Volumetric blending, mixing and extruding of polymer like materials

Side by side extruders provide an extrusion apparatus which has an imposed order of longitudinal displacement of the process material in relation to itself so that cross-shearing is directed to newly aligned material in a manner which achieves volumetric blending with little unproductive shearing. The extrusion apparatus mixes and extrudes polymer like materials with as little waste shearing as possible, so as to preserve the viscosity of the polymer materials and to produce a uniformity processed material of the highest quality possible from the starting materials.

Extrusion flow has been compared to flow through a pipe, first in first 
out. This is valid, however in a pipe the material contacting the pipe 
receives the least work, while in an extruder the material contacting the 
barrel and rotor surfaces is the most active. Temperature stratification 
develops to the extent that the material forms a cold core surrounded by 
warmed material. Cross-shearing, in either the pipe or the extruder blends 
the stratified material. If however, the non-uniformity of the material 
has length along the extruder groove, cross-shearing can not produce what 
isn't there. 0n this basis it is clear that to produce an improved mix, 
longitudinal displacement of the material is required to make 
cross-shearing most effective. 
Side by side helical groove extruders in close proximity to each other, are 
used on a sausage stuffer around the year 1880. For purpose of cleaning, 
the top section of the barrel member was removable. Observed action of the 
process material between the rotors is similar to a bank of material 
formed by a two roll mill. The extended material arriving at the bank has 
to "push" its way into the bank of material as formed between the rotors. 
This action wastes the work used to extend the material arriving at the 
bank. Also, a small marble placed between the rotors is conveyed the 
length of the extruder without being harmed. Although mixing is achieved, 
the effective use of extrusion shear can be improved. Excessive working of 
the process material can in some compounds degrade the polymer. 
The present invention relates to side by side extruders providing an 
apparatus which has an imposed order of longitudinal displacement of the 
process material in relation to itself so that cross-shearing is directed 
to newly aligned material in a manner which achieves volumetric blending 
with little unproductive shearing. 
SUMMARY OF THE INVENTION 
It is the principal feature of the present invention to provide a new and 
improved extrusion apparatus which mixes and extrudes polymer like 
materials with as little waste shearing as possible, so as to preserve the 
viscosity of the polymer materials and to produce a uniformity processed 
material of the highest quality possible from the starting materials. 
Another feature of the present invention is to provide a new and improved 
apparatus which develops longitudinal displacement of the process polymer 
like material in relation to itself so that subsequent cross-shearing is 
directed to newly aligned material in need of cross-shearing. 
Still another feature of the present invention is to provide a new and 
improved apparatus which accomplishes a uniform warming and mixing and 
which is accomplished with the input work only equal to the work required 
to warm the process polymer like material to the specified extrusion 
temperature. This is an adiabatic operation which features no change in 
extrusion temperature with changes in the screw or in the rotor speed. 
A further feature of the present invention is to provide a new and improved 
apparatus, which due to uniform processing and to the elimination of 
non-productive shearing, can process the polymer like material in the 
relatively short extruder and thereby reduce the initial cost of the 
extrusion equipment. 
Another feature of the present invention is to provide a new and improved 
apparatus which features side by side extruders which can control the rate 
of cross-shearing of the process polymer like material to the rate of 
longitudinal displacement thereof to provide an imposed order of mixing 
which extends the process material uniformly in all three directions and 
to thereby produce the extrusion with minimum unproductive shearing. 
Still another feature of the present invention is to provide a new and 
improved apparatus which has an imposed order of mixing which uniformly 
processes the material to an even temperature and thereby eliminates the 
need of "dwell time" to equalize the temperature. 
A further object of the present invention is to provide a new and improved 
apparatus which eliminates turbulent flow, which is recognized as 
directing the imposed shear to the path of least resistance, which is the 
already worked process material. 
A still further feature of the present invention is to provide a new and 
improved apparatus which eliminates the relaxing of the extended material 
as it reaches the trailing edge of the helical extruder groove. 
Still another feature of the present invention is to provide an apparatus 
which features side by side rotors with adequate capacity to fill and keep 
full both extruders through the full speed range of the extruders. 
A still further feature of the present invention is to provide a new and 
improved apparatus which features side by side extruders which warms the 
process polymer like material to the specified extrusion temperature 
without the need of cooling water or other means of cooling. 
