Note: Descriptions are shown in the official language in which they were submitted.
0
BACKGROUND OF THE INVENT ION
~ . ._ . _._ . _ . . . _
1. Field of_the Invention
This invention relates to a process for producing an
expanded article of a thermoplastic resin. More Particularly~
this invention relates to a process for producing an expanded
article of (1) a polypropylene resin, a polypropylene copolymer
resin or a mixture of a polypropylene resin and less than
about 50% by weight of a thermoplastic resin, or (2) a polyamide
resin, which has excellent chemical and heat resistance and
toughness.
2. Description of_the Prior Art
Processes for producing a thermoplastic resin foamed
article for use as a synthetic wood with woodgrain pattern
by extruding a molten foamable thermoplastic resin through a
nozzle having a number of apertures to expand the resin have
already been known as described in, for example, U.S. Patents
3,720,572 and 3,993,721 and Japanese Patent Application ~OPI~
No. 59,969/76.
These processes for producing a thermoplastic resin
foamed article are directed to the production of a foamed
resin primarily comprising a polystyrene resin. Since a
polystyrene resin has a good foamability, desired resin foamed
articles can be produced continuously over a long period of
time according to the above-described processes.
However, in applying the above conventional processes
to crystalline thermoplastic resins other than polystyrene,
e.g., polypropylene, a resin containing polypropylene as a
major component or a polyamide, it is very difficult to con~
tinuously produce resin foamed articles having good quality.
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1 No process suitable for foaming such crystalline thermoplastic
resins has so far been practically used. That is, since poly-
propylene and polyamide resins are crystalline thermoplastic
resins, their melt viscosity is sensitively temperature-dependent,
and a viscosity suitable for their expansion is in a narrow
temperature range close to a temperature at which the resins
crystallize. Generally, it is extremely difficult to conduct
extrusion and expansion while controlling the nozzle temperature
in such a narrow temperature range. In extruding such resins
10 using a nozzle having a number of apertures, the resin streams
flow in some portions with difficulty and partially crystallize
and solidify to prevent expansion. In addition, such adverse
affects on uniform, stable extrusion in respective apertures
make it difficult to produce a resin foamed article having high
quality of crystalline thermoplastlc resin.
It has been considered that such problems could be
solved by controlling a temperature of the nozzle with high
accuracy in order to avoid crystallization and solidification of
the resin. In fact, however, it is technically difficult to
control the nozzle temperature within a critical narrow ran~e
suitable for expansion in order to avoid crystallization, since
extrusion molding involves many factors which may vary widely.
For example, to equip a nozzle with a temperature-controlling
mechanism as disclosed in Japanese Patent Application tOPI)
No. 59,969/76 is not satisfactory for a polypropylene resin
or a polyamide resin; the resin crystallizes in part of a number
of apertures, which prevents stable extrusion of resin streams. -
In addition, when the resin is cooled through a frame adjacent
to a nozzle having a projection in its center as described in U.S.
Patent 3,993,721, it is difficult to extrude polyrpopylene resin
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1 quantitatively in respective apertures of the nozzle because
plugging partly occurs. Thus, stable production of a thermo-
plastic resin foamed article, such as a polypropylene resin
foamed article or a mixture thereof, or a polyamide resin
foamed article, having good quality over a long time a~ foun~
to be very difficult.
SUMMARY OF THE INVENTION
.
As a result of extensive investigations to solve the
above-described technical problems associated with the
conventional processes in the continuous production ~f a
crystalline thermoplastic resin foamed article used, for example,
as a synthetic wood with woodgrain pattern, it was found that
desired resin foamed articles with woodgrain pattern can be
stably and continuously produced by elevating the temperature
of a nozzle having a number of apertures to a level higher
than the melting point of the resin mixture used, reducing the
temperature of a frame directly connected to the nozzle,
simultaneously restricting the cross-sectional area at the
exit of extrusion zone to a given size to thereby control
expansion after extrusion through respective apertures of the
nozzle, thereby forming a plurality of soft expanded resin
strands corresponding in number to the number of strands,
bringing the strands into surface contact with each other to
fuse and bond them together to form a bonded expanded resin
mass while simultaneously removing gases generated in the course
of extrusion and expansion, passing the bonded mass into an
unconfined zone to permit the mass to further expand while
still in a softened condition, passing the further expanded
mass into a confined receiving zone of a smaller cross-sectional
area than the further expanded mass, and cooling the mass to form
an expanded article.
