PROCEDE D'EXTRUSION DE POLYMERES

ROLLER-DIE EXTRUSION OF POLYMERS

Abrégé anglais

61968-725
PROCESS FOR OBTAINING ULTRA-HIGH MODULUS PRODUCTS
Abstract of the Disclosure
A polymer is solid-state deformed under pressure through
the rollers of an extrusion rolling die, at a temperature near but
below its crystalline melting point, while controlling the
extrusion rate and the rate of rotation of the rollers so that the
rake of extrusion of the polymer is substantially the same as the
rate of rotation of the rolling die surface.

Revendications

23 61968-725
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing high-modulus semicrystalline
polymer products comprising,
solid-state extruding a polymer having an initial polymer
morphology by feeding under pressure through an
extrusion-rotation die having a static entry position
and a succeeding friction-reducing moving portion, said
succeeding friction-reducing moving portion or said die
comprising a pair of oppositely rotating members, each
having integral shaped wall surfaces strictly confining,
engaging and compressing the entire perimeter of the
polymer during extrusion and providing the geometry of a
die exit and a profile for extradate which has
practically the same cross-sectional area and lateral
dimensions as the cross-sectional area and lateral
dimensions of the die exit said static and succeeding
friction-reducing moving portions of the die having a
polymer-containing zone with convergent geometry through
which the polymer is compressed oriented and extruded
under conditions of minimal friction between the polymer
and the die surface for reducing the extrusion pressure,
said minimal friction being obtained by substantially
synchronous movement of the rotating members of the die
and the polymer, said extrusion being at a temperature
near but below the crystalline melting point of said
polymer, to obtain an extruded polymer product having a

23a 61968-725
markedly transformed morphology as compared with said
initial polymer morphology comprised of oriented and
extended molecular chains and markedly enhanced tensile
properties, the values of which are for the Young's
modulus within the range of 2 to 220 GPa and for the
tensile strength within the range of .015-4 GPa, and
which depend upon the extent of the cross-sectional area
reduction during extrusion.
2. The method of claim 1 in which the polymer is chosen
from the group consisting of polyethylene polypropylene,
polyamides polyoxymethylene, poly(ethylene terephthalate), and
poly(vinylidene fluoride).
3. The method of claim 1 in which the polymer is a
thermotropic aromatic copolyester which is processed at a
temperature above its glass transition temperature and
slightly below its solid-to-mesophase transition.

- 24 -
61968-725
4. The method of claim 3 wherein the polymer is
chosen from the group consisting of
(1)
<IMG>
where
R is <IMG> , or
<IMG>
(2)
<IMG>
where
R is <IMG> ,or <IMG>
(3)
<IMG>

- 25 - 61968-725
(4)
<IMG>
5 . The method of claim 1 in which said polymer is
in the form of a continuous solid.
6 . The method of claim 1 in which said polymer is
in the form of a powder and the method includes the step of compacting
said powder before introducing it to said die.
7 . The method of claim 1 in which said polymer is
in the form of a gel.
8 . The method of claim 1 including supplying said
polymer as a solid hollow tube and enlarging the
diameter of said tube while thinning the thickness of the
walls of tube.
9 . The method of claim 8 including slitting the
enlarged-diameter tube longitudinally to produce a sheet.
. The method of claim 1 wherein said material is
a powdered metal.
11 . The method of claim 10 wherein said metal is
chosen from the group consisting of aluminum, titanium,
aluminum alloys, titanium alloys and fiber-reinforced
aluminum and titanium.
12 . The method of claim 1 wherein said temperature
is attained by circulating heated oil through said
rollers.

26 61968-725
13. The method of claim 12 also including air-convection
heating means for preheating the material stock just prior to
entry between said rollers
14. The method of claim 1 comprising a plurality of said
extrusion rolling dies and the extrudate is sent from one said die
to a succeeding said die.
15. The method of claim 1 wherein said method is continuous.
16. The method of claim 1 comprising performing said solid
state deforming at a deformation ratio of at least 4.
17. An extrusion rolling die for carrying out the method of
claim 1 and having a periphery for producing high modulus products
having a crystalline melting point, comprising: a pair of rota-
table rollers providing a rage of rotation having an input side
and an output side and die-providing exterior shapes forming the
convergent geometry of the die and confining the entire perimeter
of material extruded therethrough at a rate or extrusion of the
material and reducing the material overall cross-sectional area,
means for keeping said rollers at a temperature near but
below the crystalline melting point of the material to be
processed,
force-applying compression means for extruding the
polymer through said rollers, and
gear control means driven by the application of external
force for controlling the rate of rotation of the rollers so that

27 61968-725
the rate of extrusion of the material is substantially the same as
the rate of rotation of the rolling die surface.
18. The die of claim 17 having a supporting frame with a
distal end and wherein said control means comprises:
a chain-engaging pulley wheel rotatably mounted on said
distal end of said frame,
one said roller having a chain-engaging wheel rigidly
mounted thereon,
a gear train means for keeping the two said rollers at
identical rotational speeds,
a chain looped around said two wheels and
cable means attached at one end to said pulley wheel
adapted for attachment of its other end to the extrudate from said
die.
19. The die of claim 18 wherein said cable means is attached
to said extrudate by a clamping block attached to said cable
means.
20. The die of claim 17 having material feed means at the
input side of said rollers.
21. The die of claim 17 having a circular periphery and a
mandrel going centrally between said rollers said mandrel having a
conical portion with an enlarged circular cross-sectional area on
the output side of the die for feeding a tube and enlarging its
diameter and simultaneously thinning the tube walls.

