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Патент USA US3068525

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Dec. 18, 1962
Filed June 1, 1960
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United States Patent 0
Peter H. l-Iofer, Berkeley Heights, N.J., assignor to Union
Carbide florporation, a corporation of New York
Filed June 1, 1960, Ser. No. 33,199
17 Claims. (Cl. 18-13)
Patented Dec. 18, 19-52
thickness of the adhering coating and the uniformity of
distribution thereof about the periphery of vthe extruded
contour while the tubing remains in an essentially un
stretched state and thereafter stretching the tubing in the
machine and transverse direction, simultaneously uni
formly thinning the adhering coating.
Apparatus is also provided comprising a primary die
for extruding seamless thermoplastic tubing, a secondary
This invention relates to surface coating of extruded
die substantially coaxial with the primary die and adapt
contours. More particularly, the invention relates to
method and apparatus for forming uniform ultra-thin 10 ed to peripherally bear against the tubing with a force
sufficient to relieve the greater part of the longitudinal
coatings on biaxially stretched thermoplastic ?lms as an
stress from the tubing therebelow and maintain said tubing
integral step in the production of such ?lms.
in an essentially unstretched state, means for applying
The use of surface coatings to alter the characteristics
adherent coating material on the essentially unstretched
of ?exible packaging is well known. By means of a func
tionally specific coating ?exible packaging material such 15 tubing as it passes from the primary die to the secondary
die and means for drawing the tubing through the sec
as paper, cellophane and thermoplastic ?lms have been
ondary die.
adapted to a great variety of end-uses. Users of cellu
It is an essential feature of the present invention to
losic packaging, i.e., paper and cellophane, are accustomed
to packaging materials “tailor-made” to meet their mar
keting needs. The advent of thermoplastic ?hn, par
ticularly stretched, biaxially oriented ?lms, brought to
the art packaging materials of theretofore unattained
strength and toughness. The packaging industry, how
ever, still demanded the speci?c end-use properties which
were available in cellulosic packaging material. In par
ticular, anti-fog properties are needed for meat and pro
apply adherent coating material onto the extruded tubing
while the tubing is essentially unstretched and subse
quently only to stretch the tubing. Because of this fea
ture more uniform ultra-thin coatings are achieved by my
invention than are obtained by pre-stretching and coating
or simultaneously stretching and coating thermoplastic
The invention will be more fully described herein
duce packaging ?lms, anti-static properties are needed to
below in conjunction with the attached drawings where’
avoid dust accumulation on window envelopes and the
like, and water vapor and gas barrier coatings are needed
to protect other goods.
To answer this need coatings have been developed for
thermoplastic ?lms. The initial methods for applying
such coatings were naturally borrowed from the cellulosic
coating art. The coating procedures involved use of
solvent or emulsion systems in a vseparate step from
thermoplastic ?lm formation. The cost of such procedures
is prohibitive for all but premium priced, highly special
ized ?lms because of (l) the initially high cost of the
thermoplastic base sheet (compared to cellulosic ma
terials), (2) the labor and equipment expense involved
in a second ?lm handling operation and (3) the capital
expenditure for application, drying and solvent recovery
equipment. Additionally the solvents necessary for cer
tain coating materials e.g., liquid hydrocarbons, have a
tendency to soften the resin base, which precludes use
of these solvents.
Extra cost factors (2) and (3) could be substantially
eliminated by performing the coating operation as an
FIG. 1 is a partly diagrammatic sectional view of the
tube extruding unit of one embodiment of the invention;
FIG. 2 is a partly diagrammatic sectional view of one
embodiment of the tube coating apparatus;
FIG. 3 is a sectional view partly in elevation of another
embodiment of the tube coating apparatus;
FIG. 4 is a sectional view partly in elevation of an
other embodiment of the tube coating apparatus illustrat
ing means for application of a coating material under
positive pressure;
FIG. 5 is a sectional View of the tube coating apparatus
illustrating simultaneous coating of inner and outer tube
FiG. 6 is an elevational view partly broken away to
show underlying parts of the tube extrusion and coating
apparatus illustrating application of coating material di
rectly from the die face onto the extruded tube;
FIGS. 7-A, 7-13 and 7—C are sectional views of modi
?cations of the secondary die in lip shape and surface.