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BF<I~:F DESCRIPTION OF THE DRAWINGS
. . _ . .
Figure 1 is a part of sectional view showing an
embodiment of the process of the present invention.
Figures 2 and 3 show an example of a nozzle which can
be used in the extruder used in the present invention. Figure 2
is a vertical side sectional view of the nozzle and Figure 3
is a part of hack view of the nozzle.
Figures 4 and 5 similarly show another example of a
nozzle. Figure 4 is a vertical side sectional view of the
nozzle and Figure 5 is a part of front view of the nozzle.
Figures 6 and 7 are vertical side sectional views
showing other examples of frames used in the present invention.
Figures 8 and 9 similarly show a further example of
a nozzle in which Figure 8 is a vertical side sectiona~ view of
the nozzle and Figure 9 is a part of front view of the
nozzle.
Figures 10 and 11 similarly show a still further example
of a nozzle in ~hich Figure 10 is a vertical side sectional
view of the nozzle and Figure 11 is a part of front view of the
nozzle.
In these Figures, E designates an extruder, 1 designates
a temperature controller, 2 a die, 3 a nozzle, 31 a projection,
32 apertures, 33 a gas-releasing groove, 4 and 4' frames, 41
and 41' channels for a cooling medium, 5 a receiving frame,
6 a plate, 7 a water bath, 71 rolls, 8 a surface-processing
apparatus, 9 take-up rolls, and 100 a foamed article.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for producing
a foam of a thermoplastic resin, such as (1) a polypropylene
resin, a polypropylene copolymer resin or a mixture of a
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1 polypropylene resin and less than about 50%, preferably 1 to
30~, by weight of a thermoplastic resin, or (2) a polyamide
resin, by extruding and expanding the resin using an extruder
equipped, on a resin channel in a die, with a nozzle having a
number of apertures, which comprises flowing a resin mixture
stream through an expansion zone while maintaining the resin
. mixture at a temperature above the melting point thereof, for
- example, up to about 20C, preferably up to 10C, above the
melting point, dividing the resin mixture stream into a plurality
of separate streams, the cross-sectional area occupied by these
streams being from about 5 to about 30%, preferably 5 to 15~, of
the cross-sectional area at the exit of the extrusion zone,
exiting these streams from the extrusion zone directly into
a confined zone maintained at a temperature at least about
30C, preferably at a temperature in the range of 50C to
100C, lower than the temperature of the resin streams prior to
the exiting, thereby forming a plurality of soft expanded resin
strands corresponding in number to the number of strands, bringing
the strands into surface contact with each other to fuse and
bond them together to form a bonded expanded resin mass while
simultaneously removing gases generated in the course of
extrusion and expansion, passing the bonded mass into an
unconfined zone to permit the mass to further expand while still
in a softened condition, passing the further expanded mass
into a confined receiving zone of a smaller cross-sectional area
than the further expanded mass, and cooling the mass to form
an expanded article.
. The process of the present invention will now be
illustrated in greater detail by reference to the attached
drawings.
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O
1 Figure 1 shows an embodiment of the present invention,
wherein temperature controller 1 is provided at the forward
end of extruder E. Temperature controller 1 includes torpedo
12 in outer cylinder 11, and the space between them forms resin
channel 13. A cavity is formed inside torpedo 12, and a heating
or cooling medium is circulated in the cavity through pipe 14
to thereby heat or cool torpedo 12. Outer cylinder 11 has
spiral channel 15 piercing therethrough, through which spiral
channel a heating or cooling medium is circulated via pipes 16
tO to thereby heat or cool outer cylinder 11. Thus, a molten resin
mixture flowing through channel 13 is controlled to a temperature
within an extremely narrow range suitable for subsequent expansion.
Band heaters 17 can be provided around outer cylinder 11.
Die 2 isprovided subsequent to temperature controller
1. Band heater 21 is provided around this die 2, and resin
channel 22 of die 2 is provlded with resin stream-adjusting plate
23 having a number of openings and nozzle 3. Since the resin
stream in resin chanel 22 flows faster at the central portion
than that of peripheral portion, diameters of the openings of
resin stream-adjusting plate 23 are properly adjusted so that
the resin stream becomes uniform. Resin channel 22 is provided
with narrow neck 24 between resin stream-adjusting plate 23
and nozzle 3, which functions to avoid premature expansion and
maintain expanding pressure.