28 61968-725
22. The die of claim 21, having a second pair of rotatable
rollers around the enlarged-diameter portion of said mandrel, said
control means being connected there to maintain said rates of
extrusion and rotation at equal speeds.
23. The die of claim 20 having air heating means with a
heated-air outlet adjacent to said material feed means for
preheating said material before extrusion.
24. The die of claims 20, wherein said material feed means
comprises a hydraulic piston.
25. The die of claim 20 wherein said material feed means has
parallel side walls.
26. The die of claim 20 wherein said material feed means has
converging parallel side walls.
27. The die of claim 17 wherein the contained convergent
geometry of the input side of the die has an exponentially shaped
profile.
28. The die of claim 17 having liquid heating means,
circulation means in said rollers for circulating heated liquid
through said rollers, and means connecting said heating means to
said circulation means.

29 61968-725
29. The die of claim 28 also having air heating means with
air outlet for heated air adjacent said rollers.
30. The die claim 17 having powder compacting means on the
input side of said die.
31. The die of claim 17 wherein the rollers are provided
with their exterior shape by separate sleeves mounted on the
rollers and having the desired exterior shapes.
32. The die of claim 17 wherein said force applying means
comprises means to apply force sufficient to achieve a deformation
ratio of at least 4.

Description

I 307~89
1 61968-725
PROCESS FOR OBTAINING ULTRA-HIGH MODULUS PRODUCTS
SPECIFICATION
leld of Invention
Thls lnvention relates to a solid-state deformation
process and apparatus ~or achievlng the productlon of ultra-high
modulus polymers of both simple and comple~ shapes, at rapld out-
put rates and under moderate processlng condltions.
Back~round of the Invention
The development of ultra-hi~h modulus polymers has been
pursued in many academic and lndustrial laboratorles by the pre-
paratlon of anlsotropic polymer morpholo~ies of highly oriented
and extended molecular chains.
It has ~een known for a long tlme that the theoretlcal
tensile modulus of a polymer should approach the modulus of steel
(~208 GPa). However, untll a decade ago, the theoretlcal calcu-
lations (for polyethylene ~240 GPa) were consldered unllkely to be
~chieved, because all known polymers had modull two orders of mag-
nitude lower. The reason ~or such a low modulus was that the
; polymer assumed a random entangled and twlsted conflguratlon whlch
had a low load bearlng capaclty. In recent years, lt was reallzed
that the greatest modulus and strength would result from an aniso-
tropic structure of hlghly oriented, extended, and densely packed
; chalns. Indeed, some polymers, ~or example polybenzamlde and

I 3 () ~
-- 2 --
1 polyethylene, have been processed into fibers that exhibit
2 moduli of 100 - 200 GPa, thereby indicating that the
3 earlier theoretical values can be approachedO
4 The development of ultra-high modulus products is
S of paramount importance in view of their significantly
6 lower density; for example, steel is about eight times
7 more dense than polyethylene. The term "specific modulus~
8 refers to the quotient of modulus divided by density;
g therefor the specific modulus of polyethylene ultra-high
10 modulus fibers is significantly higher than the specific
11 modulus of steel.
12 Conventional flexible chain polymers, e.g.,
13 polyethylene have been processed into high modulus
~ products by processes that may cause a permanent
lS deformation of the internal structure, namely, the
16 conversion of an initially isotropic and spherulitic
17 structure to a fibrillar structure. The fibrils are made
18 of oriented and extended molecular chains which ensure
19 mechanical connection between crystals and load transfer.
Thus, it can be realized that, for maximum
21 mechanical performance, all polymer cha;ns should be
22 extended along the deformation direction. Thus macroscopic
23 deformation, which involves molecular deformation and is
24 accompanied by drastic dimensional changes in the case of
flexible polymers, should not be confused with the shaping
26 processes which in general are also accompanied by
~7 dimensional changes but do not involve the transformations
28 f a spherulitic to a fibrillar morphology, which, in the
2g-case of high density polyethylene, takes place at a
deformation ratio of approximately 4. Nor should
31 macroscopic deformation be confused with the conventional
32 melt extrusion process which may involve some molecular
33 orientation. Indeed, during any melt processing operation
34 some molecular orientation is bound t.o occur because of
the viscoelastic nature of polymeric materials. ~owever,
6 the fraction of extended chains is exceedingly small, too
37 small to result in high modulus/strength performance.
38

I ~0/~89
_ 3 _
1 Furthermore, the macroscopic deformation described
2 in this specification is not confined, as to deformation
3 limits, to the natural draw o~ a particular polymer, for
4 such limits can be overcome by the process of the present
5 invention.
6 Shaping processes such as calendering or rolling
7 are small deformation processes which do not result in
8 morphological transformation necessary for the ultra-high
g modulus and strength performance and almost unequivocally
10 involve biaxial flow, i.e., deformation in both the
11 longitudinal ~machine) and the transverse direction.
12 Rolling combined with stretching may result in uniaxially
13 deformed polymer structures with significantly enhanced
14 tensile properties. However, this technology is confined
to the processing of thin sheets and i5 limited by the
16 excessive loads involved to offset the counter-force and
17 the friction between the roll and the polymer surface.
~8 Anisotropic polymer morphologies with ultrahigh
19 modulus and strength have been obtained by processing
20 conventional flexible chain polymers by solid state
~1 deformation using the extrusion and drawing techniques, by
~2 extrusion of supercooled melts and by drawing from gels
23 and dilute flowing solutions.
24 Various semicrystalline polymers have been
studied. High-density polyethylene has been studied the
26 most because of its simple composition and its high
theoretical modulus (approximately 240 GPa). Similar
28 anisotropic morphologies have been obtained by the
29 chemical construction of polymers with rigid and semirigid
backbone chains by introducing para-substituted aromatic
31 units and then processing with solution and melt
. ~
32 processes. The para-benzamide polymers and the
33 copolyesters of poly(ethylene terephthalate) and
p acetoxybenzoic acid are examples of riyid and semi-rigid
poIymers sought to be processed into ultra-high modulus
36 products, i.e., products in which the molecules are not
; 37 only oriented but are also extended.
~ 38

