent. As a curing promotor, an imidazole, e.g., -
imidazole, 2-methyl-imidazole, 2-methyl-N-(cyanomethyl)imidazole,
2-ethyl-~-~ethyl-imidazole, 2-undecyl-N-(cyanomethyl)imidazole
and 2-undecyl-imidazole, and alkyl guanidines, e.g., 1,1,3,3-
tetramethyl guanidine, 1,1,3,3-tetraethylguanidine, etc., for
example, can be used. A metallic powder and an inorganic filler
can also be incorporated in the thermosetting resin composition
, as a reinforcing agent. Preferred metallic powders are finely
divided powders of iron or aluminum.
The thermosetting resin is mixed with such a curing
agent, curing promotor and filler, and the resulting composition
is pre-formed in a partially cured state in the part to be filled
in a way that the above-described conditions are satisfied.
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According to this embodiment, the finished filled parts do not
contain air bubbles therein.
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1 In the above embodiment, the thermosetting resin
composition is pre-shaped so that the resin composition can
flow on the steel body panel at the time of heatin~ under
pressure, and then the pre-shaped article is placed in the area
to be filled. At this time, preferably the area of contact
between the steel bod~ panel and the pre-shaped article is
minimized. By so doing, air bubbles are not generated between
the steel panel surface and the resin layer after curin~ the
pre-shaped article by heating under pressure.
An especially preferred thermosetting resin composition
which can be used in the above embodiments of this invention is
a plastic solder composition comprising a matrix of an epoxy
resin and a curing agent therefor, and about 50 to 5% by volume
of a metal powder containing about 5 to 30% by vol1lme, based on
the composition, of a metallic fiber, e.g., iron, copper, nickel, -
cobalt, aluminum, stainless steel, tungsten and the like
whiskers. This plastic solder composition is a superior filling
material which meets the following requirements of filling
material for automobile bodies or the like.
(1) Electrodeposition coating of the composition
should be possible. ~
(2) No blisters of the coating should occur at the ;
filled areas.
~3) The composition should have a heat resistant
temperature of at least about 200C.
(4) The composition should have a coefficient of
linear expansion of not more than about 4 x 10 5/Co. -
(5) The composition should have a high bond strength, -
e.g., more than about 200 Kg/cm (JIS S-6040).
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1 (6) The compositlon should have the same abrasiveness
as steel plate.
(7) The composition should not permit the inclusion
of air bubbles in the filled area.
(8) The composition should not be toxic.
Specifically, the above plastic solder composition
can be prepared by mixing an epoxy resin with a curing agent
therefor, such as dicyandiamide, phthalic anhydride, diamino-
diphenyl methane, diaminodiphenyl ether, or an alkyl imidazole,
and if desired, a pigment, a filler or a reinforcing agent
such as those generally used in the art, e.g., carbon titanium
dioxide, iron dioxide, etc. as a pigment and carbon fibers,
asbestos, glass fibers, etc., as a reinforcing agent to form a
matrix, and mixing the resulting matrix with a metal powder,
such as iron, copper or aluminum, in an amount of about 50 to 5~
by volume, the metal powder containing about 5 to 30% by vblume ~-
of metallic fibers.
Any epoxy resin can be used in the plastic solder -
composition described above, but preferably those which are
semisolid or solid are satisfactory from the standpoint of
operability. For example, an epoxy resin available under the
trade nark EPI~OTE*1001 (trade mark for a glycidyl ether of
bisphenol A, produced by Shell Chemical Company, U.S.A.) can
be used.
Furthermore, any epoxy resin curing agent can be
used, but dicyandiamide is especially preferred because of its
~ good storability and rate of curing.
`~ A preferred particle size of the metal powder is not
more than about 149 microns.
~ he so-called metal whiskers are especially preferred
~as metallic fibers. For example, iron or copper whiskers
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1 can be used in this invention. The diameter of the metal
whiskers is not more than about 100 microns, e.g., about 0.1
to 100 microns, and the length-to-diameter ratio of the whiskers
is more than about 10, e.g., about 10 to 10,000, microns.
