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Патент USA US2412187

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. 3, 1946.
Filed Aug. 17, 1945
4 Sheets-Sheet 1
In we n 3071;
M7320 792C236
Dec. _3_, 1946.
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. 2,412,187
Filed Aug. 17, 1945
-4 Sheets-Sheet 2
Dec. 3, 1946.
Filed Aug. 17, 1945.
4 Sheets-Sheet 5
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Dec. 3, 1946.
4 Sheets-Sheet 4
Filed Aug. 17, 1945
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Fred E. Wiley, Hartford, Robert W. Can?eld,
West Hartford, Raymond S. Jesionowski, Hart-
ford, ‘and James Bailey, West Hartford, Conn.,
assignors to Plax Corporation, Hartford, Conn.,
a corporation of Delaware
Application August 17, 1943, Serial No. 498,970
8 Claims.’ (Cl. 18-12)
This invention relates to the production of
continuous sheet of biaxially oriented organic
polymer and has particular relation to the pro
duction of such sheet by heating and extruding
such polymer in the form of a ribbon and draw
ing the ribbon longitudinally and transversely
to form the oriented sheet in the desired width
‘and thickness.
It is well known that the strength of certain
organic polymers, such as synthetic long chain
or straight chain polymers, may be substantially
of prior processes and apparatus may largely or
entirely be overcome and biaxially oriented sheet,
having the desired transverse and longitudinal
orientation and the desired thickness and width,
may be produced e?iciently and cheaply.
More speci?cally, it is an object of this inven
tion to provide a novel method and novel appa
ratus wherein and whereby a continuous ribbon
of organic polymer is extruded and is biaxially
oriented by drawing it ?rst in one direction only ‘
and then in the other direction, and each draw
increased by drawing so as to orient the mole
ing operation is performed under predetermined
devices may so cool the edges of the ribbon as
novel apparatus for ?rst longitudinally and then
to interfere further with longitudinal drawing
and orientation.
It also has been proposed to produce oriented
sheet by rolling a previously formed sheet while
in more or less plastic condition. But the rolling
method is very ine?icient because the polymer 40
ganic polymer in which means provided for
transversely drawing ribbon‘also serves to draw
the ribbon longitudinally.
Another object of the invention is to provide
conditions of temperature and application of
cules of the polymer in the direction or direc
stress so that the desired degree of orientation
tions in which the stress is applied. Examples
of such polymers are vinyl compounds or deriva 15 in each direction and the desired relative amounts
of orientation in the two directions are obtained
tives, such as polystyrene, vinyl chloride and
in the ?nished sheet. Thus, sheet may be pro
copolymers of or including such compounds or
duced which is of approximately equal strength
in both transverse and longitudinal directions
It has been proposed to form biaxially oriented ‘
sheet from an organic polymer by extruding a 20 and such strength is of high order.
Another object is to provide for unusually
ribbon of the polymer and simultaneously draw
rapid and e?icient continuous drawing of a rib
ing the ribbon in longitudinal and transverse
bon of organic polymer, more particularly trans
directions to orient the polymer. But simulta
verse drawing thereof to form a relatively wide
neous longitudinal and transverse drawing is
objectionable because the amount of resulting 25 sheet from a relatively narrow ribbon. This is
especially advantageous where, as in the pre
orientation in one direction is dependent upon,
ferred form of the present invention; the ribbon
and limited by, the amount of orientation in the
?rst is drawn in a longitudinal direction only
other direction and this may limit the amounts
because this makes the ribbon narrower and re
of orientation in both directions. Such limita
tions are due to the fact that the desired longi 30 quires an unusually large transverse drawing to
attain a high degree of transverse orientation
tudinal stretching is, prevented by the engage
and to form a relatively wide sheet.
ment of relatively ?xed transverse drawing de
A further object of the invention is to provide
vices with the edges of the ribbon. Also such
transversely drawing an extruded ribbon of or
a novel apparatus of the above type including
novel means for gripping and transversely draw
flows much more in the central portion of the
ing the organic polymer.
sheet in a longitudinal direction than it does at
Other objects and advantages of the invention
the edge portions and very little transverse ?ow
will be brought out in the following speci?cation
can occur between the rolls. In rolling, the
polymer cannot always be kept as soft as desired 45 or will be apparent therefrom or from the accom
panying drawings to which the speci?cation
because of sticking to the rolls. In general it
refers, which drawings depict one embodiment
_ maybe said that in rolling organic polymer to
of the novel apparatus for performing the novel
form oriented sheet control of orientation is very
process and in which:
difficult, if not impossible, both as regards the
temperature and viscosity of the polymer and 50 Figure 1 is a more or less diagrammatic view
in top plan on reduced scale of apparatus em
the application of stress.
