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Патент USA US3088183

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May 7, 1963
J. w. JONES
3,088,173
PROCESS FOR PREPARING ORIENTED POLYMERIC LINEAR TEREPHTHALATE
FILM WITH A DEGLOSSED WRITEABLE SURFACE
Filed June 2, 1961
United States Patent Oiiice
1
asserts
Patented May ‘7, 1953
2
at la linear rate of speed of 50 to 500 percent per sec
3,683,173
PR®CE§S FÜR PREPARING OREENTED PGLYMER
EC ÍLHNEAR TEREPHTHALATE FEM WITH A
DEGLÜSSED WRHEABLE SURFACE
John 'Willard `lunes, Wilmington, Del., assigner to E. I.
du Pont de Nernonrs and Company, Wilmington, Del.,
a corporation ot Delaware
Filed .lune 2, 1961, Ser. No. 114,356
6 Claims. (Cl. 18-4S)
This invention relates to an oriented polymeric linear
-terephthalate film and a process for its preparation. More
particularly, this invention relates to a low luster, oriented
ond, cooling the film below its second order transition
temperature, reheating the once stretched film to a tem
perature of about 112° C. 4within -a period of time of Lat
the most 3 minutes, and stretching the iii-m after attain
ing this temperature in both the longitudinal and trans
erse directions to an `extent of at least 1.25 times its
dimensions after the first stretch `at a linear rate of speed
of 5i() to 500 percent per second, the total extent of the
10 stretch being 3 to 5 times that of the original dimensions
of the film.
Any film consisting of .a substantially amorphous
polymeric linear iterephthalate `can be employed in the
polyethylene terephthalate ñlm having a surface readily
process of this invention and Ican be formed by the process
receptive to inl; and pencil markings and a process for 15 disclosed in US. Patent 2,4613 19. The preferred film
its preparation.
Polyethylene terephthalate film, more particularly, poly
ethylene terephthalate Vfilm which has been molecularly
yoriented by stretching and/or rolling in two mutually
perpendicular directions, is a tough, durable, dimension
of this invention is substantially amorphous polyethylene
terephthalate film.
employment in drafting, recording and surfacing appli
tions lare carried out is also critical to the process. De
The process of the present invention in its broad and
preferred aspects has certain critical steps. It is neces
20 sary that there be two separate stretching operations with
a cooling of the film between stretching operations. The
ally stable film. lt possesses many desirable character
temperature at which the two separate stretching opera
istics which should make it an outstanding candidate for
tails of these step-s and other features of the process will
cations. These films, however, possess limited ability to
accept ink, pencil markings, and have undesirable high 25 be shown hereinafter.
gloss and transparency. Attempts have 'been made to over
It has been found that an oriented polyethylene
come these disadvantages by the incorporation of addi
terephthalate film with a -deglossed `writeable surface -can
be prepared by stretching the film in two stages to a
tives, the application of coatings. chemical treatments,
and mechanical abrasion. Additives to the polymer may
total extent of 3 to 10 times its initial dimensions, i.e.,
interfere with the preparation of the polymer; coatings 30 its initial transverse and longitudinal dimensions. Pref
are frequently inferior to >the base film in toughness,
erably, the total extent of the stretch should be between
3 to 5 times the initial dimensions of lthe film with the
may delaminate, or be poor in abrasion resistance. All
most preferably total stretch being 4 times the initial di
of these processes add complications and expense to the
preparation »of the desired product.
mensions of the film.
The extent of the ystretch in .the first stretching opera
It is an object of this invention to provide an oriented 35
polymeric linear yterephthalate film and a process for its
preparation. lt is a further object to provide a low luster,
tion must be at least 1.25 times the initial dimensions
of the film. The extent of the stretch in the second
oriented polyethylene terephthalate film having a surface
stretching operation must be `at least 1.25 times the dì
readily receptive to ink and pencil markings and `a proc
»mensions of the film after the iirst stretching operation,
ess for its preparation. It is still a further :object to pro 40 and be sufiicient such that the total stretch (extent of
stretch in first stretch operation multiplied by the extent
vide a process for the preparation of a low luster, oriented
polyethylene terephthalate film having a surface readily
of stretch in the second stretch operation) is at least
receptive to ink and pencil markings which is adaptable
3 and not greater than 10. ln each of the two stretch
ing ‘operations the film must be stretched to the same ex
for use as a tracing film. These and other objects will
appear hereinafter.
tent in both directions. The film can, in either stretch
ln the annexed drawings FIGS. l and 2 are graphical
ing operation, be stretched simultaneously in both the
illustrations of the results achieved by stretching film at
longitudinal and transverse directions or can -be stretched
Various temperatures as described in Example VIH, in
sequentially, i.e., `stretched first in the longitudinal direc
tra. HG. 3 is a graphical illustration of the results
tion `and then in the transverse direction or vice versa.
