Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
(1) The Field of the Invention
This invention relates to processing apparatus.
More precisely, this invention relates to multi-stage
; 5 rotary processors particularly useful for processing
plastic and polymeric materials.
(2) Description of the Prior Art
Rotary processors are known in the art. Details
relating to such processors are described in US.
Patents 4,142,805; 4,194,841, 4,207,004; 4,213,709;
4,227,816; 4,255,059; 4,289,319, 4,300,842; 4,329,065
and Canadian Patent 1,142,319.
;
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1 Multi-stage rotary processors are also known to the art.
U. S. Patent 4,227,~16 specifically relates to a rotary processor
having two stages in three sections. Rotary processors of U. S.
Patent 4,227,816 comprise a rotatable element or rotor cowering a
plurality of processing channels and a stationary element
providing a coaxial closure surface cooperatively arranged with
the channels to provide enclosed processing passages. Also
associated with the stationary element are inlets, outlets and
blocking members for each passage and material transfer passages
or grooves formed in the closure surface of the stationary
element and arranged to transfer material From a passage (or
passages) of one stage to a passage (or passages) of another
stage. As disclosed in U. S. 4,227,816, one processing stage
involves two primary or supply sections. Each primary or supply
section of the first stage is arranged at each end of the rotor
and are separated from each other by a second processing stage
adapted to receive material from each section of the first stage.
U. S. Patent 4,213,709 also relates to a multi-stage rotary
processor which provides two processing stages including a
primary processing passage interconnected -Lo a further processing
passage. The preferred processor involves two primary processing
passages, each arranged at each end of the rotor with the primary
processing passages separated by two further processing passages
adapted to receive material from -the primary processing passages.
In the processors described in to. S. Patents 4,213,709 and
.
Jo ~Z~4~3Z
1 ~,227,816, the passages adapted to receive material from passages
of another stage are of a selected limiter relative to the
geometry of the passages from which the material is received.
Essentially, the geometry is selected to provide the material
receiving passage with the capability to process and discharge
material at a volume rate which is less than the volume rate at
which material is received by the passage. Such geometries
assure complete filling of the receiving passages and accordingly
provide a uniform rate of discharge and uniform discharge
pressure for material processed in the material receiving
passage.
Serious complications however, have developed in multi-stage
rotary processors having material receiving passages in which a
different geometry is required for passages receiving material
from a passages) of another stage. For example, certain
polymeric processes require a passage geometry which provides the
passage with the capability to process and discharge material at
a volume rate greater than the rate at which material is received
by the passage. This variance or mislnatch between the rate at
which the passage receives material and the vol~lme/rate
capability of the passage to process and discharge material can
cause large pressure, flow and temperature fluctuations in
processing passages and particularly at the discharge of the
rotary processor.
This invention is directed to multi-stage rotary processors
glue
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1 having a novel, improved Lawson which provides special advantages
in terms of efficiency quality of product and overall processing
performance characteristics.
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BRIEF SUMMARY OF TIE INVENTION
The novel, multi-stage rotary processors of this invention
comprise a rotatable element carrying a plurality ox annular
channels and a stationary element providing a coaxial closure
surface operationally arranged with the channels to provide
enclosed processing passages. The so-formed processing passages
are designed to provide a plurality o-f interconnected processing
slaves which include a first processing stage and a second
processing stage having inboard and outboard sections separated
by a third processing stage. Each processing slave includes at
least one passage having inlet means, outlet means and a channel
blocking member associated with the stationary element and
arranged and adapted so that material fed to the inlet can be
carried forward by the rotatable channel walls to the blocking
member for discharge From the passage.
Material transfer grooves are formed in the coaxial surface
of the stationary element to provide means to transfer material
between the processing stages. One material transfer groove is
arranged and adapted to transfer material from the processing
passages of the first processing stage to a processing passage of
the inboard section of the second processing stage. Another
material transfer groove is arranged to transfer material From a
processing passage of the inboard section to a processing passage
443~
1 of the outboard section of the second processing stage. Finally
another material transfer groove is arranged and adapted to
transfer material -from a processing passage of the outboard
section to a processing passage of -the third processing sty.