Referring now to the drawings where like reference
integral part of the biaxially stretched thermoplastic ?lm 50 numerals indicate like parts there is shown in KG. 1 an ‘
apparatus ‘for coating and biaxially stretching extruded
forming operation. Such a course would take advantage
of the methods of thermoplastic ?lm manufacture pres
thermoplastic ?lm in a continuous manner comprising an
extruder it), a 90° elbow bend 12 through which molten
thermoplastic resin is fed to a primary die 14 which forms
55 t 1e molten thermoplastic into seamless tubing 16. Means
for cooling the tubing 16 as it emerges from the primary
is is an object, therefore, of the present invention to
die 14 comprising, for example, an air ring 13 is provided.
provide method and apparatus for surface coating ex
Spaced above and coaxial with theprimary die 14‘ is a
truded film as an integral step in the ?lm forming opera
ently used and would avoid di?iculties encountered in
trying to adapt an old coating method to a new packaging
secondary die 20 adjustably mounted on supports 22
It is another object to provide method for producing 60 which die is adapted to peripherally bear against tubing
16. A standard collapsing frame 24 and hip rolls 26
functionally specialized biaxially stretched thermoplastic
which withdraw the tubing from the dies therebelow are
?lms by application of a coating imparting the desired
provided to collapse the tubing which is then fed to a wind
properties as an integral step in the extrusion-stretching
up apparatus (not shown). A bubble generally indicated
at 28 is formed in the tubing 16 above the secondary die
It is another object to provide method and apparatus 65 2t} by maintaining in the tubing a ?uid medium introduced
for extruding, biaxially stretching and surface coating
through inlet 30 in primary die 14- and passageway 32 in
seamless tubing in a continuous manner.
die pin 34.
These and other objects are accomplished with the
Highly uniform coatings are applied to the extruded
method of the present invention by applying a thickness
tubing 16 in accordance with the present invention with
of adherent coating material to essentially unstretched 70 approximately doughnut shaped annular rolling bank 35
extruded thermoplastic tubing as the tubing emerges from
of the desired coating material mounted in the space dc‘
the forming die, simultaneously positively regulating the
The tubing 16 is stretched in both the transverse and
machine directions by being in?ated at a point above the
?ned by the wall 38 of secondary die ori?ce 4t} and the
adjacent portion of tubing 16. Formation of annular
bank 36 is accomplished by applying coating material to
‘the essentially unstretched portion of the tubing 15 locate
secondary die 20, lateral stretching being imparted by
the trapped ?uid medium and longitudinal stretching by
below the secondary die 29, conveying the applied coat
.ing material on the tubing 16 to the secondary die 2%,
drawing the tubing 16 through the secondary die ori?ce
.4_(_)_»while maintaining a controllable scraping contact be
the pulling force of the nip rolls 26. The tubing 16 is
cooled as it traverses the distance from primary die 14
to secondary die 20 either by the ambient atmosphere
or preferably by a blast of cool air from the air ring 18
directed at all‘ points on the periphery of the tubing 16.
In a preferred embodiment of the apparatus the air ring
‘18 is rotatably mounted above the primary die 14 and
tween the tubing 16 and the edge portion of the wall 38
‘of the secondary die ori?ce 4%, thereby scraping (“doctor
ing”)-from’ the tubing 16, as it passes the edge 42 of the
secondary die ori?ce 40, all coating material in excess of
is revolved slowly about the tubing 16 by a rotating
that desired on the tubing 16. i The doctored coating ma‘
teen is forced’ along the wall 38 of the secondary die
ori?ce 40 away from the tubing 16. The coating material 15
,coheres in a mass and as it again contacts the tubing 15
is carried along with the tubing toward the secondary die
ori?ce 40 where it is again scraped off the tubing between
edge portion of wall 38 and the scraping, cohering, recon
tacting cycle is repeated. This cycle causes the mass. of 20
coating material to form around the tubing 16 an annular
bank 36 having a clockwise rotation. It is easily seen
that the constant freshening of the portion of the bank 36
actually in contact with tubing 16 eliminates problems of
insu?icient coating material supply at any point on the
periphery of tubing 16. The rolling annular bank 36 en
means-such as driven belt 19‘ as said tube is drawn there
pastas ‘shown in FIGURE 6. Where air ring 18 rotates
it is convenient to similarly rotate the secondary die 25
at approximately the same speed, e.g., 1/3 to 2 revolutions
per minute, as by maintaining the said die on said air
ring as shown in FIG. 1. In this embodiment more uni
form cooling of the tubing 16 is obtained and also the
annular rolling bank 36 of coating material is given an
other motion which further insures uniform distribution
of the coating material on the tubing 16 prior to in?a
The cooled tubing 16 above the secondary die 2%) is
stretched in two directions and is thereby biaxially ori
ented, provided the tubing is at the orientation tempera
ture of the particular ?lm. Generally speaking, these ori
sures an even distribution of coating material at all points
on the tubing as it passes through the secondary die ori
entation temperatures are the temperatures at which the
?ce 40.