Nozzle 3 having a number of apertures 32, 32, ...
arranged in two rows has continuous projection 31 on a resin-
entering side between these two rows, and has gas-releasing
groove 33 which is provided inward between the two rows of
apertures 32, 32,... on a resin-leaving side. Further, square
frame 4 having a plurality of channels 41 for controlling tem-
perature is connected to the forward end of this nozzle 3
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1 subsequent to die 2. The frame 4 is connected via space 42
having a heat-insulating effect in order to avoid direct
transmission of heat from die 2. Still further, similar other
A~ frame 4' having an-o~cnir~-~ slightly enlarged sectional
area and having a plurality of similar channels 41' and similar
space 42' is provided at the forward end of frame 4. Both ends
of the above-described gas-releasing groove 33 are opened to
atmosphere and gases genera~ed after extrusion through respective
apertures 32 r 32,... are directly released into atmosphere.
Numeral 5 designates a tapered receiving frame functioning to
compress an expanded mass for reducing the sectional area
with a given compression ratio. Numeral 6 designates a plate
controlling the appearance and the dimension of the expanded
mass, numeral 7 designates a water bath for cooling and
solidifying the expanded mass, and numeral 71 designates rolls
provided in the water bath 7, which cools the mass while
controlling its dimension. Surface-processing apparatus 8
is provided subsequent to water bath 7. This surface-processing
apparatus 8 is constituted by heating and tapered compressing
20 member 81 and subsequent cooling member 82, whereby the surface
of resin foamed article is re-heated and compressed to such a
degree that the sectional area of the foam is reduced by about
3% to about 20% as compared with the sectional area prior to the
pre-heating and the compression to provide a hard surface layer
and a high dimensional accuracy of the resulting shaped expanded -~
article. Numeral 9 designates take-up rolls.
In the above-described production apparatus, the
resin kneaded with, for example, nucleating agents, blowing
agents and pigments, etc. and melted by means of heated extruder
30 E is controlled, by temperature controller 1, to a temperature
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1 slightly higher than the temperature suitable for expansion and
also above the crystallization temperature of the resin mixture,
and the resin stream is made uniform upon passing through resin
stream-adjusting plate 23, then reaching nozzle 3. Subsequently,
the resin stream is divided into a plurality of separate
streams (two streams in Figure 1) by projection 31 without
causing dwelling of the resin mixture, and further separated
through respective apertures 32, 32... and finally extruded
into frame 4 thereby forming a plurality of soft expanded resin
strands corresponding in number to the number of strands.
Gases generated at the exit of the nozzle 3 in the course of
extrusion and eY.pansion is directly removed by releasing into
atmosphere through gas-releasing groove 33 and never enter into
the expanded mass. A plurality of soft expanded resin strands
which have been extruded and expanded after being extruded through
apertures 32, 32... are cooled from the surface thereof by frame
.4 adjusted to a suitable temperature for expansion which is
lower than the temperature of nozzle 3, thus being successively
expanded and fusion bonded together in frame 4 to form a
20 bonded expanded resin mass.
Then, the resulting bonded mass passed through frame
4 is further successively expanded and allowed to pass through
receiving frame 5 reducing the sectional area of the resin
mass and through plate 6, whereby apparent dimension is con-
trolled and the bonded mass is more strongly fusion-bonded by
compression, then directly cooled with water in water bath 7
while supporting the form by rolls 71. The thus obtained cooled
expanded resin mass is, under heating, compressed by 3 to 20~
and cooled by means of heated compressing member 81 and cooling
30 member 82 to convert the surface to a hard surface layer with
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1 luster. T~us, there is obtained a shaped expanded article 1~0
with good dimensional accuracy by means of take-up rolls 9.
As the other example of nozzle 3 structure which can
be used in the process of the present invention, Figures 2 and
3 show nozzle 3 which has horizontally continuing projection 311
between two rows of a number of apertures 32, 32... spaced at
an equal distance, and which has projections 312, 312 in contact
with the upper or lower side of resin channel 22 and reaching the
upper or lower row of apertures 32, 32... . Nozzle 3 is also
provided with gas releasing groove 33 in the same manner as
nozzle 3 shown in Figure 1. Figures 4 and 5 show another type
of nozzle 3 which has two rows of horizontally continuing
projections 31 on the resin-entering side, each of which
projections 31 has on both sides thereof a number of apertur~s
32, 32... spaced at an equal distance from each other (therefoxe
3 rows in all).