Material transferred to a processing passage of the third
processing stage may be transferred to another processing passage
of the third processing stage or discharged directly from the
processor.
Details relating to the novel multi-passage rotary processor
of this invention as well as -the advantages derived frown such
processors Jill he more fully appreciated from the Detailed
Description of the Preferred Embodilnents -taken in connection with
the Drawings.
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BRIEF DESCRIPTION OF THE RINKS
The invention w-ill be described in connection with the
5 attached drawings in which:
Figure 1 is a cross-sectional view of a multistage rotary
processor of this invention showing an arrangement of processing
passages providing first, second and third processing stages.
Figure 2 is a perspective view of a rotary processor of the
invention which is partly in section with parts broken away.
figure 3 is a simplified cross-sectional view of the rotary
processor illustrated in Figure 2 taken along line 3-3 of Figure
2.
Figure is a simplified cross-sectional view of a -first
15 stage processing passage of the processor of Figure 1 taken along
line I of Figure 1.
Figure 5 is a simplified cross-sectional view of a second
stage processing passage of the processor of Figure 1 taken along
line 5-5 of Figure 1.
Figure 6 is a simplified schematic view of the
interconnection o-f processing passages of rotary processors of
the invention by means of a material transfer groove with arrows
indicating flow direction of material from one processing passage
to another.
Figure 7 is a simplified cross-sectional view of another
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1 second stage processing passage of the processor of Figure 1
taken along line 7-7 of Figure 1.
Figure 8 is a simplified cross-sectional view of still
another second-stage processing passage of the processor of
Figure 1 taken along line 8-8 o-F Figure 1.
Figure 9 is a simplified cross-sectional view of a
third-stage processing passage of the processor of Figure 1 taken
along line 9-9 of Figure 1.
Figure 10 is tracing of graphical data recorded during
operation of a rotary processor of Figure 1.
Figures 11 and 12 are simplified cross-sectional views of
second-stage processing passages substantially identical to the
passages of Figure 5 and 7 respectively, but having additional
processing elements arranged in the passages.
Figure 13 is a top cross-sectional view of the passage of
Figure 12 showing processing of material moving through the
passage.
Figure 14 is a simplified cross-sectional view of a
second-stage processing passage substantially identical to the
processing passage of Figure I, but having additional processing
elements arranged in the passage.
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DETAILED DESCRIRrlON OF PREFERRED EMBODIMENTS
Referring first to Figure 1, novel, multistage rotary
processors of this invention include a rotatable element
comprising a rotor 12 mounted on a drive shaft 14 for rotation
within a stationary element comprising a housing 16. Rotor 12
carries a plurality of processing channels 21, 23, 25, 27, 29,
31, 33 and 35 each having opposed side walls extending inwardly
from rotor surface 20. Means for rotating rotor 12 are shown as
M since such means are of any suitable type commonly used For
rotating extrudes or similar polymeric processing apparatus and
are wall known to those in the art. lousing 16 of the stationary
element provides a coaxial closure surface 38 cooperatively
arranged with surface 20 of rotor 12 to -form with channels 21,
23, 25, 27, 29, 31, 33 and 35 enclosed processing passages 22,
24, 26, 28, 30, 32, 34 and 36 respectively.
As shown in Figure 1, toe processing passages are arranged
and designed to provide a plurality of processing stages.
Processing passages 22, 24, 26 and 28 provide -the first stage.
The second stage includes inboard anal outboard sections with
passages 30 and 32 providing the inboard section while passage 36
provides the outboard section. The third stage is provided by
passage 34 and the third stage is positioned between and
separates the inboard and outboard sections of the second stage.