constituent molecules of a ?lm are permanently aligned
The edge 42 of secondary die 20 maintains a peripheral 30 by stretching. Biaxial orientation of thermoplastic ?lms
‘contact with the tubing 16. As pointed out above, at a
by means of the blown tubing method is well known to
minimum this contact is su?‘icient to relieve the greater
art and need not be further described here except to
portion of the longitudinal stress exerted on the tubing
mention that provision of a secondary die 20 spaced above
16 by the nip rolls 26 or other withdrawal means, pref
the primary die and providing a distance for the tubing
erably 90 percent and more of the stretching force ex 35 to traverse makes possible a greater amount of molecular
erted by the nip rolls 26 is relieved by the secondary die
orientation in the ?lm bubble than can be achieved by
20. The die 20 by thus relieving the stretching stress
blowing a bubble in tubular ?lm immediately upon emer
maintains the tubing 16 in an essentially unstretched state
gence from the extrusion die ori?ce.
at the time the coating material is applied thereto by the
As the tubing 16 is in?ated the coating material on the
rolling bank 36.
40 ?lm surface is drawn thinly over the expanded surface
By the term “essentially unstretched” as applied to
‘area. This drawing occurs uniformly and evenly leav
thermoplastic tubing in the present speci?cation and claims
ing a substantially constant thickness of coating material
is meant that state of the tubing wherein only a minor
over the entire ?lm surface with no bare, uncoated spots.
amount, i.e., less than 50 percent and preferably less than
Resins which can be continuously extruded, coated
10 percent stretch is imparted to the tubing. Thus, the 45 and biaxially stretched by the method of the present
amount of stretch allowed in the tubing before it passes
invention are the extrusion grades of thermoplastic resins
the secondary die is not more than 50 percent over its
capable of forming self-supporting ?lms. Among the
original length and preferably less than 10 percent of
more commercially important resins which can be used
its original length. The controlling of the amount of
in my invention are extrusion grades of polyethylene,
stretch imparted to the tubing during the coating opera
tion, i.e., coating only essentially unstretched tubing as
above described is a critical feature of my invention which
provides more uniform thickness in the coating ?nally
After the coating material has been uniformly applied
by the annular rolling bank 36 to the tubing 16 and after
it passes the secondary die 20 the tubing 16 is in?ated to
form bubble 28 by being drawn over a quantity of ?uid
medium such as air, nitrogen, argon or the like trapped
between nip rolls 26 and the primary die 14. In?ation
phenoxy, vinyl resins and polystyrene. As is indicated by
the diversity of these illustrative resins in properties and
extrusion qualities, the method herein disclosed is wide
1y applicable and is useful with all thermoplastic resins
which are extrudable into tubular ?lm.
Any coating material which adheres to a hot resin sub
strate can be applied by the method and apparatus of
the present invention. Particularly desirable coating ma
terials are those imparting speci?c functional improve
ments to the thermoplastic ?lm, for example, anti-static,
(transverse direction) stretch
anti-fog or water vapor and gas barrier properties. It is
sometimes preferable to coat with solventless systems and
' The secondary die 20 is positioned in such a manner
example, melt coating is readily carried out by heating
i of the tubing causes lateral
ing of the tubing 16.
that the stationary bubble 28 develops and is maintained
entirely above said die with no expansion in the tubing
16 occurring below the secondary die 26'. Thus, there
is no signi?cant lateral stretching of the tubing 16 be
low the secondary die 2!} and said portion of the tubing
the present method is admirably suited thereto.
the coating material in the absence of a solvent to the
melting temperature of the coating material and hold
ing the melt material in contact with the essentially un
stretched tubing as it passes from the primary to the
secondary die. The suitability of coating from a hot
remains essentially unstretched in either the transverse or
melt is a noteworthy advantage of the present invention.