If the proportion of the metal powder in the plastic
solder composition described above is less than about 5~ by
volume, the resulting composition provides unsatisfactory results
in a thermal shock test and a sedimentation test, and are
inferior in electrode positability and abrasiveness. If the
proportion of the metal powder is more than about 50% by volume,
the resulting composition exhibits poor adhesion.
Where the amount of the metal powder is the same, the
incorporation of the metallic fibers gives rise to an improved
performance of the plastic solder composition both in a thermal
shock test and in a sedimentation test, and the solder compo-
sition provides especially preferred results for the filling
purposes in accordance with this invention.
Since the metallic fibers have a high bulk density,
the upper limit of their amount present in the composition must
2~ be adjusted to 30% by weight or less.
As a plastic solder composition capable of being
cured at low temperatures and providing a cured product free
from foaming or pinholes, the present invention also provides -
a plastic solder composition comprising an epoxy resin, a
filler, and a curing agent which is dicyandiamide having a
particle diameter of less than about 74 microns, e.g., about
0.1 to less than about 74 microns.
With a view to providing a plastic solder composition
having rapid low temperature curability and strong adhesion,
experiments were performed in which an epoxy resin was cured
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1 with dicyandiamide using known curing promotors, i.e., (a) a
tetra-alkyl guanidine, (b) a 3- or 4-substituted monoamino-
pyridine, (c) a reaction product formed between phthalic
anhydride and diethylene triamine, (d) an imidazolium halide,
or (e) an inorganic acid salt of guanidine, biguanide or
guanylurea, or an organic acid salt of guanidine, and it was
found that in all cases, a temperature of at least 200C was
required in order to completely cure the composition within
5 minutes, and foaming inevitably occurred. Further experimen-
tation lead to the discovery that by adjusting the particlesize of the dicyandiamide in the above epoxy resin-dicyandiamide
system to a particle size of less than about 74 microns, pre-
ferably less than 63 microns, a plastic solder composition
capable of being cured rapidly at low temperatures without
foaming was obtained. This plastic solder composition can be -
advantageously used in the filling method of this invention.
The present invention further provides a plastic
solder composition capable of being coated electrostatically or
by electrodeposition, which comprises a thermosetting resin
and a curing agent therefor, and about 20 to 50~ by volume, based
on the composition, of a metal powder, the metal powder compris-
ing about 0 to 25% by volume of particles having a particle
size of at least about 74 microns, and about 29 to 100% by
volume of particles having a particle size of not more than
about 44 microns.
The same metal powders and epoxy resins as described
above can also be used in this plastic solder composition.
If the total amount of the metal powder in this
composition is less than about 20 % by weight, the resulting
plastic solder composition exhibits inferior characteristics
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1 in electrodeposition coating or electrostatic coating. If the
amount of the metal powder is above about 50~ by volume, the
solder composition has poor adhesion to the areas to be filled.
If the proportion of particles having a size of at
least about 74 microns in the metal powder is more than 25% by
volume~ pinholes occur on the surface coated by electrodeposition.
If the proportion of particles having a particle size of not
more than 44 microns is less than ~9% by volume, an electro-
deposited coating is difficult to form in the boundary between
the steel panel part and the resin part. Especially preferably,
the proportion of the particles having a particle size of not
more than 44 microns is 100% by volume.
The curing agent that can be used in this composition
can be any known curing agent for epoxy resins, but from the
standpoint of storability, the rate of curing, abrasiveness,
and good adhesion, dicyandiamide is especially preferred.
The following Examples are given to illustrate the
present invention in greater detail. Unless otherwise indicated,
all parts, per~ents, ratios, and the like are by weight.
EXAMPLE 1
This Example relates to the first embodiment of the
method of the present invention.