bodying the invention and in which parts are
The general object, of this invention is to pro
broken away or omitted for clarity in illustra
vicig; a novel process and novel apparatus for
theh‘continuous production of biaxially oriented
Fig. 2 is a view in vertical sectional elevation
sheet whereby the objections and disadvantages 55
and in more or less diagrammatic form of the
apparatus shown in Fig. 1 from which some of
the parts shown in Fig. 1 are omitted and to
which some parts not shown in Fig. lare added;
Fig. 3 is a view in vertical transverse section 8
of a ribbon of non-uniform thickness and of»
heating means of Figs. 1 and 2 illustrating the, '
means of a chain "which engages sprockets on
the rolls, one of which is indicated at II, the
chain ll in turn being driven by a sprocket II
on a shaft II, Figs. 2 and 6', which shaft in turn
is driven by a chain 29 through reduction gear
ll. Reduction gear II is driven through a
variable speed drive, indicated at 32, Fig. 2, which
comprises stepped pulleys, pulley a on the re
Fig. 4 is a view similar to Fig. 3, illustrating
duction gear and pulley 34 on the shaft .8 driven
the heating of a diiferent form of ribbon from 10 from motor, SI, as hereinafter explained. See
heating of such ribbon;
that shown in Fig. 3;
Fig. 6. The speed at which the rolls 0 are driven
Fig. 6 is a view in horizontal sectional top plan
may be varied. by shifting the belt 320 on the a
on enlarged scale taken approximately on the
line 5-5 of ‘Fig. 6 and illustrating cam means by “
stepped pulleys, as will be understood. Any other
suitable“ variable speed drive may be used in
which transverse drawing of the. ribbon is con
16 place of drive 32.
The oven 0 encloses the ribbon from near
Fig. 6 is a view in vertical sectional elevation
where it is extruded from the die D to a point
on enlarged scale taken approximately on the
where the sheet may be exposed to the atmos
line 6-8 of Fig. 2 looking in the direction of the
phere, as shown for example in Fig. 2. The oven
20 0 not, only provides for control of the tempera
Fig. 7 is a view in top plan on further enlarged
ture of ‘the ribbon but also prevents drafts from
scale of one of the grippers or gripper units of
' coming into contact with the ribbon which might
the apparatus shown in Figs. 1 to _6;
chill the ribbon and interfere with the drawing‘
Fig. 8 is a view-partly in vertical section and
operations. The heater H may be of any known
partlyin side elevation of the gripper unit shown - 25 type and as shown is of the hollow plate type
in Fig. 7; and
having inlet and outlet pipes I'I‘and ‘38 for the
Fig. 9 is. a view in transverse vertical section
delivery and discharge of a suitable heating
taken approximately on the line 9-9 of Fig. 8.
medium such as oil.
Referring first to Figs. 1 and 2, it will be seen
As will be more fully explained hereinafter,
that the principal parts of the apparatus in 30 the heating of the portion RI of the ribbon by
clude a stuifer S for heating organic polymer
the heater H may be varied-transversely of the
and delivering it to and forcing it through an
ribbon by means of block ll, Figs. 1, 2 and 3, or
extrusion die D in the form of a flat ribbon R;
blocks 42 and 43, Fig. 4.
a group of rolls C, four of such rolls being shown.
The heater HI may be of the coil type com
over which the ribbon R passes; an oven 0 in 35 prising a plurality of coils 45 to which a heating
which the rolls 0 are mounted and in which the
medium such as oil is admitted' through a pipe
portion of the ribbon indicated at RI is drawn
46 and from which'the heating medium may be
longitudinally as hereinafter explained, the oven
taken on‘ through valve controlled take-oil's 41
- containing a heating plate H for regulating the
leading to the discharge pipe 48. By adjustment
temperature therein; a gripping and drawing 40 of the valves in the take-offs a longitudinal tem
mechanism indicated generally at G and com
perature gradient may be maintained over the
prising two endless series‘of opposed grippers g
sheet or the temperature of the space of the
for gripping the ribbon to draw it; and a pair
sheet may be maintained at a uniform or other
of puller rolls indicated at P for maintaining
desired temperature. ' The heater H2 may be an
longitudinal tension on the ribbon and sheet.
electric resistance heater of known type to which
As shown in Fig. 2, heating means HI is pro
current is supplied through connections indicated
vided in oven 0 above the‘ portion R2 of the
at 5 I. The heater H: as shown is of the gas type
ribbon where it is drawn transversely and an
in the form of a‘ burner which, as indicated in
other heating device indicated at H2 is located
Fig. 1, extends transversely below the ribbon near
in oven 0 above the ribbon to heat it in advance 50
of the heater HI. A third heating means is
provided at H3 below'the ribbon slightly in ad
vance of the heater H2.
the end of the heater Il-I.v
Considering'now the construction of the grip
ping and drawing mechanism G, it will be seen
that grippers g are arranged in the form of two
The stufl’er 8 may be of known construction
endless series which may be and as illustrated
and as shown comprises a cylinder ll contain 65 are supported and operated by conveyor means
ing a heating jacket I! for circulation of asuit
of identical ‘construction at both sides of the
able heating medium, such as oil, to heat. the
apparatus, that is, at opposite edges of theri'b
organic polymer in the stuiler to the desired tem
bon or sheet. ‘Also the grippers g may be identi
perature. The stu?'er S contains a screw l3 for
cal in construction so that a description of one
working the organic polymer while it- is being 00
heated and for forcing it through connections
indicated at H and I5 into and through the die
D._ The stufl'er S is mounted on a suitable sup
port, as shown at It, and the die D may be sup
will su?lce for all.