As will be explained in detail later, the stages are
ISLES
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interconnected by material transfer grooves formed in
surface 38 and arranged so that material processed in
one stage can be transferred to another
Multi stage rotary processors of this invention
can provide a variety of combinations of processing
stages. Normally, the first stage involves a plastic
acting operation designed to melt, soften or otherwise
increase the flyability of material fed to the
processor. The second stage performs a compounding
operation which can involve mixing, homogenizing or
devolatilizing material processed in the first stage
or adding ingredients to or removing ingredients from
first-stage processed material. The third stage is
normally assigned a pressurizing or pumping function
to discharge second-stage processed material from the
processor. For illustrative purposes, the multi-stage
rotary processor described hereafter includes a -first
stage for melting - or at least partially melting -
polymeric material, a second stage for mixing first-
stage processed polymeric material and a third stage
for discharging the first and second-stage processed
material from the processor. A particularly suitable
melt processing stage design for rotary processors of
this invention is described and disclosed in commonly
owned US. Patent 4,389,119 in the name of Z. Tadmor
and Lo Valsamis.
Referring now to Figure 2 and 4, material such as
plasticated or unplasticated polymeric material is
suitably fed
32
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1 to the multi-stage rotary processor from a hopper 40
communicating with inlet 42, As Sheehan in Figure 2 and 4 coaxial
surface 38 of housing 16 is cylindrical over most of its extent
but is preferably provided with undercuts 44 extending over the
portions of channels 21 23, 25, and 27 and adjacent inlet 42~
Undercuts 44 have a width such that their sidewalls 46 extend out
over cylindrical portions 20 of rotor 12 to form intake chambers
designed to aid feeding of polymeric solids into each passage of
the first stage.
In operation material is supplied gravitationally or
through the use of force feeders to the processor through inlet
42 and is urged by undercuts 44 into channels 21, 23, 25 and 27.
I've situation is shown in Figure 2 and 4. Figure 2 illustrates a
section of rotor 12 carrying channels 21, 23 25, and 27 of the
first stage processing passages and channel 29 of the first
passage of the inboard section of the second stage. Figure 4
illustrates passage 28 of the -First stage Formed with channel 27
which has the same dimensiorls and arrangement of structural
elements as the other first stave passages 22, 24 and 26. Each
processing passage of the firs-t stage includes a channel blocking
member 48 arranged near first stage material transfer groove 50
which is arranged to communicate with each -first stage passage.
Transfer groove 50 is preferably spaced apart from inlet 42 a
major portion of the circumferential distance about the
us processing passage.
~204432
12 -
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l As shown, (Figure 2 and 3), each blocking member provides
a material blocking and material collecting end wall surface 52
for each passage of the first stage. Accordingly, in operation,
movement of the main body of material fed to each first stage
passage is blocked and relative movelrlent is established between
the moving channel walls and the blocked material. The
so-established relative movement generates frictional heat at the
moving wall and within the body of material. Additionally, the
channel walls of the first stage processing passages - and
lo preferably all of the channel walls of the processor are
normally heated such as by a heat transfer fluid supplied in
known manners to chambers 6 (Figure 1). De-tails relating to
suitable heating means can be found in referenced U. S. Pa-tents
4,1~2,805 and 4,194,8~1.
Normally, the action of the channel walls in dragging
material forward builds up pressure progressively about the
passage and maximum pressure in each of the First stage
processing passages is usually rocketed at surface 52 o-f blocking
member I Surface 52 of each first stage processing passage is
20 shaped and dimensioned or otherwise adapted to collect the
material for discharge from the passage.
Material processed in the first stage is discharged From
each passage through material transfer groove 50 (Figures 2 and
3). Transfer groove 50 is Formed in coaxial surface 38 adjacent
25 to and upstream of surface 52 of blocking menlber I. Transfer
43~
1 groove 50 extends parallel to the axis of rotor 12 with the open
end of groove 50 disposed to receive processed material collected
at surface 52 of each passage and to convey the received material
over surfaces 20 between the first stage passages for discharge
to second stage processing passage 30. As shown in Figures 2 and
3, the most outboard terminal portion of groove 50 provides an
inlet for passage 30.
The first stage illustrated in Figure 1 has four processing
passages of substantially identical shape and dimensions. More
or less passages may be used and first stage passages differing
in shape, dimensions and geometry from other first stage passages
may also be used.
The second processing stage of multi-stage processors of
this invention includes inboard and outboard sections separated
by at least one processing passage of the third stage. As shown
in Figure 1, passages 30 and 32 provide the inboard section of
the second stage while passage 36 provides the outboard section.