3 ~ ~
1 Typically, the ultra-high modulus products from
2 the above processes have been in the form of fibers and
3 thin films, that is, structures which ~o not have bulk
4 mechanical properties. Two recent developments of
5 ultra-high modulus products with bulk structure have been
6 obtained by injection molding of high density polyethylene
7 and the copolyester of poly(ethyleneterephthalate) and
8 P 8cetoxybenzoic acid.
9 The solid-state extrusion process has also been
investigated for i~s potential use for ~he production of
11 ultra-high modulus products with bulk structure, but it
12 has been severely restricted by low processing rates (a
13 few centimeters per minute), for it is a solid-state
14 deformation process throuyh a convergent geometry. It has
also required very high extrusion pressures, especially
16 for the preparation of products with complex or large
17 cross-sectional areas. An analysis of the extrusion
18 process shows that a high extrusion pressure is required
19 a~ to shear and elongate the polymer and b) to overcome
20 the die polymer friction. Equation (1) shows the pressure
21 balance in the solid-state extrusion process through a
22 Conical die:
23
24 PE * e (Bo )PO = e (Bo ) [orEoa()d + ~ (o ) 4 S (o ,a) ] (1
~6 where PE is the pressure of extrusion,
27 Po is the pressure at the die exit,
28 B is ~cot [a],
29 ~ ~ is the friction coefficient,
a ls the die half angle,
31 is the strain,
~ ~ . .
32 ~o is the strain at the exit of the die,
33 ~) iS the true stress at strain ,
34 S is the work of shear and shear yield at
strain o and die angle a.
36
37
38

I ~(J1~3~9
-- 5
1 Equation (1) indicates that the friction
2 coefficient term B is significant and that extrusion
3 pressure increases with increasing Eriction.
5 Summary of the Invention
6 The invention comprises a method for producing
7 high modulus products and includes solid-state deforming a
8 polymer morphQlogy under pressure through the convergent
9 geometry of the rollers of an extrusion rolling die in
10 which the polymer is confined over the entire perimeter by
11 the moving surface of the die during the deformation
12 process. This is done, at a temperature near but below its
13 crystalline melting point, while controlling the ex~rusion
14 rate and the rate of rotation of the rollers so that the
15 rate of extrusion of the polymer is substantially the same
16 as the rate o rotation of the rolling die surface. This
17 is not a two-stage process with an extrusion and then a
18 rolling. The extrusion-rolling die used in this invention
19 is a one piece apparatus in which the polymer is extruded,
20 not rolled, through the simple or complex conduit
2~ ~eometry The process is to be contrasted with
~2 conventional calendering or rolling, in which lateral
23 deformation perpendicular to ~he machine direotion may
~4 occur. In the present invention no lateral deformation is
2S permitted.
26 The invention also includes an extrusion rolling
27 die for producing high modulus polymer products. This
28 apparatus comprises a pair of rotatable rollers which are
g-kept at a temperature near but below the crystalline
30 melting point of the polymer to be processed. There are
31 foxce-applying means for applying extrusion pressure to
2 the feed zone of the rollers and control mea~s for
33 controlling the rate of rotation of the rollers so that
the rate of extrusion of the polymer is substantially the
same as the rate of rotation of the rolling die surface.
36
37
38
:

1 307~3~9
~a 61968-725
According to one aspect of the present invention therP
is provided a method for producing high-modulus semic.rystalline
polymer products comprisiny:
solid-state e2truding a polymer having an initial polymer
morphology by ~eeing under pressure through an
extrusion-rota~ion die having a static entry position
and a succeeding friction-reducing moving portion, said
succeeding friction-reducing moving portion of said die
comprising a pair of opposi~ely rota~ing members, each
having integral shaped wall surfaces strictly confining,
engaglng and compressing the entire perimeter of the
polymer durin~ extrusion and providing the geometry of a
die exit and a profile for extrudate which has
practically the same cross-sectional area and lateral
dimensions as the cross-sectional area and lateral
dimensions of the die exit said static and succeeding
friction~reducing moving portions of the die having a
; polymer-containlny zone with convergent yeometry through
which the polymer is compressed orlented and extruded
under conditions of minimal friction between the polymer
and the die surface for reducing the extrusion pressure,
said minimal frictlon being obtained by substantially
synchronous movement of the rotating members of the die
- and the polymer, said extrusion being at a temperature
near but below the crystalline melting point of said
polymer, to obtain an extruded polymer product having a
markeflly transformed morphology as compared with ~aid
initial polymer morphology comprised of oriented and
, _:

1 ~07~9
5b 61968-725
extended molecular chains and markedly enhanced tenslle
propertles, the values of which are for the Young's
modulus wlthln the range of 2 to 220 GPa and for the
tensile strength wlthln the range of .015-4 GPa, and
whlch depend upon the extent of the cross-sectlonal area
reduction durln~ extruslon.
Accordlng to a further aspect of the present ln~ention
there is provide~, an extrusion rolllng dle ~or carrylng out the
above method and ha~lng a periphery for produclng hlyh modulus
products having a crystalllne meltlng point, comprlslng: a pair of
rotatable rollers providlng a rage of rotatlon having an input
side and an output s1de and die-provldlng exterior shapes forming
the convergent geometry of the dle and confinln~ the entlre
perimeter of material extruded therethrough at a rate or e~truslon
of the material and reducing the material overall cross-ssctlonal
area,
means for keeplng said rollers at a temperature near ~ut
below the crystalline melting polnt of the materlal to be
processed,
force-applying compresslon me ns for extruding the
pol~mer through sald rollers, and
gear control means driven by the appllcatlon of e~ternal
force fQr controlling the rate of rotatlon of the rollers so that
the rate o~ extruslon of the material is substantlally the same as
the rate o~ rotation of the rolllng ~1e ~ur~ace.
;
~ ,.