An epoxy resin (EPIKOTE*1001), a nearly equivalent
amount of dicyandiamide as a curing agent, and 20 to 50% by
volume of iron powder were admixed with each other. The mixture
was heated in vacuo at about 100 to 140C for about 3 hours.
The molten mixture was then injected in a mold conforming to the
shape of an area to be filled, and aged and cooled to form a
partially cured molded article of thermosetting resin. This
resin molded article was placed in the area to be filled heated
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1 to about 100C, whereupon the surface of the resin molded
article was softened, and adhered to the surfaces of the area
to be filled. When the resin molded article was heated for 2
minutes at a pressure of about 10 to 20 Kg (total pressure)
using an applicator heated at 200C, the resin softened and
became completely buried in the area to be filled, and then
cured. The surface of the filled resin was finished by sanding
to complete the filling.
EXAMPLE 2
This Example relates to the second embodiment
of the method of this invention.
EPIKOTE*1001, a nearly equivalent amount of
dicyandiamide and 20 to 50% by volume of iron powder as a filler
were admixed with each other. The mixture was pulverized,
and then molded with a transfer molding technique. The
molded article was placed on the surface of steel panel, and
heated at 200C and at a pressure of 10 to 20 Kg(total pressure)
for 3 minutes using a heated applicator having as a surface an
impregnated cloth obtained by impregnating a glass fiber cloth
(thickness 0.8 mm) with a dispersion of polytetrafluoroethylene.
The filled part so obtained was completely unitary, and no
bubbles were formed on the surface of the filled part.
The following Examples 3 and 4 relate to the third
embodiment of the method of this invention.
EXAMPLE 3
100 parts by weight of an epoxy resin (EPI~OTE*1001)
were mixed with 300 parts by weight of iron powder which
passed through a 350 mesh sieve (not more than 44 microns in
size~ in a vacuum mixing kettle (5 liters) at 150C and 4 mmHg
for 5 hours. Then 6 parts by weight of dicyandiamide was added
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1 as a curing agent, and mixed with the above mixture at 100C
for 20 minutes. The mixture was injected in a mold with care
being taken not to incorporate air bubbles into the mixture.
The mixture was then dried by heating at 100C for 3 hours to
form a partially cured shaped article of the resin. The criterion
for determining partial curing was that the resin has a'viscosity
of about 5 x 102 poises at 140C as determined using a KOKA
flowtester ta viscometer for plastics, manufactured by Shimazu
Seisakusho Ltd. (Japan)).
In order to examine the characteristics of the above
resin composition, evaluations were performed using a test
panel (P) obtained by spot welding a cold-rolled steel plate - ~- -
(JIS-C 141) having a thickness of 0.8 mm and a width of 70 mm,
and then pressing the steel plate into the form as shown in
Figure 3(a). Each of the partially cured articles of thermo-
setting resin as shown in Table 1 below was placed in or on the
recessed area of this panel in the manner as shown in Figure 3tb) -
and Figure 3(c), and then heated at 200C and at a pressure of -
10 to 20 Kg (total pressure) for 2 minutes using a heated
~ applicator to fill the recessed area. Then, the surface of the
filled area was finished by sanding, and the extent of foaming
on the surface was observed. The results obtained are shown
in Table 1. In Figure 3, Figure 3(b) is a sectional view
showing the conditlon of shaped article 2 of Run Nb. 1 placed
on the test panel P, and Figure 3(c) shows the same view
except that the shaped article 2 is that of Run No. 3. -~
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1 Table 1
Run Number
Conditions 1 2 3 4
Test Sample Thickness (mm) 5 5 5 7
Test Sample Length (mm) 30 25 23 20
(mm) 3 0 0 0
~'(mm) 3 3 3 3
1~6~ ' 1/2 0 0 0
Air Bubbles at Point No Yes Yes Yes
~in Figure 2
Air Bubbles at PointsNo No No No
other than Point ~
It can be seen from the results in Table 1 that no
bubbles were formed in the test sample of Run No. 1 which is
within the scope of this invention.
