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Патент USA US3076730

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Feb. 5, 1963
Filed Oct. 17, 1960
Ex trader
Far-re Z
34”” 9"
/%t‘ ilk-Drying Oven
Dry/0y 0 Veil
4/5/20 C'- Pz'c'e
Kggnez‘b 77700008017
Patented Feb. 5, 1953
to include, inter alia, processes, such as flame treatment,
corona, or other electric discharge treatment, chemical
‘ 3,076,720
METHOD on coAriNo
' John C. Rice, Tena?y, N.J., and Kenneth Thompson,
Hamiiton, Ghio, assiguors to Lowe Paper Company,
Ridgeéielrl, N.J., a corporation of New Jersey
oxidation, ozonization, and high-temperature extrusion,
where the result thereof is to render a polyole?n surface
receptive to adhesives and oil-base printing inks.
It has now been discovered that the activated polyole?n
surface, and particularly the activated polyethylene sur
face, may be preserved and the printability and gluability
improved if the activated polyole?n surface soon after,
Filed Oct. 17, 1960, Ser. No. 63,147
16 Claims. (Cl. 117-15)
This application is a continuation-in-part of application
‘Serial No. 586,956, ?led May 24, 1956, now abandoned; 10 and preferably substantially immediately after, the activa
tion treatment is coated to a critical extent with a non
Serial No. 692,342, ?led October 25, 1957, now US.
polymerizing, polar, hydrophilic aqueous phase coating’
Patent No. 2,955,970; and application Serial No. 747,340,
composition. After this treatment the coated material
?led July 9, 1958, now abandoned.
may be dried and then subjected to a printing operation
This invention relates to the treatment of polyole?nic
even with oil-based inks, and then to a gluing operation
materials, and particularly polyethylene to improve its
Polyethylene ?lms are tough, semi-transparent, resistant
to many chemicals and heat scalable. Because of these
properties they are highly useful as packaging and wrap
, ping materials. Furthermore, polyethylene may be readily
and, if desired, using even the inexpensive dextrin and
starch adhesives.
It has been found that the printability and gluability of
the activated polyole?n surface is preserved if it is coated
extrusion coated onto a web backing and there is thus pre
pared a packaging material which acquires the desirable
attributes of the polyethylene ?lm.
Among the difficulties encountered with the use of poly
With a non-polymerizing, polar, hydrophilic aqueous phase
coating at coating weights (on a dry base) of from 0.07
pound to 1.4 pounds per 1000 sq. ft. of surface of the
polyole?n surface. In this aspect of the invention the
coating is preferably non-pigmented. By experimentation
ethylene either in the form of a ?lm or coated on a 25 applicants have found that with coatings below these
web backing has been that the material printed with stand
ard printing inks, which are usually oil-based inks, did
not retain the ink. In ordinary handling it was soon found
that the ink was smeared or rubbed off.
limits the activated polyole?n material soon lost its print
ability and gluability. With coatings above this range,
the printability of the activated polyole?n material was
masked and also lost.
Although applicants do not wish to be bound by any
It is known in the prior art that the ability of poly 30
theory of operation of the present invention, the criticality
ethylene to retain inks and certain coatings may be im
of the amount of coating applied to the activated polyole?n
proved by subjecting the surface of the polyethylene mate
rials to an activation treatment. This activation treatment
has taken many forms. Thus, for example, it has been
suggested that the surface be subjected to chemical oxida
tion treatment, ?ame treated, exposed to ozone, chlorine,
acid and/or electrical bombardment, etc.
In the commerce of this industry it is the usual practice
surface can be explained as follows.
The aqueous phase top~coat when applied within the
critical prescribed weight coating level to the activated
polyole?n surface forms a porous superstructure of pro
tection over the activated poly-ole?n surface. As a result
of the lattice-like porous nature of the top-coat in the
prescribed Weight coat ranges, there is accessible activated
for the polyethylene ?lm or coated Web material to be
manufactured at one place and then transported to the 40 polyole?n area which retains its readily efficient receptive
printer who applied the printing material. In the han
dling (e.g. friction contact with rollers and machine parts,
The top-coat superstructure in turn acts as a protective
mechanical barrier preventing the exposed surface of
etc.) of this material it was found that the acitvated sur
face was soon lost. Furthermore, in the ordinary han 45 activated polyole?n beneath it from being abraded by
rubbing against other sheets of materials or the machines
dling, shipping and processing of the materials within a
which handle them.