It is preierred that the ñlm be stretched simultaneously
achieved by stretching film to various extents as described
in Example X, infra.
in both «directions in the first stretching operation and the
second stretching operation. The stretching apparatus
These and other objects are accomplished by the proc
employed in the process of this invention is similar to
ess of this invention by stretching substantially amorphous
polymeric linear terephthalate film yafter attaining a tern
that described in Peterson, U.S. Patent 2,759,217.
The linear rate of `stretch in «both directions is prefer
perature within the range of 110 to 114° C. in both the
ably 50 to 500 percent per second. The most preferable
longitudinal and transverse directions to an extent of at
rate of stretch is 100 percent per second.
least 1.25 tirnes its original dimensions, cooling the film
lt is essential that between the two stretching oper
below its second order transition temperature, and stretch
ations that .the film ibe ycooled below the second order tran
ing the film a second time after attaining a temperature
sition temperature. This is defined «as the temperature
within the range of 110 to 114° C. in both the longi
tudinal and ytransverse directions to kan extent of `at least
at which a discontinuity occurs -in the curve of a first
derivative thermodynamic quantity with temperature.
1.25 times its dimensions after the first stretch, the total
lt -is correlated with yield temperature and polymer fluid
«ext-ent ofthe stretch being 3 to l0 times that of the original
dimensions of the ñlrn.
65 ity and can be observed Ifrom a plot of density, specific
A preferred embodiment of this invention is concerned
volume, specific heat, sonic modulus or index of refrac
with the process of heating substantially amorphous
tion against temperature. 'Ilhe second order transition
polymeric linear terephthalate film to a temperature of
temperature lfor polyethylene terephthalate -is approxi
about 112° C. within a period of time of at the most 3
mately 70° C. Any `air «blast apparatus can be used to
minutes, stretching the film after attaining this tempera 70 »cool 4the hlm, but generally lany conventional coating
ture in both the longitudinal and transverse :directions to
(lair) device can be employed to 'cool the film.
an extent of at least 1.25 times its original dimensions
Another critical process condition of the present -in
3,088,173
3:
vention is the temperature at which the two `stretching
in both directions at 111° to 112° C. at a linear rate of
operations are carried out. The temperature must be
maintained =within the range of 110 to 114° C. and pref
Example Il: 1.5‘X X 15X
100 percent per second to the following varying extents:
erably at about 112° C. The film before therstart of
either stretching operation must be l‘brought up to this
temperature. Depending on the type of equipment and
effectiveness of the heating means employed, it will be
necessary to preheat the film for a period of from 30
seconds to 3 minutes.
Example VI: 2X X 2X ,
Where X is the original dimensions of the film.
The iilms were cooled with `an air blast below 70° C.
Preheat times in excess of 3 min
ntes markedly increase the density of the film thereby
leading :to non-uniform stretching and development of
clear areas.
`
and .again brought up to 111 to 112° C. by preheating
for 3 minutes. They were then stretched a second time
in both directions `at a linear rate of speed of 100 percent
.
After the two stretching operations, the íilm can be
heat-set while lstill under tension to impart to the ñlm
an enhanced dimensional :stability at elevated temper
atures.