As shown in Figures 2, 3 and 4, material from the processing
passages of the First stage is discharged to the first passage 30
pa of the inboard section through transfer groove 50.
As mentioned" second stage processing passages are designed
to perform compounding operations on first stage processed
material. In the illustrated processor, the second stage is
designed to efficiently mix melted or partially melted material
25 supplied from the first stage. A processing passage assigned the
.
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1 function to provide efficient mixing of viscous material requires
a different geometry from the geometry of the first slave polymer
melting passages. As shown in Figure 1 for example, the passages
of the inboard section of the second stage have parallel sides
and are wider than the passages of the first stave. This
difference in geometry establishes a variance between the rate at
which first stage processed material is supplied to the second
stage passage and the capacity of the second stage passage. As
mentioned, the variance presents the potential for severe
fluctuations in temperature, flow and pressure in the processing
passages and especially at the discharge region of the processor
The effect of this variance can be best appreciated by
illustrating the differences which can exist between the rate of
supply of first-stage processed material and the processing and
discharge capacity of a second-staye passage having a geometry
: selected to provide efficient mixing. As mentioned, an
illustrative multi-stage rotary processor of this invention can
include a first stage having Four passages operating in parallel
designed to provide for example a total firs-t-stage processing
volume of about 300 in 3. Such processors can be operated at a
speed ranging between 50 to 150 RPM. Under such conditions, the
rate of supply of melted material to the second-stage passage can
range between 400 lbs/hr to 2500 lbs/hr depending on channel wall
speeds and polymer properties. However, a relatively wide
second-stage mixing passage is required for efficient mixing and
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a second-stage mixing passage selected for efficient
mixing can provide a geometry capable of processing
and discharging material at a rate between 7500 lbs/hr
to 22,500 lbs/hr at speeds between 50 to 150 RPM.
Rotary processors of this invention are designed to
permit the effective use of passages presenting this
variance between supply and processing or discharge
rates. Additional details relating to the variance
discussed above can be found in commonly assigned
US. Patent 4,402,616 in the name of LEN. Valsamis
and G. Donovan.
Referring again to Figures 1, 2 and 3, material
processed in the first stage is transferred by way of
groove 50 to the first passage 30 of the inboard
section of the second stage. In rotary processors of
the invention, first-stage processed material is
efficiently mixed in passage 30 by the relative move-
mint established between material blocked by blocking
member 54 (Figure 5) and the moving channel walls of
passage 30 which drag or carry the material forward
to material collecting and material blocking end wall
surface 56. In the multi-stage processors of this
invention, the blocking members ox the processing
passages of the inboard section members 54 and 60 -
Figures 5 and 7) are arranged about 180 from the
circumferential position of first-stage passage block-
in members 48. Accordingly, in the first passage 30
of the inboard section, material travels approximately
one-half a revolution through the passage before
~204432
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1 reaching blocking member I Material blocked and collected at
surface 56 of member 54 is discharged from passage 30 through
inboard section material transfer groove 58.
Transfer groove 58 is shown in Figure 6 which is an
idealized and simplified presentation with arrows indicating flow
; direction in material transfer grooves relative to blocking
members arranged in passages of the inboard and outboard sections
of the second stage and to a blocking member arranged in a
third-stage passage. As shown, transfer groove 58 is formed in
coaxial surface 38 and is designed, arranged and adapted to
receive material collected at surface 56 and transfer the
collected material over surface 20 between passage 30 and 32 of
the inboard stage. Essentially, the open end of transfer groove
58 may as shown extend parallel to the axis of rotor 12 in the
region of passage 30 upstream of surface 56 then extend
transversally to the axis of rotor 12 across surface 20 and then
extend parallel to the axis of rotor 12 in the region of passage
32 downstream of blocking member 60. When so arranged, transfer
groove 58 provides an outlet for discharging material from first
passage 30 of the inboard stage and an inlet for supplying
material to second passage 32 of the inboard section.