plant it was also found that the activated surface Was soon
Therefore, because of the protective porous top-coat,
lost. This problem was found to be most acute with poly
the deficiencies of the activated polyole?n surface, that
ethylene coated boxboard. The boxboard, after coating
with polyethylene and after surface oxidation of the 50 is, its extremely transient nature and its extremely poor
abrasion resistance are completely overcome.
polyethylene, is subjected to various cutting, stacking and
In the case where there is an insu?icient Weight coat
other handling operations wherein one sheet slides Over
level of the topcoat there is an excess of exposed acti
another sheet. In this case the loss of the activated
vated polyoletin making the topcoat ineffectual as a pro
polyethylene surface was particularly marked.
Another drawback encountered in the use of poly 55 tective barrier. Thus, the over exposed activated poly
ole?n will revert back to its original nature and retain
ethylene in the packaging art was that it could not be
properly glued and particularly could not be glued with
the low-cost dextrin and starch adhesives. Even the acti
‘vated polyethylene surfaces left much to be desired in
its normal de?ciency of poor abrasion resistance.
When there is an excess of protective topcoat the acti
vated areas of polyole?n are entirely masked and covered 7
this regard. The limited gluability of the activated poly 60 and thus receptivity is lost.
In accordance with the present invention particularly
ethylene surface was also found to be transient in char
good results are obtained with aqueous coating solutions
acter and soon lost in handling and abrasion.
It is an object'of the present invention to provide a
wherein the principal solid constituents are either pro
teins or carbohydrates. In these cases, in addition to the
‘process for preserving the printability and gluability of
above mechanism it is thought that an additional mecha
activated polyole?n surfaces.
65 nism is operating. In these instances the facts are the
It is also an object of the present invention to provide
same. Where too little coating solids are present, the
a process (and the product thereof) for manufacturing
packaging materials including activated polyethylene
which have good printability and gluability characteristics.
These and other 'more detailed objects'will be apparent 70
from the following description and drawings.
‘ By “activation,” “active,” and “activated,”~a's used in
the speci?cation and the appended claims, it' is intended
activated polyole?n soon loses its activation and does not
retain the printing inks or glue, whereas when too much
is employed the activation is masked. In this case, how
ever, in addition to the proper distribution of the porous
topcoats it is believed that the coatings themselves are
altered by virtue of their reaction with activated poly
ole?n surface. This change in chemical character of the
principal coating agent would help explain why the ordi
nary hydrophilic protein and carbohydrate overcoatings,
which are normally not ink receptive to hydrocarbon or
resin based inks, when applied to the activated ole?n sur
face coated in accordance with the present invention are
A variety of methods are known in the prior art for
the activation of the polyole?n surface to make it recep
tive to printing inks. As previously noted, they involve
?ame oxidation, chemical oxidation, treatment with a
variety of agents, ozone, chlorine, acid, electrical bom
bardment, etc. These may be employed in the present
invention. In one preferred form of this invention the
polyole?n ?lm is surface oxidized with an open ?ame.
In the prior art it was thought that to activate extruded
applied to the activated polyole?n surface are compatible
with and receptive to both the hydrophobic inks as well 10 polyethylene it was essential to subsequently subject the
highly receptive to these inks. This change in chemical
character also helps explain why these coatings when
extruded polyethylene to an activation or oxidation step.
as the hydrophilic adhesives. .
In either case we have discovered the unusual and
It has now been found that this is not essential and that
the convential ?ame treatment, for example, may be dis
pensed with if the polyethylene surface is activated (oxi
with an unexpected product to which we have imparted 15 dized) by extruding it at a minimum temperature of about
610° F. There is no upper limit to raising the tempera
permanent receptivity to ‘glues and ink by incorporating
ture above 610° F. insofar as improved ink receptivity
the ef?ciencies'of both the hydrophobic polyole?n surface
and 'gluability is concerned, but by exceeding 635° F.
and the hydrophilic top-coat and completely eliminating
the polyethylene begins to break down chemically and
the de?ciencies of both.
unique fact that by top-coating in the prescribed level as
mentioned an activated polyole?n surface we come up
The process of the present invention is applicable to 20 gives rise to odor problems.’ This narrowness of the
useful temperature range is probably the reason that the
polyole?n or polyethylene in a variety of forms. How
utility of an extrusion temperature between 610° F. and
ever, it has its greatest value in the treatment of acti
635° F. eluded 'the previous observers. Polyethylene
vated polyethylene ?lms per se or webs which have been
temperature has been measured by means of a pyrometer
extrusion coated with polyethylene.