Y
Example lll: 1.25X X 1.25X
Example lV: 1.5X X 1.5K
Example V: 2X X v2X
per second to the »following varying extents;
Example
Example
Example
Example
Example
This property `is referred to as “thermal dimen
sional stability” .and is a measure of the ability of the
film to resist shrinkage at elevated temperatures. The
-ñlm can be heat-set ‘at a temperature within the ran-ge
l1: 3Y X 3Y-total stretch 4.5X X 4.5X
Ill: 4Y X 4Y-total stretch 5X X 5X
IV: 3Y X 3Y--total stretch 4.5X X 4.5X
V: 2Y X 2Y-total stretch 4X X 4X
Vl: ZY X 2Y-total stretch 4X X 4X
20
of 15() to 235° C. and preferably at `about 185° C.
where Y is the dimensions of the iilm after the first
F[ille invention will be more fully understood by re
stretch.
ferring to the following examples.V
The effectiveness of the deglossing by the process is
EXAMPLE I
illustrated by the Iu-se of Gardner '60° `gloss meter ( Gard
VSnbstantially amorphous polyethylene terephthalate 25 ner haze meter, manufactured by the Gardner Corp. of
Bethesda, Maryland). The meter Was standardized by
iilm, 28 mils thick, was placed -in a laboratory stretcher
a reference block at 89 percent. The gloss of all >ñve
designed -for simultaneously 4stretching a polymeric ñlm
'
in both" the 'longitudinalV4 (LD) and transverse (TD) di- . t films was less than 17 percent.
Example V was :clamped in a fframe and heat set in yan
rections. The stretcher was previously heated to 112° C. ’
The iil-m'was clamped on all four sides and lallowed to 30 oven for l minute at 185° C. The surface characteristics
preheat for 3 minutes Áat 112° C.
were not >’altered by the heat-setting operation.
The physical properties of the stretched deglossed poly
The film was then
simultaneously stretched two times «its original dimen
sions (X) in both the LD »and TD (2X by 2X) at »a
linear rate of 10() percent per second.
ethylene 'terephthalate iilms compared with that of an.
unoriented substantially ‘amorphous polyethylene tereph
The ñlm was `
thalate íilrn 'are shown in Table A below.
Table A
cooled with an air Vblast to reduce the temperature to
PHYSICAL PROPERTIES OF POLYETHYLE NE TEREPHTHALATE FILM PREPARED BY TWO SEPARATE
"STRETCHING STEPS
’
Control: Snb-
Example II:
Example III:
stantially
P.T. Film
P-.T. Film
P.T. Film ~
Amorphous
stretched
stretched
Stretched
Property
Example IV:
Example V:
BT. Film
stretched
2X2, cooled,
Example 6:
P.T. Film
stretched
'Unoriented
1.5X2_, cooled
1.25X2, cooled
1.5X2, cooled
and stretched
2X2, cooled
P.T.1 Film
Y
and stretched
3Y2
and stretched
4Y2
and stretched
3Y2
2Y2; heat set
at 185° C. (l
' and stretched
2Y2
min.)
Thickness, mils ............. _.
Gloss 60° ____________________ __
TD ______ -_
_-
1.7
140
1.2
13
l. 3
l2
1. 5
13
2.8
9
2.6
10
357
410
407
389
340
420
.............................. -_
365
368
8.6
16.6
.............................. _-
17.4
17.7
7. 5
18. 7
13. 9
17. 7
500
132
Tensile Strength K
’ LD..V__________ _-
_____________________ _-
Elongation, percent:
LD _______ __
.............................. -_
200
214
TD ....... -_
450
157
227
238
Density (g./cc.)-
1.340
1. 360
1.381
1.363
1 Polyethylene terephthalate.
below the second Iorder transition temperature (70° C.)
From Ithe .table it can be seen that the iilms of IExamples Y
and removed from. the stretcher.
II to VI ‘are »satisfactorily deglossed. These films are also
The
was trans
parent and uniformly stretched.
A portion of this lllm was placed in a stretcher and
`stretched 'ai second time under the same conditions for
-the i’ifrst stretch. The lilnztv surface was drastically reduced
in gloss'. The surface would accept ball point pen, pen
cil; ink «pen 'and >typewriter substantially better than
oriented polyethylene terephthalate film prepared by
methodsl known to the `art. The pencil marks could
vreadily be erased.
60
readily receptive to surface markings. From the table
it can also be seen that the til-m prepared by the process
of the present invention exhibits enhanced physical prop
erties 'characteristic of an oriented polyethylene tere
phthalate film prepared by methods known to the art.'
