Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a process and ap-
paratus for producing a synthetic resin sheet having a col-
ored band of varying color intensity.
A process is known from DOS ~erman Unexamined
Laid-Open application~7 No. 2,035,578 for the production of a
sheet having a colored band of varying color intensity wherein
the stream of dyed synthetic resin is injected at a point in
time during which the main stream is still spreading in the
transverse direction. The injection of the dyed melt stream
herein takes place in the zone of the distributor duct, where-
by the dyed melt stream is likewise spread apart and distri-
buted additionally in the transverse direction with respect
to the extrusion direction.
A similar process and apparatus is known from Euro-
pean Laid-Open application No. 0,052,491 wherein a dyed
melt is injected, to form a colored band, into a colorless
melt stream so that the colored band is completely incor-
porated into the colorless melt. For this purpose, a
torpedo-like probe is provided arranged with the extrusion
duct being surrounded on all sides by a f]ow of colorless
melt.
In the production of transparent sheeting or films
dyed in partial zones, as utilized, for example, as inter-
layer films for automobile safety glass, it is necessary to
provide an exactly defined and dimensioned transition zone
from a colorless protion into a dyed portion with a con-
tinuous transition of color intensity; such sheets further-
more are to be manufactured so that the sheets can be repro-
duced with identical quality. One disadvantage of the process
according to DOS No. 2,035,578 is to be seen in that it is
very difficult to exactly control the desired colored band
in cross section, spread, dimensioning, and color intensity,
since the dyed composition is injected in the distributor duct
and subsequently is still subject to spreading at right angles
- 1 - '`~
~ ir
to the extrusion direction. Also, according to the process
carried out with the apparatus of ~uropean Laid-Open applica-
tion No. 0,052,491, it is difficult to maintain the desired,
exact dimensioning and course of the color gxadient, since
the dyed melt is in~ected within a stream of colorless com-
position all around, displacing this stream; and in such a
process even minor fluctuations in pressure relationships will
lead to differing colored bands with respect to intensity and
dimensioning. However, pressure fluctuations cannot be en-
tirely avoided on the side of the extruder; such fluctuations,
though, cannot be compensated by the process and apparatus
of EP-OS No. 0,052,491 with respect to the position of the
colored band.
The invention is based on the object of providing
a process and apparatus making it possible to manufacture in
a simple way, and reproducible in identical quality, sheeting
having a colored band of varying color intensity, as known,
for example, in the form of dyed safety glass films made of
polyvinyl butyral.
According to the present invention, there is pro-
vided a process for producing a sheet exhibiting a colored
band of varying color intensity, wherein a melt stream of a
thermoplastic synthetic resin palsticized in an extruder is
fed to a slot die tool and spread out by way of a distributor
duct with throttle zone in the transverse direction to the
sheet extrusion direction , and then traverses, in parallel
to the extrusion direction, a height-adjustable forward zone
up to the nozzle orifice, and wherein another melt stream of
dyed or colored thermoplastic synthetic resin is injected into
this melt stream upstream of the nozzle orifice, characterized
in that a colorless melt stream and a dyed melt stream are
shaped respectively into sheets each of a desired width Ba
and Bb, respectively, and prior to exiting from the die, are
melted together along a lateral edge into a sheet having
a width Ba + Bb; and in that there is introduced, along a
width Bc, calculated from a transition line of the dyed
sheet, into the region of the colorless sheet a wedge-like
extending colored band from a partial stream of the dyed
melt stream by way of a slot die having a wedge-shaped ori-
fice and arranged, as seen in the extrusion direction, up-
stream of a back pressure plate and downstream of the dis-
tributor duct, with a corresponding displacement of the col-
orless melt stream.
According to the present invention, there is also
provided an apparatus for producing a sheet containing a col-
ored band, with an extruder for melting a stream of thermo-
plastic synthetic resin and with a slot die tool having a
distributor duct with a throttle zone located upstream there-
of, with a back pressure plate, with a forward zone formed
between an upper lip and a lower lip including a wide nozzle
orifice to shape the sheet, wherein the slot die tool further-
more comprises an injection port for an additional, thermo-
plastic partial melt stream; said injection port comprisi.ng
a small slot die as seen in the extrusion direction positioned
at the forward side of the back pressure plate of the slot
die tool and a nozzle plate attached in front thereof, with a
narrow nozzle orifice extending at right angles to the ex-
trusion direction along the front edge of the back pressure
plate.