machine direction. The distance from the primary die 70 Heretofore attempts at hot melt coating have involved
14 to the secondary die 29 can be varied within rather
the use of a bath through which pre-formed ?lm was
wide limits, the controlling factor being the need to main
passed. The result was usually a heat shrunk or partly
tain the portion of the tubing'below the secondary die 2%
decomposed ?lm with a rather uneven coating. The sec
in an essentially unstretched state. Distances from l--35
ond heating step is not required in my method and there
inches have been found entirely suitable.
fore the advantages of biaxial orientation are retained
rials which can be applied from a melt are thermally
or other coating material is disposed for contact with ex
truded tubing 16. in this embodiment no separate heated
stable while liquid and have melting temperatures at
coating material receptacle is employed, the face of the
and uniform coatings are also achieved. Coating mate
die itself acting as the heating means. This embodiment
coated. Means for applying the coating material are Ct is particularly well suited to the con 'ng of polyethylene
tubing with wax base coating materials because:
numerous and range from a hand held spatula to positive
about or below the temperature of the extrudate to be
pressure systems. The use of a receptacle to catch mate
rial falling from the annular rolling bank either off the
(1) Polyethylene, having a characteristically poor
strength at elevated temperatures, is relatively easily torn
as it passes hard, sharp surfaces and elimination of the
secondary die or down the tube itself in order to ‘main
tain an easily replenishable supply of resin below the roll 10 receptacle surface ‘bearing against the tubing reduces by
ing bank is preferred.
One type of receptacle particularly adapted to solid
one-half the contacts which can cause tearing of the ?lm,
powdered coating materials is shown in PEG. ‘2 wherein
receptacle 44A, which is adjustably mounted below sec
ondary die it} which is in turn supported above the pri
(2) Wax base coatings generally have low melting
points, ?ow readily and spread uniformly and hence are
ideal for coating from a comparatively small supply.
The secondary die 20 can be varied with respect to the
mary die Illi- by means not shown, is provided with elec
tric heating element 46 to maintain the powdered coat
orifice 4d therein both in shape and surface. Preferred
ing material therein at an elevated temperature such that
shapes and surfaces are shown in M68. 7-A, 7—B and
contact of powdered coating material with the hot ex
7-C. The angle of the wall 33 of the ori?ce 4b can be
truded tubing 16 causes immediate fusing of the coating 20 varied in included angle “a” from just off the perpen~
material on the tubing. A portion of the adhering coat
dicular, e.g., “a”:5° to “a”=l20° with increased in
ing material is doctored from the tubing id as it passes the
cluded angle “a” providing relatively thinner coatings.
secondary die 20 and while still molten forms a rolling
Coatings of'from 0.0000001 to 0.0005 inch have been
annular bank 36. Excess coating material solidi?es and
routinely prepared on a variety of substrates using sec
falls back into the receptacle 445A whence it is again 25 ondary dies dill having various included angles. The wall
contacted with the hot tubing 56. if desired, the recep
38 of the ori?ce 4t) can have a radius of curvature as
tacle 64A can be modi?ed to provide a porous bottom
shown in FIG. 7—B if it is desired for example to provide
through which are or other gas can be blown at a rate
a less sharp edge in contact with the tubing 16. As
su?icient to form a ?uidized bed of the contained pow
shown in PPS. 7-C the wall 3% of the secondary die can
dered coating material.
be knurled to provide decorative efl'ects or spaced coatings
In FIG. 3 another receptacle 44B is shown which per
on the tubing as illustrated in Example 2 hereinbelow.
mits containment of liquid coating materials, either hot
The secondary die ori?ce 40 can be equal in diameter
melts or solutions of coating materials in solvents which
to the ori?ce of the primary die 14 or‘ may be smaller or
do not substantially adversely affect the thermoplastic
larger. The smaller the die ori?ce lit? for a given size
?lms, e.g., alcohol solvents with polystyrene tubing and
bubble 28 the greater the expansion of the tube to form
liquid hydrocarbons with polyethylene tubing et cetera.
the bubble and hence the greater stretching and/ or orien
Heat is provided on the sides and bottom of the con
tation imparted to the tubular ?lm. The edge 42 of the
tainer by heating elements 1th. The receptacle
secondary die ori?ce 45? can be fabricated of the same or
ceeds in diameter the secondary die ori?ce 40 in order
different material than the body of‘ the secondary die 20.