Each gripper 9 tom part of a gripper unit
. mounted on .the- respective gripper conveyor
means for transverse sliding movement outwardly
of the ribbon or sheet to effect a transverse draw- -
ported'in part by its connection to the stuil'er 65 ing operation and to clear the sheet and inwardly
and by an additional support shown at I‘! which
of the apparatus to permit gripping 01' ‘the-nar
is mounted on the frame It.‘
row ribbon preparatory to the transverse drawing
The rolls C have passages therethrough for
operation. In addition each Krip'per is pivotally
"the circulation of a tempereature controlling
mounted so that it may yieldingly assume a posi
medium, preferably a cooling liquid, which flows 70. tion parallel to the edge of the sheet irrespective
into one of the rolls through a pipe l9, and from
of whether the edge of the sheet is parallel to
that roll into the other rolls through U-shaped
Ithe center line ofv the apparatus or forms an
connectors 2|, 2! and 28, being discharged
angle therewith.
through the last roll through a pipe 24.’ The
As best shown in Figs. 7, 8 and 9, each gripper
rolls 0 are all driven at. the desired. SW‘! W 75. 0 comprises an upper Jaw II and a lower Jaw
55, the upper jaw being mounted on a vertical
pivot 54a in‘ lever 58 on pivot 51 and the lower Jaw
55 being mounted on vertical pivot 55a on bar 58
attached by screws as shown to slide 55 on guide
5|. The pivot 51 for lever 55 is mounted in mem
bers 52 and 58 on slide 58 which members also
8| engaged by a belt .82 which passes over ‘pulley
88 on shaft 84 of'motor 85. Motor 85 and Pulley
88 are’mo'unted on a slide 85 adjustable by means
including the ‘hand wheel 85 to vary the speed
at which the motor drives shaft 88. Such varia
tion in speed results from change in the radial
position of belt 82 in pulley 88 which‘, while not
serve as guides for the rear end portion of the
so shown in the drawings, is so constructed that
lever 55.
when the motor is moved toward or- away from
The jaws 54 and 56 are grooved, as indicated at
54, to afford a good grip on the edge of the ribbon 10 shaft 88 the belt 82 moves outwardly or inwardly
of the'pulley. The construction of such a vari
and prevent it from pulling out from between the
able speed drive is well known per se and need
jaws. The Jaw 54 is yieldingly held at right
not be further described nor illustrated. ‘
angles to the lever 55 and guide 8| by a tension
The shaft 83, Fig. 5, from which chains ‘II and
spring 54b and jaw 55 is similarly held in such
position by a tension spring 5512 connected there 15 52 are driven, as described above, also drives the
other pair of chains from the other set _of grip
to, as shown. Such springs permit the gripper
pers, one of which is indicated at ‘I la, Fig. 5. For
g to yieldingly adjust itself to any change in the
this purpose the shaft 83 is provided with an
direction of the edge of .the sheet, more particu
additional sprocket 82a and driving chain'8la
larly to be turned at an angle to the guide 8i
when the ribbon is transversely drawn with its 20 on sprocket 19a of sprocket shaft 14a. Further
description of this other pair of chains and the
‘edges in diverging relation. This swivelling ac
drive therefor is unnecessary because in the illus
tion of the grippers prevents them from wrinkling
trated embodiment these parts are duplicates of ,
or otherwise distorting the ribbon which would
corresponding parts for the chains ‘II and 12.
occurlif the jaws of the grippers could not turn
The various grippers or gripper units‘are con
horizontally. It will be understood that the ten
nected to the chains, such as chains ‘II and 12,
sion springs 54b and 550 serve to return the
by roller links ‘IIb and 12b bolted respectively to
gripper to a position at a right angle to the guide
the inner and outer ends of the guides 8| as
5| when the transverse drawing operation is
shown in Figs. 5 and 8. The roller links ‘Nb and
?nished and the edges of the sheet are parallel
to each other and to the center line of the ap- - 12b constitute parts of the chains 'II and 12
respectively, there being additional links ‘I I0 and
120, Fig. 5, interposed between the roller links of
Slide 58, which carries the gripper g, is moved
adjacent gripper units.
inwardly and outwardly on the guide 5|‘ by en
It will be understood that the sprocket shafts
gagement of cam roller 55 on the bottom of the
and drive shafts are suitably journaled in the
slidelwith cams which are described below and
frame F of the mechanism G.
which are arranged to move the grippers inward
The upper flightv of the guides 5| are guided
ly to grip the ribbon and outwardly to apply
transverse stress thereto.