Figure 6 shows still another type of nozzle.3 wherein
screen 43 containing channel 41 is additionally provided in
frame 4. Figure 7 shows the structure wherein another square
frame 4' having channel 41' is s].ightly narrowed along the way
of extrusion and is provided at the forward end o square
frame 4 via space 42'.
Figures 8 and 9 show the structure wherein gas-releasing
groove 33 with both ends opening to atmosphere is provided
inside of nozzle 3, and gas-releasing holes 331 are provided
at an equal distance from each other on the resin-leaving side
between two rows of apertures 32, 32... .
As a further example, Figures 10 and 11 show nozzle 3
wherein arc projections 31 are provided on the resin-entering
30 side and a number of gas-releasing grooves 33, 33... having both
.
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1 ends opening to atmosphere are provided crossing at right angles
to each other, and to the forward end of which is connected
square frame 4 which is narrowed along the way of extrusion.
Apertures 32 in nozzle 3 are 1 mm to 4 mm in diameter
(with respect to round apertures) and of 10 mm to 30 mm in
land length, which are spaced at a center distance of 2 mm
to 20 mm from each other. They allow to pass the foamable
resin mixture while setting the temperature of nozzle 3 to
a temperature higher than the melting point of the resin mixture used.
10 Projection 31 for preventing dwelling of a molten resin mixture
on the resin-entering side can more effectively prevent dwelling
of the resin mixture when its surface is subjected to a
smoothing finish or to chromium plating or Teflon* coating. It
is necessary to provide a gas-releasing means on the outlet side
of apertures in the nozzle in order not-to contaminate resin
streams with gases generated upon extrusion and expansion
through respective apertures 32. For this purpose, there is
provided a gas-releasing groove having communicated to atmo-
sphere on the outlet side of the nozzle.
Where wide or large moldings are formed, it is preferable
to connect a suction pump to this gas-releasing groove for
sucking generated gases.
The frame is provided for fusion bonding a plurality
of soft expanded resin strands which has been extruded through
the nozzle and slightly expanded, and for cooling to a tem-
perature suitable for expansion while restricting free expansion.
Total cross-sectional area of resin channels of respective
apertures must be set to about 5% to about 30%, preferably 5
to 15%, of the sectional area of resin channel in the frame.
30 That is, if the sectional area of resin channel in the apertures
* Trade Mark - 10 -
1 is less than about 5~, contact of the strands with the inside
surface of the frame would be so weak that the strands are
difficultly cooled and became poor in foamability, whereas if
the sectional area of the apertures is more than about 30~, gases
xeleased from the strands extruded at a higher temperature than
the temperature suitable for expansion would not be completely
removed through the gas-releasing groove and would remain between
respective strands to form voids or gaps in the resulting art-
icle or, since respective strands cannot be fully expanded within
the frame, cells would rather be extended in an extrusion di-
rection than in a vertical direction to provide a foamed article
having weak compression strength.
In addition, the section of the resin channel in the
frame may ~e enlarged or constricted in the direction of extrus-
ion. That is, the cross-sectional area of the outlet of the
frame may be enlarged or c~nstricted by about 10% aæ compared
with that of the inlet of the frame, and the length of the frame
is preferably 30 mm to lQa mm. Where expansion force is weak,
this length is preferably prolonged. Also, the temperature of
this frame must be adjusted to a lower temperature than that of
the nozzle. It is particularly preferable to adjust the temper-
ature of the frame lower than the melting point of the resin
mixture by at least about 3QC, preferably by from 50C to 100C.
For this purpose, it is desirable to provide a plurality of
channels in the frame and to circulate a cooling medium which
has been adjusted to a desired temperature through the channels.