that excess material from the rolling bank 36 which drips
Suitable materials for the fabrication‘ of the secondary
from the outermost edge of the secondary die ori?ce 40
die 20 and the edge 42 thereof are those which are rigid
will fall back into the container for reuse. A lip 48' is
at the temperatures of the extrudates which they shape.
provided on the receptacle 1248 shown in FIG. 3 to facili
Hence, metals such as steel and aluminum, and plastics
tate replenishing the supply of coating vmaterial from
time to time.
In FIG. 4 there is shown an embodiment of the ap
paratus especially adapted to pre-wetting and coating
thermoplastic tubing. As shown, the tubing ll? passes
through receptacle
in which is disposed a pro-wet
ting compound which facilitates adhesion of coating mate
The pro-wetting compound adheres to the tub
ing 15. A diluent for the coating material can also be
employed as a pre-wetting compound and thereby be ap
plied simultaneously with the coating material. Any ex
cess is doctored and, like coating materials, forms a roll
ing annular bank 36 and, after the tubing 16 has passed
through the secondary die ‘ill but prior to stretching
either longitudinally or laterally, the tubing to is sprayed
with a liquid coating material from outlets circumferen
tially spaced in applicator ring 50* by air pressure. Other
conventional mechanical and fluid pressure means can
be use 1.
Either inner or outer surface coating of extruded tub
ing or both can be accomplished with the present inven
tion. For example, in FIG. 5 there is shown an em
bodiment of the apparatus adapted to coat the outer sur
face 52' of the tubing 16 as in. FIG. 1, and also provided
with an inner doctor blade 54 which is coaxial with and
such as phenolic resins are useful as secondary die ma
The speci?c coating materials used in the examples
hereinbelow are merely illustrative of suitable coating
materials. Their chemical identities are:
“Versamid 940” the condensation product of dimer
ized linolenic acid with a diamine sold by General Mills
Molecular weight ________ _. 6000-9000.
Melting point ___________ __ l05°-ll5° C.
Viscosity _______________ __ 15~30 poises @ 150° C.
“Pentalyn A"—the pentaerythritol ester of resin‘, hav
ing' a softening point of 109—ll6° C. and sold by Her
cules Powder Company.
“Paraf?n Wax”—sold by Esso Standard Oil Company
as “Essowax 5010” and having a melting point of 149—
151° F.
“Microcrystalline Wax” sold. by Esso Standard Oil
Company as “Microvan 1650"’ and having a melting point
of 165° F.
“Aluminum Paste” sold by Aluminum Company of
America as- “Albron Aluminum Paste” (16-5 %v l'ea?'n'g alu
minum in‘ mineral spirits)‘.
The following examples are illustrative of the practice
supported by die pin 34 modi?ed to provide channels
of the present invention; All parts and percentages are
56 for coating material to be fed through die pin 34 onto
the surface 58 thereof, to be picked up by the inner sur 70 by weight unless otherwise stated. The apparatus used
in the following examples is shown in FIG. 3.
face 69 of the tubing 16. Any excess being doctored off
as the inner surface 60 of the tubing 16 passes the periph
cry 62 of inner doctor blade 54.
In FIG. 6 the receptacle is an annular niche 44D which
is provided in the face of primary die 14 wherein wax
Coating of Blown Tubular Polystyrene Film
vThe extruder used was‘ a Royle &' Sons model N0. 3
having a 41/2 inch diameter barrel. Extrusion grade
polystyrene resin having a molecular weight of about
uncoated ?lm were tested for moisture vapor transmission
as in Example 1.