The gripper g normally is held closed by a com
at their ends and thus caused to travel in a hori
zontal plane, by guides indicated at 5Ia and 5Ib,
pression spring 51 positioned between the top of 40 Figs. 1 and 6, mounted on the top of the frame F
by means of supports Mo and 5Id. Also the lower
slide 58 and the outer end of lever 55. The gripper
?ight of guides 5| slide on angle irons 5Ie and
is opened by the application of pressure to a
5|! mounted in the frame F by means of angle
button 58 on the outer end of the lever 55 and
iron supports 8 lo and Hit.
above the spring 51. Such pressure is succes
Considering now the cam means for controlling
sively applied to the grippers as they are brought 45
inward and outward movement of the slides
into position to engage the ribbon, by means of
58 to effect corresponding movements of the
an adjustable, stationary cam 58a, Fig. 2, the
button 68 being moved into engagement with
grippers g and referring particularly to Figs, 1,
to close on the edge of the ribbon. Similarly
each gripperis opened to release the sheet by
contact with the straight diagonally positioned
5 and 6, it will be seen that as the grippers in
the one end of the cam and depressed thereby
to open the gripper and then moving out'of 60 the lower ?ight move rearwardly of the appa
ratus, the rollers ‘55 on the slides 58 come into
engagement with. the cam to permit the gripper
"cam I8I, Figs. 5 and 6. The cam IN is held
in horizontal position in the frame F by trans
means of cam 581), located near the end of mech-.
anism G, Fig. 2. After releasing the sheet, the 55 verse angle irons IIlla and Hill), Fig. 5. A sim
ilar cam (not shown) is provided at the other
gripper is closed and remains closed until again
side of the apparatus for the same purpose.
opened by cam 58a.
The conveying means for’ each set or series of
Thus, an initial inward movement is imparted ‘
to the grippers as they reach the end'of their
travel in the lower ?ight and before they are
carried around and into the upper ?ight.
When the grippersor gripper units travel into
the upper ?ight of the conveyor therollers 55
of one set of gripper units successively engage
Similarly, the chain 12 is driven by sprocket 11 85 a cam I82 adjustably mounted on the grill I83.
This serves to impart further inward movement
on shaft 14 and passes around an idle sprocket
of the slides 59 and grippers carried thereby,
‘I8 on shaft ‘I5.
such inward movement being assisted by an ad
The sprocket shaft 14 carries a sprocket 19
ditional cam I84, Fig. 5, the outer edge portion
on the inner end thereof engaged and driven by
chain 8| from sprocket 82 on shaft 88. Shaft 70 I85 of which is engaged by the rollers near the
end of their engagement with cam I82. Cam
83 carries a main sprocket 84 driven by chain
I84 is so shaped as to provide an outwardly di
85 from a sprocket 85 (see Fig. 2) on shaft 81
rected edge portion I85 for initiating outward
which shaft takes power off the main drive shaft
movement of the slides 58 and grippers carried
88 through clutch 89.
thereby as a result of the action thereof on the
As shown in Fig. 6, shaft 88 carries a pulley
grippers g comprises a pair of chains, as best
shown by Fig. 5, wherein the lower ?ights of an
inner chain 'II and \an outer chain 12 are illus
trated. Chain 'II is driven by sprocket 13 on
drive shaft 14 and engages an idle sprocket 15
on shaft 15 at the other end of the mechanism.
rollers 00. ‘Further outward movement of the
rollers is e?'ected by a relatively long sectional
cam I01 also mounted on the 81111 "land which
is adjustable thereon as will presently berde
.Intheoperation ofthe above described»
'paratus for the performance of the novel process,
the organic polymer from which biaxiaiiy ori
As shown in Figs. 1 and 5,_cams I02, I04 and
' I01 are provided for both sets of conveyor chains
- for the actuation of the respective sets of grippers
solvent free condition, continuously extruded
carried thereby inwardly and outwardly of mech
anism G so that the same movements are im
parted to opposed grippers in opposite directions.
Cams I02 and .I04 are attached by means of
screws Ilia and Illa to slides I02b mounted
fortransverse adjustment in slots of grill I03.‘
Thus, cams I02 and I“ may be adjusted in
I03 and threaded through a lug I02e secured
tothe underside of cam I02.
The cam I01 comprises the sections I01a, I 01b,
I01c, I01d and I01e, the section I01a being
pivotally connected at I01)‘ to the cam I00. The
section I01a- is in turn pivotally connected to
section I01b, section I01b to M10 and I01c to
ature substantially for drawing and orientation.
In other words, drawing and orientation usually
is performed according to the invention at a
Each of said sections is slotted as indi- _
supplemented if desired by the heaterstm and
HI. Preferably‘ the organic polymer is heated
perature than that at which the drawing oper
ation is performed in the oven 0 inorderto
,extrude it in as homogeneous condition as ms
sible and to facilitate the extrusion of the poly
mer in ribbon form. When the polymer is so
heated, it is necessary to reduce its temper
' justment being e?’ected by means of a screw I020
- rotatabiy mounted in the support I02d in grill
cated at l0'lg.
through the die D and continuously conveyed by
the rolls 0 and drawn ?rst longitudinally and‘
then transversely by the grippers a while main
tained at a predetermined temperature or tem
wardLv or outwardly as a unit to change the
path of movement of the grippers 9, such ad
working condition in the stuifer 8 while in a
substantially lower temperature than that to
which the polymer is heated for extrusion‘ Such
reduction in temperature may be effected by the
rolls C by the circulation of a cooling medium
Adjustment of thesec'tional cam I01 is e?'ected
in part by the adjustment of cam I02 by screw 30 therethrough.