For example, when using a polypropylene resin or a
polypropylene resin having 1 to 30% by weight of other thermo~
plastic resin mixed, the melting point of theresin mixture is
about l50 to a~out 170C the temperature of the frame is about
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1 150 to about 120C, preferably 70 to 100C. If the temperature
of the frame is higher than about 120C, resin strands are not
~ully expanded, or the resin adheres to an inner wall of the
frame, or the cells rupture break. On the other hand, when the
temperature of the ~rameis less than about 50C, a hard skin is
formed on the surface of the resin strands in the frame and thus,
the resin stran~s are not fully expanded, and sometimes, the
resin solidifies in the nozzle due to cooling of the frame.
Cross-sectional shape of the resin channel of receiving
frame S is almost analogous to that of the resin channel in
frame 4, and it is preferable to reduce, by a~out 5% to about 5~%,
the section of the expanded mass having heen expanded with an
expansion ratio of about 1.2 to about 2.5 upon extrusion through
the frame into an unconfined zone Receiving frame 5 can also
be constituted by arranging rolls in parallel crosses~ That is,
the surface of the expanded mass extruded through frame 4 into
an unconfined zone is uneven, and reduction by less than about
5~ is not enough to smooth the surface, whereas reduction by
about more than 50~ causes too much resistance.
Thus, expanded resin strands are ~trongly fusion bonded
through constriction pressure in this occasion to provide a
bonded mass having good dimensional accuracy, which can be used,
for example~ as a smooth surface synthetic wood with distinct
woodgrain pattern.
Thus~ by appropriately settling the shape of the
channels for the resin, such as a nozzle, frame, receiving frame,
etc,, an expanded resin long article having a cross-section of,
for example, plate type, s~uare type, round type and complicated
type such as threshold or doorsill can be obtained. Further, an
expanded resin article having a high compression strength is
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1 obtained in which each strand constituting the expanded resin
article has, in cross-sectional-wise, a long rectangle or
approximate triangle in the thickness direction.
Examples of resins which can be used in the process
of the present invention are (1) a polypropylene resin, a poly-
; propylene copolymer resin, a mixture of polypropylene and less
than about 50~ by weight of a thermoplastic resin, or (2) a
polyamide resin.
Polypropylene resins which can be used are preferably
one having a melt index of less than about 5 ~measured accordingto ASTMD-1238, hereinafter the same)~
Examples of polypropylene copolymer resins which can
by used include an ethylene-propylene copolymer resin.
Examples of the thermoplastic resins which can be
blended with a polyproylene resin are a polystyrene resin, pre-
ferably one having a melt index of less than a~out 15; a poly-
methyl methacrylate resin, preferably one having a melt index of
less than about 5; a high density polyethylene resin, preferably
one having a melt index of less thanabout 3; a polycarbonate
resin; an acrylonitrile-styrene copolymer resinr preferably one
having a melt index of less than about 7; a polyamide resin; and
the like. These resins are blended usually in a proportion of
1% by weight to 30% by weight, preferably 2% by weight to 25% by
weight r based on the total resin components. Blending poly-
propylene with these resins serves to improve foamability of the
polypropylene resin and to provide a stable molding property r
thus good resin foams being continuously produced, Of the above-
descri~ed resins to be blended, a polystyrene resin, a polymethyl
methacrylate resin and a high density polyethylene resin are
particularly preferable.
.
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y~
, .. ..
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1 Examples of polyamide resins which can be used alone are
nylon 6, nylon 66, nylon 12 and the like. A particularly
preferred example of polyamide resins is nylon 12.
In the present invention, various foaming agents can
be used. Examples of foaming agents are easily volatile liquids
of aliphatic hydrocarbons such as pentane, butane, propane,
petroleum ether, etc., or halogenated hydrocarbons such as monochloro-
methane,trichlorofluoromethane, dichlorotetrafluoroethane,etc.,and
~ .z~d /~ r b onq m ide
thermally decomposable foaming agents such as ~--~U~r~ rLDe~
acid am~e~, dinitrosopentamethylenetetramine, etc. These
foaming agents can be previously mixed with the resin to be fed
to an extruder, or can be poured into the extruder to mix
upon extrusion. The amount of the foaming agent can vary
widely depending upon the desired expansion ratio, but is
usually about 1 to about 15% by weight based on the total
amount of the resin composition.
In order to uniformly form fine cells in the resin,
addition of a foaming aid or a nucleating agent in addition to
the above-described foaming agent is desirable. Examples of
such additives are fine powdery talc, silica powder,a mixture
of sodium dicarbonate and citric acid, and the like,
which are well known in the art.