The invention proceeds along a novel route in that
it is suggested to shape a colorless melt stream and a dyed
melt stream, respectively, into a sheet of a desired width
Ba and sb, respectively, and to melt such sheets together
prior to exiting from the nozzle along a lateral edge, to
obtain a sheet having a width Ba + Bb; and to introduce along
a width Bc, calculated from the transition line of the dyed
sheet, into the zone of the colorless sheet, a wedge-like
extending colored band made up of a partial stream of the
dyed melt stream, by way of a slot die (fishtail dye, flat
i2~
extrusion die, or flat sheeting die) arranged, as seen in the
extrusion direction, upstream of a back pressure plate and
downstream of a distributor duct, this slot die having a
wedge-shaped outlet orifice, with corresponding displacement
of the colorless melt stream. Thus, according to the process
of this invention, a wide sheet is produced containing a zone
of undyed sheeting and a zone of completely dyed sheeting
with the inclusion of a transition zone of dyed and undyed
melt in the shape of a color wedge band. In this connection,
the transition zone, wherein a dyed melt stream of varying
cross seciton and correspondingly different color intensity
is incorporated from one side by displacement of the color-
less melt stream, is likewise produced by means of a slot die.
The slot die makes it possible to produce an exact, colored
zone dimensioned of a corresponding cross section in accor-
dance with the length and/or width of the nozzle orifice;
due to the configuration of the slot die, it is possible to
maintain the sa~e exit speed of the dyed melt over the en-
tire width of the desired colored band, even with a differing
thickness of the same. Moreover, this makes it possible to
provide the desired, exact control of the colored band.
The basic construction of a slot die is described,
for exampel, in "Kunststoff-Maschinenfuhrer" (Plastics Machine
Guide), Carl Hanser publishers, Munich - Vienna, 1979,
pages 95-98. The apparatus for the prodution of a sheet con-
taining a colored band and exhibiting varying color intensity,
according to this invention, has the feature, in a further
development of the conventional devices, that the injection
port for the additional colored thermoplastic melt is
fashioned as a small slot die arranged, as seen in the ex-
trusion direction, on the front side of the back pressure
plate of the large slot die and a nozzle plate disposed in
front thereof, with a nozzle exit orifice extending at right
angles to the extrusion direction along the forward edge of
the back pressure plate. The feeding of the additional melt
stream according to this invention therefore takes place
downstream of the distributor duct, i.e. after the primary
melt stream has been completely spread out in the transverse
direction over the entire desired width of the sheet and is
flowing, in the zone of the back pressure plate, already in
parallel along the entire width in the extrusion direction.
The forward edge of the back pressure plate is simultaneous-
ly utilized according to this invention as the nozzle orifice
rim for the additional melt stream and is transformed in this
region into a small slot die within the entire slot die tool,
by attaching in front a nozzle plate exhibiting the worked-
in configuration of the desired nozzle or die in accordance
with the size of the nozzle plate. The apparatus of this
invention has the substantial advantage over the known in-
jection nozzles, torpedoes, or other essentially round or
oval tubular in~eciton devices, that also for the melt to be
injected, a distribution of the mass flow to a desired cross
section is effected in such a way that upon termination of
the distribution step, the exit speed of the additional melt
stream is the same at any point at the exit orifice, due to
the use of a correspondingly shaped tool or die, so that
frictionless merging with the already present mass stream
takes place.
An advantageous further development of the inven-
tion provides that the back pressure plate of the large slot
die tool exhibits a feed bore with a connecting bore to the
small slot die for the partial melt stream. Depending on
the shape of the slot die, it can be fed asymmetrically or
symmetrically, depending also on the configuration of the
die orifice and the desired cross section.
A preferred embodiment of the small slot die pro-
vides that the slot die is incorporated unilaterally into a
nozzle plate with a distributor duct, a baffle, and a nozzle
lZ~
orifice. This distributor plate is then attached to the
front edge of the back pressure plate and forms therewith,
in the worked-in region, the flow channel for the partial
melt stream.
Preferably and in order to obtain a colored band
havi.ng a wedge shape in cross section, the provision is made
according to the invention that the nozzle orifice of the
small slot die is of a wedge-like configuration and is
reduced over its length from a given slot width to zero, but
wherein the slot die is fashioned so that the partial melt
stream exhibits the same exit speed over the entire length
of the nozzle outlet orifice.
Preferably, the nozzle orifice of the small slot
die is made to be adjustable, for example by a corresponding
adjustability of the nozzle plate, for example by means of
screws, shims and similar elements.