60,000 was reduced to a ?owing condition and fed from
the extruder through a 90° elbow bend to a bottom fed
die having a 5 inch diameter annular ori?ce. Conven
MVT ( rams/100
sq. in. 24 hours)
tional collapsing and ?lm windup equipment was also
provided. A secondary die fabricated from 1/2 inch thick
steel plate, having a sharp knife-edged 4% inch diameter
_______________________ _._
(striped) ____________________ __ 4.1
ori?ce in the center with an included angle of 20° was
It is evident from the excellent MVT results with the
positioned above the die ori?ce and coaxial therewith. 10 coated sample that the wax portion of the coating was
At the start, an extruded tube was fed through the coating
over the entire ?lm surface although the aluminum paste
container, the secondary die and nip rolls to the windnp
occurred only in spaced stripes corresponding to the val
rolls. Thereafter a stationary bubble was blown with
leys in the knurled surface of the secondary die bearing
nitrogen in the tubing between the secondary die and the
against the blunt shaped base of the tubing.
nip rolls. Coating material having the composition
Versamid 940 __________________________ __ 52.5
Pentalyn A ____________________________ _._. 42.5
wax ___________________________ __
was heated to a melt in the coating container.
The coat
Samples were tested as in Example 2.
.In this manner the coating material was con
tinuously brought into uniform circumferential contact
with the extruded tube. Any excess coating material ad
hering to the tube was doctored from the ?lm surface as
the tube passed through the secondary die ori?ce. '
Extrusion conditions were:
Die temperature ______ __ 158° C.
Extrudate temperature--- 180° C.
Extrusion rate ________ _. 152 lbs/hour.
Air cooling _______ __’___ Ca. 1000 cubic feet/minute.
Drawspeed ___________ _. 60 feet/minute.
Bubble diameter/tube
diameter ratio ______ _- 7.5/1.
Bubble shape _________ _. Blunt.
Film gauge ___________ _. 0.00094—0.00l1 inch.
Coating thickness _____ __ ‘0.000005-0000006 inch.
MVT (grams/100
sq, in. / 24 hours)
ing adhered to the hot tube as it passed through the coat
ing container. As the adhering molten coating was car
ried upward on the extruded tube, the material formed
a rolling annular bank in the recess formed by the wall
of the extruded tube and the face of the secondary die
The procedure of Example 2 was followed except that
less nitrogen was maintained in the bubble so that the
bubble assumed a narrow based “tulip” shape. A continu
ous, i.e., nonstriped, coating of aluminum Was achieved.
_______________________ __
(striped) ____________________ __ 4.1
The continuity in aluminum coating obtained in this
exampleindicates that by varying the shape of the bubble
from blunt (wide base) to “tulip-like” (narrow base) the
pressure exerted on the base of the bubble by the sec
ondary die can be greatly varied. In this example, the
knurled edge of the secondary die ori?ce had no effect
on the aluminum paste in contrast with the complete block
ing of aluminum paste by the ridges of the knurled sur
faces in Example 2.
The procedure of Example 1 was used except:
The secondary die was changed to 1/2 inch steel plate
having a smooth surfaced 41/2 inch diameter ori?ce with
an included angle of 120°;
Drawspeed was 80 feet/minute;
Air at 1500 cubic feet/minute.
A polystyrene ?lm having a thickness of 0.00065
A sample of the coated ?lm and a sample of the same
0.00079 inch and a surface coating of 0.000003 inch was
?lm, but uncoated, were tested for moisture vapor trans
mission (MVT) as follows: Each of a set of standard
Testing for MVT gave the following results.
Thwing-Albert vapometer cups was ?lled with approxi
mately 55 cc. of water. Two and one-half inch diameter
sq. in.( 2ftmliiiirs)
discs of the ?lm samples were ?tted across the cup open
ings. The cups were then stored at room temperature
Coated ________________________________ __ 9.6
(ca. 25° C.) and loss of water vapor measured.
MVT (grams/ 100 sq. in./24 hrs.)
Uncoated ________________________ __ 10-13
Coated __________________________ __
The procedure of Example 1 was repeated except:
lowing composition—
cluded angle of 90° and was positioned approximately
two inches from the die ori?ce. The coating material was
the same as that used in Example 1.
Polyethylene ____________________________ __ 30
Microcrystalline wax ______________________ __ 14
Paraf?n wax
The apparatus and procedure used were similar to
those used in Examples 1-4 except that the extruder had
a three and one-half inch diameter barrel, and the
secondary die had a six inch ori?ce with an in
The coating was a wax-aluminum paste having the fol
Materials :
Coating of Blown Tubular Phenoxy Film
Aluminum paste _________________________ __ 50
The secondary die was changed to a steel plate having
a knurI-edged 41/2 inch diameter ori?ce.
Drawspeed was 55 feet per second.