The process of the present invention is constituted as
described above and, since the expanded resin strands which have
been extruded through apertures in the nozzle and once expanded
are adjusted to a suitable temperature for expansion by means
of the frame, it enables to continuously produce further
expanded mass with good quality. On the other hand, the tem-
perature of the nozzle itself can be maintained at a comparatively
hlgh level, and hence neither crystallization nor solidification
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1 occurs in the apertures o~ the nozzle, thus not causing change
in extrusion and expansion. This point also ensures stable
extrusion production of a foamed article with good quality.
In addition, the present invention enables to directly
release into atmosphere gases generated in the course of extrusion
and expansion, and enables to produce a wide or large foamed
article having no voids or gaps between a plurality of expanded
resin strands due to the generated gases.
The thus obtained shaped expanded article is superior
to polystyrene foams in heat resistance, chemical resistance
and toughness without producing black smoke upon combustion,
and hence it can be suitably used as materials for a heating
apparatus or a hot water-feeding equipment or as structural
materials for apparatus for producing industrial chemicals,
packaging materials, feeding materials, press molding materials,
etc.
The present invention will now be illustrated in greater
detail by referring to the embodiment using the molding apparatus
shown in Figure l. Unless otherwise indicated, all parts,
percents, ratios and the like are by weight.
EXAMPLE 1
A mixture prepared by uniformly mixing 2 parts of fine
powdery talc (as a nucleating agent) and 0.2 part of a brown
pigment with l00 parts of polypropylene resin (NOBLEN MH-8, made
by Mitsubishi Petrochemical Co., Ltd.) was charged into a hopper
of extruder E, which was set to 200 to 250C in the feed portion
and lS0 to 170C in the forward end. The mixture and a foaming
agent of butane added into the extruder on the way were uniformly
kneaded in the extruder and transferred to the resin temperature
controller. The mixture was transferred to nozzle 3 maintained
* Trade Mark - l5 -
llC6120
1 at a temperature o~ 170C to 180C through resin stream adjusting
plate 23 in die 2 and extruded into frame ~ and expanded on the .
outlet side of a number of apertures in nozzle 3. Then, a
plurality of soft expanded resin strands extruded through res-
pective apertures were fusion bonded together in the above-
described frame 4 controlled by circulating an oil of 85 to go&
and also circulating water of room temperature into frame 4' with
the apparent shape maintained, and, subsequently, the bonded
expanded resin mass was once released into atmosphere to further
permit expansion to such degr.ee that cross sectional area
thereof became 1.2 to 2.5 times that of the opening of mold 4,
then constricted by 5 to 50% in sectional area based on the
secc;n ola.~v
~ sectional area of the-~rrhrr/expanded resin mass by means of
receiving frame 5. The thus constricted resin mass was cooled
by passing through water bath 7, and surface-processed by
surface processing apparatus 8, followed by continuously drawing
by take-up rolls 9. Thus, there was obtained foamed article 100
having luster, hard surface and woodgrain pattern wherein lines
of juncture formed in a longitudinal direction between respective
resin streams appeared as brown lines, thus providing synthetic
wood-like appearance.
In this example, a nozzle of the structure shown in
Figures 2 and 3 was used as nozzle 3. That is, at the forward
end of die 2 was provided nozzle 3 having a rectangular cross
section of 22 mm in height and 152 mm in width and having 96
apertures of 1.6 mm in diameter in the center thereof aligned
in parallel two rows with a vertical distance of 10 ~m, with
respective apertures in each row being spaced from each other at
a horizontally equal distance of 3 mm. Outlet side of nozzle 3
was in a vertical form, and gas-releasing groove 33 of 6 mm in
width and 5 mm in depth communicated to atmosphere was provided
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1 between the upper and lower rows of apertures 32, 32,... . In
addition, frames 4 and 4' which were connected to each other had
a section, in longitudinal direction, of 13 mm in height and 150 mm
in width, had a length of 35 mm in parallel to the extrusion
direction, and supplementally had an opening of 14 x 152 mm
in cross sectional and 35 mm in length, inner surface of which
was uniformly coated with a Teflon. In addition, the frame
contained channels 41 for circulating a temperature-controlling
oil and channels 41' for circulating cooling water provided
in upper and lower parts of the mold. In the further stage,
receiving frame 5 with a cross section of 13 x 150 mm, plate 6,
and rolls 71 having an opening of rectangular cross section
in a longitudinal direction for controlling apparent dimension
were provided, followed by a water bath for cooling the
foamed resin mass with water, wherein the foamed resin mass was
cooled while being supported and constricted by rolls 71. Then, :
the once cooled resin foam was guided to surface-processing
apparatus 8 comprising heating and compressing plates 81 and
cooling plates 82 to reduce the sectional area of the resulting
article by 3 to 20% to obtain smooth surface expanded article
100 having good surface luster, surface hardness and compression
strength.