I020 and by additional screws I08, I00a, I001),
The extruded ribbon passes around the rolls
I000 and I 00d, Fig. 5. Said screws are mounted
C and is'driven'by the rolls at a predetermined
on the underside of the grill I03 by supports such
speed obtained by proper adjustment of the vari
as indicated at I00 and are connected to the
able speed drive 32. Preferably the rolls C are‘
respective cam sections by nuts, such as indi 35 driven at such speed that the thickness of the
cated at IIO, through which the screws are .
ribbon R between the die and the first roll is not
threaded, each nut carrying a pin III which ex
substantially reduced. Thus, there is no substan- .
tends upwardly and into a slot I 019 of the as
tial stretching of the ribbon between the end of
sociated cam section. '
the die and the rolls. The driving of the ribbon
From the foregoing description of cams I02 40 by the rolls 0 may be facilitated by so controlling
the temperature of the rolls that the ribbon ad
and Ill and of cams I01 and their respective
heres somewhat to the rolls.
adjusting means, it will be seen that the paths
of movement of the two sets of grippers g may
be shifted in accordance with desired variations
in width of the portion RI of the ribbon where
Preferably the temperature effect or the rolls 0
on the ribbon is so regulated as to super?cially
- chill the ribbon, leaving more or less heat in the
100a to, change the vshape of that portion of’
ribbon to assist in reheating it to predetermined
or selected temperature for the drawing opera
tions. The chilling and reheating of the ribbon
assists in bringing it to a substantially uniform
50 temperature throughout its cross section.
Usually the reheating of the ribbon in the oven
0 is
by the heater H. The oven and the
heater are made su?iciently long to accomplish
the cam I01 formed by those sections which
the desired longitudinal drawing and velongation
initially engaged by the grippers and so as to
draw the ribbon into sheet of varying widths.
Also the rate of transverse drawing may be
varied, and is controlled, by alteringthe shape
of cam I01 by changing the positions of itssec
tions. Thus the sections I01a and I 01b may be
moved outwardly or inwardly by screws I00 and
eil'ect transverse drawing. See Fig. 2. Sections 55 of the ribbon, preferably without any transverse
drawing and to permit predetermined tempera
i010 and ,Illd may be and preferably are ad
ture conditioning ‘of the ribbon.
justed into a straight line parallel to the center
line of the mechanism and of the ribbon so
that the edges of the ribbon will be held in, and
can set, in parallel relation to each other while
' so held under stress by grippers g.
Section I01e
preferably is adjusted in outwardly diverging re
Under some conditions of operation it is very
dii‘llcult to extrude the ribbon through the die D
with a uniform cross section. In cases where the
cross section is non-uniform di?iculties arise-in
drawing the ribbon because'the thicker portions
tend to stretch or draw out too rapidly due to
lation to section "1:! su?lciently to move the
their greater heat mass. It has been found that
grippers clear of the sheet after releasing it, as
65 this di?lculty may be largely, if not entirely, over
illustrated in Fig. 2.
come by variably reheating the ribbon trans
It will be understood that the twosets of cams
versely thereof in such' manner that the thicker
which‘control the movement of the two sets of
portion or portions is or are heated less than
grippers usually are adjusted to positions equi
the thinner portion or portions. Thus, if the rib
distant from the center line of the mechanism
bon is extruded in the shape illustrated in Fig.
G and or the ribbon or sheet so that the paths
3, which shows the ribbon thicker near the center
of the grippers of each opposed. pair
than at the edges, the edges may be heated more
similarly’ located and the ribbon will be drawn
than the center portion by placing a block ll
and formed symmetrically with respect to its
of wood or other insulating material‘ on the
center line.
75 heater H directly beneath the thicker portion
as illustrated in Figs. 1 and 3. This serves to
mask the heating of the thicker central portion of
polymer but are not released before such time
because if they should be, relaxation of orienta
the ribbon.
tion might occur.
One or more of such blocks may be
provided. Similarly, if the edge portions of the
ribbon are thicker than the central portion, as
illustrated in Fig. 4, blocks 42 and 43 of wood or
other insulating material may be placed on the
Fig. 1 shows that the grippers have been dis
engaged from the portion R4 of the sheet and
moved outwardly of its edges so that the grippers
may be carried downwardly and beneath the ap
heater H to inhibit the heating of such portions.
paratus without striking the sheet.
The longitudinal drawing of the portion RI of
Preferably, longitudinal tension is maintained
the ribbon is e?ected by the longitudinal pull on 10 on the sheet and the ribbon by the puller rolls P
such portion exerted by the grippers g as they
in order to inhibit or prevent longitudinal relaxa
continuously convey the ribbon and the sheet
tion of orientation during the transverse drawing
through the apparatus. The amount of elonga
operation and while the ribbon or sheet is being
tion of the ribbon is predetermined by the relative
cooled to or below the transition temperature.
speeds at which the rolls C and the grippers g 15 In the event such relaxation occurs, it may be
are driven. Such relative speeds may be adjusted
compensated by excessive elongation of portion
by means of the variable speed drive from the
RI of the ribbon, for example, by elongation up
motor 35 to the gripper conveyor chains, that is
to ten per cent (10%) and as high as twenty
by turning wheel 96, Fig. 6, and by the variable
per cent (20%) in excess of that required for the
speed drive 32, Fig. 2, through which the rolls C 20 predetermined longitudinal orientation in the
are driven. The linear speed of the grippers 9
preferably is several times greater than that of
the rolls C. For example, the linear speed of the
grippers may be approximately four times greater
than that of the rolls.v
While some of the grippers g are effecting the
longitudinal drawing of the portion RI of the
ribbon, others of them draw the portion R2 of
?nished sheet.