A final feature of the present invention is to provide a new and improved 
apparatus which features side by side extruders each of which has a feed 
means and is operable to uniformly combine and mix two different process 
materials or to blend different batches of the same process material.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, as an introduction to the present invention there is 
provided a new and improved apparatus with side by side extruders of the 
rotor and barrel type. Extruder (R) and extruder (L) are viewed from the 
drive end of the extrusion apparatus. The common hopper or feed means is 
centrally located and supplies the process material, half apparatus 
capacity to each of the extruders. The rotors of the hopper A area and the 
following forcing section B are designed to provide adequate capacity to 
completely fill both extruders. The forcing section B, of both extruders, 
consists of helical extrusion grooves adequate to warm, pressurize and 
transport the process polymer like material to the first transfer mixing 
section C. The first transfer section C of extruder (R) starts with 
multiple rotor extrusion grooves which start at full extrusion capacity 
(50% apparatus capacity) and taper to zero in the downstream direction. 
The process material entering these grooves which receives the material 
from the rotor, directs a portion to multiple rotor extrusion grooves at 
the downstream portion of the first mixing transfer section C and directs 
the remaining portion to the circumferential barrel groove extruder (L). 
The first transfer section C of extruder (L) starts with multiple extrusion 
grooves, which start at full capacity and increase taper in the downstream 
direction. The process material entering these grooves from the forcing 
section B of extruder (L) is forced outward to the co-acting 
circumferential barrel groove which combines it with material from the 
circumferential extruder (R) and forces it into multiple rotor grooves at 
the downstream portion of the first mixing transfer section C of extruder 
(L). 
The first mixing transfer section C is followed by the first longitudinal 
displacement section D in which extruders (R) and (L) are provided with 
extrusion grooves of different capacities so as to displace the process 
material longitudinally in relation to itself. Capacity is measured by 
volume per turn of the extruder grooves. Extruder (R) receives the 
material not transferred to extruder (L). Extruder (L) receives the 
portion of the material transferred from extruder (R), plus all of the 
material from the forcing section B of extruder (L). A division of the 
extruder capacity is projected to be in the range of one to three. The 
typical helical extrusion grooves tend to process the material 
non-uniformity. This section D is provided to rearrange the materials and 
therefore use of helical grooves may be an asset. 
The first mixing transfer section C transfers material from extruder (R) to 
extruder (L). In a similar manner the second mixing transfer section E, 
transfer material from extruder (R) to extruder (R). The second 
longitudinal displacement section F is provided to rearrange the process 
material for presentation to the third mixing transfer section G and is 
similar to the first longitudinal displacement section. 
The third mixing transfer section G transfers material from extruder (R) to 
extruder (L) in the same direction as the first mixing transfer section. 
It discharges the process material in two equal streams to the final 
metering pressurizing section H of each extruder. 
In the drawings, like reference numbers and letters donate the 
corresponding part throughout several views of the extrusion apparatus. 
The apparatus constructed in accordance with the invention is the preferred 
embodiment as applied to the warming, mixing and extruding of process 
polymer like material. The apparatus consists of side by side extruders 
(R) and (L). The apparatus has an elongated barrel housing 12 provided 
with a pair of longitudinally extending and intersecting bores 13. Each 
extruder consists of a hopper or hopper section A, a forcing section B, a 
first transfer mixing section C, a longitudinal displacement section D, a 
second transfer mixing section E, a longitudinal displacement section F, a 
third transfer mixing section G and an end discharge or final metering 
pressuring section H. The drive means 10, rotates the rotors 20 and 30 in 
a counter-clockwise and clockwise directions within the barrel 12 so as to 
provide an in-running "bite" between the rotors to "pull" the process 
material into both extruders. The opening 11 of hopper A is centrally 
located to serve both extruders (R) and (L). The rotors 20 and 30 are 
provided with helical extrusion grooves 21 and 31 as shown in FIG. 2. The 
rotor geometry is increased to provide capacity adequate to fill both 
extruders. 
The rotor 20 has a plurality of extrusion grooves starting with the helical 
extrusion groove 21 in the forcing section B; extrusion grooves 22 in the 
first transfer section C; helical extrusion grooves 23 in the longitudinal 
displacement section D; extrusion grooves 24 in the second transfer 
section E; helical extrusion grooves 25 in the longitudinal displacement 
section F; extrusion grooves 26 in the third transfer section G; helical 
extrusion grooves 27 in the end discharge or metering section H; and the 
discharge area or extrusion port 28. 