The resulting ?lm had a wall thickness of 0.00102
0.0013 inch. The coating was a decorative pattern of
spaced bright aluminum stripes. Samples of coated and
Extrusion conditions were:
Die temperature _______________________ __'° F__ 500
Extrudate temperature __________________ __°F_.. 475
Extrusion rate ____________________ __lbs./honr__
Drawspeed __________________ __feet/minute__ 40-50
Bubble diameter/tube diameter ratio _________ __ 2-3/1
Film gauge
Coating thickness ________________ __inches__ ~0.0001
Moisture _vapor transmission characteristics of this bi
axially oriented ?lm of the polycarbonate homopolymer
of 2,2 bis(4-hydroxyphenyl) propane were measured as
coating material due to the former being considerably less
in the previous examples.
viscous at the extrudate temperature than the latter.
MVT (grams/100
sq, ill/24 hours)
__________________________ __
Coating of Blown Tubular Polyethylene Film
Apparatus similar to that shown in FIG. 6 of the draw
ings was used. The extruder had a 21/2 inch barrel, and
the secondary die was an aluminum plate having a 6 inch
diameter smooth surfaced ori?ce. A wax coating having
Coating of Blown Tubular Vinyl Film
The apparatus used was a Royle and Sons No. 2 ex
10 the formulation
truder having a 3% inch diameter barrel connected for
Polyethylene _____________ ..~_ ____________ __ 30
horizontal extrusion with a tubular die having a 5 inch
Microcrystalline wax ____________________ __-_ l4
diameter annular ori?ce. The secondary die was heated
Para?in wax ____________________________ __' 56
aluminum plate % inch thick provided with a six inch 15
diameter smooth surfaced ori?ce and spaced approximate
was applied to the extruded tube while it wasessentially
ly three inches from the ‘primary die. The resin was
unstretched by liquefying the Wax coating on the face‘ of
TiO2 pigmented rigid vinyl chloride homopolymer. The
the die and maintaining it in a channel about the extruded
coating had the composition—
tube. The resin was polyethylene having a melt index
Parts 20 of 2.
Extrusion conditions were:
Versamid 940 __________________________ __ 52.5
Pentalyn A __________________ _e ________ __ 42.5
Para?in wax
Die temperature _______________________ __° F__ 270‘
Extrudate temperature _____ _h ___________ __° F__ 302
Extrusion rate _________________ __pounds/hour__
and was applied with a spatula to the extruded tube be
Drawspeed ____________________ "feet/minute“
tween the primary and secondary die. The effect of the
Coating thickness ______________ _._ _________ __
Bubble diameter/tube diameter ratio _________ __ 2.5/1
secondary die was to form a rolling annular bank of coat
The coated ?lm was improved in optical properties,
ing material uniform all about the circumference of the 30
being lowered from 28 percent to 21 percent and in I
tube irrespective of the point of application of the coating
gloss, values being raised from 40 to 60 units.
The effect of this coating material on thermoplastic ?lm
having been shown in the preceding examples, no further
The preceding procedure was followed except that the
tests were made on this particular ?lm, the purpose of this
extrudate temperature was 293 ° F. Moisture vapor
example being to illustrate the obtaining of uniform coat
transmission measured as in Example 1 was reduced from
ings by horizontal extrusion and hand application of coat
ing material.
17.2 to 13.6. Haze values were lowered from 27.7 to 21.3
and gloss was increased from 39.9 to 60.1.
Extrusion conditions were:
Die temperature _______________________ __° F__ 330
Extrudate temperature __________________ __° F__ 365
Secondary die temperature ______________ __° F“ 240
Extrusion rate _________________ __pounds/hour__ 60
Another polyethylene resin (density 0.96) was similarly
coated by applying the wax coating to an extruded tube
thereof which was at a temperature of 347 ° F. Moisture
vapor transmission was reduced from 12.4 to 11.7. Haze
Bubble diameter/tube diameter ratio _________ __ 1.5/1
gauge ________________________ __
values were lowered from 14.1 to 10.4 and gloss was in
creased from 61.3 to 80.8.
Haze values were measured according to ASTM
thickness ___________________ __ 0.003—0.0005
lvat'iation normal for horizontally extruded vinyl ?lm.
D-1003-52 and gloss according to ASTM D-523-537.
What is claimed is:
1. Method for coating thermoplastic ?lm comprising
extruding molten thermoplastic in the form of seamless
It will be noted coatings obtained by this method are
somewhat less uniform in thickness than coatings applied
to vertically blown tubes.