Although in the illustrated construction, the
transverse drawing operation is effected solely by
the transverse outward sliding movement of the
grippers, the transverse drawing may be assisted
or increased by arranging the sets of conveyor
chains, which carry two sets of grippers, in di
verging relation so that the ends of the sets of
the ribbon transversely as a result of the outward
chains are farther apart at the discharge end 01'
movement of the opposed grippers effected by 30 the apparatus than they are at the other end of
the cams I01, it being understood that the rate
the apparatus.
and amount of such transverse stretching will be
The process and apparatus of the invention
predetermined by the adjustment of the cams.
may be used for producing biaxially oriented sheet
The portion R2 of the ribbon preferably is main
from various types of organic polymers. Speci?
tained at a selected or predetermined tempera 35 cally, but without being limited thereto, the in
ture best suited for orientation 01' the organic.
vention contemplates the production of such
polymer of the ribbon, by means of the heater
HI, supplemented if necessary or desirable by‘the
heater H2. The heater H2 may be employed in
the production of unusually thin sheet, for ex 40
sheet from polystyrene, starting for example with
polystyrene molding powder which may have a
molecular weight of approximately 30,000 to
200,000 and an average molecular weight range
ample, sheet which is .002 to .005 of an inch thick.
of ‘70,000 to 100,000. Articles produced from poly
This usually is necessary because such exceeding
styrene ordinarily are very brittle, but being a
ly thin sheet cools very rapidly as it is drawn and
long chain type of polymer and containing rela
unless maintained at the desired temperature
tively long molecules, the polymer can be greatly,
the sheet may tear during the drawing operation. 45 strengthened by application of directional stresses
Usually the heater H3 will not be employed
to orient themolecules in the direction of stress
during normal operations but is used to heat the
application. Although it is difflcult to form _»a
ribbon when the apparatus ?rst is started up in
ribbon of polystyrene of uniform viscosity and to
order to assist in stretching it so that the edges
orient it, these difficulties are largely or entirely
may be brought out to where the grippers can 50 overcome by the present invention, ?rst, because
engage ' them.
of the manner in which the polymer is heated
When the grippers have drawn the ribbon
and the temperature of the ribbon controlled,
transversely to its ?nal width, it may be brought
second, because-of the performance of the longi
out of the oven'into the atmosphere to permit
tudinal and transverse drawing operation in sep—_
it to cool. The portion of the ribbon at B3, or 55 arate steps under controlled conditions of stress
some of it, is undergoing such cooling and this
application, and, third, by the novel means for
is continued, while the sheet or ribbon still is
drawing the ribbon whereby su?lcient stress may ,
engaged and held under stress by the grippers,
be applied at the proper time to achieve ‘a high
until the temperature of the ribbon falls below
degree of orientation in the ?nished sheet.
the “transition temperature” of the organic poly 60 In the production of biaxially oriented sheet
mer. The “transition temperature” of the or
from polystyrene inaccordance with the inven
ganic polymer is that temperature at which in
tion, polystyrene molding powder may be heated
to a temperature of 370° F.', or to a higher tem
ternal stress may be relieved, the stress drops
perature, in the stuffer S, super?cially chilled by
rapidly, high elasticity sets in and excessive “cold
flow” takes place. The “transitiontemperature” 65 the rolls C by circulating water therethrough at
approximately 160° F.,' and stretched longitudi
of the polymer may be determined by the method
nally while maintained at a temperature of ap
described in “Transition temperature and cubical
proximately 253° F., and then transversely while
expansion of plastic materials,” by Fred E. Wiley,
maintained at a temperature of approximately
Industrial and Engineering Chemistry, volume
34, page 1052, September 1942. If desired, forced 70 255°’ F. There may be a temperature drop in
cooling may be used to lower the temperature of
the ribbon.
The grippers need not be released from the
the ribbon between the rolls C and the point
where it is ?rst gripped by the grippers g. After
the ribbon has been drawn to the ?nal width of
the sheet, it is cooled to below the transition tem—
sheet immediately after its temperature‘ has
dropped below the transition temperature of the 75 perature of polystyrene which is 180°_F., while
held under stress by the grippers ‘0. At a desired
time thereafter the grippers may be disengaged
from the sheet.
The longitudinal drawing may result in an
elongation of the ribbon of three to four times
said rolls to draw the ribbon longitudinally and
to elongate it while its edges are free whereby
said ribbon is caused to contract in width prior
to its engagement by said grippers. means for
bodily sliding said grippers inwardly of said con
veyor means into position to enga8e the edges
of said ribbon, means actuating said grippers to
slide them bodily outwardly of said conveyor
means to draw the ribbon transversely a prede
the transverse drawing operation may increase‘
the width three to 'four times that of ‘the ribbon 10 termined amount, and means for causing the
grippers to release the sheet thus formed and‘ to
as extruded from die 1), this being. almost 6 to 8
move them clear of the edges of said sheet.