The rotor 30 also has a plurality of extrusion grooves, some of a different 
configuration than the grooves of rotor 20. The rotor 30 has a helical 
extrusion groove 31 in the forcing section B; extrusion groove 32 in the 
first transfer section C and which is connected to rotor 20 via the 
passage 14 provided in the center partition of the barrel 12; helical 
extrusion grooves 33 in the longitudinal displacement section D; extrusion 
grooves 34 in the second transfer section E and which are connected to the 
rotor 20 via the passage 15 provided in the center partition of the barrel 
12; helical grooves 35 in the longitudinal displacement section F; 
extrusion grooves 36 in the third transfer section G and which are 
connected to rotor 20 via the passage 16; helical extrusion grooves 37 
located in the end discharge or meter section H; and the discharge area or 
extrusion port 38. 
Hopper A forms the feed means for the apparatus and consists of dual 
hoppers, one for each extruder. Each hopper is provided with a ram, not 
shown, to assist the entering of the process material into the hopper 
barrel grooves which direct the material downstream into the forcing 
section B. Also a common hopper may be provided which is centrally located 
between the two rotors. 
The forcing section B of the rotors 20 and 30 have the extrusion grooves 21 
and 31 continuous with the hopper grooves and adapted to warm, pressurize 
and transport the process material to the first transfer mixing section C. 
The rotor of the first transfer mixing section C of extruder (R) (FIGS. 
3-5) has multiple extrusion grooves 41 (FIG. 5) which receive the material 
from extrusion groove 21 dividing it into multiple strips. Rotational 
movement of rotor 20 causes the process material in extrusion groove 41 
(FIG. 5) to enter the circumferential barrel groove 40, which transport 
the process material over obstruction 42 and delivers a portion of the 
process material to multiple rotor grooves 43. The remaining portion of 
the process material is transported via circumferential barrel groove 40 
to the co-acting barrel groove 40 of extruder (L). 
The multiple rotor extrusion grooves 44 of the first transfer mixing 
section C, extruder (L) receives the material from extrusion groove 31 
dividing it into multiple strips. Rotational movement of rotor 30 causes 
the process material in extrusion groove 44 to enter circumferential 
barrel groove 40, which transports it over the obstruction 45, combines it 
with the process material in extrusion groove 40, from extruder (R), and 
transfers both streams to multiple rotor grooves 46 (FIG. 5). 
The longitudinal displacement section D of extruder (R) receives the 
process material from multiple grooves 43 and transports it downstream via 
the low capacity helical extrusion groove 22 to the multiple rotor grooves 
51 of the second transfer mixing section E (FIGS. 6-8). 
The longitudinal displacement section D of extruder (L) receives the 
process material from multiple grooves 46 and transports it downstream via 
high capacity helical extrusion grooves 32 to the multiple rotor grooves 
54. The shorter length of groove 32, as compared to groove 22, causes the 
process material in groove 32 to move downstream ahead of the process 
material in groove 22. 
The multiple extrusion grooves 51 of the second transfer mixing section E 
of extruder (R) receives the material from extrusion groove 22 dividing it 
into strips. Rotational movement of rotor 20 causes the process material 
in groove 51 to enter circumferential barrel groove 50, which transports 
it over obstruction 52, combines it with process material from the second 
transfer mixing section E of extruder (L) and directs both streams to the 
multiple extrusion grooves 53. 
The multiple extrusion grooves 54 of the second transfer mixing section E 
of extruder (L) receives the material from extrusion groove 32 dividing it 
into strips. Rotational movement of rotor 30 causes the process material 
in extrusion grooves 54 to enter the circumferential groove 50, which 
transports it over the obstruction 55, directs a portion to multiple 
extruder grooves 53 of extruder (R) and the remaining portion to multiple 
extruder grooves 56 of extruder (L). 
The longitudinal displacement section F of extruder (R) receives the 
process material from multiple grooves 53 and transports it downstream via 
a high capacity helical extrusion groove 23 to the multiple rotor grooves 
61. 