The expanded artic~e 100 thus prepared was a plane plate
of 12 mm in thickness and 150 mm in width having been expanded
7.3 times. The resulting plate had a cross~sectional structure
comprising two parallel rows of fusion-bonded strands, each
strand having a height of 6 mm and a width of 3 mm. They did not
contain voids at the interface between fusion-bonded resin foam
streams, and the surface thereof had straight lines of juncture
between resin foam ~ streams, which provided the appearance
~ 17 ~
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1 analogous to grains of natural wood. Thus, they appeared like
natural wood having the light-weight appearance thereof.
EXAMPLE 2
A mixture prepared by uniformly mixing 1 part of fine
powdery talc and 2 parts of azodicarbonamide with 100
parts of polyamide resin (A~ILAN X-5021, made by Toray Industries
Inc.) was fed into extruder E, which was set to 180 to 260 C. The
mixture was extruded and expanded by nozzle 3 set to 160 to
170C. The temperature of frame 4 was controlled at 100 to
110C by air passing through channels 41. The thus extruded
foamable polyamide resin streams were expanded in frame 4 and
passed successively through receiving frame 5, plate 6 and rolls
71 shown in Figure 1 to thereby be fusion-bonded. Subsequently,
the bonded expanded resin mass was water-cooled with water bath
7 and solidified to obtain desired article 100 comprising an
expanded article of the polyamide resin.
The expanded article 100 thus prepared was a continuous
plane plate of 18 mm in thickness and 30 mm in width and the
density thereof was 0.4 to 0.5 g/cm .
In this example, a nozzle of the structure shown in
Figures 10 and 11 was used as nozzle 3. That is, at the forward
end of die 2 was provided nozzle 3 having a rectangular cross
section of 24 mm x 29 mm and having 39 apertures of 1.6 mm
in diameter and of 10 mm in depth, with respective apertures
in each row being spaced from each other at a horizontally equal
distance of 5 mm, as shown in Figure 11. At the outlet side
of nozzle 3 was provided gas-releasing grooves 33 of 1 mm in
width and 3 mm in depth crossly. In addition, a frame of
the structure shown in Figure 7 was used as frame 4. That is,
frame 4 had an orifice opening of 24 mm x 29 mm at inlet and
* Trade Mark - 18 -
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1 18 mm x 29 mm at outlet and of 20 mm in length, the inner
surface of which frame being plated with chromium.
Comparative Exa~
When the temperature of nozzle 3 in the foregoing
Example 1 was set to 160C, there was observed slight breakage
in the streams of foamable resin in apertures 32, whereas when
the temperature of nozzle 3 was set to 150C, there was observed
complete breakage due to crystallization of resin, resulting in
unstable extrusion and preventing subsequent expansion. Thus,
there was not obtained a uniformly expanded article with high
expansion ratio.
In addition, when frame 4 was cooled with the temperature- :
controlling oil raised to 120C, expansion of the foamable
. extruded resin streams did not start unless the temperature of
nozzle 3 was lowered to less than 160C. However, polypropylene
c ~ys~ z ~
. ~, resin used is liable to fv~m-er~t~linc at this temperature
r~l f~U rel
of nozzle 3, and eracked or broken inner portions are formed
in the resulting article. Thus, there cannot be obtained
satisfactory plane plates comprising polypropylene foam.
Next, the kind of resin and the amount of butane to be
used were changed and the resin temperature at the forward end
of extruder E, the resin temperature at the inlet of nozzle 3
and the temperature of frame 4 were controlled as shown in the
following table using the molding apparatus used in Example 1
to obtain similarly a good resin foamed article with good
quality.