EXAMPLE 4
A test panel of the form shown in Figure 4 was prepared
using a steel plate as described in Example 3, and each of the
shaped articles of the thermosetting resin as shown in Table 2
: below was filled in the recessed area of the test panel in the
same manner: as in Example 3. The occurrence of air bubbles was
examined in the same manner as described in Example 3. The ~
results obtained are shown in Table 2. - :
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~ 30 ~:
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1 Table 2
Conditions _ Run Number
6 7 8 _ 9 10
Test Sample 5 5 5 5 5 7
Thickness (mm)
Test Sample 35 28 27 26 25 20
Width (mm)
(mm) 3 2 1.5 1 0.5 0
~ (mm) 3 3 3 3 3 3
1/6 ~' 1/2 2/3 1/2 1/3 1/6 0
10 Air Bubbles at No No No No Yes Yes
Point ~ (little~
Air Bubbles at No No No No No No
Points other than
Point ~
As can be seen from the results in Table 2, no
bubbles were formed in Runs Nos. 5 to 9 which are within the
scope of this invention, but a large amount o~ bubbles occurred
in Run No. 10.
In a modified form of test panel as shown in Figure 5,
air bubbles occurred at the point y when ~ was 0. In order
to remedy this defect, the partially cured thermosetting resin
article must be placed in such a way that it is separated from
the area to be filled by the specified distance as in the case
of Runs Nos. 1 and 5. This leads to a complete elimination of
air bubbles.
EXAMPLE 5
This Example illustrates a plastic solder composition
that can be used especially advantageously in this invention.
100 parts by weight of Epikote*1001 were mixed with
6 parts by weight of dicyandiamide having a particle size of
less than 74 microns to form a matrix. The matrix was kneaded
* Trade Mark
- 2
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1 with the metal powder shown in Table 3 below for 10 minutes
using a roll kept at 100C to form various plastic solder compo-
sitions which were used to prepare test samples used in the
following tests. (in a sedimentation te.st a composition
comprising 100 parts by weight of Epikote*828, trade name for
a glycidyl ether of bisphenol A produced by Shell Chemical
Company, and 80 parts of hexahydrophthalic anhydride was used
as a composition.)
Table 3
10 Sample Amount of Amount of Amount of
Matrix Iron Powder Iron Whiskers
(Vol. %) (Vol. %) (Vol. %)
No. 1 95 0 5
No. 2 85 10 5
No. 3 80 15 5
No. 4 80 10 20 ;.
No. 5: 60 35 5
~omparison.
- No. 1 100 0 0
; No.r. 2~ 95 - 5 o
:~ 20 No. 3 80 20 0
No. 4 50 50 0 ~ ..
~: Various test pieces were prepared, and the evalua-
.tions shown in Table 4 below were conducted. The results
obtained are shown in Table 4.
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1 Table 4
Samples Coeffi- Bond Electro- Resist- Thermal Resis-
cient of Strength deposit- ance to Shock tance to
Thermal (2) ion Pro- Blister Test Sedi-
Expansion perties (4) (5) menta-
(1) (3) tion
(6
(xl 05)
No. 1 5.2 380 Good Good 8 Good
No. 2 4.0 320 Good Good 9 Good
No. 3 3.7 300 Good Good > 10 Good
No. 4 3.5 290 Good Good > 10 Good
No. 5 2.5 250 Good Good > 10 Good
Comparison
No. 1 7.7 320 Poor Poor
No. 2 5.8 355 Poor Poor 1 Poor
No. 3 4.0 295 Poor Good 6 Poor
No. 4 2.4 150 Good Good ~10 Good
Note "/" designates that the property was not measurable.
Preparation of Test Pieces and Method of Testing
(1) Coefficient of Thermal Expansion:
Test pieces were prepared, and tested, in accordance
with JIS K-6911.
(2) Bond 5trength (tensile shear strength):
Test pieces were prepared, and tested, in accordance
with JIS S-6040.
