Note: Descriptions are shown in the official language in which they were submitted.
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Process for producing a multilayer molded article
The present invention relates to a process for
producing a multilayer molded article comprising a
thermoplastic resin and a skin material. More
particularly, it relates to a process for producing a
multilayer molded article comprising a thermoplastic resin
and a skin material that covers only a desired part of the
article.
Such a multilayer molded article in which the skin
material covers only a desired part o the article is used
1~ as a door trim or a rear trim of an automobile or the
like. Such an article is hereinafter referred to as a
"skin material, partially laminated article". A known
process for producing such an article comprises molding
the thermoplastic resin by, for example, injection molding
15 and laminating the skin material with a desired shape on
the molded article with an adhesive or the like. A
process is also known that comprises making a part by
laminating the skin material on a hard board and attaching
said part to the molded article with small screws or the
like. These processes require post-processing of the
article, which is time consuming and increases the
production cost of the article.
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Japanese Patent Publication No. 28704/1981 and
Japanese Patent Kokai Publication No. 177332/1983 disclose
processes for integrally producing a skin material,
partially laminated article by injection molding, which
S comprise fixing the skin material at a desired position on
an inner wall of a mold with a fastener or a magic band,
closing the mold and then injecting the thermoplastic
resin. These processes require special means for fixing
the skin material to the mold. Further, since the resin
melt is supplied after closing the mold and it flows at a
very high flow rate in the very narrow clearance that
corresponds to the difference between the thickness of the
article and the thickness of the skin material, the rear
face of the skin material receives a large shear force so
that the skin material tends to be displaced even though a
fastener or magic band is used. In addition, the skin
material is largely influenced by heat, and, after the
supply of the resin melt, a large pressure is applied to
the skin material in a dwell time so that the grain
pattern, texture, hand or feel (hereinafter referred to as
the "feel") of the skin material tend to be impaired.
As a result of an extensive study of a process for
producing a skin material, partially laminated article
having a good feel without displacement of the skin
material, it has been found that the conditions for
supplying the resin melt are important.
In one aspect, the invention consists of a process for
producing a multilayer molded article comprising supplying
at least one piece of a skin material and a resin melt
between unclosed upper and lower molds and closing the
molds to form the multilayer molded article of the thermo-
plastic resin with the skin material covering only a part
of the article, wherein skin material of a desired shape
is placed at a predetermined location on the lower mold
and resin melt is supplied at or near a center area of a
rear face of the skin material.
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In another aspect, the invention consists of a process
for producing a multilayer molded article comprising
supplying a piece of skin material and resin melt between
unclosed upper and lower molds and closing the molds to
form the multilayer molded article of the thermoplastic
resin and the skin material, wherein a vertically movable
rod or bar is provided at a part of the lower mold on
which the skin material is positioned, and, after lifting
the skin material by the rod or bar to a position at which
at least a part of the skin material contacts a cavity
surface of the upper mold, the resin melt is supplied
between the skin material and the lower mold, the rod or
bar being returned to a determined position before the
molding is completed.
The process of the present invention will be
illustrated by making reference to the accompanying
drawings.
Fig. 1 shows a perspective view of a molded article
produced by a process according to an embodiment of the
present invention;
Fig. 2 shows a cross sectional view of the article of
Fig. 1 alony the line A-A'; and
Figs. 3 to 14 respectively show vertical cross
sectional views of apparatus at different stages in the
process-
In Figs. 1 ~ 2, numeral 1 shows a multilayer moldedarticle, 2 shows a thermoplastic resin and 3 shows a skin
material. In Figs. 3 to 14, 6 and 8 are upper and lower
platens of a rnold closing machine, respectively, and 7 and
3~ 9 are upper and lower molds, respectively.
On a cavity surface of the lower mold 9, a shallow
depression 10 is provided for determining the position in
which the skin material 3 is placed.
By using such apparatus, the process is carried out
according to the following four steps:
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l. The skin material 3 which has been cut to a
desired size is placed with its outer surface down in a
depression 10 of the lower mold 9.
2. A lifting mechanism (not shown) of the mold
closing machine is actuated to lift the lower mold 9, and
then the lower mold 9 is temporarily stopped at a position
where the clearance between the cavity surfaces of the
upper and lower molds 7 and 9 is larger than the thickness
of the article to be molded. At this position, resin melt
4 (Fig. 3) is supplied at or near the center area of the
rear face of the skin material 3 through a resin passage
(not shown) provided in the upper mold 7 by means of a
conventional resin melt supplier (not shown) such as an
extruder.
3. Thereafter, as shown in Fig. 4, the lifting
mechanism is reactuated to further lift the lower mold 9
to press the skin material 3 against the lower mold 9 and
spread the resin melt 4 in the mold cavity, whereby the
skin material 3 and the thermoplastic resin 2 are
2() integrated and the molding is completed (Fig. 4).