In multi-stage rotary processors of this invention a pin 55
ox fake
can be arranged as shown in channel 29~ Defoe #no of surface 56
of passage 30. yin 55 is associated with housing 16 and is
designed and adapted for adjustable extension into channel 29
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1 from a fully open to a fully closed position. In the fully open
position, no portion of pin 55 extends into channel 29, In the
fully closed position, pin 55 extends radially into channel 29 to
block any substantial movement of material into the transversally
extending portion of transfer groove I Pin 55 provides an
effective means for selectively adjusting and controlling the
rate of transfer of material through groove 58 to provide the
desired degree of processing in the passage and/or the desired
rate of material transfer from passage to passage. As described
in referenced U. S. Patent 4,227,816, transfer groove 58 can be
formed in removable flow director units which can be mounted in
slots in housing 16 arranged to permit cooperation of the
transfer groove with selected passages. Pin 55 and blocking
members 54 and 60 can also be carried by the removable flow
director unit.
Material transferred to the second passage 32 of the inboard
section is further mixed by the relative movement established
between material blocked by blocking menlber 60 (Figure 7) and
moving channel walls of passage 32. The moving walls drag or
carry material forward -to blocking mulberry 60 for collection at
surface 62 and discharge through inboard section material
transfer groove 64.
The inboard section of the second stage illustrated and
described includes two passages having substantially the same
dimensions shape and geometry. This preferred illustrated
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l arrangement of inboard section mixing passages can be varied.
For example, the inboard section can involve only one or more
than two passages and the shape, dimensions and geometry of the
passages can be the same or different. As illustrated, preferred
second-stage inboard section passages are those in which the
passage or passages receiving first-stage processed material has
a geometry providing a processing and discharge capacity which is
greater than the rate at which material is supplied to the
passage. Louvre, for certain second-stage processing operations
lo the selected geometry of the fist-stage material receiving
passage can provide a capacity which is equal to or less than the
supply rate of material.
Referring again to Figure 6, transfer groove 64 is formed in
coaxial surface 38 and has an open end which extends parallel to
the axis of rotor 12 from the region of passage 32 upstream of
surface 62 then transversally to the axis of rotor 12 across
surface 20 between passages 32 and 34 and then parallel to the
axis of rotor 12 across channel 33 of passage 34 and across
surface 20 between passages 34 and 36 -to the region of passage 36
downstream of blocking melnber 66. accordingly, material from the
inboard section of the second stage is transferred to the
outboard section across channel 33 of third-stage processing
passage 34 separating the inboard and outboard sections. In
operation, third stage passage 34 is designed to be sufficiently
filled and to generate high pressures so that leakage of material
~Z~44;~2
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1 from transfer groove I to channel 33 is minimal. As shown,
adjustable pin 63 can be arranged in channel 31 to provide means
to selectively adjust and control the rate of supply of material
to groove 64 in the same manner as described before for pin 55.
As shown in Figure 8, material is supplied to the second
stage section, passage 36, through transfer groove 64. The
supplied material is dragged forward by the channel walls of
passage 36 to blocking member 66 for collection at surface 68 for
discharge through outboard section material transfer groove 70.
The second-stage outboard section shown in Figures 1 and 8
consists of one passage, but rotary processors of this invention
can include those in which more -than one passage can be involved.
As illustrated in Figure 1, -the processing passage of the
second-stage outboard section differs somewhat in dimensions from
the processing passages of the second-stage inboard section. In
the illustrated processor, the passage channel 35 is narrower and
the geometry has been selected to develop sufficient pressure to
supply material to passage 34. However, the number, shape,
dimensions and geometry of the passage(s) of the outboard section
can be the same or different relative to each other or relative
to the inboard section passages.
Referring again to Figure 6, material processed in the
second-stage outboard section is transferred to a processing
passage of the third stage through material transfer groove 70.
Transfer groove 70 is formed in coaxial surface I and has an
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1 open end which extends parallel to the axis of rotor 12 across
the region of passage 36 upstream of surface 68, then extends
transversally to the axis of the rotor and then extends parallel
to the axis of the rotor in the region of passage 34 downstream
of blocking member 72. Third-stage passage 34 (Figures 1 and 9)
is primarily designed to function as a pressurizing or pumping
stage for material supplied from the outboard section of the
second stage. Accordingly, the geometry of the passage is
selected to provide a passage having a capacity which remains at
lo least partially filled at all times during operation and which is
capable of generating high discharge pressures.