A preferred embodiment of the apparatus according
to this invention for the production of colored bands of
varying color intensity in a melt stream, wherein a sheet is
produced having a colorless sheet zone and a dyed sheet zone
and a transition zone, provides that two slot die tools of
identical geometry and optionally different nozzle widths,
each being fed by respectively one extruder with a melt
stream, are arranged in side-by-side relationship and are
connected with each other in such a way that a continuous die
orifice is provided having a width constituting the total
of the individual die widths, and further provides that the
injection port, fashioned as a small slot die, projects,
starting with the transition line of the adjacently arranged
slot die tools, over a desired width into a partial zone of
one slot die tool and is connected, by way of a feed duct,
with the melt stream of the other slot die tool.
The preferred area of utilization for the invention
is the manufacture of sheeting or films based on polyvinyl
butyral, employed as intermediate films for safety glass in
automotive vehicles and in the building industry.
The lnvention will be explained in greater detail
with reference to an enbodiment illustrated in the accompa-
nying drawings wherein:
FlG.l shows a cross section through a conventional
slot die tool;
FIG.2 shows a view A of the flow cross section of
the slot die tool according to FIG. 1 in a schematic illus-
tration;
FIG.3 shows a top view of a flow cross section of
two slot die tools, arranged side-by-side, in a schematic
view;
EIG.4 shows a cross section through a sheet with a
colorless zone, a dyed zone, and a transition zone;
FIG.5 shows a schematic elevational view of an in-
stallation for the manufacture of a sheet according to FIG.4;
FIG.6 shows a fragmentary elevational view of the
opened slot die tools of FIG. 5 in the region of feeding of
the partial stream for the colored band;
FIG.7 shows a view of a cross section taken along
line B-B according to FIG.6;
FIG.8 shows a cross section of the slot die made up
of back pressure plate and nozzle plate according to FlG.7;
FIG.9 shows a view from the top of the slot die
according to FIG.~;
FIG.10 shows a view of the nozzle plate according
to section taken along line C-C of FIG.9, and
FIG.ll shows a view E onto the slot die of FIG.8.
FIG.l shows a schematic view of a slot die tool or
fishtail die 4a wherein the melt stream 1 coming from the
extruder enters the feed duct 3a and then is divided to the
desired width by way of the distributor duct 5a. The dis-
tributor duct 5a is followed by a throttle zone lOa! a duct
,~
3 ~
of constant gap height with a gap length reduced in accord-
ance with the mass pressure, wherein the flow of material
is controlled; at the end of this zone of the channel t the
channel passes over into the forward zone lla in the region
of the back pressure plate 6a and subsequently into the
nozzle orifice zone 7a. By adjusting the bac~ pressure
plate by means of the tension and pressure screw 12, corre-
esponding flow corrections can be effected in this range;
analogous considerations apply regarding the region of the
nozzle outlet zone, which is likewise adjustable by screw 13
by way of the adjustable upper lip 8a~ The molded melt then
leaves the slot die tool at the nozzle outlet orifice 9a
defined by the upper lip 8a and lower lip 8b.
In FIG.2, a schematic view is illustrated of the
configuration of the flow duct cross section from the en-
trance of the melt via the distributor duct 5a, the throttle
zone lOa, and the forward zone lla in the region of the bac~
pressure plate.
It is possible according to this invention to
fashion two large slot die tools in such a way, and couple
them in such a manner, that a superwide sheet can be pro-
duced of identical or different, unicolored of differently
colored synthetic resin. The essential factor here is that
the slot die tools 4a, 4b exhibit the same geometry with
respect to the configuration of the flow cross section, but
can exhibit differing widths Ba, Bb. The melts 1 and 2 are
preferably based on the same thermoplastic synthetic resin,
but are dyed differently or are colorless and dyed, respec-
tively. The sheet zones 20a, 20b are then of a corresponding
character and are combined into a unitary sheet 20. In
order to form a zone ofcolored band 20c in the sheet 20, use
is made of a separate slot die 21 in one of the slot die
tools 4a, 4b; in the embodiment of FIG.3 this separate slot
die is in the slot die tool 4a. Preferably, the slot die 21
is provided in the transition zone from one tool 4a to the
other wool 4b; this is, however, dependant exclusively on
the desired arrangement and design of the colored band zone
20c.