EXAMPLE VII
Samples `of polyethylene terephthalate íilm 28 mils
thick were Ystretched to a total extent of 4X in both di
rections'in two separate stretching operations as described
70 in Example I. The films were stretched .at 112° C. The
Five samples of substantially amorphous polyethylene
Preheat times were varied -from 30 seconds to 9 minutes.
satisfactorily deglossed oriented iilms were obtained when
terephthalate iilm 28 mils thick were stretched in a
preheat times of .5 to 4 minutes were employed. With a
stretcher similar to that described in Example I. Films
5 minute preheat, the stretch was non-uniform and some
were preheated ttor 3 minutes to ‘bring the temperature
to. 112° C; Theñlms were then simultaneously stretched 75 clear areas developed. The density of the iilm was found
EXAMPLES n to V1
3,088,173
.5
for 3 minutes and subjected to one of the following varied
to vary little up to 3 minutes preheat time but increased
sharply wlth longer heating periods. The optimum pre
stretching operations:
heat time, therefore, is about 3 minutes.
Example
Example
Example
Example
Example
EXAMPLE VIII
Samples of substantially amorphous polyethylene tere
phthalate iilm 28 mils thick were stretched in two stages
XI: 4X LD x 4X TD-no second stretch
MI: 4X LD x 4X TD--cooled--ZY LD only
XIII: 2X LD x 4X TD-no second stretch
55V: 2X LD x 4X 'ID-cooled-ZY LD only
XV: 3X LD x 3X TD-no second stretch
Example XVI: 3X LD x 3X TD-cooled-1.5Y LD x
to a total extent `of 4X -in both directions las described in
Example I. The iilm was vallowed to preheat at la selected 10
temperature for stretching for 3 minutes. The stretching
temperatures -were varied between 90 to 117° C. Both
stretching operations were carried out -at the same tempera
ture. The results of this operation `are shown graphically
1.5Y TD
where X and Y are -as deñned in Examples II to VI.
In Examples XI, XIII and XV the film was stretched
simultaneously in both the LD and TD at 112° C. to
Varying extents. No second stretching operation was
performed. In Examples XII and XIV the lilm was
in FIGURES 1 `and 2 of the drawing lattached hereto.
simultaneously stretched »in both the LD and TD at 112°
From FIGURE 1 it can be seen that stretching tempera
tures below 110° C. produced a uniformly stretched iilm
C. to varying extents, cooled, and then sequentially
which was not deglossed. Stretching temperatures in ex
stretched 2Y in the LD only. In Example XVI the ñlm
cess of 114° C. produced satisfactorily deglossed but non
was stretched twice in accordance with the dictates of
uniformly stretched films. FIGURE 2 illustrates the de 20 the present invention to an extent of 3X in both the LD
gree of gloss of the iilm samples as the temperature is in
land TD, cooled, and then stretched 1.5Y in both direc
creased from 90 to 117° C. As can be seen, the minimum
tions. Table B, listed below, lists the extent of stretch
gloss results at temperatures ranging between 110 to 117°
in the ñrst stretching operation, the extent of stretch in
the second Vstretching ‘operation where applicable, and
C. The preferred temperature range under the conditions
used is 112° C.-*_~l° C.
25
the gloss reading as measured by the Gardner 60° gloss
meter.
EXAMPLE IX
Table B
Substantially amorphous polyethylene terephthalate
Example
iilm 28 mils in thickness was stretched 4X in the LD only 30
at 112° C. The simultaneous stretching `apparatus of
clamps
Exampledisconnected.
I was employed
-The preheat
with either
time the
wasLD
3 minutes.
or
The -ñlm was cooled below 70° C, and again preheated
at 11.2° C. for 3 minutes. The iilm was then stretched
4X in the TD only. The resulting iilm was clear and
did not develop the desired surface characteristics, there
by showing the criticality of conducting the stretching of
the _film in two separate steps with .the cooling step inter
XI____
First Stretch
4X2.“
Second
Stretch
__ _
Gloss
si
XII____
4X2___
2Y LD_-__
35
XIII _______________________ __
2X LD~4X TD____ __________ __
42
XIV ________________________ __ 2x L1B-4x '1‘D____ 2Y LD____
45
Xv____
3x2___
as
Xvr____
3x2____
1.5Y2 ____ __
i3
As can be seen from the table, polyethylene terephthal
ate ñlm stretched at least 3X in both directions in one
40 stretching operation only, and film stretched to a total
venmg.