(3) Electrodeposition Properties:
A recess with a width of 30 mm, a length of 70 mm and
a depth of 3 mm was formed in the central part of a rolled
steel plate with a thickness of 0.8 mm, a width of 70 mm and a
length of 150 mm. The recess was filled with each of the samples
using an applicator at 2booc and a pressure of 10 to 20 (total
pressure) for 2 minutes. The surface of the filled area was
- 22 -
1 smoothened to the same degree as the steel panel part.
Electrodeposition coating was performed on this test piece at
a liquid temperature of 30 + 1C and a voltage of 200 V with
the passage of a total of 42 coulombs. When the thickness of
the coating on the filled area was more than 50~ of that of the
coating on the steel panel portion, the electrodepositing pro-
perties of the sample were evaluated as "good".
(4) Resistance to Blister:
The same test piece as used in the electrodeposition
property test was used, and subjected to pretreatment (with
iron phosphate), electrodeposition coating (under the same
coating conditions as in the above test (3), washing with
water, and then top coating. The coated test piece was immersed
in warm water at 40c for 240 hours, and the occurrence Oc
blister was observed visually.
(5) Thermal Shock Test:
The same test piece as used in the electrodeposition
property test was used, and subjected to the following thermal
shock cycling. The resistance to thermal shock was evaluated
in terms of the number of such cycles required to peel off the
filled resin portion of the test piece.
Each cycle comprised:
Immersion in distilled water 20C 10 minutes
Water removal at room25C 10 minutes
temperature
Heating 150C 30 minutes
Standing at room temperature 25C 30 minutes
(6) Resistance to Sedimentation:
A sample having a length of 5 cm was placed in a
test tube with an inside diameter of 1 cm. The test tube was
held vertical, and the sample was cured at 170C for 2 hours.
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,2~
1 A 1 cm-portion was cut off from the upper end and the lower
end of each test piece. When the deviation from the average
density of those cut pieces was within ~ 10%, the resistance
to sedimentation was evaluated as "good".
As can be seen from the results in Table 4, the
compositions shown in Example 5 had a superior coefficient of
thermal expansion, bond strength, electrodeposition properties,
resistance to blistering, resistance to thermal shock and
resistance to sedimentation, and can be used as a solder.
The following Examples 6 to 11 illustrate~ plastic
solder compositions of reduced foaming which can be used in
this invention especially advantageously.
EXAMPLE 6
This Example demonstrates that the particle size of
dicyandiamide used as a curing agent for epoxy resins is related
to the occurrence of pinholes after foaming by heating with
an application and water washing, and the properties of the
cured product obtained.
100 parts by weight of an epoxy resin (Epikote 1001) -
~ and 6 parts by weight of dicyandiamide were mixed at 100C
for 30 minutes using a 4-inch roll. The mixture (about l g)
was cured on a hot plate at 200C-for lG minutss. In order to
observe air bubbles in the cured product, the surface of this
cured product was abraded, and washed with water, whereupon
the number of holes in the surface were observed.
In order to evaluate this phenomenon, the exothermic
properties at the time of curing were examined using a differen-
tial thermal analyzer (a product of Rikaku Denki K.K.). The
curing exothermic data shown in Figure 6 (A~state) were obtained,
and it was found that this curing was a two-step reaction and
- 24 -
:,
1 that the reaction at higher temperature~ was not comple-ted unless
the-temperature was 250C or more.
The a~ove mixture was cured on a hot plate at 250C
for 10 minutes. A number of air bubbles were observed in the
cured product, but even after washing, the number of the air
bubbles did not increase. ~at a curing temperature of 230C
or more, foaming occurs.)
From these two phenomena, it was thought that before
curing, dicyandiamide is dispersed in an epoxy resin in the
epoxy resin-dicyandiamide system, and performed the following
experiments.