4. After cooling the mold, the lower mold 9 is
lowered to open the molds, and the molded article l is
removed from the mold.
In this process the timing for supplying the resin
melt 4 is not limited to the above described timing, and
the resin melt can be supplied at any time after the skin
material has been placed on the lower mold 9 and before
the upper and lower molds are closed to their final
position. In other words, besides the above timing
sequence in which the mold is stopped at an intermediate
position, the resin melt can be supplied before the mold
closing is started, or during a continuously closing of
the mold without stopping, if desired, with a decreased
mold closing rate.
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Preferably, the resin melt 4 is supplied when the mold
closing action is temporarily stopped after starting of
the mold closing, or the mold closing rate is decreased to
30 mm/sec. or less, and the cavity clearance between the
upper and lower molds 7 and 9 is not larger than (C + 100)
mm and not smaller than (C + 5) mm wherein "C" represents
the cavity clearance when the molding is completed. In
this way, the feel of the skin material is maintained.
When the resin melt 4 is supplied through two or more
passages, it is necessary to prevent confluence of the
resin melt 4 from the passages on the skin material by
adjusting the amount of resin melt supplied from each
passage based on the size and other properties of the skin
material 3, whereby to prevent penetration of the resin
melt between the skin material 3 and the lower mold 9.
Since the resin melt 4 is supplied at or near the
center area of the rear face of the skin material when the
clearance between the upper and lower molds is still
large, the resin melt 4 flows over the skin material 3
with a small shear force and spreads from the center area
towards the periphery of the skin material. Therefore,
the skin material 3 is unlikely to be moved out of
position.
During the supply of the resin melt 4, a larger
clearance between the upper and lower molds is preEerred
to decrease the shear rate when the resin melt 4 flows
over the skin material 3. However, if the clearance is
too large, the shape of the supplied resin melt is
deformed and therefore the resin melt 4 is ununiformly
spread, which can cause movement of the skin material.
Further, it takes longer from the supply of the resin melt
until the closing of the mold, so that the center area of
the skin material 3 is heated for a longer period of time
than the other parts and the feel of the skin material 3
tends to be deteriorated. In addition, the surface
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condition of the part of the article on which no skin
material is laminated tends to be deteriorated. Thus, the
clearance of the mold is adjusted to a suitable value
based on the kinds of material, the shape of the molded
article, etc.
The present invention further provides a process that
comprises placing the skin material 3 with its outer
surface facing up on the cavity surface of the lower mold
9, and supplying the resin melt 4 at or near the rear face
10 of the skin material 3 through a passage (not shown)
provided in the lower mold 9.
The skin material 3 is lifted by the resin melt 4 away
from the lower mold 9 and is pressed against a
predetermined part of the upper mold 8. In such a case,
if the supply balance of the resin melt is not adequate,
the skin material tends to be displaced. Therefore, in
this process the clearance between the upper and lower
molds during the supply of the resin melt is set to be
less than in the former process in which the resin melt is
20 supplied from passages provided in the upper mold 7.
Instead of supplying the resin melt 4 from one or more
passages in the mold, it can be supplied from a resin
passage that is inserted into and removed from the
clearance between the upper and lower molds. However,
25 this method is used only in a very limited case, since it
is difficult to adjust the clearance of the mold during
such a resin supply.
Since the skin material is not likely to be displaced,
as explained above, means for preventing displacement of
3~ the skin material need not necessarily be used. However,
it is still preferred to use such means in order to be
sure to precisely position the skin material.
As such a displacement preventing means, the various
means shown in Fig. 5 can be used. For example, as shown
35 in Fig. 5A, the depth of the depression lO is made
substantially the same as the thickness of the skin
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material; as shown in Fig. 5B, a low wall 11 surrounding
the skin material 3 is provided; as shown in Fig. 5C, a
part of the mold on which the skin material is positioned
is modified to form a telescopic element 13 that is
pressed against the resin supply side by means of an
expansion element 14, such as a spring, a hydraulic
cylinder, a pneumatic cylinder or the like during the
supply of the resin melt, and is returned to its original
position as the supply of the resin melt 4 proceeds; or,
in a case where the skin material 3 is of the fabric type,
the part of the mold on which the skin material is placed
is provided with some roughness 12, as shown in Fig. 5D.
In the case of Fig. 5D, not only is the displacement of
the skin material prevented, but also the feel of the skin
material is effectively maintained.
To supply the resin melt 4 at or near the center area
of the skin material 3, the resin melt can be supplied
from at least two inlets, the streams being integrated
with each other to reach the center area of the skin
material, or can be supplied from a single point near the
center area.