3 ~ 9
-- 6 --
1 In accordance with the present invention, a high
2 modulus product such as a high density polyethylene i5
3 produced by a solid-state deformation technique at rapid
4 output rates and in shapes of different complexity. Such a
5 high modulus is produced by deforming the polymer
6 preferably near to, bu~ below i~s crystalline melting
7 point through an extrusion rolling die.
8 The extrusion rolling die ic a key feature in
9 this invention and is composed of a feed zone reservoir
10 adjacent to a set of master rollers on which cylindrical
11 sleeYes of different diameters and~or shapes can be
12 mounted to result in converging geometries of different
13 configurations with moving wall elements. This type of die
14 design is distinctly different from the dies used in solid
15 state extrusion and the die-or-zone-drawing processes
16 which are static and use converging conical or tapered
17 slit dies with no moving wall elements.
18 The extrusion rolling die of this invention has
19 an exponential profile or trumpet shape and therefore has
20 the advantage of trumpet-shape dies for extrusion at lower
21 strains, and consequently it results in lower extrusion
22 pressures since the pressure increases with the strain and
23 the strain drops rapidly with die-half angle. According to
2~ this invention the motion of the roller elements of the
~5 extrusion rolling die and the polymer between them is
26 substantially synchronous a~d thus may result in a process
27 in which the friction between the polymer and the die
28 8urface is minimiæed and consequently the extrusion
29 pressure is reduced. The kind of synchronous motion of the
~n rollers and the polymer under ex~rusion conditions may be
31 considered analogous to a substrate drawing process. This
32 can be demonstrated in a co-extrusion experiment wherein
tbe material to be deformed is sandwiched between two
substrate layers, and the entire structure is then
co-extruded through a convergent die geometry. In this
36 configuration, the material between the two substrates
(e.g., a polyethylene film between two polyethylene
3~
.
.

1 3()7~9
1 substrates) is deformed under compression and without
2 friction on the surrounding substra~es, as lony as the
3 extrusion rates of the substrates and the material in the
4 middle are the same. An additional advantage of the
5 reduction of friction between the polymer die surfaces by
6 the synchronous motion of the rollers and the polymer, is
7 that the polymer is deformed under elongational flow
8 conditions in comparison to the shear flow conditions
g which prevail in conventional solid state extrusion. I~
10 has been suggested ~hat elongation flow is beneficial for
11 the achievement of ~ltra-high modulus products.
12 Also, the extrusion rolling process is different
13 from the calendering process which is typically a shaping
14 process between parallel rollers and is accompanied by
15 dimensional changes in two directions. The designing of
16 convergin~ geometries between the roller elements of the
17 extrusion rolling die in this invention imposes lateral
18 constraints during extrusion and results in uniaxially
19 drawn products.
The invention applies to the manufacture of
21 various shapes, including tubes.
22 The method applies to semicrystalline polymers and
23 thermotropic aromatic copolyesters.
24 Suitable semicrystalline polymers include
25 polyethylene, polypropylene, polyamides, polyoxymethylene,
26 poly(ethylene terephthalate), poly(vinylidene fluoride)
27 and polymethylpentene. Suitable thermotropic aromatic
28 copolyesters include
32 t o ~ ~ C ~ -C ~ R
33
34 where
3S
36
37

7~89
-- 8
3 0
4 R i s --O~C--, --o~ , or
6 0
9 --0~0--
ll (2)
12
~C~C~O~Il~O ~ R--0
16 where
9 F< is ~ ~ ~, or
~1
22
~3 (3)
24
~5 0 01
26 ~C ~c--CH2CH2~C~O~
28
29 :: (4)
31 O O O
36
37
38
~ ~:

`` I 307~8~
1 Brief Description of the Drawings
2 Fig~ l is a simplified and somewhat diagrammatic
3 isometric view in section of an extrusion rolling die
4 with a preceding feed zone reservoir, for use in an
S embodiment of the invention.
7 Fig. 2 is a similar view of a modifie~ form of die
8 and feed zone reservoir.
Fig. 3 is a fragmentary isometric vie~ of an
11 extrusion rolling die, showing one shape usable in
12 practicing the invention.
13
14 Fig. 4 is a fragmentary end view in perspective of
15 the shape of the polymer extruded from the die of Fig. 3.
16
17 Fig. 5 is a view like Fig. 3 showing a die of a
18 different shape.
19
Fig. 6 is a view like Fig. 4 showing the shape of
~1 the polymer extruded from the die of Fig. 5.
22
23 Fig. 7 is a diagrammatic isometric view of still
2~ another extrusion rolling die usable in the present
invention producing a differently shaped polymer
26 extrusion.
27
~8 Fig. 8 is a diagrammatic view ;n side elevation
29 and in more detail of the die of FigO 7 and associated
apparatus, illustrating the use of botb extrusion pressure
31 on the input side o the die and a pulling load on the
32 output side of the die.
33
Fig. 9 is a view in elevation of ~he back plate
thereof.
36
37
38