times the width of the ribbon Just after it has
2. Apparatus for forming continuous biaxially
been drawn longitudinally. At the selected tem
peratures of drawing speci?ed by way of example I oriented sheet or solvent-free organic polymer
above, sheet is obtained which is well oriented 15 comprising means including a die iorvextruding
solvent-free polymer at a selected extruding tem
because at such temperatures the rate of release
perature in the form of a ribbon, means posi
01' orientation under tension is relatively slow and
' the unit of length before elongation, this narrow
ing the ribbon to approximately .58 to .50 times
its width as extruded from the die ~D. Similarly,
the total relaxation is not substantial in one
' tioned adjacent to said die to super?cially chill
each successive portion of the extruded ribbon
Preferably, thwngitudinal and transverse 20 and to maintain substantially constant the di
mensions of each portion of the ribbon between
drawing are so conducted that the orientation
the die and said means, means for causing said
and strength of the sheet are equal in both said
super?cially chilled ribbon to attain a uniform
directions. However, the drawing may be soper
temperature throughout sufficiently high that it
formed that orientation in one direction will ex
ceed that in the other direction by a predeter 25 is- capable of being stretched and oriented but
below the temperature at which the ribbon is
mined amount.
extruded, and means for thereafter stretching
Various changes may be made in the process
said ribbon while at approximately said lastv
and apparatus as described above without de
minute or time.
parting from the scope of the appended claims. .
Having thus described our invention, what we
desire to claim is:
1. Apparatus for iorming continuous, biaxially
oriented sheet of solvent-freeorganic polymer
mentioned temperature both longitudinally and
transversely to orient the same.
3. Apparatus for forming continuous biaxially
_ joriented sheet of solvent-free organic polymer
_ comprising means including a die for extruding
comprising a screw stu?er for working and ex
' solvent-free polymer in the form 01 a ribbon at
truding said polymer, means for'heating said
stu?er to heat the solvent-free polymer to a
selected working temperature, -a die connected
sition temperature for the polymer, chilling rolls
positioned adjacent to said die to act on each
to said stu?‘er for forming the polymer into a
ribbon when extruded therethrough byv said stuff
a selected extruding temperature above the tran
successive portion oi’ the extruded ribbon to su
' per?cially chill it to a temperature below the
er, a set of cooperative rolls positioned for co 40 transition temperature of ‘the polymer and toy
maintain substantially constant the dimensions
operative contact with said ribbon in advance
of each portion of the ribbon between the die and
of and adjacent to said die, means to drive said
said chilling rolls, means for causing said super
rolls at a speed suitably related to the rate of
?cially chilled ribbon to be reheated and to at
extrusion of the ribbon from said die to cause
tain a uniform temperature throughout sum
said rolls to contact with successively extruded
ciently high that it is capable of being stretched
portions of said ribbon and to conduct them away
and oriented but below the-temperature at which
from said die without su?lcient pull on the por
the ribbon is extruded, means’ for thereafter
tion of the ribbon between said rolls and die to
stretching said ribbon while at approximately
cause substantial stretching thereof, said rolls
said last mentioned temperature both longitudi
being suilicient in number and so arranged in
nally and transversely to orient the vsame, and
relation to one another and to said die that any
for thereafter retaining stress on said ribbon while
‘ pull on the ribbon beyond said rollswill be pre
vented by said rolls from reaching the portion
cooling to retain orientation therein.
of the ribbon between the rolls ‘and the die,
, 4. Apparatus for forming continuous biaxially
means for circulating. a cooling medium through
oriented sheet of solvent-‘tree organic polymer
said rolls to cause them to chill super?cially the ‘
comprising means including a die for extruding
portions of the ribbon contacted thereby, an
solvent-free polymer in the form or a ribbon at
oven through which said ribbon may pass on
an extruding temperature above the transition
leaving said'rolls, heating means in said oven
temperature for the polymer, chilling rolls posi
for maintaining the ribbon at approximately‘ a
tioned adjacent to said die to act on each of
selected temperature at which substantial orien- 60 successive portions of the extruded ribbon to su
tation may beintroduced into the‘ solvent-free
per?cially chill them to a temperature below the
polymer by the application thereto of directional
transition temperature of the polymer and to
stresses, means for regulatingthe heating of said
:maintain substantially constant the dimensions
ribbon by said heating means transversely of the. .of each portion of the ribbon between the die
ribbon, and 'means for“ applying said directional 65 and the‘chilllng rolls, means for causing said
stresses to said ribbon comprising gripper con
ribbon to be reheated to a substantially uniform
veyor means located a substantial distance from
temperature above the transition temperature so
said roils,'opposed grippers carried by said con
that the ribbon is capable of being stretched and
veyor means in endless paths at opposite sides
oriented by the apparatus through the applica
oi‘ the path of travel 01' said ribbon, transverse 70 tion thereto of directional stress to cause orien
slides on the conveyor for supporting the grippers _ tation thereof but below the temperature at which
thereon, means for actuating the respective grip
the ribbon is extruded, and means for applying
pers to grip the edges of said ribbon, means for
such stresses to said ribbon while it is main
driving the gripper conveyor means at a selected
linear speed greater-‘than the linear speed of
tained at approximately said temperaturecom
prising means acting ?rst to draw an edge-free
the portion of the ribbon that has been brought
to said substantially uniform temperature longi
tudinally and transversely while maintaining the
temperature of the ribbon sufficiently high to
stretch and orient the sheet, and cooling the sheet
portion of said ribbon longitudinallyv only to elon
gate and narrow it a predetermined amount and
then to draw the ribbon transversely to form a
sheet of the ?nal thickness desired and of a
~ width in excess of the width of the ribbon before
thus formed while holding the sheet under trans
elongation and narrowing thereof, and means
verse and longitudinal stress.