As used herein, the term polyole?n refers to the poly 25 as the polyethylene melt exits from the die lips.
It has further been found that whatever change is
meric resins formed through the homopolymerization of
effected in the polyethylene surface, by holding the ex
an aliphatic monoethylenic unsaturated hydrocarbon, or
trusion temperature between 610° F. and 635° F. this
through the copolymerization of two or more unsatu
change is only temporary insofar as gluability is con
rated hydrocarbons. The monomers from which the
polyole?n is prepared are preferably the lower alkenes 30 cerned. In order to preserve gluability it is necessary
to surface coat the 610° F—635° F. extruded polyethylene
which are straight chain or branched chain. By way of
almost immediately with a hydrophilic coating (just as
illustration, the following polyole?ns may be mentioned:
polyethylene, polypropylene, polyalphabutylene, polyiso
the same hydrophillic coating was found to be bene?cial
propyl propylene, polyisopropyl butene, etc.
in preserving the glue and ink receptivity of ?ame-treated
Any backing capable of being extrusion coated with a 35
polyole?n, and particularly polyethylene, is useful in the
polyethylene) .
present invention.
The backing, however, should be a
suitable one for use in packaging. Among the suitable
backing materials may be mentioned kraft paper, box
board substrates, cloth, foil, cellophane, etc. Of particu 40
lar utility are the cellulosic backings such as kraft paper
and boxboard substrates.
The advantages of using a hydrophilic, polar topcoat
on the polyole?n surface are: (1) it greatly lowers tend
ency of the ?lm to build up static charge, (2) improves
the slip resistance of the material, (3) improves the uni
formity of the surface, and (4) adds additional resist
ance to grease and oils. By improving uniformity is
meant that the present topcoat avoids the minute imper
fections due to the heat treatment which is characteristic
of the prior art heat-treated polyethylene ?lms. One of
the major problems of the prior art processes is the dif?
culty in obtaining uniform oxidation of the polyethylene
surface. For this reason these prior art processes have
not gained wide acceptance. In contrast to this the pres
ent process provides a ?nished product wherein the sur
face has a high degree of uniformity.
In order to facilitate ready comprehension of this inven
tion and for a proper appreciation of the salient features
thereof, the invention is illustrated in the accompanying
drawings forming part thereof, and in which:
FIG. 1 is a schematic sectional view showing the
apparatus involved in the present coating operation.
FIG. 2 is ‘a schematic sectional view of a system which
may be used in a modi?cation of the present invention
which does not require the ?ame treatment of the poly
ethylene surface.
The following examples are further illustrative of the
present invention and it will be understood that the in—
vention is not limited thereto.
Example I
In FIG. 1 a web of kraft paper 36 is drawn from a reel
(not shown) and is fed over a rubber faced roller 37 into
a nip formed between the roller and a cooling drum 38.
The polyethylene is coated to the kraft paper at the nip
by any standard extrusion process common in the art.
The polyethylene ?lm coated paper so formed is then
fed over a roller 39 and under a gas burner ‘40 where
As mentioned above, the topcoats that are most suit
the surface of the polyethylene ?lm to be topcoated is
able for the present invention are hydrophilic and polar.
heated or oxidized.
In a preferred form of this invention the topcoats are
also non-polymerizing. ‘Among the useful topcoat mate
The paper is run at a speed of "approximately 200 f.p.m.
and the gas burner having a maximum ?ame temperature
‘rials may be mentioned starch, carboxymethyl cellulose,
of 3000° F. is set at a distance of from 1/2” to %" away
proteins (e.g. gelatin, casein), polyvinyl alcohol, poly
vinyl acetate, Methocel, etc. One typical topcoat formula
consists of a 10% solution of Penford Gum 260, which 6
is a hydroxy ethyl ether derivative of cornstarch. A sec
ond topcoat formulation consists of soybean protein (or
from the surface of the polyethylene ?lm so that the ?lm
passes through the oxidizing zone of the ?ame.