1 307~q
- 10
1 Fig. 10 is a view in side elevation of the back
2 plate portion of the die.
4 Fig. 11 is a more complete isometric view of a
S rolling die like that of Fig. B incorporated into a
6 thermally insulated housing and provided with heaters.
8 Fig. 12 is a view in elevation and in section of a
g modified form of rolling die also embodying the principles
10 f this invention, which can be used in the apparatus of
11 Fig. 11 to replace the rolling die of Fig. 8.
12
13 Fig. 13 is a fragmentary view in sec~ion taken
14 along the line 13-13 in Fig. 12.
16 Fig. 14 is a view in elevation at right angles to
17 Fig. 12, showing one master roller and one cylindrical
18 s1eeVe thereon.
19
2~ Fig. 15 is a view like Fig. 12 of another modified
21 form of rolling die.
22
23 Fig. 16 is a fragmentary view in section taken
24 along the line 16-16 in Fig. 15.
26 Fig. 17 is a view like Fig. 14 of a portion of
27 Fig. 15.
28
29 Fig. 18 is a diagra~matic view showing two rolling
3~ dies of the invention in series.
31
32 Fig. 19 is a view in longitudinal section of a
device for converting thick-walled~ small-diameter tubes
of polymer to thinner-walled, larger-diameter tubes.
36
37
.,

1 .~ 0 1~8q
1 Fig. 20 is a view in cross section taken along the
2 line 20-20 in Fig. 19.
4 Fig. 21 is a view in cross section taken along the
5 line 21-21 in Fig. 19.
7 Fig. 22 is a diagrammatic view showing how the
8 tube resulting from Figs. 19 - 21 can ~e used to make a
9 polymer sheet~
11 Description of Some Preferred Embodiments of the Invention
12 As shown "in Fig. 1, an extrusion rolling die 20
13 may include a pair of master rollers 21 and 22 which
14 receive the polymer under pressure on their input side
15 from a feed zone 23 having parallel side walls 24 and 25,
16 a rear wall 26, and a front wall (not shown due to the
17 section).
18 Fig, 2 shows an alternative type of die 30 having
19 master rollers 31 and 32 receiving polymer under pressure
20 from a feed zone 33 having converging side walls 34 and
21 35, as well as a front wall (not shown) and a rear wall
22 36.
23 The master rollers may be shaped (or mounted with
24 cylindrical sleeves of different diameters) to give
products of any desired degree of complexity. For exa~ple,
26 the rollers 21 and 22 are shown in Fig. 3 as provided with
27 extrusion channels 27 and 28 that produce an extrud~te 29
~8 that is square in cross section, as shown in Fig. 4.
~9 On the other hand, the rollers 31 and 32 are shown
in Fig. 5 to have channels 37 and 38 that produce an
3.1 extrudate 39 (Fig. 6) which has a tee shape in cross
32 section.
Further, Fig. 7 shows a pair of master rollers 41
34 and 42 having extrusion channels 43 and 44 shaped to
produce an extrudate 45 that has the cross-sectional shape
36 f an H.
37
38

I 307~9
-- ]2 -
1 Thus the roller (or cylindrical sleeves on them as
2 in FigO 11 et seq) can form converging dies of different
3 geometries through which a polymer can be deformed in
4 different shapes and in dif~erent sizes. The rollers of
5 each of these extrusion dies act to confine the material
6 within them, no movement widthwise is permitted. The
7 rollers may be viewed as the convergent landing surfaces
8 of the die, even through these landings surface can move
g synchronously with the solid polymer and do so in order to
10 minimize friction.
lL As shown in Figs. 10 and 11 and described below,
12 the rollers 41 and 42 can be heated over a wide range of
13 temperature conditions so that the polymer can be deformed
1~ at a temperature preferably near to but below its melting
15 point.
16 The extent of deformation is determined by the
17 deformation ratio, which is defined as the ratio of the
18 cro6s-sectional area of the entrance of ~he feed zone to
19 the sross-sectional area of the product extrudate. To
20 achieve the transformation from a spherulitic to a
~1 fibrillar morphology, a deformation ratio of at least 4 is
22 required for polyethylene.
23 The polymer can be deformed by ~his process either
24 under extrusion pressure alone ~Figs. 1-6), or a combined
25 extrusion pressure and a pulling load on the emerging
26 extrudate, as shown in Figs. 7-10. In Fig. 8, the rollers
27 41 and 42 are preceeded by a feeding zone 46 filled with
28 polymer 47, against which a hydraulic piston 48 acts to
29 provide extrusion pre~sure Simultaneously the extrudate
45 is attached to a clamping block 50 to which a pulling
31 load is ~tt^ached by a pulley wheel 51 and a wire or cable
32 52, which winds around the wheel 51. A continuous chain 53
33 links the wheel 51 and its pulling cable 52 to a pulley
34 portion 54 on the roller 41, so that the angular velocity
of the rollers 41 and 42 and the speeds of pulling and
36 extrusion are coordinated. The rollers 41 and 42 are
supported by a frame 55. ~hus, the deformation process can
38
.