for regulating the amount of transverse drawing
'7. The process of making a continuous sheet of
and the amount of longitudinal elongation to con
rlented polymer which comprises the steps of
trol the amounts of orientation respectively in
said polymer in a solvent-free condition
said two directions in the ?nished sheet.
to extrusion temperature and extruding the
5. Apparatus for forming continuous biaxially
heated polymer from a die in the form of a hot
oriented sheet of solvent-free polystyrene com
continuous ribbon and continuously forming said
prising means including a die for extruding sol
ribbon into said sheet by conveying the hot ribbon
vent-free polymer in the form of a ribbon at a se
lected extruding temperature above 180° F., means 15 away from the die without substantially stretch
ing it, super?cially chilling successive portions of
including ?uid cooled rolls over which the ribbon
the ribbon as they are conveyed away from said
passes for super?cially chilling'the ribbon to a
die to reduce the surface temperature thereof
temperature of approximately 160° F. and for
below the transition temperature of the polymer
maintaining the dimensions of the ribbon sub
stantially constant between the die and the rolls, 20 and below the internal temperature thereof, re
heating the chilled portions of the ribbon to es
means for causing said super?cially chilled ribbon
.tablish in the surface layers and the interior
to attain and maintain a uniform temperature
thereof a substantially uniform temperature at
throughout su?iciently high that the ribbon is ca
which the polymer is capable of being stretched
pable of being stretched and oriented by the ap
plication thereto of directional stresses but below 25 and oriented, said substantially uniform tempera
ture being well above the transition temperature
the temperature at which the ribbon is extruded,
of the polymer but below the temperature at which
and means for applying such stresses to said rib
it was extruded, pulling the portion of the ribbon
bon comprising gripper conveying means located a
that has been brought to said substantially uni
substantial distance from said rolls, opposed grip
pers carried by said conveying means in endless 30 form temperature longitudinally and transversely
to stretch and orient the sheet while substantially
paths at opposite sides of the path of travel of
maintaining the equalized temperature of the
said ribbon, means for actuating the respective
ribbon, and cooling the sheet thus formed to below
grippers to grip the edges of said ribbon, means
the transition temperature while holding the
for driving the gripper conveyor means at a se
sheet under transverse and longitudinal stress.
lected linear speed greater than the peripheral
8. The process of making'a continuous sheet of
speed of said rolls to draw the ribbon longitu
biaxially oriented polystyrene which comprises
dinally and to elongate it while its edges are free
the steps of heating said polystyrene in a solvent
whereby said ribbon is caused to contract in width
free condition to an extrusion temperature of at
prior to its engagement by said grippers, means
least 370° F. and extruding the heated poly
actuating said grippers to move them bodily and
styrene at the extrusion temperature from a die in
transversely in opposite directions to draw the
the form of a hot continuous ribbon of substan
ribbon transversely a predetermined amount, and
tially unoriented polystyrene and continuously
means for causing the grippers to release the sheet
forming said ribbon into said sheet by conveying
thus formed and to move them bodily outwardly to
clear the edges of said sheet.
. the hot ribbon away from the die without sub
6. The process of making a continuous sheet of
stantially stretching it, super?cially chilling a
oriented polymer which comprises the steps of
heating said polymer in a solvent-free condition
to extrusion temperature and extruding the
portion of the ribbon at a place adjacent to said
heated polymer from a die in the form of a hot 50
continuous ribbon and continuously forming said
ribbon into said sheet by conveying the hot ribbon
away from the die without substantially stretch
ing it, super?cially chilling successive portiom of
the ribbon when each such portion has moved a
short distance away from the die, said chilling be
ing in addition to any natural cooling of said rib—
die by subjecting the surface thereof tofa chilling
medium, having a temperature of approximately
160° F‘., reheating said chilled surface to establish
through said portion of the ribbon a substantially
uniform temperature of approximately 255° F.,
pulling said portion of said ribbon after it has at
tained substantially uniform temperature in a
longitudinal direction only to elongate and orient
it to several times its, unoriented length and then
transversely drawing'the ribbon to substantially
widen and orient it to several times its original
bon by the surrounding atmosphere as the ribbon
unoriented width while maintaining the tem
is extruded and conveyed away from said die and
being such as to reduce substantially the surface 60 perature of the ribbon at approximately 255° F.,
and, before substantial relaxation of said orienta
temperature of the ribbon, leaving the interior at
tion, cooling the sheet thus formed to below 180°
a higher temperature, reheating the chilled por
F. while holding the sheet under longitudinal
tions of the ribbon to establish in the surface
layers and the interior thereof a substantially
uniform temperature at which the polymer is ca 65
pable of being stretched and oriented, said sub
stantially uniform temperature being above the
transition temperature of the polymer but below
the temperature at which it was extruded, pulling
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