aggregate stretch of 3X x 3X or greater, by stretching iirst
EXAMPLE X
in both directions, cooling and then stretching in one
Samples of 28 mil thick substantially 4amorphous poly
direction only, do not exhibit satisfactorily deglossed
surfaces as evidenced by Gardner 60° gloss meter reading
ethylene terephthalate ñlm were stretched under condi
of greater than 25 (the maximum value for satisfactorily
tions substantially identical with those described in Ex
deglossed ñlm). The film, processed as described herein
ample I. 'Ihe ñlms were preheated for 3 minutes at 112°
by stretching to an aggregate stretch of 3X x 3X or
C., stretched simultaneously in both the LD and TD at
greater in two separate stretching operations with an in
112° C., cooled below 70° C., preheated to 112° C. for
termediate cooling step, displayed satisfactorily deglossed
3 minutes and then simultaneously stretched in both di
rections at that temperature. The íinal total extent of 50 surface as evidenced by a Gardner 60° gloss meter read
ing of 13.
stretch (X2 x Y2), where X2 is the extent of stretch of the
Attempts to produce a deglossed ñlm by stretching the
Íirst simultaneous two-directional stretch, «and Y2 is the
film 3 to 10 times its original dimensions in both direc
extent of stretch of the second, were varied between 1.5
and 5. For example, a nlm stretched 2X x 2X (2X2),
cooled, and stretched 2Y x 2Y (2Y2) would give a total
extent of stretch (X2 x Y2) of 4X.
The gloss of the
stretched film was measured with a Gardner 60° gloss
meter calibrated with a black glass plate of gloss 89.
tions in one stretching operation resulted in no appre
ciable lessening in the gloss of the film. Similarly, a
biaxial stretching operation followed by an unaxial stretch
ing operation, e.g., 4X x 4X followed by 2Y x GY resulted
in little or no change in degree of gloss.
The process of the present invention gives a tough,
The laverage of 4 readings on each side of the iilm was
durable, dimensionally stable polyethylene terephthalate
taken as the gloss. The results are shown in FIGURE 3 60
iilm
having a surface characterized by a low luster, en
of the attached drawing. The gloss decreased from 70
hanced receptivity to ink and pencil markings, chemical
at »a total extent of stretch of 1.5 to 10 at a total extent
treatments and applications of coatings of dissimilar ma
of stretch `of 4. There was a -slight increase in gloss (12)
terials. Such a íilm is ideally suited for such end uses
at a total extent of stretch of 5. Stretching at higher
as drafting ñlms, typing materials (e.g., top sheets for
ratios appears to increase the gloss. This was veriíied 65 a mimeograph master [Multilith]), base films for spe
by conducting two bi-directional stretches on a polyeth
cinc end use coatings, surfacing applications requiring
ylene terephthalate film with vau aggregate stretch of about
delustered materials such as wall coverings, etc., record
15X x 15X. This produced la thin film with only moderate
ing tape, adhesive tapes, deglossed surface tapes for mend
deglossing; the preferred aggregate stretch ranges between
70 ing books and papers and photo-reproduction process ma
3X x 3X to 5X x 5X.
terials such as projection base materials and materials for
EXAMPLES IX TO XVI
contact photoprinting.
What is claimed is:
"1. The process comprising: stretching substantially
phthalate film 28 mils thick were preheated to 112° C. 75 amorphous polymeric linear terephthalate tilm after at
Samples of substantially amorphous polyethylene tere
3.4.9588.,173
8
«cooling said ñhn- below its second orderl transition tem
taining a temperature Within-@grange ,Qt 110° i0 114" C#
within a period of time of at the mostl about 3 minutes
perature, reheating the once stretched ñlm to a tempera
ture of about 112° C. vvithina> period ofi time of at the
.most 3 minutes, stretching said ñlm after attaining said
in both theY _longitudinal and transverse _directions to an
` extent'of at least 1.25 times its original dimensions, cool
ing said'iilm below its- second order transition tempera
temperature in both the longitudinal and transverse direc
ture, and stretching said ñlm a second time after attaining~
a temperature Within the range of 110° to .114° C. Within
tions to an extent of at least 1.25 times its dimensions "
after the iirst stretch at a rate of 50 to 500, percent per
a period of time of at the most about 3 minutes in both
the longitudinal and transverse directions to an extent
second, the total extent of the stretch being 3 to 5 times
that of the original dimensions of said ñlm, and heat 'Y
of at least 1.25 times its dimensions after the iirst stretch, 10 setting said film after the second stretch at a temperature
within the range of 150° to 235° C.
the total extent of the stretch being 3 to 10 times that:
5. The process comprising: heating substantially
of the original dimensions of said film.