As shown in Figure 9, materiel supplied to the third-stage
processing passage is dragged forward by the channel wells of
passage 34 to blocking member 72. Material collected at surface
78 is discharged from the processor through outlet 80. Discharge
pressure and the pressure developed in passage 34 can be
controlled or adjusted by discharge control means 79 figure 9)
such as a throttling valve or like device arranged in
communication with discharge outlet 80.
Figures 1 and 9 show a third-stage processing section
consisting of one passage, but more than one passage may be used.
The passages may be connected in parallel or in series. For
example, a plurality of third-stage processing passages may be
interconnected so that material can be transferred From one
25 third-stage processing passage to another for discharge from the
443~
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1 processor. Alternatively, a plurality of third-stage processing
passages can be interconnected so that material is fed to each
passage and discharged from the processor from each passage.
Multi-stage processors of this invention present highly
efficient polymeric processors providing special operational and
design advantages. A multi-stage processor as described and
illustrated presents such advantages as compact size, low power
consumption and high production potential for efficiently
melting, mixing and discharging a polymer melt product of
uniformly high quality at substantially constant rate and at
uniform pressure and temperature. For example, a multi-stage
rotary processor of the type described with reference to Figures
1-9, has been employed to process a variety of polymeric
materials. The processor included a rotor having an OLD. of 14
in, which carried an arrangenlent o-f processing passages as shown
in Figure 1 interconnected by material transfer grooves. The
material transfer grooves were formed in the coaxial surface of
the stationary housing in substantially the same arrarlgenlents
shown in Figures 2 and 4 and in Figure 6.
The first-stage passages of the processor included four
wedge-shaped channels as shown in Figures 1, 2, and 4. Each
channel had a maximum width of 1.0, a minimum width of .65 in.
and a height of 2.45 in. The second-stage inboard section
passage included two channels having parallel sides with each
having a width of 1.0 and a height of 2.45 in. The second-stage
.
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2-
1 outboard section passage of the processor included one wedge
shaped channel having a maximum width of 0.5 in., a minimum width
of a Q.325 in. and a height of 2.45 in. The third-stage
processing passage included one wedge shaped channel having a
maximum width of 0.25 in., a minimum width of 0.162 in. and a
height of 2.45 in.
n a typical processing operation, high density polyethylene
was fed to the first stage of the heated processor at a rate of
630 lbs/hr. The processor rotor was rotated at a speed of 50
rum. A valve arranged with the third-stage passage outlet was
adjusted to provide a discharge pressure of 750 pi During
about the first five minutes of operation, severe fluctuations in
the discharge pressure were noted. Pressures varying from about
50 psi to about Lowe psi were recorded during the period.
After about five minutes of operation, however, the discharge
pressure reached a substantially steady state and stabilized at
about 750 psi. The processor was operated for about five minutes
at the stabilized pressure of about 750 psi. The valve was then
adjusted to provide a discharge pressure of about l800 psi. In
about four to Five minutes, the discharge pressure built up from
750 psi to about l800 psi and operation was continued for about
five minutes at a substantially constant discharge pressure of
1800 psi. During this period, the temperature of discharged melt
material stabilized at about 320F. The valve was again adjusted
to provide a discharge pressure of about Lowe psi. Within about
. .
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.
1 two minutes, the discharge pressure stabilized at about 2,150 psi
and remained substantially constant throu(JIIou-t operatiorl.
Figure 10 dramatically illustrates the achievement of the
substantially constant discharge pressure in the multi-stage
rotary processor described above. Figure 10 is a tracing of
actual data plotted by a strip chart recorder for discharge
pressure and outboard passage pressure recorded during operation
of the processor. ! The portion of the upper recording line to the
right of the vertical line involves the period of operation
during which the discharge pressure is built up from 1~00 psi to
about 2,150 psi. The portion o-F the recording line to the left
of the upper vertical line illustrates the substantially constant
discharge pressure achievetl. Its shown by Lowe lower recording
line, pressure fluctuations are continually recorded for the
pressures developed in the outboard passage. These fluctuations
may be caused by leakage of material from the high pressure
discharge passage to the outboard passage. Despite these
fluctuations, however, material is continually discharged
throughout operation at a substantially constant discharge rate
of 630 lbs/hr, at a substanli.llly constant; discharge pressure of
2,150 psi and at a substantially constant temperature of 320F.