Dicyandiamide particles were sieved through a 600-mesh
standard screen in accordance with Japanese Industrial Standards,
and those particles which passed through a 600-mesh screen were
used as a curing agent. In the same manner as above, differen-
tial thermal analysis was performed to measure the amount of
exothermic heat. As a result, the curing exothermic data as
shown in Figure 7 (B~state~were obtained. A mixture of the
epoxy resin and the finely divided~ dicyandiamide as a curing
~O agent was cured in the same way as described above on a hot
plate at 200C for 10 minutes, and the surface abraded and washed
with water. No pinholes were observed.
Accordingly, it was concluded that pinholes resulting
from foaming by heating with a~ applicator and washing with
water and the properties of the cured product have a great deal
to do with the particle size of dicyandiamide as a curing agent.
Thus, dicyandiamide was sieved in the sizes shown
below, and used in the following Examples 7 to 12. In these
Examples, 100 parts by weight of an epoxy resin (Epikote 1001)
were mixed with 6 parts of dicyandiamide of varying particle
* Trade Mark
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o~
1 si~es using a 4-inch roll at 100C for 30 minutes. The
nature of the samples prepared are shown in Table 5 below.
Table 5
Sample No. Sieve Dicyandiamide Particle Size
(mesh) ~)
1 600 below 21
2 500 bel~w 25
3 400 below 37
4 350 below 44
280 below 53
6 250 below 63
7 200 below 74
8 170 below 88
9 120 below 125
100 below 149
11 80 below 177
12 70 below 210
EXAMPLE 7
Each of the samples as described in Table 5
was heat cured at 200~C for 10 minutes on a hot plate.
The state determined by differential thermal analysis and
the occurrence of pinholes after washing with water are
shown in Table 6.
Table 6
Samples No. State Determined by Occurrence of Pinholes
Differential Thermal after Washing with
Analysis Water
1 B No
2 B "
3 B
4 B "
B "
- 26 -
1 (Table 6 continued)
6 A Yes
7 A "
8 A "
9 A "
A "
11 A
12 A "
EXAMPLE 8
Each of the samples was cured on a hot plate at 200C
for 10 minutes using 0.1 part by weight of tetramethyl guanidir.e
as a curing promotor. The results obtained are shown in -
Table 7.
Table 7
Sample No. State Det:ermined by Occurrent of Pinholes
Differential Thermal after Washing with
Analysis _ Water
1 B No
2 B "
3 B "
4 B
B
6 B "
7 A Yes
8 A " :
9 A ..
A "
11 A "
12 A "
EXAMPLE 9 -
Each of the samples was cured on a hot ; :~
plate a~ 200C for 10 minutes using 0.2 part by weight of
- . .... .. .: . . ::
1 guanidIne nitrate as a curing ~romotor. The results obtained
are shown in Table 8.
Sample No. State Determined by Occurrence of Pinholes
Differential Thermal after Washing with
Analvsis Water
.
1 to 6 B No
7 to 12 A Yes
EXAMP~E 10
Each of the samples was cured on a hot plate at 200C
for 10 minutes using 0.2 part by weight of aminopyridine and
0.5 part by weight of 1-dodecyl-2-methyl-3-benzylimidazole
fluoride as a curing promotor. SimiLar results to those obtained
in Example 8 were obtained.
From the results of Examples 7 to 10, it was
demonstrated that in order to pr w ent the occurrence of pinholes,
the particle size of dicyandiamide must be adjusted to less
than 74 microns, preferably less than 63 microns.
EXAMPLE 11
A recess (with a depth of about 2 to 3 mm) was provided
on a cold-rolled steel plate (0.8 mm; JIS C-141) using a
hammer. An epoxy resin composition of 50 parts by weight of
Epikote*1001, 50 parts by weight of Epikote*828, 6 parts by
weight of dicyandiamide of varying particle sizes as shown
in Table 5, and 300 parts by weight of iron powder was placed
in this recess, and heat cured at 200C for l0 minutes. The
results obtained are shown in Table 9 below.