FIG.4 shows a preferred embodiment of a sheet,
especially based on polyvinyl butyral, produced by extrusion
with a colored band, illustrated in cross section. ln this
arrangement, a sheet 20 is produced having a width Ba + Bb
exhibiting a colorless zone 20a and a dyed zone 20b. In
the transition region from the dyed sheet 20b to the undyed
sheet 20a, as seen from the transition line 27, a colored
band is provided having a color intensity that decreases in
the direction toward the colorless sheet, i.e. the sheet
zone 20c extending preferably in a wedge shape under the
angle ~, within an angular range of perferably 3-20. The
associated extrusion dies are designed in correspondence with
this sheet zone with colored band 20c, having a width Bc, as
can be seen from the embodiment of an installation shown
schematically in FIG.5. In this arrangement, the colorless
melt stream 1 is plasticezed by means of extruder 14 and fed
via melt pumps 16 and feed duct 3a to the first slot die
tool 4a. In the second extruder 13, the colored plastic
melt 2 is melted and fed via the melt pumps 16b and feed duct
3b to the second slot die tool 4b. A partial melt stream 2c
for the colored band of varying color intensity is branched
off from the melt stream 2 via conduit 3c and fed, for
example by means of a melt pump 17, to the slot die 21
additionally installed in the tool 4a in order to form the
colored band 20c in the sheet 20.
FIGS.6 and7 show the construction of the s]ot die
21 and its installation in the large slot die tool 4a in a
fragmentary illustration in greater detail. It can be seen
from the plan view of FIG.6 how the slot die tool 4a for the
colorless sheet 20a and the slot die 2b for the colored sheet
20b are arranged directly side-by-side, one passing over
~ _ _
~,,
into the other, wherein the contact area of the tools 4a,
4b simultaneously forms the transition line 27 between the
two sheet region 20a, 20b. The arrow P indicates the ex-
trusion direction for the sheet 20; as seen in the extrusion
direction, the additional slot die 21 for the injection of a
partial stream of dyed melt into the zone of the colored
melt is arranged upstream of the back pressure plate 6a.
For this purpose, the back pressure plate 6a can be formed,
for example, with a recess 28 in which is inserted a no~zle
plate 22 with the formation of the flow cross section for
the slot die 21. FIG.7 then shows the formation of the
die 21 in the zone of the tool 4a in a vertical cross section.
The colorless melt 1 comes from the distributor duct 3a and
is uniformly distributed over the throttle zone so that the
colorless melt 1, when entering the forward zone lla in the
region of the back pressure plate, flows in parallel to the
extrusion direction along the full desired width of the
sheet. At the front edge 29 of the back pressure plate 6a,
the die orifice for the partial melt stream 2c is formed
along the desired width from the slot die 21. The partial
melt stream 2c is fed, for example, through a recess, in the
back pressure plate 6a to the flow cross section of the slot
die 21. The flow cross section of the slot die is formed by
the die plate 22 attached to the front side of the back
pressure plate, leaving a corresponding space for flow cross
sections, for example by means of screws, not shown.
FIGS.8-11 illustrate an embodiment for the structure
of the slot dle 21 for feeding a partial melt stream into a
primary melt stream already flowing in distributed form in a
sl~t die. FIG.8 illustrates, in an enlarged view, again a
cross section through the back pressure plate 6a of FIG.7,
with a cutout opening or port 30 for feeding the melt stream
and a passage opening 23 into the flow cross section of the
slot die 21. The flow cross section of the slot die 21 is
formed between the front side of the back pressure plate 6a
-- 10 --
~,
121~
and the die plate 22 mounted in front thereof; the die
orifice 24 extends along the edge 29 of the back pressure
plate 6a. In FIG.9, a plan view is illustrated of the back
pressure plate and nozzle plate of FIG.8. In the illustration,
it can also be seen that it is advantageous to insert the
nozzle plate 22 in a recess 28 of the back pressure plate 6a.
The section D-D according to FIG.9 corresponds to the cross
section of FIG.8. FIG. 10 shows how the flow cross section
is worked out of the die plate 22 according to section line
C-C of FIG.9. The flow cross section of the slot die 21
comprises essentially the distributor duct 211, the baffle
210 with the function of a throttle area, and the nozzle
orifice 24. The length L of the die orifice 24 is selected
in dependence on the desired width of the introduced colored
band within the sheet.
Preferably, a wedge-shaped nozzle orifice 24 is
chosen, as can be seen from FIG.ll, wherein the orifice tapers
wedge-like from the greatest width 241 down to zero on the
opposite end 240. With such a configuration of the die
orifice 24, a unilateral feeding arrangement, as shown in
FIG.9, is advantageous.
The installation of an additional slot die into a
slot die tool, according to this invention, for the introduc-
tion of a melt differing in color in order to produce a col-
ored band of defined color intensity and defined sizes, ispossible with two coupled-together slot die tools, as in the
illustrated exemple, but can also be accomplished with the
use of only one large slot die tool provided with appropriate
feed means and flow regulating channels.