The treated polyethylene ?lm is then carried by a
series of rollers 41 into a nip formed between rollers 42
and v43. A coating solution containing
alternatively casein), which is dissolved with an excess of
ammonium hydroxide in the presence of zinc sulfate.
The composition is as follows:
Parts by weight
Soybean protein _'_ ________________________ __
Pts. by weight
___________________________________ __
Protein c.‘ ___________________ -..'-.‘ ____ _;.....'___
Zinc sulfate _______ _'__.___‘_ ________________ .._
Water ____ _'_;____‘____;;_;____;_;__‘____ ..-__'_-_
Ammonia (NH4OH) (26° Bé.) ____________ __ 26.50
Zinc sulfate _____ _._'___'_'____'_____ _-'___'_‘ ____ __
Ammonia'(NH4OI—I) (26° Bé.) ___'-___‘___;____ 26.50
is transferred from bath '44 by roller 45 to'the surface
of roller'42. This coating is then applied by roller 42
nip formed between rollers 42 and 43.
Example IV
The procedure of Example III is followed using the fol
directly tov the polyethylene ?lm as it passes through the
. t The coated polyethylene ?lm is then carried to a hot
lowing coating composition:
air "drying oven 46 where at a temperature between 120°
Parts by weight
Rand 150° F. the water is evaporated from the coating.
Soya protein _‘__ l
The ?lm is then taken over a series of rollers 47 to a
rewind roller 48.
_ 14
_ _ _ _ _ _ _ _ _ __
_ _ _ __
Ammonia (26° Bé.) _________________________ __
An alternative procedure for applying the topcoat
employs the so-called “air knife” coating operation. An
Example V
air knife ‘coatcr consists of a roller of approximately 10" 10' The procedure of Example III is followed using the
‘in diameter which rotates in a pan'of coating‘and applies
coating super?uously to a web. Immediately after pass
following coating composition:
‘ing ‘over this roll the web is reversed over a breast roll.
At this point the excess coating is blown off with a jet of
Parts by weight
air leaving the desired amount of coating material on 15 Ammonia (26° Bé.) _________________________ .._ 2
the web. This air knife is described in U.S. Patent
Example VI
1,590,417. _ The slot in the air vknife is adjustable but is
.‘usually operated between .018 and .025 of an inch. Air
‘ The procedure of Example III is followed using the
pressure is usually maintained between 1.5 and 3.5 lbs. per
following coating composition: '
Parts by weight
' '
“After the material is coated in this manner, it may
be dried through a hot air circulating tunnel ‘or on a
'festoon' rack. In the‘present process we prefer a festoon
rack with an air temperature of approximately 135° F .
____ __
Water _____
‘As previously pointed out, among the advantages of
The coating is usually dried in this atmosphere for four 25 the present invention is that the materials coated in ac
cordance with the present invention are readily printable
'or' ?ve minutes. ’
and gluable. In particular it was pointed out that the
When ?lm of polyethylene is to be treated in accord
organic based or oil based inks may be employed and
ance with the present invention a roll of preformed poly
the low-cost dextrin and starch adhesives. Although these
ethylene ?lm may replace rolls 37 and 38.~in.FIG. l.
The ?lm of polyethylene is directed under gas .burner 30 inks and adhesives may be employed to advantage, other
inks and adhesives may be used. The following are ex
40 and then-subjected to the same't-reatment as the poly
ethylene coated kraft paper described above.
Example II
The ?rst procedure described in Example I is followed 35
except that a 10% aqueous solution of Penford Gum 260
is employed as the topcoat.
40 in said example. This product was then printed on a com
mercial 2-color Harris Offset Press using Pope & Gray’s
Gloss Offset Ink #ROl1668W under standard printing
conditions. The printed ink bond to the top-coated poly
mers, polyvinyl chloride, chloride acetate copolymers, etc.