The discharge melt product was o-f excellent uniform quality,
extremely "clean" end essentially free of bubbles.
In addition to providing an especially effective capability
for processing material a-t a constant discharge rate and uniform
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l temperature and pressure, the design of multi-stage rotary
processors of this invention provides special advantages in
minimizing external leakage from the processor. Normally, seals
of the type described in U. S. Pa-tent 4,300,842 are employed to
control external leakage. Such seals are arranged on surface 20
near each end of rotor 12 to control leakage of material from
the processor through the clearance between rotor end surfaces 20
and surface 38. Preferred multi-stage processors of this
invention include such sealing means -to control external leakage.
lo Additionally, such sealing means can be arranged on surfaces 20
between processing passages to control internal leakage from one
passage to another through the clearance between surfaces 20 and
38. The preferred processors of this invention also include such
internal leakage control seals. Accordingly, in the illustrated
processor such seals would be arranged on surfaces 20 between
passages 30 and 32 of the inboard section and between passage 32
and third-stage passage 34 and on surface 20 between passage 34
and outboard section passage 36.
.1
The design of multi-stage rotary processors of this
invention, however, inherently reduces the potential for external
leakage and provides an especially effective degree of control
for external leakage. As described and shown, the -third-stage
passage is designed to pressurize and pump processed material for
discharge from the processor. Pressures in the range of about
1,000 psi to about 4,000 psi can be developed about the
SLY
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'I
1 circumference of such pumping passages thereby increasing the
potential for leakage through the clearance provided by surfaces
20 and I However, in processors of this invention, the high
pressure pumping passage is arranged between inboard and outboard
section passages which are designed to operate at relatively low
pressures. In operations involving the illustrative processor
described before, pressures between about 150 psi to about 300
psi are usually developed about the circumference of the inboard
section passage while pressures between about 150 psi to about
300 psi are developed in the outboard section passage. The
relative positioning of the outboard section passage and the
pressurizing or pumping passage dramatically reduces the
potential for external leakage from the processor at the outboard
end.
There are still other special advantages provided by the
shown and described arrangement of the high-pressure processing
passage between inboard and outboard section processing passages
operating at relatively lower pressures. Material which leaks
from the high-pressure processing passage to the inboard and
outboard section passages can be collected in these inboard and
outboard passages and recycled to the third stage passage for
discharge. Also, the material transfer groove 64 connecting the
inboard and outboard passage sections separated by the
high-pressure passage has an open end which passes over surfaces
20 between the high-pressure passage and the inboard and outboard
SLUICE
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1 section passages. The clearance between surfaces 20 and 38
defines a region in which extremely high shear forces and
temperatures can be generated. leakage material from the
high-pressure passage can be carried about the circumference of
the passage by moving surfaces 20 and undergo depredation because
of the encountered conditions of high shear and temperature. In
the multi-stage rotary processors of this invention however the
material transfer groove is arranged and adapted for collection
of leakage material carried by moving surface 20. Accordingly,
lo any such leakage material call be continually removed from surface
20 during each revolution of the rotor thereby controlling the
residence time that leakage material on surface I is subjected
to degredative conditions.
As mentioned the inboard and outboard sections of -the
second stage are adapted to perform compounding operations. The
compounding operations can include melting mixing
homogenization and devolatilization of materials among others as
well as the addition of materials to or withdrawal of materials
from the processed nlaterials. Figures 11-14 illustrate the
adaptability and versatility of second-stage processing passages
in conducting various processing operations. Figure 11
illustrates a first-stage material-receiving processing passage
of the inboard section similar to the inboard section passage
shown in Figure 5. As shown in Figure 11, one or more) mixing
US element(s) 82 is positioned between Motorola transfer grooves aye
~04~3;~
-27-
] and aye. Mixing element 82 extends into the channel of passage
aye a preselected distance to obstruct a portion of -the cross
section of passage aye to mix material processed in the passage
and/or to minimize temperature fluctuations in material processed
about the circumference of the passage. The shape, design and
dimensions of mixing element(s) 82 can vary depending upon the
degree and type of mixing desired. Mixing elements include those
which can scrape off material carried by the channel walls to
recirculate scraped off material with material blocked ho channel
13 blocking member aye. Material processed in a second-stage
passage of Figure 11 is collected at end wall surface aye for
discharge through material transfer groove aye to another
second-stage passage or to a third-stage passage.