Table 9
Sample No. State Determined by Occurrence of Pinholes
Differential Thermal after Washing with
Anal sis Water
Y
1 to 5 B No
6 to 12 A Yes
* Trade ~ark
- 2~ -
~Si~
1 The following Ex~m~les 12 to 14 illustrate plastic
solder com~ositions capable o, being coated electrostatically
or by electrodeposition which can be used especially advantage~
ously in this invention.
EXAMPLE 12
Iron powder having the particle size destribution
shown by curve D of Figure 8 was added in an amount of 10, 20,
25, 30, 40 and 50% by volume respectively to a mixture of 100
parts of an epoxy resin (Epikote*1001) and 6 parts by weight of
dicyandiamide, and the resin and powder were mixed ~y using a
4-inch roll at 100C for 30 minutes.
A recess with a length of 50 mm, a width of 25 mm
and a depth of 3 mm was provided in a steel plate with a width
of 70 mm, a length of 150 mm and a thickness of 1 mm by press-
forming.
This recess was filled with the above prepared
composition, and the resin composition was cured at 200C for
3 minutes. The surface was then finished by disc sanding to
form a test piece.
Using this test piece, electrostatic coating and
electrodeposition coating were performed under the following
conditions.
Electrostatic Coating Conditions
Coater: Gema -720 Type Electrostatic Spray Coater
Voltage: -70 V
Time: 3 seconds
Electrodeposition_Coating Conditions
Voltage: 150 V
Temperatur~: 30 + 2C
Time: 3 minutes
* Trade Mark
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1 Co~ting Composltions
For electrostatic coating, an epoxy resin powder.
For electrodeposition, a melamine-alkyd type lacquer.
The quality of the coating was evaluated visually
dye. When the coating was completely uniform, the evaluation
was "good". Other coatings were evaluated as "poor".
The results obtained are shown in Table 10 below.
Table 10
Samples No. Iron Powder Electrostatic Electrodeposition
Coating _ Coating
(vol.%)
1 10 Poor Poor
2 20 Good Poor
3 25 Good Good
4 30 Good Good
Good Good
6 50 Good Good
EXAMPLE 13
A test piece was prepared in the same manner as
described in Example 12 except that iron powders having the
particle sizes shown by curves tA) to (E) in Figure 8 was used
in an amount of 30% by volume. Using the test piece, the
electrostatic coating and electrodeposition coating properties
were examined. The results obtained are shown in Table 11 below.
- 30 -
iot;~;~
1 Table 11
_ Particle Size
Iron Powder+ 200 mesh -350 mesh Electro- Electro-
(+ 74 ~u) (- 44 ~u) static deposition
Coatlnq Coatin~
.
A51 16 Poor Poor
B34 28 Good Poor
C22 46 Good Good
D3 71 Good Good
E0 91 Good Good
EXAMPLE 14
Test pieces were prepared in the same manner as
described in Example 13 except that 30% by volume of aluminum
powders having the particle size distribution shown by curves
(A') to (E') Figure 9 were used, and the electrostatic coating
and electrodeposition coating properties were evaluated. The
results obtained are shown in Table 12.
Table 12
Particle Size Results
Aluminum + 200 mesh -350 mesh Electrostatic Electrode-
Powder(+ 74 ~) (-44 ~) Coating position
Coatinq
( % ) ( % )
A' 56 11 Poor Poor
B' 26 20 Poor Poor
C' 16 45 Good Good
D' 8 45 Good Good
E' 1 63 Good Good ~ -
When copper powders were used, the same results as
obtained in Examples 13 and 14 were obtained.
By using the plastic solder compositions shown in
Examples 12 to 14, the surface of the filled area using the
plastic solder can be coated electrostatically or by electro-
- 31 -
iX~
1 deposition just the same as the surface of the steel panel.
While the invention has been described in detail and
with reference to specific embodiments thereof, it will be
apparent to one skilled in the art that various changes and
modifications can be made therein without departin~ from the
spirit and scope thereof.
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