The addition-of synthetic polymers adds to the flexibility
‘and thermoplasticity' of the coating.
vvThe ‘following; examples are described in connection
:with 1310.; 2. j j_ ’
The 610°~635°
"ethylene surface was so tight as to resist all and any dis
Example III
heated polyethylene ?lm is extruded
according to standard practice into- the nip formed by a
’ rubber face. pressure roll 37' and a cooling drum 38' and 50
'there coated upon a paper web 36’ which is simultane
ously led into the same. nip. Substantially immediately
A white lined news ?lled boxboard calipering 0.014"
was coated on the white lined side with 1 mil of poly
ethylene which was activated incorporating a topcoat
formulation of Example I, according to method described
. The synthetic polymers which can be used in the form
of latex are styrene butadiene, butadiene acrylonitrile, var
ious polyacrylates such as ethyl acrylate, ethyl methacryl
ate, polyvinyli acetate, polyvinyl acetateacrylate copoly
amples of typical printing and gluing operations to which
the product of Example I has been subjected.
Example VII
ruption of ink particles when cellophane tape was pressed
‘tightly against the ink surface and pulled rapidly and
vigorously away. This cellophane tape test is often used
by printing industry to measure ink bond.
Example VIII
Carton blanks fabricated of news ?lled white lined
boxboard containing on the news side a 1% mil. coating
of polyethylene activated according to method outlined
upon cooling, the polyethylene coated paper web is led
in Example I and top coated with an air knife coatcr using
to the coating device which consists of three rolls:
55 topcoat formulation as described in Example VI were
(1) A pickup roll 45’
glued on an International 6F straight line glue machine
(2) A metering transfer roll 42’
using a berated dextrine adhesive, National Adhesive
(3) A backing roll 43’
#13-2260 at conventional carton sealing speeds.
The carton glue seam, when pulled apart at the end
transfer roll where the polyethylene surface is coated with 60 of the glue machine, tore ?ber completely down the glue
to maintain uniformity of coating deposition from the
a‘ non-polymerizing, polar, hydrophilic coating (soya pro
tein, 100 parts by weight; water, 638 parts by weight;
seam. This is considered excellent by all who are familiar
ammonia (26° Bé.), 26.50 parts by weight; zinc sulfate,
5.12 parts by weight) at coating weights of 0.07 pound
with this operation.
Other types of printing inks may be employed which
may be mentioned in the printing operation of Example
hydrophilic coating to the polyethylene surface.
and restricted solely by the scope of the appended claims.
to 1.4 pounds per 1000 sq. ft. The polyethylene coated 65 VII, among which are Pope & Gray’s RN10484, a letter
press ink, and IPI’s Lithogem, a litho ink.
paper web is thereupon led through a series of dryers
Although the low-cost dextrin and starch adhesives are
(gas burners 46') which are directed against the non
most preferred, other adhesives may be used. Among
polyethylene coated side of the paper web; whereupon
these may be mentioned Union Paste and Glue’s M718A,
the polyethylene coated paper web is led to a take-off
device 48’. This is practiced at speeds of 75-250 feet 70 a resin emulsion type and United Paste and Glue’s #5245,
a rubber copolymer latex type adhesive.
per minute.
While the invention has been described with particular
The speed is only limited by the rated output of the
to speci?c embodiments, it is to be understood
extruder. Furthermore, any suitable coating and drying '
that it is not limited thereto, but is‘to be construed broadly
device will su?ice to apply the non-polymerizing, polar,
What is claimed is:
v 10. A method according to claim 9, further compris
1. A polyole?n web adapted to be coated with printing
ing the step of initially extruding the polyole?n web onto
a packaging material substrate.
11. A method according to claim 10, wherein said
packaging material substrate is a paper product.
a non-polymerizing, polar, aqueous-phase, hydrophilic
12. A method for preparing a composite web, which
overcoat at a weight of 0.07 to 1.4 lbs. on a dry basis per
comprises extruding on a paper product web a polyethyl
1000 square feet of s'aid‘polyole?n web for preserving the
ene ?lm, activating the surface of said polyethylene ?lm,
printing ink and adhesive receptivity of said active poly
substantially immediately thereafter coating said active
ole?n ?lm.
,2. A composite web according to claim 1, further com 10 surface with an aqueous phase soybeanprotein coating
composition applied at a weight of 0.07 to 1.4 pounds on
prising a packaging material substrate.
a dry basis per ‘1,000 square feet of ?lm surface, drying
‘ 3. A composite web according to claim 2, wherein said
said coating, and thereafter gluing or printing on selected
packaging material substrate is a paper product.
parts of said'coating.