When the position at which the skin material 3 is
placed on the article deviates from the center of the
article, in addition to the inlet provided near the center
area of the rear face of the skin rnaterial, another inlet
can be provided at a position for balancing the flows of
resin melt. In this case, it is important that the flows
o resin melts 4,5 (Fig. 7) do not meet each other on the
skin material 3.
A laminated molded article can be produced by lifting
the skin material 3 by a vertically movable rod 16 or bar
17 (Figs. 12 and 13) provided in the lower mold 9 up to a
position at which at least a part of the skin material 3
contacts the surface of the upper mold, thereafter
supplying the resin melt 4 between the skin material 3 and
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the lower mold 9 and returning the rod 16 or the bar 17 to
its original position at least before the molding is
complete. By this method, since the skin material 3 is
held by the rod 16 or the bar 17, it is unlikely to be
S displaced and therefore the resin melt 4 need not
necessarily be supplied at the center area of the rear
face of the skin material.
The timing when the rod 16 or the bar 17 is returned
to its original position can be any time after the start
of the resin melt supply and before completion o~
molding. When a plurality of rods 16 and bars 17 are
used, it is not necessary to return all of them to their
original positions at the same time.
It is possible to use a mold that has a small wall 11
(Figs. 9 & 10) at a position on the lower mold 9 or the
upper mold 7 corresponding to a boundary where the skin
material 3 covers the thermoplastic resin 2 and a groove
15 which corresponds to the wall 11 on the other mold. In
a multilayer molded article produced by using such a mold,
2~ an edge portion of the adhered skin material is buried in
the article so that the boundary between one part of the
article that is covered by the skin material and an
adjacent part that is not, becomes distinct, and the
finish of the article is improved. The skin material is
resistant to peeling off at its edge.
Examples of skin material to be used are fabrics,
non-woven fabrics, metals, nets of thermoplastic resins,
paper, metal foils and sheets or films of thermoplastic
resins and thermoplastic elastomers. The skin material
3~ can be decorated by a rugged pattern such as embossing,
printing or dyeing, or in the form of a foam.
The skin material can be a laminated one consisting of
at least two materials bonded together by, for example, an
adhesive. In use, the skin material can be preheated, for
example, to improve the adhesivity between the skin
material and the resin.
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As the resin to be used, any one of the resins that
are conventionally used in press molding, injection
molding and extrusion molding can be used. Specific
examples of resins are non-expandable or expandable resins
of thermoplastic resins (e.g. polypropylene, polyethylene,
polystyrene, acrylonitrile-styrene-butadiene block
copolymers, nylon, etc.) and thermoplastic elastomers
(e.g. ethylene-propylene block copolymers,
styrene-butadiene block copolymers, etc.). The resin can
contain a filler (e.g. inorganic fillers and glass fibers,
etc.), pigments, lubricants, antistatic agents or the like.
The present invention will be further illustrated by
the following Examples:
Example 1
By using molding equipment in which the upper mold 7
had a passage and an inlet for supplying the resin melt 4,
a multilayer molded article was produced by the following
steps i) to iv):
i) Two pieces of a skin material cut to desired sizes
2~ (a composite material made of an embossing sheet of
polyvinyl chloride having a thickness of 0.6 mm and a
sheet of polypropylene foam having a thickness of 3 mm and
an expansion ratio of 15) were placed with their surfaces
down on the depressions 10 of the lower mold 9.
ii) The lifting mechanism of the mold closing machine
was actuated to lift the lower mold 9, and then the lower
mold 9 was stopped at a position where the clearance
between the cavity surfaces of the upper and lower molds 7
and 9 was 30 mm. At that position, resin melt kept at
3~ 200C (Sumitomo Noblen (registered trade mark) AZ 56~,
polypropylene manufactured by Sumitomo Chemical Company
Limited) was supplied at or near the center area of the
rear face of each piece of skin material 3 through the
resin passage in the upper mold 7 (Fig. 3).
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iii) Thereafter, the lifting mechanism was reactuated
to further lift the lower mold 9 at a rate of 10 mm/sec.
to press the skin material 3 against the lower mold 9.
The resin melt 4 was thereby spread in the mold cavity,
whereby the skin material 3 and the thermoplastic resin 2
were integrated and the molding was completed (Fig. 4).
iv) After cooling the mold, the lower mold 9 was
lowered to open the molds, and the molded article 1 having
a thickness of 3 mm was removed from the mold.
The produced article 1 had no displacement of the skin
material and a good feel.