Figure 12 and 13 illustrate another arrangement of elements
designed to achieve a selected compounding operation in one or
more of the second-stage processing passages. Figure 12
illustrates an inboard processing passage similar to the inboard
section passage shown in Figure 7. As shown, spreader element 84
is arranged near transfer groove aye of an inboard section
second-stage processing passage similar to that shown in Figure
7. Spreader element 84 is of substantially the same
cross-sectional shape and dimensions of challrlel aye of passage oily
and positioned near transfer groove aye and arranged and adapted
to spread material fed to the passage so that the moving walls
of the channel of passage aye drag the material through the
12~43~
I
,. t-
1 clearances provided by sides I (Figure 13) of spreader element
84 so that the spread material is carried forward as thin layers
86 (Figure 13) by the channel walls.
As best shown in Figure 13, a free central space is provided
in portions of the passage downstream of spreader member I and
the thin layers I have surfaces exposed to free central space
I Accordingly volatile in layers 86 may pass into free
central space I and be withdrawn through a port 90 with the aid
of vacuum if desired. Alternatively, port I may be used to
introduce materials to layers 86. As shown, the passage may
include more than one spreader element. Spreader element 92
respreads ant regenerates thin layers on the moving channel walls
to provide a second central free space aye downstream of spreader
member 92. Another port 94 communicating with the second free
space may be used to add ingredients to or withdraw ingredients
from the thin layers in the manner described above. Material
processed in a passage illustrated by Figures 12 and 13 is
collected at end wall surface aye no blocking member aye -for
discharge through outlet aye to another second stage processing
passage or to a third-stage processing passage.
Figure 14 illustrates still another of -the arrangements of
structural elements involved in second-stage processing passages
of multi-stage processing passages of this invention. Figure 14
illustrates an outboard processing passage similar to the
outboard passage shown in Figure I. A port I is shown
~Z~43~
-29-
, .
1 positioned in passage aye. Ingredients may be added to or
withdrawn from material processed in the passage of Figure I and
the port (or ports) can be arranged at any desired position about
the circumference of passage aye between transfer grooves aye and
aye. Material processed in the passage of Figure 14 is collected
at end wall surface aye of blocking member aye for discharge to
another outboard passage or to a third-stage passage. The
arrangement of elements in the illustrated passage is
particularly suitable for withdrawing ingredients preferably
under vacuum, from material processed in passage aye prior to
discharge from the passage.
From the above description, it should be apparent that the
novel, multi-stage rotary processors of this invention present
many distinctive and unexpected advantages. The processors
provide especially desirable polymer processing performance
characteristics. The distinctive design of the second-stage
inboard section and the second-stage outboard section separated
by a third stage permits effective utilization of second-stage
passages which can present d variance between supply rate of
first-stage processed material and the processing and discharge
capacity of second-stage processed passages. However, the design
of rotary processors of this invention effectively controls
potential fluctuations or surges in discharge rate, temperature
and pressure which can occur in processing passages because of
the variance. Moreover, the arrangemerlt of the third stage
swept:
-30-
1 relative to the inboard and outboard sections of the second stage
minimizes any potential of external leakage from the relatively
high-pressure pumping or pressurizing stage. Additionally, the
arrangement is designed to collect and recycle leakage material
from high-pressure passages and -to minimize depredation of such
leakage material. Accordingly, the invention presents to the art
novel, multi-stage rotary processors having unexpectedly improved
overall processing performance characteristics as compared to
rotary processors known to the art at the time this invention was
made.
. .