Variations in thickness are
inherent in horizontal extrusion coating; hence, this mode
of coating is best suited to applications Where a high
degree of coating uniformity is not required.
tubing, maintaining the tubing essentially unstretched for
a distance from the die, applying adhering coating ma
The procedure and apparatus of Example 6 were used
except that ‘a clear rigid vinyl chloride copolymer was
used and the coating had the composition—
__________________ __- _______ __
Microcrystalline wax _____________________ __
wax ____________________________ __ 56
Extrusion conditions were:
Die temperature _______________________ __° F__ 300
Extrudate temperature _________________ __° F" 329
Secondary die temperature _______________ __°'F__ 225
Extrusion rate _________________ __pouuds/hour__
Bubble diameter/tube diameter ratio _________ __ 1.7/1
gauge _________________________ __ 0001-0003
terial to the essentially unstretched tubing, regulating the
thickness of the adhering coating and the distribution
thereof about the periphery of the tubing by passing the
coated tubing through a secondary die peripherally bear
ing against the coated surface of the tubing, and there
after stretching the coated tubing.
2. Method for coating thermoplastic ?lm comprising
extruding molten thermoplastic in the form of seamless
tubing, maintaining the tubing essentially unstretched for
a distance from the die, applying adhering coating ma
terial to the essentially unstretched tubing, regulating the
thickness of the adhering coating and the distribution
thereof about the periphery of the tubing by passing the
coated tubing through a secondary die peripherally bear
ing against the coated surface of the tubing, and there
after stretching the coated tubing in the machine and
transverse direction.
3. Method claimed in claim 2 wherein solid, powdered
coating material is applied to the tubing and forms an
annular rolling bank ‘around the tubing.
The coatings obtained using the wax coating material
4. Method claimed in claim 2 wherein liquid coating
were more uniform than those obtained with the Versannd 75
Coating thickness ____________________ __
material is applied to the tubing and forms an annular
rolling bank around the tubing.
13. Apparatus 'claimedjin ciaim7l2 wherein between
said primary die and said secondary die there is positioned
5. Method claimed in claim 4 wherein the coating ma- ‘
terial is a melt.
with the extruded tubing,
a receptacle adapted to hold coating material in contact
6. Method claimed in claim 4 wherein the coating
material is dissolved in a solvent.
V 14. Apparatus claimed in claim 13 wherein said re
ceptacle is adapted to maintain a ?uidized bed of pow
7.‘ Method claimed in claim 4 wherein the thermo
dered coating material in contact with said'tubing.
plastic is polystyrene.
15. Apparatus claimed in claim 13 wherein said re
ceptacle is adapted. to maintain a hot melt of coating
rolling bank rotates about the tubing.
10 material in contact with the tubing.
9. Method claimed in claim 8 wherein the thermo
16. Apparatus claimed in claim 13 wherein said rigid
plastic is polystyrene.
secondary die is mounted for rotation about the tubing.
10. Method claimed in claim 9 wherein a diluent for
17. Apparatus claimed in claim 16 wherein said rigid
the coating material is employed as a pre-wetting com
secondary die is spaced from 1 to 36 inches from said
f 8. Method claimed in claim 4- wherein said annular
11. Method claimed in claim 10 wherein the diluent
is polyethylene.
12. Apparatus for applying coatings to thermoplastic
?lm comprising a primary die for extruding seamless ther
moplastic tubing, a rigid secondary die spaced above and 20
coaxial with the primary die, means for drawing the tub
ing through the secondary die, said secondary die being
primary die.
References Cited in the ?le of this patent
adapted to relieve the greater part of the longitudinal
stress from the portion of the extruded tubing between
said primary die and said secondary die to maintain said 25 2,848,747
tubing essentially unstretched, and means for applying
adherent coating material to said essentially unstretched
portion of said tubing.
Hinsky ______________ __ May 1, 1934
Hinsky ______________ __ May 1, 1934
Fenlin ______________ __ July 15, 1952
Alles _~_4_'_ ____________ __ Feb. 3, 1953
Alles ________________ __ Jan. 29, 1957
Dixon ______________ __ Aug. 26, 1958
Doyle _______________ __ Sept. 20, 1960
Fortner et a1 __________ __ Oct. 11, 1960
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