- 19 -
ll~'t;120
1 TABLE
Polypropylene Parts by
Resin Weiqht *1 *2 *3 *4 *5 *6 *7
Poly- *8
propylene100 11.0 173165 13xlS0 35 80 12x150 7.3
14x152 35 -
Talc 2 9.8 177167 13x150 35 80 12x150 4.5
Pigment 90.2 14x152 35
Poly- *8
propylene100 5.5 176 166 13x150 30 100 14x160 8.4
. Polystyrene 10 20
Talc 2 6.5 189 178 13x150 30 100 14x160 7.0
propylene100
Polystyrene 10 5 9.0 180 166 13x150 50 90 13x150 10.0
- Talc 2 - -
propylene100
*1
Polymethyl
methacrylate 20 8.3 189 178 " 90 " 8.0
Talc 2
Poly- *8
. pr~pylene 100
20 High density 12
polyethylene 20 8.3 174 169 " 85 " 8.2
Talc 2
Poly- *8 100
Polycarbonate 13 20 7.6 191 174 " 90 " 11.8
Talc 2
Ethylene-*14
propylene 100
Acrylonitrile-15
Styrene 20 8.3 187 169 " 85 " 6.5
Talc 2
- 20 -
lla~l~o
1 Polypropylene Parts by
ResinWeight *1 *2 *3 *4 *5 *6 *7
__ .
Polypro*-8
pylene 100
Polyamide 16 20 7.4 188 176 13x150 50 85 13x150 8-5
Talc 2
Ethylene- *14
propylene 100
Talc 2 10.0 172 164 13x150 35 78 12x150 5.0
*g
Pigment0.2
*l Amount of butane added, ~ by weight.
*2 Temperature of resin at the forward end of the Extruder, C.
*3 Temperature of resin at the inlet of nozzle, C.
*4 Structure of frame mold; cross section, length(mm).
*5 Temperature of oil circulated in the frame mold.
*6 Cross sectional area of molding frame in mm.
*7 Expansion ratio.
**
*8 NOBLEN MH-8, made by Mitsubishi Petrochemical Co., Ltd.,
was used as polypropylene resin, which has a melt index
of 0.3 (ASTM D-1238), a heat-distortion temperature
of 120 to 130C (ASTM D-648), and a Vicat softening point
of 145 to 150C (ASTM D-1525).
*9 PPMSSC 46315(C), made by Dainichiseika Colour & Chemicals
MFG., Co., Ltd., was used as a rouge type pigment.
**
*10 STYRON 666, made by Asahi Dow Co., Ltd., was used as a
polystyrene resin, which has a melt index of 7.5 (ASTM
D-1238), a heat-distortion temperature of 94C (JIS K-6871),
and a Vicat softening point of 97C (ASTM D-1525).
*11 DELPET 70H, made by Asahi Kasei Kogyo K.K., was used as a
polymethyl methacrylate resin, which has a melt index of
0.5 (ASTM D-1238), a heat-distortion temperature of 92 C
(ASTM D-648), and a Vicat softening point of 120C (ASTM D-152~.
** Trade Mark - 21 -
~ ',,~,' .
t;12()
1 *12 Hi-ZEX 7000F, made by Mitsui Petrochemical Ind., Co.,
Ltd., was used as a high density polyethylene resin, which
has a melt index of 0.04 (ASTM D-1238), and a Vicat
softening point of 124 C t~STM D-1525).
*13 IUPILON S2000, made by Mitsubishi Edogawa Chemical Co.,
Ltd., was used as a polycarbonate resin, which has a heat-
distortion temperature of 134 to 140 C (ASTM D-648).
*14 NOBLEN EC-9, made by Mitsubishi Petrochemical Co., Ltd.,
- was used as an ethylene/propylene copolymer resin, which
has an ethylene content of 10~ by weight and has a melt
index of 0.4 (ASTM D-1238).
*15 TYRIL 783, made by Asahi Dow Co ., Ltd., was used as an
acrylonitrile/styrene copolymer resin, which has a melt
index of 3.5 (ASTM D-1238), a heat-distortion temperature
of 94 C (JIS K-6871), and a Vicat softening point of 112 C
(ASTM D - 1525) .
*16 AMILAN X-5021, made by Toray Industries Inc., was used as
a polyamide resin, which has a heat-distortion temperature
of 52 C (ASTM D-648) .
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 departing from the
spirit and scope thereof.
** Trade Mark - 22 -