2. The process comprising: stretching substantially’
amorphous polymeric linear terephthalate film to a tem
amorphous polymeric linear terephthalate iilrn after at
perature of about 112° C. within a period of time of
taining a temperature Within the range of 110° to 114° C.
within a period of time of at the most about 3 minutes.
in both the longitudinal and transverse directions to an
extent of at least 1.25 times its original dimensions, cool
at the most 3 minutes, stretching said film after attaining
said temperature in both the longitudinal and transverse
ing said film below its second order transition tempera
cooling said iilm below its second order transition tem
perature, reheating the once stretched iilmV to atempera
ture of about 112° C. within a period of time of at the
most 3 minutes, and stretching said ñlm after attaining
directions to an extent of at least 1.25 times its original
dimensions at a rate ofv 50 to 500 percent per second,
turegstretching said iilm a second time after-attaining~ »
a temperature Within the range of 110° to 114° C, Within
a period of time of at the most about 3 lminutes in both
the longitudinal and transverse directions to an extent
said temperature to an extent of at Ie‘ast 1.25 times itsr
dimensions'after' the first stretch -in both the longitudinal
of at least 1.25 times its dimensions after the iirst stretch,
. the total extent of the stretch being 3 to 10 times that:
of the original dimensions of said ñlm, Yand heat setting
and transverse directions at a rateof 50` to 500~percent
per second, the total extent of the stretch being 4 times
that of the original dimensions ~of said iilm.
Y
said íilm after the second stretch at a temperature Within
6. A process for the production of a low luster, oriented
l the range of 150° to 235° C.
V3. The process comprising:
polyethylene terephthalateiilm comprising: heating sub
heating substantially
amorphous polymeric linear terephthalate ñlm to a tem 30 stantially amorphous polyethylene terephthalate film to a
perature of about 112° C. Within' a period of Vtime of
temperature of about 112°y C. over a period of 3 minutes,
at the most 3 minutes, stretching said iilm after attaining
stretching said film after attaining said temperature simul
said temperature in both the longitudinal and transverse
_ taneously in the >longitudinal’ and transverse directions
2 times its original dimensions at a rate of 100 percent
Y directions to an extent of at least 1.25 times its original
dimensions at a 'rate of 50,to 500 percent perrsecond, 35 per second, cooling said film below 70° C., reheating said
cooling said film below its second order transition Vtern- '
iilm to a temperature of about 112° C. over a period of
perature, reheating the once stretched -Íilm to a tempera
3 minutes, and stretching the once stretched iìlm after
ture of about 112° C. Within a period of time of at the
attaining said temperature simultaneously in the longi
most 3 minutes, and stretching said iilm after attaining
tudinal and VtransverseV directions 2 times its dimensions
said temperature in both the longitudinal and transverse
after the ñrst stretch _at a rate of 100 percent per second'.
ldirections to an extent of at least 1.25 times'its dimen
sions after the first stretch at a rate of 50 to 500 percent
References Citedin the ñle of this patent
per second, the total extent of the stretch being 3 to 5
UNITED STATES PATENTS Y
times that of the original dimensions of said ñlm.'
4. The process Y comprising: heating substantially 4.5 '- 2,352,725V
Markwood ____________ __ July 4, 1944
amorphous polymeric linearterephthalate ñlm to a tem
2,578,899
Pace ________________ __ Dec. Y18, 1951
perature of about 112° C. within a period of time of
2,884,663
Alles ____ __ __________ __ May 5, 1959
at the most 3 minutes, stretching said ñlm after attaining
` 2,948,583
Adams ________ __ _____ __ Aug. 9, 1960
said temperature in both the longitudinaland transverse
directions to an extent of at least 1.25 times its original
_dimensions at a rate of 50 to 500 percent per second,
50
.
2,951,305
_ 2,968,067
Seymour ___.'_________ __ Sept. 6, 1960
1961
, Long ____ __' ______ ______ Jan. 17,
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