The longitudinal displacement section F of extruder (L) receives the 
process material from multiple grooves 56 and transports it downstream via 
low capacity helical extrusion grooves 33 to the multiple rotor grooves 64 
of the third transfer mixing section G. The shorter length of groove 23, 
as compared to groove 33, causes the process material in groove 23 to move 
downstream ahead of the process material in groove 33. 
The multiple extrusion grooves 61 of the third transfer mixing section G of 
extruder (R) (FIGS. 9-11) receives the process material from extrusion 
groove 23 dividing it into strips. Rotational movement of the rotor 20 
causes the process material in groove 61 to enter circumferential barrel 
groove 60, which transports it over the obstruction 62, and delivers a 
portion to multiple rotor grooves 63. The remaining process material is 
transported via circumferential groove 60 to the co-acting barrel groove 
60 of extruder (L). 
The multiple extrusion grooves of the third transfer mixing section G of 
extruder (L) (FIGS. 9-11) receives the process material from extrusion 
groove 33 dividing it into strips. Rotational movement of rotor 30 causes 
the process material in groove 64 to enter circumferential barrel groove 
60, which transports it over the obstruction 65, combines it with material 
from extruder (R) and transfers both streams into multiple rotor grooves 
66. The end metering section H receives the process material from multiple 
rotor grooves 63 and 66 (FIG. 11), develops pressure and extrudes the 
material through a discharge port. 
The longitudinal displacement section D of extruder (R) receives its 
material from rotor extrusion groove 43. Its rotor is provided with three 
turns of a low capacity helical groove 22. The corresponding extruder (L) 
receives its material from rotor groove 46. It is provided with a turn and 
a half of a high capacity helical extrusion groove 32. The design tends to 
delay the material processed by extruder groove 22 as compared to extruder 
groove 32. This displacement presents newly aligned material to the second 
transfer mixing section E. 
The second transfer mixing section E of extruder (R) receives its material 
from rotor groove 22 and divides it into multiple extrusion groove 51. 
Rotational movement causes the material to leave groove 51, clear 
obstruction 52 and enter barrel groove 50. Barrel groove 50 also receives 
material from extruder (L) and combines and directs both streams to the 
multiple rotor grooves 53. 
The second transfer mixing section E of extruder (L) receives its material 
from rotor groove 32, and divides it into multiple extrusion grooves 54. 
Rotational movement causes the material to leave rotor groove 54, clear 
obstruction 55 and enter barrel groove 50 which transfers it to barrel 
groove 50 of extruder (R). Thus the second mixing transfer section E is 
provided to rearrange the process material for presentation to the second 
longitudinal displacement section F which functions in the same way as 
longitudinal displacement section D. The second longitudinal displacement 
section F rearranges the process material for presentation to the third 
mixing transfer section G which transfers the process material from 
extruder (R) to extruder (L) in the same direction as the first mixing 
transfer section. The process material is discharged in two equal streams 
via the extrusion ports 28 and 38 of the final pressurizing metering 
section H. 
The extruder is made in sections which are removable to facilitate the 
changing of the sections to accommodate new process materials. 
The extrusion apparatus disclosed herein is for mixing and extruding thermo 
plastic and rubberlike materials wherein an imposed order of extrusion 
shear extends the process material in all three directions to generate 
uniform volumetric dispersion. The imposed cross-shearing of established 
material flow lines is generated by the extrusion geometry, which directs 
the shear to newly aligned material and minimizes shear along the path of 
least resistance, the already worked process material. 
Imposed longitudinally displacement of the material in relation to itself 
realigns the material for cross-shearing and makes longitudinal blending 
possible. The imposed order of shearing uniformly warms the material so 
that "Dwell Time" required to equalize temperature as generated by unequal 
processing is not required. By eliminating unproductive shearing (and 
possibly degradation of the polymer) the input work is only equal to the 
work required to warm the process material to the specified extrusion 
temperature or adiabatic operation. 
Adiabatic operation, provides extrusions which do not change in extrusion 
temperature throughout the speed range of the extruder. Thus production 
per extruder can be fifty to one hundred percent higher than present day 
extruders. This, in addition to the reduced length of extruder required, 
and the simplification of the cooling system, combine to provide low cost 
extrusions. More important, product quality improvement can be expected to 
the extent, that the cost of the extruder is relatively unimportant.