Example 2
By using molding equipment in which the lower mold 9
had passages and inlets for supplying resin melt 4,5, a
multilayer molded article 1 was produced by the following
steps i) to iv):
i) Two pieces of a skin material 3 cut to desired
sizes (a non-woven fabric of polyester having an average
weight (METSUKE) of 300 g/m2) were placed with their
surfaces up on the depressions 10 of the lower mold 9.
ii) The lifting mechanism of the mold closing machine
was actuated to lower the upper mold 7, and then the upper
mold 7 was stopped at a position where the clearance
between the cavity surfaces of the upper and lower molds 7
and 9 was 10 mm (Fig. 6). At that position, resin melt
kept at 200C (Sumitomo Noblen (registered trade mark)
AZ 564, polypropylene manufactured by Sumitotno Chemical
Company Limited) was supplied at or near the center area
of the rear face of each piece of skin material 3 through
the resin passage in the lower mold 9. To balance the
resin melt flow, another portion of the resin melt 5 was
supplied from the other inlet. Each skin material 3 was
lifted by the resin melt 4 from the lower mold 9 and
pressed against the respective predetermined part of the
upper mold 7 having roughness 12.
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iii) Thereafter, the lifting mechanism was reactuated
to further lower the upper mold 7 at a rate of 20 mm/sec.
so as to spread the resin melt 4,5 in the mold cavity
while pressing the skin material, whereby the skin
material 3 and the thermoplastic resin 2 were integrated
and the molding was completed (Fig. 8).
iv) After cooling the mold, the upper mold 7 was
lifted to open the molds, and the molded article having a
thickness of 3 mm was removed from the mold.
The produced article l had no displacement of the skin
material and a good feel.
Comparative Example l
Under the same conditions as in Example 2 but
supplying the resin melt 4 at an edge part of the rear
face of the skin material from a passage provided in the
lower mold 9, a multilayer molded article was produced.
The skin material was found to be displaced from the
intended position in the produced article.
Comparative Example 2
2~ Under the same conditions as in Example 2 but
injection supplying the resin melt by applying a
predetermined clamrod force after closing the upper and
lower molds 7,9 to the finally closed position
(conventional injection molding), a multilayer molded
2S article was produced.
Although the produced article had no displacement of
the skin material, the resin penetrated into the skin
material 3 so that the article had a very poor feel.
Example 3
Under the same conditions as in Example 2 but using a
mold in which a small wall ll was provided on the cavity
surface of the upper mold 7 at a position corresponding to
a boundary where the skin material 3 covers the
thermoplastic resin 2, with a groove 15 on the cavity
surface of the lower mold 9 at a position corresponding to
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the small wall, a multilayer molded article was produced
(Figs. 9-11).
In the produced article, the boundaries between the
part covered with the skin material and the adjacent parts
not so covered were clear and the feel was good.
Example 4
By using molding equipment comprising a mold in which
a small wall 11 was provided on the cavity surface of the
upper mold 7 at a position corresponding to a boundary
where the skin material 3 covers the thermoplastic resin
2, with a groove 15 provided on the cavity surface of the
lower mold 9 at a position corresponding to the small
wall, and with a vertically movable rod 16 and bar 17 and
a passage and an inlet for supplying the resin melt 4
provided in the lower mold 9, a multilayer molded article
was produced by the following steps i) to v):
i) A piece of a skin material 3 cut to a desired size
(a composite material made of an embossing sheet of
polyvinyl chloride having a thickness of 0.6 mm and a
2~ fabric of woolly nylon having a thickness of 0.2 mm) was
placed with its surface up along the groove 15 of the
lower mold 9.
ii~ The lifting mechanism of the mold closing machine
was actuated to lower the upper rnold 7, and then the upper
mold 7 was stopped at a position where the clearance
between the cavity surfaces of the upper and lower molds 7
and 9 was 15 mm (Fig. 12). At that position, the rod 16
and the bar 17 were moved upwardly to lift the skin
material 3 so that it just touched a predetermined part of
the surface of the upper mold.
iii) Under such condition, resin melt kept at 240C
(Klarastic (registered trade mark) MTH-2, an ABS resin
manufactured by Sumitomo Naugatuck Company Limited) was
supplied at two areas of the surface of the skin material
3 through resin passages provided in the lower mold 9
(Fig. 13). After 0.5 and 1.0 seconds from the start of
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resin supply, the pin 16 and the bar 17 were lowered to
their original positions, respectively.
iv) Thereafter, the lifting mechanism was reactuated
to further lower the upper mold at a rate of 15 mm/sec. so
as to spread the resin melt in the mold cavity while
pressing the skin material 3, whereby the skin material 3
and the thermoplastic resin 2 were integrated and the
molding was complete (Fig. 14).
v) After cooling the mold, the upper mold 7 was lifted
to open the molds, and the molded article 1 having a
thickness of 3 mm was removed from the mold.
The produced article 1 had no displacement of skin
material and a good feel.
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