1 3 ) 7 ~ 8 9
- 13 -
1 occur under conditions of minimum friction. This is
2 another key feature of this invention and can be achieved
3 by adjusting the angular velocity of the rollers 41 and
4 42, the throughput rate, and/or the pulling rate on the
5 emerging extrudate 45, so that the polymer and the rolling
6 die surface move at the same velocity.
7 As shown in Figs. 9 and 10, the two rollers 41 and
8 42 are ~eared together near a back plate 56 of the frame
9 55 The back plate 56 supports the rollers 41 and 42, on
10 which ~ears ~7 and 58 are mounted coaxially with the
11 rollers 41 and 42. Two other gears 60 and 61 are meshed
12 together, the gear 60 being in mesh with the gears 57 and
13 61 and the gear 61 being in mesh with the gear 58, so that
14 the two rollers 41 and 42 rotate at exactly the same
15 an9Ular velocity~
16 Figs. 9 and 10 also show rotary conduits 66 and 67
17 in the rollers 41 and 42 are joined by conduits 71 and 72
18 and rotary unions 68 and 69 (see Fig. 11) to a
19 temperature-controlled oil bath 70 having a heater ~not
20 shown). Thus, as shown in Figs. 10 the processing
21 temperature may be attained by circulating hot oil through
22 the master rollers 41 and 42 from a hot silicone oil bath
23 70, thermostated at the desired temperature.
24 Fig. 11 shows a slightly different configuration.
25 The rollers 41 and 42 are again provided with conduits 66
~6 and 67 leading to rotary unions 68 and 59, which are
27 connected to a hot oil bath 70 by conduits 71 and 72.
28 Here, the rollers 41 and 42 are also shown inside a
29 chamber 73 comprising thermal insulation 74 on all side~
and provided at the bottom with hot air blowers 75 and 76
31 to supplement the hot oil bath by air convection in the
32 thermally insulated chamber 73 surrounding the rolling die
33 40, and supply additional heat~ although either heat
source could be used alone. Also the heating may be partly
obtained by preheating the polymer stock in a reservoir 77
36
37
38

1 307~89
- 14 -
1 with electrical band heaters 78 mounted around the
2 reservoir 77 and at the entrance of the 2xtrusion rolling
3 die 40.
4 The solid state deformation through extrusion
S rolling dies can be used with various semicrystalline
6 polymers such as polypropylene and polyamides to obtain
7 also products with enhanced bulk properties, --not ]ust
8 thir. films as have ~een produced by rolling combined with
9 stretching, or fibers, which are obtained by
1~ fiber-spinning operations. This has been demonstratea by
11 the preparation of high~density polyethylene extrudates
12 with circular and square cross sections at different
13 deformation ratios~
14 ~igs. 12-14 show an alternative structure of a
15 rolling die 80. ~ere, there are master rollers 81 and 82,
16 whiCh are cylindrical and preferably hollow for
17 circulation of heated liquid within them. Instead of being
18 directly machined, the master rollers 81 and 82 are
19 splined to respective cylindrical sleeves 83 and 84, each
20 having a semicircular outer periphery 85 as seen in cross-
21 section ~Fig. 14). The sleeves 83 and 84 may be replaced,
2~ as shown in Figs. 15-17 with otherwise shaped sleeves,
~3 such as sleeves 86 and 87 having a rectangular
24 CrOSS-8eCtional shape.
The feeding apparatus in Figs. 1~ and 13 comprises
26 a cylindrical tube 90 with an inner circular cylindrical
27 passage 91 and an exterior circular flange 92. A fitting
28 93 is cylindrical with a bottom, inwardly extendlng ~lange
94 and an interior thread 95 (Fig. 12), into which is
threaded the exterior thread 96 of a conduit 97.
1 The feeding apparatus of Figs. 15 and 16 is
32 similar except that it has a tube 100 with an exterior
33 flange 101 and an interior passage having a lower square
portion 102 and an upper conical portion 103.
In a typical experiment, an extrusion rolling die
6 generally like that shown in Figs. 7~10 incorporated a
series of juxtaposed cylindrical sleeves of different
38
` :

1 3078~9
diameters and widths, as shown in Figs. 12-17, to result
2 in both circular and square cavities between the rollers
3 of progressively smaller cross sectional areas. These
4 circular and square cavities between the rollers part of
5 the ex~rusion die are in sharp contrast to the open-ended
slit be~ween conventional rollers. It is important to note
7 that in the present invention the polymer is completely
8 confined widthwise. The slee-~es on the master rollers were
~ heated to 125-130C. by convection in a thermally
10 insulated chamber. Preformed samples having circular or
11 square cross-section, according to which cavities they
12 were to be fed, were placed into the die, and after
13 thermal equilibration, each sample was pulled through the
14 die by a pulling load. Minimum friction requirements were
15 met by synchronizing the rate o~ the pulling load and the
16 rotation of the rollers using the pulley system and gears
17 in Figures 8 to 10. To commence the extrusion through the
18 extrusion rolling die, the end of the initial stock was
19 trimmed to an area slightly smaller than the
20 cross sectional area between the rollers so that it could
21 be fed through the rollers section of the die and gripped
22 by the clamping block 50 as in Fig. 8.
23 Transparent extrudates of deformation ratio 12
24 were obtained by applying a pulling load of 25 MPa.
Additional compaction and drawing can be obtained
26 by use of a plurality or series of rolling dies, as shown
27 in Fig. 18, where rolling dies 110 and 111 are in series
28 and the polymer 112 is first subjected to the die 110 and
29 its extrudate 113 is then subjected to the die 111 to
produce an extrudate 114.
31 In another set of experiments, polyethylene was
2 extruded under the combined effects of an extrusion
33 pressure and a pulling load. The polyethylene was
34 crystallized in a reservoir, and, a~ter reaching thermal
equilibration at 130C. was extruded initially through a
6 straight conical die (a-20) of deformation ratio 2 and
37 under an extrusion pressure of less than 50 Mæa. The
38