4. A web adapted to be coated on selected ‘portions
13. --A-method for preserving the adhesive and oil based
“with printing inks or adhesives ‘comprising a "polyole?n
printing link 'retentiveness of a ,polyole?n surface made
?lm activated for receiving a printing ink or adhesive,
inks or adhesives, comprising a ‘?lm activated for receiv
ing a printing ink or adhesive, said ?lm having thereon
said ?lm having thereon anon-polymerizing, polar, aque
active by ‘extrusion of the v.polyole?nic web at tempera
tures between1_610° -F.j:and an?upper temperature at which
‘ous~phase, hydrophilic overcoat at a weight of 0.07-1.4
the polyole?n breaks down which comprises the steps of
lbs. 'on a dry basis per 1000 square feet of polyole?n web
further comprising adhesive or printing ink on certain 20 coating said surface substantially immediately after ex
trusion with ‘a polar, =non~polymerizing, aqueous-phase,
selected ‘portions of said overcoat.
hydrophilic coating \at'a weight of 0.077 to 1.4 pounds on
5. A packaging material comprising 'a paper product
a dry‘basis per 1,000 square feettof‘said polyole?nic sur
base, an active polyethylene coating thereon, a'soybea'n
protein overcoat applied onto said polyethylene coating
face and drying said coating.
‘in an aqueous phase 'at a weight of 0.07 to 1.4 pounds on >
14. A method vaccording to claim ‘13, further compris
ing the steps of subjecting the coated surface to printing
‘a dry basis per 1,000 square feet of polyethylene surface,
oil's-‘phase, ‘hydrophilic composition applied at a weight
and gluing on selected parts thereof.
15. 'A method accordingitoclaim v13, wherein the poly
‘ole?n is ‘polyethylene :and said upper temperature is
1,6. A method ofgpreparing a composite web, which
comprises‘extruding on a paperproduct web a polyethyl
of 0.07 to 1-.'4“po'unds on a‘dry basis per 1,000 square feet
ene ?lm at a temperature between 610° and 635° F.,
and adhesive or printing ink on certain selected portions
of said overcoat.
6. ‘In combination an active polyole?nic surface adapt
‘ed ifor'recei‘ving thereon printing inks or adhesives, and
an ov'er'coat consisting of a non-polymerizing, polar, aque
of polyole?nic surface, for preserving the printing ink and
adhesive receptivity of said active polyole?n surface.
7. In the combination according to claim 6, wherein
the polyole?nic surface is a polyethylenic surface.
8. ‘A‘method ‘for preparing-a polyole?n web for ink
‘and adhesive receptivity, which comprises the steps of
activating the surface of a polyole?n web, and applying 40
substantially immediately ‘thereafter coating said ?lm
with an aqueous-phase soybeanprotein coating composi
tion-applied at-a weight of 007m 1.4 pounds on a dry
basis per 1,000 square feet of'?lm surface, drying said
coating, ‘and thereafter gluing and printing on selected
'parts of ‘said coating.
References Cited in the ?le of this patent
‘onto the active surface a non-polymerizing, polar, aque
ous-phase, hydrophilic overcoat at a weight of 0.07 to
1.4'lbs. on a dry basis per 1000 square feet of said poly
Ball ________________ __ June 23,
ole?n web to maintain the polyole?n surface in its active
Horton _______________ "Feb. 2,
45 2,668,134
condition for receiving printing inks and adhesives.
'Kritche'ver ___________ __'July 20,
v9. A method for preparing a polyole?n web which
Irion ________________ .... Aug. 2,
comprises the steps of activating the surface of said web,
and applying to the active surface a non-polymerizing,
polar, aqueous phase hydrophilic overcoat at a weight of 50 ‘2,829,118
0.07 to 1.4 lbs. on a dry basis per 1000 square feet of
said ‘polyole?n web, said method further including the
‘steps ‘of ‘applying an adhesive or printing ink on certain
vselected portions ofsaid overcoat.
Frost _______________ __ Aug. 21, 1956
Grow _.-.., ____________ __ June 18, 1957
'Wehr ________________ __ Apr. 1, 1958
vWolinski ____________ __ Mar. 24, 1959
Rice -et al _____________ __ Oct. 11, 1960
Keller et a1. __________ __ Jan. 17, 1961
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