1 30788~
- 16 -
1 straight conical die was in close proximity to the
2 extrusion rollers, to serve as the feed zone 46 of the
3 extrusiOn rolling die shown in Fig. 8. The emerging
4 extrudate 45 from the straight conical die was pulled
5 through the extrusion rollers by adjusting the rate of
6 pulling and the rotation of the rollers 41 and 42 to
7 meet the minimum friction requirements as described
8 previously.
9 In an independent experiment, when an attempt was
10 made to pull a polyethylene sample between two freely
11 rotating rolls to a draw ratio of >10, the polymer slipped
12 on the rolls and deformed by a necking process similar to
13 a drawing process or to what is encountered in a simple
14 tensile test. The situation can be aggravated when the
15 cross-sectional area of the initial stock polymer is
16 large.
17 The extrudates under both conditions of
18 experimentation were transparent. Transparency of such
19 extruded samples arises from an increase in crystal size
20 and concentration and, most importantly, from the
21 crystalline orientation and the dense packing of ~he
22 polymer chains which are produced by extruding through a
23 contained geo~etry under the compression conditions in the
24 extrusion rolling die. When the pulling rate on the
25 emerging extrudate is higher than the rate of extrusion
~6 rollers, post necking may occur beyond the exit of the die
27 and result in translucent extrudates. Such loss of
28 transparency is associated with the formation of voids
29 during the drawing process and beyond the die exit; these
30 are known to occur in conventional solid-state drawing of
31 high-density polyethylene. The variation of output speed
32 with the pulling load and an extrusion pressure of 5-10
33 MPa is summarized in Table 1. The deformation ratios, the
34 Young's modulus and the tensile strength of the extrudates
35 are included also.
3~
37

1 307~89
17 61968-725
TA~L~ I
Pulling Load Output Speed Defol^matlon Young's Tenslle
Ratios Modulus Strength
(MPa)_Im/min) _ _ (GPa) (MPa)
4.4 2 5 2.5 1~0
10.6 2 8 5 260
16 2-3 10 8 260
24 3-5 12 10 320
Yet, in another experiment, a melt crystalllzed mor-
pholoqy of ultra-high molecular welght polyethylene, i.e., a poly-
ethylene with molecular weight of ~ 2 - 8x106, has been e~trudo-
rolled into ribbon and rod products of DR 5-8 wlth a Young's modu-
lus o~,10 GPa and tenslle strength of 0.25 GPa. UHMWPE ln con-
trast to the conventlonal hlgh density polyethylenes havlng mole-
cular welghts of up to 400, 000 ls lntrac~able. The polymer is
supplied as flne powder and ls processed lnto varlous pro~lles
uslng compresslon moldln~ and ram extruslon, whlch are known to be
slow processes. Furthermore, when the ram extruslon process was
used, solid state to extrude the UHMWPE and obtain a product of
DR~J5, an extrusion pressure as hlgh as 300 MPa was required, and
it resulted in unstable extruslon.
Thls lnventlon lncludes within its scope the processing
of melt-crystallized powder and gel morphologies of semi-
crystalllne polymers; also the processing of thermotroplc aromatlc
copolyesters. Polymer powders may be loaded lnto the feed reser-
~ voir and pre~compacted or compacted durlng the deformation process
;; under the combined effects o~ extruslon pressure and a pulling
load through the extrusion rolllng die as shown in Fig. 8. The

I 307~c~9
].7a 61968-725
polymer powder ls never used by thermal treatment above the melt-
ing polnt of the polymer. The powder is compacted ~elow thls
meltlng polnt Tm and ls also solid-state deformed below Tm, ln
contrast to efforts to fuse the
'

1 307~9
polymer powder. If, for example, a single crystal
2 morphology of polyethylene powder were to be heated to the
3 melting point of the polymer, it would transform to a
4 non-single crystal morphology. In the present invention~
5 one must stay always below the melting point of the
6 p1ymer.
7 Polymer powder morphologies exhibit high
8 deformability in comp2rison to melt-crystallized
~ morphologies. This has been shown to be associated with
10 the lack of molecular network between the powder particles
11 and the type of the powder morphology. Thus, ultra-high
12 molecular wei~ht polyethylene powders have been compacted
13 and extruaed to a 3-5 times higher draw ratio in
14 comparison to the maximum draw ratio achieved by extruding
a melt-crystallized morphology. For example, a
16 solution-grown ultra-high-molecular-weight polyethylene
17 has been deformed by this invention to a draw ratio of
1~ about 50 it then had a Youngls modulus of 40 GPa and a
19 tensile strength of 0.6 GPaO Yet the single crystal
20 morphologies O~ the ultra-high molecular weight
21 polyethylene have been compacted and drawn to an even 30
22 times higher draw ratio by a multistep extrusion-drawing
23 process. Such morphologies can be deformed to a draw of
24 ~ 150 and have a Young's modulus of ~00 GPa and a tensile
strength of 3~5 - ~ GPa. These values are one order of
26 magnitude higher than the values of polyethylenes drawn to
~7 the "natural" draw ratio. Similarly, polymer morphologies
28 prepared ~rom gels may be loaded into the feed reservoir
29; and deformed through the extrusion rolling die. Polymer
morphologies prepared from gels have high deformability
31 because o~ the reduced physical entanglements in their
32 molecular network and can be drawn to a lO times higher
33 dra~ ratio in comparison to the melt-crystallized
morphologies, and they have a Young's modulus value of
lO0 GPa and a tensile strength of 3 GPa.
36
37
38

1 30788q
19 61968-725
Table II below summarlzes the mechanlcal propertles of
solid state deforme~ ultra-high molecular welght polyethylene
(UHMWPE) from different morphologles.
TABL~ II
Young's Tensile
Modulus Strength
UHMWPE Draw Ratio (GPa) (GPa~
Melt cry~tallized 5 - 8 10 - 15 0.15 - O. 25
Compound powder of
single crystal
at 90C. 200 - 300 200 - 220 3.5 - 4
Crystall lne
morphology from
gel precursor 40 - 50 100 - 120 2 - 4
A modiflcation of the extruslon dle descrlbed above can
be u~ed for obtaining tubular products biaxlally or unlaxlally de-
form~d ln the hoop dlrectlon. Figures 19 - 21 show a schematic
representatlon of such a die modlf lcat ion which ls comprlsed of Q
cyllndrical mandrel 120 with dlameter dl whlch is connected to a
cyllndrlcal mandrel 121 of l~rger dlameter d2, vla an inverted
conlcal re~ion 122, and extrusion rollers 123 and 124, which pro-
vide a con~ined clrcular passage around the mandrel 120 to obtaln
; the clesired tubular proflles. Wh~n a polymer tubular stock 125 is
fed on the mandrel 121, lt is drlven by rollers 123 on the invert-
ed conlcal mandrel section 122. An e~panded tube 126 i9 obtalned~
: the tube 126 is deformed in the clrcumferential (hoop) direction.
The extent of deformation, the deformatlon ratlo, can be calcu-
lated from the ratlo of the diameters of the mandrels 120 and 121
at the exit and the entrance of the dle d-
dl

1 ~()188q
- 20 -
1 If ten5ion is applied on the so expanded tubel a biaxially
2 deformed product may result. The tension can be applied by
3 a pulling load of the rollers 123 and 124 or an additional
4 set of ~pulling" rollers 127 and 128 may be used to
5 provide a confining circular passage around the larger
6 diameter mandrel 121, their rotational speed being higher
7 than that o~ the rollers 123 and 124.
~ In a typical experiment with ultra high ~olecular
g wei~ht polyethylene (UHMWPE), (Mw ~ 2 x 106), a preformed
1~ tubular stock with internal diameter 0.95 cm heated at
11 180C. was placed on the mandrel 120 having diameter
12 dl = 0.95 cm preheated to 180C. (While this may seem to
13 be a high temperature for polyethylene, U~MWPE does not
14 melt-flow at this temperature.) It was driven on the
15 expanding section of the mandrel 120 by the rollers 123
16 and 124 to the larger diameter (d2 = 2O54 cm) mandrel 121,
17 where it was cooled to below 120C. and retrieved. The
18 expanded UHMWPE tubular product 126 was thus stretched in
19 the hoop direction by ~2.7x. When such a laterally
stretched tube 126 was reheated to 160C. it shrank to
21 practically its original dirnensions, thus exhibiting
22 remarkable elasticity. With this particular polymer,
23 UHMWPE, higher temperatures than 180C. can be used for
24 its deformation using this methodology that extend well
beyond 200C. as descr;bed in U.S. Patent No~ 4,587,163.
26 Like the uniaxially drawn UHMWPE rods which can be
27 obtained using the extrusion-rolling die device in Figure
28 1 or 2, the laterally drawn UHMWPE tubes 126 obtained
2g using the modified device in Figures 19 - 21 exhibit
enhanced tensile properties in the lateral direction. For
31 example, the Figs 19 - 21 drawn UHMWPE tubes 126 exhibit
3~ in ~he hoop direction a Youn~'s modulus of ~2.0 GPa and a
33 tensile strength~150 MPa, in comparison to the Young's
34 modulus of 0.6-1 GPa and tensile strength of ~40 MPa for
the isotropic UHMWPE.
36
37
38

1 301~3~9
- 21 -
1 A tubular product 126 drawn only in the lateral
2 direction using this processing methodology can be split
3 along a line 130 in the machine direction into a flat
4 sheet 131 which in a subsequent process can be stretched
5 uniaxially by pulling or rolling to a biaxially drawn
6 sheet. This is of advantage in comparison with the
7 conventional rolling process in which a biaxially
~ stretched film or sheet must be rolled first in one
g direction, then turned by gO and rolled again.
This invention includes within its scope the
11 processing of semicrystalline polymers such as
12 polypropylene, nylons (polyamides)l polyoxymethylene,
13 poly(ethylene terephthalate), poly(vinylidene fluoride)
14 and polymethylpentene, which are known to be deformable in
the solid state and which give products of high stiffness.
16 In the case of the rigid or semirigid polymers, polymers
17 within the scope of this invention are the thermotropic
18 aromatic copolyesters which may be processed at a
19 temperature above the glass transition of the polymer and
within a range near and preferably below the
21 solid-to-mesophase transition temperatuxe of the polymer.
22 The device is also useful Eor processing metal
23 powder particles into thin metal profiles. Such metals as
24 aluminum, titanium, and alloys and fiber-reinforced
aluminum composite materials can be treated in this way.
26 In this case, the straight or conical part of the
27 extrusion-rolling die serves as the feed zone of the die
28 device, and the rolling part serves for the compaction and
29 deformation of the metal powder particles.
Outstanding points of the processing in this
31 invention are
32 1. It operates under moderate conditions at rapid
output rates.
34 2~ It operates under conditions of minimum
friction.
36 3. It produces high modulus polymers of both
37 simple and complex geometrical configurations.
38

1 3()7~9
- 2~ ~
1 4. It is a continuous process.
2 5~ It is adaptable to commercially available
3 polymer processesO
4 To those skilled in the art to which this
invention relates, many changes in construction and widely
6 differing embodiments and applications oE the invention
7 will suggest themselves without depart;ng from the spirit
8 and scope of the inventionO The disclosures and the
g descriptions herein are purely illustrative and are not
intended to be in any sense limiting.
11 What is claimed ;s:
12
13
14
16
17
18
19
21
22
23
24
27
28
29
31
32
33
34
37
38

Dessin représentatif